CN108435235B - Mesoporous Zn-ZSM-5 molecular sieve and low-cost preparation method thereof - Google Patents
Mesoporous Zn-ZSM-5 molecular sieve and low-cost preparation method thereof Download PDFInfo
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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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- 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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- 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
- C10G45/02—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to eliminate hetero atoms without changing the skeleton of the hydrocarbon involved and without cracking into lower boiling hydrocarbons; Hydrofinishing
- C10G45/04—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to eliminate hetero atoms without changing the skeleton of the hydrocarbon involved and without cracking into lower boiling hydrocarbons; Hydrofinishing characterised by the catalyst used
- C10G45/12—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to eliminate hetero atoms without changing the skeleton of the hydrocarbon involved and without cracking into lower boiling hydrocarbons; Hydrofinishing characterised by the catalyst used containing crystalline alumino-silicates, e.g. molecular sieves
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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
Abstract
The invention relates to a mesoporous Zn-ZSM-5 molecular sieve and a low-cost preparation method thereof, wherein the mesoporous aperture is concentrated at 5-30nm, and the specific surface area is 300-600m2(ii)/g; the content of zinc oxide is 0.1-10 wt% of the total weight of the molecular sieve. The mesoporous Zn-ZSM-5 molecular sieve has low acid strength, good Zn dispersibility and strong anti-carbon performance, and can be used in the fields of hydrocracking, catalytic cracking, hydrocarbon isomerization and the like.
Description
Technical Field
The invention relates to the field of molecular sieve synthesis, in particular to a mesoporous Zn-ZSM-5 molecular sieve and a low-cost preparation method thereof.
Background
The ZSM-5 molecular sieve plays an irreplaceable role in the fields of catalysis, adsorption separation, ion exchange, green chemical industry and the like due to the properties of a special pore channel structure, excellent shape selectivity, hydrothermal stability and the like. However, the ZSM-5 molecular sieve has strong acidity and is easy to generate side reactions such as cracking reaction and the like, so that the application of the ZSM-5 molecular sieve in isomerization and aromatization reactions is limited. Researches show that the ZSM-5 molecular sieve is subjected to metal modification treatment, so that the acidity of the ZSM-5 molecular sieve can be reduced, and the ZSM-5 molecular sieve pore structure can be modified. Heteroatom molecular sieves have unique catalytic properties due to the introduction of heteroatoms into the molecular sieve framework, and are widely used as catalysts in petrochemical and organic chemical production processes. In recent years, a catalyst prepared by Zn modified ZSM-5 molecular sieve is widely applied due to the excellent catalytic performance.
CN200410066439.0 discloses a method for preparing a nano-sized ZSM-5 molecular sieve containing heteroatoms, which adopts the addition of alkali goldThe method belongs to salt, and comprises the steps of mixing an additive, a template agent, one of aluminum and a heteroatom source (the heteroatom comprises Ga, V, Fe, Zn, Ni, Co and Cr) and a silicon source according to a certain proportion and a certain charging sequence at the crystallization temperature of 60-120 ℃, and crystallizing for 1-15 days under a static state or stirring condition. The grain size of the molecular sieve is 40-200 nm, and the specific surface area is 300-600m2(ii) in terms of/g. The invention overcomes the limitation that the prior preparation of the nano-sized molecular sieve is only limited to the aluminum-containing ZSM-5 molecular sieve. The invention has the advantages that the synthesis conditions can be selected between static state or stirring state; non-toxic operation; the grain size is controllable, the framework contains heteroatoms, and the metal atoms are of various types; the crystallization temperature is low; the operation is simple.
