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.

以多孔固体负载杂多酸的非均相酸催化剂，已被应用于生物燃料制备的相关研究。活性炭因具备高比表面积，可实现活性相的高度分散，因而被广泛用作催化载体。本研究以油酸作为酸性脂质的模型化合物，旨在探究采用氯化锌（ZnCl₂）化学活化百香果生物质制备的活性炭（activated carbon derived from passion fruit biomass, ACP）负载12-钨磷酸（12-tungstophosphoric acid, HPW）所制催化剂，用于生物柴油合成过程中的油酸甲酯化反应。HPW/ACP复合材料的HPW负载量为10~30 wt%，分别通过水浸渍法与初湿浸渍法两种工艺制备。通过热重分析/微分热重分析（Thermogravimetric analysis, TG/DTG）、傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FTIR）、X射线衍射（X-ray diffraction, XRD）、N₂吸附-脱附测试、扫描电子显微镜（Scanning Electron Microscopy, SEM）、固态13C及31P核磁共振波谱以及X射线光电子能谱（X-ray Photoelectron Spectroscopy, XPS）对所制备的材料进行了系统表征。催化性能测试结果显示，相较于初湿浸渍法，采用水浸渍法制备的催化剂，其油酸与甲醇的转化率以及催化剂稳定性均得到提升，这归因于该工艺制备的样品具备更优异的表面覆盖度与比表面积特性，由此可见制备方法对催化剂的活性与稳定性具有决定性影响。