Furfural Research Articles

Continuous-flow reductive etherification of furfural over CuAlOx catalyst combined with HZSM-5-Al2O3 composite

Furfuryl alkyl ethers (FAEs) are considered attractive biofuels or gasoline additives. Reductive etherification of bio-based furfural (FF) is a promising method for production of these compounds. In present work, we study the catalytic behavior of Cu-Al mixed oxide in combination with HZSM-5-Al2O3 composites for the syntheses of FAEs in a flow reactor using H2 as a reducing agent. The Cu-based catalyst ensures the hydrogenation of FF to furfuryl alcohol, which then reacted with alcohol in the presence of the acid catalyst. It was found that the reaction of FF with 2-propanol over catalytic system including HZSM-5(Si/Al = 40)-Al2O3 leads to the formation of 2-(isopropoxymethyl)furan (IMF) in excellent yield due to the optimal concentration of strong Bronsted acid sites in the composite. Lower selectivity to IMF was observed in the presence of HZSM-5 with Si/Al ratio of 15, 25 and 140. In addition, the use of primary alcohols instead of 2-PrOH gives a significantly lower yield of FAEs.

Synergy between Ni3Sn2 alloy and Lewis acidic ReOx enables selectivity control of furfural hydrogenation to cyclopentanone

Selectivity controlling is a crucial and challenging issue for the hydrogenation of furfural (FAL) to cyclopentanone (CPO). Herein, Ni3Sn2-ReOx/TiO2 is synthesized via successive impregnation and exhibits full conversion and 92.5 % CPO selectivity under 3.0 MPa H2 at 140 °C, which are much higher than those of Ni/TiO2 and Ni3Sn2/TiO2. Characterizations show that Ni3Sn2 is the main active phase that remarkably restrains the over-hydrogenation of the furan ring, while ReOx plays an electrophile or Lewis acid site to activate C-OH of furfuryl alcohol and induces its rearrangement. DFT calculations verify that Sn doping weakens the furan ring adsorption on Ni3Sn2 and shifts its adsorption configuration, which consequently inhibits side reactions and favors the metal-acid (Ni3Sn2-ReOx) synergy. The catalyst is stable, recyclable and also active at even 0.5 MPa H2 and 80 °C. This study provides an advanced strategy for the rational design of superior catalysts for tuning product selectivity, with practical potential for upgrading biomass-derived platform molecules.

Production of a high molecular weight jet-fuel precursor from biomass derived furfural and 2-methylfuran using propyl sulfonic SBA-15 catalysts

An effective catalyst for the production of branched chain fuel precursors with 15 carbon atoms (C15) from low carbon number, biomass-derived molecules is reported in this work. It shows that SBA-15 silica with the incorporation of sulfonic groups (S15) is highly active and selective for C-C coupling at low temperature, without solvent and under simple reaction conditions, giving a C15 condensation product with high selectivity, greater than 95 %, via hydroxyalkylation/alkylation (HAA) of 2-methylfuran (2-MF) with furfural (FAL). As water was determined to have a great negative influence on the stability of these catalysts, synthesis modifications and various post-synthesis treatments were tested to improve yield of C15. As a result, it was possible to improve up to 12 % the efficiency of the reaction by incorporating hydrophobic groups in the synthesis of sulfonic SBA-15 by co-condensation. This catalyst can be recovered and recycled, preserving its stability over multiple reaction cycles.

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.

