Preparation of activated carbon with low ash content and high specific surface area from coal in the presence of KOH

An activated carbon with ash content less than 10% and specific surface area more than 1 600 m 2 /g was prepared from coal and the effect of K containing compounds in preparation of coal based activated carbon was investigated in detail in this paper. KOH was used in co carbonization with coal, changes in graphitic crystallites in chars derived from carbonization of coal with and without KOH were analyzed by X ray diffraction (XRD) technique, activation rates of chars with different contents of K containing compounds were deduced, and resulting activated carbons were characterized by nitrogen adsorption isotherms at 77 K and iodine numbers. The results showed that the addition of KOH to the coal before carbonization can realize the intensive removal of inorganic matters from chars under mild conditions, especially the efficient removal of dispersive quartz, an extremely difficult separated mineral component in other processes else. Apart from this, KOH demonstrates a favorable effect in control over coal carbonization with the goal to form nongraphitizable isotropic carbon precursor, which is a necessary prerequisite for the formation and development of micro pores. However, the K containing compounds such as K 2 CO 3 and K 2 O remaining in chars after carbonization catalyze the reaction between carbon and steam in activation, which leads to the formation of macro pores. In the end an innovative method, in which KOH is added to coal before carbonization and K containing compounds are removed by acid washing after carbonization, was proposed for the synthesis of quality coal based activated carbon.

High surface area biocarbon monoliths for methane storage

New energy sources that reduce the volume of harmful gases such as SO_(x)and NO_(x)released into the atmosphere are in constant development.Natural gas,primarily made up of methane,is being widely used as one reliable energy source for heating and electricity generation due to its high combustion value.Currently,natural gas accounts for a large portion of electricity generation and chemical feedstock in manufacturing plastics and other commercially important organic chemicals.In the near future,natural gas will be widely used as a fuel for vehicles.Therefore,a practical storage device for its storage and transportation is very beneficial to the deployment of natural gas as an energy source for new technologies.In this tutorial review,biomaterials-based carbon monoliths(CMs),one kind of carbonaceous material,was reviewed as an adsorbent for natural gas(methane)adsorption and storage.

A new preparation process of coal-based magnetically activated carbon

Fe/C-based magnetically activated carbon(MAC) was obtained by carbonizing and activating its precursor, that was prepared by co-precipitation of anthracite coal impregnated in ferric chloride solution. The effect of the concentrations of FeCl3 and pH of solution on BET surface area, pore volume and magnetic properties of the MAC was studied by BET N2 adsorption and VSM method. The results indicated that the magnetization of MAC gradually increases with increasing concentration of FeCl3 and pH value of solution, and BET surface area was inclined to fluctuation. The largest BET surface area and magnetization of MAC were 1327.5 m2/g and 35.56 emu/g, respectively. The form of magnetic matter in the magnetically activated carbon was mainly Fe3C by X-ray powder diffraction(XRD) and magnetic attraction test.

Effect of activated carbon and electrolyte on properties of supercapacitor

Effect of activated carbon and electrolyte on electrochemical properties of organic supercapacitor was investigated. The results show that specific surface area and mesoporosity of activated carbon influence specific capacitance. If specific surface area is larger and mesoporosity is higher, the specific capacitance will become bigger. Specific surface area influences resistance of carbon electrode and consequently influences power property and pore size distribution. If specific surface area is smaller and mesoporosity is higher, the power property will become better. Ash influences leakage current and electrochemical cycling stability. If ash content is lower, the performance will become better. The properties of supercapacitor highly depend on the electrolyte. The compatibility of electrolyte and activated carbon is a determining factor of supercapacitor’s working voltage. LiPF6/(EC+EMC+DMC) is inappropriate for double layer capacitor. MeEt3NPF4/PC has higher specific capacitance than Et4NPF4/PC because methyl’s electronegativity value is lower than ethyl and MeEt3N+ has more positive charges and stronger polarizability than Et4N+ when an ethyl is substituted by methyl.

