Oxidation of demineralized coal and coal free of pyrite examined by EPR spectroscopy

The influence of oxidation on complex paramagnetic centres system of demineralized coal and coal free of pyrite was compared. Polish orthocoking coal with a carbon content of 87.8 wt% was studied. This coal was oxidized with nitric acid (HNO₃), peroxyacetic acid (PAA) and in O₂/Na₂CO₃ system. Multi-component structure of X-band EPR spectra of the coal samples was numerically analysed. The lineshape and the parameters of the component lines: linewidths and g-factors, were determined. Concentrations of paramagnetic centres were measured. The three groups of paramagnetic centres belonging to different molecular units were found in the studied samples. They were responsible for broad Gauss (ΔB_pp: 0.49-0.84 mT), broad Lorentz 1 (ΔB_pp: 0.18-0.35 mT), and narrow Lorentz 3 (ΔB_pp: 0.04-0.08 mT) EPR lines. Properties of paramagnetic centres of the simple molecular units with broad Gauss and Lorentz 1 lines were changed during demineralization of coal and after pyrite removing from coal. g-Values of Gauss and Lorentz 1 lines increased, Lorentz 1 lines were broadened and concentrations of paramagnetic centres with Lorentz 1 lines increased. Oxidation of both demineralized coal and coal free of pyrite with nitric acid led to the highest decrease of the concentration of paramagnetic centres with Gauss lines, narrowing of these lines and increase of g-factor. The higher effects of oxidation on paramagnetic centres responsible for broad lines were observed for coal free of pyrite. Paramagnetic centres with narrow Lorentz 3 lines belonging to multi-ring aromatic units in demineralized coal and coal free of pyrite were not susceptible for oxidation.     

E.p.r. study of reduced and reductively ethylated coals

Two coals (78 and 85 wt % C) were reduced with potassium in tetrahydrofuran in the presence of naphthalene and also ethylated with ethyl iodide. The e.p.r. spectra of the coals and products consisted of two components: a narrow and a broad line. Both reduction and ethylation led to a decrease in concentration of paramagnetic centres; quenching was greater in centres related to the broad line component. A mechanism for the quenching is suggested.     

Influence of thermal decomposition on paramagnetic centres in vitrinite

Paramagnetic centres of thermally decomposed vitrinite from medium-rank Polish coal (85.6 wt.% C) were studied using X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. The aim of this work was to compare concentrations and properties of paramagnetic centres in vitrinite heated at different temperatures.The vitrinite sample (92 vol.% vitrinite) obtained from vitrain was heated at 350 and 550 °C. The EPR measurements were performed for the evacuated (10⁻⁴ Torr) samples. The line shape of the EPR spectra was numerically analysed. Amplitudes, g-factors, and line widths ΔB_pp of the EPR components were evaluated. The concentration of paramagnetic centres in the samples was determined.Three different groups of paramagnetic centres exist in the studied vitrinite. EPR spectra of vitrinite were superposition of one broad Gaussian (ΔB_pp: 0.80 mT, g: 2.0030), and broad (ΔB_pp: 0.56 mT, g: 2.0029) and narrow Lorentzian (ΔB_pp: 0.13 mT, g: 2.0028) lines. The most active during thermal decomposition were paramagnetic centres with broad Lorentzian lines. The concentrations of the all types of paramagnetic centres in vitrinite increase with temperature of heating. Spin-lattice relaxation times in vitrinite decrease with increasing of temperature of thermal decomposition.     

Excited triplet states in bituminous coal

The intensities of the broad and narrow lines constituting the e.p.r. spectrum of coal depend on the temperature of measurement. The system of paramagnetic centres related to the broad line does not obey the Curie law and consists of free radicals ($\text{S =}\text{1}\text{2}$) and of centres with singlet ground state (S = 0) and lowest-excited triplet state (S = 1). The singlet-triplet excitation energy, J, is comparable with thermal energy, kT, of lattice vibrations. The system of paramagnetic centres related to the narrow line obeys the Curie law ($\text{S =}\text{1}\text{2}$).     

Relationship of coal extraction with free radicals and coal macerals

Extraction and de-ashing of coals with N-methyl pyrrolidone (NMP) under mild conditions has been reported recently. In this work, we have studied about a dozen American coals, along with some of their residues and extracts after treatment with NMP using in situ ESR (Electron Spin Resonance) spectroscopy of free radicals. At room temperature, N-₈ (number of free radials/g) decreases whereas the percentage extraction increases with atomic H/C of coals. Also N₈ for extract (residue) is lower (higher) than that for coals, ESR spectra of the extract exhibits only the single broad component and the weighted average of N₈ for the extract and the residue nearly equals that of the parent coal. These results have led to the hypothesis that the treatment with NMP is an extraction process in which exinites and to a lesser degree vitrinites are favored, whereas the inertinites are nearly rejected by NMP.     

