Catalyst for preparing succinic acid by hydroprocessing maleic acid in aqueous phase and preparation and use thereof

Abstract

The application discloses a catalyst for preparing succinic acid by hydrogenation of maleic acid in water phase and a preparation method and application thereof. The catalyst comprises a carrier and an active metal, the carrier is a titanium dioxide carrier containing an additive, and the additive is at least one selected from La, Ga, Re, Mo, In, Ni and Mn. When the catalyst is used for preparing succinic acid by hydrogenation of maleic acid in water phase, the catalyst has the advantages of high succinic acid yield and good stability.

Description

TECHNICAL FIELD

[0001] The application relates to a maleic acid aqueous-phase hydrogenation catalyst for preparing succinic acid as well as preparation and application thereof, and belongs to the technical field of catalysts. BACKGROUND

[0002] Succinic acid is an important organic chemical raw material and intermediate, is widely used in medicine, food, chemical industry and many other fields, is the main raw material of biodegradable plastic polybutylene succinate (PBS), has huge potential market demand, and is considered to be one of the most promising bio-refining products in the future.

[0003] Preparation methods of succinic acid mainly include electrochemical synthesis, biological fermentation and catalytic hydrogenation. Among them, the catalytic hydrogenation method has the advantages of high conversion rate, high product purity, high yield, no obvious side reaction, green environmental protection and the like, and is the most widely used industrial synthesis method at present.

[0004] The catalytic hydrogenation method for preparing succinic acid can be divided into a non-aqueous phase method and an aqueous phase method. The non-aqueous phase method is to prepare succinic acid by catalytic hydrogenation under organic solvent or solvent-free conditions. It includes directly hydrogenating maleic acid to obtain succinic acid, or using maleic anhydride as a reactant, catalytically hydrogenating maleic anhydride to obtain succinic anhydride, and then hydrolyzing the succinic anhydride to obtain succinic acid. CN111841551A discloses a method for preparing succinic anhydride by using tetrahydrofuran as a solvent, and reacting maleic anhydride with hydrogen under the action of a catalyst. In the process, an organic solvent is used, the solvent consumption is large, the production cost is high, and the environment is greatly harmed. Meanwhile, the prepared succinic anhydride needs to be distilled to remove the solvent, and then further hydrolyzed to obtain succinic acid, so that the process flow is relatively complex, and unnecessary product loss is caused. The solvent-free method has a slow reaction rate and low selectivity of the target product, and there are few related reports.

[0005] The aqueous phase method is to prepare succinic acid by hydrogenating maleic anhydride or maleic acid under the action of a certain catalytic system and using water as a solvent. The existence of maleic acid and succinic acid in the aqueous solution causes the solution to have strong acidity (pH < 3), and the influence of the hot acid solution on the stability of the catalyst under the reaction conditions cannot be ignored. Therefore, the preparation of an acid-resistant catalyst is a research focus. CN101844976B discloses a method for preparing succinic acid by hydrogenating one or more of maleic anhydride, fumaric acid and maleic acid, using SiO2, ZrO2, AC, TiO2 or SiC as a carrier, and an active component selected from transition metals such as Fe, Co, Ni, Pd, Pt, Ru, Ir and the like. However, the stability of the catalyst is not investigated in the method, the problem of easy loss of the active component under the condition of hot acid cannot be ignored, and the stability of the catalyst under long-term running conditions needs to be solved urgently.

[0006] Currently, to improve the acid resistance and stability of the catalyst, the main research methods reported include carbon layer wrapping on the surface of the catalyst. Among them, CN106861702A discloses a preparation method of Cu-Ni / Al2O3@C catalyst for directly synthesizing succinic acid by hydrogenation of maleic anhydride in aqueous phase. In which, maleic anhydride is first hydrolyzed to obtain maleic acid, and then hydrogenation is carried out to obtain succinic acid. However, the main component of the catalyst carrier is amphoteric compound Al2O3. In this acidic reaction system, the carrier is prone to change in properties. At the same time, the carbon layer coating further increases the diffusion resistance and reduces the reaction rate. CN103191767B also adopts the same idea to prepare an acid-resistant catalyst coated with N-doped carbon material on the carrier γ-Al2O3. Similarly, the γ-Al2O3 carrier is prone to change in properties under the reaction conditions. At the same time, the uneven coating of the carbon layer also easily leads to the loss of the carrier γ-alumina and the deactivation of the catalyst.

[0007] On the other hand, the preparation idea of acid-resistant catalyst also includes using inert carriers. CN111330580B and CN111330581A disclose a catalyst for preparing succinic acid by hydrogenation of maleic acid in aqueous phase and its application. Activated carbon, α-alumina, silicon dioxide or silicon carbide are used as carriers, and the interaction between the inert carrier and the active component is enhanced by pretreatment or addition of additives to the surface of the carrier, thereby reducing the loss of active components and improving the stability of the catalyst. However, even after pretreatment and addition of additives, the binding force between the active component and the inert carrier is still weak. Under long-term running conditions, the loss of active components is still a problem. At the same time, activated carbon materials have a rich pore structure, and under the same loading conditions, the active component is easily attached to the inside of the pores, and the contact between the reactants and the active component may be limited by the pore structure, resulting in low catalytic activity. In addition, the catalyst preparation process is complex and difficult to scale up. CN102430404A uses activated carbon or silicon dioxide as a carrier to prepare a Ru-loaded acid-resistant catalyst for the hydrogenation of maleic acid to synthesize succinic acid, which also has the problem of weak binding force between the inert carrier and the active component. CN112979455A discloses a method for preparing succinic acid by hydrolysis and then hydrogenation of maleic anhydride, which uses carbon materials as carriers, including carbon microspheres, activated carbon, and water-resistant honeycomb activated carbon, which also has the problems of poor combination of inert carriers and active components and large diffusion resistance. CN107473954A discloses a green production method for preparing succinic acid by hydrogenation of at least one of maleic anhydride, maleic acid and fumaric acid, which uses CMK-3 mesoporous carbon, Y-MCM-41 mesoporous molecular sieve, M41S mesoporous silica and FDU-15 mesoporous resin as carrier materials. Among them, the carbon material and the silica material have the problem of weak combination with the active component, the instability of the molecular sieve carrier in the aqueous phase, and the low strength of the resin carrier, which limits the further popularization and use of such catalysts.

