Hierarchical porous carbons prepared from direct coal liquefaction residue and coal for supercapacitor electrodes

Hierarchical porous carbons were prepared from a coal liquefaction residue (CLR) and two coals, Shenhua (SH) coal with low and Shengli (SL) coal with high ash content, by KOH activation with the addition of some additives, and used as the electrode for supercapacitors. Two metal oxides (MgO and Al₂O₃) and three organic materials (sugar, urea and cetyltrimethylammonium bromide) were used as the additives, to investigate their effects on the structure and capacitive performance of the resultant carbons. The results show that the metal oxide and/or its salt formed by the reaction with KOH can serve as space fillers of nanopores in the carbonized carbon, while the gases produced by the decomposition of the organic additive can develop and/or widen some pores. Both help the carbon produced from CLR or the SH coal with low ash content to have additional meso- and macropores, but destroy the structure of the carbon from the SL coal with high ash content. Compared with the carbon without any additive, the optimized hierarchical porous carbon with each additive shows a smaller equivalent resistance, much higher capacitance in a wide range of charge–discharge rates and excellent cycle stability when the carbon was used as supercapacitor electrode.     

Preparation of carbon microfibers from coal liquefaction residue

Carbon microfibers (CMFs) were synthesized directly from coal liquefaction residue (CLR) by arc-jet plasma method at atmospheric pressure, and were examined using scanning electron microscopy and EDX spectroscopy. It has been found that the as-synthesized CMFs are smooth in surface and quite uniform in diameter that is smaller than 1 μm and centers at 700 nm. The possible mechanism involved in the formation process of CMFs is proposed and discussed in terms of the special chemical composition of CLR and the process parameters. This work may open a new way for direct and effective utilization of the CLR.     

神东煤与煤液化残渣共热解研究

为实现煤液化残渣的资源化利用,采用神东煤与液化残渣进行共热解试验,研究了神东煤粒度、残渣粒度、残渣比例对热解产物分布及热解半焦强度的影响,建立了热解半焦强度测试方法。结果表明,共热解后焦油干基收率随着液化残渣加入量的增多而增大,液化残渣的加入对焦油的生成有正协同作用。1 mm液化残渣添加量由10%增加到30%,3~6 mm神东煤共热解半焦转鼓强度增大29.3%,易碎性F值降低22.8%;同样条件下,液化残渣添加量对3~6 mm神东煤共热解半焦转鼓强度的影响更大,1 mm的液化残渣添加量对神东煤共热解半焦易碎性F值影响更大,3 mm神东煤和1 mm的液化残渣共热解半焦转鼓强度小,易碎性F值高,因此热解过程原料煤应当设置粒度下限。     

煤直接液化残渣的性质及利用现状

为了高效地利用煤直接液化残渣,从液化残渣的组成、结构特性、热解特性、溶解特性4个方面论述了液化残渣的物理化学性质的研究现状。研究发现:残渣在组成和结构特性上都保留了原煤的部分特性。在对直接液化残渣热解特性的研究中,论述了各种不同研究手段,例如热重分析仪、实验室移动床、小型焦炉、高压釜等对液化残渣的热解过程的研究进展及热解机理的解析现状。在对液化残渣的溶解性进行研究时,讨论了残渣溶解性研究的意义及其在各种溶剂中表现出的不同特征。最后论述了煤直接液化残渣的利用研究现状、分析了其潜在的高附加值利用方式、发展前景和存在的问题。     

煤炭直接液化残渣加氢研究进展

在煤炭直接液化生产过程中,会产生占液化原煤质量30％左右的液化残渣。它是一种高碳、高灰和高硫的物质,主要由未转化的煤、液化中间产物、无机矿物质以及煤液化催化剂组成。煤炭直接液化残渣有很高的利用价值,无论从经济角度还是环保角度出发,都需要对残渣进行利用,这也是煤炭直接液化工业化必须解决的问题。综述了煤炭直接液化残渣的来源、组成、性质、加氢研究现状及应用等。     

Preparation of carbon nanofibers/carbon foam monolithic composite from coal liquefaction residue

