Coprocessing using H2S as a promoter

Coprocessing of Forestburgh subbituminous coal with Cold Lake vacuum bottoms in the presence of H₂S as a promoter using a continuous-flow bench scale pilot plant resulted in high coal and pitch conversions and distillate yields. On the basis of the results, it is proposed that H₂S acts as a hydrogen donor under coprocessing conditions. The hydrogen transfer from H₂S to radicals that are formed from coal or bitumen can take place directly or via coal-derived liquids. The activity of H₂S under coprocessing conditions is also compared with the activity of pulverized coal impregnated with iron sulphate.     

Liquefaction of coal in a petroleum fraction under mild conditions

Experimental studies on a mild coal liquefaction process for extending the petroleum fuel supply are presented. In this process, coal is dissolved in bottoms from fluid catalytic cracking (FCC), a thermally stable, highly aromatic refinery stream, without added hydrogen and under mild conditions. After ash removal, the product mixture of coal liquid and FCC bottoms is a pumpable fluid and can be used as a boiler fuel. Further upgrading to turbine fuel may be possible.At 600–800°F, 0.1 to 5 h, and 0–1000 psig, conversion of a bituminous coal to pyridine soluble, gas and water was about 90%, while that of lignite was about 60%. Improved product quality was favored by increased reaction pressure. The operable solvent to coal ratio can be as low as 1.3. This ratio can be further reduced if provisions are made to recycle part of the solvent. However, the efficiency of the recovered solvent decreases with each recycle due to a gradual replacement of labile α hydrogen by β hydrogen.     

Quantitative study on cross-linking reactions of oxygen groups during liquefaction of lignite by a new model system

Cross-linking reactions (CLR) of oxygen groups during liquefaction of lignite were quantitatively studied by a new model system. Chinese Yitai lignite (YT) was first oxidized by nitric acid at 70 °C and about 98% of the oxidized sample could be dissolved in tetrahydrofuran (THF) at room temperature. Then benzyl alcohol, PhCH₂OH (BA), as a model compound was added into the oxidized coal, also acted as solvent in the subsequent liquefaction. Temperature-programmed reactions (TPR) at liquefaction conditions under hydrogen atmosphere were performed to evaluate the CLR by quantitative analysis of THF-insoluble solid products (THFI) after reaction. Extensive CLR were observed even under high pressure of H₂ at 200-400 °C, and more than 51.7% and 81.2% of the THFS fraction was converted into the THFI at 300 °C with tetralin (TET) and BA as solvent, respectively. The THFI fraction was almost solely caused by the CLR, which makes it possible to quantitatively study the CLR by analyzing the amount of the cross-linked solid products (CSP). The pyrolysis behaviours of CSP and oxidized coal were examined by TG. Other model compounds containing oxygen-functional groups (alcohol, phenol, carboxyl, carbonyl and ether groups) can also be used in this model system to study CLR of oxygen groups in low-rank coals.     

Co-liquefaction of lignite and sawdust under syngas

Individual and co-liquefaction of lignite and sawdust (CLLS) under syngas was performed in an autoclave and the effects of temperature, initial syngas pressure, reaction time and ratio of solvent to coal and biomass on the product distribution of CLLS were studied. Sawdust is easier to be liquefied than lignite and the addition of sawdust promotes the liquefaction of lignite. There is some positive synergetic effect during CLLS. In the range of the experimental conditions investigated, the oil yield of CLLS increases with the increase of temperature, reaction time (10-30 min) and the ratio of the solvent to the feedstock (0-3), but varies little with the increase of initial syngas pressure. Accordingly, the total conversion, the yield of preasphaltene and asphaltene (PA + A) and gas, changes by the difference in operation conditions of liquefaction. The gas products are mainly CO and CO₂ with a few C₁-C₄ components. The syngas can replace the pure hydrogen during CLLS. The optimized operation conditions in the present work for CLLS are as follows: syngas, temperature 360 °C, initial cold pressure 3.5 MPa, reaction time 30 min, the ratio of solvent to coal and sawdust 3:1. Water gas shift reaction occurs between CO in the syngas and H₂O from coal and sawdust moisture during the co-liquefaction, producing the active hydrogen which increases the conversion of liquefaction and decreases the hydrogen consumption.     

