Reactivity of hydrolysed coals in liquefaction

A hvA bituminous, a subbituminous and a lignite coal have been hydrolysed by 20–30% aqueous caustic solution at 100–300 °C and total pressure from ambient to 8.3 MPa (1200 psi). Reactivity of these pretreated coals toward liquefaction has been examined. The conversion to benzene-soluble material (BS) and oil increases, and the preasphaltene and char residue decreases after pretreatment. Improvement in the conversion to the BS fraction is only marginal for the pretreated bituminous coal, but substantial for the low-rank coals. For the subbituminous coal, the liquefaction reactivity (conversion to BS) increases with the severity of hydrolysis pretreatment. Analyses of chemical compositions, ¹H n.m.r. nuclei distributions and hydroxyl concentrations of the acid-insoluble hydrolysis coal extracts indicate that both O and S are enriched in the extracts with half of the oxygen atoms being in hydroxyl forms. The hydroxyl concentrations of the extracts (acid-insoluble) are ≈2 to 3 times higher than their parent coals. Coal activation by this alkali pretreatment is explained by the hydrolytic attacks on ether C–O linkages, and the removal of some constituents rich in oxygen functional groups which are responsible for poor liquefaction behaviour.     

Reactivity of coals in hydrogenation

Three coals of different rank (77.9–89.5 wt% C, daf) were hydrogenated at various temperatures to examine the influence of coal rank on the hydrogenation reactivity. Extraction of the heat treated coals with pyridine, benzene and n-hexane was also carried out to estimate the total amount of the intrinsic solvent-soluble fraction in the original coal. In the extraction of preheated coal, the largest amount of pyridine-soluble fraction was obtained for the coal of medium rank (83.9% C). This coal also showed the highest conversion, in terms of pyridine solubility, on hydrogenation. As the pyridine soluble material from hydrogenation must contain the intrinsic soluble fraction present in the original coal, it cannot be concluded that medium-rank coal shows the highest reactivity in hydrogenation. Conversion to benzene and n-hexane soluble materials is only slightly affected by the intrinsic soluble fraction, so it is better to estimate hydrogenation reactivity from the yields of these materials. On this basis, the lowest-rank coal shows the highest reactivity in hydrogenation.     

Reactivity assessment of coals via a weighted mean activation energy

A method has been developed for describing the reactivity or combustibility of solid fuels, such as lignite, bituminous coals and petroleum coke, in terms of a weighted mean apparent activation energy, derived from simultaneous $\text{TG}\text{DTG}$ readings on a 20 mg sample heated at a constant rate in a flowing air atmosphere. It is proposed that this quantity, labelled E_m′, could supplant the established method which involves recording several temperatures on the DTG (burning profile) curve.     

Studies related to the structure and reactivity of coals : 18. The chemical structures of products from reactions of a suite of higher rank Australian coals

The structure of the oils, asphaltenes and residues obtained by the thermal reactions of a suite of Australian higher rank coals under hydrogen or nitrogen have been studied by chemical and spectroscopic methods. The host-guest model that has been used to describe the structure of Australian brown coals cannot be applied directly to the higher rank coals. Evidence is provided that suggests that a modified version of the model may be of use in describing the structure of some subbituminous coals. The methodology has proved to be useful in the understanding of structural features of coals which are often not rank dependent, e.g. Callide coal (ABL2), a subbituminous coal, has been shown to have characteristics of both very high and also low rank coals.     

Some physical properties of Canadian coals and their effects on coal reactivity

The pore volume, surface area and compressibility of eleven Canadian coals, varying in rank from lignite to semianthracite, have been determined by mercury porosimetry, gas adsorption method and relations derived from helium and mercury densities. The total pore volume was measured in the diameter range of 0.2 nm–2.98 μm, which was subdivided into two groups, namely the micropore region (< 0.0036 μm) and the combined meso- and macropore region (0.0036–2.98 μm). It has been determined that the porosity of the eleven coals studied varies from 2 to 39%. It has been found that the total pore volume, micropore volume, surface area and the apparent compressibility of these coals decrease with increase in the carbon content, or the rank of the coals. The effect of the total pore volume, micropore volume and surface area on chemical reactivity of the coal is discussed separately. A good correlation was obtained between the carbon content and helium density of the coal after correction is made for the mineral content.     