[0008] In summary, the water phase hydrogenation to prepare succinic acid can avoid the use of organic solvents, reduce environmental hazards. At the same time, the product succinic acid can be separated by cooling crystallization, simple operation. But in this process, the strong corrosion of hot acid solution under heating conditions, easy to cause the change of catalyst properties, active component loss. Therefore, it is urgent to develop a high activity, acid-resistant, water phase hydrogenation of succinic acid catalyst for large-scale production, so as to produce succinic acid with low cost, low energy consumption and low pollution. SUMMARY

[0009] In view of the technical problems existing in the prior art, the present application provides a high activity and high stability catalytic agent for preparing succinic acid from maleic acid in water phase and its preparation and application. The catalytic agent has the advantages of high succinic acid yield and good stability when used for preparing succinic acid from maleic acid in water phase.

[0010] The first aspect of the present application provides a catalytic agent for preparing succinic acid from maleic acid in water phase, wherein the catalytic agent comprises a carrier and an active metal, the carrier is a titanium dioxide carrier containing an auxiliary agent, and the auxiliary agent is selected from at least one of La, Ga, Re, Mo, In, Ni and Mn, preferably at least one of La, Ga and Ni.

[0011] Further, the carrier is a titanium dioxide carrier containing an auxiliary agent, and the auxiliary agent accounts for 0.01% to 1.0% of the mass of TiO2 in the carrier in terms of oxide, preferably 0.2% to 1.0%.

[0012] Further, the number of surface hydroxyl groups per unit area of the carrier is 5 to 15 (×10 mmol / m 2 ).

[0013] Further, the carrier is a non-molded body (i.e. powder), and the average particle size is 6 to 30 μm. The carrier can also be made into a molded body. The powder can be made into a molded body of appropriate size according to actual needs by using conventional molding methods, and the average particle size of the powder before molding is 6 to 30 μm.

[0014] Further, the active metal is selected from at least one of Pd, Pt, Ru, Rh and Ir. The content of the active metal accounts for 0.1wt% to 2.0wt% of the mass of TiO2 in the carrier.

[0015] Further, in the catalytic agent, the crystal form of the carrier is anatase.

[0016] Further, the specific surface area of the catalytic agent is 10 to 40 m 2 / g.

[0017] The second aspect of the present application provides a preparation method of the above-mentioned catalytic agent, comprising:

[0018] (1) reacting a solution A containing titanium and an auxiliary agent with a solution B containing a precipitant and a surfactant;

[0019] (2) filtering, washing, drying, and steam heat treating the slurry obtained in step (1) to obtain a carrier;

[0020] (3) impregnating the carrier obtained in step (2) with a solution containing an active metal component, and drying and calcining the impregnated material;

[0021] (4) reducing the material obtained in step (3) to obtain the catalyst.

[0022] Further, in step (1), the solution A containing titanium and an auxiliary agent can use a soluble titanium salt as the titanium source and a soluble auxiliary metal salt as the auxiliary agent source. The soluble titanium salt is preferably at least one of titanyl sulfate and titanyl nitrate. The soluble auxiliary metal salt can be at least one of a nitrate salt, a sulfate salt, and a chloride salt.

[0023] Further, in step (1), the solution A containing titanium and an auxiliary agent can have a Ti concentration of 1.5 to 2.5 mol / L, and / or the auxiliary agent can be added in an amount of 0.01% to 1.0% of the titanium source by mass as TiO2, preferably 0.2% to 1.0%.

[0024] Further, in step (1), the solution B containing a precipitant and a surfactant can use at least one of urea and hexamethylenetetramine as the precipitant and at least one of dodecylbenzenesulfonic acid, anionic polyacrylamide (molecular weight: 12 to 20 million), and polyethylene glycol (molecular weight: 400 to 8000) as the surfactant. Further, in step (1), the solution B containing a precipitant and a surfactant can have a precipitant concentration of 2 to 4 mol / L. Further, in step (1), the surfactant can be added in an amount of 0.5 to 3.0% by mass of the titanium in solution A as TiO2.

[0025] Further, in step (1), the solution A and the solution B can be reacted in a forward addition or a reverse addition. In step (1), the reaction temperature can be 75 to 95°C, the reaction time can be 2 to 6 hours, and the reaction end point pH can be 1.0 to 3.0.

[0026] Further, in step (1), the solution A and the solution B can also be reacted in a parallel flow. Further, in this case, the reaction temperature can be 75 to 95°C, the reaction time can be 2 to 6 hours, and the reaction pH can be 1.0 to 3.0.

[0027] Further, in step (2), the filtering and washing are performed by using conventional methods. The washing is performed by using water. Further, in step (2), the drying conditions are as follows: the drying temperature is 50-100℃, and the drying time is 2-14h.

