CN115703065B

CN115703065B - Low temperature dehydrogenation method for hydrogenation aromatic compound

Info

Publication number: CN115703065B
Application number: CN202110945966.2A
Authority: CN
Inventors: 马安; 王丽涛; 李金�; 雷雨柔; 刘银东; 宋彬; 许倩; 韩爽; 杨行; 张博
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2021-08-17
Filing date: 2021-08-17
Publication date: 2024-05-07
Anticipated expiration: 2041-08-17
Also published as: CN115703065A

Abstract

The invention discloses a low-temperature dehydrogenation method for hydrogenating aromatic compounds, which comprises the following steps: adding a hydrogenated aromatic-rich feedstock and a dehydrogenation catalyst to a dehydrogenation reactor at a temperature of: 240-420 ℃, pressure: 0.01-2 MPa, mass airspeed: carrying out dehydrogenation reaction under the condition that the molar ratio of hydrogen to oil is 0-1.0 in 1-5 h ^‑1; the dehydrogenation catalyst is a non-sulfided catalyst and comprises an active component, a metal auxiliary agent, chloride ions and a carrier; the active component at least contains noble metal component of VIII family, accounting for 0.1-3% of the total weight of dehydrogenation catalyst; the chloride ion accounts for 0.3 to 1.2 percent of the total weight of the dehydrogenation catalyst; the metal auxiliary agent at least contains alkali metal and/or alkaline earth metal, and accounts for 0.3-0.9% of the total weight of the dehydrogenation catalyst; the mole ratio of the metal auxiliary agent to the chlorine atom is 0-1.5; the carrier is mainly gamma-Al ₂O₃. The dehydrogenation catalyst has simple composition, easy preparation and mild reaction conditions. The reaction system has high low-temperature dehydrogenation reaction activity and selectivity.

Description

Low temperature dehydrogenation method for hydrogenation aromatic compound

Technical Field

The invention belongs to the technical field of liquid organic compound hydrogen storage and catalytic materials, and particularly relates to a low-temperature dehydrogenation method for hydrogenating aromatic compounds.

Background

Hydrogen has wide application in various industries of national economy. The hydrogen can be used as petrochemical raw material, is a clean, efficient, safe and sustainable new energy, and can solve the two problems of energy and environment faced by human in technology, so the hydrogen energy is considered to be the most ideal energy in the world and is also the long-term strategic energy of human.

The related technology of hydrogen energy comprises large-scale preparation, storage and transportation and efficient utilization of hydrogen. The normal temperature and normal pressure storage and transportation of hydrogen are key bottlenecks restricting the wide range of applications. The development of an efficient liquid hydrogen storage material to realize the reversible storage and release of hydrogen becomes an important link for solving the whole hydrogen industry chain.

The liquid hydrogen storage material is hydrogenated in a hydrogen-rich place to obtain a hydride which is also liquid, and hydrogen is released through dehydrogenation. The dehydrogenation process is a heterogeneous reaction with strong heat absorption, and the reaction process is reversible, and the dehydrogenation process must be performed under the conditions of low pressure and high temperature in terms of dynamics and thermodynamics, however, the catalyst is easy to accumulate carbon and crack at high temperature, so that the activity of the catalyst and the selectivity of main products are reduced, and the stability of the dehydrogenation reaction process and the service life of the catalyst are further influenced. Therefore, the key to the large-scale application of the organic liquid hydride hydrogen storage technology is to develop a dehydrogenation catalyst with high selectivity at low temperature.

The dehydrogenation catalyst commonly used is a supported metal catalyst, the active component of which is Pt, pd, rh, ni, co or the like. There are also catalysts whose dehydrogenation activity can be further enhanced by the addition of a second metal component such as Ni, mo, W, re, rh, pd, ir, sn or the like. The support is typically alumina or a modifying component of alumina.

Most commercially available activated alumina has too many surface hydroxyl groups and too much acidity. The alumina is used as a carrier for preparing a dehydrogenation catalyst, and carbon is easy to accumulate on the surface of the catalyst in the reaction process, so that the catalyst is deactivated rapidly. In addition, the precursor of the active component often contains acidic chloride ions, and the competitive adsorbent adopted in the impregnation process of the active component also often adopts hydrochloric acid solution, so that the chloride ions are introduced, the acidity of the catalyst is increased, and the acid strength of the surface of the catalyst is further enhanced. The catalyst has moderate acidity and too strong acidity, can have isomerization and even hydrocracking effects, generates byproducts and reduces the dehydrogenation selectivity. Too weak acidity, the activity of the catalyst may decrease, affecting the dehydrogenation conversion.

Therefore, proper deacidification treatment of the catalyst is required to meet the use requirements of the catalyst. Some directly adopt non-acidic substances other than alumina as carriers, such as active carbon, molecular sieves and the like. Some of the catalyst uses a precursor of a non-chloride ion active component, and other catalyst uses a chlorine washing mode to wash away residual chloride ions in the catalyst. Some have employed the introduction of alkaline or alkaline earth metals into the catalyst to weaken the acidity of the support surface. Some modify the carrier in alkaline environments and load the active ingredient in alkaline environments.

