Combined In Situ XAFS and FTIR Study of the Hydrodeoxygenation Reaction of 2-Methyltetrahydrofuran on Ni₂P/SiO₂

Abstract

This paper deals with a study of the mechanism of hydrodeoxygenation (HDO) at 0.1 MPa and 300–350 °C of 2-methyltetrahydrofuran (2-MTHF) over a Ni2P/SiO2 catalyst. The study was conducted using in situ Fourier transform infrared (FTIR) spectroscopy to monitor the adsorbed species during reaction and in situ X-ray absorption fine structure (XAFS) to probe the oxidation state of the Ni component. The work is relevant to the upgrading of bio-oil derived from the pyrolysis of biomass. It was deduced that the initial interaction of the 2-MTHF was with OH groups on the catalyst surface, followed by adsorption on Ni sites. Ring-opening of the tetrahydrofuran led to the formation of the main products of the reaction, n-pentane by HDO and n-butane + CO by decarbonylation. The CO band appeared with a slight delay in the FTIR spectrum because the reaction to form n-pentane was favored and turned over about four times before one n-butane + CO was formed.

Active Phase Structure of the SiO₂-supported Nickel Phosphide Catalysts for Non-oxidative Coupling of Methane (NOCM) Reactions

“…Recently Ni 2 P catalysts draw many attentions. It shows a high catalytic activity in hydrogen related reactions, such as hydrodesulfurization reactions [5,6], hydrodeoxidation [7,8], and hydrogen evolution reactions [9,10], Ni 2 P has a crystal structure as shown in Figure 3 [11]. Along the c axis, two-layer structures are alternatively stacked.…”

Cerium Oxide Catalyzes the Selective Vapor-Phase Hydrodeoxygenation of Anisole to Benzene at Ambient Pressures of Hydrogen

“…First, achieving high selectivity to benzene requires either cleavage of the stronger phenolic C–O bond in anisole (homolytic bond dissociation energy (BDE) = 385 kJ mol –1 ) over the weaker aliphatic C–O bond (BDE = 243 kJ mol –1 ), or cleavage of an even stronger C–O bond in phenol formed in primary reactions (BDE = 460 kJ mol –1 ) to form benzene in secondary reactions . Second, high hydrogen pressures typically required to achieve C–O bond cleavage can result in a loss of aromaticity, resulting from HDO hydrogenation. − Third, side reactions such as C–C bond hydrogenolysis and alkylation/transalkylation can result in the formation of undesired side products. , These challenges have prompted researchers to not only look for new classes of catalysts but also to develop novel techniques including flame spray pyrolysis, for synthesizing traditional HDO catalysts, − and in situ spectroscopic techniques for developing mechanistic insights into HDO chemistry. − Despite the multitude of catalyst formulations that have been evaluated for the HDO of phenolic ethers, an inexpensive, easy to handle, stable, highly selective HDO catalyst that operates at ambient pressures of hydrogen still remains elusive.…”

High-Loading Nickel Phosphide Catalysts Supported on SiO2–TiO2 for Hydrodeoxygenation of Guaiacol

“…Ayako et al deduced that Si–OH and P–OH groups on the surface of the catalysts, which provide Brønsted acid sites, can adsorb 2-methyltetrahydrofuran by a hydrogen bond or physisorption. The adsorbed reactants will deoxygenate to form n -pentane . Zhang et al also reported that the acid sites can catalyze the rupture of the C–O bond. − The acid amount of Ni 12 P 5 /TiO 2 is the lowest as we can see from the NH 3 -TPD (Table ), which might result in relatively lower TOF of cyclohexane compared with that of the Ni x P y /SiO 2 –TiO 2 catalysts.…”

“…The adsorbed reactants will deoxygenate to form n-pentane. 52 Zhang et al also reported that the acid sites can catalyze the rupture of the C−O bond. 53−55 The acid amount of Ni 12 P 5 /TiO 2 is the lowest as we can see from the NH 3 -TPD (Table 3), which might result in relatively lower TOF of cyclohexane compared with that of the Ni x P y /SiO 2 −TiO 2 catalysts.…”