[0028] Further, in step (2), the water vapor treatment is continuous flow water vapor treatment, and the process of increasing the temperature to the water vapor treatment temperature is performed in an inert gas atmosphere. The water vapor treatment conditions are as follows: the water vapor treatment temperature is 450-700℃, the treatment time is 2-6h, the water vapor feed volume space velocity is 0.05-2.0h -1 .

[0029] Further, in step (2), during the temperature increasing process, the inert gas is preferably N2 and / or Ar.

[0030] Further, in step (2), the water vapor treatment can also contain inert gas (such as N2 and / or Ar) when the water vapor is fed, wherein the inert gas accounts for less than 50% of the volume of the water vapor.

[0031] Further, the carrier obtained in step (2) is a powder, and the average particle size is 6-30μm.

[0032] Further, in step (3), the method for impregnating the carrier obtained in step (2) with the solution containing the active metal component can use the equal volume impregnation method, the excess impregnation method, etc. The active metal source can use at least one of soluble metal salts such as chlorides, nitrates, etc.

[0033] Further, in step (3), the drying conditions are as follows: the drying temperature is 80-120℃, and the drying time is 2-14h.

[0034] Further, in step (3), the calcination conditions are as follows: the calcination temperature is 450-700℃, and the calcination time is 2-4h.

[0035] Further, in step (4), the reduction is performed in a hydrogen-containing atmosphere, preferably, the reducing gas is a mixture of hydrogen and inert gas, wherein the hydrogen accounts for 5-20% of the volume of the mixed gas. The inert gas is, for example, argon, nitrogen. The reduction conditions are as follows: the reduction temperature is 500-650℃, and the reduction time is 30min-120min.

[0036] The third aspect of the present application provides an application of the above-mentioned catalyst in the preparation of succinic acid by the water phase hydrogenation of maleic acid.

[0037] Further, the application includes: in the presence of hydrogen, the aqueous solution of maleic acid is contacted with the catalyst to obtain a product.

[0038] Further, the reaction can be carried out in a closed high-pressure reaction kettle. After the reaction is completed, the solid catalyst is recovered by hot filtration, the filtrate is cooled and crystallized to obtain the solid succinic acid, and the remaining liquid is recycled.

[0039] Further, the concentration of the maleic acid aqueous solution is 5wt%-30wt%.

[0040] Further, the catalyst dosage is 0.5wt%-5wt% of the total mass of the maleic acid aqueous solution.

[0041] Further, the reaction conditions are as follows: the hydrogen pressure is 0.7MPa-4MPa, the reaction temperature is 60℃-120℃, and the reaction time is 1h-6h.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] (1) The catalyst of the present application uses a titanium dioxide carrier containing an additive, especially a larger number of surface hydroxyl groups per unit area, which is conducive to the high dispersion and stable adhesion of the active metal component on the carrier surface, not only inhibiting the loss of the active metal component, but also further improving the hydrogenation activity and selectivity of the catalyst.

[0044] (2) In the preparation process of the catalyst carrier of the present application, water vapor treatment is used to carbonize the residual organic components in the dried precursor, and the carbonized components and water vapor undergo a water gas shift reaction to generate reducing gases H2 and CO, which is conducive to the formation of oxygen vacancies in TiO2. Among them, the addition of the additive in the precursor can serve as an active component for the water gas shift reaction, promoting the generation of reducing gases, thereby facilitating the formation of oxygen vacancies on the TiO2 carrier, increasing the number of surface hydroxyl groups on the carrier, and improving the interaction between the active metal and the carrier.

[0045] In the preparation process of the catalyst carrier of the present application, the additive is introduced into the TiO2-based carrier before water vapor treatment, which can further optimize the coordination environment of the hydrogenation active component, and is conducive to the high dispersion and stable adhesion of the hydrogenation active metal component on the carrier surface. Through the above synergistic effect, not only the loss of the active metal component is inhibited, but also the hydrogenation activity and selectivity of the catalyst are further improved. In addition, the aqueous solution containing a precipitating agent and a surfactant is reacted with the solution containing titanium and the additive, wherein the surfactant as an important component for dispersion and surface structure control can prevent the agglomeration of active components. In addition, the surfactant as an organic component can first undergo carbonization and then undergo a water gas shift reaction in the subsequent water vapor treatment process, forming a reducing atmosphere, thereby facilitating the increase in the number of hydroxyl groups on TiO2.

[0046] (3) The catalyst of the present application has high hydrogenation activity and selectivity in the preparation of succinic acid by hydrogenation of maleic acid in water phase, and can realize maleic acid conversion rate of 99.9% or above and succinic acid yield of 99.5% or above under mild reaction conditions, and can be used repeatedly and still has high succinic acid yield. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 Particle size distribution graph of the carrier in Example 1;

[0048] Figure 2 N2 adsorption-desorption isotherm of Catalyst 1 in Example 1;

[0049] Figure 3 XRD spectrum of Catalyst 1 before and after the cycle reaction in Example 1;

[0050] Figure 4 XRD spectrum of Catalyst 5 before and after the cycle reaction in Comparative Example 1;

[0051] Figure 5 Particle size distribution graph of the carrier in Comparative Example 3;

[0052] Figure 6 XRD spectrum of Catalyst 9 in Comparative Example 5. DETAILED DESCRIPTION

[0053] The technical solutions of the present application will be described in detail below in combination with examples, but the present application is not limited to these examples. Unless otherwise specified, the raw materials in the examples of the present application are purchased through commercial channels.

