Preparation and application background and overview of dipropyl carbonate
Dipropylcarbonate (dipropylcarbonate, hydrated terbium carbonate called DPC) has important applications in many aspects as a solvent, surfactant or organic synthesis intermediate. Carbonates have good electrochemical stability, high flash point and low melting point, so they have been widely used in lithium-ion batteries. Among them, dipropyl carbonate has a larger relative molecular mass than dimethyl carbonate and diethyl carbonate, and its flash point and oxidation resistance are further improved, thereby improving the electrochemical stability of the electrolyte. And battery safety is also improved accordingly. At present, the synthesis of dipropyl carbonate mainly includes phosgene method, oxidative carbonylation method, urea alcoholysis method, and transesterification method. Among them, the one-step synthesis of DPC using the transesterification method of dimethyl carbonate (DMC) and propanol can relatively simplify the process and has the advantages of safety and cleanliness. It is a promising production process.
Preparation and application of dipropyl carbonate
The synthesis methods of dipropyl carbonate include: phosgene method, transesterification method, oxidative carbonylation method, urea alcoholysis method, gas phase method oxidative carbonylation method, liquid phase method synthesis method, direct synthesis method of alcohol and carbon dioxide, and lipolysis Enzyme catalysis method and propanol oxidative carbonyl synthesis method, etc.
Method 1: Hydrotalcite-like catalyst catalyzes the synthesis of dipropyl carbonate. Add propanol and DMC (molar ratio: 3:1) to a four-necked flask with stirring. The amount of catalyst is 1% of the total mass of the reactants. The reaction temperature is 90°C. When the reaction time is 5 hours, filter off the catalyst after cooling. The yield of product DPC was 46.87%.
The preparation of hydrotalcite-like catalyst: the hydrotalcite-like catalyst is prepared by co-precipitation method. Put a certain amount of water into the beaker, heat it to about 60°C, and under strong stirring, mix the divalent nitrate (Mg2+ or Zn2+ salt) and aluminum nitrate mixed aqueous solution prepared at a certain molar ratio and the NaOH and Na2CO3 mixed alkali solution [ n(NaOH):n(Na2CO3)=4:1] are dropped into it in a parallel flow manner, and the dripping speed of the two mixed liquids is controlled to keep the pH value of the solution at 9 to 11. After the precipitation is completed, the resulting slurry is Aged at 75°C for 8 hours. Filter, wash with deionized water several times, dry at 100°C, and grind to obtain various hydrotalcite catalysts (LDHs); roast the dried LDHs sample at 500°C for 5 hours to obtain the corresponding roasted product (LDO).
Method 2: Electrode-induced carbon dioxide catalytic synthesis of dipropyl carbonate. CO2 is captured and stored in a carbon-fixing solvent. The carbon dioxide is induced by electrodes on the copper electrode in the carbon-fixing solution, and then The induced activated carbon dioxide is placed in the reactor, n-propanol is added, and the reaction is refluxed at 40 to 95°C for 2 to 4 hours under the action of a catalyst. After separation and drying, dipropyl carbonate is obtained. The main reaction equation is:
A method for electrode-induced carbon dioxide catalytic synthesis of dipropyl carbonate, the specific steps are as follows:
Step 1. Prepare the electrode-induced carbon fixation solution in proportion and stir evenly.Put it in a glass tank and put it on a bracket that can fix other items; the electrode-induced carbon fixation solution is obtained by dissolving ammonium bromide in a solvent, stirring and mixing; the mass of ammonium bromide is the electrode-induced carbon fixation solution 3-20% of the mass; the ammonium bromide is methylammonium bromide, phenyl ammonium bromide or benzyl ammonium bromide; the solvent is tetrahydrofuran or N, N-dimethylformamide (DMF);
Step 2: Fix the two electrodes of copper and titanium, the inert gas conduit and the CO2 gas feed tube on the bracket of the glass tank respectively, and pass in dry inert gas until the air in the electrode-induced carbon fixation solution is replaced. ;
Step 3: Continue to slowly introduce carbon dioxide gas into the electrode-induced carbon fixation solution. The mass of the carbon dioxide gas introduced is 20-60% of the mass of the electrode-induced carbon fixation solution (based on the mass of CO2); turn on the power and control the voltage The voltage is between 6~24V, the current is between 0.6~15A, and the electrode induces reaction for 10~40min;
