CN110026233B - Method for preparing propylene by extracting aluminum modified composite catalyst from phosphogypsum - Google Patents

Method for preparing propylene by extracting aluminum modified composite catalyst from phosphogypsum Download PDF

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CN110026233B
CN110026233B CN201910331424.9A CN201910331424A CN110026233B CN 110026233 B CN110026233 B CN 110026233B CN 201910331424 A CN201910331424 A CN 201910331424A CN 110026233 B CN110026233 B CN 110026233B
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composite catalyst
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zsm
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propylene
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CN110026233A (en
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王乐
林喜华
袁义进
李小涛
赵士豪
路东义
何凯
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China West Construction Guizhou Co Ltd
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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
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/20—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon starting from organic compounds containing only oxygen atoms as heteroatoms
    • 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
    • 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

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Abstract

The invention discloses a method for preparing propylene by extracting an aluminum modified composite catalyst from phosphogypsum, which comprises the following steps: the method comprises the following steps: acid leaching waste gypsum, separating and purifying aluminum to prepare gamma-Al2O3Using the prepared gamma-Al2O3ZSM-5 is modified by the sample to obtain the composite catalyst, and the methanol liquid is gasified and fully contacted with the catalyst for reaction to obtain the product propylene. On one hand, the method removes part of impurities in the phosphogypsum, realizes the recycling of the phosphogypsum solid waste, and simultaneously utilizes the properties of the impurities to prepare the gamma-Al2O3The @ ZSM-5 composite catalyst has long service life and high selectivity of propylene product.

Description

Method for preparing propylene by extracting aluminum modified composite catalyst from phosphogypsum
Technical Field
The invention relates to a composite material prepared by extracting aluminum from phosphogypsum, which is applied to the research of reaction for preparing propylene from methanol, and belongs to the field of propylene preparation.
Background
The ZSM-5 catalyst has a larger pore structure and lower selectivity of low-carbon olefin in the field of hydrocarbon catalytic cracking reaction. The rate of carbon formation increases exponentially with reaction temperature, resulting in a short catalyst life. In methanol thin alkylation reactions, there are many factors that affect the formation of the thin hydrocarbon product, where the acid strength and pore structure of the catalyst are critical aspects, and the product selectivity is low using a single ZSM-5 catalyst.
Phosphogypsum is the main solid waste of wet-process phosphoric acid industryReject, production of 1t phosphoric acid by wet process (in P)2O5Calculated) will yield 4.5-5.0 t phosphogypsum. At present, the average utilization rate of the Chinese phosphogypsum is less than 10%, the rest phosphogypsum is still stacked in an open-air slag yard, and the random discharge of a large amount of phosphogypsum not only pollutes the environment, but also occupies a large amount of land and has potential environmental protection risks. In addition, a large amount of cost, money and labor are needed to be spent for treating the phosphogypsum stacking problem every year, and the fundamental problem cannot be solved. The phosphogypsum usually needs to be pretreated to remove impurities such as Al during solid waste treatment, and at present, the phosphogypsum is mainly treated by adopting a water washing mode, but the method mainly removes soluble P, and some valuable impurity ions also exist in the phosphogypsum.
Disclosure of Invention
Aiming at the problems, the invention aims to extract aluminum in the impurities of the phosphogypsum to obtain AlCl by an acid-base precipitation method according to the principle that the phosphogypsum contains the impurities of phosphoric acid, aluminum, silicon, iron and the like besides calcium sulfate as a main component3·6H2O, synthesis of gamma-Al with template agent2O3Is compounded with ZSM-5 catalyst to form gamma-Al2O3The @ ZSM-5 composite catalyst is used to solve the problems of short service life and low selectivity of single ZSM-5 in MTP reaction.
