PARAFFIN WAX
P R O E F S C H R I F T
TER VERKRIJGING VAN DE GRAAD VAN DOCTOR IN DE TECHNISCHE WETENSCHAP AAN DE T E C H N I S C H E HOGESCHOOL TE D E L F T , OP GEZAG VAN DE R E C T O R MAGNIFICUS DR. O. BOTTEMA, HOOGLERAAR IN DE AFDELING DER ALGEMENE WETEN-SCHAPPEN, VOOR EEN COMMISSIE UIT DE
SENAAT TE VERDEDIGEN OP WOENSDAG 27 NOVEMBER 1957
DES NAMIDDAGS TE 2 UUR
DOOR
ANTON BERNARD RUDOLF WEBER
SCHEIKUNDIG INGENIEUR GEBOREN TE BATAVIA
die in enige v o r m aan het tot stand komen van dit proefschrift hebben m e d e g e w e r k t .
T A B L E O F C O N T E N T S S u m m a r y 5 C h a p t e r I. C o m p a r i s o n of t h e c a t a l y t i c h y d r o t r e a t i n g of p a r a f f i n w a x w i t h a F t - S i O z - A l z O s c a t a l y s t a n d a P t A l a O s C l c a t a l y s t . P r e l i m i n a r y e x -p e r i m e n t s 7 1. I n t r o d u c t i o n . 7 2. E x p e r i m e n t a l 8 3. D i s c u s s i o n of t h e r e s u l t s 13 C h a p t e r I I . D e t e r m i n a t i o n of t h e a v e r a g e n u m b e r of b r a n c h i n g s p e r m o l e c u l e in s a t u r a t e d , s o l i d h y d r o c a r b o n m i x t u r e s 16 1. I n t r o d u c t i o n 16 • 2. The a d d i t i v i t y of t h e m o l e c u l a r r e f r a c -t i o n a n d -t h e m o l e c u l a r p a r a c h o r 16 3. T h e s p e c i f i c r e f r a c t i o n s p e c i f i c p a r a -c h o r m e t h o d 17 4. A d j u s t m e n t of t h e m e t h o d f o r 70OC 20 5. A c c u r a c y of t h e m e t h o d 25 C h a p t e r III. V a p o u r p h a s e h y d r o i s o m e r i z a t i o n of p a r a f fin w a x w i t h a P t A l 2 0 3 C l c a t a l y s t . T h e i n -f l u e n c e o-f t h e r e a c t i o n t e m p e r a t u r e , m o l a r r a t i o H g / w a x a n d c o n t a c t t i m e on t h e d e g r e e of c r a c k i n g , b r a n c h i n g a n d c y c l i z a t i o n in t h e r e a c t i o n p r o d u c t s 2 7 1. I n t r o d u c t i o n 27 2. E x p e r i m e n t a l 27 3. D i s c u s s i o n of t h e r e s u l t s 28 C h a p t e r IV. T h e r e l a t i o n s h i p b e t w e e n t h e c o n v e r s i o n of p a r a f f i n w a x , t h e f o r m a t i o n of low p o u r p o i n t o i l s a n d t h e f o r m a t i o n of c r a c k e d p r o d u c t s 36 1. I n t r o d u c t i o n 36 2. E x p e r i m e n t a l 38 3. D i s c u s s i o n of t h e r e s u l t s 41 C h a p t e r V. S e l e c t i v i t y in c h e m i c a l r e a c t i o n s 54 1. I n t r o d u c t i o n 54 2. R e a c t i o n c o u r s e s f o r s i m u l t a n e o u s f i r s t o r d e r r e a c t i o n s in b a t c h p r o c e -d u r e 55 3. T h e c a t a l y t i c h y d r o g e n a t i ó n of l i n o l e i c e s t e r s a s a c o n s e c u t i v e r e a c t i o n 57
4. E x a m p l e s of r e a c t i o n c o u r s e s a c c o r d ing to equations r e p r e s e n t i n g h y p e r -bolas 62 5. D i s c u s s i o n 70 References 76 Samenvatting ( s u m m a r y in Dutch) 78
S U M M A R Y
In Chapter I the catalytic h y d r o t r e a t i n g of paraffin wax is d e s c r i b e d when using a Pt-Si02-Al203 catalyst and a Pt-Al203-Cl c a t a l y s t . The r e a c t i o n products a r e investigated with r e s p e c t to t h e i r d e g r e e of br a nc hin g , c r a c k i n g and c y c l i z a -tion. When Pt-Si02-Al203 is used as a catalyst the paraffin wax is c r a c k e d s e v e r e l y ; only the c r a c k e d products a r e b r a n c h e d . With Pt-Al203-Cl as a catalyst the h y d r o c r a c k i n g r e a c t i o n is limited and the r e a c t i o n product is b r a n c h e d over its whole m o l e c u l a r weight r a n g e . The cyclization r e a c t i o n o c c u r s t o a m i n o r extent only for both c a t a l y s t s . F r o m the e x p e r i m e n t a l r e s u l t s it is c l e a r that the Pt-Al203-Cl catalyst is m o r e suitable for the h y d r o - i s o m e r i z a t i o n r e a c t i o n than Pt-Si02-Al203.
In Chapter II the d e t e r m i n a t i o n of the d e g r e e of b r a n c h i n g , a c c o r d i n g to the specific r e f r a c t i o n s p e c i f i c p a r a c h o r m e t h od, is d i s c u s s e d . The original method, valid at 20°C, is a d j u s t e d for 70°C as the p a r t l y solid r e a c t i o n products n e c e s -s i t a t e the d e t e r m i n a t i o n of the -specific r e f r a c t i o n and the specific p a r a c h o r at an elevated t e m p e r a t u r e .
In C h a p t e r III f u r t h e r e x p e r i m e n t s v/ith Pt-Al203-Cl a s a c a t a l y s t a r e d e s c r i b e d . The influence of s o m e r e a c t i o n v a r i -ables on the d e g r e e of branching, c r a c k i n g and cyclization is studied.
In Chapter IV the h y d r o - i s o m e r i z a t i o n of paraffin wax is d e s c r i b e d when using PtAl203Cl catalysts of different c o m -position and some other c a t a l y s t s . The r e a c t i o n products a r e s e p a r a t e d in t h r e e " c o m p o n e n t s " : oil, c r a c k e d products and unconverted wax. The e x p e r i m e n t a l r e s u l t s a r e r e n d e r e d in t r i a n g u l a r d i a g r a m s . It a p p e a r s that the oil yield is depend-ent on the d e g r e e of cracking and that the r e l a t i o n s h i p can be given by an equation of a hyperbola containing two c o n s t a n t s . The equation is applied for comparing the action of s o m e other c a t a l y s t s to that of the Pt-Al203-Cl catalyst. Some t e c h n i c a l p r o p e r t i e s of the oils s e p a r a t e d a r e given (pour point, v i s c o -s i t y index).
In Chapter V the s e l e c t i v i t y of c h e m i c a l r e a c t i o n s is d i s c u s s e d m o r e g e n e r a l l y . It is shown for a number of s i m u l -taneous r e a c t i o n s that the concentration change of c e r t a i n components in a r e a c t i o n product, as a r e s u l t of the v a r i a t i o n of one r e a c t i o n v a r i a b l e , can be approximated by an equation containing two c o n s t a n t s . Two equations, r e p r e s e n t i n g h y p e r -b o l a s , a r e used to d e s c r i -b e the different c a s e s of s e l e c t i v i t y . It is suggested to apply them for the s c r e e n i n g of c a t a l y s t s and for an economic investigation of the influence of r e a c t i o n v a r i a b l e s .
C h a p t e r I
COMPARISON OF THE CATALYTIC HYDROTREATING OF PARAFFIN WAX WITH A Pt-Si02-Al203 CATALYST AND
A Pt-AlzOs-Cl CATALYST PRELIMINARY EXPERIMENTS *)
§ 1 . I n t r o d u c t i o n
P e t r o l e u m waxes a r e solid h y d r o c a r b o n m i x t u r e s which a r e p r e s e n t in different crude oils in quantities varying from l e s s than 1% to about 10%. They consist p r e d o m i n a n t l y of paraffin h y d r o c a r b o n s and a r e divided into two groups n a m e l y paraf-fin waxes and m i c r o c r y s t a l l i n e w a x e s .
Paraffin waxes a r e m i x t u r e s of n o r m a l paraffins from about eighteen to t h i r t y - f i v e carbon a t o m s and a r e usually obtained f r o m lubricating oil fractions by conventional d e -waxing t e c h n i q u e s . Isoparaffins of the s a m e boiling range a r e not p r e s e n t in paraffin waxes a s they a r e s e p a r a t e d in the d e -waxing o p e r a t i o n . The p r i n c i p a l use of paraffin wax is in the packaging and candlemaking i n d u s t r i e s . O t h e r u s e s include those of polish m a n u f a c t u r e , insulation in the e l e c t r i c a l i n -d u s t r i e s , r u b b e r s o f t e n e r s , p r e s e r v a t i o n of l e a t h e r an-d a s a constituent of p h a r m a c e u t i c a l s and c o s m e t i c s .
M i c r o c r y s t a l l i n e waxes a r e obtained f r o m crude r e s i d u e s by solvent dewaxing and a r e believed to c o n s i s t of m i x t u r e s of n o r m a l paraffins and b r a n c h e d paraffins f r o m about twen-ty-five to ftftwen-ty-five c a r b o n a t o m s . M i c r o c r y s t a l l i n e wax is used in s o m e of the s p e c i a l applications of paraffin wax.
