Decarbonylation Of Furfural Research Articles

Engineering Active Sites of Metal/Metal Oxide Catalysts by Oxide Ligand Overlayers.

Engineering sites of supported metal catalysts is essential to enhancing activity and selectivity. Such enhancement is typically achieved by particle size modification, surface alloying, or attaching molecular ligands. Yet, control strategies for complex, multifunctional molecules and catalysts, where selectivity is crucial, are lacking. Here, we demonstrate that submonolayer WOx with tunable coverage preferentially decorates well-coordinated Pt terrace sites as a stable ligand. By combining experimental kinetics with probe molecules, in situ spectroscopies, and first-principles modeling, we show that the WOx coverage on Pt modifies the metal-to-acid site balance while retaining the acid strength intact and results in optimal reactivity for metal-acid catalyzed reactions at a specific metal, size, and support-dependent WOx coverage. The oxide can also alter the reactant adsorption mode, reversing selectivity and pathways from terrace- to step-dominated, as evidenced in furfural decarbonylation and hydrogenation. The insights open avenues for improving metal/metal oxide catalysts beyond the specific system.

Engineering Active Sites of Metal/Metal Oxide Catalysts by Oxide Ligand Overlayers

Engineering sites of supported metal catalysts is essential to enhancing activity and selectivity. Such enhancement is typically achieved by particle size modification, surface alloying, or attaching molecular ligands. Yet, control strategies for complex, multifunctional molecules and catalysts, where selectivity is crucial, are lacking. Here, we demonstrate that submonolayer WOx with tunable coverage preferentially decorates well‐coordinated Pt terrace sites as a stable ligand. By combining experimental kinetics with probe molecules, in situ spectroscopies, and first‐principles modeling, we show that the WOx coverage on Pt modifies the metal‐to‐acid site balance while retaining the acid strength intact and results in optimal reactivity for metal‐acid catalyzed reactions at a specific metal, size, and support‐dependent WOx coverage. The oxide can also alter the reactant adsorption mode, reversing selectivity and pathways from terrace‐ to step‐dominated, as evidenced in furfural decarbonylation and hydrogenation. The insights open avenues for improving metal/metal oxide catalysts beyond the specific system.

Analytical (hydro)pyrolysis of pinewood and wheat straw in chloride molten salts: A route for 2-methyl furan production

2-methyl furan (MF) is a fuel additive with improved fuel characteristics compared to bio-ethanol. Unfortunately, the production of MF (from furfural (FF) hydrogenation) is not economically feasible. Interestingly, molten salts in biomass pyrolysis have shown to promote the formation of furans (mainly FF). Because molten salts hydropyrolysis could be an alternative route to both produce FF and convert it into MF, an assessment is indispensable. Molten salts pyrolysis and hydropyrolysis of pinewood and wheat straw and related model compounds were studied in a micro-reactor. The effect of hydropyrolysis process variables was assessed on the total detectable condensable vapors and MF formation.At low pressures (0.4 MPa), the chloride salts favored the production of FF and acetic regardless of the reaction atmosphere. Under a high pressure of hydrogen though (1.6 and 3.0 MPa), the conversion of FF to MF was enhanced through hydrogenation, hydrodeoxygenation and demethylation reactions. Molten salts hydropyrolysis at 350 °C and pressures of either 1.6 MPa (biomass mass fraction of 0.09) or 3.0 MPa (biomass mass fraction of 0.24) were optimal and yielded ca. 8 wt% to 9 wt% MF. Reaction temperatures >350 °C were unfavorable for the MF yield and instead promoted furfural decarbonylation to furan.

Catalytic hydro-deoxygenation of acetic acid, 4-ethylguaiacol, and furfural from bio-oil over Ni 2 P/HZSM-5 catalysts

In this paper, catalytic hydro-deoxygenation (HDO) of bio-oil’s model molecules (acetic acid, 4-ethylguaiacol, and furfural) using Ni 2 P/HZSM-5 catalyst was carried out to better identify the products and make the modeling work of HDO process more reliable. Results showed that low temperatures favored the formation of acetaldehyde and acetone during acetic acid HDO, but disfavored the formation of aromatic hydrocarbons. Acetone was produced via the self-ketonization reaction of acetic acid. In most cases of 4-ethylguaiacol HDO, phenol, cresol, and 2, 4-dimethylphenol were the primary products. For furfural HDO, the major furan and CO products proved that the direct decarbonylation of furfural was the main reaction. Accordingly, the main pathways of acetic acid, 4-ethylguaiacol, and furfural HDO were proposed, which could provide significant guidance for the upgrading of crude bio-oil.

