The increase in atmospheric carbon dioxide is linked to climate changes; hence there is an urgent need to reduce the accumulation of CO2 in the atmosphere. The utilization of CO2 as a raw material in the synthesis of chemicals and liquid energy carriers offers a way to mitigate the increasing CO2 buildup. This review covers six important CO2 transformations namely: chemical transformations, photochemical reductions, chemical and electrochemical reductions, biological conversions, reforming and inorganic transformations. Furthermore, the vast research area of carbon capture and storage is reviewed briefly. This review is intended as an introduction to CO2, its synthetic reactions and their possible role in future CO2 mitigation schemes that has to match the scale of man-made CO2 in the atmosphere, which rapidly approaches 1 teraton.

The teraton challenge. A review of fixation and transformation of carbon dioxide

Although technological practice should minimize environmental impact, this is not always economically feasible. During the past decade, for example, there has been increasing global concern over th...

CO2 Reforming of CH4

Carbon dioxide reforming of methane produces synthesis gas with a low hydrogen to carbon monoxide ratio, which is desirable for many industrial synthesis processes. This reaction also has very important environmental implications since both methane and carbon dioxide contribute to the greenhouse effect. Converting these gases into a valuable feedstock may significantly reduce the atmospheric emissions of CO2 and CH4. In this paper, we present a comprehensive review on the thermodynamics, catalyst selection and activity, reaction mechanism, and kinetics of this important reaction. Recently, research has centered on the development of catalysts and the feasible applications of this reaction in industry. Group VIII metals supported on oxides are found to be effective for this reason. However, carbon deposition causing catalyst deactivation is the major problem inhibiting the industrial application of the CO2/CH4 reaction. Ni-based catalysts impregnated on certain supports show carbon-free operation and thus attract much attention. To develop an effective catalyst for CO2 reforming of CH4 and accelerate the commercial application of the reaction, the following are identified to be the most important areas for future work: (1) selection of metal and support and studying the effect of their interaction on catalyst activity; (2) the effect of different promoter on catalyst activity; (3) the reaction mechanism and kinetics; and (4) pilot reactor performance and scale-up operation.

Carbon Dioxide Reforming of Methane To Produce Synthesis Gas over Metal-Supported Catalysts: State of the Art

Catalytic combustion, as an alternative to conventional thermal combustion, has received considerable attention during the past decade. Research efforts have been promoted by the need to meet governmental demands concerning pollution and the wish to use energy sources more efficiently. The two main advantages offered by catalytic combustors over flame combustors apply to these goals: Catalytic combustion can be carried out over a wide range of fuel concentrations in air and at low temperatures. These low temperatures result in attaining NO, emission levels substantially lower than possible with conventional combustors.

Catalytic Materials for High-Temperature Combustion

The important greenhouse effect of methane (more than an order of magnitude greater than CO2) makes it essential to eliminate/control the methane emission from natural gas engines/power plants and petroleum industries. Catalytic combustion of methane is favored over homogeneous combustion, because the former greatly facilitates the oxidative destruction of methane. Moreover, use of catalysts for methane combustion in gas-turbines affords lower working temperatures (as compared to gas-fired turbines) and thermodynamically limits NOx (which is an extremely harmful environmental pollutant) emission. A large amount of work has been undertaken to develop catalysts both for controlling methane emission as well as for generating power in high temperature natural gas-turbines. This review will address the different issues related to the variety of catalysts which have been employed for methane/lower alkane combustion. Although all the related important aspects of the combustion catalysts will be addressed, greater emphasis will be placed on recent work in this field.

Catalysts for combustion of methane and lower alkanes

This article reviews the enantio-differentiating hydrogenation of various prochiral ketones over asymmetrically modified Ni catalysts. Development from the discovery to the state of the art of the modified Ni catalyst is surveyed. Understanding and interpretation of this catalyst is discussed and new enantio-differentiation models are proposed.

Progress of enantio-differentiating hydrogenation of prochiral ketones over asymmetrically modified nickel catalysts and a newly proposed enantio-differentiation model

Asymmetrically Modified Nickel Catalyst for the Enantio-Differentiating Hydrogenation of Prochiral Ketones

Catalytic inactivities of Ni alloys expressed by surface and bulk compositions

In situ modification (( R , R )-tartaric acid and NaBr were directly added to the reaction media) of fine Ni powder (FNiP) and reduced Ni catalysts was applied to the enantio-differentiating hydrogenation of methyl acetoacetate (MAA). The high optical yield of 89% was attained by the reduced Ni catalyst. This is the highest value reported so far for the hydrogenation of methyl acetoacetate using the in situ modification. The addition of a small amount of NaBr to the reaction media increased both the optical yield and hydrogenation rate, while the hydrogenation rate decreased with the addition of NaBr to the modification solution for the conventional modification method. NaBr added to the reaction media for the in situ modification would have both of the following roles: (i) Na + increased the optical yield and the hydrogenation rate; and (ii) Br − increased the optical yield and decreased the hydrogenation rate.

Application of an in situ modification of nickel catalysts to the enantio-differentiating hydrogenation of methyl acetoacetate

The in situ modification of a reduced Ni catalyst at the first run showed a high durability for the repeated use with high optical yields in the enantio-differentiating hydrogenation of methyl acetoacetate. Reduced Ni from Ni oxide and fine Ni powder were the best materials in comparison with Raney Ni. For attaining high optical yields and high durability, in situ modification and a Ni surface suitable for the enantio-differentiating hydrogenation are necessary. One of the reasons for the low durability of the conventional pre -modified Ni with repeated use would be the desorption of tartaric acid from the catalyst surface during the hydrogenation reaction.

Osamu Takayasu

Papers

Progress of enantio-differentiating hydrogenation of prochiral ketones over asymmetrically modified nickel catalysts and a newly proposed enantio-differentiation model

Asymmetrically Modified Nickel Catalyst for the Enantio-Differentiating Hydrogenation of Prochiral Ketones

Catalytic inactivities of Ni alloys expressed by surface and bulk compositions

Application of an in situ modification of nickel catalysts to the enantio-differentiating hydrogenation of methyl acetoacetate

High durability of asymmetrically modified nickel catalysts prepared by in situ modification