Nickel-loaded hierarchical porous SAPO-34 catalyst as well as preparation method and application thereof

Abstract

The invention discloses a nickel-loaded hierarchical porous SAPO-34 catalyst and a preparation method and application thereof.The method comprises the steps that an aluminum source is added into a water solution of a phosphorus source, stirring is conducted, then a template agent and a silicon source are added, stirring and uniform mixing are conducted, and a precursor solution is prepared; carrying out hydrothermal reaction treatment on the precursor solution, and calcining a product to prepare an original SAPO-34 carrier; the preparation method comprises the following steps: putting an original SAPO-34 carrier into an organic acid solution, stirring, and drying and calcining to obtain an acid-treated SAPO-34 carrier; and adding the SAPO-34 carrier subjected to acid treatment into a Ni (NO3) 2 solution, fully stirring and uniformly mixing, drying, and carrying out heat treatment to obtain the nickel-loaded hierarchical porous SAPO-34 catalyst. The method is simple in process and reasonable in design, the catalyst has an excellent hierarchical porous structure and appropriate surface acidity, the reaction activity and selectivity of the catalyst are effectively improved, and the reaction energy efficiency is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of low-temperature plasma catalytic reforming tar, and relates to a nickel-loaded multi-level porous SAPO-34 catalyst and a preparation method and application thereof. Background Art

[0002] After gasification, municipal solid waste is converted into value-added syngas consisting of H2, CO and CH4, which provides high flexibility for thermal power generation and synthetic fuels, effectively alleviating the current situation of fossil fuel depletion. However, the gasification process will inevitably produce a byproduct, tar, which is composed of a variety of condensable organic compounds (benzene, toluene, xylene and naphthalene, etc.). Tar will cause secondary pollution to the environment, damage human organs, block and corrode gasification equipment, and limit the use of gas production in energy applications. At present, the main method for converting tar is catalytic reforming, but catalytic reforming can only break the chemical bonds of tar at 700~900℃, and the catalyst generally has deactivation problems caused by sintering and carbon deposition at high temperatures. Therefore, the development of cost-effective and stable catalysts or reducing the reaction temperature remains the main challenge for catalytic reforming of tar. Low-temperature plasma (NTP) is a promising technology that can effectively crack the tar produced by the gasification of municipal solid waste at low temperatures. The high-energy electrons generated by NTP at low temperature have an energy of 1~10 eV. They collide with gaseous molecules to produce excited atoms, molecules, ions and reactive groups, impacting and destroying the CC and CH bonds of the benzene ring in the tar components, generating CO, H2, CO2 and small molecular organic matter. At present, the common types of NTP are mainly corona discharge (CD), dielectric barrier discharge (DBD), sliding arc discharge (GAD) and microwave discharge (MW). Among them, DBD is often used for tar reforming because of its uniform electric field and electron distribution and micro-discharge. The dielectric energy of DBD limits the unlimited growth of current and avoids the complete breakdown of gas, which leads to local spark discharge or arc discharge in the discharge area. However, the product selectivity of NTP is low and there are many side reactions. Therefore, combining NTP with a catalyst can direct the conversion of products and reduce the occurrence of side reactions.

[0003] The catalyst commonly used in low-temperature plasma catalytic reforming of tar is Ni-based catalyst. This is because Ni contains unpaired electrons in its energy level, which can break the CC and CH bonds in tar compounds. Ni can also activate H2O and CO2 accumulated and adsorbed on the catalyst surface to participate in tar reforming and water gas shift (WGS) reactions. However, the current Ni catalysts have low reaction activity during the reforming process and poor selectivity for products, resulting in low overall reforming energy efficiency. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a nickel-loaded multi-level porous SAPO-34 catalyst and a preparation method and application thereof, thereby solving the technical problems in the prior art that the reaction activity of the Ni catalyst in the process of low-temperature plasma catalytic reforming of tar is low and the selectivity to the product is also poor.

[0005] The present invention is achieved through the following technical solutions: A method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst comprises the following steps: S1: adding an aluminum source to a water solution of a phosphorus source, stirring at a constant temperature, and then adding a template and a silicon source dropwise, stirring and mixing, to prepare a precursor solution; S2: subjecting the precursor solution to a hydrothermal reaction treatment, and subjecting the product to a calcination treatment to obtain an original SAPO-34 carrier; S3: placing the original SAPO-34 carrier in an organic acid solution, stirring it, and then drying and calcining it to obtain an acid-treated SAPO-34 carrier; S4: adding the acid-treated SAPO-34 carrier to the Ni(NO3)2 solution, stirring and mixing thoroughly, drying and heat-treating the carrier to obtain the nickel-loaded hierarchical SAPO-34 catalyst.

[0006] Preferably, the molar ratio of the aluminum source, phosphorus source, silicon source and template is (1-4):(1-6):(0.4-1.6):(4.5-6.9).

[0007] Preferably, in step S1, the aluminum source is added to the water solution of the phosphorus source, and the stirring temperature is 40-60° C. and the stirring time is 1-4 h during constant temperature stirring.

[0008] Preferably, in step S2, the temperature of the hydrothermal reaction treatment is 150-200° C., and the time is 24-48 h.

[0009] Preferably, in step S2, the calcination treatment is carried out at a temperature of 450-650° C. and for a time of 4-8 h.

[0010] Preferably, in step S3, the mass ratio of the original SAPO-34 carrier to the organic acid solution is (15-45):(1-5).

[0011] Preferably, in step S3, during the stirring process, the temperature is 50-90° C. and the time is 1-4 h.

