氢在多壁碳纳米管上的等量吸附热

为说明氢在多壁碳纳米管(MWCNTs)上所受吸附作用的强弱,文中基于氢和77 K氮的吸附数据,比较了由非局域密度泛函理论(NDFT)、等量吸附线和归一化等温线线性化确定的等量吸附热。结果表明,氢在MWCNTs上等量吸附热随温度变化且表现出在弱的能量不均匀表面吸附的特点,平均值约为3—4 kJ/mol;由77 K氮吸附等温线确定的孔大小分布(PSD)和比表面积影响NDFT计算初始吸附时的精度;在吸附量和吸附温度都较低时,等量吸附线标绘结果与归一化等温线线性化方程确定的等量吸附热之间的偏差较小,在200—290 K温度区间则与ND-FT计算结果更为接近。然而,当温度大于310 K时,3种方法计算结果间的偏差较大。     

氢在碳基材料穿插MIL-101(Cr)试样上的吸附平衡

为了实现由碳基材料穿插提高金属有机框架物(MOFs)储氢容量的目的，选择质量分数分别为1%的活性炭和石墨烯穿插MIL-101(Cr)。通过试样的结构表征、微观形貌观察与氢吸附等温线测试，从吸附平衡模型和吸附热两方面来比较其储氢行为。结果表明，在77.15～87.15 K、0～6 MPa，氢在AX-21活性炭穿插(AM-01)和氧化石墨烯(GO)穿插(GM-02)试样上的储氢量比穿插前提高了41.1%和17.4%；相对于Langmuir方程和Langmuir-Freundlich(L-F)方程，Toth方程的预测精度最高，77.15 K时，Toth方程预测氢在AM-01和GM-02上吸附量的平均相对误差分别为0.55%、0.41%；氢在AM-01和GM-02上的等量吸附热分别为2.96～8.64 k J·mol^-1、3.06～8.57 k J·mol^-1。由GO或高比表面积的活性炭穿插可增大储氢容量，吸附平衡分析可选用Toth方程。     

甲烷在成型前后活性炭上吸附的初步试验

通过对比试验,分析成型对活性炭储存甲烷特性的影响。首先,应用丙烯酸甲酯乳胶黏合剂对活性炭SAC-02成型,在温度区间268.15～338.15 K、压力范围0～15 MPa测试甲烷的吸附等温线;通过确定吸附量和等量吸附热,比较甲烷在成型前后活性炭上的吸附平衡。其次,测试储罐吸附床中心在室温、4个压力（6.5 MPa、5.5 MPa、4.5 MPa和3.5 MPa）下快速充放气过程的温度变化,分析成型对吸附过程热效应的影响。结果表明,成型活性炭的密度增大、比表面积减小、单位质量吸附剂上的甲烷吸附量减小;甲烷在成型前后活性炭上的等量吸附热均处于13～20.5kJ·mol^-1;成型活性炭吸附床中心温度在充放气过程中的变化幅度和变化速率均增大。比较试验结果时发现,选用黏合剂成型须综合考虑其对吸附床热导率、传质阻力及吸附剂微观结构的影响。     

CH_4和N_2在炭分子筛及13X沸石上的吸附分离

采用静态体积法测试了298.15K,313.15K和328.15K时,CH_4和N_2在太西煤基炭分子筛(T-CMS)及13X沸石上的吸附量,并使用Langmuir模型对吸附量数据进行了线性拟合,分析了拟合参数饱和吸附量qm和吸附平衡常数b值的变化.结果表明:随着温度的升高,CH_4在T-CMS上的饱和吸附量qm稍有减少,但变化不大,N_2在T-CMS上的饱和吸附量qm呈增大趋势;CH_4和N_2在13X沸石上的饱和吸附量qm均呈减小趋势,CH_4和N_2在T-CMS及13X沸石上的吸附平衡常数b值均随温度的升高而减小;CH_4和N_2在T-CMS上的分离系数均大于其在13X沸石上的分离系数,分离系数均随温度升高而减小.吸附热力学分析表明,CH_4和N_2在T-CMS上的等量吸附热平均值分别为27.30kJ/mol和22.43kJ/mol,而在13X沸石上的等量吸附热平均值分别为12.96kJ/mol和10.41kJ/mol,两种吸附剂对CH_4的吸附作用均强于其对N_2的吸附作用,且均属于物理吸附.     

