Retrogressive Reactions Research Articles

96/00245 Texaco gasification process and its application in China

This chapter discusses the synergistic effects of coprocessing originated from interactions between coal and heavy oil. In a study described in the chapter, mixtures of Japanese Taiheiyo coal and Athabasca oil sand bitumen (AOB) with different coal concentrations were used as feeds. The results of the coprocessing reactions of mixtures with different coal concentration are shown. Although the original AOB contained no benzene insoluble fraction (BI), BI was produced with 5 wt% yield after the reaction of pure AOB. A mixture containing 2 wt% coals produced larger amount of HS and smaller amount of BI than the reaction of pure AOB. The addition of a small amount of Taiheiyo coal to AOB resulted in synergistic oil production by suppressing retrogressive reactions, similarly to a mixture of Forestburg Subbituminous C coal and Cold lake vacuum bottoms. With an increase in the coal concentration, the hexane soluble yield decreased, accompanied by an increase in the BI yield. Degree of hydrogen consumption for mixtures containing less than 25 wt% coal was relatively small while a serious increase was observed for mixtures containing more than 30 wt% coal.

96/00256 Characterization of ash and char formations in advanced high temperature particulate filtration systems

This chapter discusses the synergistic effects of coprocessing originated from interactions between coal and heavy oil. In a study described in the chapter, mixtures of Japanese Taiheiyo coal and Athabasca oil sand bitumen (AOB) with different coal concentrations were used as feeds. The results of the coprocessing reactions of mixtures with different coal concentration are shown. Although the original AOB contained no benzene insoluble fraction (BI), BI was produced with 5 wt% yield after the reaction of pure AOB. A mixture containing 2 wt% coals produced larger amount of HS and smaller amount of BI than the reaction of pure AOB. The addition of a small amount of Taiheiyo coal to AOB resulted in synergistic oil production by suppressing retrogressive reactions, similarly to a mixture of Forestburg Subbituminous C coal and Cold lake vacuum bottoms. With an increase in the coal concentration, the hexane soluble yield decreased, accompanied by an increase in the BI yield. Degree of hydrogen consumption for mixtures containing less than 25 wt% coal was relatively small while a serious increase was observed for mixtures containing more than 30 wt% coal.

96/00250 The anode: Its position in carbon history

This chapter discusses the synergistic effects of coprocessing originated from interactions between coal and heavy oil. In a study described in the chapter, mixtures of Japanese Taiheiyo coal and Athabasca oil sand bitumen (AOB) with different coal concentrations were used as feeds. The results of the coprocessing reactions of mixtures with different coal concentration are shown. Although the original AOB contained no benzene insoluble fraction (BI), BI was produced with 5 wt% yield after the reaction of pure AOB. A mixture containing 2 wt% coals produced larger amount of HS and smaller amount of BI than the reaction of pure AOB. The addition of a small amount of Taiheiyo coal to AOB resulted in synergistic oil production by suppressing retrogressive reactions, similarly to a mixture of Forestburg Subbituminous C coal and Cold lake vacuum bottoms. With an increase in the coal concentration, the hexane soluble yield decreased, accompanied by an increase in the BI yield. Degree of hydrogen consumption for mixtures containing less than 25 wt% coal was relatively small while a serious increase was observed for mixtures containing more than 30 wt% coal.

Liquefaction of Black Thunder coal. 1. Petrographic examination of residues

Residues from the liquefaction of Black Thunder subbituminous and Illinois No. 6 bituminous coals in an autoclave and a bench unit were examined petrographically. Optical microscopy proved valuable for ranking the samples on the basis of overall coal conversion and presence of vitroplast, granular residue and inertinite. It was observed that in the autoclave that runs on Black Thunder coal, K 2CO 3 was a superior water gas shift reaction catalyst to NaAlO 2, or a combination of CS 2 and Fe or Mo catalysts. The amount of vitroplast showing vacuoles and cenospheric morphology in the residues was inversely related to the CO conversion, indicating that the mechanism of vitroplast dissolution is linked to the availability of active CO intermediates (e.g. formate ion, HCOO −). A CO-steam mixture was more effective than syngas or pure H 2 and N 2 in increasing Black Thunder coal conversion, and resulted in greater morphological changes to the coal particles. In contrast, for Illinois No. 6 coal pure H 2 had a greater effect on coal solubilization and overall conversion than pure CO at the same temperature; this was attributed to the absence of carboxylates to react with the formate ions. Higher mesophase and coke contents were detected in some bench unit runs on Black Thunder coal that were operated in counterflow mode. Higher severity, poorer mixing, longer residence time and a reduction in pressure by almost 3.5 MPa are believed to be responsible for the retrogressive reactions forming mesospheres in these cases.

