Green analytical chemistry

xii, 319 p.; 24 c

Determination of critical micelle concentration of surfactants

Surfactants are widely used in household and industrial cleaners, cosmetics and textiles dyeing process as leveling, dispersing and wetting agents [1]. Surfactants and some dyes are able to associate in aqueous solutions to aggregate and form micelles. This property is due to the presence of both hydrophobic and hydrophilic groups in each surfactant molecule [2]. Surfactants can persist as separated molecules up to a limiting concentration, known as the critical micelle concentration (CMC). This is perhaps the most important characteristic of surfactants and some ionic liquids (IL). An IL is a salt composed of an organic cation and, commonly, an inorganic anion that is molten when the temperature is at, or close to, room temperature [3]. The physical properties such as conductivity, surface tension and others of the surfactants solutions are sharply changing above the CMC [4]. [...]Biochemijos katedraVytauto Didžiojo universiteta

Metal-Catalyzed Degradation of Cellulose in Ionic Liquid Media

Biomass conversion to 5-hydroxymethylfurfural (HMF) has been widely investigated as a sustainable alternative to petroleum-based feedstock, since it can be efficiently converted to fuel, plastic, polyester, and other industrial chemicals. In this report, the degradation of commercial cellulose, the isomerization of glucose to fructose, and the conversion of glucose to HMF in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl]) using metal catalysts (CrCl3, ZnCl2, MgCl2) as well as tungsten and molybdenum oxide-based polyoxometalates (POM) were investigated. Tungsten and molybdenum oxide-based POMs in ionic liquids (IL) were able to degrade cellulose to majority glucose and epimerize glucose to mannose (in the case of the molybdenum oxide-based POM). A certain amount of glucose was also converted to HMF. The tungsten oxide-based POM in IL showed good activity for cellulose degradation but the overall products yield remained 28.6% lower than those obtained using CrCl3 as a catalyst. Lowering the cellulose loading did not significantly influence the results and the addition of water to the reaction medium decreased the product yields remarkably

DataSheet1_Preparation and characterization of lignin-derived carbon aerogels.pdf

Lignin is considered a valuable renewable resource for building new chemicals and materials, particularly resins and polymers. The aromatic nature of lignin suggests a synthetic route for synthesizing organic aerogels (AGs) similar to the aqueous polycondensation of resorcinol with formaldehyde (FA). The structure and reactivity of lignin largely depend on the severity of the isolation method used, which challenges the development of new organic and carbon materials. Resorcinol aerogels are considered a source of porous carbon material, while lignin-based aerogels also possess great potential for the development of carbon materials, having a high carbon yield with a high specific surface area and microporosity. In the present study, the birch hydrolysis lignin and organosolv lignin extracted from pine were used to prepare AGs with formaldehyde, with the addition of 5-methylresorcinol in the range of 75%–25%, yielding monolithic mesoporous aerogels with a relatively high specific surface area of up to 343.4 m2/g. The obtained lignin-based AGs were further used as raw materials for the preparation of porous carbon aerogels (CAs) under well-controlled pyrolysis conditions with the morphology, especially porosity and the specific surface area, being dependent on the origin of lignin and its content in the starting material.</p