[0012] Preferably, in step S3, during the calcination process, the temperature is 400-600° C. and the time is 2-6 h.

[0013] A nickel-supported multi-level porous SAPO-34 catalyst is prepared by the above method, wherein the micropore specific surface area of ​​the catalyst is 110-170 m 2 ·g -1 The mesopore specific surface area is 70~140m 2 ·g -1 , the micropore volume is 0.05~0.1cm 3 ·g -1 , the mesopore volume is 0.2~0.4cm 3 ·g -1 , the average pore size is 11~13nm.

[0014] The above-mentioned nickel-loaded multi-level porous SAPO-34 catalyst is used in tar reforming coupled with low-temperature plasma. During the application process, when the discharge power is 80W, the gas flow rate is 500mL / min, and the reaction temperature is 400°C, the conversion rate of benzene is 95%~96%, the hydrogen selectivity is 49%~53%, and the carbon monoxide selectivity is 18%~19%.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The invention discloses a method for preparing a nickel-loaded multi-level porous SAPO-34 catalyst. The method obtains an original SAPO-34 carrier with good crystallization performance through constant temperature stirring, hydrothermal reaction and calcination treatment, and then treats the carrier through an organic acid solution. On the one hand, the organic acid can act on silicon atoms in the SAPO-34 carrier to remove the silicon atoms in the carrier, and treat the surface acidity of the original SAPO-34 carrier, thereby avoiding the breakage of CH bonds and the generation of carbon deposits after the precipitation of hydrogen during the tar reforming process. In addition, the organic acid solution treatment can also optimize the pore structure of the original SAPO-34 carrier, so that multi-level mesopores and macropores are formed in the structure. The enlarged pore structure makes it easier for reactant molecules to approach the active center of the catalyst, and the product molecules can also escape from the pores more smoothly, thereby avoiding the occurrence of secondary reactions and the generation of carbon deposits, being beneficial to the diffusion of reactant molecules and the desorption of products, effectively improving the reaction activity and selectivity of the catalyst, and effectively improving the energy efficiency of the reaction.

[0016] Furthermore, another inventive point of the present invention is that the molar ratio of the aluminum source, phosphorus source, silicon source and template is (1~4):(1~6):(0.4~1.6):(4.5~6.9). First, within this molar ratio range, SAPO-34 with good crystallinity can be obtained. The quality of the crystallinity determines the microscopic pore structure of the material. Therefore, this ratio helps to form a stable catalyst structure and reduce structural changes during the catalytic reaction, thereby improving the stability and service life of the catalyst; in addition, the ratio of the aluminum source, phosphorus source and silicon source has an important influence on the number and distribution of acidic sites of the SAPO-34 carrier. By adjusting the ratio of these raw materials, the number and strength of acidic sites on the catalyst surface can be regulated, thereby optimizing its catalytic performance.

[0017] Further, another inventive point of the present invention is that in step S1, an aluminum source is added to the water dissolution of a phosphorus source, and when the constant temperature is stirred, the temperature stirring temperature is 40-60°C, and the stirring time is 1-4 h. First, the appropriate temperature can accelerate the dissolution rate of the aluminum source and the phosphorus source in water, so that the reactant molecules can contact and react more fully, and the constant temperature stirring helps to promote the chemical reaction between the aluminum source and the phosphorus source, forming a stable compound or intermediate product, and laying the foundation for obtaining a carrier with good crystallization performance in the subsequent steps. Long-term stirring can ensure that the aluminum source and the phosphorus source are evenly mixed in the solution, avoiding structural inhomogeneity caused by excessive or low local concentrations. By controlling the stirring time and temperature, the pore structure and specific surface area of ​​the SAPO-34 catalyst in the subsequent crystallization process can be affected, and appropriate stirring conditions can help form a multi-level pore structure and improve the catalytic performance of the catalyst.

[0018] Furthermore, another inventive point of the present invention is that in step S2, the temperature of the hydrothermal reaction treatment is 150-200°C and the time is 24-48 h. First, within this temperature range, the raw material molecules can obtain sufficient energy to undergo chemical reactions and form a stable crystal structure. The long reaction time ensures that the raw material molecules have enough time to undergo a sufficient crystallization reaction, which helps to form a SAPO-34 carrier with a complete structure and high crystallinity, thereby improving the catalytic performance of the catalyst; in addition, during the hydrothermal reaction treatment, by controlling the reaction temperature and time, the SAPO-34 carrier can be prompted to form a multi-level pore structure, which not only increases the specific surface area of ​​the catalyst, but also optimizes the pore distribution, which is beneficial to the diffusion of reactant molecules and the desorption of products, thereby improving the catalytic efficiency of the catalyst.

[0019] Furthermore, another inventive point of the present invention is that in step S2, the calcination temperature is 450-650°C and the time is 4-8 h. First, one of the main purposes of calcination is to remove the template in the SAPO-34 carrier. The template plays a structural guiding role in the preparation process, but it is unnecessary in the catalytic reaction. Through calcination, the template can be removed in the form of gas to form an empty skeleton structure, which is conducive to the diffusion of reactants and the desorption of products. In addition, appropriate calcination temperature and time help to stabilize the crystal structure of the SAPO-34 carrier. At high temperatures, the atoms and ions in the SAPO-34 carrier will rearrange to form a more compact and stable structure, which helps to improve the thermal and chemical stability of the catalyst. At the same time, calcination has a significant effect on the acidity of the SAPO-34 carrier. Under appropriate calcination conditions, the number and strength of acid sites on the surface of the molecular sieve can be regulated to optimize its catalytic performance. In particular, when the calcination temperature is 450°C, SAPO-34 has the largest specific surface area, the smallest grain size, and the weakest acidity of the strong acid sites, which can effectively avoid secondary hydrogenation of light olefins, thereby obtaining high light olefin selectivity.