[0054] In the present application, the surface hydroxyl quantity per unit area of the carrier is analyzed as follows: 0.3 g of the carrier is dissolved in 50 mL of a standard NaOH solution with a concentration of 0.1000 mol / L, stirred for 1 h, and then subjected to acid-base titration with a standard HNO3 solution with a concentration of 0.1000 mol / L, using neutral red as an indicator. When the titration end point is reached, the color of the solution changes from yellow to red. According to the amount of acid required for titration, the hydroxyl quantity per unit area σ can be preliminarily calculated:

[0055] σ = (C1V1-C2V2) / Sm

[0056] In the formula, σ is the surface hydroxyl quantity per unit area, mol / m 2 ; C1 is the concentration of the alkali solution, mol / L; V1 is the volume of the alkali solution, L; C2 is the concentration of the acid solution for titration, mol / L; V2 is the volume of the acid solution used for titration to the end point, L; S is the specific surface area of TiO2, m 2 / g; and m is the mass of TiO2, g.

[0057] In the present application, the particle size distribution is analyzed by BT-9300ST laser particle size distribution instrument (Dandong Bitai Instrument Co., Ltd.).

[0058] In the present application, the N2 adsorption-desorption isotherm of the sample is tested by a specific surface analyzer Tri Star II Plus of Micromeritics Company, USA. Before testing, the sample is vacuum degassed at 150 DEG C for 12 h, and the specific surface area is calculated by BET method.

[0059] In the present application, XRD characterization is performed by a D8 Advance X-ray diffractometer of Bruker Company, Germany (Cu K alpha, lambda = 0.15406 nm, scanning range is 5-70 DEG, step length is 0.02 DEG).

[0060] Example 1

[0061] Preparation of catalyst 1:

[0062] (1) 2 mol of titanyl sulfate, 0.005 mol of La(NO)3.6H2O are added to 1 L of deionized water, and A liquid is obtained after stirring uniformly; 2 mol of urea, 1 g of dodecylbenzenesulfonic acid are added to 0.5 L of deionized water, and B liquid is obtained after stirring uniformly; 20 mL of bottom water is added to a reaction container, and A liquid and B liquid are subjected to parallel flow reaction, and stirring is continuously performed. The reaction temperature is 90 DEG C, the reaction pH is 2.5, and the reaction is ended after 2 h.

[0063] (2) The slurry prepared in step (1) is filtered, washed, and dried in a 100 DEG C oven for 8 h. 5 g of the dried precursor is heated to 500 DEG C under the condition that N2 is continuously introduced at a speed of 200 mL / min, and is treated by water vapor for 2 h, wherein the volume space velocity of water vapor is 2 h -1 , and a carrier is obtained. The number of surface hydroxyl groups per unit area of the carrier treated by water vapor is determined, and the results are shown in Table 1.

[0064] (3) The metal active component Pd is loaded by using an excess impregnation method. First, palladium chloride is dissolved in a hydrochloric acid solution to prepare a chloropalladic acid solution (the concentration of Pd is 58 wt%), 13.80 mg of the chloropalladic acid solution is added to 20 mL of deionized water, and 4 g of the carrier prepared in step (2) is poured into the mixture, and stirring is performed at room temperature for 4 h, and then filtration is performed, the filter cake is dried at 100 DEG C for 8 h, and calcination is performed at 500 DEG C for 3 h to prepare a catalyst. The loading amount of the active component Pd is 0.2 wt% based on TiO2.

[0065] (4) The material prepared in step (3) is placed in a gas atmosphere furnace for reduction, 5% H2 / Ar is used as a carrier gas, and reduction is performed at 500 DEG C for 60 min to obtain catalyst 1.

[0066] The particle size distribution diagram of the carrier is as follows: Figure 1 As shown in Table 1, the particle size distribution is relatively uniform, ranging from 1.938 to 57.36 μm, with average particle sizes as shown in Table 1. The N2 physical adsorption-desorption isotherms of catalyst 1 are shown in Table 1. Figure 2 As shown, the gas adsorption capacity increases significantly when the relative pressure is greater than 0.8, indicating that it is a mesoporous material. The BET fitting results are shown in Table 1. The XRD patterns are shown below. Figure 3 As shown, it exhibits anatase-type structure.

[0067] Catalyst 1 Evaluation:

[0068] Reaction 1: Weigh 2.5g of catalyst and add it to 100g of 30wt% maleic acid aqueous solution. After replacing the air with N2 five times, hydrogen gas is introduced to replace the N2 three times, and finally 2MPa H2 is introduced. After thorough mixing with stirring, the hydrogenation reaction is carried out at 100℃. After 4 hours of reaction, heating is stopped, and the reaction is complete. Once the reactor temperature has cooled to room temperature, the mixture is removed and placed in an oven to heat to 60℃. After the solution is homogeneous, it is filtered while hot to obtain the catalyst. The filtrate is cooled and crystallized at 5℃, and the precipitated solid is succinic acid. The remaining liquid is recycled to the next cycle. The conversion rate of maleic acid and the yield of succinic acid during the cycle are shown in Table 2. The XRD pattern of catalyst 1 after eight cycles is shown in Table 2. Figure 3 As shown, no change in crystal form was observed, indicating that the catalyst is stable.

