Last modified: 2017-10-10
Abstract
Natural gas is a multi-purpose, convertible, economical and effective fuel used in various applications. There are almost 187.3 trillion cubic meters of Natural gas reserves present on earth to date. Currently discovered natural gas reservoirs are solely enough to meet almost 56 years of global energy production, as estimated. According to estimation, 1 to 9 % of the total natural gas produced or extracted leaves to the atmosphere without burning, which is equivalent to the emissions produced by 100-300 coal-fired power plants. An essential component of natural gas, methane, is 34 times more vigorous than carbon dioxide at trapping heat, which leads to the increased global warming. Methane has a low density per unit volume, hence it needs to be transported in compressed form, but compression mechanism is energy rigorous and expensive. Hence the major proportion of the natural gas obtained as a secondary product during oil drilling is flared entirely due to the economic reasons. This accounts up to 150 billion cubic meters of natural gas, which is almost 5% of natural gas consumption globally. Establishing a direct way of methane conversion to methanol can provide premises for the effective utilization of natural gas. Methanol is an energy dense liquid whose transportation is easy and economically viable within the existing infrastructure. Until now, the conversion of methane to methanol is carried out in a two-step process, starting initially from high-temperature partial oxidation of methane to hydrogen and carbon monoxide by a process known as cracking, and ends up with methanol as a final product through the catalytic conversion of syn gas at high temperature. This process is quite expensive because of the high energy requirements and the prerequisites. Alternatively, one step direct conversion of methane to methanol in the presence of enzymes or catalysts is a more economically viable approach. Striking development has been made in the field of molecular catalysis to transform methane to methanol derivatives with an economical yield of more than 10%. The purpose of this review study is to summarize all the positive approaches made in this way and to suggest the new possibilities to formulate more energy intensive process for methane to methanol formation. Catalyst characterization by means of various regeneration techniques is emphasized.