[0020] Furthermore, another inventive point of the present invention is that in step S3, the mass ratio of the original SAPO-34 carrier to the organic acid solution is (15~45):(1~5). First, within this ratio range, the organic acid solution can fully penetrate into the pores of the SAPO-34 carrier and react with the active sites inside the carrier. By controlling the reaction conditions, the SAPO-34 carrier can be prompted to form a more regular and expanded pore structure. This optimized pore structure is conducive to the diffusion of reactants and the generation of products, thereby improving the catalytic efficiency of the catalyst. If the proportion of the organic acid solution is too high, the pores of the SAPO-34 carrier may be over-etched or blocked, thereby affecting the performance of the catalyst. Within this ratio range, this situation can be avoided to ensure that the pores are unobstructed. In addition, the acidic substances in the organic acid solution can react with the active sites on the surface of the SAPO-34 carrier to adjust its acidity and acidity. Within this ratio range, the acidity and acidity of the SAPO-34 carrier surface can be precisely controlled by adjusting the concentration and reaction time of the organic acid solution. At the same time, appropriate acidity and acidity help to improve the activity and selectivity of the SAPO-34 carrier in the catalytic process. By optimizing the surface acidity, the SAPO-34 carrier can show better performance in specific catalytic reactions. By regulating the surface acidity of the SAPO-34 carrier, the distribution of its active sites and reaction paths in the catalytic reaction can be optimized, thereby avoiding the formation of carbon deposits and improving the reaction activity and selectivity of the catalyst.

[0021] Furthermore, another inventive point of the present invention is that in step S3, during the stirring process, the temperature is 50~90°C and the time is 1~4 h. First, the appropriate temperature can accelerate the chemical reaction rate between the SAPO-34 carrier and the organic acid solution, making the reaction more rapid and sufficient. Long-term stirring can ensure that the reactants are evenly mixed in the solution to avoid uneven reactions caused by local concentrations that are too high or too low. Secondly, by controlling the temperature and time during the stirring process, the process can adjust the acidity and acid content of the SAPO-34 carrier surface, thereby optimizing its catalytic performance. Appropriate acidity and acid content help to improve the activity and selectivity of the molecular sieve in the catalytic process. The temperature and time during the stirring process may also affect the pore structure of the SAPO-34 carrier. Appropriate conditions can cause the molecular sieve to form more regular and enlarged pores, which is beneficial to the diffusion of reactants and the generation of products.

[0022] Furthermore, another inventive point of the present invention is that in step S3, during the calcination process, the temperature is 400~600℃ and the time is 2~6 h. First, calcination within this temperature range can effectively remove the template and other impurities in the SAPO-34 carrier, providing a purer environment for the active sites of the catalyst. High-temperature calcination helps to stabilize the crystal structure of the SAPO-34 carrier and reduce structural defects that may be generated during the preparation process. Appropriate calcination temperature and time can promote further optimization of the pore structure of the SAPO-34 carrier, which is beneficial to the diffusion of reactants and the desorption of products. In addition, during the calcination process, the acid sites on the surface of the SAPO-34 carrier will change. By regulating the calcination temperature and time, the number and strength of the acid sites can be controlled. The optimized number and strength of the acid sites can enhance the catalytic activity of the SAPO-34 carrier, making it exhibit better performance in specific catalytic reactions. At the same time, the SAPO-34 carrier calcined at high temperature has higher thermal stability and can maintain stable catalytic performance in high-temperature catalytic reactions.

[0023] Further, another inventive point of the present invention is to use benzene as a tar model compound, and to combine a nickel-loaded multi-level porous SAPO-34 catalyst with a dielectric barrier discharge plasma to carry out a reforming reaction of benzene. Since low-temperature plasma can generate high-energy electrons sufficient to destroy the chemical bond energy of benzene molecules at low temperature and normal pressure, and high-energy electrons can activate active oxygen species adsorbed on the catalyst surface, converting them into oxygen free radicals, etc. In addition, the discharge process is accompanied by micro-discharges in the catalyst pores, which is conducive to the reaction. Since the catalyst prepared above is modified by pores, the pore volume and pore size are larger, the volume of micro-discharges is also increased, and the benzene molecules adsorbed on the surface of the catalyst are destroyed and broken by the active oxygen species and micro-discharges on the surface, thereby improving the reaction performance of benzene. In the present invention, when the discharge power is 80W, the gas flow rate is 500mL / min, and the reaction temperature is 400°C, the conversion rate of benzene is 95%~96%, the hydrogen selectivity is 49%~53%, and the carbon monoxide selectivity is 18%~19%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a schematic flow diagram of a method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst in the present invention; Figure 2 This is a diagram of an experimental device for tar reforming using a low-temperature plasma catalytic system according to the present invention; Figure 3 The SEM images of the SAPO-34 catalyst prepared in the present invention, wherein (a) is the original carrier SAPO-34, denoted as SP, (b) is the SAPO-34 modified with citric acid, denoted as NSP, (c) is the SAPO-34 modified with oxalic acid, denoted as CSP, (d) is the nickel-supported SAPO-34 catalyst modified with citric acid, denoted as Ni-NSP, and (e) is the nickel-supported SAPO-34 catalyst modified with oxalic acid, denoted as Ni-CSP; Figure 4 The SEM images of the SAPO-34 carrier prepared before and after adjusting the molar ratio of the raw materials for catalyst preparation in the present invention, wherein (a) is before adjusting the molar ratio of the raw materials for catalyst preparation, and the specific molar ratio of the aluminum source, phosphorus source, silicon source, template and water is 1:1:0.3:3:70, and (b) is after adjusting the molar ratio of the raw materials for catalyst preparation, and the specific molar ratio of the aluminum source, phosphorus source, silicon source, template and water is 1:1:0.4:4.5:60; Figure 5 It is the N2 adsorption-desorption isotherm diagram of the SAPO-34 catalyst prepared in the present invention.

