Effects of surface chemical properties of activated coke on selective catalytic reduction of NO with NH_3 over commercial coal-based activated coke

Surface chemical properties of typical commercial coal-based activated cokes were characterized by Xray photoelectron spectroscopy(XPS) and acid-base titration, and then the influence of surface chemical properties on catalytic performance of activated cokes of NO reduction with NH3 was investigated in a fixed-bed quartz micro reactor at 150 ℃. The results indicate that the selective catalytic reduction(SCR) activity of activated cokes with the increase of its surface acidic sites and oxygen content,obviously, a correlation between catalytic activity and surface acidic sites content by titration has higher linearity than catalytic activity and surface oxygen content by XPS. While basic sites content by acid-base titration have not correlation with SCR activity. It has been proposed that surface basic sites content measured by titration may not be on adjacent of acidic surface oxides and then cannot form of NO2-like species, thus the reaction of reduction of NO with NH3 have been retarded.

Study of the reaction mechanism for preparing powdered activated coke with SO_(2)adsorption capability via one-step rapid activation method under flue gas atmosphere

In this study,the impact of different reaction times on the preparation of powdered activated carbon(PAC)using a one-step rapid activation method under flue gas atmosphere is investigated,and the underlying reaction mechanism is summarized.Results indicate that the reaction process of this method can be divided into three stages:stage I is the rapid release of volatiles and the rapid consumption of O_(2),primarily occurring within a reaction time range of 0-0.5 s;stage II is mainly the continuous release and diffusion of volatiles,which is the carbonization and activation coupling reaction stage,and the carbonization process is the main in this stage.This stage mainly occurs at the reaction time range of 0.5 -2.0 s when SL-coal is used as material,and that is 0.5-3.0 s when JJ-coal is used as material;stage III is mainly the activation stage,during which activated components diffuse to both the surface and interior of particles.This stage mainly involves the reaction stage of CO_(2)and H2O(g)activation,and it mainly occurs at the reaction time range of 2.0-4.0 s when SL-coal is used as material,and that is 3.0-4.0 s when JJ-coal is used as material.Besides,the main function of the first two stages is to provide more diffusion channels and contact surfaces/activation sites for the diffusion and activation of the activated components in the third stage.Mastering the reaction mechanism would serve as a crucial reference and foundation for designing the structure,size of the reactor,and optimal positioning of the activator nozzle in PAC preparation.

Adsorption and Regeneration of Volatile Organic Compounds(VOCs)on Coal-Based Activated Carbon by Ferric Nitrate Modification

In this study,the Heishan coal was used to prepare a series of activated carbon(AC)samples via a vapor deposition method.The effects of the Fe(NO_(3))3/coal weight ratio on the physicochemical properties of the activated carbon were systematically investigated,and the AC samples were analyzed by the N2 adsorption-desorption technique,the scanning electron microscopy,the X-ray diffraction,the Raman spectroscopy,and the Fourier transform infrared spectroscopy.Furthermore,the adsorption properties of ethyl acetate were investigated.The results indicated that as the Fe(NO_(3))3/coal mass ratio increased from 1:8 to 1:2,the specific surface area,the total pore volume and the micropore volume initially increased and then decreased.The specific surface area increased from 560.86 m^(2)/g to 685.90 m^(2)/g,and then decreased to 299.56 m^(2)/g.The total pore volume and micropore volume increased from 0.29 cm^(3)/g and 0.17 cm^(3)/g to 0.30 cm^(3)/g and 0.22 cm^(3)/g,and then decreased to 0.16 cm^(3)/g and 0.10 cm^(3)/g,respectively.The optimized ratio was 1:8.During the activation process,iron ions infiltrated the activated carbon to promote the development of the pore structure,the pore size of which was between 2.5 nm and 3 nm in daimeter.This approach could enhance the capacity for adsorption of ethyl acetate.It is worth noting that the ACs displaying the largest specific surface area and total pore volume(685.90 m^(2)/g and 0.30 cm^(3)/g)were formed under the optimized activation conditions(950℃,20%(volume)of CO_(2),ratio 1:5),and the maximum AC capacity for adsorption of ethyl acetate was 962.62 mg/g.After seven repeated thermal regeneration experiments,the saturated AC adsorption capacity was still above 90%.

