In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.



Volume 54 No. 4 December 2005


Chemically bonded b-cyclodextrin stationary phase for liquid chromatographic separation of substituted aromatic compounds; 179–188

Gunnar Karelson and Jaan Pentchuk

Abstract. The effects of the mobile phase composition and the relative position of substituents in aromatic compounds on the retention behaviour on the b-cyclodextrin bonded copolymer of hydroxylethyl methacrylate and ethylene dimethacrylate (HEMA gels) were investigated. The average b-cyclodextrin amount immobilized was determined by modified Hultmann’s method. Increasing the proportion of water in the mobile phase resulted in an increase of the retention times and the relative retention of isomers. The elution order of solute isomers was independent of the methanol concentration in the mobile phase. D-, L-, and D,L-tryptophan were used to estimate the ability of the b-cyclodextrin bonded HEMA gel to separate optical isomers. It was found that the particle size, particle size distribution, and the length of the spacer influenced the efficiency of the column.

Key words: liquid chromatography, HEMA gel, b-cyclodextrin, aromatic compounds.

Separation of calcium and magnesium ions by ion chromatography with a HEMA–EDMA column; 189–193

Jaan Pentchuk, Priit Alumaa, Jüri Ivask, and Maike Käärik

Abstract. Properties of HEMA–EDMA weak cation exchange sorbent for ion chromatography are discussed. The column prepared was used for experiments with calcium and magnesium ions in single column ion chromatography. The ion chromatographic method was used for measuring the stability constants of complexes of Ca and Mg cations with the binary mixture of tartaric and pyridine-2,6-dicarboxylic acids. A retention model for binary mixtures is proposed to choose and predict the retention times for Ca and Mg ions in single ion chromatography. The stability constants calculated were tabulated for Ca and Mg complexes.

Key words: ion chromatography, HEMA–EDMA column, calcium ions, magnesium ions.

Trends in biomass thermochemical liquefaction: global experience and recent studies in Estonia; 194–229

Hans Luik, Vilja Palu, Lea Luik, Kristjan Kruusement, Hindrek Tamvelius, Rein Veski, Nikolai Vetkov, Natalia Vink, and Mikhail Bityukov

Abstract. Investigations on thermochemical liquefaction of various renewable resources of biomass carried out in many countries over the world during the last 25 years are shortly reviewed. As a rule, all kinds of the renewable biomass used as liquefaction feedstock were characterized by extremely high oxygen contents, amounting to 50 wt.%. It was found to be one of the main specific features of the chemical composition of lignocellulosic biomass. Until 1990 short contact time fast pyrolysis methods were favoured as these give a high liquid yield from renewables. As a result of fast pyrolysis the most of oxygen was transformed into the composition of pyrolysis liquids and therefore these were not fit to replace even conventional light fuel oil. Improvements to fuel products quality were badly needed. That is why during the last decade one- or two-stage upgrading processes were preferred includ­ing in situ upgrading using H-donor agents in the liquefaction or supplementary deoxygenation of fast pyrolysis primary liquids. In Estonia fundamental studies on renewable biomass liquefaction basing on both the pre-existent technologies developed as a result of prolonged kukersite oil shale processing experience and on the improved and novel ones have been initiated. Partial substitution of oil shale for renew­ables and their wastes and co-processing of fossil and renewable biomass can create a basis to sustain­able oil shale utilization and shale oil production. Opportunities to continue produc­tion of liquid fuels and chemicals simultaneously decreasing the proportion of oil shale as a feedstock, as well as modify­ing both liquid composition and qualities closer to those of natural petroleum and, concurrently, decreasing environmental risks are the main goals of those studies being carried out at the Department of Oil Shale Technology at Tallinn University of Technology since 2001. Forest waste biomass as an abundant local and global renewable resource is represented as one of the most promis­ing alternative feedstock. The results obtained in the liquefaction of sawdust, bark, and needles using semicoking, hydrogenation, and water conversion methods and chemical characteriza­tion of liquids obtained are reported as well. It was concluded that thermochemical liquefaction of forest waste bio­mass using methods known from oil shale processing results in the formation of significantly deoxy­genated liquid products compared with the initial feedstock while in the benzene soluble part of those liquids (38–86% of the total liquid product) several similarities with kukersite shale oil were found.

Key words: biomass, lignocellulosic wastes, pyrolysis, hydrogenation, water conversion, biomass-derived liquid product, chomatographic separation, infrared spectroscopy.

Abbreviations: BM – biomass, FWB – forest waste biomass, IRS – infrared spectroscopy, LP – liquid product, TCL – thermochemical liquefaction, TLC – thin layer chromatography.

Instructions to authors; 230

Contents of volume 54; 231–232