[0069] Example 2

[0070] Preparation of catalyst 2:

[0071] (1) Add 2 mol of titanium oxynitrate and 0.015 mol of Ni(NO)2 to 1 L of deionized water and stir until homogeneous to obtain solution A; add 2 mol of hexamethylenetetramine and 2 g of polyacrylamide (molecular weight 12 million) to 0.5 L of deionized water and stir until homogeneous to obtain solution B; slowly add solution B dropwise to solution A to carry out the reaction at a temperature of 90 °C, with the final pH being 2.0, and stop the reaction after 6 h.

[0072] (2) The slurry prepared in step (1) is filtered, washed, and dried in an oven at 100℃ for 8 hours. 5g of the dried precursor is taken and heated to 700℃ under continuous N2 flow at 100mL / min, and treated with steam for 2 hours, wherein the steam volume hourly space velocity is 0.5h⁻¹. -1 The carrier was obtained. The number of surface hydroxyl groups per unit area of ​​the sample after water vapor treatment was determined, and the results are shown in Table 1.

[0073] (3) Excess impregnation method was used to load the metal active component Ir. First, 57.14 mg of iridium chloride hexahydrate solution (the concentration of Ir was 35 wt%) was added to 20 mL of deionized water, and after being mixed uniformly, 4 g of the carrier was poured into it, stirred at room temperature for 4 h, and then filtered. The filter cake was dried at 100 °C for 8 h and calcined at 575 °C for 3 h to prepare the catalyst. The loading of the active component Ir was 0.5 wt% based on TiO2.

[0074] (4) The material prepared in step (3) was placed in an atmosphere furnace for reduction, and 5% H2 / Ar was used as the carrier gas. The reduction was carried out at 450 °C for 120 min to obtain catalyst 2.

[0075] The particle size analysis of the carrier was carried out, and the results are shown in Table 1. The average particle size was 24 μm. The fitting results of the BET characterization of catalyst 2 are shown in Table 1. The specific surface area was 16.84 m2 / g. 2

[0076] Evaluation of catalyst 2:

[0077] Reaction 2: 2.5 g of the catalyst was weighed and added to 100 g of a 30 wt% aqueous solution of maleic acid. After five times of N2 replacement of air, N2 was replaced by hydrogen three times, and finally 1 MPa of H2 was filled. After starting the stirring and mixing, the hydrogenation reaction was carried out at 120 °C. After 6 h of reaction, the heating was stopped, and the reaction was completed. After the kettle temperature dropped to room temperature, the kettle mixture was taken out and heated to 60 °C in an oven. After the solution was uniformly heated, it was filtered while hot to obtain the catalyst. The filtrate was cooled and crystallized at 5 °C, and the solid obtained was maleic acid. The remaining liquid was reused in the next cycle. The conversion rate of maleic acid and the yield of succinic acid in the cycle are shown in Table 2.

[0078] Example 3

[0079] Preparation of catalyst 3:

[0080] (1) 2 mol of titanium oxide nitrate and 0.008 mol of GaCl3 were added to 1 L of deionized water, and after being stirred uniformly, A liquid was obtained. 2 mol of hexamethylenetetramine and 4 g of polyethylene glycol-400 were added to 0.5 L of deionized water, and after being stirred uniformly, B liquid was obtained. B liquid was slowly added to A liquid for reaction. The reaction temperature was 95 °C, the reaction endpoint pH was 2.0, and the reaction was completed after 4 h of reaction.

[0081] (2) The slurry prepared in step (1) was filtered, washed, and dried in a 100 °C oven for 8 h. 5 g of the dried precursor was taken, and under the condition of continuous N2 flow of 400 mL / min, the temperature was raised to 450 °C, and water vapor treatment was carried out for 6 h. The water vapor space velocity was 1 h -1 ​The carrier was obtained. The number of surface hydroxyl groups per unit area of the sample after water vapor treatment was determined, and the results are shown in Table 1.

[0082] (3) The metal active component Ir was loaded by excess impregnation. First, 57.14 mg of chloroiridic acid solution (35 wt% of Ir) was added to 20 mL of deionized water, and 4 g of the carrier was poured into the mixture after uniform mixing. After stirring at room temperature for 4 h, the filter cake was dried at 100 °C for 8 h and calcined at 575 °C for 3 h to obtain the catalyst. The loading of the active component Ir was 0.5 wt% based on TiO2.

[0083] (4) The material prepared in step (3) was placed in a gas atmosphere furnace for reduction, and 5% H2 / Ar was used as the carrier gas. The catalyst 2 was obtained after reduction at 450 °C for 120 min.

[0084] The particle size analysis of the carrier is shown in Table 1, and the average particle size is 27.3 μm. The fitting results of the BET characterization of the catalyst 2 are shown in Table 1, and the specific surface area is 14.92 m 2 / g.

[0085] Catalyst 3 evaluation:

[0086] Reaction 3: 2.5 g of the catalyst was added to 100 g of a 30 wt% maleic acid aqueous solution. After five times of N2 replacement of air, three times of H2 replacement of N2, and finally 1.5 MPa of H2 was filled. After starting the stirring and mixing, the hydrogenation reaction was carried out at 100 °C. After 4 h of reaction, the heating was stopped, and the reaction was completed. After the kettle temperature decreased to room temperature, the mixture in the kettle was taken out and heated to 60 °C in an oven. After the solution was uniformly heated, the catalyst was filtered while hot. The filtrate was cooled and crystallized at 5 °C, and the solid obtained was maleic acid. The remaining liquid was reused in the next cycle. The conversion rate of maleic acid and the yield of succinic acid in the cycle are shown in Table 2.

