Hydrocracking and Hydrotreating - ACS Publications - American

3 Raflinate Hydrocracking with Palladium-NickelContaining Synthetic Mica-Montmorillonite Catalysts JOSEPH P. GIANNETTI and DONALD C. FISHER

a

Downloaded by NORTH CAROLINA STATE UNIV on May 3, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003

Gulf Research and Development Co., P. O. Drawer 2038, Pittsburgh, Penn. 15230

The demand for liquefied petroleum gas (LPG; consisting of propanes and butanes) is projected to increase rapidly in future years.(1) World consumption is dominated by the United States and Japan. Processing of natural gas accounts for the bulk of domestic LPG; however, natural gas production has leveled off forcing the LPG industry to examine other feedstock sources. Japan must look to other countries for future LPG supplies due to environmental and space limitations. An allied problem, especially in the United States, is the continuing need for isobutane to produce valuable alkylates for the gasoline pool. A recent publication(2) disclosed the use of a palladium— impregnated, nickel-exchanged synthetic mica-montmorillonite catalyst (Pd-Ni-SMM), a 2:1 layer lattice aluminosilicate clay, for the hydrocracking and hydroisomerization of various hydrocarbons including a raffinate fraction to predominately propane and butanes. The results showed that these SMM based catalysts exhibited hydrocracking and hydroisomerization activities greater than could be obtained with Pd-rare earth-zeolite or Pd-H— mordenite. It had earlier been shown that SMM had greater cracking activity than silica-alumina but less than Y zeolite. (_3) The greater activity for cracking over the silica-alumina may be due to the increased lability of the hydrogen atoms in SMM.(4) Our study was undertaken specifically to investigate the processing of a typical raffinate to produce either high yields of LPG or isobutane as well as to determine the octane improvement in the fraction due to hydroisomerization. A 0.7 wt % Pd-15 wt % Ni-SMM catalyst was used for all the experimentation. Experimental A l l u n i t s are expressed i n both the customary u n i t s as w e l l as the "SI" I n t e r n a t i o n a l System of U n i t s . The "SI" designated i s shown f i r s t followed by the customary u n i t s i n p a r e n t h e s i s . (a) Present Address - Alcoa Research L a b o r a t o r i e s , New Kensington, PA 15068

52

In Hydrocracking and Hydrotreating; Ward, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

3.