正戊烷和正己烷在5A分子筛上的液相吸附性能研究

测定了373~453K温度条件下正戊烷和正己烷在5A分子筛上的液相吸附平衡数据,用Langmuir方程和Freundlich方程对实验吸附等温线数据进行了拟合计算。结果表明,在453K温度下,正戊烷和正己烷在5A分子筛上仍可以达到7%左右的吸附容量,其吸附等温线符合Langmuir吸附等温类型,Langmuir吸附方程能够很好的拟合实验结果。Clapeyron-Clausius方程计算得到的正戊烷和正己烷在5A分子筛上吸附热、吸附熵等热力学数据表明,正戊烷、正己烷均易吸附于5A分子筛上,其吸附热为-24kJ/mol左右。     

原生煤和构造煤的吸附等量线比较及与瓦斯突出的关系研究

根据温度—压力—吸附方程及其相关变换方程,将沁水盆地大宁煤矿的原生煤和构造煤系列等温吸附实验数据,转换成可进行热力学相关比较和计算的吸附等量线;在对甲烷气体相同吸附量下,原生煤吸附等量线的温度、压力升速大于构造煤;随着吸附量的增加,原生煤的吸附等量线与构造煤的吸附等量线相交;交点之前,在相同吸附量和相同温度下,构造煤(小坚固性系数)的吸附压力大于原生煤(大坚固性系数)的吸附压力;交点之后,在相同吸附量和相同压力下,构造煤的平衡温度高于原生煤;在吸附量都为35 cm~3/g时,原生煤的单位等量解吸热为0.835 kJ·g/(mol·cm~3),比构造煤多吸热0.204 kJ·g/(mol·cm~3);相较于原生煤,构造煤优先解吸瓦斯;研究认为煤与瓦斯突出最容易发生在构造煤。     

油茶壳活性炭对西番莲废水色素的吸附性能

研究以油茶壳水热炭为原料,KOH为活化剂制备油茶壳活性炭,研究了油茶壳活性炭添加量、吸附温度、吸附时间对西番莲废水色素吸附率的影响。通过研究活性炭对废水色素的吸附等温线、动力学与热力学性质,分析活性炭吸附特性。结果表明,油茶壳活性炭对废水色素的吸附率随活性炭的增加,先增大后趋于平衡;吸附时间和温度有助于色素的吸附。油茶壳活性炭添加量0.06 g/10 mL时,废水色素吸附360 min趋于饱和,30,40,50℃对应平衡吸附率分别为74.41%,83.11%,83.89%。油茶壳活性炭对废水色素的吸附符合准二级动力学模型(R²>0.99),吸附等温线采用Freundlich模型拟合较好(R2>0.99),吸附等温线采用Freundlich模型拟合较好(R²>0.82)。活性炭对废水色素吸附的焓变ΔH和熵变ΔS分别为6.566 2×102>0.82)。活性炭对废水色素吸附的焓变ΔH和熵变ΔS分别为6.566 2×10³ J/mol、17.725 J/(mol·K),吸附过程是自发、吸热、熵增过程。     

3-己基-4-氨基-1,2,4-三唑-5-硫酮在黄铜矿表面的吸附动力学与热力学

合成了一种新型的三唑硫酮类表面活性剂——3-己基-4-氨基-1,2,4-三唑-5-硫酮(HATT),通过红外光谱和核磁共振氢谱及碳谱对其结构进行了表征,研究其在黄铜矿表面的吸附动力学和热力学。结果表明:黄铜矿吸附HATT优选的pH=4~8,吸附量随着温度的升高而增大;吸附过程符合准二级动力学方程,吸附活化能为13.06 kJ/mol;HATT在黄铜矿表面的吸附等温线符合Langmuir模型,吸附焓变ΔH=71.52 kJ/mol,熵变ΔS=348.7 J/(mol·K),吸附自由能变ΔG=-28.95 kJ/mol(298 K)。HATT可能以单分子层化学吸附于黄铜矿表面,吸附为自发的吸热过程。FTIR光谱分析进一步证实HATT以化学方式吸附在黄铜矿的表面。浮选试验结果也表明,HATT是黄铜矿的优良捕收剂。     

国内信息

甲烷在特制活性炭上吸附性能用不同的原料制得了多种高比表面的活性炭吸附剂。用标准容积法测得高压下（０～５０ＭＰａ）不同活性炭对甲烷的吸脱附等温线,得到了吸附容量和有效吸附容量。研究了温度对吸附等温线的影响。利用ＣｌａｕｓｉｕｓＣｌａｐｅｙｒｏｎ方程解析了甲烷在活性炭上的等量吸附热。结果表明,活性炭对甲烷的吸附存在着滞后现象,活性炭的比表面和堆密度是活性炭吸附性能的主要指标,找到了最佳甲烷吸附剂。（丹清摘自《应用化学》１９９９,１６（３）：３３～３６）桂油与β环糊精包合物的研究采用共沉淀法制备…     

