Heterogeneous and Homogeneous Catalytic Partial Oxidations of Methane to Methanol and Its Derivatives

Abstract

As described in Chapter 2, biological systems can accomplish the conversion of methane to methanol via direct oxidation of methane with molecular oxygen at ambient temperature and pressure. Such systems have inspired scientists to attempt to establish artificial, energy-efficient, one-step processes for methanol production from methane using molecular oxygen as the oxidant. However, methanol production in such artificial systems remains highly challenging. In this chapter, the systems for the direct conversion of methane to methanol over homogeneous or heterogeneous catalysts developed so far are reviewed. Important examples of synthetic homogeneous and heterogeneous catalytic systems for the oxidation of methane to methanol are described. In heterogeneous catalysis, materials based on several metals have been found capable of catalytically producing methanol from methane. The methanol yields obtained in these reactions were low, mainly due to the high reactivity of methanol under the reaction conditions for the activation of methane. The highly selective synthesis of methanol via methane conversion by homogeneous metal catalysts remains difficult, with far fewer successful examples than heterogeneous catalysts. On the other hand, reactions in which methanol is obtained as its more stable ester derivatives have been devised. These reactions achieved very high product selectivity even at high methane conversion, and allow the production of methyl esters with higher concentrations than can be achieved in the production of methanol. However, approaches for methanol production from methane via methanol derivatives and those for direct conversion of methane to methanol should be considered separately.