CN108452840B - Isomerization catalyst and preparation method thereof - Google Patents
Isomerization catalyst and preparation method thereof Download PDFInfo
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- CN108452840B CN108452840B CN201810251965.6A CN201810251965A CN108452840B CN 108452840 B CN108452840 B CN 108452840B CN 201810251965 A CN201810251965 A CN 201810251965A CN 108452840 B CN108452840 B CN 108452840B
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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
- B01J29/048—Zincosilicates, Aluminozincosilicates
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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
- B01J29/48—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 arsenic, antimony, bismuth, vanadium, niobium tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/024—Multiple impregnation or coating
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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
- C10G45/00—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds
- C10G45/58—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to change the structural skeleton of some of the hydrocarbon content without cracking the other hydrocarbons present, e.g. lowering pour point; Selective hydrocracking of normal paraffins
- C10G45/60—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to change the structural skeleton of some of the hydrocarbon content without cracking the other hydrocarbons present, e.g. lowering pour point; Selective hydrocracking of normal paraffins characterised by the catalyst used
- C10G45/64—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to change the structural skeleton of some of the hydrocarbon content without cracking the other hydrocarbons present, e.g. lowering pour point; Selective hydrocracking of normal paraffins characterised by the catalyst used containing 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
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
- B01J2229/183—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself in framework positions
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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
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
- B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
Abstract
The invention relates to an isomerization catalyst and a preparation method thereof, wherein the isomerization catalyst comprises 30-85 wt% of H-type mesoporous Zn-ZSM-5 molecular sieve or improved mesoporous Zn-ZSM-5 molecular sieve and 8-56 wt% of alumina, magnesium aluminum hydrotalcite and/or kaolin binder, and the preferable weight percentage is 12-48%; impregnating 0.2-14% of metal active component. The metal active component is one or more of Fe, Co, Ni, Mo and W. The catalyst has high activity and selectivity and good anti-carbon deposition performance.
Description
Technical Field
The invention relates to the field of petroleum processing catalysts, in particular to an isomerization catalyst taking a mesoporous Zn-ZSM-5 molecular sieve as a carrier and a preparation method thereof.
Background
Gasoline is one of the main fuels used in the present vehicle engine, and plays an irreplaceable role. But with the increasing enhancement of environmental protection, the gasoline standard is gradually improved. Reducing the content of sulfur and olefins, which are high octane components, is a major task in clean gasoline production, and the reduction of the content thereof tends to cause octane number loss. The octane number of the gasoline can be improved by adding ether compounds, but the added ethers pollute underground water. Although the alkylation technology can also improve the octane number of gasoline, the catalyst used in the technology is mostly strong acid which pollutes the environment and corrodes equipment. The catalytic reforming process is also limited because most of China is catalytic cracking gasoline. At present, oil refineries tend to improve the octane number of gasoline by isomerization technology, and the octane number of the gasoline can be greatly improved by isomerizing straight-chain paraffin into branched paraffin. However, most of the catalysts used in the prior isomerization technology are noble metal catalysts, so that the cost is high and the raw materials need to be pretreated in multiple steps. Therefore, the development of a highly stable isomerization catalyst which is inexpensive is one of the very effective means for improving the quality of gasoline.
The hydrocarbon isomerization technology mostly adopts a bifunctional catalyst containing a solid acidic carrier and noble metal, namely, the solid acidic carrier material provides an isomerization function, and the metal active component provides a dehydrogenation-hydrogenation function. The metal active site enables hydrocarbons to be dehydrogenated to generate carbonium ions to form an intermediate active transition state, then skeletal isomerization reaction is carried out on an acid center to generate an olefin isomerization product with a branched chain, and finally hydrogenation is carried out on the metal active site to generate branched alkane. The existence of side reactions such as hydrocarbon cracking, cyclization, oligomerization and the like in the reaction process generates a by-product with lower octane number, and the by-product forms a main source of octane number loss of the isomerization process. Therefore, the main objective of isomerization technology is to find a catalyst with high activity and high selectivity, so as to inhibit the occurrence of side reactions.
