CN114797962B - Petroleum hydrocarbon catalytic cracking catalyst - Google Patents
Petroleum hydrocarbon catalytic cracking catalyst Download PDFInfo
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- CN114797962B CN114797962B CN202110122848.1A CN202110122848A CN114797962B CN 114797962 B CN114797962 B CN 114797962B CN 202110122848 A CN202110122848 A CN 202110122848A CN 114797962 B CN114797962 B CN 114797962B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/80—Mixtures of different zeolites
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
- C10G11/02—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils characterised by the catalyst used
- C10G11/04—Oxides
- C10G11/05—Crystalline alumino-silicates, e.g. molecular sieves
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
- B01J29/085—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
- B01J29/088—Y-type faujasite
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/405—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention belongs to the technical field of catalytic cracking, and relates to a petroleum hydrocarbon catalytic cracking catalyst which comprises 50-80 wt% of carrier, 4-20 wt% of Y-type molecular sieve and 10-30 wt% of modified ZSM-5-type molecular sieve according to dry basis weight; the phosphorus content in the modified ZSM-5 molecular sieve is P 2 O 5 Not less than 0.5 wt%, and the modified ZSM-5 molecular sieve has an average grain size of less than 150nm. The catalyst has higher low-carbon olefin yield.
Description
Technical Field
The invention relates to a petroleum hydrocarbon catalytic cracking catalyst.
Background
Ethylene, propylene, butylene and other low-carbon olefins are indispensable chemical raw materials, and can be used for synthesizing resins, fibers, rubber and the like. Propylene is an important raw material for manufacturing petrochemical products, and is mainly used for producing chemical products such as polypropylene, acrylonitrile, propylene oxide and the like. At present, propylene is mainly derived from byproducts of ethylene production by thermal cracking at home and abroad, the second largest source of propylene is the FCC unit, which provides about 30% of the demand, and in the united states, half of the demand for propylene by petrochemical products. Thus, the substantial production of propylene by FCC is an effective and efficient way to meet the growing demand.
ZSM-5 molecular sieveIs a high-silicon three-dimensional straight channel mesoporous molecular sieve (USP 3702886) with MFI structure, which has unique pore canal structure, belongs to orthorhombic system and has unit cell parameters of
The number of Al atoms in the unit cell can be changed from 0 to 27, and the silicon-aluminum ratio can be changed in a wide range; the ZSM-5 skeleton contains two 10-membered ring channel systems which are mutually intersected, wherein a channel is S-shaped bent, and the aperture is +.>
The pore canal is straight, and the pore diameter is +.>
ZSM-5 has the characteristics of good shape selective catalysis and isomerization performance, high heat and hydrothermal stability, high specific surface area, wide silicon-aluminum ratio variation range, unique surface acidity and lower carbon number, is widely used as a catalyst and a catalyst carrier, is successfully used in the production processes of alkylation, isomerization, disproportionation, catalytic cracking, methanol-to-gasoline, methanol-to-olefin and the like, and has been widely used in the production of low-carbon olefin catalytic cracking catalysts.
In recent years, as the blending amount of the catalytic cracking raw material increases, the proportion of macromolecules in the raw material gradually increases, and the yield of the low-carbon olefin is reduced. In addition, due to the heavy and poor quality of crude oil, crude oil prehydrogenation technology is increasingly popular, but the content of naphthenic rings in the hydrogenated heavy oil raw material is obviously increased, compared with macromolecular straight-chain hydrocarbon, the activation energy required by the ring-opening cracking of polycyclic naphthenic hydrocarbon is higher, and hydrogen transfer reaction and dehydrogenation reaction are easy to occur to convert into polycyclic aromatic hydrocarbon, so that the heavy oil conversion rate and the low-carbon olefin yield are reduced.
Disclosure of Invention
The invention aims to provide a catalyst for producing low-carbon olefin by catalytic cracking of petroleum hydrocarbon, which has higher yield of low-carbon olefin by heavy oil cracking. The second technical problem to be solved by the invention is to provide a preparation method of the catalyst.
The invention provides a catalytic cracking catalyst, which comprises 50-80 wt% of carrier, 4-20 wt% of Y-type molecular sieve and 10-30 wt% of small-grain phosphorus modified molecular sieve with MFI structure according to dry weight; the molecular sieve with the MFI structure modified by the small-grain phosphorus is a modified ZSM-5 molecular sieve (also called a modified ZSM-5 molecular sieve), the average grain size of the modified ZSM-5 molecular sieve is less than 150nm, and the phosphorus content is not less than 0.5 weight percent.
Preferably, the modified ZSM-5 molecular sieve has an external surface area of greater than 20m after aging at 800 ℃ for 17 hours under normal pressure in a 100% by volume water vapor atmosphere 2 /g。
Preferably, the modified ZSM-5 type molecular sieve is subjected to hydrothermal aging (hydrothermal aging is aging under an atmosphere of 100% by volume of water vapor at normal pressure) at 800℃for 17 hours, and the ratio of the amount of strong L acid to the amount of weak L acid is not less than 20, for example, 20 to 40, as measured by the pyridine adsorption infrared method.
Preferably, the ratio of the amount of strong B acid to the amount of weak B acid is not less than 1.0 as measured by a pyridine adsorption infrared method after the modified ZSM-5 type molecular sieve is subjected to hydrothermal aging at 800 ℃ for 17 hours.
Preferably, the modified ZSM-5 type molecular sieve is aged at 800 ℃ for 17 hours under normal pressure in a steam atmosphere of 100% by volume, and the ratio of the amount of B acid to the amount of L acid in the total acid amount of the modified ZSM-5 type molecular sieve measured at 200 ℃ by a pyridine adsorption infrared method is 3.0 to 6.0, for example, 3.5 to 5.5 or 4 to 5.
Preferably, the modified ZSM-5 molecular sieve has a pore volume of from 35% to 55%, for example from 35% to 45%, of the total pore volume of secondary pores having a pore diameter of from 2nm to 100nm after aging at 800℃for 17 hours under normal pressure in a 100% by volume steam atmosphere. The total pore volume and the pore volume of the secondary pores with the pore diameter of 2 nm-100nm are measured by a nitrogen adsorption capacity method.
According to the catalyst provided by the present invention, the modified ZSM-5 molecular sieve preferably has an average crystallite size of from 20nm to 100nm, for example from 30 to 100nm or from 40 to 80nm.
In the invention, the grain size is the largest dimension of the grain, and the pore diameter is the pore diameter.
Preferably, the modified ZSM-5 type molecular sieve has a lattice collapse temperature of not less than 1050 ℃, more preferably, the molecular sieve has a lattice collapse temperature of 1055 ℃ to 1080 ℃, for example, 1057 ℃ to 1075 ℃.
Preferably, the modified ZSM-5 molecular sieve has a relative crystal retention of 85% or more, for example, 85 to 95% after aging at 800℃under normal pressure in a 100% by volume steam atmosphere for 17 hours.
Preferably, the modified ZSM-5 type molecular sieve has a relative crystallinity of from 60 to 85%, for example from 70 to 85% or from 60 to 70% or from 65 to 80% or from 69 to 75% after aging at 800℃for 17 hours under normal pressure in a 100% by volume steam atmosphere.
Preferably, the modified ZSM-5 type molecular sieve has phosphorus oxide content of P 2 O 5 1.0 to 10% by weight, for example 4 to 9% by weight.