GiANNETTi

A N D FISHER

53

Raffinate Hydrocracking


Materials. The r a f f i n a t e used i n t h i s study was obtained from a commercial Gulf O i l Corporation r e f i n i n g run and used as received. The composition of t h i s r a f f i n a t e i s shown i n Table I . The 15 wt % Ni-exchanged SMM c a t a l y s t s were obtained from the Baroid D i v i s i o n of NL I n d u s t r i e s . The carbon d i s u l f i d e was obtained from F i s h e r S c i e n t i f i c while the palladium tetramined i n i t r a t e reagent (36.5 wt % palladium) was purchased from Matthey Bishop C o r p o r a t i o n . Hydrogen s u l f i d e was obtained from the Matheson Gas Company. A l l the chemical reagents were used as r e c e i v e d . Hydrogen, supplied by the A i r Reduction Company, was deoxygenated and d r i e d over Linde 13X molecular s i e v e s . C a t a l y s t P r e p a r a t i o n and Processing Procedure. The 15 wt % Ni-SMM c a t a l y s t was impregnated with the palladium tetramined i n i t r a t e reagent by the i n c i p i e n t wetness technique to r e s u l t i n the i n c o r p o r a t i o n of 0.7 wt % p a l l a d i u m . Since the 15 wt % nickel-exchanged SMM c a t a l y s t was obtained from the Baroid D i v i s i o n of NL I n d u s t r i e s , no exact d e t a i l e d synthesis was ob t a i n e d ; however, a t y p i c a l synthesis from our l a b o r a t o r i e s has been d e t a i l e d . ( 2 ) A l l c a t a l y s t s were e i t h e r reduced or s u l f i d e d p r i o r to use. Approximately 50 cm of c a t a l y s t d i l u t e d w i t h 50 cm quartz was used for each r u n . The r e d u c t i o n c o n s i s t e d of 1) t r e a t i n g the c a t a l y s t with 3.5 χ 1 0 kmol H2/hr (2.9 SCF H2/hr) at atmospheric pressure while heating to 538°C (1000 F) at a r a t e of 6 5 . 6 ° C / h r ( 1 5 0 ° F / h r ) , 2) h o l d i n g at 5 3 8 ° C ( 1 0 0 0 ° F ) with the hydrogen flow f o r 1 hour, and 3) c o o l i n g to room temperature with a small n i t r o g e n flow. The s u l f i d i n g c o n s i s t e d of 1) heating the c a t a l y s t to 3 1 6 ° C ( 6 0 0 ° F ) i n n i t r o g e n , 2) s u l f i d i n g for 3 hours at 3 1 6 ° C ( 6 0 0 ° F ) with 3.6 χ 10" kmol/hr (3 SCF/hr) of a 92% H2-8% H2S gas mix, and 3) c o o l i n g i n n i t r o g e n to room temperature. The Ni-SMM c a t a l y s t s received contained e i t h e r about 1 wt % or 0.6 wt % f l u o r i d e . Some i n i t i a l processing com parisons d i d not show one to be s i g n i f i c a n t l y d i f f e r e n t from the other. Thus, no separation of the runs by f l u o r i d e l e v e l ap peared necessary. Processing runs were conducted i n a fixed-bed automated u n i t employing a 2.54 cm (1-inch) ID r e a c t o r i n r o u n d - t h e - c l o c k operations. Operating c o n d i t i o n s were 316" to 399 C (600" to 7 5 0 ° F ) , 7,000 k i l o p a s c a l s : kPa (1,000 l b / s q i n gauge: p s i g ) , 1.2 to 2 l i q u i d hourly space v e l o c i t y (LHSV) defined as cm of hydro carbon feed per cm of c a t a l y s t per hour, and 5 hydrogen-tohydrocarbon mole r a t i o (to c a l c u l a t e t h i s r a t i o , the feed was assumed to have a molecular weight of 92). Temperatures were measured by thermocouples extending through the c a t a l y s t bed. S u l f u r , i n the form of carbon d i s u l f i d e , was added to the r a f f i n a t e to give the d e s i r e d s u l f u r l e v e l . The l i q u i d feed was combined with hydrogen, preheated, and passed downflow through the c a t a l y s t . The e f f l u e n t from the reactor entered a high pressure separator where a hydrogen-rich gas sample was taken. The hydrocarbon product from the separator flowed i n t o a 3

3

- 3

3

U

3

3


HYDROCRACKING AND HYDROTREATING

Table I RAFFINATE ANALYSIS


Component

Wt %

Isopentane

0.2

n-Pentane

0.2

Hexane Isomers

19.8

n-Hexane

14.6

Methylcyclopentane

4.6

Cyclohexane

0.4

Benzene

1-0

Heptane Isomers

31.5

n-Heptane

9.7

Dimethylcyclopentane

0.5

Cg and Heavier

17.5


3.

GiANNETTi

A N D FISHER


55


s t a b i l i z e r where a C4 and l i g h t e r gaseous product and a C5 and heavier l i q u i d product were taken. The gaseous products were metered and sampled, while the l i q u i d product was c o l l e c t e d , weighed, and sampled. Analyses. Hydrocarbon analyses for the gaseous products were made using a 1200 Varian gas chromatograph with a 30.5 m (100 f t ) support coated open tubular squalene c a p i l l a r y and a 21-104 Consolidated Electrodynamics Corp. mass spectrometer. T h i s combination a n a l y s i s was necessary i n order to a c c u r a t e l y determine both the hydrogen and hydrocarbon content of the gas as w e l l as a d e n s i t y . The l i q u i d samples only r e q u i r e d analyses by the c a p i l l a r y column gas chromatograph. Micro Research octane numbers were obtained using the s t a n dard CFR (Cooperative F u e l Research) knock r a t i n g u n i t . Results and D i s c u s s i o n Previous r e s u l t s ( 2 ) had shown that a Pd-Ni-SMM c a t a l y s t was e f f e c t i v e f o r hydrocracking hexane as w e l l as a r a f f i n a t e feed. Conclusions showed that t h i s c a t a l y s t system when c o n t a i n i n g two n i c k e l atoms per u n i t c e l l (15 wt % n i c k e l ) was approximately 15 times more a c t i v e than a P d - r a r e earth-Y z e o l i t e c a t a l y s t and 1.2 times more a c t i v e than Pd-H-mordenite. T h i s same c a t a l y s t system (0.7 wt % Pd-15 wt % Ni-SMM) was chosen for our r a f f i n a t e processing s t u d i e s . Comparison of S u l f u r - C o n t a i n i n g and S u l f u r - F r e e Systems. Our i n i t i a l experimentation was designed to show the e f f e c t s of a scheme c o n t a i n i n g l a r g e amounts of s u l f u r as opposed to a completely s u l f u r - f r e e system. This experimentation was p e r formed with a s u l f i d e d 0.7 wt % Pd-15 wt % Ni-SMM c a t a l y s t (hereafter r e f e r r e d to Pd-Ni-SMM c a t a l y s t ) using a r a f f i n a t e feed c o n t a i n i n g 1500 ppm s u l f u r and a hydrogen reduced Pd-Ni-SMM c a t a l y s t with a s u l f u r - f r e e feed. The LPG y i e l d s are presented i n F i g u r e 1 with the average product component d i s t r i b u t i o n s at 3 7 1 ° C ( 7 0 0 ° F ) presented i n Table I I . These r e s u l t s showed that the s u l f u r - c o n t a i n i n g system was more a c t i v e f o r hydrocracking but experienced aging e s p e c i a l l y at the elevated temperatures. The isobutane y i e l d was constant i n both systems r e s u l t i n g i n s i g n i f i c a n t l y higher 1 0 4 / ^ 4 and ÎC4/LPG volume r a t i o s i n the s u l f u r - f r e e system. Although converting more of the feed, the s u l f u r - c o n t a i n i n g system produced s i g n i f i c a n t l y l e s s C^ + C2 than the s u l f u r - f r e e system. Various Methods of I n c o r p o r a t i n g S u l f u r . The g e n e r a l l y poorer r e s u l t s f o r LPG from the s u l f u r - f r e e system i n d i c a t e d that s u l f u r should be incorporated at l e a s t somewhere i n the p r o c e s s i n g system. To determine whether best r e s u l t s are obtained with s u l f i d i n g o n l y , s u l f u r feed a d d i t i o n o n l y , or b o t h , a s e r i e s


