CN105622385A - Process for preparing adipic acid through cleaning catalytic oxidation of cyclohexanone, catalyst, and catalyst preparation method - Google Patents

Abstract

The clean catalytic oxidation of cyclohexanone to adipic acid, a catalyst and a preparation method of the catalyst disclose a transition metal-modified composite MFI titanium-silicon molecular sieve and a preparation method thereof, as well as a preparation method of adipic acid. Wherein, the mass ratio of the preferential filtering metal salt to the titanium-silicon molecular sieve of the catalyst is (0.01-0.2):1. The preparation process of the catalyst includes the steps of dry ball milling, high temperature roasting and hydrothermal crystallization. The catalyst prepared by the above method is a composite catalyst characterized by highly dispersed transition metal oxides on the surface of the catalyst. The modified composite MFI-type titanium-silicon molecular sieve has high catalytic oxidation activity, and can be recovered and recycled.

Description

Clean and catalytic oxidation of cyclohexanone to adipic acid, catalyst and catalyst preparation method

technical field

The invention belongs to a process for preparing adipic acid by using cyclohexanone as a raw material, a catalyst used therein and a preparation method of the catalyst.

Background technique

Adipic acid is an important chemical raw material, mainly used in the manufacture of nylon-66 fiber, nylon-66 resin and polyurethane foam, and the production of plasticizer dioctyl adipate. In the organic synthesis industry, it is a The basic raw materials of nitrile, hexamethylenediamine and polyester polyols can also be used as raw materials for medicine, pesticides and adhesives. At present, the global production capacity of adipic acid has reached 3.4 million tons per year, and it is increasing year by year, with an annual growth rate of more than 3.36%.

There are three main methods for the synthesis of adipic acid in industry: cyclohexane method, cyclohexene method and phenol method. Among them, cyclohexane method is the main production route, accounting for 86%-93% of the total production capacity, followed by cyclohexene method and phenol method. It can be seen from the production process (as shown in Figure 1 below), that the current three synthesis processes inevitably use concentrated nitric acid to oxidize KA oil (cyclohexanone and cyclohexanol) to prepare adipic acid. Specific operation method: use 50-60% concentrated nitric acid, use metal copper and vanadium as catalysts, and carry out under the conditions of 60-80°C and 0.1-0.9MPa. The reaction is a series reaction, and the total conversion of KA oil during the reaction process is 100%, adipic acid selectivity is about 94%. The production of 1 ton of adipic acid product consumes 1.3 tons of 68% nitric acid, and produces 0.25 tons of N ₂ O, nitric acid vapor and waste acid liquid. Therefore, due to the use of strong oxidizing concentrated nitric acid in this method, the equipment is seriously corroded, and the N ₂ O produced is considered to be one of the causes of global warming and ozone reduction. Pollution; coupled with high energy consumption for denitrification, has been plagued by the development of adipic acid process technology. As a result, the production process of adipic acid synthesized by nitric acid oxidation method cannot meet the current requirements of green, environmental protection, and low-carbon green chemical industry, and is facing a huge challenge of energy saving and emission reduction. At present, the synthesis of adipic acid is still a worldwide technical problem, so the research and development of the green synthesis process of adipic acid has important industrial application significance.

In 1940, Loder first proposed the synthesis of adipic acid by using acetate (Co(OAc) ₂ ) as a catalyst and air oxidation instead of nitric acid oxidation. Later, many scholars improved the homogeneous system. Shimizu et al. reported in (Bulletin of the Chemical Society of Japan, 2003, 76(10): 1993) that acetic acid and a small amount of water were used as solvents to (Co(OAc ) ₂ /(Mn(OAc) ₂ as catalyst, pure oxygen oxidizes cyclohexanone, and at a reaction temperature of 70°C, the conversion rate of cyclohexanone is 100% and the selectivity of adipic acid is 77%. Patent WO01/87815A2 describes the use of nitric acid As an initiator, cobalt nitrate salt is a catalyst to catalyze molecular oxygen oxidation of cyclohexanone to prepare adipic acid technology. Patent CN102746140A describes the oxidation of cyclohexanone by molecular oxygen at a certain temperature and pressure in the presence of solvent, transition metal nitrate catalyst and initiator A method for synthesizing adipic acid. These oxidation processes are all homogeneous reactions, which require necessary reaction solvents and initiators, which are still harmful to the environment, and the reaction and separation processes are complicated, and the process flow is long.