Defect engineered efficient catalytic transfer hydrogenation of furfural to furfuryl alcohol in ethanol by Co-doped LaMnO3

As energy and CO2 concerns have become important aspects of scientific research, researchers are focusing on the development of alternative and green energies. Biomass is a significant energy source due to its cyclic utilization process and ability to renew CO2. The catalytic transfer hydrogenation (CTH) of sugar-derived furfural (FF) into furfuryl alcohol (FA) has attracted increasing attention; however, designing and synthesizing efficient nonnoble catalysts remains challenging. In this work, an oxygen defect-abundant LaMnO3 perovskite (R-LM4C-3h) was synthesized by combining the advantages of both Co heteroatom doping and H2 reduction. Raman, O2 temperature programmed desorption (O2-TPD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrochemical impedance spectroscopy (EIS) characterizations revealed that R-LM4C-3h exhibited abundant oxygen defects that improved its electronic properties. As a result, adsorption ability for FF was enhanced, the reaction energy barrier was decreased, and CTH catalytic activity was promoted. A 93.6 mol% FA yield with 100 % FF conversion was achieved using ethanol as the hydrogen source. The oxygen defect-mediated catalyst also exhibited excellent stability with almost no activity reduction after 5 cycles. This surface reconstruction strategy for obtaining perovskites by fabricating abundant oxygen defects provides a superior opportunity to better explore the structure–function relationship of catalysts and develop efficient nonnoble metal-based catalysts.

Chemobiocatalytic transfromation of biomass into furfurylamine with mixed amine donor in an eco-friendly medium

Biobased furfurylamine (FAM) is a versatile platform molecule for producing additives, pharmaceuticals, and pesticides. Recombinant E. coli HNND-AlaDH was created by co-expressing L-alanine dehydrogenase (AlaDH) and mutated Aspergillus terreus ω-transaminase (HNND), aiming to convert furfural (FUR) into FAM using inexpensive L-alanine and isopropylamine as mixed amine donors. In ChCl:FA:OA (10 wt%), pineapple peel, bagasse, barley shell, peanut shell, and corn stalk could be efficiently transformed into FUR under 170 °C for 10 min. Pineapple peel produced a high titer of FUR (183.3 mM). Additionally, the viscosity, surface tension and polarity of ChCl:FA:OA were explored. The biomass-derived FUR was fully transformed to FAM by HNND-AlaDH with amine donor (1:1:1 of L-Ala/isopropylamine/FUR mol/mol/mol) within 300 min. Accordingly, the FAM productivity was 0.58 g/(g xylan in pineapple peel). This chemobiocatalytic strategy established through the combination of chemocatalysis and biocatalysis could be applied to convert renewable biomass into valuable organic amines.

Selected Maillard Reaction Products and Their Yeast Metabolites in Commercial Wines.

During beer and wine production, Maillard reaction products (MRPs) are formed, which have a particular influence on the taste and aroma of the fermented beverages. Compared to beer, less is known about individual Maillard compounds and especially corresponding yeast metabolites in wine. In this study, 36 selected wines (Amarone, Ripasso, red, and white wines) were analyzed by HPLC-UV and GC-MS concerning the amounts of 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), methylglyoxal (MGO), glyoxal (GO), 5-hydroxymethylfurfural (HMF), and furfural (FF). 3-DG was found to be the dominant compound with values from 3.3 to 35.1 mg/L. The contents of 3-DGal, MGO, GO, HMF, and FF were in a single digit range. In addition to MRPs, the yeast metabolites originating from 3-DG, namely, 3-deoxyfructose and 3-deoxy-2-ketogluconic acid, 2,5-bis(hydroxymethyl)furan and 5-formyl-2-furancarboxylic acid, both formed from HMF, and the FF metabolites furfuryl alcohol and furan-2-carboxylic acid were detected and quantitated in wines for the first time. The amounts were between 0.1 and 53.5 mg/L with especially high contents of the oxidation products. Differences between red and white wines indicate that enological parameters like grape variety, production method, and aging may have an influence on the MRP contents in wines.