Carbon nanofibers/carbon foam composites that are made by growing carbon nanofibers (CNFs) on the surface of a carbon foam (CF) have been prepared from coal liquefaction residues (CLR) by a procedure involving supercritical foaming, oxidization, carbonization, and catalytic chemical vapour deposition (CCVD) treatment. These new carbon/carbon composites were examined using SEM, TEM and XRD. The results show that the as-made CF has a structure with cell sizes of 300-600 μm. X-ray diffraction studies show that iron-containing contaminates are present in the CLR. However, these species may act as a catalyst in the CCVD process as established in the literature. After the CCVD treatment, the cell walls of CF are covered by highly compacted CNFs that have external diameters of about 100 nm and lengths of several tens of micrometers. This work may open a new way for direct and effective utilization of the CLR.     

Hydrogenation of heavy liquids from a direct coal liquefaction residue for improved oil yield

For hydrogenation of heavy liquids in direct coal liquefaction residue (DCLR) within the direct coal liquefaction (DCL) process, heavy liquids in a DCLR derived from a bench-scale Shenhua DCL process using Shenhua coal are evaluated under two conditions. One simulates the coal liquefaction conditions of the Shenhua plant in the presence of a Fe-based Shenhua catalyst; the other one simulates the online hydrotreating conditions in the presence of a NiMo/Al₂O₃ catalyst. The results show that the heavy liquids of DCLR can be hydrogenated under these two conditions yielding less heavy products; hydrogenating the heavy liquids under the online hydrotreating conditions is more effective than that under the coal liquefaction conditions; the preasphaltene fraction is a main problem that yields non-soluble materials under these hydrogenation conditions. The results suggest that hydrogenation of toluene soluble and tetrahydrofuran soluble fractions of the DCLR under the coal liquefaction and online hydrotreating conditions is feasible, but their conversion to lighter products are inapparent under the coal liquefaction conditions, and elimination of the formation of tetrahydrofuran insoluble fraction in the online hydrotreator should be considered.     

Hydro-treatment of a direct coal liquefaction residue and its components

Direct coal liquefaction residue (DCLR) contains a significant fraction of heavy liquids. Better use of DCLR is an important task to overall economy of direct coal liquefaction. This paper studies hydro-treatment of a DCLR and its solvent-extraction components under typical direct coal liquefaction conditions. The DCLR is found hydro-treatable, resulting in more light products and less heavy products. In one case, 40 wt% heavy fractions in the DCLR are converted into light fractions. Hexane soluble fraction (HS) is the most stable while pre-asphaltene fraction (PA) is the most active during the hydro-treatment. Some synergetic effect can be observed when DCLR is treated as whole. The fractions of DCLR, before and after the hydro-treatment, are subjected to FTIR and NMR analyses, which show increase in hydrogen content and decrease in oxygen content in HS fractions after the hydro-treatment. GPC analysis reveals that the hydro-treatment results in slight decreases in molecular weight of HS fraction. The data seem to suggest that separation and hydro-treatment of liquid fractions from a DCLR is a viable option for high oil yield.     

Sulfur transfers from pyrolysis and gasification of direct liquefaction residue of Shenhua coal

The sulfur transformation during pyrolysis and gasification of Shenhua direct liquefaction residue was studied and the release of H₂S and COS during the process was examined. For comparison, the sulfur transfer of Shenhua coal during pyrolysis and that of pyrolyzed char during gasification were also studied. The residue was pyrolyzed at 10 °C /min to 950 °C. During pyrolysis about 33.6% of sulfur was removed from the residue, among which 32.1% was formed H₂S in gas and 1.5% was transferred into tar, 66.4% of the sulfur was remained in residue char. Compared with coal, the residue has generated more H₂S due to presence of Fe_1−xS which was enriched in residue during liquefaction process. There is a few COS produced at 400-500 °C during pyrolysis of coal, but it was not detected form pyrolysis of the residue. During CO₂ gasification, compared with pyrolysis and steam gasification, there are more COS and less H₂S formation, because CO could react with sulfide to form COS. During steam gasification only H₂S was produced and no COS detected, because H₂ has stronger reducibility to form H₂S than CO. After steam gasification no sulfur was detected in the gasification residue. The XRD patterns show after steam gasification, only Fe₃O₄ is remained in the gasification residue. This indicates that the catalyst added during the liquefaction of coal completely reacted with steam, resulting in the formation of H₂ and Fe₃O₄.     

