Copper-nickel mixed oxide catalysts from layered double hydroxides for the hydrogen-transfer valorisation of lignin in organosolv pulping

Abstract

Copper and nickel mixed catalysts obtained by the calcination of iron and aluminium hydrotalcites (layered double hydroxides, LDH) have been tested for the conversion of a lignin model dimer in subcritical methanol. The phase distribution and the textural properties of the catalysts were characterized by X-ray diffraction Rietveld analysis and N2 physisorption. The presence of copper was critical for effective hydrogenation, both by direct hydrogen transfer from methanol to aldehyde groups and by the reactivity of products from methanol reforming.TPR experiments showed that the hydrogenation activity was promoted by an enhanced reducibility of the Cu-catalysts, related to the presence of other oxide components.

Design of Multicationic Copper‐Bearing Layered Double Hydroxides for Catalytic Application in Biorefinery

“…The yield of CÀ C hydrogenation products was only slightly lower than the yields of CÀ O hydrogenation, indicating that the hydrodeoxygenation of the alcohol groups formed by MPV transfer was very rapidly followed by the hydrogenation of the aromatic-methyl bonds. However, as already observed for hydrogen transfer from methanol, [42] CÀ C bonds were less easily hydrogenated in volatile monomers than in dimers. Indeed, o-cresol presented a selectivity higher than guaiacol, while BMT was only observed in traces and BMB was a major product (see Table S1).…”

“…The high activity and selectivity of catalytic transfer hydrogenation was correlated with the oxidation states of copper on LDH‐derived catalysts [45] . The different activity of Cu‐ and Ni‐bearing catalysts was attributed to easier reducibility of the Cu‐bearing catalysts also in the case of BMBA conversion in methanol [42] . A synergistic effect of Ni on the reducibility of Cu−Ni mixed catalysts was also observed.…”

“…In most cases supercritical methanol has played the twin role of solvent and hydrogen donor [5b,e,41] . Tests in methanol at a lower temperature (200 °C) have also shown that it is possible to avoid supercritical conditions, not easily implementable in industrial organosolv processes [42] . The choice of methanol is interesting due to its large availability and the easier separation of gaseous CO and CO 2 , coproducts of the hydrogen transfer reaction.…”

“…[5b,e,41] Tests in methanol at a lower temperature (200 °C) have also shown that it is possible to avoid supercritical conditions, not easily implementable in industrial organosolv processes. [42] The choice of methanol is interesting due to its large availability and the easier separation of gaseous CO and CO 2 , coproducts of the hydrogen transfer reaction. However, methanol has a relevant toxicity and is generally not produced from renewable resources.…”

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

“…[37][38][39][40][41][42][43][44] The CTH reaction was even used for the stabilisation of reactive phenolic intermediates during the recently reported lignocellulosic biomass reductive catalytic fractionation (RCF) processes (Figure 2). [45][46][47] Figure 2. Successfully applied CTH processes for the valorisation of bio-based compounds.…”