Surface chemical properties and pore structure of the activated coke and their effects on the denitrification activity of selective catalytic reduction

In order to study the mechanism of selective catalytic reduction of activated coke to remove NO in low-temperature flue gas and provide some theoretical basis for the development of related technologies.The pore sizedistribution and BET specific surface area of AC were obtain by data analyzing of N2 adsorption/desorption isotherm at -196 ℃ and carbon matrix and surface chemistry of virgin activated coke samples were characterized by acid-base titration and XPS.The process of selective catalytic reduction of activated coke (AC) samples with NH3 as reducing agent was studied in a fixed bed reactor at 150 ℃.The result shows that pore size distribution or BET specific surface of activated cokes have not correlation with denitrification activity for SCR.The NO reduction activities of the activated cokes are apparent to increase with their surface oxygen element content and total amount of acidic sites.Obviously there is good linear relationship between the NH3 adsorption capacity and activity for SCR with linear correlation coefficient 0.943.It has been presented that adsorption of NH3 on acidic functional groups in the edge of large polycyclic aromatic ring of activated coke is key rate controlling step in the SCR heterogeneous catalytic reaction.

Effect of the surface properties of an activated coke on its desulphurization performance

Commercial coke was modified by H2O2 and/or NH3.H2O to obtain an activated coke containing additional oxygen functional groups and/or nitrogen functional groups. The aim of the modification was to enhance the SO2 adsorption capacity of the activated coke. Several techniques, including total nitrogen content measurements, SO2 adsorption, XPS and FTIR analysis, were used to characterize the coke samples. The XPS and FTIR spectra suggest the existence of -CONH2 groups in the H2O2 plus ammonia modified coke. The SO2 adsorption capacity of an activated coke increases slightly with an increase in H2O2 concentration during the modification process. The desulphurization performance of a modified coke is considerably enhanced by increasing the treatment temperature during ammonia modification. The amount of nitrogen in a coke modified by H2O2 plus NH3.H2O is the highest, and the SO2 adsorption capacity of the coke is also the highest (89.9 mg/gC). The NH3.H2O (only) modified sample has lower nitrogen content and lower desulphurization capacity (79.9 mg/gC). H2O modification gives the lowest SO2 adsorption capacity (28.9 mg/gC). The H2O2 pre-treatment is beneficial for the introduction of nitrogen onto the surface of a sample during the following ammonia treatment process.

Investigation on activated semi-coke desulfurization

An activated semi coke with industrial scale size was prepared by high pressure hydrothermal chemistry activation, HNO 3 oxidation and calcination activation in proper order from Inner Mongolia Zhalainuoer semi coke, which is rich in resource and cheap in sale. SO 2 adsorption capacity on this activated semi coke was assessed in the fixed bed in the temperature range of 60—170℃, space velocity range of 500—1300 h -1 , SO 2 concentration of 1000—3000 ppmv, and N 2 as balance. The surface area, elemental and proximate analysis for both raw semi coke and activated semi cokes were measured. The experimental results showed that the activated semi coke has a high adsorption capacity for sulfur dioxide than the untreated semi coke. This may be the result of increase of surface area on activated semi coke and surface oxygen functional groups with basicity characteristics. Comparison to result of FTIR, it is known that group of —C—O—C? ?may be active center of SO 2 catalytic adsorption on activated semi coke.