Aspects of gasification and structure in cokes from coals

Cokes were prepared from nine coals of different rank and characterized by surface area measurement, reactivity to carbon dioxide at 1473K and Raman-laser spectroscopy. Rates of gasification of cokes on a unit surlface area basis (K¹ = g m^?2 min^?1) decreased with increasing rank of parent coal based on maximum oil reflectances. However rates of gasification could not be related to coke structure as measured by Raman-laser spectroscopy.     

不同沉积环境下煤的热解与气化特性

采用煤热解.气化连续方法,在TG-DTA/DSC热分析仪器上对煤化程度接近但沉积环境不同的5种煤的热解与气化特性进行研究,运用Coats-Redfem积分法求解煤热解动力学参数.研究结果表明:5种煤的热解机制是相似的,反应级数n=3;还原程度较弱的SH与SF煤,热解表观活化能在43-54 kJ/mol,而还原程度较强的...     

煤焦与水蒸气加压气化反应活性的研究

采用填充床热天平反应器（ＰＢＢＲ）系统,于０．０９８ＭＰａ～２．４５ＭＰａ压力和７５０℃～１０００℃温度下进行了煤焦与水蒸气气化反应的活性研究,以基碳转化率（Ｘ）和比气化速率（Ｂ）作为反应活性的评价指标。结果表明,煤焦的Ｘ和Ｂ随着温度和压力的增加而增加;煤焦的气化反应活性顺序为：褐煤焦＞气煤焦＞贫煤焦。     

Comments on the reactivity of low-rank coals in liquefaction

This communication discusses the subject of the relative reactivities of low-rank and bituminous coals in liquefaction. Accounts given by several researchers have provided seemingly contradictory results. An explanation is presented to reconcile these opposing views.     

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.     

Reactivity of O-methylated Illinois No. 6 coal towards alkyllithiums/methyl iodide

An O-methylated Illinois No. 6 vitrain was treated repeatedly with a series of C-H indicator bases of known pK_a and quenched with ^13,14C-methyl iodide. The extent of ¹⁴CH₃ incorporation depended strongly upon base strength, increasing in the order 9-phenylfluorenyllithium < fluorenyllithium < trityllithium. A significant number of methyl groups ($\text{0.7–1.2}\text{100}$ coal carbons) were introduced with fluorenyllithium and trityllithium as the base. Additional methyl groups were added upon a second and third treatment with base and alkylating agent. After three treatments, the number of added methyl groups had doubled. The extent of base reagent incorporation was established by parallel experiments using ¹⁴C-enriched bases. CP/MAS ¹³C n.m.r. of the first coal alkylation product using trityllithium and ¹³C-enriched methyl iodide was consistent with predominantly C-alkylation. From these results, a unified picture for coal structure emerges which contains a distribution of reactive C-H sites, distinguishable on the basis of their acid-base properties. Possible reactive sub-structures are considered.     

Determination of carboxyl groups in low-rank coals

The determination of carboxyl groups in low-rank coals by exchange with barium chloride-triethanolamine reagent is re-examined. The difference in carboxyl contents calculated from the barium content of the exchanged coal, and the amount of acid used to extract the barium, is discussed. Reliable carboxyl contents are obtained providing the latter procedure is used.     

焦化除尘灰的反应性研究

为了扩大高炉喷吹用煤煤源,降低高炉喷吹用煤成本,本试验探索用廉价的焦化除尘灰代替部分无烟煤用于高炉喷吹的可行性。在对高炉喷吹用煤进行工业分析和粒度分布研究的基础上,进一步研究了高炉喷吹用煤的反应性及其影响因素。初步研究表明:高炉喷吹用煤中配入适当比例的焦化除尘灰,对高炉喷吹用煤的反应性影响不大。在焦化除尘灰的配比小于15%的条件下用作高炉喷吹是可行的。     

Fate of aliphatic groups in low-rank coals during extraction and pyrolysis processes

Information on the nature of aliphatic groups in some bituminous coals and lignites was obtained by determining their fate during extraction and pyrolysis processes of differing severity. Aromatics (neutral oils) and asphaltenes from supercritical gas and hydrogen-donor solvent extracts and from pyrolysis and hydropyrolysis tars have been characterized by an n.m.r.-based structural analysis method which identifies hydroaromatic, methyl and long alkyl (?C₈) groups. The results indicate that methyl and other alkyls account for about half of the aliphatic carbon, long alkyl chains being the major aliphatic group in the lignites. There is evidence to suggest that some of the long alkyl chains are joined to aromatic structures. Hydroaromatic groups are small consisting of only 1–2 rings and account for less of the aliphatic carbon in bituminous coals than previously thought. Their concentrations and those of long alkyl chains in the aromatics and asphaltenes generally decrease with increasing process severity.     