Preferably, the mole ratio of phosphorus to aluminum in the modified ZSM-5 molecular sieve is from 0.95 to 1.05, for example from 0.98 to 1.02.
Preferably, the modified ZSM-5 type molecular sieve has a silica-alumina ratio (silica/alumina molar ratio) of 20 to 50.
According to the catalyst provided by the invention, the modified ZSM-5 molecular sieve can be obtained by modifying a first ZSM-5 molecular sieve (or ZSM-5 molecular sieve before modification). After the first ZSM-5 molecular sieve is subjected to hydrothermal aging at 800 ℃ for 4 hours, the ratio of the amount of strong L acid to the amount of weak L acid is not lower than 2.9, for example not lower than 3.0 or 2.9-3.5 or 3.0-3.2, as measured by a pyridine adsorption infrared method.
Preferably, the first ZSM-5 molecular sieve has only L acid sites and no B acid sites as determined by a pyridine adsorption infrared method after being subjected to hydrothermal aging at 800 ℃ for 4 hours.
Preferably, the first ZSM-5 molecular sieve has an average crystallite size of less than 150nm, for example from 40 to 100nm.
In one embodiment, the method for preparing the modified ZMS-5 molecular sieve comprises the following steps: and (3) contacting the first ZSM-5 molecular sieve with a phosphorus-containing compound solution with the pH value of 4-10, drying and roasting to obtain the modified ZSM-5 molecular sieve.
The first ZSM-5 molecular sieve is contacted with a phosphorus-containing compound solution with the pH value of 4-10, and the first ZSM-5 molecular sieve can be subjected to impregnation modification by using the phosphorus-containing compound, wherein the impregnation method is the prior art, and can be, for example, equal volume impregnation or excessive impregnation; the phosphorus-containing compound may be selected from one of phosphoric acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate and ammonium phosphate or a mixture thereof.
The first ZSM-5 molecular sieve may be obtained by:
(1) Dissolving an aluminum source in water, adding an alkali source and a template agent, uniformly stirring for more than 30 minutes, for example, 30-60 minutes, adding a silicon source, and stirring for more than 0.5 hour, for example, 0.5-3 hours, for example, 1 hour to obtain a reaction mother solution; wherein, the mole ratio of the silicon source, the aluminum source, the alkali source, the template agent and the water is as follows: R/SiO 2 ＝0.06-10:1，H 2 O/SiO 2 ＝2-200:1，SiO 2 /Al 2 O 3 ＝10-200:1，Na 2 O/SiO 2 =0-2:1, wherein R represents a templating agent;
the silicon source is one or more of silica sol, water glass, methyl orthosilicate, ethyl orthosilicate and solid silica gel; the aluminum source is, for example, one or more of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum isopropoxide, aluminum sol; the alkali source is one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide; the template agent is one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine and hexamethylenediamine;
(2) Dynamic crystallization is carried out on the reaction mother liquor, and the dynamic crystallization is two-step hydrothermal crystallization: firstly, crystallizing and nucleating at a low temperature of 80-160 ℃ for 0.5-5 hours; then raising the temperature to 160-180 ℃ for high-temperature crystallization growth, wherein the crystallization time is preferably 12-36 hours;
(3) Filtering, washing and drying the crystallized product, and roasting at 500-600 ℃ for 2-6 hours to remove the template agent to obtain a roasted small-grain ZSM-5 molecular sieve;
(4) And carrying out ammonium exchange on the calcined small-grain ZSM-5 molecular sieve to obtain an H-shaped small-grain ZSM-5 molecular sieve, namely a first ZSM-5 molecular sieve.
The catalyst provided by the invention contains a Y-type molecular sieve, and the Y-type molecular sieve is preferably a modified small-grain Y-type molecular sieve.
Preferably, the modified small-grain Y-type molecular sieve is a first modified small-grain Y-type molecular sieve, na of which 2 The O content is not more than 1 wt%, the unit cell constant is 2.430-2.450nm, the non-framework aluminum content is not more than 20% of the total aluminum content, the lattice collapse temperature is not less than 1050 ℃, the ratio of the B acid amount to the L acid amount is not less than 3.0, and the acid amount of the outer surface is 220-300 mu mol/g. The ratio of the amount of B acid to the amount of L acid is the ratio of the amount of B acid to the amount of L acid (total amount of B acid to total amount of L acid) measured at 200 ℃ by a pyridine adsorption infrared method, and the amount of the acid on the outer surface is measured by using a 2,4, 6-trimethylpyridine macromolecular probe molecule.
According to the invention, the average grain size of the first modified small-grain Y-type molecular sieve is 0.3-0.9 or 0.4-0.8 microns.
Na in the first modified small-grain Y-type molecular sieve 2 The O content is preferably 0.1 to 0.7% by weight, for example, may be 0.3 to 0.7% by weight, for example, 0.35 to 0.60% by weight or 0.39 to 0.55% by weight.
The ratio of the amount of B acid to the amount of L acid of the first modified small-grain Y-type molecular sieve can be 3.0 to 4.5, such as 3.1 to 4.
The first modified small-grain Y-type molecular sieve preferably has a lattice collapse temperature of 1055 ℃ to 1085 ℃, for example 1060 ℃ to 1085 ℃.
The crystallinity retention is preferably 38-45% after the first modified small-grain Y-type molecular sieve is aged at 800 ℃ under normal pressure in a 100% by volume water vapor atmosphere for 17 hours. The normal pressure is 1atm.
The first modified small-grain Y-type molecular sieve preferably has a relative crystallinity of 50 to 70%, preferably 61 to 69%.
RE is used in the first modified small-grain Y-type molecular sieve 2 O 3 The calculated rare earth content is 0-5 wt%.
The first modified small-grain Y-shaped molecular sieve has high thermal and hydrothermal stability. The catalyst provided by the invention can have higher activity, obviously higher ethylene yield and obviously higher propylene yield by using the first modified small-grain Y-shaped molecular sieve.
