H_2O_2氧解对褐煤腐植酸及含氧官能团的影响

采用H_2O_2氧解褐煤,研究了氧解条件对褐煤腐植酸含量的影响。通过Boehm滴定和FTIR分析研究了氧解条件对含氧官能团含量和基团结构的影响。结果表明,H_2O_2可有效提高褐煤中腐植酸含量、腐植酸含氧官能团含量和褐煤活性;最佳氧解条件为:氧解时间24 h,H_2O_2浓度20%,液固比0.8 m L/g,在此条件下,褐煤中总腐植酸含量增加了12.53%;氧解反应仅使褐煤中含氧官能团含量增加,腐植酸含量增大。     

H_2O_2氧解对褐煤腐植酸及含氧官能团的影响

采用H_2O_2氧解褐煤,研究了氧解条件对褐煤腐植酸含量的影响。通过Boehm滴定和FTIR分析研究了氧解条件对含氧官能团含量和基团结构的影响。结果表明,H_2O_2可有效提高褐煤中腐植酸含量、腐植酸含氧官能团含量和褐煤活性;最佳氧解条件为:氧解时间24 h,H_2O_2浓度20%,液固比0.8 m L/g,在此条件下,褐煤中总腐植酸含量增加了12.53%;氧解反应仅使褐煤中含氧官能团含量增加,腐植酸含量增大。     

三种云南褐煤腐植酸提取对比研究

以昭通(ZT)、小龙潭(XLT)和先锋(XF)三个地区的褐煤为原料进行腐植酸(humic acid,HA)的提取研究.以褐煤中腐植酸含量、腐植酸提取率及品质因素为分析指标,考察三种褐煤提取腐植酸的适用性.通过工业分析及酸性官能团含量的检测等手段对腐植酸的品质进行综合评价.结果表明,三种褐煤腐植酸提取率分别为76.13%,47.61%和43.48%.昭通褐煤腐植酸中灰分含量(16.83%)相对较高,小龙潭褐煤腐植酸和先锋褐煤腐植酸中灰分含量分别为6.66%和4.63%,且水分、挥发分和固定碳含量也相差较小.在腐植酸含氧官能团含量上,三种褐煤腐植酸的总酸性官能团含量及羧基含量相差较小,但昭通褐煤腐植酸提取残渣中含氧官能团含量远低于另外两种提取残渣.以上分析表明,昭通褐煤腐植酸提取较为完全,在腐植酸提取方面适用性更强.     

KHCO3一步活化法制备高含氧量褐煤基超级电容器多孔炭球

作为富含含氧官能团的有机大分子，褐煤被认为是制备富氧多孔炭材料的天然前驱体。对褐煤进行酸洗氧化改性进一步增加其氧含量得到酸洗氧化褐煤(OAWSL),以KHCO₃为活化剂，在高温下分解并与碳反应生成大量气泡，气泡穿透碳层逸出形成大量孔隙，并鼓泡形成了独特的球状表面，得到了多孔炭球。同时探究了KHCO₃添加量对多孔炭结构和作为超级电容器电极材料时电化学性能的影响。研究发现，酸洗氧化褐煤与KHCO₃质量比为1∶3时得到的多孔炭球具有最均匀球状结构、最大微孔占有率(90.88%)和最高氧含量(22.17%)。以该多孔炭球为电极材料，在以6 mol/L KOH为电解液的三电极体系中得到了323 F/g的比电容(0.1 A/g),组装的超级电容器最大能量密度为6.17 W·h/kg,在2 A/g电流密度下循环20 000次后电容保持率为96%,库伦效率保持100%,可为褐煤基富氧多孔炭材料的制备提供理论支撑。     

褐煤中含氧官能团的测定与研究

煤表面的官能团的种类和数目对煤的化学性质有很大的影响,最重要的表面基团是含氧官能团。含氧官能团对煤的性质,尤其是表面性质,如亲水性、疏水性、表面电性、表面作用及表面作用方式等的影响较大,从而也对煤的选别、煤炭改质、煤炭转化及其合理加工利用影响较大。干燥后的煤样与原煤相比,固定碳含量逐步提高,氧含量呈逐步降低的趋势,O/C比逐步降低,煤样的芳碳率和平均缩环数也是随着干燥工艺的不同而呈现出递增的趋势,说明干燥后煤样的芳构化程度加深,基本结构单元的缩合度增加,干燥工艺在一定程度上提高了内蒙古褐煤的"煤阶"。     

