Hydrodealkylation catalyst, method for preparing the same, and hydrodealkylation method

Abstract

The present application relates to the field of hydrodealkylation, discloses a kind of hydrodealkylation catalyst and preparation method and hydrodealkylation method.The hydrodealkylation catalyst includes silicon-containing carrier and first active component and second active component supported on the silicon-containing carrier;Wherein, the first active component is chromium element;The second active component is selected from at least one of group VIB metal, group VIIB metal and group VIII metal;The first active component and second active component metal are different;Wherein, the ratio of the weak acid amount and the strong acid amount of the hydrodealkylation catalyst is 1:0.1-0.5.The hydrodealkylation catalyst proposed in the present application is applied to hydrodealkylation method, using alkylbenzene as raw material, converts alkylbenzene into benzene, the conversion rate of alkylbenzene is high, the benzene selectivity is high, and the aromatic ring loss rate of alkylbenzene as raw material is low, and the aromatic hydrocarbon yield can reach more than 99.92%, and the stability of catalyst is good.

Description

Technical Field

[0001] This invention relates to the field of hydrodealkylation, specifically to a hydrodealkylation catalyst, its preparation method, and a hydrodealkylation method. Background Technology

[0002] Benzene is a crucial basic organic raw material with a large consumption volume and a rich industrial chain, but its production bases are scattered. Downstream products mainly include ethylbenzene (41.0%), phenol (16%), caprolactam (16%), and cyclohexane (12%). Furthermore, in recent years, increasingly stringent environmental regulations in various regions have led to rising transportation difficulties and costs for benzene, exacerbating localized benzene resource shortages. This market environment has made efficient benzene production technologies increasingly favored by enterprises. On the one hand, these technologies can meet the market demand for benzene; on the other hand, they can provide new conversion technologies for extruding low-quality aromatics from petroleum products.

[0003] Currently, the main chemical processes for directly producing benzene include catalytic reforming, ethylene cracking, and coal-fired coking. Among these, catalytic reforming and ethylene cracking processes generate many other alkylbenzenes in addition to benzene, resulting in limited benzene production. The coal chemical industry has high carbon emissions, and future benzene production from the coking industry may be reduced. Furthermore, toluene disproportionation technology is currently the most widely used technology for increasing benzene production; however, theoretically, toluene disproportionation can only increase the production of benzene by 1 mol from 2 mol of toluene, and 1 mol from xylene. Raw material constraints prevent maximizing benzene production efficiency. Existing heavy aromatic hydrocarbon lightening technologies only target C2 hydrocarbons. + While side-chain removal is highly efficient, it cannot achieve efficient removal of methyl groups, resulting in xylene as the main product and extremely limited benzene production. Therefore, there is an urgent need to find other efficient benzene production technologies.

[0004] Aromatic dealkylation to benzene technology utilizes side-chain dealkylation to effectively remove alkyl groups, including methyl groups and above, efficiently converting aromatics into benzene. Theoretically, 1 mol of aromatics can produce 1 mol of benzene, making it the most efficient benzene production technology currently available. Aromatic dealkylation includes hydrodealkylation, non-hydrochemical dealkylation, and steam reforming dealkylation; currently, hydrodealkylation is the most industrially applied. Among these, catalytic hydrodealkylation, due to the presence of a catalyst, exhibits a lower activation energy, resulting in a faster reaction rate than thermal cracking hydrodealkylation at the same reaction temperature. Under the same conversion conditions, catalytic hydrodealkylation offers advantages such as lower reaction temperature and higher benzene selectivity. Both thermal cracking hydrodealkylation and catalytic hydrodealkylation have their own characteristics. Catalytic hydrodealkylation operates at a lower reaction temperature and primarily involves the dealkylation of alkyl aromatics and the hydrocracking of non-aromatics. It exhibits high inhibition rates for saturated hydrogenation and cracking reactions of the aromatic ring, resulting in relatively low hydrogen consumption and benzene selectivity exceeding the theoretical value of 98%. Thermal cracking hydrodealkylation technology involves high reaction temperatures and a free radical mechanism. On the one hand, the high reaction temperature leads to an increase in side reactions such as cracking and polymerization. On the other hand, the free radical reaction process easily generates biphenyl, resulting in a benzene selectivity that is about 3% lower than that of catalytic hydrodealkylation technology. Hydrogen consumption is also relatively high. However, this technology does not require the use of a catalyst, making the reaction process relatively simple. Non-aromatic hydrocarbons in the feedstock can reach 30%.

[0005] Research on aromatic hydrocarbon catalytic hydrogenation dealkylation to benzene technology, flexibly utilizing C7... + Using aromatics as feedstock and a hydrogenated fixed-bed reactor, this technology efficiently removes alkyl groups, including methyl groups, from the aromatic ring side chains via hydrogenation-dealkylation, converting alkylbenzenes into benzene. The aim is to develop a novel benzene production technology with abundant feedstock sources, high benzene production efficiency, and low equipment investment to meet the demand for increased benzene production. Therefore, developing high-conversion, high-stability hydrogenation-dealkylation catalysts for benzene production has broad market demand and promising application prospects.

[0006] CN1227193C discloses a catalyst for the lightening of heavy aromatics, comprising 0.01-2 wt% of a Group VIII metal and a composite support, wherein the composite support comprises 30-70 wt% ZSM-5 zeolite, 5-30 wt% β-zeolite, and 10-65 wt% alumina. This catalyst is used for the lightening of heavy aromatics and can improve the C9 ester content. + Improve the conversion rate of aromatics and the yield of benzene and xylene, and reduce carbon buildup.

[0007] CN1050777 C discloses a method for preparing C by treating Al2O3 with rare earth elements. 9-10A novel Cr₂O₃-RE / Al₂O₃ catalyst for the catalytic dealkylation of alkyl aromatics to xylene, toluene, and benzene exhibits stable structure and a selectivity greater than 95% (conversion rate 58%) for these three compounds. The catalyst is constructed by supporting rare earth La₂O₃ on the surface of γ-Al₂O₃, followed by high-temperature treatment to adjust the acidity of γ-Al₂O₃ and simultaneously promote the uniform distribution of Cr₂O₃ crystals on the γ-Al₂O₃ surface. This catalyst can also be used in the process of catalytic dealkylation of toluene to benzene.

[0008] CN101444745 A discloses a method for preparing a heavy aromatic hydrocarbon vapor dealkylation catalyst. The method involves impregnating a silica-alumina molecular sieve with a rare earth metal or alkaline earth metal nitrate solution, followed by water bath ion exchange, repeated rinsing until neutral, drying, and calcination. This catalyst is suitable for vapor dealkylation reactions, has low preparation cost, good stability, long lifespan, and is easy to regenerate. It can produce high-purity thallium methylbenzene with high conversion rates and purity exceeding 90% in dealkylation reactions.

