Preparation of activated carbon with high surface area for high-capacity methane storage

Activated carbon （AC） was fabricated from corncob, which is cheap and abundant. Experimental parameters such as particle size of corncob, KOHlchar weight ratio, and activation temperature and time were optimized to generate AC, which shows high methane sorption capacity. AC has high specific surface area （3227 m^2/g）, with pore volume and pore size distribution equal to 1.829 cm^3/g and ca. 1.7-2.2 nm, respectively. Under the condition of 2℃ and less than 7.8 MPa, methane sorption in the presence of water （Rw = 1.4） was as high as 43.7 wt% methane per unit mass of dry AC. The result is significantly higher than those of coconut-derived AC （32 wt%） and ordered mesoporous carbon （41.2 wt%, Rw = 4.07） under the same condition. The physical properties and amorphous chaotic structure of AC were characterized by N2 adsorption isotherms, XRD, SEM and HRTEM. Hence, the corncob-derived AC can be considered as a competitive methane-storage material for vehicles, which are run by natural gas. Key words

Molecular Simulation of Methane Adsorption in Different Micro Porous Activated Carbons at Different Temperatures

We employed the previously developed micro porous activated carbon models of different pore sizes ranges of 9-11?,10-12?,and 13-16?that were constructed by molecular simulation method based on a random packing of platelets of carbon sheets,functionalized with oxygen containing groups,to study the adsorption behavior of methane molecules.In studying methane adsorption behavior,we used Grand Canonical Monte Carlo and Molecular Dynamics methods at different temperatures of 273.15,298.15 and303.15 K.Adsorption isotherms,isosteric heats of adsorption,adsorption energy distributions and porosity changes of the models during adsorption process were analyzed and discussed.Furthermore,radial distribution Functions,relative distribution and diffusion coefficients of methane molecules in activated carbon models at different temperatures were studied.After the analysis,the main results indicated that large micro pores activated carbons were favorable for storing methane at lower temperatures and small micro pores were the most favorable for adsorbing methane molecules at higher temperatures.Interestingly,the developed model structures showed high capacities to store methane molecule at ambient temperatures and low pressure.

Effect of preparation methods on the adsorption property of municipal solid waste-based carbon materials

Three different preparation methods including steam physical activation, catalytic carbonation and KOH chemical activation methods were used to prepare municipal solid waste- based carbon materials. The methylene blue （MB） adsorption value was applied to evaluate the adsorption capabilities of the prepared carbon materials. The effects of preparation methods on adsorption capability and yield of products were investigated. The yield of carbon materials with the catalytic carbonation method is the highest, and the KOH activation method is the second level. Considering the adsorption performance, the KOH activation method is much more favorable. Among the different components of municipal solid waste-based carbon materials, the adsorption properties of the single component of paperboard, the double components of tire and paperboard, the triple components of tire, paperboard and polyvinyl chloride （PVC）, and the multi-component mixtures are better than those of other single-, double-, triple- and multi-component mixtures, respectively.

Theoretical and Experimental Study on the Adsorption and Desorption of Methane by Granular Activated Carbon at 25℃

A theoretical and experimental study was conducted to accurately determine the amount of adsorption and desorption of methane by various Granular Activated Carbon （GAC） under different physical conditions. To carry out the experiments, the volumetric method was used up to 500 psia at constant temperature of 25℃. In these experiments, adsorption as well as desorption capacities of four different GAC in the adsorption of methane, the major constituent of natural gas, at various equilibrium pressures and a constant temperature were studied. Also, various adsorption isotherm models were used to model the experimental data collected from the experiments. The accuracy of the results obtained from the adsorption isotherm models was compared and the values for the regressed parameters were reported. The results shows that the physical characteristics of activated carbons such as BET surface area, micropore volume, packing density, and pore size distribution play an important role in the amount of methane to be adsorbed and desorbed.

PREPARATION OF ACTIVATED CARBON FROM TWO CHINESE ANTHRACITES IN THE PRESENCE OF OXIDATIVE ADDITIVES

This paper broke with the conventional ways of oxidizing and catalyzing. It researched a new way to prepare activated carbon from anthracites which employed oxidative additives. It investigated the effects of the additive on adsorption and activation rate of the resultant activated carbon. The results showed that the new additives not only improved the adsorptivity but also increased the activation rate greatly, which is able to decrease the preparation cost.