HYDROCRACKING A N D H Y D R O T R E A T I N G

1

1

1

I

—ι

r - ••• 399 ° C

100

(750°F)

3* g

·-·

90

\

371 ° C ( 7 0 0 ° F)

Ο °

0

-

•

ΟΟ-ο °

343 ° C


( 6 5 0 ° F)

ι 0

ο

I

I

ι

I

100

200

ι 300

HOURS PROCESSING

Figure 1. Effect of sulfur in Pd-Ni-SMM raffinate hydrocracking. 7000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. Feed—O* ff^~ note; Φ, raffinate + 1500 ppm sulfur. Catalyst—O, reduced 0.7 wt % — 15 wt % Ni-SMM; · , sulfided 0.7 wt% -15wt% Nir-SMM. ra

Table I I EFFECT OF SULFUR IN Pd-Ni-SMM RAFFINATE HYDROCRACKING Average Product D i s t r i b u t i o n s at 371°C ( 7 0 0 ° F ) , 7,000 kPa (1,000 p s i g ) , 2 LHSV, 5 Hydrogen-toHydrocarbon Mole Ratio

Vol % Y i e l d Based on Feed

Component Methane + Ethane (Wt %)

Sulfur Containing

Sulfur Free

3.2

4.7

Propane

46.8

37.5

Isobutane

28.4

28.5

n-Butane

18.9

11.7

C5 and Heavier

27.0

37.2

C3/C4 Ratio

1.0

0.93

iC^/nC^ Ratio

1.5

2.4

i C / L P G Ratio

0.30

0.37

4


3.