[0009] CN111068769A discloses a catalyst for the catalytic hydrogenation and demethylation of xylenol, its preparation method, and its application. The catalyst comprises a composite support and an acidic active component. The composite support is a complex of modified HY molecular sieve and Al-MCM-41 molecular sieve, wherein the modified HY molecular sieve is coated with Al-MCM-41 molecular sieve, forming a HY / MCM-41 coated composite molecular sieve. The modified HY molecular sieve is a HY molecular sieve loaded with an acidic active component, namely SO4. 2 / TiO2; wherein, the mass of the modified HY molecular sieve is 20-80% of the mass of the composite support; SO4 2 The TiO2 mass is 3-8% of the HY molecular sieve mass. Its catalyst possesses suitable acidity and a micro / mesoporous structure, exhibiting high 3,4-xylenol conversion, phenol and cresol selectivity, and good stability.

[0010] As summarized above, although the preparation methods of aromatic catalytic dealkylation molecular sieves are relatively mature, almost no catalyst can solve the problem of low benzene selectivity and poor activity in aromatic hydrodealkylation catalysts. Furthermore, the additives and metals used in the molecular sieve synthesis process are expensive, resulting in high production costs. Therefore, the development of highly selective and stable hydrodealkylation catalysts for benzene production has broad market demand and promising application prospects. Summary of the Invention

[0011] The purpose of this invention is to overcome the problems of poor hydrodealkylation activity and poor benzene selectivity of existing hydrodealkylation catalysts, and to provide a hydrodealkylation catalyst, its preparation method and hydrodealkylation method. This hydrodealkylation catalyst has high hydrodealkylation activity and benzene selectivity, and low aromatic ring loss rate.

[0012] To achieve the above objectives, the present invention provides a hydrodealkylation catalyst, the catalyst comprising a silicon-containing support and a first active component and a second active component supported on the silicon-containing support;

[0013] The first active component is chromium; the second active component is selected from at least one of Group VIB, Group VIIB and Group VIII metals; the first active component and the second active component are of different metal types.

[0014] The ratio of the amount of weak acid to the amount of strong acid in the hydrogenation dealkylation catalyst is 1:0.1-0.5.

[0015] Preferably, the hydrogenation dealkylation catalyst, as measured by pyridine infrared spectroscopy, has an L acid content of 0.5-0.7 μmol / g at 150°C, 0.3-0.5 μmol / g at 250°C, and 0.1-0.3 μmol / g at 350°C.

[0016] A second aspect of this invention provides a method for preparing a hydrogenation dealkylation catalyst, comprising the following steps:

[0017] (1) The silicon-containing support is impregnated with a solution of a soluble compound containing the first active component, and then dried and calcined to obtain a catalyst intermediate;

[0018] (2) The catalyst intermediate is impregnated with an equal volume of a solution of a soluble compound containing the second active component, and then dried and calcined to obtain a hydrogenation dealkylation catalyst;

[0019] Wherein, the first active component is chromium; the second active component is selected from at least one of Group VIB metals, Group VIIB metals and Group VIII metals; the first active component and the second active component are of different metal types.

[0020] A third aspect of the present invention provides a hydrogenation dealkylation catalyst prepared by the above-described preparation method.

[0021] A fourth aspect of the present invention provides a method for hydrogenation dealkylation, the method comprising: contacting alkylbenzene, hydrogen gas and a catalyst under hydrogenation dealkylation reaction conditions;

[0022] The catalyst is the hydrogenation dealkylation catalyst provided in the first or third aspect above.

[0023] The hydrodealkylation catalyst provided by this invention, with the combination of a silicon-containing support, a first active component, and a second active component, exhibits high hydrodealkylation activity, low aromatic ring loss rate, and can improve the selectivity of benzene in the hydrodealkylation reaction of alkylbenzenes.

[0024] The method for preparing the hydrogenation dealkylation catalyst provided by the present invention involves loading the first and second active components onto a support sequentially through a specific impregnation method. This method is beneficial for optimizing the acidity of the catalyst, thereby further improving the hydrogenation dealkylation activity and benzene selectivity of the catalyst, and reducing the aromatic ring loss rate.

[0025] The hydrogenation dealkylation method provided by this invention uses alkylbenzene as raw material and utilizes the hydrogenation dealkylation reaction of aromatic ring side chains to effectively remove alkyl side chains including methyl and above, converting alkylbenzene into benzene. The alkylbenzene conversion rate is high, the benzene selectivity is high, and the aromatic ring loss rate of the alkylbenzene as raw material is low. The aromatic hydrocarbon yield can reach up to 99.92% or more, and the catalyst has good stability. Attached Figure Description

[0026] Figure 1 These are the NH3-TPD curves of the catalysts prepared in Example 1 and Comparative Example 1.

[0027] Figure 2 These are the infrared spectra of the pyridine catalysts prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0028] 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.

[0029] In this invention, "alkylbenzene" refers to a product in which at least one hydrogen atom on the benzene ring is replaced by a methyl group or more alkyl groups. The alkylbenzene described in this invention can be a mixture.

[0030] In one aspect, the present invention provides a hydrodealkylation catalyst, the catalyst comprising a silicon-containing support and a first active component and a second active component supported on the silicon-containing support;

[0031] The first active component is chromium; the second active component is selected from at least one of Group VIB, Group VIIB and Group VIII metals; the first active component and the second active component are of different metal types.

[0032] The ratio of the amount of weak acid to the amount of strong acid in the hydrogenation dealkylation catalyst is 1:0.1-0.5.

[0033] In this invention, by further adjusting the acidity of the catalyst through the combined action of the silicon-containing support, the first active component, and the second active component, the hydrogenation dealkylation activity of the catalyst can be significantly improved, and the selectivity of benzene in the hydrogenation dealkylation reaction of alkylbenzene can be increased, with a low aromatic ring loss rate.

[0034] According to the present invention, preferably, the ratio of the amount of weak acid to the amount of strong acid in the hydrodealkylation catalyst is 1:0.2-0.5. This preferred embodiment is more conducive to further improving the dealkylation performance of the catalyst.

[0035] In this invention, the acidity of the catalyst is measured by NH3-TPD. The measurement method is as follows: 100 mg of 40-60 mesh catalyst is placed in a reaction tube, He is used as the carrier gas, and the flow rate is 40 mL / min. -1 Pre-treatment at 550℃ for 3 hours, followed by cooling and full adsorption of NH3 at 120℃, then purging of residual NH3 at a rate of 10℃·min -1 The temperature was increased to 550℃, and the desorption curve was recorded using a TCD detector. The acidity of the catalyst was quantitatively calculated by software, with signal peaks above 350℃ considered strong acids and signal peaks between 120-170℃ considered weak acids.

