High pressure hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols

HIGH PRESSURE HYDROGENATION

OF UNSATURATED FATTY ACIDS TO

UNSATURATED FATTY ALCOHOLS

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HIGH PRESSURE HYDROGENATION

OF UNSATURATED FATTY ACIDS TO UNSATURATED

FATTY ALCOHOLS

BIBLIOTHEEK TU Delft P 1221 2058

HIGH PRESSURE HYDROGENATION

OF UNSATURATED FATTY ACIDS TO

UNSATURATED FATTY ALCOHOLS

PROEFSCHRIFT

TER VERKRIJGING VAN DE GRAAD VAN DOCTOR IN DE TECHNISCHE V^ETENSCHAPPEN AAN DE TECHNI-SCHE HOGESCHOOL DELFT, OP GEZAG VAN DE RECTOR MAGNIFICUS DR. IR. C. J. D. M. VERHAGEN, HOOGLE-RAAR IN DE AFDELING DER TECHNISCHE NATUURKUN-DE, VOOR EEN COMMISSIE UIT DE SENAAT TE VER-DEDIGEN OP WOENSDAG 19 JUNI 1968 TE 14.00 UUR

DOOR

JACQUES DAVID RICHTER

SCHEIKUNDIG INGENIEUR GEBOREN TE ANTWERPEN

r

DIT PROEFSCHRIFT IS GOEDGEKEURD DOOR DE PROMOTOR

PROF. DRS. P. J. VAN DEN BERG

To Pap, Mam,

I would like to e x p r e s s my g r a t i t u d e to all t h o s e who contributed t o t h e a c h i e v e m e n t of t h i s t h e s i s . And s p e c i a l l y t o :

IR. E . E . COHEN, IR. A . H . A . DOHMEN, DRS. P . W . VAN HOEVE, IR. S.K. QUE, IR. P . SLUIMER, IR. J . A . J . UITERWAAL a n d l R . G . B . VAN DER VLIES, who a s student e n g i n e e r s w e r e i n -volved in t h e execution of the e x p e r i m e n t s .

I a m v e r y grateful to the UNILEVER RESEARCH LABORATORY for furnishing t h e u r e u m adduct of m e t h y l o l e a t e , the Ni on k i e s e l g u h r c a t a l y s t , a s well a s t h e data for the p r o c e d u r e of t h e i s o m e r i z a t i o n d e t e r m i n a t i o n s . The aid of IR. F . C . DEN BOER and h i s staff by i n -t r o d u c i n g m e -t o -t h e s e -t e c h n i q u e s a r e highly a p p r e c i a -t e d .

In the different analytical m e t h o d s I a m indebted t o : MISS DRS. W. E. DE BOER of the L a b o r a t o r y for Microbiology for t h e e l e c t r o n m i c r o s c o p i c a n a l y s i s , IR. T . H . DE KEIJSER of the L a b o r a t o r y for Metalurgy for t h e x - r a y diffraction a n a l y s i s , IR. A. SINNEMA and DRS. A. VAN VEEN of the L a b o r a t o r y for Organic C h e m i s t r y for the proton m a g n e t i c r e s o n a n c e m e a s u r e m e n t s , IR. J . VAN KEMENADE of t h e L a b o r a t o r y for P h y s i c a l C h e m i s t r y for t h e e l e c t r o n s p i n r e -sonance m e a s u r e m e n t s , MRS. IR. H . M . T . BAKKER-VONK and DRS. H. G. MERKUS and t h e i r staff of the analytical s e c t i o n of the L a b o r a -t o r y for C h e m i c a l Technology for -the p o l a r o g r a p h i c , s p e c -t r o s c o p i c and c h r o m a t o g r a p h i c a n a l y s i s , whose a i d s w e r e of g r e a t v a l u e .

F o r the c o n s t r u c t i o n and m a i n t e n a n c e of the u s e d a p p a r a t u s , m y thanks go to MRS. W. VAN HEEST, A . G . VAN DER HEUVEL, J . C . KOOYMAN, R . T . NIJVERHEIM, K. SJOER, G . C . VAN WESTEN and t h e i r staff.

My acknowledgements go t o MISS C. VAN OORSCHOT for the t y p e - w o r k , MISS T . HALL for t h e c o r r e c t i o n of t h e t e x t , MR. J . J . B . VAN HOLST for the d r a w i n g s and MR. J . H. KAMPS for r e d u c i n g t h e f i g u r e s and t a b l e s .

To t h e scientific staff and s t u d e n t s of the D e p a r t m e n t for C h e m i c a l Technology, I e x p r e s s my a p p r e c i a t i o n for t h e i r help and useful d i s -c u s s i o n .

ERRATA

page

13 tenth line from the bottom: corresponding com-, read: corresponding unsaturated

com-17 eighth line from the top: dialkylalminium, read: dialkyl-aluminium

17 ninth line from the top: 2(Ri)AlH, read: 2(Ri)2AlH

29 seventh line from the bottom: Technical, read: Technolo-gical

30 sixth line from the bottom: overleap, read: overlap

33 Table 2.2: gr/gr prod., read: gr/lOOgr prod.

39 tenth line from the bottom: + 2°C, read: about 2°C

45 equation 3.1: , read: ,

48 Table 3.2. (foot note): 2,2-diisopropylpropanol acid, read: 2,2-diisopropylpropanoic acid

"He is truly free, who desires what he can perform, and does what he desires"

CONTENTS

page Introduction

1. Fatty alcohols 11 2. R e s e a r c h object 14 Chapter 1 LITERATURE SURVEY OF THE PREPARATION OF

FATTY ALCOHOLS

1.1 General 16 1.2 Catalytic high p r e s s u r e hydrogenation 18

1 . 2 . 1 Fatty acids and e s t e r s to fatty alcohols 18 1.2.2 Unsaturated fatty acids and e s t e r s to unsaturated fatty alcohols 20

Chapter 2 ANALYSIS OF THE REACTION PRODUCT CONCERNING THE CATALYST SYSTEM

2 . 1 Introduction 26 2 . 2 P r e p a r a t i o n , p r o p e r t i e s and analysis of copper hydride 27

2 . 3 Analysis of the reaction product 28

2 . 3 . 1 Polarographic analysis 29 2 . 3 . 2 X - r a y analysis 29 2 . 3 . 3 Determination of the mean oxidation degree of copper 32 '

2 . 3 . 4 Tyndall effect 34 2 . 3 . 5 Electron m i c r o s c o p y 34 2 . 3 . 6 Spectroscopy 35 2 . 4 Discussion 35 2 . 5 Experiments leading to the final conclusions 36

Chapter 3 KINETICS AND MECHANISM OF THE HIGH PRESSURE HYDROGENATION OF UNSATURATED FATTY ACIDS TO UNSATURATED FATTY ALCOHOLS USING A Cu-AND Cd-SOAP CATALYST SYSTEM

3 . 1 Introduction 39 3 . 2 Apparatus 39 3 . 3 The solvent 41 3.4 Analysis 43 3.5 Raw m a t e r i a l s 44 3.6 P r e p a r a t i o n of the m e t a l - s o a p s 44 3.7 Kinetics 44 3 . 7 . 1 Influence of the hydrogen concentration 45

3 . 7 . 2 Influence of the cadmium concentration 45 3. 7. 3 Influence of the copper concentration 46 3 . 7 . 4 Influence of the t e m p e r a t u r e 47 3. 7.5 Influence of the chain length of the acid 47

3 . 7 . 6 M l u e n c e of the addition of a low m o l e c u l a r weight acid 50

3 . 7 . 7 Influence of water 50 3 . 7 . 8 Influence of the addition of a peptizing agent 50

Chapter Chapter Chapter Chapter Appendix • 4 4 . 1 4 . 2 4 . 3 4 . 4 4 . 5 4.6 5 5.1 5.2 5 . 2 . 1 5 . 2 . 2 - 5 . 2 . 3 5 . 3 5 . 3 . 1 5 . 3 . 2 5 . 3 . 3 5 . 3 . 4 5 . 3 . 5 5 . 3 . 6 6 6 . 1 6.2 6 . 3 6 . 3 . 1 6 . 3 . 2 7 7.1 7.2 7.3 7.4

COMPARISON OF DIFFERENT CATALYST SYSTEMS Introduction

Apparatus and execution of the experiments Experiments

Thermodynamics of the reduction Discussion

Considerations about the Adkins catalyst

FURTHER CONSIDERATIONS ABOUT THE Ag- AND Cd-OLEATE CATALYST SYSTEM

Introduction Kinetics

Influence of the concentration of silver, cadmium and hydrogen Influence of the t e m p e r a t u r e

Discussion

Analysis of the reaction product X - r a y analysis

P o l a r o g r a p h i c analysis Spectroscopy

Electron microscopy

Hydrogenation reaction using the precipitated reaction product Discussion

STUDY OF THE ISOMERIZATION OF THE DOUBLE BOND Introduction

P r o c e d u r e Results

Hydrogenation with Cu- and Cd-oleate as catalysts Hydrogenation with Cu-oleate a s catalyst

DESACTIVATION OF THE ACID-SOAP MIXTURE BY AGING Introduction

Brief l i t e r a t u r e survey of the oxidation of unsaturated fatty acids Experiments and r e s u l t s

Discussion

GASCHROMATOGRAPHIC ANALYSIS OF THE REACTION PRODUCT LIST OF SYMBOLS SUMMARY SAMENVATTING SUMARIO CURRICULUM VITAE page 1 58 59 1 59 1 62 1 62 1 64 1 66 1 66 66 67 68 69 69 70 70 70 71 71 1 72 1 72 74 74 74 75 1 78 1 79 1 80 1 83 1 87 1 89 91 94 96

INTRODUCTION

1.. Fatty alcohols

Fatty alcohols are primary alipathlc alcohols with the general formula CnH2n+lOH, where n is an even niunber between 8 and 20. They are very r a r e in nature, occurring mainly tn sea animals, as saturated and unsaturated esters of fatty acids.

