Ozonolysis of the Semicoking Tar of Coal from the Shubarkol Deposit

The results of studies on the determination of the effect of ozonization on the hydrofining of coal tar from the coal of the Shubarkol deposit are reported. It was established that preliminary ozonization for 60 min makes it possible to increase the total yield of liquid products by 44.8% in the subsequent catalytic hydrogenation conversion of tar (5 MPa, 450°C, and a pseudo-homogeneous Mo-containing catalyst) and to increase the yield of a fraction with boiling points to 180°C by 17.7%, as compared with their concentrations in the parent tar.     

Paramagnetic properties of brown coal from the Kiyaktinskoe deposit before and after mechanical treatment and electron irradiation

Results of a study of the paramagnetic characteristics of brown coal from the Kiyaktinskoe deposit (Kazakhstan) in a native state and after mechanical treatment and electron irradiation are reported. The effects of these actions on changes in the paramagnetic properties of the test coal and on the intensification of a coal hydrogenation process are discussed. It was found that the concentration of free radicals changed only slightly after mechanical treatment in a ball mill at room temperature in an atmosphere of air, whereas the concentration of Fe³⁺ ions noticeably increased. Upon the electron irradiation of coal, the dose dependence of the concentration of free radicals passed through a maximum at a dose of 100 kGy. At the same radiation dose, the yield of a kerosene-gas oil fraction upon the hydrogenation of Kiyaktinskoe coal increased, and the total yield of liquid products increased upon the irradiation of coal and a catalyst (bauxite 094) to a dose of 100 kGy. It was hypothesized that Fe³⁺ ions, which were additionally formed upon coal grinding and irradiation, can serve as an internal catalyst in the course of coal hydrogenation.     

Application of Mechanochemical Activation and γ-Radiation to Increase the Reactivity of Coal from the Shubarkol Deposit in Hydrogenation

The results of the mechanochemical activation of coal from the Shubarkol deposit in an impactgrinding mill and under exposure to γ-radiation with an electron beam on a LU-6 electron accelerator are reported. It was established that, upon the hydrogenation of dispersed coal, the yields of both total liquid products and different distillate fractions increased. The maximum yields of liquid products (66.8%) and gasoline (12.8%) and diesel (18.5%) fractions were noted upon the hydrogenation of coal ground for 30 min. It was shown that the irradiation of coal with an electron beam (a dose of 150 kGy) increased its reactivity in the process of hydrogenation and also facilitated the formation of free radicals and changed the compounds of iron that are the constituents of the catalyst based on natural bauxite from the Turgai deposit.     

Cracking of a mixture of mechanically treated brown coal and petroleum residue

The combined cracking of brown coal and petroleum residue was performed, and the composition of the products obtained was studied. It was found that the mechanical treatment of coal makes it possible to increase the yield of the liquid products of pyrolysis and to improve their quality.     

Composition of hydrogenation products of Borodino brown coal

The composition of liquid products of hydrogenation of brown coal from the Borodino deposit was determined by means of ¹³C NMR spectroscopy and chemical thermodynamics methods. It was shown that the group composition of the liquid hydrogenation products at thermodynamic equilibrium is predictable from the elemental composition of the organic matter of parent coal.     

Non-isothermal liquefaction of liptobiolith coal in supercritical water flow and effect of zinc additives

