Selective synthesis of isobutanol by means of the Guerbet reaction

Guerbet condensation of methanol with n-propanol to isobutyl alcohol over heterogeneous bifunctional catalysts based on Mg–Al mixed oxides partially substituted by different metal components

“…When Rh/C was used in the place of Pd/C under the same conditions as those adopted in entry 4, no appreciable activity was ascertained. Considering that under these last conditions, both Pd/C and Rh/C//MeONa systems displayed a rather high activity to give i BuOH [3,4], these results clearly indicate that the mechanical combination of the basic component C2 with these dehydrogenating/hydrogenating supported metal species is not able, differently from the copper chromite/C2 system, to operate as a real bifunctional catalyst. Moreover, these data represent an indirect confirmation of the determinant role played on the catalytic activity by the homogeneous Pd and Rh species released in the liquid phase when MeONa was used [3,4].…”

“…In all cases, a feed with a MeOH/PrOH molar ratio equal to 12.5 and usually 200 • C as reaction temperature were used, as those optimized in previous papers for the Guerbet condensation [3,4,7]. When the reaction was performed under nitrogen atmosphere and Pd/C was pre-activated, either in MeOH at 180 • C for 5 h (entry 1) or in the presence of MeONa (subsequently eliminated by washing with MeOH) (entry 2), no activity at all was observed.…”

“…When N 2 was adopted Scheme 1. in the place of H 2 as reaction atmosphere, better catalytic performances were obtained, thus indirectly confirming that the dehydrogenation of the alcohols to the corresponding aldehydes is the rate-limiting step of the reaction. Moreover, recycle tests allowed to conclude that copper chromite essentially works in heterogeneous phase, unlike that observed for Pd-, Rh-or Ru-based catalysts where the metal leaching was favoured by the presence of the methoxide anion [3,4].…”

“…Recently, we have proposed [1][2][3][4] the selective synthesis of i BuOH starting from methanol (MeOH) and n-propanol (PrOH) through the Guerbet reaction, a condensation between alcohols promoted by bifunctional catalysts based on a basic component and a metal species with dehydrogenating/hydrogenating properties. In particular, the above mentioned reaction is characterized by the following three steps:…”

Review of catalytic systems and thermodynamics for the Guerbet condensation reaction and challenges for biomass valorization

“…It is therefore often applied in the Guerbet reaction with ethanol or n-propanol for the production of isobutanol, a product which can be processed to isobutene and methyl-tert-butyl ether. [79][80][81][82][83][84][85] The latter is often used as a fuel additive to increase octane numbers. 86 Butanol can also serve as a source of C 4 -olefins.…”