The purpose of the invention is realized by the following technical scheme:
a method for preparing propylene by extracting an aluminum modified composite catalyst from phosphogypsum comprises the following steps:
step one, preparation of composite catalyst
Step 1.1: acid leaching of waste gypsum: adding dilute hydrochloric acid into the dried waste gypsum powder according to the liquid-solid ratio of 20mL/g, stirring and leaching for 1h at the acid leaching temperature of 80 ℃, centrifuging, taking supernate, adding sodium hydroxide solution, carrying out solid-liquid separation, taking supernate, adding dilute hydrochloric acid until white precipitate is completely dissolved to generate aluminum chloride solution, evaporating and concentrating, cooling and crystallizing, and filtering to obtain AlCl3·6H2O solution;
step 1.2: gamma-Al2O3Preparation: according to the molar ratio of the raw materials, AlCl3·6H2O CTAB 12.9-13.2:1-3, and mixing with waterAlkyl trimethyl ammonium Bromide CTAB is added to AlCl prepared in step 1.13·6H2Dissolving in O solution under stirring, and pumping with peristaltic pump at 5 mL/min-1Pumping 3 mol. L-1The precipitant is added until the pH value of the solution system is 8-9, the mixture is continuously stirred for 30min, aged in water bath at the temperature of 80 ℃ for 3h, cooled to room temperature, filtered, washed, dried at the temperature of 80 ℃ for 6 h-12 h to prepare a pseudoboehmite sample, and roasted at the temperature of 600 ℃ for 3h to prepare the gamma-Al2O3A sample;
step 1.3: the gamma-Al prepared in the step 1.22O3Modifying ZSM-5 by using a sample to obtain a composite catalyst;
step two, preparation of propylene:
step 2.1: loading the composite catalyst in the step 1.3 into a fixed bed catalyst tube, and introducing nitrogen into the fixed bed catalyst tube, wherein the reaction pressure is 0.5MPa-1.0MPa, and the reaction temperature is 310 ℃ to 430 ℃;
step 2.2: under the action of carrier gas nitrogen, the prepared methanol solution is pumped by a peristaltic pump at an airspeed of 2.0h-1And conveying the methanol solution into a fixed bed catalyst tube, converting the methanol solution into methanol gas at high temperature, and fully contacting and reacting the methanol gas with the catalyst to obtain a product propylene. And further condensing the product and separating impurity gases to obtain the propylene with higher purity.
Further, the concentration of dilute hydrochloric acid in step 1.1 is 1 mol/L.
Further, gamma-Al in step 1.22O3The sample with 200 meshes is prepared by grinding and sieving.
Further, the precipitating agent in step 1.2 is NH3·H2O、Na2CO3Or NaHCO3One kind of (1).
Further, the modification treatment method in step 1.3 is as follows: according to the molar ratio of Si to Al to TPAOH to H2Adding sodium metaaluminate into deionized water, sequentially adding tetrapropylammonium hydroxide TPAOH and ethyl orthosilicate under continuous stirring to prepare a ZSM-5 precursor mixed solution, aging for 8-24h, and adding gamma-Al2O3Adding the mixed solution and ZSM-5 according to the mass ratio of 1-3:1-3, performing microwave hydrothermal reaction at 180 DEG CCooling, filtering, washing for 2h, drying at 105-110 ℃ for 6-12 h, and roasting at 450-650 ℃ for 3h to complete modification to obtain the gamma-Al2O3@ ZSM-5 composite catalyst.
Further, in the modification treatment method of step 1.3, the aging time is 12 hours.
Further, in step 1.3 modification treatment method, γ -Al2O3The weight ratio of the active carbon to ZSM-5 is 1: 1.
Further, in the modification treatment method in the step 1.3, the roasting temperature is 500-600 ℃.
Further, the methanol solution in step 2.3 has a water to methanol molar ratio of H2O:CH3OH is 1: 1.
Prepared gamma-Al2O3The @ ZSM-5 composite catalyst is applied to the production process of preparing propylene from methanol, and the B acid and the gamma-Al of the ZSM-5 composite catalyst of the modified composite catalyst2O3The L acid can form a B acid-L acid synergistic center and a B acid-L alkali center, so that the bottleneck problems of the adsorption dissociation degree of the methanol at a lower temperature and the rapid carbon deposition inactivation of the catalyst are solved; on the other hand, the micropores of ZSM-5 and gamma-Al2O3The mesopores can form a special hierarchical structure, so that the diffusion of molecules is weakened, the formation of carbon deposit of the ZSM-5 molecular sieve is relieved, and the service life of the catalyst is prolonged; meanwhile, the ZSM-5 special microporous structure is beneficial to strengthening the restriction effect of the composite catalyst, and further improves the selectivity of a target product.
Compared with the prior art, the invention has obvious beneficial effects, and the technical scheme can show that: the invention provides gamma-Al2O3The @ ZSM-5 composite catalyst and the preparation method thereof can not only improve the service life of the catalyst, but also improve the selectivity of the product propylene.
The invention is further illustrated by the following specific examples.
