Liquid-Phase Catalytic Transfer Hydrogenation of Furfural over Homogeneous Lewis Acid-Ru/C Catalysts

Size-Dependent Fe-Based Catalysts for the Catalytic Transfer Hydrogenation of α,β-Unsaturated Aldehydes

Metal-based catalysts ranging from nanoparticles (NPs) to the atomic level usually exhibit varying catalytic performance. The underlying size effect is both fascinating and evident. This study thoroughly investigates the size-dependent effects of Fe-based catalysts on catalytic transfer hydrogenation (CTH) of furfural (FF) at the atomic level. Fe was precisely loaded onto N-doped porous carbon in three forms: single atoms (Fe-SAs/NC), atomic clusters (Fe-ACs/NC), and nanoparticles (Fe-NPs/NC). This was achieved through meticulous control of the iron precursor composition. Remarkably, Fe-SAs/NC exhibited exceptional catalytic efficiency, achieving an FF conversion of 91.3% and a turnover frequency (TOF) of 262.3 h-1 at 110 °C, which is 9.2 times higher than Fe-ACs/NC and an impressive 93.7 times higher than Fe-NPs/NC. The high selectivity of Fe-SAs/NC toward furfuryl alcohol was further substantiated by theoretical calculations. These calculations indicated the benefits from the η1(O)-aldehyde adsorption configuration, formed by the vertical adsorption of FF molecules on the Fe-N4 active sites. Geometrical optimization of the catalyst at the atomic scale enhances its intrinsic catalytic activity and selectivity. The proposed size effect on catalytic activity provides deeper insights into the mechanism of single-atom catalytic hydrogenation and contributes to the exploration of high-performance catalysts at the atomic level.

Biomass-Derived, Target Specific, and Ecologically Safer Insecticide Active Ingredients

With the continuous increase in food production to support the growing population, ensuring agricultural sustainability using crop-protecting agents, such as pesticides, is vital. Conventional pesticides pose significant environmental risks, prompting the need for eco-friendly alternatives. This study reports the synthesis of new amide-based insecticidal active ingredients from biomass-derived monomers, specifically furfural and vanillin. The process involves reductive amination followed by carbonylation. The synthesis of the furfural-based carbamate yield reaches a cumulative 88 %, with catalysts Rh/Al2O3 and La(OTf)3 being recyclable at each stage. Insecticidal activity assessments reveal that the furfural carbamate exhibits competitive performance, achieving an LC50 of 254.22 μg/cm2, compared to 251.25 μg/cm2 for carbofuran. Ecotoxicity predictions indicate significantly lower toxicity levels toward non-target aquatic and terrestrial species. The importance of the low octanol-water partition coefficient of the biobased carbamate, attributed to the oxygen heteroatom and electron density of the furan ring, is discussed in detail. Building on these promising results, the synthesis strategy was extended to six other biobased aldehydes, resulting in a diverse portfolio of biomass-derived carbamates. A techno-economic analysis reveals a minimum selling price of 11.1 $/kg, only half that of comparable carbamates, demonstrating the economic viability of these new biobased insecticides.

Selective Stereoretention of Carbohydrates upon C-C Cleavage Enabling D-Glyceric Acid Production with High Optical Purity over a Ag/γ-Al2O3 Catalyst

Chiral carboxylic acid production from renewable biomass by chemocatalysis is vitally important for reducing our carbon footprint, but remains underdeveloped. We herein establish a strategy that make use of a stereogenic center of biomass to achieve a rare example of D-glyceric acid production with the highest yield (86.8 %) reported to date as well as an excellent ee value (>99 %). Unlike traditional asymmetric catalysis, chiral catalysts/additives are not required. Ample experiments combined with quantum chemical calculations established the origins of the stereogenic center and catalyst performance. The chirality at C4 in D-xylose was proved to be retained and successfully delivered to C2 in D-glyceric acid during C-C cleavage. The remarkable cooperative-roles of Ag+ and Ag0 in the constructed Ag/γ-Al2O3 catalyst are disclosed as the crucial contributors. Ag+ was responsible for low-temperature activation of D-xylose, while Ag0 facilitated the generation of active O* from O2. Ag+ and active O* cooperatively promoted the precise cleavage of the C2-C3 bond, and more importantly O* allowed the immediate fast oxidization of the D-glyceraldehyde intermediate to stabilize D-glyceric acid, thereby inhibiting the side reaction that induced racemization. This strategy makes a significant breakthrough in overcoming the limitation of poor enantioselectivity in current chemocatalytic conversion of biomass.

