Liquid-phase Hydrogenation Of Furfural Research Articles

Effects of alloying palladium with gold in furfural hydrogenation:An in situ ATR-IR spectroscopy and density functional theory study

Furfural is a versatile platform molecule and a model compound to explore the key factors influencing activity and selectivity in heterogeneous catalysis. In this study, Pd and AuPd nanoparticles (average size 3.5–4 nm) were deposited on TiO2 by sol immobilization method and were evaluated for liquid-phase furfural hydrogenation. Alloying Au and Pd caused a decrease in activity, an enhancement in stability, and a change in selectivity, favouring the complete hydrogenation of furfural over the decarbonylation reaction. These variations in catalytic performance were elucidated by combining in situ attenuated total reflectance infrared spectroscopy and density functional theory studies.

Selective hydrogenation of furfural to tetrahydrofurfuryl alcohol in 2-butanol over an equimolar Ni-Cu-Al catalyst prepared by the co-precipitation method

In order to upgrade biomass-derived platform chemicals to high value-added chemicals and liquid fuels, it is highly advantageous and desirable to synthesize suitable non-precious bimetallic catalysts that are efficient and versatile in chemical reactions. Equal moles of Ni and Cu were dispersed on varying mole ratios of Al by the co-precipitation method to synthesize Ni-Cu alloy particles to obtain a maximum yield of tetrahydrofurfuryl alcohol (THFA) by the liquid phase hydrogenation of furfural. The nickel species were active for both the furan ring (C=C) and carbonyl group (C=O) of furfural molecule, while Cu species were highly active for only the carbonyl group of furfural molecule. Systematic characterization of the prepared catalysts by XRD, TPR, STEM-EDS, and XPS analysis revealed the formation of highly active Ni-Cu alloys and near-equal Ni/Cu surface contents were achieved for the equimolar catalyst, which showcased a maximum of 98 mol% yield of THFA at 140 °C, 30 bar, 4 h. The reaction pressure and temperature showed a substantial effect on the product yield. The solvent selection also influenced the product selectivity, particularly with 2-butanol, which promoted the reaction with its hydrogen donor capacity and supported the ring hydrogenation of FAL to THFA. Moreover, the reduced Ni1Cu1-Al1 catalyst displayed good recyclability for three runs and an equal activity to that of a fresh catalyst after the regeneration.

Bimetallic PtFe-Catalyzed Selective Hydrogenation of Furfural to Furfuryl Alcohol: Solvent Effect of Isopropanol and Hydrogen Activation

Highly selective liquid-phase hydrogenation of furfural was efficiently catalyzed by PtFe alloy nanoparticles supported on CeO2. An initial reaction rate at ~1500 h-1, a near 100% selectivity towar...

Cu-Al spinel-oxide catalysts for selective hydrogenation of furfural to furfuryl alcohol

Furfuryl alcohol, one of the important platform chemicals for polymer, food, and pharmaceutical industries, was produced by the liquid-phase hydrogenation of furfural. The Cu-Al spinel-oxide catalyst (CuAl2O4) was developed for the furfural hydrogenation to furfuryl alcohol. The spinel CuAl2O4 showed excellent activity as compared to the impregnated Cu/Al2O3 and reported non-noble metal catalysts. The influences of reaction parameters including temperature, time, and H2 initial pressure were systematically investigated. The furfural conversion and the yield of furfuryl alcohol were achieved on CuAl2O4 catalyst at >99 % and >95 %, respectively. The excellent activity of CuAl2O4 catalyst could be attributed to the synergistic effect induced by the interaction between the reduced copper species (Cu0) and the copper spinel host (Cu2+) along with the high H2 sorption ability compared to the impregnated catalyst. Density functional theory (DFT) calculations suggested that the spinel structure had a stronger interaction with furfural and higher amounts of active sites for H2 dissociation, resulting in the lower reaction free energy and energy barriers for the hydrogenation than the impregnated catalyst. Furthermore, it was observed that the CuAl2O4 showed a positive effect on the tolerance against water impurity in the liquid-phase hydrogenation of furfural.

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.

