Hydrodeoxygenation of 2-Methoxyphenol over Ru, Pd, and Mo₂C Catalysts Supported on Carbon

Abstract

The hydrodeoxygenation (HDO) of 2-methoxyphenol (or guaiacol, GUA) over Pd, Ru, and Mo 2 C catalysts supported on activated carbon (AC) is compared. The activities of the catalysts for hydrogenation versus deoxygenation on a per site basis, measured over a range of temperatures in a liquid phase batch reactor at high H 2 pressure (3.4 MPa), are quantified using lumped kinetics. The overall GUA consumption rate decreases in the order Pd > Ru > Mo 2 C. Hydrogenation of the phenyl ring of GUA occurs at a low temperature (240 °C) on both the Pd/AC and Ru/AC catalysts. At a higher temperature (≥300 °C), the R−OCH 3 and R−OH bonds of the hydrogenated products are cleaved yielding cyclohexanol, cyclohexane (Pd and Ru), and benzene (Ru) as major products. On the Mo 2 C/AC catalyst, HDO of GUA occurs by direct demethoxylation yielding phenol followed by Ar−OH bond cleavage to ultimately yield benzene at high temperatures. The lumped kinetics indicate that the hydrogenation activity of the Pd catalyst (on a per site basis, as determined from CO uptake measurements) is about 6 times higher than the Ru, but Ru is more active for O removal. Although the Mo 2 C is the least active, it is the most efficient in terms of O-removal with minimal H 2 consumption.

Carbon nanofiber supported Mo2C catalysts for hydrodeoxygenation of guaiacol: The importance of the carburization process

“…were formed in much less amount, regardless of the carburization temperature. These results clearly pointed out that Mo based catalysts favored the direct cleavage of Ar-OCH 3 bond rather than the removal of the phenolic group (Ar-OH), as previously reported for Mo 2 C [47] or MoO 2 based catalysts [22].…”

“…Carbon-supported molybdenum carbides have been used in a number of reactions, such as HDO of bio-oils model compounds [22][23][24][25][26][27][28][29] and vegetable oils [23,24,[30][31][32][33], dehydrogenation of methylcyclohexane [18], hydrodesulphurization of dibenzothiophene [33], hydrodenitrogenation of indole [34], deoxygenation or hydrogenation of guaiacol [28,35], lignin ethanolysis [36], H 2 production by hydrazine [37] or ethanol decomposition [38], steam reforming of methanol [21,39] and as electrocatalyst in hydrogen evolution reactions [32,40].…”

Elucidating the reactivity of methoxyphenol positional isomers towards hydrogen-transfer reactions by ATR-IR spectroscopy of the liquid–solid interface of RANEY® Ni

“…hydride transfer or direct hydrogen transfer also known as Meerwein−Ponndorf−Verley mechanism) and compete with the reactants and intermediates The conversion of 2-methoxyphenol involves firstly the DMO of the phenolic substrate, which is followed by the HYD of the phenolic intermediate to the corresponding cyclohexanol. Conversely, under H2 pressures, the major reaction product is 2-methoxycyclohexanol, 23,25 which is formed at very low yields through the tandem H-transfer process. 6 In addition, it was verified that with Raney® Ni/2-PrOH systems 2-methoxyphenol more easily undergoes DMO under low low-severity conditions than dehydroxylation of phenol.…”

Hydrodeoxygenation of Guaiacol with Molybdenum‐Carbide‐Based Carbon Catalysts

“…The conversion route of guaiacol over molybdenum carbide catalysts is different from the one of guaiacol over noble metal catalysts. The deoxygenation of guaiacol over noble metal catalyst proceeds through preliminary pathway hydrogenation of the aromatic ring . The conversion of guaiacol over Mo 2 C/CNF was 99% at 350 °C and 55 bar H 2 pressure for 4 h. The sum of the phenol and cresols selectivities was 59%, the mass balance was 74% .…”