[0036] According to the present invention, preferably, the hydrogenation dealkylation catalyst, as measured by pyridine infrared spectroscopy, has an L acid content of 0.5-0.7 μmol / g at 150°C, an L acid content of 0.3-0.5 μmol / g at 250°C, and an L acid content of 0.1-0.3 μmol / g at 350°C.

[0037] More preferably, the hydrogenation dealkylation catalyst, as determined by pyridine infrared spectroscopy, has an L acid content of 0.52-0.69 μmol / g at 150°C, preferably 0.53-0.59 μmol / g; an L acid content of 0.31-0.45 μmol / g at 250°C, preferably 0.32-0.4 μmol / g; and an L acid content of 0.12-0.28 μmol / g at 350°C, preferably 0.15-0.2 μmol / g.

[0038] In this invention, when the L acid content of the hydrogenation dealkylation catalyst meets the above-mentioned range, it is beneficial to adjust the acidity of the catalyst, improve the hydrogenation dealkylation activity of the catalyst, and improve the selectivity of benzene in the hydrogenation dealkylation reaction of alkylbenzene, with a low aromatic ring loss rate.

[0039] In this invention, the L acid content of the catalyst is measured by pyridine infrared spectroscopy. The measurement method is as follows: approximately 10 mg of powder sample is pressed into a 15-20 mm circular disc and fixed in an infrared cell. The sample is placed in the in-situ cell and heated to 400°C for 1 hour at a heating rate of 1°C / min while simultaneously evacuating the vacuum. After cooling to room temperature, the sample is taken and first purified under vacuum (350°C, 1×10⁻⁶). -3 After 2 hours of exposure to Pa, the sample was cooled to room temperature, and the spectrum was scanned to obtain background data. Following pyridine adsorption at room temperature, vacuum desorption (1×10⁻⁶) was performed by programmed temperature increase to the determination temperature (fixed points of 150℃, 200℃, and 350℃). -3 (Pa) for half an hour, then cool to room temperature and record 1700-1400 cm. -1 Infrared spectra in the wavenumber region. The L-acid content of the catalyst was quantitatively calculated by software, with the wavenumber region being 1540 cm⁻¹. -1 Peak characterization of Brønsted acid, with 1450 cm⁻¹ -1 Peak characterization of L-acid.

[0040] The present invention allows for a wide range of choices for the second active component. Preferably, the Group VIB metal includes, but is not limited to, Mo and W. Preferably, the Group VIIB metal includes, but is not limited to, Mn, Tc, and Re. Preferably, the Group VIII metal includes, but is not limited to, Fe, Co, Ni, and noble metals.

[0041] According to the present invention, preferably, the second active component is selected from at least one of iridium, rhenium, iron and molybdenum.

[0042] More preferably, the second active component is iridium and / or rhenium.

[0043] Furthermore, the second active component is iridium. This preferred embodiment is more advantageous for improving the hydrodealkylation performance of the catalyst.

[0044] According to the present invention, preferably, the silicon-containing carrier comprises silicon oxide and optionally at least one of aluminum oxide, titanium oxide and amorphous aluminum silicate.

[0045] In this invention, the use of the above-mentioned composite support is beneficial for 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 for improving the hydrogenation and dealkylation activity of the catalyst, improving benzene selectivity, and reducing the aromatic ring loss rate.

[0046] In this invention, there is no particular limitation on the types of silicon oxide, aluminum oxide, titanium oxide and amorphous silicon aluminum used in the silicon-containing carrier, and they can be various types commonly used in the art.

[0047] According to the present invention, preferably, based on the total amount of silicon-containing carrier, the content of silicon oxide is 65% by weight or more, preferably 70-100% by weight, and more preferably 85-95% by weight.

[0048] According to the present invention, in a preferred embodiment, the silicon-containing carrier comprises silicon oxide-alumina, silicon oxide-titanium oxide, or silicon oxide-amorphous silicon-aluminum.

[0049] In this invention, based on the total amount of silicon-containing support, when the silicon oxide content meets the above range, it is beneficial to adjust the distribution of acidic sites on the support, provide conditions for loading the active components, and further improve the hydrogenation and dealkylation activity of the catalyst, improve benzene selectivity, and reduce the aromatic ring loss rate.

[0050] According to the present invention, preferably, based on the total amount of catalyst, the content of silicon-containing support is 50-95% by weight, the content of the first active component (calculated as oxide) is 2-40% by weight, and the content of the second active component (calculated as oxide) is 1-12% by weight.

[0051] More preferably, based on the total amount of catalyst, the content of the silicon-containing support is preferably 60-90% by weight, the content of the first active component (calculated as oxide) is 5-30% by weight, and the content of the second active component (calculated as oxide) is 2-10% by weight.

[0052] More preferably, based on the total amount of catalyst, the content of the silicon-containing support is preferably 75-85% by weight, the content of the first active component (calculated as oxide) is 10-20% by weight, and the content of the second active component (calculated as oxide) is 2-6% by weight. This preferred embodiment further adjusts the acidity of the catalyst, improves the hydrogenation dealkylation activity of the catalyst, and enhances the selectivity of benzene in the hydrogenation dealkylation reaction of alkylbenzenes, with a low aromatic ring loss rate.

[0053] According to the present invention, preferably, the catalyst has an average pore size of 2.5-12 nm, more preferably 4-10 nm.

[0054] According to the present invention, preferably, the total pore volume of the catalyst is 0.15-1.4 mL / g, more preferably 0.85-1.3 mL / g.

[0055] According to the present invention, preferably, the catalyst has a specific surface area of ​​90-290 m². 2 / g, preferably 135-225m 2 / g.

[0056] In this invention, the specific surface area, pore volume, and average pore size of the catalyst are determined using a low-temperature nitrogen adsorption method. Specifically, the nitrogen adsorption / desorption characterization is performed using a Micromeritics ASAP 2420 automated adsorption system. The sample is degassed at 350℃ and 1.33 Pa for 4 hours, and then tested at -196℃ using nitrogen as the adsorbate. The specific surface area is calculated using the BET method, and the total pore volume is calculated based on the amount of N2 adsorbed when p / p0 = 0.99.

[0057] A second aspect of this invention provides a method for preparing a hydrogenation dealkylation catalyst, comprising the following steps:

[0058] (1) The silicon-containing support is impregnated with a solution of a soluble compound containing the first active component, and then dried and calcined to obtain a catalyst intermediate;

[0059] (2) The catalyst intermediate is impregnated with an equal volume of a solution of a soluble compound containing the second active component, and then dried and calcined to obtain a hydrogenation dealkylation catalyst;

[0060] Wherein, the first active component is chromium; the second active component is selected from at least one of Group VIB metals, Group VIIB metals and Group VIII metals; the first active component and the second active component are of different metal types.