[0087] Example 4:

[0088] Preparation of catalyst 4:

[0089] (1) 2 mol of titanium oxynitrate and 0.008 mol of La(NO)3·6H2O were added to 1 L of deionized water, and stirred uniformly to obtain A liquid; 2 mol of hexamethylenetetramine and 1.5 g of polyacrylamide (molecular weight 12 million) were added to 0.5 L of deionized water, and stirred uniformly to obtain B liquid; A liquid was slowly added to B liquid for reaction, the reaction temperature was 75 °C, the final pH was 1.5, and the reaction was completed after 6 h of reaction.

[0090] (2) The slurry prepared in step (1) is filtered, washed, and dried in an oven at 100°C for 8h. 5g of the dried precursor is heated to 600°C under a continuous flow of N2 at 400mL / min, and treated with water vapor for 4h, wherein the water vapor space velocity is 2h -1 -1. The support is obtained. The number of surface hydroxyl groups per unit area of the sample after water vapor treatment is determined, and the results are shown in Table 1.

[0091] (3) The metal active component Ru is loaded by excess impregnation. First, 40mg of a ruthenium chloride solution (Ru concentration of 20wt%) is added to 20mL of deionized water, and 4g of the support is poured into the mixture after uniform mixing. After stirring at room temperature for 4h, the mixture is filtered, the filter cake is dried at 100°C for 8h, and the catalyst is prepared by calcination at 700°C for 3h. The Ru active component loading is 0.2wt% based on Ti02.

[0092] (4) The material prepared in step (3) is reduced in a gas furnace, using 5% H2 / Ar as the carrier gas, at 500°C for 60min, to obtain catalyst 4.

[0093] The particle size analysis of the support is shown in Table 1, and the average particle size is 13.2μm. The fitting results of the catalyst 2 characterization BET are shown in Table 1, and the specific surface area is 34.92m 2 / g.

[0094] Catalyst 4 evaluation:

[0095] Reaction 4: 1g of catalyst is added to a solution containing 100g of 10wt% maleic acid. After five times of air replacement with N2, three times of N2 replacement with hydrogen, and finally 4MPa of H2 is filled. After stirring and mixing, the hydrogenation reaction is carried out at 60°C. After 6h of reaction, the heating is stopped, and the reaction is completed. After the kettle temperature drops to room temperature, the mixture in the kettle is taken out and heated to 60°C in an oven. After the solution is uniform, it is filtered while hot to obtain the catalyst. The filtrate is cooled to 5°C to crystallize, and the solid obtained is maleic acid. The remaining liquid is reused in the next cycle. The conversion rate of maleic acid and the yield of succinic acid during the cycle are shown in Table 2.

[0096] Comparative Example 1

[0097] A catalyst with Ce02 as the support is prepared to investigate the stability of other catalysts in this system. Catalyst 5 is prepared:

[0098] (1), (2) Compared with Example 2, cerium nitrate is used instead of titanium oxide nitrate to prepare a Ce02 support doped with the additive Ni, wherein the additive Ni doping amount is 0.7%.

[0099] (3) The active component Ir was loaded by excess impregnation method. The specific method was the same as that of Example 2. The loading amount of the active component Ir was 0.5 wt% based on CeO2.

[0100] (4) The material prepared in step (3) was placed in a gas atmosphere furnace for reduction, 5% H2 / Ar was used as the carrier gas, and reduction was carried out at 450°C for 120 min to obtain catalyst 5.

[0101] Evaluation of catalyst 5:

[0102] Reaction 5: The catalyst evaluation method was the same as that of Example 2. The conversion of maleic acid and the yield of succinic acid during the cycle process are shown in Table 2. The XRD spectrum of the catalyst after eight cycles is shown in Figure 3 Compared with the catalyst before the reaction, the crystal structure of CeO2 was destroyed. This result shows that CeO2 does not have long-term stability in this system.

[0103] Comparative Example 2

[0104] Compared with Example 1, the carrier was not subjected to steam treatment.

[0105] Preparation of catalyst 6:

[0106] (1) The same as Example 1.

[0107] (2) The slurry prepared in step (1) was filtered, washed, and dried in an oven at 100°C for 8 h, and then transferred to a muffle furnace for calcination at 500°C for 2 h. After cooling, it was taken out to obtain the carrier. The number of surface hydroxyl groups per unit area of the carrier after calcination was analyzed, and the results are shown in Table 1.

[0108] (3) The active component Pd was loaded by excess impregnation method. The specific method was the same as that of Example 1. The loading amount of the active component Pd was 0.2 wt% based on TiO2.

[0109] (4) The material prepared in step (3) was placed in a gas atmosphere furnace for reduction, 5% H2 / Ar was used as the carrier gas, and reduction was carried out at 500°C for 60 min to obtain catalyst 6.

[0110] The carrier was subjected to particle size analysis, and catalyst 6 was subjected to BET fitting. The results are shown in Table 1.

[0111] Evaluation of catalyst 6:

[0112] The evaluation conditions were the same as those of Example 1. The conversion of maleic acid and the yield of succinic acid during the cycle process are shown in Table 2.

[0113] Comparative Example 3

[0114] Comparing with Example 1, the uniform precipitation method was not used in the support preparation process, but the chemical precipitation method was used, in which ammonia was used as the precipitant.

[0115] Preparation of Catalyst 7:

[0116] (1) 2 mol of titanyl sulfate, 0.005 mol of La(N0)3-6H2O were added into 1 L of deionized water, and after stirring uniformly, A liquid was obtained; 2 mol of ammonia, 1 g of dodecyl benzene sulfonic acid were added into 0.5 L of deionized water, and after stirring uniformly, B liquid was obtained; 20 mL of bottom water was added into a reaction container, and A liquid and B liquid were subjected to co-current reaction, the reaction temperature was 90°C, the reaction pH was 7, and the reaction was ended after 4 h.

