Effect of phenolic compounds on liquefaction of coal in the presence of hydrogen-donor solvent

Phenolic compounds have a remarkable positive effect on coal liquefaction in the presence of tetralin, depending strongly on the character of the coal and on the concentrations of phenols. The solvent-refined coal obtained in the presence of phenol was low in hydrogen content and high in the fraction of aromatic hydrogen; these results corresponded well to the fact that coal conversion increases without increase of hydrogen consumption in the presence of phenols. The effect of phenols on coal liquefaction may be caused mainly by accelerated scission of ether linkages, since the decomposition of 2,2′-dinaphthyl ether was considerably enhanced by the addition of phenols.     

Proton and carbon n.m.r. spectra of butylated coal

The proton and carbon n.m.r. spectra of butylated Illinois No. 6 coal which has been fractionated by gel-permeation chromatography (GPC) are reported. The chemical shifts and spin-lattice relaxation times of model compounds provide the bases for the assignment of the spectroscopic results. The spectra of the various molecular weight fractions are clearly different. There are significant variations in the degree of aromaticity, the presence of linear alkanes, the ratio of C-butylation to O-butylation, the extent of butylation on aliphatic and aromatic carbon atoms, and the amount of carbonyl and vinyl derivatives. The results suggest that electron transfer, proton abstraction, ether cleavage, and elimination reactions are important under the conditions of the Sternberg process and that both nucleophilic and free-radical substitution reactions occur. The results also strongly suggest that the distribution of functional groups in coal is not uniform.     

由煤制取芳烃化合物的研究进展

综述了国内外由煤制取芳烃化合物的三种思路：一是通过将煤直接进行液化获取,或者先将煤液化再从产物中获得芳烃化合物;二是先对煤进行溶剂抽提,然后对产物分类加工制取芳烃化合物;三是将煤进行氧化处理来获得高价值的芳烃化合物。分析了由煤制取芳烃化合物的所面临的产物分离困难、污染环境等问题,并指出了今后需要在分离工艺和催化剂以及如何实现煤的定向转化等方面进行重点研究。     

Measurement and prediction of the emission of pollutants from the combustion of coal and biomass in a fixed bed furnace

The effect of co-combustion of coal and biomass has been studied for a fixed bed appliance originally designed for coal and in widespread use in many parts of the world especially Eastern Europe. Organic, inorganic and gaseous emissions have been measured. Organic compounds have been determined for a range of fuel combinations. These include polycyclic aromatic hydrocarbons PAH, alkyl PAH, a range of oxygenated compounds (including phenols, aldehydes and ketones, oxygenated polycyclic aromatic compounds (O-PAC) and dioxins), polycyclic aromatic sulphur hydrocarbons (PASH), nitrogenated polycyclic aromatic compounds (N-PAC) and common volatile organic compounds (VOC). Inorganic species include trace heavy metals, as well as the gases, CO, CO₂, SO_x and NO_x. The concentration of the trace metals in the ash and fly ash have been compared to equilibrium calculations of the emission profiles during co-combustion.     

Solubility increase of coals by the reaction with alcohol — elucidation of reaction mechanism using model compounds

The reaction mechanism of coal-ethanol reaction was examined using model compounds: phenol, benzylphenylether, diphenylmethane and anthracene. The main reaction for these compounds was the splitting of ether bonds, ethylation of benzene nucleii, hydrogenation of aromatic nucleii and the splitting of methylene linkages. The most important reactions were the first two types. The splitting of ether linkages would reduce the molecular weight of coal and ethylation of aromatic rings would be favorable to the easy dissolution of coal in solvents.     

Effects of solvent and iron-compounds on the liquefaction of brown coal

Hydrogen-donor solvents such as hydrophenanthrene are the most effective aromatic solvents for the liquefaction of brown coal. The hydrogen-donating ability of the solvent is more important for brown coals than for bituminous coals, because the thermal decomposition and subsequent recombination of the structure of the brown coals occurs rapidly. Three-ring aromatic hydrocarbons are more effective solvents than two-ring aromatics, and polar compounds are less effective solvents with brown coals than with bituminous coals. The thermal treatment of brown coal, accompanied by carbon dioxide evolution at temperatures > 300°C, in the presence of hydrogen-donating solvent did not affect the subsequent liquefaction reaction. However, thermal treatment in the absence of solvent strongly suppressed the liquefaction reaction, suggesting that the carbonization reaction occurred after the decarboxylation reaction in the absence of hydrogen donor. To study the effect of various iron compounds, brown coal and its THF-soluble fraction were hydrogenated at 450°C in the presence of ferrocene or iron oxide. The conversion of coal and the yield of degradation products are increased by the addition of the iron compounds, particularly ferrocene, and the yield of carbonaceous materials is decreased.     

