Hydrodealkylation catalyst, process for its preparation and use

Abstract

This invention relates to the field of catalyst materials technology, and discloses a hydrodealkylation catalyst, its preparation method, and its application in the hydrodealkylation of toluene to benzene. The hydrodealkylation catalyst comprises an alumina support and a first active component and a second active component supported on the alumina support; wherein the alumina support comprises macroporous alumina and microporous alumina; the first active component is selected from at least one of alkali metals, alkaline earth metals, and phosphorus; the second active component is selected from Group VIB metals and / or Group VIII metals. The hydrodealkylation catalyst provided by this invention exhibits high toluene conversion and high benzene selectivity in the toluene hydrodealkylation reaction, with a benzene mass reaching up to 99.9%, and low aromatic ring loss rate in toluene as a raw material, with an aromatic hydrocarbon yield of over 99.25%, reaching a maximum of 99.89%; furthermore, the catalyst demonstrates good stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst materials, in particular to a hydrodealkylation catalyst, a preparation method thereof and application of the catalyst in toluene hydrodealkylation reaction to produce benzene. BACKGROUND

[0002] Benzene is an important basic organic raw material with huge demand, and its industrial chain is rich and its industrial base is scattered. The main downstream products are ethylbenzene (41.0%), phenol (16%), caprolactam (16%), cyclohexane (12%), etc. At present, the main chemical processes for directly producing benzene are catalytic reforming, ethylene cracking, and coal chemical coking, etc. Among them, in addition to producing benzene, catalytic reforming and ethylene cracking processes will also generate many other alkylbenzenes, and the benzene yield is limited. The carbon emission of the coal chemical industry is relatively high, and the future benzene yield of the coking industry may be compressed. In addition, toluene disproportionation technology is the most widely used technology for increasing benzene production at present, but toluene disproportionation technology can only theoretically produce 1 mole of benzene and 1 mole of dimethylbenzene from 2 moles of toluene, and the raw material is limited and cannot maximize the efficiency of increasing benzene production. The existing heavy aromatic lightening technology can only remove C2-C4 side chains, cannot achieve efficient removal of methyl groups, and the main product is mainly dimethylbenzene, and the benzene yield is extremely limited. Therefore, it is urgent to seek other efficient benzene production technologies. +

[0003] Aromatic dealkylation for benzene production technology is a technology that effectively removes side chain alkyl groups including methyl groups and above through side chain dealkylation, and efficiently converts aromatic hydrocarbons into benzene. Theoretically, 1 mole of aromatic hydrocarbon can produce 1 mole of benzene, which is the highest efficiency benzene production technology at present. Aromatic dealkylation includes hydrodealkylation, non-hydrodealkylation, and steam reforming dealkylation, and the currently used industrial application is hydrodealkylation technology. Among them, catalytic hydrodealkylation technology has a lower apparent activation energy due to the presence of a catalyst, so that the reaction rate of catalytic hydrodealkylation is faster than that of thermal cracking hydrodealkylation at the same reaction temperature, and under the same conversion rate conditions, it has the characteristics of low reaction temperature and high benzene selectivity. Thermal cracking hydrodealkylation and catalytic hydrodealkylation have their own characteristics. Catalytic hydrodealkylation has a low reaction temperature, mainly involves alkyl aromatic dealkylation and non-aromatic hydrocracking reactions, and has a high inhibition rate of aromatic ring saturation and cracking reactions, so that the hydrogen consumption of the technology is relatively low, and the benzene selectivity can be more than 98 mol%. The reaction temperature of thermal cracking hydrodealkylation technology is high, and the reaction process is a free radical mechanism. On the one hand, the high reaction temperature leads to an increase in cracking and polymerization side reactions, and on the other hand, the free radical reaction process is prone to generate biphenyl, so that the benzene selectivity is about 3% lower than that of catalytic hydrodealkylation technology, and the hydrogen consumption is also relatively high, but the technology does not require the use of a catalyst, so that the reaction process is relatively simple, and the non-aromatic hydrocarbon in the raw material can reach 30%. ​

[0004] The application discloses a technology for preparing benzene by catalytically dealkylating aromatic hydrocarbons. + The application discloses a technology for preparing benzene by catalytically dealkylating aromatic hydrocarbons.

[0005] CN1227193C discloses a heavy aromatic hydrocarbon catalytic dealkylation catalyst and a preparation method thereof. The catalyst comprises 0.01-2.0 wt% of Group VIII metal and a composite carrier. The composite carrier comprises 30-70 wt% of ZSM-5 zeolite, 5-30 wt% of beta zeolite and 10-65 wt% of alumina. The catalyst is used for lightening heavy aromatic hydrocarbons, can improve C9 + aromatic hydrocarbon conversion rate and benzene and xylene yield, and reduces carbon deposition.

[0006] CN1050777C discloses a Cr2O3-RE / Al2O3 novel catalyst for preparing dimethylbenzene, toluene and benzene by catalytically dealkylating C9-10 alkyl aromatic hydrocarbons. The catalyst is prepared by treating a carrier Al2O3 with rare earth, and has a structure stability and a selectivity to triphenyl of more than 95% (conversion rate 58%). The catalyst is prepared by loading rare earth La2O3 on the surface of γ-Al2O3, high-temperature treatment, adjusting the acidity of γ-Al2O3 and promoting the uniform distribution of Cr2O3 grains on the surface of γ-Al2O3. The catalyst can also be used in a process for preparing benzene by catalytically dealkylating toluene.

[0007] CN101444745A discloses a preparation method of a heavy aromatic hydrocarbon steam dealkylation catalyst. The method is realized by impregnating a nitrate solution of rare earth metal or alkaline earth metal into a silicon-aluminum type molecular sieve, then through water bath ion exchange, repeated washing until neutral, drying and calcination. The catalyst is suitable for steam dealkylation reaction, has low preparation cost, good stability, long service life, easy regeneration, and can prepare high-purity 1,3,5-trimethylbenzene with high conversion rate and purity of more than 90%.

