CN1004357B - Cracking method using silicoaluminophosphate molecular sieve catalyst - Google Patents

Abstract

Cracking catalysts comprising silicoaluminophosphate molecular sieves are disclosed, such catalysts being prepared from the specific silicoaluminophosphate molecular sieves of U.S. patent No. 4,440,871. When such catalysts are used to convert hydrocarbons, product mixtures different from those produced using aluminum silicate based catalysts may be provided.

Description

Cracking process using silicoaluminophosphate molecular sieve catalysts

The present invention relates to cracking catalysts formed from specific silicoaluminophosphate molecular sieves described in U.S. Pat. No. 4,440,871.

So far, the research of cracking catalysts has generally been limited to the preparation of modified zeolites for use as cracking catalysts, and the research has also been limited to the interaction of such zeolites with other inorganic oxide materials. The following patents are representative of prior art aspects of studying zeolite-based cracking catalysts:

the use of conversion catalysts formed from zeolites dispersed in a siliceous matrix has been disclosed in U.S. patent 3,140,249 and 352,796.

The use of doped matrix components is disclosed in U.S. patent 3,312,615, for example, the use of a catalyst comprising zeolite, an inorganic oxide matrix, and inert powders (such inert powders may be α -Al ₂O₃). Catalysts comprising an amorphous silica-alumina with the addition of alumina and a zeolite, respectively, are disclosed in U.S. patent 3,542,670, and catalysts comprising a zeolite, an amorphous hydrated alumina and alumina monohydrate are disclosed in U.S. patent 3,428,550.

It has been found that the use of low alkali metal content and unit cell diameter is less than about 24.45

The zeolite of (a) can improve the water vapor stability and thermal stability of the Y zeolite (see U.S. Pat. No. 3,293,192 and reissue patent 28,629 (reissue patent of U.S. Pat. No. 3,402,996)).

Furthermore, U.S. patent 3,591,488 has disclosed that in the temperature range of 427 ℃ to 816 ℃, water can be used to treat the hydrogen or ammonium type zeolite, or the water vapor and the water treated zeolite can then be cation exchanged with a cation, which can be a rare earth metal cation. This method increases the silica to alumina mole ratio of the zeolite while also increasing the defect structure. U.S. Pat. No. 3,676,368 discloses a rare earth ion exchanged hydrogen faujasite containing 6-14% rare earth metal oxide. U.S. patent 3,957,623 discloses a rare earth ion-exchanged zeolite containing a total of 1 to 10wt% rare earth oxide. U.S. Pat. No. 3,607,043 discloses a process for preparing zeolites having a rare earth ion content of from 0.3 to 10% by weight.

U.S. patent 4,036,739 discloses hydrothermally stable and ammonia stable Y zeolites in which a portion of the sodium ions in the sodium Y zeolite are exchanged for ammonium ions (NH <math><msup><mi></mi><msub><mi>+</mi></msup><mi>4</mi></msub></math> ) Followed by steam calcination and ion exchange with ammonium to a final sodium oxide content of less than 1 wt%, and then calcination of the re-exchanged product, or according to us patent 3,781,199, a second calcination after mixing the zeolite with a refractory oxide.

The prior art discussed above is representative of past and present Fluid Catalytic Cracking (FCC) catalyst formulations. A new class of catalysts is recently disclosed in us patent 4,400,871. The catalyst disclosed in this patent is a crystalline microporous silicoaluminophosphate molecular sieve. Its use in cracking processes is also disclosed. In U.S. Pat. No. 4,440,871, the catalytic cracking activity of several silicoaluminophosphates ("SAPOs") was evaluated using the n-butane cracking test, and the first order reaction rate constant value was calculated therefrom. Although all the silicoaluminophosphates tested showed a first order reaction rate constant with catalytic activity, the rate constant value varied between 0.2 and 7.4. The use of a mixture of aluminosilicates and specific aluminosilicates is disclosed in co-pending U.S. patent application Ser. No. 14697 filed concurrently herewith and commonly assigned thereto.