Thermal cracking of coal model diaryl ethers in aromatic solvent

Thermal cracking of nine diaryl ethers in a hydrogen donor solvent or 1-methylnaphthalene was studied kinetically. The rate of conversion of the diaryl ethers was first order with respect to the substrate concentration and increased with increase in size of the aryl structure. The relative rate constant of aryloxygen bond cleavage calculated on the basis of first order reaction has indicated that the ease of cracking depends strongly on the aromatic structure and the position of substitution. The conversion rate of 2, 2′-dinaphthyl ether was remarkably enhanced in the presence of hydrogen donor solvent, for example by a factor of ten in the presence of 9, 10-dihydroanthracene. The activation energy of thermal conversion of 2, 2′-dinaphthyl ether was 214 kJ/mole in methylnaphthalene, 151 kJ/mole in tetralin and 88 kJ/mole in dihydroanthracene. The enhancing effect of the hydrogen donor was considered due to hydrogen transfer to the aromatic nucleus of the diaryl ether from the hydrogen donor and successive fast decomposition of hydrogenated ethers.     

On a possible role for electrochemical oxidation in coal liquefaction

The feasibility of coal conversion via electrochemical liquefaction has been investigated. Because of the complicating presence of inorganic materials in coals, humic acids extracted from lignites have been used as model substrates. Considerable reductions in molecular mass, as revealed by size exclusion chromatography, were achieved by anodic oxidation at 1.7 V for slurries in acid, and more especially for solutions in alkali. NMR spectroscopy of methylated humic acids before and after oxidation suggests cleavage of ether linkages between aromatic clusters, with generation of carboxyl groups.     

真菌降解光-氧氧化内蒙古胜利褐煤产物分析

为掌握黄孢原毛平革菌降解光-氧氧化内蒙古胜利褐煤固体残渣的成分、结构和热稳定性的变化规律,以及降解液的主要物质构成,为降解工艺的改进以及降解产物的分离和利用提供参考,对降解所得的固体和液体产物进行了检测分析.结果表明:光-氧氧化煤被黄孢原毛平革菌作用后,煤残渣的水分、灰分和挥发分的质量分数均增加,固定碳的质量分数降低,...     

新疆高钙煤混烧对灰中含钙矿物熔融特性影响

选用一种高钙和一种高硅铝新疆煤,在沉降炉中进行不同比例的混煤和单煤燃烧实验。采用计算机控制扫描电镜（CCSEM）分别对燃烧后总灰矿物成分和粒径分布进行分析。基于CCSEM分析获取单颗粒灰成分数据,采用热力学平衡方法对灰中矿物液相比例进行计算,分析混煤燃烧对灰中含钙矿物熔融特性影响。结果表明,煤中有机结合态Ca极易与煤中其他矿物元素发生交互反应,交互反应后含钙矿物种类取决于煤中内在矿种类。混煤燃烧会促进灰中含钙硅铝酸盐向含钙复杂硅铝酸盐转化,同时促进含钙矿物的熔融。在低温条件下,混烧煤灰中熔融含钙矿物粒径分布受碱金属粒径分布影响;但是高温条件下,混烧促进熔融含钙矿物向大粒径煤灰迁移。     

Hydrogenolysis of coal-related model compounds by carbon monoxide-water mixture

Model organic compounds have been subject to hydrogenolysis reactions using CO and H₂O under industrial conditions as used for lignite and residual oil. Twenty-eight compounds, including diphenylmethane, indane, tetralin, anthracene, diphenyl ether, indene, benzophenone and xanthene were used. The purpose is to study the hydrogenolysis behaviour of compounds with structures as found in coal and residual oil. Using a Co-Mo catalyst, scission of the CC chain connecting two aromatic rings is enhanced by increased chain length of the molecule. Ether bonds are broken more easily than CC bonds. With the exception of decalin, cyclic CC bonds are more resistant to cleavage than linear bonds. Alcohol hydroxyl, and carbonyl groups of stilbene are the easiest to reduce but phenolic hydroxyl groups are stable. The Co-Mo catalyst promoted hydrolysis of ether bonds as well as hydrogenolysis. The method of the study is considered to be more effective for hydrogenolysis of organic compounds than the reported use of alkali and tetralin because of milder reaction conditions which are required.     

