Experimental measurements and computer simulation of methane adsorption on activated carbon fibers

Three activated carbon fibers (ACFs) with different BET specific surface areas (SSAs) were prepared. Experimental characterization and methane adsorption on the ACFs were measured by the intelligent gravimetric analyzer (IGA-003, Hiden) at 258 and 298 K. Correlations proposed between the methane adsorption capacity and SSA indicate that the SSA plays an important role on storage amount at a given temperature. A detailed experimental investigation was focused on the sample ACF3 of the highest SSF of 1511 m²/g at five temperatures, from 258 to 298 K. The temperature dependence for methane adsorption amount on ACF3 at 1.8 MPa is proposed. It shows that temperature is vital to methane storage capacity for ACF3, and adsorption storage at the temperatures below 280 K is recommended for favorite uptakes. To model ACF3, the pores are described as slit-shaped with a pore size distribution that was determined by molecular simulation and the statistics integral equation. Predictions of methane adsorption, carried out at 258 and 298 K and high pressures by molecular simulation, indicate that our sample ACF3 can reach the uptake of 14.99 wt% at 4.0 MPa and 298 K, which is comparable with the best result in the literature.     

活性炭吸附甲烷和甲苯的分子模拟研究

以石墨片微元构建的多孔碳材料作为活性炭的结构模型,采用巨正则蒙特卡罗方法(GCMC)和分子动力学方法(MD),从分子层面研究甲烷和甲苯在活性炭中的吸附和扩散特性. 结果表明,石墨片微元大小对多孔碳材料吸附甲烷和甲苯有一定影响,37个碳环构成的多孔碳材料是最佳的吸附结构;甲烷气体在活性炭材料中扩散较快,甲苯在活性炭中扩散较慢,随碳环碳原子数增加,气体在多孔碳材料中的自扩散系数逐渐增大;引入基团会使最优密度向高密度方向偏移,用不同基团表面改性的吸附量顺序为羟基>氨基>羧基>未改性,基团引入会改善材料的孔结构,有利于吸附量的增加.     

基于BP神经网络的活性炭吸附甲基紫废水过程模拟

为了研究活性炭吸附甲基紫废水过程模型,采用BP人工神经网络算法,以实验所得的32组实验数据为训练样本,建立了以甲基紫废水浓度为输入变量,以不同甲基紫废水浓度下活性炭处理后甲基紫溶液的吸光度为输出变量的吸附模型,模型输出的预测结果与实验数据吻合较好,说明该模型对活性炭吸附处理甲基紫废水过程模拟的可行性和有效性.     

Experimental and theoretical study of methane adsorption on granular activated carbons

The experimental and theoretical study of methane adsorption on granular activated carbons is presented. The adsorption data are modeled by various isotherm equations. Toth equation is found to have the best fit. The isosteric heat decreases with loading and increases weakly with temperature, which is an indication of heterogeneity of the methane and granular activated carbon system. Using optimized parameters from Toth equation, a novel procedure is developed to calculate the integral heat of adsorption, which is the total amount of isosteric heat of adsorption at a given temperature and pressure during the adsorption process. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

活性炭对模拟含酚废水的吸附实验研究

采用振荡平衡法研究了活性炭吸附苯酚的效果,确定了活性炭用量、振荡时间、温度、pH值对模拟含酚废水中苯酚吸附效果的影响。结果表明：活性炭用量1．6g,振荡时间30min,温度30℃,pH值为6的条件下,对50mL质量浓度为60mg／L的苯酚模拟废水处理效果最佳。     

Phosphoric acid activated carbon discs for methane adsorption

Phosphoric acid has been used as activating agent in the preparation of binderless activated carbon discs. The granular precursor was impregnated with different solutions of phosphoric acid, hot pressed in discs, heat treated under a flow of nitrogen and washed with distilled water to extract the excess acid. The role of the impregnation ratio and the temperature of conforming have been analysed. The discs have a bulk density higher than the granular activated carbon because there is a considerable reduction of the interparticle space, the contribution of non-microporous volume being small. The discs exhibit a high volume of microporosity accessible to both nitrogen and methane molecules. Best results (storage capacity of 131, v/v) were obtained when using an impregnation ratio X_P=0.35 g phosphorous/g precursor (maximum micropore volume and minimum interparticle space) and conforming at 100 °C (higher temperatures reduce the volume of micropores). Some discs were additionally activated under a flow of carbon dioxide, the maximum methane storage capacity (near 150, v/v) being obtained when burn-off is in the 10-40% range.     