CN109701610a relates to a modified dehydrogenation catalyst, a preparation method and uses thereof, the catalyst comprises two active components, component (a) is one or more of platinum metals, component (b) is one or more of In, cs, ga, ge, sr, the carrier is one or more of alumina, molecular sieve and silica, and the modification is nitrogen modification of the molecular sieve carrier. The organic liquid hydrogen storage material is selected from one or more of methylcyclohexane, cyclohexane, tetrahydronaphthalene, decalin, perhydroazoethylcarbazole and perhydrocarbazole. The embodiment shows that the carrier is molecular sieve, the initial conversion rate of the synthesized catalyst is 82% at 320 deg.c, and the initial conversion rate of cyclohexane, tetrahydronaphthalene, decalin and methylcyclohexane is 79% after 100 hr reaction, and the coking rate is 0.4%.

CN105582917B discloses a method for dechlorinating noble metal dehydrogenation catalyst, specifically, introducing aqueous ammonia solution with mass concentration of 1% -10% into a catalyst bed layer to perform hydrothermal dechlorination treatment, and introducing deionized water to perform hydrothermal deamination treatment after the hydrothermal dechlorination treatment is finished, so as to obtain the dechlorinated noble metal dehydrogenation catalyst. The method can remove Cl ^- in the noble metal dehydrogenation catalyst to below 0.15wt%, avoid the aggregation growth of Pt particles at high temperature, and reduce energy consumption.

CN110252422a discloses a method for washing chloride ion in catalyst, the method uses washing liquid containing ammonium salt, or ammonium salt and reducing agent to wash semi-finished catalyst after loading active component for 3-20 times, and then roasting after drying, so that the catalyst whose chloride ion content is below 10ppm can be obtained.

Several patents such as CN112452340A, CN112371193A, CN112316977a disclose methods for washing chloride ions with deionized water, all of which are repeated washing, and the solution is washed to neutrality, i.e. all acidic substances are washed away.

CN111889094a provides a hydrogen production catalyst for dehydrogenation of organic hydrogen storage compound, which comprises noble metal active component, alumina and modified metal oxide, wherein the modified metal oxide is titanium oxide and/or zirconium oxide, i.e. the carrier is a mixture of alumina and modified metal oxide. The dehydrogenation catalyst has better dehydrogenation activity and selectivity. In the embodiment, the dehydrogenation conversion rate can reach 77% at 350 ℃ and the pressure is 1MPa, and the selectivity is 95.8%.

CN110882703a discloses a cycloalkane dehydrogenation catalyst containing alkaline earth metal and a preparation method thereof, pt is used as an active metal component, sn is used as an auxiliary component, and a carrier is an alumina carrier containing alkaline earth metal, sulfur and titanium. The alkaline earth metal-Ti-Al skeleton structure formed in the process of preparing the carrier in situ can obviously improve the characteristic of single acidity of alumina on the surface of the carrier, obviously reduce the acidity of the alumina carrier, improve the carbon deposit resistance of the catalyst and improve the high-temperature activity and stability of the catalyst. Preferably used for preparing benzene by cyclohexane dehydrogenation or toluene by methylcyclohexane dehydrogenation. The embodiment shows that the catalyst is used for cyclohexane dehydrogenation, the reaction temperature is 430 ℃, the pressure is 1.0MPa, the conversion rate is 92% at most and the selectivity is 84% when the space velocity is 2h ^-1.

U.S. patent No. 3531543 discloses the dehydrogenation of hydrocarbons using a catalyst consisting of platinum, tin and a neutral metal oxide support. The preferred support is an oxide material whose inherent acidity has been substantially neutralized by an alkali metal or alkaline earth metal component. Furthermore, as the alkali metal content increases, the acidity of these aluminas correspondingly decreases. The support of this patent is preferably a non-acidic lithium oxide-containing alumina. The catalysts of this patent are preferably made of halogen-free compounds. However, halogen-containing compounds can also be used to make the catalyst, provided that residual halogen is effectively removed from the final catalyst composite.

U.S. patent No. 3745112 discloses a catalyst for hydrocarbon reforming which is composed of a platinum group component, a tin component, a halogen component and a porous support material. The patent also discloses that platinum-tin-alkali or alkaline earth metal complexes are particularly effective hydrocarbon dehydrogenation catalysts. The addition of an alkali or alkaline earth metal component to the dehydrogenation catalyst composite of this patent minimizes, if not eliminates, the amount of halogen so as to minimize or neutralize the acidity of the alumina and halogen components; this acidity can promote undesirable hydrocarbon cracking and isomerization side reactions in the industrial dehydrogenation process.

