C2H4/CO2混合体系在活性炭上吸附的实验与模型

通过重量法测定吸附等温线,研究了C2H4/CO2混合体系在活性炭上的吸附分离。采用高精度的智能重量分析仪,测定了C2H4和CO2纯组分以及混合组分在活性炭上的吸附等温线,将测量值与DL-IAST模型计算值进行比较,并计算出了C2H4的吸附选择性。结果表明,DL-IAST模型可以准确地描述C2H4和CO2纯组分在活性炭上的吸附;不同摩尔分数下,C2H4/CO2混合体系的DL-IAST模型计算值与实验值吻合得较好,C2H4摩尔分数越大,模型的相对偏差就越小;随着压力的增加,C2H4的吸附选择性减小,C2H4摩尔分数越大,C2H4的吸附选择性也减小。DL-IAST可以准确地描述C2H4/CO2混合体系的吸附等温线以及推算出C2H4的吸附选择性。     

吸附剂特性对CO2/CH4吸附分离的影响分析

用于CO2/CH4二元混合体系吸附分离的吸附剂种类较多,效果参差不齐,而吸附剂的各种特性是影响分离效果的主要原因。本文从吸附剂特性出发,总结了孔结构、可交换阳离子、表面化学以及吸附剂湿度4个因素对吸附分离效果的影响,并解释了造成各种影响的原因。得出结论：中孔有利于该二元体系的分离和胺基嫁接;在吸附剂骨架之外引入合适的可交换阳离子可促进吸附剂与CO2四极矩之间吸引力,提升分离效果;吸附剂的表面羟基也是影响胺基嫁接的重要因素;水分既有利于该体系的吸附分离,又可以促进胺基吸附剂再生。     

用于吸附分离CH4/CO2的碳分子筛的制备研究

以碳分子筛(CMS)作为吸附剂,探索其对CH4/CO2混合气的分离纯化性能。采用化学气相炭沉积法,以价格便宜的商品椰壳基活性炭为原料,以苯为沉积剂,制备碳分子筛。研究了沉积时间和沉积温度对CMS的吸附性质的影响。采用容量法对CMS吸附CH4和CO2性能进行测定。结果表明,在沉积温度为700℃,沉积时间为40min时制备的CMS平衡吸附选择性系数为58.03,远高于活性炭的5.124,对CH4/CO2有良好的分离效果。     

CO2/CH4/N2在沸石13X-APG上的吸附平衡

采用磁悬浮热天平测量了CO₂、CH₄与N₂在沸石13X-APG上的吸附等温线,温度为293、303、333和363 K,压力为0～500 kPa。对吸附平衡实验数据采用multi-site Langmuir模型和Sips模型进行拟合,均得到良好的拟合效果,非线性回归得到吸附热等模型参数,可为变压吸附工艺过程的开发提供基础热力学数据。将沸石13X-APG吸附分离性能与文献中报道的吸附材料(如沸石分子筛、活性炭、金属有机骨架材料和介孔硅分子筛)性能相比较。通过比较CO₂、CH₄与N₂吸附容量以及相对分离系数,探讨CO₂/CH₄(垃圾填埋气或者CO₂强化煤层甲烷回收气)体系、CO₂/N₂(燃煤电厂、水泥厂以及焦炭厂烟道气)体系以及CH₄/N₂(煤层气)体系吸附分离的高效材料,为未来二氧化碳吸附捕集和甲烷吸附回收提供基础数据。     

基于沸石ZSM-5的CH_4/N_2/CO_2二元体系吸附平衡

采用Rubotherm磁悬浮天平测量CH4、N2和CO2在沸石ZSM-5上的单组分吸附平衡等温线,温度273~353K,压力0~500 kPa。采用Sips模型、Toth模型和MSL模型对单组分吸附平衡实验数据进行拟合,拟合结果良好,非线性回归得到相应的模型参数。测量双组分CO2/N2、CO2/CH4和CH4/N2在沸石ZSM-5上的竞争吸附平衡等温线,实验温度为293 K,实验压力为0~500 kPa。采用基于Sips模型的理想吸附溶液理论和双组分MSL模型预测双组分气体在沸石ZSM-5上的竞争吸附平衡等温线,并与实验结果进行比较,预测结果良好。比较CO2/N2、CO2/CH4以及CH4/N2体系在沸石ZSM-5上的竞争吸附选择性系数,探究沸石ZSM-5吸附分离烟道气(CO2/N2体系)、垃圾填埋气(CO2/CH4体系)或煤层气(CH4/N2体系)的可行性,为将来进行工艺设计提供基础数据。     

