Method for preparing ethylene glycol by catalyzing one-step oxidation dihydroxylation of ethylene

Abstract

The invention provides a method for preparing ethylene glycol by catalyzing one-step oxidation dihydroxylation of ethylene, and relates to the technical field of ethylene glycol preparation. Ethylene is used as a raw material, a halogen-containing compound is used as a catalyst, water is used as a reaction medium, a reaction is performed in a high-pressure reaction kettle, and ethylene glycol is prepared through one-step oxidation dihydroxylation. The invention can solve the problems of flammable and explosive ethylene oxide in the traditional ethylene oxide hydration process, high water ratio, high energy consumption, environmental pollution and the like in the hydration process. The method has the advantages of simple and easily available catalyst, simple process and high conversion rate and selectivity, and can be used in industrial production of ethylene glycol from ethylene.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene glycol preparation, and in particular to a method for generating ethylene glycol by direct oxidation and dihydroxylation of ethylene / oxygen. Background Art

[0002] Ethylene glycol is the simplest 1,2-diol and one of the most important chemical raw materials. It is widely used in the production of chemical products such as antifreeze, lubricants, solvents, etc., and plays an important role in the synthetic fiber, textile, and plastic industries. Due to the vigorous development of the polyester industry in recent years, the output and demand of ethylene glycol have also risen rapidly. my country is a major producer and consumer of ethylene glycol. In 2023, my country's ethylene glycol output reached 16.535 million tons, and the market demand is huge.

[0003] At present, the most mature and widely used production route for ethylene glycol is the petrochemical route. This route is divided into two steps. The first step is to use ethylene as a raw material and convert it into ethylene oxide through an epoxidation reaction with oxygen. The second step is to directly hydrate or catalytically hydrate ethylene oxide to produce ethylene glycol. However, this process still has many disadvantages. In the first step, high temperature and high oxygen partial pressure are usually required, which increases the energy consumption and danger of the reaction. In addition, ethylene oxide has a low boiling point, is toxic, flammable and explosive, and is difficult to store and transport. Ethylene oxide has a wide range of explosion limits. In order to prevent it from self-polymerization or explosion, a larger water: ethylene oxide ratio (>20) is used in the second step of hydration. Therefore, the obtained product ethylene glycol solution is relatively dilute, and separation and purification requires evaporation of a large amount of water, which also makes ethylene glycol production one of the most energy-consuming chemical projects.

[0004] In addition, the emerging coal-to-ethylene glycol route has also formed a large scale in recent years. The main processes of this route can be divided into direct synthesis, methanol and oxalate. The direct synthesis method uses the coal gasification product synthesis gas as raw material and converts it into ethylene glycol in one step. This process still faces great technical difficulties. The methanol method uses synthesis gas to produce methanol, and then uses the ethylene method to produce ethylene glycol. The oxalate method converts synthesis gas into dimethyl oxalate, and then hydrogenates it to produce ethylene glycol. In view of my country's energy structure of "more coal and less oil", this technical route has certain advantages. Green and sustainable ethylene glycol preparation routes have also received widespread attention. The Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has developed a biomass ethylene glycol process. This technical route uses biomass sugar as raw material, and produces ethylene glycol through hydrocracking. The selectivity is very high (close to 80%), and the ethylene glycol produced can reach polyester grade. Its technical and economic performance is better than the existing bioethanol-bioethylene-bio-based ethylene glycol technical route. At the same time, the quality of the produced biomass ethylene glycol product is better than coal-based ethylene glycol. Since it does not use fossil fuels as raw materials, this technical route meets the industrial requirements of my country's "dual carbon" background and has broad prospects. However, the new preparation route still faces the problems of lengthy process, high energy consumption, and high cost.