Highly efficient PdNiB decorated over carbon supports for the electrochemical valorization of furfural and 5-hydroxymethylfurfural into fuels

Hydrogenation via electrocatalysis is an efficient and environmentally friendly method for converting biomass derivatives into biofuels. Developing an eco-friendly, robust, and sustainable electrocatalyst is essential for selectively producing biofuels from biomass derivatives. Herein, Palladium-Nickel-Boron nanoparticles with carbon supports (PdNiB/C) were prepared and characterized by different analytical methods. The obtained XRD patterns show the structures of Pd and NiO incorporated into the disordered graphite-like structures of date seed-activated carbon. PdNiB/C has high structural stability and exhibits high electrocatalytic activity in the conversion of biomass derivatives of furfural (FF) to furfural alcohol (FA) and 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethyltetrahydrofuran (DHMTHF). The FA and DHMTHF hydrogenated products yields were tuned by changing the carbon supports (date seed activated carbon (DSAC), carbon black (CB), and reduced graphene oxide (rGO)) and the elemental composition of Pd, Ni, and B of the PdNiB/C catalysts. The PN25/rGO catalyst with a Pd:Ni ratio of 1:3 showed the highest conversions of FF to FA and of HMF to DHMTHF with relatively high faradaic efficiencies. In electrochemical hydrogenation (ECH), the presence of boron enhanced the faradaic efficiencies (F.E.) by slowing down the competing HER. ECH conditions, including applied potential, temperature, and time, were also optimized to maximize the yield and selectivity of the hydrogenated products. This study showed the potential to convert biomass derivatives to biofuels for renewable energy production.

Ni − Promoted Cu/ZSM-5 for selective hydrodeoxygenation of furfural to produce 2 − Methylfuran

Catalytic hydrodeoxygenation (HDO) of furfural (FUR) to produce 2 − methylfuran (2 − MeF) is a green way to produce hydrocarbons with fuel − like properties. In this work, bimetallic Ni − Cu alloys supported on ZSM − 5 zeolite catalysts were prepared by wetness impregnation and used for HDO of FUR to produce 2 − MeF. Cu/ZSM − 5 catalyst favoured the adsorption of CO bonding in FUR through a tilted adsorption orientation, avoiding the saturation of furan ring. Moderate addition of Ni in Cu/ZSM-5 accelerated the conversion rate with enhanced adsorption of the FUR and H2, leading to high selectivity of 2 − MeF in the product through sequenced hydrogenation and deoxygenation procedures. Moreover, zeolite surface acid benefited the scission of CO bonding in the intermediate furfuryl alcohol (FOL), further promoting the yield of 2 − MeF. The optimized 2Ni − 6Cu/CZ catalyst (with 2 wt% Ni and 6 wt% Cu on ZSM − 5) gave 2 − MeF yield of 78.8 wt% at 220 °C after 30 min reaction. With further increased Ni concentrations, the hydrogenation of furan ring was accelerated with tetrahydrofurfuryl alcohol (THFOL) as the main product.

Effect of different pretreatments of Passiflora edulis peel biomass on the conversion process into bioproducts for biorefineries

The industrial processing of passion fruit (Passiflora edulis f. flavicarpa) generates large amounts of lignocellulosic residues that are of great economic, scientific, and technological interest. This study investigated different pretreatments – aqueous, acidic and basic – aided by ultrasound. It also verified their influence on the chemical and physical aspects of passion fruit peel and on the yield of carbohydrates, 5-hydroxymethylfurfural (HMF) and furfural (FF). The pretreatments followed a complete factorial experimental design to obtain the optimal conditions varying in concentration (2.5 % and 5 % HCl; 4 % and 8 % NaOH) and time (0.5 and 1 h) for carbohydrate yield and increased accessibility to cellulose and hemicellulose. These results were analyzed by HPLC, FT-IR and X-ray diffraction analysis. Optimized conditions for the pretreatment were 2.5 % HCl, 4 % NaOH and aqueous with a sonication time of 1 h. The pretreatments tested increased the efficiency of the hydrolysis. The highest yields of glucose (5.05 g/L), HMF (0.09 g/L), and FF (0.99 g/L) were recorded from the hydrolysis pretreated with HCl 2.5 % at 1 h. This study demonstrated the potential of using passion fruit peel in biorefinery processes, adding value to waste and promoting sustainability.

