Catalytic dehydration of bio-ethanol to heavy hydrocarbons using gallium and germanium oxide modified zeolites

Abstract

At present, oil and petrochemical consumptions are grown up rapidly, but petroleum is a nonrenewable energy. So, biomass is an attractive sustainable energy. From literature review, methanol or ethanol can be converted to gasoline range of hydrocarbons via dehydration and other reactions. It was found that SAPO-34 (8- membered ring) produced more than 70% ethylene and propylene from methanol and ethanol dehydration. H-ZSM-5 (10-membered ring) was also used as a catalyst for methanol to gasoline process by Exxon Mobil Research and Engineering Company because of its shape selectivity. These two examples show that the products from dehydration are controlled by the pore size of zeolites. Therefore, H-Beta (12- membered ring) and MSU-S/HBEA (Mesoporous catalyst), which have larger pore size than H-ZSM-5, were used in this work, and they were expected to produce larger hydrocarbons than gasoline range of hydrocarbons. The effects of acid density and acid strength in the product distribution were investigated using various Si/Al2 ratios of H-Beta zeolites. Gallium- and germanium oxide were also doped on the H- Beta zeolites by incipient wetness impregnation, since they were found to enhance single-ring aromatic formation. The catalysts were characterized by using XRD, SAA, TPD-NH3, and TPD-IPA. Afterward, the dehydration of bio-ethanol was performed, and the products were analyzed by an online GC, GC-TOF/MS, and SIMDIST-GC. As a result, it was found that the highest oil distribution was obtained from using a moderate Si/Al ratio of H-Beta (Si/Al2 ratio = 37). Moreover, MSU mesoporous catalyst enhanced C10+ aromatics production in a kerosene range of hydrocarbons.