市政污泥与石下江褐煤混合燃烧动力学及协同特性研究

采用综合热分析仪对长沙市某污水处理厂污泥和石下江煤及两者混合物的燃烧特性参数进行了研究,并通过扫描电镜和X射线荧光光谱仪对两者灰渣进行了表征.结果表明:石下江褐煤的固定碳含量较高,污泥的挥发分含量较高;灰渣表面结构差异较大,混合样的灰分颗粒没有发生熔融现象;当混合样品中污泥的质量分数低于30％时,混合样品的燃烧特性与煤...     

胜利褐煤在液化预反应中氧脱除的初步研究

采用X光电子能谱法(XPS)研究了我国内蒙胜利褐煤中有机氧的赋存形态,将其分为碳氧单键类、羰基基团和羧基基团三种类型,与元素分析法结合得到不同形态含氧官能团在胜利褐煤中的绝对含量,与化学分析法测试煤中含氧官能团进行比较.在容积为0.5 L震荡式高压釜中对内蒙胜利褐煤在液化预反应阶段氧的脱除进行了研究,实验所选温度为330 ℃,360 ℃,400 ℃和430 ℃,分别考察三种催化剂(MnO2,Fe2O3和MoO3)的脱氧效果,并与无催化剂的脱氧效果进行比较,结果表明,氢压1 MPa无催化剂在360 ℃～400 ℃的液化预反应条件下,脱氧率较高.     

CuO修饰Fe基载氧体的锡盟褐煤化学链燃烧特性分析

为提高Fe基载氧体性能以及研究锡盟褐煤化学链燃烧特性,以硝酸盐试剂及CuO粉末为原料,通过共沉淀法制备了不同质量分数CuO修饰的Fe基载氧体且使用固定床制备褐煤焦样,对制得的载氧体进行表征分析,并在小型流化床反应器中进行了褐煤及其煤焦的化学链燃烧实验。结果表明:实验制得的载氧体完成了良好的结晶过程,且经CuO修饰后的载氧体中出现了CuFe₂O₄;在褐煤化学链燃烧实验中,相比于不经CuO修饰的Fe基载氧体,修饰后的载氧体具有更好的反应活性,具体表现在碳转化率方面,通过对不同质量分数CuO修饰的Fe基载氧体进行实验分析,10%CuO修饰的载氧体褐煤化学链燃烧中碳转化率为94.84%,较不修饰情况下的89.49%提升明显,同时碳转化速率峰值为23.81mol·%·min^-1,在相同时间内较不修饰情况提升4.21mol·%·min^-1,使用10%CuO修饰的载氧体进行褐煤焦化学链燃烧实验时碳转化率高达95.80%;循环实验中,15次化学链燃烧实验循环后,褐煤化学链燃烧碳转化率为88.69%,对反应后的载氧体表征分析表明,10%CuO修饰的Fe基载氧体仍保持了较为稳定的性能。     

碳氧官能团对煤焦低温还原NO的影响

在450℃对神木煤制半焦还原NO进行研究,采用Raman、FT-IR、XPS等分析方法探究了半焦脱硝影响因素与其表面碳氧官能团的关系。结果表明：热解制焦温度、烟气中氧气浓度以及负载金属对脱硝效果的影响都与半焦表面碳氧官能团有关,降低热解温度、增大氧气浓度、负载金属均有利于增加C—O官能团。采用XPS表征对金属负载半焦表面的碳氧官能团进行分析,发现热力学相对稳定的C—O官能团含量与脱硝指标之间存在明显的线性关系(R²>0.96)。研究进一步揭示了热力学稳定的C—O官能团在半焦脱硝过程的重要地位。     

印尼褐煤无黏结剂型煤自燃与燃烧特性研究

在内辊式高压型煤机上将一种印度尼西亚褐煤压制成高强度的无黏结剂型煤,对其比表面积、孔容积和表面官能团进行分析,测定了型煤的相对着火温度和绝热氧化升温速率,研究了其热解和燃烧行为特性.结果表明,印尼褐煤在干燥和高压成型过程中,发生了孔的收缩和崩塌,特别是微孔收缩程度要更大一些;干燥和成型过程中有羟基、羰基和羧基含氧官能团的分解;经过提质处理后,褐煤的自燃着火倾向降低,热解和燃烧反应性降低.     