The liquefaction of liptobiolith coal in water vapor and supercritical water (SCW) flow at uniform increase in temperature from 300 up to 470 °C and in SCW flow at 400 °C (30 MPa) with addition of zinc shavings to coal has been investigated. Temperature dependences of the yield of liquid and volatile products and kinetic parameters of the process have been obtained. The yields of oil, resin, asphaltene and volatile products in relation to the coal organic matter (COM) are 23.2, 16.1, 5.1 and 14.1%, respectively. CO₂, CO, H₂S and C₁–C₄ alkanes prevail in the composition of volatile products. The generation of oil, resin and asphaltene are found to have occurred in terms of the simultaneous chemical reactions of cleavage of the COM aliphatic CC bonds, while the volatile products result from the consecutive transformations of the COM components in the bulk and SCW solution. Participation of H₂O molecules in thermochemical transformations of COM leads to increase in the oxygen amount in the conversion products and residue by 13.2%. Hydrogen and heat evolution during zinc oxidation by SCW provides for the hydrogenation of COM in situ. Addition of zinc to coal results in increase in the volatile products yield up to 48.6% and decrease in the conversion residue yield up to 20.8%. Under these conditions the yield of resin does not change, while the yields of oil and asphaltene decrease up to 21.2 and 2.5%, respectively. Based on the sulfur balance it is revealed that ≈40% of sulfur atoms pass into ZnS owing to the reactions of H₂S with Zn and ZnO resulting in the removal of H₂S from the volatile conversion products.     

Changes in composition of solvent-refined coal with severity of hydrogenation

The effects of mild and severe hydrogenation on the chemical composition of solvent-refined coal (SRC) produced from Wyodak subbituminous coal in the direct coal liquefaction SRC-I process were investigated. The yields of solvent-derived fractions of ‘oils’ and ‘asphaltenes’ increased with increasing severity of hydrogenation at the expense of ‘preasphaltenes’. Further separation of ‘oils’ and ‘asphaltenes’, each into three compound-class fractions, revealed more compositional changes. Concentrations of hydrocarbons, nitrogen compounds and hydroxyl aromatics in ‘oils’ increased with increasing severity of hydrogenation. ‘Asphaltenes’, containing nitrogen compounds and hydroxyl aromatic fractions but almost no hydrocarbons, showed an increase in nitrogen-compound concentration with increasing severity of hydrogenation. Hydroxyl aromatic concentration in ‘asphaltenes’ increased under mild but decreased under severe hydrogenation conditions. High-performance liquid chromatography followed by field-ionization mass spectrometry analysis of the hydrocarbon subfractions revealed a complex picture of structural transformations. Over fifty homologous series of aromatic and hydroaromatic hydrocarbons covering a carbon number range from about C₁₂ to C₅₀ were identified and approximate concentrations obtained. Small amounts of partly aromatized pentacyclic triterpane ‘biomarkers’ and their hydrogenation products were found.     

Catalytic cracking of the semicoking tar of coal from the Shubarkol deposit

The results of studies on the application of a catalytic composition synthesized based on finely dispersed silicon-containing natural clay from the Narynkol deposit (Republic Kazakhstan) and a water-soluble silicon salt (Ba–Al–Si) to the process of the catalytic cracking of the semicocking tar of coal from the Shubarkol deposit are reported. It was established that, in the presence of this composition, the yield of a gasoline fraction at a temperature of 420°C and an argon pressure of 3.0 MPa was 34%, and the yield of a diesel fraction was 50%; this fact makes it possible to consider coal tar as a potential raw material for the production of motor fuel components.     

Kinetic model of the hydrogenation of coal from the Karazhir deposit

The kinetic characteristics of the formation of liquid products by the hydrogenation of coal from the Karazhir deposit (Republic of Kazakhstan) were studied. Two kinetic models were considered to describe nonlinear (parallel-consecutive reactions) and linear (consecutive reactions) schemes. Within the frame-work of each particular reaction scheme, analytical equations were obtained to describe the yields of fractions with boiling points to 200, 200–350, and above 350°C; gas; and solid residue depending on time and corresponding calculations were performed. A comparative analysis of the experimental results was carried out according to the two kinetic schemes.     

