MILD SYNTHESIS OF COWO4, ITS REDUCED FORM, AND THE ACTIVITY IN TRANSFER HYDROGENATION OF FURFURAL

• Main Author: Hartinah Qurbayni, Siti
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/62591
• Institution: Institut Teknologi Bandung

Furfural is one of biomass derivatives developed in polymer and pharmaceutical industries. Furfural hydrogenation, hydrogenolysis and decarbonylation were reported to give furfuryl alcohol, 2-methylfuran, tetrahydrofurfuryl alcohol,1,2- pentanediol, and 1,5-pentanediol in pressurized hydrogen using platinum group metal catalyst (Ru, Rh, Ir, Os, Pd, and Pt). Polymerization of furfuryl alcohol produces polyfurfuryl alcohol with high temperature resistance and thus it is widely used in casting industries. Furfuryl alcohol is also widely used in polymer, resin, lubricant, and adhesive industries. Furfural hydrogenation under mild conditions could be facilitated by alternative hydrogen sources, such as alcohols or organic acids. This process is known as proton transfer hydrogenation Herein, cobalt(II) tungstate (CoWO4) and the reduced cobalt were evaluated as transfer hydrogenation catalysts with ethanol, isopropyl alcohol, formic acid or polymethylhydroxysilane (PMHS) as hydrogen sources. The cobalt tungstate was synthesized hydrothermally at relatively lower temperatures (< 160 °C) and relatively shorter time (< 10 hours) compared to previously reported procedures (180-200 °C, 15-24 hours). Synthesis of CoWO4 were carried out by hydrothermal and stirring methods at various temperatures, i.e., 60 °C, 80 °C, 100 °C, 120 °C, 140 °C, and 160 °C for 8 hours. The reduction of cobalt tungstate, CoWO4, to Co(0)?WO3 was carried out in a reactor with hydrogen flow of 8 mL/min at 400 °C for 2 hours. Additionally, a direct synthesis of Co(o)?WO3 from Co(II) chloride was done by a hydrothermal method (alkaline condition). The catalytic activity of Co(II) and Co(0) were evaluated in the transfer hydrogenation reaction of furfural. The synthesized cobalt compounds were characterized using P-XRD, FTIR, and XRF. Furfural conversions and products were observed by gas chromatography (GC). The reaction was carried out using hydrogen sources of ethanol, 2-propanol, or poly(methylhydrosiloxane) (PMHS). Quantitative analysis was carried out by comparing the area of furfural, furfuryl alcohol, and other products with naphthalene as an internal standard using a calibration curve. The calibration curve was obtained by plotting furfural concentration against the furfural/naphthalene area. The results of PXRD analysis showed phases of CoWO4 and Co(0) and the FT-IR analysis showed vibrations of W-O at 853 cm?1 and 667 cm?1. The EDX result showed the atomic ratio of Co, W, O atoms in the CoWO4 of 1:1:4. In this study, Co(0)?WO3 showed a relatively higher hydrogenation activity than CoWO4. Optimum conditions were carried out by varying the hydrogen source and reaction time. The percentage of furfural conversion and furfuryl alcohol yield with the addition of PMHS in the presence of CoWO4 was higher than that of formic acid, i.e., 48% and 30%, respectively. PMHS has Si-H bonds and works as the best hydrogen source. The amount of hydrogen at Si-H in PMHS is important to quantify prior to the hydrogenation reaction. The quantification was done by 1H-NMR (60 MHz) by comparing proton resonances at Si-H in PMHS with proton resonances in maleic anhydrous (internal standard). Furfural conversion and furfuryl alcohol yields with Co?WO3 were 82% and 49%, achieved by ethanol and formic acid as hydrogen sources. In addition, herein we observed the formation of 2-methylfuran and tetrahydrofurfuryl alcohol of 13% and 6%, respectively as promising products from furfural.