In the p a s t d e c a d e s cortsiderable work h a s been c a r r i e d out in Delft by W a t e r m a n and c o - w o r k e r s to study the d e s t r u c t i v e hydrogenatión of paraffin wax. The intention of t h e s e i n v e s t i -g a t o r s was to obtain a b e t t e r insi-ght in the " b e r -g i n i z a t i o n " p r o c e s s , which was applied by B e r g i u s ^ to naore co m p l i ca t e d n a a t e r i a l s such a s coal and t a r . The work in this t h e s i s can be s e e n a s a continuance of t h e s e e x p e r i m e n t s . Some fundam.ental contributions of the Delft's i n v e s t i g a t o r s a r e t h e r e -fore r e v i e w e d f i r s t . In 1930 it was proved that d e s t r u c t i v e hydrogenatión of paraffin wax was p o s s i b l e without the a d d i -tion of a c a t a l y s t 2. in 1935 the e x p e r i m e n t s w e r e continued ^ and the r e a c t i o n p r o d u c t s investigated by m e a n s of the s o -called ring a n a l y s i s , a at that t i m e newly-developed g r a p h i c a l s t a t i s t i c a l a n a l y s i s of h y d r o c a r b o n s "*. It was proved that the
n o n - c a t a l y t i c d e s t r u c t i v e hydrogenatión of paraffin wax at 450OC yields p r o d u c t s , which w e r e l e s s cyclic than those ob-tained by t h e r m a l cracking at the s a m e t e m p e r a t u r e . F u r t h e r it was found that the u s e of nickel on k i e s e l g u h r as a c a t a l y s t yields p r o d u c t s , which w e r e completely free from cyclic h y -d r o c a r b o n s . In 1953 further e x p e r i m e n t s w e r e c a r r i e -d out ^ in which the influence of different c a t a l y s t s was tested, e s p e -cially with r e s p e c t to the p r o p e r t i e s of the liquid r e a c t i o n p r o d u c t s . F r o m this work it was a l s o proved, that cyclization may be completely prevented by the combined action of hy-d r o g e n anhy-d hyhy-drogenatión c a t a l y s t s a s nickel on k i e s e l g u h r , M0S2 on active carbon and M0O3. With a s i l i c a a l u m i n a c a -t a l y s -t produc-ts w e r e ob-tained, which w e r e p a r -t l y cyclic in n a t u r e .
In 1953 the h i g h - p r e s s u r e equipment in Delft was extended with s e m i - t e c h n i c a l u n i t s , in which it was possible to work continuously. A, need was felt to r e p e a t the e x p e r i m e n t s with paraffin wax in t h e s e u n i t s . About this t i m e the h y d r o i s o m e r i z a t i o n of paraffin h y d r o c a r b o n s drew considerable a t t e n -tion, and so it was decided to study the h y d r o - i s o m e r i z a t i o n of paraffin wax and to investigate e s p e c i a l l y the p r o p e r t i e s of the r e a c t i o n p r o d u c t s , the action of different c a t a l y s t s and the effect of r e a c t i o n v a r i a b l e s on the p r o c e s s . In the p r e l i -m i n a r y e x p e r i -m e n t s the actions of two well-known c a t a l y s t s w e r e studied n a m e l y Pt-Si02-Al203 and Pt-A.l203-Cl.Ciapet-ta and Hunter ^ proved that low m o l e c u l a r weight paraffins a s n-hexane and n - o c t a n e , could be i s o m e r i z e d successfully with a Pt-Si02-Al203 catalyst in the p r e s e n c e of hydrogen; Good, Gibson and G r e e n s f e l d e r ^ , 8 r e p o r t e d the h y d r o - i s o m e r i z a t i o n of paraffin wax with the aid of platinum-containing c a t a l y s t s .
§ 2 . E x p e r i m e n t a l a. Catalyst preparation
I. P l a t i n u m on s i l i c a - a l u m i n a ^
A. solution of chloroplatinic acid in w a t e r was a d s o r b e d on c o m m e r c i a l silica-alunaina catalyst *). The added amount of H2PtCl6 6 H2O c o r r e s p o n d e d to 0.5 p e r cent by weight p l a t i -n u m based o-n d r y s i l i c a - a l u m i -n a . After dryi-ng the m a t e r i a l at lOOOC for 16 h o u r s , the catalyst was pelleted and the p e l -l e t s ( 3 x 3 mm) r e d u c e d in a hydrogen f-low at 58 0OC during 16 h o u r s .
*) The cracking catalyst was obtained from the Koninklijke/Shell-Laboratory, Amster-dam .
II. P l a t i n u m oxysulphide-alum.ina-combined halogen^ A.luminium. isppropylate ^° was hydrolized in boiling w a t e r and diluted h y d r o c h l o r i c acid added to the s u s p e n s i o n . A, c o l -loidal solution of platinum disulphide was p r e p a r e d b y p a s s i n g hydrogen sulphide through a solution of chloroplatinic acid in w a t e r . The r e s u l t i n g colloidal solution was thoroughly mixed with the aluminiumi hydroxide s u s p e n s i o n and the combined m i x t u r e oxidized with hydrogen peroxide. After e v a p o r a t i n g the w a t e r , the m a s s was d r i e d at 9 0°C during 14 h o u r s , h e a t -ed at 160°C during 12 hours and calcin-ed in an a i r s t r e a m at 600°C during 1.2 h o u r s . The r e s u l t i n g catalyst was broken and pieces of 34 mm dimensions s e l e c t e d for use in the e x p e r i -m e n t s . The catalyst contained 0.1 per cent platinu-m and 1.5 per cent combined CI *).
b. Paraffin wax
The feedstock consisted of c o m m e r c i a l white paraffin wax (Balikpapan) with a m o l e c u l a r weight range of 310-530. The a v e r a g e m o l e c u l a r weight of the wax was 375, the melting r a n g e 5 2 - 5 4 ° C , t h e boiling rangel60-250OC at 1 m m m e r c u r y , the density at 70OC 0.7719 and the r e f r a c t i v e index at 70oc
1.4305.
c. Apparatus
A simplified flow d i a g r a m of the s e m i t e c h n i c a l h i g h p r e s -s u r e unit i-s given in F i g . 1 (page 10).
The paraffin wax was molten, filtered and s t o r e d in a c a l i -b r a t e d feed-tank, which was kept at 7 0 ^ 0 . The liquid wax was charged to the f e e d - h e a t e r by a h i g h - p r e s s u r e d i s p l a c e m e n t pump. At the e n t r y of the f e e d h e a t e r the cycle g a s , c o n s i s t ing mainly of hydrogen, joined the paraffin feed. After p a s -sing the f e e d - h e a t e r the combined feed e n t e r e d the top of the r e a c t o r , a s t e e l tube with a length of 75 c m and i n t e r n a l d i a -m e t e r of 3.8 c -m . The r e a c t o r was heated e x t e r n a l l y by -m e a n s of e l e c t r i c heating w i r e s . In the middle of the r e a c t o r a c a t a -lyst bed of 25 c m height (about 300 ml of cata-lyst p i e c e s ) was placed and the r e m a i n i n g free space in the top and the bottom of the r e a c t o r was filled with p o r c e l a i n r i n g s . The r e a c t i o n product was cooled to 70^0 and s e p a r a t e d from^ the c^cle gas in a s e p a r a t o r , which was kept at 700C. The liquid p r o d u c t s w e r e collected in a bottle and the evolving dissolved gas was p a s s e d through a g a s - m e t e r . The cycle g a s was then cooled to about 2 0OC and light h y d r o c a r b o n s , if p r e s e n t , w e r e s e p
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RE«TOR < CO DLER 7Q*C-FEED-PUMP FEED Figure 1a r a t e d at r o o m - t e m p e r a t u r e in the second s e p a r a t o r . The condensed light h y d r o c a r b o n s w e r e collected in a bottle and the evolving dissolved g a s was p a s s e d through a g a s - m e t e r . The cycle g a s w a s then r e c i r c u l a t e d to the f e e d - h e a t e r by two gas c i r c u l a t i n g - p u m p s . When the density of the cycle gas b e c a m e too high owing to the p r e s e n c e of h y d r o c a r b o n g a s e s , a p a r t of the cycle g a s was vented and r e p l a c e d by hydrogen. All lines in contact with the paraffin wax and the r e a c t i o n p r o d u c t s w e r e heated to p r e v e n t solidification of the paraffin wax. The r e a c t i o n t e m p e r a t u r e was m e a s u r e d with an i r o n -constantan thermocouple placed in the catalyst bed. Other i m p o r t a n t t e m p e r a t u r e s of the unit w e r e a l s o m e a s u r e d and r e c o r d e d .
d. Procedure
After charging the catalyst to the r e a c t o r , the unit was brought to the r e a c t i o n p r e s s u r e with hydrogen and blown off in o r d e r to r e m o v e a i r f r o m the unit. This operation was r e peated. After p r e s s u r e testing of the unit, the d e s i r e d p r e s -s u r e , t e m p e r a t u r e , and hydrogen flow w e r e e -s t a b l i -s h e d . The feed-pump was s t a r t e d and paraffin wax was p a s s e d over the catalyst at the d e s i r e d r a t e . In the p r e - t e s t period the feed r a t e and t e m p e r a t u r e w e r e carefully adjusted. After r e m o v a l of the p r e t e s t period liquid product, the t e s t run was s t a r t ed. At the end of the t e s t run both the s e p a r a t o r s w e r e e m p tied again. The different t e s t runs w e r e c a r r i e d out s u c c e s -sively with the s a m e catalyst in the o r d e r a s mentioned in Table I.
e. Conditions
In Table I the conditions of the e x p e r i m e n t s a r e shown. It a p p e a r e d during the e x p e r i m e n t s that Pt-Si02-Al203 had a much s t r o n g e r splitting action than P t A l 2O3 CI. The e x p e -r i m e n t s e -r i e s No. I was t h e -r e f o -r e c a -r -r i e d out at much lowe-r t e m p e r a t u r e s than e x p e r i m e n t No. II. As 410°C is the lower limit for a vapour phase operation in the unit with the i n v e s -tigated wax, the e x p e r i m e n t s e r i e s No. I had to be c a r r i e d out in the liquid p h a s e . E x p e r i m e n t No. II was c a r r i e d out in the vapour p h a s e . The r e l a t i o n s h i p between the total p r e s s u r e (Pt), absolute t e m p e r a t u r e (T), weight hourly space velocity (a), g a s r a t e (b) and contact time (t) for the vapour phase o p -e r a t i o n , i s giv-en by th-e following formula
_ (982800)(P,)(E) ^ " (T)(a)(h + 2:^400)
Table I
Catalytic h y d r o t r e a t i n g of paraffin wax with Pt-Si02-Al203 and Pt-AlzOs-Cl c a t a l y s t s
E x p e r i m e n t s e r i e s No. I: 270 ml of .Pt-Si02-Al203 c a t a l y s t . Duration p r e - t e s t p e r i o d and t e s t r u n r e s p . : 5 h o u r s .