Assembling Co clusters via nanosized ZIF-67 sprouted from CoAl-LDH nanoflower for selective hydrogenation

Atomically dispersed cluster catalysts own versatile applications in biomass valorization, while the controllable assembly and microenvironmental regulation remain a crucial challenge. Herein, Co clusters assembled via nanosized ZIF-67 sprouted from Co-Al layered double hydroxide nanoflowers were applied for selective hydrogenation of furfural (FAL). The pyrolysis temperature can tune the microstructures and acid properties of the catalyst, which accounts for the hydrogenation of FAL to furfuryl alcohol (FOL), 2-methylfuran (2-MF), and tetrahydrofurfuryl alcohol (THFOL) with yield of 99.1 %, 96.7 %, and 82.3 %, respectively. The Co clusters favor CO bond adsorption via bridging-type adsorption mode while suppressing the furan ring adsorption. Moreover, ultra-dispersed Co clusters facilitate the cleavage of C-OH bonds in FOL intermediate, leading to a high 2-MF yield. As the pyrolysis temperature increase, the formed Co nanoparticles are conducive to the parallel adsorption of FAL, resulting in the production of THFOL. This work affords a multi-functional catalyst in catalytic biomass upgrading.

Construction of HfO2 nanoparticles with rich hydroxyl group for the efficient catalytic transfer hydrogenation of furfural

Although metal oxide has unique advantages in catalytic transfer hydrogenation (CTH) of furfural (FAL) into furfuryl alcohol (FOL), the excessive stability of the metal site and oxygen coordination leads to the inert Lewis acid site in the oxide, which affects the catalytic activity and limits its broader application. It is known that the hydroxyl group on the oxide surface can promote the adsorption of isopropanol in an alkoxide species by assisting its deprotonation, thereby activating the metal site and enhance the overall reaction activity. However, constructing metal oxide with rich hydroxyl groups is always challenging. This contribution prepared a series of HfO2 nanoparticles (NPs) with rich hydroxyl groups through hydrothermal methods. Systematic characterizations proved the presence of hydroxyl groups on the surface of HfO2 NPs, which promoted its adsorption capacity for isopropanol (hydrogen donor and reaction solvent) and substrate (FAL), thus accelerating the subsequent reaction for CTH of FAL into FOL. As a result, a 100% of FAL conversion with 95.2% of FOL yield was obtained at 160 °C in 4 h, which has significant advantages over commercial and other literature reported oxides. This finding provides a new idea for designing of efficient metal oxides for the CTH reaction by enhancing the hydroxyl group.

Synergistic effect of surface Cu0 and Cu+ species on improved selective hydrogenation of furfural to furfuryl alcohol over hydrotalcite-derived CuxMg3Al oxides

In the selective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL), it is important to develop a simple and cheap non-precious metal catalyst to replace the precious metal catalyst. Therefore, CuxMg3AlOy (x = 0.3, 0.5, 0.7, 0.9, 1.1) composite metal oxide catalysts were prepared by CuMgAl-LDHs as precursor for the selective hydrogenation of FAL to FOL. In this series of catalysts, Cu0.9Mg3AlOy has the best catalytic activity, with 99% FAL conversion and 98.4% selectivity under the mild reaction conditions of 1.6 MPa H2 pressure, 1.5 h and 120 ℃, and good reusability. XRD, TEM, H2-TPR, CO2-TPD, XPS and in-situ DRIFTS characterization were used to investigate the activate species for hydrogenation reaction. It can be proved that Cu2+ and Cu+ on the surface of CuxMg3AlOy can be partially reduced to the Cu0 species in-situ during the reaction, promoting the hydrogenation of FAL. Various studies confirm that Cu0 is mainly responsible for the activation and dissociation of H2, and both Cu0 and Cu+ are used to adsorb the carbonyl group in FAL to improve the selectivity of FOL. Moreover, the appropriate amount of the Cu0 and Cu+ species plays an important role in selective hydrogenation of FAL to FOL through their synergy.