Catalytic Pyrolyses of Rayon and the Effect on Activated Carbon Fiber

The catalytic pyrolyses of rayon have been studied respectively by thermo-gravimetric analysis (TGA) when rayon was treated with phosphoric acid (PA), three ammonium phosphate salts and ammonium sulfate (AS). The air is favorable to the catalysis of dibasic ammonium phosphate (DAP), but not to those of ADP, PA, AP, and AS obviously. It is put forward that a peak’s shape character can be described with the ratio of height to half-height-width (H/W /2) of the peak on a differential thermo-gravimetric (DTG) curve. A flat cracking peak, presenting a more moderate dehydration reaction, has a smaller ratio and could lead to higher carbonization and activation yields. The experimental results prove this view. According to expectation, the order of catalysis is: DAP≥ADP>PA> APAS no catalyst.

Copper oxide foam with high specific surface area for electrocatalytic reduction of CO_(2)to C_(2+)products

The carbon dioxide reduction reaction(CO_(2)RR)for the synthesis of high-energy-density and high-value multi-carbon(C_(2+))products has demonstrated consider-able potential for practical applications.In this work,we design a novel copper oxide foam(OD-Cu foam)catalyst through a high-temperature calcination pro-cess,characterized by a substantial specific surface area.The distinctive three-dimensional structure of the OD-Cu foam catalyst and the metal oxide particles covered on its surface provide abundant active sites.The total Faradaic efficiency of 57.3%for C_(2+)products over the OD-Cu foam is achieved at-0.85 V versus reversible hydrogen electrode(RHE).Furthermore,the partial current density for C_(2+)products over the OD-Cu foam reaches 44.1 mA cm^(-2)at-0.95 V versus RHE,surpassing significantly that both of Cu foam(3.4 mA cm^(-2))and copper oxide foil(OD-Cu foil)(1.6 mA cm^(-2)).In addition,the integrated structure of the OD-Cu foam,which does not require complex preparation processes,facilitates its application in CO_(2)RR.These results underscore the significance of three-dimensional structure and high specific surface area,emphasizing the consider-able potential of this catalyst for effective and sustainable CO_(2)conversion.

Optimal Electrochemical Performances of CO_2 Activated Carbon Aerogels for Supercapacitors

Activated carbon aerogels（ACAs） derived from sol-gel polycondensation of resorcinol （R） and formaldehyde （F） were pyrolyzed under Ar flow and activated in CO2 atmosphere. The morphology of ACAs was characterized by scanning electron microscopy （SEM） and the structural properties were determined by N2 adsorption at 77 K. The results show that ACAs have a typical three-dimensional nanonetwork structure composing of cross-linking of carbon nanoparticles. The specific surface area and the total pore volume remarkably increase with increasing activation time while the previous porous structure still remains. The specific capacitance of the 950-10-ACA electrode can reach up to 212.3 F/g in 6 mol/L KOH electrolyte. The results of constant-current charge-discharge testing indicate that the ACAs electrodes present fast charge- discharge rate and long cycle life （about 98% capacitance retained after 3000 charge-discharge cycles at 1.25 mA/cm2）. Lower internal resistances can be achieved for 950-10-ACA electrode in KOH electrolyte. Our investigations are very important to improve the wettability and electrochemical performance of electrode for supercapacitors.

Carbon cathode with heteroatom doping and ultrahigh surface area enabling enhanced capacitive behavior for potassium-ion hybrid capacitors

Potassium-ion hybrid capacitors(PIHCs)are widely regarded as highly promising energy storage devices,due to their exceptional energy density,impressive power density,and abundant potassium resources.Unfortunately,restricted by the inherent capacitive storage mechanism,the carbon cathodes possess a much lower specific capacity than battery-type anodes.Therefore,designing high-performance carbon cathodes is extremely urgent for the development of PIHCs.Herein,N,O codoped porous carbon(NOPC)was fabricated through the NaCl hard template method and combined KOH/melamine chemical activation technique,displaying the characteristics of abundant N/O content(4.7 at%/16.9 at%),ultrahigh specific surface area(3092 m^(2)g^(-1))and hierarchical pore network.The designed NOPC cathode delivers a high specific capacity(164.4 mAh.g^(-1)at 0.05 A.g^(-1))and superior cyclability(95.1%retention ratio at 2 A·g^(-1)over 2500 cycles).Notably,the adjustable ratio of micropores to mesopores facilitates the achievement of the optimal bal-ance between capacity and rate capability.Moreover,the pseudocapacitance can be further augmented through the incorporation of N/O functional groups.As expected,the graphite//NOPC based PIHC possesses a high energy density of 113 Wh·kg-at 747 W·kg^(-1)and excellent capacity retention of 84.4% fter 400 cycles at 1.0 A·g^(-1).This work introduces a novel strategy for designing carbon cathodes that enhances the electrochemical performance of PIHCs.