[0008] CN111068769A discloses a catalyst for a dimethylphenol catalytic dealkylation reaction, a preparation method and application thereof. The catalyst comprises a composite carrier and an acidic active component. The composite carrier is a composite of modified HY molecular sieve and Al-MCM-41 molecular sieve, and the modified HY molecular sieve is coated with Al-MCM-41 molecular sieve to form a HY / MCM-41 coated composite molecular sieve. The acidic active component is SO42 / -TiO2; wherein the mass of the modified HY molecular sieve is 20-80% of the mass of the composite carrier; SO4 2 / -TiO2 is 3-8% of the mass of the HY molecular sieve. The catalyst has suitable acidity and micro / mesopore structure, and shows high 3,4-dimethylphenol conversion rate, phenol and cresol selectivity, and good stability.

[0009] From the above summary, although the preparation method of the aromatic hydrocarbon catalytic dealkylation molecular sieve is relatively mature, there is almost no catalyst that can solve the problems of poor catalytic dealkylation activity, high aromatic ring loss rate, and the like. Meanwhile, the assistant and metal applied in the synthesis process of the molecular sieve are expensive, and the production cost is high. Therefore, developing a toluene catalytic dealkylation catalyst with high conversion rate and high stability has wide market demand and good application prospect. SUMMARY

[0010] The purpose of the present application is to overcome the problems of poor catalytic dealkylation activity and high aromatic ring loss rate of the hydrogenation dealkylation catalyst in the prior art, and to provide a hydrogenation dealkylation catalyst, a preparation method and application thereof. When the catalyst is used for toluene hydrogenation dealkylation reaction to prepare benzene, it has better hydrogenation dealkylation activity, and the aromatic ring loss rate of toluene as raw material is low.

[0011] In order to achieve the above purpose, the first aspect of the present application provides a hydrogenation dealkylation catalyst, which comprises an alumina carrier and a first active component and a second active component supported on the alumina carrier; wherein the alumina carrier comprises large-pore alumina and small-pore alumina; the first active component is selected from at least one of alkali metal, alkaline earth metal and phosphorus; and the second active component is selected from group VI B metal and / or group VIII metal.

[0012] The second aspect of the present application provides a preparation method of a hydrogenation dealkylation catalyst, which comprises:

[0013] (1) mixing and shaping the large-pore alumina and the small-pore alumina to obtain an alumina carrier;

[0014] (2) loading a first active source on the alumina carrier, and performing first drying and first calcination to obtain a catalyst precursor;

[0015] (3) loading a second active source on the catalyst precursor, and then performing second drying and second calcination;

[0016] Wherein, the first active source is compound I containing a first active element, the first active element being selected from at least one of alkali metal elements, alkaline earth metal elements and phosphorus; the second active source is compound II containing a second active element, the second active element being selected from group VIB elements and / or group VIII elements.

[0017] A third aspect of the present invention provides a hydrogenation dealkylation catalyst prepared by the preparation method described in the second aspect.

[0018] The fourth aspect of this invention provides the application of the hydrodealkylation catalyst described in the first or third aspect in the production of benzene from toluene via hydrodealkylation.

[0019] Through the above technical solution, the hydrogenation dealkylation catalyst provided by the present invention has high toluene conversion rate, high benzene selectivity, and benzene mass up to 99.9% in the toluene hydrogenation dealkylation reaction. Moreover, the aromatic ring loss rate of toluene as raw material is low, and the aromatic hydrocarbon yield can reach more than 99.25%, and up to 99.89%. Furthermore, the catalyst has good stability. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of the present invention provides a hydrodealkylation catalyst, the catalyst comprising an alumina support and a first active component and a second active component supported on the alumina support; wherein the alumina support comprises macroporous alumina and microporous alumina; the first active component is selected from at least one of alkali metals, alkaline earth metals and phosphorus; and the second active component is selected from Group VIB metals and / or Group VIII metals.

[0022] According to some embodiments of the present invention, the alumina support includes macroporous alumina and microporous alumina. Using the above-mentioned specific composite support is beneficial to adjusting the distribution of acidic sites on the support, providing conditions for the loading of metal active components, and at the same time, it is beneficial to improve the hydrogenation and dealkylation activity of the catalyst, improve benzene selectivity, and reduce the aromatic ring loss rate.

[0023] According to some embodiments of the present invention, preferably, the macroporous alumina has an average pore size of 80-240 nm, more preferably 110-180 nm.

[0024] According to some embodiments of the present invention, preferably, the macropore volume (i.e., the pore volume) of the macroporous alumina is 0.6-1.5 mL / g, more preferably 0.8-1.2 mL / g.

[0025] According to some embodiments of the present invention, preferably, the average pore size of the microporous alumina is 2-10 nm, more preferably 4-9 nm.

[0026] According to some embodiments of the present invention, preferably, the pore volume (i.e., the pore size) of the microporous alumina is 0.2-0.6 mL / g, more preferably 0.25-0.45 mL / g.

[0027] The above-described preferred embodiments are beneficial for adjusting the pore size distribution of the alumina support, improving diffusion efficiency, thereby further enhancing the hydrogenation and dealkylation activity of the catalyst, increasing benzene selectivity, and reducing aromatic ring loss rate.

[0028] According to some embodiments of the present invention, preferably, the alumina support further includes a binder. The type of binder can be selected from a wide range, and the present invention does not impose any particular limitation on it; for example, it can be a binder conventionally used in the art for catalyst preparation. Preferably, the binder is selected from at least one of methylcellulose, polyacrylamide, guar gum, and nitric acid, more preferably methylcellulose and / or nitric acid.

[0029] According to some embodiments of the present invention, there is no particular limitation on the content of the binder, and reference can be made to the prior art. Preferably, the content of the binder, on a dry basis, is 1-15% of the total dry weight of macroporous alumina and microporous alumina, more preferably 2-10%.