Hydrothermolysis of a Silica-Immobilized Diphenylethane

The compound 1-(4'-hydroxyphenyl)-2-phenylethane attached through an Si-O-Ar linkage to fumed silica was subjected to thermolysis (390-410 °C) under D 2 and N 2 (14 MPa). Product distributions under D 2 are similar to those previously observed in vacuum except for increases in yields of benzene and phenol expected as a consequence of hydrocracking. The high pressure of D 2 does not inhibit retrogressive reactions (rearrangement, cyclization) previously found to be promoted by restricted mass transport conditions. A demonstrated silica-promoted H-D exchange of small amounts of phenolic compounds present in equilibrium with surface-attached materials under the closed, high-pressure reactor conditions required for D 2 experiments complicates interpretation of deuterium distribution information. However, non-hydroxylated aromatic rings are immune to this process and measurement of their D incorporation shows that the normal D-atom-promoted exchange is more efficient in the gas phase than on the silica surface.

7.液化反応の初期過程に関する研究 : 水素移動と逆反応の制御

7.液化反応の初期過程に関する研究 : 水素移動と逆反応の制御

Addition Effects of Coal-Derived Oil and Coal on Upgrading of Oil Sand Bitumen

The mechanism of synergistic interaction between bitumen and coal in coprocessing was investigated in conjunction with hydrogen transfer between them. Two types of reaction systems were used in this work: the upgrading of bitumen and coal-derived oil, and the coprocessing of bitumen with either coal-derived oil or coal. Considerable retrogressive reaction was observed in the upgrading of bitumen alone at 450 °C but was effectively suppressed by the addition of either coal-derived oil or coal. These results strongly suggest that both coal-derived oil and coal act as good hydrogen donors or shuttlers in the coprocessing. Furthermore, their addition resulted in more production of light oil from bitumen. The conversion of coal into toluene solubles was influenced by the concentration of coal itself in the slurry feed, but the formation of distillable oil from coal seemed to be negligibly small.

Thermolysis of phenethyl phenyl ether. A model of ether linkages in low-rank coal

Currently, an area of interest and frustration for coal chemists has been the direct liquefaction of low rank coal. Although low rank coals are more reactive than bituminous coals, they are more difficult to liquefy and offer lower liquefaction yields under conditions optimized for bituminous coals. Solomon, Serio, and co-workers have shown that: in the pyrolysis and liquefaction of low rank coals, a low temperature cross-linking reaction associated with oxygen functional groups occurs before tar evolution. A variety of pretreatments (demineralization, alkylation, and ion-exchange) have been shown to reduce these retrogressive reactions and increase tar yields, but the actual chemical reactions responsible for these processes have not been defined. In order to gain insight into the thermochemical reactions leading to cross-linking in low rank coal, we have undertaken a study of the pyrolysis of oxygen containing coal model compounds. Solid state NMR studies suggest that the alkyl aryl ether linkage may be present in modest amounts in low rank coal. Therefore, in this paper, we will investigate the thermolysis of phenethyl phenyl ether (PPE) as a model of 0-aryl ether linkages found in low rank coal, lignites, and lignin, an evolutionary precursor of coal. Our results have uncovered a newmore » reaction channel that can account for 25% of the products formed. The impact of reaction conditions, including restricted mass transport, on this new reaction pathway and the role of oxygen functional groups in cross-linking reactions will be investigated.« less

An Investigation of Hydrogen Transfer from Naphthenes during Coprocessing

Hydrogen transfer from naphthenes to aromatics, coal, resid, and coal plus resid has been investigated at 430 °C in a N 2 atmosphere. The reaction of perhydropyrene (PHP) with anthracene (ANT) resulted in the formation of pyrene (PYR) and dihydroanthracene. The weight percents of the products formed varied according to the ratio of ANT:PHP used with a minimum appearing at a 2:1 weight ratio. Longer reaction times and high ANT:PHP ratios also yielded tetrahydroanthracene. Reactions of Illinois No. 6 coal from the Argonne Premium Coal Sample Bank with PHP, ANT, and PYR resulted in higher coal conversion with PHP and lower with ANT and PYR. Reactions of PHP with resid resulted in less retrogressive reactions occurring in the resid than with either PYR or ANT

Coal structure: inferences from catalytic hydrogenation

The early stages of low-temperature catalytic hydrogenation were studied with the aim of following changes in the macromolecular network component of coal during catalysed hydropyrolysis/hydroliquefaction. Reactions were carried out using a subbituminous coal in the presence of MoS 2 at 15 MPa H 2 and 300–450 °C in a tubing bomb reactor and a swept fixed-bed reactor. The changes in the coal structural network were characterized by volumetric swelling ratios in pyridine, infrared spectroscopy and solid-state nuclear magnetic resonance and the mineral matter content was determined by low-temperature ashing. The oils were analysed by chromatography. The use of two different reactors allowed the effect of the hydrogenation system on the coal network structure to be assessed. To infer information on coal structure, the fixed-bed reactor is preferable because retrogressive reactions are minimized. However, in the tubing bomb the hydrogenation is deeper, and less severe conditions are needed to obtain high yields of conversion products.

