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One-pot synthesized Ti-SBA-15 mesoporous materials with various Ti loadings of 0.808-6.78 mol% were applied as heterogeneous solid acid catalysts for simultaneous esterification and transesterification of vegetable oils with methanol into high-quality biodiesel fuel (BDF) at 200 o C under autogeneous pressure. According to the diffuse-reflectance (DR) UV-Vis spectra, diffuse-reflectance infrared Fourier transform (DRIFT) spectra and pulsed ammonia (NH 3 ) chemisorption studies combined with other conventional characterizations, the catalytically active site for high-quality BDF synthesis was mostly related to the tetrahedral Ti 4+ species with weak Lewis acid character, which differential heat of NH 3 adsorption was lower than 90 kJ mmol -1 . Due to that the tetrahedral Ti 4+ species were accessible on largely mesoporous framework, the Ti-SBA-15 catalyst gave much higher activity in transesterification of crude Jatropha oil (CJO) with methanol than microporous titanosilicate of TS-1 and commercial TiO 2 nanocrystallites. Among them, the 3Ti-SBA-15 catalyst with a Ti loading of 2.46 mol% showed a highest fatty acid methyl ester (FAME) content of 90 mass% at 200 o C for 3 h using a methanol-to-oil molar ratio of 27. When the reaction period and methanol-to-oil molar ratio were increased to 3-6 h and 108, respectively, a great variety of edible and non-edible vegetable oils with various acid values (0.06-190 3 mg KOH g -l ), including refined soybean oil (RSO), refined rapeseed oil (RRO), waste cooking oil (WCO), crude palm oil (CPO), CJO and palm fatty acid distillates (PFAD), was directly transformed into high-quality BDFs, which met with a European standard (EN 14214:2009), over 3Ti-SBA-15 catalyst at 200 o C. The used 3Ti-SBA-15 catalyst was easily regenerated by calcination and its high activity was maintained. Most importantly, the 3Ti-SBA-15 catalysts could resist 5 wt% of water or 30 wt% of free fatty acid (FFA), which tolerance levels were several ten times better than those of homogeneous and heterogeneous catalysts in the current BDF production technology.

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A real understanding of intrinsic acidity and catalytic property of unconventional and sulfonic acid-functionalized SBA-15 platelet catalysts synthesized with the aid of highly solvated Zr 4+ salts (shortly termed SA-SBA-15-p) for transesterification of non-edible vegetable oils into biodiesel fuel (BDF) was reported, in comparison with conventional SBA-15 catalyst (shortly termed SBA-15-conv), unconventional SBA-15 platelet catalyst (shortly termed SBA-15-p) and commercial sulfonic resins of Amberlyst-15 and SAC-13. Thorough characterizations and catalytic study revealed that the content of fatty acid methyl ester (FAME) as the main component of BDF was increased in the order of SBA-15-conv < SAC-13 < SBA-15-p < Amberlyst-15 < 5-25SA-SBA-15-p, which correlated closely with the loading, distribution, strength of acidic sites. Among them, the unconventional 15SA-SBA-15-p catalyst with proper loadings of propylsulfonic groups (1.15 mmol S -1 g -1 ) and superficial Zr 4+ clusters (0.66 mmol g -1 ) as a mixed solid Bronsted and Lewis acid, which had differential heat of NH 3 adsorption in the range of 90-125 kJ mol -1 , gave highest FAME content with low concentrations of byproducts, such as glycerides and free fatty acid (FFA). In addition to high water and FFA tolerance levels, the used 15SA-SBA-15-p catalyst could be easily regenerated by ethanol extraction and its high activity was maintain. By contrast, 3 the SBA-15-conv catalyst without any Lewis and Bronsted acids had almost no activity in BDF synthesis. The unconventional SBA-15-p catalyst with superficial Zr 4+ clusters as a pure solid Lewis acid gave a moderate FAME content accompanying with a high concentration of unreactive glycerides. Commercial sulfonic resins of Amberlyst-15 and SAC-13 with strongly phenylsulfonic and Nafion sulfonic groups as pure solid Bronsted acids gave moderate FAME contents accompanying with high concentrations of unreactive glycerides and unwanted FFA byproducts. Furthermore, they were significantly deactivated by water, FFA and regeneration treatment due to the poison and leaching of sulfonic groups and the decomposition of thermally unstable framework.Keywords: mesoporous silica materials, solid Lewis and Bronsted acids, crude and non-edible vegetable oils, the water and FFA tolerance levels, reusability.