[0026] Among them, 1. Nitrogen cylinder, 2. Mass flow meter, 3. Injection pump, 4. Temperature controller, 5. High voltage power supply, 6. Digital oscilloscope, 7. Tubular heating furnace, 8. Dielectric barrier plasma reactor, 9. Gas chromatograph, 10. Tail gas absorption device. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0029] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0030] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0031] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0032] like Figure 1 As shown, the present invention provides a method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst, comprising the following steps: S1: Add a phosphorus source into water to obtain a water solution of the phosphorus source, add an aluminum source into the water solution of the phosphorus source, stir at a constant temperature of 40-60°C for 1-4 h, then add a template and a silicon source dropwise, continue stirring for 2-6 h, mix and mix well, and obtain a precursor solution; Among them, the molar ratio of aluminum source, phosphorus source, silicon source, template and water is (1~4):(1~6):(0.4~1.6):(4.5~6.9):(60~90).

[0033] Further, the aluminum source is at least one of Al2O3 and pseudo-boehmite; The phosphorus source is at least one of phosphoric acid and P2O5.

[0034] The silicon source is at least one of silica sol, tetraethyl orthosilicate, amorphous silicon oxide powder and silicate.

[0035] The template agent is at least one of tetraethylammonium hydroxide, diethylamine, diethanolamine and triethylamine.

[0036] S2: subjecting the precursor solution to a hydrothermal reaction at 150-200° C. for 24-48 h, centrifuging the product after the hydrothermal reaction, washing it with water and a methanol solution respectively, and drying it at 80-120° C. for 8-12 h, placing the dried product in a muffle furnace under an air atmosphere, and calcining the product at 450-650° C. for 4-8 h to obtain an original SAPO-34 carrier; S3: placing the original SAPO-34 carrier in an organic acid solution, stirring at 50-90°C for 1-4 h, centrifuging and drying the acid-treated product, and calcining in a muffle furnace at 400-600°C for 2-6 h to obtain an acid-treated SAPO-34 carrier; wherein the mass ratio of the original SAPO-34 carrier to the organic acid solution is (15-45):(1-5). The organic acid is at least one of citric acid and oxalic acid.

[0037] S4: adding the acid-treated SAPO-34 carrier to the Ni(NO3)2 solution, stirring and mixing thoroughly, drying, and calcining in a muffle furnace at 400-600°C for 2-6 h to obtain the nickel-loaded hierarchical SAPO-34 catalyst.

[0038] In the present invention, benzene is selected as a model compound of tar, and the low-temperature plasma catalytic system used for benzene reforming is shown in the device diagram. Figure 2 As shown, the system mainly consists of three parts: gas supply system, reforming reaction system and detection system.

[0039] Gas supply system: mainly composed of nitrogen cylinder 1, mass flow meter 2, injection pump 3 and vaporization bottle. Benzene and water are pushed into the constant temperature 140~200℃ vaporization bottle at a certain pushing speed through two injection pumps for vaporization, and nitrogen is used as a carrier gas to push the vaporized mixed gas into the reforming reaction system.

[0040] Reforming reaction system: mainly composed of a tubular heating furnace 7, a high-voltage power supply 5, an oscilloscope 6 and a dielectric barrier plasma reactor 8.

[0041] Detection system: The initial concentration of benzene, the concentration of benzene after reforming and the concentration of products (H2, CO, CO2 and CH4) are detected online by gas chromatograph 9.

[0042] In addition, the system also includes a tail gas absorption device 10 and a temperature controller 4, wherein the inner wall of the tubular heating furnace 7 is made of corundum material, which has better high temperature resistance.

[0043] The catalyst preparation cost of the present invention is low, and the cost of preparing the multi-level porous catalyst by etching the carrier with organic acid is reduced, and the transition metal Ni is used as the active component, which is cheap and easy to obtain. The prepared nickel-loaded multi-level porous SAPO-34 catalyst shows good catalytic activity and stability in the plasma reforming of benzene. The combination of plasma and catalyst can transform the discharge form from filamentary discharge to a combination of filamentary discharge and surface discharge, forming micro-discharge in the pores of the catalyst, enhancing the electric field strength and the degree of benzene cracking. Under the action of plasma, the surface of the nickel-loaded multi-level porous SAPO-34 produces short-lived and long-lived excited active species, which improves the activity and stability of the catalyst. The invention is combined with low-temperature plasma to have high activity in reforming benzene, with a conversion rate of up to 96%, and the selectivity of CO and H2 reaches 19% and 53% respectively.

[0044] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0045] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0046] Example 1 Step 1: Weigh the aluminum source, phosphorus source, silicon source, template, and deionized water in a molar ratio of 1:1:0.4:4.5:60. First, dissolve the phosphorus source in deionized water and stir evenly at room temperature.