[0061] The method for preparing the hydrogenation dealkylation catalyst provided by the present invention, through a specific impregnation method, namely, the first active component is impregnated with an over-volume impregnation and the second active component is impregnated with an equal-volume impregnation, and the first and second active components are loaded onto the support in sequence, which is beneficial to further optimize the acidity of the catalyst, thereby further improving the hydrogenation dealkylation activity of the catalyst, improving the selectivity of benzene, and reducing the aromatic ring loss rate.

[0062] In this invention, the selection range of the second active component is the same as that of the second active component in the above-mentioned hydrogenation dealkylation catalyst, and will not be repeated hereafter.

[0063] In this invention, the support is selected from the same range as the support in the above-mentioned hydrodealkylation catalyst, and will not be described again here.

[0064] According to the present invention, when the silicon-containing carrier is a composite carrier, preferably, the preparation method of the silicon-containing carrier further includes: mixing the components of the silicon-containing carrier and obtaining the silicon-containing carrier after uniform mixing.

[0065] The mixing can be carried out using conventional methods in the art, as long as the components are mixed evenly. The present invention does not have any special limitations on this.

[0066] According to the present invention, preferably, the method for preparing the silicon-containing support further includes a molding step, which occurs before the silicon-containing support is dried. The molding method can be selected according to the needs of actual application, so that the catalyst has a certain strength and appearance. For example, the molding method can be extrusion molding.

[0067] According to a preferred embodiment of the present invention, the method for preparing the silicon-containing carrier includes: molding silicon oxide and optionally at least one of aluminum oxide, titanium oxide and amorphous aluminum silicate, followed by drying and calcination.

[0068] In this invention, the drying conditions in the preparation method of the silicon-containing carrier are not particularly limited, and conventional operating conditions in the art can be used. Preferably, the drying conditions include: a temperature of 40-120°C, more preferably 80-100°C; and a time of 2-8 hours, preferably 4-8 hours.

[0069] In this invention, the calcination conditions in the preparation method of the silicon-containing support are not particularly limited and can be performed under conventional operating conditions in the art. Preferably, the calcination conditions include calcination at 350-650°C for 0.5-24 hours, and more preferably calcination at 400-600°C for 5-8 hours.

[0070] In this invention, the range of soluble compounds for the first active component is relatively wide, and can be soluble salts of the first active component. Preferably, the soluble compound of the first active component is selected from at least one of chromium acetate, chromium nitrate, potassium chromate, sodium chromate and chromium chloride, and more preferably at least one of chromium acetate, chromium nitrate and potassium chromate.

[0071] According to the present invention, preferably, the concentration of the first active metal component chromium solution in the over-volume impregnation in step (1) is 0.1-0.6 mol / L, more preferably 0.25-0.5 mol / L.

[0072] According to the present invention, preferably, the volume ratio of the excess volume impregnation solution to the equal volume impregnation solution of the silicon-containing carrier is 1.5-6, more preferably 2-4.5.

[0073] This preferred embodiment is more conducive to ensuring sufficient contact between the active component and the silicon-containing support, thereby further improving the hydrogenation and dealkylation activity of the catalyst, increasing benzene selectivity, and reducing side reaction activity.

[0074] According to the present invention, preferably, the conditions for the over-volume impregnation in step (1) include: a temperature of 30-110°C, preferably 50-90°C; and a time of 30-150 min, preferably 50-100 min. This preferred embodiment facilitates a more uniform distribution of the first active metal component in the pores and outer surface of the support, while more effectively suppressing strong acids on the catalyst surface, thereby reducing the acidity of the catalyst surface and improving the selectivity of the catalyst in benzene production.

[0075] In this invention, there are no special limitations on the drying conditions described in step (1), and conventional operating conditions in the art can be used. Preferably, the drying conditions include: a temperature of 30-90°C, more preferably 50-80°C; and a time of 2-8 hours, more preferably 4-7 hours.

[0076] In this invention, preferably, the calcination conditions in step (1) include: a temperature of 400-650℃, preferably 450-550℃; and a time of 0.5-24h, preferably 2-12h.

[0077] In this invention, there is no particular limitation on the type of soluble compound of the second active component. It can be any soluble salt of the second active component commonly used in the art. Preferably, the soluble compound of the second active component is selected from at least one of nitrates, ammonium salts and metal halides.

[0078] According to the present invention, preferably, the conditions for the equal-volume impregnation in step (2) include: a temperature of 50-120°C, preferably 80-120°C; and a time of 30-150 min, preferably 80-130 min. This preferred embodiment is beneficial for improving the utilization rate and dispersion of the metal components and reducing production costs.

[0079] In this invention, there are no special limitations on the drying conditions described in step (2), and conventional operating conditions in the art can be used. Preferably, the drying conditions include: a temperature of 50-120°C, more preferably 90-105°C; and a time of 2-8 hours, more preferably 3-5 hours.

[0080] In this invention, preferably, the calcination conditions in step (2) include: a temperature of 500-750℃, preferably 550-700℃; and a time of 0.5-24h, preferably 4-10h.

[0081] According to the present invention, preferably, the calcination temperature in step (2) is higher than the calcination temperature in step (1), preferably 50-100°C higher. This preferred embodiment is more conducive to making the catalyst more stable at the operating temperature, increasing the interaction force between the active metal and the support, and avoiding the loss of active metal.

[0082] The present invention does not impose any particular restrictions on the specific operation methods of the over-volume impregnation and equal-volume impregnation, and can be chosen in accordance with conventional methods in the art.

[0083] According to the present invention, preferably, the amounts of the soluble compound of the first active component, the soluble compound of the second active component, and the silicon-containing support are such that, based on the total amount of the catalyst, the content of the silicon-containing support is 50-95% by weight, preferably 60-90% by weight, more preferably 75-85% by weight, the content of the first active component (calculated as oxide) is 2-40% by weight, preferably 5-30% by weight, more preferably 10-20% by weight, and the content of the second active component (calculated as oxide) is 1-12% by weight, preferably 2-10% by weight, more preferably 2-6% by weight.

[0084] A third aspect of the present invention provides a hydrogenation dealkylation catalyst prepared by the above-described preparation method.

[0085] A fourth aspect of the present invention provides a method for hydrogenation dealkylation, the method comprising: contacting alkylbenzene, hydrogen gas and a catalyst under hydrogenation dealkylation reaction conditions;

[0086] The catalyst is the hydrogenation dealkylation catalyst provided in the first or third aspect above.

[0087] This invention does not particularly limit the type of alkylbenzene, as long as it can undergo a dealkylation reaction to yield benzene. Preferably, the alkylbenzene includes C7. + At least one of the aromatic hydrocarbons, preferably toluene and / or C9 + Aromatic hydrocarbons, more preferably C9 + Aromatic hydrocarbons. The catalyst provided by this invention is particularly suitable for C9 hydrocarbons. + Benzene is prepared by hydrogenation and dealkylation of aromatic hydrocarbons.

[0088] According to the present invention, preferably, the alkylbenzene comprises C9 aromatics and / or C10 aromatics.