Novel Activated Carbon Monoliths for Methane Adsorption Obtained from Coffee Husks

Methane adsorption by different forms of activated carbon obtained from coffee husks, including monolith honeycomb and disc types, was studied by activation with zinc salts and potassium hydroxide at 298.15 K and 303.15 K and pressures up to 30.00 atm in a volumetric adsorption apparatus. We observed increased methane adsorption capacity on a mass basis in the different activated carbon monoliths with increasing surface area, total pore volume and micropore volume, with the honeycomb type displaying the highest methane absorption capacity. The maximum volumetric methane uptake by the synthesised carbon monoliths was observed to be 130 V/V at 298.15 K and 30.00 atm for honeycomb monoliths synthesised with zinc chloride (ZnCl2) and Polyvinyl alcohol (PVA) as the binder. Adsorption calorimetry results were used to describe the interaction between guest molecules and the adsorbent at low surface coverage and the energetic heterogeneous surface nature of the adsorbent.

Structure modeling of activated carbons used for simulating methane adsorption-A review

Activated carbons(ACs)are highly porous materials with a broad range of applications in industry such as gas storage,water and air purification,gas separation,and catalysis.The microstructure for ACs is still not clearly known in spite of their wide industrial uses.There have been efforts to describe the structure of activated carbons experimentally in relation to its methane adsorption characteristics.In this review,it is assumed that natural gas is sorely composed of CH_(4)for simplicity(because CH_(4)is the major component,>90%).Experimental means to unveil the microstructure and many other properties for these ACs have some limitations,to overcome these limitations,ACs structural modeling and simulation become very important to match the properties with the desired methane adsorption characteristics.The major challenge that methane adsorption simulation faces for so long,is the lack of realistic AC models.This paper reviews the current efforts to develop the realistic AC models for methane adsorption,most of the built models are based on experimental carbon structural findings from the previous studies.The structural parameters including pore size distribution(PSD),specific surface area(SSA),pore volume and extent of curvature in the carbon materials and their role to methane adsorption are discussed.The role of chemical properties,such as presence of functional groups and the nature of the functional groups to the adsorption properties of methane,are also introduced.Different pore morphologies(such as slit pore,platelet,spherical,etc.)are studied with their effect on methane adsorption and presented too.It is found that each of the mentioned parameters has its own bearing to methane adsorption.Furthermore,this work analyzes different current techniques used in modeling natural gas adsorption,and the mechanisms are able to reproduce the specific carbon materials for a certain desired set of adsorption characteristic.Some future works are also recommended in this area,so that better representations of ACs can be obtained for methane storage purposes.

Adsorption Isotherm and Kinetic Study of Methane on Palm Kernel Shell-Derived Activated Carbon

Activated carbon(AC)was synthesized from palm kernel shell(PKS)using different activating agents,i.e.,steam,carbon dioxide(CO 2),and CO 2-steam,in order to analyze the impact of acti-vating agents on the pore opening of AC.In this study,AC produced from PKS was found to have great potential as an adsorbent for methane storage.The different molecular diffusivity and reac-tivity of the combination of CO 2 and steam succeeded in producing AC with the highest burn-offof 78.57%,a surface area of 869.82 m 2/g,a total pore volume of 0.47 cm 3/g,and leading to maximum methane gas adsorption capacity of 4.500 mol/kg.All types of ACs exhibited the best fit with the Freundlich isotherm model,with the correlation coefficient(R 2)ranging from 0.997 to 0.999,indicating the formation of multilayer adsorption.In addition,the adsorption kinetic data for all ACs followed the pseudo-first-order model showing that the rate of adsorption was dependent on both the adsorbent and the adsorbate and was governed primarily by physical ad-sorption between the pore surface and methane gas.The results of intraparticle diffusion model indicated that the adsorption of methane was affected by both pore diffusion and exterior layer diffusion due to the different adsorption rates.