CN106732752A discloses a method for preparing a C5 and C6 alkane isomerization catalyst, which adopts mordenite and an inorganic binder to form a shape, and loads VIII group metals such as platinum, ruthenium, rhodium, palladium and the like after dipping the shape by a hydrophobic organic amine-alcohol solution, so that the noble metal reaches the nano-grade dispersion degree on a carrier, the activity of the catalyst is improved, the loading amount of the noble metal is reduced, and the cost is saved.
CN106799257A discloses a paraffin isomerization catalyst and a preparation method thereof, wherein the catalyst is composed of a phosphorus-silicon-aluminum molecular sieve and VIII group noble metal, and the catalyst shows more excellent performance in isomerization reaction.
CN106140189A discloses a preparation method of a light alkane isomerization catalyst and an isomerization method of light alkane, a solid super acidic catalyst is synthesized by a coprecipitation method and a hydrothermal treatment method, and then noble metal Pt is loaded for n-pentane isomerization, and the catalyst and the reaction process have the characteristics of no environmental pollution, no corrosion to equipment, high activity and selectivity and the like.
CN106635137A discloses a low-carbon alkane isomerization method, which comprises the steps of sequentially carrying out dehydration treatment and rectification treatment on low-carbon alkane, and then contacting the low-carbon alkane with chlorinated alumina to carry out hydroisomerization reaction, so that the isomerization activity of the chlorinated alumina-containing catalyst can be effectively improved, and the octane number of a product can be improved.
Although the invention improves the activity of the isomerization catalyst, the selectivity of the isomerization catalyst is not obviously improved, and the problem of high cost of noble metal is not fundamentally solved. Therefore, the invention adopts the mesoporous Zn-ZSM-5 molecular sieve with low cost, high activity and high selectivity or the improved mesoporous Zn-ZSM-5 molecular sieve as the acidic carrier, and simultaneously uses non-noble metals such as Fe, Co, Ni, Mo, W and the like as the hydrogenation-dehydrogenation active center to prepare the hydrocarbon isomerization catalyst, thereby having wide industrial application prospect.
Disclosure of Invention
In order to solve the problems, the invention provides an isomerization catalyst and a preparation method thereof, wherein the catalyst takes a mesoporous Zn-ZSM-5 molecular sieve or an improved mesoporous Zn-ZSM-5 molecular sieve as a carrier and loads active components such as Fe, Co, Ni, Mo, W and the like.
An isomerization catalyst, which comprises 30-85 wt% of H-type mesoporous Zn-ZSM-5 molecular sieve or improved mesoporous Zn-ZSM-5 molecular sieve, preferably 42-78 wt%; 8-56% of alumina, magnesium aluminum hydrotalcite and/or a binder, preferably 12-48%; impregnating 0.2-14% of metal active component, preferably 0.8-8%; the metal active component is one or more of Fe, Co, Ni, Mo and W, and the loading method is an impregnation method, preferably a multiple impregnation method.
The preparation method of the isomerization catalyst of the invention is as follows: mixing the mesoporous H-type Zn-ZSM-5 molecular sieve or the improved Zn-ZSM-5 molecular sieve with alumina, magnesium aluminum hydrotalcite and/or kaolin binder for molding, then dipping non-noble metal active components and roasting to obtain the isomerization catalyst.
The H-type mesoporous Zn-ZSM-5 molecular sieve has mesoporous aperture concentrated in 4-35nm and specific surface area of 350-680m2(ii)/g; the content of zinc oxide is 0.2-9.5% of the total weight of the molecular sieve.
The invention also provides a preparation method of the H-type mesoporous Zn-ZSM-5 molecular sieve, which comprises the following steps:
(1) uniformly mixing deionized water, an aluminum source, a zinc source, an acid source, a template agent (SDA) and a silicon source under stirring at a certain temperature to prepare gel, and adjusting the molar ratio of the materials to be (0.002-0.06) Al2O3:(0.04～0.25)Na2O:1SiO2:(10～50)H2O:(0.02～0.25)SDA:(0.001～0.12)ZnO；
(2) Aging the gel obtained in the step (1), transferring the gel to a stainless steel reaction kettle containing a polytetrafluoroethylene lining, sealing and crystallizing, cooling a crystallized product after crystallization is finished, filtering to remove mother liquor, washing a filter cake to be neutral by using deionized water, and drying to obtain a Zn-ZSM-5 molecular sieve;
(3) and (3) carrying out a series of treatments such as exchange, filtration, drying, roasting and the like on the Zn-ZSM-5 molecular sieve obtained in the step (2) to obtain the H-type Zn-ZSM-5 molecular sieve.