At the same time, the process of preparing adipic acid from cyclohexane is also reported. Patent US4902827 describes the oxidation process of cobalt and zirconium acetate as a catalyst to catalyze cyclohexane, low concentration cyclohexane acetic acid solution, reaction temperature 120 ° C and pressure The condition of 2-3MPa obtains products such as adipic acid, cyclohexanol, cyclohexanone and glutaric acid Sheldon et al. in (Advanced Synthesis & Catalysis, 2004,346(9-10): 1051) reported a method for preparing adipic acid from cyclohexane in an organic solvent using a nitroso free radical initiator (NHPH, TEMPO) and a transition metal salt as a composite catalytic system. , The reaction by-products are similar to those described in the patent US4902827, and there are a large amount of products such as cyclohexanol, cyclohexanone and glutaric acid. Although cyclohexane can be used in one step to adipic acid, the yield of adipic acid is extremely low, and a reaction solvent and initiator are required. Such homogeneous catalysis has separation difficulties and endangers the environment.

Hydrogen peroxide is also used in cyclohexanone and cyclohexene to produce adipic acid. For example, Ye Tianxu et al. reported in (Industrial Catalysis, 2009, 17(7): 46) that 30% hydrogen peroxide was used as oxidant, and alumina was used to immobilize Phosphotungstic acid is used as catalyst, phosphoric acid is used as auxiliary agent, and cyclohexanone is oxidized at 90°C for 7 hours under reflux to obtain adipic acid with a selectivity of nearly 95%. Raja et al reported in (Topics in Catalysis, 2002, 20(1-4): 85) that FeAPO-5 was used as a catalyst, the reaction temperature was 80°C, and after 6h and 20h of reaction, the conversion rate of cyclohexene could be reduced to 38% and 50% respectively. %, adipic acid selectivity can reach 65% and 78% respectively. Although these examples of hydrogen peroxide oxidation can obtain higher yields of the target product, the price of hydrogen peroxide is relatively expensive compared to molecular oxygen, resulting in increased production costs. More importantly, explosions are prone to occur at higher reaction temperatures, and there are potential safety hazards.

Contents of the invention

The object of the present invention aims at problems such as the use of corrosive concentrated nitric acid raw materials and the generation of nitrogen oxides, nitric acid vapor and waste acid liquid that seriously pollute the environment in the traditional production process of adipic acid, and proposes a compound modified by transition metal MFI-type titanium-silicon molecular sieves catalyze molecular oxygen oxidation of cyclohexanone to produce adipic acid, which solves the problems of environmental pollution, atomic interest rate and high production cost in the current production process.

Technical scheme of the present invention: a series of transition metal modified composite MFI-type titanium-silicon molecular sieve preparation methods, including the following steps in turn: a) MFI-type titanium-silicon molecular sieve with 60-80 parts by weight and 1-8 parts by weight After the transition metal salt is mixed, the ball milling aid is added and then put into a high-energy ball mill for high-performance ball milling without any protective atmosphere to obtain the precursor of the composite catalyst. b) The precursor of the composite catalyst prepared by ball milling is heated in the air at 1-10°C/min to 400-800°C for 1-8 hours at a high temperature. c) The catalyst calcined at high temperature is subjected to hydrothermal treatment under the pressure of 0.05-0.5Mpa, and the temperature is 50-300°C for 2-100 hours.