檀香醚的绿色合成

目前工业上合成檀香醚的工艺存在对设备要求高、腐蚀性强、污染环境、产物不易分离等问题,本实验通过改进传统工艺中的环氧化和催化氢化反应,实现了标题化合物的绿色合成.实验所得的中间体和檀香醚结构经1HNMR、13CNMR确定.     

Mineral matter and elemental concentrations in selected western canadian coals

Major and trace element analyses were performed on coals from various locations in western Canada, and on low-temperature (150 °C) and high-temperature (1000 °C) coal ash produced from these coals. Elemental analyses were carried out by X-ray fluorescence spectroscopy and intense neutron activation analyses. Based on their trace elements, the coals in this study fall into two groups: 1. low-rank coals (lignite-subbituminous) of late Cretaceous and Tertiary age; and 2. high-rank coal (bituminous-semianthracite) of Jurassic-Cretaceous age. The elemental analyses of the coals and coal ash indicate that the local conditions had considerable influence on the concentrations of certain trace elements.Antimony and selenium in coals are the only elements which are enriched relative to concentrations in the earth's crust; arsenic is concentrated in lignite to subbituminous coal, but is depleted in bituminous-anthracite coals; as expected the ash of these coals showed many more instances of enrichment.     

聚乙二醇单甲醚衍生物的合成

以聚乙二醇单甲醚为原料,分别合成了活性端基为羧基、氨基和巯基的聚乙二醇单甲醚,其结构用1HNMR、13CNMR和IR进行了表征。     

Comparison of the associative structure of two different types of rich coals and their coking properties

Solvent extractions of two different types of Chinese rich coals i.e. Aiweiergou coal (AG) and Zaozhuang coal (ZZ) using the mixed solvent of carbon disulfide/N-methyl-2-pyrrolidinone (CS₂/NMP) with different mixing ratios were carried out and the caking indexes of the extracted residues were measured. It was found that the extracted residues from the two types of coals showed different changing tendencies of the caking indexes with the extraction yield. When the extraction yield attained about 50% for ZZ coal, the extracted residue had no caking property. However for AG coal, when the extraction yield reached the maximum of 63.5%, the corresponding extracted residue still had considerable caking property with the caking index of 25. This difference indicated the different associative structure of the two coals although they are of the same coalification. Hydro-thermal treatment of the two rich coals gave different extract fractionation distributions for the treated coals compared to those of raw coals respectively. The coking property evaluations of the two coals and their hydro-thermally treated ones were carried out in a crucible coking determination. The results showed that the hydro-thermal treatment could greatly improve the micro-strengths of the resulting coke from the two coals, and the improvement was more significant for the more aggregated AG coal. The reactivities of hydro-thermally treated AG coal blends were almost the same as those of raw coal blends. The higher coke reactivities of AG raw coal and its hydro-thermally treated ones than those of ZZ coal might be attributed to its special ash composition.     

煤灰对气化反应性的影响

讨论了煤灰在气化过程中对气化反应性的影响,主要为:在低温下,某些矿物组分对气化过程有催化作用,但在高温下,矿物发生变化,会生成无催化活性的组分;当气化温度接近或超过煤灰熔融性温度时,煤灰发生熔融甚至团聚,导致反应比表面积降低,催化矿物分散性变差,影响气化反应性。     

应用量子化学计算研究溴与汞反应的动力学参数

引言汞是挥发性的有毒重金属元素。燃煤中含有微量的汞,这些汞在煤燃烧时会释放到烟气中,燃煤烟气中汞主要以3种形态存在:颗粒Hg(Hgp)、气态氧化Hg(Hg2+)和气态单质Hg(Hg0)。