Hydrodechlorination catalyst and preparation method thereof

Abstract

The invention relates to a hydrodechlorination catalyst and a preparation method thereof. Provided is a hydrodechlorination catalyst comprising an active metal supported on a carrier wherein the catalyst is modified with a phosphorus-containing ligand protective agent having the following general formula: Arn-X-R3-n (1) wherein X represents P or P (O); ar represents a C6-20 aryl group or a-O-C6-20 aryl group; r represents H, an alkyl group with 1 to 20 carbon atoms, a cycloalkyl group with 3 to 20 carbon atoms, an alkenyl group with 2 to 20 carbon atoms, a cycloalkyl group with 3 to 20 carbon atoms, an alkyl group with 1 to 20 carbon atoms or an alkenyl group with 2 to 20 carbon atoms; and n represents 1 or 2.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical engineering, and in particular to a hydrodechlorination catalyst and a preparation method thereof. Background Art

[0002] In the industry chain of benzene chlorination to produce dichlorobenzene, a large amount of trichlorobenzene and tetrachlorobenzene by-products are inevitably produced. The accumulation of these by-products will seriously affect the production rate and occupy the production area. The incineration method for treating chlorocarbon waste will produce a large amount of hydrogen chloride, causing air pollution, and the economic value of this treatment method is low. Therefore, converting polychlorinated benzenes into high-value-added dechlorination products through hydrogenation process is a green and environmentally friendly strategy with high economic value. In the benzene chlorination industry chain, 1,2,4-trichlorobenzene is produced in large quantities as a by-product. However, due to the reduction in demand for downstream applications, its economic value is greatly reduced. Hydrogenation and dechlorination of 1,2,4-trichlorobenzene to produce high-value-added dechlorination products through hydrogenation process is an effective strategy for dealing with by-products. In this process, dichlorobenzene is the most valuable product, especially meta-dichlorobenzene. However, due to the steric effect, ortho-dichlorobenzene accounts for the highest proportion of dichlorobenzene products produced by hydrogenation reaction.

[0003] There are two main catalytic methods for the hydrodechlorination of polychlorinated benzenes, which are divided into alkali neutralization kettle hydrogenation process and alkali-free fixed bed hydrogenation process. The traditional alkali neutralization kettle hydrogenation process requires the addition of alkali solution to neutralize the HCl produced by the reaction to avoid catalyst poisoning. The problem with this process is that the reaction requires a large amount of alkali, which is costly and produces a large amount of wastewater. The alkali-free fixed bed hydrogenation process can operate continuously, greatly improving production efficiency and output. At the same time, the process does not require the addition of additional alkali, has low cost, low wastewater volume, and is green and environmentally friendly. In addition, the process is short, and the generated dechlorination products can be directly separated and processed. The challenges faced by this process are that the catalyst is easily deactivated, the operating life is short, and the product selectivity is difficult to control.

[0004] CN 114057537 A reported that palladium-carbon catalyst was applied to the hydrogenation reaction of polychlorobenzenes, but the only product generated was benzene with low added value. CSSrikanth et al. (Catalysis Communications 13, (2011), 69–7) reported that Ru / γ-Al2O3 catalyst was applied to the hydrogenation reaction of 1,2,4-trichlorobenzene, achieving a conversion rate of 5.1% and a dichlorobenzene selectivity of 100%, but the catalyst was completely deactivated after 9 hours of reaction. The catalysts reported so far are difficult to simultaneously meet the requirements of high conversion rate, long operating life, and high dichlorobenzene selectivity. In addition, due to the steric effect, among the dichlorobenzene products, o-dichlorobenzene accounts for the highest proportion, while m-dichlorobenzene with high added value accounts for a relatively small proportion. Conventional catalysts are difficult to achieve regulation of the distribution of o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene products.

[0005] Therefore, it is of great significance to develop catalysts for the hydrodechlorination of polychlorinated benzenes to achieve high conversion rates, high dichlorobenzene selectivity, and especially to increase the proportion of meta-dichlorobenzene. Summary of the invention

[0006] The purpose of the present application is to provide a catalyst for hydrodechlorination of polychlorobenzenes, which can achieve high conversion rate and high dichlorobenzene selectivity, especially increase the proportion of meta-dichlorobenzene.