[0117] (2) The slurry prepared in step (1) was filtered, washed, and dried in a 100°C oven for 8 h. The material after drying was subjected to water vapor treatment, and the specific method was the same as that in Example 1. The support after water vapor treatment was analyzed for the number of surface hydroxyl groups per unit area, and the results are shown in Table 1.

[0118] (3) The excess impregnation method was used to load the metal active component Pd, and the specific method was the same as that in Example 1. The active component Pd loading was 0.2 wt% based on TiO2.

[0119] (4) The material prepared in step (3) was placed in a gas atmosphere furnace for reduction, 5% H2 / Ar was used as the carrier gas, and the reduction was carried out at 500°C for 60 min to obtain catalyst 7.

[0120] The support was analyzed for particle size, and the results are shown in Table 1. Using ammonia as the precipitant, the average particle size of the finally prepared sample can reach 125 μm, and the particle size distribution graph is shown in Figure 5 The BET fitting results of catalyst 7 are shown in Table 1.

[0121] Evaluation of Catalyst 7:

[0122] Reaction 7: The evaluation conditions were the same as in Example 1, and the conversion of maleic acid and the yield of succinic acid during the cycle process are shown in Table 2.

[0123] Comparative Example 4

[0124] Comparing with Example 4, the adjuvant was loaded after the support preparation.

[0125] Preparation of Catalyst 8:

[0126] (1) 2 mol of titanyl nitrate was added into 1 L of deionized water, and after stirring to be uniform, A liquid was obtained; 2 mol of hexamethylenetetramine and 1.5 g of polyacrylamide (molecular weight 12 million) were added into 0.5 L of deionized water, and after stirring to be uniform, B liquid was obtained; A liquid was slowly added into B liquid for reaction, the reaction temperature was 75 ℃, the reaction end point pH was 1.5, and the reaction was ended after 6 h of reaction.

[0127] (2) The slurry prepared in step (1) was filtered, washed, dried, and treated with water vapor, and the specific method was the same as in Example 4.

[0128] (3) The active component Ru and the auxiliary component La were loaded by an excess impregnation method. First, 40 mg of a ruthenium chloride solution (Ru concentration was 20 wt%) and 65.5 mg of La(NO)3·6H2O were added into 20 mL of deionized water, and after being mixed uniformly, 4 g of the carrier was poured into the mixture, and after stirring at room temperature for 4 h, filtration was performed, the filter cake was dried at 100 ℃ for 8 h, and the catalyst was prepared by calcining at 700 ℃ for 3 h. The active component Ru loading was 0.2 wt% based on TiO2, and the auxiliary component La accounted for 0.816 wt% of the mass of TiO2 based on the oxide.

[0129] (4) The material prepared in step (3) was reduced in an atmosphere furnace, 5% H2 / Ar was used as the carrier gas, and reduction was performed at 500 ℃ for 60 min to obtain catalyst 8.

[0130] The particle size analysis of the carrier and the BET fitting of the catalyst were performed, and the results are shown in Table 1.

[0131] Catalyst 8 evaluation:

[0132] Reaction 8: The same as in Example 4, and the conversion of maleic acid and the yield of succinic acid during the cycle are shown in Table 2.

[0133] Comparative Example 5

[0134] Compared with Example 1, the water vapor treatment temperature was increased.

[0135] Preparation of catalyst 9:

[0136] (1) The same as in Example 1.

[0137] (2) The slurry prepared in step (1) was filtered, washed, and dried in a 100 ℃ oven for 8 h. 5 g of the dried precursor was heated to 950 ℃ under the condition that 200 mL / min of N2 was continuously introduced, and water vapor treatment was performed for 2 h, wherein the water vapor space velocity was 2 h -1 The surface hydroxyl number of the carrier after water vapor treatment was determined, and the results are shown in Table 1.

[0138] (3) The active component was impregnated under the same conditions as in Example 1.

[0139] (4) The material prepared in step (3) was reduced in an atmosphere furnace using 5% H2 / Ar as carrier gas at 500°C for 60 min to obtain catalyst 9.

[0140] The particle size analysis of the support is shown in Table 1. The XRD analysis of catalyst 9 is shown in Table 1. Figure 5 As can be seen from the figure, the catalyst 9 prepared is in rutile phase.

[0141] Evaluation of catalyst 9:

[0142] Reaction 9: Same as Example 1. The conversion of maleic acid and the yield of succinic acid during the cycle are shown in Table 2.

[0143] Table 1 Analysis of properties of different catalysts

[0144]

[0145] D50 (μm) represents the median particle size, i.e. the particle size corresponding to 50% of the cumulative particle size distribution of a sample. 50

[0146] Table 2 Reaction performance of catalysts in cycle experiments

[0147]

[0148] The above detailed the specific embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, the technical features of the present application can be combined in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed range of the present application, and all belong to the protection scope of the present application.​

Claims

1. A catalyst for the hydro genation of maleic acid in aqueous phase to succinic acid, characterized in that: The catalyst comprises a carrier and an active metal, the carrier is a titania carrier containing an auxiliary agent selected from at least one of La, Ga, Re, Mo, In, Ni and Mn, and the active metal is selected from at least one of Pd, Pt, Ru, Rh and Ir; The catalyst is prepared by the following method: (1) reacting a solution A containing titanium and an auxiliary agent with an aqueous solution B containing a precipitant and a surfactant; (2) filtering, washing, drying and steam treating the slurry obtained in step (1) to obtain the carrier; (3) impregnating the carrier obtained in step (2) with a solution containing an active metal component, and drying and calcining the impregnated material; (4) reducing the material prepared in step (3) to obtain the catalyst; The steam treatment temperature is 450-700°C.

