Presence Of Hydrogen Donor Solvent Research Articles

Effect of decomposition of oxygen-containing structures on the conversion of lignite in the presence of hydrogen donor solvent

In this paper, pyrolysis behaviors of oxygen-containing structures of Xilinhaote (XLHT) lignite in hydrogen donor solvent (HDS) were investigated to reveal the effect of HDS on the pyrolysis sequence characteristics of XLHT and the difference of the pyrolysis behaviors of oxygen-containing structures in the presence or absence of HDS. Results showed that coal conversion was closely associated to the decomposition of oxygen-containing structures of lignite, and HDS could promote the cleavage of oxygen-containing groups and inhibit the resolidification of decomposed products, while its effect on the pyrolysis sequence of different structures of lignite was tiny. Thermal cleavage of weak aryl-alkyl ether bonds and carbonyl groups of lignite at relatively low temperatures of 280−380 °C contributed to the depolymerization of XLHT lignite to form preashphaltene (PA) with coal conversion and PA yield increasing from 12.85 % and 1.98 % to 64.58 % and 13.08 %, respectively. As the temperature rose to 430 °C, coal conversion was up to 84.13 %, and HDS could promote the cleavage of relatively stable oxygen-containing groups, aryl-aryl ethers, and methylene structures, which was the major contributor to increase coal conversion at relatively high temperatures during liquefaction. Besides, C–O and CO moieties retained on the surface of LR at 430 °C, which netted 12.54 % and 3.52 % of carbon single bond forms, respectively.

Co-liquefaction of enriched coal maceral constituents and sawdust : Wang, Y. et al. Guocheng Gongcheng Xuebao, 2002, 2, (2), 156–160

Co-liquefaction of coal and sawdust was studied in the presence of hydrogen-donor solvent, tetralin. Coal samples were prepared through floatation of the Xinwen coal, followed by enrichment of maceral constituents. Sample I was rich in vitrinite and Sample II fusinite. Effects of reaction temperature, time and initial cold H2 pressure were studied on conversion, yield, especially oil yield, through comparison between these two samples. Because it is more difficult to be liquefied, Sample II, is greatly affected by changes in temperature and time. However, it is almost independent of change in initial cold H2 pressure, owing to the role of tetralin as hydrogen vehicle. Certain product(s) formed from thermolysis of sawdust can help hydrogenation of the intermediate (asphaltene and preasphaltene) in further forming oil products.

Thermal reduction of 7H-benz[d,e]anthracen-7-one and related ketones under hydrogen-transfer conditions.

In the presence of hydrogen donor solvents and at elevated temperatures, aromatic ketones can be selectively deoxygenated to the corresponding hydroaromatic compounds. The kinetics for reduction of 7H-benz[d,e]anthracen-7-one (benzanthrone, 6) into 7H-benz[d,e]anthracene (benzanthrene, 1) in 9,10-dihydroanthracene (3) solvent has been investigated in detail. The relatively slow hydrogenation of 6 is due to reversibility of the initial hydrogen-transfer step according to a reverse radical disproportionation (RRD). The dynamics could well be rationalized using the energetics of species computed by density functional theory (DFT). The application of hydrogen donors such as 1 as a hydrogen-transfer agent, although favorable in terms of a low benzylic carbon-hydrogen bond dissociation enthalpy, is limited due to the slow self-hydrogenation, which in case of 1 gives 5,6-dihydro-4H-benz[d,e]anthracene (7).

Reactions of Coal Model Compounds in the Presence of Hydrogen Donor Solvents and Highly Dispersed Catalysts

Reactions of 1,2-(1,1‘-)dinaphthylethane (DNE) and 1,2-diphenylethane (DPE) in a hydrogen donor solvent in the absence or in the presence of highly dispersed catalysts such as Mo(CO)6-S and Ru(acac...

Mn(III) promoted N-O bond reduction of N-hydroxy-2-azetidinones

Abstract Treatment of various N-hydroxy-2-azetidinones with Mn(III) acetate unexpectedly afforded the corresponding reduced N-unsubstituted-2-azetidinones in the presence of hydrogen donor solvents.