Detailed Description
Comparative example 1: the unmodified ZSM-5 catalyst is applied to the reaction of preparing propylene from methanol.
Preparation of ZSM-5 catalyst: according to the mol ratio of Si to Al to TPAOH to H2Adding sodium metaaluminate into deionized water at normal temperature, continuously stirring, sequentially adding tetrapropylammonium hydroxide and ethyl orthosilicate to prepare a mixed solution, aging for 12 hours, carrying out microwave hydrothermal reaction at 180 ℃ for 2 hours, cooling, filtering, washing, drying at 105-110 ℃ for 6-12 hours, and roasting at 550 ℃ for 3 hours to obtain the ZSM-5 catalyst.
The ZSM-5 catalyst is applied to the process of preparing propylene from methanol, and the reaction pressure is as follows: normal pressure, reaction temperature: 380 ℃, weight hourly space velocity: 2h-1Nitrogen flow rate: 20 mL/min-1，H2O:CH3The OH molar ratio is 1:1, the selectivity of propylene is 37.8 percent, and the service life is 6.2 h.
Example 1
Step 1.1: acid leaching of waste gypsum: adding dilute hydrochloric acid into the dried waste gypsum powder according to the liquid-solid ratio of 20mL/g, stirring and leaching for 1h at the acid leaching temperature of 80 ℃, centrifuging, taking the supernatant, adding a sodium hydroxide solution into the obtained supernatant, performing solid-liquid separation, taking the supernatant, adding dilute hydrochloric acid into the supernatant until all white precipitates are dissolved to generate an aluminum chloride solution, evaporating and concentrating, cooling and crystallizing, and filtering to obtain AlCl3·6H2O; wherein the concentration of the dilute hydrochloric acid is 1mol/L,
step 1.2: gamma-Al2O3Preparation: according to the molar ratio of the raw materials, AlCl3·6H2CTAB ═ 12.9-13.2:1-3, cetyltrimethylammonium bromide CTAB was added to the AlCl prepared in step 1.13·6H2Dissolving in O solution under stirring, and pumping with peristaltic pump at 5 mL/min-1Pumping 3 mol. L-1NH of (2)3·H2Adding O precipitant until the pH value of the solution system is 8-9, continuously stirring for 30min, aging in water bath at 80 ℃ for 3h, cooling to room temperature, filtering, washing, drying at 80 ℃ for 6-12 h to obtain pseudoboehmite sample, and roasting at 600 ℃ for 3h to obtain gamma-Al2O3Sample, gamma-Al2O3Grinding and sieving a sample to 200 meshes;
step 1.3: the gamma-Al prepared in the step 1.22O3Modifying ZSM-5 by using a sample to obtain a composite catalyst; the modification treatment method comprises the following steps: according to the molar ratio of Si to Al to TPAOH to H2O＝Adding sodium metaaluminate into deionized water, sequentially adding tetrapropylammonium hydroxide TPAOH and ethyl orthosilicate under continuous stirring to prepare a ZSM-5 precursor mixed solution, aging for 12h, and adding gamma-Al2O3Adding the mixed solution and ZSM-5 according to the mass ratio of 1:1, carrying out microwave hydrothermal reaction at 180 ℃ for 2h, cooling, filtering, washing, drying at 105-110 ℃ for 6-12 h, and roasting at 450 ℃ for 3h to complete modification to obtain the gamma-Al2O3@ ZSM-5 composite catalyst.
Step two, preparation of propylene:
step 2.1: loading the composite catalyst in the step 1.3 into a fixed bed catalyst tube, and introducing nitrogen into the fixed bed catalyst tube, wherein the reaction pressure is 0.5MPa-1.0MPa, and the reaction temperature is 310 ℃ to 430 ℃;
step 2.2: under the action of carrier gas nitrogen, the prepared methanol solution is pumped by a peristaltic pump at an airspeed of 2.0h-1And (2) conveying the mixture into a fixed bed catalyst tube, wherein the methanol solution is changed into methanol gas at high temperature, and the methanol gas is fully contacted and reacted with the catalyst to obtain a product propylene, wherein the selectivity of the propylene is 38.8%, the service life of the composite catalyst is 7.8h, the product selectivity is improved by 1.0% compared with that of an unmodified ZSM-5 catalyst, and the service life of the catalyst is prolonged by 1.6 h.
