The aim of this research is to investigate how ammonia treatment of the surface can influence the activity of a viscose-based activated carbon cloth (ACC) for the oxidative retention of H2S and SO2 in humid air at 25°C. Surface basic nitrogen groups were introduced either by treatment with ammonia/air at 300°C or with ammonia/steam at 800°C. The pore structure of the samples so prepared was examined by adsorption measurements. Changes in the surface chemistry were assessed by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and temperature programmed desorption (TPD). The change of ACC activity could not be merely attributed to surface nitrogen groups but to other changes in the support. Ammonia/steam treatment improved ACC performance the most, not only by introducing nitrogen surface groups, but also by extending the microporosity and by modifying the distribution of surface oxygen groups. Successive adsorption–regeneration cycles showed important differences between oxidative retention of H2S and SO2 and the subsequent catalyst/support regeneration process.

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.

The preparation of active carbons containing nitrogen surface functions is considered by ammoxidation of various raw materials like pinewood, peat and lignite. To have an accurate knowledge of the nitrogen functions introduced, diffuse reflectance IR/FT and X-ray photoelectron spectroscopies were used. Taking into account the complexity of the raw materials, the structural characterisation of the cellulose ammoxidation products was undertaken in the first step of our study, since cellulose is one of the major compounds of woods. The thermal treatment of cellulose, at around 250°C and at different durations (1, 2, 4 h), was realised for comparison under several conditions: air, argon, ammonia and air–ammonia mixtures (ammoxidation). Several nitrogenated structures were characterised. The mechanism of their formation from the C4 fragment formed from the heterolytic cleavage of cellulose by thermal treatment was proposed pointing out the fundamental role of intermediate imine function.

One investigated way to prepare selective adsorbents towards mixtures of volatile organic compounds (VOCs) is to modify lignite by nitrogen-enrichment. These chemically modified coals are prepared by condensation of urea with the lignite before the carbonization/activation steps. This study describes a set of analytical tools able to explain in term of surface composition and of quantitative molecular interaction parameters the evolution of the selective behavior of three adsorbents. For this purpose, the evolution of the surface chemistry and the selectivity with three percentage of burn-off of a nitrogen-enriched lignite is followed by infrared and X-ray photoelectron spectroscopies and gas chromatography (GC)/linear solvation energy relationship (LSER) method. Then, the selectivity of these materials towards two test-pairs of VOCs is discussed. This QSBR investigation reveals the complementarity of these methods linking composition data of the active carbons and their selective properties.

The adsorption of water vapour on microporous carbons derived from the carbonization of coconut shell has been studied. The adsorption and desorption characteristics of water vapour on the activated carbons were investigated over the pressure range p/p0 0–0.95 in a static water vapour system. In these experiments the process of water adsorption/desorption was investigated by both kinetic and equilibrium experimental data. Activated carbons differing by the degree of burn-off have shown the importance of the microstructure. A carbon enriched with nitrogen functions underlined the influence of the surface chemistry.

The ammoxidation of various carbonaceous materials was used as a route to obtaining nitrogen-enriched precursors of active carbons containing nitrogen surface functions. The reaction conditions were studied and their effect on the nitrogen incorporation was evaluated.

A subbituminous coal and a lignite were treated with some nitrogen reagents in several solvents with the aim of obtaining enriched coal samples which could behave as active carbon precursors. This paper deals with the structural characterization of the samples obtained with urea before and after activation. The attention is focused on the identification of the main functional groups able to react with urea, on the nature of the nitrogen functions introduced in the coal network, and on the behavior of these functions during the activation. The samples were investigated by infrared spectroscopy (DRIFT), X-ray photoelectron spectroscopy(XPS). It was shown that ester/lactone and carboxylic acid groups are mainly concerned in the reaction with urea, which is solvent dependent. The identification of nitriles proved the occurrence of amides in the first step of the reaction. The participation of ketones, though to a lesser extent, suggests the possibility of further heterocyclization. The nitrogen enrichment of the coals is evidenced by XPS. On the basis of Literature data, four nitrogen groups were characterized according to the binding energies. They were assigned to pyrrolic and several pyridinic forms. Their behavior during thermal treatments and steam activation is discussed.

Activated carbons were prepared by carbonization and steam activation of nitrogen-enriched low-rank coals. N-enrichment was performed by reaction of ammonia or its derivatives (ammonium carbonate, hydrazine, hydroxylamine, urea) with the carboxyl groups either naturally occurring in coal or artificially introduced by performic oxidation. Urea at an elevated temperature and pressure appeared to be the most efficient. The yields of the products and their nitrogen contents suggest the chemistry of these reactions involving not only urea itself but also its thermal transformation products. The activated chars obtained from the selected nitrogen-enriched precursors had considerable effective surface areas and displayed excellent sulfur removal.

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.

The mobility of macromolecular network has been found to be the fundamental property of both brown and bituminous coals governing the reactivity for hydrogenation with tetralin. In Kansk-Achinsk brown coal, this was primarily affected by carboxylate cross-linking via polyvalent cations like Ca.

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+.

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.

The chemistry of the reaction of coal with methanol and sodium hydroxide involves not only hydrogenation, mainly through the mechanism of hydride transfer from alcohol anion, and alkylation of aromatic systems but also several other types of coal structure transformations: hydrolytic cleavage of bonds, mainly ether bridges, and elimination and chemical blocking (O-alkylation) of oxygen functional groups. Coal solubilization by reaction with methanol and sodium hydroxide is a result of combined effects of the above transformations. In this study, the effects of a preliminary reduction of carbonyl groups with lithium aluminium hydride and/or of a preliminary O-methylation with dimethyl sulfate on the conversion of the Kansk-Achinsk lignite under methanol-sodium hydroxide solubilization were investigated by means of structural characterization, sequential solvent extraction, and programmed pyrolysis of the lignite and of its solubilization byproducts. In spite of a decrease in susceptibility to hydrogenation and alkylation reactions, which otherwise play a critical role during the CH3OH-NaOH treatment of bituminous coal, blocking of the numerous free carboxyl and hydroxyl groups of the lignite increases the conversion yields, as a result of a prevention of repolymerization reactions. O-Methylation of the hydroxyl groups released by hydrolytic cleavage would also stabilize the reactive oxygen groups of the lignite.

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, LiAlH4 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 LiAlH4 reduction enhance denitrogenation of the coal during M treatment and subsequent pyrolysis.

The effect was studied of pretreatment techniques, including O-methylation with (CH3)2SO4, reduction with both K-isopropanol in THF and LiAlH4, reductive methylation with KCH3I 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.