The present invention relates to a cracking catalyst and a fluid catalytic cracking process. Such catalysts include a particular class of silicoaluminophosphate molecular sieves disclosed in U.S. Pat. No. 4,440,871 and having a specific pore size, which are preferably used in combination with at least one inorganic oxide present as a binder and/or matrix component.

The present invention relates to the catalytic cracking of crude oil feedstocks to produce low boiling hydrocarbons. The process of the present invention is carried out by contacting the feedstock with a particular class of silicoaluminophosphate molecular sieves disclosed in U.S. Pat. No. 4,440,871.

U.S. patent 4,440871 issued 4/3 in 1984 describes silicoaluminophosphates for use in the present invention, which are characterized in that they have an adsorption of at least 2% by weight of isobutane at a pressure of 500 mmhg and a temperature of 20 ℃. In another embodiment, such silicoaluminophosphates are further characterized in that their calcined form has an adsorption of greater than 5% by weight for triethylamine at a pressure of 2.6 mmHg and a temperature of 22 ℃.

The present invention relates to novel catalytic cracking catalysts comprising silicoaluminophosphate molecular sieves and methods for their use in catalytic cracking processes. The catalytic cracking catalyst of the present invention is prepared from the novel silicoaluminophosphates disclosed in U.S. Pat. No. 4,440,871, incorporated herein by reference.

The silicoaluminophosphates used in the present invention are referred to herein as "SAPO" molecular sieves solely for ease of reference, and this abbreviation is consistent with the abbreviation used in U.S. patent 4,440,871. The catalysts to be discussed hereinafter using SAPO are certain silicoaluminophosphate catalysts comprising U.S. patent 4,440,871 and are generally always used with at least one inorganic oxide matrix component.

The term "SAPO" as used herein is referred to as "SAPO" molecular sieves in U.S. patent 4,440871. The "SAPO" molecular sieves disclosed in U.S. patent 4,440871 are microporous crystalline silicoaluminophosphates, the micropores in the molecular sieves being of uniform size and having a nominal diameter of greater than about 3

(Angstrom) the basic empirical chemical composition of molecular sieves in the as-synthesized and anhydrous forms is:

mR:(Si_xAl_yP_z）O₂

Wherein "R" represents at least one organic templating agent present in the micropore system within the crystal, the value of "m" is 0.02 to 0.03, the "m" represents the number of moles of "R" present per mole (Si _xAl_yP_z）O₂), and "X", "Y" and "Z" represent the mole fractions of silicon, aluminum and phosphorus, respectively, present as tetrahedral oxides, within the composition range of the pentagons defined by the points A, B, C, D and E on the ternary diagram of FIG. 1 of U.S. Pat. No.4,440,871. The molecular sieves of U.S. Pat. No.4,440,871 also have a PO <math><msup><mi></mi><msub><mi>+</mi></msup><mi>2</mi></msub></math> ,AlO <math><msup><mi></mi><msub><mi>-</mi></msup><mi>2</mi></msub></math> And a three-dimensional microporous network structure of SiO ₂ tetrahedral units, the basic empirical chemical composition of the anhydrous form of which is:

mR:(Si_xA_yP_z）O₂

Wherein "R" represents at least one organic templating agent present in the crystalline internal pore system, "m" represents the number of moles of "R" present in Si _xA_yP_z）O₂; "m" has a number from 0 to 0.3; "X", "Y" and "Z" represent the mole fractions of silicon, aluminum and phosphorus, respectively, present as oxide moieties, within the composition range defined by the A, B, C, D and E points on the ternary diagram of FIG. 1, the silicoaluminophosphate has a characteristic X-ray powder diffraction pattern having at least the d-spacing set forth in any of tables I, III, V, VII, IX, XIII, XXI, XXIII or XXV of U.S. Pat. No. 4,440,871. Furthermore, the SAPO molecular sieves may be calcined at a temperature high enough to remove at least a portion of the organic templating agent present in the crystalline internal pore system.

