Nattaporn Tonanon

Influence of surfactants on porous properties of carbon cryogels prepared by sol–gel polycondensation of resorcinol and formaldehyde

Abstract The role of surfactants on carbon cryogels is investigated by using three different surfactants, nonionic (SPAN80), cationic (trimethylstearylammonium chloride; C18) and nonionic polymeric fluorinated (FC4430) surfactants. By using different SPAN80 concentrations (10.0, 5.0, 2.5, 1.0 and 0.5 vol.%), double-structure carbon microspheres with SBET (630–700 m2/g) and Vmes (0.51–0.93 cm3/g) are obtained. Mesoporous carbon cryogels with different SBET and Vmes are prepared by using C18 with different volume ratios of cyclohexane to water in a C18/water/cyclohexane mixture. Carbon cryogels with SBET (690–810 m2/g) and Vmes (0.83–1.74 cm3/g) are obtained when cyclohexane is contained in the mixture, on the contrary, when there is no cyclohexane in the mixture, a water-based carbon cryogel with low SBET (480 m2/g) and Vmes (0.29 cm3/g) is obtained. Carbon cryogels prepared by using C18 have larger mesopore size and broader mesopore size distribution compared with carbon cryogels prepared by using other surfactants. Microcellular (sponge-like) carbon cryogels with mesoporous surface, SBET (210–660 m2/g) and Vmes (0.37–0.92 cm3/g), are obtained by introducing FC4430 (two concentrations) to two starting RF solutions (C/W=6,45). Low FC4430 concentration leads to carbon cryogels with higher SBET (610 and 660 m2/g) and narrower mesopore size distributions compared to the high concentration counterpart. Hence, it is found that different surfactant types have interesting effects on morphologies and porous properties of RF carbon cryogels.

Preparation of microcrystalline cellulose from dissolving cellulose by cryo-crushing and acid hydrolysis

An interesting method in the preparation of microcrystalline cellulose (MCC) from dissolving cellulose by cryo-crushing, followed by acid hydrolysis is presented in this research. Dissolving cellulose with high cellulose content (more than 90 wt.%) was frozen with liquid nitrogen, after that the frozen pulp was milled. This experimental result showed that an average diameter of cellulose fiber was reduced from 121.11 μm to 87.51 μm and a specific surface area was increasing from 161.13 m2/kg to 184.97 m2/kg. In hydrolysis process, sulfuric acid was selected to remove an amorphous region in cellulose fibrils and to introduce sulfate groups to form stable suspensions in organic media. This hydrolysis result demonstrated that MCC had an average diameter of 14.47 μm and a specific surface area of 427 m2/kg. The morphology of MCC was observed by optical microscopy.