Step 4. After the electrode induction is completed, slowly move the induction liquid to the reactor with a reflux device, slowly add n-propanol dropwise into the reactor, and add the catalyst at the same time; the ratio between the n-propanol and CO2 The molar ratio is 2:1; the added mass of the catalyst is 0.2-1% of the mass of n-propanol; then an oil bath is used for temperature-controlled heating, and the reaction is refluxed at 40-95°C for 1-4 hours, and then cooled to below 30°C. Obtain a mixed reaction liquid; transfer the mixed reaction liquid into a separator, and wash it several times with saturated brine at a temperature of 60°C until all the remaining catalyst is removed; the upper layer is the product and solvent, the lower layer is water and impurities, and finally the second layer is used Wash once with methyl chloride, and dry the collection with anhydrous magnesium sulfate to obtain a mixture of dipropyl carbonate, carbon fixation inducing solvent and methylene chloride; steam the mixture out of the carbon fixation inducing solvent and methylene chloride on a vacuum distiller, When no liquid flows out at 75°C, adjust the vacuum degree to 2 to 10 mmHg, and collect the dipropyl carbonate product that flows out when the temperature is 49 to 65°C.
Preparation and application of dipropyl carbonate
Dipropyl carbonate (DPC) is a widely used intermediate that can be used as an electrolyte additive for lithium batteries and a raw material for the synthesis of drugs, pesticides, and polycarbonates. Examples of its application are as follows:
1) The preparation of polycarbonyl urea involves the synthesis of urea condensation polymers, which solves the problem of existing urea condensation polymer preparation methods that use raw materials that are harmful to the human body and the environment, have low yields, and produce substances that are harmful to the human body and the environment. by-product issues. In the present invention, dipropyl carbonate is heated to 40~50°C in a reactor, then urea and catalyst are added respectively, and then the temperature is raised to a temperature above the melting point of urea, heated for 5~10 hours, then cooled to room temperature under stirring conditions, and filtered Recover n-propanol in the liquid phase, wash the solid phase with ethanol to remove n-propanol and dipropyl carbonate adhering to its surface, and then dry it at 90~100°C to obtain polycarbonyl urea. The method of the invention is a green synthesis process, does not produce by-products harmful to the human body, and can flexibly control the degree of polymerization of the generated polycarbonyl urea.
2) Prepare a special slow-release fertilizer for camellia. The specific steps are: add urea, potassium tert-butoxide and 2-chloroaniline to dipropyl carbonate, melt and react, stir and cool to room temperature, filter to obtain polyurea; Add dipotassium hydrogen phosphate to polyurea, stir and react to obtain polyurea slow-release fertilizer; take polyurea slow-release fertilizer, cottonseed meal humic acid, cottonseed amino acid, multi-element micro-fertilizer, and adhesive by weight. , mix evenly, and prepare into conventional dosage forms such as granules and powders to obtain slow-release fertilizer. The beneficial effects are: the slow-release fertilizer of the present invention can slowly release nutrients, improve the effective utilization of nitrogen, phosphorus, potassium and other nutritional elements, alleviate environmental problems, improve soil, degrade toxic substances and prevent camellia diseases, and improve the brightness of camellias. It can delay the flowering period of camellia and has a high yield of slow-release fertilizer.
3) Prepare propylated-β-cyclodextrin, including the following steps: A) React β-cyclodextrin and dipropyl carbonate in DMF solvent at a temperature of 70-145°C in the presence of K2CO3 or Na2CO3 0.5-56 hours, the entire reaction process must be filled with protective gas; B) filter to remove K2CO3 or Na2CO3 and other insoluble matter, distill the solvent DMF under reduced pressure, and concentrate the solution to a DMF mass percentage of less than 5%; the process conditions of the present invention are simple, β -The conversion rate of cyclodextrin is high. The conversion rate of β-cyclodextrin after the reaction is 30-95%. The average substitution degree of the product is 0-7, which is environmentally friendly.