For the fatty alcohols and their derivatives there are various uses, such as in the textile industry (scouring, kier boiling, wetting, bleaching, etc.) lubricating oils, natural waxes, dye baths, metal cleaning, ore flotation, insecticidal sprays, cosmetics (emulgators, softeners), and many others. But, their main use lies in the product-ion of detergents. It is said that the development of the fatty alcohol processes is narrowly linked to the development of the synthetic de-tergents (1).

The first synthetic detergent to appear on the market was a fatty alcohol sulfate with the general formula CnH2n+lOS03Na (n = 8 - 18), developed by Böhme Fettchemie (2), using a high pressure hydroge-nation process of fatty acids to obtain the fatty alcohols.

Due to the shortage of natural fatty oils, new detergents appeared using oil fractions as raw materials, which are considerably cheaper and their properties (detergency, wetting, foaming, solubility, among others) are as good or better than those derived from the fatty alcohols. Table 1 gives a review of the production of detergents in the United States in 1962 (3), in the absence of more recent data.

In 1964, new specifications about detergents appeared, including the property of bio-degradability. In some countries it is now even enforceable by law that at least up to 80% of the detergents should be bio-degradable. This gave an impetus to the detergent chemistry to find compounds which could easily be degradated, which is not the case with alkylbenzene sulfonates.

The following points must be borne in mind:

Table 1. Production of detergents in the United States in 1962.

Detergent

Alkylbenzene sulfonate (ABS) Alcohol sulfate Alkylphenol ethoxylates Alcohol ethoxylates Others in m i l . l b s . 470 120 110 80 70

Table 2. The increase in total production of surfactants in the United States (4) taking 1960 as 100%.

Production

1960 1964 1968* 100 140 206 * Estimated.

— the larger the chain, the smaller the degradability. — branching difficults the bio-degradation.

— secondary sulfates lower the degradation.

— alkyl sulfates, which have the C-O-S- linkage, are readily hydro-lized and therefore break down to the alcohol and inorganic sulfate meanwhile sulfonates with a C-S linkage form a more stable bond (5).

To meet these demands, other raw materials were brought onto the detergent market, such as n-paraffins, a-olefins and synthetic fatty alcohols (see chapter 1).

The future of the raw materials, taking France as an example (due to the availability of fairly recent data), is roughly given in table. 3 (6), where the production of fatty alcohols is expected to increase considerably.

In the past, two main types of naturally derived fatty alcohols were used as raw materials for the preparation of alcohol sulfates and ethoxylates, the coconut and the tallow fatty alcohols (table 4).

Sodium lauryl and myristyl alcohol sulfates, the main products from coconut oil, have quite good detergent properties indicated by a maximum in the detergency curve at a number of C-atoms correspond-ing to 14. Foamcorrespond-ing, wettcorrespond-ing and solubility properties are better than

Table 3. Production of raw materials fol- detergents

Production in tons Alkylbenzenes

Nat. and synth. fatty alcohols Alkylfenols

Alkane sulfonates Ethoxylated alcohols Ethoxylated alkylfenols Amines and quaternary ammonium s a l t s 1962 53000 2300 2262 — 1300 2500 4600 1965 (estimated) 75600 2200 4500 — 2300 4100 5500 1970 (estimated) 82000 45000 8050 10000 8300 7000 lOOOU

Table 4. Coconut nod tallow oil fatty acid composition (7)

Raw

Coconut oil

Talluw (beef) oil

Saturated acids Wt % ^i '^lO ^^12 '^M ^16 '^IS ^^20 7.9 7.2 48.0 17.5 9.0 2.1 0.2 3.1 24.9 24.1 0.8 Monoenolc ^^14 '^le '^18 5.7 0.4 2.4 41.8 Dienoic ^^18 2.6 1.8 Trienoic = 18 0 . 5

the corresponding higher molecular weight homologous (8). The much cheaper tallow oil (9), containing Cig and Ci8 alcohols, if saturated form products inferior in surfactant properties to coconut oil fatty alcohol (8), mainly concerning solubility.

Saturated fatty alcohol sulfates of high molecular weight (Cie -Cis) are not such good detergents on the whole, but the corresponding com-pounds have indeed better properties, mainly due to their higher solu-bility (10) and bio-degradasolu-bility; they may also be used as builders, mixed with stearyl sulfates (11,12). The selective hydrogenation, retaining the double bond, would make tallow fatty alcohols with the same properties as coconut fatty alcohols and having the advantageous price of the raw material, which if carried out in a large scale could

economically be of great interest.

The three biggest producers of fatty alcohols, through high p r e s s -ure hydrogenation of natural fats are (13,14):

Procter and Gamble

Henkei and Cie Marchon P r o d . Comp.

Catalyst suspended C u - C r - O fixed bed Cu basis suspended C u - C r - O Oil Palm Coconut, Palm Kernel Palm Kernel P r o d , / y e a r 90.000 ton 35.000 ton 25.000 ton 2. Research object.

Based on the Dutch Patent 83.379 (1956) from "Olieraffinaderij Zuilen" in Maarsen, where the catalyst for the selective high pressure hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols is added to the acid substrate in the form of Cu and Cdsoaps, r e -search work has been carried out at the Technological University of Delft, published in a thesis written by B. Stouthamer (1964). From kinetic measurements and anal3rtical procedures, it is concluded that the reaction is homogeneously catalyzed by copper hydride, CuH, originated in accordance with the theory of Halpern (15), through the homogeneous activation of hydrogen by cupro-oleate :

cupro-oleate + H ^ "~ CuH + oleic acid.

A mechanism is proposed in which CuH forms a complex with the carboxyl group of the acid and this complex would be hydrogenated to the alcohol with an aldehyde as intermediate :

OH OH ^ OH R - c;' H ' — • R - C - H ^ R - C - H * C u * — ' R - C - O ^ H - O ^ C u * ' I I I I ' ^ " 0 Cu* 0 - C u OH H H H ^ H R - C = 0 * C u H — • R - C " p — ' R - C - O C u '-^ R - C - O H - C u ' H Cu-H H H

The reaction of CuH with the acid would be the rate determining step. Aldehyde was not detected. The function of Cd could not be entirely described, presumably it inhibited the decomposition of CuH to copper and hydrogen, its presence could not increase the hydride concentra-tion.

that by heating the precipitate obtained from the reaction product (by addition of alcohol) hydrogen was liberated.

From the foregoing, the hypothesis is clear, that the homogeneous catalyzed reaction proceeds through a CuH-acid complex, where Cd would act, in one way or another, as a stabilizer.

The task which lies ahead, is to gain better knowledge of the reaction mechanism of the selective high pressure hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols with Cu and Cd soaps as catalysts. Not only to look for the function of cadmium, but also to get more information about the copper catalyst. This will be achieved through analytical methods employing techniques where the constitution of the catalyst system can be measured more directly, as for example, X-rays, spectroscopy and others.

Further, kinetic measurements will be carried out with catalysts concentrations where the reaction does not always have a great select-ivity . The influence of the chain length of the fatty acids and of some compounds which may show inhibiting effects is a subject to be ob-served, taking into accoimt the influence of the reactor material on the catalyst. By substituting one or both metal soapsfor other cations, a better insight on the catalyst mechanism will eventually be achieved. A study on the positional and geometrical isomerization of the double bond will be carried out to observe the behaviour of the catalyst system.

The cause of the desactivation of the catalyst-acid mixture through aging will also receive attention in this thesis.