Chemistry of hydrogen sulphide under coal liquefaction conditions: 1. Modelling hydrogen transfer catalysis

The work reported here represents initial attempts to develop a complete kinetic and mechanistic understanding of the reaction chemistry of H₂S under coal liquefaction conditions, using both model systems and coal. Hydrogen sulphide was found to promote/catalyse the transfer of hydrogen from tetralin to 2-hydroxyquinoline (2-HOQ). The presence of H₂S can increase the rate of hydrogen transfer from tetralin to 2-HOQ by a factor of 10 compared with the same reaction run in the absence of H₂S. The energy of activation for hydrogen transfer was found to decrease by ≈5 kcal mol⁻¹ in the presence of H₂S. The presence of H₂S was also found to promote loss of oxygen from 2-HOQ to form small amounts of quinoline. No evidence of CC or CN bond cleavage in 2-HOQ was noted under any of the reaction conditions studied. These results suggest that the presence of H₂S reduces the temperatures necessary to promote effective hydrogen transfer from tetralin by 50–75 °C. Moreover, they imply that similar effects occur in H₂S-promoted coal liquefaction.     

Catalytic liquefaction of various coals using a mixture of carbon monoxide and water

In a batch-autoclave, twenty coals were liquefied using a cobalt-molybdenum oxide catalyst with a mixture of CO and H₂0 at 400 °C with or without vehicle oil. Furthermore, lignite and peat were liquefied on tungsten oxide catalyst at 300 °C in the absence of CO. The reactivity of coal in this liquefaction is found to depend strongly on its rank. The vehicle oil significantly influences the extent of the water-gas shift reaction, especially when bituminous coals are liquefied, by dissolving such coals. Liquefaction of coal by this process is considered to take place via three routes: hydrogenolysis by the nascent hydrogen produced from the shift reaction; dissolution of coal into the vehicle oil which is an initial stage of hydrogenolysis; and a solvolytic reaction with H₂O, such as hydrolysis.     

Coal feed flexibility in the Exxon Donor Solvent coal liquefaction process

The Exxon Donor Solvent (EDS) Process has been successfully employed to liquefy coals of varying rank. Bituminous, subbituminous and lignitic coals have been processed in the continuous, integrated 40 kg day^?1Recycle Coal Liquefaction Units and 1 t day^?1 Coal Liquefaction Pilot plant located at Baytown, Texas. Recent operations show that significant improvements in total liquid yield, as well as additional flexibility in product distribution, can be achieved with recycle of liquefaction bottoms. The impact of the type of coal and mode of operation on product yield and distribution as well as pilot unit operability are discussed. Specific changes in process configuration have been explored and are desirable for different coals and can be used to produce a variety of products. The implication of these recent results on defining the coal liquefaction reaction paths is discussed.     

Differences in the behaviour of US bituminous and subbituminous coals during short contact time liquefaction

The short contact time (SCT) liquefaction of Belle Ayr subbituminous coal has been compared with that of Illinois No. 6 and Pittsburgh seam bituminous coals. Each bituminous coal was highly solubilized (90 wt%, daf coal) in 3–4 min at 450 °C and 13–16 MPa hydrogen pressure. More than 80 wt% of each coal was converted to solvent-refined coal (SRC, pyridine-soluble residuum), with only small quantities of distillate oil and C₁–C₄ gas being formed. A longer reaction (up to 30 min) gave only a small increase in total conversion, but gas and distillate yields increased significantly. Iron sulphides did not appear to catalyse coal solubilization. By contrast, only 65 wt% of the Belle Ayr coal dissolved rapidly in SCT liquefaction and pyrite addition catalysed the conversion of the remaining insoluble organic matter (IOM). With an equivalent amount of pyrite present the Belle Ayr coal also gave more C₁–C₄ gas and substantially more distillate in SCT liquefaction than the bituminous coals. These differences in product distributions obtained from bituminous and subbituminous coals in SCT liquefaction can be rationalized on the basis of differences in the structures of the starting coals. However, the origin of high IOM yields with the Belle Ayr coal remains unclear.     

