A Co-UZM-35 molecular sieve catalyst and its preparation method and application

Abstract

The present invention is a kind of Co-UZM-35 molecular sieve catalyst and its preparation method and application. A kind of preparation method of Co-UZM-35 molecular sieve catalyst, comprising the following steps: (1) adding potassium hydroxide, sodium hydroxide and aluminum hydroxide to water, after mixing, reacting at 150-170 DEG C; (2) adding DMDPAOH, MCM-68 crystal seeds, cobalt nitrate and ethylenediamine to the material after the reaction in the described step (1), after mixing, crystallizing at 160-180 DEG C for 2-5 days; (3) washing, drying and calcining the material after the reaction in the described step (2) to obtain the Co-UZM-35 molecular sieve catalyst. A kind of Co-UZM-35 molecular sieve catalyst of the present invention and its preparation method and application, prepare Co-UZM-35 molecular sieve by one-step hydrothermal synthesis method, it can use the method for rapid pyrolysis, convert cotton stalk into chemicals in a very short time, and possess excellent aromatics selectivity, for the industrial application of cotton stalk proposes a new possible approach.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a Co-UZM-35 molecular sieve catalyst and a preparation method and application thereof. Background Art

[0002] Bio-oil contains a wealth of high-value-added compounds. However, due to its complex composition and the relatively low relative abundance of various chemical components, direct purification and isolation of high-value chemicals from bio-oil is difficult and costly. If the pyrolysis reaction can be manipulated to increase the concentration of target products in bio-oil and improve its quality, the subsequent processing complexity can be greatly reduced, its application value can be increased, and thus the resource utilization of biomass waste can be promoted.

[0003] In recent years, the selective production of high-value-added target chemicals through catalytic pyrolysis of biomass has become a novel and highly anticipated research direction in biomass thermochemical conversion. Catalysts can provide targeted control over specific reactions within complex reaction systems. In biomass catalytic pyrolysis research, catalysts regulate dehydration, decarbonylation, decarboxylation, cracking, aromatization, ketonization, and reforming reactions during pyrolysis to enhance the final yield and enrichment of specific products.

[0004] Aromatic hydrocarbons, a basic raw material for chemical synthesis and a common organic solvent, are a reflection of the development level of a country's chemical industry. UZM-35 molecular sieve, with its unique three-dimensional pore structure, exhibits excellent catalytic activity and selectivity in pyrolysis reactions. However, the long microporous channels in conventional UZM-35 restrict diffusion, severely hindering the diffusion of aromatic products and leading to catalyst deactivation.

[0005] Therefore, it is necessary to regulate its pores to improve the selectivity of aromatic hydrocarbons, which can improve the benzene conversion rate, xylene selectivity and catalytic stability.

[0006] In view of this, the present invention proposes a new UZM-35 molecular sieve catalyst and its preparation method and application, introduces Co metal active centers into the porous material, and regulates its pores to improve the selectivity of aromatic hydrocarbons, which can improve the benzene conversion rate, xylene selectivity and catalytic stability. Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing a Co-UZM-35 molecular sieve catalyst, and to prepare a Co-UZM-35 molecular sieve with good dispersion, uniform morphology and small particles by a one-step hydrothermal synthesis method.

[0008] In order to achieve the above objectives, the technical solutions adopted are:

[0009] A method for preparing a Co-UZM-35 molecular sieve catalyst comprises the following steps:

[0010] (1) Add potassium hydroxide, sodium hydroxide, and aluminum hydroxide to water, mix well, and react at 150-170°C;

[0011] (2) adding DMDPAOH, MCM-68 seed crystals, cobalt nitrate and ethylenediamine to the material after the reaction in step (1), mixing evenly, and crystallizing at 160-180° C. for 2-5 days;

[0012] (3) washing, drying, and calcining the material after the reaction in step (2) to obtain the Co-UZM-35 molecular sieve catalyst.