U.S. patent No. 3892657 discloses that indium is a good promoter for platinum group containing catalysts when the atomic ratio of indium to platinum is from about 0.1:1 to about 1:1. The patent also discloses the addition of a group IVA component selected from germanium, tin and lead to an indium containing acidic catalyst which may be used in reforming applications. The acid catalyst is composed of platinum group component, IVA group component, indium component, halogen component and porous carrier material. For reforming applications, the acidic catalyst contains up to about 3.5% by weight of halogen, while for isomerization and cracking applications, the acidic catalyst contains up to about 10% by weight of halogen. In the dehydrogenation catalysts of this patent, the halogen content is kept to the lowest possible value, about 0.1% by weight, despite the addition of alkali or alkaline earth metal components.

U.S. patent No. 3909451 discloses a novel process for making a dehydrogenation catalyst comprising a platinum component, a tin component and an alkali or alkaline earth metal component. This patent discloses in example V a composition of platinum, tin and potassium containing less than 0.2% by weight of chlorine in the combined state.

U.S. Pat. Nos. 4329258 and 4363721 disclose a catalyst comprising a refractory oxide-mineral support of the platinum group metal, tin, an alkali or alkaline earth metal and a compound halogen. The atomic ratio of alkali metal or alkaline earth metal to platinum group metal in the catalysts of these patents is from 0.2 to 10. The patentees found that the addition of parts per million of an alkali or alkaline earth metal component to a catalyst containing platinum group metals, tin and halogen helped increase the yield of C +5 during reforming.

British patent 1499297 discloses a dehydrogenation catalyst comprising platinum and at least one of the elements gallium indium thallium, and alkali metals, in particular lithium and potassium, using alumina as a support. The catalysts of this patent also contain halogen in an amount of from 0.01 to 0.1% by weight. The halogen content is deliberately reduced to within such a low weight percentage in order to increase the selectivity and stability of the catalyst.

The patent CN 111686718A treats the support in an alkaline solution and loads the active component in an alkaline environment to increase the steric hindrance and metal loading rate of the metal loading compound in the impregnation solution, prevent agglomeration of metal particles, and improve the dispersibility and uniformity of the catalyst active component. The result shows that the conversion rate can reach 99.5% and the selectivity can reach more than 99% at 430-450 ℃.

In summary, the compounds involved in dehydrogenation mainly include low alkanes (e.g., propane, butane) and cycloalkanes and hydrides of heteroatom-containing aromatic hydrocarbons. In order to reduce the acidity of the catalyst surface and to increase the stability of the dehydrogenation catalyst, researchers have generally taken two measures, one of which is to completely remove or to keep as low as possible the chlorine, generally less than 0.1% by weight, and always less than 0.2% by weight, calculated on an elemental basis. Secondly, the mode of doping alkali metal or alkaline earth metal in the preparation process of the carrier plays a role in weakening acid on the surface of the catalyst.

In the prior art, the dehydrogenation catalysts known above consist of a platinum group component, a IVA group component and an alkali metal or alkaline earth metal component, the atomic ratio of alkali metal or alkaline earth metal component to platinum group component being greater than 10, while the halogen component has been completely excluded or kept to the lowest possible level.

Disclosure of Invention

The invention aims to overcome the defect that the existing dehydrogenation catalyst is low in conversion rate and selectivity, and particularly the conversion rate is low under the low-temperature condition. The invention provides a low-temperature dehydrogenation method of a hydrogenated aromatic compound, which has high reaction activity and high dehydrogenation conversion rate of the hydrogenated aromatic compound, and the selectivity reaches 100 percent.

The technical scheme adopted by the invention is as follows:

The invention provides a low-temperature dehydrogenation method of a hydrogenated aromatic compound, which comprises the steps of adding a raw material rich in the hydrogenated aromatic compound and a dehydrogenation catalyst into a dehydrogenation reactor, wherein the temperature is as follows: 240-420 ℃, pressure: 0.01-2 MPa, mass airspeed: and (3) carrying out dehydrogenation reaction under the condition that the molar ratio of hydrogen to oil is 0-1.0 in 1-5 h ^-1. The dehydrogenation catalyst is a non-sulfided catalyst and comprises an active component, a metal auxiliary agent, chloride ions and a carrier. The active component at least contains noble metal component of VIII family, accounting for 0.1-3% of the total weight of dehydrogenation catalyst. The chloride ion accounts for 0.3 to 1.2 percent of the total weight of the dehydrogenation catalyst. The metal auxiliary agent at least contains alkali metal and/or alkaline earth metal, accounting for 0.3-0.9% of the total weight of the dehydrogenation catalyst, and the mole ratio of the metal auxiliary agent to chlorine atoms is 0-1.5. The carrier is mainly gamma-Al ₂O₃.

Preferably, the active component accounts for 0.1 to 0.6 percent of the total weight of the low-temperature dehydrogenation catalyst; the chloride ion accounts for 0.35 to 0.9 percent of the total weight of the low-temperature dehydrogenation catalyst; the mole ratio of the metal auxiliary agent to the chlorine atom is 0.4-1.2.

The active component of the invention comprises at least one of Pt, pd and Rh.

Preferably, the active component is Pt.

The carrier is mainly gamma-Al ₂O₃, the content of gamma-Al ₂O₃ in the carrier is more than 50wt percent, preferably 100wt percent, and GrO ₂,CeO₂, molecular sieve, active carbon and the like can be further contained in the carrier.

