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CPD NR 3281

Conceptual Process Design

Process Systems Engineering

DelftChemTech - Faculty of Applied Sciences

Delft University of Technology

Subject:

Industrial green catalytic oxidation of 1-butanol in an aqueous solvent.

Authors (Study nr.) Telephone

C.I.S. Lesueur (1160052) 0613912140

S. Sijbesma (1057669) 0641190577

J.F. Cornax (9162255) 0647576626

S. Balkenende (9032401) 0614481783

Keywords:

green catalytic oxidation 1-butanol butanal aque-ous palladium bathophencuproine homogeneaque-ous

Assigment Issued: September 30, 2002 Report Issued: December 31 , 2002

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Summary

A conceptual process design is presented for oxidation of 1-butanol to butanal (butyraldehyde) with a novel green catalytic method. The catalytic method used is under development at Delft University of Technology. This new catalytic process is based on a water soluble bathophen-cuproine palladium complex. No other (design) application is known until now. A single aqueous phase reactor at 21 bar and 403 K is designed. Butanal is mainly separated by ‡ashing and stripping and butanoic acid, a by-product, is separated by distillation and sold. Some process options are developed and a process with preseparation of 1-butanol and 2-butanol is used for design. Total capacity of the plant is 121 kton/y of butanal.

Butane is increasingly produced in nafta crackers due to change in polyethylene market. Eth-ylene production is decreased and larger ole…ns are produced. Butane fraction in the product stream of the nafta crackers increases with the increasing production of larger ole…ns. Butane is used as fuel, but by converting it to butanal via 1-butanol a valuable intermediate for poly-mer industry can be synthesized. Prices for butane, 1-butanol, butanal and butyric acid are $188/ton, $772/ton, $1234/ton and $1000/ton respectively.

Global butanal market demand exceeds 1000 kton/y. Competitive market players (BASF, Ruhrchemie, etc.) produce 300 kton/y, mainly by hydroformylation of propene (LP OxoT M

Low Pressure Oxo Process). Minor processes in use are hydrogenation of crotonaldehyde and dehydrogenation of butanol. Impact of the designed plant on global market is expected to be minimal because growing butanal demand and own use for polymer division.

Total investment for the plant will be 12.07 M$, and economical life time is expected to be 20 years. Additional time for designing and construction will be 4 years. An on-stream factor of 0.91 is expected. The process is liquid based, no solids are present and low fouling is expected. The NPW is M$ 211 (based on discount rate of 10%), DCFROR is 55% and ROR will be 88%. 10% higher variable cost and 10% lower income results in a DCFROR of 29% and a ROR of 19%.

From the design it can be concluded that the plant is feasible (high cash ‡ow and ROR), the plant is safe according to DOW F&EI and HAZOP studies, little waste is produced and no (environmental) toxic chemicals are used. Recommendations for further studies and de-tailed design are necessary to obtain more information on catalyst deactivation and catalyst performance at higher temperatures. Also veri…cation of reaction constants from experimental data and possible use of in-situ membrane reactor for decreasing amount of catalyst in process equipment is recommended.

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Contents

Summary xvi

1 Introduction 1

1.1 Project objective . . . 1

1.2 Novel catalytic cycle . . . 1

1.3 Product . . . 2

1.4 Market situation . . . 2

1.5 Design strategy . . . 3

2 Process options and selection 5 2.1 Product selection . . . 5

2.1.1 Existing processes . . . 5

2.2 Butanol production . . . 6

2.3 Mode of operation . . . 7

2.4 Block scheme selection . . . 7

2.4.1 Block scheme options . . . 7

3 Basis of design 11 3.1 Description of design . . . 11

3.1.1 Included in design . . . 11

3.1.2 Excluded from design . . . 11

3.2 Process de…nition . . . 11

3.2.1 Process concept . . . 11

3.2.2 Stoichiometry and catalyst . . . 11

3.2.3 Kinetics . . . 12

3.2.4 Experimental data . . . 12

3.2.5 Process conditions . . . 13

3.2.6 Blockscheme . . . 14

3.2.7 Thermodynamic properties . . . 15

3.2.8 Pure component properties . . . 15

3.3 Basic assumptions . . . 15

3.3.1 Plant capacity . . . 15

3.3.2 Location . . . 16

3.3.3 Battery limit . . . 16

3.3.4 Streams across battery Limit . . . 17

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CPD 3281 - Basis of Design

4 Thermodynamic properties and reaction kinetics 19

4.1 Thermodynamic properties . . . 19

4.1.1 Thermodynamic and physical properties of components . . . 19

4.2 Thermodynamic model . . . 20

4.3 Solubility data . . . 21

4.3.1 1-butanol in water . . . 21

4.3.2 Catalyst complex in water . . . 21

4.4 Kinetics . . . 23

4.4.1 Catalytic cycle . . . 23

4.4.2 Reaction order in alcohol concentration . . . 23

4.4.3 Reaction order in oxygen . . . 24

4.4.4 Reaction order in palladium concentration . . . 24

4.4.5 Rate expression . . . 24

4.4.6 1-butanol vs. 2-butanol competition . . . 26

4.4.7 Selectivity . . . 26

4.4.8 Catalyst deactivation . . . 26

5 Process structure and description 29 5.1 Pre-reaction section . . . 29

5.2 Conversion section . . . 29

5.2.1 Conceptual reactor design . . . 29

5.2.2 Assumptions for the reactor design . . . 31

5.2.3 Reactor design decisions . . . 31

5.2.4 Oxygen recycle . . . 35

5.3 Product puri…cation and catalyst recycle . . . 35

5.3.1 General considerations . . . 36

5.3.2 Catalyst separation and recycle . . . 37

5.3.3 Butanal recovery . . . 37

5.3.4 Alcohol recycle . . . 38

5.4 Process Flow Scheme (PFS) . . . 38

5.4.1 Section 100 . . . 39 5.4.2 Section 200 . . . 39 5.4.3 Section 300 . . . 39 5.5 Utilities . . . 39 5.6 Process Yields . . . 40 6 Process Control 41 6.1 Pre-reaction section . . . 41 6.2 Conversion section . . . 41 6.2.1 Reactor . . . 41

6.3 Product puri…cation and catalyst recycle . . . 42

6.3.1 Vapor/liquid separator . . . 42 6.3.2 Collection vessels . . . 42 6.3.3 Flash drum . . . 42 6.3.4 Stripping column . . . 43 6.3.5 Decanter . . . 43 6.3.6 Splitter . . . 43 6.3.7 Distillation column . . . 44

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CONTENTS

7 Mass and heat balances 45

7.1 Reactor balance set-up . . . 45

7.1.1 Mass balance . . . 45

7.1.2 Heat balance . . . 47

7.2 Balance for total streams . . . 47

7.2.1 Individual units . . . 47

7.2.2 Total plant . . . 47

7.3 Stream component balance . . . 47

7.4 Total plant imbalance . . . 47

7.5 Heat pinch . . . 48

8 Process and equipment design 49 8.1 Process simulation in ASPEN . . . 49

8.2 Pre-reaction separation . . . 49

8.2.1 Unit C101, alcohol distillation . . . 49

8.2.2 Re‡ux drums and collection vessels . . . 51

8.2.3 Pumps and compressors . . . 51

8.3 Conversion section . . . 52

8.3.1 Reactor optimization and design . . . 52

8.3.2 Hydrodynamic ‡ow regime . . . 53

8.3.3 Temperature . . . 53

8.3.4 Reactor composition . . . 54

8.3.5 Pressure . . . 56

8.3.6 Reactor dimensions . . . 57

8.3.7 Heat removal . . . 60

8.3.8 Unit V201, vapor / liquid separation . . . 62

8.4 Product puri…cation and catalyst recovery . . . 63

8.4.1 Unit V304, decanter . . . 63

8.4.2 Unit C301, butanal stripper . . . 64

8.4.3 Unit C302, butanal distillation . . . 65

8.4.4 Unit C303, butanol recycle puri…cation . . . 65

9 Wastes 67 9.1 Direct waste summary . . . 67

9.2 Direct waste . . . 67

9.2.1 Excess water, <319> . . . 67

9.2.2 Bleed streams, <313> & <320> . . . 68

9.3 Prevention of waste by design . . . 68

9.3.1 Alcohol vapor recycle . . . 68

9.3.2 Pure oxygen as O2 source . . . 69

9.3.3 Pre-separation of 2-butanol . . . 69

9.4 Further waste reduction possibilities . . . 69

9.4.1 Excess water use . . . 69

9.4.2 Optimization of column C302 and C303 . . . 69

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CPD 3281 - Basis of Design

10 Process safety 71

10.1 HAZOP . . . 71

10.1.1 Reactor HAZOP study . . . 71

10.2 Dow Fire & Explosion Index . . . 72

10.3 Explosion limits . . . 73

10.3.1 Pure components . . . 73

10.3.2 Explosion limits in a mixture . . . 73

11 Economy 75 11.1 Investment . . . 75

11.1.1 Section 100: 1-butanol/2-butanol separation . . . 75

11.1.2 Section 200: Reaction section . . . 75

11.1.3 Section 300: Separation section . . . 76

11.1.4 Total Investment . . . 76 11.1.5 Catalyst investment . . . 77 11.2 Operating costs . . . 77 11.2.1 Utilities . . . 77 11.2.2 Raw material . . . 78 11.2.3 Waste . . . 78 11.2.4 Labour costs . . . 78 11.2.5 Total . . . 78 11.3 Income . . . 79 11.4 Cash ‡ow . . . 79 11.5 Economic criteria . . . 79