[0013] Furthermore, in the steps (1)-(2), the molar ratio of MCM-68 seed crystals, aluminum hydroxide, DMDPAOH, potassium hydroxide, sodium hydroxide, cobalt nitrate and water is 1:0.08-0.12:0.3-0.5:0.15-0.25:0.15-0.25:0-0.03:35-37;

[0014] The molar ratio of cobalt nitrate to ethylenediamine is 1:2.

[0015] In the step (3), the calcination temperature is 450-600° C. and the calcination time is 6-8 hours.

[0016] Furthermore, in the steps (1)-(2), the molar ratio of MCM-68 seed crystals, aluminum hydroxide, DMDPAOH, potassium hydroxide, sodium hydroxide, cobalt nitrate and water is 1:0.1:0.4:0.2:0.2:0-0.03:36.8;

[0017] In the step (3), the calcination temperature is 550°C, the calcination heating rate is 2°C / min, and the calcination time is 8h.

[0018] Furthermore, in the step (2), the seed crystal of MCM-68 is silicon dioxide.

[0019] Another object of the present invention is to provide a Co-UZM-35 molecular sieve catalyst prepared by the above-mentioned preparation method.

[0020] Another object of the present invention is to provide the application of the above-mentioned Co-UZM-35 molecular sieve catalyst for catalyzing the rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons. By utilizing the rapid catalytic pyrolysis technology, the biomass solid waste cotton stalks can be converted into high-value-added chemicals in a relatively short period of time, thereby expanding the application field of industrial biomass solid waste cotton stalks.

[0021] In order to achieve the above objectives, the technical solutions adopted are:

[0022] The application of the above-mentioned Co-UZM-35 molecular sieve catalyst in the production of aromatics by biomass pyrolysis.

[0023] Furthermore, the aromatic hydrocarbons contain at least one of toluene, xylene, and p-xylene.

[0024] Furthermore, the process of producing aromatics by pyrolysis is as follows: biomass material and the above-mentioned Co-UZM-35 molecular sieve catalyst are catalytically pyrolyzed at 500-550° C. for 5-10 minutes.

[0025] Furthermore, the biomass is cotton stalks.

[0026] Furthermore, the cotton stalks need to be crushed, sieved through 60-80 meshes and then dried.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The technical solution of the present invention is to synthesize a Co-doped molecular sieve catalyst in one step, regulate the pores of the molecular sieve catalyst, and use the synthesized molecular sieve to catalyze the rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons. The cotton stalks are converted into high-value-added chemicals by rapid catalytic pyrolysis, which greatly shortens the reaction time and achieves efficient resource utilization.

[0029] 2. The technical solution of the present invention is that the Co-UZM-35 molecular sieve catalyst converts cotton stalks into chemicals in a very short time during the rapid pyrolysis process, and has excellent aromatics selectivity, which provides a new possible approach for the industrial application of cotton stalks.

[0030] 3. Conventional pyrolysis products of cotton stalks produce a large number of oxygen-containing compounds. In the technical solution of the present invention, the Co-UZM-35 molecular sieve catalyst significantly promotes deoxygenation and aromatization during the rapid pyrolysis of cotton stalks to produce aromatic hydrocarbons. The product has high selectivity for aromatic hydrocarbons and produces new high-value aromatic hydrocarbons (toluene, xylene, and p-xylene), thereby improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the SEM image of UZM-35 prepared by conventional method;

[0032] Figure 2 is the SEM image of Co-UZM-35;

[0033] Figure 3 This is the product distribution diagram of the rapid catalytic pyrolysis of cotton stalks by UZM-35 molecular sieve;

[0034] Figure 4This is the N2 adsorption-desorption curve of conventional UZM-35;

[0035] Figure 5 This is the pore size distribution diagram of Co-UZM-35. DETAILED DESCRIPTION

[0036] To further illustrate the Co-UZM-35 molecular sieve catalyst, its preparation method, and its application, and to achieve the intended purpose of the invention, the following, in conjunction with preferred embodiments, describes in detail a Co-UZM-35 molecular sieve catalyst, its preparation method, and its application, as well as its specific implementation, structure, features, and efficacy. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0037] The following is a detailed description of a Co-UZM-35 molecular sieve catalyst, its preparation method, and its application in conjunction with specific embodiments.

