CA1298804C

CA1298804C - Cracking process

Info

Publication number: CA1298804C
Application number: CA000576216A
Authority: CA
Inventors: Fu M. Lee; Clifford M. Shiblom, Jr.
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1987-10-19
Filing date: 1988-08-31
Publication date: 1992-04-14
Anticipated expiration: 2009-04-14
Also published as: JPH05433B2; EP0312981A1; NO884617L; US4781816A; NO173789C; NO173789B; JPH01146989A; NO884617D0

Abstract

Abstract of the Disclosure A process for cracking hydrocarbon containing feed streams, which have an initial boiling point of at least 400°F and contain at least about 5 ppmw vanadium, is carried out in the presence of a catalyst composition comprising a physical mixture of (a) zeolite embedded in an inorganic refractory matrix material and (b) magnesium oxide on silica.

Description

lZ9880~

CRACXING PROCESS
Background of the Invention This invention relates to a catalytic cracking process. In another aspect, this invention relates to a process for cracking heavy oils.
Cracking catalysts comprising zeolite embedded in a matrix of inorganic refractory materials are known. Also the use of these cracking catalysts for cracking of hydrocarbon containing oils, such as gas oil, is known. Frequently, these known cracking catalysts exhibit conversion and selectivity problems when heavier feedstocks, such as topped crudes and hydrotreated residua, which also contain metal impurities, are employed. This invention is directed to the use of a cracking catalyst composition which exhibits improved cracking performance in processes for cracking heavy oils which contain vanadium compounds as impurities.
Summary of the Invention It is an object of this invention to provide a process for cracking hydrocarbon containing feedstocks, which contain vanadium compounds as impurities. It is another object of this invention, to provide a cracking process wherein a blend of an inorganic refractory material and a zeolite catalyst composition is employed. Other objects and advantages will become apparent from the detailed description and the - appended claims.
In accordance with this invention, a catalytic cracking process comprises the step of contacting in a cracking zone a hydrocarbon containing feed stream having an initial boiling point of at least 400F, measured at ~k ~Z98804 32303CA

about 0 psig, and containing at least about 5 ppmw vanadium, with a cracking catalyst composition comprising a physical mixture of (a) zeolite embedded in an inorganic refractory matrix material, and (b) at least one oxide of a metal selected from the group consisting of Be, Mg, Ca, Sr, Ba and La (preferably MgO) on a support material comprising silica, under such cracking conditions as to obtain at least one liquid hydrocarbon containing product stream (i.e., one or two or more than two product streams) having a lower initial boiling point and a higher API
gravity than said feed stream.
Preferably, the cracking process of this invention comprises the additional steps of removing said cracking catalyst composition from said cracking zone after it has been used in said cracking zone;
separating the thus removed cracking catalyst composition from gases and said at least one liquid product stream;
exposing at least a portion of the thus separated catalyst composition to flowing steam (for stripping of adhered liquids from the catalyst composition); and heating the thus steam-stripped cracking catalyst composition with a free oxygen containing gas, so as to substantizlly remove coke deposits from the catalyst composition, substantially convert vanadium compounds deposited thereon to vanadium oxide, and thus obtain a regenerated catalyst composition.
More preferably, the cracking process of this invention comprises the additional step of recycling at least a portion of the regenerated catalyst ~to which more preferably fresh, unused catalyst composition has been added so as to provide an equilibrium catalyst) to said cracking zone.
Detailed Description of the Invention Crackin~_Catalyst Composition The zeolite component of the cracking catalyst composition used in the process of this invention can be any natural or synthetic crystalline aluminosilicate zeolite which exhibits cracking activity.