[0030] According to some embodiments of the present invention, the first active component is selected from at least one of alkali metals, alkaline earth metals, and phosphorus. Preferably, the first active component is selected from at least one of sodium, potassium, magnesium, calcium, barium, and phosphorus; more preferably, at least two of magnesium, calcium, barium, and phosphorus; more preferably, at least two of magnesium, barium, and phosphorus; even more preferably, magnesium and phosphorus; and even more preferably, the weight ratio of magnesium to phosphorus, based on oxides, is 1:0.8-1. The above-described preferred embodiments are beneficial for optimizing the pore structure and promoting the diffusion of toluene feedstock within the pores, thereby further improving the hydrogenation dealkylation activity of the catalyst, increasing benzene selectivity, and reducing the aromatic ring loss rate.

[0031] According to some embodiments of the present invention, the second active component is selected from Group VIB metals and / or Group VIII metals. Preferably, the second active component is selected from at least one of chromium, molybdenum, cobalt, nickel, and platinum, and more preferably at least one of chromium, molybdenum, and cobalt. The above-described preferred embodiments are beneficial for reducing the acidity of alumina, improving the metal catalytic activity, and further enhancing the catalytic efficiency of the catalyst.

[0032] According to some embodiments of the present invention, using the above-mentioned specific composite active components in combination with a composite alumina support is beneficial to further improve the dealkylation efficiency of the catalyst on the basis of improving pore diffusion.

[0033] According to some embodiments of the present invention, the first active component and the second active component may exist in the form of oxides, sulfides, elements, etc., and there are no particular restrictions on this. They can be converted according to actual needs.

[0034] According to some embodiments of the present invention, preferably, the proportion of macroporous alumina is 20-80%, more preferably 30-50%, based on the total amount of the alumina carrier on a dry basis; and / or, the proportion of microporous alumina is 20-80%, more preferably 50-70%, based on the total amount of the alumina carrier on a dry basis.

[0035] According to some embodiments of the present invention, preferably, the weight ratio of macroporous alumina to microporous alumina is (0.3-3):1 on a dry basis, more preferably (0.4-1):1, and more preferably (0.4-0.8):1.

[0036] The above-described preferred embodiments are beneficial for adjusting the distribution of acidic sites on the support, providing conditions for loading the metal active components, thereby further improving the hydrogenation and dealkylation activity of the catalyst, increasing benzene selectivity, and reducing the aromatic ring loss rate.

[0037] According to some embodiments of the present invention, preferably, the weight of the first active component, based on oxides, is 0.5-2.5% of the weight of the alumina support; more preferably, the weight of the first active component, based on oxides, is 0.8-2.3% of the weight of the alumina support. The above preferred embodiments are beneficial for optimizing the pore structure and promoting the diffusion of toluene feedstock within the pores.

[0038] According to some embodiments of the present invention, preferably, the weight of the second active component, based on oxides, is 3-15% of the weight of the alumina support; more preferably, the weight of the second active component, based on oxides, is 3.5-12% of the weight of the alumina support. The above preferred embodiments are beneficial for reducing the acidity of alumina, improving the metal catalytic activity, and further enhancing the catalytic efficiency of the catalyst.

[0039] According to some embodiments of the present invention, the content of the alumina support and the first and second active components loaded on the alumina support in the catalyst is calculated based on the amount of raw materials fed.

[0040] According to some embodiments of the present invention, preferably, the pore volume of the catalyst is 0.2-1.2 cm³. 3 / g, preferably 0.4-1cm 3 / g.

[0041] According to some embodiments of the present invention, preferably, the specific surface area of ​​the catalyst is 80-210 m². 3 / g, preferably 130-200m 3 / g. The pore volume and specific surface area of ​​the catalyst were measured using a low-temperature nitrogen adsorption method.

[0042] According to some embodiments of the present invention, preferably, the catalyst has an average pore size of 5-10 nm, more preferably 6-9 nm.

[0043] According to some embodiments of the present invention, preferably, the strength of the catalyst is 40-150 N / cm, more preferably 60-120 N / cm. The strength of the catalyst is measured using a catalyst (solid) strength tester.

[0044] The above-described preferred embodiments are beneficial for further improving the hydrogenation dealkylation activity of the catalyst, increasing benzene selectivity, and reducing the aromatic ring loss rate.

[0045] A second aspect of the present invention provides a method for preparing a hydrogenation dealkylation catalyst, the method comprising:

[0046] (1) Mix macroporous alumina and microporous alumina and shape them to obtain an alumina carrier;

[0047] (2) The first active source is loaded onto the alumina support and subjected to first drying and first calcination to obtain a catalyst precursor;

[0048] (3) The second active source is loaded onto the catalyst precursor, and then subjected to a second drying and a second calcination.

[0049] Wherein, the first active source is compound I containing a first active element, the first active element being selected from at least one of alkali metal elements, alkaline earth metal elements and phosphorus; the second active source is compound II containing a second active element, the second active element being selected from group VIB elements and / or group VIII elements.

[0050] According to some embodiments of the present invention, in step (1), macroporous alumina, microporous alumina, and a binder are mixed and molded to obtain an alumina carrier. The molding process can give the alumina carrier a certain strength and morphology.

[0051] According to some embodiments of the present invention, the macroporous alumina and the microporous alumina can be selected as described above, and will not be repeated here.

[0052] According to some embodiments of the present invention, preferably, the weight ratio of macroporous alumina to microporous alumina is (0.3-3):1, more preferably (0.4-1):1, and more preferably (0.4-0.8):1.

[0053] According to some embodiments of the present invention, preferably, in step (1), the mixed raw materials further contain a binder. The binder can be selected as described above, and will not be repeated here. There is no particular limitation on the amount of the binder, and reference can be made to the prior art. Preferably, based on dry weight, the amount of the binder is 1-15% of the total dry weight of macroporous alumina and microporous alumina, preferably 2-10%.

[0054] According to some embodiments of the present invention, the first active source is a compound I containing a first active element, wherein the first active element is selected from at least one of alkali metal elements, alkaline earth metal elements, and phosphorus. Preferably, the first active element is selected from at least one of sodium, potassium, magnesium, calcium, barium, and phosphorus, more preferably at least two of magnesium, calcium, barium, and phosphorus, more preferably at least two of magnesium, barium, and phosphorus, further preferably magnesium and phosphorus, and even more preferably, the weight ratio of magnesium to phosphorus, calculated as oxides, is 1:0.8-1.