Systematic investigation of SO_(2) adsorption and desorption by porous powdered activated coke:Interaction between adsorption temperature and desorption energy consumption

Porous carbon materials have been widely used for the removal of SO_(2) from flue gas.The main objective of this work is to clarify the effects of adsorption temperature on SO_(2) adsorption and desorption energy consumption.Coal-based porous powdered activated coke(PPAC)prepared in the drop-tube reactor was used in this study.The N_(2) adsorption measurements and Fourier transform infrared spectrometer analysis show that PPAC exhibits a developed pore structure and rich functional groups.The experimental results show that with a decrease in adsorption temperature in the range of 50–150℃,the adsorption capacity of SO_(2) increases linearly;meanwhile,the adsorption capacity of H_(2)O increases,resulting in the increase in desorption energy consumption per unit mass of adsorbent.The processes of SO_(2) and H_(2)O desorption were determined by the temperature-programmed desorption test,and the desorption energies for each species were calculated.Considering the energy consumption per unit of desorption and the total amount of adsorbent,the optimal adsorption temperature yielding the minimum total energy consumption of regeneration is calculated.This study systematically demonstrates the effect of adsorption temperature on the adsorption–desorption process,providing a basis for energy saving and emission reduction in desulfurization system design.

Activation mechanisms on potassium hydroxide enhanced microstructures development of coke powder

Coke powder is expected to be an excellent raw material to produce activated carbon because of its high carbon content. Potassium hydroxide(KOH), as an effective activation agent, was reported to be effective in activating coke powder. However, the microstructures development in the coke powder and its mechanisms when KOH was applied were still unclear. In this study, effects of KOH on the microstructure activation of coke powder were investigated using the surface area and pore structure analyzer, scanning electron microscope(SEM) and thermogravimetry-differential scanning calorimetry-mass spectrometry(TG-DSC-MS), etc. Results revealed that the addition KOH at its lower ratio(mass ratios of KOH and coke powder in a range of 0.5 and 1) decreased the specific surface area and average lateral sizes, but sharply increased of the specific surface area to 132 m^2·g^-1 and 355 m^2·g^-1 and decreased of the space size of aromatic crystallites upon the further increase of the KOH addition amounts(ratios of KOH and coke powder in a range of 3 and 7), generating a number of new micropores and mesopores. The mechanisms study implied surface reactions between KOH and aliphatic hydrocarbon side chain and other carbon functional groups of the coke powder to destruct aromatic crystallites in one dimension and broaden pores at lower KOH addition. In the activation process, KOH was decomposed to be more active components, which can be rapidly destruct the aromatic layers in spatial scope to form developed porous carbon structures within coke powder at higher KOH addition.

Intrinsic properties of active sites for hydrogen production from alcohols without coke formation

The detailed reaction pathway and coke formation mechanism over Pt/metal oxide nanoparticles during the steam reforming of ethanol （SRE） at 300℃ were studied. The catalysts were prepared by incipient wetness impregnation method and were characterized with CO pulse chemisorption, BET surface measurement, oxygen adsorption, ethanol-TPD, NH3-TPD, and TPO. The SRE activity of the catalysts with steam/ethanol molar ratio of 3/1 was tested using a continuous fixed-bed reactor. Strong interaction between Pt and supports causes lower H2 production temperatures and no C2H4 formation, while weak interaction leads to C2H4 formation and strong bonded CO on Pt particles during ethanol- TPD. H2 production over Pt-based catalysts is mainly resulted from the decomposition and dehydrogenation of ethanol, and decarbonylation of acetaldehyde. Meanwhile, coke can be formed from acetaldehyde, acetone, C2H4 and CO. However, when the interaction between Pt and supports is weak, more coke is formed especially from acetone, C2H4 and CO. When the interaction is strong, no coke formation is observed due to high oxygen storage capacity of the catalyst.

Co-Ce-Ni Ternary Metal Oxide Modified N-activated Carbon:The Superior Low Temperature NH3-SCR Performance

Introducing reduced metal and nitrogen species is a powerful strategy to improve the reactivity of carbon-based materials for selective catalytic reduction of NO_(x) with NH_(3).To further improve the NH_(3)-SCR performance of non-pitch coal activated coke(NPAC),a series of metal oxides(e.g.,Co,Ce,and Ni)were loaded on nitrogen modified NPAC.The outstanding performance of NPAC-N-CoCeNi as well as the superior SO_(2)-and H_(2)O-tolerate performance are attributed to the extra electrons caused by the modification of N species,and these extra electrons are more conducive to the electron transfer.More importantly,the interaction of the major active component Co^(3+)and the promoter catalysts CeO_(2),NiOx,or CoNiO_(2) can also increase the charge transfer and produce more oxygen vacancy and unsaturated chemical bonds,leading to improving the redox performance of NPAC-N-CoCeNi.In addition,the NH3-SCR reaction is promoted after the metal oxides co-doping mainly via the Mars-van-Krevelen mechanism.