E x p e r i m e n t No. II: 300 nal of Pt-Al203-Cl c a t a l y s t . Duration p r e - t e s t period and t e s t r u n r e s p . : 2 h o u r s .
E x p e r -iment No. la lb Ic Id le If Ic' II T e m p e r -a t u r e OC 3 2 7 ± 4 321 t 2 299 ±2 290 ± 2 2 78 ± 2 261 ±2 301 ± 2 420 ± 2 P r e s s u r e a t m . (Pt) 30 30 30 30 30 30 30 50 Weight hourly s p a c e velocity k g / L / H r (a) 0.766 0.744 0.746 0.753 0.748 0.744 0.730 1.100 G a s r a t e 1 H2/Kg wax (b) 605 605 605 605 605 605 605 5,550 Contact t i m e seconds (t) 8.6 Molar r a t i o H2/wax 10 10 10 10 10 10 10 93 The p o r o s i t y of the catalyst bed (E) was about 0.75 and the a v e r a g e m o l e c u l a r weight of the paraffin wax (M) was 375.
f. Method of analysis
The r e a c t i o n p r o d u c t s w e r e investigated with r e s p e c t to t h e i r d e g r e e of b ra n ch in g, cracking and cyclization.
As the d e t e r m i n a t i o n of the d e g r e e of branching r e q u i r e s a product free from olefins and a r o m a t i c s , the following p r o -c e d u r e was followed.
The olefinic unsaturation of the r e a c t i o n p r o d u c t s was d e t e r -mined according to the modified Mcllhiney method
It a p p e a r e d that the p r o d u c t s w e r e p r a c t i c a l l y s a t u r a t e d . By m e a n s of the formolite r e a c t i o n ^^ it was proved that the r e -action products did not contain a r o m a t i c compounds. The p r o d u c t s were then distilled to 180OC and the r e s i d u e s h y d r o -genated in an autoclave (200°C, 200 a t m . , 1 hour, 20 p e r cent nickel on k i e s e l g u h r ) . T h i s was done to r e m o v e t r a c e s of non-s a t u r a t e d productnon-s and to obtain waterwhite p r o d u c t non-s . The hydrogenated r e s i d u e s and the s t a r t i n g m a t e r i a l w e r e then d i s t i l l e d in vacuum in an a p p a r a t u s with ground g l a s s joints. Use was made of a Claisen distillation head with a fractionating side a r m of 20 cm. The f r a c t i o n s obtained w e r e a n a -lysed for m o l e c u l a r weight, density, s u r f a c e tension and r e f r a c t i v e index. D e n s i t i e s at 70^0 w e r e d e t e r m i n e d in
pycnometers, molecular weights by measuring freezing-point
depressions in cyclohexane, refractive indices at 70°C with
an Abbe refractometer and surface tensions at 70OC
accord-ing to the raccord-ing method (apparatus of Cenco-du Nouy) ^^.
From these data the degree of branching in the fractions
was determined according to the specific
refraction-spec-ific parachor method as discussed in Chapter II. The mean
total number of rings per molecule was determined
accord-ing to the n-d-M method ^^ and the degree of crackaccord-ing
follow-ed from the distillation curves.
§ 3 . D i s c u s s i o n of r e s u l t s
In Fig. 2 and Fig. 3 the distillation curves of the reaction
products obtained with Pt-Si02-Al203 and Pt-Al203-Cl are
represented.
By comparing the curves in Fig. 2 and Fig. 3 and the reaction
temperatures used, it can be concluded that the Pt-Si02-Al203
catalyst has a much stronger splitting action than the
P t - A i p 3 - C l catalyst.
The average number of branchings per molecule in the r e s i
-dues are given in Fig. 4. It can be seen that the product,
ob-tained with Pt-Al203-Cl as a catalyst, is much more
branch-ed than the products obtainbranch-ed with Pt-Si02-Al203 as a
cata-lyst. Further it can be noted that only the cracked molecules
(molecular weight below 300) are branched, when
Pt-Si02-AI2O3 is used as a catalyst. With Pt-Al203-Cl as a catalyst,
both the residue and the cracked products are branched. It
can therefore be concluded that the investigated Pt-Si02-Al203
catalyst is less suitable for the hydro-isomerization of
par-affin wax, the hydrocracking reaction being too much
pro-nounced. It must however be mentioned, that the cracking
activity of the Pt-Si02-Al203 catalyst can be decreased
without harming its isomerization ability, by reducing the s u r
-face area of the silica-alumina component. This can for
example be accomplished by a treatment with superheated
steam ^^
As regards the cyclization reaction it was found, that this
reaction occurs to a limited extent only. The total number of
rings per average molecule (R^). a s determined according
to the n-d-M method, varied between 0.0-0.2 in the
hydro-genated distillation fractions.
From the above results it was therefore decided to use the
Pt-Al203-Cl catalyst in the further experiments.
« L ^ W E ^ T o * bb bU Ai HU yü
F i g u r e 2
Distillation c u r v e s of the r e a c t i o n p r o d u c t s obtained with the Pt-Si02-Al203 catalyst
500 400 ^ 300 0) ^ 200 3
1 100
n 1 Pi . ^ / / 1 r-/ / ^ /^ \l2C )3-f 1 — :i c • PA A RE) ^CT 1 — / :aLalyst > 1 RAFFIN WAX ION-PRODUCT20
40 60
80 100
weight %
F i g u r e 3Distillation curve of the r e a c t i o n product obtained with the Pt-Al203-Cl catalyst
10 UI o» c o S 8 .o o numbe r cul e en OIO , «E '• < Q . ' 2 2 -^ ~ )0 4 2 0 ^ . -• — ' 3 2 1 ' ^ ^ _ _ 2 9 S ! C 3 0 1 ^ — ^ 290'C • ^ \
\ 1
300 Pt-AI^Oj-CI catalyst Pt-Si02-Al203 catalyst 400 500 •Molecular weightFigure 4
Average number of branchings per molecule
in the distillation residues
C h a p t e r I I
DETERMINATION OF THE AVERAGE NUMBER OF BRANCHINGS P E R MOLECULE IN SATURATED,
SOLID HYDROCARBON MIXTURES *)
§ 1 . I n t r o d u c t i o n
The d e t e r m i n a t i o n of the d e g r e e of branching in oil f r a c -tions ( a v e r a g e n u m b e r of s i d e - c h a i n s p e r molecule) is one of the p r o b l e m s in oil a n a l y s i s that a r e not solved s a t i s f a c t o r y yet. Many a t t e m p t s have been made to c o r r e l a t e functions with the d e g r e e of branching, the m o s t succesfuU functions being the m a g n e t o - o p t i c a l r o t a t i o n and the specific p a r a c h o r . The study of the m a g n e t o - o p t i c a l r o t a t i o n was e s p e c i a l l y u n d e r t a k e n by W i e r s m a , W a t e r m a n , Westerdijk e n B r o e r s m a . A. r e c e n t d i s c u s s i o n of the usefullness of this function h a s been given by De Booys ^^ and the i n t e r e s t e d r e a d e r is r e f e r -r e d to this wo-rk.
The application of the specific p a r a c h o r a s a m e a s u r e of the d e g r e e of b r a n c h i n g was studied by W a t e r m a n and L e e n d e r t s e i^, who developed the wellknown specific r e f r a c t i o n -specific p a r a c h o r method. This method was intended for the investigation of s a t u r a t e d , liquid h y d r o c a r b o n m i x t u r e s , and included the m e a s u r e m e n t s of the density, the r e f r a c t i v e index and the surface tension of the oil at 20^0 and its m o l -e c u l a r w-eight. F o r th-e inv-estigation of th-e p a r t l y solid hy-d r o c a r b o n m i x t u r e s a s obtainehy-d in the e x p e r i m e n t s , the m e a s u r e m e n t of the physical constants had to be c a r r i e d out at an elevated t e m p e r a t u r e , 70OC being chosen. The original method was adjusted for this t e m p e r a t u r e .
§ 2 . T h e a d d i t i v i t y of t h e m o l e c u l a r r e f r a c t i o n a n d t h e m o l e c u l a r p a r a c h o r
L o r e n t z ^^ and L o r e n z ^^ defined the m o l e c u l a r r e f r a c t i o n a s
n 2 - 1 M n 2 -H 2 • d
*) Published work. S c h e n k , P . , Vervoom, A .B .H. , Waterman, H. I. , and Weber, A.B. R . , J.Inst.Petroleum, 42, 205-210, (1956).
w h e r e n = r e f r a c t i v e index, usually m e a s u r e d at 2 0OC for the s o d i u m - D - l i n e .
d = density of the liquid at the s a m e t e m p e r a t u r e ( g r a m s / m l ) .
M = m o l e c u l a r weight.
A c c o r d i n g to L o r e n t z and L o r e n z , the m o l e c u l a r r e f r a c tion i s an additive a t o m i c function, i . e . its value can be d e -r i v e d f-rom the m o l e c u l a -r s t -r u c t u -r e by s u m m a t i o n of the a t o m i c r e f r a c t i o n s .
Sugden 2° introduced the m o l e c u l a r p a r a c h o r p = _ d _ jy[
^ d - D • ^^^
w h e r e a = s u r f a c e tension ( d y n e s / c m )
d = density of the liquid, m e a s u r e d at the s a m e t e m -p e r a t u r e a s the s u r f a c e tension.