Example 2
Step 1.1: acid leaching of waste gypsum: adding dilute hydrochloric acid into the dried waste gypsum powder according to the liquid-solid ratio of 20mL/g, stirring and leaching for 1h at the acid leaching temperature of 80 ℃, centrifuging, taking the supernatant, adding a sodium hydroxide solution into the obtained supernatant, performing solid-liquid separation, taking the supernatant, adding dilute hydrochloric acid into the supernatant until all white precipitates are dissolved to generate an aluminum chloride solution, evaporating and concentrating, cooling and crystallizing, and filtering to obtain AlCl3·6H2O solution; wherein the concentration of the dilute hydrochloric acid is 1mol/L,
step 1.2: gamma-Al2O3Preparation: according to the molar ratio of the raw materials, AlCl3·6H2CTAB ═ 12.9-13.2:1-3, cetyltrimethylammonium bromide CTAB was added to the AlCl prepared in step 1.13·6H2Dissolving in O solution under stirring, and pumping with peristaltic pump at 5 mL/min-1Pumping 3 mol. L-1NH of (2)3·H2Adding O precipitant until the pH value of the solution system is 8-9, continuously stirring for 30min, aging in water bath at 80 ℃ for 3h, cooling to room temperature, filtering, washing, drying at 80 ℃ for 6-12 h to obtain pseudoboehmite sample, and roasting at 600 ℃ for 3h to obtain gamma-Al2O3Sample, gamma-Al2O3Grinding and sieving a sample to 200 meshes;
step 1.3: the gamma-Al prepared in the step 1.22O3Modifying ZSM-5 by using a sample to obtain a composite catalyst; the modification treatment method comprises the following steps: according to the molar ratio of Si to Al to TPAOH to H2Adding sodium metaaluminate into deionized water, sequentially adding tetrapropylammonium hydroxide TPAOH and ethyl orthosilicate while continuously stirring to prepare a ZSM-5 precursor mixed solution, aging for 12h, and adding gamma-Al2O3Adding the mixed solution and ZSM-5 according to the mass ratio of 1:1, carrying out microwave hydrothermal reaction at 180 ℃ for 2h, cooling, filtering, washing, drying at 105-110 ℃ for 6-12 h, and roasting at 500 ℃ for 3h to complete modification to obtain the gamma-Al2O3@ ZSM-5 composite catalyst.
Step two, preparation of propylene:
step 2.1: loading the composite catalyst in the step 1.3 into a fixed bed catalyst tube, and introducing nitrogen into the fixed bed catalyst tube, wherein the reaction pressure is 0.5MPa-1.0MPa, and the reaction temperature is 310 ℃ to 430 ℃;
step 2.2: under the action of carrier gas nitrogen, the prepared methanol solution is pumped by a peristaltic pump at an airspeed of 2.0h-1And (2) conveying the mixture into a fixed bed catalyst tube, wherein the methanol solution is changed into methanol gas at high temperature, and the methanol gas is fully contacted and reacted with the catalyst to obtain a product propylene, wherein the selectivity of the propylene is 40.6%, the service life of the composite catalyst is 9.5h, the product selectivity is improved by 2.8% compared with that of an unmodified ZSM-5 catalyst, and the service life of the catalyst is prolonged by 3.3 h.