Vapor-Phase Furfural Decarbonylation over a High-Performance Catalyst of 1%Pt/SBA-15

A high-performance Pt catalyst supported on SBA-15 was developed for furfural decarbonylation. Compared to Pt catalysts loaded on microporous DeAl-Hbeta zeolite and hierarchical micro-mesoporous MFI nanosheet (NS) materials, the 1%Pt/SBA-15 catalyst afforded notably higher activity, furan selectivity and stability owing to the negligible acid sites and proper mesopores on the SBA-15 support. Among a set of 1%Pt/SBA-15 catalysts bearing Pt nanoparticles (NPs) with sizes of 2.4–4.3 nm, the catalyst with 3.7 nm Pt NPs afforded the highest furan selectivity. Over the optimal catalyst, 88.6% furan selectivity and ca. 90% furfural conversion were obtained at 573 K and a high weight hourly space velocity (WHSV) of 16.5 h−1. Moreover, the reaction temperatures at 440–573 K and the ratios of H2 to furfural at 0.79–9.44 did not affect the reaction selectivity notably, showing that the reaction over 1%Pt/SBA-15 can be conducted over a wide range of conditions. The catalyst was stable under the harsh reaction conditions and lasted for 90 h without significant deactivation, demonstrating the superior property of SBA-15 as a catalyst support for furfural decarbonylation.

Theoretical investigation of decarbonylation mechanism of furfural on Pd(111) and M/Pd(111)(M = Ru, Ni, Ir) surfaces

In this paper, decarbonylation of furfural on the surface of Pd(111) and M/Pd(111) (M=Ru,Ni,Ir) has been studied by DFT calculation. The adsorption energy, activation energy and reaction energy of decarbonylation of furfural on different metal surface were calculated and compared. The decarbonylation mechanism of furfural on the surfaces of Pd(111), Ni/Pd(111), Ru/Pd(111) and Ir/Pd(111) was discussed from two reaction routes and four elementary reactions. It is found that the energy of C4H3O*+H*→C4H4O is the highest, which is the rate determining step. The difference between the two reaction paths of the four catalysts shows that bimetallic catalyst can lower the activation energy of each reaction step more than single metal catalyst. Compared with the other three metals, on Ir/Pd(111) surface, all the reactions are exothermic with low activation energy. It is suggested that Ir/Pd(111) may be the best catalyst for decarbonylation of furfural.

Microwave-Assisted Decarbonylation of Biomass-Derived Aldehydes using Pd-Doped Hydrotalcites.

Catalytic decarbonylation is an underexplored strategy for deoxygenation of biomass-derived aldehydes owing to a lack of low-cost and robust heterogeneous catalysts that can operate in benign solvents. A family of Pd-functionalized hydrotalcites (Pd-HTs) were synthesized, characterized, and applied to the decarbonylation of furfural, 5-hydroxymethylfurfural (HMF), and aromatic and aliphatic aldehydes under microwave conditions. This catalytic system delivered enhanced decarbonylation yields and turnover frequencies, even at a low Pd loading (0.5 mol %). Furfural decarbonylation was optimized in a benign solvent (ethanol) compatible with biomass processing; HMF selectively afforded an excellent yield (93 %) of furfuryl alcohol without humin formation; however, a longer reaction favored the formation of furan through tandem alcohol dehydrogenation and decarbonylation. Yields of the substituted benzaldehydes (37-99 %) were proportional to the calculated Mulliken charge of the carbonyl carbon. Activity and selectivity reflected loading-dependent Pd speciation. Continuous-flow testing of the best Pd-HT catalyst delivered good stability over 16 h on stream, with near-quantitative conversion of HMF.