Composition, structure, and properties of coal from the 2.2 Ulug bed of the Elegestsk deposit in Ulug-Khemsk coal basin

Coal from the 2.2 Ulug bed of the Elegestsk deposit in Ulug-Khemsk coal basin is investigated in terms of international quality certification. According to State Standard GOST 25543-88, the coal is of rank Zh and technological group 2Zh. The coal’s code according to the international system and State Standard GOST 30313-95 is 08 0 01 8 38 05 04 36. Attention is paid to the composition and structure of the coal, which are associated with elevated clinkering properties at high vitrinite reflectance, as well as maximum yield and fluidity of thermostable liquid products in the coal’s plastic mass. These features indicate that the coal’s organic mass contains considerable quantities of thermally unstable hydroaromatic and aliphatic structures. On account of the low oxygen content in the organic mass of coal from the Ulug bed, with high quantities of carbon and hydrogen, much of the hydrogen formed on thermal destruction reacts with the radicals formed, which prevents their polycondensation, and considerable quantities of relatively low-molecular liquid products of the plastic mass are produced. The mineral component is characterized by low content of silicon and aluminum oxides (51.65%) and relatively high content of iron oxide (15.96%) and calcium oxide (15.07%). Accordingly, the base/acid ratio I _b and basicity index B _b are high: 0.692 and 6.29, respectively. The Donets Basin has no counterparts of this coal. Coal from the 2.2 Ulug bed of the Elegestsk deposit in Ulug-Khemsk coal basin may be regarded as a valuable component of coal batch.     

Alcohols as H-donor media in coal conversion. 2. Base-promoted H-donation to coal by methyl alcohol

At 400 °C in 20 min runs, coal was converted by methanol/KOH systems to a product which was extractable by pyridine fully, and 15–25% by methanol. The methanol-sotuble fraction is significantly enriched in hydrogen relative to the starting coal, reduced in both N and organic S, and was fluid at room temperature. It was established that this liquid product was derived from the coal, and not the methanol. The liquid was distillable at 300 °C/133 Pa (1 torr), and an analysis of the liquid by gas chromatography/mass spectrometry techniques shows it to consist of significant quantities of butyrolactone, polymethyl phenols, and some unidentified compounds having major C₄H₇O and C₄H₇O₂ MS fragments. The methanol-insoluble products were hydrogen-enriched also, but to a lesser degree. The suggested conversion scheme is similar to that proposed for isopropyl alcohol, where alkoxide ion donates hydride to the coal, followed by proton abstraction by the anionic intermediate from the alcohol medium. In model-compound studies at 400 °C with the system, it was found that phenyl ether was converted in 33% yield to a collection of polymethyl phenols, similar to those found in the coal distillate. Anthracene was converted in about 80% yield to 9,10-dihydroanthracene. Biphenyl, phenanthrene and bibenzyl were found to be unreactive in our system.     

Hydrogenation of coal from transbaikalia deposits in the presence of a recirculating paste-forming agent

Data on the hydrogenation of coal from the Zashulanskoe field in Transbaikalia in three cycles in the presence of a recirculating coal distillate solvent with a boiling point of 300–425°C are reported. It was found that the degrees of conversion of the organic matter of coal (OMC) into liquid and gaseous products reached in the second and third cycles were 85–88%. The yields of liquid products and gases were 81–85 and 6.9–7.4%, respectively, and the consumption of hydrogen was 2.3–2.4%.     

Hydrogenation of the inertinite macerals of Bayswater coal

Yields of products from the hydrogenation of the inertinite and vitrinite+exinite macerals of the Bayswater (New South Wales, Australia) coal in a batch autoclave were investigated. Samples were hydrogenated for 1 h at 400 and 450 °C with tetralin as vehicle, hydrogen as charge gas and no added catalyst. The results show that the inertinite macerals contributed significantly to the liquid hydrogenation products, in particular to the oil yield obtained at 450 °C.     

