presulfiding

8/4/2019 Presulfiding

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Chemistry an d Technology o f Fuels and O ils . Ibl . 34. No. 6. 19 98

P R E S U L F I D i] q G O F H Y D R O T R E AT I N G C ATA LY ST B Y E L E M E N TA LS U L F U R O U T S ID E O F T H E R E A C T O R

R. K. Nasirov, S .A . Dianova, N .A. Ko val 'chuk,and L R. Nasi rov U D C 6 6 5 . 6 5 8 . 2 . 0 9 7 . 3

T h e e c o l o g i c a l s a f e t y o f p e t r o l e u m p r o d u c t s i s t h e m o s t i m p o r t a n t f a c t o r i n t h e s t e a d y d e v e l o p m e n t op r o c e s s i n g i n d u s t r y. To l o w e r t h e c o n t e n t o f s u lf u r, n i t ro g e n , a n d a r o m a t i c h y d r o c a r b o n s i n p e t r o l e u m f u e l s t h e o f h y d r o g e n a t i n g p r o c e s se s h a v e b e e n s t e p p e d u p b y r e c o n s t r u c t i o n a n d m o d e r n i z a t i o n o f e x i s t in g u n i t s f o r h y da n d h y d r o c r a c k i n g , o n t h e o n e h a n d , a n d c o n s t r u c t i o n o f n e w o n e s , o n t h e o t h e r. A t t h e s a m e t i m e g r e a t c o n sh a s b e e n g i v e n t o d e v e l o p i n g a n d b r i n g i n g i n t o u s e n e w c a t a l y t ic s y s t e m s o f h i g h e f f e c t i v e n e s s b e c a u s e e vi m p r o v e m e n t s i n c a t a l y s t c h a r a c t e r i s t i c s i n c r e a s e t h e t o t a l p r o f i t a b i l i t y o f t h e p r o c e s s .

T h e m o s t w i d e s p r e a d i n d u s t r ia l c a t a l y st s f o r p e t r o l e u m d i s t i l l a te h y d r o t r e a t i n g a r e a l u m i n a - c o b a l t - m o la n d a l u m i n a - n i c k e l - m o l y b d e n u m sy s t e m s i n t h e f o r m o f o x i d e s . T h e i r o p t i m a l a c t i v i t y i s p r o v i d e d b y t o t a l S u l f i d i n g i n s u f f i c i e n c y r e s u l t s i n a d e c r e a s e i n t h e a c t i v i t y a n d s e l e c t iv i t y o f t h e c a t a l y st , r e d u c t i o n o f i t s s ei n c r e a s e i n t h e i n i t i a l t e m p e r a t u r e o f t h e p r o c e s s a n d t h e r e f o r e r e d u c t i o n o f th e i n t e r r e g e n e r a t i o n c y c l e .

T h e r e a r e f i v e i n d u s t r ia l p r o c e s s e s o f s u l f i d in g : u s i n g a g a s m i x t u r e o f h y d r o g e n s u l f i d e a n d h y d r o g e n ; a fa m i x t u r e o f fe e d a n d s u l f a t i n g a g e n t s ; e l e m e n t a l s u l fu r ; p r e i m p r e g n a t i o n w i t h o rg a n o s u l f u r c o m p o u n d s ( p r e so u t s i d e t h e t e c h n o l o g i c a l p l a n t .

T h e m o s t w e l l i n v e s t i g a t e d m e t h o d i s s u l f i d i n g b y h y d r o g e n s u lf i d e . Wi t h t h i s s u l f i d i n g a g e n t , t h e c a t a l yis e x c l u d e d . L o n g p r o c e s s i n g i n t h e a t m o s p h e r e o f h y d r o g e n , h o w e v e r, r e s u l t s i n o v e r r e d u c t i o n o f it s a c ti v e c o ma n d d e c r e a s e s i t s h y d r o d e s u l f u r i z a t io n a c t iv i ty. S u l f i d i n g i n t h e g a s p h a s e p r o c e e d s m u c h m o r e r a p i d l y t h al i q u i d p h a s e b u t i s a c c o m p a n i e d b y lo c a l o v e r h e a t i n g d u e t o t h e l o w h e a t c a p a c i t y o f th e g a s a n d h i g h e x o t h e rt h e r e a c t i o n . L o c a l o v e r h e a t i n g a n d d e f i c it o f h y d r o g e n s u l f id e m a y r e s u l t i n c a t a l y s t s p o i l in g . M o r e o v e r, hs u l f i d e is r e m a r k a b l e f o r i ts h i g h t o x i c i t y a n d p u n g e n t u n p l e a s a n t s m e l l . I n i n d u s t r y t h i s m e t h o d i s g e n e r a l l y uU S A .

