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

Abstract

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.

Utilization of Formic Acid as C1 Building Block for the Ruthenium‐Catalyzed Synthesis of Formaldehyde Surrogates

“…In detail, one molecular ruthenium catalyst allowed the sequential reduction and acetalization transformation . Subsequent optimization studies using the established catalyst lead structure allowed reactions with increased TONs . Additionally, a non‐precious and efficient cobalt‐triphos system could be established for this hydrogenation sequence of CO 2 to DMM .…”

“…Accordingly, the present investigation with formic acid was initiated with this [Ru(triphos)(tmm)] catalyst and aluminum tris(trifluoromethanesulfonate) Al(OTf) 3 as Lewis acidic co‐catalyst. The Al(OTf) 3 acid was selected for this work as it showed the best results of previous reported work on DMM synthesis from CO 2 . Generally, first reactions were carried out using molecular hydrogen at a pressure of 80 bar and 80 °C.…”

Challenges and Opportunities in the Production of Oxymethylene Dimethylether

“…More recently, the group of Trapp used the developed catalyst lead structure and prepared catalysts derivatives (ruthenium/N‐triphos/Al(OTf) 3 ) in combination with consequent optimization of the reaction conditions for OME 1 and MF synthesis from CO 2 /H 2 and methanol. The authors extensively investigated the effects of variations in the reaction conditions with respect to temperature, partial pressure of H 2 and CO 2 , reaction time, and additive as well as catalyst and Lewis acid concentration. Consequently, the optimized conditions resulted in the formation of OME 1 and MF in TONs of 786 and 533 (Scheme ).…”

Identifying high-performance catalytic conditions for carbon dioxide reduction to dimethoxymethane by multivariate modelling

“…25,26 Recently, we applied a univariate optimisation approach including several hundred catalytic reactions to improve the selective ruthenium-catalysed transformation of carbon dioxide to dimethoxymethane (DMM) reaching a turnover number (TON) of 786 (Scheme 1). 27,28 The product DMM itself is a high value feedstock for biofuels, but can also be hydrolysed yielding formaldehyde and methanol or directly employed as a formaldehyde synthon. 29,30 Beside the desired product, only methyl formate (MF) was formed with TONs of up to 1290 (Scheme 1).…”

“…29,30 Beside the desired product, only methyl formate (MF) was formed with TONs of up to 1290 (Scheme 1). 27 Previously, two studies on the selective hydrogenation of CO 2 by the group of Klankermayer showed the formation of DMM and MF by using a homogeneous ruthenium catalyst 31 with TONs of 214 and 104 or a cobalt catalyst 32 with TONs of 157 and 37, respectively. Further selective reductions toward the formaldehyde oxidation state were reported utilising hydroboration, [33][34][35][36][37] hydrosilylation, 38,39 and frustrated Lewis pairs, 40,41 however, being mainly of academic interest due to the stoichiometric use of reducing reagents.…”