[0007] After extensive research, the inventors of the present application have found that the use of phosphorus-containing ligand-modified catalysts can achieve high conversion rates and high dichlorobenzene selectivity, especially increasing the proportion of meta-dichlorobenzene.

[0008] In one aspect, the present application provides a hydrodechlorination catalyst, the catalyst comprising an active metal supported on a carrier, wherein the catalyst is modified with a phosphorus-containing ligand protective agent, and the phosphorus-containing ligand protective agent has the following general formula:

[0009] Ar n -XR 3-n (1)

[0010] Wherein, X represents P or P(O);

[0011] Ar represents C 6-20 Aryl or -OC 6-20 Aryl;

[0012] R stands for H, C 1-20 Alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, -OC 3-20 Cycloalkyl, -OC 1-20 Alkyl or -OC 2-20 alkenyl;

[0013] n represents 1 or 2.

[0014] On the other hand, the present application provides a method for preparing a hydrodechlorination catalyst, the method comprising the following steps:

[0015] (1) impregnating the support in an active metal precursor solution and drying to obtain a catalyst precursor;

[0016] (2) subjecting the precursor to a reduction treatment to obtain a reduced catalyst precursor; and

[0017] (3) mixing the reduced catalyst precursor and the phosphorus-containing ligand protective agent, and drying to obtain a hydrodechlorination catalyst,

[0018] The phosphorus-containing ligand protective agent has the following general formula:

[0019] Arn -XR 3-n (1)

[0020] Wherein, X represents P or P(O);

[0021] Ar represents C 6-20 Aryl or -OC 6-20 Aryl;

[0022] R stands for H, C 1-20 Alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, -OC 3-20 Cycloalkyl, -OC 1-20 Alkyl or -OC 2-20 alkenyl;

[0023] n represents 1 or 2.

[0024] In another aspect, the present application provides a method for selective hydrodechlorination of polychlorinated benzenes, the method comprising the following steps:

[0025] (1) providing the hydrodechlorination catalyst described in the present application; and

[0026] (2) Using the catalyst to selectively hydrodechlorinate polychlorinated benzenes. DETAILED DESCRIPTION

[0027] "Scope" disclosed herein is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The scope defined in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0029] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0030] In the present application, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0031] In this application, unless otherwise specified, the terms "include" and "comprising" mentioned herein may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0032] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and "several" in "one or several" means two or more.

[0033] In the description herein, unless otherwise specified, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0034] Herein, unless otherwise specified, percentage (%) or part refers to percentage by weight or part by weight relative to the composition.

[0035] Herein, if there is no contrary description, the sum of the contents of the various components in the composition is 100%.

[0036] Herein, if there is no contrary description, the sum of the parts of each component in the composition may be 100 parts by weight.

[0037] In this context, unless otherwise specified, "a combination thereof" means a multi-component mixture of the elements described, for example a mixture of two, three, four and up to the maximum possible multi-component mixture.

[0038] If not specifically stated, the terms "a" or "an" used in the present specification means "at least one".

[0039] Herein, unless otherwise stated, all reactions are carried out at normal temperature and pressure.

[0040] In one aspect, the present application provides a hydrodechlorination catalyst, the catalyst comprising an active metal supported on a carrier, wherein the catalyst is modified with a phosphorus-containing ligand protective agent, and the phosphorus-containing ligand protective agent has the following general formula:

[0041] Ar n -XR 3-n (1)

[0042] Wherein, X represents P or P(O);

[0043] Ar represents C 6-20 Aryl or -OC 6-20 Aryl;

[0044] R stands for H, C 1-20 Alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, -OC 3-20 Cycloalkyl, -OC 1-20 Alkyl or -OC 2-20 alkenyl;

[0045] n represents 1 or 2.