Preparation of Activated Carbons from Mongolian Lignite and Sub-Bituminous Coal by a Physical Method

Preparation of activated carbons by a physical activation technique is performed using the methods of coal pyrolysis and gasification at different temperatures. As increasing pyrolysis temperature from 520°C to 700°C, the yield of activated carbons from the Khuut (KH) sub-bituminous coal is lowered, and amount of micropores increases gradually;however there is no development of mesopores by the KH coal pyrolysis. When the KH coal has a small loss during its physical activation due to difficulty and inactivity of its macrostructure decomposition, the smaller porosity is developed in the resulting carbons. The Aduunchuluun (AD) lignite is activated by pyrolysis and gasification at the highest temperature of 700°C in the present study. It is identified that the gasification of AD lignite develops well a porous structure with the highest surface area of 522 m2/g which is three times larger than that (155 m2/g) of the activated carbon produced by pyrolysis of the same lignite. The IR and SEM analysis confirm a significant difference in chemical and structural changes between the AD, KH raw coals and corresponding carbon samples in the physical activation processes.

活性焦孔结构与含氮官能团协同构筑对低温NO还原特性影响

低温NH_(3)-SCR是排烟温度低的非电力行业烟气脱硝的重要技术选择,低成本、结构可调性好的碳材料是最具潜力的低温NH_(3)-SCR催化剂之一,但面临脱硝效率低的瓶颈。本文以低成本、大储量准东煤为原料,基于一步催化活化工艺制备了具有典型孔隙配组与含氮官能团的活性焦催化剂,探究了活性焦孔隙配组与表面官能团对不同烟气条件下低温NH_(3)-SCR的影响。研究结果表明分级孔与含氮官能团对NH_(3)-SCR均有显著促进作用,兼具分级孔与含氮官能团的氮掺杂分级孔活性焦由于同时改善了传质通道与反应动力学,具有最优的NH_(3)-SCR性能,160℃条件下的脱硝效率高达83.5%,相比氮掺杂微孔活性焦、无掺杂分级孔焦和微孔活性焦分别提升了14.0%、26.5%和110.9%;在SO_(2)或H_(2)O存在条件下,分级孔和含氮官能团对NH_(3)-SCR性能的提升作用更加明显,微孔活性焦脱硝效率会由39.6%衰减至13.8%和34.9%,而氮掺杂分级孔焦脱硝效率有所提升,达86.4%和86.7%,这可能与官能化分级孔环境强化不同烟气组分间的协同效应有关。探明了碳基低温NH3-SCR性能与碳材料理化结构之间的依存关系,为发展高性能碳基低温NH3-SCR技术提供了新思路。

超级电容器用活性炭的研究进展

简述了超级电容器的工作原理和超级电容炭的市场情况,分析了植物类、石油焦类、树脂类不同原料制备电容炭(无定型粉末炭)的性能特点及制备工艺,介绍了煤焦油沥青基球形活性炭和煤液化沥青球形活性炭的研究进展,对比了无定型粉末活性炭与球形活性炭的性能优劣,最后对煤液化沥青球形活性炭用于超级电容器的优势及推广应用进行了展望。

安钢高炉煤气精脱硫技术工业实践

结合当前环保形势和政策背景,分析了高炉煤气的典型特点和主流工艺路线,提出预处理水解和兰炭吸附的工艺组合,阐述了该工艺的技术原理和工业实践情况,该技术的应用和推广将带来广泛的环境效益和经济社会效益。

