A safer and greener chlorohydrination of allyl chloride with H2O2 and HCl over hollow titanium silicate zeolite

Abstract

Industrial production of dichloropropanols through chlorohydrination of allyl chloride suffers from a series of disadvantages such as use of hazardous Cl2, low atom economy, low dichloropropanol concentration and serious pollution. In this work, a safer and greener route for chlorohydrination of allyl chloride with H2O2 and HCl over hollow titanium silicate (HTS) at mild condition is developed. Unlike the traditional Cl2-based chlorohydrination, this novel method is initiated via synergistic effect of Lewis acidity (HTS) and Brønsted acidity (HCl) to promote occurrence of oxidation, protonation and nucleophilic reaction of allyl chloride simultaneously and hence dichloropropanols are generated. Owing to a completely different reaction route, the formation of 1,2,3-trichloropropane by-product is depressed and the content of dichloropropanol exceeded 22wt%, which increase by about 4 times compared with traditional Cl2-based chlorohydrination (the content of dichloropropanol is below 4wt%). At the optimized conditions, both of the allyl chloride conversion and dichloropropanol selectivity could approach 99% simultaneously and the waste is minimized. What’s more, the HTS was reusable. Concentrated HCl solution treatment was adopted to test HTS’s stability. The characterization and catalytic evaluation results reveal that, although parts of the framework Ti species have transformed into non-framework Ti and then leached into the solution, HTS remains structural stable, and the allyl chloride conversion and dichloropropanol selectivity didn’t decrease obviously during the treatment.