Example 3
Step 1.1: acid leaching of waste gypsum: adding dilute hydrochloric acid into the dried waste gypsum powder according to the liquid-solid ratio of 20mL/g, stirring and leaching at the acid leaching temperature of 80 ℃ for 1h, centrifuging, taking the supernatant, adding a sodium hydroxide solution into the obtained supernatant, performing solid-liquid separation, taking the supernatant, adding dilute hydrochloric acid into the supernatant, and dryingHydrochloric acid until the white precipitate is completely dissolved to generate an aluminum chloride solution, evaporating and concentrating, cooling and crystallizing, and filtering to obtain AlCl3·6H2O solution; wherein the concentration of the dilute hydrochloric acid is 1mol/L,
step 1.2: gamma-Al2O3Preparation: according to the molar ratio of the raw materials, AlCl3·6H2CTAB ═ 12.9-13.2:1-3, cetyltrimethylammonium bromide CTAB was added to the AlCl prepared in step 1.13·6H2Dissolving in O solution under stirring, and pumping with peristaltic pump at 5 mL/min-1Pumping 3 mol. L-1NH of (2)3·H2Adding O precipitant until the pH value of the solution system is 8-9, continuously stirring for 30min, aging in water bath at 80 ℃ for 3h, cooling to room temperature, filtering, washing, drying at 80 ℃ for 6-12 h to obtain pseudoboehmite sample, and roasting at 600 ℃ for 3h to obtain gamma-Al2O3Sample, gamma-Al2O3Grinding and sieving a sample to 200 meshes;
step 1.3: the gamma-Al prepared in the step 1.22O3Modifying ZSM-5 by using a sample to obtain a composite catalyst; the modification treatment method comprises the following steps: according to the molar ratio of Si to Al to TPAOH to H2Adding sodium metaaluminate into deionized water, sequentially adding tetrapropylammonium hydroxide TPAOH and ethyl orthosilicate while continuously stirring to prepare a ZSM-5 precursor mixed solution, aging for 12h, and adding gamma-Al2O3Adding the mixed solution and ZSM-5 according to the mass ratio of 1:1, carrying out microwave hydrothermal reaction at 180 ℃ for 2h, cooling, filtering, washing, drying at 105-110 ℃ for 6 h-12 h, and roasting at 550 ℃ for 3h to complete modification to obtain the gamma-Al2O3@ ZSM-5 composite catalyst.
Step two, preparation of propylene:
step 2.1: loading the composite catalyst in the step 1.3 into a fixed bed catalyst tube, and introducing nitrogen into the fixed bed catalyst tube, wherein the reaction pressure is 0.5MPa-1.0MPa, and the reaction temperature is 310 ℃ to 430 ℃;
step 2.2: under the action of carrier gas nitrogen, the prepared methanol solution is pumped by a peristaltic pump at an airspeed of 2.0h-1Transporting to a fixed bed catalyst tube, converting the methanol solution into methanol gas at high temperature, and catalyzingThe catalyst is fully contacted and reacted to obtain a product propylene, the selectivity of the propylene is 58.58%, the service life of the composite catalyst is 15.6h, the product selectivity is improved by 20.78% compared with the use of an unmodified ZSM-5 catalyst, and the service life of the catalyst is prolonged by 9.4 h.
Example 4
Step 1.1: acid leaching of waste gypsum: adding dilute hydrochloric acid into the dried waste gypsum powder according to the liquid-solid ratio of 20mL/g, stirring and leaching for 1h at the acid leaching temperature of 80 ℃, centrifuging, taking the supernatant, adding a sodium hydroxide solution into the obtained supernatant, performing solid-liquid separation, taking the supernatant, adding dilute hydrochloric acid into the supernatant until all white precipitates are dissolved to generate an aluminum chloride solution, evaporating and concentrating, cooling and crystallizing, and filtering to obtain AlCl3·6H2O solution; wherein the concentration of the dilute hydrochloric acid is 1mol/L,
step 1.2: gamma-Al2O3Preparation: according to the molar ratio of the raw materials, AlCl3·6H2CTAB ═ 12.9-13.2:1-3, cetyltrimethylammonium bromide CTAB was added to the AlCl prepared in step 1.13·6H2Dissolving in O solution under stirring, and pumping with peristaltic pump at 5 mL/min-1Pumping 3 mol. L-1NH of (2)3·H2Adding O precipitant until the pH value of the solution system is 8-9, continuously stirring for 30min, aging in water bath at 80 ℃ for 3h, cooling to room temperature, filtering, washing, drying at 80 ℃ for 6-12 h to obtain pseudoboehmite sample, and roasting at 600 ℃ for 3h to obtain gamma-Al2O3Sample, gamma-Al2O3Grinding and sieving a sample to 200 meshes;
step 1.3: the gamma-Al prepared in the step 1.22O3Modifying ZSM-5 by using a sample to obtain a composite catalyst; the modification treatment method comprises the following steps: according to the molar ratio of Si to Al to TPAOH to H2Adding sodium metaaluminate into deionized water, sequentially adding tetrapropylammonium hydroxide TPAOH and ethyl orthosilicate while continuously stirring to prepare a ZSM-5 precursor mixed solution, aging for 12h, and adding gamma-Al2O3Adding the mixed solution and ZSM-5 according to the mass ratio of 1:1, carrying out microwave hydrothermal reaction at 180 ℃ for 2h, cooling, filtering, washing, drying at 105-110 ℃ for 6-12 h, and roasting at 600 ℃ for 3h to complete modification to obtain the gamma-Al2O3@ ZSM-5 composite catalyst.