[0046] In this article, the term “C 6-20 "Aryl" is a group obtained by removing a hydrogen atom from an aromatic hydrocarbon having 6 to 20 carbon atoms. In one example of the present application, the term "C 6-20 The "aryl" group may include C 6-12 Aryl, C 6-10 In one example of the present application, the term "C 6-20 The term "aryl" includes phenyl, tolyl, xylyl, mesityl, biphenyl or naphthyl.

[0047] In this article, the term “C 1-20 "Alkyl" is a group obtained by removing a hydrogen atom from an alkane having 1 to 20 carbon atoms. In one example of the present application, the term "C 1-20 The "alkyl" may include C 1-12 Alkyl, C 1-10 Alkyl or C 1-4 In one example of the present application, the term "C1-20 The term "alkyl" includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl.

[0048] In this article, the term “C 3-20 A "cycloalkyl" is a group obtained by removing a hydrogen atom from a cycloalkane having 3 to 20 carbon atoms. In one example of the present application, the term "C 3-20 The "cycloalkyl" may include C 3-16 Cycloalkyl, C 3-12 Cycloalkyl or C 4-10 In one example of the present application, the term "C 3-20 "Cycloalkyl" includes cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.

[0049] In this article, the term “C 2-20 "Alkenyl" is a group obtained by removing a hydrogen atom from an alkene having 2 to 20 carbon atoms. In one example of the present application, the term "C 2-20 The "alkenyl" group may include C 2-12 Alkenyl, C 2-10 Alkenyl or C 2-6 In one example of the present application, the term "C 2-20 "Alkenyl" includes ethenyl, propenyl or butenyl.

[0050] In one example of the present application, the carrier may be a carrier commonly used in the art for catalysts, such as a porous carrier and a non-porous carrier. In one example of the present application, the carrier is selected from one or more of activated carbon, zeolite, Al2O3, CeO2, SiO2, ZrO2, and TiO2.

[0051] In one example of the present application, the active metal may be a catalytically active metal commonly used in the art for dechlorination and hydrogenation. For example, the active metal includes one or more of Pd, Pt, Ru, Fe, Co, Cu, Ni and Rh.

[0052] In one example of the present application, based on the total weight of the catalyst, the mass fraction of the active metal is 0.1-20 wt %, such as 0.2-15 wt %, 0.5-10 wt %.

[0053] In one example of the present application, based on the total weight of the catalyst, the mass fraction of the phosphorus-containing ligand is 0.05-10 wt %, such as 0.1-8 wt %, 0.2-4 wt %.

[0054] In one example of the present application, based on the total weight of the catalyst, the mass fraction of the carrier is 70-99.85 wt %, such as 77-99.7 wt %, 86-99.3 wt %.

[0055] On the other hand, the present application provides a method for preparing a hydrodechlorination catalyst, the method comprising the following steps:

[0056] (1) impregnating the support in an active metal precursor solution and drying to obtain a catalyst precursor;

[0057] (2) subjecting the precursor to a reduction treatment to obtain a reduced catalyst precursor; and

[0058] (3) mixing the reduced catalyst precursor and the phosphorus-containing ligand protective agent, and drying to obtain a hydrodechlorination catalyst,

[0059] The phosphorus-containing ligand protective agent has the following general formula:

[0060] Ar n -XR 3-n (1)

[0061] Wherein, X represents P or P(O);

[0062] Ar represents C 6-20 Aryl or -OC 6-20 Aryl;

[0063] R stands for H, C 1-20 Alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, -OC 3-20 Cycloalkyl, -OC 1-20 Alkyl or -OC 2-20 alkenyl;

[0064] n represents 1 or 2.

[0065] In one example of the present application, the carrier may be a carrier commonly used in the art for catalysts, such as a porous carrier and a non-porous carrier. In one example of the present application, the carrier is selected from one or more of activated carbon, zeolite, Al2O3, CeO2, SiO2, ZrO2, and TiO2.

