The photo-assisted thermal decomposition of methanol and isopropanol in a fluidized bed
Abstract
The principal objective of this work is the direct use of high-flux solar radiation to carry out endothermic reactions. This is accomplished by absorbing the radiation on to the surface of a fluidized bed whose particles contain the catalyst with the reactant molecules adsorbed on the surface. This configuration allows the solar radiation to be absorbed directly at the reaction site where both the reactant molecule and catalyst are present. The solar energy spectrum is simulated using a xenon lamp. Since the fluidized bed particles are chosen to be inert to the chemical reaction, the reaction medium should be free of corrosion. Furthermore, if the fluidized bed particles have the proper optical absorption characteristics, the energy collection efficiency should be high.
The studies focus on the nature of the fluidized bed particles and how solar radiation can be used to carry out the endothermic reaction. Particular attention is given to possible photocatalysts which may be used to initiate the reaction by formation of essential radicals that may be used to carry out a chain mechanism. The decomposition of simple aliphatic alcohols was used to test the system and establish essential parameters. The decomposition of methanol has been studied over several catalysts. The reaction with chromium(III) oxide on alumina gives principally carbon dioxide and hydrogen at ~ 500 °C. Presumably, the carbon dioxide comes from the reaction with water which is adsorbed in the alumina. The reaction of methanol over vanadium pentoxide on alumina-silica gives a different reaction pathway to dimethyl ether and water at low temperatures. At high temperatures (~ 500 °C) the dimethyl ether undergoes decomposition to methane, carbon monoxide, and hydrogen. The reaction rate increases significantly when the catalyst is exposed to simulated solar radiation. However, the rate is not significantly affected by the u.v. portion of the spectrum. The increase in rate is apparently due to localized heating on the particle surface which arises from direct absorption of the radiation. The reaction of other aliphatic alcohols and recent studies of hydrocarbon reforming also will be discussed.- Publication:
-
Energy
- Pub Date:
- 1987
- DOI:
- 10.1016/0360-5442(87)90091-0
- Bibcode:
- 1987Ene....12..319W