In the catalyst provided by the invention, the first modified small-grain Y-shaped molecular sieve can be prepared by a preparation method comprising the following steps:
(1) The small-grain NaY molecular sieve is contacted with rare earth salt solution and/or ammonium salt solution to carry out ion exchange reaction, and is filtered and washed to obtain the Y-type molecular sieve with the conventional unit cell size and reduced sodium oxide content; wherein the rare earth solution is also called rare earth salt solution; preferably, the exchange is carried out to ensure that the rare earth oxide content in the finally obtained modified small-grain Y-type molecular sieve is RE 2 O 3 No more than 5% by weight; the small-grain NaY molecular sieve has an average grain size of no more than 0.9 microns, preferably 0.3 to 0.9 microns, for example 0.4 to 0.8 microns;
(2) Roasting the conventional unit cell size Y-type molecular sieve with reduced sodium oxide content, wherein the roasting treatment is preferably that the conventional unit cell size Y-type molecular sieve with reduced sodium oxide content is roasted at 450-650 ℃ for 4.5-7 hours, and optionally drying to obtain a roasted Y-type molecular sieve; wherein the water content of the calcined Y-type molecular sieve preferably does not exceed 1 wt.%; if the water content in the Y-type molecular sieve sample obtained by the modification treatment in the step (2) (in the Y-type molecular sieve sample obtained by roasting) is not more than 1 weight percent, the Y-type molecular sieve sample can be directly used for being contacted with silicon tetrachloride to carry out the reaction, and if the water content in the Y-type molecular sieve sample obtained by the roasting in the step (2) is more than 1 weight percent, the Y-type molecular sieve obtained by the roasting in the step (2) is dried to ensure that the water content is lower than 1 weight percent;
(3) Mixing the calcined Y-type molecular sieve with SiCl 4 Gas contact reaction; wherein the reaction temperature is preferably 300-550 ℃, siCl 4 : the weight ratio of the calcined Y-type molecular sieve obtained in step (2) on a dry basis is preferably 0.1 to 0.7:1, the reaction time is preferably 10 minutes to 5 hours, and then the modified Y-type molecular sieve with reduced unit cell constant (called modified Y-type molecular sieve I) is obtained through washing and filtering; and
optionally (4) contacting the product of step (3) with an ammonium salt solution for ion exchange so that the sodium oxide content in the molecular sieve is not more than 1 weight percent, and obtaining a product called a modified Y-type molecular sieve II;
(5) And (3) contacting the molecular sieve with the sodium oxide content of less than 1 weight percent obtained in the step (3) or the step (4) with an ammonium fluosilicate solution. Wherein water: ammonium fluorosilicate: the weight ratio of molecular sieves is preferably from 5 to 20:0.002 to 0.3:1, for example water: ammonium fluorosilicate: the weight ratio of the molecular sieve is 5-10:0.005-0.1:1 or 5-15:0.05-0.2:1.
according to the catalyst provided by the invention, in the preparation method of the first modified small-grain Y-type molecular sieve, in the step (1), the small-grain NaY molecular sieve and the rare earth solution and/or the ammonium salt solution are subjected to ion exchange reaction so as to obtain the Y-type molecular sieve with the conventional unit cell size and reduced sodium oxide content. The small-grain NaY molecular sieves, which are commercially available or prepared according to existing methods, have a unit cell constant of 2.465 to 2.472nm, a framework silica to alumina ratio (SiO 2 /Al 2 O 3 Molar ratio) of 4.5 to 5.2, a relative crystallinity of 85% or more, for example, 85 to 95%, and a sodium oxide content of 13.0 to 13.8% by weight.
According to the catalyst provided by the invention, in the preparation step (1) of the first modified small-grain Y-type molecular sieve, the small-grain NaY molecular sieve and the rare earth solution and/or the ammonium salt solution are subjected to ion exchange reaction, wherein the exchange temperature is preferably 15-95 ℃, for example 65-95 ℃, and the exchange time is preferably 30-120 minutes, for example 45-90 minutes. The ion exchange reaction can be carried out by contacting with a solution containing rare earth salt and a solution containing ammonium salt respectively, or by contacting with a solution containing both rare earth salt and ammonium salt. The ion exchange reaction may be carried out one or more times. Preferably, the small-grain NaY molecular sieve (on a dry basis) is a rare earth salt and/or ammonium salt (rare earth salt is RE) 2 O 3 Meter (meter): H 2 O=1:0-0.10:5-15 weight ratio, wherein the weight ratio of the sum of rare earth salt and ammonium salt to NaY molecular sieve is not less than 0.001:1, rare earth salts and/or ammonium salts: the weight ratio of the NaY molecular sieve is, for example, 0.01 to 0.08:1. small grain NaY molecular sieves (on a dry basis) of rare earth salts and/or ammoniumSalt (rare earth salt RE) 2 O 3 Meter (meter): H 2 O is, for example, 1:0.005-0.10:5-15. Preferably, the weight ratio of rare earth salt to NaY molecular sieve (on a dry basis) is 0-0.05:1, the weight ratio of the ammonium salt to the NaY molecular sieve (based on dry basis) is 0-0.1:1. the rare earth salt and/or ammonium salt solution is an aqueous solution of rare earth salt and/or ammonium salt.
According to the catalyst provided by the invention, in the preparation step (1) of the first modified small-grain Y-type molecular sieve, in one implementation mode, the ion exchange reaction of the NaY molecular sieve and the rare earth solution comprises the steps of according to the NaY molecular sieve, rare earth salt and/or ammonium salt, and H 2 The weight ratio of o=1:0.001 to 0.10:5 to 15 forms a mixture of small-grain NaY molecular sieve (also known as NaY zeolite), rare earth salt and/or ammonium salt and water, such as decationized water, deionized water or a mixture thereof, with stirring at 15 to 95 ℃, such as 65 to 95 ℃, preferably for 30 to 120 minutes, to exchange rare earth ions and/or ammonium ions for sodium ions. Small-grain NaY molecular sieve, rare earth salt and/or ammonium salt and water are formed into a mixture, naY molecular sieve and water can be formed into slurry in a ratio of 1:5-15, and then aqueous solution of rare earth salt and/or ammonium salt and/or aqueous solution of ammonium salt is added into the slurry. The solution of rare earth salt is simply referred to as rare earth solution. The rare earth salt is preferably rare earth chloride and/or nitrate, and the ammonium salt is one or more of ammonium nitrate, ammonium sulfate and ammonium chloride. One or more of the rare earths, for example La, ce, pr, nd, and mischmetal containing, in one embodiment, one or more of La, ce, pr, and Nd, or at least one of the rare earths other than La, ce, pr, and Nd.
According to the catalyst provided by the invention, in the preparation step (1) of the first modified small-grain Y-type molecular sieve, the washing in the step (1) aims at washing out exchanged sodium ions, for example, deionized water or decationizing water can be used for washing. Preferably, the rare earth content of the conventional unit cell size Y-type molecular sieve with or without rare earth having reduced sodium oxide content obtained in step (1) is RE 2 O 3 0-5 wt%, e.g. 0-3 wt%, and sodium oxide content of not more than 12 wt%, e.g. 4-11.5 wt% or 4-9 wt.%, for example 5.5-8.5 wt.% or 5.5-7.5 wt.%, with a unit cell constant of 2.465nm-2.472nm.
In a preferred embodiment, the synthesis method of the small-grain NaY molecular sieve comprises the following steps:
(s 1) preparing a NaY molecular sieve crystallization directing agent;
(s 2) SiO in molar ratio 2 ：Al 2 O 3 Aluminate is added into NaY synthetic mother liquor according to the proportion of (5-18), and pH value is adjusted to (5-12) to prepare silica-alumina gel slurry;
(s 3) filtering and washing the silica-alumina gel slurry of (s 2) to obtain a gel filter cake, wherein the molar composition of the gel filter cake accords with Na 2 O：Al 2 O 3 ：SiO 2 ：H 2 O=0.5-2.5: 1:5-18:100-500 parts of a mixture ratio;
(s 4) uniformly mixing the gel filter cake in (s 3), the NaY molecular sieve crystallization directing agent in (s 1) and alkali liquor to obtain a synthetic gel mixture, wherein the composition of the synthetic gel mixture accords with Na 2 O：Al 2 O 3 ：SiO 2 ：H 2 O=1.5-8: 1:5-18:100-500 mol ratio, wherein Al in the NaY molecular sieve crystallization directing agent 2 O 3 Is contained in the synthetic gel mixture 2 O 3 1% -20% of the total amount;
(s 5) crystallizing the synthetic gel mixture obtained in the step (s 4) at the temperature of 70-120 ℃ for 10-50 h to obtain the small-grain NaY molecular sieve.
