Mechanism of pyrolysis of p-xylene

• 1.1. The pyrolysis of p-xylene at temperatures of 830°–1000°C with different hydrocarbon partial pressures (argon/p-xylene=10 : 1, 20 : 1, 30 : 1) has been investigated.
• 2.2. The suggested radical-chain mechanism of p-xylene pyrolysis at high temperatures has an initiation stage leading to the formation of a p-methylbenzyl radical.
• 3.3. It is concluded that toluene is formed mainly by the hydrodealkylation of p-xylene under the given conditions.

     

对二甲苯氧化产物的色谱分析

提出用气相色谱快速定量溶剂醋酸,用液相色谱法快速分析对二甲苯氧化反应体系的所有含苯环的组分的方法。应用Agilent1100高效液相色谱仪,采用D iamonsilC18(D5μm×4.6 mm×150 mm)色谱柱,用甲醇-乙腈-水为流动相,用外标法采用三元梯度洗脱程序分析固相产物中的对羧基苯甲醛和对苯二甲酸含量。以异丙苯为内标物,应用Agilent1100高效液相色谱仪,用甲醇-乙腈-水为流动相,采用三元梯度洗脱程序分析液相产物中的含苯环组分对甲基苯甲醛、对甲基苯甲酸、对羧基苯甲醛、对苯二甲酸、苯甲酸、对二甲苯和内标物异丙苯,应用Sh imazu6A气相色谱仪分析液相中的溶剂醋酸和内标物异丙苯,气相和液相结果通过内标物异丙苯关联。该法准确简捷、且分析周期短。     

对-二甲苯深度氯化产物的结晶法分离及结构研究

根据国标GB／T21845—2008选择结晶所用溶剂为4：1（体积比）的丙酮和水混合溶液，用结晶法对深度氯化的对-二甲苯产物进行分离，分离产率达到82％以上；气相色谱法测定产物为纯度达99．63％的α，α，α，α＇，α＇，α＇-六氯对二甲苯。用紫外光谱（UV）和红外光谱（IR）对分离所得产物结构进行表征。     

Fast pyrolysis of agricultural wastes: Characterization of pyrolysis products

This study deals with pyrolysis of three agricultural wastes (corncob, straw and oreganum stalks) at 500 °C in a fluidized bed reactor. The yields of char, liquid and gas were quantified. Pyrolysis liquids produced were in two separate phases; aqueous phase and oil. Oil yields varied between 35 and 41%, depending on biomass type, whereas the yields of aqueous phases were almost similar, around 6%, for all feedstock. For characterization, oils were fractionated by water extraction into two fractions; water solubles and water unsolubles. Both aqueous phase and water-soluble fraction were analyzed by gas chromatography–mass spectrometry and high-performance liquid chromatography. In addition, water content and elemental analysis of the oils were determined. Chemical compositions of gas and char products relevant to fuel applications were determined.     

Note on acetone-soluble material in cottonseed meals

Summary In connection with a study of methods of eliminating traces of “free” gossypol from cottonseed meals a procedure for isolation of gossypol from the 70% acetone extracts of the meals by transfer to benzene solution has ben developed. A procedure is also given for quantitative determination of the isolated gossypol. Analysis of four samples of cooked cottonseed meats and meal by the method showed that in each instance substances other than gossypol are measured by the A.O.C.S. method for “free” gossypol in meals containing low concentrations of residual “free” gossypol. This procedure promises to provide another analytical tool for the study of residual material in processed cottonseed meal that causes egg discoloration when fed to laying hens. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

废旧轮胎热解及热解产物研究展望

热解作为废旧轮胎处置的重要技术手段,可以有效实现其减量化、无害化和资源化利用。本文综述了废旧轮胎热解的影响因素以及热解产物的研究进展,对废旧轮胎热解的经济、环境和社会效益进行了说明,指出当前工业化热解废旧轮胎存在的问题,并展望了未来节能环保式热解工艺的应用前景。结合现有的工业化热解设备,优化工艺条件和反应器结构型式,进一步分析了热解产物即热解气、热解油及热解炭的成分结构与应用,通过对热解产物改性活化与提质处理,创造更大的经济效益。提出应基于环境法规要求和绿色发展理念,糅合多种处理技术,研制适合废旧轮胎热解的工艺装备,开发集收集/预处理/热解/产物回收与提质于一体的废旧轮胎处置技术,实现废旧轮胎高效清洁转化和高值利用。     