[0055] According to some embodiments of the present invention, preferably, compound I is selected from at least one of sulfate, nitrate, phosphate and carbonate.

[0056] According to some embodiments of the present invention, the second active source is a compound II containing a second active element, wherein the second active element is selected from Group VIB elements and / or Group VIII elements. Preferably, the second active element is selected from at least one of chromium, molybdenum, cobalt, nickel, and platinum, and more preferably at least one of chromium, molybdenum, and cobalt.

[0057] According to some embodiments of the present invention, preferably, compound II is selected from at least one of nitrate, chloroplatinic acid, molybdate and sulfate.

[0058] According to some embodiments of the present invention, preferably, the weight of the first active source, based on the oxide of the first active element, is 0.5-2.5% of the weight of the alumina support; more preferably, the weight of the first active source, based on the oxide of the first active element, is 0.8-2.3% of the weight of the alumina support.

[0059] According to some embodiments of the present invention, preferably, the weight of the second active source, based on the oxide of the second active element, is 3-15% of the weight of the alumina carrier; more preferably, the weight of the second active source, based on the oxide of the second active element, is 3.5-12% of the weight of the alumina carrier.

[0060] According to some embodiments of the present invention, in step (2), a first active source is loaded onto the alumina support, and subjected to a first drying and a first calcination to obtain a catalyst precursor. The present invention does not impose any particular limitation on the loading method, as long as the first active source can be loaded onto the alumina support. Preferably, the loading includes: providing a first impregnation solution containing the first active source, and then contacting the alumina support with the first impregnation solution for a first impregnation.

[0061] According to some embodiments of the present invention, preferably, the first impregnation is an equal-volume impregnation.

[0062] According to some embodiments of the present invention, preferably, the first immersion time is 6-24 hours, more preferably 8-18 hours.

[0063] According to some embodiments of the present invention, preferably, the conditions for the first drying include: a temperature of 90-150°C, preferably 100-130°C; and / or a time of 1-9 hours, preferably 2-8 hours.

[0064] According to some embodiments of the present invention, preferably, the conditions for the first calcination include: a temperature of 350-650°C, preferably 400-650°C; and / or a time of 2-8 hours, preferably 2-6 hours.

[0065] According to some embodiments of the present invention, in step (3), a second active source is loaded onto the catalyst precursor, followed by a second drying and a second calcination. The present invention does not impose any particular limitation on the loading method, as long as the second active source can be loaded onto the catalyst precursor. Preferably, the loading includes: providing a second impregnation solution containing the second active source, and then contacting the catalyst precursor with the second impregnation solution for a second impregnation.

[0066] According to some embodiments of the present invention, preferably, the second impregnation is an equal-volume impregnation.

[0067] According to some embodiments of the present invention, preferably, the second immersion time is 12-36 hours, more preferably 12-30 hours.

[0068] According to some embodiments of the present invention, preferably, the conditions for the second drying include: a temperature of 90-150°C, preferably 90-140°C; and / or a time of 2-5 hours, preferably 2-4 hours.

[0069] According to some embodiments of the present invention, preferably, the conditions for the second calcination include: a temperature of 400-600°C, preferably 450-550°C; and / or a time of 2-8 hours, preferably 2-6 hours.

[0070] According to some embodiments of the present invention, loading the first and second active sources onto the alumina support in the above-described specific loading sequence is beneficial to further optimize the pore structure, reduce the acidity of the alumina, improve the metal catalytic ability, thereby further improving the hydrogenation and dealkylation activity of the catalyst, increasing the benzene selectivity, and reducing the aromatic ring loss rate.

[0071] A third aspect of the present invention provides a hydrogenation dealkylation catalyst prepared by the preparation method described in the second aspect.

[0072] According to some embodiments of the present invention, the hydrogenation dealkylation catalyst is the same as or similar to the hydrogenation dealkylation catalyst described in the first aspect, and will not be described again here.

[0073] The fourth aspect of this invention provides the application of the hydrodealkylation catalyst described in the first or third aspect in the production of benzene from toluene via hydrodealkylation.

[0074] According to some embodiments of the present invention, when the hydrogenation dealkylation catalyst is applied to the toluene hydrogenation dealkylation reaction to produce benzene, those skilled in the art can reasonably select the specific process conditions for the hydrogenation dealkylation reaction and achieve considerable technical effects.

[0075] According to some embodiments of the present invention, preferably, the catalyst may further include a step of reducing the catalyst before use. The reduction is to at least partially convert the second active component into an element. More preferably, the reduction step includes: contacting the catalyst with hydrogen gas; more preferably, the contact temperature is 400-600°C, the time is 1-5 h, and the heating rate is 1-5°C / min.

[0076] According to some embodiments of the present invention, preferably, the conditions for the hydrogenation dealkylation reaction include: a temperature of 400-600°C, preferably 420-550°C; and / or a pressure of 0.1-5 MPa, preferably 0.5-3.5 MPa; and / or a toluene mass hourly space velocity of 1-10 h⁻¹. -1 Preferably 2.0-5.0h -1 .

[0077] Unless otherwise specified, all pressures mentioned in this invention are gauge pressures.

[0078] The present invention will be described in detail below through embodiments.

[0079] Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0080] In the following examples, the specific surface area and pore volume of the catalyst were determined using a low-temperature nitrogen adsorption method. Specifically, nitrogen adsorption / desorption characterization was performed using a Micromeritics ASAP 2420 automated adsorption system. The sample was degassed at 350℃ and 1.33 Pa for 4 hours, and then tested at -196℃ using nitrogen as the adsorbate. The specific surface area was calculated using the BET method, and the microporous and external specific surface areas were calculated using the t-plot method. The total pore volume was calculated based on the amount of N2 adsorbed at p / p0 = 0.99. The microporous and mesoporous pore volumes were calculated using the t-plot and BJH methods, respectively.