[0066] In one example of the present application, the active metal can be a catalytically active metal commonly used in the art for dechlorination and hydrogenation. For example, the active metal includes one or more of Pd, Pt, Ru, Fe, Co, Cu, Ni and Rh. The active metal precursor can be a salt of an active metal, such as a nitrate, a sulfate, an organic acid salt (such as acetate, formate), a halide (such as chloride, bromide, etc.), a complex (such as an acid of an active metal and a salt thereof (such as ammonium salt, sodium salt, potassium salt)) or a combination thereof. In one example of the present application, the complex can be, for example, palladium acid, bromopalladium acid, chloropalladium acid, platinic acid, bromoplatinic acid, chloroplatinic acid, rhodic acid, bromorhodic acid, chlororhodic acid and a salt thereof (such as ammonium salt, sodium salt, potassium salt). The solvent of the solution can be water or an organic solvent, including but not limited to water, alcohol (such as methanol, ethanol, etc.), ether (such as ether), etc.

[0067] In one example of the present application, the amount of the active metal precursor used is such that the mass fraction of the active metal is 0.1-20 wt %, such as 0.2-15 wt %, 0.5-10 wt %, based on the total weight of the final catalyst.

[0068] In one example of the present application, based on the total weight of the catalyst, the mass fraction of the carrier is 70-99.85 wt %, such as 77-99.7 wt %, 86-99.3 wt %.

[0069] In the above step (1), the immersion time can be 0.5-72 hours (e.g., 2-48 hours, 4-36 hours, 6-24 hours), the drying temperature is 60-200°C (e.g., 60-180°C, 80-150°C), and the drying time is 1-72 hours (e.g., 4-48 hours, 4-36 hours, 6-24 hours).

[0070] In the above step (1), the solid-liquid ratio of the impregnation can be, for example, 1:(0.5-25), generally 1:(1-20), preferably 1:(1-15).

[0071] In one example of the present application, in the above step (2), the reduction precursor can be reduced by chemical reduction (such as sodium borohydride, hydrazine hydrate, etc.) and gas reduction, preferably gas reduction. In one example of the present application, the gas includes a reducing gas or a gas flow containing a reducing gas. In one example of the present application, the reducing gas is selected from H2, CO, CH4 or a combination thereof. In one example of the present application, the inert gas includes a rare gas (helium, neon, argon, krypton or xenon), nitrogen, carbon dioxide or a combination thereof. In one example of the present application, the volume fraction of the reducing gas to the total amount of gas ranges from 1-100%, such as 1-80%, 1-60%, 1-40%, 1-20%, 1-10%.

[0072] In the examples of the present application, the reduction is carried out under heating conditions. For example, the catalyst can be reduced at a heating rate of 0.5-30°C / min (e.g., 1-15°C / min) to the reduction temperature, the reduction temperature is 100-600°C (e.g., 150-550°C, 200-450°C), the reduction time is 0.5-10 hours (e.g., 1-5 hours, 2-4 hours), and the mass space velocity of the gas is 0.01-10h - (e.g. 0.05-5h -1 , 0.1-4h -1 , 0.5-3h -1 , 1-2h -1 ).

[0073] In one example of the present application, the mass fraction of the phosphorus-containing ligand is 0.05-10% by weight, such as 0.1-8% by weight, and 0.2-4% by weight, based on the total weight of the final catalyst. The phosphorus-containing ligand protective agent can be provided in the form of a solution, wherein the solvent can be a commonly used solvent in the art, including but not limited to aromatic hydrocarbons (such as toluene, benzene, xylene), alcohols (such as methanol, ethanol, propanol), amides (N,N-dimethylformamide), ketones (such as acetone, butanone), cycloalkanes (such as cyclohexane), and ethers (such as methyl ether, ethyl ether, and methyl ethyl ether). In the above step (3), when the phosphorus-containing ligand protective agent is provided in the form of a solution, the solid-liquid ratio of the reduced catalyst precursor to the protective agent solution can be, for example, 1: (0.5-25), generally 1: (1-20), and preferably 1: (1-15).

[0074] In one example of the present application, in the step (3), the drying temperature is 40-200°C (eg, 50-150°C, 50-120°C, 50-80°C), and the second drying time is 1-72 hours (eg, 4-24 hours).