The invention further improves the mesoporous Zn-ZSM-5 molecular sieve to obtain the H-Zn-ZSM-5 molecular sieve, and then impregnates a zinc-containing compound on the surface of the H-Zn-ZSM-5 molecular sieve by an impregnation method to modify, so that the surface zinc content of the molecular sieve is higher than the internal zinc content of the molecular sieve, and the Zn-modified improved H-Zn-ZSM-5 molecular sieve, namely the improved Zn-ZSM-5 molecular sieve, is obtained by preferably equal-volume impregnation. Wherein the zinc-containing compound is one or more of zinc nitrate, zinc acetate, zinc chloride and zinc sulfate, and preferably zinc acetate.
The improved mesoporous Zn-ZSM-5 molecular sieve has the mesoporous aperture concentrated at 4-35nm and the specific surface area of 350-680m2(ii)/g; the content of zinc oxide is 0.2-9.5% of the total weight of the molecular sieve, and the content of zinc on the surface of the molecular sieve is higher than that of zinc in the molecular sieve, preferably 0.2-2 times higher. The silicon source in the step (1) is one or more of water glass, silica sol, ethyl orthosilicate and solid silica gel; the aluminum source is sodium metaaluminate, aluminum isopropoxide and aluminum sulfateOne or more of (a); the zinc source is one or more of zinc nitrate, zinc acetate, zinc chloride and zinc sulfate.
The silicon source in the step (1) can be one or two of diatomite and opal, the aluminum source can be one or more of kaolin, rectorite, perlite and montmorillonite, and the zinc source can be one or two of smithsonite and zincite.
In the step (1), the SDA is one or more of Trimethylamine (TMA), methylethylamine, pyrrole and morpholine, or one or more of commonly used tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr), 1, 6-hexanediamine, n-butylamine and hexanediol, preferably one or more of Trimethylamine (TMA), methylethylamine, pyrrole and morpholine.
The acid source in the step (1) is one or a mixture of more of sulfuric acid, hydrochloric acid, nitric acid, oxalic acid and acetic acid, preferably one or more of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the acid solution is 0.1-8 mol/L.
The aging temperature in the step (2) is 30-85 ℃, and preferably 40-80 ℃; the aging time is 1-24 h, preferably 2-16 h.
The crystallization temperature in the step (2) is 120-210 ℃, and preferably 130-185 ℃; temperature programming is carried out in 1-5 sections, and 1-3 sections are preferred; preferably, carrying out non-isothermal temperature rise in sections and non-isothermal temperature rise in sections, wherein the temperature rise rate is fast first and then slow, the temperature rise rate is 6-8 ℃/min before 100 ℃, 20-30 ℃ is a temperature rise section, and the processing time of the temperature section is 0.5-5 hours; the temperature is raised at a rate of 3-5 ℃/min between 100 ℃ and 200 ℃, 10-20 ℃ is a temperature raising section, and the treatment time of the temperature section is 0.5-8 hours. The method adopts non-isothermal segmented temperature rise treatment, is beneficial to controlling the nucleation rate and the growth rate in the crystallization process of the Zn-ZSM-5 molecular sieve, can control the size and the number of mesopores, and further can improve the activity of the catalyst and the selectivity of a target product. The crystallization time is 10-96 h, preferably 24-72 h.
The roasting temperature in the step (3) is 420-780 ℃, and preferably 450-650 ℃; roasting for 1-8 h; the exchange reagent is one of hydrochloric acid, nitric acid, sulfuric acid, ammonium chloride or ammonium nitrate;
the surface modification of the molecular sieve in the step (3) adopts isovolumetric impregnation of a zinc-containing compound, wherein the mass fraction of ZnO is 0.5-15%, and preferably 0.5-10%.
The isomerization catalyst is used for the hydroisomerization reaction of n-octane at the temperature of 180-450 ℃ and the pressure of 0.5-4.2 MPa and the WHSV of 0.8-8 h-1Under the condition that the volume ratio of the normal octane to the hydrogen oil is 80-450, the conversion rate of the normal octane is higher than 88%, and the selectivity of the iso-octane is higher than 85.06% at 200 ℃.