The SAPO catalysts of the present invention are prepared using the silicoaluminophosphates of U.S. patent4,440,871, which, as described above, are further characterized by a calcined form having an adsorption of at least 2% by weight of isobutane at a pressure of 500 mmhg and a temperature of 20 ℃. In another embodiment, the SAPO is characterized as having an adsorption of greater than 5 weight percent of triethylamine in its calcined form at a pressure of 2.6 millimeters of mercury and a temperature of 22 ℃. The characterization of Silicoaluminophosphates (SAPOs) used in the present invention described above relates to an adsorption characterization of SAPOs that have been subjected to a post-synthesis treatment, such as calcination or chemical treatment, to remove a substantial portion of the template "R" added as a result of the synthesis of the molecular sieve. Although the particular SAPO of the present invention is characterized by its adsorption to isobutane or triethylamine in its calcined form, the present invention also necessarily includes the use of an uncalcined SAPO characterized by the above adsorption to its calcined form because when such uncalcined form of SAPO is used in the present process under catalytic cracking conditions, the SAPO will be calcined or hydrothermally treated in situ to have such characteristic adsorption to isobutane or triethylamine. Thus, because of the presence of template "R", which is added during synthesis of the molecular sieve, the SAPO will be processed in situ into a form characterized by the above-described adsorption of isobutane, but the calcined form of SAPO-11 is characterized by the above-described adsorption of isobutane and triethylamine. Thus, references to a SAPO having particular adsorption characteristics in its calcined form are not meant to exclude the use of a SAPO in its as-synthesized form, which would have such adsorption characteristics when calcined, hydrothermally treated, or otherwise treated (e.g., ion exchanged).

The term "heat treatment" is used herein to mean both a thermal bake in the presence of air or an inert gas (e.g., nitrogen) and a hydrothermal bake (thermal bake in the presence of water vapor). The heat treatment is typically carried out at a temperature above 300 ℃ for a period of time above 0.25 hours, and when the heat treatment is a hydrothermal treatment, the treatment is typically carried out in the presence of at least about 20% by volume of water vapor in air. The source of the water vapor is not critical, and it may be provided from an external source of water vapor or may be generated in situ at the heating temperatures used for the hydrothermal treatment. As noted above, the SAPO in its as-synthesized form may also be used in the process, as a hydrothermal treatment will be provided in situ when the as-synthesized form of the SAPO is added to the process under catalytic cracking conditions.

It is also possible to use a silicoaluminophosphate molecular sieve (with or without an inorganic oxide matrix component) with at least one cation capable of forming hydrogen, such as NH <math><msup><mi></mi><msub><mi>+</mi></msup><mi>4</mi></msub></math> The solution of H ⁺ and quaternary ammonium ions is contacted to ion exchange the SAPO. It is generally recognized that the selected SAPO may also include cations selected from groups IIA, IIIA, IIIB to VIIB and rare earth cations selected from cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and mixtures thereof. At present, it has not been observed that the presence of rare earth cations with SAPO molecular sieves is beneficial to the activity of SAPO components. Although their presence may be advantageous in some cases, the nature of the relationship between the multivalent cations and the SAPO catalyst is not yet clear. Because of ion exchange, the silicoaluminophosphates may contain at least one cation, for example, a hydrogen-forming cation, which is different from those cations that were initially associated with the silicoaluminophosphate molecular sieve in the synthesis. The cations present as a result of the ion exchange are preferably present in an effective amount of between 0.1% and 20% by weight, and generally in an effective amount of between 0.5% and 10% by weight, based on the starting weight of the silicoaluminophosphate molecular sieve.

Of course, the heat treatment and ion exchange mentioned above may be performed one or more times in any order, and such variations are within the scope of the present invention.

Ion exchange is typically performed by first preparing a slurry of the silicoaluminophosphate catalyst by adding 5 to 15 volumes of water per volume of catalyst, followed by adding a solution containing the selected cation. Ion exchange is typically performed at room temperature, and the resulting solution is then heated to above about 50 ℃ and stirred at that temperature for 0.5-3 hours. The mixture is then filtered and washed with water to remove excess anions introduced by the addition of the cationic salt solution.