The mass ratio of the preferentially filtered metal salt to the titanium-silicon molecular sieve is (0.01-0.2): 1, the ball milling time is 1-3 hours, the high-temperature calcination temperature in the priority step c is 450-700°C, and the heating rate is 3-6°C/ min, roasting for 4-7 hours.

The titanium-silicon molecular sieve in the catalyst is a titanium-silicon molecular sieve with an MFI structure, a pore size of 5-6Å, and a silicon-to-titanium ratio of 10-250. The transition metal salt is a complex of nitrate, acetate, sulfate, chloride, oxalate and acetylacetone of Cr, Co, Fe, Cu, Mn, V, W, Zr, Pd and Au, preferably Co , Mn, Fe, Cr, Cu, V and Zr nitrate, acetate, chloride and acetylacetone complexes.

The ball milling aid is stearic acid, the mass ratio of the added ball milling aid to the mixture to be tested is 1-2:100, the ball-to-material ratio in the high-performance ball milling process is 5-40:1, and the ball milling time is 1 -3 hours, the ball milling speed is 300-1200 rpm.

The solid of the present invention adopts transition metal salt and titanium silicon molecular sieve, after adding a certain amount of ball milling agent, it is added into the high-performance ball mill according to a certain proportion, and the appropriate high-energy ball mill process parameters are selected, and a series of Reaction, while the unreacted metal salt and the resulting material are immersed in the titanium silicon molecular sieve. Perform high-performance ball milling in an air atmosphere to form a transition metal-modified composite MFI-type titanium-silicon molecular sieve precursor. Since the high-energy ball milling will refine the powder and increase the specific surface area of the powder, a large number of defects and freshness will be formed on the surface of the powder. Surface, these defects and fresh surface can enhance the activity of the catalyst, and at the same time, the transition metal salt is easy to compound with the catalyst support under the condition of high-energy ball milling to form a catalyst with strong activity, which not only makes the transition metal salt evenly dispersed on the catalyst solid, It can also improve the specific surface area and overall catalytic performance of the composite catalyst.

The transition metal salt modification of the present invention uses high-temperature roasting to treat the catalyst to form a composite catalyst to improve the selectivity and activity of the catalyst. The catalyst prepared by the above method has the characteristics of high dispersion of transition metal oxides on the surface of the catalyst.

The transition metal salt modification described in the present invention is a selective treatment using hydrothermal crystallization to displace transition metal ions on the catalyst. Hydrothermal treatment, as a modification method with simple operation, can further expand the catalyst The channel and the tortuosity of the channel are increased, and the catalyst calcined at high temperature is subjected to hydrothermal crystallization treatment, the treatment temperature is preferably 80-250°C, and the treatment time is preferably 10-50 hours.

According to the present invention, the composite catalyst prepared by dry ball milling, high-temperature calcination and hydrothermal crystallization has high specific surface area and high catalytic performance and is used to catalyze air oxidation of cyclohexanone to synthesize adipic acid, which has not yet been proposed.

The series of catalysts modified by the method of the invention can be used in the selective oxidation of cyclic ketones, and are especially suitable for catalyzing the oxidation of cyclohexanone by molecular oxygen to prepare adipic acid. The oxidation reaction conditions include reaction temperature 40-180°C, reaction pressure normal pressure to 3.0MPa, oxidant air or oxygen, reaction time 1-24h, and the amount of catalyst used is 0.01%-20.0% of the mass of cyclohexanone. During the reaction, a small amount of initiator or organic solvent can be added to speed up the oxidation reaction. Initiators are azonitriles (azobisisobutyronitrile and azobisisoheptanonitrile), peroxides (hydrogen peroxide, dibenzoyl peroxide, tert-butyl hydroperoxide and cyclohexane peroxide Ketones) and nitroso (N-hydroxyphthalimide), the solvents are acetic acid, acetone, butanone, dichloromethane and ethyl acetate.

detailed description

The following examples are intended to illustrate the present invention rather than limit the present invention, in which conversion and selectivity calculation expressions (Figure 2).