Compared with the prior art, the invention has the following advantages:
1. the isomerization catalyst prepared by the invention adopts the mesoporous Zn-ZSM-5 molecular sieve or the improved mesoporous Zn-ZSM-5 molecular sieve, and non-noble metal is used as the active center component of the hydrogenation-dehydrogenation metal, so that the poisoning of the active center of the catalyst metal caused by S and other miscellaneous elements contained in the raw materials is greatly slowed down, the stability of the catalyst is improved, the service life of the catalyst is prolonged, and the activity and the selectivity of the catalyst are improved.
2. The Zn-ZSM-5 molecular sieve with the framework containing Zn is synthesized by a one-step method, the synthesis method is simple, the Zn enters the molecular sieve framework to cause the crystal structure to be changed, the mesoporous is generated, the dispersity of the Zn is improved, the diffusion resistance of reactants is reduced, the carbon deposition resistance is improved, and the carbon deposition rate is low.
3. The Zn-ZSM-5 molecular sieve has higher surface zinc content than the zinc content in the molecular sieve, and the interaction of surface Zn atoms and Al hydroxyl groups leads the strength of strong acid to be weakened to medium strong acid, so that the acid strength of the molecular sieve is reduced, the occurrence of side reactions such as hydrocarbon cracking and the like is radically reduced, and the selectivity of isomeric hydrocarbon is improved.
Drawings
FIG. 1 is an X-ray diffraction (XRD) spectrum of Zn-ZSM-5 molecular sieve prepared in example 1 of the present invention.
FIG. 2 is the N of Zn-ZSM-5 molecular sieve prepared in example 1 of the present invention2Adsorption-desorption isotherms.
FIG. 3 is a pore size distribution diagram of the Zn-ZSM-5 molecular sieve prepared in example 1 of the present invention.
FIG. 4 is NH of Zn-ZSM-5 molecular sieves (synthesized samples) and commercial ZSM-5 molecular sieves (commercial samples) prepared in example 1 of the present invention3Temperature programmed desorption (NH)3-TPD) spectrum.
Detailed Description
The following detailed description is provided for the purpose of illustrating the embodiments and the advantageous effects thereof, and is not intended to limit the scope of the present invention. The commercial sample used in the examples was SiO2/Al2O3ZSM-5 molecular sieve with the mol ratio of 40.
To reflect the isomerization capability of the catalyst on n-octane, the following evaluation indexes were defined: the calculation of the conversion X of n-octane and the selectivity S of iso-octane are given by the equations (1) and (2).
In the formula:
[A]raw materialsThe percentage of the peak area of n-octane in the raw material is percent;
[A]product ofThe percentage of the peak area of n-octane in the product is percent;
[B]product ofIs the proportion of the sum of all the isooctane peak areas in the product.
Example 1
The embodiment provides a Ni-Mo/Zn-ZSM-5 catalyst, and the preparation method comprises the following steps:
1. preparation of mesoporous Zn-ZSM-5 molecular sieve
(1) 0.44g NaAlO was weighed2And 2.14g Zn (NO)3)2·6H2O is dissolved in 49.55g of deionized water, then 2.00g of sulfuric acid (3mol/L) is added dropwise, 0.93g of TMA is added after stirring for 5min, and 14.20g of water glass (containing 27.6 wt% of SiO) is added after stirring for 1h27.1 wt% of Na2O and 65.3 wt% of H2O) is mixed and stirred for 2 hours at room temperature, and the molar composition of the mixture is 0.003Al2O3:0.25Na2O:1SiO2:50H2O:0.24SDA:0.11ZnO。
(2) Heating the mixture obtained in the step (1) to 75 ℃, aging for 6h, pouring the solution into a stainless steel crystallization kettle with a polytetrafluoroethylene lining, heating to 130 ℃, crystallizing for 12h, heating to 180 ℃, standing and crystallizing for 24 h. And after crystallization is finished, cooling, filtering to remove mother liquor, washing to be neutral, and drying at 120 ℃ to obtain a crystallized product Zn-ZSM-5 molecular sieve.
