P.D. Salbut

Comparison of three active carbons using LSER modeling: prediction of their selectivity towards pairs of volatile organic compounds (VOCs)

Abstract In order to classify chemically modified active carbons in terms of selectivity towards pairs of Volatile Organic Compounds (VOCs), and in order to follow their chemical treatment, two active lignites were characterized by the Linear Solvation Energy Relationship (LSER) equation of Abraham et al. Results are compared to those obtained with a commercial active carbon used as a reference material. Three LSER equations were determined by using gas–solid partition coefficients at infinite dilution of 13 probe molecules in gas chromatographic method of elution by characteristic point. In this way, the three active carbons were characterized in term of molecular interaction parameters. Their significance is discussed and is in good agreement with known chemical composition data. The study shows that the commercial material is the most selective adsorbent for the test-pair (methylethylketone/dichloroethane) and that both activated lignites are selective for the other test-pair of VOCs. Then, the limits of the predictions of selectivity towards the test-pair of VOCs (methanol/dichloromethane) are also discussed.

Solvolysis of three Polish coal samples by treatment with N-methyl-2-pyrrolidinone and an NaOHCH3OH mixture☆

Abstract This study concerns the extractable materials obtained by solvolysis of three Polish coals. N-methyl-2-pyrrolidinone extraction and NaOH CH 3 OH treatment of these coals were compared using several analytical procedures (extrography, sonication, gas capillary column chromatography, and i.r. and 1H n.m.r. spectroscopy). Thermodesorption, on line with gas chromatography and mass spectrometry, was also applied to these coal samples.

Effect of chemical pretreatment on coal solubilization by methanol-NaOH

Chemical pretreatment including reduction with metallic potassium (K-THF-isopropanol), reductive methylation (K-THF-CH3I), decarboxylation, reduction with LiAlH4 and O-methylation was used to modify the structure of coals. The effect of this pretreatment on solubilization by methanol-NaOH was evaluated. The results indicate that preliminary reduction with potassium enhances the reactivity of coal, whereas preliminary reductive methylation decreases its susceptibility to solubilization. The other three pretreatments, involving elimination, transformation or derivatization of the carboxyl and hydroxyl groups in coal, also have negative effects on solubilization, showing that these groups, apart from participating in the physical effects of disintegration and dissolution of the coal in the reaction medium, greatly affect coal reactivity.

The nature of the synergistic effect of binary tetralin-alcohol solvents in Kansk-Achinsk brown coal liquefaction

Abstract Kansk-Achinsk brown coal hydrogenation and swelling in tetralin, in low molecular alcohols, in other solvents and in binary mixtures were studied. Tetralin was found to be the most effective liquefaction solvent, but methanol and ethanol were the active ones in coal swelling. Synergistic effects were observed when the mixtures of tetralin and methanol or ethanol were used for liquefaction and swelling. The effect of binary solvents was shown to be due to the ability of alcohol components to cause brown coal to swell improving the availability of the fragments of coal matter for the reactive hydrogen donor tetralin molecules.

Coal characterization for liquefaction in tetralin and alcohols

Abstract Kansk-Achinsk lignite hydrogenation in tetralin, isopropanol, ethanol and methanol was studied. Tetralin was the most active solvent. Synergetical effects were observed when the mixture of tetralin and alcohols was used for liquefaction. The variations in liquid product composition were analysed by a mechanistic numerical model incorporating two competing reactions: alkylation and hydrogen donation. The effect of preliminary O -methylation with (CH 3 ) 2 SO 4 , reduction with LiAlH 4 and with K/isopropanol and reductive methylation with K CH 3 J on the oxygen functional group composition and liquefaction behaviour were examined for three coals with different rank. Coal pretreatments were shown to cause dramatic effects on the oxygen-containing group distribution. The liquefaction reactivity with methanol in the presence of ZnCl 2 and NaOH catalysts decreased slightly. The liquefaction behaviour is strongly influenced by coal rank.

Preliminary oxidation effect on the conversion of coal in the reaction with methanol and sodium hydroxide

Abstract Coals of different rank were oxidized with performic acid to the stage of regenerated humic acids. Both crude and oxidized coals were treated with methanol and sodium hydroxide at 350°C. The final products obtained from the oxidized coals showed higher degree of hydrogenation and solubilization as compared with the corresponding products from crude coals.

Quantitative relation between the macromolecular characteristics of brown coal and its reactivity in conversion with tetralin

Abstract The reactivity of Kansk-Achinsk brown coal in thermochemical conversion with tetralin is a linear function of the network flexibility, which is primarily controlled by ionic cross-linking with carboxylate bridges via polyvalent cations such as Ca2+.

Chemical alteration of coals and their reactivity with tetralin and methanol under liquefaction conditions

Abstract The effect was studied of pretreatment techniques, including O-methylation with (CH 3 ) 2 SO 4 , reduction with both K-isopropanol in THF and LiAlH 4 , reductive methylation with KCH 3 I in THF and combination thereof, on the extractability in THF of coals of different rank and on their reactivity in non-catalytic hydroliquefaction in methanol and tetralin at 380 °C. Dramatic changes in composition of the treated coals and products were found. Chemical pretreatment had a beneficial effect on coal solubility in THF and on hydroliquefaction in tetralin. O-methylation was the most effective for lignite, but reductive methylation had the most beneficial effect for high-rank coal. With methanol as solvent, reduction and O-methylation had a small effect on coal reactivity for liquefaction. The role of cross-links is discussed in order to explain the liquefaction behaviour of coals in solvents.

The behaviour of chemically altered coals in ZnCl2-catalysed reaction with hydrogen and methanol

Abstract A series of chemically altered coals was investigated in the reaction with methanol and hydrogen in the presence of ZnCl2 as a catalyst. Significant beneficial effects were observed when high-rank coals were altered by reductive and reductively methylating pretreatments. The behaviour of altered low-rank brown and subbituminous coals was affected by both the mode of chemical pretreatment and the reaction conditions.

Effects of methanol-NaOH treatment of coal on tar and gas formation during pyrolysis

Abstract Vitrain from a bituminous coal was modified by selective chemical reaction to reveal particular structural characteristics of the organic matter responsible for the change in conversion during solubilization by methanol-NaOH treatment (M treatment). The selective reactions were alkylating and non-alkylating reduction according to Sternberg, performic acid oxidation, thermal decarboxylation of the oxidized vitrain, LiAlH 4 reduction of the oxidized vitrain and O-methylation of the residual hydroxyl groups. The products of M treatment were pyrolysed in a stream of helium at atmospheric pressure, and the volatile compounds were continuously detected by flame ionization or mass spectrometry. The changes in structure and reactivity during M treatment were assessed by comparing gas evolution during programmed pyrolysis of the M product with that of the initial vitrain and its modified by-products. The M treatment strongly increased the pyrolytic conversion, and correspondingly reduced the formation of molecular hydrogen during secondary pyrolysis. The methylation of aromatic systems in the coal by M treatment is a main component of this process. The oxidized vitrain and its oxidized products show the highest conversion, indicating the critical role of hydrogenation in bond-breaking and in prevention of regressive reactions during M treatment. Pre-oxidation and LiAlH 4 reduction enhance denitrogenation of the coal during M treatment and subsequent pyrolysis.