11.5.1 Discounted cash ‡ow . . . 79

11.5.2 Discounted cash-‡ow rate of return (DCFROR) . . . 79

11.5.3 Rate of Return (ROR) . . . 79

11.5.4 Project cash ‡ow diagram . . . 80

11.6 Sensitivities . . . 80

12 Creativity and group process achievements 81 12.1 Creativity . . . 81

12.1.1 Goals . . . 81

12.1.2 Creativity: First approach . . . 81

12.1.3 BOD review: Change in approach . . . 84

12.1.4 Creative session with Mr. Grunwald and Mrs. Arends (7/11/’02) . . . 84

12.1.5 Creativity: …nal approach . . . 85

12.1.6 Review creativity tools and results . . . 86

12.2 Group interaction . . . 87

12.2.1 Participation pro…le (4/10/’02) . . . 87

12.2.2 BOD review meeting (4/11/’02) . . . 87

12.2.3 First team performance review (5/11/’02) . . . 88

12.2.4 DOW trip (11-12/11/’02) . . . 88

12.2.5 Second team performance review (19/11/’02) . . . 89

13 Conclusions and Recommendations 91 13.1 Conclusions . . . 91

13.1.1 Strength’s & weaknesses . . . 91

13.1.2 Technical and economical risks . . . 91

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CONTENTS 13.2 Recommendations . . . 92 13.2.1 Design reliability . . . 92 13.2.2 Cost reduction . . . 93 13.2.3 HES performance . . . 93 13.2.4 Creative designing . . . 93 List of symbols 94 Bibilography 97 A LP OxoT M Low Pressure Oxo Process 101 B Literature research 103 B.1 Initial research . . . 103

C Process options and selection 105 C.1 Block scheme selection . . . 105

C.1.1 Option 1, no alcohol separation . . . 105

C.1.2 Option 2, alcohol separation . . . 105

C.1.3 Comparison option 1 and 2 . . . 105

D De…nition of all streams crossing battery limits 107 D.1 1-Butanol/2-butanol feedstock . . . 107 D.2 Catalyst . . . 107 D.2.1 Paladiumacetate . . . 107 D.2.2 Ligand . . . 107 D.3 Oxygen . . . 107 D.4 1-Butanol/2-butanol sidestream . . . 108 D.5 Water . . . 108 D.6 Butanal . . . 108 D.7 Butanoic acid . . . 108 D.8 Exhaust Gasses . . . 108 E Thermodynamic model 111 F Thermophysical properties 113 F.1 Heat capacities of gaseous pure components . . . 113

F.2 Heat capacities of liquid pure components . . . 114

F.3 Vapour pressure of pure components . . . 115

F.4 Density of the pure liquid components . . . 116

F.5 Viscosity of the pure components . . . 117

G PhenS*Pd(OAc)2 solubility experiments 119 G.1 Introduction . . . 119

G.2 Experimental . . . 119

G.3 Results . . . 119

G.4 Conclusion & discussion . . . 120

H PFS and tables 121

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CPD 3281 - Basis of Design

J Balance for stream components 129

K Ternary diagrams reactor system 133

L Cooling equipment design 135

L.1 Symbols used . . . 137

L.1.1 regular . . . 137

L.1.2 Greek . . . 138

L.1.3 Subscripts . . . 138

M Mass transfer of oxygen 139 M.1 Introduction . . . 139

M.2 Transfer coe¢cient value kL . . . 139

M.3 Interfacial area . . . 140

M.3.1 Bubble column . . . 140

M.3.2 Stirred unit . . . 141

M.3.3 kLa value in‡uencing factors . . . 141

N Solubility of gasses in liquids 143 N.1 Oxygen solubility . . . 143

N.2 Henry constant . . . 143

O Henry constant in pure liquids 145 O.1 Henry constant of oxygen in water . . . 145

O.2 Henry constant of oxygen in butanol . . . 145

O.3 Henry constant of oxygen in butanal . . . 146

P Pre-reactor separation 147 P.1 Trayed column . . . 147

P.1.1 Minimum re‡ux ratio and number of stages . . . 147

P.1.2 RadFrac model . . . 147 P.1.3 Column e¢ciency . . . 148 P.2 Packed column . . . 148 P.2.1 Packing design . . . 148 Q Stirrer design 151 Q.1 Geometric parameters . . . 151 Q.2 Power consumption . . . 152

Q.2.1 Single liquid phase system . . . 152

Q.2.2 Two-phase stirred system . . . 153

Q.3 Mass transfer parameters . . . 153

Q.3.1 Gas holdup . . . 153

Q.3.2 Interfacial area . . . 154

R Equipment summary & speci…cation sheets 155 S HAZOP study on reactor 167 S.1 Start-up and shut-down procedures . . . 167

S.1.1 Start-up procedure . . . 167

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CONTENTS

T Dow Fire & Explosion Index sheets 171

U Purchased equipment costs 189

U.1 Section 100: 1-butanol/2-butanol separation . . . 189

U.1.1 Column shell and internals . . . 189

U.1.2 Reboiler . . . 189

U.1.3 Condenser . . . 189

U.1.4 V101 . . . 189

U.2 Section 200: reaction section . . . 189

U.2.1 Oxygen compressor . . . 189

U.2.2 Reactor with agitator . . . 190

U.2.3 Oxygen recycle compressor . . . 190

U.2.4 Feed pump . . . 190

U.2.5 Liquid recycle pump . . . 190

U.2.6 V202 . . . 190

U.3 Section 300: separation section . . . 190

U.3.1 C301 . . . 190 U.3.2 C302 . . . 190 U.3.3 C303 . . . 190 U.3.4 V302 . . . 191 U.3.5 V303 . . . 191 U.3.6 V305 . . . 191 U.3.7 V306 . . . 191

V Creativity tools and results 193 V.1 Creative technique inventory . . . 193

V.2 Literature research (8/10/’02) . . . 193

V.3 Matec (25/10/’02) . . . 193

V.4 Grunwald Session (7/11/’02) . . . 195

V.4.1 In…nite amount of small reactors . . . 195

V.4.2 Doughnut shaped reactor . . . 195

V.4.3 Flexible reactor . . . 196

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List of Figures

2.1 Brief description on process sequence . . . 7

2.2 Block scheme for 1-butanol oxidation without preseparation . . . 8

2.3 Block scheme for 1-butanol oxidation with preseparation of reactants . . . 8

3.1 Structure of the active palladium-bathocuproine complex . . . 12

3.2 Main reactions occuring in the oxidation process . . . 12

3.4 Block scheme for 1-butanol oxidation with preseparation of reactants . . . 14

3.3 The bubble and dewpoint curves for a 1-butanol, 2-butanol, butanal, butanone and water mixture (mass fraction: 1:1:1:1:3). The model used is UNIQUAC . . . 14

3.5 Streams crossing the battery limits . . . 17

4.1 xy diagram for a 2-butanol/1-butanol mixture at P = 1.013 bar [17, p. 150]. . . . 21