Microwave-Assisted One Pot Cascade Conversion of Furfural to γ-Valerolactone over Sc(OTf)3

γ-Valerolactone (GVL) is considered as a star biochemical which can be used as a green solvent, fuel additive and versatile organic intermediate. In this study, metal triflate (M(OTf)n ) was utilized as the catalyst for one-pot transformation of furfural (FF) to GVL in alcohol media under microwave irradiation. Alcohol plays multiple functions including solvent, hydrogen donor and alcoholysis reagent in this cascade reaction process. And process efficiency of GVL production from FF upgrading is strongly related to the effective charge density of selected catalyst and the reduction potential of selected alcohol. Complex (OTf)n -M-O(H)R, presenting both Brønsted acid and Lewis acid, is the real catalytic active species in this cascade reaction process. Among various catalysts, Sc(OTf)3 exhibited the best catalytic activity for GVL production. Various reaction parameters including the Sc(OTf)3 amount, reaction temperature and time were optimized by the response surface methodology with the central composite design (RSM-CCD). Up to 81.2 % GVL yield and 100 % FF conversion were achieved at 143.9 °C after 8.1 h in the presence of 0.16 mmol catalyst. This catalyst exhibits high reusability and can be regenerated by oxidative degradation of humins. In addition, a plausible cascade reaction network was proposed based on the distribution of product.

Transfer Hydrogenation of Furfural to Furfuryl Alcohol Under Microwave Irradiation Using Mixed Oxides

The reaction to obtain furan alcohols is one of the most important in the upgrading of furan derivates. An attractive route is the transfer hydrogenation of furfural using acidic-basic catalysts. In this work, mixed oxides derived from ternary hydrotalcites were employed to obtain furfuryl alcohol from furfural assisted by microwave irradiation. These materials were characterized via X-ray diffraction (XRD), N2 adsorption-desorption isotherms, Fourier-transform infrared (FTIR) and the CO2 temperature-programmed desorption (CO2 -TPD) analyses. The lamellar structure of hydrotalcite-type materials collapses during the calcination process, resulting in the loss of carbonate anions and hydroxyl groups, present in the interlayer space. This leads to the formation of mixed oxides that exhibit larger surface areas. Furthermore, these changes alter the basic nature of these materials, giving rise to the formation of strong basic sites. The reaction was studied using containing Co2+ and Ni2+ in their structure and was then optimized using distinct primary and secondary alcohols as hydrogen donor sources, as well as distinct temperatures and initial concentrations of furfural. The yields to furfuryl alcohol are strongly dependent on the type of Me2+ in layered oxides mainly due to higher basicity and to the donor employed in the reaction. The mixed oxide containing Co2+ showed complete conversion of furfural and higher yields to furfuryl alcohol (>95 %) at short times of reaction (<1 h).

Ultrafine Ruthenium Clusters Shell-Embedded Hollow Carbon Spheres as Nanoreactors for Channel Microenvironment-Modulated Furfural Tandem Hydrogenation

