The competition between dehydrogenation and dehydration reactions for primary and secondary alcohols over gallia: unravelling the effects of molecular and electronic structure via a two-pronged theoretical/experimental approach

Abstract

The relative dehydrogenation/dehydration reactivity imparted by nanostructured gallium(iii) oxide on alcohols was investigated via electronic structure calculations, reactivity tests and DRIFT-IR spectroscopy.

Non‐oxidative Dehydrogenation of Methanol to Formaldehyde over Bulk β‐Ga2O3

“…Also, a small amount of methyl formate (MF) was observed (Y(MF) = 4.5 % at 430 °C). This product distribution is in line with previous studies on ChemCatChem methanol decomposition over β-Ga 2 O 3 at 400 °C reported by Izzo et al [36] In addition to DME, they also detected carbon oxides in the product stream, which was explained by the decomposition of either CH 2 O to CO and H 2 and of MF to CO 2 and CH 4 . The reported conversion was higher (> 95 %) despite the higher methanol concentration in the feed stream (18 %) due to the higher catalyst amount (1 g vs. 50 mg) and the longer residence time (1 s vs. < 0.11 s) in comparison to the reaction conditions in this study.…”

“…Also, a small amount of methyl formate (MF) was observed ( Y (MF)=4.5 % at 430 °C). This product distribution is in line with previous studies on methanol decomposition over β‐Ga 2 O 3 at 400 °C reported by Izzo et al [36] . In addition to DME, they also detected carbon oxides in the product stream, which was explained by the decomposition of either CH 2 O to CO and H 2 and of MF to CO 2 and CH 4 .…”

“…devoted to the conversion of CH 3 OH to hydrocarbons, it was demonstrated that Ga 2 O 3 is almost inert for the conversion of CH 3 OH at 400 °C (WHSV=0.7 h −1 ). In contrast, recently Izzo et al [36] . showed that bulk Ga 2 O 3 can effectively catalyze the dehydrogenation of primary and secondary alcohols and, according to their DFT calculations, this reaction pathway is preferred over alcohol dehydration.…”

Transition Metal B-Site Substitutions in LaAlO3 Perovskites Reorient Bio-Ethanol Conversion Reactions

“…The role of gallium deserves a special attention, as its position in the periodic table should impart amphoteric properties to its oxide. Gallia has been shown to be more active in dehydrogenation than in dehydration of ethanol [103]. This result is coherent with the high basicity imparted to LaAlO 3 by incorporation of gallium, as indicated by the results of isopropanol conversion on Ga25.…”

Unrevealing the hidden link between sustainable alkylation and hydrogen transfer processes with alcohols

“…[13] Interestingly, gallium oxide (Ga2O3) has also proven to have a peculiar catalytic activity in the dehydrogenation of alcohols. [14] However, Ga is considered a technologically critical element, not only because of its limited production (mainly as a by-product of Al production from bauxite) but also because it finds applications in several strategic high-tech products. [15] Notably, the inclusion of small amounts of Ga as a promoter in the lattice of magnesium oxide (MgO) have proven to be sufficient for fostering in situ methanol dehydrogenation to formaldehyde, making it possible to greatly enhance the alkylation of phenol to TMP compared to MgO.…”