Reactions of acetylene and ammonia in a continuous-flow microwave discharge reactor

Both pure acetylene and mixtures of acetylene and ammonia have been passed continuously through a microwave discharge reactor. The reaction products from the gas mixtures were hydrogen cyanide, hydrogen and nitrogen. When the input reactant ratio (ammonia to acetylene) was below a critical value, the extent of reaction was negligible. When the critical ratio was exceeded, high conversions were obtained. When reaction did occur, the conversions of both reactants were linear functions of the power absorption in the discharge. The conversion of acetylene to hydrogen cyanide varied linearly with the input volumetric flow rate. Comparison of the present work with previous studies shows that hydrogen cyanide is not produced exclusively by the route when mixtures of benzene and ammonia react in a microwave discharge.     

Composition of gaseous combustion products of polymers

The gaseous products generated by the flaming combustion of ten kinds of synthetic polymers and a kind of wood (cedar) under the same conditions (sample weight, 0.1 g; temperature, 700°C air flow rates, 50 and 100 l./hr) were quantitatively analyzed by infrared spectrophotometry, gas chromatography, and colorimetric tube method. The main hydrocarbons generated were methane, ethylene, and acetylene. The amount of acetylene generated by the flaming combustion of polymers was much larger than the amount of acetylene formed by pyrolysis at 700°C in nitrogen. Acetylene increased in quantity with increasing air. For nitrogen compounds, hydrogen cyanide was generated from every polymer containing nitrogen used, but ammonia was detected only for nylon 66 and polyacrylamide. Nitrogen monoxide and nitrogen dioxide were detected only in small amounts. Nitrous oxide was detected in the gaseous products generated by the nonflaming combustion of urea resin and melamin resin. It was also found that about 70% of the nitrogen in N-66 and PAA was converted into nitrogen gas (N₂) by combustion under the conditions described above.     

Reactions of coal with discharge-generated (excited) nitrogen species

Reaction between coal and nitrogen in a discharge furnishes hydrogen cyanide and smaller amounts of cyanogen, as well as some carbon monoxide and carbon dioxide; the cumulative yields of hydrogen cyanide and cyanogen depend upon rank. The apparent activation energies for formation of hydrogen cyanide and cyanogen are in the order of 2–4 kcal mol⁻¹ but increase sharply to ≈13–14 kcal mol⁻¹ at ≈200 °C (possibly coincident with incipient thermal decomposition of the coal). The cyanogen/hydrogen cyanide ratio increases with rank, and also depends upon the reaction temperature — falling with increasing temperature up to ≈200 °C, and thereafter rising progressively. Rate measurements and i.r. spectral changes accompanying the reaction suggest that hydrogen cyanide is mainly formed from non-aromatic carbon-hydrogen configurations in the coal, and that cyanogen derives for the most part from aromatic carbon — though some can also be generated from non-aromatic CH in competition with formation of hydrogen cyanide.     

Reactions of coal with nitrogen/ hydrogen mixtures in a discharge

In-discharge reaction of coal with nitrogen/hydrogen mixtures rather than nitrogen alone raises rates of hydrogen cyanide generation by a factor of 10–50, and makes hydrogen cyanide account for ≈70–90% of the total product-gas volume. From these results and parallel tests with a pure carbon, it is concluded that enhanced formation of hydrogen cyanide is controlled by transient hydrogenation of aromatic carbon and consequent creation of additional (non-aromatic) reaction centres which can be abstracted by N^*.     

几种年轻煤在氮热等离子体中的热解

研究了几种中国年轻煤在氮电弧热等离子体中的热解行为,考察了煤的基本性质、煤的粒度及加煤速率等条件对煤热解特性的影响.结果发现,煤在氮等离子体条件下热解所得气体产物中的主要成分是氢、乙炔、一氧化碳和丙炔腈,此外还有甲烷和乙烯等小分子烃.乙炔的收率随煤种的不同和操作条件的变化而波动.煤中的挥发分含量愈高、加煤速率愈低,乙炔收率则愈高.其中扎赉诺尔褐煤的乙炔收率最高可达22.3%(以煤中碳为基准);原料煤在氮等离子体中热解后,除部分芳香C—C键得以保留外,煤有机结构中的外围官能团全部消失,同时在热解半焦中有新的氮基官能团(如—C(?)N)引入.     