R e f e r e n c e s :

1. M . L . Kastens & H. Peddicord, I . E . C . , 4 1 , 438 (1949) 2. A. Löhr, Tex 25, 450 (1966)

3. J. Rubinfeld & H.D. C r o s s , Soap and Chem. Spec. 43, 41 (1967) 4. L. Raphael, Manuf. Chem. and Aerosol Nws, 43 (3), 42 (1967) 5. Ibidem., 4 3 ( 1 0 ) , 77 (1967)

6. H. L e p a t r e , Ind. C h i m . , 1966, 74

7. R . E . K i r k & D . F . Othmer, Encyclopedia of Chem. Techn. I n t e r s c . Publ. 2nd. e d . , vol. 8, N . Y . (1965)

8. E . E . D r e g e r e t a l . , I . E . C . , 36, 610 (1944) 9. B. Marti, Seifen Ole Fette Wachse, 93, 251 (1967) 10. J . K . W e i l e t a l . , J. Am. Oil Chem. S o c , 36, 241 (1959) 11. A. Kobashi, Yakagaku, 16, 194 (1967)

12. R . S . Klonowski et a l . . Soap and Chem. S p e c , 43, (6), 53 (1967) 13. E. Haidegger, L. Hodossy & J . Metzing, F . S . A . , 66, 205 (1965) 14. W. Haage, Fette Seifen Anstrichmittel, 67, 205 (1965)

15. A . J . Chalk & J . Halpern, J . Am. Chem. S o c , 81, 5846 (1959)

CHAPTER 1

LITERATURE SURVEY OF THE PREPARATION OF FATTY ALCOHOLS

1.1 General

The natural sources of fatty alcohols are generally fats and waxes from sea fishes or sea animals-. The alkaline saponification and successive distillation of these oils, gave as final products s a -turated and unsa-turated fatty alcohols.

The growing necessity of fatty alcohols forced new methods of preparation:

a) Bouveault and Blanc (1) discovered a method based on the reaction of fats or fatty acid ester with sodium in ethanol. The alcohol formed had the same chain length as the original acid. The double bonds of the mono-unsaturated acids remained unchanged, while those of the poly-unsaturated were a little affected (2). Besides ethanol, amyl, butyl or alcohols identical to those produced are used as reduction alcohol (3,4,5). This method, using naturally derived products, is being replaced by high pressure hydrogenation. b) Catalytic high pressure hydrogenation of fats, fatty acids and their e s t e r s , is practically the only process used nowadays for the p r e -paration of fatty alcohols from natural oils.

c) The Alfol process, developed by Ziegler (6). The starting material is an alkyl aluminium compound, such as aluminium triethyl, which is polymerized with ethylene to aluminium alkyls, at high pressure and temperatures about 130°C. Oxidation and hydrolysis yields primary straight chain saturated fatty acids.

(S«4)x - ^ « 5

/

A1(C H ) + (x+y+z) C H^—^Al - (CgH^) - CgH^ \

R, ORi / ^ / ^ Al - Rg + 3/2 ©2 ^ Al - ORg ^ R3 ^ OR3 OR 1 /

2 Al - ORg + 3H2SO4 Al2(SO_^)3 + 2.

\ OR 3 ^ " 3 Rj-OH Rg-OH L R„-OH

This process is, commercially, the most important in the product-ion of synthetic fatty alcohols. Developed by Continental Oil and in production since 1962, it consists of nine process-steps (7). The final product is an alcohol mixture, rather than a single molecular weight component.

d) Aluminium hydride compounds are used at laboratory scale for the preparation of fatty alcohols. The reaction of a fatty acid ester with dialkylalminium hydride, yields fatty alcohols (8-10).

R-COOCH3 + 2(R^)A1H — R-CH20-Al(Rj)2 + CH30-A1(R^)2 R-CH20-A1(R^)2 + 3H2O—~Al(OH)3 + 2RjH + R-CH2OH Rj^ and R are alkyl groups.

The change in the unsaturatlon depends on the temperature and reaction time.

e) The Oxo-synthesis is a reaction between an o-olefin, carbon monoxide qpd hydrogen, in the presence of cobalt carbonyl (at 200 kg/cm^ and 150-200°C) or metallic cobalt (11), rhenium or ruthenium at 50-150 atm. and 250°C (12). According t o :

R-CH=CH2 + 2CO + 2H2

<

R-CH2CH2CHO R-CHCH„

CHO

the resulting aldehydes are further reduced to the corresponding alcohols. Technically, it is an interesting process, but it has the disadvantage of giving a product which is a mixture of branched and non-branched alcohols. Union Carbide Chem. Co., Humble Oil & Refining Co., Amoco Chem. Corp. and Gulf Oil Co.> among others, manufacture iso-alcohols through this process (13). f) Oxidation of n-paraffins by air in the presence of boric acid. The

products have the same linearity as the initial alkanes, are main-ly secondary alcohols,but contain also small quantities of primary

alcohols (14). Union Carbide, through a self developed process, oxidizes C.... to C.,- to linear secondary alcohols (15).

1.2 Catalytic high p r e s s u r e hydrogenation 1.2.1 Fatty acids and esters to fatty alcohols.

Nermann developed the high p r e s s u r e hydrogenation to fatty alco-hols, using CUCO3 on kieselguhr (16,17), Adkins et al. (18-20) and Schrauth et al (21-23), at the same time obtained good results with a copper chromium oxide catalyst. Adkins used a barium-stabilized copper chromium oxide catalyst, reaching a higher reaction rate ia the same acid the higher the molecular weight of the ester. Free fatty acids retarded the hydrogenation (20). Schmidt (24), reduced ethyloleate to octadecyl alcohol with copper chromium oxide on kiesel-guhr in the gas phase at atmospheric pressure, and came to the con-clusion that the activity of the catalyst is of main importance.

The activity of the copper chromium oxide catalyst has been an interesting study for several authors. Adkins verified that a copper chromium oxide catalyst was inactive if the percentage of copper was reduced to zero (25).

Finely divided metallic copper would be the substantial active part (26, 27), meanwhile through x-ray diffraction studies of the un-reacted, used and regenerated catalyst,it seems that the active part is metallic copper + CuCr^O. (28).

Besides copper chromiimi oxide, other metal combinations, or metal soaps are used as catalysts for the preparation of fatty alcohols. Table 1.1. gives some features about them.

The hydrogenation of esters is a reversible reaction, and its concentration at equilibrium is a fimction of the hydrogen pressure (43), at low pressures the alcohols can be converted to their esters (44). If the pressure is too low, a slow hydrogenation takes place. The result may be an ester, through the Tishchenko reaction of alde-hydes (45).

Schrauth (21) observed that for each catalyst there is a threshold value for the pressure and temperature, which are characteristic for the end product. Adkins et al.(46) observed that if a high ratio of catalyst to ester was used, even lower temperatures gave high alcohol yields.

The first to give a kinetic picture to the problem, were Haidegger and Hodossy (47), who investigated the effect of temperature, pressure, liquid flow, catalyst concentration and the gas-liquid proportion on the hydrogenation of triglycerides to fatty alcohols on a copper chromium oxide catalyst, coming to the optimal conditions of 320 to 340°C, 325

Table 1.1. Hydrogenation of fatty acids to fatty alcohols Raw m a t e r i a l Oleic acid Ethyl oleate Butyl oleate Methyl l a u r a t e S t e a r i c acid Methyl s t e a r a t e Coconut oil Ethyl l a u r a t e P a l m i t i c acid P a l m i t i c acid P a l m oil Methyl oleate Ethyl oleate Methyl s t e a r a t e Olive oil P a l m i t i c acid Cu oleate

Coconut oil Pb soap

Catalyst C u - C r - O C u - C r - O C u - C r - O C u - C r - B a - O C u - C r - Z n - O C u - C r - C o - O C u - C r - C d - O on active alumina C u - C r - Z n - C d - O Cu-Mg-O C u - Z n - M n - O ' g u h r Co-Ag- O on guhr Cu on guhr Ni-Cd on guhr Co-V Co Cu palmitate -Cat. cone, weight % 17.6 15 10 4 10 3 fixed bed fixed bed 10 6 7.5 10 7.5 10 5 25 -P r e s s u r e a t m . 270 330 204 190 280 200 200 210 260 260 211 250 204 200 200 155 270 270 T e m p . °C 280 250 250 300 325 230 250 300 270 270 260 310 325 230 230 275 340 340 Conversion 64 ? ? 96.6 ? ? 99 80 95 55 85.2 96 95 100 100 95 98 74 Alcohol yield % • ? 83 86 94 80 95 99 80 53 59 8 5 . 2 90 70 100 100 95 ? 74 References 29 30 31 32 21 33 34 35 36 36 37 16 38 39 39 40 41 42

a t m . , l , 0 k g / l / h r . , 1,5 weight % and 2-5 Nmvkg, respectively. The mechanism of the hydrogenation of fatty acids or esters to fatty alcohols, has never been thoroughly studied, which is for a great deal due to the difficulties of the high pressure techniques.

Norman (16) proposed a hydrogenation mechanism through a hemiacetal, which was, later, indirectly confirmed (48), although the presence of aldehyde, as intermediate, was supposed, on the basis of experiments with fluorinated compounds, which, according to the author, could be generalized for all alkyl groups.

RCOOR^ + H2 RCH(OH)ORj RCHO + H2

According to Adkins (45) aldehydes are always an intermediate compound, which are hydrogenated to the corresponding alcohol. On the basis of kinetic measurements, Muttzall concluded that the hydro-genation of fatty esters to alcohols, using a barium modified copper chromium oxide catalyst, proceded through

RCOOCH2R + Hg ^ ^ 2RCH2OH

without the formation of intermediary compounds (49).