Rationally modulating the catalytic microenvironment is important for targeted induction of specific molecular behaviors to fulfill complicated catalytic purposes. Herein, a metal pre-chelating assisted assembly strategy is developed to facilely synthesize the hollow carbon spheres with ultrafine ruthenium clusters embedded in pore channels of the carbon shell (Ru@Shell-HCSs), which can be employed as nanoreactors with preferred electronic and geometric catalytic microenvironments for the efficient tandem hydrogenation of biomass-derived furfural toward 2-methylfuran. The channel-embedding structure is proved to confer the ultrafine ruthenium clusters with an electron-deficient property via a reinforced interfacial charge transfer mechanism, which prompts the hydrogenolysis of intermediate furfuryl alcohol during the tandem reaction, thus resulting in an enhanced 2-methylfuran generation. Meanwhile, lengthening the shell pore channel can offer reactant molecules with a prolonged diffusion path, and correspondingly a longer retention time in the channel, thereafter delivering an accelerated tandem hydrogenation progression. This paper aims to present a classic case that emphasizes the critical role of precisely controlling the catalytic microenvironment of the metal-loaded hollow nanoreactors in coping with the arduous challenges from multifunctional catalyst-driven complex tandem reactions.

A novel and highly efficient Zr-containing catalyst supported by biomass-derived sodium carboxymethyl cellulose for hydrogenation of furfural

Functional use of biomass based on its structural properties is an efficient approach for the valuable utilization of biomass resources. In this work, carboxymethyl cellulose zirconium-based catalyst (Zr-CMC) was constructed by the coordination between the carboxylic groups in sodium carboxymethyl cellulose (CMC-Na) with transition metal Zr4+. The prepared catalyst was applied into the synthesis of furfuryl alcohol (FAL) by catalytic transfer hydrogenation of biomass-derived furfural (FF) using isopropanol as hydrogen donor. Both the preparation conditions and the reaction conditions of Zr-CMC catalyst were investigated and optimized. The results showed that Zr-CMC was efficient for the reaction with the FF conversion, FAL yield and selectivity reaching to 92.5%, 91.5 %, and 99.0%, respectively, under the mild conditions (90°C). Meanwhile, the Zr-CMC catalyst could be reused at least for five times without obvious decrease in efficiency, indicating the catalyst had excellent stability. With the advantages of sustainable raw materials, high efficiency, and excellent stability, the prepared catalyst is potential for application in the field of biomass conversion.

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...

Density Functional Investigation of the Conversion of Furfural to Furfuryl Alcohol by Reaction with i-Propanol over UiO-66 Metal-Organic Framework

Carbonyl C═O bond reduction via catalytic transfer hydrogenation (CTH) is one of the essential processes for biomass conversion to valuable chemicals and fuels. Here, we investigate the CTH of furfural to furfuryl alcohol with i-propanol on UiO-66 metal-organic frameworks using density functional theory calculations and linear scaling relations. Initially, the reaction over two defect sites presented on Zr-UiO-66, namely, dehydrated and hydrated sites, have been compared. The hydrated active site is favored over that on the dehydrated active site since the activation free energy of the rate-determining reaction step occurring on the hydrated active site is lower than that occurring on the dehydrated active site (14.9 vs 17.9 kcal/mol). The catalytic effect of exchanged tetravalent metals (Hf and Ti) on Zr-UiO-66 is also considered. We found that Hf-UiO-66 (13.5 kcal/mol) provides a lower activation energy than Zr-UiO-66 (14.9 kcal/mol) and Ti-UiO-66 (19.4 kcal/mol), which corresponds to it having a higher Lewis acidity. The organic linkers of UiO-66 MOFs play a role in stabilizing all of the species on potential energy surfaces. The linear scaling relationship also reveals the significant role of the UiO-66 active site in activating the carbonyl C═O of furfural, and strong relationships are observed between the activation free energy, the charge of the metal at the MOF active sites, and the complexation energies in reaction coordinates.

Recent catalytic routes for the preparation and the upgrading of biomass derived furfural and 5-hydroxymethylfurfural