The pyrolysis of organic compounds under conditions of carbon formation

Studies of the pyrolysis of furan, thiophene, pyrrole and cyclopentadiene at ca. 1000°C have involved analysis of the gaseous products and determination of the structure and properties of the resulting surface carbons. The principal hydrocarbon products formed from each ring compound are methane and benzene, which appear to be stable, and acetylene and ethylene, which are reactive intermediates. When the starting compound contains a hetero-element, this is almost completely absent from the deposited carbon and appears in the gaseous products as water, hydrogen sulphide or hydrogen cyanide. Nitric oxide, when added in sufficient quantities, inhibits the formation of all gaseous products. The nature of the decomposition products, together with thermochemical considerations, support the conclusion that the ring compounds decompose by similar mechanisms and that the hydrocarbon fragments involved in carbon formation are essentially the same. The observed differences in the properties of the carbons are best explained in terms of the scavenging action of free radicals derived from the heterocyclic compounds. It appears that these radicals, which are formed at an early stage of decomposition, tend to remove blocking groups from crystallite edges and thereby promote crosslinking between the carbon crystallites.     

热等离子体转化煤的研究进展

介绍了热等离子体裂解煤制乙炔、富勒烯、碳纳米管和炭黑,以及热等离子体煤气化制合成气的原理、研究现状、存在的主要问题及发展前景。指出热等离子煤转化是一种高效、洁净的技术,在煤化工等领域具有巨大的应用和发展空间,尤其是热等离子体裂解煤制乙炔联产氢与纳米碳材料工艺,值得重视和开发。     

Thermodynamic analysis of coal pyrolysis to acetylene in hydrogen plasma reactor

A systematic re-examination of the thermodynamic study on the process of coal pyrolysis to acetylene in a hydrogen plasma reactor was performed with referenced pilot-plant data at the scale of 2-MW plasma. At the ultra-high temperature conditions, the gas phase composition may reach thermodynamic equilibrium immediately no matter whether the solid carbon exists or not. The mass ratio of C/H in the gaseous phase plays a significant role in the acetylene concentration at the thermodynamic equilibrium states. It is demonstrated either in thermodynamics calculation or in hot tests that a mass ratio of C/H near or above 2 is essential to gain an acceptable concentration of acetylene in the mixed gases, which indicates that the mixing efficiency between gas and coal particles near the coal injection point becomes pivotal to the yield of acetylene for its direct influence on the devolatilization of coal, i.e., the gaseous C/H ratio. Being consistent with the hot test experience, the extra amount of water added into the system may inhibit the production of acetylene. However, the addition of methane might impose a positive effect on the yield of acetylene and therefore on the overall reactor performance.     

Analysis of products of high-temperature pyrolysis of various hydrocarbons

Ethane, ethylene, acetylene, propane and neopentane have been pyrolyzed at 1173 K, and methane at 1372 K in a flow system, and the volatile pyrolysis products analyzed. Eleven aromatic hydrocarbons, containing 14 or fewer carbon atoms, accounted for 98 + % of the liquid products recovered in each case. Benzene was the main product, followed by naphthalene. No compounds with branched chains or multiple substituents were present, and compounds containing even numbers of carbons comprised 93–99% of each mixture. Acetylene was a major component of the gaseous effluent from each of the initial hydrocarbons. The effect of temperature on the composition of the gaseous effluent during pyrolysis of methane, ethane and ethylene was determined. Carbon film deposition from methane commenced at about 1273 K; from ethane at 1015 K and from ethylene at 1100 K, in each instance coinciding with the appearance of acetylene in the effluent. As the temperature was raised, at first the increase in the rate of carbon deposition closely followed the increase in the concentration of acetylene in the effluent. It is proposed that acetylene may be a common factor in the pyrolysis of aliphatic hydrocarbons, perhaps acting as the precursor of both surface carbon and aromatic hydrocarbons by a process of head-to-tail linkage of two-carbon units at active surface sites to form chains that then undergo dehydrogenation to carbon or cyclization and desorption as aromatic species.     

Oxygen, Nitrogen, and Sulfur Removal Reactions in Donor Solvent Coal Liquefaction

There are a number of ways coal can be converted to liquid fuel. It can be pyrolyzed to produce gas, liquid, and char. It can be first converted to carbon monoxide and hydrogen which can then be converted to liquid fuel via Fischer-Tropsch synthesis. It can be hy-dropyrolyzed to produce gases, naphtha range liquids, and heavy residues. Finally, it can be liquefied in the presence of a hydrogen donor solvent to produce liquid and gaseous products. This review is concerned with the last method for conversion of coal to liquid fuel.     