S u l f i d i n g i n t h e l i q u i d p h a s e b y a f e e d s t o c k i s m o r e w i d e s p r e a d i n J a p a n , a n d t h a t b y a m i x t u r e o f a fs u l f u r i n g a g e n t s - i n t h e W e s t a n d t h e U S A . T h e r e i s n o p o s s i b il i t y t o a c h i e v e t o t a l s u l f i d i n g b y n o n r e f i n e d o i l di n t h i s c a s e t h e c a t a l y s t is c o k e d . T h e p r o c e s s o f s u l f i d i n g b y a f e e d s t o c k m a y b e r e c o m m e n d e d a t l o w t e m po n l y. I t t a k e s a l o n g t i m e t o r e a l i z e t h i s p r o c e s s i n i n d u s t ry.

E x p e r i e n c e i n h y d r o t r e a t i n g p la n t s h a s s h o w n t h a t c a t a l ys t s s u l f i d e d b y a f e e d s t o c k w i t h a d d i t i o n o f a sa g e n t a r e m o r e a c t i v e t h a n t h o s e s u l f i d e d b y a f e e d o r a m i x t u r e o f h y d r o g e n s u l f i d e a n d h y d r o g e n . I n t h e fs u l f i d i n g i s m o s t l y p r o v i d e d b y s u l f u r o f a s u l f u r i n g a g e n t a d d e d a t a c o n c e n t r a t i o n i n a f e e d s t o c k o f I w t . %o rg a n i c c o m p o u n d s d e c o m p o s i n g a t l o w te m p e r a t u r e s h a v e b e e n c h o s e n a s s u l f u r i n g a g e n t s ( Ta b le 1 ).

C a r b o n d i s u l f i d e w a s u s e d f o r p r e s u l f i d i n g b e fo r e . I t i s q u i te d a n g e r o u s , h o w e v e r, f o r t h e e n v i r o n m e na p p l i c a t i o n i s r a t h e r l i m i t e d d e s p i t e o f it s h i g h s u l f u r c o n t e n t . M e r c a p t a n s a r e g o o d s u l f u r i n g a g e n t s , b u t t h e i ru n p l e a s a n t s m e l l h a s f o r c e d u s e r s t o l o o k f o r o t h e r v a r ia n t s . A t p r e s e n t d i m e t h y l s u l f i d e a n d d i m e t h y l d i s u

s u c c e s s f u l ly u s e d a s s u l f u r i n g a g e n t s .D i m e t h y l s u l f i d e , h o w e v e r, is d i f f ic u l t t o t r a n s p o r t a n d p i p e d u e t o i t s h i g h v o l a t i li t y, i n f l a m m a b i l i t y, a n d

s m e l l . T h e a d v a n t a g e s o f d i m e t h y l d i s u l f i d e a r e i t s l o w e r v a p o r p r e ss u r e , w h i c h r e d u c e s i t s c o n c e n t r a t i o n i n t h e a ta n d d e c r e a s e s t h e r i s k o f p o i s o n i n g t o p e r s o n n e l , a n d i t s l o w e r d e c o m p o s i t i o n t e m p e r a t u r e a n d h i g h e r f l a( 1 8 ~

O rg a n i c p o l y s u l f i d e s , s p e c i f i c a l l yd i - t e r t - n o n y l p o l y s u l f i d e ,a r e e f f e c t i v e p r e s u l f i d i n g a g e n t s , b u t i t i s v e r

O p e n - Ty p e J o i n t S t o c k C o m p a n y " S o y u z N e f t e E K o l o g i y a . " Tr a n s l a t e d f r o mK h i m i y a i Te k h n o l o g i y a To p l i v iM a s e i , No. 6 , pp . 19 - 22 , Nov em ber - Decem ber, 1998.