Capping Agent Effect on Pd-Supported Nanoparticles in the Hydrogenation of Furfural

The catalytic performance of a series of 1 wt % Pd/C catalysts prepared by the sol-immobilization method has been studied in the liquid-phase hydrogenation of furfural. The temperature range studied was 25–75 °C, keeping the H2 pressure constant at 5 bar. The effect of the catalyst preparation using different capping agents containing oxygen or nitrogen groups was assessed. Polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and poly (diallyldimethylammonium chloride) (PDDA) were chosen. The catalysts were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization data suggest that the different capping agents affected the initial activity of the catalysts by adjusting the available Pd surface sites, without producing a significant change in the Pd particle size. The different activity of the three catalysts followed the trend: PdPVA/C > PdPDDA/C > PdPVP/C. In terms of selectivity to furfuryl alcohol, the opposite trend has been observed: PdPVP/C > PdPDDA/C > PdPVA/C. The different reactivity has been ascribed to the different shielding effect of the three ligands used; they influence the adsorption of the reactant on Pd active sites.

Highly dispersed Pd catalysts supported on various carbons for furfural hydrogenation

Furfural (FAL), one of the important platform molecules derived from lignocellulosic biomass, can be converted into valuable chemicals such as furfuryl alcohol or cyclopentanone via hydrogenation. While carbon materials have been used as versatile catalyst supports for FAL hydrogenation, systematic studies on the structure of the catalytic performances are lacking. In this work, we prepare various types of carbon supports to investigate the impact of carbon structures for Pd-catalyzed FAL hydrogenation. Mesoporous carbons, including CMK-3, CMK-5, CMK-8, and MSU-F-C, as well as carbon nanotube and Vulcan XC are used as carbon supports. For the preparation of highly dispersed Pd-supported carbon (Pd/C) catalysts, chemical reduction by sodium borohydride is applied, in which trisodium citrate plays a critical role in anchoring small Pd clusters on the carbons. In the liquid-phase hydrogenation of FAL, CMK-5 with the largest surface area and hexagonal hollow tubular framework is proven to be the most efficient carbon support for Pd/C catalysts, with the highest conversion of FAL in both 2-propanol (100%) and water (86.4%) solvents. It is also demonstrated that the product selectivity in FAL hydrogenation over various Pd/C catalysts is changed dramatically depending on the type of solvent. The Pd/C catalysts exhibit similar fractions of product distributions containing furfuryl alcohol, cyclopentanol, tetrahydrofurfuryl alcohol, and minor products in 2-propanol. However, the production of cyclopentanone is increased when water is used as a solvent.

Mesoporous mixed CuCo oxides as robust catalysts for liquid-phase furfural hydrogenation

A series of highly ordered mesoporous CuCo oxide catalysts with a controlled composition are successfully synthesized by nanocasting from mesoporous silica, KIT-6 template. Liquid-phase furfural (FAL) hydrogenation is carried out to find the optimal composition of the CuCo oxide catalysts to achieve the best catalytic performance. As-prepared mesoporous mixed CuCo oxides exhibit a high surface area (60‒135 m2 g−1) and a well-defined ordered mesostructure with homogenous dispersion of Cu and Co. Among various compositions of CuxCoy oxides (x = 1–9) studied, the Cu1Co5 oxide catalyst shows the highest conversion in the hydrogenation of FAL, which is superior to those achieved with mesoporous monometallic oxides, CuO and Co3O4. While 2-methylfuran is produced from furfuryl alcohol via aldehyde hydrogenation and subsequent hydrogenolysis, the formation of 2-methylfuran increased with a decrease in the Cu/Co ratio of the CuCo oxide catalyst. The mixed CuCo oxide catalyst is readily reduced under the reaction environment to produce metallic CuCo as the active species. The synergistic interactions between Cu and Co in the mixed CuCo oxide catalysts play an important role in the outstanding catalytic performance for FAL hydrogenation, which could not be achieved with either of the monometallic catalysts or their physical mixtures. The excellent stability and recyclability of mesoporous mixed CuCo oxide catalysts as well as the exceptionally high activity, surpassing those of the monometallic oxides, render them promising as a low-cost and efficient catalyst for the industrial upgrading of biomass-derived FAL.

