NIRE and RITE have jointly performed a national R&D project on methanol synthesis from CO 2 and hydrogen in order to contribute to CO 2 mitigation. In the first step, many attempts were made at developing high-performance catalysts for methanol synthesis. The roles of metal oxides contained in Cu/ZnO-based catalysts were classified into two categories: (1) Al 2 O 3 or ZrO 2 improves the dispersion of copper particles in the catalyst; (2) Ga 2 O 3 or Cr 2 O 3 increases the activity per unit copper surface area of the catalyst. The long-term stability of Cu/ZnO-based catalysts during methanol synthesis from CO 2 and hydrogen was improved by adding a small amount of silica to the catalysts, and then calcining the catalysts at high temperatures around 873 K. Silica added to the catalysts suppressed the crystallization of ZnO contained in the catalysts, which was probably caused by the action of water produced together with methanol. Based on those two important findings, high-performance Cu/ZnObased multicomponent catalysts (SiO 2 ) were developed. The catalysts developed were found to be highly active and extremely stable in methanol synthesis from CO 2 and hydrogen. In the next step, a bench plant with a capacity of 50 kg day À1 of CH 3 OH, which was equipped with facilities for recycling unreacted gases and gaseous products, was successfully operated. The activity of the Cu/ZnO/ZrO 2 / Al 2 O 3 /SiO 2 catalyst was 580 g h À1 of CH 3 OH per liter of catalyst under the reaction conditions of 523 K, 5 MPa and SV = 10,000 h À1 in 1000 h on stream. The selectivity to methanol synthesis was as high as 99.7%, and the purity of crude methanol produced was 99.9 wt%, whereas the purity of crude methanol produced from syngas in a present-day commercial plant was reported as 99.6 wt%.

The behavior of oxygen, O2− and O− radicals adsorbed on the partially reduced V2O5–SiO2 catalysts has been investigated. Oxygen is adsorbed mainly in a molecular state at room temperature, the sum of amounts of paramagnetic adsorbed species O2− and O− being less than 10% of total amount of adsorbed oxygen. High degree of reduction, high content of V2O5 and low pressure of oxygen at adsorption equilibrium are favorable for the formation of O− radical. It was confirmed by the quantitative analysis of reaction products and the adsorbed species that O2−, not O−, is the active species in the oxidation of propylene at room temperature. A mechanism involving an intermediate of an epoxide structure was proposed.

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A small-scale test plant with a methanol production capacity of 50 kg day À1 has been designed and constructed in order to examine the performance of a previously developed Cu/ ZnO-based catalyst under practical reaction conditions. The reaction model for methanol synthesis over the developed catalyst is presented. In addition, the methanol production rates measured in the test plant were found to fit the rates calculated based on the kinetic equations. A 4000 t day À1 methanol synthesis plant from CO 2 and H 2 was designed based on the kinetic equations and the selectivity to methanol over the developed catalyst.