GIANNETTI

57


A N D FISHER


of c a t a l y s t s was treated and t e s t e d . The r e s u l t s are presented i n Table I I I . The f i r s t two runs (A and B) have already been discussed (Figure 1, Table II) and show the e f f e c t of a s u l f u r f r e e system and a s u l f i d e d c a t a l y s t along w i t h s u l f u r doping of the feed. Run C shows that a reduced c a t a l y s t with s u l f u r i n the feed ( i n - s i t u s u l f i d i n g ) was g e n e r a l l y comparable to a s u l f i d e d c a t a l y s t with the feed s u l f u r (Run Β with compensation made f o r aging). F i n a l l y , a s u l f i d e d c a t a l y s t (Run D) with no feed s u l f u r , while a c t i v e , produced high C3 and C i + C2 y i e l d s . I t appears from t h i s that whether the c a t a l y s t was reduced or s u l f i d e d had l i t t l e e f f e c t on product d i s t r i b u t i o n i f s u l f u r was present i n the feed. E f f e c t of Feed S u l f u r L e v e l on S u l f i d e d C a t a l y s t s . The im portance of s u l f u r i n the feed l e d to examining v a r y i n g s u l f u r levels. P r i o r to t h i s i n v e s t i g a t i o n , a l l s u l f u r doping was at the 1500 ppm l e v e l . During t h i s i n v e s t i g a t i o n an extended run was made i n which the s u l f u r i n the feed was incorporated at 0 ppm, 75 ppm, 200 ppm, and f i n a l l y 500 ppm. The r e s u l t s are presented i n Figures 2, 3, and 4. Looking f i r s t at F i g u r e 2, i t can be seen that the e n t i r e product d i s t r i b u t i o n remained constant at a high 108 v o l % LPG l e v e l through the 200 ppm doping. When the s u l f u r l e v e l increased to 500 ppm, however, pronounced aging began. This aging was accompanied by a de crease i n C 3 , n C 4 , and C^ + C2 y i e l d s , and an increase i n 1C4 and C5+ y i e l d s . A c t u a l l y , i f one assumes that i C 4 i s the most v a l u a b l e hydrocracked product, the d i s t r i b u t i o n became more favorable as the c a t a l y s t aged. This i s more d r a m a t i c a l l y shown i n F i g u r e 3 where v a r i o u s product r a t i o s are presented. The increase i n 1C4 accompanied by decreases i n the nC4 and C3 y i e l d s brought about a more favorable C 3 / C 4 , i C 4 / n C 4 and 1C4/LPG r a t i o s . T h i s i n d i c a t e s that the LPG composition can probably be a l t e r e d with processing s e v e r i t y . Thus i f one wished to produce maximum per pass C 3 , high processing s e v e r i t y should be employed while i f 1C4 y i e l d i s to be maximized, a lower processing s e v e r i t y would be i n o r d e r . No mention has yet been made of the C 5 m a t e r i a l . Since the feed was e s s e n t i a l l y C 6 , the C 5 s were formed from h y d r o c r a c k i n g ; however, they have been included i n with the C 6 m a t e r i a l s i n c e they would not normally be separated out but would e i t h e r be r e c y c l e d with the C 6 for f u r t h e r h y d r o c r a c k i n g , o r , i n a oncethrough o p e r a t i o n , be perhaps added with the C 6 to the g a s o l i n e pool. One t h i n g that occurred to both the C 5 s formed and to the remaining C 6 s was that there was a high r a t i o of the branched isomers to t h e i r normal c o u n t e r p a r t s . These r e s u l t s are i n keeping with those of Swift and Black(_2) who showed that Pd-Ni-SMM c a t a l y s t s are very e f f e c t i v e f o r h y d r o i s o m e r i z a t i o n . F i g u r e 4 d e t a i l s the i C 5 / n C 5 and i C 5 / n C 6 r a t i o s . The i C 5 / n C 5 r a t i o was r e l a t i v e l y constant at about 2.4 i n the product while the iCfc/nCfc r a t i o increased from a feed l e v e l of 1.4 to between +

+

f

+

+

+

f

?



(1,000 F ) , No S u l f u r

(1,000 F ) , 1500 ppm S u l f u r 5.2

2.2

26.8

31.8

28.4 (33)

28.5

1C4

18.0

16.8

18.9 (20)

11.7

nC/,

107.8

99.8

94.1 (106)

77.7

T o t a l LPG

Volume % Y i e l d

p r i o r to aging.

63.0

51.2

(a) Numbers i n parenthesis estimated at i n i t i a l throughputs

(D) S u l f i d i n g (600 F ) , No S u l f u r

(C) Reduction

46.8 (53)

3.2 (2.6) U )

Ç3 37.5

2

4.7

Ci + C

Wt % Y i e l d

371°C (700°F), 7,000 kPa (1,000 p s i g ) , 2 LHSV 5 Hydrogen-to-Hydrocarbon Mole Ratio 0.7 Wt % Pd-15 Wt % Ni-SMM

(B) S u l f i d i n g (600 F ) , 1500 ppm S u l f u r

(A) Reduction

C a t a l y s t Treatment

Catalyst —

Conditions —

EFFECT OF VARIOUS MEANS OF INCORPORATING SULFUR ON HYDROCRACKING

Table I I I


5

+

14.1

22.9

27.0 (18)

37.2

c

ο >

§5

GiANNETTi


A N D FISHER

^•·· ·,·-···

I

* * " · " " · - - · & , VOL ?{|

i Ο-οΌθΌ-ΟΟ-Ο-Ο-αο-0-Ο-ΟΟ

AO-o-o-o 4 i C

n J 0

__ C D

5

+

V O L

*

VOL%

n C VOL%_| 4


Cj + CgWT%

J

ο >

ι

105 0 PPM S

I

' 75 PPM S 200

'

* \

200 PPM SI 500 PPM S ^

I

300

700

400

HOURS PROCESSING

Figure 2. Effect of sulfur level in product yields from hydro cracking. 371°C (700°F), 7,000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. 0.7 wt % Pd — 15 wt % Ni-SMM, sulfided.