Sulfonic acid-functionalized platelet SBA-15 mesoporous silica with an acid capacity of 2.44mmol H(+) g-cat(-1) (shortly termed 15SA-SBA-15-p) was one-pot synthesized by co-condensation method. When applied as solid acid catalyst in synthesis of Jatropha biodiesel fuel (BDF), the 15SA-SBA-15-p catalyst showed higher activity and resistances to water and free fatty acid (FFA) than commercial sulfonic resins of Amberlyst-15 and SAC-13. For the continuous Jatropha BDF production, a steady 75-78wt% of fatty acid methyl ester (FAME) content was obtained over 15SA-SBA-15-p catalyst at 150°C for 75h, whereas the Amberlyst-15 and SAC-13 catalysts were quickly deactivated due to the decomposition of thermally unstable framework and serious leaching of sulfonic acids. More importantly, the quality, stability and cold flow characteristic of Jatropha BDF synthesized by 15SA-SBA-15-p catalyst were better than those synthesized by Amberlyst-15 and SAC-13 catalysts, making the blending with petro-diesel an easy task.

A one-pot and environmental-friendly route to synthesizing carbonaceous Ti-SBA-15 materials as weakly Lewis solid acids for transesterification of Jatropha oil with methanol to high-quality Jatropha biodiesel fuel (BDF) was successfully developed. The chemical environment and location of Ti species were controlled by the molar ratios of hydrochloride (HCl) to titanium tetraisoproproxide (TTIP) in the Ti precursors. With a HCl/TTIP molar ratio of 2.5, the tetrahedrally coordinated Ti species with weakly Lewis acid character were maximized in the superficial areas and they were associated with the catalytically active sites for transesterification. The thin carbon film, which was derived from direct carbonization of the P123 template originally existed in the channeling pores of as-made materials without adding sugar or sulfuric acid, could keep mesoporous silica framework safe from leaching during the processing steps to make Jatropha BDF. As a result, the carbonaceous Ti-SBA-15 materials gave excellent activity and durability in synthesis of high-quality Jatropha BDF, which fulfills with the specification of the international fuel standard, in both batch-type and continuous fixed-bed reaction systems. By contrast, the conventional Ti-SBA-15 materials with bare and amorphous silica framework were instable in synthesis of Jatropha BDF, in 3 which a large amount of silica species was eluted. Although the crystalline silica framework is relatively firmed, the commercial TS-1 zeolite gave moderate activity in synthesis of Jatropha BDF, associated with the slow molecular diffusion through the micropores. The powdered or extruded TiO 2 nanoparticles with limited numbers of tetrahedrally coordinated Ti sites gave poor activities in synthesis of Jatropha BDF, and little amounts of silica and titania species from the contaminations were eluted into the Jatropha BDF.

A heterogeneous catalyst, FeOx/SiO2, prepared by the pore‐filling method, was found to be active in the transesterification of crude Jatropha oil with methanol. When the transesterification reaction was carried out with a reaction temperature of 220 °C, a catalyst amount of 15 wt%, a methanol/oil molar ratio of 218:1, and a reaction time of 3 h, the yield of fatty acid methyl esters (FAME) in the product exceeded 99.0 %, and met with EN standards for allowable contents of glycerine and mono‐, di‐, and tri‐glycerides. The correlation between the FAME production activity and measured acidity of the FeOx/SiO2 catalysts showed that the transesterification reaction was promoted via the acidic function of these catalysts, which are less inhibited by coexisting free fatty acids in the feedstock triglycerides.