CN201510031312.3 discloses a preparation method and application of a template-free small-grain Zn-ZSM-5 catalyst, relating to the preparation of small-grain molecular sieves. Mixing an aluminum source with an alkali solution to obtain a mixed solution; adding a silicon source and a zinc salt into the mixed solution, aging, carrying out hydrothermal treatment, filtering, washing, drying and roasting to obtain a Zn-ZSM-5 molecular sieve catalyst; the particle size is 200-300nm, the Zn-ZSM-5 molecular sieve catalyst is subjected to ion exchange in an ammonium salt solution, and then the Zn-ZSM-5 catalyst without the template agent and small crystal grains is obtained by filtering, washing, drying and roasting, and the Zn-ZSM-5 catalyst without the template agent and small crystal grains can be applied to the preparation of gasoline by adopting methanol. In the preparation process of the catalyst, no template agent is needed to be added, the obtained Zn-ZSM-5 is a small-grain molecular sieve with uniform grain size and regular appearance, and the Zn-ZSM-5 catalyst is obtained in one step, so that the step of loading Zn by the traditional method is reduced.
CN201510946456.1 discloses a preparation method of a methanol-to-gasoline catalyst nano Zn-ZSM-5, relating to deep processing of methanol. 1) Preparing a mixed solution of an aluminum source, a template agent and an alkali solution; 2) adding a silicon source and a zinc salt into the mixed solution, stirring uniformly, refluxing, and performing centrifugal separation, drying and roasting on the obtained turbid solution to obtain the nano Zn-ZSM-5 molecular sieve; 3) and (3) carrying out ion exchange, centrifugal separation, drying and roasting on the nano Zn-ZSM-5 molecular sieve obtained in the step 2) to obtain the methanol to gasoline catalyst nano Zn-ZSM-5, wherein the methanol to gasoline catalyst nano Zn-ZSM-5 can be applied to methanol to gasoline. The nano Zn-ZSM-5 catalyst for preparing gasoline from methanol shows good performance in the reaction of preparing gasoline from methanol.
One common problem with the above nano or small crystallite Zn-ZSM-5 molecular sieves is that: the crystal grain of the molecular sieve is in a nanometer level, the separation from the mother liquor after synthesis is difficult, and the centrifugal separation is usually selected, which has the problems of low separation efficiency and high operation cost in industrial production.
Disclosure of Invention
In order to solve the problems, the invention provides a mesoporous Zn-ZSM-5 molecular sieve and a preparation method thereof, and a catalyst based on the molecular sieve and the preparation method thereof, wherein the mesoporous Zn-ZSM-5 molecular sieve can be used in the fields of hydrocracking, catalytic cracking, hydrocarbon isomerization and the like.
A mesoporous Zn-ZSM-5 molecular sieve, the mesoporous aperture is concentrated at 5-30nm, the specific surface area is 300-600m2(ii)/g; the content of zinc oxide is 0.1-10% of the total weight of the molecular sieve.
Further improves the molecular sieve, namely a mesoporous Zn-ZSM-5 molecular sieve, the mesoporous aperture is concentrated at 5-30nm, and the specific surface area is 300-600m2(ii)/g; the content of zinc oxide is 0.1-10% 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 invention also provides a preparation method of the 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 (0.005-0.05) Al2O3:(0.05～0.25)Na2O:1SiO2:(20～60)H2O:(0.01～0.2)SDA:(0.001～0.1)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 nitrate.
The silicon source in the step (1) is one or more of commercially available water glass, silica sol, ethyl orthosilicate and solid silica gel; the aluminum source is one or more of sodium metaaluminate, aluminum isopropoxide and aluminum sulfate.
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 zinc source in the steps (1) and (3) 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.
The aging temperature in the step (2) is 25-80 ℃, and preferably 35-70 ℃; the aging time is 2-16 h, preferably 3-10 h.
The crystallization temperature in the step (2) is 100-200 ℃, and preferably 120-180 ℃; 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 12-120 h, preferably 24-96 h.
The roasting temperature in the step (3) is 400-800 ℃, and preferably 400-600 ℃; roasting for 2-10 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 invention also provides an isomerization catalyst and a preparation method thereof, wherein the isomerization catalyst comprises 35-90 wt% of H-type Zn-ZSM-5 molecular sieve or improved Zn-ZSM-5 molecular sieve, preferably 45-85 wt%; 5-60% of aluminum hydroxide dry glue binder, preferably 10-50%; impregnating 0.5-15% of metal active component, preferably 0.5-10%; the metal active component is one or more of Fe, Co, Ni and Mo, and the loading method is an impregnation method, preferably equal-volume impregnation.
