Synthesis of Nanostructured Molybdenum Carbide as Catalyst for the Hydrogenation of Levulinic Acid to γ-Valerolactone

Abstract

The effect of the morphology and size of unsupported molybdenum carbide (b-Mo 2 C) was investigated in the selective hydrogenation of levulinic acid to cvalerolactone (GVL) in aqueous phase. Nanostructured bMo 2 C was synthetized by two different approaches: (i) using multiwalled carbon nanotubes (CNT) as both hard template and source of carbon and; (ii) using 1D nanostructured a-MoO 3 as precursor. Depending on the type of synthesis used, the morphology of the resulting b-Mo 2 C was different. Well-oriented b-Mo 2 C nanoparticles with a fibril morphology were formed when CNTs were used as hard template and source of carbon at 700°C for 6 h under inert environment, while well-defined b-Mo 2 C 1D nanostructures were formed after carburization of the nano-sized a-MoO 3 precursor at 650°C/2 h under 20 % (v/v) CH 4 /H 2 atmosphere. The catalytic performance of the materials was investigated at 30 bar H 2 and 180°C in a batch reactor and compared with a Mo 2 C synthesized by temperatureprogrammed carburization of commercial MoO 3 . The bMo 2 C 1D nanostructures presented a relatively higher activity than the others probably as a result of more exposed active sites, confirmed by the higher CO chemisorption uptake. All of the catalysts were highly selective to GVL ([85 %). Deep hydrogenation products such as 1,4 pentanediol and methyltetrahydrofuran were observed in minor amounts, underlining the hydrogenation potential of molybdenum carbide based materials.

Metal Carbides for Biomass Valorization

“…Quiroz et al prepared Mo 2 C carbide with varying sizes and shapes [35]. Well-oriented β-Mo 2 C nanoparticles with a fibril morphology were formed when carbon nanotubes (CNTs) were used as the source of carbon at 700 • C for 6 h under an inert environment.…”

“…Although not mentioned here, other methods are also used to characterize the prepared carbides for reactions. Raman spectroscopy confirms the introduction of oxygen-containing functional groups on the CNTs' surface [35]. CO-pulsed chemisorption measurements, thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) were utilized to characterize nanostructured molybdenum carbide [35].…”

“…Raman spectroscopy confirms the introduction of oxygen-containing functional groups on the CNTs' surface [35]. CO-pulsed chemisorption measurements, thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) were utilized to characterize nanostructured molybdenum carbide [35]. Microcalorimetry of CO adsorption was performed to determine the CO uptake and to calculate the dispersion of active sites [43].…”

“…All catalysts were active. After 6 h reaction, 20%, 45% and 60% LA conversion was obtained for Mo 2 C_PM, Mo 2 C_C and Mo 2 C_N, respectively [35]. For a better understanding of the catalytic performance, CO chemisorption was carried out.…”

Efficient formation of angelica lactones in a vapor-phase conversion of levulinic acid

“…ALs over a Brønsted acid [36,37], whereas detailed formation routes were not discussed. We proposed a formation route of LA lactonization to ALs, as shown in…”