Conversion of γ‐Valerolactone to Ethyl Valerate over Metal Promoted Ni/ZSM‐5 Catalysts: Influence of Ni⁰/Ni²⁺ Heterojunctions on Activity and Product Selectivity

Abstract

Promoter (Cr, Mo and W) modified Ni/ZSM‐5 catalysts were explored in the vapor phase conversion of γ‐valerolactone (GVL) to ethyl valerate (EV; gasoline blender) at atmospheric pressure. Among the three different promoters (Cr, Mo and W) tested the Mo‐modified catalyst was found to be the best candidate. In addition, this catalyst was found to be stable up to 50 h reaction time with an insignificant decrease in activity. The good catalytic performance is related to an optimal ratio of acid and hydrogenation functions provided by Ni2+ and Ni0, respectively. In situ FTIR spectroscopic studies revealed a strong adsorption of GVL on all catalysts which quickly reacts with dosed ethanol by formation of EV, most pronounced on the Mo‐modified catalyst, while VA was identified as side product. These findings suggest the preferred GVL ring opening by cracking the C−O bond on the methyl side of the GVL molecule on this type of catalysts leading to pentenoic acid as intermediate, which is quickly hydrogenated and esterified.

Mechanistic Insights into the Solvent-Driven Adsorptive Hydrodeoxygenation of Biomass Derived Levulinate Acid/Ester to 2-Methyltetrahydrofuran over Bimetallic Cu–Ni Catalysts

“…The aqueous phase reforming (APR) process allows the mild and selective conversion of lignocellulose to versatile value-added chemicals and fuel molecules that has greatly enriched the downstream chemical family. , Several building blocks were selected by the US Department of Energy as platform molecules, which can be readily prepared from raw biomass and further converted to multifunctional chemicals through different technologies . Levulinic acid (LA) and its esters were included as platform molecules due to their ease of scale-up production via acid-hydrolysis/alcoholysis from carbohydrates and high reactivity to be transformed into a wide range of chemicals such as γ-valerolactone, − 2-methyltetrahydrofuran (2-MTHF), 1,4-pentanediol (1,4-PeD), , and valerate acid/ester. − Particularly, 2-methyltetrahydrofuran (2-MTHF) has drawn much attention as a fuel molecule, possessing good hydrophobicity, high heating value, and a suitable octane number, indicating that it can be directly blended up to 70% of regular gasoline …”

Recent advances in the chemical valorization of cellulose and its derivatives into ester compounds

“…Most of the reported systems are based on a liquid phase reaction at high pressure; the continuous- flow mode has been of less concern. Velisoju et al 83 investigated the ring-opening hydrogenation of GVL to ethyl valerate over Cr, Mo, W promoted Ni/ZSM-5 in the vapor phase under ambient pressure conditions. They found that doping of the metal Mo significantly enhanced the selectivity of ethyl valerate (EtVal) due to the formation of the mixed metal oxide phase NiMoO 4 , providing lower Ni(0) species and BAS/LAS ratio, which was demonstrated to favor EtVal production.…”

The relevance of Lewis acid sites on the gas phase reaction of levulinic acid into ethyl valerate using CoSBA-xAl bifunctional catalysts

“…These weak LAS acid centers are capable of opening the ring of GVL, their less intrinsic activity is compensated with the higher concentration of these centers. Recently Velisoju et al 45 have described the formation of Ni 2+ /Ni 0 in Ni/ZSM5 catalysts promoted by the incorporation of Mo. They suggest that the Ni 2+ species stabilized by interaction with Mo can perform the GVL opening ring by cracking the C-O bond on the methyl group side of the GVL molecule.…”