Structure‐Reactivity Relations in Ruthenium Catalysed Furfural Hydrogenation

AbstractFurfural is an abundant and low‐cost bio‐derived platform chemical, obtained by xylose dehydration, and an important precursor to furfuryl alcohol and furan resins. The liquid phase selective hydrogenation of furfural to furfuryl alcohol was systematically investigated over silica supported Ru nanoparticles to elucidate structure‐reactivity relations and obtain mechanistic insight. Furfural hydrogenation to furfuryl alcohol is weakly structure sensitive for Ru nanoparticles spanning 2 to 25 nm, and the dominant reaction pathway reaching 95 % selectivity under our conditions (<25 bar H2 and 100–165 °C). In contrast, furfural decarbonylation to furan exhibits a strong structure sensitivity, being favoured over sub‐10 nm particles. Increasing pH2 from 10 to 25 bar resulted in a modest increase in C=O hydrogenation, while higher temperatures promoted ring‐opening of furfuryl alcohol.

Thermochemistry and kinetic analysis for the conversion of furfural to valuable added products.

Furfural is a valuable oxygenated compound derived from the thermal decomposition of biomass, and is one of the major problems of bio-oil upgrading. Due to its high reactivity, this compound requires further upgrading to more stable products such as furfuryl alcohol, 2-methylfuran (MF), furan, 2-methyltetrahydrofuran, and tetrahydrofuran. The thermochemical data and kinetic analysis of the reactions involved in the conversion of furfural were investigated by molecular modelingto guide experimental investigations in the process of designing efficient catalysts that allows the control of the reaction pathways in specific directions, towards the production of fuel precursors or chemicals. All calculations for reactants, intermediates, and products were performed using the long range corrected functional WB97XD, with the basis set 6-311+g(d,p), under the density functional theory framework. Thermochemistry results suggest that furfural hydrogenation to form furfuryl alcohol is spontaneous up to a temperature of 523K, but beyond this temperature the reaction becomes a nonspontaneous process. By contrast, the decarbonylation of furfural was thermodynamically favored at temperatures greater than 523K. Therefore, furan is a thermodynamically favored product, while furfuryl alcohol is kinetically preferred. Once furfuryl alcohol is formed, the hydrogenolysis path to produce methylfuran is favored kinetically and thermodynamically, compared to the ring-hydrogenation towards tetrahydrofurfuryl alcohol. Gas phase thermodynamic properties and rate constants of the reactions involved in the conversion of furfural were calculated and compared against existing experimental data. This study provides the basis for further vapor phase catalytic studies required for upgrading of furans/furfurals to value-added chemicals. Graphical abstract Furan is a thermodynamically favored product, while furfuryl alcohol is kinetically preferred.

Rhodium-catalyzed Carbonylative Annulation of 2-Bromobenzylic Alcohols with Internal Alkynes Using Furfural via β-Aryl Elimination

In spite of the significant progress made in transformations of unstrained benzylic (tert-)alcohols through β-aryl elimination, catalytic carbonylation has not yet been developed extensively because alkoxycarbonylation is probably favored over β-aryl elimination. In this letter, we report on the rhodium(I)-catalyzed carbonylative annulation of α,α-dimethyl-(2-bromoaryl)methanols with internal alkynes using furfural leading to the formation of indenones. The key to the success of the reaction is the timely generation of the carbonyl source via the decarbonylation of furfural.

Catalytic Hydrogenation and Hydrodeoxygenation of Furfural over Pt(111): A Model System for the Rational Design and Operation of Practical Biomass Conversion Catalysts.

Furfural is a key bioderived platform chemical whose reactivity under hydrogen atmospheres affords diverse chemical intermediates. Here, temperature-programmed reaction spectrometry and complementary scanning tunneling microscopy (STM) are employed to investigate furfural adsorption and reactivity over a Pt(111) model catalyst. Furfural decarbonylation to furan is highly sensitive to reaction conditions, in particular, surface crowding and associated changes in the adsorption geometry: furfural adopts a planar geometry on clean Pt(111) at low coverage, tilting at higher coverage to form a densely packed furfural adlayer. This switch in adsorption geometry strongly influences product selectivity. STM reveals the formation of hydrogen-bonded networks for planar furfural, which favor decarbonylation on clean Pt(111) and hydrogenolysis in the presence of coadsorbed hydrogen. Preadsorbed hydrogen promotes furfural hydrogenation to furfuryl alcohol and its subsequent hydrogenolysis to methyl furan, while suppressing residual surface carbon. Furfural chemistry over Pt is markedly different from that over Pd, with weaker adsorption over the former affording a simpler product distribution than the latter; Pd catalyzes a wider range of chemistry, including ring-opening to form propene. Insight into the role of molecular orientation in controlling product selectivity will guide the design and operation of more selective and stable Pt catalysts for furfural hydrogenation.