D = density of the vapour in e q u i l i b r i u m with the liquid under the conditions of m e a s u r e m e n t .
M = m o l e c u l a r weight.
According to Sugden the m o l e c u l a r pai'achor i s an a p p r o x i m a t e l y additive function. Mumford and P h i l l i p s ^^ i n v e s t i g a t -ed the additivity of the p a r a c h o r function and have found that the p a r a c h o r was not a s i m p l e additive function, but that the value of the function depends on the d e g r e e of b r a n c h i n g . They p r o p o s e d a negative c o r r e c t i o n to be applied for each b r a n c h i n g in a chain.
This different behaviour of t h e s e two functions, with r e spect to t h e i r additivity, was the s t a r t i n g point for the s p e -cific r e f r a c t i o n - s p e c i f i c p a r a c h o r method, which o r i g i n a l form is d i s c u s s e d below.
§ 3 . T h e s p e c i f i c r e f r a c t i o n - s p e c i f i c p a r a c h o r m e t h o d
W a t e r m a n and L e e n d e r t s e b a s e d t h e i r method on the fol-lowing s t a r t i n g points:
(1) The e x p e r i m e n t a l e v i d e n c e , that the m o l e c u l a r p a r a c h o r of s a t u r a t e d h y d r o c a r b o n s depends on t h e i r d e g r e e of branching.
(2) The a s s u m p t i o n that the m o l e c u l a r r e f r a c t i o n of s a t u -r a t e d h y d -r o c a -r b o n s i s p -r a c t i c a l l y independent of the d e g r e e of branching.
(3) The a s s u m p t i o n that s a t u r a t e d oils could be c o n s i d e r e d a s m i x t u r e s of n - a l k a n e s , i s o a l k a n e s , and m o n o - and p o l y - c y c l i c six carbon r i n g naphthenes with one alkyl group.
2 - 1 1
-(4) The use of the specific functions " .: . ^ and ^ , a s n2 -^ 2 d d ^ t h e s e a r e m o r e convenient for a g r a p h i c r e p r e s e n t a t i o n than the m o l e c u l a r functions.
The method c o n s i s t s of two s t e p s n a m e l y the d e t e r m i n a t i o n of the " t r u e " n u m b e r of r i n g s of the s a t u r a t e d oil fraction (R^-'') and the " a p p a r e n t " ring n u m b e r of the fraction (R.pP). DETERMINATION OF R T ' : The " t r u e " n u m b e r of r i n g s was d e t e r m i n e d a c c o r d i n g to the specific r e f r a c t i o n - m o l e c u l a r weight method ^. Use was made of a d i a g r a m in which calcu-lated specific r e f r a c t i o n s of s e v e r a l homologous s e r i e s of h y d r o c a r b o n s ( n - a l k a n e s , m o n o - c y c l i c and p o l y - c y c l i c naph-thenes) were plotted against m o l e c u l a r weight. The specific r e f r a c t i o n s w e r e calculated from the a t o m i c r e f r a c t i o n s of E i s e n l o h r (C = 2.418, H = 1.100); l a t e r ^^ these values w e r e c o r r e c t e d and the following a t o m i c r e f r a c t i o n s w e r e used (C = 2.400; H = 1.114). In fig. 5(a) the calculated lines of the n - a l k a n e s and the n - a l k y l c y c l o h e x a n e s a r e indicated. After m e a s u r i n g the value of n, d and M of the s a t u r a t e d oil f r a c -tion, the specific r e f r a c t i o n was calculated and plotted in the d i a g r a m . The a v e r a g e n u m b e r of r i n g s (Rj'') was then d e -t e r m i n e d by l i n e a r i n -t e r p o l a -t i o n be-tween -the calcula-ted c u r v e s . This r i n g n u m b e r was called the " t r u e " n u m b e r of r i n g s a s it was a s s u m e d that the specific r e f r a c t i o n of a hy-d r o c a r b o n was inhy-depenhy-dent of its hy-d e g r e e of branching.
DETERMINATION OF R-p^: The " a p p a r e n t " n u m b e r of r i n g s was d e t e r m i n e d from an analogous d i a g r a m , the specific r e -fraction being r e p l a c e d by the specific p a r a c h o r i^. Starting f r o m the atomic p a r a c h o r values of Mumford and P h i l l i p s (C = 9.0, H = 1 5 . 5 , the i n c r e m e n t for a six carbon r i n g = 0.8, and the i n c r e m e n t for t e r t i a r y carbon = - 3.0) the lines of the s a m e homologous s e r i e s of s a t u r a t e d h y d r o c a r b o n s w e r e calculated and plotted in the d i a g r a m . In fig. 5(b) the calculated lines of the n a l k a n e s and n a l k y l c y c l o h e x a n e s a r e i n -dicated. After d e t e r m i n i n g the values of the specific p a r a c h o r and the m o l e c u l a r weight of the fraction, the a v e r a g e r i n g -n u m b e r ( R T ^ ) was fou-nd by l i -n e a r i-nterpolatio-n betwee-n the c u r v e s .
T h i s r i n g n u m b e r was called the " a p p a r e n t " r i n g n u m b e r a s the p r e s e n c e of branched m o l e c u l e s in the fraction caused a too high ring n u m b e r .
The difference in ring n u m b e r ( R J P - R J ' ' ) gave an indica-tion r e g a r d i n g the d e g r e e of b r a n c h i n g in the oil investigated. It was derived that a difference of 0.1 ring c o r r e s p o n d e d to one branching in the m o l e c u l e .
03i50 Z O o < o: 11. u cc o UI o. l/l 03(00 03250 0.3200 12 11 10 Figure S(a)
SPECIFIC REFRACTION-MOLECULAR WEIGHT DIAGRAM
A-lines calculated from the atomic refractions of Eisenlohr (C = 2 . 4 1 8 , H = 1.100), both at 20OC; B-lines calculated from revised atomic refractions (C = 2 . 4 0 0 , H = 1 114)
both at 20°C a. O I o < IT < a. u u 0. 2SS0
Ï'
( c-t ^ 1K
V Ê 1N
r 10^m
Part of (/)< dtag ram
used in tht analysis » ^ . ,
N
dl^3
^ >^%^^^'4/J
. ^ ^ A
cJSbepjies :<,^ ^ ••J 2M7 2B52 6 5 1000 . M Figure 5(b)SPECIFIC PARACHOR-MOLECULAR WEIGHT DIAGRAM A-lines calculated from the atomic parachors of ^4umfo^d and Phillips
§ 4 . A d j u s t m e n t of t h e m e t h o d f o r 7 0 O C
In o r d e r to study the d e g r e e of branching in oils obtained by h y d r o - i s o m e r i z a t i o n of paraffin wax, L e e n d e r t s e ' s method was applied to t h e s e p r o d u c t s . However, the following adjust-m e n t s of the adjust-method w e r e n e c e s s a r y :
(1) A specific p a r a c h o r d i a g r a m and a specific r e f r a c t i o n d i a g r a m w e r e c o n s t r u c t e d for 70OC instead of 20°C. (2) The position of the c u r v e s in t h e s e d i a g r a m s was not
calculated f r o m a v e r a g e a t o m i c i n c r e m e n t s , but the c u r v e s r e p r e s e n t e x p e r i m e n t a l data of n - a l k a n e s and n - a l k y l c y c l o h e x a n e s at 70OC.
(3) The influence of chain b r a n c h i n g on the specific r e f r a c tion is too high to be neglected. T h i s effect was t h e r e -fore taken into account.
The a d j u s t m e n t s mentioned a r e d i s c u s s e d below.
(1) As the g r e a t e r p a r t of the investigated p r o d u c t s w e r e p a r t l y solid at r o o m t e m p e r a t u r e , m e a s u r e m e n t of the p h y s -i c a l constants had to be c a r r -i e d out at elevated t e m p e r a t u r e s , e . g . 70OC. However, the t e m p e r a t u r e dependence of the s p e -cific r e f r a c t i o n and the spe-cific p a r a c h o r is of such an o r d e r that d i a g r a m s valid at 70°C differ c o n s i d e r a b l y from dia-g r a m s valid at 20OC.
Table II shows data on specific r e f r a c t i o n and m o l e c u l a r r e -fraction and specific p a r a c h o r and m o l e c u l a r p a r a c h o r of s o m e p u r e h y d r o c a r b o n s . T h e s e values w e r e calculated from t a b l e s a s given by the API P r o j e c t 44 22 x h e d i a g r a m s used in this investigation w e r e c o n s t r u c t e d by plotting the specific r e f r a c t i o n s and specific p a r a c h o r s of the n a l k a n e s and n a l -kylcyclohexanes at 70°C against lOOO/M. This is shown in F i g . 5(a and b), where a l s o the lines valid at 20OC a r e drawn. F i g . 5(a) a l s o shows the d i a g r a m used by L e e n d e r t s e (atomic r e f r a c t i o n s of E i s e n l o h r ) and the d i a g r a m b a s e d on r e v i s e d a t o m i c r e f r a c t i o n s (van Nes and van Westen). Fig. 5(b) a l s o shows the d i a g r a m calculated by L e e n d e r t s e from the atomic p a r a c h o r s of Mumford and P h i l l i p s . The l i n e s of the n a l -k a n e s m u s t i n t e r s e c t the lines of the n-al-kylcyclohexanes when M is infinite or when lOOO/M = 0.