[0075] In another aspect, the present application provides a method for selective hydrodechlorination of polychlorinated benzenes, the method comprising the following steps:

[0076] (1) providing the hydrodechlorination catalyst described in the present application; and

[0077] (2) Using the catalyst to selectively hydrodechlorinate polychlorinated benzenes.

[0078] The catalyst described in the present application can be used for selective hydrogenation and dechlorination of polychlorobenzenes. In this article, the "polychlorobenzenes" include one or more of dichlorobenzenes (e.g., 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene), trichlorobenzenes (e.g., 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene), tetrachlorobenzenes (e.g., 1,2,3,4-tetrachlorobenzene, 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene), pentachlorobenzene, and hexachlorobenzene. In a preferred embodiment of the present application, the catalyst selectively dechlorinates and hydrogenates polychlorobenzenes (preferably trichlorobenzenes (e.g., 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene or 1,3,5-trichlorobenzene)). Preferably, the catalyst of the present application can selectively dechlorinate and hydrogenate trichlorobenzenes to form dichlorobenzenes, preferably meta-dichlorobenzene.

[0079] In one example of the present application, the content of intermediate dichlorobenzene in the dechlorination hydrogenation product is at least 50% by weight, such as 50-90% by weight, preferably 55-85% by weight, and more preferably 60-80% by weight.

[0080] In the present application, the conditions for selective hydrodechlorination of polychlorinated benzenes using the catalyst may be the hydrodechlorination conditions commonly used in the art.

[0081] The advantages of this application are:

[0082] (1) The present application adopts a ligand protection strategy to modify a suitable protective ligand on the surface of the active metal to achieve selective adsorption of the substrate chlorine atoms, thereby effectively increasing the proportion of intermediate dichlorobenzene in the product dichlorobenzene.

[0083] (2) The catalyst effectively solved the problem of difficult-to-control selectivity of the hydrodechlorination reaction of polychlorinated benzenes, greatly promoting the industrialization process of the process.

[0084] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0085] Main reagents for the experiment

[0086]

[0087]

[0088] Main experimental instruments

[0089] Instrument Name model Manufacturer Single channel catalyst evaluation device EMC-1 Oushisheng (Beijing) Technology Co., Ltd. High temperature tube furnace GWL Henan Guoding Furnace Industry Co., Ltd. Constant temperature blast drying oven DHG Chengdu Ruipaisi Technology Co., Ltd. Gas Chromatograph GC-2010Pro Shimadzu China

[0090] Specific test methods used in the examples

[0091] The reaction liquid of hydrodechlorination was analyzed on Shimadzu China's GC-2010Pro gas chromatograph using a hydrogen flame detector (FID). The conversion rate (x, %) and product selectivity (y, %) of hydrodechlorination were calculated using the area normalization method, and the calculation methods are shown in ①② respectively.

[0092] ①: x=(A 总 -A1) / A 总 *100%

[0093] ②: y = A n / (A 总 -A1)*100%

[0094] Among them A 总 A is the sum of the gas chromatographic peak areas of all organic components in the reaction solution except the solvent; A1 is the gas chromatographic peak area of ​​the unreacted raw material; A n is the corresponding gas chromatographic peak area of ​​the calculated product.

[0095] Example 1

[0096] 100g of activated carbon was immersed in an aqueous solution of 2 wt% chloropalladic acid, and the first solid-liquid weight ratio was 1:2. After immersion for 24 hours, the first drying was carried out, the first drying temperature was 110°C, and the first drying time was 10 hours to obtain a reduced precursor. The mass fraction of Pd in ​​the reduced precursor was 1% of the total weight of the catalyst. The reduced precursor was reduced by gas reduction method. The gas was a mixture of hydrogen and nitrogen, in which the volume of hydrogen accounted for 5% of the total volume fraction of the gas. The catalyst was reduced at a heating rate of 5°C / min to a reduction temperature of 250°C, the reduction time was 2 hours, and the mass space velocity of the gas was 0.05h -1 , and obtain a modified precursor. The modified precursor is mixed with a ligand protective agent and then dried for the second time. In the ligand protective agent, the mass fraction of methyl diphenyl phosphine in the total weight of the ligand protective agent is 0.5%, cyclohexane is used as a solvent, and the second solid-liquid weight ratio is 1:2. The second drying temperature is 60°C, the second drying time is 12h, and a modified hydrodechlorination catalyst is obtained. The mass fraction of phosphorus in the modified hydrodechlorination catalyst in the total weight of the catalyst is 0.4%.