Thermodynamic analysis of the gasification of coal from the Daurskoe deposit

The equilibrium composition of the products of the fluidized-bed pressure gasification of brown coal from the Daurskoe deposit in Transbaikalia krai for the production of process gas (in particular, synthesis gas) was calculated with the use of a method of chemical thermodynamics. The gasification was performed at P = 0.1 MPa and the blast coefficient α₁ = 0.3–0.35 in the presence of 36 wt % of water vapor in a temperature range of 100–1500°C. It was found that, at a Cl₀ pressure of 0.1 MPa, a temperature of 850°C, and the air-steam blast composition of α₁ = 0.3 and α₀ + 36 wt % H₂O, the gasification products of the organic matter of coal (OMC) mainly consisted of CO and H₂.     

Direct hydroliquefaction of a low rank soft brown coal

The behaviour of the soft brown coal from the Kostolac Mine (Serbia, Yugoslavia) was investigated during hydroliquefaction carried out in a batch reactor by direct catalytic hydrogenation of the pulverized coal (−160 μm) dispersed in tetralin. The effects of temperature (ranging from 365 to 440°C), pressure (13.5 to 15.0 MPa) and residence time (1 to 8 h) on the yield of individual liquefaction products as well as the petrographic composition of the coal residues were closely followed by separation and analysis of the products. These consisted of liquid products soluble in n-heptane (light oils), n-heptane insoluble products (asphaltenes), the solid coal residue and gaseous products. A good reactivity of this soft brown coal was observed. The yield of liquid products varied from 23 to 64 wt.% (based on dry ash-free coal). A total coal conversion of 80 to 86% was achieved. Petrographic composition and optical properties of the solid coal residues were analyzed microscopically in order to establish the character and intensity of the coal changes. The solid residues were found to consist of 12 various grain categories. The low proportions of unreacted or partly reacted coal grains confirmed the good reactivity of the Kostolac soft brown coal in the applied liquefaction process.     

Liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit

The liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit (800°C; 1 h; activator, KOH) were studied by thermal analysis, IR spectroscopy, and ¹H and ¹³C NMR spectroscopy. They were formed in ∼30% yield; they consisted of pyrogenic water (∼50%) and a resinous mixture of organic substances with increased hydrogen and oxygen contents and decreased carbon and sulfur contents. On heating, potassium hydroxide completely decomposed the quinoid structures of coal, decreased the concentration of aromatic components in resin, and increased the concentrations of CH₃-, -CH₂-, and OH-groups. This is consistent with the well-known thermally initiated reactions of alkaline degradation and dehydrogenation at high temperatures (400–800°C). The thermal lability of resinous products was evaluated, and the heats of combustion (32.4–32.7 MJ/kg) were determined; the latter values indicate that these products can be used as fuel.     

Hydrogenation of the semicoking tar of coal from the Shubarkol deposit

The results of the hydrogenation processing of the semicoking tar (AO Sary Arka Spetskoks, Karaganda, Republic of Kazakhstan) of coal from the Shubarkol deposit in the presence of Mo- and Ni-containing pseudohomogeneous catalytic systems for the production of motor fuel components and chemical substances are reported. It was established that the yield of a gasoline fraction at a temperature of 400°C (5.0 MPa, a 0.015% S additive) was 18.7% with the use of a molybdenum catalyst or 10.6% with a nickel catalyst; therefore, the coal tar can be considered as a potential raw material for obtaining motor fuel components.     

Chemical structure of the high-molecular-weight hydrogenation products of coal from the Zashulanskoe field

The results of experimental studies on the determination of the chemical structure of asphaltenes and preasphaltenes in the liquid products of the hydrogenation of coal from the Zashulanskoe field in the Chita oblast. It was found that, in the preasphaltenes, the value of f _a and the concentrations of oxygen groups (OH, COOH, and C=O) were greater and the concentrations of CH₂ and CH₃ groups were smaller that those in the asphaltenes. The highest concentration of CH₂ groups was found in substances soluble in n-hexane (oils). It is likely that the change in the character of high-molecular-weight hydrogenation products formed from the structural fragments of the organic matter of coal (OMC) largely depended on reaction conditions, namely, the rate of heating and the isothermal exposure time.     