Hydroliquefaction of Wyodak coal using bottoms recycle

Wyodak coal has been liquefied using recycle solvents consisting of blends of Wyodak coal-derived distillates and SRC or SRC oils, asphaltenes and oils plus asphaltenes. Whilst the quality of the distillate portion of the bottoms recycle is maintained by hydrogenation and distillation in the Exxon Donor Solvent (EDS) process, no reported efforts have been made to hydrogenate the nondistillable portion of the EDS bottoms recycle solvent nor the bottoms recycle solvent in the SRC-II process. As hydrogenation of the distillate portion of the recycle solvent in the EDS process increased Wyodak coal distillate yields, this study was initiated to determine whether hydrogenation of the nondistillable portions of Wyodak coal-derived bottoms recycle solvent would show similar beneficial effects. Results suggest that distillable liquid yields in the range of 55–60 wt% of dry Wyodak coal can be obtained using mildly hydrogenated SRC or SRC oils plus asphaltenes as a bottoms recycle solvent component. This result can be compared to distillable liquid yields of 40 wt% of dry, Wyodak coal obtained from the EDS process using bottoms recycle. Further, the unhydrogenated, SRC-derived oil and asphaltene portions of the recycle solvent also appear to be effective solvent components. However, the most effective solvents were obtained using hydrogenated SRC or SRC-derived oils plus asphaltenes.     

Coal liquefaction catalysis: Iron pyrite and hydrogen sulphide

An unreactive hvC bituminous coal has been hydrogenated in a batch-stirred reactor using pyrite, hydrogen sulphide, and pyrite+hydrogen sulphide as catalysts. The data indicate that H₂S is an active homogeneous catalyst for coal liquefaction, and suggest that pyrite may be acting indirectly as a catalytic agent via H₂S release.     

Catalysis of gasification of coal-derived cokes and chars

Calcium is the most important in-situ catalyst for gasification of US coal chars in O₂, CO₂ and H₂O. It is a poor catalyst for gasification of chars by H₂. Potassium and sodium added to low-rank coals by ion exchange and high-rank coals by impregnation are excellent catalysts for char gasification in O₂, CO₂ and H₂O. Carbon monoxide inhibits catalysis of the CH₂O reaction by calcium, potassium and sodium; H₂ inhibits catalysis by calcium. Thus injection of synthesis gas into the gasifier will inhibit the CH₂O reaction. Iron is not an important catalyst for the gasification of chars in O₂, CO₂ and H₂O, because it is invariably in the oxidized state. Carbon monoxide disproportionates to deposit carbon from a dry synthesis gas mixture (3 vol H₂ + 1 vol CO) over potassium-, sodium- and iron-loaded lignite char and a raw bituminous coal char, high in pyrite, at 1123 K and 0.1 MPa pressure. The carbon is highly reactive, with the injection of 2.7 kPa H₂O to the synthesis gas resulting in net carbon gasification. The effect of traces of sulphur in the gas stream on catalysis of gasification or carbon-forming reactions by calcium, potassium, or sodium is not well understood at present. Traces of sulphur do, however, inhibit catalysis by iron.     

An investigation of the role of hydrogen sulphide in coal liquefaction catalysis by high-temperature and high-pressure e.s.r.

The role of hydrogen sulphide (H₂S) as a coal liquefaction catalyst was tested using two typical coals having different ash content and mineral matters by means of high-temperature and high-pressure e.s.r. For Illinois No. 6 coal having pyrite as minerals, a slight increase in radical concentration in a coal/H₂S system was observed at about 500 K and then drastic increase in radical concentration at above 620 K. On the other hand, in a coal/N₂ system, the increase in radical concentration was much smaller.The effect of H₂S on the change of radical concentration for Yallourn coal which has little ash content was not remarkable. It was concluded that H₂S is a promoter of liquefaction in presence of iron, but has little inherent catalytic function itself. High-temperature and high-pressure e.s.r. is found to be a useful tool to understand the synergistic effect of H₂S-iron sulphide in a coal liquefaction catalyst.     

