连二硫酸锰碳化干渣热解回收硫酸钠的研究

利用软锰矿进行湿法冶金或烟气脱硫技术研究时,因其即可控制大气污染亦可回收锰资源而备受关注。然而,反应过程会生成影响脱硫尾液中硫酸锰的品质的副产物—连二硫酸锰（杂质）,如何回收或去除该杂质是技术研发和推广的难题。本文提出了连二硫酸锰先经碳酸氢钠碳化得到连二硫酸钠和碳酸锰,两产物分离后,结合低温热解的方法将连二硫酸钠制备成无水硫酸钠;实验考察了热解制备过程的各产物和控制反应步骤的温度,进而推理出动力学参数和反应机理。热解实验结果表明：255 ℃（摄氏度）是连二硫酸钠热解制备无水硫酸钠的最佳热解反应温度,并且热解反应过程经历脱硫和脱水两大步骤;热解产物的X射线衍射（XRD）和离子色谱（IC）表征结果表明：产物为单一相的立方体结构硫酸钠晶体。利用热重示差扫描热分析（TG-DSC）对连二硫酸钠热解过程进行表征,结合Kissinger微分法和Coats-Redfern积分法对热解法中脱水和脱硫过程中的活化能进行推算,脱水和脱硫活化能分别在14.75-18.11 kJ/mol（千焦/摩尔）和132.61-137.18 kJ/mol范围内。热解尾气测定结果表明：连二硫酸钠热解制备无水硫酸钠时释放出的尾气主要为二氧化硫。因此,经低温热解工艺处理软锰矿脱硫尾液中连二硫酸根的方法是可行的,不仅可以避免液相处理工艺中酸性废水产生的问题,还可以利用热解制备过程中的尾气去除残留的碳化剂（碳酸钠）,以达到资源化回收目的。     

Characterization of carbon nanofiber composites synthesized by shaping process

Catalytically grown carbon nanofibers (CNFs) are shaped into pellets in desired size and configuration by a conventional molding process so as to extend the potential applications of CNFs in industrial heterogeneous catalysis. After shaping, a novel carbon nanofiber composite with sufficient mechanical strength is produced, in which isolated CNFs are connected by a carbon network formed through polymer binder carbonization. Characterization of the synthesized CNF composite is performed by using HRTEM, XRD, Raman, N₂ physisorption, TPD and TGA. A comparison of the textural and structural properties, as well as the surface chemistry is made amongst the CNFs, the CNF composite, and a commercial coal-based activated carbon, in order to attain a comprehensive understanding of the CNF composite. The results show that the CNF composite preserves the mesoporous texture of the CNFs which will be beneficial to those reactions of mass transfer control. The modification effect of oxidative treatments on physico-chemical properties of the CNF composite is also investigated. More surface oxygen-containing groups are introduced to the composite by treating the material either in boiling HNO₃ solution or in static air at 400 °C.     

Carbonization of petroleum feedstocks II: Chemical constitution of feedstock asphaltenes and mesophase development

The characterization of the asphaltene fractions of a range of petroleum feedstocks by FT-IR, ¹H and ¹³C NMR spectroscopy indicated distinct differences in the molecular structure of the asphaltenes. Some of these differences could be related to the variations in the size of the principal optical texture of the semi-cokes produced by carbonization. The principal optical texture size was observed to increase steadily with the increasing hydrogen aromaticity of the asphaltenes over the whole range of the feedstocks used. There was no consistent correlation, however, between the carbon aromaticity of the asphaltenes and the optical texture size. The correlation between the hydrogen aromaticity and the principal optical texture size was attributed to structural differences among the asphaltenes that are critically important for the mesophase development.     

Changes of porosity during carbonization of bituminous coals: effects due to pores with radii less than 2500 nm

Based on both available reports and the results of experimental studies, the pores in coal chars have been divided into three groups. The first group comprises of pores with radii <7.5 nm, the second one consists of the pores with radii in the range 7.5≤r≤2500 nm and the third group consists of the pores with r>2500 nm. Based on the results of the experimental study conducted for ten Polish bituminous coals, the set of equations describing volume changes of the pores with r≤2500 is derived and discussed for slow carbonization of selected coals up to 1000 °C. The equations describe both the transformation processes of the primary pores and the formation and development of new pores depending on the final temperature of carbonization and properties of the parent coal. These properties include the Gieseler temperatures of softening and resolidification as well as the characteristics of the chemical structure of coal organic matter. The impact of the coal's organic matter contraction and the coal's total mass loss on the pore volume (cm³/g) are also taken into account.     

Analysis of the microporosity shrinkage upon thermal post-treatment of H3PO4 activated carbons

Starting from a commercial pelletized phosphoric acid based activated carbon, with a typical opened and developed micro and mesoporosity, a post-heat-treatment in KOH, at different KOH/activated carbon ratios, has been studied. In all the cases, a pore size shrinkage has been observed. To find an explanation for the reason of this micropore size distribution shrinkage different factors have been studied, among them: (a) effect of the presence of impurities coming from the activation process with phosphoric acid; (b) effect of the KOH post-treatment temperature; (c) heat-treatment temperature of the precursor (without chemical agent); (d) effect of the reagent nature (NaOH, NaCl and KCl vs. KOH). The variable that produces the most intense shrinkage effect, and the disappearance of the mesoporosity, is the heat-treatment in presence of hydroxide, which affects even using a low hydroxide/activated carbon ratio. Such a low hydroxide/activated carbon ratio does not produce activation, nor porosity development of the starting activated carbon during the treatment. This shrinkage phenomenon, which seems to be independent of the method of preparation used to prepare the activated carbon, can be understood considering our previous studies about the reactions involved during chemical activation by hydroxides.     

聚丙烯腈基碳纤维的研究进展

本文简要介绍了聚丙烯腈基碳纤维的国内外发展历程和现状,碳纤维及其复合材料的应用进展,详细介绍了碳纤维生产工艺包括原丝制备、预氧化、碳化的一些新进展,并对我国聚丙烯腈基碳纤维的发展提出了一些建议。