T h e s e limiting values of the specific r e f r a c t i o n and the specific p a r a c h o r may be calculated in the following way:
As the m o l e c u l a r r e f r a c t i o n is an additive function, the specific r e f r a c t i o n of an n a l k a n e C„H2ii+2 ^it'^ i'^^i'^ite m o l e -c u l a r weight must be equal to:
l i m i^RcH2 •^ 2RH ^ RcH2 n - ^ ~ 14.026n + 2.016 14.026 in which
Tabel II Compound M 1000 Speoiflc refraction 20° 0 70» 0 Molecular refraction 20° 0 70° C Specific parachor 20° 0 70° C Molecular parachor 20° C 70° C n-Heptane n-Octane n-Nocane n-Decane n-Undecane n-Dodeoone n-Trideoane n-Tetradecane n-Pentadecane n - Hexadecane n-Heptadecane n-Octadeoane n-Nonadeoana n-Eicosane n-Heptane 2-Methylhexane 3-Methylhexane 3-Ethy Ipentane 2,2-Dimetby Ipentane 2,3-Dimethylpentane 2,4-Dime thy Ipentane 3,3-Dimethy Ipentane 2,2,3 -Trimethylbutane n-Octane 2 - Methylheptane 3 - Methy Iheptane 4 - Methylheptane 3-Ethylhexane 2,2 -Dimethy Ihexane 2, S-Dimethylhexane 2,4-Dünethy Ihexane 2,5-Dimethylhexane 3,3-DimethylhexEUie 3,4-Dimethylhexane 2 • Methyl - 3 -ethy Ipentane 3 -Methyl - 3-ethylpentane 2,2,3- Trimethyïpentane 2,2,4-Trimethylpentane 2,3,3-Triniethylpentane 2,3,4-Trimethylpent€Uie 100-20 114-23 128-26 142-28 166-30 170-33 184-36 198-38 212-41 226-44 240-46 264-49 268-61 282-64 9-980 1 8-764 7-797 7-028 6-398 6-871 6-424 6-041 4-708 4-416 4-159 3-920 3-724 3-639 1 100-20 100-20 100-20 100-20 100-20 100-20 100-20 100-20 100-20 9-980 1 9-980 9-980 9-980 9-980 9-980 9-980 9-980 9-980 1 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 114-23 8-764 1 8-764 8-764 8-764 8-764 8-764 8-764 8-764 8-764 8-754 8-764 8-754 8-754 8-754 8-764 8-754 8-764 1 0-34482 0-34312 0-34186 0-34076 0-33990 0-33913 0-33864 0-33793 0-33751 0-33711 0-3367 0-3364 0-3361 0-3358 0-34482 0-34622 0-34302 0-34216 0-34648 0-34266 0-34651 0-34266 0-34306 0-34312 034346 0-34231 0-34246 0-34094 0-34364 0-34127 0-34267 0-34371 0-34161 0-34008 0-34000 0-33896 0-34078 034373 0-33935 0-34028 n-Alkanes 0-3469 • 0-3450 • 0-3434 • 0-3425 • 0-3416 • 0-3407 • 0-3401 • 0-3394 • 0-3390 • 0-3383 • 0-3382 • 0-3378 • 0-3376 • 0-3372 » Heptanes 0-3469 — .— — — — — Octanee 0-3450 — — — — — .— — — — — — .— — 34-660 39-192 43-842 48-481 63-127 67-764 62-412 67-039 71-690 76-333 80-96 86-60 90-26 94-89 34-76 • 39-41 • 44-04 • 48-73 • 63-38 » 68-03 • 62-70 • 67-33 • 72-01 • 76-60 * 81-32 • 86-97 • 90-65 • 96-27 • 3-106 3075 3-049 3-029 3013 3-000 2-988 2-977 2-969 2-964 2-957 2-952 2-947 2-942 3103 3073 3-047 3031 3-016 3-005 2-996 2-987 2-982 2-973 2-966 2-968 2-961 2-960 311-1 1 361-2 3910 431-0 470-9 611-0 560-9 590-6 630-6 671-1 711-0 751-3 791-3 831-2 1 34-660 34691 34-460 34-283 34-617 34-324 34-619 34-332 34374 — — — — — — — — 3-105 3-090 3-071 3-047 3-060 3-042 3070 3-036 3-018 3-103 3-079» 3-065 • 3-060 3 049 3036 • 3-057 • 3-027 • 3-003» 311-1 1 309-8 307-7 305-3 306-6 304-8 307-6 304-2 302-4 1 39-192 39-231 39-100 39-117 38-944 39-262 38-981 39130 39-280 39-009 38-846 38-838 38-717 38-925 39-262 38-762 38-868 — — — — — — — — — — — — — — — — 3-075 3-063 3-040 3-039 3-018 3-027 3-006 3-022 3-040 3-002 2-999 2-996 2-978 2-979 3-009 2-968 2-982 3-073 3-060 • 3-038 • 3 036 • 3018 • 3-027 • 3-005 • 3-022 • 3-045 3-000 • 3-0OI • 2-991 • 2-970' 2-971 • 3-005 2-962 • 2-979* 361-2 1 348-7 347-2 347-1 344-7 346-8 343-4 345-2 347-3 342-9 342-6 342-1 340-2 340-3 343-7 339-0 340-6 1 ci/cZoHexane . Methylci/c/ohexane . Ethylcj/cZohexane . n-PropyIcj/ctóhexane n-Butylcyctohexane n-Decyloc^c2ohexane 84-16 98-18 112-21 126-24 140-26 224-42 11-882 10-185 8-912 7-921 7-130 4-456 n-Al 0-32926 0-33106 0-32988 033016 0-33026 033043 kylcyciohea 0-3312 • 0-3324 • 0-3313* 0-3314* 0-3312* 0-3316* Ain£S 27-709 32-603 37-015 41-677 48-322 74-166 27-87 * 32-64 • 37-18* 41-84* 46-45 * 74-42 * 2-873 2-868 2-867 — — — 2-868 * 2-863 * 2-847 • — — — 241-8 1 281-8 320-6 — — — 310-9 361-0 390-8 431-2 471-4 511-8 562-3 592-6 633-4 673-2 713-2 766-3 795-1 8383 3109 308-6 • 3071 * 306-6 306-6 304-2* 306-3 • 303-3 * 300-9* 361-0 348-4 • 347-0 * 346-7 * 344-7 * 345 8 • 343-3 • 346-2 * 347-8 342-7 * 342-8 * 341-7 • 339-3 • 339-4 • 343-3 338-3* 340-3 * 241-4* 281-1 • 319-6* * Extrapolated values.
The calculation of the extrapolated values at 70° C was carried out in the followirLg way :
n-Alkanes
Specific parachor, No extrapolation was necessary as data on surface tension and density are known.
Specific refractiort. The refractive indices of n-Ci-n-Cj, and n-C,, are available an precise measurements at 20° and 25° C
(five decimals). The values a t 70° C were found by linear extrapolation and plotted, against the corresponding densities. A straight line was obtained and the values of the refractive indices of n-Cu-n-Cjo determined from this line.
Heptanes and Octanes
Specific parachor. The surface tensions are known at 70° C, As most of the densities are only known up to 50° or 60° C,
the densitiee a t 70° C were determined by linear extrapolation.
n-AlkyUiyc\ohcxanes
Specific parachor. The densities are known at 70° C. As the surface tensions are only known up to 60° C, the values a t
70° C were determined by linear extrapolation.
Specific refraction. The refractive indices at 70° C were determined by linear extrapolation of the values of the precise
measurements a t 20° and 25° C.
Owing to these extrapolations the position of the n-alkanes and n-alkylcyclohexanes lines in the diagrams (especially the specific parachor line of the n-alkylcyciohexanes) is not absolutely certain.
RcH2 ~ l^he a v e r a g e group contribution of the CHg group. RH = the a v e r a g e group contribution of an H - a t o m . The specific r e f r a c t i o n s of the n - a l k y l c y c l o h e x a n e s m u s t be constant and equal to
tiRcH2 = RcH2 14.026n 14 026
F r o m the data on the m o l e c u l a r r e f r a c t i o n of n-Cy - n-C2o at 70OC, it a p p e a r s that RCH2 ^^ equal to 4.655 so that the l i m -iting value of the specific r e f r a c t i o n at 70OC is equal to (4.655/14.026) = 0.3319.
At 20OC the value of RCH2 a p p e a r s to be 4.642 and the l i m -iting value of the specific r e f r a c t i o n 0.3310.
As the specific r e f r a c t i o n was d e t e r m i n e d with an a c c u r a c y f r o m one to two units in the fourth d e c i m a l , its t e m p e r a t u r e dependence in the t e m p e r a t u r e range 20O-70oc cannot be neglected.
F r o m the m o l e c u l a r p a r a c h o r data of nCy nC2o it a p -p e a r s that the a v e r a g e CH2 grou-p contribution at 70OC and at 20OC h a s a value of r e s p e c t i v e l y 40.4 and 40.0. The limiting values of the specific p a r a c h o r at 70O and 2 0 o c a r e t h e r e f o r e equal to (40.4/14.026) = 2.88 and (40.0/14.026) = 2.85, r e -spectively.
F r o m Table II it follows that the CH2 group contribution of the p a r a c h o r is not absolutely constant. Other i n v e s t i g a t o r s 23 have found that the CH2 contribution b e c o m e s g r e a t e r with i n c r e a s i n g m o l e c u l a r weight. The calculated limiting values may t h e r e f o r e be too low. As the specific p a r a c h o r was d e -termuned with an a c c u r a c y of six units in the third d e c i m a l , a l s o in this case the t e m p e r a t u r e dependence cannot be neg-lected.
(2) F r o m the values of the m o l e c u l a r r e f r a c t i o n and the m o l e c u l a r p a r a c h o r of n-C7-n-C2o at 70oc, a v e r a g e atomic con-t r i b u con-t i o n s of C and H can be d e r i v e d . Wicon-th con-these values icon-t would be possible to ca lc u la te , e . g . the position of the line of the n - a l k a n e s in the d i a g r a m s . As the constancy of the CH2 contribution of the p a r a c h o r i s disputable it is m o r e c o r r e c t to draw a line through the points r e p r e s e n t i n g the e x p e r i m e n t a l data.
