Synthesis Of Heavy Alkylbenzene Over Immobilized AlCl₃ Catalyst

Heavy alkylbenzne sulfonate(HABS)is an important surfactants with favorable interfacial properties and have been widely applied in enhanced oil recovery(EOR)in China. In industry,the raw material to synthesis alkylbenzene sulfonate surfactant for EOR is the byproducts formed in the alkylation reaction of benzene with C_10-13⁼ olefins.However,the cheap price of this raw material can not gloss over its disadvantages such as complex and indeterminate composition.In addition,its production mostly involves HF as the catalyst, which is a source of pollution and equipment corrosion.Thus,many efforts have been concentrated on solid acid catalysts for its environmentally friendly manufacture.In this paper,heavy alkylbenzene(HAB)was synthesized over immobilized AlCl₃ catalyst via alkylation reaction of benzene,toluene and ethylbenzene with industrial mixed heavy olefins(C_14-18⁼),and then was sulphonated by oleum to form HABS surfactants for EOR.The effects of support properties,reaction conditions and aromatic types on catalytic performance of the catalyst in the alkylation reaction were investigated.Three heavy alkylbenznes of C_14-18linear alkylbenzene,C_14-18methyl-alkylbenzene and C_14-18ethyl-alkylbenzene were synthesized over the higher-performance catalyst in the optimum conditions,and the structure and surface property of its sulfonates were investigated.The main results are as follows:(1)Pore diameter of support greatly influences the stability of catalyst.It is found that support pore diameter mainly influences the stability of the catalyst.The catalyst of AlCl₃ immobilized over SiO₂ with meso-pore structure exhibits good lifetime with 7 recycles under reaction temperature of 80℃,with olefin conversion of 100%.Reaction conditions influences catalyst stability and product selectivity.With the increase of reaction time,reaction temperature or the benzene/olefin ratio,the stability of the AlCl₃/SiO₂ enhances.However, the higher reaction temperature is not beneficial to 2-LAB selectivity.The optimun condition is molar ratio of aromatics/olefins of 20:1,reaction temperature of 80℃and reaction time of 3 hours.(2)The results of surface tension and interfacial tension of HABS showed that cmc andγ_cmcdecrease with the increase of carbon number of the main alkyl chain.The HABS with both methyl and C_14-18alkyl chains shows the ultra low interfacial tension of 10^-4mN/m formed between Daqing crude oil and water containing 1.2%NaOH,when its concentration is 0.05%.