1298804 323Q3C~

Non-limltlt~g examplQs of su.h 200lites are fallJasite, chabaæite~ morden~:Q~ offretite~ erioM:ite, ~eolon~ %eolite X~ zeolite Y, zeolite L, zeolite ZS~I~ flnd the like~ flnd mi~tures thereof. Additional examples of suitable zeolites are listed in U.S. Patent 4~158,621. It is within the scope of this invention to use zeolites from which a portion of Al has been removed f~om the crystalline framework, and/or which have been ion-exchanged with rare earth metal or ammonium or by other conventional ion-exchange methods. Preferably, a synthetic faujasite of the Y-type (zeolite Y), more preferably a rare earth-exchanged zeolite Y
(REY zeolite),-is employed as catalyst component (a).
The inorganic refractory matrix material in which the zeolite is embedded can be any suitable amorphous or crystalline refractory material, such as silica, alumina, stlica-alumina, aluminosilicates (e.g., clays), alumin~lm phosphate, and the like, and mixtures thereof.
Preferably, amorphous silica-alumina is used as matrix material, in particular one used in commercially available zeolite-containing cracking catalyst compositions.
The zeolite can be embedded in the inorganic refractory matrix material in any suitable manner so as to prepare cracking catalyst component (a). Preferably, a slurry of the zeolite in a liquid (more preferably in water) and a slurry of the matrix material ln a liquid (more preferably water) are mixed; the thus obtained dispersed zeolite/matrix mixture is separated by any suitable method (more preferably by filtration) from the liquid portion of the slurry mlxture;
the separated intimate zeolite/matrix mixture is at least partially dried (more preferably at about 100-200C) and then calcined (more preferably by hea-ting in air, at about 600-900C for about 1-5 hours). The æeolite/matrix mater;al can be ground and sieved during sny phase of the preparation (preferably after drying) so as -to obtain a material having a desired particle size range (preferably 10/40 mesh). The material can also be exposed to steam, e.g., at about 700-lS00F.
Catalyst component (a), i.e., the calcined intimate mixture of zeolite and matrix material (i.e., zeolite embedded in the inorganic refractory matrix material) generally has a BET/N2 surface area (ASTM) lZ98804 32303CA

D3037) in the range of from about 50 to about 800 m2/g, preferably from about lOO to about 400 m2/g. Generally, the weight ratio of zeolite to the matrix material is in the range of from about 1:30 to about 1:1, preferably from about 1:15 to about 1:3. A non-limiting example of a suitable commercial zeolite/matrix cracking catalyst composition is GX-30, described in Example 1.
Component ~b) of the cracking catalyst composition comprises at least one metal oxide selected from the group consisting of BeO, Mg~, CaO, SrO, BaO and La2O3, and a support material comprising silica.
Preferably, the metal oxide is MgO and the support material consists essentially of silica. More preferably, silica has a BET/N2 surface area of about 100-500 m2/g. Generally, the weight ratio of MgO to SiO2 is in the range of from about 0.1:1 to about 20:1, preferably from about 0.5:1 to about 5:1.
Component tb) can be prepared by any suitable means. Preferably a silica-containing material (preferably SiO2) is impregnated with a suitable magnesium compound dissolved in a suitable liquid (preferably water or an alcohol such as methanol), dried and calcined at conditions substantially the same as those described for cracking catalyst component (a), so as to substantially decompose the Mg compound to MgO.
Non-limiting examples of suitable Mg compounds are Mg(NO3)2, Mg(HCO3)2, Mg(HSO4)2, MgSO4, Mg formate, Mg acetate, Mg oxalate and other Mg carboxylates, and mixtures of two or more Mg compounds. Preferably Mg acetate is used for impregnating silica. The BET/N2 ~urface area (ASTM
D3037) of catalyst component (b) is generally in the range of from about 100 to about 500 m2/g.
Cracking catalyst components (a) and (b) can be mixed (blended) by any suitable method, such as dry-blending (presently preferred) in a suitable mechanical mixing/blending device; or blending of a slurry (e.g., in water) of component (a) with a slurry of component (b), followed by drying and calcining. The weight ratio of catalyst component (a) to catalyst component (b) generally is in the range of from about 1:2 to about 20..1, preferably in the range of from about 2:1 to about 8:1.
It is within the scope of this invention to have from about 0.1 to about 2.0, in particular from about 0.2 to about 0.7, weight-% V (as ~Z98804 32303CA