(3) F r o m the m o l e c u l a r r e f r a c t i o n s of the heptanes and octanes at 20OC (Table II) it a p p e a r s that on the whole chain branching c a u s e s a l s o a lowering of the m o l e c u l a r r e f r a c t i o n . Counting the influence of a q u a t e r n a r y carbon a t o m as caused by two t e r t i a r y carbon a t o m s , it a p p e a r s that the a v e r a g e lowering of the m o l e c u l a r r e f r a c t i o n is 0.057 p e r branching for the h e p t a n e s , for the octanes this value is 0.089.
The d e t e r m i n e d difference in ring n u m b e r ( R P T - R ' ' 7 ) will
now be e x p r e s s e d in b r a n c h i n g s p e r m o l e c u l e . In F i g . 6 it will be derived that one branching in a n - a l k a n e c a u s e s a ring difference equal to 0.09 r i n g .
- M O L . WEIGHT
Figure 6
GRAPHICAL REPRESENTATION OF THE FORMULA FOR I L P ^
If Pv is the a v e r a g e lowering in m o l e c u l a r p a r a c h o r of a n - a l k a n e a s a r e s u l t of one branching and np i s the n u m b e r of b r a n c h i n g s in the nalkane that c a u s e s an a p p a r e n t ring n u m -b e r of one, it -b e c o m e s c l e a r from F i g . 6 that the following equations holds:
1
HpPv = PC„H2„,2 - (Pc„H2n + 7 ^CH2) " (1)
PciiH2n+2 ~ m o l e c u l a r p a r a c h o r of the n - a l k a n e .
PcnH2n ~ m o l e c u l a r p a r a c h o r of the n-alkylcyclohexane with the s a m e n u m b e r of carbon a t o m s as the n - a l k a n e .
PcH2 ~ the value of the CH2 p a r a c h o r group contribution. In view of the additivity of the p a r a c h o r function, one may w r i t e
^C2H2n+2 " ^ P H + Pr " Pc2H2n- (2)
where Pr = i n c r e m e n t of the m o l e c u l a r p a r a c h o r caused by the formation of a six c a r b o n r i n g naphthene with one alkyl group.
P H = p a r a c h o r value of one H - a t o m . Combining equations (1) and (2) y i e l d s :
npP, = 2 P H -P, -111 PcH2 o r
" P
2 P i Pr - 1/7 PcHz
F r o m the m o l e c u l a r p a r a c h o r data of n-Cy - n - C n at 70OC
it a p p e a r s that the a v e r a g e value of PCH2 in this r a n g e i s
4 0 . 1 . The value of 2 P H can be obtained by s u b t r a c t i n g n t i m e s
the value of PCH2 f r o m the value of Pc2H2n+2- ^^ doing this
it will a p p e a r that P H = 15.0. The a t o m i c p a r a c h o r value of C is a p p a r e n t l y PCH2 " 2 P H = 40.1 - 30.0 = 1 0 . 1 .
By c o m p a r i n g the m o l e c u l a r p a r a c h o r data of the i s o m e r i c h e p t a n e s and o c t a n e s with t h o s e of n - h e p t a n e and n - o c t a n e it a p p e a r s that in this r a n g e Py = 3.5. The value of P^ can be e v a l u a t e d by s u b t r a c t i n g n t i m e s PCH2 f r o m PcnH2n • F r o m the data on m e t h y l - and e t h y l c y c l o h e x a n e it a p p e a r s that P^ = - 0 . 5 . Substitution in equation (3) g i v e s : n - (2) ( 1 5 . 0 ) + 0.5 - ( 1 / 7 ) (40.1) _ np 3 ^ i.i o r one b r a n c h i n g in a n a l k a n e c a u s e s a lowering of 1/7.1 -0.14 r i n g in the specific p a r a c h o r d i a g r a m .
The s a m e d e r i v a t i o n can be applied for the specific r e f r a c -tion at 70OC, so that
2 R H - Rr - 1/7 RcH2 H R = 5 -• Jttv w h e r e R H . R r . ^ C H 2 a n d Ry a r e d e f i n e d i n t h e s a m e w a y a s f o r t h e p a r a c h o r . It c a n be c a l c u l a t e d f r o m T a b l e II t h a t a t 70OC R ^ = 1.085, Rr = - 0 . 0 0 8 , a n d R C H 2 = 4 . 6 5 5 . T h e v a l u e of Ry c a n n o t be e v a l u a t e d f o r 7 0 o c a s n o d a t a on t h e s p e c i f i c r e f r a c t i o n of t h e i s o m e r i c h e p t a n e s a n d o c t a n e s a r e a v a i l a b l e . It i s , h o w e v e r , p l a u s i b l e t h a t t h e v a l u e of Ry w i l l n o t v a r y m u c h w i t h t h e t e m p e r a t u r e . F r o m t h e m o l e c u l a r r e f r a c t i o n s of n i n e h e p t a n e s a n d s e v e n t e e n o c t a n e s ( T a b l e U) a t 20OC, i t a p p e a r s t h a t Ry = 0 . 0 7 3 . B y a p p r o x i m a t i o n one m a y w r i t e _ (2) ( 1 . 0 8 5 ) + 0.008 - ( 1 / 7 ) ( 4 . 6 5 5 ) _ nR - Q Q,^3 ^ u . / o r o n e b r a n c h i n g i n a n - a l k a n e c a u s e s a l o w e r i n g of 1 / 2 0 . 7 = 0 . 0 5 r i n g i n t h e s p e c i f i c r e f r a c t i o n d i a g r a m . T h e p r e s e n c e of o n e b r a n c h i n g i n a n - a l k a n e w i l l c a u s e t h e r e f o r e a r i n g dif-f e r e n c e odif-f 0.14 - 0 . 0 5 = 0.09 r i n g . T h e r e dif-f o r e , o w i n g t o t h e p r e s e n c e - o f e l e v e n b r a n c h i n g s in a n - a l k a n e one w i l l find a r i n g d i f f e r e n c e of o n e . D u e t o l a c k of d a t a in t h e h i g h e r m o l e c u l a r w e i g h t r a n g e , t h e d e r i v a t i o n m e n t i o n e d a b o v e w a s c a r r i e d o u t f o r t h e l o w e r m o l e c u l a r w e i g h t r a n g e . B y a p p l y i n g t h e m e t h o d t o t h e p r o d -u c t s it w a s a s s -u m e d t h a t t h e r e s -u l t of t h e d e r i v a t i o n ( e l e v e n b r a n c h i n g s f o r ( R P T R ' x ) 1) i s a l s o v a l i d f o r h i g h e r m o l -e c u l a r w -e i g h t s .
§ 5 . A c c u r a c y of t h e m e t h o d
The following physical constants w e r e m e a s u r e d : n, d, a, and M. The p r e c i s i o n of the m e a s u r e m e n t s was:
for n: ± 0.0002
for d: ± 0.0002 ( g / m l ) for 0: ± 0 . 2 ( d y n e s / c m ) for M: ± 2 p e r cent.
With t h e s e data the following calculation of e r r o r s can be c a r r i e d out: n' 2 _ 1 r e l a t i v e e r r o r in , , „ n'' + 2 r e l a t i v e e r r o r in d r e l a t i v e e r r o r in r = n-^ 1 1 0.04 p e r cent for n = 1.42 0.03 p e r cent for d == 0.77 g / m l 0.07 p e r cent, i . e . ± 0.0002 for r = 0.34 n2 + 2 d
At a value in the specific r e f r a c t i o n d i a g r a m of M = 200, this c o r r e s p o n d s with 0.03 ring
M = 300, this c o r r e s p o n d s with 0.04 r i n g M = 400, this c o r r e s p o n d s with 0.05 r i n g .
F o r the specific p a r a c h o r an analogous calculation can be c a r r i e d out: e r r o r in e r r o r in r e l a t i v e r e l a t i v e r e l a t i v e e r r o r in r e l a t i v e a 1 d 1 e r r o r in p = ^ 0.8 p e r cent for o = 25.0 d y n e s / c m 0.2 p e r cent for a = 25.0 d y n e s / c m 0.03 p e r cent for d = 0.77 g / m l 0.23 p e r cent, oiby a p p r o x i m a t i o n 0.2 "^ per cent. When p = 2.9 the absolute e r r o r will be 0.006. At a value in the specific p a r a c h o r d i a g r a m of
M = 2 00, this c o r r e s p o n d s with 0.05 r i n g M = 300, this c o r r e s p o n d s with 0.075 r i n g M = 400, this c o r r e s p o n d s with 0.10 r i n g .
Up to the p r e s e n t t i m e , the influence of an e r r o r in M was not d i s c u s s e d . An e r r o r in M c a u s e s an i n c o r r e c t r e a d i n g of the r i n g content in both the specific r e f r a c t i o n d i a g r a m and the specific p a r a c h o r d i a g r a m . In the calculation of the a v e r -age n u m b e r of b r a n c h i n g s , however, the value of the differ-ence in ring content ( R P T " R ' T ) was u s e d . F o r this r e a s o n the r e l a t i v e e r r o r in M plays no i m p o r t a n t r o l e in the d e t e r -mination of the n u m b e r of b r a n c h i n g s p e r m o l e c u l e .
T h i s is explained by the following e x a m p l e . A substance with a m o l e c u l a r weight of 200, a value of R'"T = 0.15 and R P T = 0.45 is c o n s i d e r e d . ( R P J - Wj) is then 0.30. If the r e l a t i v e e r r o r in M i s 2 p e r cent, M can have a value of 204 o r 196. F r o m the d i a g r a m s it can be r e a d , that for
M = 196 R ' x = 0.164 RPy = 0.459 RPj r R-^^ = 0.295 M = 204 R'-T = 0.133 RPj = 0.443 RPj - R ' T = 0.310 F o r this r e a s o n , the e r r o r in RP-p - R''^, a s a - r e s u l t of the i n a c c u r a c y of M, will be m a x i m a l 0.01 r i n g . F o r M = 300 ± 6 and M = 400 ± 8 the s a m e r e s u l t is obtained.
