GB2084892A - Hydrocarbon conversion zeolite- containing catalysts and processes utilizing the same - Google Patents

Abstract

A catalyst suitable for conversion of hydrocarbon oils to lower boiling products, comprises an ultrastable Y-type crystalline alumino- silicate zeolite, an inorganic oxide matrix, discrete particles of alumina dispersed in the matrix, and rare earth metal. The rare earth metal is in an amount such that the ratio of wt% rare earth metal (as oxide) to wt% zeolite is from 0.01 to 0.08. The zeolite prior to being composited with the matrix has a unit cell size not greater than about 24.5 Angstroms. A cracking process utilizing the catalyst is also provided.

Description

SPECIFICATION Hydrocarbon conversion zeolite-containing catalysts and processes utilizing the same The present invention relates to hydrocarbon conversion zeolite-containing catalysts and processes utilizing the same, e.g. in a catalytic cracking process. More particularly, the invention relates to a catalytic cracking process having improved activity and selectivity for producing high octane number naphtha.

Hydrocarbon conversion catalysts comprising a zeolite dispersed in a siliceous matrix are known. See, for example, U.S. Patent 3,140,249 and U.S. Patent 3,352,796.

A catalyst comprising a zeolite, an inorganic oxide matrix and inert fines, which may be alpha alumina, is known. See U.S. Patent 3,312,615.

A catalyst comprising an amorphous silica-alumina, separately added alumina and a zeolite is known. See U.S. PAtent 3,542,670.

A catalyst comprising a zeolite, an amorphous hydrous alumina and alumina monohydrate is known. See U.S. Patent 3,428,550.

To improve the steam and thermal stability of zeolites, it is known to produce zeolites having a low level of alkali metal content and a unit cell size less than about 24.45 Angstroms. See U.S. Patents 3,293,192 and RE28,629 (Reissue of U.S. Patent 3,402,996).

It is also known to treat hydrogen or ammonium zeolite with H20 at a temperature ranging from about 800 to 1500"F 1500OF, and subsequently cation exchanging the steam and water treated zeolite with cations which may be rare earth metal cations. The method increases the silica to alumina mole ratio of the zeolite. See U.S. Patent 3,591,488.

U.S. Patent 3,676,368 discloses a rare earth exchanged-hydrogen faujasite containing from 6 to 1 4 percent rare earth oxides.

U.S. Patent 3,957,623 discloses a rare earth exchanged zeolite having a total of 1 to 10 weight percent rare earth metal oxide.

U.S. Patent 3,607,043 discloses a process for preparing a zeolite having a rare earth content of 0.3 to 10 weight percent.

U.S. Patent 4,036,739 discloses hydrothermally stable and ammonia stable Y zeolite in which a sodium Y zeolite is ion exchanged to partially exchange sodium ions for ammonium ions, followed by steam calcination and a further ion exchange with ammonium to reduce the final sodium oxide content to below 1 weight percent, followed by calcination of the reexchanged product, or according to U.S. Patent 3,781,199, the second calcination may be conducted after the zeolite is admixed with a refractory oxide.

SUMMARY OF THE INVENTION In accordance with the invention there is provided, a catalyst comprising: (a) an ultrastable Y-type crystalline alumino-silicate zeolite; (b) an inorganic oxide matrix, and (c) discrete particles of alumina; Said zeolite prior to being composited with (b) having a unit cell size not greater than about 24.5 Angstroms, and said catalyst having a rare earth metal content such that the ratio of weight percent rare earth metal, calculated as the rare earth metal oxide, based on the total catalyst, divided by the weight percent zeolite based on the total catalyst ranges from about 0.01 to about 0.08.

In accordance with the invention there is further provided a catalytic cracking process utilizing the above stated catalyst.

DETAILED DESCRIPTION OF THE INVENTION The catalyst of the present invention must have a rare earth content such that the ratio of weight percent rare earth metal oxide based on the total catalyst divided by the weight percent zeolite based on the total catalyst ranges from about 0.01 to about 0.08, preferably from about 0.01 to about 0.06, more preferably from about 0.01 to about 0.04.

The rare earth metal may be a single rare earth metal or a mxture of rare earth metals of elements having atomic numbers ranging from 57 to 71.