4.2 Ternary diagram for water/1-butanol/butanal at 30 bar and 393 K . . . 22

4.3 Proposed catalytic cycle for alcohol oxidation by PhenS*Pd(II)[3] . . . 23

4.4 PhenS*Pd(OAc)2 dimer . . . 24

4.5 Rate constant as a function of the number of carbon atoms of the molecule . . . 25

5.1 The conversion versus space time for a PFR and a CSTR . . . 32

5.2 Reactor with feeds and products. . . 34

5.3 The recycle structure for oxygen . . . 36

5.4 Residue curve map for butanal/water/1-butanol at 1 bar. . . 38

5.5 Process blockscheme with yields . . . 40

7.1 Streams entering and leaving the reactor . . . 45

8.1 Txy diagram of 2-butanol/1-butanol at 1.013 bar . . . 49

8.2 Two di¤erent types of column packing . . . 50

8.3 Liquid volume versus conversion at given temperatures. . . 54

8.4 The ternary diagram of the reactor composition at 30 bar and 130±C : . . . 55

8.5 . . . 59

8.6 Artist impression of reactor design . . . 60

8.7 Gas-liquid separator V201 sketch . . . 63

8.8 Decanter V304 sketch . . . 64

10.1 Simple reactor scheme with in and out ‡ows . . . 72

11.1 The project cash ‡ow for the …rst 10 years of the project . . . 80

12.1 Preliminairy reactor idea . . . 84

12.2 Possible set-up for a tubular membrane reactor . . . 85

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CPD 3281 - Basis of Design

A.1 Schematic overview of a LPO process [31]. . . 101

E.1 xy diagram for a water/1-butanol mixture at P = 1.013 bar [16, p. 245-253]. . . 111

E.2 xy diagram for a butanal/water mixture at P = 1.013 bar [16, p. 212 - 218] . . . 112

E.3 xy diagram for a 2-butanol/1-butanol mixture at P = 1.013 bar [17, p. 150 - 154].112 F.1 Heat capacity of the gaseous pure components as a function of temperature . . . 114

F.2 Heat capacity of the liquid pure components as a function of temperature . . . . 115

F.3 Vapour pressure of the pure liquids as a function of temperature . . . 116

F.4 Density of the pure liquids as a function of temperature . . . 117

F.5 Viscosity of the pure liquids as a function of temperature . . . 118

H.1 Process stream summary . . . 123

H.2 Process stream summary (continued) . . . 124

H.3 Process stream summary (continued) . . . 125

H.4 Process yield values . . . 125

H.5 Summary of utilities . . . 126

J.1 . . . 129

J.2 . . . 130

J.3 . . . 131

K.1 Ternary diagram for water/1-butanol/butanal, at various temperatures . . . 133

P.1 N*(R+1) versus N, optimum number of stages according to shortcut . . . 147

P.2 SULPAK input parameters and results for calculation on packing for the 1-butanol/1-butanol separation tower . . . 149

Q.1 Drawing of a multiple turbine stirrer tank . . . 151

T.1 Dow Fire and Explosion Index sheet for equipment C101 . . . 172

T.2 Dow Fire and Explosion Index sheet for equipment E101 . . . 173

T.3 Dow Fire and Explosion Index sheet for equipment P101 . . . 174

T.4 Dow Fire and Explosion Index sheet for equipment E201 . . . 175

T.5 Dow Fire and Explosion Index sheet for equipment E202 . . . 176

T.6 Dow Fire and Explosion Index sheet for equipment K201 . . . 177

T.7 Dow Fire and Explosion Index sheet for equipment K202 . . . 178

T.8 Dow Fire and Explosion Index sheet for equipment P201 . . . 179

T.9 Dow Fire and Explosion Index sheet for equipment R201 . . . 180

T.10 Dow Fire and Explosion Index sheet for equipment C301 . . . 181

T.11 Dow Fire and Explosion Index sheet for equipment C302 . . . 182

T.12 Dow Fire and Explosion Index sheet for equipment C303 . . . 183

T.13 Dow Fire and Explosion Index sheet for equipment E303 . . . 184

T.14 Dow Fire and Explosion Index sheet for equipment E304 . . . 185

T.15 Dow Fire and Explosion Index sheet for equipment P305 . . . 186

T.16 Dow Fire and Explosion Index sheet for equipment V301 . . . 187

T.17 Dow Fire and Explosion Index sheet for equipment V304 . . . 188

V.1 . . . 196

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List of Tables

1.1 Main butanal proccesses world wide . . . 2

2.1 Overview of choice of product to be produced . . . 6

2.2 Prices of butane, 1-butanol and butanal . . . 6

2.3 Preferred process conditions butane fermentation[41] . . . 7

2.4 Separation opportunities . . . 9

2.5 Separation di¢culties . . . 9

3.1 Pro’s and Con’s of use of high pressure in the Green Catalytic Oxidation method 13 3.2 Pro’s and Con’s of use of high temperature in the Green Catalytic Oxidation method . . . 13

3.3 Pure component properties, part 1 . . . 16

3.4 Pure component properties, part 2 . . . 16

3.5 Mass ‡ows of In- and Out-going streams . . . 17

3.6 Important equipment inside battery limits . . . 17

3.7 Stream numbers crossing the battery limits . . . 18

3.8 Margin calculation . . . 18

4.1 Thermodynamic properties of pure components at standard state . . . 19

4.2 Heat of reaction, Gibbs free energy of reaction and entropy generated at standard state . . . 20

4.3 Used databases for binairy interaction parameters . . . 20

4.4 binary data for 1-butanol/water . . . 21

4.5 binary data for butanal/water . . . 22

4.6 Calculated henry coe¢cients for oxygen in di¤erent solvents . . . 22

4.7 Rate constant values . . . 25

4.8 Rate constant values versus temperature for 1-butanol . . . 26

4.9 Catalyst deactivation . . . 27

5.1 Estimation of the oxygen price versus its purity . . . 34

6.1 Controlled and manipulated variables for the …rst distillation column . . . 41

6.2 Controlled and manipulated variables for the reactor . . . 42

6.3 Controlled and manipulated variables for the mixers . . . 42

6.4 Controlled and manipulated variables for the ‡ash drum . . . 43

6.5 Controlled and manipulated variables for the stripping column . . . 43

6.6 Controlled and manipulated variables for the …rst distillation column . . . 44

7.1 Cooling requirements . . . 48

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CPD 3281 - Basis of Design

8.1 Cost estimation for a trayed 1-butanol/2-butanol distillation column . . . 51

8.2 Cost estimation for a packed 1-butanol/2-butanol distillation column . . . 51

8.3 Vessel geometric data . . . 52

8.4 Pump characteristics . . . 52

8.5 Compressor characteristics . . . 52

8.6 In‡uence of temperature in the reactor . . . 53

8.7 Reactor composition and temperature . . . 56

8.8 Parameters determining reactor pressure . . . 56

8.9 Reactor composition, temperature and necessary pressure for a bubble column . 57 8.10 Number and size of the reactor for di¤erent temperatures . . . 58

8.11 Reactor dimensions . . . 60

8.12 Feed stream temperature after heat exchange . . . 61

8.13 Heat transfer properties . . . 61

8.14 Cooling water properties . . . 62

9.1 Waste stream summary, 1 . . . 67

9.2 Waste stream summary, 2 . . . 68

10.1 Deviations generated by each guide word . . . 71

10.2 Heat of combustion for di¤erent components . . . 73

10.3 Explosion limits for substances in pure oxygen . . . 73

10.4 Composition of the mixture in the overhead of the reactor, without oxygen dilution 74 10.5 Composition of the mixture in the overhead of the reactor, with oxygen dilution 74 11.1 Equipment in the pre separation section . . . 75

11.2 Equipment in the reaction section . . . 76

11.3 Equipment in the separation section . . . 76

11.4 Raw material costs . . . 78

11.5 Income from product sales . . . 79

11.6 Sensitivities to worse economical circumstances, costs +10%, income -10% . . . . 80

12.1 Delft Design Matrix and implemented creativity methods . . . 82

12.2 Results from the MATEC method . . . 83

12.3 Brief representation creative session guided by Mr. Grunwald and Mrs. Arends . 85 12.4 not pursued creative ideas during design period . . . 86

12.5 Identi…ed team strengths and weaknesses . . . 88

13.1 Strengths of the design . . . 91

13.2 Weaknesses of the design . . . 91

A.1 Process properties LPO process . . . 101

D.1 Stream properties of the alcohol stream . . . 107

D.2 Stream properties of the Palladium catalyst stream . . . 108

D.3 Stream properties of the ligand stream . . . 108

D.4 Stream properties of the oxygen/air stream . . . 109

D.5 Stream properties of the alcohol stream . . . 109

D.6 Stream properties of the water stream . . . 109

D.7 Stream properties of the butanal stream . . . 109

D.8 Stream properties of the butanoic acid stream . . . 110

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LIST OF TABLES

E.1 Used databanks for binairy parameters . . . 111

F.1 Heat capacities for gaseous components . . . 113

F.2 Heat capacities for liquid components . . . 114

F.3 Vapour pressure data for pure components . . . 115

F.4 Density data for pure components . . . 116

F.5 Liquid viscosity data for pure components . . . 117

G.1 The catalyst complex solutions . . . 119

I.1 Control objectives and explanation of their in‡uence . . . 128

L.1 Physical properties of reactor mixture (303 K) and cooling water (averaged) . . . 136