Example 1: At a temperature of 90° C. and a pressure of 0.6 MPa, air is used as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M1-TS are put into a reactor for reaction. The result of reacting for 9 hours was as follows: the conversion rate of cyclohexanone was 31.6%, and the selectivity of adipic acid was 88.3%.

Example 2: At a temperature of 90° C. and a pressure of 0.6 MPa, air is used as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M2-TS are put into a reactor for reaction. The result of reacting for 9 hours was as follows: the conversion rate of cyclohexanone was 36.0%, and the selectivity of adipic acid was 92.1%.

Example 3: At a temperature of 90°C and a pressure of 0.6 MPa, using air as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M3-TS were put into a reactor for reaction. The result of reacting for 9 hours was as follows: the conversion rate of cyclohexanone was 66.7%, and the selectivity of adipic acid was 91.3%.

Example 4: At a temperature of 90°C and a pressure of 0.6 MPa, using air as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M4-TS were put into a reactor for reaction. The result of reacting for 9 hours was as follows: the conversion rate of cyclohexanone was 51.2%, and the selectivity of adipic acid was 88.7%.

Example 5: At a temperature of 100°C and a pressure of 0.6 MPa, air was used as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M3-TS were put into a reactor for reaction. After 10 hours of reaction, the results were as follows: the conversion rate of cyclohexanone was 85.2%, and the selectivity of adipic acid was 88.9%.

Example 6: At a temperature of 90°C and a pressure of 0.8 MPa, using air as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M3-TS were put into a reactor for reaction. After 12 hours of reaction, the results were as follows: the conversion rate of cyclohexanone was 89.2%, and the selectivity of adipic acid was 87.1%.

Example 7: At a temperature of 100°C and a pressure of 0.6 MPa, air was used as an oxidant, 400 g of cyclohexanone and 1.0 g of the catalyst M3-TS that was reused for the eighth time were put into a reactor for reaction. After 10 hours of reaction, the results were as follows: the conversion rate of cyclohexanone was 81.1%, and the selectivity of adipic acid was 90.1%.

Example 8: At a temperature of 100°C and a pressure of 0.6 MPa, air was used as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M4-TS were put into a reactor for reaction. After 10 hours of reaction, the results were as follows: the conversion rate of cyclohexanone was 73.6%, and the selectivity of adipic acid was 86.0%.

Example 9: At a temperature of 80°C and a pressure of 0.8 MPa, using air as an oxidant, 400 g of cyclohexanone and 1.0 g of catalyst M4-TS were put into a reactor for reaction. After 12 hours of reaction, the results were as follows: the conversion rate of cyclohexanone was 78.4%, and the selectivity of adipic acid was 92.3%.

Example 10: At a temperature of 80°C and a pressure of 0.8 MPa, using air as an oxidant, 400 g of cyclohexanone and 1.0 g of the catalyst M4-TS that was reused for the eighth time were put into a reactor for reaction. After 12 hours of reaction, the results were as follows: the conversion rate of cyclohexanone was 74.2%, and the selectivity of adipic acid was 91.3%.

Example 11: At a temperature of 80°C and a pressure of 0.8 MPa, air is used as an oxidant, 400 g of cyclohexanone, 1.0 g of a catalyst M4-TS, and 0.4 g of an initiator tert-butanol are put into a reactor for reaction. The results of the reaction for 5 hours were as follows: the conversion rate of cyclohexanone was 62.2%, and the selectivity of adipic acid was 90.1%.

Accompanying drawing 1 is the industrial synthesis process of adipic acid; Accompanying drawing 2 conversion rate and selectivity calculation expression.