1.2.2 Unsaturated fatty acids and esters to imsaturated fatty alcohols. The selective high pressure hydrogenation of the carbonyl group in the presence of a double bond in the molecule is, thermodynamically, not probable. It is only possible with a very selective catalyst (the hydrogenation of the double bond has a free enthalpy of formation of -13 kcal/mole, meanwhile that of the carbojgfl to the hydroxyl group is 4 kcal/mole). It has also to be borne in mind that the activity of the catalyst must not be very high, otherwise hydrocarbons will be formed, thus influencing the selectivity (defined as the percentage unsaturatlon attained) and the conversion (defined as the resulting acid to alcohol conversion) of the overall reaction.

Already in 1923 unsaturated acid chlorides were hydrogenated to un-saturated aldehydes where the activity of the catalyst was lowered by poisons as SOT and Cl~(50).

It is of no use to divide the different catalysts or systems used in this selective high pressure hydrogenation according to their group, such as metals,metal oxides and metal soaps, because in the reaction they probably will be present in some other form. Dividing the catalysts into two types, copper-free and copper-containing catalysts, one can hope to get a better picture of the different processes.

•:;-^^ RCH(OH)OR

fast _{RCHO + RjOH}

1.2.2.1 Copper-free catalysts.

These catalysts are generally based on zinc, which is not such an active hydrogenation catalyst as copper. Sauer and Adkins (31) carried out several hydrogenations using zinc chromium oxide in a very high ratio to ester and long reaction time. The highest alcohol jdeld was 68% with a significant saturation of the double bond.

Japanese authors (51) made a rather extensive study on the catalyst systems for the selective hydrogenation of the carbonyl group, without, however, trying to elucidate their mechanism. It may be interesting to sum up some of their conclusions :

— the addition of Ba, Al or Fe decreased the conversion and select-ivity of a zinc chromium oxide catalyst.

— if, in avZn-Cr-O catalyst, zinc was substituted by other metals, the best results were obtained by Cd and Fe.meanwhile if Cr was replaced by Al or Fe, higher alcohol yields at lower p r e s s u r e s were the result.

— the catalyst prepared in alkaline medium gives higher conversions than the one prepared in acid medium.

According to patents, some metal soaps of oleic acid are select-ively hydrogenated to their imsaturated fatty alcohol, among others, C r - , Cd-, P b - , Zn-soaps, (52,53), or combinations of Cr-Cd (41), Pb-Sn (54) etc. Also the addition of a metal soap to oleic acid may lead to oleylalcohol. For further details see table 1.2.

1.2.2.2 Copper-containing catalysts.

As copper chromium oxide was used for the preparation of fatty alcohols, in general, it is quite obvious that this catalyst would be used as basis for the preparation of unsaturated fatty alcohols. But its selectivity towards the carboxyl group is not high enough, needing the presence of another metal which will in one way or another inhibit the hydrogenation of the double bond. The addition of cadmium as oxide (51), carbonate (58,65) soap as such (66) or as a modification during the preparation of the basis catalyst (67) will result in a rather selective carbonyl hydrogenation, depending on the ratio Cu-Cr-O to Cd.

Further experiments showed that chromium caused a greater saturation of the double bond, so that a CuO/CdO catalyst (51, 68) was employed, which probably was totally or partly converted to the r e s -pective soaps through the reaction of the oxides with the acids or e s t e r s .

Using metal soaps as such, oleylalcohol may be prepared by hy-drogenation, e . g . , Cu and Cd-oleate, meanwhile other Cu-metal

Table 1.2. Hydrogenation of unsaturated fatty acids or esters to unsaturated fatty alcohols with copper-free catalysts Catalyst Zn-Cr-O " " Zn-Cr-O (pre-red.) Zn-Cr-O on AlgOg Zn-Cr-O+ CdC03 Zn-AI-O Zn-Al-Cr-O Zn-Fe-O Zn-Mo-O Zn-Cr-Ba-O Zn-V-O Fe-Cr-O Cd-Cr-O Cd-Cr-O Cd-Sn-0 Cd-Ag-O Zn-Cr Cd on AljOj Zn oleate-t-Cd oleate Cr oleate Al oleate -Raw material

Hlce oil ethyl eetere Cottonseed oil me esters Butyl oleate Methyl oleate Ethyl oleate So]a bean oil f. acid Rice oil methyl esters Methyl oleate Soja bean oil Ethyl oleate Oleic acid Butyl oleate Rice oU ethyl ester Rice oil ethyl ester Oleic acid SoJa bean oil Oleic acid Oleic acid Sperm oil oleic acid Oleic acid Oleic acid Pb oleate Zn oleate Cr oleate Zn oleate + Cr oleate Cd oleate + Cr oleate cd oleate + Co oleate Cd oleate Cd oleate + Ni oleate Pressure atm. 200 320 >100 250 200 250 300-430 375 100* >100 260 50 8 0 " 200 220* 100 220* 220' 200 300 280 250 270 240 240 240 245 270 240 270 Temp. 335 320 300 286 280 265 330 315 330 280 280 280 320 335 280 330 280 280 250 340 310 310 340 340 340 340 340 340 340 340 Conversion % 7 99 7 100 90 46.3 95 100 84.5 7 99 99 7 75 37 56 4 3 4 3 100 95 93 94 79 68 60 68 90 57 51 95 Alcohol yield % 84 95.5 65 100 75 22.8 91.7 100 80 67 99 80 6 9 71 0 . 5 56 0 . 6 10,5 100 . 86 85.5 85.5 77 2 27 35 90 7 51 85 Unsaturatlon % 92 75 87 100 91 92 87 75.5 74 87 97 99 84 82 95 82 96 97 100 97.5 97.5 97.5 85 73.5 100 67 92 95 97 78 neferences 51 55 31 56 57 58 59 60 51 31 61 62 51 51 6 3 51 6 3 63 34 64 64 64 52 52 52 52 42 5 3 41 41 • initial pressure

Table 1.3. Hydrogenation of unsaturated fatty acids or esters to unsaturated fatty alcohols with copper-contain ing catalysts

Catalyst Cu-Cr-O + CdCOj „ „ " + Cd oleate Cu-Cd-O Cu-Cd-O on guhr Cu/Cd on guhr Cu-Cd-Cr Cu-Cd-Cr-O (Cu<Cd) Cu-Cd-Cr-O (Cu>Cd) Cu-Cd-Cr-Zn-O Cu-Zn on ALOg Cu-Cd-Zn on graphite Cu-Cd-Al Cu-Cd-Fe-O Cu oleate+Cd oleate „ „ -Raw material Oleic acid Soja bean oil f. acids Linseed oil f. acids Oleic acid Oleic acid Oleic acid Oleic acid Oleic acid Oleic acid Oleic acid Castor oil Sperm, oil Rape oil Methyl oleate Oleic acid Oleic acid Oleic acid Oleic acid Cu oleate Cu oleate + Cd oleate (9:1) Pressure atm. 202 250 250 270 130' 235 130' 250 220* 220' 185 200 220 120 300 266 260 150-350 270 270 T e ^ p . 265 265 265 280 250 286.5 260 300 280 280 390 250 280 260 280 250 260-305 200 340 340 Conversion % 96.5 92.6 95 93 94 88.2 96.5 99 92 92.5 60 -100 - 99 72 99 98 93.5 94 -100 90 Alcohol yield % 89 79 92.8 85 9 3 92.4 93 99 85.5 85 60 -100 - 99 80 97.9 95 85-95 ? 99 90 Unsaturatlon 97 70 54 80 76 90.4 76.2 82 95.5 57 62 -100 -100 82 74 89 98 93 14 87 References 65 58 58 66 51 76 75 76 6 3 6 3 77 34 78 79 74 70 73 72 4 2 41 *initial pressure

oleates such as Sn, yield stearyl alcohol (69). If the metal soaps are used as catalysts, added to their acids, a Cu-and Cd-oleate combination yields as final product oleylalcohol (70-73). The presence of Cd-soap seems to be of fundamental importance if a selective hydrogenation to unsaturated alcohols is desired, meanwhile with Cd-soap alone, there is no reaction at all. Table 1.3. gives an idea of the different Cu-containing catalysts.

Waterman et al (71) reduced oleic acid to oleylalcohol with the addition of Cu- and Cd-soaps, that were supposed to become a colloidal Cu/Cd catalyst at the reaction conditions. This state would lead to the substrate reduction. Optimal conditions were chosen as being a ratio Cu: Cd (soaps) of 6,1 : 2,7 mole %, a temperature of 300°C and initial p r e s s u r e about 190 atm.

From these results it is now obvious that the ratio Cu/Cd governs the selectivity and alcohol yield, so if the ratio is high, higher hydro-genation r a t i o alcohol yields and saturation, if the ratio is low, higher selectivity towards the double bond and higher ester yields.