Tailoring the 3D Structure of Pd Nanocatalysts Supported on Mesoporous Carbon for Furfural Hydrogenation

AbstractBy quantitative 3D structural characterization of Pd nanoparticles supported on mesoporous carbon, we identify the most important structural aspects of the catalysts, which are responsible for the activity, selectivity and stability in liquid phase furfural hydrogenation. A systematic series of catalysts were prepared by three synthetic methods: incipient wetness impregnation, wet impregnation and immobilization of preformed PVA stabilized nanoparticles in order to control the Pd nanoparticle distribution on the external and internal surfaces of the mesoporous carbon. The activity and selectivity of these catalysts are highly affected by the particle locations. More Pd nanoparticles located inside pores promote the formation of 2‐methyl furan, while selectivity to furfuryl alcohol and tetrahydrofurfuryl alcohol is suppressed correspondingly. Through recycling tests we find that leaching depends on the synthesis process and plays an important role with respect to catalytic stability.

Slowing the Kinetics of Alumina Sol-Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity.

Catalyst overcoating is an emerging approach to engineer surface functionalities on supported metal catalyst and improve catalyst selectivity and durability. Alumina deposition on high surface area material by sol-gel chemistry is traditionally difficult to control due to the fast hydrolysis kinetics of aluminum-alkoxide precursors. Here, sol-gel chemistry methods are adapted to slow down these kinetics and deposit nanometer-scale alumina overcoats. The alumina overcoats are comparable in conformality and thickness control to overcoats prepared by atomic layer deposition even on high surface area substrates. The strategy relies on regulating the hydrolysis/condensation kinetics of Al(s BuO)3 by either adding a chelating agent or using nonhydrolytic sol-gel chemistry. These two approaches produce overcoats with similar chemical properties but distinct physical textures. With chelation chemistry, a mild method compatible with supported base metal catalysts, a conformal yet porous overcoat leads to a highly sintering-resistant Cu catalyst for liquid-phase furfural hydrogenation. With the nonhydrolytic sol-gel route, a denser Al2 O3 overcoat can be deposited to create a high density of Lewis acid-metal interface sites over Pt on mesoporous silica. The resulting material has a substantially increased hydrodeoxygenation activity for the conversion of lignin-derived 4-propylguaiacol into propylcyclohexane with up to 87% selectivity.

Supported Pd nanoparticle catalysts with high activities and selectivities in liquid-phase furfural hydrogenation

Highly dispersed and ultrafine Pd nanoparticles (NPs) deposited on carbon, silica, and alumina supports were prepared by chemical reduction (CR) using sodium borohydride, in the presence of trisodium citrate as a stabilizer. For comparison, supported Pd catalysts were also prepared through impregnation followed by thermal reduction (TR) and capillary inclusion of the colloidal Pd NPs (CI). The activities and selectivities of the prepared catalysts were evaluated in the liquid-phase furfural (FAL) hydrogenation reaction under 20 bar H2 at 180 °C. Under these conditions, FAL was converted via two distinct pathways to produce either furan via decarbonylation or furfuryl alcohol (FA) via aldehyde hydrogenation. Subsequently, furan and FA were converted to tetrahydrofuran and tetrahydrofurfuryl alcohol (THFA), respectively, via ring hydrogenation. 2-Methylfuran was also produced from the hydration of FAL. To verify the efficiency of the preparation methods, the size of the Pd NPs, the degree of metal dispersion, and the type of supports were correlated with the catalytic conversions and selectivities of FAL hydrogenation. It was confirmed that the 5 wt% Pd/C catalysts possessed highly dispersed small Pd NPs with large metallic Pd surface areas, which resulted in high conversions and selectivities towards THFA in the FAL hydrogenation reaction compared to conventional supported catalysts.

Reduction of Furfural to Furfuryl Alcohol in Liquid Phase over a Biochar-Supported Platinum Catalyst

In this work, the liquid phase hydrogenation of furfural has been studied using a biochar-supported platinum catalyst in a batch reactor. Reactions were performed between 170 °C and 320 °C, using 3 wt % and 5 wt % of Pt supported on a maple-based biochar under hydrogen pressure varying from 500 psi to 1500 psi for reaction times between 1 h and 6 h in various solvents. Under all reactive conditions, furfural conversion was significant, whilst under specific conditions furfuryl alcohol (FA) was obtained in most cases as the main product showing a selectivity around 80%. Other products as methylfuran (MF), furan, and trace of tetrahydrofuran (THF) were detected. Results showed that the most efficient reaction conditions involved a 3% Pt load on biochar and operations for 2 h at 210 °C and 1500 psi using toluene as solvent. When used repetitively, the catalyst showed deactivation although only a slight variation in selectivity toward FA at the optimal experimental conditions was observed.

