Table 2 Catalytic hydrogenation of carbon dioxide to formic acid in different solvent mixtures.

From: Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media

Entry Solvent H 2 O (%) Solvent (%) HCOOH (M) TON
1 H2O 100 0.11 40
2 [BMIM][BF4] 50 50 0.15 54
3 [BMIM][tos] 52 48 0.19 69
4 [BMIM][tos] 40 60 0.10 36
5 [BMIM][BF4] 20 80 0.14 51
6 [BMIM][BF4] 10 90 0.12 43
7 THF 50 50 0.095 34
8 DMSO 50 50 0.34 123
9 DMSO 20 80 0.98 355
10 DMSO 10 90 1.31 475
  1. THF, tetrahydrofuran.
  2. Reaction conditions: [RuCl2(PTA)4] (2.76 mM), P(total)=100 bar, P(H2)/P(CO2) ratio of 1, t=50 °C, reaction time 120 h, solvent (2 ml containing DSS, 0.0130 M), average values of several (two to three) measurements for each cycle, reproducibility is±15%.