Sol-Gel Parameters Orthogonal Optimization and Porous Structure Analysis of Carbon Xerogels

Carbon xerogels (CXs) were prepared by the sol-gel polycondensation of resorcinol (R) and furfural (F) by the catalyst of hexamethylenetetramine (H) in an isopropanol (I) solution, followed by ambient pressure drying and sintering in the protection of nitrogen gas. An orthogonal array (OA) design OA(9)(3(3)) was applied to select the optimum conditions of additives. The microstructures of CXs were investigated by means of SEM, XRD, FR-IR and low-temperature N-2 adsorption. The results show that the R/F molar ratio of 0.7, the R/H molar ratio of 25 and the R/I volumn ratio of 0.07 are the most optimal ratio. The lowest density of CXs is 0.083 g/cm(3). The FT-IR results show that -CH2 and CH2-O-CH2 are the bridge bands, which consist of the nanometer cross-linking structures of RF xerogels. In addition, the carbon structure of CXs shows amorphous phase with minor crystalline structure from the analysis of XRD. CXs present mesoporous structure which is characteristic of high specific surface area of 550-800 m(2)/g and small average mesopore size of 2-9 nm.