Complete Conversion Of Furfural Research Articles

Tandem catalysis of furfural to γ-valerolactone over polyoxometalate-based metal-organic frameworks: Exploring the role of confinement in the catalytic process

Polyoxometalate-based metal-organic frameworks (POMOFs) with bifunctional Lewis-Brønsted acid were designed by confining polyoxometalates (POMs: phosphotungstic acid (PW), phosphomolybdic acid (PMo) or silicotungstic acid (SiW)) within the Zr-MOFs. The confined POMs not only have their own Brønsted acid, but can also regulate the Lewis acid strength of the POMOFs via charge regulation, ultimately allowing the POMOFs to display superior catalytic performance in the tandem catalysis of furfural (FAL) to γ-valerolactone (GVL). Among the three catalysts (POMOF-PW, POMOF-PMo and POMOF-SiW), a complete conversion of FAL was achieved, while POMOF-PW exhibited the highest GVL yield (58.1 %) at 160 °C within 23 h. The leaching experiment and structural characterization of the catalyst before and after recycling confirmed the stability of the catalyst structure. The humin originates from the polymerization of furan ring-containing compounds driven by Brønsted acid. The adsorption configuration of the substrate molecules on the catalyst offers a new explanation for the tandem reaction process, i.e. that perpendicular adsorption performs only the first step of the tandem reaction, while the coexistence of perpendicular and horizontal adsorption permits the entire reaction process. This work gives unique insights into the tandem reaction of FAL and can guide the design of efficient tandem reaction catalysts.

Phosphotungstic acid supported on Zr-SBA-15 as an efficient catalyst for one-pot conversion of furfural to γ-valerolactone

Development of high-performance solid catalysts for the utilization of biomass has become an important research topic in heterogeneous catalysis and sustainable chemistry. Herein, A series of phosphotungstic acid (HPW) supported on Zr-SBA-15 were prepared by a post-synthesis procedure and evaluated for the one-pot conversion of furfural (FUR) to γ-valerolactone (GVL) using 2-propanol as the H-donor and solvent. Those catalysts were detailed and characterized by XRD, N2 physisorption, FTIR, SEM, TEM, NH3-TPD, and pyridine-DRIFT techniques. Among those catalysts, a complete conversion of FUR was achieved, while the selectivity of GVL was significantly affected by the ratio of HPW and Zr. The HPW/Zr-SBA-15 (2-4-15) (the mass ratio of HPW: ZrOCl2: SBA-15 = 2:4:15) showed the highest GVL yield (83%) under optimized reaction conditions. Correlating the catalyst performance with the B/L ratio (Brønsted acid sites (BAS)/Lewis acid sites (LAS)) ratio uncovers that the balance between the BAS and LAS would be the key to higher catalytic performance. Different reaction parameters including reaction temperature, time, and FUR concentration were also studied. In addition, the catalyst showed good stability and regeneration.

Significant effect of Ca modification on improving catalytic stability of Cu-catalyst in gas-phase furfural hydrogenation to furfuralcohol

The gas-phase hydrogenation of furfural to furfuralcohol over Cr-free Cu-based catalysts has attracted increasing attention due to its environmentally friendly nature and mild operating conditions. Although reduced pure nano-sized CuO exhibits complete furfural hydrogenation and nearly 100% furfuralcohol selectivity, it suffers from rapid deactivation caused by sintering. In this study, we conducted comparative investigations on the catalytic performance and stability of two Cu-based catalysts: 90%CuO-10%SiO2 and 90%CuO-5%CaO-5%SiO2, in the gas-phase furfural hydrogenation. The reaction is carried out under various conditions, including temperatures ranging from 120 to 170 ℃, LHSVs of 1 to 2.2 h−1, and H2 to furfural molar ratios of 3.5 to 12.5. The results indicate that under optimal conditions, the Ca-modified catalyst achieves nearly complete furfural conversion and almost 100% furfuralcohol selectivity for a test duration of 31 h. In contrast, the unmodified catalyst exhibits stable performance for only seven hours despite the similar initial performance. XRD analysis confirms that the gradual deactivation of both catalysts is attributed to the oxidation of reduced metallic Cu sites to Cu oxides. Further characterizations of the two spent catalysts using HRTEM and XPS analyses, along with DFT calculations, suggest that the presence of Ca in Cu lattices prevents the loss of electrons from low-valence Cu sites or the reduced metallic Cu sites, thus inhibiting their oxidation to high-valence Cu oxides. This phenomenon contributes to suppressing the deactivation of Cu-catalysts in the gas-phase furfural hydrogenation process.