L.2 Input and results of heat exchange calculations . . . 137

L.3 Calculated values for heat transfer calculations . . . 138

M.1 orders of magnitude of mass transfer parameters for a bubble column . . . 139

M.2 liquid …lm transfer coe¢cient versus temperature . . . 140

O.1 Henry constant of oxygen in pure water . . . 145

O.2 Henry constant of oxygen in pure butanol . . . 145

O.3 Henry constant of oxygen in pure butanol comparison . . . 146

O.4 Henry constant of oxygen in pure butanol used to calculate the reactor pressure . 146 O.5 Henry constant of oxygen in pure butanal . . . 146

Q.1 geometrical parameters for a turbine stirrer tank . . . 152

S.1 HAZOP study, guide word NONE . . . 168

S.2 HAZOP study, guide word MORE OF . . . 169

S.3 HAZOP study, guide word LESS OF . . . 169

S.4 HAZOP study, guide word PART OF . . . 170

S.5 HAZOP study, guide word MORE THAN . . . 170

S.6 HAZOP study, guide word MORE THAN . . . 170

T.1 Degree of hazard according to the Dow Fire & Explosion Index for every equipment171 V.1 Creativity methods . . . 193

V.2 coming out of the brainstorm session . . . 194

V.3 Matrix with chain associations from ’oxygen’ . . . 194

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1 | Introduction

In this report a design is presented which is designed within the framework of the course Conceptual Process Design at the DelftChemTech (DCT) Department of the Faculty of Applied Sciences (TNW) at Delft University of Technology (DUT). In this course students are supposed to produce an innovative, integrated, consistent and sound process design [28, p. i]. In this chapter the project objective, bene…ts of the design, available processes, current market, impact of plant design on market and design strategy will be presented.

1.1 Project objective

The project’s objective is:

A novel catalytic method for the oxidation of alcohols has been developed. An industrial application for this new, green technology is to be found. Improvements in environmental burden and economical performance must be realized

The Biocatalysis and Organic Chemistry research group at the DCT Department of TNW at DUT has issued the stated objective and the research group presented by principal Dr. I. Arends. Dr. Arends is employed with the Biocatalysis and Organic Chemistry department and participated in the development of the novel catalytic method. Her interest in the project is the industrial application of this experimental catalytic oxidation method.

1.2 Novel catalytic cycle

The catalytic oxidation method has big advantages. The special features of this method are: ² use of water as a solvent

² no stoichiometric amounts of heavy metal oxidants as waste ² selective towards reactant and desired product

² use of oxygen as oxidant

A whole range of possible reactants are described[3]. The environmental advantages are obvious: no organic solvent is used and less waste is generated. Smaller waste streams reduces costs for waste removal. The speci…c economic advantages will depend on the type of process which will be designed. The oxidations described [3] have a high yield and are very selective. The only main by-product is caused by the over-oxidation of aldehydes to the corresponding acids. Also oxidation of impurities can occur. Some expected design di¢culties were the limited

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CPD 3281 - Basis of Design

solubility of the oxidant (molecular oxygen) and the limited solubility of the alcohol. In the design these di¢culties were overcome by working at little elevated temperature to obtain a total miscible phase.

Due to the state of the art catalytic method the amount of accessible and present information is small. During the design some assumptions had to be made to overcome this problem. A test on catalyst solubility was performed to obtain information for reactor design optimization. More details on the catalytic method and the catalytic cycle are presented in chapter 4.

1.3 Product

After elaborate literature research and exploration of industrial oxidizing reactions (see chapter 2), we decided to design a plant for butanal production from 1-butanol. This process is currently under investigation by the Japanese company Asahi-Kasei. Experiments on oxidation of butanol are at the moment investigated at DUT by Mr. T. Kodama, a guest researcher of Asahi-Kasei at the biocatalysis and organic chemistry research group. The conceptual design is based on the main product butanal.

Butanal is a colorless, ‡ammable liquid with a pungent penetrating odor. The vapor has a narcotic e¤ect and irritates mucous membranes. Butanal is miscible with organic solvents, such as alcohols, ethers, and benzene [31]. More details on product properties can be found in paragraph 3.2.8.

Butanal has moderate toxicity to aquatic life. By itself it is not likely to cause environmental harm at levels normally found in the environment. Butanal can contribute to the formation of photochemical smog when it reacts with other volatile substances in air [5].

Butanal is of special interest to Asahi-Kasei for the production of 2-ethyl-2-(hydroxymethyl)-1,3-Propanediol (Etriol), a cross-linking agent for the polymer industry. Butanal is used as a chemical intermediate in the production of plasticizers, rubber accelerators, synthetic resins, solvents and high molecular weight polymers [4].

The main butanal producing processes used are [31] given in table 1.3 in order of industrial use.

Table 1.1: Main butanal proccesses world wide

Process Reactants Main products Temperature

range Pressure range [K] [Bar] Hydroformylation of propene Propylene, syn-thesis gas n-Butanal, i-butanal 363 - 453 25 - 350 Hydrogenation of crotonalde-hyde Acetaldehyde, hydrogen n-Butanal, wa-ter - -Dehydrogenation of butanol

Butanol Butanal,

hydro-gen

-

-1.4 Market situation

The polyethylene production of Asahi-Kasei in Japan is currently under pressure. Cheap poly-ethylene from Saudi Arabia is putting prices down. Therefore, Asahi-Kasei is changing its output of its nafta crackers in Japan from ethylene to heavier components. Most of these

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1.5. DESIGN STRATEGY components o¤er a good alternative to ethylene. Butane however, which is now also produced increasingly, has almost no value. It is currently used or sold as fuel. The biological process which will be used for producing butanol from cheap butane is currently under investigation. The butanal produced via the butanol oxidation provides a valuable feedstock for Asahi-Kasei’s polymer divisions. Details on the economical feasibility are presented in chapter 11.

Throughout the world more than 3.2¢106tons of butanal is manufactured each year by the

hydroformylation of propylene (e.g. LP OxoT M Low Pressure Oxo Process patented by DOW).

A block scheme of this process is shown in appendix A. Large-scale plants such as those in operation at BASF, CWH, Ruhrchemie, or UCC each have an annual output of 200 –3.0¢105tons.

The hydroformylation process is by far the largest process used in butanal production [31]. Butanal is produced in very large amounts (almost 0.9¢106tons in 1992) by …ve companies in

the United States. U.S. demand for butyraldehyde is likely to remain steady for the next several years [5]. The production volume indicates that the world wide market situation is large.

It is not expected that operating this plant will have signi…cant impact on the world market. Demand for intermediates in polymer industry is growing as an e¤ect on growing demand for plastics.

1.5 Design strategy

For the design planning and splitting up design in distinct levels the Delft design matrix (DDM) was used. DDM provides design teams with a structured approach on the design. Also a method for reactor design and evaluation developed by R. Krishna and S.T. Sie [21] was utilized to facilitate reactor design. Creativity methods and methods to enhance group dynamics improved team performance and cooperation during the design trajectory. Applied methods and results are presented in chapter 12.

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2 | Process options and selection

2.1 Product selection

The project objective requires the novel catalytic method to be used in a process which results in lower environmental burden and an increase in economic performance. Di¤erent components and processes for synthesis of these components were investigated for potential design or re-design.

2.1.1 Existing processes

An important environmental bene…t of the new alcohol oxidation method is the use of mole-cular oxygen as oxidant. This is a great advantage over the use of stoichiometric amounts of metal oxidants. The generation of waste is avoided and the atom e¢ciency of the process is dramatically increased. The use of metal oxidants for alcohol oxidation in industry is nowadays limited to the …ne chemicals production. Our …rst focus was on this branch of industry. Fine chemical industry

A large amount of aldehydes produced are used in ‡avors and fragrances and in medicine industry. Several sources (IFF, Givaudan, Diosynth, NEA, VNCI) were consulted. Di¤erent other sources were investigated which are pointed out in chapter 12 Industry was not willing to provide detailed information on processes, production quantities, products and raw material prices. Substances found in literature are given in appendix B.

Information of companies (IFF, Givaudan and Diosynth) pointed out that the chromium salt oxidation is hardly performed. Chromium salts are used because of high selectivity, high yield and easy usage. Especially selectivity is important. Alcohols can have other active groups (steroidalcohols, Amine groups, Sulphur groups, double bonds etc.). The new catalyst can not handle components with other active groups due to coordination to the active site, and this will prevent the hydroxyl group from reacting.