Furans represent one of the most important classes of intermediates in the conversion of non-edible lignocellulosic biomass into bio-based chemicals and fuels. At present, bio-furan derivatives are generally obtained from cellulose and hemicellulose fractions of biomass via the acid-catalyzed dehydration of their relative C6-C5 sugars and then converted into a wide range of products. Furfural (FUR) and 5-hydroxymethylfurfural (HMF) are surely the most used furan-based feedstocks since their chemical structure allows the preparation of various high-value-added chemicals. Among several well-established catalytic approaches, hydrogenation and oxygenation processes have been efficiently adopted for upgrading furans; however, harsh reaction conditions are generally required. In this review, we aim to discuss the conversion of biomass derived FUR and HMF through unconventional (transfer hydrogenation, photocatalytic and electrocatalytic) catalytic processes promoted by heterogeneous catalytic systems. The reaction conditions adopted, the chemical nature and the physico-chemical properties of the most employed heterogeneous systems in enhancing the catalytic activity and in driving the selectivity to desired products are presented and compared. At the same time, the latest results in the production of FUR and HMF through novel environmental friendly processes starting from lignocellulose as well as from wastes and by-products obtained in the processing of biomass are also overviewed.

Synergetic effects of hydrogenation and acidic sites in phosphorus-modified nickel catalysts for the selective conversion of furfural to cyclopentanone

Nickel phosphide species can tailor the selectivity of hydrogenation sites. The yields of CPO and CPL reached 93.5% over 15%Ni–25%P/Al₂O₃. The balanced distribution of hydrogenation/acid sites maximizes the yield of CPO.

gem-Diol-Type Intermediate in the Activation of a Ketone on Sn-β Zeolite as Studied by Solid-State NMR Spectroscopy

Lewis acid zeolites have found increasing application in the field of biomass conversion, in which the selective transformation of carbonyl-containing molecules is of particular importance due to their relevance in organic synthesis. Mechanistic insight into the activation of carbonyl groups on Lewis acid sites is challenging and critical for the understanding of the catalytic process, which requires the identification of reaction intermediates. Here we report the observation of a stable surface gem-diol-type species in the activation of acetone on Sn-β zeolite. ¹³ C, ¹¹⁹ Sn, and ¹³ C-¹¹⁹ Sn double-resonance NMR spectroscopic studies demonstrate that only the open Sn site ((SiO)₃ Sn-OH) on Sn-β is responsible for the formation of the surface species. ¹³ C MAS NMR experiments together with density functional theory calculations suggest that the gem-diol-type species exhibits high reactivity and can serve as an active intermediate in the Meerwein-Ponndorf-Verley-Oppenauer (MPVO) reaction of acetone with cyclohexanol. The gem-diol-type species offers an energy-preferable pathway for the direct carbon-to-carbon hydrogen transfer between ketone and alcohol. The results provide new insights into the transformation of carbonyl-containing molecules catalyzed by Lewis acid zeolites.

Hydrogenation of Furfural to Cyclopentanone under Mild Conditions by a Structure-Optimized Ni-NiO/TiO2 Heterojunction Catalyst

The catalytic conversion of biomass-derived furfural (FFA) into cyclopentanone (CPO) in aqueous solution is an important pathway to obtain sustainable resources. However, the conversion and selectivity under mild conditions are still unsatisfactory. In this study, a catalyst consisting of Ni-NiO heterojunction supported on TiO₂ with optimized composition of anatase and rutile (Ni-NiO/TiO₂ -Re450) is prepared by pyrolysis at 450 °C. With Ni-NiO/TiO₂ -Re450, as catalyst, complete conversion of FFA and 87.4 % yield of CPO are achieved under mild reaction conditions (1 MPa, 140 °C, 6 h). 95.4 % FFA conversion is retained up to the fifth run, indicating the high stability of the catalyst. Multiple characterizations, control experiments, and theoretical calculations demonstrate that the good catalytic performance of Ni-NiO/TiO₂ -Re450 can be attributed to a synergistic effect of the Ni-NiO heterojunction and the TiO₂ support. This low-cost catalyst may expedite the catalytic upgrading and practical application of biomass-derived chemicals.