oxide) present on the catalyst composition~ in particular when said catalyst composition comprises regenerated catalyst composition (defined below) that has been used in a process for cracking vanadium-containing heavy oils. When such heavy oils are catalytically cracked, vanadium compounds from the feed are deposited on the catalyst, and these deposits are substantially converted to vanadi~n oxide during oxidative regeneration. It is understood that the above-recited vanadium contents are average values for the entire catalyst composition, including equilibrium catalyst composition (defined below), and it is most likely that component (b) contains a higher weight percentage of ~ than component (a).
Cracking Process The hydrocarbon containing feed stream for the process of this invention can be any feedstock containing at least 5 ppmw V (parts by weight of vanadium per million parts by weight of feed stream), preferably about 5-200 ppmw V, more preferably about 5-50 ppmw V, and having an initial boiling point (ASTM D 1160) in excess of about 400F, preferably boiling in the range of from about 400 to about 1300F, more preferably boiling in the range of from about 600 to about 1200F, all measured under atmospheric pressure conditions (about 0 psig = 1 atm). A
particularly preferred feed stream is a heavy oil, at least about 90 volume-% of which boils above 650F (at atmospheric pressure). The APl60 gravity (measured at 60F) of the feed generally is in the range of from about 5 to about 40, preferably from about 10 to about 30. Frequently these feedstocks also contain Ramsbottom carbon residue (ASTM D524;
generally about 0.1-20 weight-%), sulfur (generally about 0.1-5 weight-O , nitrogen (generally about 0.01 weight-O , and nickel (generally about 0.1-50 ppmw).
Non-limiting examples of suitable feedstocks are topped crudes (residua), distillation bottom fractions, heavy gas oils, heavy cycle oils, slurry oils (decant oils), hydrotreated residua (i.e., having been hydrotreated in the presence of a promoted hydrotreating catalyst, preferably a Ni, Co, Mo-promoted alumina catalyst), heavy liquid coal pyrolyzates, heavy liquid products from extraction of coal, heavy liquid products from liquefaction of coal, heavy liquid products from tar sand, ~Z98804 3~3C~

Sllflle o.il~ he~vy frnct:iolls of sllale oils~ nn~l the like. rre.sently most prererre~ fe~dstocks are hydrotrented resldllfl.
~ ny sllitnble reactor can be used for the cfltaIyst cracking process of this invention. Generally a fluidi7,ed-bed catalytic cracking (FCC) reflctor (preferably contflining one or two or more risers) or a moving bed catfllytic cracking reactor (e.g., a Thermofor catalytic cracker) is employed. Presently preferred is a FCC riser cracking unit.
Examples o~ such FCC crflcking units flre described in U.S. Pstents 4,377,470 flnd 4,424~116. The cracking catalyst composition that has been umlsed in the cracking process (commonly ca]led "spent: catalyst") contains deposits of coke and metals or compoMnds of met~ls (in pnrticular nickel and vanadium compounds). The spent catalyst is generfll~y removed from the cracking zone and then separated from formed gflSes and liquid products by flny conventiona] separat:ion means (e.g.~ in a cyclone), flS is described in the above-cited patents and also in "Petroleum Ref;ning" by James Tl. Gary and Glenn E. Handwerk, Marcel Dekker, Inc. 1975.
Adhered liquid oil is generally stripped from the spent catalys-t by flowing steam (preferably having fl temperature of about 700-1,500F). The steam-stripped catalyst is generally heated in a free oxygen-containing gas stream in the regenerfltion unit of the crflcking reflctor, as is shown in the above-cited references, so flS to produce a regenerated cfltalyst. Genera]ly, air is used as the free oxygen containing gas; flnd the temperflture of the cfltalyst during regeneration with air preferably is about llOO-1400F (:i.e., about 590-760C).
Substantially flll coke deposits are burned o~f and metal deposits (in particular vflnadium compounds) are flt leflst pflrtifllly converted to metal oxides during regeneration. Enough fresh~ ullllsed cracklng cfltfllyst is generally fldded to the regenernted crnck;ng cntfllyst, so flS to provlde fl so-called equilibrium catalyst o~ desirably high cracking act:ivity. ~t leflst a port:ion of t:he regenerflted catalyst~ prefernlly e~uilibrium catalyst, is generally recycled to the cracking reactor. Preferably the recycled regenerated cfltfllyst, preferflbly recycled equilibrium catalyst, is transported by means of a suitable lift gas stream (e.g., steam and/or lZ98804 32303CA