[0005] Based on the above background, shortening the process and reducing costs have become the research focus of the ethylene glycol industry. The most ideal synthesis process is to synthesize ethylene glycol in one step. In the laboratory, osmium tetroxide can be used as a catalyst to catalyze the oxidation of olefins for the small-scale preparation of 1,2-diol, but the extremely high price and toxicity of osmium tetroxide make it difficult to expand to industrial production. In recent years, studies have reported that ethylene glycol can be synthesized from ethylene in high yield using hydrogen peroxide as an oxidant and titanium silicon molecular sieve as a catalyst. However, hydrogen peroxide is expensive and easy to decompose, which increases the production cost of ethylene glycol. From the perspective of green chemistry, oxygen is cheap and easy to obtain, and the atomic utilization rate of the reaction is 100% when oxygen is used as an oxidant. Therefore, using oxygen as an oxidant and water as a solvent and reactant, one-step oxidation and dihydroxylation of ethylene to ethylene glycol is an extremely attractive production process. However, there are few patents and literature reports on related research and inventions. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing ethylene glycol by one-step oxidation dihydroxylation using ethylene as a raw material, oxygen as an oxidant, a halogen-containing reagent as a catalyst, and water as a solvent and a reactant. The selectivity of ethylene glycol in the product is 80-99%, the reaction rate is fast, the mass fraction of ethylene glycol in the solution is high, and the energy consumption in the purification process is reduced.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] The present invention provides a method for preparing ethylene glycol by catalyzing one-step oxidation dihydroxylation of ethylene, comprising the following steps:

[0009] Reacting ethylene and oxygen in the presence of a catalyst and a reaction medium to obtain ethylene glycol;

[0010] The catalyst is a halogen-containing reagent and the reaction medium is water.

[0011] The reaction process of direct oxidation and dihydroxylation of ethylene / oxygen to produce ethylene glycol provided by the present invention is as follows:

[0012]

[0013] The active ingredient of the catalyst is a simple substance or compound of a Group VII A element, such as a simple substance or compound of bromine, iodine or chlorine. Preferably, the catalyst can be selected from one of the following:

[0014] A) one or more of iodine, hydroiodic acid and its metal salts, hypoiodous acid and its metal salts, iodic acid and its metal salts, periodic acid and its metal salts, preferably one or more of iodine, hydroiodic acid and its metal salts, such as HI, I 2 ,KI,HIO 3 , KIO 3 , H 5 IO 6 , KIO 4 wait;

[0015] B) One or more of bromine, hydrobromic acid and its metal salts, such as HBr, KBr, NaBr, FeBr 3 ,CoBr 2 、NiBr 2 , CuBr 2 、ZnBr 2 ;

[0016] C) One or more of hydrochloric acid and its metal salts, such as HCl, KCl, CuCl 2 、FeCl 3 ;

[0017] The cation of the metal salt is a third, fourth, fifth or sixth period metal ion, preferably a fourth period transition metal ion.

[0018] Preferably, the amount of the catalyst added is 10-100 mg per 1 mL of reaction medium, that is, the concentration of the catalyst is 10-100 g / L.

[0019] The reaction gas of the present invention is C 2 H 4 , O 2 The reaction medium is H 2O, the reaction temperature is 100-240°C, the total reaction pressure is 0.5-6MPa, and C 2 H 4 The pressure is 0.5-3MPa, O 2 The pressure is 0.5-4MPa, the reaction time is 0.5-12h, and the catalyst is a halogen-containing reagent.

[0020] Preferably, the reaction medium is ultrapure water.

[0021] Preferably, the reaction temperature is 140-200°C.

[0022] Preferably, the reaction stirring speed is 300-1500 rpm.

[0023] Preferably, the volume of the high-pressure reactor is 30 mL-500 L.

[0024] Preferably, C 2 H 4 With O 2 The volume fraction ratio is 0.25-4.

[0025] In some specific embodiments, the method comprises the following steps:

[0026] 1) Add the catalyst into a high-pressure reactor equipped with a polytetrafluoroethylene liner and magnetic or mechanical stirring, add the reaction medium, and then introduce the reaction gas ethylene and oxygen, the ethylene partial pressure is 0.5-3MPa, the oxygen partial pressure is 0.5-4MPa, and the total reaction pressure is 0.5-6MPa;

[0027] 2) Raise the temperature of the reactor to 140-200°C and react for 0.5-12h to obtain the product;

[0028] 3) The products were separated and qualitatively (quantitatively) analyzed by gas chromatography: propylene carbonate was used as an internal standard, and the conversion rate and selectivity were calculated by gas chromatography analysis.