[0089] According to the present invention, preferably, the weight ratio of C9 aromatic hydrocarbons to C10 aromatic hydrocarbons in the alkylbenzene is (7-9):(1-3).

[0090] In the above-mentioned hydrogenation dealkylation method, alkylbenzene is used as raw material. The hydrogenation dealkylation reaction of aromatic ring side chains is used to effectively remove alkyl side chains including methyl and above, converting alkylbenzene into benzene. The conversion rate of alkylbenzene is high, the selectivity of benzene is high, and the aromatic ring loss rate of alkylbenzene as raw material is low.

[0091] According to the present invention, those skilled in the art can rationally select the specific process conditions for the hydrodealkylation reaction and achieve considerable technical effects. Preferably, the hydrodealkylation reaction conditions include: a reaction temperature of 500-700℃, more preferably 420-600℃; a pressure of 0.1-5 MPa, more preferably 1-3.5 MPa; and a reaction mass hourly space velocity of 1-10 h⁻¹. -1 Preferably 2-5h -1 The hydrogen-to-oil volume ratio is 500-1500, preferably 800-1200.

[0092] According to the present invention, preferably, the method further includes: reducing the catalyst by contacting it with hydrogen gas before use. The present invention allows for a wide range of choices regarding the reduction method and conditions, as long as at least a portion of the active component can be converted into an element.

[0093] According to the present invention, preferably, the reduction conditions include: a temperature of 400-650°C, preferably 500-650°C, a time of 1-5 h, preferably 2.5-4 h, and a hydrogen flow rate to catalyst volume ratio of 1000-1500:1, preferably 1100-1300:1.

[0094] Unless otherwise specified, all pressures mentioned in this invention are gauge pressures.

[0095] The present invention will be described in detail below through embodiments.

[0096] In the following examples and comparative examples, the amorphous silicon aluminum was purchased commercially from Shandong Guohua Chemical Co., Ltd., and its grade was BC712.

[0097] The acidity of the catalyst was measured by NH3-TPD. The measurement method was as follows: 100 mg of 40-60 mesh catalyst was placed in a reaction tube, He was used as the carrier gas, and the flow rate was 40 mL / min. -1 Pre-treatment at 550℃ for 3 hours, followed by cooling and full adsorption of NH3 at 120℃, then purging of residual NH3 at a rate of 10℃·min -1 The temperature was increased to 550℃, and the desorption curve was recorded using a TCD detector. The acidity of the catalyst was quantitatively calculated by software, with signal peaks above 350℃ considered strong acids and signal peaks between 120-170℃ considered weak acids.

[0098] The amount of L acid in the catalyst was measured by pyridine infrared spectroscopy as described above.

[0099] The specific surface area, pore volume, and average pore size of the catalyst were determined using a low-temperature nitrogen adsorption method. The specific testing method was as follows: Nitrogen adsorption / desorption characterization was performed using a Micromeritics ASAP 2420 automated adsorption system (USA). The sample was degassed at 350℃ and 1.33 Pa for 4 h, and then tested at -196℃ using nitrogen as the adsorbate. The specific surface area was calculated using the BET method, and the total pore volume was calculated based on the amount of N2 adsorbed when p / p0 = 0.99.

[0100] Example 1

[0101] a. The catalyst weight percentage is based on a carrier: chromium trioxide: second metal oxide ratio of 80:18:2;

[0102] b. Select silica and titanium dioxide as a mixed support, and knead them in a ratio of 90%:10% to form a strip support with a diameter of 1.5 mm; dry at 100℃ for 6 h and calcine at 550℃ for 6 h to obtain the catalyst support;

[0103] c. Prepare a 0.3 mol / L chromium acetate solution. At 90 °C, take 10 g of the catalyst support obtained in b) and impregnate it in the chromium acetate solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnated by volume is 4. After impregnation for 100 min, dry it at 60 °C for 6 h and calcine it at 550 °C for 6 h to obtain a chromium oxide-containing catalyst intermediate. The content of the first active component, calculated as Cr2O3, is 18% of the target catalyst mass.

[0104] d. Prepare an iridium nitrate solution. At 100°C, take the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the iridium nitrate solution in equal volume for 100 min. After impregnation, dry it at 80°C for 8 h and calcine it at 600°C for 6 h to obtain the iridium oxide-containing catalyst product. The content of the second active component, calculated as iridium oxide, is 2% of the target catalyst mass.

[0105] The ratio of weak acid to strong acid in the finished catalyst is 1:0.25. The L acid content in the pyridine infrared test is 0.59 μmol / g (150℃), 0.35 μmol / g (250℃), and 0.18 μmol / g (350℃).

[0106] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0107] Figure 1 This is an NH3-TPD curve of the catalysts in Example 1 and Comparative Example 1. (From...) Figure 1It can be seen that the catalyst exhibits NH3 desorption peaks at 165℃ and 405℃, corresponding to the weak acid and strong acid, respectively. In Example 1, the NH3 desorption peak of the strong acid in the catalyst disappears, leaving only a relatively obvious NH3 desorption peak at the weak acid site at 165℃. The NH3 desorption peak of the strong acid is significantly reduced. Compared with Comparative Example 1, Example 1 reduces surface acidity by suppressing the strong acid in the catalyst, which can improve the catalyst stability and benzene selectivity in the product.

[0108] Figure 2 These are the pyridine-IR spectra of the catalysts in Example 1 and Comparative Example 1. Figure 2 It can be seen that no Bronsted acid adsorption peak (1540 cm⁻¹) appeared on the catalysts of Example 1 and Comparative Example 1. -1 Only the characteristic adsorption peak of pyridine at the Lewis acidic site (1450 cm⁻¹) was observed. -1 The pyridine infrared spectrum shows that the catalyst prepared by the steps in Example 1 has a further decrease in L acid content compared to Comparative Example 1, indicating that the steps in Example 1 have a more significant effect in suppressing the acidity of the catalyst surface.

[0109] Example 2

[0110] a. The catalyst weight percentage is based on a carrier: chromium trioxide: second metal oxide ratio of 80:18:2;

[0111] b. Select silica and alumina as mixed supports, and knead them in a ratio of 85%:15% to form strips with a diameter of 1.5 mm; dry them at 100℃ for 6 h and calcine them at 550℃ for 6 h to obtain the catalyst support;

[0112] c. Prepare a 0.35 mol / L chromium nitrate solution. At 90 °C, take 10 g of the catalyst support obtained in b) and impregnate it in the chromium nitrate solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnated by equal volume is 2. After impregnation for 100 min, dry at 60 °C for 6 h and calcine at 550 °C for 6 h to obtain a chromium oxide-containing catalyst intermediate. The content of the first active component, calculated as Cr2O3, is 18% of the target catalyst mass.