Development of standard direct coal liquefaction activity tests for fine-particle size, iron-based catalysts

The use of low amounts (≤ 0.5 wt %) of unsupported, fine-particle size (< 40 nm), iron-based catalysts in direct coal liquefaction has the potential to enhance desired reactions and minimize retrogressive reactions because of the very high surface areas and good dispersions attainable with these catalysts. The objectives of this project are to establish standard activity test procedures for these types of catalysts and to use these procedures at Sandia National Laboratories for evaluating and comparing the activities of the many catalyst formulations being developed in the Advanced Research Coal Liquefaction Program that is funded by the United States Department of Energy's Pittsburgh Energy Technology Center (PETC)

Supercritical toluene extraction of maceral concentrates obtained from Turkish coals

Five Turkish coals of rank varying from high volatile bituminous to sub-bituminous C were separated into four fractions by sequential sink-float treatment with cesium chloride solutions of different densities. Following the maceral analysis, each fraction was subjected to supercritical toluene extraction at 400°C and 100 atm. The extracts were separated into three fractions, namely preasphaltene, asphaltene and oil. Oil fractions were further separated into paraffinic, aromatic and polar sub-fractions. It is observed that SCG toluene extraction produces higher extract yields in lighter maceral concentrates when compared with those obtained from denser fractions. The average molecular weights of the extracts obtained from coals and from their corresponding maceral concentrates are all coal specific. The average molecular weights of the SCG extracts indicated that retrogressive reactions during SCG extractions are more prominent in low-rank coals. The oil fractions are dominating in the SCG toluene extracts and this is more prominent in the extracts obtained from sub-bituminous coals. The gaseous product formations during SCG extraction of the whole sub-bituminous coals are substantial but this is remarkably reduced during the SCG extraction of the corresponding maceral concentrates.

Model compound studies on coal/oil coprocessing chemistry. Part I: Sulfur-hydrogen compound interactions

Interaction of sulfur model compounds with aliphatic, aromatic and hydroaromatic hydrocarbons under various conditions mimicking proposed coprocessing techniques are described. Results suggest that aliphatic thioether compounds will be much more reactive than aromatic sulfur compounds unless an effective hydrogen supply is present to hydrogenate these compound types. In the absence of an effective hydrogen source, phenyl sulfide and benzothiophene underwent retrogressive reactions producing higher molecular weight products containing new aromatic CC and CS bonds.

A comparison by stable isotope mass spectrometry of coal-oil coprocessing under severe-hydrotreatment and thermal conditions

The 13C 12C ratios of saturated, aromatic, polar and asphaltene fractions produced by coprocessing of Point of Ayr coal with heavy petroleum residues under severe hydrotreatment conditions were measured by isotope ratio mass spectrometry. The incorporation of coal carbon into the different fractions was assessed after corrections for catalytic hydrocracking of the end members and for retrogressive reactions. For aromatic, polar and asphaltene products, incorporation of coal carbon was similar to that previously observed for thermal coprocessing and was independent of the oil used. An increase in the saturated fraction during severe hydrotreatment is attributed to hydrothermolysis of bound long alkyl chains, and is consistent with gas chromatographic analysis.

液化における逆反応の解析

The object of this paper is to reduce production of residue discharged from coal liquefaction. Some kinds of residue, for example difference of reaction temperature, have been examined for their boiling point distribution. From these results, the process of retrogressive products is estimated.In addition, to make sure the mechanism of retrogressive reaction on coal liquefaction, the corresponding raw coal was reacted at various conditions.

ロシアにおける石炭液化研究

The present status of coal liquefaction technology (ST-5 and ST-75 projects) in Russia was investigated. The ST-5 project (7-10t-coal/d process development unit) was promoted by Fossil Fuel Institute and its opearation study at Tula was begun in 1986. The coal sample used was mainly Borodinsky brown coal from Kansk -Achinsk basin, which is abundantly reserved in the province of Krasnoyarsk.The process is characterized by the low hydrogen pressure of less than 10MPa, the use and recovery of higher active and dispersion molybdenum catalyst, the addition of organic compounds for the suppression of retrogressive reaction, and the use of hydrotreated recycle solvent. The conversion of coal into gas, water and liquid fractions was more than 70 wt% daf under standard reaction conditions.The ST-75 project (100t-coal/d pilot plant) was started near Beryozovo deposit in Kansk-Achinsk basin in 1986 to produce gasolin, diesel and jet fuels. However, the project was quited in 1992 for financial reason and a part of the equipments purchased was transfered to the ST-5 plant.

