Study On The Removal Of Organochlorine From Crude Oil Based On The Mechanism Of Phase Transfer In Nucleophilic Substitution Reaction

Chlorine additives,added in the extraction,transportation and processing of crude oil,will increase the chlorine content in crude oil,which causes a series of problems,such as corroding devices,clogging pipelines,poisoning catalysts and so on.It is important to develop the dechlorination reagent with high-efficiency used in the process of electric desalination for "safe,stable,long,full and excellent" production in refineries.In this paper,seven typical chlorinated alkanes were selected as model compounds.The dechlorination reagents were developed to examine their dechlorinating effects on model compounds,the dechlorinating rates of the seven organochlorines were obtained as follows:epichlorohydrin>1,2-dichlorobutane>1,2-dichloroethane>1,3-dichloropropane>2-chloropropane>1-chlorobutane>chloroisobutane.By analyzing the organochlorine model components in the simulated oil in the process of dechlorination,the dechlorinating reaction mechanism of the model compounds was studied.The process is divided into two steps:phase transfer and nucleophilic substitution.The chlorinated alkanes are first transferred to the water phase by interacting with the quaternary ammonium base as phase transfer catalyst,and generate quaternary ammonium chlorides,which will be converted to water-soluble inorganic chloride ions by reacting with the hydroxide in water,and can be removed.The reaction kinetics were calculated in the different dechlorinating systems and the apparent activation energies of the reactions were obtained.The apparent activation energy of the phase transfer nucleophilic substitution reaction of epichlorohydrin with epoxy group structure is low,only 19.68 kJ/mol,so it can be easily removed.The transition states and energy potentials of phase transfer reactions were calculated by using DFT.The phase transfer process of organochlorines is a heat-absorbing reaction,and the order of the energy potentials of the transition states of the reaction is consistent with the order of the apparent activation energy of the phase transfer nucleophilic substitution reaction of organochlorines.On this basis,the dechlorination reagent,with ethylenediamine as the nucleophilic reagent and tetrabutylammonium hydroxide as the phase transfer agent,was developed and applied to the dechlorination of Iranian crude oil.Under the reaction temperature of 95℃ and the reaction time of 80 min,the removal rate of the total chlorines of Iranian crude oil could reach up to 87.9%and the removal rate of the organic chlorines of Iranian crude oil could reach up to 82.2%.The removal rates of the total chlorines of the crude oils from Qinghai,Yunnan and Daqing could be more than 76.0%.