多孔蜂窝活性炭材料对CO2吸附热力学研究

以4种不同品牌多孔蜂窝活性炭为研究对象,采用N₂物理吸附、扫描电镜SEM、透射电镜TEM和XRF等方法对活性炭物化结构进行了表征,探讨了不同品牌蜂窝活性炭材料的成分和孔隙结构对CO₂吸附的影响。并通过对比0,20,40℃下CO₂的吸附等温线,分析CO₂在不同蜂窝活性炭材料表面的吸附热力学特性,拟合出CO₂气体吸附量与等量吸附热之间的关系。结果表明：N₂和CO₂吸附等温线属于Ⅰ型吸附等温线,样品主要以微孔结构为主,存在少量介孔结构;不同温度下活性炭吸附CO₂曲线均符合Langmuir吸附模型;温度升高,CO₂在活性炭材料上的吸附量均减小,说明升温不利于CO₂在活性炭上的吸附;相同条件下,泰州800活性炭(TZ800)的吸附量高于淄博800活性炭(ZB800)的吸附量,表明CO₂更易吸附于TZ800活性炭上,这可能得益于其丰富和发达的微孔结构。同时TZ...     

Pt、Rh及Pt-Rh合金电极上氢的吸附

The hydrogen adsorption on Pt-Rh alloys in sulfuric acid aqueous solutions was studied by the method of cathode pulses. Hydrogen adsorption on the electrode with all ratio of alloy components (ωRh = 0-100%) is well described by the Temkin logarithmic isotherm. The surface coverage by adsorbed hydrogen at the same potential is decreased with increasing content of rhodium in the system. A linear dependence of adsorption peak potential on the alloy compositions in the case of weakly bonded adsorbed hydrogen is established. Hydrogen adsorption heat as a function of surface coverage for Pt-Rh-electrodes was obtained. The shape of the current-potential curve and position of the weakly bonded hydrogen adsorption on the potential scale are all related to alloy compositions, thus can serve as the basis for the determination surface composition of allovs.     

Adsorption of reaction species for hydrogenation of o-nitrotoluene on copper chromite under catalytic conditions

Adsorption of reaction species involved in vapour phase hydrogenation of o-nitrotoluene (viz. o-nitrotoluene, o-toluidine and water) on copper chromite in presence of an inert gas (He) or hydrogen (which is one of the reactants) at temperature (473-560 K) and partial pressures at which the catalytic reaction is carried out has been investigated using the gas chromatographic pulse technique. The presence of hydrogen was found to cause a very significant decrease in the adsorption of toluidine but a little effect on the adsorption of water. The adsorption data for all the reaction species could be fitted to the Freundlich adsorption equation. The isoteric heats of adsorption obtained from the adsorption isotherm indicated that o-toluidine and water are physically absorbed, whereas o-nitrotoluene is chemisorbed on the catalyst. The heat of adsorption of water and o-nitrotoluene was found to decrease with the increase in the surface coverage, indicating repulsive interactions between the adsorbed species. On the other hand the heat of adsorption of o-toluidine (in presence or absence of H₂) was found to increase with the increase in the surface coverage, suggesting attractive interactions between the absorbed species.     

碳基吸附剂储氢吸附热的密度泛函理论

为比较狭缝孔、纳米管两种典型碳基吸附剂的储氢性能,应用非局域密度泛函理论、微观物理学、吸附平衡原理、典型吸附剂储氢试验结果计算并分析了典型碳基吸附剂的氢等量吸附热.结果表明,两类吸附剂的氢等量吸附热相差不大,等温线变化规律相似,并且只有在低温（液氮）、适度压力时吸附储氢的质量密度才有望达到DOE标准.     

Combination rate of hydrogen atoms adsorbed on a polycrystalline platinum electrode at hydrogen underpotentials in sulphuric acid solution

Steady-state cathodic currents i_c passing through a polycrystalline, smooth Pt electrode in 0.5 M H₂SO₄ were measured at constant potentials in the range from 0.45 to 0.05 V, at which the coverage by adsorbed hydrogen on the electrode surface is less than unity. It was found that current i_c, which results from the combination of adsorbed hydrogen atoms, depends on both the adsorption state and the coverage on the electrode surface. The characteristic variation of i_c with hydrogen coverage was explained in terms of the geometric arrangement of the adsorption sites. The combination rate constant and the mobility of the adsorbed hydrogen atoms estimated from the steady-state current measurement were in agreement with those obtained using the open-circuit decay method.     