煤直接液化残渣萃取技术现状及发展趋势

为实现煤液化残渣的高效利用,分析了煤直接液化残渣特性,论述了煤直接液化残渣经萃取提取高附加值有机物,如沥青和重油的研究现状,阐述了煤直接液化残渣萃取溶剂的种类、萃取工艺条件的选择以及萃取物的性能和用途等,提出了煤直接液化残渣萃取技术的发展趋势。采用合适的萃取剂和萃取条件可从液化残渣中萃取出制备沥青的原料和可作为液化循环溶剂使用的油分,萃取剂可包括各种已知的常规萃取溶剂及其混合物、离子液复合萃取剂和各种煤液化或石化馏分油,萃取出的沥青类物质可制备高级碳材料,特别是碳纤维材料,萃取出的油分可用作煤液化循环溶剂或燃料。提出未来应开发针对煤直接液化残渣的高效、低廉的新型有机溶剂萃取剂,研究多步或多级萃取工艺,实现萃取工艺的进一步优化和简化,形成萃取工艺和其他工艺,如加氢裂化工艺和加氢精制工艺结合的复合工艺。     

煤直接液化残渣性质及高附加值应用研究进展

介绍了煤直接液化残渣的组成，结构和性质，综述了液化残渣高附加值研究现状。总结前人研究成果，取得成绩及面临问题的基础上，指出了今后研发的焦点——沥青改性剂和炭材料，摒弃液化残渣的传统低效率应用，对于中国的煤直接液化事业具有重要的指导意义。     

煤炭直接液化溶剂的研究

讨论了煤炭直接液化过程中溶剂的特点、作用及质量要求,煤液化溶剂具有一般溶剂的功能,同时还具有良好的供氢和传递氢的功能特点,起到溶解、分隔煤裂解生成的自由基的作用,溶剂必须具有一定的分子结构和分子大小。初步讨论了表征煤液化循环溶剂供氢性的指标,指出普通溶剂如四氢萘和二氢萘等部分饱和的芳香化合物可直接用作煤液化溶剂,多环芳烃含量较高的煤焦油和石油系重质油,经过预加氢处理提高溶剂的供氢性后,可作为煤液化过程的起始溶剂或替代溶剂。     

Synthesis of a carbon nanofiber/carbon foam composite from coal liquefaction residue for the separation of oil and water

A carbon nanofiber (CNF)/carbon foam composite was fabricated from coal liquefaction residue (CLR) through a procedure involving template synthesis of carbon foam and catalytic chemical vapor deposition (CCVD) treatment. The high solubility and high pyrolysis yield make CLR a promising carbon precursor for the synthesis of carbon materials using the template method. The carbon foam has cell size of about 500 μm and a porosity as high as 95 vol.%. Fe species naturally present in the CLR disperse homogeneously on the surface of the carbon foam acting as a catalyst in the CCVD process. After the CCVD treatment, the whole surface of the carbon foam is covered by entangled CNFs with external diameters of 20–100 nm and lengths of several tens of micrometers. The obtained CNF/carbon foam composites are effective selective adsorbents in the separation of oil and water, through a combination of hydrophobicity and capillary action.     

木屑液化剩余物制备活性炭的探索研究

以木屑加压液化的固体剩余物为原料,分别用磷酸、水蒸气为活化剂,详细考察两种制备方式所得活性炭在得率、性能上的特性。研究结果显示,两种制备方法均得到高收率的活性炭产品,其中磷酸法得率为69.8%,水蒸气法得率为37.3%。在所制备的活性炭微观结构上,磷酸法活性炭表现出较集中的孔径分布,通过N2吸附-脱附表征,其平均孔径为1.99 nm,比表面积1 255 m2/g;而水蒸气法活性炭孔径分布比较分散,微孔、中孔呈现连续式的分布状态,平均孔径为2.46 nm,比表面积665 m2/g,N2吸附-脱附等温线在高相对压力时出现滞后回环。     

