Nickel catalysts supported on MgO with different specific surface area for carbon dioxide reforming of methane

In this paper, three kinds of MgO with different specific surface area were prepared, and their effects on the catalytic performance of nickel catalysts for the carbon dioxide reforming of methane were investigated. The results showed that MgO support with the higher specific surface area led to the higher dispersion of the active metal, which resulted in the higher initial activity. On the other hand, the specific surface area of MgO materials might not be the dominant factor for the basicity of support to chemisorb and activate CO2, which was another important factor for the performance of catalysts. Herein, Ni/MgO(CA) catalyst with proper specific surface area and strong ability to activate CO2exhibited stable catalytic property and the carbon species deposited on the Ni/MgO(CA) catalyst after 10 h of reaction at 650 ?C were mainly activated carbon species.

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.

Effects of specific surface area of metallic nickel particles on carbon deposition kinetics

Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature programing oxidation test and Raman spectrum results indicated the formation of complex and ordered carbon structures at high deposition temperatures. The values of I（D）/I（G） of the deposited carbon reached 1.86, 1.30, and 1.22 in the first, second, and third stages, respectively. The structure of carbon in the second stage was similar to that in the third stage. Carbon deposited in the first stage rarely contained homogeneous pyrolytic deposit layers. A kinetic model was developed to analyze the carbon deposition behavior in the first stage. The rate-determining step of the first stage is supposed to be interfacial reaction. Based on the investigation of carbon deposition kinetics on nickel powders from different resources, carbon deposition rate is suggested to have a linear relation with the square of specific surface area of nickel particles.

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.

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.

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.

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.

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.

生物质碳材料的孔道分析

生物质碳材料的孔道类型和孔径大小制约着材料有效的活性位点数量,影响材料的性能。孔道分类又是孔径分析的前提条件,因此,建立孔道分类的方法非常有意义。随着生物质碳材料的深入研究,研究者对其孔道分析的要求逐渐提高。由于实际的吸脱附等温线具有不规则性,难以匹配IUPAC规范中的吸脱附等温线,所以,用实际的吸脱附等温线与IUPAC规范中的吸脱附等温线进行匹配对生物质碳材料的孔道进行分类准确度不能得到保证。使用自制生物质碳材料,运用物理吸附仪对其进行表征,采用BET方程(Brunauer-Emmett-Teller)、T-plot方法(Thickness-plot)、DFT方法(Non-local Density Functional Theory)、BJH(Barrett Joyner And Halenda)方法对其孔道进行分析。研究表明,采用孔隙率和比表面积占有率对其进行孔道分类,可以准确地定义出微孔生物质碳材料、介孔生物质碳材料和微介孔生物质碳材料,从而建立了孔隙率和比表面积占有率的孔道分类新方法。用标准样品对孔隙率和比表面积占有率的孔道分类新方法进行论证,结果一致。方法准确可靠、实用性高。

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。

What are the practical limits for the specific surface area and capacitance of bulk sp^2 carbon materials?

The possible practical limits for the specific surface area and capacitance performance of bulk sp^2 carbon materials were investigated experimentally and theoretically using a variety of carbon materials. We find the limit for the specific surface area to be 3500–3700 m^2 g^(-1), and based on this, the corresponding best capacitance was predicted for various electrolyte systems. A model using an effective ionic diameter for the electrolyte ions was proposed and used to calculate the theoretical capacitance. A linear dependence of experimental capacitance versus effective specific surface area of various sp^2 carbon materials was obtained for all studied ionic liquid, organic and aqueous electrolyte systems. Furthermore, excellent agreement between the theoretical and experimental capacitance was observed for all the tested sp^2 carbon materials in these electrolyte systems, indicating that this model can be applied widely in the evaluation of various carbon materials for supercapacitors.

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)。

煤气化渣制备碳硅介孔材料及甲基橙吸附性能研究

开发了一种煤气化渣低成本制备碳硅介孔材料的方法,探究了影响孔结构的因素和在甲基橙中的吸附性能。采用酸浸法制备碳硅介孔材料,通过材料的孔隙结构和金属氧化物浸出率对制备工艺进行优化。结果表明,温度和时间影响较小,原料粒径和酸浓度影响较大。粒径较小的原料酸浸之后比表面积更大,酸浓度对于碳硅介孔材料的影响比较明显,最佳的酸浓度为16%(质量分数),金属氧化物浸出率和残余碳含量综合影响着比表面积和孔容的大小。煤气化渣基碳硅介孔材料的吸附过程与伪二阶吸附模型最为接近,吸附平衡符合Langmuir模型,对甲基橙最大的吸附量为89.13 mg/g。