Trimetallic Cu-Ni-Re/Hβ catalyst for the direct conversion of furfural to 2-Methyltetrahydrofuran

The direct conversion of furfural (FUR) to 2-methyltetrahydrofuran (2-MTHF) was investigated over a trimetallic CuNiRe/Hβ catalyst. Under optimal reaction conditions at 240 °C under 3 MPa H2 for 1 h, almost complete conversion of FUR and high-yield of 2-MTHF (81 %) was achieved. This is the highest yield reported for the direct conversion of FUR to 2-MTHF. HR-TEM demonstrated that the growth of Cu nanoparticles (NPs) on the surface of Hβ was inhibited after loading Ni or Re resulted in the smaller Cu particle size and better hydrogenation and hydrodeoxygenation activity. H2-TPR characterization exhibited that the reducibility of bimetallic and trimetallic catalysts was higher than that of monometallic catalysts·NH3-TPD explained that Hβ acid sites mainly contributed to FUR deoxygenation. The adsorption configurations of FUR, furfuryl alcohol (FOL) and 2-methylfuran (2-MF) on the catalyst were revealed by ATR-IR. Catalyst evaluation and control experiments proved that FUR was first hydrogenated to FOL, followed by hydrodeoxygenation to 2-MF, and finally hydrogenated to 2-MTHF catalyzed by the combination of three metals.

Catalysts Derived from Nickel-Containing Layered Double Hydroxides for Aqueous-Phase Furfural Hydrogenation

Changes in the structural and textural properties of NiAl-layered double hydroxides (LDHs) (with 2–4 molar ratios of metals) and state of nickel that occur in different steps of the synthesis of nickel catalysts were studied using XRD, thermal analysis, TPR, low-temperature nitrogen adsorption, XANES, EXAFS, and electron microscopy methods. Relations between nickel content, catalyst reduction conditions, state of nickel, and its catalytic properties were revealed. It was shown that the use of NiAl LDH as the catalyst precursor even at a high content of active metal allows for the obtaining of the dispersed particles of supported nickel that are active in the aqueous-phase hydrogenation of furfural. The catalyst activity and conversion of furfural were found to increase with elevation of the catalyst reduction temperature and the corresponding growth of the fraction of reduced nickel. However, a lower reduction temperature (500 °C) makes it possible to form smaller nickel particles with the size of 4–6 nm, and a high Ni content (Ni:Al = 4) can be used to obtain the active Ni@NiAlOx catalyst. Under mild reaction conditions (90 °C, 2.0 MPa), the furfural conversion reached 93%, and furfuryl alcohol was formed with the selectivity of 70%. Under more severe reaction conditions (150 °C, 3.0 MPa), complete conversion of furfural was achieved, and cyclopentanol and tetrahydrofurfuryl alcohol were the main hydrogenation products.

Facile ultrasound-assisted grafting of silica gel by aminopropyltriethoxysilane for aldol condensation of furfural and acetone.

This work focuses on the development of a simple method to prepare heterogeneous catalysts with tunable basicity and stability for aldol condensation of furfural and acetone. Silica gel was grafted by aminopropyltriethoxysilane (APTES) with 20, 30, 40 and 50 wt. % of APTES using probe-type ultrasonicator with a power of 130 W and a frequency of 20 kHz. The grafted samples were studied by XRD, SEM, N2 sorption, FTIR, XPS, CHN and TG analysis, and CO2-TPD. The sonication facilitated the bond formation between APTES and the silica gel with less pore blocking than the conventional grafting method. The basicity of the samples was tunable with the quantity of APTES loading. The grafted samples were active catalysts for aldol condensation between furfural and acetone at 60 °C. The catalyst with 30 wt. % APTES grafting (30APS-U) provided a nearly complete furfural conversion and high furfurylbutenone selectivity. The conversion and selectivity increased with time and reached the highest values at 24 h. Thus, the catalysts with tunable basicity prepared by ultrasound-assisted grafting of silica with various APTES amounts were effective in furfural valorization.

Synthesis of maleic acid from biomass-derived furfural in the presence of KBr/graphitic carbon nitride (g-C3N4) catalyst and hydrogen peroxide

A one-step, liquid-phase hydrogen peroxide reaction system, which was heterogeneously catalyzed by KBr-doped graphitic carbon nitride (KBr/g-C3N4), was developed for the conversion of furfural to maleic acid (MA). At first, a 68.0% MA yield was achieved in a homogeneous reaction system catalyzed by KBr-KOH. Next, a series of K-doped g-C3N4 catalysts with various potassium salts (KBr, KCl, KNO3, and KOH) was synthesized and tested for the conversion of furfural to MA, 2-buten-1,4-olide (FRO), and succinic acid (SA). When comparing the various K-doped g-C3N4 catalysts, KBr/g-C3N4 enhanced MA selectivity, which resulted in complete furfural conversion and a 70.4% MA yield (at 100 °C for 180 min). Furthermore, a synergistic interaction was observed between KBr and the g-C3N4 support, which could explain why KBr/g-C3N4 had the highest MA selectivity.