Step two, preparation of propylene:
step 2.1: loading the composite catalyst in the step 1.3 into a fixed bed catalyst tube, and introducing nitrogen into the fixed bed catalyst tube, wherein the reaction pressure is 0.5MPa-1.0MPa, and the reaction temperature is 310 ℃ to 430 ℃;
step 2.2: under the action of carrier gas nitrogen, the prepared methanol solution is pumped by a peristaltic pump at an airspeed of 2.0h-1And (2) conveying the mixture into a fixed bed catalyst tube, wherein the methanol solution is changed into methanol gas at high temperature, and the methanol gas is fully contacted and reacted with the catalyst to obtain a product propylene, wherein the selectivity of the propylene is 43.9%, the service life of the composite catalyst is 9.6h, the product selectivity is improved by 6.1% compared with that of an unmodified ZSM-5 catalyst, and the service life of the catalyst is prolonged by 3.4 h.
Example 5
Step 1.1: acid leaching of waste gypsum: adding dilute hydrochloric acid into the dried waste gypsum powder according to the liquid-solid ratio of 20mL/g, stirring and leaching for 1h at the acid leaching temperature of 80 ℃, centrifuging, taking the supernatant, adding a sodium hydroxide solution into the obtained supernatant, performing solid-liquid separation, taking the supernatant, adding dilute hydrochloric acid into the supernatant until all white precipitates are dissolved to generate an aluminum chloride solution, evaporating and concentrating, cooling and crystallizing, and filtering to obtain AlCl3·6H2O solution; wherein the concentration of the dilute hydrochloric acid is 1mol/L,
step 1.2: gamma-Al2O3Preparation: according to the molar ratio of the raw materials, AlCl3·6H2CTAB ═ 12.9-13.2:1-3, cetyltrimethylammonium bromide CTAB was added to the AlCl prepared in step 1.13·6H2Dissolving in O solution under stirring, and pumping with peristaltic pump at 5 mL/min-1Pumping 3 mol. L-1NH of (2)3·H2Adding O precipitant until the pH value of the solution system is 8-9, continuously stirring for 30min, aging in water bath at 80 ℃ for 3h, cooling to room temperature, filtering, washing, drying at 80 ℃ for 6-12 h to obtain pseudoboehmite sample, and roasting at 600 ℃ for 3h to obtain gamma-Al2O3Sample, gamma-Al2O3Grinding and sieving a sample to 200 meshes;
step 1.3: prepared in step 1.2gamma-Al of (2)2O3Modifying ZSM-5 by using a sample to obtain a composite catalyst; the modification treatment method comprises the following steps: according to the molar ratio of Si to Al to TPAOH to H2Adding sodium metaaluminate into deionized water, sequentially adding tetrapropylammonium hydroxide TPAOH and ethyl orthosilicate while continuously stirring to prepare a ZSM-5 precursor mixed solution, aging for 12h, and adding gamma-Al2O3Adding the mixed solution and ZSM-5 according to the mass ratio of 1:1, carrying out microwave hydrothermal reaction at 180 ℃ for 2h, cooling, filtering, washing, drying at 105-110 ℃ for 6 h-12 h, and roasting at 650 ℃ for 3h to complete modification to obtain the gamma-Al2O3@ ZSM-5 composite catalyst.
Step two, preparation of propylene:
step 2.1: loading the composite catalyst in the step 1.3 into a fixed bed catalyst tube, and introducing nitrogen into the fixed bed catalyst tube, wherein the reaction pressure is 0.5MPa-1.0MPa, and the reaction temperature is 310 ℃ to 430 ℃;
step 2.2: under the action of carrier gas nitrogen, the prepared methanol solution is pumped by a peristaltic pump at an airspeed of 2.0h-1And (2) conveying the mixture into a fixed bed catalyst tube, wherein the methanol solution is changed into methanol gas at high temperature, and the methanol gas is fully contacted and reacted with the catalyst to obtain a product propylene, wherein the selectivity of the propylene is 36.8%, the service life of the composite catalyst is 5.8h, the product selectivity is reduced by 1.0% compared with that of an unmodified ZSM-5 catalyst, and the service life of the catalyst is shortened by 0.4 h.

