Published September 2003
As the controversial but certain ban lurks on methyl tertiary butyl ether (MTBE) in California, methanol market suffers from fear of possible jolts since MTBE is the second major global outlet for methanol. Ban in California is feared to trigger similar actions in other states also. Significant portion of methanol capacities might need to be closed down or throttled worldwide as a consequence of loss of above methanol market. Interestingly, a need for alternate and environmentally clean fuels is also growing and strengthening over the past several years paving a way for methanol for use as an alternate fuel for on-road and off-road power production in place of conventional fuels, which generate more air pollutants in burning than methanol. Extensive amount of research and development is going on worldwide to refine methanol-based fuel systems for stationary and mobile applications. Such fuels systems are designed for direct as well as indirect use of methanol. The indirect systems would use methanol as an intermediate energy storage source and subsequently transform methanol into hydrogen. The latter would then be used in fuel cell-a device that can cleanly generate electricity for stationary and mobile power consumers since hydrogen is does not pollute the surrounding environment in combustion.
Direct use of hydrogen, whether in stationary or in mobile applications, requires costly investments for its storage, transport and distribution infrastructure due to low energy density of gas both on one-time as well as on recurring cost basis. Such infrastructure is scant at present. For that reason, methanol offers a viable option as stored or high-density energy source. Once hydrogen use in fuel cells is commercialized, it would open an unfathomable outlet for methanol.
Methanol can be transformed into hydrogen via: (a) methanol decomposition (b) methanol steam reforming (c) methanol partial oxidation, and (d) methanol oxidative steam reforming. The steam reforming process, a generally preferred method, is carried out using copper-zinc-aluminum oxide catalysts at low temperatures [338 - 572°F (170 - 300°C)]. Barium or lanthanum may also be used in place of zinc. Zirconium oxide is sometimes used as promoter. Partial oxidation processes usually employ alumina-supported platinum or palladium metals. For hydrogen as the final product, reforming pressure is kept close to atmospheric.
This Review presents our evaluation of a 500 Nm3/hr-capacity, grassroots hydrogen plant based on catalytic oxidative steam reforming of methanol. Our estimates indicate that the methanol-to-hydrogen route is approximately 25% costlier than natural gas-to-hydrogen route, and hence, is appropriate for areas that do not have excess to natural gas (see cost details inside).