光催化CO2和CH4重整催化剂研究进展

太阳能驱动的CO₂与CH₄转化为合成气是一种非常有前景的生产可再生燃料的技术,然而太阳能驱动的CH₄重整催化剂存在转化效率低、光生电子与空穴复合速率快及催化剂稳定性差等问题。本文简述了光催化CO₂与CH₄重整的可能机理,包括CO₂和CH₄的吸附、光生电子与空穴的迁移及产物的脱附过程。重点介绍了光催化CO₂和CH₄重整过程中贵金属催化剂、非贵金属催化剂及碳氮化合物等催化剂的研究进展,并总结归纳了各类催化剂的优点与不足。最后,本文探讨了光催化转化CO₂与CH₄制合成气研究领域未来可能的发展方向：开发设计高效的光催化剂提高反应效率;通过密度泛函理论计算及高端表征技术探究催化机理。     

基于沸石ZSM-5的CH4/N2/CO2二元体系吸附平衡

采用Rubotherm磁悬浮天平测量CH₄、N₂和CO₂在沸石ZSM-5上的单组分吸附平衡等温线,温度273～353 K,压力0～500 kPa。采用Sips模型、Toth模型和MSL模型对单组分吸附平衡实验数据进行拟合,拟合结果良好,非线性回归得到相应的模型参数。测量双组分CO₂/N₂、CO₂/CH₄和CH₄/N₂在沸石ZSM-5上的竞争吸附平衡等温线,实验温度为293 K,实验压力为0～500 kPa。采用基于Sips模型的理想吸附溶液理论和双组分MSL模型预测双组分气体在沸石ZSM-5上的竞争吸附平衡等温线,并与实验结果进行比较,预测结果良好。比较CO₂/N₂、CO₂/CH₄以及CH₄/N₂体系在沸石ZSM-5上的竞争吸附选择性系数,探究沸石ZSM-5吸附分离烟道气（CO₂/N₂体系）、垃圾填埋气（CO₂/CH₄体系）或煤层气（CH₄/N₂体系）的可行性,为将来进行工艺设计提供基础数据。     

沸石分子筛对CO_2/CH_4混合气的分离效果研究

选取5A沸石分子筛作为脱碳吸附材料,考察了其对CO2及CH4单组份的吸附效果。结果表明,5A分子筛真空解吸在1 h 50 min即可达到解吸、脱碳、再生的目的,且经8次重复吸附-解吸后仍具有较高及较稳定的脱碳效率。将5A分子筛应用到沼气实际分离实验中,在沼气中n(CO2)∶n(CH4)=40∶60的条件下,经单塔处理可达0.17 m3/kg处理量,甲烷纯度可达97%以上,且连续处理速率为0.60 m3/(h·kg),该研究为今后的沼气分离工程提供了技术参数。     

Ni-Fe/BaTiO3-γ-Al2O3催化剂在低温条件下CO2和CH4重整中的应用

采用等体积浸渍法制备了一系列不同Ni和Fe添加量的Ni-Fe/BaTiO3/γ-Al2O3双金属催化剂,并在固定床反应装置上考察了在873～1 073 K温度范围内催化剂对CO2和CH4重整反应的催化活性。实验结果表明:Ni、Fe负载质量分数均为5.0%的Ni-Fe/BaTiO3/γ-Al2O3催化剂活性最好。通过TPR、TPD和TPO表征并与单金属催化剂Ni/BaTiO3/γ-Al2O3相比,Ni-Fe/BaTiO3/γ-Al2O3催化剂具有更高的催化活性、脱附和抗积炭性能。     