The present invention is not particularly limited to the shape of the carrier, and may be at least one of a sphere, a bar, a column, and a clover.

The invention is not particularly limited, and the specific surface area is 180-240 m ²/g, pore volume is 0.5-2.0 mL/g, and pore diameter is 2-20 nm.

In the above technical scheme, the raw material rich in hydrogenated aromatic compounds refers to a product obtained by hydrogenating the aromatic compounds to obtain complete hydrogenation or partial hydrogenation.

In the technical scheme, the aromatic compound comprises 1-3 ring aromatic hydrocarbon and 1-3 ring heterocyclic aromatic hydrocarbon containing N hetero atoms. The 1-3 cyclic aromatic hydrocarbon may contain 0-3 side chains, the length of which is 1-3 carbon numbers.

The present invention is not limited to the dehydrogenation reaction form, but a fixed bed reaction form is adopted in the present technical scheme.

The dehydrogenation reaction conditions are preferably reaction temperatures: 260-320 ℃, reaction pressure: 0.01-0.5 MPa, mass airspeed: 1-3 h ^-1, and the molar ratio of hydrogen to oil is 0-0.6.

The present invention is not particularly limited to the preparation method of the dehydrogenation catalyst, but preferably adopts the following preparation process:

the preparation method of the dehydrogenation catalyst can comprise the following steps:

S1, preparing a metal salt solution containing active components, and adjusting the pH value to be 0-3 to form an active component impregnation liquid containing chlorine;

S2: mixing the impregnating solution and the carrier, impregnating for 3-6 hours, removing residual solution, drying for 2-6 hours at 120-200 ℃, transferring into a tube furnace, roasting for 4-8 hours at 400-600 ℃, and cooling to obtain a dehydrogenation catalyst precursor-1;

S3: preparing a metal salt solution containing a metal auxiliary agent to form a metal auxiliary agent impregnating solution, mixing the metal auxiliary agent impregnating solution with a dehydrogenation catalyst precursor-1, impregnating for 3-6 hours, drying for 2-6 hours at 120-200 ℃ after removing residual solution, transferring into a tube furnace, and roasting for 3-6 hours at 400-600 ℃ to obtain a dehydrogenation catalyst precursor-2;

s4: and reducing the dehydrogenation catalyst precursor-2 in a hydrogen atmosphere at 300-600 ℃ for 4-8 h to obtain the dehydrogenation catalyst.

The dehydrogenation catalyst of the present invention can also be prepared according to the following steps:

S1, preparing a metal salt solution containing an active component and a metal auxiliary agent, and regulating the pH value to be 0-3 to form a chlorine-containing active component and metal auxiliary agent impregnating solution;

S2: mixing the impregnating solution and the carrier, impregnating for 3-6 hours, removing residual solution, drying for 2-6 hours at 120-200 ℃, transferring into a tube furnace, roasting for 4-8 hours at 400-600 ℃, and cooling to obtain a dehydrogenation catalyst precursor;

S3: reducing the dehydrogenation catalyst precursor in a hydrogen atmosphere at 300-600 ℃ for 4-8 hours to obtain a dehydrogenation catalyst;

s1, preparing a metal salt solution containing a metal auxiliary agent, forming a metal auxiliary agent impregnating solution, mixing the metal auxiliary agent impregnating solution with a carrier, impregnating for 3-6 hours, drying for 2-6 hours at 120-200 ℃ after removing residual solution, transferring into a tube furnace, and roasting for 3-6 hours at 400-600 ℃ to obtain a dehydrogenation catalyst precursor-1;

S2: preparing a metal salt solution containing active components, and adjusting the pH value to be 0-3 to form an active component impregnation liquid containing chlorine;

S3: mixing the active component impregnating solution and the dehydrogenation catalyst precursor-1, impregnating for 3-6 hours, removing residual solution, drying for 2-6 hours at 120-200 ℃, transferring into a tube furnace, roasting for 4-8 hours at 400-600 ℃, and cooling to obtain a dehydrogenation catalyst precursor-2;

In the above technical solution, the active component includes at least one of Pt, pd, rh, preferably Pt, and the metal salt solution of the active component may be one or more of chlorate solution, nitrate solution, and sulfate solution.

In the above technical scheme, the metal salt corresponding to the metal auxiliary agent is at least one of chloride, hydroxide, nitrate, sulfate, citrate and oxalate.

In the above technical scheme, the chlorine in the chlorine-containing impregnating solution can be derived from chlorate solution of the active component, can be derived from chlorine-containing acidic component added in the impregnating solution, and can be derived from metal salt of the metal auxiliary agent.

The impregnated carrier of the invention is finished in a circulating air atmosphere with deionized water being introduced without washing. The mode of carrying deionized water by air is not limited, and the air can pass through normal-temperature deionized water, boiling hot water or HCl solution with a certain concentration, and the air flow airspeed of roasting passing through is 16-20 min ^-1.