References :

1. L. Bouvault 6 G. Blanc, Comp. rend. 136, 1676 (1903) 2. M. Fukushima, Fette Seifen Anstrichm. 65, 678 (1963) 3. M.L. Kastens & H. Peddicord, I . E C 41, 438 (1949) 4. v . Blinoff (Sinnova on Sadie), U.S. Pat. 2.460.969 (1949) 5. R . J . Rosser & H. Swan ( I . C . I . ) , U.S. Pat. 2.070.318 (1937) 6. D. Osteroth, NatUrliche Fettsauren als Rohstoffe fUr die Chem.

Ind., Stuttgart (1966)

7. P . A . Lobo, c h e m . Engng. P r o g r . 58^(5), 85 (1962) 8. H. Reinheckel, Tenside 2, 249 (1965)

9. H. Reinheckel, Oleagineux 20 (1), 31 (1965) 10. B . A . S . F . A . G . , Ger. Pat. 1.126.872 (1962)

11. G. Gawalek, W a s c h u . Netzmittel, Akad. Verlag, Berlin (1962) 12. A . F . Millidge (Distillers Co. Ltd.), F r . Pat. 1.411.602 (1965) 13. R . E . K i r k & D . F . Othmer, Encycl. of Chem. Techn., 2nd. ed.

vol. 1, Intersc. Publ. N.Y. (1963) 14. J . E . Germain, Chim. et Ind. 91, 519 (1964) 15. E.C.N. 13^(313), 26 (1968)

16. W. Normann, Z. Angew. Chem. 44, 714 (1931)

17. W. Normann (Böhme Fettchemie GmbH), Ger. Pat. 639.527(1936) 18. H. Adkins & R. Connor, J. Am. Chem. Soc. 53, 1095 (1931) 19. H. Adkms & K. Folkers, J . Am. Chem. Soc. 53, 1091 (1931) 20. K. Folkers & H. Adkins, J . Am. Chem. Soc. 54, 1145 (1932) 21. W. Schrauth, O. Schenck t K. Stickdom, Ber. 64, 1314 (1931) 22. W. Schrauth (Deutsches Hydrierw. GmbH), Ger. Pat. 607.792(1939)

2 3 . I b i d e m , G e r . P a t . 6 2 9 . 2 4 4 (1936) 2 4 . O. Schmidt, B e r . 6 4 , 2051 (1931)

2 5 . H. Adkins, E . E . Burgoyne & H. J. S c h n e i d e r , J. A m . C h e m . S o c . 72, 2626 (1950) 26. I. R a b e s & R. Sehenck, Z. E l e k t r . 51^, 37 (1948) 27. R. Miyake, J. P h a r m . S o c . Japan 6 8 , 14 (1948); C A . 44, 352 (1950) 2 8 . J . D . Stroupe, J. A m . C h e m . S o c . 7 1 , 569 (1949) 2 9 . P r o c t e r & G a m b l e , B r i t . P a t . 5 6 9 . 9 2 3 (1943) 3 0 . W . A . L a z i e r ( E I . Du Pont de N e m o u r s ) , U . S . Pat. 2 . 0 7 9 . 4 1 4 (1932) 3 1 . J. Sauer & H. A d k i n s , J. A m . C h e m . S o c . 5 9 , 1 (1937) 3 2 . J . M . Church, I . E . C 4 9 , 8 1 3 (1957)

3 3 . O. Schmidt (Gen, Aniline & F i l m C o . ) , U . S . P a t . 2 . 3 2 2 . 0 9 5 (1943) 34. F a r b w e r k e Hoechst A . G . , G e r . P a t . 1 . 1 4 6 . 4 8 3 ( 1 9 6 3 ) 3 5 . W . A . L a z i e r ( E . I . Du Pont de N e m o u r s ) , B r i t . P a t . 3 8 5 . 6 2 5 (1933) 36. G. S c h i l l e r (I.G. Farben), U . S . P a t . 2 . 1 2 1 . 3 6 7 (1938) 37. Röhm 8i Haas, F r . P a t . 8 0 2 . 5 4 2 ( 1 9 3 6 ) ' 3 8 . H.R. Arnold t W . A . L a z i e r ( E I . Du Pont de N e m o u r s ) , U . S . P a t . 2 . 1 1 6 . 5 5 2 (1938)

3 9 . I.G. Farben, B r i t . Pat. 3 5 6 . 7 3 1 (1931) 4 0 . The Givaudan C o . , U . S . Pat. 2 . 5 9 0 . 1 0 5 (1945)

4 1 . A . S . R i c h a r d s o n & J . E . T a y l o r ( P r o c t e r fc Gamble), U . S . P a t . 2 . 3 4 0 . 6 8 7 (1944)

4 2 . A S . Richardson & J E . T a y l o r ( P r o c t e r <i Gamble) U . S . Pat. 2 . 3 4 0 . 3 4 3 (1944); B r i t . Pat. 5 6 9 . 9 2 3 (1943)

4 3 . R. Burke J r . ii H. Adkins, J . A m . C h e m . S o c . 6 2 , 3300 (1940) 4 4 . H. Adkins, I . E . C . 32, 1189 (1940)

4 5 . H. Adkins, Org. R e a c t i o n s , v o l . 8, J. Wiley & S o n s , London (1954) 4 6 . H. Adkins <i H . R . B i l l i c a , J . A m . C h e m . S o c . 7 0 , 3121 (1948) 47. E. Haidegger & L . Hodossy, Fette Seifen A n s t r i c h m . 6 4 , 326 (1962) 4 8 . T . Y . Van, L . F . Albright <i L . C . C a s e , I . E . C . prod. & r e s . d e r . 4 ,

101 (1965)

4 9 . K . M . K . Muttzall, T h e s i s , Delft (1966)

5 0 . K. Rosenmund & F . Z e t z s c h e , B e r . 56, 1481 (1923)

5 1 . H. B e r t s c h , H. R e i m h e c k e l & K. Haage, F e t t e Seifen A n s t r i c h m . 66, 763 (1964)

5 2 . A . S . R i c h a r d s o n «I J . E . T a y l o r ( P r o c t e r & Gamble), U . S . Pat. 2 . 3 4 0 . 3 4 4 (1944)

5 3 . Ibidem. U . S . Pat. 2 . 3 4 0 . 6 8 9 (1944)

5 4 . K a o S o a p C o . I n c . , J a p . P a t . 4 3 5 . 8 5 0 (1952); C . A . 4 7 , 3330f (1953) 5 5 . D . B . Orechkin et a l . , C . A . 57, 12652f (1962); 6 1 , 12215c, 16320d (1964) 56. H. Rutger & W. R i t t m e i s t e r (Henkel & C i e . ) , G e r . P a t . 1 . 2 2 8 . 6 0 3 (1966) 5 7 . R u s . Pat. 1 5 8 . 5 6 7 (1963); S e i f e n - O l e - F e t t e - W a c h s e 9 1 , 368 (1965) 5 8 . J . M . Martinez Moreno, e t a l . , G r a s a y A c e i t e s , 10, 56 (1959) 5 9 . I. Bseda «I S. Komori, J. Jap. Oil C h e m . S o c , 14, 58 (1965) 6 0 . S o c . B e i g e de 1'Azote, U . S . Pat. 2 . 8 4 4 . 6 3 3 (1958)

6 1 . W. R i t t m e i s t e r (Deutsch. Hydrierw. GmbH), B r i t . P a t . 8 0 6 . 6 1 9 (1958), G e r . P a t . 9 6 5 . 2 3 6 (1955)

6 2 . W. R i t t m e i s t e r ( A m . H y a s o l C o . ) . U . S . P a t . 2 . 3 7 4 . 3 7 9 (1940)

6 3 . E . A. Duintjer, T h e s i s , ZUrich (1941) 6 4 . K. Negi, F r . P a t . 1 . 3 7 5 . 4 7 2 (1964)

6 5 . J . M . Martinez Moreno et a l . , G r a s a s y A c e i t e s 9, 60 (1958) 6 6 . A . S . Richardson & J . E . T a y l o r ( P r o c t e r & G a m b l e ) , U . S . P a t .

