Transfer hydrogenation of furfural to furfuryl alcohol over modified Zr-based catalysts using primary alcohols as H-donors

Low-Temperature Catalytic Transfer Hydrogenation of Biomass-Derived Furfural over Irreversibly Adsorbed and Highly Dispersed Zr(IV) Species

Developing pure inorganic catalysts for low-energy transfer hydrogenation of biomass-derived furfural and alcohols below 100 °C is still challenging. This work reports highly dispersed Zr(IV) species catalysts prepared by irreversible adsorption of different solvent-dissolved Zr(IV) cations such as Zr4+ or [Zr4(OH)8(H2O)16]8+ on/in SBA-15 through Zr-O coordination, without adding an alkaline precipitant and calcination treatment. In the transfer hydrogenation of furfural to furfuryl alcohol, the Zr(IV) species catalysts exhibited unexpectedly outstanding transfer hydrogenation activity at low temperatures of 70 and 85 °C, superior to other transition-metal (Zr4+, Hf4+, Fe3+, etc.)- and main-group metal (Al3+, etc.)-based inorganic catalysts, which need high reaction temperatures above 100 °C, and comparable to the best-performing metal-organic hybrid catalysts with precise defect engineering modification or specific macromolecular ligands, and had negligible Zr leaching amounts (<0.01%) in water and in the collected liquid reaction medium from 7 cycles of reactions. In addition, the large strong Lewis acidic site amount rather than the large total acidic amount is a crucial condition for the catalysts to obtain high transfer hydrogenation activity, and basic sites were also involved in catalysis, and their absence would induce the acetalization side reaction. Furthermore, the catalysts were universal for low-temperature transfer hydrogenation of other aldehydes.

Ti/Zr/O Mixed Oxides for the Catalytic Transfer Hydrogenation of Furfural to GVL in a Liquid-Phase Continuous-Flow Reactor

This work aims to develop an efficient catalyst for the cascade reaction from furfural to γ-valerolactone in a liquid-phase continuous reactor. This process requires both Lewis and Brønsted acidity; hence, a bifunctional catalyst is necessary to complete the one-pot reaction. Ti/Zr/O mixed oxide-based catalysts were chosen to this end as balancing metal oxide composition allows the acidity characteristics of the overall material to be modulated. Oxides with different compositions were then synthesized using the co-precipitation method. After characterization via porosimetry and NH3-TPD, the catalyst with equimolar quantities of the two components was demonstrated to be the best one in terms of superficial area (279 m2/g) and acid site density (0.67 mmol/g). The synthesized materials were then tested using a plug flow reactor at 180 °C, with a 10 min contact time. Ti/Zr/O (1:1) was demonstrated to be the most promising catalyst during the recycling tests as it allowed obtaining the highest selectivities in the desired products (about 45% in furfuryl isopropyl ether and 20% in γ-valerolactone) contemporaneously with 100% furfural conversion.

Catalytic Transfer Hydrogenation of 5-Hydroxymethylfurfural with Primary Alcohols over Skeletal CuZnAl Catalysts

Catalytic transfer hydrogenation (CTH) with alcohols has been increasingly employed as effective tool for biomass upgrading, however, relying predominantly on secondary alcohols. Herein, for the first time skeletal CuZnAl catalysts were employed for the activation of a primary alcohol, ethanol, for the hydrogenation 5-hydroxymethylfurfual (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) under a mild condition. The catalysts were extensively characterized to reveal the structure characteristics and surface compositions. Over 90 % yield of BHMF were obtained over the optimal CuZnAl-0.5 catalyst at the reaction temperatures of 100-120 °C. Reaction kinetics indicated a competitive adsorption between HMF and ethanol on the catalyst surface, with the activation of ethanol being the rate-determining step (apparent activation energy E_a =70.9 kJ mol^-1 ). Preliminary adsorption investigation using combined attenuated total reflectance infrared spectroscopy and density functional theory calculation proposed a η² -(O,O)-aldehyde, furoxy perpendicular configuration of HMF on catalyst surface. The catalyst was further applied to the CTH of various aldehydes to the corresponding alcohols with high yields, demonstrating the broad applicability of the current system.

Hydrogenation of furfural to furfuryl alcohol over MOF-derived Fe/Cu@C and Fe3O4/Cu@C catalysts

With Cu-MOF-loaded Fe(NO3)3 as the precursor (Fe(NO3)3/Cu-MOF), Fe/Cu@C and Fe3O4/Cu@C catalysts were prepared from heating under the H2 and N2 atmosphere, respectively. When Fe(NO3)3/Cu-MOF was heated under different atmospheres, Cu-MOF...

Porous SiO2 Nanospheres Modified with ZrO2 and Their Use in One-Pot Catalytic Processes to Obtain Value-Added Chemicals from Furfural

Porous SiO2 nanospheres were modified with different loadings of ZrO2 to obtain catalysts with a Si/Zr molar ratio from 2.5 to 30. These materials were characterized by X-ray diffraction, transmission and scanning electron microscopies, N2 adsorption-desorption at -196 °C, X-ray photoelectron spectroscopy and pyridine and 2-6-dimethylpyridine thermoprogrammed desorption. The characterization of these catalysts has revealed that a high proportion of Zr favors the formation of Lewis acid sites, which are implied in catalytic transfer hydrogenation processes, whereas the low Brönsted acidity promotes a dehydration reaction, being possible to give rise to a large variety of products from furfural through consecutive reactions, such as furfuryl alcohol, i-propyl furfuryl ether, i-propyl levulinate, and γ-valerolactone, in a range of temperature of 110-170 °C and 1-6 h of reaction.

Recent advances in the conversion of furfural into bio-chemicals through chemo- and bio-catalysis

Furfural is a promising renewable platform molecule derived from hemi-cellulose, which can be further converted to fossil fuel alternatives and valuable chemicals due to its highly functionalized molecular structure. This mini-review summarizes the recent progress in the chemo-catalytic and/or bio-catalytic conversion of furfural into high-value-added chemicals, including furfurylamine, C₆ carboxylic acid, i.e., furandicarboxylic acid, furfural alcohol, aromatics, levulinic acid, maleic acid, succinic acid, furoic acid, and cyclopentanone, particularly the advances in the catalytic valorization of furfural into useful chemicals in the last few years. The possible reaction mechanisms for the conversion of furfural into bio-chemicals are summarized and discussed. The future prospective and challenges in the utilization of furfural through chemo- and bio-catalysis are also put forward for the further design and optimization of catalytic processes for the conversion of furfural.