[0029] The ethylene conversion number and product selectivity of the reaction are determined by the following formula:

[0030]

[0031] Technical effect:

[0032] 1) The present invention significantly reduces economic costs by using common halogen-containing reagents as catalysts.

[0033] 2) The synthesis method used in the present invention is simple, easy to operate, and suitable for industrial production and scale-up.

[0034] 3) The method adopted by the present invention has good ethylene single-pass conversion rate, ethylene glycol selectivity and continuous reaction capacity for the direct oxidation and dihydroxylation of ethylene / oxygen to produce ethylene glycol.

[0035] 4) The method adopted by the present invention has good cycle performance for the direct oxidation and dihydroxylation of ethylene / oxygen to produce ethylene glycol.

[0036] 5) The catalytic reaction conditions of the present invention are relatively safe, and the reaction products are environmentally friendly and pollution-free. It can be used to replace the existing ethylene epoxidation-ethylene oxide hydration process for large-scale promotion and application.

[0037] The present invention has been described in detail above, but the above embodiments are only illustrative in nature and are not intended to limit the present invention. In addition, this article is not limited by any theory described in the above prior art or invention content or the following examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a comparison chart of the reaction activities of different catalysts. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed for the present invention.

[0040] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.

[0041] Example 1

[0042] This example investigates the effects of different halogen-containing catalysts on the ethylene oxidation dihydroxylation reaction. Take 100 mg of hydroiodic acid solution (47 wt%, containing 47 mg of HI) and put it into a high-pressure reactor with a polytetrafluoroethylene liner. Then add 4 mL of water to the reactor, purge the reaction device with ethylene three times, and pass a mixed gas of ethylene and oxygen (the volume ratio of ethylene to oxygen is 2:1) to make the total pressure 3 MPa. React at 180 ° C and 1000 rpm for 3 hours, then cool the reactor quickly, and analyze the product situation in the reaction solution by gas chromatography. The same experiment is carried out with other halogen-containing substances (iodine, potassium iodide, iodic acid, potassium iodate, orthoperiodic acid, potassium periodate, hydrobromic acid, potassium bromide) as catalysts to make the substance concentration of halogen in the reaction solution the same. The reaction evaluation results are shown in Table 1.

[0043] Table 1 Effect of different catalysts on the reaction of ethylene oxidative dihydroxylation to produce ethylene glycol

[0044]

[0045] The results in Table 1 show that hydroiodic acid, elemental iodine and iodic acid have the highest catalytic activity. The main product of the reaction is ethylene glycol, and the main by-products are ethylene glycol dimerization products (diethylene glycol, 1,4-dioxane), as well as a small amount of acetaldehyde, acetic acid and other products.

[0046] Example 2

[0047] This example investigates the effect of different temperatures on the catalytic activity of hydroiodic acid. Take 50 mg of hydroiodic acid solution (47 wt%, containing 23.5 mg of HI) and put it into a high-pressure reactor lined with polytetrafluoroethylene. Then add 2 mL of water to the reactor, purge the reaction device with ethylene three times, and pass a mixed gas of ethylene and oxygen (the volume ratio of ethylene to oxygen is 2:1) to make the total pressure 3 MPa. React at 180 ° C and 1000 rpm for 3 hours. After the reaction, the reactor is quickly cooled and the product in the reaction solution is analyzed by gas chromatography. The same experiment is carried out at different reaction temperatures, and the reaction evaluation results are shown in Table 2.

[0048] Table 2 Effect of different reaction temperatures on the preparation of ethylene glycol by oxidative dihydroxylation of ethylene

[0049]

[0050] The results in Table 2 show that the reaction is sensitive to temperature, and the reaction rate increases rapidly with increasing temperature. The increase in reaction temperature also leads to more conversion of ethylene glycol into dimerization products, which reduces the selectivity of ethylene glycol.