2 . 3 7 5 . 4 9 5 (1945)

6 7 . H. B e r t s c h , H. Reinheckel & E. König, F e t t e Seifen A n s t r i c h m . 69, 387 (1967)

6 8 . G. Natta, Kal. P a t . 4 3 0 . 7 9 4 (1948) 6 9 . A. B e r n a r d , C h i m . e t Ind. 72, 919 (1954)

70. A . J . Pantulu «I K . T . Achaya, J . A m . Oil C h e m . S o c . £ 1 , 511 (1964) 7 1 . C B o e l h o u w e r , J. v . Mourik & H . I . W a t e r m a n , C h i m . et Ind. 83,

875 (1960)

72. N . V . Olieraffinaderij Zuilen, Neth. Appl. 6 . 4 0 4 . 6 7 9 (1966) 73. Idem, Dutch Pat. 8 3 . 3 7 9 (1956)

7 4 . E . A . F r o e h l i c h , T h e s i s , ZUrich (1960) 75. C. V. Schuckmann ( A m . Hyasol C o . ) U . S . P a t . 2 . 3 3 2 . 8 3 4 (1943) 76. E . König, J. P r a k t . C h e m . 15, 277 (1962) 77. S o c . B e i g e de 1'Azote, B r i t . P a t . 7 9 2 . 8 9 6 (1958) 7 8 . E . König e t a l . , ( D e u t s c h . H y d r i e r w . GmbH), E a s t G e r . P a t . 3 7 . 3 7 0 (1965) 79. Kyowa F e r m . Ind. C o . L t d . , F r . P a t . 1 . 3 8 7 . 4 5 8 (1965)

CHAPTER 2

ANALYSIS OF THE REACTION PRODUCT CONCERNING THE CATALYST SYSTEM

2.1 Introduction

The reaction product of the high pressure hydrogenation of a fatty acid with a catalyst system consisting of a Cu and a Cdsoap, is a deep red-brown coloured solution, containing dark particles.

This chapter will deal only with the catalyst system, not consider-ing the products resultconsider-ing from the fatty acid reduction.

Previous work (1), as seen in the Introduction, has indicated that CuH was the compound which gave the solutions its colour and at the same time was the active part of the catalyst. To try this hypothesis, a series of tests were carried out with the solution and with the sub-stance precipitated from the solution by ethylalcohol.

In order to become acquainted with the known properties of the reaction product, a summing up will follow :

In contact with air, the solution turns green, meanwhile under N2 it keeps its properties. Discoloration occurs under the influence of an oxygen-free organic cupric solution. No Tyndall effect or sedi-mentation at a field of 3000 g in a centrifuge had been observed. The dried precipitate is a black-brown powder, which dissolves in ether, benzene or undecane as a red solution, the same occurring to the s u s -pension of the reaction product. The alcoholic filtrate contains no Cu, only Cd-oleate. The solid substance reacts with benzoylchloride to aldehyde; on heating under N2 at 250°C, H2 is released, and reacting it with J2 solution, to determine the amount of copper ions, a molar relation H2 : J2 of 1: 3, 8 was found (theoretically for CuH 1:4). These properties were e^qjlained by the reactions :

2 CuH —— 2 Cu + Hg and J^ + CuH — — CuJ + HJ By slowly heating the solid under N2, CO2 and H2 are formed, evolution begins at 150°C and ends at 225°C, the CO2 is supposed to come from the cupro-oleate. On heating the dry powder and treating

the sample diluted with undecane with cupri capronate, the results suggested that not all the Cu is present as CuH, but that there is an equilibrium between CuH, cupro-oleate and H„.

2.2 Preparation, properties and analysis of CuH

It seemed quite reasonable then to prepare CuH, and test its hy-drogenation activity towards an acid. The hydride of copper differs from all other metalhydrides in properties and preparation methods. It is the only hydride which can be prepared through

oxidation-reduc-tion reacoxidation-reduc-tions in aqueous soluoxidation-reduc-tion. Also an interesting aspect is the effective bond radius of the metals in a two-atomic hydride molecule and its own metal bond radius, where in nearly all metals, the former is greater than the latter, meanwhile Cu (and also Ag and Au), give the opposite picture of the case (16).

CuH was first prepared by Wurtz (5), and following his thoughts, several authors (6) used the same principle :

2Cu"^^ + SHgPOg + 3H2O —i- 2 CuH + 3 HgPOg + 4 H"^ The first to prepare CuH water-free were Wiberg and Henle (7) using LiAlH. as hydrogenation agent:

4 CuJ + LiAlH^ — ^ LiJ + AlJg + CuH

although this equation seems to be much more complex (12).

CuH decomposes irreversibly already at room temperature, even under H2 atmosphere, in Cu and H2. At 80 C, after 10 min., 91%of the CuH is decomposed (2).

The velocity with which CuH decomposes depends on its liquid medium because organic solvents may partially inhibit the decomposi-tion.

The properties of CuH depend strongly on the manner in which CuH is prepared, for example, tn the "dry" method , CuH is soluble in pyridine and small quantities of water increase the decomposition, meanwhile in the "wet" method, it is insoluble, small quantities of water stabilizing CuH.

This contradiction puts up a question If CuH, as such, exists at all and really which is its stoichiometry.

Some literature sources on x-ray diffraction studies of CuH, mention that it has a hexagonal lattice with a close packing of the cop-per atoms (2,3,6,19).

Both preparation methods were tested and their products analyzed. The "wet" method was followed through the procedure described by Mikheeva and Mal'tseva(4), and the "dry" method the one used by Bacon and Hill (8), with the remark that the filtrations and reprecipitations were carried out at temperatures about 20°C (9). The p r e p a r -ation and purific-ation of CuH were carried out in an atmosphere of N2.

X-ray spectra from both products were made immediately after their preparation, giving a quite different picture (see table 2.1). The measured lines Indicated the presence of CuH and Cu in the "wet" method, this latter probably a product of the decomposition of the former, showing a very strong CuH line at 6 = 20, 5? The diffraction pattern of the "dry" method showed the presence of CuH (some lines) and some unidentified components.

The copper content of 86% for the "wet" method, instead of 98, 4% for pure CuH, meanwhile in the "dry" method it only reached 40%, an emission spectrum shows small amounts of impurities from Li and Al.

Infrared analysis of CuHprepared according to the "wet" method showed no absorption as had already been observed (13), but if on contact withtraces of oxygen, an absorption peak appears at 615 cm"-*-due to CU2O. With magnetic resonance methods like N.M.R. and E.S.R. no responses were observed.

CuH prepared according to both methods is insoluble in alcohol, aceton, benzene, ether, oleic acid, carbon tetra chloride, undecane, water,carbon disulfide, dimethylformamide and dioxane. Only the hy-dride prepared in pyridine is soluble in this solvent, with a dark red colour.

From the results obtained it seems quite reasonable that the reaction equation proposed by Wiberg and Henle is more complex than stated by the authors, where the reaction product will consist not only of CuH but also of some complex of Cu, Li, Al and even py-ridine. Infrared analysis of the complex product showed absorption peaks of pyridine even if the material was thoroughly washed with ether.

Furthermore, the different unidentified lines of the x-ray dia-gram, which are not from CuJ, AIJ3, LiJ or LiAlH4 (14,17,18), con-firm the possibility of other compounds.

2 • 3 Analysis of the reaction product

As the reaction product and CuH are readily oxidized by the oxy-gen of the air, it is to be observed that these compounds must be

manipulated tn an atmosphere of an inert gas. Nitrogen was chosen as such. The nitrogen is deoxygenized on a heated column filled with activated copper on silicagel, absorbing small quantities of oxygen (10), and dried on silicagel and P2O5. An alkaline pyrogallol solution which was prepared under a helium atmosphere remained colourless for at least 10 hours, when the oxygen-free nitrogen was bubbled through it.

The red-brown reaction product was sampled and kept in a nitro-gen atmosphere. Ethylalcohol which had been subjected to a double distillation under a stream of nitrogen, was added to the red-brown solution, about ten times its volume.

A dark precipitation occurred, which was filtered and thoroughly washed with the oxygen-free alcohol. After evaporating the alcohol under vacuum, a black powder remained.

2 . 3 . 1 Polarographic analysis

The amount of Cu and Cd in the sample has been determined after destruction of the organic material by means of polarography using a dropping mercury electrode.

The organic matter is destroyed by fuming the samples several times with concentrated nitric acid until no more nitrous vapours are formed. The residue is dissolved in about 2 ml. concentrated HCl and diluted with water to the desired concentration. After addition of con-centrated ammonia to pH 9,5, filtration and addition of an aqueous gelatine solution (maximum suppressor) to lower the superficial tens-ion, the polarographic analysis is performed using an aqueous solution of equimolar amounts of NH4CI and NH4OH as supporting electrolyte. Usually direct current polarography is applied, but for very low con-centrations, alternating current polarography is used.

On analyzing the precipitated reaction product solution (through polarography), besides a large amount of copper, also from 0, 2 to 0, 5% of Cd was found. On the other hand, in the alcoholic filtrate, no copper was found, only cadmium.

2.3.2 X-ray analysis

To obtain a x-ray diffraction pattern, the Debye-Scherrer dia-gram of a Straumanis photo from a Philips camera from the Labora-tory for Metallurgy of the Technical University Delft was used. The photographs were taken with the Cu-Kabeam, the g-radiation be-ing absorbed by a Ni screen. Cadmium bebe-ing present as one of the components in the sample, an aluminium folio was set in between the film and the x-ray source to diminish the effect of fluorescence. The exposure time was 2 hours for solids and 4 hours for solutions.

For the calculation of the values of the scattering angle,

mg to Bragg:

^ ^ Ö = 2d7ïi

and

26 = (L/2 irr) . 360°

the camera's diameter being 57, 3 mm, L in mm will be equal to e in degrees.

