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%.

Role of Ni(NO_3)_2 in the preparation of a magnetic coal-based activated carbon

The role of Nil（NO3）2 in the preparation of a magnetic activated carbon is reported in this paper. Magnetic coal-based activated carbons （MCAC） were prepared from Taixi anthracite with low ash content in the presence of Ni（NO3）2. The MCAC materials were characterized by a vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, a scanning electric microscope （SEM）, and by N2 adsorption. The cylindri- cal precursors and derived char were also subjected to thermogravimetric analysis to compare their behavior of weight losses during carbonization. The results show that MCAC has a larger surface area （1074 m21g） and a higher pore volume （0.5792 cm3/g） with enhanced mesopore ratio （by about 10~）. It also has a high saturation magnetization （1.6749 emu/g） and low coercivity （43.26 Oe）, which allows the material to be magnetically separated. The MCAC is easily magnetized because the nickel salt is con- vetted into Ni during carbonization and activation. Metallic Ni has a strong magnetism on account of electrostatic interaction. Added Ni（NO3）2 catalyzes the carbonization and activation process by accelerat- ing burn off of the carbon, which contributes to the development of mesopores and macropores in the activated carbon.

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.

Purification process of coal-based coke powder as anode for Li-ion batteries

A process of purification of coal-based coke powder as anode the treatment of coke powder with dilute hydrofluoric acid solution, for Li-ion batteries was attempted. The process started with followed by united-acid-leaching using sulfuric acid and hydrochloric acid. The effects of altering the hydrofluoric acid addition, hydrofluoric acid concentration, contact time, temperature and acid type were investigated. A minimum ash content of 0.35% was obtained when proper conditions were applied. The electrochemical performance of purified coke powder shows greatly improved electrochemical performance. The as-purified coke powder presented an initial reversible capacity of 257.4 mAh/g and a retention rate of 95% after 50 cycles. The proposed purification process paves a way to prepare a promising anode material with good performance with low cost of coke powder for Li-ion batteries.

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.

Coal-based activated carbon prepared by H2O activation process for supercapacitors using response surface optimization method

The scalable production of high grade activated carbon from abundant coal for supercapacitors application is an efficient way to achieve high value-added utilization of coal sources.However,this technology is challenging due to lack of comprehensive understanding on the mechanism of activation process and effect of external factors.In this paper,the effect of activating temperature and time on the specific capacitance of coal-based activated carbon prepared by H2O steam activation was studied using the response surface method.Under optimal conditions,coal-based activated carbon exhibits the largest specific capacitance of 194.35 F·g^(−1),thanks to the appropriate pore/surface structure and defect degree.Density functional theory calculations explain in detail the mechanism of contraction of aromatic rings and overflow of H2 and CO during the activation.Meanwhile,oxygen-containing functional groups are introduced,contributing to the pseudocapacitance property of coal-based activated carbon.This mechanism of reactions between aromatic carbon and H2O vapor provides understanding on the role of water during coal processing at the molecular level,offering great potential to regulate product distribution and predict rate of pore generation.This insight would contribute to the advancement of other coal processing technology such as gasification.

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.

不定型煤基活性焦制备及预处理影响研究

我国煤炭燃烧排放大量的SO2和NOx等导致了严重的空气污染,需要寻找一种清洁高效的烟气联合脱硫脱硝技术.煤基活性焦因其脱除效率高,再生能力强等诸多优点备受关注,但目前的研究主要集中在柱状和粉末状活性焦上.为研究大粒径煤基活性焦的制备参数和预处理对活性焦理化特性的影响,对原煤颗粒进行高温空气预氧化处理,并通过炭化-水蒸气活化两步法制备活性焦.结果表明:低温长时间活化可使炭化料内部孔隙充分刻蚀,显著提高比表面积和孔容,以水蒸气作为活化剂有利于微孔和介孔协同发展,适合制备大粒径分级孔结构活性焦.700℃活化3 h制得的府谷煤活性焦比表面积为429.54 m^(2)/g,介孔占比27.80%;850℃活化3 h制得的大同煤活性焦比表面积为892.20 m^(2)/g,介孔占比21.46%.高温空气预氧化能够改变原煤内部结构,对府谷煤颗粒在200℃下预氧化15 h后,氧化煤内部成分和结构基本稳定,脂肪结构被消耗的同时生成了大量含氧官能团.预氧化处理对炭化过程的影响较为显著,氧化煤在炭化过程中热塑性特征显著降低,减少了焦油对孔隙的堵塞,此外,含氧官能团的交联作用也促进了煤中大分子的缩聚和孔隙的形成,从此促进初步孔隙的发展.虽然预氧化使得活性焦的比表面积和孔容都有所增大,但活化剂和样品之间的成孔路径未产生改变.

气化渣基脱硫活性焦制备工艺与性能评价

煤气化过程中产生的气化渣的处置问题日趋严重。气化渣中的残余炭具有较发达的孔隙结构和较大的比表面积,具有制备活性炭和其他高附加值碳材料的潜质。通过水介重力分选方法得到高品质气化渣分离炭后,采用配煤法制备脱硫活性焦,可实现气化渣的高附加值利用。通过单因素试验法及正交试验法考察在气化渣分离炭高掺比条件下配煤种类、比例及炭化、活化工艺条件对脱硫活性焦结构和性能影响。研究表明,气化渣分离炭在掺入比例为50%时,活性焦的最佳配煤组成为:焦煤29%、长焰煤8%、煤沥青13%;最佳炭化条件为:升温速率5℃/min、炭化温度700℃、炭化时间30 min;最佳活化条件为:活化温度900℃、升温速率8℃/min、活化时间120 min、活化水量1.0 mL/(g·h)。利用固定床反应装置对气化渣基脱硫活性焦进行脱硫和再生性能评价,在最佳配方和工艺条件下,公斤级试验制备的脱硫活性焦耐磨强度为97.26%,耐压强度为696.3 N(实测值),灰分为11.66%,碘吸附值为378.78 mg/g,脱硫值为28.5 mg/g,满足脱硫用煤质颗粒活性炭指标A型优级品的技术指标且再生性能良好。以气化渣分离炭作为碳源制备脱硫活性焦在大幅降低活性焦生产成本的同时,也为气化渣的高值化利用提供了一条可行途径,对气化渣的减量化、资源化、高值化利用具有重要意义。

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。