The alkali metal content of the total catalyst is suitably less than about 0.6 weight percent, preferably less than about 0.3 weight percent, calculated as the alkali metal oxide, based on the total catalyst.

The required amount of rare earth metal can be incorporated into the catalyst either by preparing a zeolite having the required rare earth content and then compositing the zeolite with a conventional matrix or the required amount of rare earth in the catalyst can be obtained by utilizing a zeolite having essentially no rare earth metal cations, that is, less than 1 weight percent rare earth oxide, based on the zeolite, or less than the required amount of rare earth metal and subsequently treating the composite catalyst (that is, zeolite dispersed in a matrix) with a solution comprising rare earth metal components to incorporate the required amount of rare earth metals into the catalyst.

The Ultrastable Y-type Zeolite Component Ultrastable Y-type zeolites are well known. They are described, for example, in U.S. Patent 3,293,192; U.S. Patent RE28,629 (Reissue of U.S. Patent 3,402,996); U.SL Patent 4,036,739; U.S. Patent 3,781,199; U.S. Patent 4,036,739, the teachings of which are hereby incorporated by specific reference. They are also described in the publication, Society of Chemical Engineering (London) Monograph Molecular Sieves, p. 1 86 (1 968) by C." McDaniel and P.K. Maher.The term "ultrastable" with reference to a Y-type zeolite refers to a zeolite which has improved resistance to degradation of crystallinity by high temperature and steam treatment and is characterized by an alkali metal content (Na, K or any other alkali metal ion) of less than about 4 weight percent, calculated as the alkali metal oxide based on the zeolite, a unit cell size not greater than about 24.5 angstroms, preferably not greater than about 24.4 Angstroms and a silica to alumina mole ratio of at least about 3. The ultrastable Y-type zeolite is identified both by the smaller unit cell size and the low level of alkali metal cations. The particle size of the zeolite may vary widely and is not critical. Usually, the particle size of the zeolite ranges from about 0.1 to 10 microns in diameter, preferably from about 0.5 to 3 microns.

The zeolite may comprise rare earth metal cations and may additionally comprise hydrogen cations and cations of Group IB to Vlil metals of the Periodic Table of Elements. The Periodic Table referred to herein is given in Handbook of Chemistry and Physics, published by the Chemical Rubber Company, Cleveland, Ohio, 45th Edition, 1 964. When additional cations are pesent other than rare earth metals and alkali metals, the preferred additional cations are calcium, magnesium, hydrogen and mixtures thereof. The concentration of hydrogen present in the finished zeolite will be that concentration equivalent to the difference between theoretical cation concentration of the particular zeolite in question and the amount of cation present in the form of, for example, rare earth and residual alkali metal ion.

When the rare earth content and low alkali metal of the catalyst are controlled by utilizing a zeolite which has been treated to comprise at least a portion of the required rare earth metal, for example, as rare earth metal cations, the zeolite having the desired rare earth metal component can be obtained by various methods.

One method of producing a required zeolite having only a limited amount of rare earth metal cations and low alkali metal content is to start with an ultrastable Y-type zeolite having a unit cell size not greater than about 24.5 Angstroms, preferably not greater than about 24.4 Angstroms, having less than 4 weight percent alkali metal, calculated as the alkali metal oxide, based on the zeolite, and contact the ultrastable Y-type zeolite with a fluid medium comprising rare earth metal of a single rare earth metal or cations of a mixture of rare earth metals. The ion exchange is conducted in a conventional way such as by utilizing salts of the desired rare earth metals. Ion exchange methods are well known in the art and are described, for example, in U.S.

Patent 3,140,249; U.S. Patent 3,140,251; U.S. Patent 3,140,253, the teachings of which are hereby incorporated by reference.

The amount of rare earth metal used is such that it does not exceed the limits of the range required for the catalyst of the present invention. The total amount of required rare earth may be exchanged into the zeolite itself or only a portion of the amount required by the catalyst of the present invention may be exchanged into the zeolite and the balance of the desired required amount may be composited with the finished catalyst, for example, by posttreating the finished catalyst with a solution comprising rare earth metal components that become associated with the finished catalyst.