[0113] d. Prepare an iridium nitrate solution. At 100°C, take the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the iridium nitrate solution in equal volume for 100 min. After impregnation, dry it at 80°C for 4 h and calcine it at 600°C for 6 h to obtain the iridium oxide-containing catalyst product. The content of the second active component, calculated as iridium oxide, is 2% of the target catalyst mass.

[0114] The ratio of weak acid to strong acid in the finished catalyst is 1:0.5. The L acid content in the pyridine infrared test is 0.53 μmol / g (150℃), 0.33 μmol / g (250℃), and 0.19 μmol / g (350℃).

[0115] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0116] Example 3

[0117] a. The catalyst weight percentage is based on a carrier: chromium trioxide: second metal oxide ratio of 90:8:2;

[0118] b. Select silica and titanium dioxide as a mixed support, and knead them in a ratio of 80%:20% to form a strip support with a diameter of 1.5 mm; dry at 100℃ for 6 h and calcine at 550℃ for 6 h to obtain the catalyst support;

[0119] c. Prepare a 0.4 mol / L potassium chromate solution. At 90℃, take 10 g of the catalyst support obtained in b) and impregnate it in the potassium chromate solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnation solution is 3.5. After impregnation for 100 min, dry it at 60℃ for 6 h and calcine it at 550℃ for 6 h to obtain a chromium oxide-containing catalyst intermediate. The content of the first active component, calculated as Cr2O3, is 8% of the target catalyst mass.

[0120] d. Prepare an ammonium perrhenate solution. At 120°C, take an equal volume of the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the ammonium perrhenate solution. After impregnation for 90 min, dry it at 80°C for 8 h and calcine it at 620°C for 6 h to obtain the finished catalyst containing rhenium oxide. The content of the second active component, calculated as rhenium oxide, is 2% of the target catalyst mass.

[0121] The ratio of weak acid to strong acid in the finished catalyst is 1:0.27. The L acid content in the pyridine infrared test is 0.53 μmol / g (150℃), 0.34 μmol / g (250℃), and 0.17 μmol / g (350℃).

[0122] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0123] Example 4

[0124] a. The catalyst weight percentage is based on a carrier: chromium trioxide: second metal oxide ratio of 80:18:2;

[0125] b. Select silica as the single support and knead it into a strip-shaped support with a diameter of 1.5 mm; dry it at 100℃ for 6 h and calcine it at 550℃ for 6 h to obtain the catalyst support;

[0126] c. Prepare a 0.25 mol / L chromium acetate solution. At 90 °C, take 10 g of the catalyst support obtained in b) and impregnate it in the chromium acetate solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnated by volume over-volume impregnation solution is 3.5. After impregnation for 100 min, dry at 60 °C for 6 h and calcine at 550 °C for 6 h to obtain a chromium oxide-containing catalyst intermediate. The content of the first active component, calculated as Cr2O3, is 18% of the target catalyst mass.

[0127] d. Prepare an iridium nitrate solution. At 100°C, take an equal volume of the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the iridium nitrate solution for 100 min. After impregnation, dry it at 80°C for 8 h and calcine it at 600°C for 6 h to obtain the finished catalyst containing iridium oxide. The content of the second active component, calculated as iridium oxide, is 2% of the target catalyst mass.

[0128] The ratio of weak acid to strong acid in the finished catalyst is 1:0.29, and the L acid content in the pyridine infrared test is 0.63 μmol / g (150℃), 0.44 μmol / g (250℃), and 0.14 μmol / g (350℃).

[0129] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0130] Example 5

[0131] a. The catalyst weight percentage is based on a carrier: chromium trioxide: second metal oxide ratio of 80:14:6;

[0132] b. Select silica and amorphous silica-alumina as a mixed support, and knead them in a ratio of 70%:30% to form a strip support with a diameter of 1.5 mm; dry at 100℃ for 6 h and calcine at 550℃ for 6 h to obtain the catalyst support;

[0133] c. Prepare a 0.5 mol / L sodium chromate solution. At 90 °C, take 10 g of the catalyst support obtained in b) and impregnate it in the sodium chromate solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnation solution is 4. After impregnation for 100 min, dry it at 60 °C for 6 h and calcine it at 550 °C for 6 h to obtain a chromium oxide-containing catalyst intermediate. The content of the first active component, calculated as Cr2O3, is 14% of the target catalyst mass.

[0134] d. Prepare an ammonium molybdate solution. At 100°C, take the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the ammonium molybdate solution in equal volume for 100 min. After impregnation, dry it at 80°C for 6 h and calcine it at 600°C for 6 h to obtain the finished catalyst containing molybdenum oxide. The content of the second active component, calculated as molybdenum oxide, is 6% of the target catalyst mass.

[0135] The ratio of weak acid to strong acid in the finished catalyst is 1:0.11, and the amount of L acid in the pyridine infrared test is 0.62 μmol / g (150℃), 0.44 μmol / g (250℃), and 0.18 μmol / g (350℃).

[0136] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0137] Example 6

[0138] a. The catalyst weight percentage is based on a carrier: chromium trioxide: second metal oxide ratio of 60:30:10;

[0139] b. Select silica and titanium dioxide as a mixed support, and knead them in a 50%:50% ratio to form a strip support with a diameter of 1.5 mm; dry at 100℃ for 6 h and calcine at 550℃ for 6 h to obtain the catalyst support;

[0140] c. Prepare a 0.15 mol / L chromium chloride solution. At 90 °C, take 10 g of the catalyst support obtained in b) and impregnate it in the chromium chloride solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnated by volume over-volume impregnation solution is 3.5. After impregnation for 100 min, dry at 60 °C for 6 h and calcine at 550 °C for 6 h to obtain a chromium oxide-containing catalyst intermediate, wherein the content of the first active component, calculated as Cr2O3, is 30% of the target catalyst mass.

[0141] d. Prepare a ferric chloride solution. At 100°C, take the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the ferric chloride solution in equal volume for 100 min. After impregnation, dry it at 80°C for 6 h and calcine it at 650°C for 6 h to obtain the ferric oxide-containing catalyst product. The content of the second active component, calculated as ferric oxide, is 10% of the target catalyst mass.

[0142] The ratio of weak acid to strong acid in the finished catalyst is 1:0.31, and the amount of L acid in the pyridine infrared test is 0.55 μmol / g (150℃), 0.38 μmol / g (250℃), and 0.19 μmol / g (350℃).

[0143] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0144] Example 7

[0145] a. The catalyst weight percentage is based on a carrier: chromium trioxide: second metal oxide ratio of 80:18:2;

[0146] b. Select silica and alumina as mixed supports, and knead them in a ratio of 90%:10% to form strips with a diameter of 1.5 mm; dry them at 40℃ for 6 h and calcine them at 350℃ for 1 h to obtain the catalyst support;

[0147] c. Prepare a 0.6 mol / L chromium nitrate solution. At 110 °C, take 10 g of the catalyst support obtained in b) and impregnate it in the chromium nitrate solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnated by volume over-volume impregnation solution is 2.5. After impregnation for 150 min, dry at 90 °C for 8 h and calcine at 650 °C for 24 h to obtain a chromium oxide-containing catalyst intermediate. The content of the first active component, calculated as Cr2O3, is 18% of the target catalyst mass.