Exploring the Reaction Mechanisms of Furfural Hydrodeoxygenation on a CuNiCu(111) Bimetallic Catalyst Surface from Computation

In this study, the selectively catalytic hydrodeoxygenation of furfural (F-CHO) to 2-methylfuran (F-CH₃) on the CuNiCu(111) bimetallic catalyst surface was systematically investigated based on the periodic density functional theory, including dispersion correction. The formation of furfuryl alcohol (F-CH₂OH) involved two steps: the preferred first step was the hydrogenation of the branched C atom, forming the alkoxyl intermediate (F-CHO + H = F-CH₂O), and the second step was H addition to the alkoxyl group, resulting in furfuryl alcohol (F-CH₂O + H = F-CH₂OH), which was the rate-controlling step. In contrast, in the formation of 2-methylfuran, the first step was the dehydroxylation of furfuryl alcohol, resulting in alkyl (F-CH₂) and OH (F-CH₂OH = F-CH₂ + OH) groups, the second step was the hydrogenation of F-CH₂ (F-CH₂ + OH + H = F-CH₃ + OH), and the rate-controlling step was the hydrogenation of OH to H₂O (OH + H = H₂O). Based on the comparison results of the NiCuCu(111), Cu(111), and CuNiCu(111) surfaces, it was concluded that the catalytic performance of the catalyst was closely related to the adsorption structure of furfural. These results provide a basis for studying the intrinsic activity of NiCu catalysts during the hydrodeoxygenation of refined oxygenated compounds involving biomass-derived oils.

Ruthenium on phosphorous-modified alumina as an effective and stable catalyst for catalytic transfer hydrogenation of furfural

Supported ruthenium was used in the liquid phase catalytic transfer hydrogenation of furfural. To improve the stability of Ru against leaching, phosphorous was introduced on a Ru/Al₂O₃ based catalyst upon impregnation with ammonium hypophosphite followed by either reduction or calcination to study the effect of phosphorous on the physico-chemical properties of the active phase. Characterization using X-ray diffraction, solid state ³¹P nuclear magnetic resonance spectroscopy, X-ray absorption spectroscopy, temperature programmed reduction with H₂, infrared spectroscopy of pyridine adsorption from the liquid phase and transmission electron microscopy indicated that phosphorous induces a high dispersion of Ru, promotes Ru reducibility and is responsible for the formation of acid species of Brønsted character. As a result, the phosphorous-based catalyst obtained after reduction was more active for catalytic transfer hydrogenation of furfural and more stable against Ru leaching under these conditions than a benchmark Ru catalyst supported on activated carbon.

Phosphorous induces structural changes in Ru/Al₂O₃ that make it more active and more stable for liquid phase hydrogenation of furfural.

On demand production of ethers or alcohols from furfural and HMF by selecting the composition of a Zr/Si catalyst

Silica is used to tailor the acid–base properties of ZrO₂ to selectively transform furfural and HMF into alcohols or ethers.

Theoretical Study of the Mechanism of Furfural Conversion on the NiCuCu(111) Surface

The full potential energy surface for the hydrodeoxygenation of furfural to furan and other ring-opening products has been systematically investigated using periodic density functional theory including dispersion corrections (PBE-D3) on the bimetallic NiCuCu(111) surface. For furan formation, the most favorable first step is the dehydrogenation of furfural into furoyl (F-CHO + H = F-CO + 2H), the successive step is decarbonylation of furoyl into furanyl (F-CO + H = F + CO + 2H), and the third step of furan formation from the hydrogenation of furanyl (F + CO + 2H = FA + CO + H) is the rate-determining step. In addition, on the basis of the most stably adsorbed furan and H, the ring opening of furan was found to be more favorable for producing many chemicals such as propane, butanal, butanol, and butene. In summary, furan is the main product of furfural conversion on the NiCuCu(111) surface. Since results have been obtained only for the NiCuCu(111) surface constructed by replacing the topmost Cu atoms by Ni atoms, the entire experimentally observed reactivity and selectivity of bimetallic CuNi catalysts for different construction methods cannot be fully rationalized. Nevertheless, the results provide the basis for investigating the intrinsic activity of CuNi catalysts in the hydrodeoxygenation of oxygenates involved in the refining of biomass-derived oils.