Thermal cracking of petroleum residues: 1. Kinetic analysis of the reaction

In order to define a kinetic scheme and to calculate the kinetic parameters of the thermal cracking of petroleum residues, a vacuum residue of Belaym crude was thermally cracked at 410, 430, 450 and 470 °C for reaction times up to 120 min. The concentration of three pseudo-components, namely vacuum residue, distillate and coke, was detected during conversion and the data from these experiments were used for the definition of the kinetic model. Distillate production can be described as a simple first-order reaction while coke formation seems to be the consequence of consecutive reactions, in particular involving asphaltenes. A study of the structural changes of asphaltenes as a function of severity was also performed and the variations of the average molecular parameters with conversion were correlated. The results of this work have been used as reference data for a subsequent study of residue conversion in the presence of hydrogen-donor solvents.

Thermal cracking of coal model diaryl ethers in aromatic solvent

Thermal cracking of nine diaryl ethers in a hydrogen donor solvent or 1-methylnaphthalene was studied kinetically. The rate of conversion of the diaryl ethers was first order with respect to the substrate concentration and increased with increase in size of the aryl structure. The relative rate constant of aryloxygen bond cleavage calculated on the basis of first order reaction has indicated that the ease of cracking depends strongly on the aromatic structure and the position of substitution. The conversion rate of 2, 2′-dinaphthyl ether was remarkably enhanced in the presence of hydrogen donor solvent, for example by a factor of ten in the presence of 9, 10-dihydroanthracene. The activation energy of thermal conversion of 2, 2′-dinaphthyl ether was 214 kJ/mole in methylnaphthalene, 151 kJ/mole in tetralin and 88 kJ/mole in dihydroanthracene. The enhancing effect of the hydrogen donor was considered due to hydrogen transfer to the aromatic nucleus of the diaryl ether from the hydrogen donor and successive fast decomposition of hydrogenated ethers.

Kinetics of short contact time coal liquefaction. Part II: Effect of nature of coal and solvent

AbstractA bituminous coal (Powhatan No. 5) and a subbituminous coal (Belle Ayr) were liquefied in the presence of hydrogen donor solvents. Statistical analyses of the data showed that for contact times up to 10 min, the coal conversion, measured in terms of tetrahydrofuran solubles, was not significantly different for the two coals. However, the subbituminous coal gave more asphaltenes than the bituminous coal.The hydrogen‐donating capacity of the solvent was varied by the addition of hydrogenated phenanthrene to SRC‐II recycle solvent. The results indicated that there are two routes for the formation of oils from coal. One is by adduct formation giving asphaltenes and preasphaltenes, which in turn gives oils, and the other is direct oil formation from coal. The preferred route depends on the hydrogen‐donating capacity of the solvent. The kinetic model, proposed in Part I of this paper, is extended to account for the change in the donor capacity of the solvent.

Hydrogenation of coal-derived liquids in the presence of rhodium complexes

Hydrogenation of 473–573 K distillate derived from the product of catalytic hydrogenation of coal in the presence of hydrogen-donor solvent and ethyl alcohol and dimethyl-formamide extracts of the tar from low-temperature (fluidized-bed) coal carbonization have been investigated in the presence of rhodium complexes. The complexes used (293–393 K; 0.1–5 MPa) bpth in homogeneous and in immobilized forms are catalytically active in hydrogenation of those coal-derived liquids. However, the increase of H/C atomic ratio is low. The catalysts in the immobilized form have not been deactivated in several catalytic cycles following.

Effect of phenolic compounds on liquefaction of coal in the presence of hydrogen-donor solvent

Phenolic compounds have a remarkable positive effect on coal liquefaction in the presence of tetralin, depending strongly on the character of the coal and on the concentrations of phenols. The solvent-refined coal obtained in the presence of phenol was low in hydrogen content and high in the fraction of aromatic hydrogen; these results corresponded well to the fact that coal conversion increases without increase of hydrogen consumption in the presence of phenols. The effect of phenols on coal liquefaction may be caused mainly by accelerated scission of ether linkages, since the decomposition of 2,2′-dinaphthyl ether was considerably enhanced by the addition of phenols.

Recent Studies on the Chemical Structure of Solvent Refined Coal

Fundamental reactions in coal liquefaction process in the presence of hydrogen-donor solvent was explained, and the effect of coal property along with reaction conditions such as temperature, time and solvent on the chemical structure of SRC was briefly reviewed. Recent progress on the separation tequniques and chemical analysis made clear that SRC was composed of many fractions from oils to asphaltols with high aromaticity. The fate of oxygen-containing structure during the coal liquefaction process was also discussed.