727.    ---------------.  [DOLGOV, B. N., AND KARPINSKII, M. N.]  [Methanol Synthesis.  VI.  Synthesis From Carbonic Acid and Hydrogen.]  Khim. Tverdogo Topliva, vol. 4, 1933, pp. 69-79; Chem. Zentralb., 1934, I, p. 2652; Chem. Abs., vol. 28, 1934, p. 5805.

     These experiments were carried out with a decreasing pressure and the activity of the catalysts was investigated at 226°-400°.  In another synthesis carried out at constant pressure and with introduction of additional portions of gases during the process, a circulating Fischer retort of 4.5-l. capacity was used.  The gas mixture was prepared by mixing CO₂ and H₂, compressing it, and keeping it in steel bottles.  The reaction CO₂+3H₂→CH₃OH+H₂O, as shown by the experiments, proceeds in 2 stages (1) CO₂+H₂→CO+H₂O and (2) CO+2H₂→CH₃OH.  The velocities of the reactions differ, depending upon the ratio of gases, temperature, catalyst, etc.  19 different catalysts and their mixtures were investigated, and it was found that the maximum lies at 300°-325°, that is, 75° lower than that for MeOH from CO and H₂.  The following catalysts were used in various combinations:  MgO, Fe₂O₃, ZnO, ThO₂, V₂O₅, Ce₂O₃, CuO, Ni₂O₃, CdO, MnO, and Cr₂O₃.  The highest MeOH yields were obtained with ZnO+4.5% CdO+5% Fe₂O₃ and ZnO+2% Fe₂O₃+1% CuO, reaching 51.5% and 50%.  However, when maintaining a constant pressure by the introduction of new portions of gas, working at 325°, 200-210 atm., and using the catalyst ZnO+5% CdO, the yield of CH₃OH could be raised to 63% by weight.  Changes in the velocity of the flow of the gas mixture caused lower yields of MeOH because of the slowing down of the conversion of CO₂ to CO.  The crude MeOH contained C₁₁H_2n traces, C_nH_2n+2 none, HCHO none, AcH traces, AcOEt none, AcOH about 0.05-0.06%, and Fe(CO)₅ none.  A pure 98% MeOH is obtained by distillation and rectification.  The gas used in the synthesis consisted of 1 vol. CO₂/3-3.5 vol. H₂ with the admixture of 0.2-0.8% CO and 0.4-3.0% N₂.