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

Abstract

The Guerbet condensation reaction is an alcohol coupling reaction that has been known for more than a century. Because of the increasing availability of bio-based alcohol feedstock, this reaction is of growing importance and interest in terms of value chains of renewable chemical and biofuel production. Due to the specific branching pattern of the alcohol products, the Guerbet reaction has many interesting applications. In comparison to their linear isomers, branched-chain Guerbet alcohols have extremely low melting points and excellent fluidity. This review provides thermodynamic insights and unravels the various mechanistic steps involved. A comprehensive overview of the homogeneous, heterogeneous and combined homogeneous and heterogeneous catalytic systems described in published reports and patents is also given. Technological considerations, challenges and perspectives for the Guerbet chemistry are discussed.

Ni−Cu Hydrotalcite‐Derived Mixed Oxides as Highly Selective and Stable Catalysts for the Synthesis of β‐Branched Bioalcohols by the Guerbet Reaction

“…The condensation of fatty alcohols has not been commonly reportedi nt he literature;h owever,t he importance of the Guerbet reaction in converting these types of substrates is reflected the number of patents that concern such reactions. [7] Although high conversionsa nd selectivities can be obtained with these types of homogeneous systems (base and homogeneous catalyst), issues relatedt ot he product purification, recovery,a nd cost of the catalysta nd waste treatment are important for the industrialp roduction of Guerbet alcohols. [3] Typically,t he Guerbet reactiono ft hese types of fatty alcohol substrates can be carriedo ut by using ab ase (e.g.,K OH) and ac atalyst to acceleratet he overall reactionr ate and to favor the selectivity of the process to the target molecule.…”

Recent advances on the utilization of layered double hydroxides (LDHs) and related heterogeneous catalysts in a lignocellulosic-feedstock biorefinery scheme

“…[199][200][201] The condensation of ethanol (self-and cross-condensation) by the Guerbet reaction have been reported under either batch or continuous operation mode, using different types of homogeneous, homogeneous/heterogeneous or totally heterogeneous catalytic systems. 202,203 In 1990, Ueda et al 204 selectively synthesized propan-1-ol and 2-methylpropan-1-ol from methanol and ethanol at atmospheric pressure using different types of basesolid catalysts such as MgO, ZnO, CaO and M n+ -containing Among them, MgO showed the best catalytic performance towards the Guerbet alcohols (up to 80% total alcohol selectivity), whereas ZnO was mainly selective to the dehydrogenation of ethanol to ethanal. Ndou et al 205 performed the dimerisation of ethanol over alkali earth metal oxides and modified MgO catalysts.…”

Ethanol: A Promising Green Solvent for the Deconstruction of Lignocellulose

“…Yields of products from ethanol( 100 mL) degradation without and with kraft lignin (KL) added at 280 8Cf or 240 min over Mo/Al 2 O 3 catalyst (0.5 g) at an initial 0.1 MPa of N 2 . [37] Reprinted with permission from Ref. [33].…”