[0038] Metal active centers are introduced into porous materials, especially molecular sieves to form metal-zeolite materials, which are widely used in catalytic applications such as dehydrogenation, hydrogenation, and oxidation. The catalytic effect of molecular sieves in the reaction depends not only on the active sites located on the zeolite, but also on the microenvironment around the proton or metal center. The limited nanospace close to the size of a molecule provides a reliable active center for the activation and conversion of reactants. The constructed metal-zeolite catalytic system helps the reactants to adsorb, activate, reach the transition state and generate products through the synergistic effect of the metal active sites and the reaction microenvironment, thereby realizing a catalytic cycle that optimizes the reaction path in some typical reactions, which is necessary for industrial applications. Co belongs to Group VIII metals and has good dual electron transfer ability and good deoxidation properties (mainly decarboxylation properties). Therefore, the introduction of Co nanometal particles in UZM-35 can further improve the problem of high oxygen content in bio-oil. The technical solution of the present invention is:

[0039] A method for preparing a Co-UZM-35 molecular sieve catalyst comprises the following steps:

[0040] (1) Add potassium hydroxide, sodium hydroxide, and aluminum hydroxide to water, mix well, and react at 150-170°C;

[0041] (2) adding DMDPAOH, MCM-68 seed crystals, cobalt nitrate and ethylenediamine to the material after the reaction in step (1), mixing evenly, and crystallizing at 160-180° C. for 2-5 days;

[0042] (3) washing, drying, and calcining the material after the reaction in step (2) to obtain the Co-UZM-35 molecular sieve catalyst.

[0043] Preferably, in steps (1)-(2), the molar ratio of MCM-68 seed crystals, aluminum hydroxide, DMDPAOH, potassium hydroxide, sodium hydroxide, cobalt nitrate and water is 1:0.08-0.12:0.3-0.5:0.15-0.25:0.15-0.25:0-0.03:35-37;

[0044] The molar ratio of cobalt nitrate to ethylenediamine is 1:2.

[0045] In the step (3), the calcination temperature is 450-600° C. and the calcination time is 6-8 hours.

[0046] Further preferably, in the steps (1)-(2), the molar ratio of MCM-68 seed crystals, aluminum hydroxide, DMDPAOH, potassium hydroxide, sodium hydroxide, cobalt nitrate and water is 1:0.1:0.4:0.2:0.2:0-0.03:36.8;

[0047] In the step (3), the calcination temperature is 550°C, the calcination heating rate is 2°C / min, and the calcination time is 8h.

[0048] Preferably, in the step (2), the seed crystal of MCM-68 is silicon dioxide, which needs to meet the requirements of the characteristic peak of MCM-68 (FAU) XRD.

[0049] A Co-UZM-35 molecular sieve catalyst is prepared by the above-mentioned preparation method.

[0050] The application of the above-mentioned Co-UZM-35 molecular sieve catalyst in the production of aromatics by biomass pyrolysis.

[0051] Furthermore, the aromatic hydrocarbons contain at least one of toluene, xylene, and p-xylene.

[0052] Furthermore, the process of producing aromatics by pyrolysis is as follows: biomass material and the above-mentioned Co-UZM-35 molecular sieve catalyst are catalytically pyrolyzed at 500-550° C. for 5-10 minutes.

[0053] Furthermore, the biomass is cotton stalks.

[0054] Furthermore, the cotton stalks need to be crushed, sieved through 60-80 meshes and then dried.

[0055] The raw materials used in the examples are conventional raw materials in the art.