Heterogeneous Catalytic Upgrading of Biofuranic Aldehydes to Alcohols

Heterogeneous catalytic conversion of lignocellulosic components into valuable chemicals and biofuels is one of the promising ways for biomass valorization, which well meets green chemistry metrics, and can alleviate environmental and economic issues caused by the rapid depletion of fossil fuels. Among the identified biomass derivatives, furfural (FF) and 5-hydroxymethylfurfural (HMF) stand out as rich building blocks and can be directly produced from pentose and hexose sugars, respectively. In the past decades, much attention has been attracted to the selective hydrogenation of FF and 5-hydroxymethylfurfural using various heterogeneous catalysts. This review evaluates the recent progress of developing different heterogeneous catalytic materials, such as noble/non-noble metal particles, solid acids/bases, and alkali metal salts, for the efficient reduction of bio-based furanic aldehydes to alcohols. Emphasis is laid on the insights and challenges encountered in those biomass transformation processes, along with the focus on the understanding of reaction mechanisms to clarify the catalytic role of specific active species. Brief outlook is also made for further optimization of the catalytic systems and processes for the upgrading of biofuranic compounds.

Catalytic Transfer Hydrogenation of Biomass-Derived Substrates to Value-Added Chemicals on Dual-Function Catalysts: Opportunities and Challenges

Aqueous-phase hydrodeoxygenation (APH) of bioderived feedstocks into useful chemical building blocks is one the most important processes for biomass conversion. However, several technological challenges, such as elevated reaction temperature (220-280 °C), high H₂ pressure (4-10 MPa), uncontrollable side reactions, and intensive capital investment, have resulted in a bottleneck for the further development of existing APH processes. Catalytic transfer hydrogenation (CTH) under much milder conditions with non-fossil-based H₂ has attracted extensive interest as a result of several advantageous features, including high atom efficiency (≈100 %), low energy intensity, and green H₂ obtained from renewable sources. Typically, CTH can be categorized as internal H₂ transfer (sacrificing small amounts of feedstocks for H₂ generation) and external H₂ transfer from H₂ donors (e.g., alcohols, formic acid). Although the last decade has witnessed a few successful applications of conventional APH technologies, CTH is still relatively new for biomass conversion. Very limited attempts have been made in both academia and industry. Understanding the fundamentals for precise control of catalyst structures is key for tunable dual functionality to combine simultaneous H₂ generation and hydrogenation. Therefore, this Review focuses on the rational design of dual-functionalized catalysts for synchronous H₂ generation and hydrogenation of bio-feedstocks into value-added chemicals through CTH technologies. Most recent studies, published from 2015 to 2018, on the transformation of selected model compounds, including glycerol, xylitol, sorbitol, levulinic acid, hydroxymethylfurfural, furfural, cresol, phenol, and guaiacol, are critically reviewed herein. The relationship between the nanostructures of heterogeneous catalysts and the catalytic activity and selectivity for C-O, C-H, C-C, and O-H bond cleavage are discussed to provide insights into future designs for the atom-economical conversion of biomass into fuels and chemicals.

How Catalysts and Experimental Conditions Determine the Selective Hydroconversion of Furfural and 5-Hydroxymethylfurfural

Furfural and 5-hydroxymethylfurfural stand out as bridges connecting biomass raw materials to the biorefinery industry. Their reductive transformations by hydroconversion are key routes toward a wide variety of chemicals and biofuels, and heterogeneous catalysis plays a central role in these reactions. The catalyst efficiency highly depends on the nature of metals, supports, and additives, on the catalyst preparation procedure, and obviously on reaction conditions to which catalyst and reactants are exposed: solvent, pressure, and temperature. The present review focuses on the roles played by the catalyst at the molecular level in the hydroconversion of furfural and 5-hydroxymethylfurfural in the gas or liquid phases, including catalytic hydrogen transfer routes and electro/photoreduction, into oxygenates or hydrocarbons (e.g., furfuryl alcohol, 2,5-bis(hydroxymethyl)furan, cyclopentanone, 1,5-pentanediol, 2-methylfuran, 2,5-dimethylfuran, furan, furfuryl ethers, etc.). The mechanism of adsorption of the reactant and the mechanism of the reaction of hydroconversion are correlated to the specificities of each active metal, both noble (Pt, Pd, Ru, Au, Rh, and Ir) and non-noble (Ni, Cu, Co, Mo, and Fe), with an emphasis on the role of the support and of additives on catalytic performances (conversion, yield, and stability). The reusability of catalytic systems (deactivation mechanism, protection, and regeneration methods) is also discussed.