Fibrous activated alumina prepared through phase transformation using dawsonite as a template

Fibrous activated alumina is widely applied in catalysts,adsorbents,and composite materials.This work presents a green approach in preparing the fibrous activated Al_(2)O_(3) with high purity and specific surface area through multistep phase transformation of aluminum-bearing substances using intermediate dawsonite as a template.Thermodynamic calculations and experimental results show that increasing the concentration of Na_(2)CO_(3) and(NH_(4))_(2)CO_(3) is remarkably beneficial to the formation of dawsonite and ammonium aluminum carbonate hydroxide,respectively.Based on determination of dissolution and precipitation mechanism,the ultrafine granular gibbsite is converted to the uniform fibrous dawsonite with a ratio of length to diameter over 50,and the fibrous dawsonite changes into the long fibrous ammonium aluminum carbonate hydroxide with a ratio of length to diameter is about 80 in above 70 g/L(NH_(4))_(2)CO_(3) solution.Furthermore,the activated alumina remains fibrous morphology after roasting ammonium aluminum carbonate hydroxide at a slow heating rate,plentiful open mesopore and weak aggregation of particles,which contributes to the high specific surface area of 159.37 m^(2)/g at 1273 K for the activated alumina.The complete transformation of dawsonite to ammonium aluminum carbonate hydroxide and high specific surface area contribute to the purity of the activated fibrous alumina above 99.9%with low Na and Fe content.

Adsorption of naphthalene onto a high-surface-area carbon from waste ion exchange resin

A high-surface-area carbon （KC-1） was prepared from waste polystyrene-based ion exchange resin by KOH activation and used for naphthalene adsorption. The carbon exhibited a good hydrophobic nature with developed porous structure, favoring the adsorption of organic compounds. The Brunauer-Emmett-Teller surface area and total pore volume of KC- 1 were 3442.2 and 1.68 cm3/g, respectively, which can be compared with those of KOH-activated carbons prepared from other precursors. Batch experiments were carded out to investigate the adsorption of naphthalene onto KC-1. The equilibrium data were analyzed by the Langmuir, Freundlich, and Polanyi- Manes isotherms and agreed with the Polanyi-Manes Model. The adsorption of naphthalene depended greatly on the porosity of the carbon, and the dispersive interactions between naphthalene and carbon could be relatively weak. The pH variation in aqueous solution had little effect on the adsorption process. The equilibrium time for 0.04 g/L of carbon dose was around 5 hr. Different models were used to evaluate the kinetic data and the pseudo second-order model was suitable to describe the kinetic process of naphthalene adsorption onto KC-1. Regeneration of spent carbon could be carded out effectively by alcohol treatment. The results indicated that KC-1 was a promising adsorbent for the removal of polycyclic aromatic hydrocarbons from aqueous solutions.

Nitrogen-doped hierarchical few-layered porous carbon for efficient electrochemical energy storage

