Guerbet Reactions for Biofuel Production from ABE Fermentation Using Bifunctional Ni-MgO-Al2O3 Catalysts

To upgrade biomass-derived alcohol mixtures to biofuels under solvent-free conditions, MgO–Al2O3 mixed metal oxides (MMO) decorated with Ni nanoparticles (Ni–MgO–Al2O3) are synthesized and characterized. Based on the result, Ni nanoparticles are highly dispersed on the surface of MgAl MMO. As the Ni loading content varies from 2 to 10 wt.%, there is a slight increase in the mean Ni particle size from 6.7 to 8.5 nm. The effects of Ni loading amount, reducing temperature, and Mg/Al ratio on the conversion and product distribution are investigated. With the increase in both the Ni loading amount and reducing temperature, dehydrogenation (the first step of the entire reaction network) is accelerated. This results in an increase in the conversion process and a higher selectivity for the dialkylated compounds. Due to the higher strength and density of basic sites under high Mg/Al ratios, double alkylation is preferred and more long-chain hydrocarbons are obtained. A conversion of 89.2% coupled with a total yield of 79.9% for C5–C15 compounds is acquired by the as-prepared catalyst (prepared with Ni loading of 6 wt.%, reducing temperature of 700 °C, and Mg/Al molar ratio of 3. After four runs, the conversion drops by 17.1%, and this loss in the catalytic activity can be attributed to the decrease in the surface area of the catalyst and the increase in the Ni mean particle size.

Iridium Complex-Catalyzed C2-Extension of Primary Alcohols with Ethanol via a Hydrogen Autotransfer Reaction

The development of a C2-extension of primary alcohols with ethanol as the C2 source and catalysis by [Cp*IrCl₂]₂ (where Cp* = pentamethylcyclopentadiene) is described. This new extension system was used for a range of benzylic alcohol substrates and for aliphatic alcohols with ethanol as an alkyl reagent to generate the corresponding C2-extended linear alcohols. Mechanistic studies of the reaction by means of intermediates and deuterium labeling experiments suggest the reaction is based on hydrogen autotransfer.

Influence of Reaction Parameters on the Catalytic Upgrading of an Acetone, Butanol, and Ethanol (ABE) Mixture: Exploring New Routes for Modern Biorefineries

Here we present a comprehensive study on the effect of reaction parameters on the upgrade of an acetone, butanol and ethanol mixture-key molecules and platform products of great interest within the chemical sector. Using a selected high performing catalyst, Fe/MgO-Al2O3, the variation of temperature, reaction time, catalytic loading, and reactant molar ratio have been examined in this reaction. This work is aiming to not only optimize the reaction conditions previously used, but to step toward using less energy, time, and material by testing those conditions and analyzing the sufficiency of the results. Herein, we demonstrate that this reaction is favored at higher temperatures and longer reaction time. Also, we observe that increasing the catalyst loading had a positive effect on the product yields, while reactant ratios have shown to produce varied results due to the role of each reactant in the complex reaction network. In line with the aim of reducing energy and costs, this work showcases that the products from the upgrading route have significantly higher market value than the reactants; highlighting that this process represents an appealing route to be implemented in modern biorefineries.

Nanolayered cobalt-molybdenum sulphides (Co-Mo-S) catalyse borrowing hydrogen C-S bond formation reactions of thiols or H2S with alcohols

Nanolayered cobalt-molybdenum sulphide (Co-Mo-S) materials have been established as excellent catalysts for C-S bond construction. These catalysts allow for the preparation of a broad range of thioethers in good to excellent yields from structurally diverse thiols and readily available primary as well as secondary alcohols. Chemoselectivity in the presence of sensitive groups such as double bonds, nitriles, carboxylic esters and halogens has been demonstrated. It is also shown that the reaction takes place through a hydrogen-autotransfer (borrowing hydrogen) mechanism that involves Co-Mo-S-mediated dehydrogenation and hydrogenation reactions. A novel catalytic protocol based on the thioetherification of alcohols with hydrogen sulphide (H2S) to furnish symmetrical thioethers has also been developed using these earth-abundant metal-based sulphide catalysts.

Monodispersed Pd Nanoparticles Supported on Mg-Al Mixed Metal Oxides: A Green and Controllable Synthesis

Aimed at the green synthesis of supported noble metal nanoparticles without any additional reducing agents or stabilizers at room temperature, a new strategy in which monodispersed Pd nanoparticles were successfully immobilized on Mg-Al mixed metal oxides derived from layered double hydroxides was developed, and the reduction mechanism was also proposed. It allowed the in situ immobilization of monodispersed Pd nanoparticles with a face-centered cubic structure, using only alcohols with α-hydrogen atom as the solvent and reducing agent. Control over the mean particle size and content of Pd nanoparticles was realized by adjusting the temperature, initial concentration, and type of alcohol. With the content of Pd varied from 6.4 to 42.3 mg/g, the mean particle size of Pd increased from 1.1 to 4.9 nm. The as-prepared catalyst showed high catalytic activity for oxidation of benzyl alcohol: when the Pd content was 6.4 mg/g, conversion of 60.3% and selectivity of 99.2% were obtained with a turnover frequency of 4807 h^-1. Similarly, on the basis of the high stand electrode potentials, immobilized Ag (5.6 nm) and Au (4.7 nm) nanoparticles were also prepared through this methodology. Moreover, the choice of supports was extended to other powder supports that would react with the byproduced acid. Overall, this facile method opens up new opportunities for controllable synthesis of supported nanoparticle catalysts in a green way.

Upgraded biofuel from alcohol–acetone feedstocks over a two-stage flow-through catalytic system

Over a two-stage flow-through catalytic system an advantageous mixture of various straight and branched alkanes can be obtained. In the second reactor the commercial NiMo/Al₂O₃ hydrodeoxygenating catalyst shows similar good properties as alkylating Pd-catalysts in the first stage.