[0097] Prepare 30wt% 1,2,4-trichlorobenzene toluene solution, use hydrogen as the reaction gas, and control the reaction space velocity to 2h -1, the reaction temperature was 160°C, the hydrogen / 1,2,4-trichlorobenzene molar ratio was 30, and the 1,2,4-trichlorobenzene solution and hydrogen were subjected to hydrogenation reaction in a catalyst bed of a fixed bed containing 5g of modified hydrodechlorination catalyst to obtain a dechlorinated product. The conversion rate of 1,2,4-trichlorobenzene was 90.4%, and the product selectivities were 74.3% for m-dichlorobenzene, 9.5% for p-dichlorobenzene, 12.8% for o-dichlorobenzene, 3.1% for chlorobenzene, and 0.3% for benzene.

[0098] Comparative Example 1 (No Ligand Protecting Agent Modification)

[0099] The catalyst was prepared and tested according to the same method as in Example 1, except that the modified precursor was not treated with a ligand protecting agent.

[0100] The conversion rate of 1,2,4-trichlorobenzene was 93.1%, and the product selectivities were 23.3% for m-dichlorobenzene, 24.7% for p-dichlorobenzene, 43.6% for o-dichlorobenzene, 6.3% for chlorobenzene, and 2.1% for benzene.

[0101] Example 2 (Al2O3 as carrier)

[0102] The catalyst was prepared and tested according to the same method as in Example 1, except that Al2O3 was used as the carrier.

[0103] The conversion rate of 1,2,4-trichlorobenzene was 93.1%, and the product selectivities were 71.2% for m-dichlorobenzene, 8.9% for p-dichlorobenzene, 10.1% for o-dichlorobenzene, 6.9% for chlorobenzene, and 2.9% for benzene.

[0104] Example 3 (ZSM-5 molecular sieve as carrier)

[0105] The catalyst was prepared and tested according to the same method as in Example 1, except that ZSM-5 molecular sieve was used as the carrier.

[0106] The conversion rate of 1,2,4-trichlorobenzene was 90.7%, and the product selectivities were 70.1% for m-dichlorobenzene, 9.7% for p-dichlorobenzene, 13.1% for o-dichlorobenzene, 6.9% for chlorobenzene, and 0.2% for benzene.

[0107] Example 4 (Al2O3 and SiO2 mixture as carrier)

[0108] The catalyst was prepared and tested according to the same method as in Example 1, except that a mixture of Al2O3 and SiO2 (70 wt% Al2O3) was used as the support.

[0109] The conversion rate of 1,2,4-trichlorobenzene was 90.1%, and the product selectivities were 70.3% for m-dichlorobenzene, 9.4% for p-dichlorobenzene, 11.1% for o-dichlorobenzene, 6.9% for chlorobenzene, and 2.3% for benzene.

[0110] Example 5-10

[0111] Based on Example 1, the impregnation time, the first drying temperature and the first drying time in step 1 were changed, and the catalyst performance was evaluated as follows:

[0112]

[0113] Examples 11-20

[0114] Based on Example 1, the first solid-liquid ratio, metal precursor and metal loading in step 1 were changed, and the catalyst performance was evaluated as follows:

[0115]

[0116] Examples 21-26

[0117] Based on Example 1, the reducing gas and gas space velocity in step 2 were changed, and the catalyst performance was evaluated as follows:

[0118]

[0119] Examples 27-31

[0120] Based on Example 1, the reduction temperature, heating rate and reduction time in step 2 were changed, and the catalyst performance was evaluated as follows:

[0121]

[0122] Examples 32-35

[0123] Based on Example 1, the second solid-liquid ratio, the second drying temperature and the second drying time in step 3 were changed, and the catalyst performance was evaluated as follows:

[0124]

[0125] Examples 36-41

[0126] Based on Example 1, the type of phosphorus-containing ligand, the type of solvent, the loading amount of phosphorus-containing ligand and the concentration of phosphorus-containing ligand protection solution in step 3 were changed, and the catalyst performance was evaluated as follows:

[0127]

[0128] Examples 42-46

[0129] Based on Example 1, 1,2,4-trichlorobenzene was replaced with other polychlorobenzenes, and the catalyst performance was evaluated as follows:

[0130]

[0131] The contents of the present invention are not limited to the contents of the embodiments of the present invention.

