Carbon–silica composites prepared by the precipitation method. Effect of the synthesis parameters on textural characteristics and toluene dynamic adsorption

Abstract

Three synthesis routes are presented here that leads to carbon–silica composites. These were characterized by nitrogen physisorption, by thermogravimetric analysis and by dynamic toluene adsorption test similar to Ashrae standard I45.1. The carbon–silica composites possess high microporosity and mesoporosity as well as large surface areas. Furthermore, the control of the microporosity as well as pore size distribution is possible because they depend on the amount of carbon used and of the synthesis route. Following routes I and III a wide micro-mesoporous pore size (1–32 nm) was obtained where as by route II narrow micro-mesoporous pore size (1–4 nm) was observed. In addition, pore diameters center in the range of 1.13–1.17 nm was observed when carbon content was 32 or 45 wt%. The dynamic adsorption of toluene was evaluated for carbon–silica composites obtained by three preparation routes at two different carbon contents, 32 and 45 wt% The results showed that a composite with 45 wt% carbon content and obtained via preparation route I gave the highest toluene adsorption capacity (27.6 wt% relative to carbon content). The large uptake capacity of this composite was attributed to the presence of high microporosity volume and a wide (1–32 nm) bimodal pore system consisting of extensive mesopore channels (2–32 nm) as well as large surface area. These capacity values of carbon–silica composites are by weight relative to carbon content and are competitive to, results obtained for commercial coconut activated carbon (31.1 wt%) and significantly better than a commercial alumina-carbon composite (9.5 wt%) at 0% efficiency.