Residue-based activated carbon from passion fruit seed as support to H3PW12O40 for the esterification of oleic acid

Heterogeneous acid catalysts using heteropolyacid supported on porous solids have been studied for the production of biofuel. Activated carbon is widely used as catalytic supports because of its high surface area, which allows high dispersion of the active phase. The aim of this work was to study the methyl esterification of oleic acid as a model compound for acidic lipids for the production of biodiesel using 12-tungstophosphoric acid (HPW) supported on activated carbon derived from passion fruit biomass (ACP), prepared by chemical activation using ZnCl2. The composites (HPW/ACP) were prepared containing 10-30 wt% of HPW by following two procedures: aqueous impregnation method and incipient moisture. The materials were characterized by Thermogravimetric analysis (TG/DTG), Fourier transform infrarred spectroscopy (FTIR), X-ray diffraction (XRD), N2 adsorption-desorption, scanning electron microscopy (SEM), solid state NMR 13C and 31P and X-Ray photoelectron spectroscopy (XPS). Catalytic results indicated that the conversion of oleic acid with methanol as well as the stability of the catalyst improved in the aqueous impregnation prepared samples due to the greater surface coating of the material observed in the surface area. The preparation method, thus, was determinant for the activity and stability of the catalysts.以负载于多孔载体的杂多酸（heteropolyacid）为活性组分的多相酸催化剂，已被应用于生物燃料的制备研究。活性炭因具有高比表面积，可实现活性相的高度分散，因此被广泛用作催化剂载体。本研究旨在以油酸作为酸性脂质的模型化合物，探究采用氯化锌（ZnCl₂）化学活化制备的百香果生物质衍生活性炭（ACP）负载12-磷钨酸（HPW）催化体系下，用于生物柴油制备的油酸甲酯化反应性能。本研究采用水溶液浸渍法与初湿浸渍法两种制备工艺，合成了HPW负载量为10~30 wt%的HPW/ACP复合催化剂。通过热重-差热重分析（TG/DTG）、傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、氮气吸附-脱附测试、扫描电子显微镜（SEM）、固态碳-13与磷-31核磁共振波谱以及X射线光电子能谱（XPS）对所制备的材料进行了表征。催化性能测试结果表明，采用水溶液浸渍法制备的样品，其油酸与甲醇的转化率以及催化剂稳定性均有所提升，这归因于该方法制备的材料具有更优异的表面包覆效果，该结论可通过比表面积表征数据得到验证。因此，制备工艺对催化剂的活性与稳定性起到决定性作用。