The e r r o r in R P J - R'^T will be higher when the value of
W-^ is v e r y low (the line of the n - a l k a n e s is sloping in the
d i a g r a m ) . As the p r o d u c t s had. a r i n g content Wj m o r e than 0.15, it is only n e c e s s a r y to c o n s i d e r the value of 0.01 r i n g . The following conclusions can be drawn:
The a c c u r a c y of RP-J- - R'-p is for: M = 200: 0.03 + 0.05 + 0.01 = 0.09 ring M = 300: 0.04 + 0.075 + 0.01 = 0.12 r i n g M = 400: 0.05 + 0.10 + 0.01 = 0.16 r i n g .
A s the p r o d u c t s have a m o l e c u l a r weight range of 300-400, the a v e r a g e a c c u r a c y of RP-p - R''-i- is 0.14 r i n g . The a v e r a g e a c c u r a c y in the n u m b e r of b r a n c h i n g s p e r molecule is t h e r e fore 0.14 X 11 = 1.5. It can be noted, however, that the a c -c u r a -c y m u s t be h i g h e r , a s the r i n g -content figures a r e r e a d f r o m a v e r a g e c u r v e s . T h e s e a v e r a g e c u r v e s w e r e obtained f r o m a s e r i e s of d i s t i l l a t i o n f r a c t i o n s of one product. A s an a p p r o x i m a t i o n it can be said that the a c c u r a c y of the method is one branching p e r m o l e c u l e .
C h a p t e r I I I
VAPOUR PHASE HYDRO-ISOMERIZATION OF PARAFFIN WAX WITH A Pt-Al203-Cl CATALYST. THE INFLUENCE
OF THE REACTION T E M P E R A T U R E , MOLAR RATIO Hz/WAX AND CONTACT TIME ON THE DEGREE OF
CRACKING, BRANCHING AND CYCLIZATION IN THE REACTION PRODUCTS *)
§ 1 . I n t r o d u c t i o n
In Chapter I a c o m p a r i s o n was made between the i s o m e r i -zation ability of a P t - S i O 2 - A I P 3 catalyst and a Pt-Al203-Cl c a t a l y s t . Pt-A.l203-Cl was chosen for f u r t h e r e x p e r i m e n t s and it was found that t h r e e r e a c t i o n s o c c u r r e d during the hy-d r o - i s o m e r i z a t i o n with this catalyst namely, i s o m e r i z a t i o n (chain branching), h y d r o c r a c k i n g and, to a m i n o r extent, cyclization. The d e g r e e of c r a c k i n g was found f r o m a d i s t i l lation c u r v e , the d e g r e e of branching in hydrogenated d i s t i l lation fractions was d e t e r m i n e d a c c o r d i n g to the specific r e -f r a c t i o n - s p e c i -f i c p a r a c h o r method a s d i s c u s s e d in C h a p t e r 11, and the a v e r a g e total n u m b e r of r i n g s p e r molecule in the f r a c t i o n s was d e t e r m i n e d a c c o r d i n g to the n - d - M method.
In this chapter further e x p e r i m e n t s with the Pt-Al203-Cl catalyst a r e d e s c r i b e d and the influence of the r e a c t i o n t e m -p e r a t u r e , contact t i m e and m o l a r r a t i o H2/wax is studied with r e s p e c t to the t h r e e s i m u l t a n e o u s r e a c t i o n s naentioned.
§ 2 . E x p e r i m e n t a l
The c a t a l y s t p r e p a r a t i o n , feedstock, a p p a r a t u s , e x p e r i -m e n t a l p r o c e d u r e and -method of a n a l y s i s a r e the s a -m e as d e s c r i b e d in § 2 of C h a p t e r I.
C o n d i t i o n s
In Table III the conditions of the e x p e r i m e n t s a r e shown.
*) Published work . S c h e n k , P . , Vervoom, A . B . H . , Waterman, H . I. , and Weber, A.B. R . , J.Inst.Petroleum, 4 2 , 210-216 (1956).
Table III
H y d r o - i s o m e r i z a t i o n of Paraffin Wax Catalyst: Pt-Al203-Cl
Catalyst volume: 300 ml
Duration p r e - t e s t p e r i o d and t e s t run: 4 hour
E x p e r i -m e n t no. Ti
Tz
Ts
T4 P i P 2 P 3 P 4 C l C2 C3 T e m p e r a -t u r e , OC 410 420 435 450 433 435 435 435 435 435 435 P r e s -s u r e A t m (Pt) 52 52 52 52 32 52 72 102 52 52 52 W e i g h t h o u r l y s p a c e v e l o c i t y k g / L / h r (a) 1.04 1.01 0.97 1.00 0.99 1.12 1.01 0.96 1.13 0.89 0.75 G a s r a t e 1 H z / k g (b) 5 , 2 6 0 5 , 3 1 0 5 , 4 4 0 5 , 1 5 0 3 . 2 1 0 4 , 7 2 0 7 , 2 5 0 1 0 , 9 1 0 3 , 5 3 0 3 , 6 6 0 3 , 4 6 0 C o n t a c t -t i m e s e c -o n d s (t) 10.1 10.2 10.2 10.2 10.3 10.1 10.1 10.1 13.3 16.4 2 0 . 5 M o l a r r a t i o H 2 / w a x 88 89 91 86 54 79 121 183 59 61 58 P a r t i a l p r e s s u r e of p a r a f f i n w a x (Atm) 0.58 0.58 • 0.56 0.60 0.58 0.65 0.59 0.56 0.87 0.83 0.88 § 3 . D i s c u s s i o n of t h e r e s u l t sa. The degree of cracking in the reaction products
Table IV shows d i s t i l l a t i o n data of the hydrogenated r e a c -tion p r o d u c t s and the s t a r t i n g m a t e r i a l .
By plotting the weight p e r c e n t a g e distilled against the a v e r a g e m o l e c u l a r weight of the fractions the d e g r e e of c r a c k -ing in the r e a c t i o n p r o d u c t s can be r e v e a l e d . F i g s . 7, 8, and 9 show the influence of t e m p e r a t u r e , r e a c t i o n p r e s s u r e , and contact time on the h y d r o c r a c k i n g r e a c t i o n . It a p p e a r s that longer contact t i m e s , lower m o l a r r a t i o s H2/wax, and higher t e m p e r a t u r e s favour h y d r o c r a c k i n g .
b. The degree of branching in the reaction products
The specific r e f r a c t i o n s and the specific p a r a c h o r s of the d i s t i l l a t i o n fractions a r e shown in Table IV and plotted a g a i n s t lOOO/M in F i g s . 10(a and b), l l ( a and b), and 12(a and b). The discontinuity in the c u r v e s at a m o l e c u l a r weight of about 300 (initial m o l e c u l a r weight of the s t a r t i n g m a t e r i a l = 310) is a r e s u l t of the p r e s e n c e of u n c o n v e r t e d wax in these f r a c t i o n s .
20 ^0 60 80 100
WEIGHTS
20 ÜO 60 80 100
" • • W E I G H T S
WEIGHT %
Figures 7, 8, and 9
INFLUENCE OF TEMPERATURE, MOLAR RATIO H2/WAX AND CONTACT TIME ON HYDROCRACKING G = paraffin wax
^9
T a b e l IV Experiment no. Paraffin wax T , T , T , T< P , P , P , P . C l c, c, Distillation Fraction no. 1 2 3 4 a 6 1 2 3 4 5 1 2 3 4 6 6 1 2 3 4 6 6 1 3 4 6 6 7 1 2 3 4 6 6 1 2 3 4 6 a 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 6 6 2 3 4 6 6 7 Weight, 5-6 15-7 17-7 20-6 16-9 23-3 1 6 4 19-0 16-8 19-3 29-6 12-7 15-4 16-7 19-7 18-0 17-5 8-8 12-6 16-9 24-7 17-3 19-7 1-7 10-9 8-9 9-4 16-6 23-8 29-6 12-5 13-6 19-2 19-9 19-7 1 5 0 8-2 10-1 14-7 16-7 21 6 28-7 6-6 8-6 17-3 20-6 16-2 31-7 9-0 17-9 20-2 16-9 13-9 22-1 12-2 11-3 1 8 0 14-0 17-0 27-6 12-8 11-7 17-9 17-7 19-0 20-8 2-3 11-6 10-3 15-6 17-6 19-7 23-3 nl' 1 4269 1-4273 1-4288 1-4306 1-4328 1 4364 1-4241 1-4283 1-4299 1-4319 1-4364 1-4221 1-4280 14294 1-4310 1-4329 1-4363 1-4119 1-4268 1-4286 1-4296 1-4319 1-4366 1-4043 1-4142 1-4224 1-4276 1-4302 1-4331 1-4117 1-4260 1-4290 1-4304 1-4325 1-4361 1-4168 1-4263 1-4286 1-429T 1-4313 1-4361 1-4104 1-4244 1-4278 1-4294 1-4312 1-4347 1-4161 1-4272 1-4292 1-4313 1-4324 1-4349 1 4162 1-4271 1-4290 1-4308 1-4316 1-4349 1-4124 1 4260 1-4284 1-4301 1-4318 1-4351 1-4069 1-4206 1-4273 1-4291 1-4303 1-4344 Physical constants <J7 0-7642 0-7646 0-7675 0-7718 0-7760 0-7826 0-7699 0-7666 0-7698 0-7734 0-7807 0-7662 0-7663 0-7688 0-7722 0-7758 0-7828 0-7376 0-7641 0-7685 0-7702 0-7767 0-7819 0-7264 0-7433 0-7679 0-7676 0-7726 0-7784 0-7374 0-7638 0-7688 0-7718 0-7760 0-7827 0-7447 0-7648 0-7678 0-7699 0-7736 0-7806 0-7334 0-7606 0-7664 0-7697 0-7734 0-7800 0-7460 0-7666 0-7689 0-7732 0-7764 0-7804 0-7416 0-7646 0-7679 0-7719 0-7739 0-7798 0-7375 0-7639 0-7689 0-7712 0-7745 0-7806 0-7276 0-7646 0-7671 0-7708 0-7732 0-7801 