Copper and lanthanum mixed oxides as catalysts for ethanol Guerbet coupling: The role of La³⁺ on the production of long‐chain alcohols

Abstract

Mixed oxides derived from the calcination of modified hydrotalcites precursors with copper and lanthanum were synthetized by the co‐precipitation method and characterized and applied as catalysts for ethanol Guerbet coupling reactions. The oxides obtained were used to convert ethanol into 1‐butanol and long‐chain alcohols, mostly 1‐hexanol. The selectivity for 1‐butanol and 1‐hexanol reached 62% and 10% for Cu‐MgAl(O) at 280°C. The addition of 1 mol% of La3+ (CuLa‐MgAl(O)) increased the number of basic sites comparing to Cu‐MgAl(O) changing the selectivity for 1‐butanol and 1‐hexanol reaching 16.70 and 41.7% at 280°C. The addition of lanthanum and consequently the increase on the catalyst basicity was related to the obtainment of long‐chain alcohols due to the enolate formation during the aldol condensation of Guerbet coupling.

Boosting the C–C Coupling of Bioethanol to Higher Alcohols by Inhibiting Aqueous Phase Reforming Reaction

“…Recently, many works have demonstrated the Guerbet reaction of bioethanol to butanol as fuel additives. − Rechi Siqueira and co-workers reported a Cu-based catalyst derived from a hydrotalcite precursor for upgrading ethanol to butanol, which gave an ethanol conversion of ∼80% and butanol selectivity of 32% . Wang et al reported that CaC 2 exhibited a superior catalytic activity with a 1-butanol yield of 24.5 C-mol% in C–C coupling of ethanol .…”

Insights on Guerbet Reaction: Production of Biobutanol From Bioethanol Over a Mg–Al Spinel Catalyst

“…In recent times, the same authors used a Mg–Al–Ce hydrotalcites with Mg/(Al + Ce) = 2 and obtained a slightly higher butanol selectivity (68%) ( Larina et al, 2021 ). Perrone et al (2021) used a Cu–MgAl (O) catalyst at 280°C, obtaining a selectivity to butanol and hexanol of 62 and 10%, respectively. The addition of La (CuLa–MgAl (O)) increased the number of basic sites compared to that of Cu–MgAl (O), which changed the selectivity to butanol (16.7%) and 1-hexanol (41.7%) at 280°C.…”