Chemical composition and toxicological activity of liquefaction materials derived from different feed coal ranks

Samples of recycle solvent from the bottoms recycle mode of the EDS direct coal liquefaction process using bituminous, sub-bituminous, and lignite coal feeds were chemically characterized and tested for toxicological response. The H-Coal heavy fuel oils derived from bituminous and sub-bituminous coals were also analyzed. Chemical methods of analysis included adsorption column chromatography, high-resolution gas chromatography, gas chromatography/mass spectrometry, and low-voltage probe-inlet mass spectrometry. The toxicological activity of selected samples was evaluated using the standard histidine reversion microbial mutagenicity assay, an initiation/promotion assay for mouse-skin tumorigenicity, and a static bioassay with Daphnia magna for aquatic toxicity of the water-soluble fractions. Both materials derived from the bituminous coals had the following chemical characteristics as compared to their sub-bituminous coal and/or lignite-derived counterparts: higher concentrations of polycyclic aromatic hydrocarbons (PAH), nitrogen-containing polycyclic aromatic compounds, and hydroxy-substituted PAH; lower concentrations of aliphatic hydrocarbons; and a generally increased molecular weight distribution of approximately ten atomic mass units. Toxicological testing indicated a general trend of increased biological activity of the coal liquefaction products with increasing feed coal rank.     

Catalytic hydrotreating of 1-methylnaphthalene as a screening test

Catalytic hydrotreating of 1-methylnaphthalene, a component of most recycle vehicles in coal liquefaction processes, can provide a useful screening test for three catalytic functions: ring hydrogenation, hydrodemethylation (HDM), and ring hydrocracking to give substituted benzenes. Detailed information is obtained from the pressure change on reaction and from gas chromatographic analyses of both the product gas and the product liquid. A commercial Co/Mo/Al₂O₃ catalyst tested at 450°C shows very little incremental HDM compared with a no-catalyst control, no ring hydrocracking, but subtantial ring hydrogenation. At 500°C, all reactions are more extensive. A low-temperature ash from Kentucky coal is relatively inactive at 450°C except for HDM.     

Highly active limonite catalysts for direct coal liquefaction

The properties of limonite in Australia and Indonesia were examined by using X-ray diffraction, Mössbauer spectroscopy, Thermal gravimetric analysis (TGA) and TEM–EDX in relation to the catalytic activities in the liquefaction of low-rank coals. The molar ratio of H₂O/Fe in limonite was determined from the weight loss resulting from the dehydration reaction of FeOOH to Fe₂O₃ during heating from 120 to 400 °C in TGA. The H₂O/Fe molar ratio varied from 0.06 for hematite to 0.60 for limonite YY, depending on the hematite content. Results from the pulverization tests showed that the higher value of H₂O/Fe molar ratio resulted in lesser abrasion of medium balls. A unique limonite YY in Australia, containing no hematite, was easily pulverized to sub-micron particle size and showed an excellent oil yield in coal liquefaction. It appeared that H₂O/Fe molar ratio could be one of the most important factors to select the better limonite catalyst for coal liquefaction. Moreover, it was found that Ni containing limonite SO in Indonesia exhibited a higher liquefaction activity than YY catalyst, because of transformation into a smaller crystallite size of pyrrhotite (Fe_1−xS). The agglomeration of pyrrhotites may be suppressed by a strong interaction between FeOOH and Al(OH)₃ such as Fe–O–Al. TEM–EDX analysis suggests that Ni may be located near the Fe_1−xS structure. Oil yield was significantly increased from 43 to 62 wt% daf by CLB addition to the coal slurry in the liquefaction of Banko coal. Finely pulverized limonite catalyst (SO) can be advantageously used in a commercial plant for coal liquefaction in Indonesia due to the low catalyst cost and a high liquefaction activity to obtain a high oil yield.     