MOFs-多孔碳的制备及吸附性能研究

本文以均苯三酸和二水合醋酸锌为原料,分别用咪唑和2-甲基苯并咪唑作为为第二配体,在50℃条件下合成了两种金属有机框架结构MOFs-Im和MOFs-Me。氮气氛围中900℃煅烧得到多孔碳材料MOFs-Im-C和MOFs-Me-C。利用红外光谱仪、荧光光谱仪、同步热分析仪对配合物的结构、发光性以及热稳定性进行了表征;对煅烧后样品采用场发射扫描电子显微镜、比表面及孔径分析仪等进行表征,并通过对亚甲基蓝和罗丹明B的脱除来测试其吸附性能。结果表明,煅烧后生成的MOFs-Im-C多孔碳材料对亚甲基蓝的吸附率在120 nim时几乎达到100%,说明该多孔碳材料对亚甲基蓝具有较好的吸附性能。

Two-dimensional porous carbon derived from pollen with enlarged interlayer distance enhanced electrocatalytic oxidation of n-valeraldehyde to octane

Electrocatalytic n-valeraldehyde oxidation reaction was an inexpensive and eco-friendly method to control n-valeraldehyde contamination and produce high value-added octane.However,low-cost and readily available electrocatalysts with high current efficiency were urgently needed.Herein,two-dimensional porous carbon derived from pollen with enlarged interlayer distance was built by alkali activation method,applying in electrocatalytic n-valeraldehyde oxidation reaction.The enlarged interlayer distance was verified by X-ray diffraction(XRD)and high-angle annular dark-field scanning transmission electron microscope(HAADF-STEM).Electrocatalytic experiments consequences showed activated biomass derived carbon possessed a higher electrocatalytic activity and octane selectivity than unactivated catalyst.Systematic tests and in situ infrared experiments demonstrated that enlarged interlayer distance was positively correlated with specific surface area of catalysts,large specific surface area provided abundant absorption sites,facilitated the adsorption for n-valeraldehyde,and further promoted the transformation of n-valeraldehyde to octane.This work also provides a new avenue for creating high-performance electrocatalysts in terms of lattice engineering.

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。

天然气氧化裂解伴生碳化学活化制备多孔碳

以天然气氧化裂解伴生碳为原料,采用化学活化法在管式炉中制备了多孔碳,考察了活化剂类型、剂碳质量比、活化温度与活化时间对多孔碳比表面积和碘吸附值的影响。结果表明:在以NaOH为活化剂、剂碳质量比1∶1、活化温度750℃、活化时间2 h的优化条件下,多孔碳比表面积为894.58 m^(2)/g、碘吸附值为847.97 mg/g;多孔碳富含介孔结构,主要分布在2~4 nm,还含有少部分微孔结构,其各项技术指标满足行业标准《生活垃圾焚烧烟气净化用粉状活性炭》(征求意见稿)中的要求,对二苯并呋喃的吸附性能优异,具备用作商品活性炭的前景。

凝灰岩粉比表面积对水泥浆体性能的影响

采用不同比表面积的凝灰岩粉取代30%水泥(按总胶凝材料质量计),研究了不同比表面积凝灰岩粉对水泥净浆流动度、胶砂强度、水化热的影响,以及凝灰岩粉取代水泥对碳排放量的影响。结果表明:比表面积381 m^(2)/kg的凝灰岩粉取代水泥可提升净浆初始流动度,但随着凝灰岩粉比表面积增大,净浆初始流动度明显降低;不同比表面积凝灰岩粉对3 d胶砂抗压强度的贡献与粉煤灰、矿渣粉相近,但对28、56 d胶砂抗压强度的贡献低于粉煤灰和矿渣粉;凝灰岩粉比表面积增大有利于提升胶砂抗压强度,但比表面积由495 m^(2)/kg增至700 m^(2)/kg时,对胶砂抗压强度的提升效果有限,综合考虑经济性和抗压强度,作矿物掺和料时凝灰岩粉宜磨细至比表面积495 m^(2)/kg;粉煤灰、矿渣粉和凝灰岩粉取代水泥均能降低水化放热速率峰值和72 h累计放热量,比表面积700 m^(2)/kg的凝灰岩粉对水泥水化进程的加速效果强于粉煤灰、矿渣粉和其他比表面积凝灰岩粉;495 m^(2)/kg比表面积的凝灰岩粉取代30%水泥后制成的复合胶凝材料,碳排放量降低29.5%。

水泥中熟料与混合材比表面积定量表征方法的研究

明确水泥中熟料与混合材的比表面积是设计配制水泥,降低水泥熟料系数的基础。本文利用水泥中熟料与混合材密度差异的特点,通过划分水泥粒度区间,采用试验加计算的方式研究了水泥中熟料与混合材比表面积的定量表征方法。结果表明,随着水泥粒径的增加,熟料含量逐渐增加,混合材含量逐渐降低。P·C 42.5水泥0~20μm区间的比表面积为612.9 m^(2)/kg,熟料含量为64%;>45μm区间的比表面积为61.8 m^(2)/kg,熟料含量为93%。经计算,比表面积为380 m^(2)/kg的P·C 42.5水泥中,熟料比表面积约为334 m^(2)/kg,混合材表面积约为639 m^(2)/kg。