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Catalysis Looks to the Future
Dissociated methanol can also be used as an efficient peaking gas turbine fuel utilizing the heat recovery from exhaust gas. The endothermic methanol dissociation reaction is also promising for cooling critical systems such as engine cooling for hypersonic jets when dissociated methanol is used as a fuel. Methanol can be produced on a large scale in a remote location for shipping. The methanol dissociation reaction can be modified to yield a wide range of H2 to CO ratios. It would provide an economically competitive and convenient source of CO or H2, especially on a small scale, and could be used in chemical plants, materials processing plants, and fuel cells on-board a vehicle.
Because of these emerging applications, there is renewed interest in developing methanol dissociation technology. Insufficient catalyst activity at low temperature and catalyst deactivation have been reported. These are two major challenges for catalysis research for on board applications. Generally, copper-based catalysts are used at 250-300° C. Zinc-chromium and precious-metal-based catalysts are utilized at 350° C or higher. Improvements in catalyst performance are being sought. For example, the activity of copper-based catalysts can be increased by adding appropriate promoters and improving pretreatment environments. Catalyst stability depends on reaction temperatures. Active catalysts would allow reaction at lower temperature and would improve catalyst stability. Methanol dissociation could operate at near atmospheric pressure for passenger cars. Extension to about 15-20 atm is needed for turbine applications and to more than 100 atm for diesel engines.
Public interest in protecting the environment has increased and expanded greatly. These public concerns manifest themselves in many different ways. The challenge is to preserve the benefits of modern technology without seriously contaminating the natural world.
Three strategies are available for reducing the impact of chemicals on the environment: waste minimization, emission abatement, and remediation. Waste minimization calls for the design and development of products and processes that are inherently low-polluting or non-polluting. The abatement of emissions can often be achieved by trapping harmful effluents or converting them to harmless substances (e.g., conversion of nitric oxide to nitrogen). Where an environmental insult has occurred, effective means of remediation are needed to restore the environment to its "green" state. As shown by the examples presented below, catalysis can contribute to these three approaches.