Claims (11)

1. A kind of green technology that cyclohexanone is converted into adipic acid is characterized in that oxidation reaction comprises the steps: take cyclohexanone as raw material, the composite MFI class titanium silicon molecular sieve modified by transition metal salt is made catalyst, and air or oxygen As an oxidizing agent, under the conditions of operating pressure of 1Pa~3MPa, operating temperature of 40~180℃, catalyst dosage of 0.01%~20.0% of the mass of cyclohexanone, and reaction time of 1-24h, it can be converted into hexanone by catalytic conversion Acid-based products. 2. Initiators and organic solvents can be used to speed up the oxidation reaction. 3. a kind of cyclohexanone conversion adipic acid process as described in right 1, it is characterized in that described operating pressure is 0.05MPa～1.5MPa, and operating temperature is 50～150 ℃, and the consumption of catalyst is cyclohexane The yield of adipic acid is the highest under the conditions of 0.05%~10.0% of ketone mass and reaction time of 3-16h. 4. a kind of cyclohexanone conversion adipic acid process as described in right 1 is characterized in that described initiator is azonitriles (azobisisobutyronitrile and azobisisoheptanonitrile), Oxides (hydrogen peroxide, dibenzoyl peroxide, tert-butyl hydroperoxide and cyclohexanone peroxide) and nitroso types (N-hydroxyphthalimide). 5. a kind of cyclohexanone conversion system adipic acid process as claimed in right 1 is characterized in that described solvent is acetic acid, acetone, methyl ethyl ketone, dichloromethane, benzene and ethyl acetate. 6. A kind of green process of cyclohexanone conversion system adipic acid is characterized in that the preparation of catalyst and catalyst comprises the steps: a kind of cyclohexanone conversion system adipic acid process as described in any of claims 1-4 Used catalyzer, it is characterized in that described catalyzer is the complex MFI class titanium silicon molecular sieve of transition metal salt modification, and transition metal salt is mainly the nitrate of elements such as Co, Mn, Fe, Cr, Cu, Zr and V, Complexes of acetate, chloride and acetylacetone. 7. as the used catalyst of a kind of cyclohexanone conversion system adipic acid technique described in 1-4 of claim, it is characterized in that the composite MFI class titanium silicon molecular sieve weight percentage composition of described transition metal salt modification, Transition metal compounds account for 0.2-20%, and MFI titanium-silicon molecular sieves account for 80-99.8%. 8. as the arbitrary described a kind of cyclohexanone conversion system adipic acid technique described in 1-4 of claim 1-4, the compound MFI class titanium silicon molecular sieve catalyst preparation method that the transition metal salt modification used is characterized in that comprising the steps: a ) Mix MFI titanium-silicon molecular sieves with transition metal salts, add balls in a certain proportion, put them into a high-performance ball mill, and perform high-performance ball milling without any protective atmosphere to obtain high dispersion and high specificity. The precursor of the composite catalyst on the surface; b) the precursor of the composite catalyst obtained by ball milling is heated to 400-800°C in the air at 1-10°C/min for high-temperature roasting; c) the catalyst that has been roasted at a high temperature is baked under a certain pressure and The composite catalyst is obtained by carrying out hydrothermal crystallization treatment at low temperature. 9. The ball milling aid as claimed in claim 1-4 is stearic acid, the mass ratio of the added ball milling aid to the mixture to be tested is 1-2:100, and the ball-to-material ratio in the high-strength ball process is 5-40 : 1, the ball milling time is 1-3 hours, and the ball milling speed is 300-1200 rpm. 10. The preparation method of the composite MFI-type titanium-silicon molecular sieve according to claim 1-4, characterized in that the precursor modified by the transition metal salt is calcined at a high temperature of 400-800° C. for 1-8 hours. 11. The preparation method of the composite MFI-type titanium-silicon molecular sieve according to claim 1-4, characterized in that the catalyst calcined at high temperature is subjected to hydrothermal crystallization treatment at a pressure of 0.05-0.5Mpa, and is treated at a temperature of 50-300°C 2-100 hours.