The rare earth-exchanged zeolite is recovered, for example, by filtration, and washed with water to remove soluble matter and calcined, for example, at a temperature ranging from about 700 F to 1600"F for about 0.5 to 6 hours, preferably from about 900"F to 1200"F for about 1 to 3 hours in the absence or in the presence of H20 which may be steam or water.

The final zeolite may be composited with other catalytic metal components, such as metals of Groups 1IA, II IA, IVA, IB, IIB, IlIB, IVB, and VIII of the Periodic Table of Elements.

The particle size of the zeolite component will generally range from about 0.1 to 10 microns, preferably from about 0.5 to 3 microns. Suitable amounts of the zeolite component in the total catalyst will range from about 1 to 60, preferably from about 1 to 40, more preferably from about 5 to 40, most preferably from about 8 to 35 weight percent, based on the total catalyst.

The Alumina Component The catalyst of the present invention comprises a porous alumina component. The porous alumina component is present in the preferred catalyst of the present invention.

The porous alumina component of the catalyst of the present invention comprises discrete particles of various porous aluminas, preferably crystalline alumina, which are known and commercially available. In general, the porous alumina component of the catalyst of the present invention are discrete particles having a total surface area, as measured by the method of Brunauer, Emmett and Teller (BET) greater than about 20 square meters per gram (m2/g), preferably greater than 145 m2/g, for example, from about 145 to 300 m2/g. Preferably the pore volume (BET) of the alumina will be greater than 0.35 cc/g. The average particle size of the alumina particles would generally be less than 10 microns, preferably less than 3 microns.

Preferably, the porous alumina will be a material having initially, if used alone, prior to being composited with the other components, inherently less catalytic cracking activity of its own than the inorganic matrix component of the catalyst. Preferably, the porous alumina will be bulk alumina. The term "bulk" with reference to the porous alumina is intended herein to designate a material which has been preformed and placed in a physical form such that its surface area and pore structure are stabilized so that when it is added to an impure, organic gel containing considerable amounts of residual soluble salts, the salts will not alter the surface and pore characteristics measurably nor will they promote chemical attack on the preformed porous alumina which could undergo change.For example, addition of "bulk" alumina will mean use of a material which has been formed by suitable chemical reaction, the slurry aged, filtered, dried, washed free of residual salt and then heated to reduce its volatile content to less than about 1 5 weight percent. The porous alumina component may suitably be present in the catalyst of the present invention in an amount ranging from about 5 to about 40 weight percent, preferably from about 10 to 30 weight percent, based on the total catalyst.

Alternatively and optionally, an alumina hydrosol or hydrogel or hydrous alumina may be used initially in the catalyst preparation as precursor of the discrete particles of alumina in the finished catalyst.

The Inorganic Oxide Matrix Component The inorganic oxide matrices suitable as component of the catalyst of the present invention are amorphous catalytic inorganic oxides, such as silica, alumina, silica-alumina, silica-zirconia, silica-magnesia, alumina-boria, alumina-titania and the like and mixtures thereof. Preferably, the inorganic oxide matrix is a silica-containing gel; more preferably the inorganic oxide gel is an amorphous silica-alumina component such as a conventional silica-alumina cracking catalyst, several types and compositions of which are commercially available. These materials are generally prepared as a cogel of silica and alumina or as alumina precipitated on a preformed and preaged hydrogel.In general, the silica is present as a major component in the catalytic solids present in said gels, being present in amounts ranging from about 55 to 100 weight percent; preferably the silica will be present in amounts ranging from about 70 to about 90 weight percent. Particularly preferred are two cogels, one comprising about 75 weight percent silica and 25 weight percent alumina and the other comprising about 87 weight percent silica and 1 3 weight percent alumina. The inorganic oxide matrix component may suitably be present in the catalyst of the present invention in an amount ranging from about 40 to about 99 weight percent, preferably from about 50 to about 80 weight percent, based on the total catalyst.It is also within the scope of this invention to incorporate in the catalyst other materials, to be employed in cracking catalysts such as various other types of zeolites, clays, carbon monoxide oxidation promoters, etc.

