(ⅰ)CO2(g)+3H2(g) CH3OH(g)+H2O(g) △H1=-49.3 kJ/mol
(ⅱ)CO2(g)+H2(g) CO(g)+H2O(g) △H2=+41.1 kJ/mol
由CO也能直接加氢合成甲醇:(iii) 2H2(g)+CO(g) CH3OH(g) △H