3 4 4 0 0 0 9 - 3 0 9 2 /9 8 / 3 4 0 6 - 0 34 4 5 2 0 . 0 0 @ 1 9 9 9 K l u w e r A c a d e n f i c / P l e n u m P u b l i s h e rs



TA B L E 1

] Tem perature, *CSulfur ing agent Content of sulfur, wt .% decompo si t ion [ presulfidin8

Carbon disulfide 84.2 175 240 - 260Dirnethy ldisulfide 68.1 200 250Dim ethylsu lfide 51.1 250 270n-Butylmeresptane 34.7 225 260Di-tert-non ylpolys ulfide 37.0 160 250

TABLE 2

Index

LG-I I /300-95

JSCOdessa

PetroleumR e f m e r yGO-70

CK)-30-7

L - 3 5 - I I I 3 0 0N o v o p o l o t s k -

n e f t e o r g -sintez

Hydrotreat in8 a t the uni tLC-24/7 LK-6u

JSC JSCUkrtatnef t Shimkent-

nef teorg-sintez

LK-6uM S E

Nefiegas

L C - 2 4 / 5JS C

M o s c o wPetroleumRefmery

C a ta l yt ic y s t e m G O - 7 0 A C M - M G O - 7 0 G P - 5 3 4 G K D - 2 0 20 0 - 3 0 - 7 G K D - 2 0 2 p I S - 6 8 s h G O - 7 0 G K D - 2 0 5

special (regenerated) GO - 117 GO -70agent ( regenerated) DT-005N

Feedstock characteristicsD e ns i t y a t 2 0 " C , k g / m s 7 3 8 7 3 4 8 3 6 8 3 7 8 4 3 8 4 9C o n t e n t o f s u lf ur , t . % 0 . 0 3 9 0 . 0 1 9 1 . 2 0 . 2 4 0 . 9 1 1 . 0

Distillation, *CIBP 87 83 189 210 204 16910~ 102 100 221 230 228 24050% 119 120 255 277 277 28490% 1 5 3 1 5 6 2 9 0 3 5 0 3 6 0 3 4 7EP 192 179 308 360 368 377

Product characteristicsContent of sulfur,

wt. % - - 0.0105 0.01 0.03 0.064ppm 0.26 0.23 . . . .

Process parameterspressure, M Pa 2.9 2.9 3.2 4.5 4.6 3.1

Tem perature, *C 320 330 367 350 355 357Feed stock space 5.2 5.0 3.0 4.0 3.4 2.5v d o d t y, h aHy drogen c ieh gas" 310 330 320 346 230feedstoc k, m3/m3Hy drogen concenVation, 91.5 89 72 79 86 80vol. %

expens ive to ge t su l fu r f rom th em [1] . The p rocess o f su l f id ing by these agen t s i s opera t ive ly checked and con t rTo exc lude ca ta lys t cok ing , th e p rocess t em pera tu re shou ld be l e s s than 3400C.

Ma ny pa ten t s o f the l a s t 15 yea rs have sugges ted d i ffe ren t ways to p resu l f ide the hydrop rocess ca ta lys t s outhe ca ta ly t i c r eac to r [2 - 10]. S ince 1986 more tha n 30 ,000 tons o f hydro t rea t ing ca ta lys t s were success fu l ly wh ich had bee n p resu l f ided ou t s ide the t echno log ica l un i t s accord ing to the Su l f i ca t me thod o f the f i rm Euroca t

In accord ance wi th tha t t echno logy, the ca ta lys t is impreg na ted by an o rgan ic po lysu l f ide comp ound and keh igh er t empera tu re . The amo unt o f su l fu r adsorbed by the ca ta lys t co r responds to the s to ich iomet r i c quan t i ty nto conver t the ac t ive compo nen t s in to the ac t ive fo rm of su l fide . The ac t ive meta l s (m olybdenu m, cobal t , n icke l ) ca ta lys t su l fided in such a way a re in th e fo rm of a s t ab le in te rmedia te oxysu l f ide .

Ac t iva t ion o f the p resu l f ided ca ta lys t i s rea l i zed us ing hydro gen in a ca ta ly t ic r eac to r a t 300-350~ In conto the usua l w ay o f su l f id ing ins ide the t echno log ica l un it , t h i s m e thod m akes i t poss ib le to ob ta in a ca ta lys t o fac t iv i ty, speeds up and s impl i f i e s b r ing ing a un i t in to opera t ion and does no t r equ i re add i t iona l am ounts o f s

345



3 0 0 ~ " ~ 7

250

150

100

2

//

0 2 4 6 8

Height o f the catalyst iayeg m.

Fig . 1 . Tem pera tu re p ro f il e 4 h a~er s t a r t o f su l f id ing : 1 ,2) in the f i rs t and second reactors , respect ively.