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

Adsorption/desorption isotherms of supercritical methane on superactivated carbon have been measured in the range of 0–10 MPa and 233–333 K (20 K interval). The reversibility of the physical adsorption process is acknowledged. The heat of adsorption of 16.5 kJ/mol is determined from the isotherms, and a new modeling strategy for isotherms with maximum is presented. The model yields fits to the experimental isotherms with precision of ±2%, maintaining the constancy of the characteristic energy of adsorption. The exponent of the model equation expresses the pore size distribution feature of the adsorbent. The density of the supercritical adsor-bate is evaluated as a parameter of the model. It is shown that the conventional isotherm theory works too at supercritical condition if the limit state of supercritical adsorption is introduced into isotherm modeling.

Characterization and Methanol Adsorption of Walnutshell Activated Carbon Prepared by KOH Activation

Walnut-shellactivated carbons（WSACs）were prepared by the KOH chemicalactivation.The effects of carbonization temperature,activation temperature,and ratio of KOH to chars on the pore development of WSACs were investigated.Fourier transform infrared spectroscopy（FTIR）,X-ray powder diffraction（XRD）,and scanning electron microscopy（SEM）were employed to characterize the microstructure and morphology of WSACs.Methanoladsorption performance onto the optimalWSAC and the coal-based AC were also investigated.The results show that the optimalpreparation conditions are a carbonization temperature of 700 ℃,an activation temperature of 700 ℃,and a mass ratio of 3.The BET surface area,the micropore volume,and the micropore volume percentage of the optimalWASC are 1636 m^2/g,0.641 cm^3/g and 81.97%,respectively.There are a lot of micropores and a certain amount of meso-and macropores.The characteristics of the amorphous state are identified.The results show that the optimalWSAC is favorable for methanoladsorption.The equilibrium adsorption capacity of the optimalWSAC is 248.02mg/g.It is shown that the equilibrium adsorption capacity of the optimalWSAC is almost equivalent to that of the common activated carbon.Therefore the optimalWSAC could be a potentialadsorbent for the solar energy adsorption refrigeration cycle.

Effects of micropore structure of activated carbons on the CH_(4)/N_(2) adsorption separation and the enrichment of coal-bed methane

In the process of enriching CH4 from coal-bed methane,the separation of CH_(4)/N_(2)is very difficult to accomplish by an adsorption process due to the similar physico-chemical properties of the two molecules.A series of coconut-shell-based granular activated carbons(GACs)with different pore structures were prepared,which were characterized by different methods.The influence of the pore structure on the separation properties was investigated in detail.The results show that one of the carbons prepared(GAC-3)has high CH4 equilibrium adsorption capacity(3.28 mol·kg–1)at 298 K and equilibrium separation coefficient(3.95).The CH_(4)/N_(2)separation on the GACs is controlled by adsorption equilibrium as compared with the dynamic effect.Taking the specific surface area,for example,the common characterization index of the pore structure is not enough to judge the separation performance of the GACs.However,the microstructure of carbon materials plays a decisive role for CH_(4)/N_(2)separation.According to the pore-structure analysis,the effective pore size for the CH_(4)/N_(2)separation is from 0.4 to 0.9 nm,with the optimum effect occurring in the range of 0.6–0.7 nm,followed by the range of 0.7~0.9 nm.Also,a four-bed vacuum pressure swing adsorption process was adopted to evaluate the performance of GACs for the separation of CH4 from nitrogen.

Preparation and adsorption performances of mesopore-enriched bamboo activated carbon

Activated carbon with high specific surface area and considerable mesopores was prepared from bamboo scraps by phosphoric acid activation.The effect of activation conditions was studied.Under the conditions of impregnating bamboo with 80%H3PO_(4) at 80℃ for 9 days and activation at 500℃ for 4 h,the prepared activated carbon had the highest mesopore volume of 0.67 cm3/g,a specific surface area of 1567 m2/g,and the mesopore ratio reached 47.18%.The study on adsorption isotherms of CH4,CO_(2),N2 and O_(2) on the activated carbon were carried out at 298 K.The considerable difference in the adsorption capacity between CO_(2) and the other gases was observed,which would be of interest for the adsorptive separation/purification of gaseous CO_(2) from its mixtures,especially from mixtures with N2 and/or O_(2).