Metal-acid dual sites in Pd/SiO2-Al2O3 synergistically catalyze selective hydrogenation-etherification of furfural to bioether

Production of ethers from biomass-derived platform compounds is a substantial scientific challenge and industrial pursuit. In this study, an effective bifunctional Pd/SiO2-Al2O3-30 catalyst was synthesized for the selective hydrogenation-etherification of furfural (FAL) to furfuryl ether and exhibited an 86.2% 2-(isopropoxymethyl)furan yield with the synergistic catalysis of Pd particles and Brønsted–Lewis acid sites. The incorporation of Si with Al2O3 in the catalysts weakened the metal-support interaction and resulted in larger Pd particles, which inhibited the hydrogenation of the furan ring. Meanwhile, the formation of Brønsted acid centers catalyzed the etherification step and promoted the selectivity to corresponding ethers. Furthermore, extensive reaction results and characterizations uncovered the metal-acid synergistic catalysis mechanism for the selective hydrogenation-etherification of FAL. This work provides an innovative strategy for preparing effective metal-acid bifunctional catalysts for the hydrogenation-etherification of bio-aldehydes to ethers.

Efficient Cu-Co bimetallic catalysts for the selective hydrogenation of furfural to furfuryl alcohol

It has important research value for effectively upgrading furfural (FAL) to furfuryl alcohol (FOL) with cheap metals. In this work, a series of layered double hydroxides (LDH) derived CunCo1/MgAlOx (n = 1, 2, 3, and 4) catalysts with different metal ratios were prepared by a simple one-pot method and applied in FAL hydrogenation to FOL. It was found that the synergistic interaction between Cu and Co significantly improves the catalyst activity and favors the formation of Cu2O, which can act as a Lewis acid site and polarize the carbonyl group (C = O), thus promoting the formation of FOL. And in-situ DRIFTS shows that the Cu3Co1/MgAlOx preferentially adsorbs and activates C = O rather than furan rings. Moreover, DFT calculations show that the Cu3Co1 (111) crystal surface with the lowest d-band center and the strongest synergistic interaction between Cu and Co exhibits the highest adsorption energies of H2 and FAL, the lowest adsorption energies of H* and FOL, and the lowest energy barriers of FAL to alkoxy intermediate that is conducive to form FOL. Herein, as a favorable contender for efficient hydrogenation of FAL to FOL, the Cu3Co1/MgAlOx gives a 99.9% yield to FOL and presents excellent cycling stability.

Comparison of Phenolic and Volatile Compounds in MD2 Pineapple Peel and Core.

The peel and core discarded from the processing of MD2 pineapple have the potential to be valorized. This study evaluated the functional and volatile compounds in the extracts of MD pineapple peel and core (MD2-PPC). The total soluble solids, pH, titratable acidity, sweetness index, and astringency index were 9.34 °Brix, 4.00, 0.74%, 12.84, and 0.08, respectively, for the peel and 12.00 °Brix, 3.96, 0.32%, 37.66, and 0.03, respectively, for the core. The fat and protein contents of the peel and core were found to be significantly different (p < 0.05). The total phenolic (TPC) and flavonoid contents (TFC) were significantly higher in the peel. The peel also showed better antioxidant activity, with a half-maximal inhibitory concentration (IC50) of 0.63 mg/mL for DPPH free radical activity compared with the core. The TPC of different phenolic fractions from peel extract was highest in the glycosylated fraction, followed by the esterified, insoluble-bound, and free phenolic fractions. GC-MS analysis identified 38 compounds in the peel and 23 in the core. The primary volatile compounds were 2-furan carboxaldehyde, 5-(hydroxymethyl), and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP). The identification of phenolics and volatile compounds provides important insights into the valorization of (MD2-PPC) waste.