The Debye-Scherrer diagram for a hexagonal lattice uses the formula:

sin^ e = xV3a^ (h^ -^ hk + k^) +X ^40^ . 1^

sin^ 6 = (X / 2 a ) ^ . ZH^

From a and c, which are known values, 6 can be calculated. The photographs give the value of 2 L.

The samples to be analyzed were handled in a glove-box, intro-duced in a capillary tube of lithium aluminium borate glass and both ends sealed.

A Debye-Scherrer diagram of the red-brown solution at different Cu and Cd concentrations and at different reaction times indicates only the presence of metallic copper. The strongest lines obtained in solution could only be classified as medium, due to the relatively low concentration of the components which could produce a diffraction pattern (see Table 2.1).

From table 2.1 it can be seen that the copper line at 9 between

21 and 22, 5° is very broad, indicating the presence of very small particles. The same is to be observed in the reaction product p r e c i -pitated by alcohol, which showed exactly the same pattern as the solution. Cd-oleate, Cu-oleate, oleic acid and a mixture of these components, resulted only in a very broad diffuse oleate ring, which appeared in all photos, of a 2 6 value of 1 8 - 2 1 ° , which does not overleap CuH, Cu and its oxides or Cd, its oxides and Cd(OH)„.

Diffraction lines of the particles which were found on the glass walls of the reactor after the reaction has been completed, show a crowded picture which could not be entirely interpretated, but it was clear that Cd and Cu in all oxidation degrees and Cd(OH)2 were p r e -sent.

^ i U N r o E N T I F I E D LINES t o i h - >— < < N> < * O O 1 u CA < t ->^ 00 « o t n * O O 1 i-* OD M° O) < ^ c u Oï < o O i « o c ^^ 0 1 f-* Ül o ° < t ^ t s o ^^ 4^ i 1 o •Ik. - j "o Oi < •o - 3 > O i < - J t o »f>-< _^--_C3 00 Ü> t o i • o o O i OD O -^ -« •o 1 O i o - 3 < O i 00 O en 00 * tU D 1 1 O •f>-a 1 •p • 1 s T l . h3 ^^ ' 1 O 3 i TJ • ' T l . • >-• K-Ü l M i -o t o >^ en o * « 4k O lO * •u o ro < •f. t n 0 t o < ro ^ 1 QO i 0 00 < o 00 co " o i o 00 * co -t OD « u UD B o >— OI i - " 1— >^ t o t o * 3 t o t o t o t o « * J".? t o t o t o t o t n t-* o o t o t o " < 3 o o o H* CJ o t o o - V * a t o t o t o o o o t o - C 1 w « 3 t o t o t o en t o »• ' o o o t o - C;i - v < GO ^— _o o r o ff) o t o •^ t o « ' C3 1— o o h -to g co o co co co co 00 - o O i t o o o o 0 . - rf^ h - ^ 00 00 O i t o en o o o 3 < 3 < 1 1 1 1 not present not present ~ o t o t o m co O i t n >C>-i t o < o t o o o en D c o ^ <p - J ^ t A ;o ^ V tfl t o o * CO o 3 o * o o ^ - J o t o ^ - J t n 3 o O i < not present not present not present ^ CD ö a CD " (D S'

- 1

-® 1

-1

CuH prepared according to (4) CuH prepared according to (8)

r . p r . s . of 28,6 mole % CuOl^ and 14,3 mole ' CdOl, In oleic acid, heated under initial Hg pressure of 190 atm. up to 250°C

idem as (r) only Cu/Cd : 5/2, 5 mole % and 30 min. at 250°C idem as (r) only Cu/Cd : 40/20 mole %

powder obtained by alcoholic precipitation of the reaction pr. s . not present

2 . 3 . 3 Determination of the mean oxidation degree of copper

Polarographic analysis showed the presence of copper in the r e -action product which was precipitated by alcohol, but it was not pos-sible to get information about its oxidation state. The quantitative differentiation through chemical analysis of the different oxidation states of copper is a rather more difficult task than the determination of the mean oxidation degree.

The equilibrium:

Cu^"^+ Cu° - r — 2Cu"^

is established if a system containing the three oxidation states of cop-per, Cxfi , Cul and CuO, comes into contact with water. This equili-brium is shifted to the left in a 4 N sulfuric acid solution and to the right In a 4N hydrochloric acid solution. Treating the sample with a diluted sulfuric acid solution, Cu"*^ will be converted to Cu^"*" and Cu°, meanwhile a diluted solution of hydrochloric acid will promote the oxidation of Cu° by the Cu^"*" ions, if the latter are present. From these facts it will be clear that it is not possible to determine separa-tely the different oxidation degrees of copper. If we exclude the oxi-dation by air, a mean oxioxi-dation degree value, defined as x in CuO can be measured; the value of x being calculated by (11):

_ J _ % copper as calculated from permanganometry % total copper

The followed procedure (11) consisted in treating the dried precipita-ted reaction product with an oxygen-free 2 N sulfuric acid solution at room temperature in the glovebox, and stirring vuitil the solid m a -terial was suspended. A ferri ammoniumsulfate solution is added to the suspension and the whole boiled during 1 hour, oxidizing Cu° to Cu2+:

Cu° + 2Fe^^ ^ Cu^"" + 2Fe^"^

The ferro ions formed are titrated with a 0,1 N potassium p e r -manganate solution.

The total amount of copper is determined by treating the reaction product with a 2N hydrochloric acid solution, the greenish water layer separated from the oil, by extracting the latter with ether, both layers being completely homogeneous and clear. To the water layer is added a 10% solution of KJ and the excess back-titrated with a 0,1N thiosulfate solution.

The values of x vary from 0 to 1, the lower the values of x, the greater the amoimt of reduced copper.

To determine the mean oxidation degree of copper in the react-ion, samples were taken at different stages of the reactreact-ion, two at a

time. One was kept in the glove-box and the other was left to be oxi-dized by the air, after which the total amount of copper is determined.

As stated already In item 2 . 3 . 1 no copper was found in the alco-holic filtrate.

Some tests were effected and it was observed that in boiling the acid treated solution with the ferric salt under nitrogen, the same results were obtained as if boiling it in the atmosphere. Cadmium did not interfere in the determination of copper, nor did oleic acid.

The results are given in table 2.2. After a reaction of one hour the copper content decreased rapidly and no reproducible measure -ments could be made. The sampling time was taken the moment the reaction temperature was 25(Pc and the pressure 250 atm. of H„. These conditions were kept constant throughout the e:!q)eriment.

Table 2.2. Mean oxidation degree of copper in the sample

sampling time 15 min. 30 min. 45 min. 60 min. Cu« g r / g r prod. 0,964 0,966 0,966 0,965 total Cu g r / g r prod. >oo 0,973 0,972 0,973 0,973 medium value X 0,009 0,006 0,007

0,008 1

From the results ejqjosed in table 2. 2 it is quite evident that Cu is the oxidation state in which copper is present ia the reaction p r o -duct. That the value of x is not exactly equal to zero, can be explain-ed by traces of oxygen which came into contact with the sample during manipulation, notwithstanding the extreme care taken.

When the mean oxidation degree of copper in CuH prepared by the Wurtz method was determined it was found that it consisted of Cu+. For samples prepared by the "dry" method there was too much inter-ference by other compoimds to draw conclusions.

2.3.4 Tyndall effect

Careful examination of the red-brown samples by an ultramicros-cope with an immersion objective showed a Tyndall effect. This effect was very difficult to observe because of the dark colour of the solution. An improvement could be made, however, by diluting with a paraffin mixture to 50%.

2.3.5 Electron microscopy

To determine the size of the copper particles, an electron m i -croscope was used. The reaction product precipitated by alcohol, is embedded tn Vestopal W obtained from M. Jaeger (Ztlrich), which is left to polymerize at 65° C for 48 hours or at room temperature for 4 days. After cutting the polymer in sections, it is applied on a copper grid by the "formvar" techmique. The electron micrograph (fig. 2.1) was obtained with a Philips EM 200 microscope at the Laboratory for Microbiology of the Technological University of Delft.

o

The average particle size is 48 A. Because of the good d i s p e r s -ion of the particles due to dissolut-ion of ca(i.nium oleate and oleic acid in the resin it is presumed that this is the size of the primary particles. The agglomerates are visible as dark patches.

• • •

. *^. . , •. .• ^

' • • • • % • » . t « ' •

Fig. 2 . 1 . Electron micrograph of the precipitated reaction product. Enlargement: 94.000 x.

2.3.6 Spectroscopy

fiifrared spectroscopy of the dry powder pressed with KBr into a pellet or dissolved in a paraffin mixture, showed a spectrum cor-responding to an oleate.

The same can be said for the ultra-violet spectroscopical results.