The silicoaluminophosphate molecular sieve is typically employed with at least one inorganic oxide matrix component, so far commonly employed in the formulation of Fluid Catalytic Cracking (FCC) catalysts, including amorphous inorganic catalytic oxides such as catalytically active silica/alumina, clays, silica, alumina, silica-zirconia, silica-magnesia, alumina boria, alumina titania and the like, and mixtures thereof. The matrix may be in the form of a sol, hydrogel or gel, but is typically alumina, silica or silica-alumina component, such as conventional silica-alumina cracking catalysts, several of which are commercially available, as well as combinations thereof. The matrix itself may act as a catalyst, such as that observed for silica/alumina, or the matrix itself may be substantially inert. In some cases, the matrix may act as a "binder" although in some cases it may be possible to spray dry or shape the final catalyst without the need for a binder. These matrix materials may be made as a cogel of silica and alumina, or as alumina deposited on a preformed and pre-aged hydrogel. The silica may be present in the matrix as a major matrix component, for example, in an amount of between about 5 and 40% by weight, and most preferably between about 10 and 30% by weight. The silica may also be used in the form of a cogel having a composition of about 75 weight percent silica and about 25 weight percent alumina or about 87 weight percent silica and about 13 weight percent alumina. In the final catalyst, the inorganic oxide matrix component is typically between about 0 and 99 weight percent, and most preferably between about 5 and 90 weight percent, based on the total weight of the catalyst. Other materials, such as clays, carbon monoxide oxidation promoters, etc., may also be employed in the final cracking catalyst along with the silicoaluminophosphates and are within the scope of the present invention.

Representative of matrix systems that may be used in the present invention are disclosed in British patent Specification No. 1315553, published 5/2/1973, and in U.S. Pat. Nos. 3446727 and 4086187, which are incorporated herein by reference.

As mentioned above, the catalyst of the present invention may be used with a matrix component which may be a silica or alumina component. The alumina component may include dispersed particles of various aluminas, such as pseudoboehmite. The alumina particles in dispersed form have a total surface area, as measured by BET, of greater than about 20 square meters (meters ²/gram) per gram, and most preferably greater than 145 meters ²/gram, for example, from about 145 to 300 meters ²/gram. The micropore volume of the alumina component is typically greater than 0.35 cc/g. The average particle size of the alumina particles is generally less than 10 microns, and most preferably less than 3 microns. The alumina component may be used as a matrix alone or in combination with other matrix components. The alumina component may be any alumina and is preferably preformed and is in a physical form which stabilizes both its surface area and its microporous structure so that when added to an impure inorganic gel containing substantial amounts of residual soluble salts, the soluble inorganic salts will not measurably alter the surface and microporous properties of the alumina nor promote their chemical attack on the preformed porous alumina which may be altered. For example, the alumina is typically one that has been formed after an appropriate chemical reaction, aging the slurry, filtering, drying, washing to remove portions of residual salts, and then heating to reduce its volatile content to less than 15% by weight. The amount of alumina component present in the finished catalyst may be from about 5 to about 95 wt%, and preferably from about 10 to about 30 wt%, based on the total amount of catalyst, and in addition, an aqueous alumina solution or hydrogel, or hydrated alumina slurry may be used in the catalyst preparation.

The mixture of one or more silicoaluminophosphate molecular sieves and one or more inorganic matrix components may be formed into a finished catalyst using standard catalyst forming techniques including spray drying, pelletizing, extrusion, and other suitable conventional methods. In preparing the catalyst, a spray drying step is the preferred method, and such a step is well known in the art. After the catalyst is formed into extruded pellets and dried in air, it is then typically crushed and sieved to a particle size of less than 150 microns.