[0132] The structure and implementation methods of the present invention are described in this article using specific examples, and the description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A hydrodechlorination catalyst comprising an active metal supported on a carrier, wherein the catalyst is modified with a phosphorus-containing ligand protective agent, and the phosphorus-containing ligand protective agent has the following general formula: Ar n -X-R 3-n (1) in, X represents P or P(O); Ar represents C 6-20 Aryl or -OC 6-20 Aryl; R stands for H, C 1-20 Alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, -OC 3-20 Cycloalkyl, -OC 1-20 Alkyl or -OC 2-20 alkenyl; n represents 1 or 2.

2. The catalyst according to claim 1, wherein Ar represents C 6-12 Aryl or -OC 6-12 Aryl; or Ar represents C 6-10 Aryl or -OC 6-10 Ar represents C6 aryl or -O-C6 aryl; Ar represents phenyl, tolyl, xylyl, mesityl, biphenyl or naphthyl; or R stands for H, C 1-12 Alkyl, C 3-16 Cycloalkyl, C 2-12 Alkenyl, -OC 3-16 Cycloalkyl, -OC 1-12 Alkyl or -OC 2-12 alkenyl; or R represents H, C 1-10 Alkyl, C 3-12 Cycloalkyl, C 2-10 Alkenyl, -OC 3-12 Cycloalkyl, -OC 1-10 Alkyl or -OC 2-10 alkenyl; or R represents H, C 1-4 Alkyl, C 4-10 Cycloalkyl, C 2-6 Alkenyl, -OC 4-12 Cycloalkyl, -OC 1-4 Alkyl or -OC 2-6 or R represents H, methyl, -O-methyl, ethyl, -O-ethyl, n-propyl, -O-n-propyl, isopropyl, -O-isopropyl, n-butyl, -O-n-butyl, isobutyl, -O-isobutyl, tert-butyl, -O-tert-butyl, cyclopropyl, -O-cyclopropyl, cyclobutyl, -O-cyclobutyl, cyclopentyl, -O-cyclopentyl, cyclohexyl, -O-cyclohexyl, vinyl, -O-vinyl, propenyl, -O-propenyl, butenyl or -O-butenyl; or The carrier is selected from one or more of activated carbon, zeolite, Al2O3, CeO2, SiO2, ZrO2, TiO2; or The active metal includes one or more of Pd, Pt, Ru, Fe, Co, Cu, Ni and Rh; or The mass fraction of the active metal is 0.1-20 wt %, such as 0.2-15 wt %, 0.5-10 wt %, based on the total weight of the catalyst; or Based on the total weight of the catalyst, the mass fraction of the phosphorus-containing ligand is 0.05-10 wt %, such as 0.1-8 wt %, 0.2-4 wt %.

3. A method for preparing a hydrodechlorination catalyst, the method comprising the following steps: (1) impregnating the support in an active metal precursor solution and drying to obtain a catalyst precursor; (2) subjecting the precursor to a reduction treatment to obtain a reduced catalyst precursor; as well as (3) mixing the reduced catalyst precursor and the phosphorus-containing ligand protective agent, and drying to obtain a hydrodechlorination catalyst, The phosphorus-containing ligand protective agent has the following general formula: Ar n -X-R 3-n (1) Wherein, X represents P or P(O); Ar represents C 6-20 Aryl or -OC 6-20 Aryl; R stands for H, C 1-20 Alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, -OC 3-20 Cycloalkyl, -OC 1-20 Alkyl or -OC 2-20 alkenyl; n represents 1 or 2.