Design and control of a process to produce furan from furfural

Abstract The design and control of a process for the production of furan by the catalytic decarbonylation of furfural is studied. Starting with a conceptual flowsheet presented in the literature [8] modifications to the flowsheet are proposed and optimal values of design variables minimizing the total annual cost of the process are determined. After an optimal process design is determined the control of the process is also studied. Two control structures are considered: one in which production rate changes are accommodated by changing the catalyst concentration, and one in which production rate changes are accommodated by changing the reactor temperature. Both control structures work well for both production rate changes of ±20% and changes in the concentration of water impurity in the feed.

Regeneration of Spent Catalysts for Furfural Decarbonylation

The article discusses the reasons for the decontamination of industrial catalysts for furfural decarbonylation. Various methods for regenerating of the supported catalyst are studied. For example, organic and inorganic solvents were used for the regeneration of spent catalyst for obtaining industrial furan. To improve the activity of spent-regenerated samples of CDF-1 catalyst, the method of modifying with d-metals additives from aqueous solutions was applied. Iron, cobalt, and nickel were used as modifying additives. Results for furfural decarbonylation on additives regenerated-modified with transitive d-metals batches of spent CDF-1 catalyst shows that implementing spent modifying additives to the regenerated catalyst increases the stability and activity. The article provides methods for regenerating spent CDF-1 catalyst, and modifying the regenerated catalyst and its reusing in the process of decarbonylation.

Coverage-Induced Conformational Effects on Activity and Selectivity: Hydrogenation and Decarbonylation of Furfural on Pd(111)

Adsorption, hydrogenation, and decarbonylation of furfural on hydrogen-covered Pd(111) was investigated using density functional theory calculations. It was found that both the energy and the conformation of adsorbed furfural vary with increasing coverage of hydrogen or furfural. Furfural lies flat at low coverage but becomes tilted on crowded surfaces. The energy profiles of hydrogenation and decarbonylation reactions on a hydrogen-covered Pd(111) change profoundly compared to those on bare Pd(111). The energy span theory shows that the furfural hydrogenation and decarbonylation effective barriers exhibit a maximum with increasing hydrogen coverage. In contrast, the selectivity to hydrogenation toward furfuryl alcohol over decarbonylation is favored with increasing hydrogen coverage. Microkinetic modeling suggests that the conformation change with increasing H coverage has a significant effect on reaction rates (up to orders of magnitude) and induces a selectivity reversal from furan as the main product ...

Liquid phase catalytic transfer hydrogenation of furfural over a Ru/C catalyst

Methyl furan production through catalytic transfer hydrogenation of furfural in the liquid phase has been investigated over a Ru/C catalyst in the temperature range of 120–200°C using 2-propanol as a solvent. It has been found that furfural hydrogenation produces furfuryl alcohol, which undergoes hydrogenolysis to methyl furan. Small amounts of furan and traces of tetrahydrofurfuryl alcohol are also produced via furfural decarbonylation and furfuryl alcohol ring hydrogenation, respectively. Furfuryl alcohol can dimerize or produce ether with 2-propanol. The yield of methyl furan is enhanced with increasing reaction temperature and/or reaction time. Optimum results are attained after 10h of reaction at 180°C, where furfural conversion and methyl furan yield reach 95% and 61%, respectively, which is the highest reported yield in the liquid phase at temperatures lower than 200°C. The reaction network has been investigated by analysing the evolution of reaction intermediates and products and by starting from furfuryl alcohol, methyl furan, and furan hydrogenation. Intermediates, as well as methyl furan, are produced faster when starting with furfuryl alcohol as the reactant, rather than furfural, indicating that initial hydrogenation of furfural to furfuryl alcohol is slow. Catalyst recycling experiments over spent Ru/C catalyst show that, although furfural conversion does not decrease significantly, furfuryl alcohol yield increases at the expense of methyl furan. The initial catalytic activity and selectivity are regained completely after catalyst regeneration. We show evidence that the active phase of the catalyst involves Ru and RuOx.