2. The catalyst of claim 1, wherein: The auxiliary agent is selected from at least one of La, Ga and Ni.

3. The catalyst of claim 1, wherein: The carrier is a titania carrier containing an auxiliary agent, and the auxiliary agent accounts for 0.01-1.0% of the mass of TiO2 in the carrier in terms of oxide.

4. The catalyst of claim 3, wherein: The auxiliary agent accounts for 0.2-1.0% of the mass of TiO2 in the carrier in terms of oxide.

5. The catalyst of claim 1, wherein: The number of surface hydroxyl groups per unit area of the carrier is 5 to 15 (x 10 mmol / m 2 ).

6. The catalyst of claim 1, wherein: The content of the active metal accounts for 0.1-2.0% of the mass of TiO2 in the carrier.

7. The catalyst of claim 1, wherein: The specific surface area of the catalyst is 10-40 m 2 / g.

8. A process for the preparation of a catalyst according to any one of claims 1 to 7, characterized in that: It comprises: (1) reacting a solution A containing titanium and an auxiliary agent with an aqueous solution B containing a precipitant and a surfactant; (2) filtering, washing, drying and steam treating the slurry obtained in step (1) to obtain the carrier; (3) impregnating the carrier obtained in step (2) with a solution containing an active metal component, and drying and calcining the impregnated material; (4) reducing the material prepared in step (3) to obtain the catalyst; The steam treatment temperature is 450-700°C.

9. The method of claim 8, wherein: In step (1), the solution A containing titanium and an auxiliary agent uses a soluble titanium salt as the titanium source and a soluble auxiliary metal salt as the auxiliary agent source; the soluble titanium salt is at least one of titanyl sulfate and titanyl nitrate; the soluble auxiliary metal salt is at least one of a nitrate, a sulfate and a chloride.

10. The method according to claim 8 or 9, characterized in that: In step (1), the solution A containing titanium and an auxiliary agent has a Ti concentration of 1.5-2.5 mol / L, and / or the auxiliary agent is added in an amount of 0.01-1.0% of the mass of the titanium source in terms of TiO2.

11. The method of claim 10, wherein: The auxiliary agent is added in an amount of 0.2-1.0% of the mass of the titanium source in terms of TiO2.

12. The method of claim 8, wherein: In step (1), the aqueous solution B containing a precipitant and a surfactant uses at least one of urea and hexamethylenetetramine as the precipitant and at least one of dodecylbenzenesulfonic acid, anionic polyacrylamide and polyethylene glycol as the surfactant; In step (1), the aqueous solution B containing a precipitant and a surfactant has a precipitant concentration of 2-4 mol / L; In step (1), the surfactant is added in an amount of 0.5-3.0% of the mass of titanium in solution A in terms of TiO2.

13. The method of claim 8, wherein: In step (1), the reaction mode of A liquid and B liquid is forward addition or reverse addition; wherein, the reaction temperature is 75℃-95℃, the reaction time is 2h-6h, and the reaction end point pH value is 1.0-3.

0.

14. The method of claim 8, wherein: In step (1), the reaction mode of A liquid and B liquid is parallel flow; wherein, the reaction temperature is 75℃-95℃, the reaction time is 2h-6h, and the reaction pH value is 1.0-3.

0.

15. The method of claim 8, wherein: In step (2), the drying condition is as follows: the drying temperature is 50℃-100℃, and the drying time is 2h-14h.

16. The method of claim 8, wherein: In step (2), the water vapor treatment is continuous flow water vapor treatment, the process of heating to the water vapor treatment temperature, the dry solid is in an inert gas atmosphere, and the water vapor treatment conditions are as follows: the treatment time is 2 h to 6 h, the water vapor feed volume space velocity is 0.05 to 2.0 h -1 .

17. The method of claim 8, wherein: In step (3), the drying condition is as follows: the drying temperature is 80℃-120℃, and the drying time is 2h-14h. In step (3), the calcination condition is as follows: the calcination temperature is 450℃-700℃, and the calcination time is 2h-4h.

18. The method of claim 8, wherein: In step (4), the reduction is carried out in a hydrogen-containing atmosphere, and the reduction gas is a mixture of hydrogen and inert gas, wherein the hydrogen accounts for 5%-20% of the volume of the mixed gas; the reduction condition is as follows: the reduction temperature is 500℃-650℃, and the reduction time is 30min-120min.

19. Use of the catalyst of any one of claims 1-7 or the catalyst prepared according to the method of any one of claims 8-18 in the preparation of succinic acid by the aqueous-phase hydrogenation of maleic acid.

20. The use according to claim 19, characterized in that: The use comprises: in the presence of hydrogen, the aqueous solution of maleic acid is contacted with the catalyst to obtain a product; The concentration of the aqueous solution of maleic acid is 5wt%-30wt%; The catalyst is used in an amount of 0.5wt%-5wt% of the total mass of the aqueous solution of maleic acid; The reaction condition is as follows: the hydrogen pressure is 0.7MPa-4MPa, the reaction temperature is 60℃-120℃, and the reaction time is 1h-6h.

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