hydrogen and/or gaseous hydrocarbons) to the crackin~ reactor and introduced to the cracking zone (with or without the lift gas).
Specific operating conditions of the cracking operation depend greatly on the type of feed, the type and dimensions of the cracking reactor and the oil feed rate. Examples of operating conditions are described in the above-cited references and in many other publications.
In an ~CC operation, generally the weight ratio of catalyst composition to oil feed (i.e., hydrocarbon-containing feed) ranges from about 2:1 to about 10:1, the contact time between oil feed and catalyst is in the range of about 0.2 to about 3 seconds, and the cracking temperature is in the range of from about 800 to about 1200F. Generally steam is added with the oil feed to the FCC reactor so as to aid in the dispersion of the oil as droplets. Generally the weight ratio of steam to oil feed is in the range of from about 0.01:1 to about 0.5:1. Hydrogen gas can also be added to the cracking reactor; but presently H2 addition is not a preferred feature of this invention. Thus, added hydrogen gas should preferably be substantially absent from the cracking zone.
The separation of liquid products into various gaseous and liquid product fractions can be carried out by any conventional separation means, generally by fractional distillation. The most desirable product fraction is gasoline (ASTM boiling range: about 180-400F). Non-limiting examples of such separation schemes are shown in "Petroleum Refining" by James ~. Gary and Glenn E. Handwerk, cited above.
The following examples are presented to further illustrate the invention and are not to be considered unduly limiting the scope of this invention.
Example I
This example illustrates the preparation of several cracking catalyst compositions, their impregnation with vanadium, and the performance of these V-impregnated catalyst compositions in cracking tests (so as to simulate cracking performance of V contaminated equilibrium cracking catalysts). Composition A was prepared as follows.
59.5 grams of Grade 52 silica (provided by Davison Chemical Division of ~. R. Grace and Company, Baltimore, MD; surface area: 340 m2/g) were ~1~9~804 mi~ed with a solution of 7.9 grams of Mg(CH3CO2~2-4H2O in 150 cc methanol. The thus obtained mixture was dried on a hot plate (at about 210F), slowly heated to 900F in N2 (so as to decompose organic compounds), and then calcined in air at 1200F for about 1 hour. The calcined material (1.5 weight-% Mg as MgO on silica) was then impregnated with a solution of vanadium acetylacetonate, dried and calcined again (as described above), so as to form Composition AV comprising 0.5 weight-% V
(as oxide) and 1.5 weight-h Mg (as oxide) on SiO2.
Two parts by weight of Composition AV were dry-blended with 8 parts by weight of Composition C, a commercial zeolite-based cracking catalyst, GX-30 (provided by Davison Division of W. R. Grace and Company); surface area: 195 m2/g; pore volume: 0.34 cc/g; containing about 33 weight-~ alumina). This mixture of AV and C is labeled Composition ACV and is a simulated V-contaminated cracking catalyst composition.
Composition B was Grade 52 silica (without MgO), which was impregnated with 0.5 weight-% V, dried and calcined, as described above, so as to provide Composition BV. 2 parts by weight of Composition BV
were mixed (dry-blended) with 8 parts of commercial cracking Composition C (GX-30) so as to provide Composition BCV.
Composition C (commercial catalyst GX-30) was impregnated with 0.5 weight-% V, dried and calcined, as described above, so as to provide Composition CV.
Compositions ACV, BCV and CV were evaluated in microactivity cracking tests (MAT), substantially in accordance with ASTM D3907-80, employing a gas oil having a 700-900F boiling range (at atmospheric conditions) as feed. Cracking conditions were: cracking temperature of 950F; catalyst:oil weight ratio of 3:1; 5.0 g catalyst composition employed; 1.25 minute feed injection, followed by a 10 minute nitro~en purge; weight hourly space velocity of feed oil: 16 (g/g catalyst/hour).
All three catalyst compositions had been steam-treated at 1425F for 7 hours in a stream of 100b steam before the cracking tests were carried out. Test results are summarized in Table I.

