Preparation method of plasticizer diethylene glycol dibenzoate

Abstract

The invention relates to a preparation method of a plasticizer, particularly a preparation method of a plasticizer diethylene glycol dibenzoate, which comprises the following steps: heating benzoic acid and diethylene glycol until the benzoic acid is dissolved, adding a catalyst to carry out reflux reaction, starting a vacuum pump, heating to 200-220 DEG C, keeping the temperature to react under reduced pressure, and stopping the reaction when no water is distilled out, thereby obtaining a diethylene glycol dibenzoate crude product; and cooling the obtained diethylene glycol dibenzoate crude product, neutralizing with an Na2CO3 water solution to remove excessive benzoic acid, washing, separating out the ester layer, and dehydrating by vacuum distillation to obtain a colorless transparent oil liquid which is the plasticizer diethylene glycol dibenzoate product. The technique is simple, does not use any water-carrying agent, continuously distils out water in the reaction under negative pressure, breaks the chemical equilibrium of the esterification reaction, shortens the reaction time, greatly enhances the benzoic acid conversion rate, has the advantages of high esterification rate (up to higher than 98%), favorable catalyst selectivity, fewer side reactions, light product color and no need of activated carbon for decolorization, and is suitable for industrial production and environment-friendly.

Description

technical field [0001] The invention relates to a method for preparing a plasticizer, in particular to a method for preparing an environment-friendly plastic plasticizer, diethylene glycol dibenzoate. Background technique [0002] Plasticizers are one of the plastic additives with the largest production and consumption in the world. Adding them to plastics can increase the plasticity and flexibility of plastics. Due to the fact that the traditional plasticizer dioctyl phthalate (DOP) has been approved by the American Cancer Institute (NCI) suspected carcinogenic effect, its scope of use was greatly restricted. Compared with DOP, diethylene glycol dibenzoate (DEDB) has the characteristics of good compatibility, good cold resistance, antistatic property, remarkable anti-pollution performance, outstanding thermal stability, low volatility, and good photochromic resistance. , and low toxicity, it is an environmentally friendly plasticizer, an ideal substitute for DOP, and has a...

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Problems solved by technology

[0004] (1) Transesterification method, Li Lingge et al. Methyl benzoate and diethylene glycol are used as raw materials for transesterification to generate DEDB and methanol. The reaction time of this method is short, and the active ingredient of the plasticizer reaches 99%, but the reaction temperature is higher, and the color is darker and yellowish at the end of the reaction. smell

[0005] (2) Acyl halide method, Wang Shuqing et al. (Wang Shuqing, Sun Dongbing, Gao Chong. Research on the synthesis process of plasticizer diethylene glycol dibenzoate [J]. Plastic Additives, 2010, (03): 23-25) Utilize the action of benzoyl chloride and diethylene glycol to generate DEDB and hydrogen chloride. This method has the advantages of simple process, short reaction time and mild conditions. However, due to the continuous generation of hydrogen chloride gas in the reaction, the corrosion of equipment is relatively serious, and benzene Formyl chloride is relatively expensive for benzoic acid, which limits the industrial application of this method

The traditional method of synthesizing DEDB is to directly esterify diethylene glycol and benzoic acid under the catalysis of sulfuric acid. Direct Catalytic Synthesis of DEDB by Sulfuric Acid

Wang Ying et al. (Wang Ying. Synthesis of diethylene glycol dibenzoate [J]. Journal of Shenyang Institute of Education, 2005, (02):108-110) Catalyzed the reaction of benzoic acid and diethylene glycol with p-toluenesulfonic acid , the post-treatment of the product is complex, requiring neutralization, washing, decolorization and other processes, the discharge of three wastes is large, and the pollution is serious

Zhang Long et al. (Zhang Long, Wang Shujiang, Yang Wenlong, et al. Synthesis of diethylene glycol dibenzoate catalyzed by immobilized heteropolyacid catalyst PW_(12) / C [J]. Petrochemical Industry, 1998, 8) used self-made solid Supported heteropolyacid catalyst PW 12 / C catalyzed the synthesis of DEDB, and the activity of the catalyst did not decrease significantly after repeated use, but its preparation method was complicated and its price was high, which limited its industrial application; Liang Shiqiang et al. (Liang Shiqiang, Mu Xiaomei. 4 2- / TiO 2 Catalytic synthesis of diethylene glycol dibenzoate [J]. Fine Chemical Industry, 2005, 9:685-687) using glass beads as a carrier to prepare solid superacid SO 4 2- / TiO 2 Catalyst synthesis of DEDB, the catalyst is greatly affected by the preparation conditions, and the cost is high, which restricts its application in industrial production; Wang Zhengping (Wang Zhengping, Zhang Hanping. Synthesis of new plasticizer diethylene glycol dibenzoate[J] .Applied Science and Technology, 2004, (09):53-55) DEDB was synthesized by using tetrabutyl titanate as a catalyst, water separation and reflux reaction for 4 hours, this method used water-carrying agent and antioxidant, and the product needed to be decolorized with activated clay ; Ren Weiheng et al. (Ren Weiheng, Wei Yongsheng, Wei Xiuju. Synthesis and process conditions of plasticizer diethylene glycol dibenzoate [J]. Journal of South Central University for Nationalities (Natural Science Edition), 1995, 04) catalyzed benzoic acid and Diethylene glycol reacts to synthesize DEDB. This method uses xylene as a water-carrying agent. The post-treatment process of the product is complicated and requires decolorization with activated carbon; Liu Wensheng and Meng Qi (Liu Wensheng. Active stannous oxide catalyzed synthesis of diethylene glycol dibenzoate[ J]. Chemical Times, 1992, (03): 9-13; Meng Qi, Zhang Feixia, Wang Juanlin. Synthesis of diethylene glycol dibenzoate catalyzed by active stannous oxide [J]. Journal of Jiangsu Institute of Chemical Technology, 1989, (02 ):53-58) DEDB was synthesized by using toluene as the water-carrying agent and SnO as the catalyst for water separation and reflux reaction respectively. High, and the amount of catalyst is more, the reaction time is longer

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