[0081] The strength of the catalyst was measured using a catalyst (solid) strength tester;

[0082] The formulas for calculating toluene conversion, benzene selectivity, aromatic ring loss rate, and benzene mass are as follows:

[0083]

[0084]

[0085]

[0086]

[0087] Furthermore, aromatic yield = 100% - aromatic ring loss rate

[0088] Stability evaluation: Catalyst stability refers to the ability of a catalyst to maintain its activity, selectivity, antitoxicity, thermal stability, and other properties and structures unchanged during a catalytic reaction. In this invention, catalyst stability refers to the time it takes for the toluene conversion rate to drop to 90% of the initial conversion rate during the reaction.

[0089] Examples 1-12 illustrate the hydrodealkylation catalyst and its preparation method provided by the present invention.

[0090] Example 1

[0091] a. Select macroporous alumina with an average pore size of 125 nm and a macropore volume of 1.1 mL / g, and microporous alumina with an average pore size of 5.5 nm and a micropore volume of 0.35 mL / g. With a weight ratio of macroporous alumina to microporous alumina of 30:70, and the mass of the binder methylcellulose being 5.0% of the total dry weight of macroporous alumina and microporous alumina, knead and extrude the macroporous alumina, microporous alumina, and methylcellulose to form an alumina carrier.

[0092] b. Prepare a mixed solution of magnesium sulfate and diammonium hydrogen phosphate, wherein the weight of magnesium sulfate, calculated as MgO, is 1.0% of the weight of the alumina support; and the weight of diammonium hydrogen phosphate, calculated as P2O5, is 0.8% of the weight of the alumina support. Impregnate the alumina support in the mixed solution of magnesium sulfate and diammonium hydrogen phosphate for 12 hours by equal volume impregnation, dry at 130°C for 6 hours, and calcine at 650°C for 6 hours to obtain the catalyst precursor.

[0093] c. Prepare a chromium nitrate solution, wherein the weight of chromium nitrate, calculated as Cr2O3, is 6.0% of the weight of the alumina support. The catalyst precursor is impregnated in the chromium nitrate solution for 12 hours using an equal-volume impregnation method, dried at 90℃ for 4 hours, and calcined at 500℃ for 6 hours to obtain the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0094] Example 2

[0095] a. Select macroporous alumina with an average pore size of 200 nm and a macropore volume of 1.5 mL / g, and microporous alumina with an average pore size of 3.5 nm and a micropore volume of 0.5 mL / g. Using a weight ratio of macroporous alumina to microporous alumina of 40:60, and with the binder methyl cellulose at 5.0% of the total dry weight of the macroporous and microporous alumina, knead and extrude the macroporous alumina, microporous alumina, and methyl cellulose to form an alumina carrier.

[0096] b. Prepare a mixed solution of magnesium sulfate and diammonium hydrogen phosphate, wherein the weight of magnesium sulfate, calculated as MgO, is 1.0% of the weight of the alumina support; and the weight of diammonium hydrogen phosphate, calculated as P2O5, is 0.8% of the weight of the alumina support. Impregnate the alumina support in the mixed solution of magnesium sulfate and diammonium hydrogen phosphate for 12 hours by equal volume impregnation, dry at 130°C for 6 hours, and calcine at 650°C for 6 hours to obtain the catalyst precursor.

[0097] c. Prepare a chromium nitrate solution, wherein the weight of chromium nitrate, calculated as Cr2O3, is 6.0% of the weight of the alumina support. The catalyst precursor is impregnated in the chromium nitrate solution for 12 hours using an equal-volume impregnation method, dried at 90℃ for 4 hours, and calcined at 500℃ for 6 hours to obtain the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0098] Example 3

[0099] a. Select macroporous alumina with an average pore size of 125 nm and a macropore volume of 1.1 mL / g, and microporous alumina with an average pore size of 5.5 nm and a micropore volume of 0.35 mL / g. With a weight ratio of macroporous alumina to microporous alumina of 30:70, and the mass of nitric acid as the binder being 5.0% of the total dry weight of macroporous alumina and microporous alumina, knead and extrude the macroporous alumina, microporous alumina, and nitric acid into a strip to form an alumina carrier.

[0100] b. Prepare a magnesium sulfate solution, wherein the weight of magnesium sulfate, calculated as MgO, is 1.8% of the weight of the alumina support. Impregnate the alumina support in the magnesium sulfate solution for 12 hours by equal volume impregnation, dry at 130°C for 6 hours, and calcine at 650°C for 6 hours to obtain the catalyst precursor.

[0101] c. Prepare a cobalt nitrate solution, wherein the weight of cobalt nitrate (calculated as CoO) is 6.0% of the weight of the alumina support. The catalyst precursor is impregnated in the cobalt nitrate solution for 12 hours by equal-volume impregnation, dried at 90°C for 4 hours, and calcined at 500°C for 6 hours to obtain the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0102] Example 4

[0103] a. Select macroporous alumina with an average pore size of 125 nm and a macropore volume of 1.1 mL / g, and microporous alumina with an average pore size of 5.5 nm and a micropore volume of 0.35 mL / g. With a weight ratio of macroporous alumina to microporous alumina of 30:70, and the mass of the binder methylcellulose being 5.0% of the total dry weight of macroporous alumina and microporous alumina, knead and extrude the macroporous alumina, microporous alumina, and methylcellulose to form an alumina carrier.

[0104] b. Prepare a mixed solution of magnesium sulfate and barium nitrate, wherein the weight of magnesium sulfate, calculated as MgO, is 1.2% of the weight of the alumina support; and the weight of barium nitrate, calculated as BaO, is 1.2% of the weight of the alumina support. Impregnate the alumina support in the mixed solution of magnesium sulfate and barium nitrate for 6 hours by equal volume impregnation, dry at 110°C for 9 hours, and calcine at 600°C for 6 hours to obtain the catalyst precursor.

[0105] c. Prepare a nickel nitrate solution, wherein the weight of nickel nitrate, calculated as NiO, is 6.0% of the weight of the alumina support. The catalyst precursor is impregnated in the nickel nitrate solution for 12 hours using an equal-volume impregnation method, dried at 90°C for 4 hours, and calcined at 500°C for 6 hours to obtain the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0106] Example 5

[0107] a. Select macroporous alumina with an average pore size of 200 nm and a macropore volume of 1.5 mL / g, and microporous alumina with an average pore size of 3.5 nm and a micropore volume of 0.5 mL / g. Using a weight ratio of macroporous alumina to microporous alumina of 40:60, and with the binder methyl cellulose at 5.0% of the total dry weight of the macroporous and microporous alumina, knead and extrude the macroporous alumina, microporous alumina, and methyl cellulose to form an alumina carrier.