Tuning catalytic selectivity of liquid-phase hydrogenation of furfural via synergistic effects of supported bimetallic catalysts

Bimetallic catalysts supported over TiO2–ZrO2 binary oxides were prepared by co-impregnation methods and used for catalyzing liquid-phase hydrogenation of furfural. Highly selective hydrogenation catalysts can be developed based on bimetallic synergistic effect. The coexistence of small proportion of palladium with supported nickel species greatly improves the catalytic performance and transfer the reaction selectivity from partial hydrogenation to total hydrogenation. The catalyst with Ni–Pd mole ratio of 5:1 shows the best performance. The yield of tetrahydrofurfuryl alcohol (THFA) reaches 93.4%. Ni–Pd synergistic effect is interpreted through XPS measurement and a hydrogen-transfer mechanism is proposed. Pt–Re bimetallic catalyst is an excellent partial hydrogenation catalyst for furfural conversion. Furfural can be totally converted and the selectivity of partial hydrogenation product (FA) reaches 95.7%. When rhenium oxide species are located on the Pt surface, the hydrogen species on Pt are transferred to adsorbed CO bond to achieve selective hydrogenation.

Hydrogenation of furfural over Pd–Cu/Al2O3 catalysts. The role of interaction between palladium and copper on determining catalytic properties

This paper studies the effect of copper on the activity and selectivity of home-made supported palladium catalysts during liquid phase hydrogenation of furfural. Bimetallic Pd–Cu/Al2O3 catalysts containing 5wt.% Pd and 1.5–6wt.% Cu showed high activity. However, the incorporation of Cu limited the formation of tetrahydrofurfuryl alcohol in comparison to monometallic Pd/Al2O3 catalysts. Activating the catalysts at 300°C in a hydrogen atmosphere led to the formation of Pd–Cu alloys, as confirmed by XRD, SIMS-ToF, SEM-EDS, FTIRS-CO and TPR-H2. The composition of the alloys depended on the amount of copper incorporated into the catalysts. The incorporation of copper can therefore be assumed to modify the catalytic properties of bimetallic Pd–Cu/Al2O3 systems used in the hydrogenation of furfural.

Selective liquid-phase hydrogenation of furfural to furfuryl alcohol over Cu-based catalysts

In this work, the liquid-phase furfural hydrogenation over different Cu-based catalysts was studied. The catalysts were prepared by incipient wetness impregnation (Cu/SiO2-I), precipitation–deposition (Cu/SiO2-PD) and co-precipitation (CuMgAl, CuZnAl and Cu-Cr) methods. CuMgAl, CuZnAl and Cu/SiO2-PD showed higher Cu dispersion and H2 chemisorption capacity than Cu-Cr and Cu/SiO2-I. The selectivity to furfuryl alcohol, at 383K and 10bar, using 2-propanol as solvent, was 100% in all of the cases. The pattern for the hydrogenation rate per gram of Cu was: CuMgAl>Cu/SiO2-PD>CuZnAl>Cu-Cr>Cu/SiO2-I. Instead, the hydrogenation rate per Cu atom on the surface (TOF) followed the pattern: CuMgAl>Cu-Cr>Cu/SiO2-PD≅CuZnAl>Cu/SiO2-I. These are promising results for the future replacement of polluting Cu-Cr industrial catalysts by a Cr-free one. The highest activity of CuMgAl was attributed to an intimate and effective interaction between Cu0 atoms and Mg2+ cations in a spinel-like matrix. Additional catalytic tests, varying reactant initial concentration and temperature, were performed with CuMgAl catalyst. A negative reaction order (≅−1) respect to furfural and a high apparent activation energy (≅127KJmol−1) were estimated, indicating a very strong adsorption of furfural on metal copper surface.

Liquid-phase furfural hydrogenation employing silica-supported PtSn and PtGe catalysts prepared using surface organometallic chemistry on metals techniques

Platinum–germanium and platinum–tin catalysts supported on silica, containing different amounts of Sn and Ge, were synthesized using the surface organometallic chemistry on metals technique. The catalysts were characterized using transmission electron microscopy, X-ray photoelectron spectra and X-ray absorption near edge structure and extended X-ray absorption fine structure; and were tested in the liquid-phase selective hydrogenation of furfural. The atomic ratio between the two metals resulted the key factor towards the optimization of the activity and selectivity of the bimetallic catalysts. The bimetallic catalysts were more active than the parent Pt/SiO2 catalyst in the hydrogenation of furfural. These results can be accounted for by considering a new type of active site having an architecture which would favor the hydrogenation of the C=O group is created, allowing an increased activity towards obtaining furfuryl alcohol. All the studied systems allowed to obtain furfuryl alcohol with high selectivity.