Production of coal pitch by the oxidation of coal extracts in anthracene oil

If anthracene oil is used to produce extracts from 2B, D, 2G, GZh coal, coal pitch may be produced by oxidation of the extracts using atmospheric oxygen. The resulting pitch is characterized by higher yield and by a greater coke residue than is observed in pitch produced from anthracene oil without added coal in analogous conditions. Ultrasound treatment for 3 h on an IL10-0.63 unit ensures complete solution of the coal (4–9%) in the anthracene oil. The mineral component of the coal also enters the solution and is then concentrated in the pitch formed. To reduce the ash content of the pitch, ash must preliminarily be removed from the initial coal. For the example of 2B and D coal, it is found that reducing the ash content of the coal to ~1% and subsequent solution in the anthracene oil to a coal concentration of 5–8% yields a coal extract such that pitch with no more than 0.4% ash and up to 41% coke residue is formed on oxidation by atmospheric oxygen.     

Properties and structure of group components separated from vitrites of coking coals by selective thermosolvolysis

The process of progressive and continuous thermosolvolysis of coking coal vitrites was carried out. The properties and structure of the extracts and the extraction residue as well as the influence of the degree of extraction on the properties of the resultant group components were examined. An increase in aromatic character of the extracts with increasing degree of extraction is observed, and the same increase of aromatic character can be seen for the extracts obtained in the same extraction time with an increase of the degree of coalification of the parent vitrites. The changes in the coal structure after extraction of thermobitumens depend on the degree of coalification of the parent vitrites, they are largest for the gascoal vitrite.     

1H n.m.r. spin—lattice relaxation study in bituminous coal

¹H n.m.r. studies of spin-lattice relaxation of a bituminous coal were performed at temperatures between 128 and 308 K. The relaxation function was observed to be two-component over the whole temperature range. The component with the shorter relaxation time was assumed to be the molecular phase in coal and the component with the longer relaxation time to be the macromolecular phase. Mechanisms of spin-lattice relaxation through spin diffusion to paramagnetic centres and through modulation of dipolar interactions by molecular motions are suggested.     

低阶煤有机溶剂萃取的研究进展

鉴于煤有机溶剂萃取的迅速发展,以低温和高温热萃取作对比,对相应的萃取机理、影响因素及萃取物的应用等进行分析。结果表明:萃取温度在200℃以下的多为低温物理萃取,萃取率一般较低,所得萃取物多用于研究煤的分子结构;而温度在300~400℃的萃取多为高温溶剂萃取,所得萃取率较高,萃取过程中会伴随化学键的断裂及相应化学反应的发生,所得萃取物多用在研究配煤炼焦、劣质煤的气化液化、新型煤基材料等领域。     

1H n.m.r. relaxation in bituminous coal and semicoke

Temperature and frequency-dependent proton relaxation measurements, in conjunction with spin concentrations determined by e.s.r., have shown that for fresh and oxidized coal the relaxation mechanism involves spin-diffusion to paramagnetic centres and to rotating methyl groups on alkyl chains. ¹H relaxation in semicokes is more complex; probably both direct relaxation to paramagnetic centres as well as spin-diffusion contribute.     

干馏渣替代煤矸石在预分解窑上的应用

油页岩低温干馏制取页岩油,其干馏产生的干馏渣和硅铝质原料(煤矸石)的化学成分相近并含有一定发热量。基于此,某新型干法生产线利用干馏渣替代部分硅铝质原料(烧煤矸石、黏土)用于水泥生料配料生产水泥熟料,介绍了其生产操作调整措施。实践证明,干馏渣替代部分硅铝质原料生产水泥是切实可行的,不仅能改善生料易烧性且价格低廉,降低了熟料煤耗和生产成本,具有广阔的市场应用前景。     

微波条件下氯化锌对乙醇抽提神府煤的影响

微波条件下,研究了在乙醇抽提神府煤中加入氯化锌对其结果的影响。采用气相色谱/质谱联用的方法分析了乙醇和乙醇-氯化锌抽提物的组成;利用傅里叶红外光谱技术分析了神府脱矿物质煤、乙醇抽余煤和乙醇-氯化锌抽余煤的结构。分析结果显示:在乙醇溶剂中添加少量的氯化锌,其抽提物的组成发生了改变;乙醇-氯化锌抽余煤与原脱矿物质煤和乙醇抽余煤相比,芳环吸收强度降低,表明在抽提过程中可能伴随着烷基化反应的发生。     

呼伦贝尔褐煤溶剂萃取及萃余煤的双氧水氧化产物分析

以CS2、乙醇和丙酮作为溶剂,对呼伦贝尔褐煤进行连续萃取,并利用气相色谱/质谱联用(GC/MS)技术对萃取物进行分析。结果表明:CS2萃取物主要由长链脂肪烃和芳烃组成,而这些脂肪烃存在于3种溶剂萃取物中。在40℃条件下,用H2O2溶液采用恒温水浴和超声两种方式氧化萃余煤,超声条件下氧化剧烈,并用FTIR分析了原煤、萃余煤、氧化煤的化学结构的变化。氧化后的水溶物用乙酸乙酯萃取后,用GC/MS检测萃取物,恒温水浴氧化可以检测到30种化合物,而超声氧化只检测到14种,且都是以酯类为主。     

E.p.r. studies of outburst-prone anthracite coal

Changes in the macroscopic structure of coal have been observed as an outburst-prone area is approached. Associated with this structural change was an increase in the concentration of paramagnetic centres. Initial results suggested that this increase was not due to variation in maceral content within the coal samples but to the mechano-chemical degradation of the coal as a result of tectonic forces applied over geological time.     