4. The method of claim 1, wherein: Ar represents C 6-12 Aryl or -OC 6-12 Aryl; or Ar represents C 6-10 Aryl or -OC 6-10 Ar represents C6 aryl or -O-C6 aryl; Ar represents phenyl, tolyl, xylyl, mesityl, biphenyl or naphthyl; or R stands for H, C 1-12 Alkyl, C 3-16 Cycloalkyl, C 2-12 Alkenyl, -OC 3-16 Cycloalkyl, -OC 1-12 Alkyl or -OC 2-12 alkenyl; or R represents H, C 1-10 Alkyl, C 3-12 Cycloalkyl, C 2-10 Alkenyl, -OC 3-12 Cycloalkyl, -OC 1-10 Alkyl or -OC 2-10 alkenyl; or R represents H, C 1-4 Alkyl, C 4-10 Cycloalkyl, C 2-6 Alkenyl, -OC 4-12 Cycloalkyl, -OC 1-4 Alkyl or -OC 2-6 or R represents H, methyl, -O-methyl, ethyl, -O-ethyl, n-propyl, -O-n-propyl, isopropyl, -O-isopropyl, n-butyl, -O-n-butyl, isobutyl, -O-isobutyl, tert-butyl, -O-tert-butyl, cyclopropyl, -O-cyclopropyl, cyclobutyl, -O-cyclobutyl, cyclopentyl, -O-cyclopentyl, cyclohexyl, -O-cyclohexyl, vinyl, -O-vinyl, propenyl, -O-propenyl, butenyl or -O-butenyl; or The carrier is selected from one or more of activated carbon, zeolite, Al2O3, CeO2, SiO2, ZrO2, TiO2; or The active metal includes one or more of Pd, Pt, Ru, Fe, Co, Cu, Ni and Rh; or The mass fraction of the active metal is 0.1-20 wt %, such as 0.2-15 wt %, 0.5-10 wt %, based on the total weight of the catalyst; or Based on the total weight of the catalyst, the mass fraction of the phosphorus-containing ligand is 0.05-10 wt %, such as 0.1-8 wt %, 0.2-4 wt %.

5. The method of claim 3, wherein: In the above step (2), the precursor can be reduced by chemical reduction (such as sodium borohydride, hydrazine hydrate, etc.) and gas reduction, preferably gas reduction; or The gas comprises a reducing gas or a gas stream comprising a reducing gas; or The reducing gas is selected from H2, CO, CH4 or a combination thereof.

6. The method of claim 3, wherein: The reduction is carried out under heating conditions; or The catalyst is reduced at a heating rate of 0.5-30°C / min (e.g., 1-15°C / min) to the reduction temperature, the reduction temperature is 100-600°C (e.g., 150-550°C, 200-450°C), the reduction time is 0.5-10 hours (e.g., 1-5 hours, 2-4 hours), and the mass space velocity of the gas is 0.01-10h - (e.g. 0.05-5h -1 , 0.1-4h -1 , 0.5-3h -1 , 1-2h -1 ).

7. The method of claim 3, wherein: In the step (3), the drying temperature is 40-200° C. (eg, 50-150° C., 50-120° C., 50-80° C.), and the second drying time is 1-72 hours (eg, 4-24 hours).

8. A method for selective hydrodechlorination of polychlorinated benzenes, comprising the following steps: (1) providing the hydrodechlorination catalyst according to claim 1; as well as (2) Using the catalyst to selectively hydrodechlorinate polychlorinated benzenes.

9. The method of claim 8, wherein: The polychlorinated benzenes include one or more of dichlorobenzene (e.g., 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene), trichlorobenzene (e.g., 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene), tetrachlorobenzene (e.g., 1,2,3,4-tetrachlorobenzene, 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene), pentachlorobenzene, and hexachlorobenzene; preferably, the polychlorinated benzene is trichlorobenzene (e.g., 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene or 1,3,5-trichlorobenzene).

10. The method of claim 8, wherein: The products formed by the selective dechlorination hydrogenation include dichlorobenzenes, preferably meta-dichlorobenzene.

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