Sulfur distribution within coal pyrolysis products

The pyrolysis of coal leads to distribution of sulfur compounds in pyrolysis gas, char and tar generated during the process. The effect of the process parameters of autothermal coal pyrolysis in the circulating fluidized bed reactor on total sulfur distribution has been investigated. Several experimental tests were performed at the temperature of 920°C. Non-coking coal from the Wieczorek Mine (Upper Silesian Coal Basin) and brown coal from the Bełchatów Mine were examined for sulfur distribution. It was found that distribution of total sulfur in coal pyrolysis products is basically affected by coal to air ratio and addition of steam or acceptor to the pyrolysis process.     

褐煤及其热解产品利用现状

为了提高褐煤利用率,介绍了国内褐煤资源的储量形态、分布。分析了目前褐煤的利用途径,包括共伴生资源的利用、直接燃烧、干燥脱水与成型、气化、液化、制水煤浆与热解。并进一步分析了褐煤热解气、液、固产品的利用方向。提出了褐煤半焦利用的新方法,即利用半焦干法气化,或将半焦和热解废水等制成水煤浆,通过湿法气化制得合成气,再通过甲烷化催化剂将合成气制成甲烷,或将合成气通过费托合成制成汽油柴油。     

轮胎粒径对热解产物的影响

最终热解温度500℃,升温速率20℃/min的条件下,以管式炉热解实验和热重分析为基础,研究了轮胎粒径对废轮胎热解产物的影响。结果表明,在轮胎样品粒径从2 mm减少到0. 1 mm时,热解油产率增加了12. 9%;固体产物产率由52. 1%降低到了39. 4%;同时减小轮胎样品粒径有助于降低热解炭中结焦与积炭的含量;当轮胎粒径达到0. 2 mm后继续减小轮胎样品粒径对热解油产率几乎没有提高。     

轮胎粒径对热解产物的影响

最终热解温度500℃,升温速率20℃/min的条件下,以管式炉热解实验和热重分析为基础,研究了轮胎粒径对废轮胎热解产物的影响。结果表明,在轮胎样品粒径从2 mm减少到0. 1 mm时,热解油产率增加了12. 9%;固体产物产率由52. 1%降低到了39. 4%;同时减小轮胎样品粒径有助于降低热解炭中结焦与积炭的含量;当轮胎粒径达到0. 2 mm后继续减小轮胎样品粒径对热解油产率几乎没有提高。     

Characterisation of products from pyrolysis of waste sludges

The pyrolysis of waste sludges was investigated using thermogravimetry/mass spectrometry (TG/MS) and a fixed-bed reactor. Two types of sludge were used, namely mixed sludge and oil sludge. In TGA/MS measurements, two degradation steps were observed. Degradation of organic structures, in sludge took place in the first step, while inorganic materials in sludge were mainly decomposed in a second step (above 500 °C). In a fixed-bed reactor, the catalytic effect of inorganic matter in addition to organic matter was monitored the quality and yield of products from pyrolysis. Pyrolysis of oil sludge produced a larger amount of oil containing more aliphatic compounds and a high calorific value. On the other hand, pyrolysis of mixed sludge gave a smaller amount of oil being rich in polar compounds. The gaseous products from pyrolysis consist of high amount of combustable gases. Landfilling was found to be the best alternative to dispose off the pyrolytic char obtained from pyrolysis.     

Characterization of the heavy products of coal pyrolysis

In order to obtain information about the production mechanism of large molecules in coal pyrolysis, a subbituminous and two bituminous coals were heated at 500 ° C for 30 s under vacuum. The heavy products were dissolved in tetrahydrofuran (THF) and analysed by ¹H n.m.r. spectroscopy and gel-permeation chromatography in an atmospheric-pressure column. Parallel GPC, ¹H n.m.r. and ¹³C n.m.r. studies were conducted with THF extracts of the same coals. The results are combined with elemental analysis data to obtain structural parameters of the extracts and pyrolysates.     

Gaseous products of microwave pyrolysis of scrap tires

The results of microwave pyrolysis of scrap tires are presented. The composition of pyrolysis gas, in which hydrogen prevails, was established.     