In the synthesis method of the small-grain NaY molecular sieve, the aluminate can be one or a mixture of more of aluminum sulfate, aluminum chloride, aluminum nitrate and aluminum phosphate.
In the synthesis method of the small-grain NaY molecular sieve, the guiding agent is prepared from a silicon source, an aluminum source, alkali liquor and deionized water according to (15-18) Na 2 O:Al 2 O 3 :(15-17)SiO 2 :(280-380)H 2 Mixing the O in a molar ratio, uniformly stirring, and standing and aging for 0.5-48h at the temperature of between room temperature and 70 ℃.
In the synthesis method of the small-grain NaY molecular sieve, the silicon source can be sodium silicate, the aluminum source is sodium metaaluminate, and the alkali liquor is sodium hydroxide solution.
In the synthesis method of the small-grain NaY molecular sieve, preferably, the SiO in the step (s 2) 2 ：Al 2 O 3 ＝7-10。
In the synthesis method of the small-grain NaY molecular sieve, the pH value in the step (s 2) is=7-10.
In the synthesis method of the small-grain NaY molecular sieve, the gel filter cake in the step (s 3) preferably comprises Na in molar composition ratio 2 O：Al 2 O 3 ：SiO 2 ：H 2 O＝1-2：1：6-10：150-400。
In the synthesis method of the small-grain NaY molecular sieve, the mixture ratio of the synthesis gel in the step (s 4) is preferably Na 2 O：Al 2 O 3 ：SiO 2 ：H 2 O＝2-6：1：7-10：150-400。
In the synthesis method of the small-grain NaY molecular sieve, preferably, in the step (s 4), al in the directing agent 2 O 3 Is contained in Al in the synthetic gel mixture 2 O 3 5-15 mole% of the total amount.
The synthesis method of the small-grain NaY molecular sieve can also comprise the process of collecting the synthetic mother liquor obtained in the step (s 5) after the step (s 5), and the collected synthetic mother liquor is mixed with the mother liquor of the conventional synthesis process to prepare the silica-alumina gel for the next cycle.
According to the catalyst provided by the invention, in the preparation method of the modified small-grain Y-type molecular sieve, the Y-type molecular sieve with the conventional unit cell size containing rare earth is roasted at the temperature of 450-650 ℃, such as 450-600 ℃ in the step (2), the roasting time is preferably 4.5-7 hours, such as 5-6.5 hours, and the roasting temperature in the step (2) is preferably 500-600 ℃ and the roasting time is 5-6 hours.
According to the catalyst provided by the invention, in the preparation method of the first modified small-grain Y-type molecular sieve, siCl is added in the step (3) 4 : the weight ratio of the Y-type zeolite (on a dry basis) is preferably 0.3 to 0.6:1, the temperature of the reaction is preferably 300-550 ℃, and the washing method in the step (3) The method can employ a conventional washing method, and can be washed with water such as deionized water or deionized water, in order to remove Na remaining in the zeolite + 、Cl - Al and Al 3+ Such soluble byproducts, e.g., wash conditions, may be: the weight ratio of the washing water to the molecular sieve can be 5-20:1, typically molecular sieves: h 2 O weight ratio=1:6-15, pH value is preferably 2.5-5.0, washing temperature is 30-60 ℃. Preferably, the washing is performed such that no free Na is detected in the washing solution after washing + 、Cl - Al and Al 3+ Plasma, preferably Na in the washing water after washing + 、Cl - Al and Al 3+ The respective content of ions is not more than 0.05% by weight. The modified Y-type molecular sieve having a reduced unit cell constant in step (3) preferably has a unit cell constant of 2.430nm to 2.450nm.
According to the catalyst provided by the invention, in the first preparation method of the modified small-grain Y-type molecular sieve, if the sodium oxide of the modified Y-type molecular sieve with the reduced unit cell constant obtained in the step (3) is higher than 1 weight percent, preferably, the preparation method further comprises the step (4) of contacting the product of the preparation step (3) of the modified small-grain Y-type molecular sieve with an ammonium salt solution for ion exchange so that the sodium oxide content in the molecular sieve is not more than 1 weight percent. Such as one or more of ammonium chloride, ammonium nitrate, ammonium sulfate.
According to the catalyst provided by the invention, in the preparation method of the first modified small-grain Y-type molecular sieve, in the step (5), the molecular sieve obtained in the step (4) is contacted with an ammonium fluosilicate solution, wherein the contact temperature is preferably 70-90 ℃, and the contact time is preferably 0.5-2h.
According to the catalyst provided by the invention, in the preparation method of the first modified small-grain Y-type molecular sieve, the step (5) can further comprise roasting, wherein the roasting temperature is preferably 400-600 ℃, and the roasting time is preferably 1-5h.
Preferably, in one embodiment, step (5), the modified Y-type molecular sieve I with a reduced unit cell constant obtained in step (3) or the modified Y-type molecular sieve II obtained in step (4) is mixed with water, such as deionized water, in a ratio of 1:5-10, and an ammonium fluorosilicate solution with a concentration of 0.05-0.4mol/L, such as 0.1-0.3mol/L, is added at 70-90 ℃, and the resulting mixture is stirred at 70-90 ℃ for 0.5-2 hours, preferably, the ratio of ammonium fluorosilicate to water in the mixture is preferably 0.01-0.1mol/L, such as 0.03-0.08mol of ammonium fluorosilicate/L water; then filtering, drying and washing, and roasting for 1-5 hours at 400-600 ℃ to obtain the modified Y-type molecular sieve III, namely the first modified small-grain Y-type molecular sieve provided by the invention. The unit cell constant is preferably 2.330nm to 2.450nm.
The first modified small-grain Y-shaped molecular sieve obtained by the method provided by the invention is used for the catalyst provided by the invention, has higher activity, and can be used for catalytic cracking of heavy oil, so that the yield of low-carbon olefin is higher, and the yield of propylene is obviously higher, compared with the molecular sieve obtained by the step (4).
In the catalyst provided by the invention, the carrier can be a carrier commonly used for catalytic cracking catalysts. For example, the catalyst support provided by the present invention may optionally contain the following components: (1) A binder, such as an aluminum binder and/or a silicon binder, which may be selected from pseudo-boehmite and/or an aluminum sol; the silicon binder is one or more of acidic silica sol, neutral silica sol, alkaline silica sol and water glass, preferably silica sol. The binder may be present in an amount of 5 to 60 wt%, e.g. 10 to 55 wt%, or 20 to 50 wt%, or 30 to 50 wt%, based on the weight of the catalyst, on a dry basis. In one embodiment, the silica sol binder is present in an amount of 1 to 15 wt.%, preferably 5 to 15 wt.%, based on the total weight of the catalyst, on an oxide basis. (2) The inorganic oxide matrix is 0-80 wt%, preferably 10-70 wt%, based on the total weight of the catalyst, and is one or more of inorganic oxide matrixes commonly used in cracking catalysts, preferably one or more of alumina, silica, amorphous silica-alumina and clay. The clay is selected from clay commonly used for cracking catalyst, such as one or more selected from kaolin, halloysite, montmorillonite, kieselguhr and rectorite, preferably kaolin. The precursor of amorphous silica-alumina can be selected from silica-alumina sol, mixture of silica-sol and alumina sol, silica-alumina gel One or more of them. The precursor of the silica matrix may be selected from one or more of silica gel, solid silica gel, etc., such as various forms of alumina such as χ -Al 2 O 3 、δ-Al 2 O 3 、η-Al 2 O 3 、κ-Al 2 O 3 、θ-Al 2 O 3 、ρ-Al 2 O 3 、α-Al 2 O 3 And gamma-Al 2 O 3 One or more of the following.