~ g s

3 2 0 3 3 0 3 4 0 3 5 0 3 6 0

Temperature, ~

F i g . 2 . I n f l u e n c e o f t e m p e r a t u r e o n f e e d s t o cc o n v e r s io n i n h y d m s u l f u r a t io n w i t h t h e c a t a l y st G O70: 1 ) su lf ided by e lem enta l su l fu r ins ide the reac to2) p resu l f ided by e lem enta l su l fu r ou t s ide the reac to

c o m p o u n d s . T h e p r o b l e m s o f d e v e l o p i n g a n d a p p l y i n g t h e p r e s u l f i d e d c a ta l y s ts h a v e b e e n t h o r o u g h l y d i s c u s16].

T h e p r o c e s s o f s u l f i d i n g h y d r o t r e a t i n g c a t a l y s t s b y e l e m e n t a l s u l f u r i s w i d e l y u s e d a t o i l p r o c e s s i n g pRuss ia . The re i s no d i sadv an tage in l~ren t in su l f id ing by hydroge n su l f ide o r a f eeds tock wi th add i t ion o f su l fu r iT h e r i s k o f f ir e a n d t o x i c i ty a re l o w e r i n t h i s c a s e a n d t h i s m e t h o d t ak e s l e ss t i m e a n d i s t e s s e x p e n s iv e . W h e n uop t imal cond i t ions th i s m e tho d makes i t poss ib le to ach ieve 100% su l f id ing , wh ich p rov ides h igh ac t iv i ty and good oproper t ies of th e cata lyst [ 17 - 20] .

In in dus tw 15 wt . % e leme nta l su l fu r fo r ca ta lys t su l f id ing i s charged in to the reac to r e i the r over the l aymix ing wi th the top l ayer. In th i s p rocess su l fu r occup ies some space , wh ich becom es f ree o f the ca ta lys t a ft e r su l freduces i ts cha rge in the reac to r and m ay resu l t in uneven pack ing o f the l ayer and the re fo re i t s non-op t im al con tafeeds tock ; wh en a gas - f iqn id mix tu re i s cha rged , the l iqu id feeds tock in f il t r a tes th roug h m ore open cha nne l s , c rleast res is tance to f low.

Th e t em pera tu re p ro fi l e o f the e lemen ta l su l fu r su l f id ing p rocess i s ve w complex . F igure 1 shows i t s changthe package o f a lum ina-n icke l -m olybdenu m and a lumina-coba l t -m olybdenum ca ta lyst i s su l f ided a t the L-24 /7 uJo in t S tock Com pany "~ lq izhegorodne~eorgs in tez '.

Indus t r i a l ca ta lyst s d i ffe r one f ro m ano th er no t on ly by the m ethod o f p roduc t ion bu t by the sup por t qucom pos i t ion , i t s t ex tu re charac te r is t i c s, an d the con ten t o f ac t ive com ponen t s and mod i fy ing add i t ives . Thus , w henthe ca ta lys t (base and aux i l i a ry ) packa ge as w e l l a s the me thod o f su l f id ing , the ind iv idua l charac te r i s ti c s o f the feehydro t rea t ing un i t s and the requ i rements o f the p roduc t s a re t aken in to cons ide ra tion .

Th e spec i f ic charac te ri s t i c s o f opera t ing the ca ta ly t ic sys tems have b een ex tens ive ly deve loped and inves t igElec t rogorsk Ins t itu te fo r Pe t ro leum Process ing (E l 1NP). Ca ta ly t i c packages o f domes t i c a lum ina-n icke l -m olybda lumina -coba l t -molybde num ca ta lyst s were charged in to the reac to r s fo r hydro t rea t ing gaso l ine and d iese l d i s tin u m b e r o f oi l p ro c e s s in g p l a n ts o f t h e f o rm e r U S S R . T h e r e s u l t s o f i n d u s t r i a l o p e r a t i o n o f c a t a l y t ic s y s t e m s s ue l e m e n t a l s u l f u r a c c o r d i n g t o th e E l I N P m e t h o d a r e s h o w n i n Ta b le 2 .