[0047] Step 2: Place the above solution that has been stirred evenly in a constant temperature magnetic stirrer at 40°C, add the weighed aluminum source to the stirring solution, and stir for 2 h.

[0048] Step 3: Add triethylamine and silica sol dropwise to the stirring solution and stir for 2 h.

[0049] Step 4: Transfer the stirred solution into a stainless steel reactor lined with polytetrafluoroethylene and perform hydrothermal reaction at 200 °C for 48 h.

[0050] Step 5: The product after the hydrothermal reaction was centrifuged, washed with deionized water and methanol solution, respectively, and dried at 80 °C for 12 h.

[0051] Step 6: The dried product was placed in a muffle furnace under air atmosphere and calcined at 550° C. for 6 h to obtain the original carrier SAPO-34.

[0052] Step 7: The citric acid solution was fully contacted with the SAPO-34 support at a solid-liquid ratio of 20:1. The solution was stirred under a constant temperature magnetic stirrer at 70°C for 2 h.

[0053] Step 8: The product treated with citric acid was centrifuged, dried, and calcined in a muffle furnace at 500° C. for 4 h to obtain a citric acid-modified hierarchical porous SAPO-34 carrier.

[0054] Step 9: Mix Ni(NO3)2·6H2O with a certain amount of deionized water, add a certain amount of SAPO-34 treated with citric acid into the solution, and stir well to mix.

[0055] Step 10: The uniformly stirred product was centrifuged, dried, and calcined in a muffle furnace at 550° C. for 4 h to obtain a citric acid-modified nickel-loaded SAPO-34 catalyst, recorded as Ni / (N)SAPO-34, abbreviated as Ni-NSP.

[0056] Step 11: Place the prepared citric acid-modified nickel-loaded SAPO-34 catalyst in the discharge region of a dielectric barrier discharge plasma, control the reaction temperature at 400°C, the discharge power at 80W, the gas flow rate at 500mL / min, and conduct a reforming reaction of 1000ppm of benzene.

[0057] Example 2 Step 1: Weigh the aluminum source, phosphorus source, silicon source, template, and deionized water in a molar ratio of 1:1:0.4:4.5:60. First, dissolve the phosphorus source in deionized water and stir evenly at room temperature.

[0058] Step 2: Place the above solution that has been stirred evenly in a constant temperature magnetic stirrer at 40°C, add the weighed aluminum source to the stirring solution, and stir for 2 h.

[0059] Step 3: Add triethylamine and silica sol dropwise to the stirring solution and stir for 2 h.

[0060] Step 4: Transfer the stirred solution into a stainless steel reactor lined with polytetrafluoroethylene and perform hydrothermal reaction at 200 °C for 48 h.

[0061] Step 5: The product after the hydrothermal reaction was centrifuged, washed with deionized water and methanol solution, respectively, and dried at 80 °C for 12 h.

[0062] Step 6: The dried product was placed in a muffle furnace under air atmosphere and calcined at 550° C. for 6 h to obtain the original carrier SAPO-34.

[0063] Step 7: The oxalic acid solution was fully contacted with the SAPO-34 support at a solid-liquid ratio of 20:1. The solution was stirred under a constant temperature magnetic stirrer at 70°C for 2 h.

[0064] Step 8: The product treated with oxalic acid was centrifuged, dried, and calcined in a muffle furnace at 500° C. for 4 h to obtain a hierarchical porous SAPO-34 carrier modified with oxalic acid.

[0065] Step 9: Mix Ni(NO3)2·6H2O with a certain amount of deionized water, add a certain amount of SAPO-34 treated with oxalic acid into the solution, and stir well to mix.

[0066] Step 10: The uniformly stirred product was centrifuged, dried, and calcined in a muffle furnace at 550° C. for 4 h to obtain an oxalic acid-modified nickel-supported SAPO-34 catalyst, recorded as Ni / (C)SAPO-34, abbreviated as Ni-CSP.

[0067] Step 11: Place the prepared oxalic acid-modified nickel-loaded SAPO-34 catalyst in the discharge region of a dielectric barrier discharge plasma, control the reaction temperature at 400°C, the discharge power at 80W, the gas flow rate at 500mL / min, and conduct a reforming reaction of 1000ppm of benzene.

[0068] Table 1 shows the porosity test results of the original carrier SAPO-34, citric acid-modified SAPO-34, oxalic acid-modified SAPO-34, citric acid-modified nickel-loaded SAPO-34 catalyst and oxalic acid-modified nickel-loaded SAPO-34 catalyst in the present invention. It can be seen from Table 1 that organic acid treatment can effectively expand the void structure of the original carrier SAPO-34.

[0069] Table 1 Porosity test results of original carrier SAPO-34, citric acid modified SAPO-34, oxalic acid modified SAPO-34, citric acid modified nickel supported SAPO-34 catalyst and oxalic acid modified nickel supported SAPO-34 catalyst in the present invention

[0070] Comparative Example 1 Step 1: Weigh the aluminum source, phosphorus source, silicon source, template, and deionized water in a molar ratio of 1:1:0.4:4.5:60. First, dissolve the phosphorus source in deionized water and stir evenly at room temperature.

[0071] Step 2: Place the above solution that has been stirred evenly in a constant temperature magnetic stirrer at 40°C, add the weighed aluminum source to the stirring solution, and stir for 2 h.

[0072] Step 3: Add triethylamine and silica sol dropwise to the stirring solution and stir for 2 h.