Bulk processes

A large amount of bulk aldehydes are produced in gas phase processes with heterogenous catal-ysis. These processes are widely used and have large production capacities (benzaldehyde, formaldehyde etc.). Benzene derivatives are mostly produced, and are not or little soluble in water. This is one of the main issues why the process based on water as a solvent cannot com-pete with gas phase synthesis. Margins on the products are relatively low compared to ‡avors and fragrances.

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CPD 3281 - Basis of Design

Possible substrates and products

After an extensive search on suitable substrate we found several products which might be produced using the novel catalytic method. Some are presented in table 2.1.

Table 2.1: Overview of choice of product to be produced

Product Advantage and/or disadvantage

Pentanoic acid Small amount of available data.

3,3-dimethylbutanal Used for neotame production. Mainly

produced in gasfase reactions[44]. No big bene…ts expected.

Menthone Produced by other processes than

al-cohol oxidation. 4-tert-Butyl-®-methylhydrocinnamic

aldehyde

Synthesis from corresponding alcohol is not e¢cient.

2-Methyl-3-(4-tert-butylphenyl)-propanal (Lilial)

Oxidation of the corresponding alco-hol is not e¢cient.

Butanal Soluble alcohol, no other active

groups,

The design team decided to use green oxidation method for a butanal process

This process is currently under investigation by the Japanese company Asahi-Kasei. Exper-iments are currently conducted by a guest research worker of Asahi-Kasei at the research group Organic Chemistry at DUT.

Butane is produced in large amounts (¼100,000 tons/year) by Asahi-Kasei. The price of butane, calculated from fuel price [6, page 135]. Prices are shown in table 2.1.1. Butanal will be worth at least 6.5 times the value of butane.

Table 2.2: Prices of butane, 1-butanol and butanal Component Price $/ton Butane 188 1-Butanol 772 Butanal 1234

2.2 Butanol production

To make a sound decision on to use unit operations, combinations of operations and eventually integration of unit operations di¤erent options have to be investigated. The designed oxidation process is a part of a sequence of distinct processes which is brie‡y described in …gure 2.1.

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2.3. MODE OF OPERATION

Figure 2.1: Brief description on process sequence

Butane is produced in the nafta crackers. Butane will be fermented to 1-butanol. The process which will be used is also selected by the design team, but is not designed. 1-Butanol will be converted to butanal by the designed plant. Etriol is produced by aldol condensation at elevated temperature in an aqueous basic mixture with methanal. The process for etriol will not be discussed in this report.

The 1-butanol production by fermenting butane is described in [41]. Mentioned process in this patent is capable of oxidizing butane. Processes described in other patents [41, page 13] are mainly limited to oxidizing hexane or higher alkanes. The process described in [41] is chosen as the process which will supply the feed for the reactor based on high selectivity towards 1-butanol. The process conditions are shown in table 2.2[41].

Table 2.3: Preferred process conditions butane fermentation[41] Temperature [oC] 20 - 40

Pressure [bar] 1 - 10

pH [-] 5.5 - 8

modes of operation batchwise, fed-batch and continuous

oxidizing agent O2

product composition 5% 2-butanol, 95% 1-butanol

We assume that the products of the fermentation will be separated from the broth by the fermentation plant. The product of the alcohol fermentation plant and thus the feed of the designed plant will consist solely of alcohols. Details on feed stream are given in appendix D.

2.3 Mode of operation

The decision between batch or continuous is made using guidelines from [6, page 108]. From a production rate point of view, the process will be a continuous. The capacity of the plant to be designed will exceed 100,000 ton/y of 1-butanol. This is way beyond the upper limit for batch processes (capacity batch processes 500 - 5,000 t/y).

The reaction rate is not high, but it is expected that it is su¢ciently fast for realizing a continuous process without excessive large equipment. Butanal isn’t a season depending product and no operational problems within a continuous process for butanal are expected (high throughput, no solids).

A continuous process will be designed

2.4 Block scheme selection

2.4.1 Block scheme options

As described in the preliminary basis of design report [42], a choice between two di¤erent block schemes is made. Both block schemes are presented in …gure 2.2 and 2.3.

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CPD 3281 - Basis of Design

Figure 2.2: Block scheme for 1-butanol oxidation without preseparation

Figure 2.3: Block scheme for 1-butanol oxidation with preseparation of reactants The main di¤erence between the two ‡owsheets is separation of 2-butanol from 1-butanol before the reaction section. The choice for whether or not to use pre-separation is based on margin di¤erence, number of needed theoretical separation steps and expected equipment size. A short overview on separation sections of both ‡owsheets is presented in appendix C.1. Results from the comparison between the mentioned block scheme are shown in table 2.4 and 2.5.

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2.4. BLOCK SCHEME SELECTION

Table 2.4: Separation opportunities

Both Without preseparation With preseparation

Flashing product mixture will remove excess water and aldehyde from recylce stream

Butanone will be present in low quantities (5%)

Distillation possible for 2-butanol separation from 1-butanol

Separation by extraction of aldehyde and ketone is pos-sible

No 2-butanol will be

present in reactor

Table 2.5: Separation di¢culties

Both Without preseparation With preseparation

Distillation for water re-moval is not favored

Butanal/butanone separa-tion (by distillasepara-tion) is very di¢cult (® ¼ 1:01)

An extra separation step is necessary to remove 2-butanol from reactant mix-ture

Removal of butanoic acid from aqueous catalyst recy-cle stream is necessary

Waste water will contain larger amount of 2-butanol and its products

1-butanol should be pure, this results in high purity separation

An extra separation step is necessary for butanone re-moval.

As has been pointed out in the preliminary BOD report, the margin di¤erence (…rst stage economical potential analysis) is small. Margin of the …rst block scheme is 39 M$=y and 38 M$=y for the second block scheme. The di¤erence between margins is too small to make a sound decision for one of both options. Equipment size will reduce with option 2, because 2-butanol does not have to be processed. This will reduce volume and power/heat duty of process equipment. Because of the expected advantages in separation, low margin di¤erence between block schemes, the block scheme with pre separation will be used for the design.

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3 | Basis of design

3.1 Description of design

A process will be designed for the conversion of 1-butanol into butanal on a large scale in an aqueous environment with homogeneous catalyst. The method described in [3] is used for this. The target production is 112 ton/year. The catalyst is the water soluble palladium acetate PhenS* complex. The feed is a mixture of 95% 1-butanol and 5% 2-butanol. A separation section is designed to separate 1- from 2-butanol. 1-butanol is converted into butanal in the reactor. A downstream separation section separates the product and produced water from catalyst and by-products.

3.1.1 Included in design

A butanal production unit, product and catalyst separation will be designed. An economic evaluation of the whole production and separation will be performed.

3.1.2 Excluded from design

The design of the plant will not be …t in an existing complex although it is assumed that the new plant will be placed on an existing site. Reason is that nothing is known about on-site utilities and other plants. The utilities, oxygen supply and waste water treatment will not be designed. Those are assumed to be available.

3.2 Process de…nition

3.2.1 Process concept

The incoming 1-butanol/2-butanol mixture will be separated …rst. The 1-butanol will be fed to a reactor. After the reactor, catalyst will be separated from the product and product from unreacted reactants. The catalyst and reactants will be recycled to the reactor. The product stream will contain butanal and may contain water as this is not harmful for the downstream application.

A continuous reactor will be designed which produces about 100 kiloton per year. It will operate at elevated pressure to facilitate oxygen transfer to the liquid phase. Elevated tempera-ture is necessary for a reasonable rate of reaction. The exothermic reaction requires the reactor to be cooled. Oxygen is a reactant and thus or air or oxygen is introduced in the reactor.

3.2.2 Stoichiometry and catalyst

The catalyst is a water soluble complex of palladium with bathocuproine, stable and recyclable, whose formula in neutral aqueous solution is PhenS*Pd2+ and shown in …gure 3.1.

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CPD 3281 - Basis of Design N N C H3 CH3 SO3Na NaO3S Pd2+

Figure 3.1: Structure of the active palladium-bathocuproine complex

The 1-butanol feed contains 2-butanol, which leads to two products: butanal and butanone. The reactions leading to those products are shown in …gure 3.2.

Figure 3.2: Main reactions occuring in the oxidation process

The selectivity of the catalyst is high. The catalyst selectively reacts with alcohols to produce their corresponding aldehyde or ketone. Experiments showed selectivities of 90% and higher[3].