The SAPO-containing catalyst can be prepared by any conventional method. One method of preparing such catalysts using silica-alumina and porous alumina is to react sodium silicate with an aluminum sulfate solution to form a silica/alumina hydrogel slurry, then age the resulting gel slurry to obtain the desired microporous properties, filter to remove a large amount of extraneous and undesired sodium and sulfate ions, and then slurrying in water. The alumina can be prepared by reacting a sodium aluminate solution with an aluminum sulfate solution under suitable conditions, aging the slurry to obtain the desired microporous properties of the alumina, filtering, drying, slurrying in water to remove sodium and sulfate ions and drying to reduce the volatile content to 15% by weight. The alumina can then be slurried in water and mixed in appropriate amounts with an impure silica-alumina hydrogel slurry. The SAPO molecular sieve component can then be added to this mixture. A sufficient amount of each component is applied to provide the desired final composition. The resulting mixture is then filtered to remove some of the extraneous soluble salts remaining therein. The filtered mixture is then dried to produce a dry solid. This dry solid is then slurried in water and washed substantially free of unwanted soluble salts. The catalyst is then dried to a residual water content of less than about 15% by weight. Such catalysts are generally used after calcination, but may also be calcined in situ during catalytic cracking conditions.

Catalytic cracking with the catalyst of the present invention may be carried out in any conventional catalytic cracking process under effective catalytic cracking conditions, suitable catalytic cracking conditions including temperatures ranging from about 204 to 871 ℃, preferably 371 to 871 ℃, and pressures ranging from below 1 atmosphere to several atmospheres, typically pressures ranging from about one atmosphere (1.03 kg-force/cm) to about 7 kg-force/cm. This process can be carried out in a fixed bed, moving bed, ebullated bed, slurry reactor, pipe reactor, riser reactor or fluidized bed. The catalysts of the invention can be used to convert any conventional hydrocarbon feedstock used in catalytic cracking, that is, the catalysts of the invention can be used to crack naphtha, gas oil and resids having a high metal contaminant content. The catalyst of the invention is particularly suitable for cracking hydrocarbons in the gas oil boiling range, i.e. for cracking hydrocarbon oils boiling in the range of 216 ℃ to 982 ℃ at one atmosphere into naphtha to produce products having not only a lower boiling point than the starting material but also an increased octane number.

The term "crude oil feedstock" is used herein to refer to any whole crude oil recovered from a general or offshore oil field, primary, secondary, or tertiary oil recovery, and feedstocks produced from such crude oils. "crude oil feedstock" may include any whole fraction of "synthetic crude oil" ("syncrude"), such as those that may be produced from coal, shale oil, tar sands, and bitumen. Such crude oil may be straight run or produced synthetically by blending. It is generally preferred to first desalt the crude oil because sodium chloride is known to be a poison for most cracking catalyst operations. In addition, the term "crude oil feedstock" is used to include the components of crude oil that are typically used as catalytic cracking feedstock or potential feedstocks thereof and includes, for example, distillate gas oils, vacuum heavy gas oils, atmospheric or vacuum gas oils, synthetic crude oils (produced from shale oils, tar sands, coal), feedstocks produced from hydrocracking units, hydrotreating units, coker units, pyrolysis processes, and high boiling FCC product recycle fractions, as well as conventional end-boiling fractions boiling above the gasoline boiling range, which typically include compounds containing eleven carbon atoms or more, and mixtures thereof.

In addition, the present catalyst can be effectively used in FCC (fluid catalytic cracking) processes. Wherein a small molecular weight carbon-hydrogen compound (CHFC) is used in combination with a crude oil feedstock. This process is referred to herein as the FCC-CHFC process.

The term "small carbon-hydrogen molecule compound" is used herein to denote substances having a lower number of carbon atoms than substances in the gasoline boiling range, preferably those having a carbon number of 5 or less, which fall into any of the following categories:

a) Hydrogen-rich molecules, i.e., molecules having a hydrogen% content in the range of 13.0 to 25.0% by weight, include light alkanes, i.e., CH ₄,C₂H₆,C₃H₈, and other materials.

B) The chemical structure of the molecule can be used for allowing or facilitating the conversion of small carbon-hydrogen molecules. These molecules include CH ₃ OH, other low boiling alcohols such as ethanol, n-propanol, isopropanol, n-butanol, isobutanol, etc., aliphatic ethers such as dimethyl ether and other oxygenates (acetals, aldehydes, ketones).

C) Secondary reaction products of the substances in the above (a) or (b), which are small molecular weight carbon-hydrogen compounds themselves, or transferred hydrogen, include olefins, naphthenes or alkanes.