[0056] DMDPAOH is dimethyldipropylammonium hydroxide.

[0057] Co loading amount=Co / (Co-UZM-35+cobalt nitrate)×100%.

[0058] 1. Implementation

[0059] Example 1.

[0060] A molecular sieve-catalyzed rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons comprises the following steps:

[0061] (1) 0.0026 mol of KOH and 0.0026 mol of NaOH were added to deionized water and stirred until dissolved. Then, 0.0013 mol of Al(OH)3 was added and stirred for 30 min. The mixture was placed in a hydrothermal synthesis kettle and placed in an oven at 160°C for reaction for 24 h.

[0062] 0.0052 mol of DMDPAOH and 0.013 mol of MCM-68 seed crystals (silicon dioxide) were added, stirred for 1 hour, and then placed in an oven at 170° C. for crystallization for 4 days.

[0063] Finally, the catalyst was washed and dried, and then calcined in a muffle furnace at 550°C for 8 hours at a heating rate of 2°C / min. After cooling, the catalyst was taken out and ground to obtain catalyst 0-Co-UZM-35.

[0064] Among them, the molar ratio of SiO2:Al(OH)3, DMDPAOH, KOH, NaOH and H2O is 1:0.1:0.4:0.2:0.2:36.8.

[0065] (2) Crush the cotton stalks, pass them through a 60-80 mesh sieve, and then dry them at 100°C.

[0066] The dried cotton stalks and the catalyst were subjected to a rapid catalytic pyrolysis experiment in a mass ratio of 1:1. The specific conditions were: the pyrolysis furnace was heated to 500°C, the retention time was 10 minutes, and the pyrolysis products were sent to GC-MS for qualitative and quantitative analysis.

[0067] Example 2.

[0068] A molecular sieve-catalyzed rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons comprises the following steps:

[0069] (1) 0.0026 mol of KOH and 0.0026 mol of NaOH were added to deionized water and stirred until dissolved. Then, 0.0013 mol of Al(OH)3 was added and stirred for 30 min. The mixture was placed in a hydrothermal synthesis kettle and placed in an oven at 160°C for reaction for 24 h.

[0070] 0.0052 mol of DMDPAOH and 0.013 mol of MCM-68 seed crystals (silicon dioxide) were added, and 0.0001 mol of cobalt nitrate hexahydrate and 0.0002 mol of ethylenediamine were added, and the mixture was stirred for 1 hour and then placed in an oven at 170° C. for crystallization for 4 days.

[0071] Finally, the catalyst was washed, dried, placed in a muffle furnace, and calcined at 550°C for 8 hours at a heating rate of 2°C / min. After cooling, the catalyst was taken out and ground to obtain catalyst 0.0075Co-UZM-35.

[0072] Among them, the molar ratio of SiO2:Al(OH)3, DMDPAOH, KOH, NaOH, Co(NO3)2·6H2O, ethylenediamine and H2O is 1:0.1:0.4:0.2:0.2:0.0075:0.015:36.8.

[0073] (2) Crush the cotton stalks, pass them through a 60-80 mesh sieve, and then dry them at 100°C.

[0074] The dried product was mixed with the catalyst in a mass ratio of 1:1 for a rapid catalytic pyrolysis experiment. The specific conditions were: the pyrolysis furnace was heated to 500°C, the retention time was 10 minutes, and the pyrolysis products were sent to GC-MS for qualitative and quantitative analysis.

[0075] Example 3.

[0076] A molecular sieve-catalyzed rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons comprises the following steps:

[0077] (1) 0.0026 mol of KOH and 0.0026 mol of NaOH were added to deionized water and stirred until dissolved. Then, 0.0013 mol of Al(OH)3 was added and stirred for 30 min. The mixture was placed in a hydrothermal synthesis kettle and placed in an oven at 160°C for reaction for 24 h.

