Elucidation of interactive effects of synthesis conditions on the characteristics of mesoporous silicas templated using polyoxide surfactant

Abstract

A series of mesoporous silicas (MS-1-MS-9) were synthesized at different gel compositions using a triblock copolymer (TCP), poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), as the surfactant. The interactive effects of acidity, the contents of tetraethyl orthosilicate (TEOS) and the surfactant, and the gelling temperature on the characteristics of the final material were simultaneously characterized. Increasing acidity favored mesopore formation. A material with a surface area of 760 m 2 /g, mostly in the mesoporous range, was obtained at 1.0(TEOS):0.017(TCP):7.3HCl:115.7H 2 O. Mesopore formation was predominantly determined by the TEOS:TCP ratio and was promoted with its increase from 1.56:1 to 2.09:1. A further increase to 2.61:1 was detrimental. Whereas increasing the TCP content to 3.5% w/w improved micellization, a further increase to 4.6% should be avoided. Mesoporous silicas showed low crystallinity but a high degree of hexagonal mesoscopic organization. The weak surface acidity was attributed to surface silanols, the number of which was proportional to mesoporosity. r

Biocatalytic esterification of citronellol with lauric acid by immobilized lipase on aminopropyl-grafted mesoporous SBA-15

“…It is clearly noted that both samples show the arrays of long-range mesopore channels, which are similar to the image of SBA-15 reported in the literature [3,11,16]. The result suggests that the critical micelle concentration (cmc) was reached or exceeded at a P123:H 2 O ratio of nearly 1:12,000 when the synthesis was conducted at 40 • C. This solution was slightly more dilute than that reported by Kim et al [15] (1:10,700) for a synthesis at 40 • C and Abdullah et al [9] (1:6800) for a synthesis at 60 • C. This suggested that the cmc could be reached at lower P123 concentrations if the synthesis was conducted at lower synthesis temperature.…”

“…Mesoporous SBA-15 was prepared using a sol-gel method as reported earlier [9]. In brief, 150 ml of HCl solution at a concentration of 2.0 M was shaken in an orbital shaker at 40 • C for an hour.…”

“…All these characteristics make the materials potential candidates to act as suitable support materials for large molecules like enzymes. In our earlier work, a highly porous SBA-15 material with well-organized array of straight channels and narrow pore size distribution has been developed [9]. The correlations between its surface characteristics and the synthesis conditions have also been successfully elucidated.…”

Optimal Synthesis of Hierarchical Porous Composite ZSM-5/SBA-16 for Ultradeep Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene. Part 2: The Influence of Aging Temperature on the Properties of NiMo Catalysts

“…This is also evidenced by the reduced orderliness observed from TEM images. In addition, the hydrophobicity of the hydrophilic end (EO) of the surfactant increased; hence, the stretched hydrophilic end becomes curved and moves closer to the hydrophobic end (PO), which makes the micellar particles change from sphere to irregular shape . This eventually leads to irregularities in the shape of the material.…”

“…In addition, the hydrophobicity of the hydrophilic end (EO) of the surfactant increased; hence, the stretched hydrophilic end becomes curved and moves closer to the hydrophobic end (PO), which makes the micellar particles change from sphere to irregular shape. 46 This eventually leads to irregularities in the shape of the material. Moreover, the sizes of the micellar particles become larger in this process, leading to an augment of the pore size of the synthesized materials, which is consistent with the result of nitrogen adsorption−desorption.…”