修饰的COF-102吸附和分离CO2/CH4的计算机模拟（英文）

Covalent organic framework (COF) is a porous material with low density and large BET (Brun-auer-Emmett-Teller) surface area. They have great potential in gas adsorption and separation. In this work, the ad-sorption of pure CO2 and CO2/CH4 mixture on modified COF-102 was simulated by using GCMC (grand canonical Monte Carlo). Metal Li was incorporated into COF-102 through three doping methods, including charge exchange, O--Li+ dipolar interaction and O--Li+ chemical bonding. The influence of Li doping on the adsorption of CO2 was studied. The results showed that among the three methods, the dipole doping is the best way to improve CO2 ad-sorption performance. Further, the ligands of COF-102 were replaced by extended aromatic moieties, such as di-phenyl and pyrene. The adsorption capacity of CO2 and CH4, and the selectivity of CO2/CH4 on the ligand-replaced COF-102 were studied. The capacity of CO2 and CH4 on the ligand-replaced COF-102 had obvious changes; hence the selectivity of CO2/CH4 can be adjusted accordingly.     

Separation of Methane and Nitrogen by Adsorption on Carbon Molecular Sieve

Abstract

Adsorption equilibrium of methane and nitrogen on CMS 3K from Takeda Corp. were gravimetrically measured at 298, 308, and 323 K and at pressures up to 2000 kPa. The most adsorbed gas is methane followed by nitrogen. The adsorption loading at 550 kPa and 308 K is 1.73 mol/kg for methane and 0.91 mol/kg for nitrogen. Experimental data were fitted with the multisite Langmuir model. Single component uptake of these gases at low pressures was used to determine the adsorption kinetics. Adsorption of nitrogen is much faster than methane, although this gas is preferentially adsorbed. The adsorption rate of both gases was controlled by a surface barrier resistance at the mouth of the micropore combined with micropore diffusion. Breakthrough curves of pure gases and their binary mixtures were measured at ambient temperature. A bi‐LDF (Linear Driving Force) model was used to predict the fixed‐bed behavior. Large differences in the adsorption kinetics were observed: at 308 K the LDF constant ratio was K_μ,N2 /K_μ,CH4 =133, although because of much higher adsorption of methane, the overall kinetic selectivity was 1.9 at 308 K. The data obtained in this work can be used for adsorption separation processes modeling for methane purification from nitrogen‐contaminated streams.     

Separation of Methane and Carbon Dioxide Gas Mixtures by Pressure Swing Adsorption

Abstract

Two pressure swing adsorption processes for separation of methane and carbon dioxide gas mixtures are described. One process simultaneously produces a high purity CH₄ and a high purity CO₂ product with high recoveries of both components from the feed gas. The other process only produces a high purity CH₄ product with high recovery. Test data for these processes are reported and their relative advantages are discussed.     

氮气和氧气在碳分子筛上的吸附相平衡研究

用双柱定容容量法测定了氮气和氧气在碳分子筛上温度分别为25、30、35、40及45℃时的吸附等温线,平衡压力最高达到1 Mp,等温线用Langmuir方程拟合能得到良好的实验结果,并求出了氮气和氧气在这两种吸附剂上的吸附热。     

Separation of Trimethylbenzene Isomers on Molecular Sieves 13X in High Pressure Carbon Dioxide

Abstract

An experimental study of the separation of 1,2,4-and 1,3,5-trimethylbenzenes from a mixture containing the weight composition 56% 1,2,4-trimethylbenzene and 44% 1,3,5-trimethylbenzene on molecular sieves 13X in high pressure carbon dioxide was performed. For a pulse of 1.18 cm³ of trimethylbenzene isomers and 40 g of molecular sieves 13X, the effects of pressure, temperature, and flow rate on separation effectiveness were examined. The results indicated that the most appropriate operating conditions for obtaining a higher recovery of each isomer with a purity of at least 98% and a shorter mean retention time for 1,3,5-trimethylbenzene were a temperature of around 363 K, a pressure of 74.8 atm, and a flow rate of 15.0 cm³/min.     