[0078] 0.0052 mol of DMDPAOH and 0.013 mol of MCM-68 seed crystals (silicon dioxide) were added, and 0.0002 mol of cobalt nitrate hexahydrate and 0.0004 mol of ethylenediamine were added, stirred for 1 hour, and then placed in a 170° C. oven for crystallization for 4 days.

[0079] Finally, it was washed, dried, placed in a muffle furnace, and calcined at 550°C for 8 hours with a heating rate of 2°C / min. After cooling, it was taken out and ground to obtain the catalyst 0.015Co-UZM-35 (the Co loading was about 1%).

[0080] Among them, the molar ratio of SiO2:Al(OH)3, DMDPAOH, KOH, NaOH, Co(NO3)2·6H2O, ethylenediamine, and H2O is 1:0.1:0.4:0.2:0.2:0.015:0.03:36.8.

[0081] (2) Crush the cotton stalks, pass them through a 60-80 mesh sieve, and then dry them at 100°C.

[0082] The dried product was subjected to a rapid catalytic pyrolysis experiment with the catalyst in a mass ratio of 1:1. The specific conditions were: the pyrolysis furnace was heated to 500°C, the retention time was 10 minutes, and the pyrolysis products were sent to GC-MS for qualitative and quantitative analysis.

[0083] Example 4.

[0084] A molecular sieve-catalyzed rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons comprises the following steps:

[0085] (1) Add 0.0026 mol of KOH and 0.0026 mol of NaOH to deionized water and stir until dissolved. Then add 0.013 mol of Al(OH)3 and stir for 30 min. Then put the mixture into a hydrothermal synthesis kettle and place it in an oven at 160°C for reaction for 24 h.

[0086] 0.0052 mol of DMDPAOH and 0.013 mol of MCM-68 seed crystals (silicon dioxide) were added, and 0.0003 mol of cobalt nitrate hexahydrate and 0.0006 mol of ethylenediamine were added, stirred for 1 hour, and then placed in a 170° C. oven for crystallization for 4 days.

[0087] Finally, the catalyst was washed, dried, placed in a muffle furnace, and calcined at 550°C for 8 hours at a heating rate of 2°C / min. After cooling, the catalyst was taken out and ground to obtain catalyst 0.0225Co-UZM-35.

[0088] Among them, the molar ratio of SiO2:Al(OH)3, DMDPAOH, KOH, NaOH, Co(NO3)2·6H2O, ethylenediamine, and H2O is 1:0.1:0.4:0.2:0.2:0.0225:0.045:36.8.

[0089] (2) Crush the cotton stalks, pass them through a 60-80 mesh sieve, and then dry them at 100°C.

[0090] The dried product was subjected to a rapid catalytic pyrolysis experiment with the catalyst in a mass ratio of 1:1. The specific conditions were: the pyrolysis furnace was heated to 500°C, the retention time was 10 minutes, and the pyrolysis products were sent to GC-MS for qualitative and quantitative analysis.

[0091] Example 5.

[0092] A molecular sieve-catalyzed rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons comprises the following steps:

[0093] (1) Add 0.0026 mol of KOH and 0.0026 mol of NaOH to deionized water and stir until dissolved. Then add 0.013 mol of Al(OH)3 and stir for 30 min. Then put the mixture into a hydrothermal synthesis kettle and place it in an oven at 160°C for reaction for 24 h.

[0094] 0.0052 mol of DMDPAOH and 0.013 mol of MCM-68 seed crystals (silicon dioxide) were added, and 0.0004 mol of cobalt nitrate hexahydrate and 0.0008 mol of ethylenediamine were added, stirred for 1 hour, and then placed in a 170° C. oven for crystallization for 4 days.

[0095] Finally, the catalyst was washed, dried, placed in a muffle furnace, and calcined at 550°C for 8 hours at a heating rate of 2°C / min. After cooling, the catalyst was taken out and ground to obtain catalyst 0.03-Co-UZM-35.