2.4 Discussion

From the experiments it i s clear that:

— not only copper is present in the powder sample of the precipitated reaction product, but small amounts of cadmium as well

— the powder sample contains oleate

— the mean oxidation degree of the copper in the powder sample is 0,0075, indicating the presence of Cu° as the major component — no copper, only cadmium is present in the alcoholic filtrate sample

of the reaction product

— only Cu lines were found tn a xray diagram of the reaction p r o -duct solution and powder sample

— a Tjmdall effect has been observed in the reaction product solution further:

— no proton resonance signal and no signal for unpaired spin resonance in both, solution and powder sample was observed, when NMR and ESR investigation methods were used

— no electroforesis could be observed when tried in a simple Burton-cell, probably due to the high dielectric constant of the medium and the small size of the particles

— the powder sample is soluble in n-paraffins, ether, benzene, and not soluble In oleic acid, alcohol and water at room temperature.

By analyzing these results it may be concluded that copper is present as the metal. The broadening of the x-ray diffraction pattern, indicates particles which are very small, and the observation of the Tyndall effect can be an indication of particle size in the range of colloids.

As cadmium has not been observed as a metal in any x-ray dia-gram, but spectroscopy identifies an oleate it seems reasonable to conclude that cadmium is not reduced in the reaction and remains as cadmium oleate.

2.5 Experiments leading to the final conclusions

To test the reducing capacities of the dried powder, a serie of hydrogenations of oleic acid were carried out at 250°C and 200 atm. using a paraffin solvent (for apparatus and operations see next chap-t e r ) . Besides chap-these experimenchap-ts also chap-the alcoholic filchap-trachap-te (evaporachap-ted in a vacuum at room temperature) and CuH were hydrogenated at the same conditions, the results are shown in table 2 . 3 .

Table 2 . 3 . Hydrogenation of oleic acid with the addition of different copper containing compounds (experiments 1 to 4 w e r e c a r r i e d out in a paraffin solvent). Mr. 1. 2. 3. '4. 5. 6. 7. Additives 0,16 g (a) 0,16 g (a) + 0,8 g CdOlg filtrate (d) 0, 2 g CuH (b) 0, 5 g CuH (b) + 2,4 g CdOlg 0,5 g CuH (c) 0,5 g CuH (c) + 0,8 g CdOlg Reaction t i m e 60 m i n . 60 m i n . 60 m i n . 120 m i n . 20 m i n . 20 m i n . 20 m i n . Conversion P r e s e r v a t i o n of to alcohol the double bond

60 % 50 % 60 % 100 % no reaction no reaction no reaction 1 30 % 100 % no reaction 1

(a) precipitate obtained from reaction product (b) according t o (4)

(c) according to (7)

(d) alcoholic f i l t r a t e , obtained as specified above

From these experiments some interesting features may be ob-served :

In the first place the dark powder obtained from the reaction product is the active hydrogenating part of the catalyst, but a selective hydro-genation requires the presence of cadmium oleate. Only a small amount of this cadmium soap is present in the precipitate, not being enough to carry out the hydrogenation selectively. In cases 1 and 2 the samples were red-brown, but in case 1 the solution was turbid and in 2 completely homogeneous. With CuH the samples do not acquire the red-brown colour and there is no conversion, except in one

ex-periment where the compound prepared according to the Wiberg-Henle method was used, but it should be noted, that when Cd oleate was add-ed no reaction occurradd-ed. This could be explainadd-ed by the fact that some LiAlH4 or LiH is present together with CuH, and it is known that the former hydrogenates selectively acids to alcohols (20). If a cadmium soap is thus present, a reaction of Cd with those components may occur before the reduction of the acid.

CuH (prepared according to the "dry" method) dissolved in quln-oline to a red-brown solution is not able to hydrogenate quinone. Whilst a red solution of a partly dissolved copper film in quinoline, catalyzes the quinone reduction with hydrogen (21).

It is now assumed that a copper sol is the active part of the cata-lyst system, bringing about the hydrogenation. Cadmium oleate acts as a stabilizer for the colloid system.

It is known that high molecular weight acids and their metal soaps act as surface-active agents stabilizing colloid particles. The pep-tizing properties of the latter are even better. If the conditions, temp-erature, medium and sol-soap (or acid) concentration are suitable, the stabilization will be complete, the metallic part of the soap (or the polar part of the acid) is adsorbed to the sol particles, thus p r e -venting agglomeration.

By the addition of alcohol, the polarity of the solution increases and part of the metal soap is dispersed into it, retaining only a mono-molecular film of the stabilizer adsorbed to the particle, so that they may approach each other, without, however, entering each other's sphere of attraction,protected by the monomolecular soap film.

The unimolecular soap layer, which is chemisorbed to the p a r t -icles does not desorb when the concentration of the solution is reduced, this film remaining unimolecular in thickness (15).

The dry gel left after filtration of the alcoholic solution, may be redispersed by the addition of a paraffin, benzene or ether, forming a red-brown solution.

As to the remark in the beginning of this chapter where it was stated that the chemical analysis of the reaction product showed p r o -perties and reducing capacities which could be believed to be those of CuH, these properties are better explained by the adsorption of hydro-gen. The appearance of CO2 is due to the decomposition of the soap oleate and eventually oleic acid adsorbed to the metal particles.

References :

1. B. Stouthamer, Thesis, Delft (1964)

2. R. FOrthmann & A. Schneider, Naturwissenschaften, 53, 500 (1966) 3. J . C . Warf &W. Feitknecht, Helv. Chim. Acta, 33, 613 (1950)

4. V.I. Mikheeva & N.N. Mal'tseva, Russ. J. Inorg. Chem. 6 ( 1 ) , 1 (1961)

5. A. Wurtz, Compt. r e n d . , 18, 702 (1844)

6. H. M U l l e r & A . J . Bradley, J. Chem. S o c , 1669 (1926); J . A . Goedkoop & A . F . Andresen, Acta C r y s t . 8, 118 (1955)

7. E. Wiberg & W. Henle, Z. NatUrforschung 7B, 250 (1952) 8. R . G . R . B a c o n & H . A . O . HiU, J . Chem. Soc. 1118 (1964) 9. R. FOrthmann, personal communication

10. Houben Weyl, Methoden der Organischen Chemie, Allgemeine Laboratorium-p r a x i s , 2. Teil, 4. Auflage, Stuttgart (1959), Laboratorium-pag. 327

11. C. Okkerse et a l . , J. Am. Oil Chem. S o c , 44, 152 (1967) 12. E. Wiberg, personal communication

13. V . I . Mikheeva & N . N . Mal'tseva, J . of Struct. Chem., 4 (5), 643 (1963) 14. A. Taylor & B . J . Kagle, Crystallographic Data on Metal and Alloy Structures,

New York (1963)

15. W. Hirst & J . K . L a n c a s t e r , T r a n s . F a r a d . S o c , 47, 315 (1951) 16. L. Pauling, The Nature of the Chemical Bond, 3rd. e d . , N. York (1960) 17. E. Zintl & A. Harder, Z. P h y s . Chem. B 2 8 , 478 (1935)

18. J. Rice J r . & G. Chizinky, P . B . Report 127867 (1959) 19. J. Bousquet et a l . , Bull. S o c Chim. de F r a n c e , 3852 (1967)

20. A . I . Vogel, P r a c t i c a l Org. C h e m . , 3rd. e d . , Longmans, London (1962) 2 1 . D.A. Dowden, Disc, of the F a r a d . S o c 29, 260 (1960)

CHAPTER 3

KINETICS AND MECHANISM OF THE HIGH PRESSURE HYDROGENATION OF UNSATURATED FATTY ACIDS TO UNSATURATED FATTY ALCOHOLS USING A Cu- AND

Cd-SOAP CATALYST SYSTEM

3.1 Introduction

From the foregoing chapters it is clear that unsaturated fatty acids can be hydrogenated, selectively, to their unsaturated fatty alcohols using metal-soaps which leads to the formation of a catalyst or are hydrogenated as such. The highest selectivities and convers-ions are obtained with a Cu/Cd soap system, in which the amount of catalyst and the Cu/Cd ratio play a major part.

In the light of the results mentioned in the foregoing chapter, ex-periments which were done by Stouthamer (1) were partly repeated, now using an inset vessel.

3.2 Apparatus

The experiments were carried out batchwise in a rocking auto-clave system of stainless steel 316 (fig. 3.1). The autoauto-clave system consists of two vessels, a larger one of 230 cc and a smaller one of 45 cc, mounted on the former. Both vessels are electrically heated. The temperature control is carried out by a Pt resistance thermo-meter element of 100 ohm coupled to a relais; the accuracy is + 2°C. The sampling is made through vessel F, where it may be cooled or heated, depending on the samples being liquid or solid.

The maximum working pressure and temperature depend mainly on the O-ring used, the best results being obtained with "Viton", 250 atm. and 300°C respectively.

Vessel C contains a glass inset vessel to avoid the coating of the reactorwall by copper and cadmium as experienced previously (2). Although experiments can be done with a copper-cadmium layer form-ed in the reactor it does not seem advisible to introduce these foreign factors.

A : injection tube B : vessel 45cc C : vessel 230cc D : sampling tube E : thermocouple pocket F : vessel 10cc G : support M: manometer O : o. ring