Growth and coalescence of mesophase in pitches with carbon black additives and in coal

The techniques of polatized light optical microscopy and of washing the surfaces of solid pyrolysis products with chloroform prior to SEM examination are used to monitor the growth and coalescence of growth units of mesophase in a petroleum pitch, a coal extract and a caking coal. Additions of 1 wt% of carbon black retard growth and coalescence and promote clustering of these units because of adhesion of carbon black particles. This has the effect ultimately of reducing the size of the optical texture in coke from the coal extract, but not with coke from the petroleum pitch which has lower viscosity. With the coal, mesophase growth units tend to form clusters and do not coalesce. Mesophase can form an anisotropic skin on the inside of developing pores (bubbles) in the fluid phase and this may limit their growth.     

Formation of mesophase in coal tar pitches. Influence of pyrolytic carbon particles

Hitherto it has been considered that the pyrolytic particles present in pitch as a result of high temperature cracking accelerate the formation of mesophase by the nucleation process. It has been demonstrated by optical and hot stage microscopy that the contrary is the case. The pyrolytic particles in pitch retard the development of mesophase so that mesophase starts to be detectable only at higher temperatures of pyrolysis and the coalescence is suppressed or even prevented by pyrolytic particles surrounding the mesophase spheres originally formed.     

Rheological study of eucalyptus tar pitches

The development of advanced carbonaceous materials (ACMs) from biopitches is important to increase the revenue of the charcoal making industry and to stimulate the use of biomass, thereby attending to the appeals for environmental preservation. A pioneer study on the rheological behavior of eucalyptus tar pitches was carried out in this work. This behavior plays an important part in obtaining ACMs from pitch, particularly in the spinning step of carbon fiber production. Our results showed that biopitches have a strong dependence on the viscosity and temperature/softening point ratio. An Arrhenius‐type law gave the activation energies for viscous flow. Different from conventional polymers, this energy was higher for more polymerized pitches because of their higher molecular stiffness. The results obtained by the Williams–Landel–Ferry equation showed that the viscosity can be associated with the free volume. Lower viscosities correspond to larger free volume. The plot of the apparent viscosity versus the shear time at constant temperature and shear rate showed that the pitches have a purely viscous flow. Experiments that changed the shear rate showed that biopitches behave as Newtonian fluids. Purely viscous and Newtonian behaviors are desirable for more stable spinning. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 900–908, 2002; DOI 10.1002/app.10096     

煤与废塑料共热解特性研究进展

煤与塑料共热解既能回收废塑料中的碳氢资源,又可以实现废塑料的资源无害化处理,是一种很有前景的废塑料资源化回收利用方式。本文概述了煤与塑料共热解的热解特性及其产物性质,分析了煤与塑料共热解的机理及共热解过程中氯的迁移规律,简要介绍了煤和塑料的不同混合方式及其对共热解特性的影响。文中指出煤与塑料共热解具有明显的增油减水效应,在煤热解过程中添加一定量的废塑料不仅可以改善焦油品质,同时对热解半焦的结构和反应性也有一定的影响,因此煤-塑料共热解是一种绿色高效资源化的废塑料处理方式,对于废塑料循环利用、解决白色污染问题及提高煤炭利用率具有重要意义。     

Mechanism study of iron-based catalysts in co-liquefaction of coal with waste plastics

The state and active site of iron-based catalysts in co-liquefaction of coal with low-density polyethylene (LDPE) have been discussed. The catalysts used were sulfur-promoted iron oxides (Fe₂O₃+S), ferrous sulfide (FeS), ferrous sulfate (FeSO₄·7H₂O) and the mineral pyrite (FeS₂). It was found by X-ray photoelectron spectrometry that the active site in the working state of Fe₂O₃+S catalyst was not Fe_1−XS and the main form of sulfur existing in the spent Fe₂O₃+S catalyst was sulfate, followed by sulfite (SO₃²⁻). A finding from autoclave tests was that the ferrous sulfate before and after oxidation treatments showed sufficiently high activity for the co-liquefaction of coal with LDPE. It was concluded that an active site of the iron-based catalysts was sulfate species formed on the catalyst surface during the hydroliquefaction process of coal.     