[0096] Among them, the molar ratio of SiO2:Al(OH)3, DMDPAOH, KOH, NaOH, Co(NO3)2·6H2O, ethylenediamine, and H2O is 1:0.1:0.4:0.2:0.2:0.03:0.06:36.8.

[0097] (2) Crush the cotton stalks, pass them through a 60-80 mesh sieve, and then dry them at 100°C.

[0098] The dried product was subjected to a rapid catalytic pyrolysis experiment with the catalyst in a mass ratio of 1:1. The specific conditions were: the pyrolysis furnace was heated to 500°C, the retention time was 10 minutes, and the pyrolysis products were sent to GC-MS for qualitative and quantitative analysis.

[0099] Example 6.

[0100] A molecular sieve-catalyzed rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons comprises the following steps:

[0101] (1) Add 0.0020 mol of KOH and 0.0020 mol of NaOH to deionized water and stir until dissolved. Then add 0.010 mol of Al(OH)3 and stir for 30 min. Then put the mixture into a hydrothermal synthesis kettle and place it in an oven at 150°C for reaction for 24 h.

[0102] 0.0039 mol of DMDPAOH and 0.013 mol of MCM-68 seed crystals (silicon dioxide) were added, and 0.0003 mol of cobalt nitrate hexahydrate and 0.0006 mol of ethylenediamine were added, and stirred for 1 hour, and then placed in a 160° C. oven for crystallization for 5 days.

[0103] Finally, the catalyst was washed, dried, placed in a muffle furnace, and calcined at 450°C for 7 hours at a heating rate of 2°C / min. After cooling, the catalyst was taken out and ground to obtain catalyst 0.0225-Co-UZM-35.

[0104] Among them, the molar ratio of SiO2:Al(OH)3, DMDPAOH, KOH, NaOH, Co(NO3)2·6H2O, ethylenediamine, and H2O is 1:0.08:0.3:0.15:0.15:0.0225:0.045:35.

[0105] (2) After the cotton stalks are crushed, they are passed through a 60-80 mesh sieve and then dried at 80°C.

[0106] The dried product was subjected to a rapid catalytic pyrolysis experiment with the catalyst in a mass ratio of 1:1. The specific conditions were: the pyrolysis furnace was heated to 520°C, the retention time was 8 minutes, and the pyrolysis products were sent to GC-MS for qualitative and quantitative analysis.

[0107] Example 7.

[0108] A molecular sieve-catalyzed rapid pyrolysis of cotton stalks to prepare aromatic hydrocarbons comprises the following steps:

[0109] (1) Add 0.0033 mol of KOH and 0.0033 mol of NaOH to deionized water and stir until dissolved. Then add 0.016 mol of Al(OH)3 and stir for 30 min. Then put the mixture into a hydrothermal synthesis kettle and place it in an oven at 170°C for reaction for 24 h.

[0110] 0.0065 mol of DMDPAOH and 0.013 mol of MCM-68 seed crystals (silicon dioxide) were added, and 0.0004 mol of cobalt nitrate hexahydrate and 0.0008 mol of ethylenediamine were added, stirred for 1 hour, and then placed in an oven at 180° C. for crystallization for 2 days.

[0111] Finally, it was washed, dried, placed in a muffle furnace, and calcined at 600°C for 6 hours with a heating rate of 2°C / min. After cooling, it was taken out and ground to obtain catalyst 0.03-Co-UZM-35.

[0112] Among them, the molar ratio of SiO2:Al(OH)3, DMDPAOH, KOH, NaOH, Co(NO3)2·6H2O, ethylenediamine, and H2O is 1:0.12:0.5:0.25:0.25:0.03:0.06:37.

[0113] (2) Crush the cotton stalks, pass them through a 60-80 mesh sieve, and then dry them at 110°C.