The catalyst of the present invention may be prepared by any one of several methods. The preferred method of preparing one of the catalysts of the present invention, that is, a catalyst comprising silica-alumina and porous alumina, is to react sodium silicate with a solution of aluminium sulfate to form a silica-alumina hydrogel slurry which is then aged to give the desired pore properties, filtered to remove a considerable amount of the extraneous and undesired sodium and sulfate ions and then reslurried in water.Separately, the bulk alumina is made, for example, by reacting solutions of sodium aluminate and aluminum sulfate under suitable conditions, aging the slurry to give the desired pore properties of the alumina, filtering, drying, reslurrying in water to remove sodium and sulfate ions and drying to reduce volatile matter content to less than 1 5 weight percent. The alumina is then slurried in water and blended in proper amounts, with a slurry of impure silica-alumina hydrogel.

The zeolite component is added to this blend. A sufficient amount of each component is utilized to give the desired final composition. The resulting mixture is then filtered to remove a portion of the remaining extraneous soluble salts therefrom. The filtered mixture is then dried to produce dried solids. The dried solids are subsequently reslurried in water and washed substantially free of the undesired soluble salts. The catalyst is then dried to a residual water content of less than about 1 5 weight percent. The dried catalyst is recovered. The catalyst of the present invention is particularly suited for use in catalytic cracking of hydrocarbons.

Catalytic cracking with the catalyst of the present invention can be conducted in any conventional catalytic cracking manner. Suitable catalytic cracking conditions include a temperature ranging from about 700"F to about 1 300'F and a pressure ranging from about subatmospheric to several hundreds of atmospheres, typically from about atmospheric to about 100 psig. The process may be carried out in a fixed bed, moving bed, ebullating bed, slurry, transferline, or fluidized bed operation. The catalyst of the present invention can be used to convert any of the conventional hydrocarbon feeds used in catalytic cracking, that is, it can be used to crack naphthas, gas oil and residual oils having a high content of metal contaminants.It is especially suited for cracking hydrocarbons boiling in the gas oil range, that is, hydrocarbon oils having an atmospheric pressure boiling point ranging from about 450 to about 1100çF to yield not only products having a lower boiling point that the initial feed but also a naptha product having an improved octane number.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples are presented to illustrate the invention.

EXAMPLE 1 A large sample of a catalyst, herein designated catalyst A, was divided into 5 equal portions.

Catalyst A comprised 20 weight percent ultrastable Y type zeolite, 20 weight percent of discrete particles of porous alumina dispersed in a matrix of 60 weight percent silica-alumina gel based on the total catalyst (75 weight percent silica and 25 weight percent alumina). One portion was left unreacted. The remaining four portions were treated to different levels of rare earth metals by post-exchange, that is, by treating the composite catalyst. Post-exchange was accomplished by slurrying one part of catalyst by weight with 3 parts of water by weight. Enough nitric acid was added to adjust the slurry pH to between 6.0 and 6.5 and the slurry was heated to 135OF.

A mixed rare earth chloride solution was then added to the slurry to achieve the desired level of exchange. The rare earth solution contained the equivalent of 484 grams of rare earth oxide per liter of solution. After the rare earth solution had been added, the slurry was heated and stirred in an additional 60 minutes. The wet cake was then dried and calcined. This procedure was used to produce four catalysts, catalysts B, C, D and E, that differed from the parent catalyst only in the amount of rare earths added. All of the catalysts were then steamed 1 6 hours at 1400"F to stimulate the deactivation that would occur in a commercial cracking unit. The catalysts were then evaluated in two ways. Each was tested for activity using the standard microactivity test (MAT).Each catalyst was also evaluated using a circulating fluidized bed catalytic cracking unit with reactor and regenerator vessels. The feed used in this test is described in Table I. The operating conditions are described in Table II. Yield and product quality data from this test are given in Table Ill along with the rare earth levels and microactivity test results. It can be seen from Table ill that as rare earth level increases, activity and naphtha yields also increase. Coke and gas yields decreased. These very desirable effects are accomplished at some small loss in clear octane number. The octane number loss did not become significant until the ratio of rare earth oxide to zeloite as defined on page 2, was over 0.08.

Catalysts B and C are catalysts in accordance with the present invention. Catalysts A and D are not catalysts in accordance with the present invention.

