4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

Transformation of carbon dioxide.

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

A plethora of methods have been developed over the years so that carbon dioxide can be used as a reactant in organic synthesis. Given the abundance of this compound, its utilization in synthetic chemistry, particularly on an industrial scale, is still at a rather low level. In the last 35 years, considerable research has been performed to find catalytic routes to transform CO(2) into carboxylic acids, esters, lactones, and polymers in an economic way. This Review presents an overview of the available homogeneous catalytic routes that use carbon dioxide as a C(1) carbon source for the synthesis of industrial products as well as fine chemicals.

Transformation of Carbon Dioxide with Homogeneous Transition-Metal Catalysts: A Molecular Solution to a Global Challenge?

The need to reduce the accumulation of CO2 into the atmosphere requires new technologies able to reduce the CO2 emission. The utilization of CO2 as a building block may represent an interesting approach to synthetic methodologies less intensive in carbon and energy. In this paper the general properties of carbon dioxide and its interaction with metal centres is first considered. The potential of carbon dioxide as a raw material in the synthesis of chemicals such as carboxylates, carbonates, carbamates is then discussed. The utilization of CO2 as source of carbon for the synthesis of fuels or other C1 molecules such as formic acid and methanol is also described and the conditions for its implementation are outlined. A comparison of chemical and biotechnological conversion routes of CO2 is made and the barriers to their exploitation are highlighted.

Utilisation of CO2 as a chemical feedstock: opportunities and challenges

The synthesis of organic carbonates from carbon dioxide.

Selective Conversion of Carbon Dioxide to Dimethyl Carbonate by Molecular Catalysis.

Polychlorinated biphenyls (PCBs) were made harmless using supercritical water hydrolysis with an alkali catalyst such as sodium hydroxide. PCBs over a wide concentration range from 2 wt% in transformer oil to pure state were dechlorinated to biphenyl and, in some parts, decomposed to phenol, gases and other small molecules at 30 MPa, 653-723 K, and 20-100 min of reaction time. Furthermore no dioxins were detected in both gaseous and liquid products. Supercritical water hydrolysis has advantages as follows: (1) it dechlorinates pure PCBs rapidly and completely, (2) it realizes the selective dechlorination of dilute PCBs in transformer oil without thermal deterioration of the oil, and (3) it can reduce corrosion problems by neutralizing the product of hydrogen chloride.

Dechlorination of PCBs with Supercritical Water Hydrolysis

Homogeneous catalysis in liquefied gas proves to be a promising approach to functionalize gaseous alkanes selectively; upon illumination, RhCl(CO)(PMe3)2 catalyzes carbonylation of liquefied propane at room temperature to produce butanal with high regioselectivity.

Homogeneous Catalysis in Liquefied Gas. Complex-Catalyzed Selective and Direct Conversion of Propane to Butanal at Room Temperature

A method of decomposing a polychlorobiphenyl compound-containing material into an unharmful state, wherein the material is treated with a supercritical water containing an alkaline substance at a temperature higher than the critical temperature of water and a pressure higher than the critical pressure of water.

Method of decomposing polychlorobiphenyls

PROBLEM TO BE SOLVED: To detoxicate polychlorinated biphenyl by decomposing it with supercritical water alone, supercritical water admixed with alkali or supercritical water admixed with alkali and an oxidizing agent. SOLUTION: About 50-150 weight units of water, based on one weight unit of PCB, 50-150 weight units of water and 1-5 weight units of such an alkali as sodium hydroxide or 50-150 weight units of water, 2-20 weight units of an oxidizing agent such as hydrogen peroxide and 1-5 weight units of an alkali such as sodium hydroxide are filled in a reactor and heated above the critical temp. of water in a heating furnace. The reaction pressure is adjusted in accordance with the weight of water filled in the reactor, and the reaction time is controlled to 5-60min. Oxygen, air, etc., are used as the oxidizing agent as well as hydrogen peroxide. Sodium carbonate is used as the alkali besides sodium hydroxide. Consequently, the high reaction temp. and long reaction time are not needed to make polychlorinated biphenyl harmless without causing the resynthesis of PCB.

Makoto Okano

Papers

Selective Conversion of Carbon Dioxide to Dimethyl Carbonate by Molecular Catalysis.

Dechlorination of PCBs with Supercritical Water Hydrolysis

Homogeneous Catalysis in Liquefied Gas. Complex-Catalyzed Selective and Direct Conversion of Propane to Butanal at Room Temperature

Method of decomposing polychlorobiphenyls

Method for detoxicate polychlorinated biphenyl by supercritical water