Study On The Process Of Benzene Chlorination With Three-phase Catalytic Distillation

Chlorobenzene is one of the most major products in aromatic hydrocarbon chloride. It is an important intermediate used in organic synthesis. It is also directly used as a solvent.At present, chlorobenzene is produced by continuous boiling chlorination of benzene and chlorine in a column reactor. The process has several ten-year production history, it is rightly mature and widely used, but it has defects as follows:(1) The per pass conversion of benzene was low, material process quantity is large and the operation cost is high. In order to avoiding chlorobenzene from further chlorination, per pass conversion of benzene was controlled in the range of 25³5%(wt.), i.e. three -quarter raw material of benzene was needed to be separated and circulated. Thus, the mixture quantity of process increased in the various operations of wash, neutralization, distillation, cooling and drying of benzene to be circulated. Thereby, equipment investment, operation cost and energy comsuming increased.(2) The whole process was long and complicated, waste water quantity was large, environmental pollution was serious. In order to avoiding FeCl₃ and HCl in chlorinated mixture from corroding and plugging for subsequent equipment, the operations of wash, neutralization were necessary. Thus, long process flow path, large equipment investment and high operation cost were needed, simultaneously, a large quantity of waste water was drained and environment was polluted.(3) The reaction heat was not utilized. The chlorination of benzene and chlorine is a strong exothermal reaction (ΔH=-131.5 kJ/mol), the generated heat is removed by the evaporation of benzene, and it was wasted.According to the defects mentioned above, an idea was firstly put forth that the technique of reactive distillation was used to prepare chlorobenzene from the chlorination of benzene in this thesis. The experiments of the continuous chlorination with distillation of benzene and chlorine at the presence of Fe catalyst were made. The results were obtained that per pass conversion of benzene was about 99 % and the selectivity of chlorobenzene was 97%. Thus, the feasibility of the reactive distillation...