Raw Material Pretreatment And Catalyst Performance Study Of Fischer-Tropsch Oil Synthesis Of Alkyl Benzene

Linear alkylbenzene(LAB)is a very important chemical intermediate with good biodegradability and solubility,generally synthesized by benzene and long-chain α-olefins by Friedel-Crafts alkylation reaction,and used in the synthesis of various detergent products and surfactants linear alkyl benzene sulfonate(LAS)production.At present,the industrial production process of linear alkylbenzene is still produced by the petroleum catalytic cracking synthesis route α-olefins as raw materials,and the traditional liquid hydrofluoric acid as the catalyst.The route has a complex process and high production cost;Liquid hydrofluoric acid is polluted,corrosive and toxic,difficult to separate,and does not conform to the concept of green chemical industry,so this paper conducts a green process research on the synthesis of alkyl benzene from Fischer-Tropsch oil.Firstly,the dynamic adsorption method was used to carry out X-type molecular sieve adsorption deoxidation treatment and A-type molecular sieve adsorption dehydration treatment for Fischer-Tropsch oil,and through the investigation and optimization of the initial concentration of oxygencontaining compounds and the process conditions of feed flow,under the condition of feed flow of 9ml/min and initial concentration of oxygenated compounds of 998.7ppm,13 X adsorption deoxidation treatment and 3A and 4A molecular sieve dehydration treatment were carried out to obtain mixed raw materials without oxygenated compounds and water content ≤20 ppm.Five zeolite catalysts,Hβ,MCM-22,HMOR,HY and HZSM-5,were screened by structural characterization methods,as well as the activity evaluation device of kettle batch reactor and fixed-bed continuous reactor,and it was found that HY zeolite performed better catalytic performance in the alkylation reaction of Fischer-Tropsch oil α-olefins and benzene.Through nitrogen constant temperature adsorption and desorption,ammonia programmed temperature desorption,and thermogravimetric analysis,the structural changes before and after inactivation of molecular sieve were studied,and it was found that the blockage caused by macromolecular coking inside the molecular sieve pores was mainly caused,and finally caused inactivation.Multi-stage porous HY catalysts with different molar silicon-aluminum ratios were prepared by hydrothermal synthesis without template agent secondary crystallization.Through the characterization of micromorphology,acid characteristics,pore structure and the evaluation of fixed bed reaction performance,it is found that when the silicon-aluminum ratio is 5,the surface of HY molecular sieve is smoother and more regular,the skeleton is firmer,the pore size distribution range is wider,the acid amount is larger,and the active site is more,so the alkylation performance is better and the life is longer.Then,when using the catalyst,the influence of raw material pretreatment,temperature,pressure,airspeed,molar ratio of phenylene and other process conditions was studied,and it was found that under the conditions of temperature 130~150℃,pressure 1.0~2.0 MPa,airspeed 3~6 h-1,phenylene molar ratio of 15,oxygen-containing carbonyl concentration of 0 ppm,and water content of ≤20 ppm,the alkylation life of porous grade HY molecular sieve in Fischer-Tropsch oil as raw material can reach 290 h.