Dehydration-Dehydrogenation of Ethanol on Chromia-Alumina and Magnetite-Alumina Nano-Composite Catalysts

Abstract

Chromia-alumina and hematite-alumina nano-composite materials are prepared by ultrasonic assisted co-precipitation method. The prepared materials are tested for their suitability in the catalytic conversion of ethanol in a fixed bed reactor at a space velocity 0.6 h–1 by using either O2 and/or N2 as carrier gas with a flow rate of 40 mL/min at temperature range 200–500°C. The prepared nano-composite materials are characterized by XRD, DTA, TGA, DLS, TEM, NH4-TPD and surface measurements, which informed the formation of amorphous chromia-alumina material with low surface area, wide pore size and weak surface acidity. On contrary crystalline hematite-alumina with high surface area, narrow pore size and large number of strong surface acidity is formed. The catalytic activity results indicate that the main converted products are acetaldehyde, ethylene and diethyl ether. The dehydrated products (ethylene and diethyl ether) are prevailing by using chromia-alumina nano-composite in the presence of nitrogen carrier gas with ethanol conversion 74% at 500°C. In the presence of oxygen carrier gas, acetaldehyde is the predominant product with selectivity 38.5%. Hematite-alumina nano-composite emphasizes the same trend towards the formation of the dehydrogenated compounds, at 500°C in the presence of the oxygen carrier gas (acetaldehyde) with selectivity 42%, besides formation of the dehydrated products with selectivity 32.8%.