The preparation method of the isomerization catalyst of the invention is as follows: the obtained H-type Zn-ZSM-5 molecular sieve or improved Zn-ZSM-5 molecular sieve is mixed with aluminum hydroxide dry glue for molding, then non-noble metal active components are impregnated and calcined to obtain the isomerization catalyst.
The isomerization catalyst is used for hydroisomerization reaction of n-octane at 200-400 ℃ and 1-4 MPa and WHSV of 1-10 h-1Under the condition that the volume ratio of the normal octane to the hydrogen oil is 100-500, the conversion rate of the normal octane is higher than 85%, and the selectivity of the iso-octane is higher than 87.37% at 220 ℃.
Compared with the prior art, the invention has the following advantages:
1. 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, and the dispersity of the Zn is improved, so that the diffusion resistance of reactants is reduced, and the carbon deposition resistance is improved.
2. 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.
3. The mesoporous Zn-ZSM-5 molecular sieve prepared by the invention is used in the fields of hydrocracking, catalytic cracking, hydrocarbon isomerization and the like, and the loaded non-noble metal is used as a hydrogenation-dehydrogenation metal active center component, so that the poisoning of the catalyst metal active center caused by S and other miscellaneous elements contained in the raw materials is greatly slowed down, the stability of the catalyst is improved, and the service life of the catalyst is prolonged. Particularly, one or more of Fe, Co, Ni and Mo are used as active components, and the activity and the selectivity of the catalyst can be simultaneously improved when the catalyst is used for hydrocarbon isomerization reaction.
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 1-1 of the present invention3Temperature programmed desorption (NH)3-TPD) spectrum.
Detailed Description
The following detailed description of the embodiments and the advantageous effects thereof is provided to help better understand the nature and features of the present invention, and is not intended to limit the scope of the present inventionAnd (4) defining the circumference. The commercial sample used in the examples was SiO2/Al2O3ZSM-5 molecular sieve with the molar ratio of 50.
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) Weighing 7.4g NaAlO2And 170g Zn (NO)3)2·6H2O is dissolved in 6100g deionized water, then 200g sulfuric acid (4mol/L) is added dropwise, 60g TMA is added after stirring for 5min, 1420g water glass (containing 27.6 wt% SiO) is added after stirring for 1h27.1 wt% of Na2O and 65.3 wt% of H2O), mixing and stirring for 4h at 30 ℃ and the molar composition of the mixture is 0.005Al2O3:0.25Na2O:1SiO2:60H2O:0.15SDA:0.09ZnO。
(2) Heating the mixture obtained in the step (1) to 70 ℃, aging for 4h, pouring the solution into a stainless steel crystallization kettle with a polytetrafluoroethylene lining, heating to 130 ℃, crystallizing for 24h, heating to 170 ℃, and standing for crystallizationAnd (5) dissolving for 48 hours. 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. The XRD spectrum (figure 1) can prove that the synthesized sample is a high-purity Zn-ZSM-5 molecular sieve prepared 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, the mesoporous pore size is concentrated at 5-30nm, and the specific surface area is 580m2(ii) in terms of/g. The Zn-ZSM-5 molecular sieve N of the invention2The adsorption-desorption isotherm has double hysteresis loop distribution, the acid strength is low, and the prepared catalyst has strong anti-poisoning ability.
(3) Adding the Zn-ZSM-5 molecular sieve into 1mol/L ammonium chloride solution 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, and roasting for 6 hours at 550 ℃ in a muffle furnace to obtain the H-type Zn-ZSM-5 molecular sieve; then impregnating ZnO with the mass fraction of 5%. From NH3The TPD spectrum (FIG. 4) demonstrates that the strong acid desorption temperature of the synthesized Zn-ZSM-5 molecular sieve is 350 ℃ and that the strong acid desorption temperature of the commercial sample is 450 ℃, which indicates that the synthesized Zn-ZSM-5 molecular sieve has a significantly lower acid strength.