High Structure Sensitivity of Vapor-Phase Furfural Decarbonylation/Hydrogenation Reaction Network as a Function of Size and Shape of Pt Nanoparticles

Vapor-phase transformations of furfural in H(2) over a series of Pt nanoparticles (NPs) with various particle sizes (1.5-7.1 nm size range) and shapes (rounded, cubes, octahedra) encapsulated in poly(vinylpyrrolidone) (PVP) and dispersed on MCF-17 mesoporous silica were investigated at ambient pressure in the 443-513 K temperature range. Furan and furfuryl alcohol (FFA) were two primary products as a result of furfural decarbonylation and hydrogenation reactions, respectively. Under conditions of the study both reactions exhibited structure sensitivity evidenced by changes in product selectivities, turnover rates (TORs), and apparent activation energies (E(A)'s) with Pt particle size and shape. For instance, upon an increase in Pt particle size from 1.5 to 7.1 nm, the selectivity toward FFA increases from 1% to 66%, the TOR of FFA production increases from 1 × 10(-3) s(-1) to 7.6 × 10(-2) s(-1), and E(A) decreases from 104 kJ mol(-1) to 15 kJ mol(-1) (9.3 kPa furfural, 93 kPa H(2), 473 K). Conversely, under the same experimental conditions the decarbonylation reaction path is enhanced over smaller nanoparticles. The smallest NPs (1.5 nm) produced the highest selectivity (96%) and highest TOR values (8.8 × 10(-2) s(-1)) toward furan formation. The E(A) values for decarbonylation (∼62 kJ mol(-1)) was Pt particle size independent. Furan was further converted to propylene via a decarbonylation reaction, but also to dihydrofuran, tetrahydrofuran, and n-butanol in secondary reactions. Furfuryl alcohol was converted to mostly to 2-methylfuran.

A study of furfural decarbonylation on K-doped Pd/Al 2O 3 catalysts

Vapor-phase decarbonylation of furfural to furan was performed on K-doped Pd/Al 2O 3 catalysts in a fixed-bed reactor. A series of K-doped catalysts were prepared by impregnation method with various potassium salt precursors and different potassium content. The catalyst evaluation results revealed that the doping of K not only promoted the furfural decarbonylation, but also suppressed the hydrogenation side reaction. Among the investigated catalysts, Pd–K 2CO 3/Al 2O 3 (K% = 8 wt.%) presented the best performance and achieved the furan yields up to 99.5% at 260 °C. The selectivity of 2-methylfuran would approach zero at high K content (K% > 4 wt.%). Furthermore, the catalysts were characterized by BET, SEM, ICP, H 2-TPR, H 2-TPD, H 2-chemisorption, CO-FTIR, furfural-TPSR, and furfural-FTIR experiments. It was shown that the dopant phase had a remarkable effect on the precursor Pd 2+ and the reduced Pd metal particles. Furfural-TPSR and furfural-FTIR exhibited that K-doped catalysts enhanced the furfural adsorption and promoted the decarbonylation reaction, which was due to the different adsorption mode and intensity of furfural on K-doped and undoped samples. Besides, the decrease of C–O adsorption of furfural ( η 2(C,O)-furfural) by K doping is the main reason for suppressing the furfural hydrogenation.

Furfural decarbonylation catalyzed by charcoal supported palladium: Part I — Kinetics

The rate of furfural decarbonylation was investigated in the presence of a charcoal supported palladium catalyst using potassium carbonate as accelerator in the liquid phase between 150 and 160°C. Reaction speed varied with the quantity of catalyst and increased exponentially with temperature. Activation energy under these experimental conditions was 310 kJ/mol. Reaction by-products were mainly of high molecular weight, resulting from various dimerization reactions involving furan and/or 2-methyl furan. These products covered the surface of the catalyst and blocked active sites, resulting in deactivation.

Furfural decarbonylation catalyzed by charcoal supported palladium: Part II — A continuous process

During continuous furfural decarbonylation, using a carbon supported palladium catalyst, a high catalytic activity (36 000 g of furan per g of palladium) was observed. Furan productivity remained almost constant for 45 h and then decreased gradually to reach a new low level after 90 h. Analysis of residues indicated that by-products are partly responsible for the decrease in furan productivity.

Catalytic decarbonylation of furfural in a fixed‐bed reactor

AbstractThe oxidative decarbonylation of furfural was studied in a fixed‐bed reactor. Mixtures of Mn, Zn, Cd, Sr and K oxides supported on spherical and cylindrical alumina were used as catalysts. In this paper the effect of the temperature and feed flow on the reaction yield for the catalysts tested and hence optimum reaction conditions are reported. Catalysts employed in this work are compared with Pd‐catalysts, frequently used for the decarbonylation of furfural.