The chlor-alkali industry is an industrial process for the production of sodium hydroxide(caustic soda),hydrogen and chlorine by electrolysis of sodium chloride solution.As one of the main products of the chlor-alkali industry,chlorine gas is the key to the production of thousands of downstream chemical products,which can be used to prepare polyvinyl chloride(PVC),bleach,pharmaceuticals,etc.In the industrial production with chlorine as the main raw material,by-product hydrogen chloride(HCl)is mostly produced,and the amount of by-products far exceeds the amount that can be absorbed by the market.The common HCl treatment method absorbs it into hydrochloric acid through water,which leads to an oversupply of hydrochloric acid and causes elemental quality The loss of chlorine,which is not only a waste of resources,but also endangers the natural environment and human health.How to utilize hydrochloric acid efficiently is the key problem that plagues the development of chlor-alkali industry.As an important chemical raw material,chlorinated aromatic compounds play an important role in organic synthesis and are important intermediates in material science and industrial chemicals.If excess hydrochloric acid is used for the preparation of chlorinated aromatic compounds,it can not only Consuming hydrochloric acid can also produce high value-added chemical intermediates.Using hydrogen peroxide as a green oxidant,oxidizing hydrochloric acid to generate chlorine gas and hypochlorous acid,which undergo chlorination reaction with aromatic hydrocarbon compounds.In order to solve the problems that hydrochloric acid is highly toxic and corrosive and the reaction conditions are not easy to control,it is proposed to use a microchannel reactor to make the material quantitatively accurate,the exotherm to be easily controlled,and the process safety is significantly improved.In view of the above-mentioned industrial background,this study took benzene series compounds with different substituents(toluene,anisole,phenol and p-methoxyphenol)as the research objects,took hydrochloric acid as the chlorine source,and took hydrogen peroxide as the oxidant on the selected benzene series compounds.Oxychlorination was carried out to synthesize chlorinated organic compounds.The reactants and products were qualitatively and quantitatively analyzed by gas chromatography,and the conversion rate and yield were calculated.The results of the study are as follows:(1)Chlorotoluene was synthesized by the oxychlorination of toluene in a batch reactor.The effects of reaction temperature,reaction time and reactant ratio on the conversion of toluene and the yield of chlorotoluene were studied.The results showed that:The optimal reaction conditions are reaction temperature 40℃,reaction time 4 h,n(toluene):n(HCl):n(H2O2)=1:4:3.Under this condition,the conversion rate of toluene and the yield of chlorotoluene can reach47%and 35%,respectively.On this basis,the chlorination reaction of toluene was strengthened by using a microchannel reactor capable of continuous reaction.The results showed that compared with the batch reactor,the continuous reaction process in the microchannel reactor was safe and controllable and greatly shortened The reaction time is shortened,and the conversion rate of toluene and the yield of chlorotoluene are improved at the same time.Under the conditions of n(toluene):n(HCl):n(H2O2)=1:7:3,the reaction temperature is 65℃,and the residence time is 3.5 min,the toluene conversion and the chlorotoluene yield can be increased to 71%,respectively.and 61%.(2)By changing the substituents on the benzene ring,the conversion rate and yield of the oxychlorination reaction are improved.The results show that the optimal conditions for the oxychlorination of anisole in the batch reactor are n(anisole):n(HCl):n(H2O2)=1:4:2,and the reaction temperature is 40℃,the reaction time is 4 h,at this time the conversion rate of anisole and the yield of chloroanisole are 89%and 60%,respectively;the optimal conditions for the oxychlorination of phenol are n(phenol):n(HCl):n(H2O2)=1:4:1,the reaction temperature was30°C,and the reaction time was 6 h.At this time,the conversion rate of phenol was 100%,and the yield of chlorophenol was 96%;the optimal conditions for the oxychlorination of p-methoxyphenol is n(p-methoxyphenol):n(HCl):n(H2O2)=1:4:1,the reaction temperature is30°C,the reaction time is 4 h,the conversion rate of p-methoxyphenol is 98%,and a single product The yield of 2-chloro-4-methoxyphenol was 62%.In the microchannel reactor,the optimal experimental conditions were n(anisole):n(HCl):n(H2O2)=1:4:1,the residence time was3 min,and the reaction temperature was 60°C.The conversion and chloroanisole yields were47%and 52%,respectively.The conversion of anisole in the microchannel reactor is lower than that in the batch reactor,mainly because anisole is volatile.In the reaction system described in the paper,hydrochloric acid will react with hydrogen peroxide to generate chlorine gas and hypochlorous acid,and then undergo electrophilic substitution reaction with aromatic hydrocarbons to obtain ortho and para chlorinated products.The electron-donating ability of methyl group,methoxy group and hydroxyl group increased in turn,and their activation effect on the benzene ring was strengthened in turn,which was the reason for the increase in the conversion rates of toluene,anisole and phenol.After using methoxy to occupy the para position of phenol,the yield of the product 2-chloro-4-methoxyphenol reached 62%.In the micro-channel reactor,the use of hydrochloric acid and hydrogen peroxide system can realize the efficient oxychlorination of aromatic hydrocarbons. |