(3) Adding a Zn-ZSM-5 molecular sieve into an ammonium chloride solution with the concentration of 1mol/L according to the solid-to-liquid ratio of 1:10, mixing and stirring for 4 hours at 60 ℃, carrying out suction filtration, drying, exchanging once again by the same method, putting into a muffle furnace, roasting for 6 hours at 550 ℃ to obtain an H-type Zn-ZSM-5 molecular sieve, and proving that a synthesized sample is the high-purity Zn-ZSM-5 molecular sieve by an XRD spectrogram (figure 1); from N2The adsorption-desorption isotherm (figure 2) and the pore size distribution diagram (figure 3) prove that the synthesized Zn-ZSM-5 molecular sieve has a mesoporous structure with double hysteresis ring distribution, the mesoporous aperture is concentrated at 5-30 nm, and the specific surface area is 580m2/g；NH3The strong acid desorption temperature of the synthesized Zn-ZSM-5 molecular sieve is 350 ℃ as proved by a TPD spectrogram (figure 4), and the strong acid desorption temperature of a commercial sample is 480 ℃, which indicates that the synthesized Zn-ZSM-5 molecular sieve has obviously lower acid strength, the total acid amount is 20 percent lower than that of the commercial ZSM-5 molecular sieve, and the prepared catalyst has strong carbon deposition resistance. Then impregnating ZnO with the mass fraction of 5%.
2. Preparation of Ni-Mo/Zn-ZSM-5 catalyst
Mixing 30g of the treated Zn-ZSM-5 molecular sieve, 15g of alumina and 20g of deionized water uniformly, extruding the mixture to form strips, drying the strips at 120 ℃ for 4 hours, roasting the strips at 550 ℃ for 5 hours to obtain a molecular sieve carrier, and then soaking 5.0 wt% of NiO and 5.0 wt% of MoO by adopting a multi-time soaking method3To prepare the Ni-Mo/Zn-ZSM-5 catalyst.
Example 2
This example provides a Co-Mo/Zn-ZSM-5 catalyst, which is prepared by the same steps as example 1, with only some parameters being adjusted as follows:
(1) solid silica gel is taken as a silicon source, aluminum sulfate is taken as an aluminum source, zinc nitrate is taken as a zinc source, hydrochloric acid (2mol/L) is taken as an acid source, a mixture (the molar ratio is 1:1) of pyrrole and morpholine is taken as SDA, and the feeding amount is adjusted to ensure that the molar ratio of a molecular sieve synthesis system is 0.02Al2O3:0.06Na2O:1SiO2:15H2O:0.03SDA:0.002ZnO。
(2) Aging conditions are as follows: at 50 ℃ for 8 h; crystallization conditions are as follows: crystallizing at 120 deg.C for 12 hr, crystallizing at 150 deg.C for 24 hr, and crystallizing at 170 deg.C for 24 hr.
(3) The solution used for exchange is 0.5mol/L hydrochloric acid solution, the roasting temperature is 450 ℃, the roasting time is 8h, and the mass fraction of the impregnated zinc oxide is 12 wt%.
(4) The binder is kaolin, the active metal loading is 2 wt% of CoO and 6 wt% of MoO3。
Example 3
This example provides a Ni-Mo/Zn-ZSM-5 catalyst, which is prepared by the same steps as example 1, with only some parameters being adjusted as follows:
(1) solid silica gel is taken as a silicon source, aluminum sulfate is taken as an aluminum source, zinc chloride is taken as a zinc source, acetic acid (6mol/L) is taken as an acid source, methylethylamine is taken as SDA, and the feeding amount is adjusted to ensure that the molar ratio of a molecular sieve synthesis system is 0.04Al2O3:0.15Na2O:1SiO2:30H2O:0.15SDA:0.06ZnO。
(2) Aging conditions are as follows: at 40 ℃ for 12 h; crystallization conditions are as follows: carrying out segmented non-isothermal temperature rise, firstly raising the temperature at the rate of 7 ℃/min, wherein 20 ℃ is a temperature rise section, and the processing time of the temperature section is 0.5 hour; after 100 ℃, heating at the heating rate of 4 ℃/min, wherein 10 ℃ is a heating section, and the treatment time of the temperature section is 0.5 hour; the nucleation rate and the growth rate of the Zn-ZSM-5 molecular sieve crystallization process by non-isothermal segmented temperature rise treatment are controllable, the size and the number of mesopores can be controlled (the mesopores are more uniformly distributed and mainly concentrated at 6-12nm, and the number of the mesopores is increased by 25%), and further the activity of the catalyst and the selectivity of a target product can be improved.