宁武煤和废塑料的共处理液化研究

在 50mL的小型反应器内 ,进行了煤和废塑料共液化处理的研究 ;结果表明 ,废塑料在一定的条件下 ,可有效地促进煤的转化 ,提高转化率 ,降低氢耗量 ,缓和反应条件     

废塑料在炼焦配煤中的应用研究

介绍了宁钢应用塑料型煤技术,在满足焦炭质量要求的前提下,扩大了炼焦煤中添加废塑料的比例,而且在限定废塑料添加比例的条件下稳定了焦炭质量,为科学、合理、经济地治理白色污染提供了理论依据和工业经验。     

Catalytic coprocessing of coal and petroleum residues with waste plastics to produce transportation fuels

Coprocessing reactions with waste plastics, petroleum residues and coal were performed to determine the individual and blended behavior of these materials using lower pressure and cheaper catalysts. The plastic used in this study was polypropylene. The thermodegradative behavior of polypropylene (PP) and PP/petroleum residues/coal blends were investigated in the presence of solid hydrocracking (HC) catalysts. A comparison among various catalysts has been performed on the basis of observed temperatures. The higher temperatures of initial weight loss of PP shifted to lower values by the addition of petroleum residues and coal. The catalysts were also tested in a fixed-bed micro reactor for the pyrolysis of polypropylene, petroleum residues and coal, alone and blended together in nitrogen and hydrogen atmosphere. High yields of liquid fuels in the boiling range 100-480 °C and gases were obtained along with a small amount of heavy oils and insoluble material such as gums and coke. The results obtained on the coprocessing of polypropylene with coal and petroleum residues are very encouraging as this method appears to be quite feasible to convert plastic materials into liquefied coal products and to upgrade the petroleum residues and waste plastics.     

Rheological characteristics of coal tar and petroleum pitches with and without additives

An extensive study of rheological characteristics of coal tar and petroleum pitches with and without additives, namely, petroleum coke, natural graphite and carbon black has been made. It is found that all pitches, pure or mixed with a carbon additive are not Newtonian as reported in the literature, but behave Theologically as Bingham plastics with certain yield stress and plastic viscosity at all temperatures of measurement between 85–180°C. The yield stress and plastic viscosity both decrease with increase in temperature of the pitch. A pure petroleum pitch having the same softening point as that of a coal tar pitch is found to have a lower viscosity compared to that of the latter at all temperatures of measurement. This suggests that the criterion of softening point as a measure of suitability of a coal tar pitch binder in the manufacture of artificial carbon is not sufficient for petroleum pitches. Addition of ten parts of carbon black by weight of pitch results in a considerable decrease in viscosity change with temperature of the coal tar pitch compared to almost insignificant change in the case of the petroleum pitch of the same softening point. However, the addition of petroleum coke or natural graphite makes the pitch more viscous but does not change the temperature dependence of viscosity of either of the two types of pitches. The implications are discussed.     

Anomalous capillary flow of coal tar pitches

Capillary flow of liquid coal tar pitch into a coke bed was studied. Anomalies in the flow could not be attributed to a plugging effect for mesophase content lower than 20 wt%. The flow behaviour of small pitch droplets can be correlated with the change in physicochemical properties, as measured by the glass transition temperature, on penetration into the coke bed.     

Interaction of thermosetting plastics with clinkering coal

The influence of phenol-formaldehyde resin on the clinkering properties of coal batch is studied by means of the dilatometric method proposed by the Institute of Mining and Dnepropetrovsk Metallurgical Institute. For comparison, its influence on the clinkering ability is studied by the Roga method. The results show that this organic additive has a similar influence in both cases.     

废旧塑料的回收与利用

综述了利用区块链技术进行废旧塑料的回收.使用区块链技术建立的塑料银行可以激励人们自发地回收废旧塑料.废旧塑料的回收流程大多是线下的,监管困难,使用区块链技术可以使用户在区块链上查询全流程的回收数据,便于监管.在废旧塑料的分选和利用方面,介绍了聚乙烯和聚丙烯的分选,聚对苯二甲酸乙二酯与聚氯乙烯混合固体塑料的分选.废旧塑料...     

Re-use and separation of waste plastics

Commercial and pilot-scale methods for the re-use of clean, unmixed scrap plastic are described. Mixed scrap presents greater problems and efforts have been made to improve its properties with additives or by altering its composition. Separation methods are surveyed. Mixed wastes find limited re-use in low quality products. Re-use of waste plastics as fuel is now probably the most economical alternative. Economic rather than technical obstacles remain for this recycling.     