甲烷在成型纳米活性炭中的吸附动力学特性

为提高天然气储气装置的单位体积储气量,模压成型的大尺寸吸附剂得到越来越多的应用,有关甲烷在这种吸附剂的吸附动力学问题也成为关注热点。采用差压穿透实验,在较宽广的温度和压力范围内测量了甲烷在成型纳米活性炭中吸附过程的表面扩散系数,利用Maxwell-Stefan模型分析了表面扩散、Knudsen扩散和黏性流扩散对总吸附过程的影响以及与温度和压力变化的相关性,并根据实验结果导出表面扩散系数的经验关联式。研究结果表明,在实验温度和压力范围内,表面扩散对甲烷在纳米活性炭型炭中的吸附过程起主导作用,但在低压条件下Knudsen扩散也非常重要。随压力升高,表面扩散系数趋于定值,而黏性流扩散作用持续增强,成为吸附过程的重要影响因素。     

Interpretation of methane adsorption on activated carbon by nonisothermal and isothermal calculations

Experimental breakthrough curves for methane absorption on activated carbon are analyzed using isothermal and nonisothermal models. Interaction of heat and mass transfer effects vary from being almost negligible to being quite pronounced. Some rather large radial temperature gradients were measured in the bed. In spite of these, the fit of the experimental data to the nonisothermal model is reasonably good. Stability problems in the nonisothermal solution are discussed.     

甲烷在石墨化炭黑上吸附平衡的分子模拟

采用GCMC法对不同温度和压力下纯CH4在石墨化炭黑上的吸附平衡进行了分子模拟研究,选用Lennard-Jones 12—6势能函数和联合原子力场参数（TraPPE）对体系进行势能计算,并将吸附平衡预测结果与实验数据进行了比较分析。结果表明,在所研究的温度范围内,除了在低压的一定区间外,GCMC模拟结果在中压和高压条件下与实验数据基本吻合,表明采用GCMC方法模拟甲烷分子在石墨化炭黑上的吸附平衡数据是可以进行准确预测的。在此基础上,利用模拟的吸附平衡数据计算不同温度下CH4的Henry常数进而到得极限吸附热,计算结果与实验数据接近。     

Determination of pore size distribution and adsorption of methane and CCl4 on activated carbon by molecular simulation

A combined method of grand canonical Monte Carlo (GCMC) simulation and statistics integral equation (SIE) for the determination of pore size distribution (PSD) is developed based on the experimental adsorption data of methane on activated carbon at ambient temperature, T=299 K. In the GCMC simulation, methane is modeled as a Lennord-Jones spherical molecule, and the activated carbon pore is described as slit-shaped with the PSD. The well-known Steele’s 10-4-3 potential is used to represent the interaction between the fluid molecule and the solid wall. Covering the range of pore sizes of the activated carbon, a series of adsorption isotherms of methane in several uniform pores were obtained from GCMC. In order to improve the agreement between the experimental data and simulation results, the PSD is calculated by means of an adaptable procedure of deconvolution of the SIE method. Based on the simulated results, we use the activated carbon with the PSD as the prototype of adsorbent to investigate adsorption. The adsorption isotherms of methane and CCl₄ at 299 K in the activated carbon with the PSD are obtained. The adsorption amount of CCl₄ reaches 20 mmol/g at ambient temperature and pressure. The results indicate that the combined method of GCMC and SIE proposed here is a powerful technique for calculating the PSD of activated carbons and predicting adsorption on activated carbons.     

Experimental and artificial neural network modeling study on soot formation in premixed hydrocarbon flames

The formation of soot in premixed flames of methane, ethane, propane, and butane was studied at three different equivalence ratios. Soot particle sizes, number densities, and volume fractions were determined using classical light scattering measurement techniques. The experimental data revealed that the soot properties were sensitive to the fuel type and combustion parameter equivalence ratio. Increase in equivalence ratio increased the amount of soot formed for each fuel. In addition, methane flames showed larger particle diameters at higher distances above the burner surface and propane, ethane, and butane flames came after the methane flames, respectively. Three-layer, feed-forward type artificial neural networks having seven input neurons, one output neuron, and five hidden neurons for soot particle diameter predictions and seven hidden neurons for volume fraction predictions were used to model the soot properties. The network could not be trained and tested with sufficient accuracy to predict the number density due to a large data range and greater uncertainty in determination of this parameter. The number of complete data set used in the model was 156. There was a good agreement between the experimental and predicted values, and neural networks performed better when predicting output parameters (i.e. soot particle diameters and volume fractions) within the limits of the training data.     