Effects of Xinjiang high calcium coal co-firing on melting characteristics of Ca-bearing minerals in ash

In this study, a high-calcium coal, a high-silicon-aluminum Xinjiang coal and their blends were burnt in a drop tube furnace. The computer-controlled scanning electron microscope (CCSEM) was used to analyze the total ash mineral composition and particle size distribution after combustion. Based on CCSEM analysis, the composition data of single particle ash was obtained. The thermodynamic equilibrium method was used to calculate the liquid phase ratio of minerals in the ash, and the effect of coal blending on the melting characteristics of calcium-containing minerals in the ash was analyzed. The results show that the organically bound Ca easily interacts with other minerals in the coal. The mineral species of Ca-bearing minerals in the bulk ash mainly depend on the included minerals in coal. Co-firing will promote the conversion of calcium-containing aluminosilicate in the ash to calcium-containing complex aluminosilicate, and at the same time promote the melting of calcium-containing minerals. Under low temperature conditions, the particle size distribution of molten calcium-containing minerals in co-fired coal ash is affected by the particle size distribution of the alkali metal; however, under high temperature conditions, co-firing promotes the migration of molten calcium-containing minerals to large particle size ash.     

Quantitative determination of degree of conversion in photocured poly(urethane‐dimethacrylate)s by Fourier transform infrared spectroscopy

In this work, infrared spectroscopy was used to characterize the degree of double bonds conversion (DC) in six series of poly(urethane‐dimethacrylate)s, derived from dicarbamates of oligoethylene glycols monomethacrylates and aliphatic, cycloaliphatic and aromatic diisocyanates. To evaluate the degree of conversion in polymers devoid of aromatic moieties, two methods of calculation have been proposed: internal band ratio method, with carbonyl stretching vibrations as a standard, and a method involving the direct observation of the decrease in the intensity of C?C stretching band. The validity of these methods has been checked on polymers with aromatic structures, by comparing the results with those obtained by the internal band ratio method applying an aromatic band as a reference. A good correlation between the degree of conversion from two internal standard methods, using aromatic band and carbonyl band as references, was obtained. It was shown that the degree of conversion increases as the number of oxyethylene units increases. Polymerization of monomers with aliphatic cores resulted in higher DC values, while those with cycloaliphatic and aromatic cores—resulted in lower DC values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

利用拉曼光谱研究助熔剂对煤灰矿物转化行为影响

在还原性气氛下,利用拉曼光谱研究添加不同助熔剂对高灰熔点煤灰的矿物转化行为的影响.结合X射线衍射(XRD)的表征,分析了助熔剂对煤灰渣矿物转化的作用.结果表明,1000℃时ZJX煤灰渣的拉曼特征峰多且复杂,而随着温度自1200℃升高到1500℃,煤灰渣中的钙长石、石英、镁橄榄石等多种矿物逐渐形成了共熔矿物,非晶态矿物含量增加,导致拉曼特征峰明显变少.添加6%单钙基助熔剂时,煤灰渣在1421℃时形成共熔物;添加6%单镁基助熔剂在1355℃时形成共熔物;煤灰添加钙镁复配(WCaO:WMgO=1)助熔剂在1290℃时就已经形成共熔物,所以钙镁助熔剂复配对共熔矿物的形成有促进作用.     

Solubilization of Illinois bituminous coal: the critical importance of methylene group cleavage

The extent of solubilization of an Illinois bituminous coal achieved by hydroliquefaction at various temperatures with and without catalyst was determined. The coal was also solubilized by treatment in suspension in THF with potassium in the presence of naphthalene. The original coal was also extracted with THF without prior treatment. After removal of solvent the soluble fractions were examined by ¹H n.m.r. spectroscopy. It is concluded that there are two temperature regimes which affect coal conversion: in the 350–400 °C region, hydroliquefaction proceeds principally by ether cleavage; whereas in the 400–450 °C range, hydroliquefaction results in additional cleavage of methylene groups joining aromatic or heteroaromatic units. Comparison of solubilization by hydroliquefaction with solubilization achieved with potassium in THF seems to indicate the initial degradation of coal by both techniques proceeds by ether cleavage and that further degradation is achieved in both cases by attack at the methylene bridge. The n.m.r. studies on hydroliquefaction products indicate that Illinois bituminous coal is structurally quite homogeneous because the product composition is largely independent of the degree of solubilization. Thus, solubilization results from molecular weight degradation rather than from preferential-degradation to different structural units.     

