Hydrogen Production by Low-Temperature Oxidative Water-Steam Reforming of Ethanol on Ni/ZnO Catalyst

Abstract

The paper investigates the process of oxidative low-temperature water-steam reforming of ethanol in the flow tube of a quartz reactor at atmospheric pressure over a temperature range 300-450 °C in order to obtain hydrogen with a minimum content of carbon monoxide on the previously developed Ni/ZnO catalyst (20 wt.% nickel). The catalyst was prepared by impregnating industrial zinc oxide powder with nickel nitrate followed by calcination and reduction of nickel oxide. Water-ethanol mixtures with the ethanol-water molar ratios from 1: 2 to 1:13 were used. The flow of the liquid mixture was 0.45-1.55 g / h. Air with the mixture was supplied to the reaction zone so that the oxy-gen/ethanol molar ratio varied in the range of 0.5-1.2. A gas phase analysis was carried out on a gas chromatograph “Tsvet-500”. A catarometer was used as a detector. The research has shown a rather high efficiency of the Ni/ZnO catalyst in the hydrogen production in the process of oxidizing water-steam reforming of ethanol at relatively low temperatures. Hydrogen, methane and carbon dioxide are the main products of ethanol reforming. The conversion of ethanol takes place already at 300 °C and is almost completely at 450 °C (99%). The hydrogen content in the reforming products in all the studied cases is over the range of 45-60 vol% and constitutes the yield of 1.6 mole of hydrogen per 1 mole of ethanol at a temperature of 450 °C. At the same time, a higher content of carbon dioxide reaching 45 vol% and a lower content of methane, 4-10 times less than hydrogen, are observed in contrast to water-steam reforming of ethanol, where the content of carbon dioxide is 15-20 vol%, and methane is only 2-2.5 times less than hydrogen. There is almost no carbon monoxide over the entire studied temperature range with a short contact time (0.5-0.6 s) of the reaction mixture with a catalyst and with an increased oxygen/ethanol molar ratio in the gas phase. It is possible to use the mixture enriched in hydrogen to power the fuel cells on proton conducting membranes.