Aqueous-phase hydrogenation of furfural over supported palladium catalysts: effect of the support on the reaction routes

The effect of the support nature (different carbons, aluminum oxide, mixed MgAl oxide) on the activity of palladium catalysts and on the reaction routes of aqueous-phase hydrogenation of furfural at a temperature of 423 K and a pressure of 3 MPa was investigated. The carbon-supported catalysts were found to be the most active, and almost complete conversion of furfural is achieved. In the presence of these catalysts, the reaction proceeds predominantly through two parallel water-involved routes depending on the nature of carbon support: catalysts supported on carbon nanoglobules are selective to 4-oxopentanal (selectivity up to about 63%), while catalysts supported on carbon nanotubes give mainly cyclopentanone (selectivity up to 57%). The palladium catalysts based on the oxide supports (γ-Al2O3, MgAlOx) are much less active in the aqueous-phase hydrogenation of furfural compared to carbon-supported catalysts, and complete conversion of furfural does not occur (only up to 55%). In the presence of catalysts prepared using basic support (i.e., MgAl oxide), there are no reactions involving water, and furfuryl alcohol and tetrahydrofurfuryl alcohol are the principal products. According to the results of catalyst characterizations, the revealed differences in performance of palladium catalysts are caused by the effect of the support nature on the formation and dispersion of supported Pd nanoparticles, as well as by the distinctions in the structure and acid–base properties of the supports.

Highly efficient catalytic valorization of biomass-derived furfural in methanol and ethanol

Catalytic valorization of furfural (FUR) using a simple and low-cost metal catalyst has been considered as a hot topic in sustainable chemistry. In this work, a new Ni@R-Ca catalyst is prepared via the auto-combustion and in situ reduction method. When it is employed to promote the catalytic valorization of FUR in aliphatic alcohol, a nearly complete FUR conversion with excellent product selectivity is obtained under mild reaction conditions. Using methanol as reaction medium, the sole product is furfuryl alcohol (FA) in which ca. 99% yield of FA was attained. While, in ethanol, the obtained products mainly contain FA and furan-2-acrolein (FUA) in which a 94% conversion of FUR with a 91% total selectivity of FA and FUA was acquired. Based on the characterization of catalyst including XRD, SEM, XPS and H2-TPR techniques, it is concluded that the synergy effect of metal Ni and R-Ca crystal lattice plays a crucial role in the efficient conversion of FUR in aliphatic alcohol.

Catalytic transfer hydrogenation of biomass-derived furfural to furfuryl alcohol over in-situ prepared nano Cu-Pd/C catalyst using formic acid as hydrogen source

Catalytic transfer hydrogenation (CTH) of bio-derived furfural (FF) to furfuryl alcohol (FFA) was performed using the physically mixed CuO-Pd/C as catalyst and formic acid (FA) as hydrogen donor. The evolution investigation of Cu showed the precursor CuO firstly dissolved into Cu2+ by FA and then formed coordination polymer-copper(II), which uniformly dispersed in reaction solution of 1, 4-dioxane. Subsequently the Cu2+ was in-situ reduced and Cu-Pd alloys formed simultaneously. The in-situ prepared nano Cu-Pd/C catalyst exhibited the best performance with a complete FF conversion and FFA selectivity of 98.1%. Reaction conditions test suggested that the FFA selectivity was greatly dependent on the Cu content. The underlying mechanism revealed that the Pd in Cu-Pd alloys mainly promoted the FF conversion by enhancing hydrogen adsorption, while the nano Cu for increasing FFA selectivity; the Cu-Pd alloys functioned in synergistic way. Leaching and recycling tests demonstrated an excellent stability of the Cu-Pd/C catalyst.

Palladium–Ruthenium Catalyst for Selective Hydrogenation of Furfural to Cyclopentanol

Bimetallic Pd–Ru/C catalyst was shown to be much more active in the aqueous-phase hydrogenation of furfural (473 K, 8 MPa) in comparison with both Pd/C and Ru/C catalysts. The enhanced hydrogenation activity manifested itself as an increased yield of cyclopentanol (77%) at a complete conversion of furfural. The observed synergistic effect between palladium and ruthenium in the tested reaction can be related to changes in the electronic state and particle size of supported metals upon interaction with each other and the Pd–Ru alloy formation.

Selective aqueous-phase hydrogenation of furfural to cyclopentanol over PdRu/C catalyst

The bimetallic PdRu catalyst supported on carbon nanotubes were found ot provide an efficient synthesis of cyclopentanol in aqueous-phase hydrogenation of furfural. Under the chosen reaction conditions (temperature of 473 K, total pressure of 8 MPa), the selectivity towards cyclopentanol reaches 77% at a complete conversion of furfural. A high activity of this catalyst can be associated with changes in the electronic state and dispersion of the supported metals caused by their mutual interaction and formation of PdRu alloy.