[0108] b. Prepare a mixed solution of magnesium sulfate and barium nitrate, wherein the weight of magnesium sulfate, calculated as MgO, is 1.2% of the weight of the alumina support; and the weight of barium nitrate, calculated as BaO, is 1.2% of the weight of the alumina support. The alumina support is impregnated in the mixed solution of magnesium sulfate and barium nitrate for 6 hours by equal-volume impregnation, dried at 110℃ for 9 hours, and calcined at 600℃ for 6 hours to obtain the catalyst precursor.

[0109] c. Prepare a chromium nitrate solution, wherein the weight of chromium nitrate, calculated as Cr2O3, is 6.0% of the weight of the alumina support. The catalyst precursor is impregnated in the chromium nitrate solution for 12 hours using an equal-volume impregnation method, dried at 90℃ for 4 hours, and calcined at 500℃ for 6 hours to obtain the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0110] Example 6

[0111] a. Select macroporous alumina with an average pore size of 200 nm and a macropore volume of 1.5 mL / g, and microporous alumina with an average pore size of 3.5 nm and a micropore volume of 0.5 mL / g. Using a weight ratio of macroporous alumina to microporous alumina of 40:60, and with the binder methyl cellulose at 2.5% of the total dry weight of the macroporous and microporous alumina, knead and extrude the macroporous alumina, microporous alumina, and methyl cellulose to form an alumina carrier.

[0112] b. Prepare a mixed solution of magnesium sulfate and barium nitrate, wherein the weight of magnesium sulfate, calculated as MgO, is 1.2% of the weight of the alumina support; and the weight of barium nitrate, calculated as BaO, is 1.2% of the weight of the alumina support. Impregnate the alumina support in the mixed solution of magnesium sulfate and barium nitrate for 6 hours by equal volume impregnation, dry at 110°C for 9 hours, and calcine at 600°C for 6 hours to obtain the catalyst precursor.

[0113] c. Prepare a mixed solution of chromium nitrate and chloroplatinic acid, wherein the weight of chromium nitrate (based on Cr₂O₃) is 4.0% of the weight of the alumina support; and the weight of chloroplatinic acid (based on PtO₂) is 2.0% of the weight of the alumina support. The catalyst precursor is impregnated in the mixed solution of chromium nitrate and chloroplatinic acid for 12 hours by equal-volume impregnation, dried at 90°C for 4 hours, and calcined at 500°C for 6 hours to obtain the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0114] Example 7

[0115] a. Select macroporous alumina with an average pore size of 125 nm and a macropore volume of 1.1 mL / g, and microporous alumina with an average pore size of 5.5 nm and a micropore volume of 0.35 mL / g. With a weight ratio of macroporous alumina to microporous alumina of 30:70, and the mass of the binder methylcellulose being 5.0% of the total dry weight of macroporous alumina and microporous alumina, knead and extrude the macroporous alumina, microporous alumina, and methylcellulose to form an alumina carrier.

[0116] b. Prepare a calcium sulfate solution, wherein the weight of calcium sulfate, calculated as CaO, is 2.5% of the weight of the alumina support. Impregnate the alumina support in the calcium sulfate solution for 18 hours by equal volume impregnation, dry at 130°C for 8 hours, and calcine at 650°C for 6 hours to obtain the catalyst precursor.

[0117] c. Prepare an ammonium molybdate solution, wherein the weight of ammonium molybdate, calculated as MoO3, is 9.0% of the weight of the alumina support. The catalyst precursor is impregnated in the ammonium molybdate solution for 12 hours using an equal-volume impregnation method, dried at 125℃ for 4 hours, and calcined at 550℃ for 6 hours to obtain the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0118] Example 8

[0119] The method of Example 1 was followed, except that in step b, a mixed solution of magnesium sulfate and barium nitrate was prepared, wherein the weight of magnesium sulfate, calculated as MgO, was 1.0% of the weight of the alumina support; and the weight of barium nitrate, calculated as BaO, was 0.8% of the weight of the alumina support. All other parameters were the same as in Example 1, resulting in the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0120] Example 9

[0121] The method of Example 8 was followed, except that in step c, a mixed solution of chromium nitrate and chloroplatinic acid was prepared, wherein the weight of chromium nitrate, calculated as Cr2O3, was 5.0% of the weight of the alumina support; and the weight of chloroplatinic acid, calculated as PtO2, was 1.0% of the weight of the alumina support. All other parameters were the same as in Example 8, resulting in the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0122] Example 10

[0123] The method of Example 9 was followed, except that in step b, a magnesium sulfate solution was prepared, wherein the weight of magnesium sulfate, calculated as MgO, was 1.8% of the weight of the alumina support; and in step c, a chromium nitrate solution was prepared, wherein the weight of chromium nitrate, calculated as Cr2O3, was 6.0% of the weight of the alumina support. All other steps were the same as in Example 9, resulting in the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0124] Example 11

[0125] The method of Example 10 was followed, except that in step c, a chloroplatinic acid solution was prepared, wherein the weight of chloroplatinic acid, calculated as PtO2, was 6.0% of the weight of the alumina support. All other parameters were the same as in Example 10, resulting in the finished catalyst. The physicochemical properties of the finished catalyst, including pore volume, specific surface area, average pore diameter, and strength, are shown in Table 1.

[0126] Example 12

[0127] The method of Example 1 was followed, except that in step a, the weight ratio of macroporous alumina to microporous alumina was 50:50, while all other aspects were the same as in Example 1, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as pore volume, specific surface area, average pore diameter, and strength, are shown in Table 1.

[0128] Comparative Example 1

[0129] Following the method of Example 1, except that no small-pore alumina was added in step a, the rest were the same as in Example 1, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as pore volume, specific surface area, average pore diameter, and strength, are shown in Table 1.