2. Preparation of Ni-Mo/Zn-ZSM-5 catalyst
Uniformly mixing 30g of the treated Zn-ZSM-5 molecular sieve, 15g of alumina hydrate dry gel and 20g of deionized water, 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 an equal-volume 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 0.02Al2O3:0.05Na2O:1SiO2:20H2O:0.05SDA: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 180 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) Active metal loading of 2 wt% CoO and 6 wt% 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 0.03Al2O3:0.15Na2O:1SiO2:40H2O:0.10SDA:0.05ZnO。
(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 5-10nm, and the number of the mesopores is increased by 20%), 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 active metal loading is 5wt percent NiO and 3wt percent 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 0.01Al2O3:0.10Na2O:1SiO2:30H2O:0.20SDA:0.08ZnO。
(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 8-15nm, 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 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 0.03Al2O3:0.15Na2O:1SiO2:40H2O0.10 SDA 0.05 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
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 220 ℃ 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 9g/h, the system pressure is 1.5MPa, and the hydrogen-oil volume ratio is 300. The results of the catalytic reaction are shown in Table 1.
Example 7
In this example, the catalyst was used for the activity test in a fixed bed reaction, the procedure was the same as in example 6, except that: the catalyst was the catalyst obtained in example 2, and the reaction temperature was 240 ℃.
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 6, except that: the catalyst was the catalyst obtained in example 3 and the reaction temperature was 260 ℃.
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 6, except that: the catalyst was the catalyst obtained in example 4, the reaction temperature being 280 ℃.
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 6, except that: the catalyst was the catalyst obtained in example 5, and the reaction temperature was 260 ℃.
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 6, 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 9.
TABLE 1 measurement results of isomerized products of examples and comparative examples
| Conversion (%) | Isomer selectivity (%) | Cracking Rate (%) | Coke rate (%) | |
| Example 6 | 87.86 | 87.37 | 12.21 | 0.2 |
| Example 7 | 92.27 | 86.07 | 12.06 | 0.25 |
| Example 8 | 98.12 | 89.03 | 10.61 | 0.3 |
| Example 9 | 98.31 | 78.07 | 17.16 | 0.25 |
| Example 10 | 98.23 | 89.05 | 10.51 | 0.28 |
| Comparative example 2 | 99.30 | 2.10 | 97.92 | 1.1 |
| Comparative example 3 | 97.43 | 65.14 | 32.23 | 0.41 |
As can be seen from table 1, the mesoporous Zn-ZSM-5 catalyst provided by the present invention has excellent isomerization activity, higher isoparaffin selectivity and lower cracking rate (i.e., high liquid yield) and coking rate compared to the comparative example. The catalyst was subjected to stability tests under the conditions described in example 8, and the results showed that after 800h of reaction, the conversion and isomer selectivity of the catalyst remained above 98.05 and 88.95%, respectively, and the cracking rate and coke formation rate were below 10.70 and 0.3%, respectively. Therefore, the mesoporous Zn-ZSM-5 catalyst provided by the invention has more excellent isomerization capability and activity stability. In addition, the mesoporous Zn-ZSM-5 molecular sieve is prepared by a one-step method, has simple process, adopts non-noble metal as a metal active component, has low price and has good economic benefit and industrial application prospect.