Solvent Tunes the Selectivity of Hydrogenation Reaction over α-MoC Catalyst

Selective activation of chemical bonds in multifunctional oxygenates on solid catalysts is a crucial challenge for sustainable biomass upgrading. Molybdenum carbides and nitrides preferentially activate C═O and C-OH bonds over C═C and C-C bonds in liquid-phase hydrogenation of bioderived furfural, leading to highly selective formations of furfuryl alcohol (FA) and its subsequent hydrogenolysis product (2-methyl furan (2-MF)). We demonstrate that pure-phase α-MoC is more active than β-Mo₂C and γ-Mo₂N for catalyzing furfural hydrogenation, and the hydrogenation selectivity on these catalysts can be conveniently manipulated by alcohol solvents without significant changes in reaction rates (e.g., > 90% yields of FA in methanol solvent and of 2-MF in 2-butanol solvent at 423 K). Combined experimental and theoretical assessments of these solvent effects unveil that it is the hydrogen donating ability of the solvents that governs the hydrogenation rate of the reactants, while strong dissociative adsorption of the alcohol solvent on Mo-based catalysts results in surface decoration which controls the reaction selectivity via enforcing steric hindrance on the formation of relevant transient states. Such solvent-induced surface modification of Mo-based catalysts provides a compelling strategy for highly selective hydrodeoxygenation processes of biomass feedstocks.

Selective Transfer Hydrogenation of Furfural into Furfuryl Alcohol on Zr-Containing Catalysts Using Lower Alcohols as Hydrogen Donors

A series of zirconium-based catalysts were prepared for the selective transfer hydrogenation of biomass-derived furfural (FFR) into furfuryl alcohol with lower alcohols as hydrogen sources. The sample structures were clearly characterized using various methods, such as X-ray powder diffraction, thermogravimetric analysis, scanning electron microscope, NH₃-temperature-programmed desorption (TPD), CO₂-TPD, and nitrogen physisorption. Excellent furfuryl alcohol yield of 98.9 mol % was achieved over Zr(OH)₄ using 2-propanol as a hydrogen donor at 447 K. The poisoning experiments indicated that basic centers displayed pronounced effect for FFR transfer hydrogenation. Moderate monoclinic phase content in ZrO₂-x enhanced the conversion rate and furfuryl alcohol selectivity, whereas acid-basic site density ratio had slight influence on FFR conversion. Besides, Zr(OH)₄ revealed good performance and stability after being repeated four times. The possible mechanism for this transfer hydrogenation process over Zr(OH)₄ catalyst with 2-propanol as the hydrogen source was proposed.

Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol over Nitrogen-Doped Carbon-Supported Iron Catalysts

Iron-based heterogeneous catalysts, which were generally prepared by pyrolysis of iron complexes on supports at elevated temperature, were found to be capable of catalyzing the transfer hydrogenation of furfural (FF) to furfuryl alcohol (FFA). The effects of metal precursor, nitrogen precursor, pyrolysis temperature, and support on catalytic performance were examined thoroughly, and a comprehensive study of the reaction parameters was also performed. The highest selectivity of FFA reached 83.0 % with a FF conversion of 91.6 % under the optimal reaction condition. Catalyst characterization suggested that iron cations coordinated by pyridinic nitrogen functionalities were responsible for the enhanced catalytic activity. The iron catalyst could be recycled without significant loss of catalytic activity for five runs, and the destruction of the nitrogen-iron species, the presence of crystallized Fe2 O3 phase, and the pore structure change were the main reasons for catalyst deactivation.

Pd–Ru/TiO2 catalyst – an active and selective catalyst for furfural hydrogenation

The selective hydrogenation of furfural at ambient temperature has been investigated using a Pd/TiO₂ catalyst.