Removal Of Organochlorine From Oil By Reactive Adsorption Over TiO₂-Based Oxides And Modified 13X Zeolites

Organochlorine can corrode oil processing equipments and easily poison hydrofining and catalytic reforming catalysts.Thus,the realization of deep removal of organochlorine from oil has aroused considerable attention.The application of catalytic hydrodechlorination technology needs to be carried out under harsh conditions,such as high temperature and high pressure.In addition,HCl will be generated during the catalytic hydrodechlorination process.HCl will not only corrode and lead to safety risks,but also poison the catalysts.Thus,catalytic hydrodechlorination is restricted to be applied extensively.Adsorption dechlorination technology is a prospective dechlorination technology with the characteristics of simple operation,low reaction conditions and low energy consumption.However,the dechlorination capacities of the developed adsorbents are still low,and the mechanism of adsorption dechlorination is still needed to be clarified.Therefore,this study aims to develop adsorbents with high adsorption capacities for organochlorine,and focuses on the study of the structure-activity relationship of reactive adsorption dechlorination at high temperature（≥120℃）.The mechanism of reactive adsorption dechlorination was proposed based on the study of structure-activity relationship and analysis of reaction products.The dechlorination performance of TiO₂-based oxides was studied at20-150℃.The characterization results showed that both acidity and basicity of TiO₂-Ce O₂ played great important influence on the dechlorination performance.TiO₂ prepared with urea as precipitant（TiO₂-U）had larger specific surface area,acid amount and base amount than TiO₂prepared with ammonia as precipitant（TiO₂-A）.Therefore,TiO₂-U showed better dechlorination performance than TiO₂-A.Among various Ti_（1-x）Ce_xO₂ bimetallic oxides with different Ti/Ce molar ratio and single oxides,Ti_0.7Ce_0.3O₂ and Ti_0.3Ce_0.7O₂ exhibited higher dechlorination performance than TiO₂.Under the condition of 150℃,the chlorine removal of Ti_0.7Ce_0.3O₂ can reach 82.8%after adsorption for 3 h.Mixing 5 wt%Ba O with Ti_0.7Ce_0.3O₂ mechanically promoted the dechlorination performance,and the chlorine removal of Ti_0.7Ce_0.3O₂-Ba O reached 92.1%.The dechlorination performance increased with the increase of adsorption temperature.Ion chromatography and GC-MS analysis showed that organochlorine were converted to Cl^-and corresponding 1-octanol on the adsorbent at 150℃.Ti_0.7Ce_0.3O₂ showed great recycling effect,and still exhibited excellent dechlorination performance after four cycles.The dechlorination performances of different zeolites were investigated,and 13X zeolite was modified by ion exchange method and taken for dechlorination test.Ag-13X zeolite showed the best dechlorination performance,and the chlorine removal reached 97.2%at120℃.The characterization results showed that the acidity of the adsorbents played significant effect on the adsorption dechlorination performance,and more acid amount was beneficial to the removal of organochlorine.Ag-13X zeolite exhibited great regeneration performance.After three regeneration-dechlorination cycles,the chlorine removal still reached 87.7%.The dynamic dechlorination performances of 13X and Ag-13X were studied in the fixed-bed reactor,the selectivity and mechanism of reactive adsorption dechlorination were also be studied.The results showed that the chlorine removal on Ag-13X zeolite can be maintained at 72.1%after 100h in fixed bed when the simulated oil feed rate was 0.15 m L/min and the fixed bed temperature was 150℃.The analysis results of GC-MS and ion chromatography showed that the reactive products of chlorooctane and chlorocyclohexane were olefin and alcohol,and the inorganic products were chloride ions.Whereas,the conversion of dichlorobenzene was not observed.The straight chain aliphatic organochlorine and circular organochlorine followed the mechanism of reactive adsorption.Organochlorine was adsorbed on the acid sites of the adsorbent,and then elimination reaction and substitution reaction were occurred.Finally,the corresponding olefin and alcohols were generated,and organochlorine was converted into inorganic chlorine during the reactive adsorption.