Adsorption Study of Methane on Activated Meso-carbon Microbeads by Density Functional Theory

A combined method of density functional theory (DFT) and statistics integral equation (SIE) for the determina-tion of the pore size distribution (PSD) is developed based on the experimental adsorption data of nitrogen on acti-vated mesocarbon microbead (AMCMB) at 77 K. The pores of AMCMB are described as slit-shaped with PSD. Based on the PSD, methane adsorption and phase behavior are studied by the DFT method. Both nitrogen and methane molecules are modeled as Lennard-Jones spherical molecules, and the well-known Steeles 10-4-3 poten-tial is used to represent the interaction between the fluid molecule and the solid wall. In order to test the combined method and the PSD model, the Intelligent Gravimetric Analyzer (IGA-003) was used to measure the adsorption of methane on the AMCMB. The DFT results are in good agreement with the experimental data. Based on these facts, we predict the adsorption amount of methane, which can reach 32.3 w at 299 K and 4 MPa. The results indicate that the AMCMBs are a good candidate for adsorptive storage of methane and natural gas. In addition, the capillary condensation and hysteresis phenomenon of methane are also observed at 74.05 K.

核桃青皮改性活性炭对锌离子的吸附研究

陇南市拥有大量的锌矿和锌冶炼厂,并且拥有大量的核桃青皮资源,基于活性炭对锌离子的吸附作用,本文在不同温度下对核桃青皮进行了炭化,并利用NaCl、HCl和NaOH进行改性,然后考察了不同条件下改性核桃青皮活性炭对含锌废水中锌离子的吸附作用。分析结果表明,500℃条件下炭化的核桃青皮具有最好的吸附性能,记为WP-500;NaOH对WP-500改性效果较好,对锌离子的吸附性能最强,改性后的活性炭记为WP3-500;在WP3-500用量4 g/L、温度30℃、时间30 min的条件下,WP3-500对锌离子的去除率为81.11%,吸附量为10.14 mg/g;动力学分析表明,准一级动力学模型可以描述WP3-500对锌离子的吸附行为,其主要受物理吸附控制;相较于玉米秸秆、花生壳和稻壳等废弃生物炭化制备吸附剂,利用核桃青皮制备活性炭的方法更简单、成本更低,而且对锌离子的去除效果更好。本研究为核桃青皮的资源化利用及废水中锌离子的去除提供了新思路。

氨水改性活性炭吸附-水合耦合储存甲烷实验研究

活性炭可以通过碱改性的方法有效提高其对客体分子的储存能力。针对适于吸附-水合耦合储存甲烷的椰壳活性炭进行改性,以氨水为改性剂制备了改性活性炭,对比研究了活性炭改性前后的孔隙结构、表面化学变化及其对甲烷储存性能的影响。表征结果表明:氨改性增加了活性炭的比表面积和微孔容积,并减小了平均孔径;改性还影响了活性炭表面官能团组成,降低了活性炭表面O(氧)元素含量并略微增加了N(氮)元素含量,降低了活性炭表面的极性和亲水性。以原炭和NaOH(氢氧化钠)改性炭为对照组,进行甲烷储量实验和动力学实验,发现用体积分数为0.4%浓氨水改性效果最好,在1℃、8 MPa温压条件下储量能达到16.99 mmol/g,是未改性时的1.2倍,且动力学优秀,诱导时间最短为19 min。

(NH_(4))_(2)S_(2)O_(8)/AC电极制备及其电吸附性能

为了制备电化学性能更优的活性炭电极,利用(NH_(4))_(2)S_(2)O_(8)浸渍得到改性后的APS-AC,运用EST技术筛选石墨烯微片、导电炭黑、碳纳米管中更佳的导电剂,制备电化学性能更优的APS-AC电极;通过CV、EIS、GCD和CA等测试手段比较APS-AC电化学性能,并结合吸附行动力学分析电吸附性能和吸附规律。结果表明:导电炭黑制备的APS-AC电极性能更佳,比电容为275.208 F/g;表征发现APS-AC电极的接触角变小,亲水性提高;充放电周期大,充放电性能和电荷储存能力更好。溶液中不同阴阳离子的吸附效果不同,离子去除率为K^(+)>Na^(+)、Cl^(-)>SO_(4)^(2-),吸附过程更符合准二级吸附动力学。

Experimental evaluation of activated carbon derived from South Africa discard coal for natural gas storage