Volatile products from lignite pyrolysis and hydropyrolysis

Samples of three Louisiana lignites were subjected to atmospheric pressure pyrolysis and hydropyrolysis over a temperature range of 400–800 °C. Volatile products were collected in cold traps containing dichloromethane solvent and immersed in a salted ice bath. Volatiles were analysed using coupled gas chromatography/mass spectrometry and approximately 150 separate compounds were noted. Because the product complexity made definite identification of each compound impossible, all components were assigned to one of eleven compound groups and subsequent analysis of results was based upon these groups. The effect of atmosphere, nitrogen versus hydrogen, was found to have a significant impact on volatile composition. Increased concentrations of alkyl benzenes and other single ring compounds were found in the hydrogen product with corresponding reductions in alkanes and alkenes. Only trace concentrations of polyaromatic compounds containing more than two rings were found in either atmosphere. Volatile product composition differences between the three lignites were small. Similarly, the effect of temperature on composition was relatively unimportant.     

甲基苯基混合硅油的热裂解-气质联用分析

对甲基苯基混合硅油进行了热裂解-气质联用分析.在其裂解组分中鉴定出10个主要组分,包括二甲基环硅氧烷、1个苯基取代的二甲基环硅氧烷,以及少量1,2-二苯基四甲基环三硅氧烷的顺、反异构体;并计算了裂解产物中的苯基含量为0.0024 mol/g;此外,在裂解产物中还检测出苯等副产物.证实在反应过程中存在取代基丢失.     

褐煤低温干馏及产物的利用

介绍了褐煤的性质及褐煤提质的常规方法。重点介绍了国内外褐煤低温干馏的典型工艺、特点及开发应用现状。分析了干馏工艺中不同的加热方式、热载体类型以及干馏条件对干馏过程和产品的影响。阐述了褐煤低温干馏产品-褐煤半焦、低温煤焦油以及焦炉煤气的综合利用途径。基于目前国内外褐煤低温干馏工艺大多数处于试验或示范性装置运营阶段,未实现大规模运行,指出未来褐煤低温干馏工艺应走大型化、多联产的新型工业化道路,进一步拓宽干馏产品的应用领域,提高其附加值和利用率,才能实现褐煤资源综合效益最大化和可持续发展。     

Heating value of biomass and biomass pyrolysis products

Studies conducted on the heating value of various types of biomass components and their pyrolysis products such as char, liquids and gases are presented. Heating values of chars are comparable with those of lignite and coke; heating values of liquids are comparable with those of oxygenated fuels such as methanol and ethanol, which are much lower than those of petroleum fuels. Heating values of gases are comparable with those of producer gas or coal gas and are much lower than that of natural gas. It is also found that the heating values of products are functions of the initial composition of biomass; correlations are developed to express these. Also, correlations are developed which explain the influence of ash elements on heating values of the pyrolysis products and on percentage distribution of energy in the products.     

Numerical study of polyethylene burning in counterflow: Effect of pyrolysis kinetics and composition of pyrolysis products

The burning behavior of polyethylene in the counterflow of oxidizing air has been studied numerically with a coupled model describing feedback heat and mass transfer between gas‐phase flame and polymeric solid fuel. A 2‐dimensional elliptic equation in axisymmetric formulation (revealing the cylindrical shape of the polymer sample used in the experiment) has been employed to simulate heat transfer in solid fuel, and a set of 1‐dimensional hyperbolic equations has been used to determine the solid‐to‐gas conversion degree of the pyrolysis reaction. Four sets of products compositions and two modifications for the kinetic parameters of solid fuel pyrolysis reaction have been taken into account. Gas‐phase formulation is presented by set of 1‐dimensional conservation equations for multi‐component flow with detailed kinetic mechanism of combustion. The profiles of temperature and species concentrations in the flame zone have been calculated and compared with the results of experimental study of combustion of ultrahigh molecular weight polyethylene. Higher hydrocarbon composition (dodecane) has been found to show the best agreement between the temperature and species concentration profiles with the measurements, especially for the low‐level mass fractions of the by‐product components—propylene, butadiene, and benzene.     

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.     

Liquid products of the microwave pyrolysis of scrap tires

The pyrolysis of automobile tires was performed in a microwave electromagnetic field on an experimental microwave setup. The compositions of the obtained pyrolysis gas, liquid products, and a solid pyrolysis residue were determined. The experimental data showed that the products of pyrolysis are valuable chemical raw materials, and they can be successfully used in industry.