The invention does not emphasize the heating mode in the roasting process, but the temperature programming is preferable in the technical scheme, and the heating rate is 2-5 ℃/min.

According to the invention, in the preparation process of the catalyst, the surface acidity of the catalyst can be effectively reduced by reducing the chlorine content of the catalyst, the dehydrogenation conversion rate and selectivity are improved, but chlorine washing conditions are required to be controlled, the moderate or high chlorine ion content is ensured to be at a specific content, the conversion rate is improved to a limited extent, and the low-temperature conversion rate is further improved by introducing a metal auxiliary agent on the basis of dechlorination. On the basis of washing chlorine to a reasonable interval, a certain amount of alkali metal or alkaline earth metal is loaded on the catalyst, so that the low-temperature activity of the catalyst can be further remarkably improved while the selectivity is maintained, and the conversion rate of the compound at each temperature is remarkably improved.

Compared with the prior art, the invention has the following advantages:

(1) The dehydrogenation catalyst disclosed by the invention is simple in composition, easy to control conditions and good in product repeatability, and the surface acidity of the catalyst is improved from two layers by controlling the chloride ion content of the catalyst and adding the metal auxiliary agent for modification;

(2) The dehydrogenation reaction has wide raw material sources and can be industrially prepared in a large scale;

(3) The reaction form can be a fixed bed, and is mature and reliable;

(4) When the dehydrogenation catalyst is used for dehydrogenation of an aromatic compound hydrogenation product, the reaction condition is mild, the conversion rate and the selectivity are high, and the dehydrogenation catalyst shows excellent low-temperature dehydrogenation activity.

Detailed Description

The present invention will be specifically described below by way of examples. It is noted herein that the following examples are given solely for the purpose of illustration and are not to be construed as limiting the scope of the invention, as many insubstantial modifications and variations of the invention will become apparent to those skilled in the art in light of the above disclosure.

Example 1

(1) Catalyst

The carrier adopts a spherical agent, the gamma-Al ₂O₃ content is 98wt%, the specific surface area is 230.4m ²/g, the pore volume is 1.05mL/g, and the pore diameter is 15.2nm. Pt content 0.3wt%, cl content 1.01wt%, K content 0.81wt% and K/Cl molar ratio 0.73.

(2) Catalyst preparation

Sequentially adding 4mL of chloroplatinic acid salt solution with the concentration of 15mg/mL and 8mL of hydrochloric acid solution with the concentration of 80mg/mL into a triangular flask, adding 28mL of deionized water, and adjusting the pH value to be 1 to prepare an impregnating solution. Adding 20g of carrier into the soaking liquid, sealing the triangular bottle mouth with a sealing film, and placing on a shaking table for shaking and soaking for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for roasting is 16min ^-1, deionized water is carried by air and enters a tube furnace, the temperature is programmed, the temperature rising rate is 2 ℃/min, the temperature is raised to 500 ℃ for roasting for 4h, and the catalyst precursor-1 is obtained after cooling. 36mL of potassium nitrate solution with the potassium ion concentration of 13.32mg/mL is prepared, 20g of calcined catalyst precursor-1 is added, the excessive solution is filtered and removed after soaking for 4 hours, the solution is dried at 120 ℃ for 2 hours and then is transferred to a tube furnace again, and the solution is calcined in an air atmosphere at 500 ℃ for 4 hours to obtain catalyst precursor-2. Catalyst precursor-2 was reduced at 500℃under a hydrogen atmosphere for 4h to give catalyst A, the composition data of which are shown in Table 1.

(3) Dehydrogenation reaction process

Dehydrogenation is carried out in a fixed bed reaction system, 10g of prepared catalyst A is filled in a fixed bed reactor, the pressure of a reaction device is set to be 0.1MPa, the mass space velocity is set to be 2h ^-1, the molar ratio of hydrogen to oil is set to be 0.5, the temperature is raised after the raw materials are fed, the temperature is raised from 260 ℃, sampling is carried out every 6h, and the temperature is raised to be 20 ℃ until 400 ℃. The product composition was analyzed by GC-MS, and the conversion of the feedstock dehydrogenation and the selectivity to the target aromatics-full dehydrogenation product were calculated based on the composition. The dehydrogenation conversion performance of the catalyst on hydrogenated aromatic compounds such as benzene, toluene, naphthalene, carbazole and N-ethylcarbazole was evaluated. For several raw materials participating in the evaluation, the reaction difficulty of methylcyclohexane is the greatest from the self-structure, and the influence of the reaction performance of the catalyst and the process conditions on the conversion rate can be reflected, so that only the dehydrogenation conversion rate of methylcyclohexane is illustrated in the examples. The dehydrogenation effect of methylcyclohexane at various temperatures is shown in Table 2.

Comparative example 1

(1) Catalyst

The carrier was the same as in example 1. Pt content 0.3wt%, cl content 0.40wt%, K content 0.75wt% and K/Cl molar ratio 1.71.