Claims (8)

1. The method for preparing propylene by extracting the aluminum modified composite catalyst from the phosphogypsum is characterized by comprising the following steps of:
step one, preparation of composite catalyst
Step 1.1: acid leaching of waste gypsum: adding dilute hydrochloric acid into the dried waste gypsum powder according to the liquid-solid ratio of 20mL/g, stirring and leaching for 1H at the acid leaching temperature of 80 ℃, centrifuging, taking supernate, adding a sodium hydroxide solution, carrying out solid-liquid separation, taking supernate, adding dilute hydrochloric acid until white precipitates are completely dissolved to generate an aluminum chloride solution, evaporating and concentrating, cooling and crystallizing, and filtering to obtain an AlCl3.6H2O solution;
step 1.2: preparation of gamma-Al 2O 3: adding Cetyl Trimethyl Ammonium Bromide (CTAB) into the AlCl 3.6H2O solution prepared in the step 1.1 according to the molar ratio of AlCl 3.6H2O to CTAB of 12.9-13.2:1-3 of raw materials, stirring until the solution is dissolved, pumping 3 mol.L-1 precipitator by a peristaltic pump at the speed of 5 mL.min-1 until the pH value of the solution system is 8-9, continuously stirring for 30min, carrying out water bath aging at 80 ℃ for 3H, cooling to room temperature, carrying out suction filtration, washing, drying at 80 ℃ for 6-12H to prepare a pseudo-boehmite sample, and roasting at 600 ℃ for 3H to prepare a gamma-Al 2O 3 sample;
step 1.3: modifying ZSM-5 by using the gamma-Al 2O 3 sample prepared in the step 1.2 to obtain a composite catalyst;
the modification treatment method comprises the following steps: adding sodium metaaluminate into deionized water according to a molar ratio of Si to Al to TPAOH to H2O being 360:1:19:8077, sequentially adding tetrapropylammonium hydroxide TPAOH and tetraethoxysilane under continuous stirring to prepare a ZSM-5 precursor mixed solution, aging for 8-24H, adding gamma-Al 2O 3 and ZSM-5 into the mixed solution according to a mass ratio of 1-3:1-3, carrying out microwave hydrothermal reaction at 180 ℃ for 2H, cooling, filtering, washing, drying at 105-110 ℃ for 6-12H, and roasting at 450-650 ℃ for 3H to obtain the gamma-Al 2O 3@ ZSM-5 composite catalyst after modification;
step two, preparation of propylene:
step 2.1: loading the composite catalyst in the step 1.3 into a fixed bed catalyst tube, and introducing nitrogen into the fixed bed catalyst tube, wherein the reaction pressure is 0.5MPa-1.0MPa, and the reaction temperature is 310 ℃ to 430 ℃;
step 2.2: under the action of carrier gas nitrogen, the prepared methanol solution is conveyed into a fixed bed catalyst tube by a peristaltic pump at an airspeed of 2.0h < -1 >, and the methanol solution is changed into methanol gas at high temperature and fully contacts and reacts with the catalyst to obtain a product propylene.
2. The method for preparing propylene by using the ardealite extraction aluminum modified composite catalyst according to claim 1, wherein the concentration of the dilute hydrochloric acid in the step 1.1 is 1 mol/L.
3. The method for preparing propylene by using the ardealite extraction aluminum modified composite catalyst as claimed in claim 1, wherein the gamma-Al 2O 3 sample in the step 1.2 is 200 meshes, and is prepared by grinding and sieving.
4. The method for preparing propylene by using the ardealite extraction aluminum modified composite catalyst according to claim 1, wherein the precipitator in the step 1.2 is one of NH 3. H2O, Na 2CO 3 or NaHCO 3.
5. The method for preparing propylene by using the ardealite extracted aluminum modified composite catalyst according to claim 1, wherein in the modification treatment method in the step 1.3, the aging time is 12 hours.
6. The method for preparing propylene by using the ardealite extracted aluminum modified composite catalyst according to claim 1, wherein in the modification treatment method in the step 1.3, the proportion of gamma-Al 2O 3 to ZSM-5 is 1:1 by mass.
7. The method for preparing propylene by using the ardealite extraction aluminum modified composite catalyst according to claim 1, wherein in the modification treatment method in the step 1.3, the roasting temperature is 500-600 ℃.
8. The method for preparing propylene by using the ardealite extracted aluminum modified composite catalyst according to claim 1, wherein the methanol solution in the step 2.2 is prepared from water and methanol in a molar ratio of H2O to CH 3OH to 1: 1.
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