I n d u s t r i a l e x p e r i e n c e i n t h e o p e r a t i o n o f c a ta l y t ic s y s t e m s s u l f i d e d by e l e m e n t a l s u l f u r h a s s h o w n t h e i r a dover ind iv idua l ca ta lys t s , wi th respec t to the i r ac t iv i ty, se rv ice l i f e , and re l i ab i l i ty, bu t app l i ca t ion o f these syo i l p r o c e s s i n g u n i t s i n R u s s i a i s l im i t e d . A s t h e o r e t i c a l i n v e s t i g a ti o n s a n d l o n g - t e r m p i l o t t e s ts h a v e s h o wc o n n e c t e d , f i r s t o f a ll , w i t h d i f f i c u lt i e s in c o n t r o l l i n g t h e p r o c e s s o f s u l f i d i n g l a rg e a m o u n t s o f c a t a ly s t a s wl a c k o f t e c h n o l o g i c a l e q u i v a l e n c y b e t w e e n c a t a l y t i c p a c k a g e s a n d t h e i r c o m p o s i t i o n .

A s a r e s u lt , t h e p r o b l e m o f d e v e l o p i n g t h e m e t h o d o f p r e s u l fi d a t i o n o f a h y d r o t r e a t i n g c a t a ly s t b y e ls u l f u r o u ts i d e a c a t a l y ti c r e a c t o r h a s b e e n s e t up . T h i s w o u l d a l l o w u t i l i z i n g t h e o p e r a t i n g s p a c e o f t h e r e a c t o r

3 4 6



as poss ib le and reduc ing exo thermic e ffec t s dur ing ac t iva t ion by hydro gen due to even d is t r ibu t ion o f su l fca ta lys t pores , and i t s p re l imin aq , reac t ion wi th the ac t ive com pone nts resu l t ing in the format ion of oxysul f id rop in the ac t iva t ion tempera ture .

Wi th t he ab no r m a l beh av io r o f t he m e l t e d su l fu r i n m ind , w h ich can be e xp l a ine d b y t h e c hange i n t he mst ruc ture and mu tua l convers io n of i ts mo di f ica t ions because of hea t ing , the tempera ture range of the mel tedcontac t wi th th e ca ta lys t has been cho sen as 120 to 180"C. The ca ta lys t spec imen wi th the ca lcu la ted am oun t- f rom s to ich iom et r ic up to 70 wt . % in the ca talys t - was charged in to a f lask , deaera ted under vacuum, and a n i t rogen s t ream up to the ass igned tempera ture . The f lask was con s tan t ly ro ta ted for even d is tr ibu t ion of sucontac t o f the la t te r wi th the ca ta lys t should be long enough for i t s pene t ra t ion in to the ca talys t pores . Th ecooled in a n i t rogen s t ream. T his techn ology is a l so appl icab le to reg enera ted ca ta lys t s.

Th e ca ta lys t su l f ided in such a w ay inc ludes su l fur in quant i t i es g rea te r than s to ich iomet r ic . I t can be uea ta lys t -ac t iva tor charged in to the reac tor as a top layer. Charg ing the ca ta lys t -ac t iva tor wi th the necessary csu l fur in pores i s m ore promis ing tha n i t s par t ia l un loading a f te r regenera t ion and rep lac ing i t wi th the f resh

Pre su l f i d i ng t he a lu min a - n i ck e l - m o lybd enu m and a lumin a -c ob a l t -mo lybd en u m ca t a l y s t by e l emen tacont r ibu tes to a subs tan t ia l increase in the ca ta lys t s t rength , wh ich m akes i t poss ib le to reduce the leve l o fdur in g charg ing o f a hydro t rea t ing reac tor. Format ion o f smal l ca ta lys t par tic les resu lt s in a n increase in thed i ffe ren t ia l in the reac tor dur in g the process .

To confirm pyrophorici ty the presulf ided catalyst specimen with 30 % content of sulfur in the pores, w hich cooled down to the amb ient temperature, was blasted by air. The temperature in the m iddle of the layer was ch efimcfion of t ime w ith a thermocouple. It remain ed constant as long as 1 h.

Th e resu l t s o f ac t iv i ty tes t s have show n tha t a f te r the ac t iva t ion un der condi t ions equiva len t to those in by e lemen ta l su l fur ins ide the ca ta ly t ic reac tor accord ing to the p rev ious ly deve loped method a l l ca ta lys t s p rby e lemen ta l su l fur were charac te r ized by a comparable or h ig her ac t iv i ty in the reac t ions of hydrodesu l furates t resu lt s o f the indus t r ia l a lumina-cob a l t -molybden um hydro t rea t ing ca ta lys t GO-70 in the o x ide ( samplpresu l f ided ( sample 2) form are presen ted in F igure 2 . The concen t ra t ion of su l fur in the in i t i a l ca ta lys t o f Swas 10 wt . %, w hich was som ewha t h igh er than i t s s to ich iomet r ic amoun t . Su l fur charg ing in the case of ins ide the reac tor was the same.

