A tunable process: catalytic transformation of renewable furfural with aliphatic alcohols in the presence of molecular oxygen

Highly Dispersive Gold Nanoclusters Confined within Micropores of Defective UiO-66 for Highly Efficient Aldehyde Oxidation at Mild Conditions

The oxidative esterification of aldehydes under mild conditions remains a significant challenge. This study introduces a unique defective UiO-66 to achieve gold nanoclusters (AuNCs) for efficient aldehyde oxidation under mild conditions. The construction and characterization of these materials are thoroughly investigated by techniques of XRD, SEM and TEM images, FT-IR, Raman, and XPS spectrum, emphasizing the unique microporous in defective UiO-66 are conducive to the fabrication of AuNCs. The catalytic performance of the prepared materials in aldehyde oxidation reactions is systematically evaluated, demonstrating the remarkable efficiency of dispersed Au@UiO-66-25 with high-content (9.09 wt%) Au-loading and ultra-small size (~2.7 nm). Moreover, mechanistic insights into the catalytic process under mild conditions (70 °C for 1 h) are provided, elucidating the determination of defective UiO-66 in the confined fabrication of AuNCs and subsequent furfural adsorption, which underlie the principles governing the observed enhancements. This study establishes the groundwork for the synthesis of highly dispersed and catalytically active metal nanoparticles using defective MOFs as a platform, advancing the catalytic esterification reaction of furfural to the next level.

Progress of Reactions between Furfural and Aliphatic Alcohols via Catalytic Oxidation Processes: Reaction Routes, Catalysts, and Perspectives

Furfural is one of the most important biomass platform compounds and can be used to prepare various high-value-added chemicals. The reactions of furfural with aliphatic alcohols via an oxidative esterification reaction or oxidative condensation reaction can bond two carbon molecules together and produce longer hydrocarbon chains chemicals, including methylfuroate and some low-volatility liquid biomass fuels. Thus, these reactions are considered significant utilization routes of furfural, and many inspiring catalytic systems have been designed to promoted these reactions. In this work, the reported catalytic systems for the oxidative esterification and oxidative condensation reactions are reviewed separately. The catalysts for the oxidative esterification reaction are reviewed for the classification of noble metal catalysts and non-noble metal catalysts, according to the active metals in the catalysts. For the oxidative condensation reactions, the studies using oxygen as the oxidant are reviewed firstly, and then the studies conducted using the hydrogen transfer process are analyzed subsequently. Furthermore, suggestions for future research directions for the oxidative esterification and oxidative condensation reactions are put forward.

Oxidative N-Formylation of Secondary Amines Catalyzed by Reusable Bimetallic AuPd-Fe3O4 Nanoparticles

Bimetallic catalysts are gaining attention due to their characteristics of promoting reactivity and selectivity in catalyzed reactions. Herein, a new catalytic N-formylation of secondary amines using AuPd–Fe₃O₄ at room temperature is reported. Methanol was utilized as the formyl source and 1.0 atm of O₂ gas served as an external oxidant. The bimetallic catalyst, consisting of Au and Pd, makes the reaction more efficient than that using each metal separately. In addition, the catalyst can be effectively recycled owing to the Fe₃O₄ support.

Oxidative Condensation of Furfural with Ethanol Using Pd-Based Catalysts: Influence of the Support

PdO nanoparticles were deposited on several supports (β-zeolite, Al2O3, Fe2O3, MgO, and SiO2), which displayed different crystallinity, textural properties, and amount of acid and basic sites. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms at −196 °C, NH3 and CO2 thermoprogrammed desorption analyses (NH3- and CO2-TPD, and X-ray photoelectron spectroscopy (XPS). Pd-based catalysts were tested in the oxidative condensation of furfural with ethanol to obtain value-added chemicals. The catalytic results revealed high conversion values, although the presence of a high proportion of carbonaceous deposits, mainly in the case of the PdO supported on β-zeolite and Al2O3, is also noteworthy. The presence of basic sites led to a beneficial effect on the catalytic behavior, since the formation of carbonaceous deposits was minimized. Thus, the 2Pd-MgO (2 wt.% Pd) catalyst reached the highest yield of furan-2-acrolein (70%) after 3 h of reaction at 170 °C. This better catalytic performance can be explained by the high basicity of MgO, used as support, together with the large amount of available PdO, as inferred from XPS.

Facile synthesis of a highly efficient Co/Cu@NC catalyst for base-free oxidation of alcohols to esters

Co/Cu nanoparticle co-decorated N-doped carbon exhibits excellent activity and stability for base-free oxidation of alcohols to esters.

Oxidation of lignocellulosic platform molecules to value-added chemicals using heterogeneous catalytic technologies

This minireview gives an overview about heterogeneous catalytic technologies for the oxidation of key platform molecules (glucose, 5-hydroxymethylfurfural, furfural and levulinic acid) into valuable chemicals.

One-pot conversion of biomass-derived xylose and furfural into levulinate esters via acid catalysis

Direct conversion of biomass-derived xylose and furfural into levulinic acid, a platform molecule, via acid-catalysis has been accomplished for the first time in dimethoxymethane/methanol. Dimethoxymethane acted as an electrophile to transform furfural into 5-hydroxymethylfurfural (HMF). Methanol suppressed both the polymerisation of the sugars/furans and the Aldol condensation of levulinic acid/ester.

Direct conversion of C6 sugars to methyl glycerate and glycolate in methanol

The present work deals with the one-pot conversion of C6 sugars to methyl glycerate and glycolate via a cascade of retro-aldol condensation and oxidation processes catalyzed by using MoO₃ as the Lewis acid catalyst and Au/TiO₂ as the oxidation catalyst in methanol. Methyl glycerate (MGLY) is the product of C6 ketose (fructose), while methyl glycolate (MG) is produced from C6 aldose (mannose, glucose). It is found that a good one-pot match between two reactive processes is the key to the production of MGLY and MG with high yield (27.6% MGLY and 39.2% MG). A separated retro-aldol condensation and oxidation process greatly decreases their yields, and even no MGLY can be obtained in this separated process. We attribute this to high instability of glyceraldehyde/glycolaldehyde and their different reaction pathways which mainly depend on whether acetalization of retro-aldol products (glyceraldehyde and glycolaldehyde) occurs with methanol or not. This result opens a new prospect on the accumulation of C3 products other than lactate from biomass-derived carbohydrates.

Methyl glycerate (MGLY) and methyl glycolate (MG) are directly produced in maximum yield by the one-pot conversion of hexose, and the formation of MGLY and MG experience different reaction routes.

The controlled catalytic oxidation of furfural to furoic acid using AuPd/Mg(OH)2

The selective oxidation of furfural to furoic acid is achieved at mild reaction conditions over an AuPd/Mg(OH)₂ heterogeneous catalyst.

Oxidative esterification of furfural over Au–Pd/HAP-T and Au–Ag/HAP-T bimetallic catalysts supported on mesoporous hydroxyapatite nanorods

Core–shell (Au–Pd) and alloy (Au–Ag) architectured bimetallic mesoporous hydroxyapatite nano rods in the oxidative esterification of furfural.

A smart catalyst system for the valorization of renewable furfural in aliphatic alcohols

A highly efficient and selective oxidative condensation–hydrogenation process of renewable furfural with aliphatic alcohols mediated by supported Pt catalysts in a one-pot reactor is developed.