Oxygen,Nitrogen, and Sulfur Removal Reactions in Donor Solvent Coal Liquefaction

There are a number of ways coal can be converted to liquid fuel. It can be pyrolyzed to produce gas, liquid, and char. It can be first converted to carbon monoxide and hydrogen which can then be converted to liquid fuel via Fischer-Tropsch synthesis. It can be hy-dropyrolyzed to produce gases, naphtha range liquids, and heavy residues. Finally, it can be liquefied in the presence of a hydrogen donor solvent to produce liquid and gaseous products. This review is concerned with the last method for conversion of coal to liquid fuel.     

Reactions of benzene and ammonia in a continuous-flow microwave discharge reactor

Gaseous mixtures of benzene and ammonia have been passed through a continuous-flow microwave discharge reactor. The principal reaction products were hydrogen cyanide, hydrogen, nitrogen and acetylene. Aniline and butadiene were produced in smaller amounts. At a pressure of 4 × 10^?2 bar, no reaction occurred unless the molar ratio of ammonia to benzene exceeded 1 : 1. At 9.3 × 10 ^?2 bar, no reaction occurred unless the reactant ratio exceeded 2:1. The presence of nickel wire affected the distribution of reaction products. The conversions of benzene were less than those which had previously been found in pure benzene. The maximum conversions of ammonia were much higher than the conversions obtained in pure ammonia. The consumption of both benzene and ammonia were found to be zero order rate processes. The consumption rates of the reactants varied linearly with power absorption in the reactor.     

热等离子体热解煤焦油制乙炔

利用热等离子高温、高焓等特性热解煤焦油制乙炔是一条清洁高效的乙炔生产技术。在实验室对热等离子体热解煤焦油反应中的原料进样温度、反应气氛、输入比焓等关键因素展开了研究。结果表明,热等离子体可将煤焦油直接转化为乙炔及其他小分子气态产品,预热煤焦油可改善其流动性从而提高煤焦油和等离子体射流的初始混合效率;氢等离子体的加入可显著提高煤焦油转化率和乙炔收率并减少结焦;随着输入比焓的增加,煤焦油转化率、乙炔收率和气态产品总收率均得到提高。在实验中得到的煤焦油转化率最高为86.3%,乙炔收率最高为24.6%,气态产品总收率最高为51.7%。煤焦油在热等离子体的热解过程中副产乙烯,乙烯收率达到7.9%。乙炔收率和乙烯收率的比值可用于预测气相体系温度。     

煤基炭素活性材料的研究进展

对煤基活性炭，煤基活性炭纤维，煤基纳米结构材料等煤基活性炭素材料在制备方面的进展进行了评述，在此基础上提出了煤基超级活性炭，煤沥青基活性炭纤维和煤基纳米结构材料是开发煤基高附加值产品，拓展煤层甲烷和煤气化产品中烃组分新用途的有潜力的方向。     

A shock tube study of the high temperature reactions of nitrogen with hydrocarbons

A single pulse shock tube has been used to study the reactions of nitrogen with methane, ethane and acetylene at 1400°-6000°K. Reactants heated by the reflected shock for about 1–1.5 milliseconds are cooled by rarefaction waves, and samples obtained through a quick-opening check valve are analyzed by gas chromatography. The effect of nitrogen on hydrocarbon pyrolysis appears to be negligible below about 2000°K. At higher temperatures, vibrationally excited nitrogen molecules react with free radicals and produce hydrogen cyanide. Activation energies in the range 23 to 54 Kcal/mole are calculated for the formation of hydrogen cyanide.     

Composition and volume of gas released by crushing coal from West Virginia,Kentucky and Alabama

Analyses of the composition and volume of gaseous inclusions in samples of coal from West Virginia, Alabama and Kentucky have been made at room temperature by mass spectrometric techniques. This was done by crushing the coal in the high-vacuum inlet system of a research mass spectrometer. The gases observed were composed of C, S, H, O, N, He and Ar atoms. Water was the most abundant gas; others were hydrogen, helium, methane, ammonia, methanol, ethanol, carbon monoxide, nitrogen, ethane, oxygen, hydrogen sulphide, argon and carbon dioxide. Gas compositions were found to be a function of the source of the coal. For example, over 6% of the gas from Alabama coal was methane, but West Virginia coal contained only 0.1% methane. The volume of gas also was a function of the coal source. Coal from Kentucky contained 2.3 cm³ g^?1 (STP), whereas coal from West Virginia contained 0.4 cm³ g^?1.     