Evolution of microstructure and combustion reactivity of lignite during high-temperature drying process

The evolutions of the microstructure characteristics and the combustion reactivity of lignite during high temperature drying process at 600–800°C were addressed in the paper. The information about the oxygen functional groups, carbon skeleton, pore structure, and combustion reactivity of the lignite before and after the drying treatment was obtained by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller technique, Raman spectroscopy and thermogravimetric analyzer, respectively. The results show that a different evolutionary trend of the chemical structure of the lignite appears at the high drying temperature of 700°C at which the carbonyl, carboxyl, and carboxylate significantly decomposed and the treatment gave a slight elimination of structural imperfections and the formation of new cross-linking structures. Then, at the drying temperature of 800°C, a slight increase of the oxygen functional groups was found. The break of the aromatic ring or heterocycle contributed to the rapid increase of amorphous carbon to some extent. During the drying process, the surface area of the resulted lignite gradually increased until 700°C and then decreased. The evolution may be attributed to the decomposition of organic compounds, shrinkage forces, and thermal relaxation effect. The investigation indicates that the change in chemical nature of the coal had a greater impact on the combustion reactivity than the internal pore structure did. In addition, the combustion intensity and performance of the treated lignite was enhanced by the drying process.     

Porous nitrogen doped carbon foam with excellent resilience for self-supported oxygen reduction catalyst

Fabrication of graphitized carbon materials (e.g. carbon nanotubes and graphene) normally entails the assistance of transition metal catalyst. In this paper, a nitrogen doped carbon foam (NCF) with both graphitized and porous carbon structure was fabricated by direct pyrolysis of melamine foam (MF) without using any transition metal catalyst. The graphitized carbon structure was possibly attributed to the triazine moieties in the MF precursor. The introduction of oxygen groups in the oxidation step resulted in the formation of large amount of micro- and mesopores and therefore high specific surface area. The NCF exhibited a three-dimensional cellular network consisting of carbon microfiber with abundant micro- and mesopores and giving rise to a specific surface area over 980 m² g⁻¹. Due to such graphitized porous structure, the NCF was demonstrated to have superior resilience, excellent electrocatalytic activity and good durability for oxygen reduction.     

生物质和煤基活性炭制备过程的活化特性比较

分别以稻壳、木屑及褐煤为原料用水蒸气活化法制备了活性炭,比较了所得活性炭的吸附性能和炭化料的反应活性,探明了造成不同原料活化特性差异的原因。结果表明,活化过程中生物质原料的反应活性优于褐煤,炭化料的活化速率遵循脱灰稻壳>木材炭化料>稻壳炭化料>褐煤炭化料。通过对炭化料进行元素分析、气化反应活性分析、BET、SEM、XRD、FTIR、XPS等物理和化学性质的表征,揭示了不同原料表现出不同活化特性的原因。结果表明,在相同炭化和活化条件下,原料挥发分越高,灰分越低,炭化料有机含氧量越高,则水蒸气的活化速率越快,更容易在短时间内制备出高性能的活性炭。     

Efficient drying and oxygen-containing functional groups characteristics of lignite during microwave irradiation process

To remove the high moisture of ZhaoTong lignite, the efficient drying characteristics and oxygen-containing functional groups changes in lignite during microwave irradiation process were highlighted in this study. As the microwave absorbers, lignite char and NaNO₃ were added to microwave drying of ZhaoTong lignite. The minimum chemical oxygen demand of waste water generated from microwave drying process of lignite was 99.89?mg?O₂?L^?1. The effects of microwave power, lignite mass, the weight ratio of lignite char to lignite and NaNO₃ content on the drying rate, and moisture diffusion coefficient of lignite were investigated during lignite microwave irradiation process. It was found that the drying rate and moisture diffusion coefficient of lignite increased with increasing microwave power, the weight ratio of lignite char to lignite and NaNO₃ content, but decreased with increasing lignite mass. Lignite char and NaNO₃ were mixed with lignite that can enhance the instantaneous surface temperature of lignite sample under microwave irradiation. Compared with addition of lignite char to lignite, the addition of NaNO₃ to lignite can decrease the unit electric power consumption of moisture evaporating. And the minimum unit electric power consumption of moisture evaporating was 9.44?Wh?g^?1. The FTIR technology was used to investigate the oxygen-containing functional groups changes in lignite during microwave drying process. The oxygen-containing functional groups of lignite were effectively removed with increasing microwave power.     