[0148] d. Prepare an iridium nitrate solution. At 120°C, take the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the iridium nitrate solution in equal volume for 150 min. After impregnation, dry it at 120°C for 8 h and calcine it at 750°C for 20 h to obtain the iridium oxide-containing catalyst product. The content of the second active component, calculated as iridium oxide, is 2% of the target catalyst mass.

[0149] The ratio of weak acid to strong acid in the finished catalyst is 1:0.35. The L acid content in the pyridine infrared test is 0.52 μmol / g (150℃), 0.31 μmol / g (250℃), and 0.12 μmol / g (350℃).

[0150] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0151] Comparative Example 1

[0152] Referring to Example 1, the over-volume impregnation step in operation c of Example 1 is changed to equal-volume impregnation, and the other steps are performed in accordance with Example 1.

[0153] The ratio of weak acid to strong acid in the finished catalyst is 1:0.62. The L acid content in the pyridine infrared test is 0.48 μmol / g (150℃), 0.25 μmol / g (250℃), and 0.08 μmol / g (350℃).

[0154] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0155] Comparative Example 2

[0156] Referring to Example 1, the equal volume impregnation step in operation d of Example 1 is changed to over-volume impregnation. The over-volume impregnation step is operated exactly as in Example 1, and the other steps are performed as in Example 1.

[0157] The ratio of weak acid to strong acid in the finished catalyst is 1:0.52. The L acid content in the pyridine infrared test is 0.18 μmol / g (150℃), 0.11 μmol / g (250℃), and 0.06 μmol / g (350℃).

[0158] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0159] Comparative Example 3

[0160] Referring to Example 1, the over-volume impregnation step of chromium oxide in operation c of Example 1 is omitted, and the other steps are performed in accordance with Example 1.

[0161] The ratio of weak acid to strong acid in the finished catalyst is 1:0.78. The L acid content in the pyridine infrared test is 0.18 μmol / g (150℃), 0.23 μmol / g (250℃), and 0.35 μmol / g (350℃).

[0162] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0163] Comparative Example 4

[0164] Referring to Example 1, the equal-volume impregnation step in operation d of Example 1 is omitted, and the other steps are performed in accordance with Example 1.

[0165] The ratio of weak acid to strong acid in the finished catalyst is 1:0.81. The L acid content in the pyridine infrared test is 0.44 μmol / g (150℃), 0.13 μmol / g (250℃), and 0.21 μmol / g (350℃).

[0166] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0167] Comparative Example 5

[0168] Referring to Example 1, after step b, step d is performed first, followed by step c, and the rest is the same as in Example 1.

[0169] The ratio of weak acid to strong acid in the finished catalyst is 1:0.58. The L acid content in the pyridine infrared test is 0.78 μmol / g (150℃), 0.21 μmol / g (250℃), and 0.32 μmol / g (350℃).

[0170] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0171] Comparative Example 6

[0172] Referring to Example 1, the active metal Cr2O3 in step c was replaced with an equal mass of Co2O3, while other conditions remained unchanged.

[0173] The ratio of weak acid to strong acid in the finished catalyst is 1:0.92. The L acid content in the pyridine infrared test is 0.33 μmol / g (150℃), 0.13 μmol / g (250℃), and 0.42 μmol / g (350℃).

[0174] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0175] Comparative Example 7

[0176] a. Based on the total amount of catalyst, the ratio of support: first metal oxide: second metal oxide content is 70:20:10;

[0177] b. Titanium oxide was selected as the single support and kneaded into strips with a diameter of 1.5 mm; after drying at 100℃ for 6 h and calcining at 550℃ for 6 h, the catalyst support was obtained.

[0178] c. Prepare a 0.35 mol / L potassium chromate solution. At 90 °C, take 10 g of the catalyst support obtained in b) and impregnate it in the potassium chromate solution by volume over-volume impregnation. The volume ratio of the volume of the over-volume impregnation solution to the volume of the silicon-containing support impregnation solution is 4. After impregnation for 100 min, dry it at 60 °C for 6 h and calcine it at 550 °C for 6 h to obtain a chromium oxide-containing catalyst intermediate. The content of the first active component, calculated as Cr2O3, is 20% of the target catalyst mass.

[0179] d. Prepare an iridium nitrate solution. At 100°C, take an equal volume of the chromium oxide-containing catalyst intermediate obtained in c and impregnate it in the iridium nitrate solution for 100 min. After impregnation, dry it at 80°C for 6 h and calcine it at 600°C for 6 h to obtain the finished catalyst containing iridium oxide. The content of the second active component, calculated as iridium oxide, is 2% of the target catalyst mass.

[0180] The ratio of weak acid to strong acid in the finished catalyst is 1:0.71, and the amount of L acid in the pyridine infrared test is 0.44 μmol / g (150℃), 0.50 μmol / g (250℃), and 0.40 μmol / g (350℃).

[0181] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 1.

[0182] Table 1

[0183] catalyst Total pore volume mL / g <![CDATA[Specific surface area m 2 g]]> Average pore size (nm) Example 1 1.25 220 6.8 Example 2 1.20 224 7.0 Example 3 1.16 160 7.0 Example 4 1.09 195 6.6 Example 5 0.99 187 5.5 Example 6 0.65 149 3.2 Example 7 0.82 126 6.2 Comparative Example 1 0.24 135 3.5 Comparative Example 2 0.36 120 4.5 Comparative Example 3 0.42 95 5.6 Comparative Example 4 0.12 99 6.7 Comparative Example 5 0.16 102 3.8 Comparative Example 6 0.57 122 4.2 Comparative Example 7 0.74 135 5.0

[0184] The following test examples are used to evaluate the catalytic performance of the hydrogenation dealkylation catalyst provided by the present invention in the hydrogenation dealkylation of alkylbenzene to benzene reaction.

[0185] Test case

[0186] Take 5.0 g of the finished catalyst prepared in the above examples and comparative examples, respectively, and load it into a micro adiabatic fixed-bed reactor with an inner diameter of 1.5 cm. Glass beads are filled at both the top and bottom of the reaction bed. Then, hydrogen gas is introduced, ensuring a uniform flow through the catalyst bed. The volume ratio of hydrogen to catalyst is 1200:1. After a 120-minute programmed temperature rise to 600°C, and held at this temperature for 2 hours, the same temperature is maintained. Alkylbenzene feedstock, a mixture of C9 and C10 aromatics, is introduced using a metering pump, with a C9:C10 weight ratio of 9:1. The mass hourly space velocity (MHS) of the organic reactants is maintained at 2 h⁻¹. -1 The reaction pressure was 3.0 MPa, and the hydrogen-to-oil volume ratio was 10:20. By metering and analyzing the oil phase and tail gas in the catalytic reaction effluent, the alkylbenzene conversion, benzene selectivity, aromatic ring loss rate, and stability of the reaction were calculated. Specific results are shown in Table 2.

