A highly dispersed palladium catalyst supported on nitrogen-doped carbon nanotubes was studied in CO2 hydrogenation to formic acid in the liquid phase at temperatures of 100-150 °C and high pressure. It has been shown that an increase in the catalyst loading (from 1.6 to 4.0 g/L), total pressure (from 20 to 40 atm) and PH2/PCO2 ratio (from 1 : 1 to 2 : 1) in the reactor allows increasing the yield of formic acid by over 5 times. At 150 °C, the maximum formic acid yield (27.6 g/gPd) with a selectivity of 98 % was obtained. The presence of a lot of single palladium atoms in the catalyst, in addition to its nanoparticles 1.5 nm in size, was determined to have a positive effect on the course of CO2 hydrogenation, as in the case of formic acid decomposition. On the basis of the high efficiency of this catalytic system in the reaction of formic acid decomposition to produce pure hydrogen, a conclusion was made about its potential for use in the cycle of chemical storage of hydrogen based on CO2.
Коробова et al. (Fri,) studied this question.