Highly efficient hydrogenation of carbon dioxide to methyl formate over supported gold catalysts

Abstract

Transformation of carbon dioxide (CO 2 ) into valuable chemicals is an interesting topic in green chemistry. Hydrogenation of CO 2 to methyl formate (MF) in the presence of methanol is an important reaction. In this work, Au nanocatalysts immobilized on different supports were prepared and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectrometer (XPS). The catalytic performances of the catalysts for the reaction were studied. It was demonstrated that the Au/ZrO 2 , Au/CeO 2 and Au/TiO 2 were very active and selective for the reaction in the absence of any basic additives. The Au/ZrO 2 was more active than Au/CeO 2 and Au/TiO 2 if the sizes of Au particles on the supports were similar. Moreover, for the Au/ZrO 2 catalysts, Au particles with smaller size had higher activity. The possible mechanism of the catalytic reaction was proposed.

Carbon Dioxide Transformation in Imidazolium Salts: Hydroaminomethylation Catalyzed by Ru‐Complexes

“…Finally,b yt he addition of P(OEt) 3 ,t he high-field hydride signal becamep redominant and no organometallic speciesa ssociated with P-ligands were detected. Indeed, none of the signals coupled with 13 Pb y 1 H, 13 C, or 31 PNMR spectroscopy,t hus reinforcing the decomposition path of P(OEt) 3 into H 3 PO 4 [52] (observed by 31 PNMR) that is an extra source of H + necessary in the protonation step. [32] We have also observed CO and water in the gas phase (by GC) of the reaction of 60 bar = 6MPa CO 2 /H 2 (1:1) at 120 8Cf or 24 h, hence indicatingt he occurrence of RWGS reactiona tt his relative low temperature.…”

“…In contrast, phosphites [i.e.,P (OEt) 3 ]p rovided an improvement in both the catalytic activity and oxo-product selectivity,a sa lso observed by others. [28] However, 31 PNMR experiments revealed that this apparent ligand effect wasc aused by the formation of phosphoric acid (H 3 PO 4 )u nder our reaction conditions. [33] It is reasonable to assume, that even in the case of reactions involving CO 2 /H 2 in imidazolium salt IL media, it will be possible to shift the selectivity towards the CO path by fine-tuning the reaction conditions.…”

“…[23] These include the Ru-catalyzed reductive methylation of imines, [24,25] amines, [26] and CÀHb onds, [27] as well as the Ru- [28][29][30] or Rhcatalyzed carbonylation of alkenes,o re ven Au-promoted formation of methyl formate. [31] In the Ru-catalyzed carbonylations, it has been proposed that the first step of the reaction involves the presence of cationic Ru-hydrido ([Ru-H + ]) complexes and the addition of ap rotons ource usually significantly improves the catalytic activity. [32] Generally,s ophisticated ligandsa re required to control the reactivity of [Ru-H] + species andt oi mprove both catalytic activity and selectivity.…”

Direct Synthesis of Methyl Formate from CO2 With Phosphine‐Based Polymer‐Bound Ru Catalysts

“…[3] Ap otential approach to circumvent this problem is the use of alcohols such as methanoli nstead of water as the solvent to perform CO 2 hydrogenation. [14] Most recently, Urakawa and co-workers demonstrated the continuous hydrogenation of CO 2 to MF in af ixed-bedr eactorc atalyzed by aS iO 2 -supported Ag catalyst. [4] In contrast to formic acid, the resulting MF can be readilyd istilledf rom the product mixture owing to its very low boilingp oint (31.7 8C) as well as its negligible bondingw ith bases.…”

“…[13] In 2015, Wu et al reported an impressive TOF of up to 534 h À1 by using ZrO 2 -supported Au nanoparticlesi nt he absence of base under harsh conditions (200 8C, 160 bar). [14] Most recently, Urakawa and co-workers demonstrated the continuous hydrogenation of CO 2 to MF in af ixed-bedr eactorc atalyzed by aS iO 2 -supported Ag catalyst. 100 %s electivity towards MF at a methanol conversion of 4% waso btained at 280 8C and 300 bar with ag as hourly space velocity (GHSV) of 9000 h À1 .…”