Catalyst ~`able I BCV CV
Composition ~Invention)(Control) ~Control) Conversion (Wt-%) 51.9 43.4 47.8 Gasoline Yield (Wt-%) 37.4 32.7 34.4 Light Cycle Oil Yield (Wt-%) 17.9 16.4 17.2 Heavy Cycle Oil Yield twt-%) 30.2 40.3 35.2 Gas Yield (Wt-O 7.3 6.4 6.7 Coke Yield (Wt-Z) 4.4 3.9 4.9 Test results in Table 1 clearly show that Composition ACV (80 weight-% GX-30 + 20 weight-% V/MgO/SiO2) produced better cracking results (in terms of hiBher feed conversion and higher gasoline yield) than Composition BCV (80 weight-% GX-30 + 20 weight-% V/SiO2) and Composition CV (V/GX-30).
Example II
In this example, the effect of MgO/SiO2 on the cracking performance of a V-contaminated zeolite-containing cracking catalyst is compared with that of sepiolite (a clay comprising about 28 weight-% Mg, as disclosed in U.S. Patent 4,464,588, Table III).
Sepiolite was impregnated with about 0.5 weight-% V dried and calcined, essentially in accordance with the procedure described in Example I so as to provide Composition DV. 2 parts by weight of Composition DV were physically mixed (blended) with 8 parts by weight of Composition C (GX-30) so as to provide Composition DCV.

2~ Invention Compositions ACV and DCV were steam-treated (as described in Example 1) and then tested in MAT cracking tests, in accordance with the procedure described in Example 1. Test results are summarized in Table II.

Table II
Catalyst ACV DCV
Composition (Invention) (Control) Conversion (Wt-O 48.1 22.7 Gasoline Yield (Wt-b) 36.3 16.8 Lig~t Cycle Oil Yield (Wt-%) 18.3 11.4 Heavy Cycle Oil Yield (Wt-%) 33.6 65.9 Gas Yield (Wt-%) 8.7 3.9 Co~e Yield (Wt-%) 3.1 2.1 ~298804 32303CA
1~
Test results clearly show superior cracking performance (in terms of higher conversion, higher gasoline yield~ higher light cycle oil yield and lower heavy cycle oil yield) of Composition ACV ~80 weight-~GX-30 + 20 weight-% V/MgO/SiO2) versus Composition DCV (80 weight-% GX-30 + 20 weight-% V~Sepiolite).
Reasonable variations, modifications and adaptations for various usages and conditions can be made within the scope of the disclosure and the appended claims, without departing from the scope of this invention.

Claims

THAT WHICH IS CLAIMED IS

1. A catalytic cracking process comprising the step of contacting a hydrocarbon containing feed stream having an initial boiling point of at least 400°F, measured at about 0 psig, and containing at least about 5 ppmw vanadium with a catalyst composition comprising a physical mixture of (a) zeolite embedded in an inorganic refractory matrix material, and (b) magnesium oxide on a support material consisting essentially of silica, under such cracking conditions as to obtain at least one liquid hydrocarbon containing product stream having a lower initial boiling point and a higher API60 gravity than said feed stream;
wherein component (b) of said catalyst composition has been prepared by a method comprising the steps of impregnating SiO2 with a suitable magnesium compound dissolved in a suitable liquid, drying the thus impregnated SiO2 and calcining the dried, impregnated SiO2 under such conditions as to substantially convert said magnesium compound to MgO.