[0114] The dried product was subjected to a rapid catalytic pyrolysis experiment with the catalyst in a mass ratio of 1:1. The specific conditions were: the pyrolysis furnace was heated to 550°C, the retention time was 5 minutes, and the pyrolysis products were sent to GC-MS for qualitative and quantitative analysis.

[0115] 2. Experiment

[0116] 1. Physical properties

[0117] (1) The specific surface areas and other properties of the catalysts of Examples 1 and 3 were measured, and the results are shown in Table 1. The Co-UZM-35 in Table 1 is the catalyst of Example 3.

[0118] Comparative Example: Co-UZM-35 (IWI) was prepared by impregnation method, and its preparation process is as follows:

[0119] 0.0026 mol of KOH and 0.0026 mol of NaOH were added to deionized water and stirred until dissolved. 0.0013 mol of Al(OH)3 was then added and stirred for 30 minutes before being placed in a hydrothermal synthesis reactor and placed in a 160°C oven for 24 hours. 0.0052 mol of DMDPAOH and 0.013 mol of MCM-68 seeds (silicon dioxide) were added and stirred for 1 hour before crystallization in a 170°C oven for 4 days. The mixture was then washed, dried, and calcined in a muffle furnace at 550°C for 8 hours to produce UZM-35. Finally, 1 g of the resulting UZM-35 was added to a cobalt nitrate hexahydrate solution (containing 0.05 g of cobalt nitrate hexahydrate) and stirred for 24 hours. The mixture was then centrifuged and dried to yield Co-UZM-35 (IWI), with a Co loading of approximately 1%.

[0120] Table 1 Physical properties

[0121]

[0122] Combined with Table 1, it can be seen that the conventionally prepared UZM-35 has a relatively low area and is mainly micropores, which will produce more carbon deposits during the catalytic process.

[0123] Co was loaded on UZM-35 by impregnation method, and the specific surface area was reduced to 276 m 2 / g, indicating that the impregnated loaded Co will block the catalyst pores, resulting in a decrease in the specific surface area of ​​the catalyst.

[0124] The Co-UZM-35 prepared by the one-step hydrothermal synthesis method of the present invention does not cause pore clogging because Co is in the molecular sieve framework, so the specific surface area does not decrease, and it has integrated meso-micropores, so it has less carbon deposits than Co-UZM-35 (IWI).

[0125] (2) The catalysts of Example 1 and Example 3 were scanned by electron microscope. The results are as follows Figure 1-2 shown.

[0126] Figure 1-2 The figures show UZM-35 prepared by conventional methods and Co-UZM-35 prepared by a one-step hydrothermal synthesis method. As can be seen from the figure, the UZM-35 molecular sieve prepared by conventional methods has larger particles, sticks together, and has poor dispersion; while the Co-UZM-35 molecular sieve prepared by a one-step hydrothermal synthesis method has better dispersion, uniform morphology, and significantly smaller particles.

[0127] 2. Catalytic performance

[0128] Cotton stalks were rapidly catalytically pyrolyzed using the catalysts of Examples 1-5 and the catalyst of Comparative Example 1, and their product distributions were measured.

[0129] The results are as follows Figure 3 As shown in the figure, UZM-35 is the catalyst prepared in Example 1, Co / UZM-35 is the catalyst prepared by the impregnation method (i.e., comparative example Co-UZM-35 (IWI)), 0.0075Co-UZM-35, 0.015Co-UZM-35, 0.0225Co-UZM-35, and 0.03Co-UZM-35 are the catalysts prepared in Examples 2-5, respectively.

[0130] Depend on Figure 3 Conventionally prepared UZM-35 exhibits a BTEX selectivity of 0% and an aromatics selectivity of 23.48%. After impregnation with Co, the aromatics selectivity increased to 25.76%. Furthermore, the one-step hydrothermally synthesized Co-UZM-35 exhibits a significant increase in total aromatics selectivity and a significant decrease in phenols and other non-aromatic products compared to conventional UZM-35 and Co / UZM-35.

