Direct Synthesis of Mesoporous Sulfated Silica-Zirconia Catalysts with High Catalytic Activity for Biodiesel via Esterification

Abstract

A solid acid material of high loading of sulfated zirconia on mesoporous silica SBA-15 has been successfully synthesized by a direct-synthesis under strong acidic condition. The materials were characterized by powder X-ray diffraction, N 2 adsorption-desorption, UV-visible diffuse reflectance spectroscopy, transmission electron microscopy (TEM), ICP-mass, and NH 3 temperature-programmed-desorption (TPD). The zirconia content and well-ordered mesostructure of SiO 2 -SZ are controllable by tuning the molar ratios of sulfate to zirconia and silica to zirconia. UV-visible spectra and TEM observations confirm the incorporation of zirconium (IV) onto the mesoporoes framework. Acidity is enhanced in comparison with unsupported sulfated zirconia. Much improved catalytic performance under mild temperature condition in the esterification of lauric acid and palmitic acid with the direct-synthesis SiO 2 -SZ catalyst was observed as compared to un-supported SZ. The good catalytic performance of the sulfated silica-zirconia materials is attributed to a higher dispersion of zirconia to give higher acid site density and also to better tolerance of water. The solid acid catalytic materials have many advantages over liquid acids in its environmentally friendliness and easy separation.

Catalytic Activity of Sulfated and Phosphated Catalysts towards the Synthesis of Substituted Coumarin

“…The catalytic activity of zirconium, titanium and tin metal phosphate and tungestate has been assessed for a Pechmann condensation reaction of phenols and methyl acetoacetate [47]. Sulfated zirconia supported on silica (SiO 2 -SZ) and unsupported sulfated zirconia (SZ) have been used as acidic solid catalysts for measuring the catalytic activity of the esterification reaction between lauric acid and palmitic acid [48], while phosphated zirconia has been employed as a catalyst for the condensation reaction of phenols and ethyl acetoacetate to achieve coumarin derivatives [25]. Furthermore, microwave has been used to prepare coumarin derivatives in the presence of sulfated zirconia, commercial sulfonic acid resin or amberlite-15 [25,49].…”

Catalysing sustainable fuel and chemical synthesis

“…Mesoporous silicas from the SBA family [73] have been examined for biodiesel synthesis, and include materials grafted with sulfonic acid groups [74,75] or SO 4 /ZrO 2 surface coatings [76]. Phenyl and propyl sulfonic acid SBA-15 catalysts are particularly attractive materials with activities comparable to Nafion and Amberlyst resins in palmitic acid esterification [77].…”

On the influence of Si:Al ratio and hierarchical porosity of FAU zeolites in solid acid catalysed esterification pretreatment of bio-oil

“…To address these issues, development of a noncorrosive and recoverable heterogeneous catalyst for esterification pretreatments is critical [5]. In this respect, various solid acid catalysts have been studied for organic acid esterification, including SO 4 / ZrO 2 [8][9][10], sulfonic acid functionalised (hierarchical) mesoporous SBA-15 [7,[11][12][13][14][15] KIT-6 [16] and PMO [17] silicas, Cs-exchanged heteropolyacids [18][19][20][21][22], tungstated zirconia [23], zirconium phosphate [24][25][26] and Nafion/SiO 2 composite (SAC-13) [27]. Among the solid acid catalysts, zeolites are efficient catalysts for esterification [28][29][30] due to their strong Brønsted acidity and tunable physical and chemical properties through altering their framework Si:Al ratio and structure.…”