[0073] Step 4: Transfer the stirred solution into a stainless steel reactor lined with polytetrafluoroethylene and perform hydrothermal reaction at 200 °C for 48 h.

[0074] Step 5: The product after the hydrothermal reaction was centrifuged, washed with deionized water and methanol solution, respectively, and dried at 80 °C for 12 h.

[0075] Step 6: The dried product was placed in a muffle furnace under air atmosphere and calcined at 550° C. for 6 h to obtain the original carrier SAPO-34, abbreviated as SP.

[0076] Step 7: Place the prepared original carrier SAPO-34 in the discharge region of the dielectric barrier discharge plasma, control the reaction temperature at 400°C, the discharge power at 80W, the gas flow rate at 500mL / min, and carry out a reforming reaction of 1000 ppm of benzene.

[0077] Comparative Example 2 Step 1: Weigh the aluminum source, phosphorus source, silicon source, template, and deionized water in a molar ratio of 1:1:0.4:4.5:60. First, dissolve the phosphorus source in deionized water and stir evenly at room temperature.

[0078] Step 2: Place the above solution that has been stirred evenly in a constant temperature magnetic stirrer at 40°C, add the weighed aluminum source to the stirring solution, and stir for 2 h.

[0079] Step 3: Add triethylamine and silica sol dropwise to the stirring solution and stir for 2 h.

[0080] Step 4: Transfer the stirred solution into a stainless steel reactor lined with polytetrafluoroethylene and perform hydrothermal reaction at 200 °C for 48 h.

[0081] Step 5: The product after the hydrothermal reaction was centrifuged, washed with deionized water and methanol solution, respectively, and dried at 80 °C for 12 h.

[0082] Step 6: The dried product was placed in a muffle furnace under air atmosphere and calcined at 550° C. for 6 h to obtain the original carrier SAPO-34.

[0083] Step 7: The citric acid solution was fully contacted with the SAPO-34 support at a solid-liquid ratio of 20:1. The solution was stirred under a constant temperature magnetic stirrer at 70°C for 2 h.

[0084] Step 8: The product treated with citric acid was centrifuged, dried, and calcined in a muffle furnace at 500° C. for 4 h to obtain a citric acid-modified SAPO-34 carrier, denoted as (N) SAPO-34, abbreviated as NSP.

[0085] Step 9: Place the prepared citric acid-modified SAPO-34 carrier in the discharge region of a dielectric barrier discharge plasma, control the reaction temperature at 400° C., the discharge power at 80 W, and the gas flow rate at 500 mL / min, and conduct a reforming reaction of 1000 ppm of benzene.

[0086] Comparative Example 3 Step 1: Weigh the aluminum source, phosphorus source, silicon source, template, and deionized water in a molar ratio of 1:1:0.4:4.5:60. First, dissolve the phosphorus source in deionized water and stir evenly at room temperature.

[0087] Step 2: Place the above solution that has been stirred evenly in a constant temperature magnetic stirrer at 40°C, add the weighed aluminum source to the stirring solution, and stir for 2 h.

[0088] Step 3: Add triethylamine and silica sol dropwise to the stirring solution and stir for 2 h.

[0089] Step 4: Transfer the stirred solution into a stainless steel reactor lined with polytetrafluoroethylene and perform hydrothermal reaction at 200 °C for 48 h.

[0090] Step 5: The product after the hydrothermal reaction was centrifuged, washed with deionized water and methanol solution, respectively, and dried at 80 °C for 12 h.

[0091] Step 6: The dried product was placed in a muffle furnace under air atmosphere and calcined at 550° C. for 6 h to obtain the original carrier SAPO-34.

[0092] Step 7: The oxalic acid solution was fully contacted with the SAPO-34 support at a solid-liquid ratio of 20:1. The solution was stirred under a constant temperature magnetic stirrer at 70°C for 2 h.

[0093] Step 8: The product after oxalic acid treatment is centrifuged, dried, and calcined in a muffle furnace at 500° C. for 4 h to obtain an oxalic acid-modified SAPO-34 carrier, denoted as (C) SAPO-34, abbreviated as CSP.

[0094] Step 9: Place the prepared oxalic acid-modified SAPO-34 carrier in the discharge region of a dielectric barrier discharge plasma, control the reaction temperature at 400°C, the discharge power at 80W, and the gas flow rate at 500mL / min, and conduct a reforming reaction of 1000 ppm of benzene.

[0095] Comparative Example 4 A single plasma reforming experiment was conducted without filling a catalyst. The reaction temperature was adjusted to 400°C, the discharge power was 80W, the gas flow rate was 500mL / min, and the discharge frequency was 10kHz, and the target product synthesis gas was obtained through the reforming reaction.

[0096] Comparative Example 5 The catalyst was prepared according to the steps and conditions of Example 4, and the catalytic reforming experiment was carried out. The reaction temperature was adjusted to 700° C., the gas flow rate was 500 mL / min, and the target product, synthesis gas, was obtained through the reforming reaction.

[0097] Comparative Example 6 The catalyst was prepared according to the steps and conditions of Example 5, and the catalytic reforming experiment was carried out. The reaction temperature was adjusted to 700° C., the gas flow rate was 500 mL / min, and the target product, synthesis gas, was obtained through the reforming reaction.