Claims (6)
1. A preparation method of a mesoporous Zn-ZSM-5 molecular sieve is characterized by comprising the following steps: the mesoporous aperture of the mesoporous Zn-ZSM-5 molecular sieve is concentrated at 5-30nm, and the specific surface area is 300-600m2The zinc oxide content in the molecular sieve is 0.1-10% 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;
the preparation method of the mesoporous Zn-ZSM-5 molecular sieve comprises the following steps: (1) uniformly mixing deionized water, an aluminum source, a zinc source, an acid source, a template agent and a silicon source at a certain temperature under stirring to prepare gel, and adjusting the molar ratio of materials to be (0.005-0.05) Al2O3: (0.05~0.25)Na2O: 1SiO2: (20~60)H2O: (0.01~0.2)SDA: (0.001~0.1)ZnO；
(2) Aging the gel obtained in the step (1), transferring the gel to a 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 step is used for carrying out sectional unequal temperature rise treatment, wherein the temperature rise rate is fast first and then slow, the temperature is raised at the temperature rise rate of 6-8 ℃/min before 100 ℃, the temperature rise section is at 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) and (3) impregnating a zinc-containing compound on the surface of the Zn-ZSM-5 molecular sieve for modification, so that the zinc content of the surface of the molecular sieve is higher than that of the interior of the molecular sieve.
2. The preparation method of the mesoporous Zn-ZSM-5 molecular sieve of claim 1, wherein: the zinc content on the surface of the molecular sieve is 0.2-2 times higher than that in the molecular sieve.
3. The preparation method of the mesoporous Zn-ZSM-5 molecular sieve of claim 1, wherein: and (3) adopting equal volume to impregnate a zinc-containing compound for surface modification of the Zn-ZSM-5 molecular sieve.
4. The preparation method of the mesoporous Zn-ZSM-5 molecular sieve of claim 1, wherein: the crystallization temperature is 100-200 ℃, and the temperature is programmed in 1-5 sections.
5. The preparation method of the mesoporous Zn-ZSM-5 molecular sieve of claim 1, wherein: in the step (1), the template agent is one or more of trimethylamine TMA, methylethylamine, pyrrole and morpholine, or the template agent is one or more of tetrapropylammonium hydroxide, tetrapropylammonium bromide, 1, 6-hexanediamine, n-butylamine and hexanediol.
6. The preparation method of the mesoporous Zn-ZSM-5 molecular sieve of claim 1, wherein: the zinc source in the step (1) and the zinc-containing compound in the step (3) are one or more of zinc nitrate, zinc acetate, zinc chloride or zinc sulfate; or the zinc source in the step (1) and the zinc-containing compound in the step (3) are one or two of calamine and zincite;
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;
the silicon source in the step (1) is one or more of water glass, silica sol, ethyl orthosilicate and solid silica gel; or, the silicon source in the step (1) is one or two of diatomite and opal;
the aluminum source in the step (1) is one or more of sodium metaaluminate, aluminum isopropoxide and aluminum sulfate; or, the aluminum source in the step (1) is one or more of kaolin, rectorite, perlite and montmorillonite.
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| CN109317188A (en) * | 2018-11-14 | 2019-02-12 | 福州大学 | A kind of preparation method and application of mesoporous FeCu-ZSM-5 molecular sieve |
| CN111718751B (en) * | 2019-03-20 | 2022-03-29 | 中国石油天然气股份有限公司 | Method for preparing aromatic hydrocarbon and light oil by catalytic conversion of straight-run diesel oil |
| CN112047358A (en) * | 2019-06-06 | 2020-12-08 | 中国石油天然气股份有限公司 | Zinc or/and nickel-containing ZSM-5 molecular sieve with multi-stage structure and preparation method and application thereof |
| CN110743608B (en) * | 2019-10-18 | 2022-08-05 | 中国科学院广州能源研究所 | Catalyst for efficiently cracking isomerization to prepare short-chain isoparaffin in one step and preparation method and application thereof |
| CN115140745B (en) * | 2021-03-30 | 2023-11-10 | 中国石油化工股份有限公司 | Metal modified hierarchical pore ZSM-5 molecular sieve and preparation method thereof |
| CN115196650B (en) * | 2021-04-09 | 2023-11-10 | 中国石油化工股份有限公司 | Metal modified mesoporous ZSM-5 molecular sieve and preparation method thereof |
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