γ-Valerolactone Production from Levulinic Acid Hydrogenation Using Ni Supported Nanoparticles: Influence of Tungsten Loading and pH of Synthesis

Abstract

γ-Valerolactone (GVL) has been considered an alternative as biofuel in the production of carbon-based chemicals; however, the use of noble metals and corrosive solvents has been a problem. In this work, Ni supported nanocatalysts were prepared to produce γ-Valerolactone from levulinic acid using methanol as solvent at a temperature of 170 °C utilizing 4 MPa of H2. Supports were modified at pH 3 using acetic acid (CH3COOH) and pH 9 using ammonium hydroxide (NH4OH) with different tungsten (W) loadings (1%, 3%, and 5%) by the Sol-gel method. Ni was deposited by the suspension impregnation method. The catalysts were characterized by various techniques including XRD, N2 physisorption, UV-Vis, SEM, TEM, XPS, H2-TPR, and Pyridine FTIR. Based on the study of acidity and activity relation, Ni dispersion due to the Lewis acid sites contributed by W at pH 9, producing nanoparticles smaller than 10 nm of Ni, and could be responsible for the high esterification activity of levulinic acid (LA) to Methyl levulinate being more selective to catalytic hydrogenation. Products and by-products were analyzed by 1H NMR. Optimum catalytic activity was obtained with 5% W at pH 9, with 80% yield after 24 h of reaction. The higher catalytic activity was attributed to the particle size and the amount of Lewis acid sites generated by modifying the pH of synthesis and the amount of W in the support due to the spillover effect.

Nickel—Alumina Catalysts for the Transformation of Vegetable Oils into Green Diesel: The Role of Preparation Method, Activation Temperature, and Reaction Conditions

“…The 60NiAl wi precursor sample was easily reduced, appearing as two reduction peaks with maxima at 275 and 290 °C and a wide shoulder zeroing at about 700 °C. This profile indicates that the main fraction of NiO interacts weakly with γ-Al 2 O 3 , while a smaller part interacts moderately with it [ 36 , 37 ]. However, the XRD results ( Figure 3 ) showed that the corresponding catalyst activated at 400 °C contained a significant amount of NiO, and one should expect that this NiO would be reduced at higher temperatures, but according to H 2 -TPR results ( Figure 4 ), this was not the case.…”

“…The reduction peak at 330 °C is attributed to NiO weakly interacting with Al 2 O 3 . The wide reduction peak extended from 410 up to 880 °C shows, in addition, the formation of various NiO-species, which interact stronger with Al 2 O 3 forming non-stoichiometric surface aluminates (NiAlxOy) that are highly dispersed on the surface of the support, and stoichiometric NiAl 2 O 4 [ 37 ]. Finally, we have to note that the hydrogen consumption in the 60NiAl cp sample was found to be 42% higher than that in the 60NiAl wi .…”