Study On Catalysts For Dehydration Of Lactic Acid To Acrylic Acid And Process Optimization

Currently the traditional industrial method use process of acrylic acid with two-step propylene oxidation. This process is based on non-renewable oil resources, which caused the rise in the production cost of acrylic acid. At the same time, the traditional industrial method has other problems, such as a longer process, more chemical equipment, larger investment and hieher energy consumption. To solve these problems, lactic acid from biomass via fermentation as raw materials, and HZSM-5as research object, the dehydration of lactic acid to acrylic acid was studied from aspects of modified method, modified condition and reaction condition.the stability and regeneration performance of the catalyst were investigated. It is expected to provide useful information for industrial application.(1) The alkaline source was introduced into molecular sieve by an impregnation method. The effect of alkali, alkaline concentration, alkaline treatment time, calcination temperature, reaction temperature and others on the dehydration of lactic acid to acrylic acid were investigated. The results were:HZSM-5was modified by NaOH, alkaline concentration of0.5mol/L, time of8h, soaking temperature of80℃, no calcination, catalyst had best catalytic performance. The optimal technological conditions were reaction temperature of375℃, feed liquid concentration of40wt%, flow rate of0.08mL/min, N2flow rate of35mL/min. By the stable performance of NaOH/ZSM-5catalyst, the reaction run55h, the yield of acrylic acid decreased by20%, while regeneration performance of catalyst was poor.(2) NaOH/ZSM-5was modified by metal ion exchange, and the effect of mental ion, concentration and exchange time on catalytic properties was investigated. The results were: Cs+as mental ione, concentration of0.025mol/L, exchange time of8h, catalyst had best catalytic performance, the conversion of lactic acid was100%and the yield of acrylic acid reached67.91%; And compared to NaOH/ZSM-5-0.5-8catalyst, under the same reaction conditions, Cs-0.025-8/ZSM-5-0.5-8catalyst obtained more stability and regeneration performance. The optimal combination was obtained by the orthogonal experiment:reaction temperature of390℃, feed liquid concentration of30wt%, flow rate of0.12mL/min, the yield of acrylic acid was68.63%.