Preparation and activity evaluation of NiMoB/γ-Al 2O 3 catalyst by liquid-phase furfural hydrogenation

Amorphous MoNiB/γ-Al 2O 3 alloy catalysts were prepared by reducing NiCl 2·6H 2O and (NH 4) 6Mo 7O 24·4H 2O supported on γ-Al 2O 3 with NaBH 4 as reducing agent. Using liquid-phase hydrogenation of furfural (FFR) as a probe reaction, the activity of MoNiB/γ-Al 2O 3 was examined. Compared to NiB and NiMoB, NiMoB/γ-Al 2O 3 exhibited excellent activity and selectivity towards furfuryl alcohol (FFA). After reaction for 3.0 h at 80 °C and 5.0 MPa in methanol, FFR conversion reached 99% with FFA yield of 91%. The effects of doping amount of Mo and calcination temperature before NaBH 4 reduction on hydrogenation activity were also investigated. The optimum Mo/Ni atom ratio and calcination temperature were found to be 1:7 and 300 °C, respectively. XRD patterns and SEM images indicated that NiMoB over the surface of γ-Al 2O 3 was amorphous and highly dispersed, which was responsible for the high thermal stability of the title catalyst.

Bimetallic PtSn catalyst for the selective hydrogenation of furfural to furfuryl alcohol in liquid-phase

Bimetallic PtSn catalysts, containing different amounts of tin, were obtained by means of controlled surface reactions and used in the liquid-phase hydrogenation of furfural. All the studied systems allowed to obtain fufuryl alcohol with high selectivity (96–98%). A minor product was detected when alcoholic solvent were employed, coming from the reaction between furfuryl alcohol and the solvent. Nonalcoholic and non-polar solvents caused a drastic activity decrease.

A Ce-promoted Ni–B amorphous alloy catalyst (Ni–Ce–B) for liquid-phase furfural hydrogenation to furfural alcohol

A Ce-doped Ni–B amorphous catalyst (Ni–Ce–B) was prepared by chemical reduction of mixed NiCl 2 and CeSO 4 with KBH 4 in aqueous solution. During liquid-phase hydrogenation of furfural (FFR), all the as-prepared Ni–Ce–B amorphous catalyst exhibited excellent selectivity to furfural alcohol (FFA) owing to the unique amorphous structure and the electronic interaction between the metallic Ni and the alloying B. With the increase of the Ce dopant, the activity first increased and then decreased. The optimum Ce/(Ce+Ni) molar ratio ( X Ce) was determined as 1.28%. The X-ray photoelectron spectroscopy (XPS) spectra revealed that most of the Ce species in the Ni–Ce–B sample were present in the form of Ce 2O 3. On one hand, the Ce 2O 3 might serve as a support for the Ni–B amorphous alloy particles, resulting in the higher surface areas ( S BET). On the other hand, the Ce 2O 3 might serve as a Lewis acid which could strongly adsorb and further polarize the CO group in the FFR molecule. These two factors could successfully account for the promoting effect of the Ce dopant on the hydrogenation activity of the Ni–B amorphous alloy. Very high content of the Ce dopant ( X Ce>1.28%) resulted in the decrease of the hydrogenation activity because too many Ni active sites were covered by Ce 2O 3 species. Treatment of the Ni–Ce–B catalyst at high temperature also caused a decrease in activity due to the transformation from the amorphous structure to the crystalline structure and the loss of the surface area.

Furfural Hydrogenation to Furfuryl Alcohol over a Novel Ni–Co–B Amorphous Alloy Catalyst

Abstract The ultrafine Ni–Co–B amorphous catalysts were employed in liquid-phase furfural hydrogenation, which showed higher activity and better selectivity to furfuryl alcohol than either Ni–B, or Co–B, or the mixture of Ni–B and Co–B catalysts. The promoting effect of Co-dopant was briefly discussed.