Hydrogen Production by the Steam Reforming of Bio-Ethanol over Nickel-Based Catalysts for Fuel Cell Applications

Abstract

Abstract:The bio-ethanol steam reforming over nickel-based catalysts when the temperature is within the range of 700 to 800 K is studied for fuel cell applications. The effect of operating conditions such as the temperature, space time, water-to-ethanol molar ratio, and oxygen-to-ethanol molar ratio on the product distribution is evaluated. The water-gas shift reaction is examined in the reforming process. Adjusting feed ratios to favor carbon removal from the surface is discussed in detail. It is shown that a nickel-supported-on-alumina catalyst completely converts bio-ethanol and high hydrogen yields are obtained. High temperatures and water-to-ethanol ratios can promote hydrogen production. There is no evidence that the water-gas shift reaction occurs over nickel-based catalysts. Carbon formation can be minimized by using high water-to-ethanol ratios. The presence of oxygen in the feed plays a favorable effect on the carbon deposition, but the carbon monoxide production is not reduced. There are several reaction pathways that could occur in the bio-ethanol steam reforming process, and the catalyst produces ethylene and acetaldehyde as intermediate products. The region of carbon formation depends on the temperature as well as the water-to-ethanol and oxygen-to-ethanol molar ratios. Finally, an overall reaction scheme as a function of temperature is proposed. The best catalysts appear to be those that are sufficiently basic to inhibit the dehydration of ethanol to ethylene, which subsequently polymerizes and causes coke formation.

An Experimental Performance Study of a Catalytic Membrane Reactor for Ethanol Steam Reforming over a Metal Honeycomb Catalyst

“…In the process of hydrogen production from ethanol, deactivation of the catalyst is generally cased by sintering of the metal particles and/or carbon deposition resulting from transformation of coke precursors (ethylene, acetaldehyde, acetone, acetic acid, etc.) [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. In this work, the potential for carbonaceous compounds formation was examined by calculating carbon balance over the reactor taking into account only CO, CO 2 , and CH 4 products, not so active in carbon deposition, and the content of which was continuously recorded by the gas analyzer.…”

“…Thus, according to mass spectrometric studies of the gas phase in reaction conditions [ 35 ], acetaldehyde, hydrogen, and methane may exist irrespectively of the presence of water. Today, it is generally accepted that while low reaction temperatures favor formation of carbon through the Boudouard reaction or ethylene formation and polymerization, carbon formation through the decomposition of hydrocarbons is the main routes at higher temperatures [ 36 , 37 ]. It is evident that steam reforming reactions with their high production rate for hydrogen, which can be both a primary and a secondary product, require high temperatures, 700–900 °C.…”

Production of Hydrogen and their Use in Proton Exchange Membrane Fuel Cells

“…However, its direct use is difficult due to the rupture of CdC bond on platinum or platinum alloy electrodes. The ethanol-steam reforming reactions take place in different steps with endothermic/exothermic reactions [33,34]. For ethanol-steam reforming reaction the chemical reactions are:…”