Flowing-solvent Reactor Research Articles

Alkanes and solvent dimers in successive extract fractions released from coal during liquefaction in a flowing-solvent reactor

Types of alkanes present in liquefaction product fractions released from coal during successive time—temperature intervals were examined by g.c.—m.s. Experiments were carried out in a flowing-solvent reactor where solubilized products are continuously removed from the reaction zone; tetralin, quinoline and hexadecane were used as the solvent. At 450°C (with 400 s holding) total conversions in tetralin, quinoline and hexadecane were 82.5, 74.7 and 24 wt% (daf), respectively. In tetralin, alkanes were released from coal more readily and at lower temperatures than in quinoline or hexadecane; m.s. signal intensities fell rapidly with increasing reaction temperature. In quinoline, lower intensities of alkane peaks were observed than in tetralin, although the trend with temperature was similar. In hexadecane however, the trend of intensity with temperature was reversed compared with liquefaction in tetralin or in quinoline; the range of alkanes detected was also smaller than in tetralin or in quinoline. The presence of alkenes in the hexadecane extracts suggested a pyrolytic mechanism for the thermal breakdown. Isoprenoid alkanes, pristane and phytane, were detected in the tetralin and quinoline extracts but not those prepared in hexadecane. Materials present in product mixtures and thought to originate with each solvent were briefly investigated: dimers were the most prominent species in tetralin extracts, with only low-intensity dimers being found in quinoline extracts and no apparent formation of higher homologues from hexadecane. These results were compared with the pattern of alkane release from coal during liquefaction in tetralin in a conventional minibomb reactor and in the pentane-soluble fraction of the total (unfractionated) extract from the F-S reactor.

95/01297 Characterization of successive extract fractions released from a sample of coal during liquefaction in a flowing-solvent reactor

95/01297 Characterization of successive extract fractions released from a sample of coal during liquefaction in a flowing-solvent reactor

95/01298 Characterization of successive time/temperature-resolved liquefaction extract fractions released from coal in a flowing-solvent reactor

An experimental study was conducted to investigate the relative efficiency of phenol-water-ether mixture and nitrobenzene system for deasphalting low-asphaltic crude oil residue. Results obtained from the gas-liquid, adsorption-elution and gel permeation chromatographic analyses of the raffinate and extract products revealed an upward trend of the solubility power and the selectivity of the phenol system (for asphaltic material) with solvent-to-residue ratio (SRR). This led to an oil recovery efficiency of 98% at an SRR of 6 compared to 93% achieved with nitrobenzene. However, the deasphalted oil (raffinate) obtained with nitrobenzene contains more of the most desirable saturates. There is also an evidence of improved oil composition at lower solvent-to-residue ratio, due principally to the decline in the selectivity of nitrobenzene toward the asphaltic component at higher solvent proportions. Judging by all the information obtained from this study, phenol-water-ether mixture appears to be a more efficient solvent system than nitrobenzene for deasphalting low-asphaltic crude oil residue.

Characterization of successive time/temperature-resolved liquefaction extract fractions released from coal in a flowing-solvent reactor

This paper reports the characterization of successive extract fractions collected during the liquefaction in tetralin of a UK low-rank bituminous coal (Linby), by the use of size exclusion chromatography and u.v. absorption and u.v. fluorescence spectroscopies in a closely related manner. Successive liquefaction product fractions shift progressively to greater molecular masses with increasing extent of reaction and increasing intensity of reaction conditions; parallel increases in relative concentrations of larger aromatic ring systems are observed. These data suggest that material released from coal during earlier stages of the liquefaction process would be easier to hydrocrack than that released during later stages, under more intense reaction conditions. However, quantitative differences in reactivity between product fractions, resulting from such structural changes, remain to be demonstrated. The results also provide evidence that local distribution densities of larger aromatic ring systems might severely affect the relative ease with which coal dissolution (or in pyrolysis, tar precursor formation) takes place at any given intensity of reaction. This is explained in terms of large aromatic ring systems serving as cross-linking points of high coordination number in coal. Increased densities of larger fused aromatic ring systems near edges or external surfaces of potential molecular fragments would render fragment release from the coal mass — i.e. the depolymerization process — progressively more difficult. This picture of coal thermal breakdown would be consistent with existing data showing (1) yields and molecular mass distributions of pyrolysis tars decreasing rapidly with increasing coal rank for high-rank coals, and (2) yields and molecular mass distributions of liquefaction products decreasing rapidly beyond ∼87 wt% carbon content.