[0130] Comparative Example 2

[0131] Following the method of Example 1, except that step b was omitted, all other steps were the same as in Example 1, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as pore volume, specific surface area, average pore diameter, and strength, are shown in Table 1.

[0132] Comparative Example 3

[0133] Following the method of Example 1, except that step c was omitted, all other steps were the same as in Example 1, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as pore volume, specific surface area, average pore diameter, and strength, are shown in Table 1.

[0134] Comparative Example 4

[0135] The method of Example 1 is followed, except that after step a, step c is performed first, in which the alumina support is impregnated in a chromium nitrate solution by equal-volume impregnation to obtain the catalyst precursor. Then, step b is performed, in which the catalyst precursor is impregnated in a mixed solution of magnesium sulfate and diammonium hydrogen phosphate by equal-volume impregnation. The rest is the same as in Example 1, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as pore volume, specific surface area, average pore size, and strength, are shown in Table 1.

[0136] Table 1

[0137] Catalyst Pore volume, mL / g Specific surface area, m 3 / g]] Average pore diameter, nm Strength, N / cm Example 1 0.934 197 7.9 92 Example 2 0.866 165 7.5 80 Example 3 0.854 183 7.2 84 Example 4 0.765 156 7.4 69 Example 5 0.890 142 6.5 98 Example 6 0.651 171 7.1 64 Example 7 0.718 155 6.8 81 Example 8 0.743 156 6.8 79 Example 9 0.735 161 7.3 69 Example 10 0.781 147 7.2 81 Example 11 0.691 156 6.8 80 Example 12 0.702 162 6.6 68 Comparative Example 1 0.654 151 7.2 60 Comparative Example 2 0.763 165 6.4 69 Comparative Example 3 0.656 162 6.6 72 Comparative Example 4 0.681 162 6.6 74

[0138] Test Examples 1-12 were used to evaluate the catalytic performance of the hydrodealkylation catalyst provided by the present invention in the toluene hydrodealkylation reaction to benzene.

[0139] Take 5.0 g of the finished catalyst prepared in Examples 1-12 respectively, and load it into a micro adiabatic fixed-bed reactor with an inner diameter of 1.5 cm. The reaction bed is filled with glass beads both above and below, and then hydrogen gas is introduced to ensure uniform flow through the catalyst bed. After a 120-minute programmed temperature increase to 600°C and held at that temperature for 2 hours, pure toluene feedstock is introduced using a metering pump, maintaining a mass hourly space velocity (MSV) of 1.0 h⁻¹ for the organic reactants. -1 The reaction pressure was 3.0 MPa. By metering and analyzing the oil and aqueous phases in the catalytic reaction effluent and the reaction tail gas using gas chromatography, the toluene conversion rate, benzene selectivity, aromatic ring loss rate, benzene mass, and stability of the reaction were finally calculated. Specific results are shown in Table 2.

[0140] Comparative test cases 1-4

[0141] Following the method of the test examples, the only difference was that the finished catalysts prepared in Comparative Examples 1-4 were used for catalytic performance evaluation, while the rest were the same as in the test examples. By metering and analyzing the oil and water phases in the catalytic reaction effluent and the reaction tail gas using gas chromatography, the toluene conversion rate, benzene selectivity, aromatic ring loss rate, benzene mass, and stability of the reaction were finally calculated. Specific results are shown in Table 2.

[0142] Table 2

[0143]

[0144]

[0145] The results above show that the hydrogenation dealkylation catalyst provided by this invention has a high toluene conversion rate and high benzene selectivity in the toluene hydrogenation dealkylation reaction, with a benzene mass of up to 99.9%. Furthermore, the aromatic ring loss rate of toluene as a raw material is low, and the aromatic hydrocarbon yield can reach more than 99.25%, with a maximum of 99.89%. In addition, the catalyst has good stability.

[0146] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A hydrodealkylation catalyst characterized in that, The catalyst comprises an alumina carrier and a first active component and a second active component supported on the alumina carrier; wherein the alumina carrier comprises large-pore alumina and small-pore alumina; the first active component is magnesium and phosphorus; and the second active component is selected from at least one of Group VI B metal and / or Group VIII metal; In the first active component, the weight ratio of magnesium to phosphorus, in terms of oxides, is 1:(0.8-1); The average pore diameter of the large-pore alumina is 110-180 nm; The average pore diameter of the small-pore alumina is 4-9 nm; The preparation method of the hydrodealkylation catalyst comprises: (1) mixing and molding the large-pore alumina and the small-pore alumina to obtain an alumina carrier; (2) supporting a first active source on the alumina carrier, and performing first drying and first calcination to obtain a catalyst precursor; (3) supporting a second active source on the catalyst precursor, and then performing second drying and second calcination.

2. The catalyst of claim 1, wherein, The pore volume of the large-pore alumina is 0.6-1.5 mL / g; And / or, the pore volume of the small-pore alumina is 0.2-0.6 mL / g; And / or, the alumina carrier further comprises a binder; the binder is selected from at least one of methyl cellulose, polyacrylamide, sesbania powder and nitric acid; And / or, the content of the binder, in terms of dry weight, is 1-15% of the total weight of the large-pore alumina and the small-pore alumina.

3. The catalyst of claim 2, wherein, The pore volume of the large-pore alumina is 0.8-1.2 mL / g; And / or, the pore volume of the small-pore alumina is 0.25-0.45 mL / g; And / or, the binder is selected from methyl cellulose and / or nitric acid; And / or, the content of the binder, in terms of dry weight, is 2-10% of the total weight of the large-pore alumina and the small-pore alumina.

4. The catalyst of claim 1, wherein, The second active component is selected from at least one of chromium, molybdenum, cobalt, nickel and platinum.

5. The catalyst of claim 4, wherein, The second active component is selected from at least one of chromium, molybdenum and cobalt.

6. The catalyst of claim 1, wherein, The weight ratio of the large-pore alumina to the small-pore alumina, in terms of dry weight, is (0.3-3):1; And / or, the weight of the first active component, in terms of oxides, is 0.5-2.5% of the weight of the alumina carrier; And / or, the weight of the second active component, in terms of oxides, is 3-15% of the weight of the alumina carrier.