回收NMP-CS2混合溶剂萃取原煤基本性状研究

以平顶山煤和徐州煤为原料,利用回收NMP与CS_2混合溶剂和反萃取剂将两种煤全组分分离成萃余煤组分、沥青质组分、精煤组分和轻质组分四大族组分,主要对比原煤及各族组分的真密度、工业分析与元素分析。结果表明,萃余煤组分真密度最大,分别为1.59和1.45,精煤组分与沥青质组分真密度低于原煤。轻质组分具有较多非共价键成键点,易与水分子形成氢键,水分含量最高,分别为6.09%和5.77%,而萃余煤组分水分含量最低,分别为0.96%和0.63%。沥青质组分接近无灰。挥发分含量以轻质组分沥青质组分精煤组分原煤萃余煤组分顺序降低。C元素含量以精煤组分与沥青质组分相对较高,萃余煤组分C元素含量较两者偏低,分别为80.91%和80.65%。轻质组分中N、O和S元素含量较高,C元素含量最低。     

童亭煤族组分的溶剂萃取及萃取物分析

采用正己烷、甲醇、丙酮和氯仿4种溶剂对童亭煤经CS2/NMP混合溶剂萃取和反萃取所分离的3个族组分(沥青质组分、精煤和萃余煤组分)进行索氏分级分次萃取,以FTIR和GC为分析测试手段,研究各组分萃取物的结构特征和其中小分子的赋存规律。结果表明:各族组分在不同溶剂中溶解能力差异显著,沥青质组分在正己烷中有很高的萃取率,而精煤则在丙酮中有大量物质被溶出,萃余煤在氯仿中表现出较高的可溶性;各族组分可溶物在溶出行为和组成结构上既有相似性又存在一定的差别;各族组分可溶物中均有小分子化合物存在,且这些GC可检测的小分子主要集中于一定的保留时间区域内;不同族组分中的小分子的赋存形态具有相似性,且这种赋存形态是影响小分子溶出行为的决定性因素。     

Correlation between the sudden and regular releases of coal-bed methane and the structures of the organic matter of natural coals

A correlation between the structure of the organic matter of coal and the ability of coal to release gases upon thermal and mechanical actions was considered. It was found that coal-bed methane released in different modes (regular and sudden) during coal-bed mining is of mechanochemical rather than sorption nature. Relationships were proposed to determine the natural methane content of coals and the sorption capacity of coals from a metamorphic series for methane using a structure-chemical parameter: the concentration of paramagnetic centers calculated from a broad line of the EPR signal. The use of spectroscopic techniques provides an opportunity to considerably simplify and make cheaper a very labor intensive technology for the determination of natural gas content. The regulations of methane safety in coal mines should be corrected based on the original concepts of the nature of coal-bed methane.     

肥煤的热抽提及其抽提物的性能研究

主要考察了肥煤在不同温度及不同溶剂下的热抽提性能,并对热抽提物性质进行了分析。实验结果表明,提高热抽提温度,肥煤热抽提率增大,并在其软化点附近达到最高值,而后随温度的升高而降低;增大溶剂极性,肥煤热抽提率也显著升高。热重和红外分析显示了热抽提物结构的变化,其基本无灰的特点有望成为煤洁净利用的突破口。     

基于超临界流体萃取的渣油掺炼煤焦油的脱沥青油性能评价

为寻求减压渣油的有效利用,采用"超临界流体萃取技术"对减压渣油/煤焦油混合原料进行溶剂脱沥青实验,并对脱沥青油(DAO)性质进行了详细评价。结果表明,当煤焦油掺炼量低于20%时,脱沥青油收率明显提高;且相同收率下脱沥青油性质有所改善,其催化裂化反应性能明显优于减压渣油的脱沥青油。减压渣油掺炼煤焦油以溶剂脱沥青-催化裂化组合工艺进行加工有一定的优势和可行性。     

Supercritical-gas extraction of Turkish coking coal

Treatment of Zonguldak coal with toluene at 360 °C gave yields of extract which increased from 19–32% as the pressure of the extraction was increased from 11.6 to 29 M Pa. These yields were similar to those previously obtained by supercritical-gas extraction of lignites but the composition of the extracts differed. The lignite extracts contained a much higher proportion of petroleum ether-soluble material and only half the proportion of material insoluble in both petroleum ether and benzene than the Zonguldak coal extract. Benzene, biphenyl, naphthalene, phenanthrene, pyrene, benzoanthracene and be-nzophenanthrene nuclei were identified in the coal extract. Comparison of the yields of substituted benzenes with those obtained by low-temperature carbonization suggests that the proportions of different substitution pattern is determined by the structure of the fuel. Less naphthalene nuclei were found than expected but relatively large yields of biphenyls were obtained which were attributed to their formation from toluene in the presence of phenols.