A thermodesorption method for the investigation of hydrogen adsorption on electrodes; its application to tungsten carbide,along with electrochemical methods

A method for direct determination of hydrogen adsorption on large surface area electrodes or on electro-conductive powders in electrolyte solutions, at any given potential, is proposed. It consists of hydrogen desorption from the electrode by heating (thermodesorption) after complete adsorption and a quantitative chromatographic analysis of the gas collected during thermodesorption. The proposed method was used in this work to investigate hydrogen adsorption on tungsten carbide powder in a H₂SO₄ solution. The potential-dependence of adsorption was found, confirming the authors previous suggestion of an extensive coverage of tungsten carbide by chemisorbed hydrogen and of the potential region of adsorption (up to 0·35–0·4 V).The tungsten carbide surface was also investigated by the method of charging and potentiodynamic curves. Reversibility of these curves up to 0·35–0·4 V is shown. Hydrogen adsorption is correlated with the quantity of electricity calculated from the charging curve and it is shown that a considerable portion of the charge is associated with hydrogen chemisorption but some portion of the total charge is consumed even in the hydrogen region for other non-defined redox processes occurring on the tungsten carbide surface.     

A Degradation Model for Solid Oxide Fuel Cell Anodes due to Impurities in Coal Syngas: Part I Theory and Validation

A new phenomenological one‐dimensional model is formulated to simulate the typical degradation patterns observed in solid oxide fuel cell (SOFC) anodes due to coal syngas contaminants such as arsenic (As) and phosphorous (P). The model includes gas phase diffusion and surface diffusion within the anode and the adsorption reactions on the surface of the Ni‐YSZ‐based anode. Model parameters such as reaction rate constants for the adsorption reactions are obtained through indirect calibration to match the degradation rates reported in the literature for arsine (AsH₃), phosphine (PH₃), hydrogen sulfide (H₂S), and hydrogen selenide (H₂Se) under accelerated testing conditions. Results from the model demonstrate that the deposition of the impurity on the Ni catalyst starts near the fuel channel/anode interface and slowly moves toward the active anode/electrolyte interface as observed in the experiments. Parametric studies performed at different impurity concentrations and operating temperatures show that the coverage rate increases with increasing temperature and impurity concentration, as expected. The calibrated model was then used for prediction of the performance curves at different impurity concentrations and operating temperatures. Good agreement is obtained between the predicted results and the experimental data reported in the literature.     

TRANSIENT STUDY OF CYCLOHEXANE DEHYDROGENATION IN A CSTR-II

Transient response data for the cyclohexane dehydrogenation reaction were collected on a surface coated Pt-Al₂O₃ catalyst. Mathematical analysis with the surface coated catalyst is considerably simpler due to the absence of intraparticle gradients. The data, which often displayed a characteristic overshoot type of response, were correlated by a surface coverage model where the π/σa-bonded benzene transition surface complex can reversibly orient itself to a σ-bonded hydrogen deficient surface species which cannot desorb. As in previous work cyclohexane adsorption was found to be slow and surface reactions involving the adsorbed hydrocarbon species were found to be rapid.     

Gas/Surface Titration Microcalorimetry. Energetics of Oxygen Adsorption on Supported Iridium Catalysts

Measurements of the heat of adsorption of hydrogen on Ir/Al₂O₃ catalysts of different metal particle size were made by employing adsorption microcalorimetry. The values of this quantity were different for each sample and the results also indicated the heterogeneity of the iridium surface. In contrast to this, the heat of adsorption of oxygen measured on the same samples in the same manner was practically the same for all of them. The heat of oxygen adsorption as presented in the differential calorimetric isotherms was constant up to half the monolayer coverage for all the samples. This result is unexpected and in contradiction to the presence of surface heterogeneity in the iridium crystallites, as revealed by hydrogen adsorption. To clarify these anomalies the energetics of oxygen adsorption was determined using a different method. Titration experiments with hydrogen of preadsorbed oxygen were carried out. The heat of adsorption of oxygen was calculated from these results by means of adopting a thermochemical cycle. The values of heat of adsorption obtained as a function of the amount adsorbed unveiled the heterogeneity of the iridium surface. The differences found between the samples can be correlated to both the different particle size and degree of sintering of the samples.     

甲烷在石墨烯和活性炭上的吸附

以研制新型吸附式天然气(ANG)吸附剂为目的,比较了甲烷在石墨烯和活性炭上的吸附平衡。首先,在温度区间273~293 K、压力范围0~8 MPa,测试甲烷在比表面积分别为300和2074 m²·g^-1石墨烯和活性炭上的吸附平衡数据。其次,应用格子理论导出的通用吸附等温方程,通过吸附平衡态能量分析及10-4-3相互作用势函数求解,确定甲烷分子在石墨烯平面和活性炭上的最大面密度、受到的壁面吸附作用势及其在吸附层内的作用能。结果表明,在相同温度下,吸附甲烷分子在石墨烯上吸附层内的相互作用能较其在活性炭上的大,甲烷分子在石墨烯平面上的集聚更为密集。提高石墨烯的比表面积将有效提高甲烷在其上的吸附容量。