Thermal behavior of coals at temperatures as low as 100-350.degree.C: heat treatment of THF-insoluble extract from carbon disulfide-NMP mixed solvent extraction of Zao Zhuang coal

Heat treatment of THF-insoluble, CS 2 -N-methyl-2-pyrrolidinone (NMP) mixed solvent (1:1 by volume) soluble fraction (TIMS) of the extract, which was obtained from the extraction of Zao Zhuang coal with the same mixed solvent at room temperature, was carried out in several organic solvents at 100-350°C under N 2 atmosphere. Retrogressive reaction of TIMS, i.e., its conversion to the mixed solvent-insoluble fraction (MI), was observed in tetralin (TET), naphthalene (NAP), and 9,10-dihydrophenanthrene (DHP) at temperatures as low as 100 and 175°C, while MI formation at 175°C was suppressed by adding 9,10-dihydroanthracene (DHA) or 1,4,5,8,9,10-hexahydroanthracene (HHA), which are much stronger hydrogen donors than TET, NAP, or DHP

Pyridine treatment of illinois no. 6 coal: The effect of pyridine removal on particle morphology and the liquefaction characteristics of the soluble and insoluble components

Illinois no. 6 coal was swollen and extracted with pyridine to produce pyridine-soluble and pyridine-insoluble fractions. The morphology and liquefaction behaviour of the pyridine-insoluble fraction was affected by the manner in which the residual pyridine was removed. Vacuum drying at 110 °C caused collapse of the pore structure compared to the starting coal. This is evidenced by a loss in macropore surface area (measured with N 2) and a decrease in porosity. Using supercritical CO 2 extraction to remove the residual pyridine maintained the expanded pore structure. Both the macropore and micropore (measured with CO 2) surface areas and the porosity increased. The expanded structure, however, collapsed with time. Thermal and catalytic liquefaction of the supercritical-CO 2-extracted sample showed marginal improvements in conversion compared to results for the vacuum-dried sample. Additional liquefaction tests were performed on both the pyridine-soluble and insoluble fractions of the Illinois no. 6 coal, and on samples reconstituted from these fractions in proportions similar to those in the unextracted coal. A hydrogen-donor solvent or catalyst was found to be necessary to prevent retrogressive reactions from occurring in the pyridine-soluble material. The conversion of a reconstituted sample under catalytic liquefaction conditions was less than that observed for the original coal but higher than the value estimated from the conversions of the separate pyridine-soluble and pyridine-insoluble components.

Enhancing low severity coal liquefaction reactivity using mild chemical pretreatment

We describe results from a study in which mild chemical pretreatment of coal has been used to enhance low severity liquefaction reactivity. We have found that ambient pretreatment of eight Argonne coals using methanol and a trace amount of hydrochloric acid improves tetrahydrofuran (THF)-soluble conversions by 24.5 wt% (daf basis) for Wyodak subbituminous coal and 28.4 wt% for Beulah-Zap lignite with an average increase of 14.9 wt% for liquefaction of the eight coals at 623 K (350 °C) reaction temperature and 30 min reaction time. Similar enhancement results occurred using hexane or acetone in place of methanol. Pretreatment with methanol and HCl separately indicated that both reagents were necessary to achieve maximum liquefaction improvement. Acid concentration was the most important pretreatment variable studied; liquefaction reactivity increased with increasing acid concentration up to 2vol%. No appreciable effect on reactivity was observed at higher acid concentrations. Although vapour phase alcohol/HCl mixtures have been shown to partially alkylate bituminous coals, analysis of Wyodak and Illinois no. 6 coal samples indicated that no organic phase alteration occurred during pretreatment; however, over 90 wt% of the calcium was removed from each coal. Calcium is thought to catalyse retrogressive reactions during coal pyrolysis, and thus calcium removal prior to low severity liquefaction minimizes the rate of THF-insoluble product formation.

Effect of exchangeable cations on liquefaction of low rank coals

Exchangeable alkali and alkaline earth metal cations such as, Na +, K + and Ca 2+, have been found to reduce conversion and product quality during liquefaction of a Wyodak subbituminous coal and a North Dakota lignite. The adverse effect, which increases in the order Na + < K + ⪡ Ca 2+, is probably due to these cations inhibiting hydrogen transfer from the donor solvent or H 2 gas to the coal free radicals, thus promoting retrogressive reactions. The deleterious effect of metal cations may be significantly reduced by preswelling coals prior to liquefaction. Preswelling enhances both the liquefaction yield and product quality. The magnitude of the enhancement is determined by the type of cations present on the coal surface. We have also found that the catalytic activity of iron deposited on a lignite by ion exchange is far superior to the same iron species deposited by slurry mixing.