3.2.3 Kinetics

The rate of reaction is …rst order in alcohol and half order in catalyst. The rate constant k has a value between 2.3E-3 `1=2:mol¡1=2:s¡1(at 100 ±C) and 3.31E-2 `1=2:mol¡1=2:s¡1(at 150 ±C).

The rate expression used is

¡rA= k¢ [alcohol] ¢ [catalyst] 1

2 (3.1)

Di¢culty in this expression is the concentration. In systems where the solute does not contribute to the total volume, concentration expressed in mol per unit volume can be used. In our case, the concentration of 1-butanol is too high to neglect the volume e¤ect. Calculations will be done on a mol per mol basis.

3.2.4 Experimental data

The most important document as a source for experimental data is the Ph.D. thesis ’Green Catalytic Oxidations”, by G.J. ten Brink[3]. This is as far as we know the only document containing information on the palladium bathocuproine complex catalyzed oxidation of alcohols in water. In the thesis, various alcohol oxidations are described, but regretfully no C4-alcohol oxidations. Nevertheless, the data presented in the thesis is very useful, because very similar

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3.2. PROCESS DEFINITION alcohols are used in the experiments. With these data, predictions will be made for the 1-butanol and 2-butanol oxidations.

3.2.5 Process conditions

Temperature and Pressure in the reaction section

The temperature and pressure used in the available experimental data on the reaction is 100±C

and 30 bar. Instead of copying these values for the large scale process, …rst the pro’s and con’s of high temperature and pressure in the reaction section are considered. Then, an estimation is made for the ideal temperature and pressure for the large scale process. The pro’s and con’s are presented in table 3.1 and 3.2.

Table 3.1: Pro’s and Con’s of use of high pressure in the Green Catalytic Oxidation method

pro’s rate con’s rate other rate

higher O2 solu-bility ++ higher cap-ital costs (equipment, compressors) - - product will be a liquid at high P -higher oper-ating costs (power)

-Table 3.2: Pro’s and Con’s of use of high temperature in the Green Catalytic Oxidation method

pro’s rate con’s rate

higher reaction rate ++ lower O2 solubility

-higher alcohol solubility ++ higher aldehyde solubility

-heating necessary

+/-Next to these considerations in tables 3.1 and 3.2 for choosing the pressure and temperature, certain constraints can be identi…ed:

² Water should be a liquid

² No critical pressure and/or temperatures are allowed ² No explosive mixtures should be possible

² Temperature should be below autoignition temperature

The high pressure used in the laboratory experiments is only necessary to maintain a certain level of oxygen dissolved in the reaction mixture. Also, temperature and pressure conditions of the upstream and downstream blocks are important. For example, when high pressure is needed anyway in an upstream or downstream process, the con’s of using high pressure in the reaction section become less important. The operation point in the reactor will be far from the bubble point, as can be seen in …gure 3.3.

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CPD 3281 - Basis of Design

Figure 3.4: Block scheme for 1-butanol oxidation with preseparation of reactants

Figure 3.3: The bubble and dewpoint curves for a 1-butanol, 2-butanol, butanal, butanone and water mixture (mass fraction: 1:1:1:1:3). The model used is UNIQUAC

3.2.6 Blockscheme

The chosen blockscheme di¤ers from the rejected scheme only slightly. The di¤erence is an extra separation section before the reactor. Explanation on the choice can be found in chapter 2. Main reason is easier separation of 1- and 2-butanol than butanal and butanone. This will re‡ect on process economy. Figure 3.4 shows the chosen blockscheme.

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2-3.3. BASIC ASSUMPTIONS butanol. 1-butanol is then fed to the reaction section where the oxidation reaction with the same components (except 2-butanol) as in the …rst process takes place. In this separation section, the catalyst is continuously recycled and the butanoic acid removed. The mixture that comes out of the reaction section is fed to the separation section where 1-butanol, butanal and butanoic acid are separated. The unconverted 1-butanol is then recycled to the reactor.

3.2.7 Thermodynamic properties

This paragraph contains key thermodynamic information. A more elaborate thermodynamic study is presented in chapter 4. Where applicable and possible, modelled data is veri…ed with data from the Dechema data series[11].

Thermodynamic model

The thermodynamic model used is UNIQUAC. This model is capable of predicting thermody-namics of polar systems at elevated pressures. NRTL is also suitable for these type of systems but UNIQUAC is more capable of handling components with very di¤erent properties (for instance water and butanal).

Catalytic cycle

In the catalytic cycle, the palladium dimer reacts selectively with the alcohol, with the corre-sponding aldehyde and water as a product. Oxygen regenerates the catalyst to its original state after which it reacts again with alcohol. If no oxygen is available after the aldehyde split-o¤, the catalyst will degenerate to palladium black, which makes the catalyst useless.

Solubility of 1-butanol and butanal in water

A study is done to the solubility of 1-butanol and butanal in water. The immiscibility area in the ternary system gets smaller at higher temperature. There is a small area where the organics are dissolved in water and a much larger area where water is dissolved in the organics.

3.2.8 Pure component properties

Tables 3.3 and 3.4 present the pure component properties[10][43].

3.3 Basic assumptions

3.3.1 Plant capacity

The available amount of butane as a raw material for the butanol process is about 100,000 ton/y. Assumed is that the butanol plant will produce about 124,000 ton per year. The incoming butanol stream is 60.30 mol/s on a 8000 production hours per year basis and has a composition of 95% 1-butanol and 5% 2-butanol. With 8000 production hours per year the planned and unplanned downtime and possible production losses due to capacity limitations or lack of feed are included. The chemicals used in catalytic amount are considered to stay in the system, no degradation of catalyst and other substances is reviewed. The economical plant life is 20 years. See chapter 11. Table 3.5 shows the incoming and outgoing streams.

Utilities at the existing site probably will not have the capacity to supply extra steam to the plant. A rough estimation will be made on necessary steam and power generating utilities.

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CPD 3281 - Basis of Design

Table 3.3: Pure component properties, part 1

property MW BP (1) MP(1) ½25 MAC LD50 OR

unit [kg/kmol] oC oC kg=m3 mg/m3 mg/kg

oxygen 32.00 -183 -218 1.31 n.e. n.e.

butanal 72.11 75 -100 797 n.e. 2490

butanone 72.11 80 -86 799 590 3400

2-butanol 74.12 99 -89 805 300 6480

water 18.02 100 0 998 n/a n/a

1-butanol 74.12 118 -89 806 300 790

butanoic acid 88.11 164 -4.5 953 n.e. 2940

PhenS* 564.6 n/a ~300 n.e. n.e. n.e.

Palladium acetate 224.5 n/a ~195 n.e. n.e. 2100

Sodium actate 82.04 n/a 324 1528 n.e. 6891

(n.e.: not established; n/a: not applicable) (1) at atmosperic pressure

Table 3.4: Pure component properties, part 2

property CAS # formula LD50 SR solubility in

water(20oC;1 bar) unit [-] [-] mg/kg g/l oxygen 7782-44-7 O2 n.e. 100 butanal 123-72-8 C4H8O 3560 85 butanone 78-93-3 C4H8O 13,000 275 2-butanol 78-92-2 C4H10O - 125

water 7732-18-5 H2O n/a n/a

1-butanol 71-36-3 C4H10O 3400 77

butanoic acid 107–92-6 C4H8O2 530 1

PhenS* 52698-84-7 C24H14N2Na2O6S2 n.e.

Palladium acetate 3375-31-3 P d(OAc)2 n.e.

Sodium acetate 127-09-3 N aOAc 10

3.3.2 Location

The Asahi-Kasei company is located in near Osaka in Japan, not far from the sea. The butanal plant will be built on the site of Asahi-Kasei. Infrastructure, some utilities, sewers, etc. are present. The new plant will possibly use more steam and energy than can be generated by existing equipment. There probably are possibilities for integration of some parts of the old and new plant.

3.3.3 Battery limit

The main equipment is shown in table 3.6. The block scheme of the process can be seen in …gure 3.4. Cooling water, LP and MP steam and electricity are assumed available from outside battery limits. A wastewater cleaning facility is assumed to be present outside battery limits.