Lacking in literature is the use of discard coal to produce activated carbon and in its subsequent use in the storage of natural gas. In this study, the characterization and gas storage evaluation of a largely porous activated carbon with large surface area synthesized from discard coal were investigated. Discard coals are waste material generated from coal beneficiation process. In developing the activated carbon, chemical activation route with the use of KOH reagent was applied. The effects of KOH/discard coal weight ratio (1:1, 2.5:1, 4:1), temperature (400-800 ℃) and particle size (0.15-0.25 mm, 0.25-0.5 mm, 0.5-1 mm) on the adsorptive properties of the activated carbon were methodically evaluated and optimized using response surface methodology. The synthesized activated carbon was characterized using BET, SEM/EDS, and XRD. The results showed that for each activation process, the surface area and pore volume of the resulting activated carbon increased with increased temperature and KOH/discard coal weight ratio. The maximum surface area of 1826.41 m2/g, pore volume of 1.252 cm^3/g and pore size of 2.77 nm were obtained at carbonization temperature of 800 ℃ and KOH/discard coal weight ratio of 4:1. Methane and nitrogen adsorption data at high pressure were fitted to Toth isotherm model with a predictive accuracy of about 99%. Adsorption parameters using the Toth model provides useful information in the design of adsorbed natural gas storage system. According to the requirements of adsorbent desired for natural gas storage, it could be stated that the synthesized activated carbon could well be applied for natural gas storage.

Removal of lead(II) from aqueous solutions by activated carbon developed from surplus sludge

Activated carbon(AC) was prepared from surplus sludge using chemical activation method with the assistance of ZnCl2. The influences of process parameters on the AC's specific surface area and adsorption capacity for Pb2+ were examined to optimize these parameters. The optimal conditions for the preparation of AC were determined to be activation temperature of 500 °C, activation time of 1 h, impregnation ratio of 1:1(solid-to-liquid volume) with the 30% ZnCl2 solution(mass fraction), giving the BET surface area of 393.85 m2/g and yield of 30.14% with 33.45% ash. Also, the pyrolysis temperature was found to be the most important parameter in chemical activation. FTIR spectra provided the evidence of some surface structures such as C=C and C—O—C. In the adsorption studies, a rise in solution pH led to a significant increase in adsorption capacity when the pH value varied from 3.0 to 7.0, and the optimal pH for removal of Pb2+ was 7.0. It was observed that the pseudo-second-order equation provided better correlation for the adsorption rate than the pseudo-first-order and the Langmuir model fitted better than the Freundlich model for adsorption isotherm. The adsorption capacity of AC to Pb2+ was 11.75 mg/L at solution pH 7.0, the equilibrium time 480 min and 25 °C. Moreover, the adsorption process is endothermic according to the value of enthalpy change.

活性炭复合材料对有毒工业气体吸附性能的研究进展

活性炭复合材料结合了活性炭与多种功能材料的优点,在有毒气体治理领域展现出了巨大应用潜力。本文综述了活性炭与分子筛、金属有机骨架材料、金属氧化物、矿物聚合物等进行复合的方法,并详细探讨了这些复合材料用于有毒工业气体吸附的研究进展。通过对比分析,总结了活性炭复合材料在吸附性能上的优势与不足,并展望了其未来的发展方向。

甘肃省低阶煤基活性炭的制备及性能研究

活性炭是一种经特殊处理的炭。煤基活性炭是一种以煤炭为原料,经过磨粉、成型、炭化、活化等工序制成的活性炭。以甘肃省中部地区窑街煤电金河煤炭为原料,在对原料煤进行工业分析、元素分析、二氧化碳反应活性测定的基础上,利用水蒸气活化法,通过单因素试验和正交试验设计,制备得到金河煤基活性炭,考察了活化时间、活化温度、水蒸气流量等因素对活性炭性能的影响。研究结果发现当活化温度为900℃,活化时间4h,水蒸气流量0.20mL/min时,金河煤基活性炭的最高碘吸附值为588mg/g,经酸法脱灰后,其吸附值增加至716mg/g。同时,将脱灰后的活性炭对初始浓度400mg/L苯酚废水进行处理,当投炭量0.10g、初始溶液pH值为7时,去除率可达79%。通过性能表征和吸附试验,验证了制备所得煤基活性炭具有良好的介孔结构和吸附性能。