Constitution of tars from flash pyrolysis of Australian coals: 3. A structural study of Millmerran asphaltene components by hydrogenolysis

Asphaltenes derived from tar from the flash pyrolysis of Millmerran coal have been separated into acid, base, polyfunctional and neutral fractions by ion-exchange chromatography. Each fraction was studied by high-pressure catalytic hydrogenolysis followed by g.c.-m.s. analysis of the volatile products. The high content of n-alkanes from C₉ to C₃₂ in the organic products highlights the unusual maceral composition of Millmerran coal and its high $\text{H}\text{C}$ ratio. The results show that most of the asphaltenes are made up of small 1 — or 2-ring aromatic units probably linked by methylene chains bonded through intermediate functional groups. In some cases, the asphaltene structures appear to be ‘simpler’ than the corresponding coal-tar resin structures in the maltenes. Because no amphoteric molecules were detected these results support the concept of an acid-base structure for coal-derived asphaltenes.     

Constitution of tars from the flash pyrolysis of Australian coals: 1. Separation

Separation of the maltene fraction of Millmerran flash-pyrolysis coal tar by ion-exchange and adsorption chromatography produced coal-tar resins, aromatic hydrocarbons (AH) and an alkane/alkene fraction. The coal-tar resins comprise acid, base, neutral and polyfunctional fractions. Derivatives of benzene and naphthalene are the main volatile constituents of the AH fraction, while the alkane/alkene fraction consists mainly of straight-chain hydrocarbons from C₁₀ to C₃₄ and small amounts of isoprenoid hydrocarbons, steranes and triterpanes. Fuller's Earth, used in the separation of the maltenes, suffers from the disadvantage of irreversibly adsorbing organic material.     

Coal flash pyrolysis: 2. Polymethylene compounds in low temperature flash pyrolysis tars

Pyrolysis of coals at low temperatures (< 600 °C) produces tars containing the precursors of the low molecular weight aliphatic hydrocarbons, such as ethylene and propylene, observed on flash pyrolysis of the coals at higher temperatures (700–800 °C). This is shown by further pyrolysis of these low temperature tars at high temperatures. Various methods, including isolation by h.p.l.c. were used to confirm the presence of straight chain paraffin and olefin pairs (C₁₄C₂₆ and above) in the low temperature tars. Pyrolysis of pure paraffins and olefins in this molecular weight range at temperatures > 700 °C produce ethylene, propylene and other cracking products similar to those obtained on flash pyrolysis of coal.     

Constitution of tars from the flash pyrolysis of Australian coals: 2. Structural study of Millmerran coal-tar resins by hydrogenolysis

The structures of the acid, base, polyfunctional and neutral resin fractions of Millmerran coal tar have been studied by high-pressure catalytic hydrogenolysis followed by g.c.-m.s. analysis of the volatile products. n-Alkanes from C₉ to C₃₂ constitute 4–24% of the organic products. Each fraction shows a characteristic n-alkane distribution. The alkanes are considered to be an integral part of the coal-tar resin structure. The results show that 40–70% of the coal-tar resin fractions consist of 1- or 2-ring aromatic units substituted or linked by long methylene chains.     

Viscosity modification of flash pyrolysis tars

A study was made of the effect of a number of additives on the viscosity of a characteristic tar produced by the flash pyrolysis of indigenous Australian coals. The results indicate that aliphatic compounds are more effective than aromatic compounds in lowering the viscosity. This observation is of significance in the selection of suitable recycle solvents and the dissolution of aged tars.     

Chemical nature of pre-asphaltenes from flash pyrolysis tars and supercritical gas extracts

Pre-asphaltenes from flash pyrolysis tars of three Australian coals and a supercritical gas extract of one of these coals were studied by ¹³C and ¹H n.m.r. of the silylated pre-asphaltenes. Further information was obtained by hydrogenolysis of one of the pre-asphaltenes followed by g.c. analysis. ¹³C n.m.r. studies of the silylated derivatives and g.c. analysis of the hydrogenated pre-asphaltene showed the presence of long alkyl chains. The aromaticity of the pre-asphaltenes from the flash pyrolysis tars increased as the rank of the coal increased. The pre-asphaltene from the supercritical gas extract was less aromatic than that from the flash pyrolysis tar of the same coal. Average structural data for each of the pre-asphaltenes are reported.     

