Catalytic dehydration of Bio-ethanol to hydrocarbons over SnOx-and SbOx-doped SAPO-34

Abstract

Recently, bio-ethanol used as a feedstock for catalytic dehydration to obtain aromatic compounds or light hydrocarbons received much attention. SAPO-34 has been employed as a solid acid catalyst for ethanol conversion to light olefins. The introduction of a metal oxide strongly influences on catalytic behavior. Tin oxide and antimony oxide were found to increase the acid strength of SAPO-34, which also increases with the amount of oxygen substitution on the central atom. The aim of this project was to study the impacts of oxidation state of tin and antimony oxides changed with various loading percentages and calcination temperature on bio-ethanol dehydration product. The sole metal oxides were also tested in order to observe its influence for basis in composition. It was found that Sn and Sb metals have hydrogenation properties, resulting in high selectivity of cooking gas. SnO2 enhanced oligomerization and aromatization reactions of light olefins to bigger hydrocarbons, whereas SnO promotes oxygenate compounds due to its low acidity. For antimony oxide, the selectivity of propylene, cooking gas and butylenes from using Sb2O5 was higher than those from Sb203. On SAPO-34, tin oxide (SN+4) was found to enhance propylene, cooking gas, and oxygenates, whereas tin oxide with oxidation 0 was found to promote aromatization to form benzene and C10+ aromatics. The oxidation state of tin oxide +2 was found to enhance oxygenates due to the basic property. Antimony oxide with oxidation state +5 was found to enhance the selectivity of propylene and cooking gas due strong acid strength. Moreover, the increase of calcination temperature was found to promote the agglomeration of Sb203. Sb203 on SAPO-34, therefore, behaves like sole antimony oxide. At calcination temperature 700 ℃, Sb203 (Sb+3) was observed to promote oxygenate formation, while Sb2O5 (Sb+5) enhanced the formation of non-aromatics and benzene.