O 0.4

329 °C ( 6 2 5 ° F),

329 °C ( 6 2 5 ° F),

318 ° C ( 6 0 5 ° F),

1.2 LHSV

1.2 LHSV

2 LHSV


g

9

20

9 •

C

3

50

O

i C

4 3

n

C

100

4 •

C

5

C^C =

+

2

150

200 HOURS

~

·

0.8 to 1.2 WT % T H R O U G H O U T

250

300

350

400

PROCESSING

Figure 6. Product distribution in hydrocracking for maximum isobutane yields. 7,000 kPa (1,000 psig), 5 hydrogen-to-hydrocarbon mole ratio, 200 ppm sulfur in feed. 0.7 wt % Pd — 15 wt % Ni-SMM, sulfided.

329 °C ( 6 2 5 ° F ) , 2 LHSV

318 °C (605 ° F ) . 1.2 LHSV

329 °C (625 ° F ) , 1.2 LHSV

150

200

250

300

350

400

HOURS PROCESSING

Figure 7. Product ratios in hydrocracking for maximum isobutane yields. 7,000 kPa (1,000 psig), 5 hydrogen-to-hydrocarbon mole ratio, 200 ppm sulfur in feed. 0.7 wt % Pd — 15 wt % Nir-SMM, sulfided.



GIANNETTT


A N D FISHER

329 ° C (625 ° F ) ,

329 °C (625 ° F ) ,

318 ° C (605 ° F ) ,

1.2 L H S V

1.2 LHSV

2 LHSV τ

τ-

1

—ι

1

r—

iCg/nCg, F E E D = 1.4

5.0

Ο — Ο

Ο Ο

Ο

Ο

O

4.0

3.0

iC /nC 5

~°

•

5

• •

• é

2.0

0

•

50

·

100

150

200

1

I

1

1_

250

300

350

400

HOURS PROCESSING

Figure 8. Isomer distributions in products from hydrocracking for maximum isobutane yields. 7,000 kPa (1,000 psig), 5 hydrogen-to-hydrocarbon mole ratio, 200 ppm sulfur in feed. 0.7 wt % Pd — 15 wt % Ni-SMM, sulfided.


64

HYDROCRACKING AND HYDROTREATING +

clear, was about 80 while the C6 feed was only 54. Thus, a significant upgrading of the normally liquid portion of the product over the feed was obtained. This C5 fraction could have application as a blending component to the gasoline pool. By process manipulations, it would be possible to alter the isobutane-C5 yield octane to meet specified needs. +

+

Acknowledgement


The authors would like to express their appreciation to Dr. Sun W. Chun of Gulf Research & Development Company for his interest and timely suggestions. Abstract High yields of LPG or isobutane and octane improvement of the C5+ fraction can be simultaneously obtained by hydrocracking raffinate over a palladium-impregnated, nickel-substituted synthetic mica-montmorillonite catalyst (0.7 wt % Pd-15 wt % Ni-SMM). A critical sulfur level of about 100 to 200 ppm in the feed is essential to combine the features of desired product yields and good aging characteristics. Processing conditions ranged from 316° to 339°C (600° to 750°F), 7,000 kilopascals (1,000 psig), 1.2 to 2.0 LHSV and 5 hydrogen-to-hydrocarbon mole ratio with the lower temperatures allowing the high isobutane yields and the higher temperatures maximizing the total LPG yields. No significant aging was observed over 20 days processing as the sulfur level in the feed was increased to 200 ppm. Literature Cited (1) Muse, T. P., Hydrocarbon Proc., (1974), 53, 5, 85. (2) Swift, H.E., and Black, E.R., Ind. Eng. Chem., Product Res. Develop., (1974), 13, 106. (3) NL Industries, Baroid Division Brochure Introducing Barasym SMM. (4) Hattori, H., Milliron, D. C., and Hightower, J. W., Division of Petroleum Chemists Inc., Preprints, 165th National Meeting of the American Chemical Society, Dallas, Texas, (April, 1973), Vol 18, pp 33-51.


Hydrocracking and Hydrotreating - ACS Publications - American

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