The catalyst provided by the invention can be prepared by adopting the following method: mixing Y-type molecular sieve, modified ZSM-5-type molecular sieve, carrier and water, pulping, drying and obtaining cracking catalyst. The support preferably comprises an inorganic oxide matrix and a binder such as a silicon binder and/or an aluminium binder. The solids content of the slurry formed by beating is generally from 10 to 50% by weight, preferably from 15 to 30% by weight. The drying condition after beating is the drying condition commonly used in the preparation process of the catalytic cracking catalyst. Generally, the drying temperature is from 100 to 350℃and preferably from 200 to 300 ℃. The drying may be by a drying, forced air drying or spray drying method, preferably a spray drying method.
The invention further provides a heavy oil catalytic cracking method, which comprises the step of carrying out contact reaction on heavy oil and the catalyst provided by the invention.
The catalyst provided by the invention is used for heavy oil conversion, and has higher low-carbon olefin yield. Preferably, the catalyst provided by the invention has higher stability, is used for catalytic cracking of macromolecular hydrocarbon such as heavy oil, can have higher conversion activity and higher low-carbon olefin yield, can have higher propylene yield and has obviously higher ethylene yield.
Detailed Description
The catalyst provided by the invention comprises the following components in percentage by weight based on the dry weight of the catalyst: 50-80 wt%, preferably 55-75 wt% of the carrier on a dry basis; 4-20 wt%, preferably 10-20 wt%, of the Y-type molecular sieve on a dry basis; the modified ZSM-5 molecular sieve is present in an amount of from 10 to 30 wt%, for example from 10 to 25 wt%, preferably from 15 to 25 wt%, on a dry basis.
The catalyst provided by the invention contains a modified ZSM-5 type molecular sieve, the average grain size of the modified ZSM-5 type molecular sieve is less than 150nm, and the external surface area is more than 20m 2 /g, lattice collapse temperature not lower than 1050 ℃; after the ZSM-5 molecular sieve before modification is subjected to hydrothermal aging at 800 ℃ for 4 hours, determining that only L acid sites are available and B acid sites are unavailable by using a pyridine adsorption infrared method, wherein the ratio of the amount of strong L acid to the amount of weak L acid is not lower than 3.0; after the modified ZSM-5 molecular sieve is subjected to hydrothermal aging at 800 ℃ for 17 hours, the ratio of the amount of strong B acid to the amount of weak B acid is not lower than 1.0, and the ratio of the amount of strong L acid to the amount of weak L acid is not lower than 20.0, as measured by a pyridine adsorption infrared method. The Y-type molecular sieve is preferably a modified small-grain Y-type molecular sieve, na of which 2 The O content is not more than 1 wt%, the unit cell constant is 2.430-2.450nm, the non-framework aluminum content is not more than 20% of the total aluminum content, the lattice collapse temperature is not less than 1050 ℃, the ratio of the B acid amount to the L acid amount is not less than 3.0, and the acid amount of the outer surface is 220-300 mu mol/g.
The support is preferably one or more of a clay, an alumina support, a silica support and a silica-alumina support, for example the support is a natural clay/alumina support, a natural clay/alumina/silica support. Alumina supports such as alumina and/or precursors of alumina such as pseudo-boehmite and/or alumina sol; such as solid silica gel and/or silica sol. The silicon-aluminum carrier is one or more of mesoporous silicon-aluminum materials, silicon-aluminum gel and silicon-aluminum sol. Preferably, the carrier comprises silica sol, and the silica sol is one or more of neutral silica sol, acidic silica sol or alkaline silica sol, and SiO is used in the catalyst 2 The content of silica sol is preferably 1 to 15% by weight.
The reaction condition of the heavy oil catalytic cracking method provided by the invention is the conventional reaction condition of the general hydrocarbon cracking process, such as the reaction temperature is 400-600 ℃, preferably 450-600 ℃, for example 520-580 ℃, and the weight hourly space velocity is 5-30 hours -1 Preferably 8-25 hours -1 The ratio of the agent to the oil is 1-10, preferably 2-7. The catalyst to oil ratio refers to the weight ratio of catalyst to raw oil.
The invention will be further illustrated by the following examples, which are not to be construed as limiting the invention.
Comparative example ZSM-5 molecular sieve starting material was purchased from Kaolin, inc. of petrochemical catalyst, inc. The detailed parameters are shown in table 1.
NaY1 molecular sieve (also called NaY zeolite) is provided by Qilu division of China petrochemical catalyst Co., ltd, the sodium oxide content is 13.5 weight percent, and the skeleton silicon-aluminum ratio (SiO 2 /Al 2 O 3 Molar ratio) =4.6, unit cell constant of 2.470nm, relative crystallinity of 90%; the average crystallite size of the NaY1 molecular sieve was 600nm.
The kaolin used was an industrial product of China Kaolin company, having a solids content of 84% by weight; the pseudo-boehmite is produced by Shandong aluminum factory, and the alumina content of the pseudo-boehmite is 35 weight percent; the alumina sol was produced by catalyst works in Shandong country and had an alumina content of 21 wt%. Silica sol was produced by Beijing chemical plant, and had a silica content of 25% by weight and a pH of 10.
The analysis method comprises the following steps: in each of the comparative examples and examples, the elemental content of zeolite was determined by X-ray fluorescence spectrometry; the unit cell constant, relative crystallinity of the zeolite was measured by X-ray diffraction.
The method for measuring the relative crystallinity is described in "petrochemical analysis method (RIPP test method)" (Yang Cuiding et al, scientific Press, 1990, published) as RIPP 146-90 standard method.
The powder diffraction method (XRD) was carried out by using RIPP145-90 (see, e.g., petrochemical analysis method (RIPP test method) Yang Cuiding, published by science Press, 1990), and the framework silica-alumina ratio of zeolite was calculated from the following formula: siO (SiO) 2 /Al 2 O 3 ＝(2.5858-a0)×2/(a0-2.4191)]Wherein a0 is a unit cell constant in nm; the total silicon-aluminum ratio of the zeolite is calculated according to the content of Si and Al elements measured by an X-ray fluorescence spectrometry, and the ratio of skeleton Al to total Al can be calculated according to the ratio of skeleton Si-Al measured by an XRD method to the ratio of total Si-Al measured by an XRF method, so that the ratio of non-skeleton Al to total Al is calculated.
The collapse temperature of the crystal structure was determined by Differential Thermal Analysis (DTA).
