Immobilizing Ni (II)-Exchanged Heteropolyacids on Silica as Catalysts for Acid-Catalyzed Esterification Reactions

Abstract

Biodiesel was synthesized from oleic acid using Ni (II)-exchanged heteropolyacids immobilized on silica (Ni0.5H3SiW / SiO2 ) as a solid acid catalyst. Based on detailed analyses of FT-IR, XRD, TG and SEM, the structural, surface and thermal stability of Ni0.5H3SiW / SiO2 were investigated. Obtained results demonstrated that the Keggin structure was well in the immobilization process and possess a high thermal stability. Various esterification reaction conditions and reusability of catalyst were studied. High oleic acid conversion of 81.4 % was observed at a 1:22 mole ratio (oleic acid: methanol), 3 wt. % catalyst at 70 °C for 4 h. The Ni0.5H3SiW / SiO2 catalyst was reused for several times and presented relatively stable. More interestingly, the kinetic studies revealed the esterification process was compatible with the first order model, and a lower activation energy was obtained in this catalytic system.

Kinetics for the biodiesel production from lauric acid over Keggin heteropolyacid loaded in silica framework

“…For this reason and in order to overcome these problems, different supports were employed to immobilize HPAs, for example activated carbon, zeolites, silica, zirconium, titanium, MCM-41, and polymers among others [24,25]. Different HPAs in heterogeneous form have been tested in biodiesel production such as cesium-doped heteropoly tungstate (HPW), HPW/ZrO2, HPW/γ-Al2O3 and HPW/SiO2 for the simultaneous esterification and transesterification of 10% oleic acid-soybean oil mixture [26]; core-shell nanostructured heteropoly acidfunctionalized zeolitic imidazolate frameworks-8 (ZIF-8) for rapeseed oil transesterification [18]; HPW/kaolinite, HPW/bentonite and HPW/montmorillonite for acetic acid esterification [27]; HPW/SiO2 and cesium-doped HPW for rapeseed oil transesterification [28]; H3PMo12O40/bentonite [29] for esterification of a waste from palm oil; H3PW12O40/KIT-6 for neem oil transesterification [30]; 12-tungstophosphoric HPA/ZrO2 [31], and H3PW12O40 and H3PMo12O40 supported on activated carbon fibers [32] for palmitic acid esterification; Ni0.5H3SiW/SiO2 [33], NiHSiW/UiO-66 [34] and Sn1.5PW12O40/Cu-BTC [35] for oleic acid esterification.…”

Synthesis of Silicotungstic Acid/Ni-Zr-O Composite Nanoparticle by Using Bimetallic Ni-Zr MOF for Fatty Acid Esterification

“…Compared with fossil-based fuels, biodiesel is known as a renewable, biodegradable, nontoxic, and ecofriendly energy source. Its emits a relatively small amount of carbon dioxide, and possesses an appropriate cetane number and high flash point [3,4]. In general, biodiesel refers to fatty acid methyl ester obtained through the catalytic esterification or transesterification of fatty acids (e.g., oleic acid, palmitic acid, lauric acid, etc.)…”