Effect of mechanical thermal expression drying technology on lignite structure

Mechanical thermal expression (MTE) is a developing nonevaporative lignite dewatering technology. It has been proved to be effective to dewater high moisture content in low-rank coals via the application of mechanical force and thermal energy at elevated temperatures. In this paper, the dewatering behavior of the Xiaolongtang lignite in Yunnan province, China during the MTE process was studied with three process parameters: time, temperature, and pressure. Meanwhile, the mechanism was also explored of how variations in temperature and pressure during the MTE process affect the surface oxygen functional groups and pore structure, which was mainly conducted by means of Fourier transform-infrared spectrometer (FTIR) and mercury intrusion porosimetry (MIP). Increases in MTE temperature and pressure resulted in significant reductions in residual moisture content and moisture-holding capacity, along with the increase in fixed carbon content and content reductions of other elements, especially oxygen content, this could be largely attributed to the destruction of the surface oxygen functional groups and porosity in the lignite. Technologically, the optimal conditions for temperature and pressure are 150–220°C and 6–10?MPa. The residual moisture content of the lignite treated by MTE at 200°C, 10?MPa is lower than 8%; the dewatering rate reaches over 76% with the calorific value being approximately 22?MJ/kg. Carboxyl and hydroxyl groups break down at drying temperatures above 120°C and constant applied pressure 10?MPa; with the pore volume significantly reduced, only few pores (diameter?相似文献   

Electrochemical oxidation of coals: Voltammetry and mass spectrometry

The anodic oxidation of sulphuric acid slurries of lignite, bituminous, and anthracite coals; a high-yield extract of coal; and carbon black, has been investigated voltammetrically and with simultaneous m.s. monitoring of evolved gases. The previously reported evolution of carbon dioxide at very low voltages was shown to be chemically released from minerals. The low rank coals and the asphaltite did show considerable electrochemical activity near to 1.0–1.2 V, mainly from the conversion of leached ferrous ion to the ferric form. Further activity near 1.4–1.5 V arose from the oxidation to CO₂ of leached organic matter. For well-washed low rank coals, the coal extract and the anthracite, CO₂ release was only observed at high (>2.8V) anode voltages, with simultaneous release of oxygen. Electrochemical gasification of coal via anodic oxidation of macromolecules at low voltages did not occur.     

Probing the influence of K2CO3- and Na2CO3-addition on the flash pyrolysis of a lignite and a bituminous coal with Curie-point pyrolysis techniques

The effect of K₂CO₃- or Na₂CO₃- addition on the composition of volatiles generated during the flash pyrolysis of a lignite and a medium-volatile bituminous coal was studied by means of analytical Curie-point pyrolysis mass spectrometry, g.c. and g.c.-m.s. At 358 °C no pyrolysis of the coal samples took place but there was desorption or evaporation of trapped components. Pyrolysis of the lignite occurred at a lower temperature than the medium-volatile bituminous coal, confirming that the bonds within the bituminous coal matrix are stronger as compared with the lignite. Alkali-carbonate addition suppressed the evolution of phenolic compounds originating from structures in the coal matrix with -OH and -COOH functional groups. No difference was observed between K₂CO₃ and Na₂CO₃. For the lignite the formation of o-methoxyphenol was not influenced by addition of alkali-carbonate because it is thought to derive from a structure in the lignitic coal matrix which does not contain an -OH functional group but is bonded within the coal matrix via an ether linkage. The phenolic compounds produced during flash pyrolysis of the medium-volatile bituminous coal are not reduced in abundance by the additives, indicating that this coal hardly contains hydroxyl functional groups and a major part of the oxygen is present in the form of ether linkages.     

褐煤汽爆提质新方法

利用汽爆方法对内蒙褐煤进行了汽爆粉碎和改质初步研究,考察了汽爆设备、工艺条件和汽爆效果,同时进行了汽爆工艺条件对褐煤改质的影响。结果显示,单次汽爆过程对褐煤具有明显的粉碎效果,汽爆过程对褐煤具有显著的改质作用。停留1h,随着汽爆温度的提高,褐煤水分降幅达63．6％,挥发分降低11．3％,氧质量分数降低48％,含碳量提高了12．9％,褐煤质量得到明显改善。