65results about How to "Removed in time" patented technology

The invention provides a method for preparing p-chlorotoluene and o-chlorotoluene by toluene chlorination. The method comprises the following steps that: after raw material toluene is dried in a drier, the raw material toluene and chlorine are directly chlorinated in the presence of a catalyst so as to obtain mixed chlorotoluene, by-product hydrochloric acid and minor residual; and the mixed chlorotoluene obtained by the chlorination process is used as a raw material to be delivered to a process for separating the mixed chlorotoluene so as to obtain the o-chlorotoluene, the o-chlorotoluene and minor residual liquid through precise fractionating. By the method, a tower type fixed bed circulating chlorination process ensures that gas and liquid are contacted more sufficiently, reaction heat energy can be removed in time, so the reaction effect is better, side products are reduced, and the problem of environmental pollution caused by leakage of chlorine hydride gas in a positive pressure or normal pressure system in the prior absorbing process can be solved. Generation of wastewater is prevented, a rectifying separation mode of two serially connected towers reduces assembly height of the tower and improves separation efficiency, and purities of final products, namely p-chlorotoluene and o-chlorotoluene are both more than or equal to 99.9 percent by weight.