In each of the comparative examples and examples, the acid center type of the molecular sieve and the acid amount thereof were determined by infrared analysis of pyridine adsorption. Experimental instrument: bruker company IFS113V type FT-IR (Fourier transform Infrared) spectrometer, U.S. The acid amount measurement experiment method by pyridine adsorption infrared method at 200 ℃ comprises the following steps: and (3) performing self-supporting tabletting on the sample, and sealing in an in-situ cell of an infrared spectrometer. Heating to 400 ℃, and vacuumizing to 10 DEG C -3 Pa, keeping the temperature for 2h, and removing gas molecules adsorbed by the sample. Cooling to room temperature, and introducing pyridine vapor with the pressure of 2.67Pa for 30min to keep adsorption balance. Then heating to 200 ℃, vacuumizing to 10 DEG C -3 Desorbing for 30min under Pa, cooling to room temperature, photographing, and scanning the wave number range: 1400cm -1 ～1700cm -1 And obtaining a pyridine adsorption infrared spectrogram of the sample subjected to desorption at 200 ℃. According to 1540cm in pyridine adsorption infrared spectrogram -1 And 1450cm -1 The intensity of the characteristic adsorption peak to obtain the total molecular sieve
The relative amounts of acid centers (B acid centers) and Lewis acid centers (L acid centers).
In each of the comparative examples and examples, the secondary pore volume was measured as follows: the total pore volume of the molecular sieve was determined from the adsorption isotherm according to the standard method RIPP 151-90, petrochemical analysis method (RIPP test method) (Yang Cuiding et al, scientific Press, 1990), and then the micropore volume of the molecular sieve was determined from the adsorption isotherm according to the T-plot method, and the secondary pore volume was obtained by subtracting the micropore volume from the total pore volume.
The grain size of the molecular sieve is the size of the widest part of the projection plane of the grain of the molecular sieve. Can be obtained by measuring the maximum circumscribed circle diameter of the crystal grains or particles of a projection electron microscope (TEM) image or a Scanning Electron Microscope (SEM) image of the molecular sieve. The average grain size is an average of 10 grain sizes measured randomly; the average particle size is the average of 10 randomly measured particle sizes.
The chemical reagents used in the comparative examples and examples are not particularly noted and are chemically pure in specification.
Molecular sieve preparation example 1
(1) 3.05 g of sodium aluminate is dissolved in 70 g of water, 6.5 g of sodium hydroxide and 14.5 g of tetrapropylammonium bromide are added, after stirring for 30 minutes, 21.7 g of solid silica gel is added, and stirring is carried out for 1 hour; obtaining a reaction mother solution;
(2) Placing the reaction mother solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining for dynamic crystallization, wherein the dynamic crystallization is two-step hydrothermal crystallization: firstly, crystallizing and nucleating at a low temperature of 80 ℃ for 5 hours; then raising the temperature to 170 ℃ for crystallization growth for 24 hours;
(3) Filtering, washing and drying the crystallized product, roasting at 550 ℃ for 4 hours, and removing the template agent; obtaining a small-grain ZSM-5 molecular sieve after roasting;
(4) Ammonium exchange is carried out on the calcined small-grain ZSM-5 molecular sieve to obtain an H-type small-grain ZSM-5 molecular sieve, which is marked as Z1, and the properties are shown in Table 1.
Will be 1.35g H 3 PO 4 Dissolving (concentration 85 wt%) in 10g deionized water, adding into 10g ZSM-5 molecular sieve Z1 (average grain size 50nm, solid content 94 wt%) and using 25 wt% ammonia water to regulate pH value of the mixture to 6, and fully and uniformly mixing; after filtration, drying for 4 hours at 115 ℃ under air atmosphere; then roasting at 550 ℃ for 2 hours; the modified ZSM-5 type molecular sieve provided by the invention is obtained and is marked as PZ1, and the physicochemical properties are shown in Table 1. After PZ1 was aged at 800℃for 17 hours with 1atm and 100% by volume of water vapor in a bare state, the relative crystallinity before and after aging of PZ1 was analyzed by XRD and the relative crystallinity retention after aging was calculated, and the results are shown in Table 1.
Molecular sieve preparation example 2
(1) 3.05 g of aluminum isopropoxide is dissolved in 9 g of water, then 0.7 g of sodium hydroxide and 28 g of tetrapropylammonium hydroxide are added, and after stirring for 30 minutes, 20.0 g of solid silica gel is added and stirring is carried out for 1 hour; obtaining a reaction mother solution;
(2) Placing the reaction mother solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining for dynamic crystallization, wherein the dynamic crystallization is two-step hydrothermal crystallization: firstly, crystallizing and nucleating at a low temperature of 120 ℃ for 2 hours; then raising the temperature to 170 ℃ for crystallization growth for 24 hours;
(3) Filtering, washing and drying the crystallized product, roasting at 550 ℃ for 4 hours, and removing the template agent; obtaining a small-grain ZSM-5 molecular sieve after roasting;
(4) And (5) carrying out ammonium exchange on the calcined small-grain ZSM-5 molecular sieve to obtain an H-type small-grain ZSM-5 molecular sieve, which is marked as Z2.
1.55g (NH) 4 ) 2 HPO 4 Dissolving (content 99%) in 10g deionized water, adding into 10g ZSM-5 molecular sieve Z2 (solid content 94 wt%), adjusting pH to 6 with 25 wt% ammonia water, and mixing thoroughly; after filtration, drying for 4 hours at 115 ℃ under air atmosphere; then roasting at 550 ℃ for 2 hours; the modified ZSM-5 type molecular sieve was obtained and designated PZ2. The retention of crystals after aging at 800℃under 1atm for 17 hours with 100% by volume of water vapor in the bare state is shown in Table 1.
Molecular sieve preparation example 3
(1) 2.5 g of aluminum chloride hexahydrate is dissolved in 145 g of water, 1.3 g of sodium hydroxide and 26.4 g of tetrapropylammonium hydroxide are added, and after stirring for 30 minutes, 25 g of ethyl orthosilicate is added and stirred for 1 hour; obtaining a reaction mother solution;
(2) Placing the reaction mother solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining for dynamic crystallization, wherein the dynamic crystallization is two-step hydrothermal crystallization: firstly, crystallizing and nucleating at a low temperature of 100 ℃ for 3 hours; then crystallizing and growing at 170 ℃ for 24 hours;
(3) Filtering, washing and drying the crystallized product, roasting at 550 ℃ for 4 hours, and removing the template agent; obtaining a small-grain ZSM-5 molecular sieve after roasting;
(4) And (3) carrying out ammonium exchange on the calcined small-grain ZSM-5 molecular sieve to obtain an H-type small-grain ZSM-5 molecular sieve, which is marked as Z3.
1.35g NH 4 H 2 PO 4 Dissolving (content 99%) in 10g deionized water, adding into 10g ZSM-5 molecular sieve Z3 (solid content 94 wt%), adjusting pH of the mixture to 6 with 25 wt% ammonia water, and mixing thoroughly; after filtration, drying for 4 hours at 115 ℃ under air atmosphere; then roasting at 550 ℃ for 2 hours; the modified ZSM-5 type molecular sieve was obtained and designated PZ3. The retention of crystals after aging at 800℃under 1atm for 17 hours with 100% by volume of water vapor in the bare state is shown in Table 1.
TABLE 1
* Properties after aging at 800℃under normal pressure in a 100% by volume water vapor atmosphere for 17 hours.
Preparation of molecular sieves comparative example 1
1.55g (NH) 4 ) 2 HPO 4 Dissolving (content 99%) in 10g deionized water, adding into 10g ZSM-5 molecular sieve (average grain size 600nm, solid content 94 wt%, denoted as Z4), adjusting pH to 6 with 25 wt% ammonia water, and mixing thoroughly; after filtration, drying for 4 hours at 115 ℃ under air atmosphere; then roasting at 550 ℃ for 2 hours; the modified ZSM-5 type molecular sieve was obtained and was designated DZ1. The physicochemical properties are shown in Table 1. The retention of crystals after aging at 800℃under 1atm for 17 hours with 100% by volume of water vapor in the bare state is shown in Table 1.