Adsorption of Acetaldehyde,Propionaldehyde, and Butyraldehyde on Molecular Sieve 13X

Abstract

Adsorption isotherms for acetaldehyde, propionaldehyde, and butyraldehyde on Davison molecular sieve 13X were determined gravimetrically at three temperatures. The isoteric heat of adsorption of acetaldehyde and propionaldehyde decreased initially with the increase in loading, then increased up to a certain point after which it decreased again. For butyraldehyde the heat of adsorption initially increased and then decreased with increased loading. The equilibrium adsorption data reduce to a single characteristic curve when correlated according to Polanyi's potential theory. Recently proposed isotherm equations for heterogeneous surfaces by Sircar and Hines et al. were used to correlate the isotherm data. The BET equation gave a good correlation of the data for a relative pressure range of 0.05 ≤ P/P, ≤ 0.25. The monolayer surface coverage and surface area were calculated by the Langmuir and the BET equations. The Langmuir equation consistently provided a larger estimate of the surface area than did the BET equation.     

CTMAB-13X分子筛的制备及对水中甲基橙的吸附

用十六烷基三甲基溴化铵(CTMAB)对13X分子筛进行改性制备CTMAB-13X分子筛,研究了不同条件下CTMAB-13X分子筛对废水中甲基橙的吸附性能、影响因素及动力学过程.结果表明:CTMAB-13X分子筛投加量为0.1 g/L,吸附时间10 min后对甲基橙吸附可达平衡,此时去除率达到88.9％.CTMAB-13X分子筛吸附容量为275mg/g,高于活性炭的182 mg/g.Zeta电位分析说明经阳离子表面活性剂CTMAB改性的13X分子筛表面带正电,对水中带负电的酸性染料甲基橙有较强的吸附效果.由红外吸收光谱(FTIR)看出CTMAB的特征峰出现在CTMAB-13X分子筛中,说明CTMAB接枝改性到13X分子筛表面.分析X-射线图谱得出CTMAB改性剂没有破坏13X分子筛自身的晶体结构,进一步证明CTMAB是接枝在分子筛表面.从扫描电镜(SEM)可以看出改性后的CTMAB-13X分子筛更为分散,因此可以为染料分子提供更多的吸附点位.激光粒度测定结果表明CTMAB-13X分子筛平均粒径Dav由17.45 μm下降到12.41 μm,比表面积(S/V)由5143.69 cm2/cm3增大到7752.48 cm2/cm3,与SEM分析结果一致.     

Separation of Methane and Carbon Dioxide Gas Mixtures Using Activated Carbon Modified with 2‐Methylimidazole

Activated carbon was modified by loading 2‐methylimidazole (mIm), ethanol, and glycol onto its surface and adopted to capture CO₂ using the absorption‐adsorption method. The modified activated carbon showed high selectivity for separating CH₄+CO₂ gas mixtures, compared with other methods to modify activated carbon given in the literature. The separation factor was 4.75 times higher than that for the fresh activated‐carbon system, and the separation performance of the activated carbon increased with increasing amount of mIm. The addition of glycol showed greater potential to enhance the selectivity of the activated carbon than ethanol. A recycling test verified the stability of the modified activated carbon for CH₄+CO₂ gas mixture separation.     

苯-水混合蒸气在活性炭上的二元吸附平衡

Adsorption equilibrium isotherms of benzene in the concentration range of 500-4000 mg·@m-3 on two commercial activated carbons were obtained using long-column method under 30℃ and different humidity conditions. Results show that the benzene and water vapors have depression effects upon the adsorption of each other and that the unfavorable effect of water vapor resembles its single-component isotherm on activated carbon. A competitive adsorption model was proposed to explore the depression mechanisms of the non-ideal, non-similar binary adsorption systems. A modified Polanyi-Dubinin equation was set up to correlate the binary adsorption equilibrium and to calculate the isotherms of benzene on activated carbon in presence of water vapor with considerable precision.     

Pure and Binary Adsorption Equilibria of Methane and Carbon Dioxide on Silicalite

Abstract

For the separation of CH₄ and CO₂ from landfill gas, pure and binary adsorption behavior of these gases were studied up to 5 atmosphere pressure at 40, 70, and 100°C for silicalite as the adsorbent. Pure and binary adsorption isotherms were determined experimentally and compared to predicted isotherms by several equilibrium models, as well as the other available data in the literature. Experimental binary isotherms at different concentrations were determined by using three concentration pulse methods (CPM). HT–CPM (Harlick‐Tezel CPM) was observed to be the best one to describe the behavior of this binary system. Equilibrium phase diagrams and separation factors were obtained from the experimental binary isotherms. For this system, the integral thermodynamic consistency tests were also shown and discussed.