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Abstract: Asphaltene (AS) is one of important heavy intermediates of direct coal liquefaction (DCL). It has significant influences on the technology of liquefaction, such as the coking property and the liquefaction efficiency. In this paper, the structure of AS derived from the liquefaction of Xiaolongtan lignite (XLT, a Chinese lignite) was characterized by element analysis, FTIR, UV and fluorescence spectroscopy, and its association was studied by the fluorescence spectroscopy. Results indicate that the aromatic system of AS derived at different liquefaction temperatures mainly consists of 2–3 rings aromatic nucleuses. With the increase of liquefaction temperature, the aliphatic structure is gradually cracked, and the aromaticity of AS and the proportion of large size aromatic nucleus increase. AS molecules easily form the nano-aggregates in a certain concentration of THF solution. The size of the nano-aggregates is independent of the liquefaction temperature and the AS concentration. The associations of ASs, which including intermolecular association and intramolecular association, originate mostly from the π–π interactions between aromatic nucleuses of AS rather than the hydrogen bonding interaction. [Copyright &y& Elsevier]

Abstract: Co-liquefactions of a Chinese Shenfu sub-bituminous coal (SFSBC) and rice straw (RS) over four different coal liquefaction catalysts were carried out and the co-liquefied product preasphaltene (PA) was characterized by elemental analysis, FTIR and gel permeation chromatograms (GPC) measurements. It was found that the four catalysts gave different catalytic activities in the liquefaction of SFSBC and RS alone. Co Mo/Al2O3 and /ZrO2 promoted the oil formation for RS liquefaction due to their solid acidic property, but FeS+S gave the highest catalytic activity for the liquefaction of SFSBC among the four catalysts used in this study. There existed a positive synergistic effect in the co-liquefaction of SFSBC and RS, and the main synergistic interaction was reflected by the promoted formation of oil and PA. The catalytic activities of the four catalysts in the co-liquefaction were quite different from their catalytic activities in the individual liquefaction of SFSBC and RS. FeS gave the lowest catalytic activity for the coal liquefaction alone among the four catalysts, but had the highest promotion to the synergistic effect in the total yield of liquefaction products in the co-liquefaction of SFSBC and RS. /ZrO2 diminished this synergistic effect for the co-liquefaction of SFSBC and RS due to its solid acidic property. It was found that the four catalysts used have higher catalytic activity for the PA, which is from coal liquefaction and converting this part of PA into AS and oil fraction. The average molecular weights of PAs from /ZrO2 and Co Mo/Al2O3 catalysts were lower than those of PAs from FeS and FeS+S catalysts, suggesting that the catalytic hydrogenation activities of /ZrO2 and Co Mo/Al2O3 are higher than those of FeS and FeS+S catalysts. [Copyright &y& Elsevier]

Abstract: In order to understand the molecular structure of coal and the mechanism of coal direct liquefaction, the heavy intermediates of coal liquefaction such as asphaltene (AS) and preasphaltene (PA) were separated into different sub-fractions by column chromatography, respectively. The distributions of fused aromatic nucleuses (FAN) of sub-fractions were determined by synchronous fluorescence combined with the fitting technique of multiple peaks of spectrum. The results indicated that the PA and AS obtained from liquefactions of three Chinese coals were separated into 4 and 2–4 sub-fractions, respectively. The content of three rings FAN was the highest in the major sub-fractions of AS. The major sub-fractions of PA contained not only more single ring aromatic nucleus but also larger FAN than those of AS. Meanwhile, there were more complex aggregations in PA compared to AS. [Copyright &y& Elsevier]

Abstract: The investigation of hydro-conversion behavior of the heavy intermediate products derived from coal direct liquefaction is advantageous to optimize the technological conditions of direct coal liquefaction and improve the oil yield. In this paper, the hydro-conversion of preasphaltenes catalyzed by SO4 2−/ZrO2 solid acid was investigated based on the structural characterization of preasphaltenes and its hydro-conversion products, and the determination of products distribution and the kinetics of preasphaltenes hydro-conversion. The results indicated that the content of condensed aromatic rings increased, and the contents of hydrogen, oxygen and aliphatic side chains of preasphaltenes decreased with the increase of coal liquefaction temperature. The preasphaltenes showed higher hydro-conversion reactivity while SO4 2−/ZrO2 solid acid was used as catalyst. Higher temperature and longer time were in favor of increasing the conversion and the oil+gas yield. The conversion of preasphaltenes hydro-conversion under 425°C, for 40min reached 81.3% with 51.2% oil+gas yield. SO4 2−/ZrO2 solid acid was in favor of the catalytic cracking rather than the catalytic hydrogenation in the hydro-conversion of preasphaltenes. The activation energy of preasphaltenes conversion into asphaltenes was 72kJ/mol. The regressive reactions were only observed at a higher temperature. [Copyright &y& Elsevier]

Abstract: Aggregation of heavy products of coal liquefaction such as preasphaltene is one of important influencing factors on the coking properties of liquefaction technology. In this paper, the aggregation of coal-derived PA in tetrahydrofuran and N-methyl-2-pyrrolidinone has been investigated by gel chromatography, absorption and fluorescence spectroscopy. The results indicate that PA is a complex mixture with lower H/C (atomic ratio 0.61) and contains different chromophores and fluorophores. It shows strong propensity of aggregation and can form nanoaggregates even in the very dilute solution such as 6.25mg/l. With the increasing of PA concentration, the concentration of aggregates increases but the dimension of aggregates is basically invariable. Although a flexion point of the fluorescence intensity integrated can be observed with increasing of PA concentration, it cannot present the concentration where any aggregation starts. It varies with the excitation wavelength. [ABSTRACT FROM AUTHOR]

Hydro-liquefaction of an asphaltene from thermal dissolution of Xinlinguole lignite (XLAS) was carried out, and the effects of catalyst, temperature and reaction time on oil yield and cyclanes content in oil for the potential jet fuel were probed in this study. Comparing the hydrogenation activities of three catalysts i.e. Cu-Ni/γ-Al 2 O 3 , Ni/ZSM-5 and Ni-Mo-S/γ-Al 2 O 3 , it was found that Ni-Mo-S/γ-Al 2 O 3 was the most beneficial for jet fuel production from coal liquefied oil due to it contained a continuous distribution of weaker to stronger acidic sites. It gave the highest oil yield of 68.8%, and cyclanes content of 20.5% in the oil, which displayed the highest hydrogenation activity for arenes saturated hydrogenating among the three catalysts used in the hydro-liquefactions of XLAS at 360 °C for 90 min. For Cu-Ni/γ-Al 2 O 3 , it only contained weak acidic sites therefore it gave the lowest saturated hydrogenating activity. With rising of temperature, oil yield increased, but cyclanes content in oil decreased in the hydro-liquefactions of XLAS under Ni-Mo-S/γ-Al 2 O 3 catalyst. The highest content of cyclanes (29.3%) in oil was obtained at 280 °C for 90 min. Reaction time remarkably affected cyclanes content in oil. With the reaction time prolonging from 30 to 60 min, oil yield and cyclanes content in oil increased. Further prolonging reaction time to 90 min, oil yield hardly increased, but cyclanes content in oil decreased from 23.6% to 20.5% at 360 °C with Ni-Mo-S/γ-Al 2 O 3 catalyst. Some oxygen-containing compounds (OCs) may convert into cyclanes by hydro-deoxygenation (HDO) with increasing of reaction time. [ABSTRACT FROM AUTHOR]