(3) The solution used for exchange is 0.5mol/L sulfuric acid solution, the roasting temperature is 520 ℃, the roasting time is 4 hours, and the mass fraction of the impregnated zinc oxide is 6 wt%.
(4) The binder is magnesium aluminum hydrotalcite, the active metal loading is 5 wt% of NiO and 3 wt% of MoO3。
Example 4
The preparation procedure of the Ni-Mo/Zn-ZSM-5 catalyst provided in this example is the same as that of example 1, only some parameters are adjusted, and the specific steps are as follows:
(1) solid silica gel is taken as a silicon source, aluminum sulfate is taken as an aluminum source, zinc chloride is taken as a zinc source, sulfuric acid (5mol/L) is taken as an acid source, morpholine is taken as SDA, and the feeding amount is adjusted to ensure that the molar ratio of a molecular sieve synthesis system is 0.05Al2O3:0.12Na2O:1SiO2:20H2O:0.05SDA:0.01ZnO。
(2) Aging conditions are as follows: 60 ℃ for 10 h; crystallization conditions are as follows: carrying out sectional non-isothermal temperature rise, firstly raising the temperature at the rate of 8 ℃/min, wherein 20 ℃ is a temperature rise section, and the processing time of the temperature section is 0.5 hour; heating at a heating rate of 3 ℃/min after 100 ℃, wherein 10 ℃ is a heating section, and the treatment time of the temperature section is 0.5 hour; the nucleation rate and the growth rate of the Zn-ZSM-5 molecular sieve crystallization process by non-isothermal segmented temperature rise treatment are controllable, the size and the number of mesopores can be controlled (the mesopores are more uniformly distributed and mainly concentrated at 10-20nm, and the number of the mesopores is increased by 32%), and further the activity of the catalyst and the selectivity of a target product can be improved.
(3) The solution used for exchange is 0.5mol/L ammonium nitrate solution, the roasting temperature is 580 ℃, and the roasting time is 2 hours.
(4) The active metal loading is 5wt percent NiO and 3wt percent MoO3。
Example 5
This example provides a Ni-Mo/Zn-ZSM-5 catalyst, which is prepared by the same steps as example 3, with only some parameters being adjusted as follows:
(1) taking activated opal as a silicon source, activated rectorite as an aluminum source, activated calamine as a zinc source, acetic acid (6mol/L) as an acid source and methylethylamine as SDA, and adjusting the feeding amount to ensure that the molar ratio of a molecular sieve synthesis system is 0.015Al2O3:0.20Na2O:1SiO2:40H2O0.09 SDA 0.04 ZnO. The activation of the opal is to roast the opal for 4 hours at the temperature of 600 ℃, the activation of the rectorite is to mix the rectorite mineral and NaOH according to the mass ratio of 1:1.5, then add a small amount of water to extrude the mixture into strips for molding, and dry the strips at the temperature of 160 ℃, and the activation of the calamine is to roast the calamine for 4 hours at the temperature of 800 ℃.
Example 6
This example provides a Ni-Mo/Zn-ZSM-5 catalyst, which is prepared by the same steps as example 1, except that the catalyst preparation in step 2 is modified as follows:
(1) mixing 28g of the treated Zn-ZSM-5 molecular sieve, 13g of alumina and 16g of deionized water uniformly, extruding the mixture to form strips, drying the strips at 120 ℃ for 4 hours, roasting the strips at 600 ℃ for 5 hours to obtain a molecular sieve carrier, and then dipping 7.0 wt% of NiO and 4.5 wt% of MoO by adopting a multi-dipping method3To prepare the Ni-Mo/Zn-ZSM-5 catalyst.