D) Structurally or chemically equivalent to (c), in particular olefins, etc., and

E) A composition of all or any of the substances of classes (a) to (d).

Preferred small carbon-hydrogen compounds are methanol, dimethyl ether and C ₂-C₅ olefins, with methanol, dimethyl ether being most preferred.

In addition, the FCC-CHFC process is generally considered to involve chemical combination reactions that are generally considered to be effective in removing sulfur, oxygen, nitrogen and metal contaminants from the whole crude oil or its heavy hydrocarbon portion, at least in part.

The operation of the FCC-CHFC type process is generally carried out at a temperature in the range of 204 ℃ to about 760 ℃, and typically in the range of 371 ℃ to 649 ℃, and at a pressure selected from the range of less than 1 atmosphere up to several tens of kilovolts per square centimeter, but typically less than 14 kilovolts per square centimeter. Preferred conditions include a temperature in the range of 427 ℃ to about 621 ℃ and a pressure in the range of atmospheric pressure to 7 kgf/square centimeter or more.

The small carbon-hydrogen molecule compound, so long as it is present when it is contacted with the catalyst material, may be provided to the process by any of the most commonly used methods, i.e., in situ generation is suitable.

In a preferred operation of the FCC-CHFC, methanol is used with a hydrocarbon feedstock of the gas oil type. The weight percent of methanol in the hydrocarbon feedstock passed to the cracking or conversion operation may vary widely and may be selected in the range of from about 1% to about 25%, and is preferably maintained at a level of from about 5% to about 20% by weight of the feedstock. However, this percentage can vary, and the particular percentage depends on the hydrogen deficiency of the high molecular weight hydrocarbon feed, the amount of sulfur, nitrogen, and oxygen in the oil, the amount of polycyclic aromatic hydrocarbon, the type of catalyst used, and the desired conversion. It is desirable to avoid providing any substantial or significant excess of methanol to the feed, as under certain conditions methanol has a tendency to react with each other.

Preferably, the FCC-CHFC process uses a fluidized catalyst system at low pressure without the need for high pressure hydrogen. Such fluidized catalyst systems promote efficient contact between relatively inexpensive small carbon-hydrogen compounds and heavy, difficult-to-crack molecules in the presence of high surface area cracking catalysts. Intermolecular hydrogen transfer interactions, such as methylation and catalytic cracking reactions, are carried out in the presence of fluidized catalyst particles and serve to minimize problems caused by diffusion/mass transfer control and/or heat transfer.

The FCC-CHFC process can utilize relatively inexpensive small molecular weight carbon-hydrogen compounds readily available in petroleum refineries, such as light gas fractions, light olefins, low boiling point liquid streams, and the like, and can use, inter alia, methanol, a product that can be transported either as a process for conversion of foreign natural gas or as a product gasified from large-scale coal, shale oil, or tar sands. The FCC-CHFC process may also utilize carbon monoxide (used with a "contributor" such as water or methanol) which is readily provided by refinery-generated flue gas (or other incomplete combustion process) or by gasification of coal, shale oil, tar sands. The hydrocarbon-hydrogen small molecule compound can also be circulated with high efficiency.

The following examples are presented to illustrate the invention and are not intended to limit the invention.

Example 1

Two catalysts were prepared and their performance was evaluated according to ASTM test method D-3907 (microreactor activity test). The two catalysts were prepared using a non-zeolitic molecular sieve, SAPO-5, and zeolite LZ-210. SAPO-5 was prepared according to the method of U.S. patent 4,440,871 and was used after air calcination. LZ-210 (SiO ₂ to Al ₂O₃ ratio of 9.0) was prepared according to the method described in publication No. 82.211.

After SAPO-5 was prepared, it was treated in 100% steam at 760 ℃ for 2 hours to simulate the effect of practical use in the cracking process. The LZ-210 component was then subjected to rare earth ion exchange to provide a rare earth exchanged LZ-210 containing 9.9% by weight of rare earth ions (expressed as oxides). The rare earth ion exchange is performed with a rare earth chloride solution containing 46.0% by weight of rare earth elements, the rare earth components expressed as oxides having a composition of 60.0% lanthanum (La ₂O₃), 21.5% neodymium (Nd ₂O₃), 10.0% cerium (CeO ₂), 7.5% praseodymium (Pr ₆O₁₁) and about 1.0% of other rare earth elements.

