Aqueous-phase Hydrogenation Of Furfural Research Articles

Aqueous-Phase Hydrogenation of Furfural in the Presence of Supported Metal Catalysts of Different Types. A Review

Aqueous-Phase Hydrogenation of Furfural in the Presence of Supported Metal Catalysts of Different Types. A Review

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.

A kinetic model of multi-step furfural hydrogenation over a Pd-TiO2 supported activated carbon catalyst

The multi-step, aqueous phase hydrogenation kinetics of furfural (FUR) to furfuryl alcohol (FA), 2-methylfuran (2MF), tetrahydrofurfuryl alcohol (THFA) and 5-hydroxy-2-pentanone (5H2P) over Pd-TiO2 on an activated carbon catalyst (derived from a monolith structure) was studied (180 °C, 2.1 MPa). Titanium addition created a metal–acid functional catalyst and promoted 5H2P synthesis from furfural. A Langmuir-Hinshelwood model with two active sites (a metal site for hydrogenation steps and an acid site for ring opening step) was applied to fit the kinetic data and parameters of the reaction system were obtained using non-linear regression of experimental data. The kinetic model showed an acceptable agreement with the experimental data with R2 of 0.93–0.96 and concentration residuals (experimental-model) typically ≤ 5%. Adsorption constants of 2MF and THFA were significantly lower than the adsorption constants of the other three compounds. A reaction rate constant of 1.6–1.8 mol/gcat.h for furfural consumption was predicted by the model. Reaction rates of 0.2–0.35 mol/gcat.h, 0.1–0.13 mol/gcat.h and 0.8–1.0 mol/gcat.h were predicted for formation of 2-methylfuran, tetrahydrofurfuryl alcohol and 5-hydroxy-2-pentanone, respectively. External and internal mass transfer criterion indicate intrinsic rate parameters were estimated and indicate the model can be used to perform monolithic reactor design for aqueous phase hydrogenation of furfural.

The effect of Pd(II) chloride complexes anchoring on the formation and properties of Pd/MgAlOx catalysts

Pd(II) chloride complexes were anchored using magnesium-aluminum layered double hydroxides (LDHs) with interlayer anions (CO32– and OH–), which possess different exchange properties, and MgAl mixed oxide during its rehydration. It was shown that the catalysts of the same chemical composition with different size, morphology and electronic state of supported palladium particles can be synthesized by varying the localization of Pd precursor. The properties of Pd/MgAlOx catalysts were studied in aqueous-phase hydrogenation of furfural. Anchoring of the Pd precursor in the interlayer space of LDHs is accompanied by the formation of non-isometric agglomerated palladium particles which contain less oxidized metal and show a higher activity toward hydrogenation of furfural. Magnesium-aluminum oxides in Pd/MgAlOx catalysts are rehydrated in the aqueous-phase reaction to yield the activated MgAl-LDH species as a support, which promotes the furfural conversion via hydrogenation of the furan cycle.

WxC-β-SiC Nanocomposite Catalysts Used in Aqueous Phase Hydrogenation of Furfural.

This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of β-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO2 in the presence of WO3 at 1550 °C in argon resulted in the formation of WxC-β-SiC nanocomposite powders with significant variations in particle morphology and content of WxC-tipped β-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite WxC-β-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest WxC crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

Aqueous phase hydrogenation of furfural using carbon-supported Ru and RuSn catalysts

The aqueous phase hydrogenation (APH) of furfural was studied over carbon-supported monometallic Ru and bimetallic RuSn catalysts at 90°C and 1.25MPa. Tin was added via Surface Organometallic Chemistry on Metals techniques and its effect was a function of the Sn/Ru atomic ratio. Thus, the addition of Sn in a Sn/Ru ratio of 0.4 promoted the CO hydrogenation reaching a selectivity towards furfuryl alcohol over 85% throughout the course of the reaction. A higher concentration of tin does not improve the situation. It seems to be a compromise between the dilution of Ru sites, active for the hydrogenation reaction, and the promoting effect of Sn. TEM, TPR and XPS characterization indicate the strong interaction between Ru and Sn in all the bimetallic catalysts. Finally, the reuse of the catalyst was analyzed.

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.