7. The catalyst of claim 6, wherein, The weight ratio of the large-pore alumina to the small-pore alumina, in terms of dry weight, is (0.4-1):1; And / or, the weight of the first active component, in terms of oxides, is 0.8-2.3% of the weight of the alumina carrier; And / or, the weight of the second active component, in terms of oxides, is 3.5-12% of the weight of the alumina carrier.

8. The catalyst of claim 7, wherein, The weight ratio of the large-pore alumina to the small-pore alumina, in terms of dry weight, is (0.4-0.8):

1.

9. The catalyst of claim 1, wherein, The catalyst has a pore volume of 0.2-1.2 cm 3 / g; and / or, a specific surface area of 80-210 m 3 / g; and / or, an average pore diameter of 5-10 nm; and / or, a strength of 40-150 N / cm.

10. The catalyst of claim 9, wherein, The pore volume of the catalyst is 0.4-1 cm 3 / g; and / or, the specific surface area is 130-200 m 3 / g; and / or, the average pore diameter is 6-9 nm; and / or, the strength is 60-120 N / cm.

11. A process for preparing a hydrodealkylation catalyst, characterized by, The preparation method comprises: (1) mixing and molding the large-pore alumina and the small-pore alumina to obtain an alumina carrier; (2) supporting a first active source on the alumina carrier, and performing first drying and first calcination to obtain a catalyst precursor; (3) supporting a second active source on the catalyst precursor, and then performing second drying and second calcination. (3) loading a second active source on the catalyst precursor, followed by a second drying and a second calcination; wherein the first active source is compound I containing a first active element, the first active element being magnesium and phosphorus; the second active source is compound II containing a second active element, the second active element being selected from the group consisting of Group VI B elements and / or Group VIII elements; in the compound I, the weight ratio of magnesium to phosphorus, in terms of oxides, is 1:(0.8-1); the average pore size of the large-pore alumina is 110-180 nm; the average pore size of the small-pore alumina is 4-9 nm.

12. The method of making according to claim 11, wherein, the large-pore volume is 0.6-1.5 mL / g; and / or, the small-pore volume is 0.2-0.6 mL / g; and / or, the weight ratio of the large-pore alumina to the small-pore alumina is (0.3-3):1; and / or, in step (1), the mixed raw materials further contain a binder; and / or, the amount of the binder, in terms of dry weight, is 1-15% of the total weight of the large-pore alumina and the small-pore alumina.

13. The method of making according to claim 12, wherein, the large-pore volume is 0.8-1.2 mL / g; and / or, the small-pore volume is 0.25-0.45 mL / g; and / or, the weight ratio of the large-pore alumina to the small-pore alumina is (0.4-1):1; and / or, in step (1), the binder is selected from at least one of methyl cellulose, polyacrylamide, sesbania powder and nitric acid; and / or, the amount of the binder, in terms of dry weight, is 2-10% of the total weight of the large-pore alumina and the small-pore alumina.

14. The production method according to claim 13, wherein the weight ratio of the large-pore alumina to the small-pore alumina is (0.4-0.8):1; and / or, in step (1), the binder is methyl cellulose and / or nitric acid.

15. The method of making according to claim 11, wherein, the second active element is selected from at least one of chromium, molybdenum, cobalt, nickel and platinum; and / or, the compound I is selected from at least one of sulfate, nitrate, phosphate and carbonate; and / or, the compound II is selected from at least one of nitrate, chloroplatinic acid, molybdate and sulfate; and / or, the weight of the first active source, in terms of oxide of the first active element, is 0.5-2.5% of the weight of the alumina carrier; and / or, the weight of the second active source, in terms of oxide of the second active element, is 3-15% of the weight of the alumina carrier.

16. The method of manufacturing according to claim 15, wherein, the second active element is selected from at least one of chromium, molybdenum and cobalt; and / or, the weight of the first active source, in terms of oxide of the first active element, is 0.8-2.3% of the weight of the alumina carrier; and / or, the weight of the second active source, in terms of oxide of the second active element, is 3.5-12% of the weight of the alumina carrier.

17. The method of making according to claim 11, wherein, in step (2), the loading comprises: providing a first impregnation solution containing a first active source, and then contacting the alumina carrier with the first impregnation solution for first impregnation; and / or, the first impregnation is isovolumetric impregnation; and / or, the time of the first impregnation is 6-24 h; and / or, the conditions of the first drying comprise: the temperature is 90-150°C; and / or, the time is 1-9 h; And / or, the first calcination comprises: temperature of 350-650 ℃; and / or, time of 2-8 h.

18. The method of making according to claim 17, wherein, In step (2), the first impregnation comprises: providing a first impregnation solution containing a first active source, and then contacting the catalyst precursor with the first impregnation solution for a first impregnation time; and / or, the first impregnation is an equal-volume impregnation; and / or, the first impregnation time is 8-18 h. And / or, the first drying comprises: temperature of 100-130 ℃; and / or, time of 2-8 h. And / or, the first calcination comprises: temperature of 400-650 ℃; and / or, time of 2-6 h.

19. The method of making according to claim 11, wherein, In step (3), the loading comprises: providing a second impregnation solution containing a second active source, and then contacting the catalyst precursor with the second impregnation solution for a second impregnation; and / or, the second impregnation is an equal-volume impregnation; and / or, the second impregnation time is 12-36 h. And / or, the second drying comprises: temperature of 90-150 ℃; and / or, time of 2-5 h. And / or, the second calcination comprises: temperature of 400-600 ℃; and / or, time of 2-8 h.

20. The method of making according to claim 19, wherein, In step (3), the second impregnation time is 12-30 h. And / or, the second drying comprises: temperature of 90-140 ℃; and / or, time of 2-4 h. And / or, the second calcination comprises: temperature of 450-550 ℃; and / or, time of 2-6 h.

21. Use of the hydrodealkylation catalyst according to any one of claims 1-10 in a toluene hydrodealkylation reaction to produce benzene.

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