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3.3. BASIC ASSUMPTIONS

Table 3.5: Mass ‡ows of In- and Out-going streams stream

substance In [ton/h] Out [ton/h]

1-butanol 14.64 1.46 2-butanol 0.77 0.08 butanal 12.17 butanone 0.67 butanoic acid 0.78 O2 3.14 H2O 3.21

Table 3.6: Important equipment inside battery limits

Equipment Purpose

Distillation column 1 puri…cation of feed

Reactor conversion of feed

Compressor 1 oxygen supply

Flash vessel …rst catalyst separation step

Stripping column second catalyst separation step Distillation column 2 product separation

Distillation column 3 butanoic acid removal

3.3.4 Streams across battery Limit

1- and 2-butanol will be supplied by pipeline. The butanal is transported by pipeline from outside battery limits. A ‡are is assumed to be present on the site. The emergency release system for a part of the process will be connected to it. Water will be made in stoichiometric quantities of 1 mole of water per mole of butanal during the oxidation reaction. Water with organic impurities will be transported outside battery limits by pipeline. A summarizing …gure on streams entering and leaving the battery limits is …gure 3.5. References to descriptions of the in- and outgoing streams are given in table 3.7.

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CPD 3281 - Basis of Design

Table 3.7: Stream numbers crossing the battery limits

Stream Stream number Table in appendix D

1&2 butanol <101> D.1 catalyst D.2 and D.3 1&2 butanol <105> D.5 Oxygen <201> D.4 butanal <314> D.7 exhaust gasses <213> D.9 waste water <319> D.6 butanoic acid <318> D.8 butanone <314> D.7

3.4 Economic margin

The margin of the process is the di¤erence between the value of the product stream and the feedstock stream. Table 3.8 shows the mass ‡ow and costs per year of the product streams and the feedstock streams. Values are recalculated from paragraph 11.3 and paragraph 11.2.2.

Table 3.8: Margin calculation

Products Feedstock’s

kton/y M$/y kton/y M$/y

1-butanol 122.4 94.4 2-butanol 6.3 4.9 oxygen 26.2 1.2 butanal 114.3 141.2 butanoic acid 19.3 19.3 1-, 2-butanol 7.8 1.1 Total 141.4 161.5 155.0 100.5

The calculated margin is M$ 61.0 per year. This is higher than calculated in the preliminary BOD report [42]. This is due to higher production volume in terms of butanal and butanoic acid production. The added value in terms of margin is 61%. According to the margin, the process is likely to be economical pro…table. More details on economy are given in chapter 11.

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4 | Thermodynamic properties and

reaction kinetics

4.1 Thermodynamic properties

4.1.1 Thermodynamic and physical properties of components

For all the components the heat of formation, Gibbs energy of formation and entropy at standard state are tabulated in table 4.1[47].

Table 4.1: Thermodynamic properties of pure components at standard state Components ¢Hf;liquido ¢Hf;gaso Sliquido Sgaso

Unit [kJ/kmol] [kJ/kmol] [J/kmol K] [J/kmol K]

1-butanol -327.3 -274.9 225.8 361.98 [?] 2-butanol -342.6 -292.8 214.9 359.5 butanal -239.2 -204.8 246.6 343.7 butanone -247.3 -215.7 239.0[?] -butanoic acid -533.8 -475.9 222.2 353.26 [?] oxygen 0 0 - 205.2 water -285.8 -241.8 70.0 188.8

Enthalpy, entropy and Gibbs free energy of reaction are calculated by equations 4.1, 4.2, 4.3.

¢Hro = ¢Hreactantso ¡ ¢Hproductso (4.1)

¢Sro = ¢Sreactantso ¡ ¢Sproductso (4.2)

¢Gor = ¢Hro¡ T ¢Sro (4.3)

Oxidation reactions are exothermic. The amount of heat produced during the reactions at standard state are shown in table 4.2. The reaction of 1-butanol to butanal is moderate exothermic.

In appendices F.1, F.2, F.3, F.4 and F.5 tables are presented with coe¢cients for correlations on speci…c thermodynamic and physical properties. No data on solubility of pure components in water is shown, because of the multicomponent process and components’ in‡uence on activity coe¢cients. Data shown was obtained from [10].

The heat capacity of the gaseous pure components as a function of temperature is given in …gure F.1. Heat capacity of the liquid pure components as a function of temperature is given in …gure F.2. The vapor pressure of the liquid pure components as a function of temperature is given in …gure F.2.. Density of the pure liquid components as a function of temperature is

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CPD 3281 - Basis of Design

Table 4.2: Heat of reaction, Gibbs free energy of reaction and entropy generated at standard state

Reaction ¢Ho

R ¢SRo ¢GoR

Unit kJ/mol [kJ/molK] kJ/mol.K]

1-butanol to butanal -197.7 -0.0118 -194.18

2-butanol to butanone -190.5 -0.0085 -187.97

butanal to butanoic acid -294.6 -0.1270 -256.75

given in …gure F.4. The viscosity of the pure liquid components as a function of temperature is given in …gure F.5. Data is obtained from [10] and the coe¢cients are shown in appendix F.5.

4.2 Thermodynamic model

To make a sound decision on thermodynamic models for modelling LL and VLL equilibria, polar properties, dipole-dipole interactions, hydrogen bonding, etc. should be taken into account. The process which has to be modelled consists mainly of alcohols, water, aldehyde and ketone. The elevated pressure, elevated temperature and the number of components have to be taken into account as well when a decision on a thermodynamic model has to be made. The number of components is high, which results in a large amount of interaction parameters. Due to the hydrogen bonding, dipole-dipole interactions, number of components, two generally used models can be applied: NRTL and UNIQUAC. The Wilson model can only be applied when no phase separation will occur.

NRTL and UNIQUAC models can handle strong polar, multicomponent systems. The UNIQUAC model is favored, because this model is capable of handling di¤erent components with very di¤erent properties [46]. The Wilson model is discarded because phase separation is expected.

The thermodynamic model is veri…ed by comparing Dechema experimental data with AS-PEN generated data. UNIQUAC was chosen as a model, and binary interaction parameters are retrieved from di¤erent databases within ASPEN. Table 4.3 presents some examples of the di¤erent binary interaction parameters which are used for modelling. It is very important to choose correct binary interaction parameters for modelling.

Table 4.3: Used databases for binairy interaction parameters

mixture Used database

1-butanol/water LLE-LIT

butanal/water VLE-RK

1-butanol/2-butanol VLE-LIT

1-butanol/butanal VLE-RK

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4.3. SOLUBILITY DATA xy diagram 2-butanol/1-butanol` 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

liquid mole fraction 2-butanol

vapour mole fraction 2-butanol

Dechema ASPEN+ VLE-LIT

Figure 4.1: xy diagram for a 2-butanol/1-butanol mixture at P = 1.013 bar [17, p. 150]. Figures with data from the model and data from literature are presented in appendix E.

4.3 Solubility data

4.3.1 1-butanol in water

A ternary diagram of the reactor composition (water, 1- butanol and butanal) is used to …nd the suitable operation region. 2-butanol, butanone and butanoic acid are not taken into account, this because of their small molar fraction. The temperature is taken 393 K: The objective was to …nd out at what range of compositions no organic phase exists. ASPEN is used to calculated the compositions of the two di¤erent phases at certain feed compositions. In order to validate the model with the used parameters the calculation was compared with literature. Data for two binary systems was used, taken from [12] and [11]. In table 4.4 and 4.5 the values are shown.

Table 4.4: binary data for 1-butanol/water T = 393 K

Solubility of 1-butanol in water (mole %)

Dechema ASPEN

4.3 4.5

solubility of water in 1-butanol (mole %)

Dechema ASPEN

78.7 80

A decanter block in ASPEN is used to calculate at what compositions liquid phase splitting occurs, and the corresponding compositions of the two di¤erent liquid phases are calculated. The resulting ternary diagram is given is …gure 4.2.

4.3.2 Catalyst complex in water

The rate expression is half order in catalyst concentration. A higher catalyst concentration can therefore result in smaller reactor size and lower residence time. Catalyst concentration de-scribed in [3] resulted in a large reactor volume. To obtain a reasonable rate per unit volume and as a result an acceptable reactor volume, solubility tests with PhenS*Pd(OAc)2were performed

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CPD 3281 - Basis of Design

Table 4.5: binary data for butanal/water T = 311 K

Solubility of butanal in water (mole %)

Dechema ASPEN

2.0 1.9

solubility of water in butanal (mole %)

Dechema ASPEN

13 14

Figure 4.2: Ternary diagram for water/1-butanol/butanal at 30 bar and 393 K

to investigate solubility of this component. Results from this test are described in appendix G. A concentration of 1.438 mmol/l was taken for reactor design. At higher cocentrations oxygen transfer can be limiting and heat removal becomes a problem (pragraph 8.3.7).

Oxygen

Solubility data for oxygen in organic and inorganic components at di¤erent temperatures is di¢cult to obtain. Most data presented in literature is at standard state conditions. An excep-tion is the binairy system of water and oxygen. This system is studied thoroughly. Solubility data for oxygen is obtained from [26]. To obtain Henry coe¢cients at di¤erent temperatures a method described in [25, page 607] was used. This method is described in appendix N. Henry coe¢cients at reaction temperature (403 K) for oxygen in di¤erent components are presented in table 4.6.