Unlocking the Potential of Bio‐Based Nitrogen‐Rich Furanic Platforms as Biomass Synthons

AbstractThe demand for new biomass‐derived fine and commodity chemicals propels the discovery of new methodologies and synthons. Whereas furfural and 5‐hydroxymethylfurfural are cornerstones of sustainable chemistry, 3‐acetamido‐5‐acetyl furan (3A5AF), an N‐rich furan obtained from chitin biomass, remains unexplored, due to the poor reactivity of the acetyl group relative to previous furanic aldehydes. Here we developed a reactive 3‐acetamido‐5‐furfuryl aldehyde (3A5F) and demonstrated the utility of this synthon as a source of bio‐derived nitrogen‐rich heteroaromatics, carbocycles, and as a bioconjugation reagent.

Unlocking the Potential of Bio-Based Nitrogen-Rich Furanic Platforms as Biomass Synthons.

The demand for new biomass-derived fine and commodity chemicals propels the discovery of new methodologies and synthons. Whereas furfural and 5-hydroxymethylfurfural are cornerstones of sustainable chemistry, 3-acetamido-5-acetyl furan (3A5AF), an N-rich furan obtained from chitin biomass, remains unexplored, due to the poor reactivity of the acetyl group relative to previous furanic aldehydes. Here we developed a reactive 3-acetamido-5-furfuryl aldehyde (3A5F) and demonstrated the utility of this synthon as a source of bio-derived nitrogen-rich heteroaromatics, carbocycles, and as a bioconjugation reagent.

Furfural adsorption on the g-C3N4 monolayer: A DFT analysis

Graphitic carbon nitride (g-C3N4) has attracted much attention in recent years as a material for catalytic processes due to its promising structural and physicochemical properties. However, the role played by the g-C3N4 during the catalytic activity is often briefly discussed. Consequently, the mechanism behind these substrate-adsorbate processes involving g-C3N4 still needs to be better understood. This study analyzed furfural (FAL) adsorption on h-g-C3N4 monolayers based on DFT, including Van der Waals (vdW) interactions. To elucidate the role of the h-g-C3N4 in catalytic systems, the adsorption of a FAL molecule was evaluated at high and low coverages. At high coverage, due to proximity effects, FAL molecules interact with neighboring FAL molecules forming a monolayer that lays over the h-g-C3N4 nanosheet. At low coverage, weak interactions govern the FAL-h-g-C3N4 interaction. In both cases, vdW interactions are the main forces that bring stability to the composites. No chemical interactions are observed. The obtained results led us to conclude that in reactions including FAL and h-g-C3N4 nanosheets, the latter will serve as a support structure that favors the adsorbate mobility to reach the reactive centers.

Ultrafine Pd on a La Metal–Organic Framework for Selective Hydrogenation of Furfural via a Metal–Support Electronic Effect

It is challenging to synthesize a stable ultrafine Pd catalyst with high selectivity and activity at low temperatures toward hydrogenation of furfural (FF). We report an approach of applying C═N and S–O entities in a highly stable La metal–organic framework (La-MOF) (LaQS) as the platform support that confines Pd nanoparticles (NPs) through coordination, resulting in a stable Pd/LaQS catalytic system. The catalytic conversion of FF into tetrahydrofurfuryl alcohol (THFA) using this catalyst can be done as simply as one-step hydrogenation at room temperature, with a high selectivity of >99% maintained even at 120 °C. The outstanding catalytic activity and selectivity are mainly attributed to the electronic effect of metal–support in Pd/LaQS, which produces electron-rich Pd and enhanced Lewis-acid LaQS. Especially, this electronic effect can be facilely tuned by the Pd loading in Pd/LaQS. On the one hand, electron-rich ultrafine Pd promotes the activation of H2 and improves the reaction activity. On the other hand, the acid-enhanced LaQS support not only promotes the activation of FF and improves its activity, but also the positive electricity of the LaQS support is conducive to the reactant adsorption and product desorption, thus improving the THFA selectivity. This work develops a stable LaQS support for the stabilization of ultrafine metal nanoparticles via the metal–support interaction for enhanced catalysis, which sheds light on the construction of efficient MOF-based catalysts for task-specific applications.