Selective Ruthenium-Catalyzed Transformation of Carbon Dioxide: An Alternative Approach toward Formaldehyde

Formaldehyde is an important precursor
to numerous industrial processes
and is produced in multimillion ton scale every year by catalytic
oxidation of methanol in an energetically unfavorable and atom-inefficient
industrial process. In this work, we present a highly selective one-step
synthesis of a formaldehyde derivative starting from carbon dioxide
and hydrogen gas utilizing a homogeneous ruthenium catalyst. Here,
formaldehyde is obtained as dimethoxymethane, its dimethyl acetal,
by selective reduction of carbon dioxide at moderate temperatures
(90 °C) and partial pressures (90 bar H2/20 bar CO2) in the presence of methanol. Besides the desired product,
only methyl formate is formed, which can be transformed to dimethoxymethane
in a consecutive catalytic step. By comprehensive screening of the
catalytic system, maximum turnover numbers of 786 for dimethoxymethane
and 1290 for methyl formate were achieved with remarkable selectivities
of over 90% for dimethoxymethane.