Example 7
In this example, the catalyst was used for the activity test in a fixed bed reaction, comprising the following steps:
5g of the catalyst prepared in example 1 was loaded into a reaction tube of a mini fixed bed reactor apparatus, the temperature was raised at room temperature at a rate of 2 ℃/min to 140 ℃ to start sulfidation, the temperature was raised to 320 ℃ and maintained for 2 hours to complete sulfidation, the temperature was naturally lowered to 200 ℃ to react for 2 hours, and the reaction product was collected for analysis. In the whole process, the normal octane feeding rate is kept at 10g/h, the system pressure is 2.0MPa, and the hydrogen-oil volume ratio is 300. The results of the catalytic reaction are shown in Table 1.
Example 8
In this example, the catalyst was used for the activity test in a fixed bed reaction, the procedure was the same as in example 7, except that: the catalyst was the catalyst obtained in example 2 and the reaction temperature was 250 ℃.
Example 9
In this example, the catalyst was used for the activity test in a fixed bed reaction, the procedure was the same as in example 7, except that: the catalyst was the catalyst obtained in example 3 and the reaction temperature was 300 ℃.
Example 10
In this example, the catalyst was used for the activity test in a fixed bed reaction, the procedure was the same as in example 7, except that: the catalyst was the catalyst obtained in example 4, the reaction temperature being 280 ℃.
Example 11
In this example, the catalyst was used for the activity test in a fixed bed reaction, the procedure was the same as in example 7, except that: the catalyst was the catalyst obtained in example 5, and the reaction temperature was 260 ℃.
Example 12
In this example, the catalyst was used for the activity test in a fixed bed reaction, the procedure was the same as in example 7, except that: the catalyst was the catalyst obtained in example 6 and the reaction temperature was 250 ℃.
Comparative example 1
In order to prove the technical effect of the technical scheme, the invention is also provided with a comparative example, the molecular sieve adopted in the comparative example is a commercial microporous ZSM-5 molecular sieve, and the steps of forming, impregnating and the like are the same as the example 1.
Comparative example 2
In this example, the catalyst was used for the activity test in a fixed bed reaction, the procedure was the same as in example 7, except that: the catalyst was the catalyst obtained in comparative example 1, and the reaction temperature was 280 ℃.
Comparative example 3
The preparation of the comparative example carrier is the same as that of example 4, except that the crystallization process is segmented isothermal temperature rise, crystallization is carried out at 140 ℃ for 12 hours, and crystallization is carried out at 170 ℃ for 24 hours. The catalyst was prepared and composed in the same manner as in example 4, and the evaluation conditions were the same as in example 8.
TABLE 1 measurement results of isomerized products of examples and comparative examples
| Conversion (%) | Isomer selectivity (%) | Cracking Rate (%) | Coke rate (%) | |
| Example 7 | 88.60 | 85.06 | 14.36 | 0.18 |
| Example 8 | 91.03 | 86.19 | 13.20 | 0.20 |
| Example 9 | 95.68 | 88.69 | 11.01 | 0.24 |
| Example 10 | 92.55 | 87.31 | 12.33 | 0.15 |
| Example 11 | 90.94 | 89.52 | 10.12 | 0.25 |
| Example 12 | 88.54 | 83.79 | 15.53 | 0.42 |
| Comparative example 2 | 99.18 | 3.56 | 95.27 | 1.12 |
| Comparative example 3 | 96.67 | 70.28 | 28.31 | 0.95 |
As can be seen from table 1, the catalyst provided by the present invention has excellent isomerization activity, higher isoparaffin selectivity and lower cracking rate (i.e., high liquid yield) and coke formation rate compared to the comparative example. The catalyst was subjected to stability tests under the conditions described in example 9, and the results showed that after 1000h of reaction, the conversion and isomer selectivity of the catalyst remained above 90.0 and 88.5%, respectively, and the cracking rate and coke formation rate were below 10.5 and 0.28%, respectively. Therefore, the catalyst provided by the invention has more excellent isomerization capability, and has good economic benefit and industrial application prospect.