Structural differences in the tars and chars from the pyrolysis of coals of different rank in hydrogen and in nitrogen

Two British coals—Linby high-volatile bituminous and Abernant anthracite — and an Australian brown coal were pyrolysed at 575 °C in hydrogen or nitrogen at 0.1, 5 and 30 MPa in an inclined, single-stage reactor. Hydrogen pressures of ? 5 MPa led to increased yields of tars which were more aromatic than those produced in nitrogen. The high-volatile bituminous coal fused under all conditions, whereas the anthracite and brown coal fused and agglomerated only in hydrogen at 30 MPa.     

Investigation of the flash pyrolysis of some coals

Five bituminous coals, an anthracite and a lignite have been flash-pyrolysed by the electrically-heated grid technique or by means of an electrically-heated fluidized-bed. In the experiments using a heated grid, data were obtained on rates of rapid devolatilization and on the composition of the gases and tars evolved with heating rates up to 3000 Ks^?1 and peak temperatures up to 1400 K. Similar, but more limited data were obtained using the fluidized-bed system. Mathematical models based on overall single- or two-reaction pathways were compared with the experimental results. Good agreement could be achieved by the latter with activation energies of 16 and 35 kJ mol^?1.     

Upgrading of flash pyrolysis tars to synthetic crude oil: 1. First stage hydrotreatment using a disposable catalyst

The hydrotreatment of tars produced by flash pyrolysis of Millmerran (subbituminous), Loy Yang and Yallourn (both brown) Australian coals was investigated in a continuous reactor containing a packed bed of sulphided steelwool. Reactor performance and product yields are reported for each tar. Overall mass balances of 96.7–100.3% and carbon balances of 96.0–100.2% were achieved. Recovered yields of product oil were 82.7–86.8%, 62.1% and 75.5% wt/wt dry, char-free tar for Millmerran, Loy Yang and Yallourn tars respectively. The steelwool reactor was found to decrease the coking propensity, specific gravity, viscosity and heteroatom levels and to increase the hydrogen content of the tars. It also acted as a filter to remove the char fines present in the tar. The operating life of the reactor was limited by the build up of carbonaceous deposits within the steelwool.     

印尼褐煤快速热解试验研究

为考察神雾快速热解炉的产品产率及产品性质,将神雾蓄热式快速热解工业炉型按一定比例缩小,在实验室自建的快速热解小试试验装置上,考察了热解温度对热解产物产率的影响,并对产物性质进行分析。结果表明,印尼褐煤快速热解最佳反应温度为590℃,印尼褐煤油收率为9.91%,高达格金含油率的95%,快速热解装置油收率较高。与固定床热解煤焦油相比,快速热解煤焦油的密度、黏度、凝点和残炭含量均较低。模拟蒸馏结果表明,快速热解煤焦油中汽油馏分为2%,柴油馏分为44%,重油馏分为54%。印尼褐煤快速热解气中的主要组分是CH4和H2,热值较高。     

Coal flash pyrolysis: 5. Pyrolysis in an atmosphere of methane

Flash pyrolysis of coal at temperatures above 700°C and in the presence of methane produces substantially more ethylene and other low molecular weight hydrocarbons than are produced by pyrolysis of coal in the presence of nitrogen alone. Evidence is presented to show that the increase is due to pyrolysis of the methane quite independently of the coal, except with the possible catalysis by the coal, coke or mineral matter in the coal ash. This is contrary to recent reports in the literature.     

Coal flash pyrolysis: 1. An indication of the olefin precursors in coal by CP/MAS 13C n.m.r. spectroscopy

The results reported indicate that the low molecular weight olefins (ethylene, propylene and butadiene) which are major gaseous hydrocarbon products of flash pyrolysis of coal derive from the same precursors in coal, whereas methane, benzene and other pyrolysis products are mainly formed from different components in the coal. CP/MAS ¹³C n.m.r. spectra suggest that the olefin precursors are long-chain polymethylene structures (chemical shift 31 ppm), either chemically bound or mechanically trapped in the coal and thus not solvent-extractable.     