2. A process in accordance with claim I wherein said zeolite is selected from the group consisting of faujasite , chabazite, mordenite, offretite, erionite, Zeolon, zeolite X, zeolite Y, zeolite L, zeolite ZSM, and mixtures thereof; and said inorganic refractory matrix material is selected from the group consisting of silica, alumina, silica-alumina, aluminosilicates, aluminum phosphate and mixtures thereof.

3. A process in accordance with claim 2 wherein the weight ratio of said zeolite to said inorganic refractory matrix material is in the range of from about 1:3 to about 1:1, and the BET/N2 surface area of component (a) of said catalyst composition is in the range of from about 50 to about 800 m2/g.

4. A process in accordance with claim l wherein in component (b) of said catalyst composition the weight ratio of MgO to SiO2 is in the range of from about 0.1:1 to about 20:1.

5. A process in accordance with claim 4 wherein the surface area of said component (b) of said catalyst composition has a BET/N2 surface area in the range of from about 100 to about 500 m2/g.

6. A process in accordance with claim 1 wherein in said catalyst composition the weight ratio of component (a) to component (b) is in the range of from about 1:2 to about 20:1.

7. A process in accordance with claim 6 wherein said weight ratio of component (a) to component (b) is in the range of from about 2:1 to about 8:1.

8. A process in accordance with claim l wherein said cracking catalyst comprises about 0.1 to about 2.0 weight-% V as vanadium oxide.

9. A process in accordance with claim 1 wherein said feed stream contains about 5-200 ppmw V and has a boiling range of from about 400 to about 1300°F, measured about 0 psig.

10. A process in accordance with claim 9 wherein said feed stream has an API60 gravity in the range of from about 5 to about 40 and contains about 0.1-20 weight-% Ramsbottom carbon residue and about 0.1-5 weight-% sulfur.

11. A process in accordance with claim 9 wherein said feed stream is selected from the group consisting of residua, distillation bottom fractions, heavy gas oils, heavy cycle oils, slurry oils, hydrotreated residua, heavy liquid coal pyrolyzates, heavy liquid products from extraction of coal, heavy liquid products from liquefaction of coal, heavy liquid products from tar sand, shale oils and heavy fractions of shale oils.

12. A process in accordance with claim 1 wherein said contacting is carried out ln a fluidized-bed catalytic cracking reactor.

13. A process in accordance with claim 1 wherein said cracking conditions comprise a weight ratio of said catalyst composition to said hydrocarbon containing feed stream in the range of from about 2:1 to about 10:1, and a cracking temperature in the range of from about 800 to about 1200°F.

14. A process in accordance with claim 1 wherein steam is present during said contacting under cracking conditions and the weight ratio of steam to said hydrocarbon containing feed stream is in the range of from about 0.01:1 to about 0.5:1.

15. A process in accordance with claim 1 comprising the additional steps of removing said cracking catalyst composition from said cracking zone after it has been used in said cracking zone, separating the thus removed cracking catalyst composition from gases and said at least one liquid product stream, exposing at least a portion of the thus separated cracking catalyst composition to flowing steam so as to strip adhered liquids from said cracking catalyst composition, and heating the thus steam-stripped cracking catalyst composition with a free oxygen containing gas so as to substantially remove coke deposits from said steam-stripped cracking catalyst composition, substantially convert vanadium compounds deposited thereon to vanadium oxide, and thus obtain a regenerated cracking catalyst composition.

16. A process in accordance with claim 18 further comprising the additional step of recycling at least a portion of said regenerated cracking catalyst composition to said cracking zone.

17. A process in accordance with claim 19, wherein fresh, unused cracking catalyst composition has been added to said regenerated catalyst composition before said recycling.