Highly selective liquid-phase hydrogenation of furfural over N-doped carbon supported metallic nickel catalyst under mild conditions

In this work, N-doped activated carbon supported metallic nickel (Ni/NAC) catalysts were fabricated by two-step calcination method in N2 atmosphere for liquid-phase hydrogenation of furfural (FAL). It was found that the pyrolysis temperature and amount of melamine as N doping source have important influence on N doping content and type in activated carbon (AC) support, resulting in the subsequently formed Ni nanoparticles on N-doped AC with different sizes and thus affording different catalytic hydrogenation activities. The results demonstrated that using N-doped AC with 1.0g melamine at 1073K in N2 atmosphere as support, the obtained Ni/NAC at 873K in N2 atmosphere with Ni nanoparticle sizes of ∼13.1nm (denoted as Ni/NAC-1-1073) exhibits a N doping content of 3.65at.% and a surface area of 561.2m2g−1 with a microporous structure. As catalyst for FAL hydrogenation, Ni/NAC-1-1073 demonstrated the best catalytic performance among all investigated catalysts, achieving almost 100% selectivity of tetrahydrofurfuryl alcohol (THFOL) with a complete FAL conversion at 353K after 3h reaction, while only 76.7% selectivity of THFOL with a FAL conversion of 86.4% was obtained using Ni/AC catalyst without N doping under the identical experimental conditions. Furthermore, it was found that almost 100% conversion of FAL to furfural alcohol (FOL) can be reached by transfer hydrogenation pathway in 2-proponal solvent using Ni/NAC-1-1073 at 413K after 5h reaction, whereas Ni/AC without N doping can only afford 30.2% conversion of FAL to FOL under the same conditions. The superior catalytic performance of Ni/NAC-1-1073 could be ascribed to a synergistic effect of nanosized Ni providing catalytic active sites, suitable N doping content and type in AC to promote catalytic performance, and advantageous structure characteristics of high surface area and porous structure favourable for the exposure of catalytic active sites and mass transport.

Inhibition Effects of Furfural on Aerobic Batch Cultivation of Saccharomyces cerevisiae Growing on Ethanol and/or Acetic Acid.

Physiological effects of furfural on Saccharomyces cerevisiae growing on ethanol (15 g·l−1) or acetate (20 g·l−1) as the carbon and energy source were investigated. Furfural (4 g·l−1), which was added during the exponential growth phase in batch cultures, was found to strongly inhibit cell growth on both carbon sources. No biomass formation occurred in the presence of furfural. However, furfural was in both cases converted to furfuryl alcohol and furoic acid, and growth resumed after complete conversion of furfural. During growth on ethanol, a rapid initial conversion of furfural to furfuryl alcohol was observed during the first few minutes after the addition of furfural, after which the conversion rate decreased to approximately 0.15 g·g−1·h−1 for the remaining conversion time. Acetaldehyde accumulated in the medium during the first few hours of conversion. Interestingly, addition of acetate after furfural addition resulted in an increased conversion rate of furfural and a higher carbon dioxide evolution rate, but no growth was observed until after complete conversion of furfural. Furfural addition to cells growing on acetate as the sole carbon source induced no formation of acetaldehyde, and the furfural conversion rate was lower than that on ethanol. The relationship between inhibition effects of furfural and NADH consumption is discussed.

Inhibition effects of furfural on aerobic batch cultivation of Saccharomyces cerevisiae growing on ethanol and/or acetic acid

Physiological effects of furfural on Saccharomyces cerevisiae growing on ethanol (15 g· l −1) or acetate (20 g· l −1) as the carbon and energy source were investigated. Furfural (4 g· l −1), which was added during the exponential growth phase in batch cultures, was found to strongly inhibit cell growth on both carbon sources. No biomass formation occurred in the presence of furfural. However, furfural was in both cases converted to furfuryl alcohol and furoic acid, and growth resumed after complete conversion of furfural. During growth on ethanol, a rapid initial conversion of furfural to furfuryl alcohol was observed during the first few minutes after the addition of furfural, after which the conversion rate decreased to approximately 0.15 g·g −1·h −1 for the remaining conversion time. Acetaldehyde accumulated in the medium during the first few hours of conversion. Interestingly, addition of acetate after furfural addition resulted in an increased conversion rate of furfural and a higher carbon dioxide evolution rate, but no growth was observed until after complete conversion of furfural. Furfural addition to cells growing on acetate as the sole carbon source induced no formation of acetaldehyde, and the furfural conversion rate was lower than that on ethanol. The relationship between inhibition effects of furfural and NADH consumption is discussed.