Silica gel

About: Silica gel is a research topic. Over the lifetime, 22313 publications have been published within this topic receiving 325516 citations. The topic is also known as: Amorphous silica & Precipitated amorphous silica.

Deglycerolization of Biodiesel Streams by Adsorption Over Silica Beds

Abstract: A simple method for the almost complete removal of glycerol from methanol-free biodiesel streams coming out from industrial transesterification reactors is presented. The method is posed as a “dry” alternative to the conventional “wet” methods involving water washing. It is based on the use of silica beds and relies on the adsorption at room temperature to retain the small amounts of glycerol dissolved in the solutions of fatty acid methyl esters and adjust their content to the quality standards for biodiesel fuel. Fresh silica has a great processing capacity and the breakthrough of the bed depends mainly on the feed rate, the concentration of glycerol, and the mass of adsorbent. In the case of the silica gel used, the saturation capacity was found to be 0.13 g of glycerol per gram of silica. If the particle diameter is 1−1.5 mm, the breakthrough and saturation point almost coincide and the full capacity of the bed is used. However, industrial adsorption units with 1/8 in. silica beads suffer from mass-tr...

Structure of poly(vinylpyrrolidone)-silica hybrid

Abstract: This paper is concerned with the solid structure of a new group of transparent glass materials which consist of an organic polymer and a metal oxide, namely a combination of poly(vinylpyrrolidone) and dry silica gel. The structure was analyzed by Atomic Force Microscopy (AFM), BET analysis method, and CP MAS13C-NMR. BET measurement showed that the hybrid material had a quite dense structure which was much less porous than the reference dry silica gel prepared by the conventional sol-gel process. AFM analysis gave the same conclusion, i.e., it showed a granular structure of silica of about 1 nm size. Silica and PVP domains did not show any considerable aggregation. The transparent, homogeneous, and dense structure was attributed to the hydrogen-bond formation between PVP(carbonyl group) and silanol, as demonstrated by CP MAS13C-NMR spectroscopy.

Determination of hydrogen-bonding acid sites on silica using the Cal-Ad method

Abstract: Silica gel, under various hydration conditions, was investigated using a novel calorimetric adsorption (Cal-Ad) method. This method combines data from calorimetric and adsorption titrations of a solid surface using a small probe molecule in a noninteractive solvent. The Cal-Ad method proved to be more sensitive than other characterization techniques (e.g. temperature-programmed desorption) and calorimetric techniques. Previously, it was believed that the silica surface consisted of one type of hydrogen-bonding site. The Cal-Ad method has elucidated three hydrogen-bonding sites of different strengths using pyridine as the basic probe molecule