Large surface area,high conductivity,and rich active site of carbon electrode materials are necessary characteristics for energy storage devices.However,high conductivity and high nitrogen doping of carbon electrode materials are difficult to coordinate.Here,a facile method via the carbonization of nitrogen-containing Schiff base polymer has been developed to prepare high conductivity and high nitrogen-doped hierarchical porous carbon.The organic components with a benzene ring structure in the polymer promote the formation of more sp^(2)-graphitized carbon,which is beneficial for the improvement of electrical conductivity.Nitrogen-doped hierarchical porous carbon calcined at 900℃ under the NH3 atmosphere possesses high nitrogen content of 7.48 at%,a large specific surface area of 1613.2m2/g,and high electrical conductivity of 2.7 S/cm.As electrode materials in an aqueous-based supercapacitor,nitrogen-doped hierarchical porous carbon exhibits superior specific capacitance of 385 F/g at 1 A/g as well as excellent rate performance(242 and 215 F/g at a current density of 100 and 200 A/g,respectively).In addition,the specific capacitance of electrode measured in a two-electrode system is 335 F/g at 1 A/g,and the long-term cycling stability can be achieved with more than 94%initial capacitance after 10000 cycles.The constructed symmetric supercapacitor delivers high energy density and high power density.The outstanding electrochemical performances combined with the novel and scalable synthetic approach make the nitrogen‐doped hierarchical porous carbon potential electrode material for electrochemical devices.

Electrochemical Impedance Spectroscopy Study on Novel Carbon-Sulfur Nano-Composite Cathodes in Lithium Rechargeable Batteries

Carbon-sulfur nano-composite cathodes for lithium rechargeable batteries were investigated by electrochemical impedance spectroscopy (EIS). The novel carbon-sulfur nano-composite material was synthesized by heating sublimed sulfur and high surface area activated carbon (HSAAC) in certain conditions. Equivalent circuits were used to fit the spectra at different discharge states. The variations of impedance spectra, charge-transfer resistance and double layer capacitance were discussed. The changes of EIS with potential were analyzed based on a plausible electrical equivalent circuit model, and some parameters were measured and analyzed about electrochemical performance and state of charge and discharge of the electrode. The good accuracy in fitting values of the model to the experimental data indicates that the mathematical model gives out a satisfying description upon the mechanism of high rate of capacity fade in lithium-sulfur battery.

稻草秸秆-煤基压块活性炭的制备及工艺优化

为降低压块破碎活性炭的制备成本,以稻草秸秆炭和大同不黏煤为主要原料,利用配煤工艺,经过成型、炭化、H_(2)O_((g))-CO_(2)联合活化成型炭制备压块破碎活性炭。采用碘吸附法、亚甲蓝吸附法以及BET、FTIR和Boehm滴定方法测试和表征不同条件下制备的压块破碎活性炭。实验结果表明,加入适量稻草秸秆炭和H_(2)O_((g))-CO_(2)联合活化对活性炭的碘吸附值和亚甲蓝吸附值均有明显提升作用。Boehm滴定结果表明,活性炭具有丰富的酸性和碱性官能团。当活化温度为900℃、活化时间为2.5 h、H_(2)O_((g))和CO_(2)流量比为2时,制备的活性炭的碘吸附值、亚甲蓝吸附值和比表面积分别达到790 mg/g、262 mg/g和809 m^(2)/g。

有机胺改性树脂基球形活性炭对二氧化碳的吸附行为

以球形结构的固废离子交换树脂为原料,经CO_(2)活化、酸洗处理制得具有较高比表面积和较大中孔孔容的树脂基球形活性炭(HRSAC),然后在其表面负载聚乙烯亚胺(PEI)制得吸附材料PEI-HRSAC。系统考察了PEI负载量和吸附温度对CO_(2)吸附性能的影响,结果表明,在活化温度为950℃、活化时间为1 h的最佳活化工艺条件下,所制得的树脂基球形活性炭经酸洗处理后其比表面积为1365 m^(2)/g,中孔孔容为2.04 cm^(3)/g,中孔孔径主要分布在10~40 nm;PEI-HRSAC吸附材料对CO_(2)的吸附性能随吸附温度和PEI负载量的升高先增大后减小;当PEI负载量为65%、吸附温度为75℃时,PEI-HRSAC吸附材料对CO_(2)的吸附量最高,约为4.09 mmol/g,在经过4次循环吸/脱附后吸附量仍保持在较高水平(3.66 mmol/g)。