[0098] Table 1 Reforming indicators of SAPO-34 series catalysts (reaction temperature 400℃, discharge power 80W)

[0099] By comparing five groups of examples, it can be seen from Table 1 that among the SAPO-34 series catalysts, the Ni / (C)SAPO-34 catalyst treated with oxalic acid has the best performance. Under the conditions of reaction temperature of 400°C, discharge power of 80W and gas flow rate of 500mL / min, the conversion rate of benzene is 96%, and the selectivity of CO and H2 reaches 19.2% and 52.8% respectively.

[0100] in addition, Figure 3The SEM images of the SAPO-34 catalyst prepared in the present invention, (a) is the original carrier SAPO-34, recorded as SP, (b) is the SAPO-34 modified with citric acid, recorded as NSP, (c) is the SAPO-34 modified with oxalic acid, recorded as CSP, (d) is the nickel-supported SAPO-34 catalyst modified with citric acid, recorded as Ni-NSP, (e) is the nickel-supported SAPO-34 catalyst modified with oxalic acid, recorded as Ni-CSP. As can be seen from the figure, the original carrier SAPO-34 has a traditional typical cubic shape. In contrast, small pores appear on the surface of NSP and CSP, and the latter has a large number of pores. This is because oxalic acid is stronger than citric acid, and more Si is removed from the surface of SAPO-34, so that more micropores are synthesized into mesopores or macropores. The Ni of Ni-NSP and Ni-CSP is loaded on the surface of the cube, making its surface rough.

[0101] Figure 4 SEM images of the SAPO-34 carrier prepared before and after adjusting the molar ratio of the raw materials for catalyst preparation, wherein (a) is before adjusting the molar ratio of the raw materials for catalyst preparation, specifically, the molar ratio of the aluminum source, phosphorus source, silicon source, template and water is 1:1:0.3:3:70, and (b) is after adjusting the molar ratio of the raw materials for catalyst preparation, specifically, the molar ratio of the aluminum source, phosphorus source, silicon source, template and water is 1:1:0.4:4.5:60. It can be seen from the figure that after adjusting the molar ratio of the silicon source, template and water, the original carrier SAPO-34 has a better degree of crystallization on a macroscopic scale, most of which is a cubic morphology, the material has better morphological uniformity, and the cage structure in the cubic morphology increases the stability of the catalyst.

[0102] Figure 5The N2 adsorption-desorption isotherms of the SAPO-34 catalyst prepared in the present invention are shown in Figure 1. (a) is the adsorption-desorption isotherms of the SAPO-34 series catalysts, and (b) is the pore size distribution of the SAPO-34 series catalysts. It can be seen from the figure that all samples show type I isotherms. The isothermal adsorption curve of the original carrier SAPO-34 has a hysteresis loop in the medium pressure region, and the adsorption curve is upturned in the high pressure region. This shows that the SAPO-34 crystal itself contains mesopores. The degree of upturn of the adsorption isotherm of NSP in the high pressure region is increased, and the degree of upturn of the adsorption isotherm of CSP is even greater. This is because the acidity of oxalic acid is stronger than that of citric acid, and more mesopores are etched on the catalyst surface. After Ni is loaded, the degree of upturn of the adsorption isotherms of the two tends to be gentle, which is due to the blocking of some pores by Ni. The pore size distribution of the samples shows that the mesopore diameter is concentrated in 12~40 nm, and the number of mesopores in this range of CSP is greater than that of NSP. After Ni is loaded, the number decreases. On the one hand, the increase in pore size and pore volume helps the adsorption of macromolecular substances such as benzene, increases the residence time of benzene molecules in the reaction system, and thus enhances the conversion performance of benzene; on the other hand, the acidity of the catalyst surface is reduced, providing milder reaction conditions for the reaction.

[0103] Example 3 A method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst comprises the following steps: S1: phosphoric acid is added into water to obtain a water solution of phosphorus source, Al2O3 is added into the water solution of phosphorus source, after constant temperature stirring at 40°C for 4 h, tetraethylammonium hydroxide and silica sol are added dropwise, stirring is continued for 2 h, and mixing is performed to obtain a precursor solution; Wherein, the molar ratio of Al2O3, phosphoric acid, silica sol, tetraethylammonium hydroxide and water is 1:1:0.4:4.5:60.

[0104] S2: The precursor solution was subjected to a hydrothermal reaction at 150° C. for 48 h, the product after the hydrothermal reaction was centrifuged, washed with water and methanol solution respectively and dried at 80° C. for 12 h, the dried product was placed in a muffle furnace under an air atmosphere, and the product was calcined at 450° C. for 8 h to obtain an original SAPO-34 carrier; S3: placing the original SAPO-34 carrier in a citric acid solution, stirring at 50°C for 4 h, centrifuging and drying the acid-treated product, and calcining in a muffle furnace at 400°C for 6 h to obtain an acid-treated SAPO-34 carrier; wherein the mass ratio of the original SAPO-34 carrier to the organic acid solution is 15:1.

[0105] S4: adding the acid-treated SAPO-34 carrier to the Ni(NO3)2 solution, stirring and mixing thoroughly, drying, and calcining in a muffle furnace at 400°C for 6 h to obtain the nickel-loaded hierarchical SAPO-34 catalyst.

[0106] Example 4 A method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst comprises the following steps: S1: P2O5 is added into water to obtain a water solution of a phosphorus source, pseudo-boehmite is added into the water solution of the phosphorus source, after constant temperature stirring at 50°C for 2 h, diethanolamine and ethyl orthosilicate are added dropwise, stirring is continued for 2-6 h, and mixing is performed to obtain a precursor solution; Among them, the molar ratio of pseudo-boehmite, P2O5, tetraethyl orthosilicate, diethanolamine and water is 4:6:1.6:6.9:90.