Molecular sieve preparation comparative example 2
1.55g (NH) 4 ) 2 HPO 4 Dissolving (content 99%) in 10g deionized water, adding into 10g ZSM-5 molecular sieve (average grain size 2.0 μm, solid content 94 wt%, denoted as Z5), adjusting pH of the mixture to 6 with 25 wt% ammonia, and mixing thoroughly; after filtration, drying for 4 hours at 115 ℃ under air atmosphere; then roasting at 550 ℃ for 2 hours; the modified ZSM-5 type molecular sieve was obtained and was designated DZ2. The physicochemical properties are shown in Table 1. The retention of crystals after aging at 800℃under 1atm for 17 hours with 100% by volume of water vapor in the bare state is shown in Table 1.
Molecular sieve preparation comparative example 3
Z1 was aged at 800℃under 1atm for 17 hours with 100% by volume of water vapor in a bare state, and the properties thereof were measured, and the results are shown in Table 1.
Molecular sieve preparation example 4
2000 g of NaY1 molecular sieve (dry basis) was added to 20L of decationized aqueous solution and stirred to mix well, 68ml of RE (NO) was added 3 ) 3 Solution (rare earth solution concentration with RE) 2 O 3 319 g/L), stirring, heating to 90-95deg.C, maintaining for 1 hr, filtering, washing, and drying the filter cake at 120deg.C to obtain powder with unit cell constant of 2.471nm, sodium oxide content of 8.9 wt%, and RE 2 O 3 Y-type molecular sieve with rare earth content of 1 wt%, roasting at 450 deg.C in air atmosphere for 6 hr to water content lower than 1 wt%, and SiCl treatment 4 : y-type molecular sieve (dry basis) =0.5: 1 weight ratio, siCl vaporized by heating is introduced 4 Reacting gas at 350 ℃ for 2 hours to obtain a Y-type molecular sieve with a unit cell constant of 2.455nm, washing with 20 liters of deionized water, filtering, washing, drying, exchanging with 20.0L of 2 wt% ammonium sulfate solution at 70 ℃ for 1 hour, filtering, washing, drying, and repeating the exchanging, filtering, washing and drying steps for 1 time to obtain a QZ-1 molecular sieve with a sodium oxide content of less than 1.0 wt%;
Mixing the QZ-1 molecular sieve and deionized water according to the weight ratio of 1:8, heating to 90 ℃, adding 10.0L of ammonium fluosilicate solution with the concentration of 0.1mol/L, stirring for 1h at 90 ℃, filtering, drying, washing, and roasting for 2h at 550 ℃ to obtain the modified small-grain Y-type molecular sieve, which is denoted as SZ-1. The physical and chemical properties are shown in Table 2, and after SZ-1 was aged at 800℃for 17 hours with 1atm and 100% steam in the bare state, the relative crystallinity of the molecular sieve before and after the aging of SZ-1 was analyzed by XRD and the relative crystallinity retention after the aging was calculated, and the results are shown in Table 2.
Molecular sieve preparation comparative example 4
A conventional crystalline Y-type molecular sieve (average grain size: 1100 nm) was subjected to gas-phase superstable treatment in accordance with the method of example 4, and the fluorosilicic acid treatment was not performed, and was designated as DZ4.
TABLE 2
Catalyst preparation examples 1 to 4
(1) Mixing pseudo-boehmite (aluminum stone for short) and water uniformly, adding concentrated hydrochloric acid (chemical purity, product of Beijing chemical plant) with the mass concentration of 36% under stirring, wherein the acid-aluminum ratio is 0.2 mol ratio (36% hydrochloric acid to pseudo-boehmite calculated by alumina), and heating the obtained mixture to 70 ℃ for aging for 1.5 hours to obtain the aged pseudo-boehmite slurry. The alumina content of the aged pseudo-boehmite slurry was 12% by weight.
(2) And uniformly mixing the modified ZSM-5 molecular sieve, alumina sol, silica sol, Y-type molecular sieve, kaolin and the aged pseudo-boehmite slurry with deionized water to obtain slurry with the solid content of 28 weight percent, and spray drying.
The modified ZSM-5 molecular sieves (molecular sieves are also referred to herein as zeolites) and Y-type molecular sieve types used in the examples are shown in Table 3 on a dry basis.
The weight percentage composition of the catalyst is shown in Table 4, and the contents of the modified ZSM-5 type molecular sieve, the binder, the Y type molecular sieve and the kaolin are calculated.
TABLE 3 Table 3
TABLE 4 Table 4
Comparative examples 1 to 3
Catalysts were prepared according to the methods of catalyst preparation examples 1 to 3, the amounts of the catalyst charged are shown in Table 3, and the compositions of the catalysts are shown in Table 4.
Catalysts A1 to A4 and B1 to B3 were aged at 800℃with 100% by volume of water vapor for 4 hours or 17 hours, and the light oil micro-reaction activity of the catalysts was evaluated, and the evaluation results are shown in Table 5.
The light oil micro-reverse activity evaluation method comprises the following steps:
the micro-reactivity of the light oil of the sample is evaluated by adopting a standard method of RIPP92-90 (see the method of petrochemical analysis (the method of RIPP test) Yang Cuiding, et al, published by scientific press, 1990), the catalyst loading is 5.0g, the reaction temperature is 460 ℃, the raw oil is big port light diesel oil with the distillation range of 235-337 ℃, the product composition is analyzed by gas chromatography, and the micro-reactivity of the light oil is calculated according to the product composition.
Light oil micro-reaction activity (MA) = (gasoline yield + gas yield + coke yield below 216 ℃ in the product)/total feed x 100%.
TABLE 5
Hydrocarbon oil reaction examples 1 to 4
After aging the A1, A2 and A3 catalysts at 800 ℃ for 17 hours under a 100% steam atmosphere, the catalytic cracking reaction performance was evaluated on a small fixed fluidized bed reactor (ACE), and the cracking gas and the product gas were collected and analyzed by gas chromatography respectively. The catalyst loading was 9g, the reaction temperature was 570℃and the weight hourly space velocity was 16h -1 The ratio of the agent to the oil (weight ratio) is shown in Table 7, the properties of the raw oil in the ACE experiment are shown in Table 6, and the evaluation results are shown in Table 7.
Hydrocarbon oil reaction comparative examples 1 to 3
Catalysts B1, B2 and B3 were subjected to 100% steam aging at 800℃for 17 hours, and then the catalytic cracking reaction performance was evaluated on a small fixed fluidized bed reactor (ACE) by the method shown in hydrocarbon oil reaction example 1, the raw material properties of the ACE experiment are shown in Table 6, and the evaluation results are shown in Table 7.
