Dominique Brodzki

Comparison by g.c.-m.s. of liquefaction extracts from coal maceral concentrates

Abstract Differences between the compositions of partly hydrocracked hexane-soluble extract fractions from the liquefaction of maceral concentrates were investigated by gas chromatography-mass spectrometry. The technique identifies components within only a relatively narrow range of molecular masses, but some systematic differences were nevertheless observed. Dibenzofuran derivatives were significantly more abundant in extracts derived from inertinite concentrate than in liptinite or vitrinite extracts. Within the retention time interval where dibenzofuran and its derivatives were identified in inertinite extracts, products prepared from liptinite and vitrinite concentrates were found primarily to contain biphenyls and acenaphthene derivatives. Extract fractions from inertinite were also characterized by almost negligible contents of phenol derivatives, a class of compounds much in evidence in the liptinite and vitrinite extract fractions. These findings have suggested some differences between oxygen functionalities in, and types of chemical bonds connecting, basic structural units in different coal macerals. Basic structural units in inertinites appear to be joined more frequently by alkyl or other bridges than by linear ether bonds, in comparison with other maceral groups. This provides one likely structural explanation for the relatively low yields obtained during the liquefaction of the inertinite concentrate.

Comparison of product distributions from the thermal reactions of tetralin in a stirred autoclave and a flowing-solvent reactor

Abstract Products from the thermal reactions of tetralin in a stirred micro-autoclave and a flowing-solvent reactor were compared by gas chromatography-mass spectrometry, to study the effect on product composition of residence time in the reaction zone: of the order of seconds in the flowing-solvent reactor and normally 1 h in the stirred micro-autoclave. Significant differences were found between the products obtained in the two reactors; greater quantities of by-products from thermally induced reactions of tetralin — mainly naphthalene, butylbenzene and 1-methylindane — were found in the heated tetralin from the autoclave. A number of compounds, mainly of mass 262 and 258 u (apparently tetralin-tetralin dimers and tetralin-naphthalene adducts), were also identified in the products from both reactors; many of these products have not previously been reported in connection with the thermal reactions of tetralin. The total concentration of this class of compounds did not exceed ~ 1 wt% of the total solvent. Greater concentrations of the relatively stable dimers and adducts were identified in products from the autoclave than in those from the flowing-solvent reactor. These findings have immediate implications for the evaluation by g.c.-m.s. of coal liquefaction products prepared using tetralin as vehicle, since compounds similar to tetralin-derived by-products have also been found in product solutions from actual coal solubilization experiments.

HDN of 1–4 tetrahydroquinoline over MoNxOy and NbNxOy: effect of transition metal, solvent and ammonia

Oxynitrides of early transition metals are bifunctional catalysts active in hydrodenitrogenation (HDN). The strength of the hydrogenating function and the acidic properties of molybdenum and niobium oxynitrides were investigated, as well as the inhibiting effect of ammonia and the effect of solvent (cyclohexane or tetradecane) on HDN of 1,2,3,4‐tetrahydroquinoline (1–4 THQ). Even under high hydrogen pressure (4.5 MPa) the reaction was found to be able to proceed without hydrogenation of the aromatic cycle of 1–4 THQ before C–N bond scission, which is not the case over sulfided NiMo supported catalysts in HDN. Experiments in presence of ammonia permitted to support a bifunctional dual site concept.

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+.

Liquefaction of coal and maceral concentrates in a stirred micro-autoclave and a flowing-solvent reactor

Abstract Compositions of lighter liquefaction product fractions from a stirred micro-autoclave and a flowing-solvent reactor were compared by gas chromatography-mass spectrometry (g.c.-m.s.). Tetralin was used as vehicle for liquefaction of a set of coals and maceral concentrates; high-pressure hydrogen and a mixture of finely powdered Fe 2 O 3 catalyst precursor and elemental sulfur were used in the micro-autoclave. Similar conversions (sample weight loss) were observed in the two reactors when relatively long hold times (400 s) were used in the flowing-solvent reactor. Compared with products prepared in the micro-autoclave, only a negligible proportion of material released from the coal in the flowing-solvent reactor could be detected within the molecular mass interval between tetralin itself and the upper detection limit of the Chromatographic column: most aromatic constituents observed by g.c.-m.s. in products from the flowing-solvent reactor were identified as resulting from the thermal reactions of tetralin. This result suggests that nearly all components identified in products from the stirred micro-autoclave were formed from larger and/or more polar species released from the coal during secondary reactions of primary coal solubilization products. The concentrations of a limited number of alkylaromatic homologous series identified in the oil fraction of the stirred autoclave products were quantitatively determined by g.c.-m.s.. Analysis of successive product fractions from the flowing-solvent reactor, collected during time-temperature-resolved experiments, indicated that the greater part of the C 20 –C 36 straight-chain aliphatic hydrocarbons identified in the product mixture was released from the coal between 340 and 390 °C.

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.