Table 4.6: Calculated henry coe¢cients for oxygen in di¤erent solvents Solvent HO2

[bar]

water 6.59¢104

1-butanol 3.80¢102

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4.4. KINETICS With these coe¢cients a henry coe¢cient for the mixture was calculated of 3.99¢104 bar.

See appendix N for details.

4.4 Kinetics

4.4.1 Catalytic cycle

A catalytic cycle was proposed for alcohol oxidation [3]. The catalyst is a bathophencuproine-disulphonate palladium complex (PhenS*Pd(OAc)2). The cycle is shown in …gure 4.3. The

separate reactions are shown below.

Figure 4.3: Proposed catalytic cycle for alcohol oxidation by PhenS*Pd(II)[3] 1. 1

2(Pd2(OH)2)

2++ ROH

! PdOHROH+ (Pd

2(OH )2)2+ = palladium dimer

2. PdOHROH+! H

2O + P dRO+ PdOH ROH+ = palladium with alcohol

3. PdRO+ ! RO + Pd+ PdRO+ = complex with aldehyde

4. Pd++ O

2! PdO+2 Pd+ = palladium hydride complex

5. PdO+

2 + H2O! 12(Pd2(OH)2)

2++ H

2O2 PdO+2 = reoxidated palladium complex

6. H2O2 "P d"! H2O +12O2

It must be noted that this catalytic cycle is a proposed cycle, it has not been proven yet. A detailed description of this cycle and experimental data can be found in [3].

4.4.2 Reaction order in alcohol concentration

The reaction order in alcohol is pseudo zero order for little soluble alcohols. The limited solu-bility makes the concentration of the alcohol constant, and with making sure that no di¤usion limitation existed, a pseudo zero-order in alcohol concentration could be established. The real order of alcohol concentration is determined using a completely soluble alcohol , then an order of one is observed.

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CPD 3281 - Basis of Design

Figure 4.4: PhenS*Pd(OAc)2dimer

4.4.3 Reaction order in oxygen

The re-oxidation of the palladium complex (step 5) is done with oxygen. In the experiments oxygen pressure had little in‡uence on the reaction rate. The rate of reoxidation of the complex per unit volume reaction mixture was not the rate determining step during the experiments. Oxygen transfer might become limited in a large scale process. Then, the oxygen pressure probably will have in‡uence on the reaction rate.

4.4.4 Reaction order in palladium concentration

The order in palladium concentration was shown to be half order. The reason for this is that probably the catalytically active palladium monomer is in equilibrium with the dihydroxy-bridged palladium dimer. The palladium dimer is shown in …gure 4.4.

The optimum ratio of ligand (PhenS*) to palladium (Pd(OAc)2) has been investigated. The

variation of the ligand to palladium showed that the ratio ligand:palladium of 1:1 was optimal. Many alcohol oxidations are carried out in presence of a base. Without going into the mechanistic details, it is stated here that during experiments there was no in‡uence of base on the reaction rate.

4.4.5 Rate expression

The rate expression will be used as a basis for reactor calculations. The rate constant k will be discussed below.

¡rA= k¢ [alcohol] ¢ [catalyst] 1

2 (4.4)

In systems where the solute does not contribute to the total volume, concentration expressed in mol per unit volume can be used. In our case, the concentration of 1-butanol is too high to neglect the volume e¤ect. Calculations will be done on a mol per mol basis.

Rate constant

Reliable data on reaction kinetics are needed as a basis to judge the in‡uence of temperature on the reactor’s e¢ciency and scale.

It turns out that no experiments with butanol were carried out in [3]. This has been done in comparison with the experiments with 1-pentanol, 1-hexanol and 1-heptanol [3, page 62], whose reaction rates are calculated in table 4.7 by means of equations from 4.5 to 4.7, in a batch reactor at 100±C without any oxygen transfer limitation, which is assumed to be the case

in our reactor. t = FA0 Z X o dX ¡rv¤ VR (4.5)

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4.4. KINETICS where t is the reaction time, FA0the ‡ux of reactant A in the inlet and dX the conversion

derivative.

rv=¡k ¤ [Pd]1=2¤ [OH] (4.6)

k =¡ln (1¡ X)

[Pd]1=2¤ t (4.7)

Yields table 4.7 and …gure 4.5 at 100±C, leading to equation 4.8.

Table 4.7: Rate constant values reactant k [`1=2:mol¡1=2:s¡1]

1-pentanol 2.29¢10¡3

1-hexanol 2.19¢10¡3

1-heptanol 1.79¢10¡3

Rate constant versus number of carbon atoms

0.0E+00 5.0E-04 1.0E-03 1.5E-03 2.0E-03 2.5E-03 4 5 6 7

number of carbon atoms

k [l 1/2 .mol -1/2 .s -1]

Figure 4.5: Rate constant as a function of the number of carbon atoms of the molecule

k = 2:3¤ 10¡3`1=2:mol¡1=2:s¡1at 100±C (4.8)

Temperature dependence rate constant

A problem in investigation of the kinetics is a lack of experimental data versus the temperature in [3]. Experiments were performed at 100±C, so that the temperature dependency has not been

investigated. From [3] a value for the activation energy of Ea = 70 kJ/mol was obtained.

To calculate the rate constant at di¤erent temperatures, the Arrhenius Law is used (equation 4.9). Table 4.8 presents the rate constant values for a temperature range from 100 to 150±C.

kT = A¤ exp(¡Ea

RT) (4.9)

where kT is the rate constant at the desired temperature T (K) and A is the frequency factor.

k2= k1¤ exp ½ ¡ERa ¤ (T1 2¡ 1 T1) ¾ (4.10)

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CPD 3281 - Basis of Design

Table 4.8: Rate constant values versus temperature for 1-butanol T [±C] k [`1=2:mol¡1=2:s¡1] 100 2.3¢10¡3 110 4.14¢10¡3 120 7.25¢10¡3 130 1.23¢10¡2 140 2.04¢10¡2 150 3.31¢10¡2

Calculations are performed on 1-butanol. The assumption is made that the rate constant of 2-butanol is the same as the one of 1-butanol.

4.4.6 1-butanol vs. 2-butanol competition

In the oxidation of the primary and the secondary alcohols together (…gure 2.2) , the alcohols have to compete (intermolecular competition). Di¤erent factors in‡uence this competition:

² di¤erent solubility

² di¤erent molecular structure (di¤erent steric properties) ² increased electron density of the secondary alcohol

No literature data is available on the competition between palladium catalyzed oxidation of 1-butanol and 2-butanol. However, on comparable alcohols competition experiments were done. In the case of alcohols with one carbon atom less, the isomeric propanols, competition did not show any clear preference (kprim/ksec v1). But on the intermolecular competition between the

two alcohol functionalities on 1,5-hexanediol, the oxidation of the primary alcohol functionality showed a clear preference (kprim/ksec v 0:2).

For the design, it has been assumed that 1-butanol and 2-butanol have the same rate con-stant. Calculations were proceeded with the rate constant of 1-butanol.

4.4.7 Selectivity

The selectivity of the reaction to aldehyde is assumed to be 100%. The only possible side reaction is the over-oxidation of aldehyde to butanoic acid. This over-oxidation will occur in the organic phase only because water acts as a anti-oxidant. Competition between 1-butanol and 2-butanol is expected. Nevertheless, the amount of 2-butanol is very small in comparison to the amount of 1-butanol, so oxidation of 2-butanol and possible side reactions are not taken into account for the design. This results in three main reactions:

1. 1-butanol + 0.5 O2 ! butanal + H2O

2. butanal + 0.5 O2! butyric acid + H2O

3. 2-butanol + 0.5 O2 ! butanone + H2O

4.4.8 Catalyst deactivation

The catalyst deactivation has been studied as showed in the table 4.9. The experiment has been carried out with 10 mmol 1-hexene, leading to 2-hexanone, 0.1 mmol PhenS*Pd(OAc)2, 42.5 g

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4.4. KINETICS

Table 4.9: Catalyst deactivation

cycle with 10 mmol NaOAC without NaOAc

1-hexene con-version selectivity to 2-hexanone 1-hexene con-version selectivity to 2-hexanone 1st 48 99 47 99 2nd 44 96 28 97 3rd 40 95 15 96

These values are obtained in a laboratory were all the reconversion steps have to be made by hand. In a plant, this reconversion can be much more e¢cient.

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