Extensive experimental and computational study of hemicellulose-derived furfural hydrogenation, hydrodeoxygenation, oligomerisation and etherification has been conducted over Pd/C catalyst. In-situ reduction of PdO surfaces was observed, forming predominately Pd(111). Tetrahydrofurfuryl alcohol was observed as the main product. Selected solvent (solventless conditions, tetrahydrofuran, isopropanol), atmosphere (nitrogen, hydrogen), temperature (100–200 °C), pressure (25–75 bar) and stirring speed were varied. A micro-kinetic model was developed incorporating thermodynamics (hydrogen solubility), mass transfer, adsorption, desorption and surface reactions. The above-listed phenomena and their contribution to the surface coverages, TOF’s and global reaction rates were studied. Approximately 66 % of active sites were estimated to be covered by the solvent, 5 % by furanic species, while hydrogen coverage was low and limiting. Both furfural ring and aldehyde group hydrogenation have low activation energies (19.1 kJ mol- 1 and 23.5 kJ mol- 1 ), although subsequent hydrogenation of tetrahydrofurfural (Ea = 42.5 kJ mol- 1 ) is preferred at higher temperatures compared to furfuryl alcohol (Ea = 24.0 kJ mol- 1 ) hydrogenation. Complete hydrogenation can be achieved at room temperature, while deoxygenation becomes considerable above 150 °C (Ea = 59.6 kJ mol- 1 ), leading to complete conversion in most tests, yielding up to 77 % tetrahydrofurfuryl alcohol at 75 bar in isopropanol.
COBISS.SI-ID: 39261699
Valorization of lignocellulosic biomass, particularly catalytic hydrotreatment of hemicellulose-based furfural (FUR), has been studied for the production of value-added chemicals. A three-phase batch reactor has been used for hydrotreatment in isopropanol over various commercially available unsupported MoOx catalysts, at various temperatures (170–230 °C), pressures (0–80 bar H2), catalyst loadings (0–2 wt%), and reactant concentrations (5–20 wt%). No significant difference in catalytic activity or selectivity has been observed among the three different MoO3 and one MoO2 catalysts, while NiMo/Al2O3, Mo2C and WO3 were much less active. Data-points collected have been used to propose a detailed reaction pathway network for a micro-kinetic model, which also took into consideration the thermodynamics, and adsorption, desorption, and surface reaction kinetics. The alcoholysis of FUR yielded valuable isopropyl levulinate (IPL) as the major product under all tested reaction conditions, while other value-added compounds (furfuryl alcohol, isopropyl furfuryl ether, furfuryl acetone, angelica lactone) were observed in smaller quantities. It was found that neither the presence nor the absence of the gaseous H2 pressure contributes to the global reaction rate, or selectivity, since the solvent acts as a sufficient hydrogen donor. Additionally, density functional theory (DFT) calculations provided further insight into the active planes present by the implementation of the Wulff construction. Furthermore, the reaction mechanism was explained based on reaction energies, which were in silico determined and compared for several surfaces. The results were consistent with the characterization and activity-testing results. The furfural ring-opening reaction, yielding valuable IPL in the absence of gaseous H2, over a cheap bulk MoOx is reported for the first time.
COBISS.SI-ID: 46020611
Ruthenium catalyzed and magnetically heated hydrogenation of furfural in a slurry-type reactor is demonstrated in this work. We have developed a catalyst composed of magnetic nanoparticles which contains alumina carrying Ru nanoparticles on its surface. When exposed to an AC magnetic field, the conversion of furfural to furfuryl alcohol over the catalyst in the same time interval reached 95%, but only 63% when conventional heating was applied.
COBISS.SI-ID: 25023491
Biomass conversion into fuels and added-value chemicals, in high yield and with good selectivity, is still a great issue and an attractive research topic. The design and the optimization of defunctionalisation processes require accurate kinetic models that take into account the solubility of various gases in the bio-based chemicals present in the process. Some of the promising platform bio-based compounds that can be further converted to valuable chemicals are furfural and furfuryl alcohol. Hydrogen solubility in furfural and furfuryl alcohol was studied at three temperatures from the range (323.15–423.15) K and at pressures up to 25 MPa. Hydrogen dissolves better in furfural than in furfuryl alcohol, for about 15 %. The obtained experimental data were modelled using the Soave-Redlich-Kwong and Peng-Robinson cubic equations of state, as well as the PC-SAFT equation of state. The parameters of the PC-SAFT equation of state for pure compounds were defined for furfural and furfuryl alcohol. The binary interaction parameters, crucial for the prediction of phase-equilibrium behaviour, were determined for both examined systems. The interaction parameters obtained for the cubic equations of state were temperature dependent, while the interaction parameters optimized for the PC-SAFT equation of state were almost the same at all three temperatures for each studied system. The average absolute percentage deviations between the measured equilibrium pressures and those calculated using the mentioned models were under 4 %.
COBISS.SI-ID: 45985283
Catalytic hydrodeoxygenation of hydroxymethylfurfural was investigated in a three-phase batch reactor over a range of reaction temperatures (170–230 °C), under 5 MPa of hydrogen, and tetrahydrofuran solvent. Nickel based carbon-supported catalysts were also promoted by lanthanum and niobium, despite promoters alone demonstrated no activity. Based on experimentally-obtained liquid products, a reaction pathway was proposed and a microkinetic model was established, by considering adsorption, desorption and surface reaction kinetics, mass transfer and thermodynamics. An unpromoted Ni/C resulted in primarily unsaturated furan diol, a highly desirable intermediate in the polymer industry. As reaction temperatures increased )200 °C, dehydration yielded deoxygenated products suitable for solvents and biofuel. In spite of enhancements to reducibility, La promotion significantly decreased both hydrogenation (8-times) and deoxygenation (25-times) rate constants. Alternatively, Nb-incorporation offered additional acidity, while lower activation energies resulted in 200 % higher deoxygenation rates via dehydration reactions and humin formation at lower temperatures. It exhibited the highest deoxygenation activity.
COBISS.SI-ID: 35846147