(2) Catalyst preparation

Sequentially adding 4mL of chloroplatinic acid salt solution with the concentration of 15mg/mL and 5mL of hydrochloric acid solution with the concentration of 80mg/mL into a triangular flask, adding 27mL of deionized water, and adjusting the pH value to be 1 to prepare an impregnating solution. Adding 20g of carrier into the soaking liquid, sealing the triangular bottle mouth with a sealing film, and placing on a shaking table for shaking and soaking for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for roasting is 16min ^-1, deionized water is carried by air and enters a tube furnace, roasting is carried out for 6h at 500 ℃, and the catalyst precursor-1 is obtained after cooling. 36mL of potassium nitrate solution with the potassium ion concentration of 13.32mg/mL is prepared, poured into 20g of the roasted catalyst precursor-1, soaked for 4 hours, filtered to remove redundant solution, dried at 120 ℃ for 2 hours, transferred into a tube furnace again, and roasted for 4 hours in an air atmosphere at 500 ℃ to obtain the catalyst precursor-2. Catalyst precursor-2 was reduced at 500℃under a hydrogen atmosphere for 4h to give catalyst B, the composition data of which are shown in Table 1.

(3) Dehydrogenation reaction process

The same evaluation method as in example 1 was used, and the results are shown in Table 2.

Comparative example 2

(1) Catalyst

The carrier was the same as in example 1, and had a Pt content of 0.3wt%, a Cl content of 0.60wt%, a K content of 0.0wt% and a K/Cl molar ratio of 0.

(2) Catalyst preparation

Sequentially adding 4mL of chloroplatinic acid salt solution with the concentration of 15mg/mL and 5mL of hydrochloric acid solution with the concentration of 80mg/mL into a triangular flask, adding 27mL of deionized water, and adjusting the pH value to be 1 to prepare an impregnating solution. Adding 20g of carrier into the soaking liquid, sealing the triangular bottle mouth with a sealing film, and placing on a shaking table for shaking and soaking for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for calcination was 16min ^-1, the air carried deionized water was fed into a tube furnace, and calcined at 500℃for 5 hours to obtain catalyst precursor-1, and catalyst precursor-1 was reduced at 500℃under a hydrogen atmosphere for 4 hours to obtain catalyst C, the composition data of which are shown in Table 1.

(3) Dehydrogenation reaction process

The same evaluation method as in example 1 was used, and the evaluation results are shown in Table 2.

Comparative example 3

(1) Carrier body

The carrier was the same as in example 1. Pt content 0.3wt%, cl content 1.3wt%, K content 0.0wt% and K/Cl molar ratio 0.

(2) Catalyst preparation

Sequentially adding 4mL of chloroplatinic acid salt solution with the concentration of 15mg/mL and 5mL of hydrochloric acid solution with the concentration of 80mg/mL into a triangular flask, adding 27mL of deionized water, and adjusting the pH value to be 1 to prepare an impregnating solution. Adding 20g of carrier into the soaking liquid, sealing the triangular bottle mouth with a sealing film, and placing on a shaking table for shaking and soaking for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for roasting is 16min ^-1, the air directly enters a tube furnace, roasting is carried out for 6 hours at 500 ℃ to obtain a catalyst precursor-1, and the catalyst precursor-1 is reduced for 4 hours in a hydrogen atmosphere at 500 ℃ to obtain a catalyst D, wherein the composition data are shown in Table 1.

(3) Dehydrogenation reaction process

Comparative example 4

(1) Catalyst

The same carrier as in example 1 was used. Pt content 0.3wt%, cl content 0.25wt%, K content 0.0wt% and K/Cl molar ratio 0.

(2) Catalyst preparation

Sequentially adding 4mL of chloroplatinic acid salt solution with the concentration of 15mg/mL and 5mL of hydrochloric acid solution with the concentration of 80mg/mL into a triangular flask, adding 18mL of deionized water, and adjusting the pH value to be 1. Configured to impregnate the solution. Adding 20g of carrier into the soaking liquid, sealing the triangular bottle mouth with a sealing film, and placing on a shaking table for shaking and soaking for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for roasting is 16min ^-1, air carries water vapor and enters a tube furnace to be roasted for 6 hours at 500 ℃ to obtain a catalyst precursor-1, the catalyst precursor-1 is reduced for 4 hours in the atmosphere of 500 ℃ hydrogen, and the composition data of the catalyst E are shown in table 1.

(3) Dehydrogenation reaction process

Example 2

(1) Catalyst

The carrier was the same as in example 1. Pt content 0.52wt%, cl content 0.67wt%, K content 0.43wt% and K/Cl molar ratio 0.58.

(2) Catalyst preparation

8ML of chloroplatinic acid salt solution with the concentration of 15mg/mL and 10mL of hydrochloric acid solution with the concentration of 80mg/mL are sequentially added into a triangular flask, 0.414g of potassium nitrate is added, 27mL of deionized water is added, and the pH value is regulated to 0.5, so as to prepare the impregnating solution. Adding 20g of carrier into the soaking liquid, sealing the triangular bottle mouth with a sealing film, and placing on a shaking table for shaking and soaking for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for roasting is 16min ^-1, air carries water vapor molecules to enter a tube furnace, roasting is carried out for 5h at 500 ℃, a catalyst precursor is obtained after cooling, the catalyst precursor is reduced for 4h in a hydrogen atmosphere at 500 ℃, and a catalyst F is obtained, and the composition data of the catalyst F are shown in table 1.