高比表面多孔碳酸钙用于高效吸附结晶紫研究

以石灰石为原料,采用碳化法+模板法制备石灰石基多孔碳酸钙,所得碳酸钙颗粒表面粗糙,呈孔状结构,比表面积高达60.17m^(2)·g^(-1)。该多孔碳酸钙对结晶紫的吸附实验结果显示,多孔碳酸钙对结晶紫的吸附去除率达到93.36%、吸附量816.89mg·g^(-1)。多孔碳酸钙吸附结晶紫前后的红外光谱图表明结晶紫成功被吸附在多孔碳酸钙上。采用等温吸附模型拟合发现,多孔碳酸钙吸附结晶紫过程遵循Langmuir模型,属于非均匀的单分子层吸附。同时,动力学拟合与准二级吸附模型吻合,表明吸附过程以化学吸附为主。

活性炭负载锌催化剂的制备及其处理煤化工废水的试验研究

为实现煤化工高盐废水水质处理效能的提升,以宁夏生产的煤制活性炭为载体,采用直接浸渍法、沉淀-煅烧法2种负载方法,选取Zn元素作为催化剂的活性组分,制备了用于臭氧氧化降解工艺用催化剂,考察了催化剂对宁夏宁东地区煤化工高盐废水中COD去除情况的探究。结果表明:将活性炭与浓度为0.4 mol/L的氯化锌溶液按照m(活性炭)∶V(溶液)=1∶3的比例混合,完全沉淀后,在氮气环境保护下,在恒定300℃的温度下煅烧2 h,制得活性组分为氧化锌的ZnO/AC催化剂,其比表面积为1063.45 m2/g,COD去除率高达71.7%,处理后废水中Zn^(2+)质量浓度增加99.8882 mg/L,高比表面积有利于发挥物理吸附与化学催化的协同作用,提高活性炭基催化剂的催化性能。该臭氧催化剂催化效果显著,可用于煤化工高盐废水中有机物的去除。

高表面活性炭制备工艺的优化

为解决化学活化法制备高表面活性炭成本高、能耗大的问题,在对高表面活性炭制备工艺简单概述的基础上,结合实践生产对当前活化比条件下的生产工艺参数进行调试;为达到降低能耗和生产成本的目的对活化比参数以及活化剂添加时间点进行优化,最终达到产品比表面积等指标满足要求的基础上降低生产成本的目的。

活性炭二次活化工艺研究进展

活性炭二次活化是指对已经完成活化的活性炭进行再活化的过程。活性炭二次活化技术作为一种活性炭孔隙调控手段,在合适的工艺条件下,可以使活性炭的孔隙结构更为发达,并且使孔径分布更为集中,从而赋予活性炭特异性功能。综述了二次活化工艺在活性炭孔隙调控方面的研究进展及应用途径,并对其未来的应用及发展方向进行展望,为高性能活性炭的开发和应用提供参考。

科学研究成果与物理化学实验的融合——溶液法测定棉秸秆活性炭比表面积

在“新工科”建设背景下,探索科学研究成果与《物理化学实验》课程教学相融合的实验教学模式改革,将科研实验“生物质活性炭的制备”融入“溶液吸附法测定固体比表面积”实验。实验教学中引导学生探索利用农业废弃物“新疆阿克苏长绒棉秸秆”制备活性炭并测定其比表面积,同时考察吸附温度对吸附平衡常数K的影响,得到该吸附反应的吸附热力学函数。将科学研究与物理化学实验相融合,把验证型实验改造成创新性、综合性实验,增强学生的创新能力和科学素养的培育,促进应用型人才培养质量提升。

KOH/NaOH活化法辣椒秸秆制备高表面积活性炭与表征

以废弃辣椒秸秆为原料,KOH/NaOH为活化剂,采用正交试验,研究了活化温度、时间、炭化温度及KOH/NaOH/C对吸附性能的影响,得出最佳工艺条件即活化温度为700℃、活化时间为80min、炭化温度为450℃、KOH/NaOH/C为3∶1∶1。此条件下制得的样品Langmuir比表面积高达3217.237m2/g,吸附平均孔径为3.590nm,皆高于单一KOH活化样品(SLangmuir=3159.200m2/g,D=2.672nm)。同时采用SEM和FT-IR对KOH/NaOH活化样品的表面形貌和官能团进行分析,并与单一KOH活化样品进行对照,发现它们的化学组成相似,并皆具有丰富和发达的孔隙结构,但KOH/NaOH活化样品出现更多的中孔和一定量的大孔。