Sorption and catalytic properties of Latvian clay powders

Abstract

The characteristics of the most important Latvian clay deposits are considered. The locations of the deposits, the thickness of the cover and the industrial bed, demonstrated and inferred reserves of clays as well as the content of their main fractions and chemical composition are reported. A survey on the surface properties and sorption phenomena of Latvian clay is given. Adsorption and desorption isotherms of nitrogen, argon (at -195 °C), water, methanol, benzene, n-hexane and carbon tetrachloride (at ambient temperature) have been measured. It was established that the values of the specific surface area were between 10 and 120 m2/g. Two types of pore size distribution curves are given. The samples from Devonian and Quaternary deposits (main component illite) are characterised by pore size distribution curves without remarkable maxima. The samples from Triassic clay (main component smectite) ex hibit a characteristic shoulder at the closure of the hysteresis loop of the sorption isotherms. This corresponds to the maximum on the curve of pore size distribution which was due to the presence of slit-shaped pores. Increasing the treatment temperature decreases the magnitude of the specific surface area of the samples as well as their total pore volume. The treatment of natural samples with acids (sulphuric, hydrochloric, phosphoric) changes the specific surface area. The cation-exchange capacity was evaluated. The samples of Latvian clay might be successfully used for the bleaching of the local rape-seed oil. Recently, it was found that Latvian clay samples may be used as catalysts for 1,4-butanediol dehydration into tetrahydrofuran.