活性炭吸附焦化VOCs技术的研究与应用

焦化过程产生的挥发性有机物(VOCs)具有成分复杂、污染排放控制难等特点,是我国VOCs治理的重要行业之一。简述了焦化VOCs的排放工艺节点及各种治理与控制技术,重点分析了活性炭比表面积、孔道结构、表面官能团对其吸附焦化VOCs的影响规律,建议利用炼焦废弃焦粉作为活性炭制备原料,可解决活性炭吸附剂成本高、焦化固废高值利用难等问题。

煤基针状焦制备超级电容器电极材料及其电化学性能

为了探究煤基针状焦的电化学性能,利用中温煤焦油沥青针状焦生焦和KOH活化剂,通过高温热处理法,制备了用于超级电容器的多孔碳材料,并进行了SEM、XRD、红外光谱表征和氮气吸附-脱附测试,对碳材料电极进行了循环伏安测试、电化学阻抗谱、恒电流充放电等电化学性能测试,研究了KOH添加量对碳材料电极的电化学性能影响。结果表明:当碱碳比为2∶1时,电流密度为0.1 A/g时,其质量比电容达到222.83 F/g;电流密度从0.5 A/g增至10 A/g时,电容保持率能够达到93.2%;5 A/g循环10 000圈之后,比电容能够保持100%。

活化深度对多孔碳正极材料的影响及其电化学性能研究

以石油焦为前驱体,通过碱活化的方式制备出锂离子电容器多孔正极材料,再通过调整碱焦质量比,探索不同活化深度对正极材料微观性质以及电化学性能的影响。结果表明:当碱焦比为3∶1时,QDPC系列多孔正极材料的比表面积最大,对电流密度的响应度最高,且倍率性能最好。由此推断,随着碱焦比的增加,材料的比表面积随之增大,优化了材料的孔道结构的同时,加快了离子和电子的扩散和传输速率,并为孔道内部提供了更多的储锂位点,提升了材料的电化学性能。

煤质与木质活性炭吸附处理焦化RO浓水及再生试验研究

以某钢铁厂焦化RO浓水为研究对象,采用煤质颗粒活性炭与木质颗粒活性炭进行吸附处理,考察了活性炭投加量、pH值、吸附时间对吸附效果的影响,同时进行2种活性炭的Freundlich吸附等温线研究,研究了再生温度、再生时间、再生次数对活性炭再生后吸附性能及再生损失的影响。结果表明,在最佳吸附条件下,煤质和木质活性炭对废水中COD的去除率分别为61.1%、56.3%。最佳再生温度为500℃,煤质和木质活性炭最佳再生时间分别为1.5 h和1.0 h。多次再生试验证明,煤质活性炭可进行大于6次的再生,使用寿命优于木质活性炭。

塔式喷淋与活性焦组合工艺在污泥好氧发酵废气领域的应用研究

污泥好氧发酵产生的废气具有成分复杂、臭气浓度高等特点,难以被传统的生物除臭法所去除,除臭问题成为制约污泥好氧发酵的瓶颈问题。郑州某污泥处理厂采用化学吸收、火山岩除湿和活性焦吸附等组合新技术解决这一难题。结果表明:化学吸收法可以将空间和堆体氨气浓度降低至15mg/m^(3)和20mg/m^(3)以下,去除率高达85%,喷淋方式可以将堆体气体温度从62℃降低至40℃,臭气浓度在此阶段也得到了大幅度减少。经过火山岩除湿系统,可以将气体相对湿度从80%降低至50%左右,可延长活性焦的使用寿命。而活性焦吸附则主要去除好氧发酵气体废气中的非极性气体,将臭气浓度控制在1000以下,使气体稳定达标排放。

焦化生化废水处理pH值调节技术研究与应用

拜城县众泰煤焦化有限公司现有焦化废水处理采用A^(2)/O工艺技术,采用固体碳酸钠作为调节废水pH的药剂。由于碳酸钠为固体,在调节p H的过程中存在调整不及时导致p H指标超标、人工劳动强度增大的弊端。通过实验发现,采用30%的氢氧化钠溶液代替碳酸钠固体调节生化废水pH,能有效解决原有工艺技术存在的弊端,调节效果非常明显,且每年节约废水处理药剂费用约40万元。