(3) Dehydrogenation reaction process

Example 3

(1) Catalyst

The carrier was the same as in example 1. Pt content 0.3wt%, cl content 0.50wt%, K content 0.40wt% and K/Cl molar ratio 0.73.

(2) Catalyst preparation

0.305G of potassium chloride was added to 36mL of deionized water to prepare a potassium ion impregnation solution. Adding 20g of carrier into the soaking liquid, sealing the triangular bottle mouth with a sealing film, and placing on a shaking table for shaking and soaking for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for roasting is 16min ^-1, the air carries water vapor to enter a tube furnace, roasting is carried out for 4 hours at 500 ℃, and the catalyst precursor-1 is obtained after cooling. 8mL of Pt salt solution with the concentration of 15mg/mL and 10mL of hydrochloric acid solution with the concentration of 80mg/mL are added into a triangular flask, and the pH value is regulated to 0.5. Adding 18mL deionized water to prepare an active component impregnating solution, adding the active component impregnating solution into the catalyst precursor-1, and placing the catalyst precursor on a shaking table for oscillating and impregnating for 4 hours. And taking down the triangular flask, removing redundant impregnating solution, putting the triangular flask into an oven, drying the triangular flask at 120 ℃ for 2 hours, and transferring the triangular flask into a tube furnace for roasting. The air space velocity used for roasting is 16min ^-1, air carries water vapor molecules to enter a tube furnace, programming is carried out, roasting is carried out for 4h at 500 ℃, and the catalyst precursor-2 is obtained after cooling. Catalyst precursor-2 was reduced for 4h at 500℃under a hydrogen atmosphere to give catalyst G, the composition data of which are shown in Table 1.

(3) Dehydrogenation reaction process

Comparative example 5

(1) Catalyst

The same as in example 1.

(2) Catalyst preparation

The same as in example 1

(3) Dehydrogenation reaction process

The dehydrogenation is carried out in a fixed bed reaction system, 10g of prepared catalyst A is filled in a reactor, the pressure of a reaction device is set to be 2.5MPa, the mass space velocity is set to be 2h ^-1, the molar ratio of hydrogen to oil is set to be 1.5, methylcyclohexane is adopted as a raw material, the temperature is raised after the raw material is fed, the temperature is raised from 260 ℃, after sampling is carried out every 6h, the temperature is raised to be 20 ℃ until 400 ℃. The sample is analyzed by GC-MS to analyze the product composition, and the conversion rate of raw material dehydrogenation and the selectivity of target aromatic toluene are calculated according to the composition. The dehydrogenation effect of methylcyclohexane at various temperatures is shown in Table 2.

Example 4

(1) Catalyst

The same as in example 1.

(2) Catalyst preparation

The same as in example 1

(3) Dehydrogenation reaction process

The dehydrogenation and the preparation are carried out in a fixed bed reaction system, 10g of prepared catalyst A is filled in a reactor, the pressure of a reaction device is set to be 0.1MPa, the mass space velocity is set to be 0.5h ^-1, the molar ratio of hydrogen to oil is 0, the reaction is carried out by adopting temporary nitrogen, the raw material of the reaction is methylcyclohexane, the temperature is raised after the raw material is fed, the continuous operation is carried out at 320 ℃, and the sampling is carried out every 12 h. The sample is analyzed by GC-MS to analyze the product composition, and the conversion rate of raw material dehydrogenation and the selectivity of target aromatic toluene are calculated according to the composition. The dehydrogenation effect on methylcyclohexane continuous operation is shown in Table 3.

Example 5

(1) Catalyst

The same as in example 1.

(2) Catalyst preparation

The same as in example 1

(3) Dehydrogenation reaction process

The dehydrogenation and the loading of 10g of the prepared catalyst A in a fixed bed reaction system are carried out, the pressure of a reaction device is set to be 0.1MPa, the mass space velocity is set to be 0.5h ^-1, the molar ratio of hydrogen to oil is set to be 0.5, the raw materials of the reaction are methylcyclohexane, the temperature is raised after the raw materials are fed, the continuous operation is carried out at 320 ℃, and the sampling is carried out every 12 h. The sample is analyzed by GC-MS to analyze the product composition, and the conversion rate of raw material dehydrogenation and the selectivity of target aromatic toluene are calculated according to the composition. The dehydrogenation effect on methylcyclohexane continuous operation is shown in Table 3.

As can be seen from comparative examples 4 and 5, although the initial activity of the reaction was higher under non-hydrogen conditions, the activity was decreased more rapidly in long-period operation, so that the hydrogen conditions were more advantageous for the long-period operation of the catalyst.