Liquefaction mechanism of Wandoan coal using tritium and 14C tracer methods: 2. Liquefaction using 3H labelled gaseous hydrogen

Tritium labelled gaseous hydrogen was used to clarify the role of gaseous hydrogen in coal liquefaction. Wandoan coal was hydrogenated under 5.9 MPa (initial pressure) of ³H-labelled hydrogen and in unlabelled solvents such as tetralin, naphthalene and decalin at 400 °C and for 30 min in the presence or absence of NiMoAl₂O₃ catalyst. Without a catalyst, liquefaction proceeded by addition of the hydrogen from donor solvent. The NiMoAl₂O₃ catalyst enhanced both hydrogen transfer from gas phase to coal and hydrocracking of coal-derived liquids. With NiMoAl₂O₃ catalyst, liquefaction in naphthalene solvent proceeded through the hydrogen-donation cycle: naphthalene → tetralin → naphthalene. The amount of residues showed that this cycle was more effective for coal liquefaction than the direct addition of hydrogen from gas phase to coal in decalin solvent. The ³H incorporated in the coal-derived liquids from gas phase was found to increase in the following order: oil < asphaltenes < preasphaltenes < residue.     

Fate of solvents in the non-catalytic depolymerization of Kentucky bituminous coal

To study the fate of the solvents in the non-catalytic liquefaction of Kentucky bituminous coal, a number of batch liquefaction experiments have been carried out using hydrophenanthrenes and coal-derived hydrogenated recycle solvents. Filtrates from the first runs have been rehydrogenated and used as solvents for additional liquefaction experiments. The reactions have been followed by detailed analysis of the feeds and products.At constant temperature and reaction time, the conversion levels are affected by the amount of transferable hydrogen, H_s (up to a value of about 0.6 wt.% of the feed), by the coal concentration and, to a lesser extent, by the pressurizing gas.The solvents are depleted by isomerization, cracking, and adduction-polymerization reactions. Only about 50% of the initial solvent is available for use in the second-pass runs. In addition, the quality of the second-pass solvents is lower than that of the initial solvents due to a decrease of 6-membered hydroaromatic rings and an increase of 5-membered hydroaromatic rings which are poor hydrogen donors.     

The economics of hydrogen and carbon monoxide separation with cuprous ammonium lactate solutions

A process is proposed for making hydrogen from coal which completely eliminates low temperature and reduces the amount of high temperature shift conversion. The resulting 1:1 H₂CO mixture is separated by absorption and reaction in a cuprous ammonium lactate solution at 1000 p.s.i.a. The hydrogen is used for large scale coal liquefaction. Regeneration of the cuprous ammonium lactate solution results in a sulfur and particulate free carbon monoxide stream suitable for electric power generation.A comparison of the economics of this alternative with conventional high and low temperature shift conversion shows an increase in the process efficiency as well as reduction in the amount of capital required. This, plus other savings, results in carbon monoxide costing 0.988 $/MSCF or 3.095 $/MM Btu. On an equivalent Btu basis, this is 70.9% of the cost of hydrogen by conventional coal conversion. Thus, substitution of separation for shift conversion results in a substantial product cost reduction.     

Removal of sulfur in the reduction of iron-ore concentrates by coal

In lean coal and lignite, sulfur is predominantly present as organic compounds. According to experiments with a QMC-230 mass spectrometer and an IR absorption analyzer, the removal of sulfur in the reduction of iron-ore concentrates is hindered by the adsorption of sulfur-bearing gases and its absorption by the reduced iron to form FeS, which is not reduced by carbon or hydrogen. Considerable sulfur removal is only observed within a calcium-oxide overburden, by the reaction CaO + H₂S = H₂O + CaS.     

煤炭直接液化技术研究

我国煤炭直接液化技术研究已达到国际先进水平．兖州、天祝、神府烟煤和先锋．沈北、东胜褐煤都是较好的直接液化原料煤。煤直接液化的馏分油最适宜生产高辛烷值汽油、优质喷气燃料和催化重整制取芳烃原料油．两段催化液化由1t无水无灰煤生产5bb1馏分油．煤油共炼与直接液化相比较，简化了工艺过程，改进了馏分油产率和质量。我国煤直接工艺发展方向是煤油共炼或两段催化液化工艺。