Catalyst Recycling in the Reactive Distillation of Primary Alcohols to Olefins Using a Phosphoric Acid Catalyst

Olefins are essential basic chemicals in all areas of the chemical industry and can be produced from alcohols by dehydration. The amount of alcohols produced from biomass sources is expected to rise in the next decade. Various heterogeneously catalyzed processes have been developed in previous works operating at a high reaction temperature of 350 degrees C to obtain olefins from alcohols. In this work, we present the conversion of C-7 to C-12 alpha-alcohols to the corresponding olefins using phosphoric acid as a strong inorganic homogeneous acid catalyst. The reaction network was investigated using a microwave reactor. A system with a reactive distillation of the produced water and olefins was developed to shift the equilibrium of the reaction toward the olefins. Mild reaction conditions were utilized with temperatures ranging between 170 and 230 degrees C. The catalyst was recycled successfully over 12 runs in batch reactions and in semi-continuous flow experiments at 190 degrees C over 6 h. Up to 93% yield of olefinic products were obtained with the corresponding ether as the major side product.