Pyrolysis-gasification of plastics, mixed plastics and real-world plastic waste with and without Ni-Mg-Al catalyst

Polypropylene, polystyrene, high density polyethylene and their mixtures and real-world plastic waste were investigated for the production of hydrogen in a two-stage pyrolysis-gasification reactor. The experiments were carried out at gasification temperatures of 800 or 850 °C with or without a Ni-Mg-Al catalyst. The influence of plastic type on the product distribution and hydrogen production in relation to process conditions were investigated. The reacted Ni-Mg-Al catalysts were analyzed by temperature-programmed oxidation and scanning electron microscopy. The results showed that lower gas yield (11.2 wt.% related to the mass of plastic) was obtained for the non-catalytic non-steam pyrolysis-gasification of polystyrene at the gasification temperature of 800 °C, compared with the polypropylene (59.6 wt.%) and high density polyethylene (53.5 wt.%) and waste plastic (45.5 wt.%). In addition, the largest oil product was observed for the non-catalytic pyrolysis-gasification of polystyrene. The presence of the Ni-Mg-Al catalyst greatly improved the steam pyrolysis-gasification of plastics for hydrogen production. The steam catalytic pyrolysis-gasification of polystyrene presented the lowest hydrogen production of 0.155 and 0.196 (g H₂/g polystyrene) at the gasification temperatures of 800 and 850 °C, respectively. More coke was deposited on the catalyst for the pyrolysis-gasification of polypropylene and waste plastic compared with steam catalytic pyrolysis-gasification of polystyrene and high density polyethylene. Filamentous carbons were observed for the used Ni-Mg-Al catalysts from the pyrolysis-gasification of polypropylene, high density polyethylene, waste plastic and mixed plastics. However, the formation of filamentous carbons on the coked catalyst from the pyrolysis-gasification of polystyrene was low.     

废旧塑料的综合利用

综合利用废旧塑料,解决“白色污染”,已成为全球的研究热点。本文从废旧塑料的直接利用、改性利用、热分解、与煤共液化等几个方面综述了废旧塑料的综合利用途径,其中废旧塑料与煤共液化处理技术很有发展前途,将成为今后研究的新热点。     

用废聚苯乙烯泡沫塑料制备涂改液

将废聚苯乙烯泡沫塑料溶解在乙酸乙酯中,制成高分子胶粘液,向其中加入表面活性剂十二烷基硫酸钠、增塑剂邻苯二甲酸二丁酯和遮盖剂氧化锌、二氧化钛,经球磨机研磨制成涂改液。通过控制变量法,探讨了各组分对涂改液性能的影响,确定了制备涂改液的最佳配方。该法工艺简单,操作方便,不需要特殊设备,且变废物为原料,既降低了产品的成本,减少了涂改液对人体的毒害性,又对减轻白色污染的危害作了有益的探索。     

利用废杂塑料制备燃料油

为使废杂塑料的产物回归石油产品，介绍了废杂塑料制备燃料油工艺中原料的分离、原料的预处理、催化剂的使用以及热分解、裂解工艺条件。     

废旧塑料分选技术

废旧塑料的回收包括 3个阶段 :收集、分选、加工或再生等步骤。只有清洁的废旧塑料才能生产高质量的产品 ,这需要有效的塑料分选方法。评述了光选、电选、风力分选、密度分选、浮选等废旧塑料分选技术 ,指出浮选在废旧塑料分选方面具备独特优势     

Dissolution of waste plastics in biodiesel

The dissolution behavior of polystyrene (PS) and low‐density polyethylene (LDPE) in biodiesel was investigated with an eye towards developing methods to dispose waste plastics by burning them with fuel. To complement and guide the experimental investigations, molecular dynamics simulations were performed to calculate solubility parameters, cohesive energy densities, Flory‐Huggins χ parameters and phase diagrams of the target systems. Dissolution kinetics of PS and LDPE in methyl esters was monitored by gravimetry, from which parameters such as dissolution rates, activation energies, and scaling indices were estimated. The shear viscosity of the polymer solutions was measured to ascertain their suitability as fuel mixtures. The dissolution of PS in biodiesel appears to be controlled by the diffusion of polymer chains through a boundary layer adjacent to the polymer/solvent interface. Taken together, the experimental and modeling studies provide a predictive toolbox to design biodiesels of different compositions that will dissolve commodity polymers such as PS and LDPE to be used as fuels in engines. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Liquid-phase methanol synthesis in apolar (squalane) and polar (tetraethylene glycol dimethylether) solvents

The kinetics of the three-phase methanol synthesis over a commercial Cu–Zn–Al₂O₃ catalyst were studied in an apolar solvent, squalane and a polar solvent, tetraethylene glycol dimethylether (TEGDME). Experimental conditions were varied as follows: P=3.0–5.3 MPa, T=488–533 K and Φ_vG/w=7.5×10⁻³–8×10⁻³ Nm³ s⁻¹kg⁻¹_cat. The nature of the slurry–liquid influences the activation energy and the kinetic rate constant by interaction between adsorbed species and solvent and by competitive adsorption of the solvent on the catalyst surface. The rate of reaction to methanol observed in TEGDME appeared to be about 10 times lower than in squalane. TEGDME reduces the reaction rate, which is a disadvantage for its use as a solvent.