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Mechanistic investigation of Ni and NiCu for catalytic transfer hydrogenation of methyl levulinate to γ-valerolactone: A combined experimental and DFT study
(2023-06-25)
Chitpakdee, Chirawat
;
Boonyoung, Pawan
;
Pansakdanon, Chaianun
;
Suttisintong, Khomson
;
Faungnawakij, Kajornsak
Recently various supported bimetallic catalysts have been employed as effective catalysts for γ-valerolactone (GVL) production from levulinic acid or its esters. However, previous reports have shown synergetic roles of active metals and supports as important keys for superior catalytic performance. This work combines both experimental and simulation studies to focus solely on the role of bimetallic formation between nickel (Ni) and copper (Cu). The experimental results suggest that both Ni and nickel-copper alloy (NiCu) catalysts are good for hydrogenation of methyl levulinate (ML) to an intermediate species, 4-hydroxypentanoic acid (HPA). However, only NiCu has a better tendency to accelerate the conversion of HPA to GVL via cyclization process. Activation energy from experimental study of cyclization step over Ni is about two times larger than that of NiCu (E<inf>a</inf><sup>K2</sup> values are 121.7 and 56.0 kJ mol K<sup>−1</sup> for Ni and NiCu, respectively) provided strong evidence of superior GVL production over NiCu catalyst. Density Functional Theory (DFT) simulation results reveal solid finding to support the high efficiency of NiCu over Ni catalyst for GVL production. The calculated energy barrier for HPA conversion to GVL over the NiCu is 1.0 eV which is lower than that of the Ni catalyst (1.54 eV). The Ni provided only one concerted pathway to transform from ML to GVL, while NiCu could provide either a concerted or nonconcerted pathway where the latter one requires lower activation energy for GVL production. The combination of these experimental and simulation results leads to a better understanding of bimetallic catalyst design for GVL production via catalytic transfer hydrogenation without any support materials.
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Fantastic carbon material for nickel/carbon support catalyst reducing via calcination enhanced with hydrothermal carbonization
(2016-01-01)
Jomhataikool, Buntita
;
Gunpum, Wachiraporn
;
Kraithong, Wasawat
;
Viriya-Empikul, Nawin
;
Eiad-Ua, Apiluck
In generally, the metal catalyst which synthesis by conventional techniques is usually in metal oxide form or easily oxidize in the air thus the metal catalyst must reduce to metallic form before using. It was complex process and dangerous. In the research, Carbon material from cattail flower (CF) were used as supporter of Nickel/Carbon supported metal catalyst (Ni/C). This research were studied effect of used carbon material from CF as supporter of Ni/C and varying nickel loading. The Ni/C catalyst were prepared by hydrothermal, impregnation and calcination process. Firstly, Dried CF has been pretreat via hydrothermal process with optimized condition at 180°C for 8h. Then, the nickel solution was added to support via impregnation method by varying Ni loading from 20 to 60 wt% of supported. Finally, the sample has been pelleted into 0.5mm-Ni/C pellet and calcined at 900°C for 2h under nitrogen atmosphere. Ni/C were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), surface area and pore size distribution was determined by N2 adsorption. The result indicate that nickel particle on Ni/C were in the free metal from without reduction and well dispersed on supported surface. Particle size and surface area of Ni/C were decreases at the increase metal loading. Nickel/Carbon supported metal catalyst were ready to use and could be controlled particle size, surface area and crystallinity by metal loading.

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