The comparison shows that besides the catalyst composition, the process condition selection has great influence on the dehydrogenation conversion rate and the low-pressure high-temperature conversion rate is higher. The catalyst composition and the reaction condition have great influence on the conversion rate under the low-temperature condition, and the temperature becomes a reaction dominant factor under the high-temperature condition, so that the influence of the catalyst composition and the reaction condition is small.

TABLE 1 composition and Properties of the catalysts

TABLE 2 dehydrogenation effect of catalyst on methylcyclohexane

TABLE 3 effect of whether or not hydrogen is present on the long-run operation of dehydrogenation systems

Run time, h	EXAMPLE 4 non-Hydrogen-critical	EXAMPLE 5 hydrogenation
			12	100.00	99.80
100	80.90	99.60

It should be noted that the above examples are only for illustrating the technical solution of the present invention and are not limiting thereof. Although the present invention has been described in detail with reference to the examples given, those skilled in the art can make modifications and equivalents to the technical solutions of the present invention as required, without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A low temperature dehydrogenation process for hydrogenating aromatic compounds, characterized in that a raw material rich in hydrogenated aromatic compounds and a dehydrogenation catalyst are fed into a dehydrogenation reactor at a temperature of: 240-320 ℃, pressure: 0.01-2 MPa, mass airspeed: carrying out dehydrogenation reaction under the condition that the molar ratio of hydrogen to oil is 0-1.0 in 1-5 h ^-1, wherein the molar ratio of hydrogen to oil is not 0; the dehydrogenation catalyst is a non-sulfided catalyst and consists of an active component, a metal auxiliary agent, chloride ions and a carrier; the active component at least contains a noble metal component of a VIII family, and accounts for 0.1-3% of the total weight of the dehydrogenation catalyst; the chloride ions account for 0.3-1.2% of the total weight of the dehydrogenation catalyst; the metal auxiliary agent at least contains alkali metal and/or alkaline earth metal, and accounts for 0.3-0.9% of the total weight of the dehydrogenation catalyst; the molar ratio of the metal auxiliary agent to the chlorine atom is 0-1.5, and the metal auxiliary agent does not contain 0; the content of gamma-Al ₂O₃ in the carrier is more than 50wt%;

The raw material rich in the hydrogenated aromatic compound refers to a product obtained by hydrogenating the aromatic compound to obtain complete hydrogenation or partial hydrogenation;

the active component comprises at least one of Pt, pd and Rh;

The dehydrogenation catalyst is prepared by the following method:

s1: preparing a metal salt solution containing active components, and adjusting the pH value to 0-3 to form an active component impregnation liquid containing chlorine;

S3: preparing a metal salt solution containing a metal auxiliary agent, forming a metal auxiliary agent impregnating solution, mixing the metal auxiliary agent impregnating solution with a dehydrogenation catalyst precursor-1, impregnating for 3-6 hours, drying at 120-200 ℃ for 2-6 hours after removing residual solution, transferring into a tubular furnace, and roasting at 400-600 ℃ for 3-6 hours to obtain a dehydrogenation catalyst precursor-2;

s4: reducing the dehydrogenation catalyst precursor-2 in a hydrogen atmosphere at 300-600 ℃ for 4-8 hours to obtain a dehydrogenation catalyst;

the roasting process of the step S2 and the step S3 is carried out in a circulating air atmosphere containing deionized water; the roasting process is a temperature programming process, and the temperature rising rate is 2-5 ℃/min.

2. The low temperature dehydrogenation process according to claim 1, characterized in that the active component accounts for 0.1 to 0.6% of the total weight of the dehydrogenation catalyst; the chloride ions account for 0.35-0.9% of the total weight of the dehydrogenation catalyst; the molar ratio of the metal auxiliary agent to the chlorine atom is 0.4-1.2; the specific surface area of the carrier is 180-240 m ²/g, the pore volume is 0.5-2.0 mL/g, and the pore diameter is 2-20 nm; the carrier is at least one of spherical, bar-shaped, cylindrical and clover-shaped.

3. The low temperature dehydrogenation process according to claim 1, wherein the active component is Pt; the aromatic compound comprises 1-3 ring aromatic hydrocarbon and 1-3 ring heterocyclic aromatic hydrocarbon containing N hetero atoms; the 1-3 cyclic aromatic hydrocarbon contains 0-3 side chains, and the length of the side chains is 1-3 carbon numbers.

4. The low-temperature dehydrogenation method according to claim 1, wherein the dehydrogenation reaction is carried out at a reaction temperature of 260-320 ℃, a reaction pressure of 0.01-0.5 mpa, a mass space velocity of 1-3 h ^-1, a hydrogen-oil molar ratio of 0-0.6, and no 0.

5. The low temperature dehydrogenation process according to claim 1, wherein the metal salt solution of the active component is at least one of a nitrate solution and a sulfate solution.

6. The low temperature dehydrogenation process according to claim 1, wherein the metal salt solution of the active component is a chloroplatinic acid salt solution.

7. The low temperature dehydrogenation process according to claim 1, wherein the metal salt of the metal promoter is at least one of chloride, nitrate, sulfate, citrate and oxalate.