The t i t ra t i on c on d i t i on s w e r e: h y d rogen p r e s su re 3 M Pa ; f e ed s tock space ve lo c it y 3 h t ; hyd rogen : f e200 m3/m3 (normal condi t ions) ; t empera ture 320 , 330 , 340 , 350 , 360~ The feeds tock used was a st ra igh t d ie

dens i t y 843 kg /m3 at 20~ dist i l la t ion, ~ IBP 179, 50% 286, 90% 360, EP 367; con tent of sulfur 1.2 wt. %.The condit ions of presutf iding and subsequent act ivat ion depend on the method of production (coprecipi

impregnation) , the texture character is t ics of the catalyst , the qual i tat ive and quanti tat ive conten t of act ive comp onas w ell as the support comp osi t ion. A catalyt ic system of high act ivi ty can be achieved only i f the individual characcatalysts are taken into considerat ion.

Th e m ethod o f presu l f ided ca ta lys t p roduct ion can be eas i ly rea l ized a t th e ex is t ing ca ta lys t p lan ts : ero ta t ing furnaces or appara tus for suppor t impregnat ing . Appl ica t ion o f the sa fes t su l fur ing agent - e lemen tashould be regarded as an ad vantage o f the process because th i s agen t i s nonvola t i l e , nonf lammable , nontomoreover, i s ne i ther scarce nor expens ive product (mos t o i l p rocess ing p lan ts a rc provided wi th Claus un i t s fproduct ion ; in 1989 i t s average re ta i l p r ice in the U SA was $78 .8 / ton) .

Elem enta l su l fur eas i ly pene t ra tes the ca ta lys t pores dur ing h ea t ing and remains there a f te r cooling . Theof su l fur incorpora ted depends on po re vo lume and co nten t o f ac t ive meta l s . The ca ta lys t p resu l f ided in suchnot pyrop hor ic and in cont ras t to mos t ca ta lys t s o f s imi la r na tu re does no t requi re pro tec t ion f rom the a i r.

Th e adv antages of appl ica t ion o f such ca ta lys t a re as fo l lows: sh or te r t ime o f ac t iva t ion ; h igh ca ta ly t iclower in i t i a l t empera ture o f the hydro t rea t ing process ; longer in te r reg enera t ion cyc le .

R E F E R E N C E S

1. Ha[lie Ha rman ,O i l a n d G a s J . , 20, No. 51, 69 - 74 (1982).2. U.S. Pat. 3,453,217.3. U.S. Pat. 356,91 2.4. U.S. Pat. 4,177,13 6.

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5. U.S . Pat. 4,530,91 7.6. U.S. Pat . 4 ,943,547.7. U.S. Pat . 5 ,041,404.8 . 1%F. Pat. 2,584,311 .9. R.E Pat . 2 ,680,704.

10. Pat . of Au str ia 81,308.11. J .H . W i l son and G Ber rebi ,Off-s i te Presuifiding o f Hydro processing Catalyst, Am .Che m. Sac . , Toron to Mee t ing ,

1988 .12. E Dufresne, G Berrebi , and J . H. W ilsonA N ew Way to Star tup Hydrocrackers , A m .Chem. Sac . , San Franc i sco

Meet ing , 1989 .13 . J .H . Wi l son .Innovat ions in O ff-s i te Catalyst Services , Am . InsLChem . Eng . , Spr ing Na t iona l Mee t ing , 1991 .14. M D e Wind, J . J. L. Heinerman, S. L. Lee, e t a l . , Oi l and G as J . , February 24,199 2, pp. 56 - 61.15. S. 1% M u r~ E. A. Carl is le , P. Dufresoe , e t a t , T heSulf icat Presu lf ided Catalyst Experience, A m .C h e m . S a c ., D e n v e r

Mee t ing , 1993 .16. J . G Welch, P. Paym er, and 1% E Skeel ly,O il an d Gas,] . , O ctob er 10, 1994, pp. 56 - 64.17 . US SR Inven to r ' s Cer t i f ica te 701 ,699 .18 . US SR Inven to r ' s Cer t i f ica te 1 ,069 ,415 .19 . US SR Inven to r ' s Cer t i f ica te 1 ,300 ,717 .20. G V. Isagul 'ants , A. A. Greish, V. M. Kogan, e t a l . ,Kinet. Katai.,30, No . 4, 1000 - 1003 (1988).

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