TABLE 6
| Hydrocracking oil | |
| Density (20 ℃ C.)/(g/cm) 3 ) | 0.890 |
| Viscosity (80 ℃ C.)/(mm 2 /s) | 6.837 |
| Viscosity (100 ℃ C.)/(mm) 2 /s) | 4.863 |
| Freezing point/°c | 4 |
| Carbon residue value/% | 0.23 |
| Carbon mass fraction/% | 87.09 |
| Hydrogen mass fraction/% | 12.9 |
| Sulfur mass fraction/(μg/g) | 640 |
| Nitrogen mass fraction/(μg/g) | 118 |
| Heavy oil four component mass fraction/% | |
| Saturated hydrocarbons | 67.9 |
| Aromatic hydrocarbons | 17.2 |
| Colloid | 14.9 |
| Asphaltenes | <0.1 |
TABLE 7
As can be seen from the results shown in Table 5 and Table 7, the catalyst provided by the invention has higher yield of low-carbon olefin. The modified small-grain Y-type molecular sieve has higher activity, obviously higher ethylene yield, obviously higher propylene yield and higher low-carbon olefin yield.
Claims (21)
1. The catalyst for producing low-carbon olefin by using petroleum hydrocarbon catalytic pyrolysis contains (by dry weight) 50-80% of carrier, 4-20% of Y-type molecular sieve and 10-30% of modified ZSM-5 type molecular sieve; the phosphorus content in the modified ZSM-5 molecular sieve is P 2 O 5 Not less than 0.5 wt%, and the modified ZSM-5 molecular sieve has an average grain size of less than 150 nm;
the external surface of the modified ZSM-5 type molecular sieveThe product is larger than 20m 2 After the modified ZSM-5 type molecular sieve is subjected to hydrothermal aging at 800 ℃ for 17 hours, the ratio of the amount of strong B acid to the amount of weak B acid is not less than 1.0, and the ratio of the amount of strong L acid to the amount of weak L acid is not less than 20, as measured by a pyridine adsorption infrared method; aging for 17 hours at 800 ℃ in a normal pressure and 100 volume percent steam atmosphere, wherein the pore volume of secondary pores with the pore diameter of 2 nm-100 nm in the modified ZSM-5 molecular sieve accounts for 35-55% of the total pore volume; after aging for 17 hours at 800 ℃ in a normal pressure and 100 volume percent steam atmosphere, the relative crystallization retention degree of the modified ZSM-5 molecular sieve is more than 85 percent; after aging for 17 hours at 800 ℃ in a normal pressure and 100 volume percent steam atmosphere, the relative crystallinity of the modified ZSM-5 molecular sieve is 60-85%;
The Y-shaped molecular sieve is a modified small-grain Y-shaped molecular sieve, and Na of the modified small-grain Y-shaped molecular sieve 2 The O content is not more than 1 weight percent, the unit cell constant is 2.430-2.450nm, the proportion of non-framework aluminum content to the total aluminum content is not more than 20 weight percent, the lattice collapse temperature is not less than 1050 ℃, the ratio of the B acid amount to the L acid amount is not less than 3.0, and the acid amount of the outer surface is 220-300 mu mol/g; the average grain size of the modified small grain Y-shaped molecular sieve is 0.3-0.9 microns; after the modified small-grain Y-shaped molecular sieve is aged for 17 hours at 800 ℃ under normal pressure in a 100 volume percent steam atmosphere, the relative crystallization retention degree of the modified small-grain Y-shaped molecular sieve is 38-45%; the relative crystallinity of the modified small-grain Y-shaped molecular sieve is 50-70%.
2. The catalyst of claim 1 wherein the modified ZSM-5-type molecular sieve has a ratio of strong L acid to weak L acid of 20 to 40 as measured by pyridine adsorption infrared method after hydrothermal aging at 800 ℃ for 17 hours.
3. The catalyst of claim 1 wherein the modified ZSM-5-type molecular sieve has an average crystallite size of 20 nm to 100 nm.
4. The catalyst according to claim 1, wherein after aging for 17 hours at 800 ℃ under normal pressure in a 100 vol.% steam atmosphere, the modified ZSM-5 molecular sieve has a pore volume of 35% -45% of the total pore volume of secondary pores with a pore diameter of 2 nm-100 nm.
5. The catalyst of claim 1, wherein the modified ZSM-5-type molecular sieve has a lattice collapse temperature of 1055 ℃ to 1080 ℃ after aging at 800 ℃ in an atmosphere of normal pressure and 100% by volume water vapor for 17 hours.
6. The catalyst according to claim 1, wherein the ratio of the amount of B acid to the amount of L acid in the total acid amount of the modified ZSM-5-type molecular sieve measured at 200 ℃ by a pyridine adsorption infrared method after aging at 800 ℃ under normal pressure in a 100 vol.% water vapor atmosphere for 17 hours is 3.0 to 6.0.
7. The catalyst of claim 1, wherein the modified ZSM-5-type molecular sieve has a relative crystal retention of 85 to 95% after aging at 800 ℃ for 17 hours in a 100 vol.% steam atmosphere at atmospheric pressure.
8. The catalyst according to claim 1, wherein the modified ZSM-5-type molecular sieve has a relative crystallinity of 60 to 70% after aging at 800 ℃ under normal pressure in a 100 vol.% water vapor atmosphere for 17 hours.
9. The catalyst according to any one of claims 1 to 8, wherein the modified ZSM-5 type molecular sieve has a phosphorus oxide content of 1 to 10 wt%, and the modified ZSM-5 type molecular sieve has a silica to alumina ratio of 20 to 50.
10. The catalyst of claim 1 wherein the modified ZSM-5 molecular sieve is modified from a first ZSM-5 molecular sieve, wherein the first ZSM-5 molecular sieve has only L acid sites, no B acid sites, and a ratio of the amount of strong L acid to the amount of weak L acid of not less than 2.9 as measured by pyridine adsorption infrared after hydrothermal aging at 800 ℃ for 4 hours.
11. The catalyst according to claim 10, wherein the process for preparing the modified ZMS-5 type molecular sieve comprises: and (3) contacting the first ZSM-5 molecular sieve with a phosphorus-containing compound solution with the pH value of 4-10, drying and roasting to obtain the modified ZSM-5 molecular sieve.
12. The catalyst of claim 1 wherein the modified small-crystallite Y-type molecular sieve has an average crystallite size of from 0.4 to 0.8 microns.
13. The catalyst of claim 1 wherein the modified small-crystallite Y-type molecular sieve has Na 2 The O content is 0.1-0.7 wt.%.
14. The catalyst of claim 1 wherein the modified small-crystallite Y-type molecular sieve has a ratio of B acid amount to L acid amount of 3.0 to 4.5.
15. The catalyst of claim 1 wherein the modified small-crystallite Y-type molecular sieve has a lattice collapse temperature of 1055 ℃ to 1085 ℃.
16. The catalyst of claim 1 wherein the modified small-crystallite Y-type molecular sieve has a relative crystallinity of 61 to 69%.
17. The catalyst of claim 1 wherein the RE in the modified small-crystallite Y-type molecular sieve 2 O 3 The content is 0 to 5 wt%.
18. The catalyst of claim 1 wherein said support is one or more of a clay, an alumina support, a silica support.
19. The catalyst of claim 18 wherein the silica support is a silica sol, and wherein the catalyst comprisesSiO 2 The content of silica sol is 1-15 wt%.
20. The catalyst of claim 19, wherein the silica sol is one or more of a neutral silica sol, an acidic silica sol, or an alkaline silica sol.
21. A method for catalytic cracking of heavy oil, comprising the step of contacting the heavy oil with the catalyst of any one of claims 1 to 20.
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