[0187] The formulas for calculating alkylbenzene conversion, benzene selectivity, aromatic ring loss rate, and aromatic yield are as follows:

[0188]

[0189]

[0190]

[0191] Aromatic yield (%) = 100% - Aromatic ring loss rate

[0192] Catalyst stability refers to the time during a reaction when the conversion rate of the reactants drops to 90% of the initial conversion rate.

[0193] Table 2

[0194]

[0195]

[0196] The results above show that the hydrogenation dealkylation catalyst provided by this invention has a high alkylbenzene conversion rate and high benzene selectivity in the hydrogenation dealkylation reaction of alkylbenzene, and the aromatic ring loss rate of the alkylbenzene used as raw material is low, with the highest aromatic yield reaching 99.92%; moreover, the catalyst has good stability.

[0197] 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 hydrogenation dealkylation catalyst, characterized in that, The catalyst comprises a silicon-containing support and a first active component and a second active component supported on the silicon-containing support; The first active component is chromium; the second active component is selected from at least one of Group VIB, Group VIIB and Group VIII metals; the first active component and the second active component are of different metal types. The ratio of the amount of weak acid to the amount of strong acid in the hydrogenation dealkylation catalyst is 1:0.1-0.

5.

2. The catalyst according to claim 1, wherein, The hydrogenation dealkylation catalyst, as measured by pyridine infrared spectroscopy, has an L acid content of 0.5-0.7 μmol / g at 150°C, 0.3-0.5 μmol / g at 250°C, and 0.1-0.3 μmol / g at 350°C. Preferably, the hydrogenation dealkylation catalyst, as measured by pyridine infrared spectroscopy, has an L acid content of 0.52-0.69 μmol / g at 150°C, an L acid content of 0.31-0.45 μmol / g at 250°C, and an L acid content of 0.12-0.28 μmol / g at 350°C.

3. The catalyst according to claim 1, wherein, The silicon-containing carrier includes silicon oxide and optionally at least one of aluminum oxide, titanium oxide and amorphous aluminum silicate; Preferably, based on the total amount of silicon-containing carrier, the content of silicon oxide is 65% by weight or more; And / or, the second active component is selected from at least one of iridium, rhenium, iron and molybdenum.

4. The catalyst according to any one of claims 1-3, wherein, Based on the total amount of catalyst, the content of silicon-containing support is 50-95% by weight, preferably 60-90% by weight, the content of the first active component based on oxide is 2-40% by weight, preferably 5-30% by weight, and the content of the second active component based on oxide is 1-12% by weight, preferably 2-10% by weight.

5. The catalyst according to any one of claims 1-4, wherein, The catalyst has an average pore size of 2.5-12 nm, preferably 4-10 nm; Preferably, the total pore volume of the catalyst is 0.15-1.4 mL / g, more preferably 0.85-1.3 mL / g; And / or, the specific surface area of ​​the catalyst is 90-290 m². 2 / g, preferably 135-225m 2 / g.

6. A method for preparing a hydrogenation dealkylation catalyst, characterized in that, Includes the following steps: (1) The silicon-containing support is impregnated with a solution of a soluble compound containing the first active component, and then dried and calcined to obtain a catalyst intermediate; (2) The catalyst intermediate is impregnated with an equal volume of a solution of a soluble compound containing the second active component, and then dried and calcined to obtain a hydrogenation dealkylation catalyst; Wherein, the first active component is chromium; the second active component is selected from at least one of Group VIB metals, Group VIIB metals and Group VIII metals; the first active component and the second active component are of different metal types.

7. The preparation method according to claim 6, wherein, The silicon-containing carrier includes silicon oxide and optionally at least one of aluminum oxide, titanium oxide and amorphous aluminum silicate; Preferably, based on the total amount of silicon-containing carrier, the content of silicon oxide is 65% by weight or more; Preferably, the method for preparing the silicon-containing carrier includes: shaping silicon oxide and optionally at least one of aluminum oxide, titanium oxide and amorphous aluminum silicate, followed by drying and calcination; more preferably, the calcination conditions include: calcination at 350-650°C for 0.5-24 hours.

8. The preparation method according to claim 6 or 7, wherein, The amounts of the soluble compound of the first active component, the soluble compound of the second active component, and the silicon-containing support in the prepared catalyst are such that, based on the total amount of catalyst, the content of the silicon-containing support is 50-95% by weight, preferably 60-90% by weight, the content of the first active component (calculated as oxide) is 2-40% by weight, preferably 5-30% by weight, and the content of the second active component (calculated as oxide) is 1-12% by weight, preferably 2-10% by weight.

9. The preparation method according to any one of claims 6-8, wherein, In step (1), the concentration of the first active metal component chromium solution in the over-volume impregnation is 0.1-0.6 mol / L, preferably 0.25-0.5 mol / L; And / or, the volume ratio of the over-volume impregnation solution to the equal-volume impregnation solution for the silicon-containing carrier is 1.5-6, preferably 2-4.5; And / or, the conditions for the over-volume impregnation in step (1) include: a temperature of 30-110°C, preferably 50-90°C; and a time of 30-150 min, preferably 50-100 min; And / or, the conditions for the equal volume impregnation in step (2) include: a temperature of 50-120°C, preferably 80-120°C; and a time of 30-150 min, preferably 80-130 min.

10. The preparation method according to any one of claims 6-9, wherein, The roasting conditions in step (1) include: a temperature of 400-650℃, preferably 450-550℃; and a time of 0.5-24h, preferably 2-12h. And / or, the roasting conditions in step (2) include: a temperature of 500-750℃, preferably 550-700℃; and a time of 0.5-24h, preferably 4-10h.

11. The hydrogenation dealkylation catalyst prepared by the preparation method according to any one of claims 6-10.

12. A method for hydrogenation dealkylation, characterized in that, The method includes: contacting alkylbenzene, hydrogen gas, and a catalyst under hydrodealkylation reaction conditions; The catalyst is the hydrogenation dealkylation catalyst according to any one of claims 1-5 and 11; Preferably, the alkylbenzene comprises C7. + At least one of the aromatic hydrocarbons; Preferably, the hydrodealkylation reaction conditions include: a reaction temperature of 500-700℃, more preferably 420-550℃; a pressure of 0.1-5 MPa, more preferably 1-3.5 MPa; and a mass hourly space velocity (HHSV) of 1-10 h⁻¹. -1 Preferably 2-5h -1 The hydrogen-to-oil volume ratio is 500-1500, preferably 800-1200.

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