[0107] S2: The precursor solution is subjected to a hydrothermal reaction at 200° C. for 24 h, the product after the hydrothermal reaction is centrifuged, washed with water and a methanol solution respectively, and dried at 120° C. for 8 h, the dried product is placed in a muffle furnace under an air atmosphere, and the product is calcined at 650° C. for 4 h to obtain an original SAPO-34 carrier; S3: placing the original SAPO-34 carrier in an oxalic acid solution, stirring at 90°C for 1 h, centrifuging and drying the acid-treated product, and calcining in a muffle furnace at 600°C for 2 h to obtain an acid-treated SAPO-34 carrier; wherein the mass ratio of the original SAPO-34 carrier to the organic acid solution is 45:5.

[0108] S4: adding the acid-treated SAPO-34 carrier to the Ni(NO3)2 solution, stirring and mixing thoroughly, drying, and calcining in a muffle furnace at 600°C for 2 h to obtain the nickel-loaded hierarchical SAPO-34 catalyst.

[0109] Example 5 A method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst comprises the following steps: S1: phosphoric acid is added into water to obtain a water solution of phosphorus source, Al2O3 is added into the water solution of phosphorus source, after constant temperature stirring at 40-60°C for 1-4 h, triethylamine and amorphous silicon oxide powder are added dropwise, stirring is continued for 2-6 h, and mixing is performed to obtain a precursor solution; Wherein, the molar ratio of Al2O3, phosphoric acid, amorphous silicon oxide powder, triethylamine and water is 2:3:1:5:80.

[0110] S2: The precursor solution is subjected to a hydrothermal reaction at 180° C. for 30 h, the product after the hydrothermal reaction is centrifuged, washed with water and a methanol solution respectively, and dried at 100° C. for 10 h, the dried product is placed in a muffle furnace under an air atmosphere, and the product is calcined at 500° C. for 6 h to obtain an original SAPO-34 carrier; S3: placing the original SAPO-34 carrier in a citric acid solution, stirring at 70°C for 2 h, centrifuging and drying the acid-treated product, and calcining in a muffle furnace at 500°C for 4 h to obtain an acid-treated SAPO-34 carrier; wherein the mass ratio of the original SAPO-34 carrier to the organic acid solution is 30:2. The organic acid is at least one of citric acid and oxalic acid.

[0111] S4: adding the acid-treated SAPO-34 carrier to the Ni(NO3)2 solution, stirring and mixing thoroughly, drying, and calcining in a muffle furnace at 500°C for 4 h to obtain the nickel-loaded hierarchical SAPO-34 catalyst.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst, characterized in that: The following steps are involved: S1: adding an aluminum source to a water solution of a phosphorus source, stirring at a constant temperature, and then adding a template and a silicon source dropwise, stirring and mixing, to prepare a precursor solution; S2: subjecting the precursor solution to a hydrothermal reaction treatment, and subjecting the product to a calcination treatment to obtain an original SAPO-34 carrier; S3: placing the original SAPO-34 carrier in an organic acid solution, stirring it, and then drying and calcining it to obtain an acid-treated SAPO-34 carrier; S4: adding the acid-treated SAPO-34 carrier to the Ni(NO3)2 solution, stirring and mixing thoroughly, drying and heat-treating the carrier to obtain the nickel-loaded hierarchical SAPO-34 catalyst.

2. The method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst according to claim 1, characterized in that: The molar ratio of the aluminum source, phosphorus source, silicon source and template is (1-4):(1-6):(0.4-1.6):(4.5-6.9).

3. The method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst according to claim 1, characterized in that: In step S1, an aluminum source is added to the water solution of a phosphorus source, and the stirring temperature is 40-60° C. and the stirring time is 1-4 h during constant temperature stirring.

4. The method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst according to claim 1, characterized in that: In step S2, the temperature of the hydrothermal reaction treatment is 150-200° C., and the time is 24-48 h.

5. The method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst according to claim 1, characterized in that: In step S2, the calcination treatment is carried out at a temperature of 450-650°C and for a time of 4-8 hours.

6. The method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst according to claim 1, characterized in that: In step S3, the mass ratio of the original SAPO-34 carrier to the organic acid solution is (15-45):(1-5).

7. The method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst according to claim 1, characterized in that: In step S3, during the stirring process, the temperature is 50-90° C. and the time is 1-4 h.

8. The method for preparing a nickel-supported hierarchical porous SAPO-34 catalyst according to claim 1, characterized in that: In step S3, during the calcination process, the temperature is 400-600° C. and the time is 2-6 h.

9. A nickel-supported hierarchical SAPO-34 catalyst, characterized in that: The catalyst is prepared by the method according to any one of claims 1 to 8, wherein the micropore specific surface area of ​​the catalyst is 110 to 170 m 2 ·g -1 The mesopore specific surface area is 70~140m 2 ·g -1 , the micropore volume is 0.05~0.1cm 3 ·g -1 , the mesopore volume is 0.2~0.4cm 3 ·g -1 , the average pore size is 11~13nm.

10. Use of a nickel-supported multi-level porous SAPO-34 catalyst as claimed in claim 9 in tar reforming coupled with low-temperature plasma, characterized in that: In the application process, when the discharge power is 80W, the gas flow rate is 500mL / min, and the reaction temperature is 400°C, the conversion rate of benzene is 95%~96%, the hydrogen selectivity is 49%~53%, and the carbon monoxide selectivity is 18%~19%.

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