神华上湾煤恒温阶段直接液化反应动力学

为考察神华上湾煤的直接液化性能及反应动力学,以加氢蒽油-洗油混合油作为溶剂、负载型FeOOH作为催化剂,在0.01 t·d^-1煤直接液化连续实验装置上考察了不同反应温度（435~465℃）、不同停留时间（7~110 min）下液化产品组成的演变规律。研究发现,随着煤的裂解及加氢反应的进行,煤及沥青类物质（PAA）收率不断减小,重质液化产物逐步向轻质液化产物转化。当反应温度为455℃、停留时间为90 min时,煤转化率为90.41%（质量分数（,油收率为61.28%（质量分数（。随着反应条件进一步苛刻,油收率下降。基于上湾煤直接液化反应特性及其产物收率变化规律建立了11集总煤直接液化反应动力学候选模型,以BFGS优化算法对实验数据搜索、选优,确定了动力学模型参数。检验结果表明所建立的动力学模型可用于恒温阶段直接液化行为的模拟计算。     

神华煤液化残渣的加氢反应动力学

在微型反应管中,以神华煤液化残渣为原料,四氢萘为溶剂,在氢初压6 MPa、反应温度425～485℃、反应时间为0～30 min条件下,进行了煤液化残渣加氢实验,研究了煤液化残渣的加氢动力学特性。将氢化产物分为油气、沥青质和四氢呋喃不溶有机质,根据集总概念建立了煤液化残渣的加氢动力学模型,所建模型与实验值吻合程度高。在实验条件下,四氢呋喃不溶有机质向沥青质转化的活化能为147.41 kJ·mol^-1,沥青质向油气转化的活化能为34.81 kJ·mol^-1,沥青质缩合为四氢呋喃不溶有机质的活化能为173.48 kJ·mol^-1。     

Co-pyrolysis characteristics and interaction route between low-rank coals and Shenhua coal direct liquefaction residue

To reasonably utilize the coal direct liquefaction residue (DLR), contrasting research on the co-pyrolysis between different low-rank coals and DLR was investigated using a TGA coupled with an FT-IR spectrophotometer and a fixed-bed reactor. GC-MS, FTIR, and XRD were used to explore the reaction mechanisms of the various co-pyrolysis processes. Based on the TGA results, it was confirmed that the tetrahydrofuran insoluble fraction of DLR helped to catalyze the conversion reaction of lignite. Also, the addition of DLR improved the yield of tar in the fixed-bed, with altering the composition of the tar. Moreover, a kinetic analysis during the co-pyrolysis was conducted using a distributed activation energy model. The co-pyrolysis reactions showed an approximate double-Gaussian distribution.     

Bundle-like carbon nanofibers grown from methane decomposition

Bundle-like carbon nanofibers (CNFs) were prepared from methane decomposition over Ni nanoparticles supported by grooved SiC nanowires. In the bundle-like CNFs, several CNFs grow in a parallel mode and form a bundle of CNFs. Large loading of Ni and limited space of nanoscale grooves on the nanowires lead to aggregation of Ni nanoparticles in the nanoscale grooves. The aggregated Ni nanoparticles generate several CNFs, which close up each other and form the bundle-like CNFs. The bundle-like CNFs become curved due to the difference in growth rates of different CNFs.     

提高煤直接液化催化剂活性的研究进展及展望

为制备高效的煤直接液化催化剂,综述了提高煤直接液化催化剂活性的方法,分析了各方法对煤直接液化催化剂性能影响的作用原理,指出了煤直接液化催化剂研究中各方法的关键点和难点,各方法之间并非相互孤立,应有机组合以提高催化剂的活性。针对目前煤直接液化催化剂存在的问题提出了发展展望。煤直接液化催化剂活性提升的方法主要有提高催化剂前驱体的分散度,提高活性相的抗聚结性能和利用多元金属/非金属的复合/协同效应,后续研究应加强煤中灰组成对催化剂性能的影响,深入研究非金属元素对催化剂加氢和抑焦性能的影响,探索多种协同复合的催化剂制备系统,针对特定煤种研制专用高效直接液化催化剂。