快速热解低温煤焦油的初步分析

对多联产煤焦油的基本性质进行测定,利用色谱-质谱联用仪（GC-MS）对其主要成分进行了分析,结果表明多联产煤焦油与常规煤焦油有很大区别,甲苯不溶物、软化点、水分和灰分比常规煤焦油高得多;酚类化合物含量较高。     

低温煤热解焦油产率和品质影响因素研究

煤焦油是低温煤热解技术的主要产物,是重要的化工原料,其产率和品质是评价煤热解工艺的重要指标。从原煤性质(煤种和煤粒径)、热解反应器结构形式及热解工艺条件(原煤预处理、热解温度、压力、升温速率、停留时间、热解气氛及催化剂)等方面综合分析了煤热解焦油产率和品质的影响因素,认为通过优选煤种和热解反应器,对煤样进行适当预处理,选择合适的工艺操作条件和引入加氢催化热解等有助于提高焦油产率和品质。     

喷动载流床中温度对霍林河褐煤快速热解产物的影响

在喷动载流床反应器内对霍林河褐煤的快速热解进行了研究,并对该煤的热解机理进行了初步分析。考察了在500～850℃范围内温度对热解产品产率分布及气体和液体产品具体组成的影响。分别利用气相色谱和色质联用仪来分析气体和液体产物的组成。实验结果表明,气体总产率及CO、H2和C1～5烃类的产率随热解温度的提高而增大;在热解温度为650℃时,液体产率最高,在煤粉粒径为0.125～0.18mm,液体产品的总产率可达23%,其中正己烷可溶物的产率可达30%以上,沸点340℃前馏分也达30%以上。液体产品中酚类产品较多;温度对液体产品的组成有极大的影响。     

Gas evolution during rapid,low-temperature pyrolysis of a North Dakota lignite

Low-temperature pyrolysis of low-rank coals is proposed as a possible technique for producing high-heating value solids. Results are presented showing gas yields and char compositions from low-temperature pyrolysis of a lignite at very short residence times. Tar evolution is observed even at temperatures less than 570K coinciding with the first release of CO₂, presumably from carboxyl groups.     

The role of low-molecular-weight components in the pyrolysis of pitches

Two pitches of different volatile contents, obtained from the same coal tar by different procedures, were characterized by elemental analysis, solubility, ¹H n.m.r., donor—acceptor ability, FT-i.r., extrography and size-exclusion chromatography. Their pyrolysis behaviour was followed by hot-stage microscopy and thermogravimetric analysis. The pitches were carbonized in a horizontal furnace and the resulting cokes were characterized by optical microscopy. Three partly devolatilized pitches were prepared by thermal treatment of the two pitches and their pyrolysis behaviour was compared in terms of mesophase development and optical texture of coke. The results indicate a significant influence of low-molecular-weight components of pitch on the development of mesophase but no effect on the subsequent optical texture of the coke.     

胜利褐煤快速热解特性

为考察热解温度对热解产物品质及挥发分残留的影响,在10 kg/h自制褐煤快速热解提质试验设备上,以胜利褐煤为试验原料,考察了400~900℃热解提质温度对热解产物产率、气体产物组成、半焦微观结构以及残余挥发分的影响。结果表明,随着热解温度的升高,半焦产率逐渐降低,气体产率升高,焦油的产率先升高后降低,700℃时焦油产率最大;热解气体中的CO_2随着热解温度的升高逐渐降低,H_2和CO含量随着热解温度的升高而增加;随着热解温度的升高,挥发分不断释放导致半焦含氧官能团以及高活性的小的缩合芳环减少;热解温度≥700℃,半焦残留的挥发分较低,固定碳较多,基本满足电石用焦的要求。     

Analytical pyrolysis as a tool for the study of plastic coals

The technique of analytical pyrolysis has been used to characterize 40 similar mid-rank western Kentucky coals of widely differing ASTM Gieseler plasticity. Certain pyrolysis/g.c. variables were shown to correlate well with both ASTM Gieseler and isothermal plasticity. Highly plastic coals were shown to exhibit certain characteristic peaks in the 450 °C pyrogram which were absent in the pyrogram of the non-plastic coals. Two coals, representing the two extremes in plasticity, were selected for further study. After extraction with solvents such as DMF the characteristic peaks were absent in the 450 °C pyrogram of the extraction residue of the highly plastic coal. These peaks were also shown to decrease with increasing severity of air oxidation of the plastic coal. This technique appears to be a useful tool for the analysis of mid-rank plastic coals and supports the view that the substances contained in the bitumen fraction of these coals are involved in the development of the plastic state.     

Coal flash pyrolysis: 4. Polymethylene moieties in coal macerals

An analysis for polymethylene moieties in purified coal macerals has shown the (CH₂)_n (wheren?5) content, by a liquefaction—¹ H n.m.r. method, to be highest in exinite macerals and lower in vitrinite and inertinite macerals. From any particular coal, the (CH₂)_n content of the vitrinite was higher than the inertinite but lower than the exinite. Pyrolysis of these macerals gave ethylene yields proportional to the (CH₂)_n content.