Main applications of dibutyl oxalate_Kain Industrial Additives

Background and overview^[1]

Dibutyl oxalate is a slightly white liquid with a slight odor. The relative density is 0.989~0.993 (20/20℃), and the boiling point is 240~250℃. Insoluble in water, miscible with alcohols, ketones, esters, oils and hydrocarbons. It is produced by the esterification reaction of n-butanol and oxalic acid. Used in organic synthesis and as a special organic solvent for some substances. The traditional method of synthesizing dibutyl oxalate mostly uses concentrated sulfuric acid as a catalyst. The disadvantages are low esterification rate, serious corrosion of equipment, and the production of a large amount of acidic wastewater. In recent years, the use of other catalysts to replace concentrated sulfuric acid for the synthesis of dibutyl oxalate has been explored. Among them, organic acids have attracted attention due to their advantages of not corroding equipment, simple preparation, and easy separation. Sulfamic acid is an organic acid that is cheap, easy to obtain, and has good stability. It has a good catalytic effect on the esterification reaction of organic acids and does not corrode equipment.

Apply^[2-3]

Dibutyl oxalate is a colorless oily liquid, commonly used as raw material, solvent and diesel cetane number improver in organic synthesis. Examples of its application are as follows:

1) Synthesis of N-butoxyoxalyl amino acid butyl ester, the synthesis method includes the following steps: in n-butanol, combine the amino acid represented by formula (II) and the oxalic acid represented by formula (III) and dibutyl oxalate as shown in the formula (IV) are reacted at 50°C to 200°C for 5 to 150 hours. During the reaction, the water generated by the reaction is removed by distillation, and the reaction liquid is post-processed to obtain the reaction solution as shown in the formula (I). N-butoxyoxalyl amino acid butyl ester shown; the material ratio of the amino acid, oxalic acid, and dibutyl oxalate is 1:1~10:1~10; in formula (I) and formula (II), R is hydrogen, C1 to C6 alkyl, phenyl, benzyl, substituted phenyl or substituted benzyl, and the substituents of the substituted phenyl or substituted benzyl are each methyl or hydroxyl. The advantages of the invention are: there is no need to use a strong acid catalyst during the reaction process, the reaction does not need to be carried out step by step, the process is simplified, the equipment and raw materials are reduced, the corrosion of the equipment is reduced, and waste water is not generated during production to harm the environment.

2) Prepare an additive to improve the low-temperature startability of methanol diesel, consisting of 10 to 30 parts of ethyl acetate, 15 to 45 parts of dibutyl oxalate, 20 to 40 parts of diisoamyl oxalate, and 0.3 to 5 parts of tert. Ethylene carbonate 10, 0.2~3 parts of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, 7~20 parts of 2,5-dimethoxytetrahydrofuran, 2~15 parts Zirconium isooctanoate, 8 to 25 parts of 2-nitro-2-methylpropyl nitrate, 10 to 40 parts of 2-methoxyethyl nitrate, 15 to 30 parts of 3-tetrahydrofuran nitrate, 12 to 30 parts Methyl benzyl alcohol nitrate, 0.2~10 parts of 3-methyl-2-nitro-2-hexene, 0.2~10 parts of 3-ethyl-2-nitro-2-hexene, 0.1~10 parts of nitric acid Barium, composed of 0 to 10 parts of manganese dioxide and 0 to 20 parts of potassium pentachloride. Mixing this additive into methanol diesel can improve the low-temperature startability of methanol diesel, make the combustion performance of methanol diesel better, and significantly improve exhaust emissions.

Preparation^[4-6]

Method 1: Synthesis of dibutyl oxalate catalyzed by sulfamic acid. Add oxalic acid, n-butanol, cyclohexane and a certain amount of catalyst in a 100mL three-neck flask according to a certain measurement ratio, install a thermometer, a water separator (add a certain amount of water in advance) and a reflux condenser, start the stirrer, and heat After reflux and water separation for a certain period of time, stop heating, cool slightly, pour out the reaction solution, combine the organic layers, first neutralize with saturated sodium bicarbonate solution, then wash with saturated brine, saturated calcium chloride solution, anhydrous magnesium sulfate After drying, distill, collect the 228-230°C fraction, weigh and calculate the yield of dibutyl oxalate, and measure the refractive index and infrared spectrum of the product.

Method 2: Acidified bentonite catalytically synthesizes dibutyl oxalate. The reaction was carried out in a 500mL four-necked flask equipped with a stirrer, condenser, water separator, liquid phase node thermometer and gas phase thermometer, and a temperature-controlled electric heater was used for heating. Add measured amounts of n-butanol and oxalic acid to the four-necked flask. Heat and stir. When the reaction liquid phase reaches the specified temperature, use a sampler to take samples to measure the initial acid value of the reaction liquid. At the same time, add SO42-/Bentonite catalyst and start timing. Take samples at certain intervals to measure the acid value. The acid value was determined by titration of sodium hydroxide ethanol standard solution. In the boiling state, the water produced by the reaction and n-butanol are azeotropically evaporated, and the aqueous phase n-butanol is separated in the water separator for reflux. As the reaction proceeds, the temperature of the reaction solution gradually increases. Control the temperature of the reaction solution within 130°C, react for a certain period of time, and then terminate the reaction. After cooling and filtering out the catalyst, the reaction liquid is a colorless oily liquid. Excess n-butanol is recovered by distillation. The fraction at (183~185)°C is collected at 0.016MPa and analyzed by infrared spectrum.

Method 3: Ferric chloride catalyzes the synthesis of dibutyl oxalate. Add oxalic acid, n-butanol, cyclohexane and a certain amount of catalyst in a 100mL three-neck flask according to a certain measurement ratio, install a thermometer, water separator (add a certain amount of water in advance) and a reflux condenser, start the stirrer, and heat the reflux After water separation for a certain period of time, stop heating, cool slightly, pour out the reaction solution, combine the organic layers, first neutralize with saturated sodium bicarbonate solution, then wash with saturated brine and saturated calcium chloride solution, and dry over anhydrous magnesium sulfate After distillation under normal pressure, collect the (228-230) °C fraction, weigh and calculate the yield of dibutyl oxalate, and measure the refractive index and infrared spectrum of the product.