Experimental and statistical analysis of trichloroethylene adsorption onto activated carbon

Adsorption processes have long been used in water and wastewater treatment and a deterministic approach has been often adopted for the analysis of fundamental mechanisms.In this research, a new approach based on statistical treatment of modelling data is adopted for the analysis of trichloroethylene (TCE) adsorption on granular activated carbon (GAC) from synthetic groundwater. The work starts from an experimental analysis aimed at the assessment of the influence of thermodynamic parameters (concentration, pH, salinity, temperature and the presence of an organic non-ionic compound, i.e. ethyl acetate) on TCE adsorption capacity. A wide range of process parameters have been considered to simulate highly polluted groundwater, as when leachate infiltrations occur at solid waste landfill.Experimental results show that adsorption capacity decreases by increasing the temperature and the ethyl acetate concentration, while neither pH nor salinity have any influence.A thorough understanding of adsorption mechanism and the individuation of the model with highest physical and mathematical significance is carried out by a thermodynamic analysis and a statistical methodology based on Analysis of Variance (ANOVA). The latter indicates that in dilute solutions the Freundlich model is the best data fitting model for TCE adsorption, among those which are commonly adopted.     

Preparation of powdered activated carbon from rice husk and its methane adsorption properties

Success of adsorbed natural gas (ANG) storage process is mainly based on the characteristics of the adsorbent, so various synthesized adsorbents were analyzed for methane adsorption on a thermodynamic basis. Activated carbon from rice husk (AC-RH) was synthesized and its methane adsorption capacities were compared with phenol based activated carbons (AC-PH₂O and AC-PKOH). The adsorption experiments were conducted by volumetric method under various constant temperatures (293.15, 303.15, 313.15 and 323.15 K) and pressure up to 3.5MPa. Maximum methane adsorption was observed in AC-RH as its surface area is higher than the other two adsorbents. The experimental data were correlated well with Langmuir-Fruendlich isotherms. In addition, isosteric heat of adsorption was calculated by using Clausius-Clapeyron equation.     

人工神经元网络在甲烷催化转化反应中的研究进展

人工神经元网络(ANN)是一种通过模拟大脑处理信息的方式发展起来的数据处理技术,在石油和天然气领域中被广泛用于产量预测、甲烷物性计算、甲烷吸附与分离以及甲烷催化转化等领域。针对甲烷催化转化领域,综述了近年来ANN技术在甲烷干重整、蒸汽重整、联合重整和氧化偶联反应中的应用进展,结果表明：ANN在预测甲烷转化率、产物收率等方面具有准确性好、泛化能力强、鲁棒性好的优点,在催化工艺优化、催化剂组成优化等方面也有很好的应用,对该领域存在的问题以及未来的研究方向进行了总结和展望。     

活性炭对对苯二酚的吸附试验研究

在静态条件下,采用活性炭对对苯二酚废水进行处理,比较了不同条件下活性炭对对苯二酚废水的吸附效果,确定了处理废水的pH值、活性炭用量、振荡时间、温度、废水中对苯二酚浓度、振荡速率以及电解质对吸附效果的影响。试验结果表明:在pH值为6.5、活性炭投加量为35g/L、振荡时间3.5h、温度35℃左右的条件下,对质量浓度为100mg/L的对苯二酚废水的处理效果最好,去除率可达99%。     

Molecular dynamic simulation of carbon dioxide,methane, and nitrogen adsorption on Faujasite zeolite

Removing impurities such as carbon dioxide and nitrogen from natural gas is a technical challenge and one of the major concerns in natural gas treatment process. In this study, adsorption of CH₄, N₂, and CO₂ on the Faujasite(FAU) zeolite has been studied using molecular dynamics simulation at temperatures of 293, 308, and 323 K and pressures up to 1 MPa. COMPASS force field was used to model the interactions between zeolite and guest molecules. Ewald and atom-bas...     

活性炭/聚苯胺复合材料的制备及吸附性能研究

分别以盐酸、醋酸和十二烷基苯磺酸掺杂,制备聚苯胺活性炭复合材料,用于对废水中有机污染物苯酚进行选择性吸附。结果表明,盐酸、醋酸和十二烷基苯磺酸掺杂都能制得聚苯胺活性炭复合材料,其中醋酸掺杂的活性炭/聚苯胺材料吸附性能最好,对苯酚的吸附效率可达94.7%。