M 3 1 5 3 2 6 3 4 0 3 6 2 3 9 6 4 6 7 2 8 7 3 4 7 3 5 5 3 6 6 4 5 9 2 7 1 3 4 1 3 4 9 3 7 6 3 9 2 4 6 0 193 3 0 3 314 336 3 7 3 4 0 6 184 2 0 7 2 6 1 2 9 8 344 3 9 8 194 274 3 2 6 3 5 2 3 8 1 4 2 0 2 2 0 3 0 6 3 2 7 3 4 5 376 4 2 6 197 2 9 6 3 2 2 3 4 8 3 7 7 4 1 8 2 2 8 3 1 7 3 4 0 3 6 8 4 0 1 4 3 2 2 2 6 2 9 8 3 2 6 3 4 8 3 7 1 4 1 6 2 1 8 2 9 4 3 2 1 340 3 6 6 3 9 9 189 2 3 8 3 1 2 3 2 6 3 6 3 3 6 2 o " 25-3 25-4 26-8 26-1 26-6 27-0 24-8 25-6 25-8 26-3 26-8 24-0 25-4 26-6 26-9 26-2 26-5 21-8 24-6 24-9 26-2 25-6 25-9 20-2 22-0 23-2 23-9 24-6 26-0 21-2 2 4 0 24-3 25-1 25-3 26-7 22-2 24-3 24-9 25-4 25-5 25-8 21-4 24-1 24-8 25-4 25-6 26-0 22-8 24-7 25-6 26-8 25-6 25-8 22-2 24-7 25-1 25-4 25-6 25-9 21-6 2 4 3 26-0 26-0 25-4 25-7 20-1 22-9 24-3 24-6 26-1 26-6 Specific refraction 0-3369 0-3360 0-3358 0-3361 0-3362 0-3343 0-3369 0-3363 0-3355 0-3353 0-3345 0-3361 0-3357 0-3366 0-3352 0-3349 0-3342 0-3373 0-3362 0-3362 0-3361 03343 0-3341 0-3374 0-3363 0-3366 0-3349 0-3346 0-3339 0-3372 0-3356 0-3353 0 3350 0-3346 0-3341 0-3368 0-3362 0-3365 0-3363 0-3348 0-3343 0-3381 0-3368 0-3366 0-3362 0-3348 0-3343 0-3369 0-3366 0-3364 0-3360 0-3348 0-3343 0-3379 0-3369 0-3367 0-3362 0-3349 0-3346 0-3377 03364 0-3349 0-3360 0-3348 0-3343 0-3383 0-3368 0-3349 0-3345 0-3343 0-3341 Specific parachor 2935 2-936 2-937 2-929 2-928 2-913 2-937 2-931 2-922 2-928 2-914 2-927 2-930 2-926 2-921 2-916 2-898 2-929 2-912 2-907 2-909 2-900 2-886 2-923 2-914 2-896 2-881 2-880 2-873 2-910 2-898 2-888 2-900 2-890 2-877 2-916 2-903 2-909 2-916 2-906 2-887 2933 2-913 2-912 2-917 2-908 2-895 2933 2-912 2025 2-916 2-901 2-888 2-927 2-916 2-916 2-908 2-907 2-893 2-920 2-906 2-908 2-899 2-899 2-884 2-911 2-899 2-894 2-889 2-896 2-883 1000 'M 3-17 3-08 2-94 2-76 2-63 2-14 3-48 2-88 2-82 2-74 2-18 3-69 2-93 2-87 2-66 2-55 2-17 5-18 3-31 3-19 2-98 2-68 2-46 S-44 4-83 3-83 3-36 2-91 2-51 6-16 3-66 3 0 7 2-84 2-63 2-38 4-66 3-27 3-06 2-90 2-67 2-35 6-08 3-38 3-11 2-87 2-65 2-39 4-39 3-16 2-94 2-72 2-49 2-32 4-43 3-36 3-07 2-87 2-70 2-40 4-59 3-40 3-12 2-94 2-73 2-51 5-29 4-20 3-21 3-08 2-83 2-76 « r n-d-M analysis 0-01 - 0 - 0 4 - 0 - 0 4 , 0-00 0-08 0-oa 0-09 - 0 - 0 9 - 0 - 0 4 0-01 - 0 - 1 0 0 1 0 - 0 0 6 - 0 0 3 - 0 0 5 - 0 0 1 - 0 - 0 2 0 2 6 0 1 4 0-16 0-10 0-13 0-16 0-20 0-29 0-22 0-24 0 1 7 0-14 0-26 0-24 0-09 0-07 0-08 0-13 0-20 0-13 0-06 0-03 0-02 0-03 0-16 0-06 0-06 0-03 0-02 0-06 0-14 0-06 0-03 0-03 - 0 0 4 0-01 0-06 0-11 0-04 0-06 0-04 0-03 0 0 7 0-16 0-16 O i l 0-09 0 1 3 0-13 0-28 0-17 0 2 1 0-16 0-28
By linear interpolation between the lines of the n-alkanes
and the n-alkylcyclohexanes at several values of M, R''^ and
RPj were determined for each experiment and the average
number of branchings calculated by multiplying (R^x " R'^T)
by eleven. This is shown in Figs. 13(b, c, and d), 14(b, c,
and d), and 15(b, c, and d). It appears from Figs. 13(d),
14(d), and 15(d) that the application of higher temperatures
and lower molar ratios H2/wax (lower hydrogen partial p r e s
-sure) favour the isomerization reaction. However, in these
cases also the hydrocracking reaction becomes more p r o
-nounced. The application of longer contact times have little
influence on the isomerization, while hydrocracking is
in-creased.
c The degree of cyclization in the reaction products
In Chapter II it is stated that the specific refraction is
sensible for both rings and branchings. Therefore no
com-plete information about the cyclization reaction can be
ob-tained from Figs. 13(b), 14(b), and 15(b), where R^ is
shown for the experiments. However, the average number of
rings per molecule in an oil fraction can be calculated from
the values of n, d, and M ^^. These values are shown in
Table IV and plotted against M in Figs. 13(a), 14(a), and
15(a). By comparing the curves of R'^T ^i^d R-j-, it appears
that on the whole R''T is greater than R T , which is another
indication that chain branching causes a small apparent
de-gree of cyclization.
In regard to the cyclization reaction it appears from Figs.
13(a), 14(a), and 15(a) that this reaction occurs to a limited
extent only. An increase of temperature and contact time
causes a higher degree of cyclization in the reaction
prod-ucts, while the application of higher p r e s s u r e s suppresses
the cyclization reaction.
d. Quantitative comparison of the degree of branching in the
reaction products
In order to select an optimal isomerization condition a
quantitative comparison has to be made of the degree of
branching in the reaction products.
Assuming that the reaction products consist entirely of
paraffins, the following calculation can be made for each
ex-periment.
In Figs. 7, 8, and 9 100 grams of product is considered and
the molecular weight range 300-400 (main part of the products)
divided into small intervals. For each interval the c o r r e
-Figures 10(a) and (b) . INFLUENCE OF CONTACT TIME
Specific refraction and specific parachor of the fractions
Figures 11(a) and (b)
INFLUENCE OF MOLAR RATIO H2/WAX Specific refraction and specific parachor of the fractions
sponding quantity ( g r a m s ) is r e a d and the n u m b e r of m o l s of an i n t e r v a l (N) is calculated by dividing this quantity by the a v e r a g e m o l e c u l a r weight of the i n t e r v a l . In F i g s . 13(d), 14(d), and 15(d) the a v e r a g e n u m b e r of b r a n c h i n g s p e r mol (or the n u m b e r of g r a m a t o m s t e r t i a r y carbon p e r mol) i s r e a d for each m o l e c u l a r weight of the i n t e r v a l s (V). The product (N) (V) is the n u m b e r of g r a m a t o m s t e r t i a r y c a r b o n in an i n t e r v a l and s u m m a t i o n of t h e s e i n t e r v a l values M = 400
Z (N) (V) yields the n u m b e r of g r a m a t o m s t e r t i a r y M - 300
c a r b o n in the m o l e c u l a r weight range 3 00400. A. b e t t e r p i c -t u r e is ob-tained if 1410 g of produc-t is c o n s i d e r e d ins-tead of 100 g, for it can be calculated from the distillation curve of the paraffin wax, that 141 Og of paraffin wax contain 100 g r a m
M = 400
a t o m s of carbon. The values of Z (N) (V) (14.1) a r e M = 300
t h e r e f o r e the n u m b e r s of g r a m a t o m s of t e r t i a r y carbon in the r a n g e M = 300-400, obtained from a quantity of paraffin wax which contains 100 g r a m a t o m s of carbon.
Figures 12(a) and (b)
INFLUENCE OF REACTION TEMPERATURE Specific refraction and specific parachor of the fractions
Table V shows the r e s u l t s of this calculation and the a b s o -lute e r r o r s . It was a s s u m e d that the e r r o r in V is one branching p e r mol (see Chapter II). The e r r o r in N is about 2 p e r cent and can be neglected.
^ M «»
Figures 13, 14, and 15
is defined a s the weight p e r c e n t a g e of the product with a m o l e c u l a r weight below 300.
If a m a x i m a l i s o m e r i z a t i o n and a c r a c k i n g l o s s below 20 p e r cent is demanded, it a p p e a r s from Table V that the e x -p e r i m e n t s no. T3, P2, and Ci a r e o-ptimal conditions in the investigated s e r i e s . Table V E x p e r i m e n t no. P a r a f f i n wax T i T 2 T 3 T 4 P i P 2 P 3 P 4 C l C2 C3 C r a c k e d m a t e r i a l , % 9 9 16 39 27 11 11 11 18 21 29 M = 400 S (N) (V) (14 M = 300 1 ± 3 2 ± 3 4 ± 3 9 ± 3 -14 ± 3 9 ± 3 7 ± 3 6 ± 3 10 i 3 11 ± 3 -1)