TABLE I VACUUM GAS OIL FEED INSPECTIONS Gravity, "API at 60"F 22.5 Molecular weight 530.0 Carbon/hydrogen, wt. % 86.6/12.3 Sulfur, wt. % 1.243 Nitrogen, ppm 746 Conradson carbon, wt. % 0.44 Metals, wppm Fe 5.5 Ni 0.28 V 0.33 Bromine No. cgm/gm 5.16 Aniline Point, "F 183 Pour Point, F 98 Refractive index at 67"C 1.4937 Distillation, "F at Vol. % 5% 636 10/20 671/721 30/40 753/785 50 816 60/70 854/891 80/90 928/976 95% 1015 TABLE II OPERATING CONDITIONS Reactor Temperature, "F 925 Catalyst/oil wt. ratio 4.0 Feed rate(1), W/Hr/W 14 to 30 Regenerator Temperature, "F 1100 to 11 25 Carbon remaining on catalyst, wt. % 0.05 to 0.25 (1) Varied to change conversion TABLE 111 RARE EARTH POST-EXCHANGED CATALYSTS 20% USY, 20% Al203, 60% silica-alumina Catalyst A B C D RE203, wt. %( 0 0.022 0.036 0.098 RE203, wt. % on total catalyst 0 0.56 0.89 2.46 MAT Conversion, LV %(2) 64.7 69.1 70.2 70.2 Product Yields at 65 vol. % Conversion H2, wt. % of feed 0.051 0.043 0.049 0.024 Coke, wt. % 2.6 2.8 2.4 2.3 C3, wt. % 5.6 5.1 4.8 4.1 C5/430 Fnaphtha, vol. % 58.5 60.0 61.5 62.5 RON Clear3 93.9 92.8 92.8 90.4 MON Clear(4) 80.0 79.6 79.5 79.1 (1) Wt. % rare earth metal oxide based on total catalyst divided by wt. % zeolite on total catalyst.

(2) MAT is microactivity test. See Oil a Gas Journal 1966, vl. 64, pp. 7, 84, 85 and Nov. 2, 1971, pages 60-68.

(3) Research Octane Number Clear (4) Motor Octane Number Clear EXAMPLE 2 Two catalysts, catalysts E and F, were prepared and the composite catalyst E was post treated (post exchanged) with a rare earth metal salt solution in a manner similar to that described in Example 1. The catalysts E and F comprised 25 weight percent ultrastable Y type zeolite, 20 weight percent of discrete particles bulk porous alumina, dispersed in a matrix of 55 weight percent (based on total catalyst) silica alumina gel. The catalysts were evaluated in a microactivity test (MAT) and also in the same catalytic cracking unit described in Example 1.

Feed and operating conditions were the same as given in Tables I and II.

The results of these tests are summarized in Table IV.

TABLE IV Catalyst E F RE2Q, wt. %"' 0.067 0 Na2O, wt % on total catalyst 0.15 0.24 RE203 on total catalyst, wt. % 1.34 0 MAT Conversion, LV % 73.2 65.1 Product Yields at 65% Conversion H2,wt % on feed 0.029 0.030 Coke, wt % 2.6 2.6 C3-,wt.% 4.5 4.5 Cs/4306Fnaphtha, vol. % 61.0 59.4 RON Clear 92.2 92.4 MON Clear 79.3 79.9 (1) Wt. % rare earth metal oxide based on total catalyst divided by wt. % zeolite on total catalyst.

Catalyst E is a catalyst in accordance with the present invention. As can be seen from the data of Table IV, at a rare earth metal oxide to zeolite ratio of 0.067, there is only a slight decrease in octane number.

EXAMPLE 3 Three catalysts (catalysts H, I, J) comprising rare earth metal oxides at different levels were compared with a reference catalyst (herein designated catalyst G). All 4 catalysts comprised 20 weight percent ultrastable Y zeolite, 20 weight percent alumina in the form of discrete particles dispersed in a matrix of 60 weight percent (based on total catalyst) silica-alumina gel (75 wt. % silica; 25 wt. % alumina). Catalyst H was prepared by the post exchange of the composite catalyst procedure described in Example 1. Catalysts I and J were prepared by pre-exchanging only the ultrastable Y zeolite with a mixed rare earth chloride solution prior to adding the zeolite to the other catalyst components. Catalysts H and J are catalysts in accordance with the present invention. Catalysts G and I are not catalysts of the present invention.After the rare earth exchange step, the ultrastable Y zeolite was washed with water and then calcined 2 hours at 1000"F to ensure that the rare earth ions would remain in the ultrastable Y zeolite during the subsequent catalyst preparation steps. Catalysts G, H, I and J were evaluated using the same procedure described in Example 1 except that catalyst J was not tested in the fluidized bed catalytic cracking unit. The data obtained are summarized in Table V.