[0131] And, by Figure 3 It can be seen that the products generated by the catalytic pyrolysis reaction of Co-UZM-35 synthesized by one-step hydrothermal method of the present invention are new aromatic hydrocarbons: toluene, xylene, and p-xylene.

[0132] 3. The specific surface area and pore structure of the catalysts of Example 1, Example 3 and the comparative example were characterized. Figure 4-5 The Co-UZM-35 in the figure is the catalyst of Example 3.

[0133] Figure 4 It can be seen that the N adsorption-desorption curves of the catalysts prepared in Example 1 and the comparative example conform to Type I curves, while the catalyst in Example 3 conforms to Type IV curves. This indicates that the catalysts in Example 1 and the comparative example have microporous structures, while the presence of a distinct hysteresis loop in Example 3 indicates the presence of mesopores in the catalyst in Example 3. This demonstrates that the introduction of mesopores into the molecular sieve catalyst prepared by the present invention facilitates the passage of macromolecular compounds and reduces the formation of carbon deposits, thereby reducing the production of byproducts and improving the selectivity of aromatics.

[0134] Figure 5 It can be seen that the Co-UZM-35 molecular sieve synthesized in one step of hydrothermal synthesis has multi-level pores of about 3 nm and a significantly increased specific surface area; this is the reason for its high selectivity for aromatics, because direct pyrolysis of cotton stalks will produce many large molecular compounds.

[0135] The above is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the embodiments of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the embodiments of the present invention are still within the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a Co-UZM-35 molecular sieve catalyst, characterized in that: The following steps are involved: (1) Add potassium hydroxide, sodium hydroxide and aluminum hydroxide to water, mix well, and react at 150-170°C; (2) adding DMDPAOH, MCM-68 seed crystals, cobalt nitrate and ethylenediamine to the material after the reaction in step (1), mixing evenly, and crystallizing at 160-180° C. for 2-5 days; the molar ratio of cobalt nitrate to ethylenediamine is 1:2; The molar ratio of the MCM-68 seed crystals, aluminum hydroxide, DMDPAOH, potassium hydroxide, sodium hydroxide, cobalt nitrate and water is 1:0.08-0.12:0.3-0.5:0.15-0.25:0.15-0.25:0-0.03:35-37; wherein the amount of the cobalt nitrate is not 0; (3) Washing, drying, and calcining the material after the reaction in step (2) to obtain the Co-UZM-35 molecular sieve catalyst.

2. The preparation method according to claim 1, characterized in that In the step (3), the calcination temperature is 450-600°C and the calcination time is 6-8 hours.

3. The preparation method according to claim 2, characterized in that In the steps (1)-(2), the molar ratio of MCM-68 seed crystals, aluminum hydroxide, DMDPAOH, potassium hydroxide, sodium hydroxide, cobalt nitrate and water is 1:0.1:0.4:0.2:0.2:0-0.03:36.8; In the step (3), the calcination temperature is 550°C, the calcination heating rate is 2°C / min, and the calcination time is 8h.

4. The preparation method according to claim 1, characterized in that In the step (2), the seed crystal of MCM-68 is silicon dioxide.

5. Use of the Co-UZM-35 molecular sieve catalyst prepared by the preparation method according to any one of claims 1 to 4 in the production of aromatics by pyrolysis of biomass.

6. The use according to claim 5, characterized in that The aromatic hydrocarbons contain at least one of toluene, xylene and p-xylene.

7. The use according to claim 5, characterized in that The process of producing aromatic hydrocarbons by pyrolysis is as follows: biomass materials and the Co-UZM-35 molecular sieve catalyst prepared by the preparation method according to any one of claims 1 to 4 are catalytically pyrolyzed at 500-550° C. for 5-10 min.

8. The use according to claim 7, characterized in that The biomass is cotton stalks.

9. The use according to claim 8, characterized in that The cotton stalks need to be crushed, sieved through 60-80 meshes and then dried.

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