Claims (6)
1. An isomerization catalyst characterized by: the modified mesoporous Zn-ZSM-5 molecular sieve comprises 30-85 wt% of modified mesoporous Zn-ZSM-5 molecular sieve, 8-56 wt% of alumina, magnesium aluminum hydrotalcite and/or kaolin binder, and 0.2-14 wt% of metal active components, wherein the metal active components are one or more of Fe, Co, Ni, Mo and W;
the preparation method of the improved mesoporous Zn-ZSM-5 molecular sieve comprises the following steps:
(1) at a certain temperature, deionized water, an aluminum source, a zinc source, an acid source, a template agent SDA and a silicon source are uniformly mixed under stirring to prepare gel, and the molar ratio of the materials is adjusted to be Al2O3: Na2O: SiO2:H2O: SDA:ZnO=(0.002~0.06):(0.04~0.25): 1: (10~50): (0.02~0.25): (0.001~0.12)；
(2) Aging the gel obtained in the step (1), transferring the gel to a stainless steel reaction kettle containing a polytetrafluoroethylene lining, sealing and crystallizing, cooling a crystallized product after crystallization is finished, filtering to remove mother liquor, washing a filter cake to be neutral by using deionized water, and drying to obtain a Zn-ZSM-5 molecular sieve; the crystallization temperature in the step (2) is 120-210 ℃, the step of carrying out segmented unequal temperature rise treatment in 1-5 sections, wherein the temperature rise rate is fast first and slow later, the temperature rise rate is 6-8 ℃/min before 100 ℃, the temperature rise period is 20-30 ℃, and the treatment time of the temperature section is 0.5-5 hours; heating at a heating rate of 3-5 ℃/min at 100-200 ℃, wherein 10-20 ℃ is a heating section, and the treatment time of the temperature section is 0.5-8 hours;
(3) exchanging, filtering, drying and roasting the Zn-ZSM-5 molecular sieve obtained in the step (2) to obtain an H-type mesoporous Zn-ZSM-5 molecular sieve;
(4) and (3) impregnating the H-type mesoporous Zn-ZSM-5 molecular sieve with a zinc-containing compound for modification, so that the surface zinc content of the molecular sieve is higher than the internal zinc content of the molecular sieve, and the improved mesoporous Zn-ZSM-5 molecular sieve is obtained.
2. The isomerization catalyst of claim 1 wherein: the improved mesoporous Zn-ZSM-5 molecular sieve has mesoporous aperture concentrated in 4-35nm and specific surface area of 350-680m2The zinc oxide content is 0.2-9.5% of the total weight of the molecular sieve, and the zinc content on the surface of the molecular sieve is higher than that in the interior of the molecular sieve.
3. The isomerization catalyst of claim 2 wherein: the zinc content of the surface of the improved mesoporous Zn-ZSM-5 molecular sieve is 0.2-2 times higher than that of the zinc content in the molecular sieve.
4. A process for preparing an isomerization catalyst as claimed in claim 1, characterized in that: which comprises the following steps: the improved mesoporous Zn-ZSM-5 molecular sieve is mixed with alumina, magnesium aluminum hydrotalcite and/or kaolin adhesive for molding, then non-noble metal active components are dipped and roasted to obtain the isomerization catalyst.
5. The method for producing an isomerization catalyst according to claim 4, characterized in that: the aluminum source in the step (1) is one or more of sodium metaaluminate, aluminum isopropoxide and aluminum sulfate; the silicon source is one or more of water glass, silica sol, ethyl orthosilicate and solid silica gel; the zinc source is one or more of zinc nitrate, zinc acetate, zinc chloride and zinc sulfate.
6. The method for producing an isomerization catalyst according to claim 4, characterized in that: the silicon source in the step (1) is one or two of diatomite and opal, the aluminum source is one or more of kaolin, rectorite, perlite and montmorillonite, and the zinc source is one or two of calamine and zincite.
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| CN111905800A (en) * | 2019-05-10 | 2020-11-10 | 中国石油天然气股份有限公司 | Molybdenum-containing and nickel-or/and zinc-containing ZSM-5 molecular sieve with multi-stage structure, and preparation method and application thereof |
| CN112007652A (en) * | 2019-05-31 | 2020-12-01 | 中国石油化工股份有限公司 | Solid acid catalyst and application thereof |
| CN111185226A (en) * | 2020-03-06 | 2020-05-22 | 中化泉州石化有限公司 | Preparation method of Zn modified molecular sieve loaded Ni/W bimetal heterogeneous pour point depressing catalyst |
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