Effect of temperature,catalyst and charge gas on the mean chemical structures of the products from hydrogenation of Liddell coal

Liddell coal (New South Wales, Australia) has been hydrogenated at 400, 425 and 450 °C with excess tetralin as vehicle and nitrogen or hydrogen as charge gas for 4 h at reaction temperature. In some experiments a nickel-molybdenum catalyst was used. The structures of the liquid and solid products were investigated by nuclear magnetic resonance spectroscopy, gel permeation chromatography and combustion analysis. Increasing the hydrogenation temperature from 400 to 450 °C decreases the yield of liquid products but increases conversion. At higher temperatures the liquid products are smaller in molecular size and molecular weight and contain a greater proportion of aromatic carbon and hydrogen; the solid residues also contain a greater proportion of aromatic carbon. The changes in variation of yield and structure with temperature are independent of the presence of catalyst under nitrogen and the nature of the charge gas. However, as the reaction system is capable of absorbing more hydrogen than can be supplied by the tetralin, the products from reactions with hydrogen as charge gas contain more hydrogen, some in hydroaromatic groups. Catalyst has little, if any, role in dissolution of the coal when a nitrogen atmosphere is used. When nitrogen is used as charge gas, reactions of coal-derived liquids with the catalyst do not alter the hydrogen, carbon or molecular size distributions in the products. The results show that the changes in composition of the liquid and solid products with increase in hydrogenation temperature are due to pyrolytic reactions and not to increased hydrogenation of aromatic rings.     

Calculation of Decomposition Products from Components of Gunpowder by using ReaxFF Reactive Force Field Molecular Dynamics and Thermodynamic Calculations of Equilibrium Composition

The major combustion products from munitions containing nitro‐based propellants are water, carbon monoxide, carbon dioxide, hydrogen, and nitrogen. In addition, compounds including hydrogen cyanide, ammonia, methane, nitrogen oxides, benzene, acrylonitrile, toluene, furan, aromatic amines, benzopyrene, and various polycyclic aromatic hydrocarbons are detected in minor concentrations. The literature shows that the thermodynamic prediction of the major decomposition products agrees fairly well with the measurements. However, poor agreement is found for the minor species. We have studied the thermal decomposition products of the main gunpowder ingredients. Each of the components nitrocellulose, nitroglycerine, and the nitrate ester stabilizers diphenylamine and ethyl centralite were thermally decomposed with ReaxFF reactive force field molecular dynamics and equilibrium thermodynamics. The molecular dynamics results for the major decomposition products from nitrocellulose were partly consistent with measurements. Compared to the thermodynamic calculations, the molecular dynamics simulations agreed considerably better with experimental results for minor species like hydrogen cyanide. The nitrate ester stabilizers are the main sources for ammonia and aromatic combustion products, whereas hydrogen cyanide is produced from nitrocellulose as well as from the stabilizers when gunpowder is combusted.     

热等离子体裂解天然气和煤制乙炔乙烯

乙炔和乙烯均属化学工业基础原料,现在主要由石油和电石制得．随着石油资源的枯竭和人们环保意识的提高,人类正在寻求其他资源途径和技术途径来获得需要的诸如乙炔和乙烯等化工基本产品．利用相对丰富的天然气(NG)和煤炭资源,采用热等离子体技术制备乙烯和乙炔是很有前途的方法之一．     

High-resolution FTIR analysis of coal gas

Coal gas samples collected from a laboratory scale gasifier have been analysed using high-resolution (0.125 cm^?1) Fourier transform infrared spectrometry (FTIR). The gas samples were introduced into an evacuated 8.76 m path-length gas cell and backfilled with nitrogen to 1 atm. Carbonyl sulphide and ammonia were quantified in samples with concentrations ranging from trace to 370 ppm, and non-detectable to 25 ppm, respectively. Other compounds identified in the coal gas samples include: methane, ethane, ethylene, ?C₃ hydrocarbons, acetylene, carbon monoxide, carbon dioxide, ethylene oxide, methane thiol, hydrogen cyanide, formaldehyde, cyanogen (?), ethane thiol (?), methanol, and nitric acid (?). Several compounds were sought but were not present in detectable quantities (less than ≈ 1 ppm). These include: nickel carbonyl, arsine, benzene, methyl chloride, methylamine, HCI, nitrogen oxides, and phosgene. Selected compounds, e.g. ammonia, were quantified by calibration with a standard gas. High resolution FTIR, a nearly universal detector, is especially useful for determining presence or absence of specific pollutants or interest which are not easily determined by routine gas chromatographie methods.