Ash deposition behavior of cynara-coal blends in a PF pilot furnace

Biomass is nowadays considered as a very interesting option to substitute conventional fossil fuels. Although biomass could be burnt alone, it can also be co-fired together with coal in existing power plants, at a lower cost. One of the main problems related with biomass used in thermal applications is its propensity to form ash deposits. Slagging and fouling caused by ash may derive in heat transfer losses, corrosion in the tubes or even boiler shutdown. A deposition probe has been designed and proved to study this phenomenon. Several combustion tests have been performed in a 500 kW_th PF pilot test rig burning cynara blended with two coals at different shares in energy basis. Different analyses have been performed to those ash samples collected during the tests. From the results, it is observed that the quantity of collected ash in the deposition probe did not increase noticeably when increasing the biomass share up to 15% in energy basis. However, the opposite was detected in Spanish coal tests, due to its higher ash content. Major components of ash samples were aluminosilicates coming from coal clays. These components may act as protective ash coal compounds, but inorganic elements such as calcium or potassium also appeared and their presence increased with the biomass share. Although chlorine content in cynara was high, no important presence of this element was encountered in none of the ash samples collected. Experimental results agree with other experimental studies showing that aluminosilicates from coals may act as protective ash compounds, preventing chlorine deposition on heat transfer surfaces. The beneficial effect is also detected at pulverized fuel conditions.     

Direct Coal Liquefaction Using Iron Carbonyl Powder Catalyst

Direct coal liquefaction involves catalyzed interactions between molecular hydrogen and coal‐oil slurries at elevated pressure and temperature, typically in the presence of an iron‐based catalyst. Iron carbonyl powder as an alternative first‐stage catalyst was investigated. A series of experimental tests under mild liquefaction conditions were carried out with a high‐pressure batch reactor in order to compare the performance of the iron carbonyl precursor to the traditional superfine iron oxide catalyst. The carbonyl iron powder performed very well in terms of total conversion of coal as well as yield of coal oil product. The iron carbonyl powder acts as an effective precursor for the in situ generation of active iron sulfide. The simple kinetic models for coal liquefaction in the literature were found to be qualitatively consistent with the yields of preasphaltenes, asphaltenes, and oils obtained from the experiments.     

A new method for determining the conversion of low-ash coals using synthetic ash as a tracer

Victorian brown coal represents a significant resource for power generation in Australia. The typical ash content for these coals can be as low as 1% (dry basis). While low ash content is obviously a major advantage for the utilisation of these coals, it is a problem for researchers in that the low ash content leads to large inaccuracies when using the ‘ash tracer’ method to determine coal conversion in flow reactors. To address this problem, a modified ash tracer method has been developed to determine coal conversion which involves adding perlite as an artificial ash to the coal. This method has been successfully applied to measure coal conversion during the pyrolysis of Loy Yang coal in a drop tube furnace.     

Ab initio determination of dark structures in radiationless transitions for aromatic carbonyl compounds

Mechanistic photodissociation of a polyatomic molecule has long been regarded as an intellectually challenging area of chemical physics, the results of which are relevant to atmospheric chemistry, biological systems, and many application fields. Carbonyl compounds play a unique role in the development of our understanding of the spectroscopy, photochemistry, and photophysics of polyatomic molecules and their photodissociation has been the subject of numerous studies over many decades. Upon irradiation, a molecule can undergo internal conversion (IC) and intersystem crossing (ISC) processes, besides photochemical and other photophysical processes. Transient intermediates formed in the IC and ISC radiationless processes, which are termed "dark", are not amenable to detection by conventional light absorption or emission. However, these dark intermediates play critical roles in IC and ISC processes and thus are essential to understanding mechanistic photochemistry of a polyatomic molecule. We have applied the multiconfiguration complete active space self-consistent field (CASSCF) method to determine the dark transient structures involved in radiationless processes for acetophenone and the related aromatic carbonyl compounds. The electronic and geometric structures predicted for the dark states are in a good agreement with those determined by ultrafast electron diffraction experiments. Intersection structure of different electronic states provides a very efficient "funnel" for the IC or ISC process. However, experimental determination of the intersection structure involved in radiationless transitions of a polyatomic molecule is impossible at present. We have discovered a minimum energy crossing point among the three potential energy surfaces (S1, T1, and T2) that appears to be common to a wide variety of aromatic carbonyl compounds with a constant structure. This new type of crossing point holds the key to understanding much about radiationless processes after photoexcitation of aromatic carbonyl compounds. The importance of ab initio determination of transient structures in the photodissociation dynamics has been demonstrated for the case of the aromatic carbonyl compounds. In addition, the detailed knowledge of mechanistic photochemistry for aromatic carbonyl compounds forms the basis for further investigating photodissociation dynamics of a polyatomic molecule.     

Concerning the 1600 cm−1 region in the i.r. spectrum of coal

The assignment of the 1600 cm^?1 band in the i.r. spectra of coals has been a matter of controversy for some 20 years. The two most probable assignments of the band are to aromatic ring stretching or to highly conjugated, hydrogen-bonded carbonyl. In the present study, careful deconvolution of coal spectra obtained using a high resolution Fourier transform infrared spectrometer provides-additional support for the assignment of the band to an aromatic stretching mode.