[0051] Example 3

[0052] This example investigates the catalytic performance during continuous reaction. Take 50 mg of hydroiodic acid solution (47 wt%, containing 3.5 mg of HI2) and put it into a high-pressure reactor lined with polytetrafluoroethylene. Then add 2 mL of water to the reactor, purge the reaction device with ethylene three times, and introduce a mixed gas of ethylene and oxygen (the volume ratio of ethylene to oxygen is 2:1) to make the total pressure 3 MPa. React at 180°C and 1000 rpm for 3 hours. After the reaction is completed, release the residual gas, re-fill the reactor with the aforementioned mixed gas, and start the reaction again. Take each reaction liquid separately, and analyze the product in the reaction liquid by gas chromatography. The reaction evaluation results are shown in Table 3.

[0053] Table 3 Effect of reaction times on the preparation of ethylene glycol by oxidative dihydroxylation of ethylene

[0054]

[0055] The results in Table 6 show that as the reaction proceeds and the number of reactions increases, the ethylene conversion number gradually increases and the ethylene glycol selectivity gradually decreases. After four reactions, the ethylene glycol selectivity is still 66.7%, and the mass fraction of ethylene glycol in the aqueous solution can reach 17%, which significantly reduces the energy consumption during concentration and purification.

[0056] Comparative Example 1

[0057] Add 2 mL of water to a polytetrafluoroethylene-lined autoclave, then purge the reaction device with ethylene three times, and introduce a mixture of ethylene and oxygen (the volume ratio of ethylene to oxygen is 2:1) to a total pressure of 3 MPa. React at 180°C and 1000 rpm for 3 h. After the reaction, the autoclave was quickly cooled, and the product in the reaction solution was analyzed by gas chromatography. The reaction evaluation results are shown in Table 4.

[0058] Table 4 Comparative Example Experiment

[0059]

[0060] The comparative experiment shows that when no catalyst is added, ethylene and oxygen do not produce any target products, which proves the catalytic effect of halogen-containing compounds in the reaction.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and essence of the claims of the present invention; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A method for preparing ethylene glycol by catalytic one-step oxidation dihydroxylation of ethylene, characterized in that: The following steps are involved: Reacting ethylene and oxygen in the presence of a catalyst and a reaction medium to obtain ethylene glycol; The catalyst is a halogen-containing reagent and the reaction medium is water.

2. The method according to claim 1, characterized in that The catalyst is selected from one of the following: A) one or more of elemental iodine, hydroiodic acid and its metal salts, hypoiodous acid and its metal salts, iodic acid and its metal salts, periodic acid and its metal salts; B) one or more of bromine, hydrobromic acid and its metal salts; C) one or more of hydrochloric acid and its metal salts; The cation of the metal salt is a third, fourth, fifth or sixth period metal ion, preferably a fourth period transition metal ion.

3. The method according to claim 1, characterized in that The concentration of the catalyst is 10-100 g / L.

4. The method according to claim 1, characterized in that: The reaction temperature is 100-240°C, the total reaction pressure is 0.5-6MPa, and the reaction time is 0.5-12h.

5. The method according to claim 4, characterized in that The volume fraction ratio of ethylene to oxygen is 0.25-4, the pressure of ethylene is 0.5-3MPa, and the pressure of oxygen is 0.5-4MPa.

6. The method according to claim 4, characterized in that The reaction temperature is 140-200°C.

7. The method according to claim 1, characterized in that The following steps are involved: 1) Add the catalyst into the autoclave, add the reaction medium, and then introduce the reaction gases ethylene and oxygen, the ethylene partial pressure is 0.5-3MPa, the oxygen partial pressure is 0.5-4MPa, and the total reaction pressure is 0.5-6MPa; 2) Heat the reactor to 140-200°C and react for 0.5-12h to obtain the product.

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