Characterization of Successive Extract Fractions Released from a Sample of Coal during Liquefaction in a Flowing-Solvent Reactor

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacterization of Successive Extract Fractions Released from a Sample of Coal during Liquefaction in a Flowing-Solvent ReactorBin Xu, E. Sebnem Madrali, Fan Wu, Chun-Zhu Li, Alan A. Herod, and Rafael KandiyotiCite this: Energy Fuels 1994, 8, 6, 1360–1369Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November 1994https://doi.org/10.1021/ef00048a027RIGHTS & PERMISSIONSArticle Views94Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

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

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 2O 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.

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

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.

Liquefaction of coals and maceral concentrates in a flowing-solvent reactor

A flowing-solvent liquefaction reactor with a continuous solvent sweep through a fixed bed of coal has been developed. The reactor is heated by computer-controlled direct electrical resistance heating, allowing the application of variable heating rates between 0.1 and 10 K/s to temperatures up to 450 °C and holding times at peak temperature between zero and 1600 s. In contrast to liquefaction experiments using closed (batch) reactors, where products remain within the reactor for the duration of the experiment, solubilised liquefaction products are continuously swept out of the reaction zone, thus minimising the probability of secondary reactions. The apparatus has been proved by performing liquefaction experiments on a selection of European and American coals and maceral concentrates

Comparison of fast atom bombardment mass spectrometry and size exclusion chromatography in defining high molecular masses in coal-derived materials

The detection by fast atom bombardment mass spectrometry (f.a.b.-m.s.) of high molecular mass (greater than 1000 Da) material in coal-derived products was investigated. The pentane insoluble (PI) fractions of liquefaction extracts from maceral concentrates of two UK coals (Linby and Cortonwood), prepared in a low-residence time (less than 10 s) flowing-solvent reactor and fractions of hydropyrolysis tar prepared in a hot-rod reactor at 500 °C were examined.F.a.b.-m.s. spectra of the Cortonwood liptinite concentrate liquefaction extract PI-fraction mounted in a thiodiethanol matrix indicated ions up to molecular masses of about 4000 Da. This appears to be the highest reported molecular mass identified by fast atom bombardment in a coal-derived material. Other liquefaction extract PI-fractions showed somewhat lower molecular masses. The phenolic, basic nitrogen and aromatic fractions of the hydropyrolysis tar indicated ionization up to molecular mass limits between 1500 and 2000 Da. Comparison of these results with size exclusion chromatography (s.e.c.) showed agreement with results for the hydropyrolysis tar fractions; however, the presence of molecular masses in excess of 10000 Da was indicated by s.e.c. for the liquefaction extract PI-fractions. Not all problems associated with vaporization, ionization and detection of high molecular mass materials in f.a.b.-m.s. appear to have been solved, with the choice (polarity) and preparation of matrices for sample mounting remaining an empirical procedure.

A flowing solvent reactor for coal liquefaction with direct electrical resistance heating

A flowing solvent reactor for coal liquefaction has been developed, which uses direct electrical resistance heating of the reactor tube wall to achieve rapid, controllable heating. A computerized control system previously developed for a wire-mesh pyrolysis apparatus is used for temperature control; heating rates between 0.1 and 10 K/s, peak temperatures up to 450 °C, and isothermal holding times from 5 to 1600 s have been obtained. Alternating current is used for heating, allowing a simple thyristor bridge to be used for power control. Solvent is fed from a pressurized reservoir at up to 100 bars, obviating the need for a supply pump. Using this apparatus the effects of a variety of parameters on primary coal liquefaction processes can be examined; the design of the system and typical results are presented.

Liquefaction of coal in a flowing-solvent reactor

A flowing-solvent liquefaction reactor has been used to examine the primary solubilization potential of a range of coals. The reactor configuration allows the suppression of secondary reactions by sweeping the heated zone with a continuous flow of solvent. The design of the system combines low thermal inertia and direct electrical resistance heating to provide closely controlled time-temperature ramping, and a variable preset holding time at the target temperature. Heating rates of 0.1–15K s −1 up to temperatures of 450 °C and hold times of 0–1600 s can be achieved. Data are reported for a range of European and US coals with elemental carbon contents ranging from 74 to 91%. The effect on conversion of reactor pressure, heating rate, temperature, holding time at temperature and solvent flow rate have been determined. In contrast with pyrolysis, results suggest that liquefaction reactivities are relatively insensitive to changes in the heating rate. Comparison with results from micro-bomb reactors has shown that the continuous solvent sweep allows the relatively intact removal of primary solubilization products from the reaction zone. Molecular mass distributions of solubilized products thus obtained have been found to increase with increasing carbon content of the substrate coal (up to ~85%), and to decline with further increases up to 91% carbon content. In general, this reactor configuration appears to offer a promising avenue for analytically probing the more reactive structures of coals without interference from effects of secondary reactions.