Early coal hydrogenation catalysis

Three inputs were necessary to make catalytic hydrogenation of coal possible. One was the ammonia synthesis which, in 1910, introduced high pressure and temperature into the chemical industry. The second was the experimentation by F. Bergius who showed, in 1913, that coal can be liquefied by adding hydrogen at high pressure and temperature. The liquid products were similar to coal tar. They were not of the quality required for gasoline or diesel fuel production. The use of catalysts to refine the coal oil appeared then to be hopeless since coals contained sulfur, a poison for all then known hydrogenation catalysts. The third input was methanol synthesis in 1923. M. Pier found selective, oxidic catalysts that were less sensitive to sulfur than e.g. the metallic catalyst for the ammonia synthesis.In 1924 M. Pier, in the laboratories of the BASF, prepared sulfur resistant coal hydrogenation catalysts: sulfides and oxides of molybdenum, tungsten, and the iron group metals. With these catalysts it became possible to add hydrogen; split carbon-carbon bonds; and eliminate such heteroelements as sulfur, oxygen and nitrogen from coals and oils. Thus fuels were produced that met petroleum fuel specifications.Optimum catalyst action was achieved by subdividing coal hydrogenation into two stages. The coal was converted, with a dispersed catalyst in the “liquid phase”, into middle oil. This was then hydrogenated over fixed bed catalyst, in the “vapor phase”, to gasoline. On this basis a large scale demonstration plant for the liquefaction of central German brown coal was erected in 1927.The development of catalysts for these two stages proceeded on different routes. Liquid phase catalysts were discarded after one pass through the reactor. They were cheap, or used in very small amounts. It was found soon that coal of different rank required different catalysts, and that the mineral matter of the coal played an important role.The first commercially used vapor phase catalysts were of the hydrorefining type. Hydrocracking activity was achieved by using high temperatures. A great step forward was made in 1930 when a special preparation of tungsten disulfide permitted hydrocracking activity at low temperatures. Thus the first essentially dual function catalyst was found. Its hydrocracking activitity was further increased, and gasolines with a higher octane number were obtained by using it on acidic supports such as materials containing alumina-silica.Such supported catalysts were poisoned by the nitrogen compounds present in coal oils. Therefore a refining step for these oils was needed. The vapor phase was subdivided into the “prehydrogenation” (hydrorefining) and “splitting hydrogenation” (hydrocracking) steps. Further development of catalysts with specific functions for these two steps proceeded rapidly. In addition, separate catalysts were developed for the production of gasolines with a high content of aromatics.The various catalysts developed primarily for the hydrogenation of coal derived oils introduced hydrogen processing into the petroleum refining industry. There they were further modified and improved for the processing of petroleum. These improved catalysts, in turn, will be of help to a future coal liquefaction industry.     

Co-pyrolysis as a method of upgrading some products of coal processing

Co-pyrolysis was investigated as a method of upgrading various products resulting from coal processing. Co-pyrolysis of vacuum residue (VR) with coal extraction products as well as with primary tars from flash pyrolysis leads to a considerably enhanced yield of liquid products. It has been established that superheated steam and increased outgassing rate, favour the yield of liquid products. The proportion of the ingredients in the mixture as well as the quality of the VR also have a definite effect. The excess yield of liquid products in co-pyrolysis of coal extraction products was 8–23 wt%, depending on operating conditions and the composition of the mixture. The flash co-pyrolysis of primary tars yielded a 1.5–15.9 wt% surplus of liquid products depending on the mixture composition. Products originating from co-pyrolysis of these raw materials with VR are characterized by relatively high atomic hydrogen to carbon ratio, usually not less than 1.5 and the total abscence of asphaltenes. Generally, co-pyrolysis of VR with various products of coal processing is comparable with hydrogenation in the light of good yields of liquid products.