The matrices of SAPO-5 and LZ-210 were prepared by mixing 90 wt.% silica/alumina (sold by Davison division of W.P.Grace, commercially available under the trade designation Msub/110) with 10 wt.% microcrystalline fiber extrusion aid. The mixture was extruded into 0.16 cm pellets and dried in air at 110 ℃ for about 16 hours and then deactivated in 100% water vapor at 760 ℃ for another 2 hours. Finally, the steam-deactivated material is crushed and sieved to 60 to 200 mesh (U.S. standard) particles.

SAPO-5 and LZ-210 catalysts were prepared by mixing 15 wt% of the selected material with 85 wt% of the matrix, respectively. LZ-210 was steam deactivated in 100% steam at 760℃for 2 hours prior to catalyst preparation. The finished catalyst mixture was then calcined in air at 590 ℃ for 3 hours. Each catalyst was evaluated in a single test according to ASTM test method D-3907 and with the following 4 modified ASTM test method D-3907. The first modification is that the final boiling point of the product, which is determined to be a gasoline product, is 222 ℃. The second modification is that the nitrogen post-stripping of the catalyst is carried out at 30 ml/min for 23-27 minutes. A third modification is that the conversion is a measured conversion, not a standard conversion of ASTM test methods. The fourth modification is that the feedstock used in the test method has an API gravity of 24.0 ℃ and an Initial Boiling Point (IBP) of 179 ℃, a final boiling point (fbp) of 581 ℃ and a UOP K coefficient of 11.8.

"Percent conversion (by weight)" is the percent conversion measured by weight. "gasoline weight percent" is the weight percent of hydrocarbons in the product from C ₅ hydrocarbons to hydrocarbons having a boiling point below 222 ℃. "gas weight percent" is the weight percent of those hydrocarbons in the product having a boiling point below C ₄, expressed as a weight percent of the feed, and "coked weight" is the weight percent of the residue left on the used catalyst after post-stripping according to ASTM test method D-2907, expressed as a percentage of the feed. "C ₄ S% (by weight)" is the weight percent of isobutane, n-butane and butene in the product. The following are the above results in weight percent:

Catalyst

SAPO-5 LZ-210

Conversion (wt.%) 57.7.57.2

Gasoline (wt%) 37.2.41.4

Gas% by weight 6.6.5.5

Coking% (weight) 3.9.3.1

C ₄ s% by weight 10.0.7.33

The above results demonstrate that SAPO-5 is an active cracking catalyst that provides substantially the same conversion as an LZ-210 catalyst containing aluminosilicate zeolite, but provides a different product distribution.

Example 2

A gas oil feedstock comprising vacuum heavy gas oil is used in a cracking operation to perform an FCC-CHFC process. The vacuum gas oil is characterized by an API gravity (15.6 ℃) of 20.7, an average molecular weight of about 400+ -10, and a boiling point range of 371 ℃ to 593 ℃. The small carbon-hydrogen molecule compound is methanol, which is present in an amount of 10% by weight. The catalyst contained SAPO-5, which was passed into the riser FCC unit after it was heated to about 538 ± 7 ℃. The hydrocarbon product has an increased selectivity to engine fuel (hydrocarbon) products due to the addition of methanol, characterized by the presence of hydrocarbon fuel therein having a boiling point below the boiling point range of the gas oil feed.