As can be seen from Table V, catalyst J compares favourably with catalysts at the same weight percent RE203 prepared by post exchanging the composite catalyst. Catalyst 1 showed no advantage over catalyst G which contained zero rare earth. The rare earth level of catalyst I was too low to change significantly the MAT conversion or the product yields and quality.

TABLE V Catalyst G H I J RE203, wt. %l1) 0 0.035 0.008 0.043 Na2O, wt. % on catalyst 0.12 0.08 0.07 0.15 Total RE2O3, wt. % 0 0.63 0.16 0.86 RE203 on USY, wt. % 0 3.5 0.8 4.31 MAT Conversion, LV % 64.0 68.3 61.4 71.9 TABLE V (continued) Catalyst G H I J Products Yields at 65% Conversion H2, wt. % on feed 0.058 0.036 0.036 Coke, wt. % 2.7 2.9 3.2 C3, wt. % 5.6 4.6 5.7 - C5/430 F naphtha, vol. % 57.5 62.0 56.5 RON Clear 93.6 92.7 93.6 MON Clear 80.1 79.7 80.2 (1) Wt. % rare earth metal oxide based on total catalyst divided by wt. % zeolite on total catalyst.

In this patent specification, temperatures expressed in "F are converted to "C by subtracting and then dividing by 1.8, and pressures in pounds per square inch guage (psig) are converted to gauge pressures in kg/cm2 by multiplying the former by 0.07031.

Claims (14)

1. A catalyst characterized in that it comprises: (a) an ultrastable Y-type crystalline alumino-silicate zeolite; (b) an inorganic oxide matrix, and (c) discrete particles of alumina; said zeolite prior to being composited with (b) having a unit cell size not greater than about 24.5 Angstroms, and said catalyst having a rare earth metal content such that the ratio of weight percent rare earth metal, calculated as the rare earth metal oxide, based on the total catalyst, divided by the weight percent zeolite based on the total catalyst ranges from about 0.01 to about 0.08.

2. The catalyst of claim 1 wherein said rare earth metal oxide ratio changes from about 0.01 to about 0.06.

3. The catalyst of claim 1 or claim 2 wherein said rare earth metal oxide ranges from about 0.01 to about 0.04.

4. The catalyst of any of claims 1 to 3 wheren said zeolite prior to being composited with (b) has a unit cell size not greater than about 24.4. Angstroms.

5. The catalyst of any of claims 1 to 4 wherein said zeolite is present in an amount ranging from about 1 to about 60 weight percent.

6. The catalyst of any of claims 1 to 5 wherein said catalyst has an alkali metal content of less than about 6 weight percent, calculated as the alkali metal oxide, based on the total catalyst.

7. The catalyst of any one of claims 1 to 6 wherein said particles of alumina have a surface area greater than about 20 m2/g and a pore volume greater than about 0.35 cc/g.

8. The catalyst of any one of claims 1 to 7 wherein said particles of alumina in themselves have less cracking activity than said organic oxide matrix.

9. The catalyst of any one of claims 1 to 8 wherein said particles of alumina are present in an amount ranging from about 5 to about 40 weight percent, said zeolite is present in an amount ranging from about 1 to about 40 weight percent and said inorganic oxide matrix is present in an amount ranging from about 40 to about 90 weight percent, each based on the total catalyst.

1 0. The catalyst according to any one of claims 1 to 9 substantially as hereinbefore described.

11. The catalyst according to claim 10 substantially as hereinbefore described with reference to the examples.

1 2. A process for the catalytic cracking of a hydrocarbon feedstock comprising said feedstock at catalytic cracking conditions with a catalyst as claimed in any one of claims 1 to 11.

1 3. A process for the catalytic cracking of a hydrocarbon feedstock according to claim 1 2 substantially as hereinbefore described with reference to the examples.

14. Catalytically cracked products of a process according to claim 1 2 or claim 1 3.