Claims (14)

1. A process for cracking a crude oil feedstock to produce low boiling hydrocarbons, the process comprising contacting said crude oil feedstock or a hydrocarbon feedstock having a boiling point of 216°C to 982°C selected from naphtha, distillate gas oils, vacuum residues, atmospheric residues, synthetic crudes and mixtures thereof, at a temperature of 371°C to 871°C and a pressure of 1.03 kgf/ ^cm2 to 7 kgf/ ^cm2 with a catalyst comprising at least one silicoaluminophosphate molecular sieve characterized in that, in its calcined form, it has an adsorption rate for isobutane of at least 2% by weight at a pressure of 500 mmHg and a temperature of 20°C; and contains from 0 to 99% by weight of an inorganic oxide matrix. 2. The process of claim 1 wherein said silicoaluminophosphate molecular sieve is further characterized in that in its calcined form it has an adsorption rate for triethylamine greater than 5% by weight at a pressure of 2.6 mmHg and a temperature of 22°C. 3. The process according to claim 1, wherein said silicoaluminophosphate molecular sieve contains 0.1 to 20% by weight of at least one cation selected from the group consisting of: H ⁺ , <math><msup><mi>NH</mi><msub><mi>+</mi></msup><mi>4</mi></msub></math> , Group IIA, Group IIIA, Group IIIB to Group VIIB, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and mixtures thereof. 4. The process according to claim 1, wherein at least a portion of the cations in said silicoaluminophosphate molecular sieve are hydrogen ions or hydrogen-forming cations. 5. The method according to claim 4, wherein said hydrogen-forming cation is selected from at least H ⁺ and

A cation in . 6. The process according to claim 4, wherein the silicoaluminophosphate molecular sieve is selected from the group consisting of SAPO-5, SAPO-11, SAPO-31, SAPO-37, SAPO-40, SAPO-41 and mixtures thereof. 7. The method according to claim 6, wherein the silicoaluminophosphate is SAPO-5. 8. The method according to claim 6, wherein the silicoaluminophosphate is SAPO-11. 9. The method according to claim 6, wherein the silicoaluminophosphate is SAPO-31. 10. The method according to claim 6, wherein the silicoaluminophosphate is SAPO-40 11. The method according to claim 6, wherein the silicoaluminophosphate is SAPO-41. 12. The method of claim 1 wherein said silicoaluminophosphate is a microporous crystalline silicoaluminophosphate having pores of uniform size and having a nominal diameter greater than about 3 angstroms, said silicoaluminophosphate having an essential empirical chemical composition in its as-synthesized and anhydrous form: mR _{： （ SixAlyPz} ） _O2 wherein "R" represents at least one organic template present in the microporous system within the crystal; the value of "m" is 0.02 to _0.03 ; "m" represents the number of moles of "R" present per mole _of ( _SixAlyPz ) _O2 ; and "x,""y," and "z" represent the mole fractions of silicon, aluminum, and phosphorus, respectively, when present as tetrahedral oxides, said mole fractions being within the range of the pentagonal composition defined by the five points A, B, C, D, and E on the ternary diagram of FIG1 of U.S. Patent No. 4,440,871. 13. The method according to claim 1, wherein said silicoaluminophosphate molecular sieve has a PO <math><msup><mi></mi><msub><mi>+</mi></msup><mi>2</mi></msub></math> 、AlO <math><msup><mi></mi><msub><mi>-</mi></msup><mi>2</mi></msub></math> and a three-dimensional microporous framework structure of _SiO2 tetrahedral units. Its basic empirical chemical composition in anhydrous form is: mR _{： （ SixAlyPz} ） _O2 wherein "R" represents at least one organic template present in the microporous system within the crystal; "m" represents the number of moles of "R" present per mole _{of ( SixAlyPz} ) _O2 and has a value ranging from 0 to 0.03; "x", "y" and "z" represent the mole fractions of silicon, aluminum and phosphorus, respectively, present as oxide moieties, said mole fractions being within the composition range defined by the five points A, B, C, D and E on the ternary diagram of FIG1, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern having at least the following d-spacings listed in any one of Tables I, III, V, VII, IX, XIII, XVII, XXI, XXII or XXV of U.S. Patent No. 4,440,871. 14. The process of claim 1, wherein the catalyst comprises 5 to 95 weight percent of at least one inorganic oxide matrix component selected from the group consisting of clay, silica, alumina, silica-alumina, silica-zirconia, silica-magnesia, alumina-boria and alumina-titania.