IGC技术表征HFC-134a在改性活性炭上的吸附特性

在323. 15～373. 15 K温度区间,采用反相气相色谱(IGC)技术分别测定了四氟乙烷(HFC-134a)在酸改性、碱改性、盐改性前后活性炭上的吸附热及脱附活化能,绘制了脱附曲线。结果表明,改性前,HFC-134a在活性炭上吸附热和脱附活化能分别为-31. 889,-31. 554 k J/mol;酸改性后,活性炭对HFC-134a的吸附热和脱附活化能分别为-49. 788,-51. 600 k J/mol;碱改性后,活性炭对HFC-134a的吸附热和脱附活化能分别为-46. 567,-57. 206 k J/mol;盐改性后,活性炭对HFC-134a的吸附热和脱附活化能分别为-42. 259,-43. 462 k J/mol。     

苯在改性活性炭上的脱附活化能

采用浸渍法制备了KH560/改性活性炭、1706/改性活性炭和A172/改性活性炭等3种活性炭,并利用程序升温脱附技术测定了苯在这3种改性活性炭上的脱附活化能. 结果表明,苯在经改性的活性炭上的脱附活化能均大于其在未改性活性炭上的脱附活化能,表明用有机硅烷改性活性炭可以提高其对苯的吸附能力. IGC分析结果表明,经硅烷改性的活性炭的特殊作用吸附自由能DGs均小于原始活性炭的DGs,这4种活性炭表面与苯的特殊作用吸附自由能DGs大小顺序与苯在这些活性炭上的脱附活化能大小顺序正好相反,这表明DGs越小,吸附质与活性炭表面形成的吸附越牢固,吸附质从其表面脱附所需的活化能越大.     

气相催化加氢脱氯合成HFC-134a

报道了1,1,1,2-四氟-2-氯乙烷(分子式CFClHCF3,缩写HCFC-124)在Pd/C催化剂作用下,气相催化加氢脱氯合成1,1,1,2-四氟乙烷(分子式CFH2CF3,缩写HFC-134a).探讨了反应温度、氢气与HCFC-124的流量比、接触时间对转化率和选择性的影响.制备的改性Pd/C催化剂,连续反应200h,HFC-134a的选择性大于95%,HCFC-124转化率在95%左右.     

活性炭纤维在吸附领域的应用

活性炭纤维是一种新型高效吸附材料。本文阐述了活性炭纤维的结构与吸附性能间的关系，并介绍了它在吸附领域的应用。     

Cr-Zn-Al催化剂气相氟化法合成HFC-134a

用共沉淀法制备了Cr-Zn-A l型催化剂,用于催化1,1,1-三氟-2-氯乙烷(HCFC-133 a)与HF的反应,制备了1,1,1,2-四氟乙烷(HFC-134 a)。BET法表征了催化剂的比表面积;GC-MS方法分析了不同反应条件下HCFC-133 a的转化率、HFC-134 a的收率、以及副产物组成。结果表明,催化剂按一定程序烧结、活化后,反应温度为350~370℃、n(HF)/n(HCFC-133 a)=8~12时,HFC-134 a的收率为30%~38%,反应产物中HFC-134 a的选择性大于99%。连续反应720 h后,催化剂的活性不变。     

改性活性炭吸附脱除二氧化碳中微量乙烷

我国对食品级二氧化碳要求较高,在其生产过程中乙烷的脱除是难点。文章首先考察了市售的不同吸附剂,包括Y型、X型、A型等分子筛类,椰壳和煤基活性炭以及吸附树脂等吸附剂对CO2中微量C2H6的吸附效果,之后考察了不同浓度盐酸酸改性与氢氧化钠碱改性、双氧水氧化改性、氨水还原改性等改性条件对吸附剂吸附性能的影响。研究表明,具有高比表面积、丰富微孔和适量中孔结构的活性炭更有益于二氧化碳中微量乙烷的吸附;浓度为1%的盐酸溶液浸渍活性炭3 h后,能增强其对CO2中微量C2H6的吸附能力;浓度3%、浸渍时间6 h为氢氧化钠碱溶液改性活性炭的最佳条件;弱氧化剂双氧水改性能略微提高活性炭对二氧化碳中乙烷的吸附能力,弱还原剂氨水改性对吸附效果无明显影响。     

金属离子改性活性炭对二氯甲烷脱附活化能的影响

主要研究了金属离子改性活性炭对二氯甲烷脱附活化能的影响。通过浸渍法分别将6种不同金属离子负载在活性炭表面,采用ASAP 2010M测定该系列改性活性炭的孔径分布和比表面积,利用程序升温脱附技术测定了二氯甲烷在系列改性活性炭上的脱附活化能,应用软硬酸碱理论分析和讨论了活性炭表面负载不同金属离子对二氯甲烷脱附活化能的影响。结果表明,二氯甲烷在Al(Ⅲ)/SY-6AC、Li(Ⅰ)/SY-6AC、Mg(Ⅱ)/SY-6AC、Fe(Ⅲ)/SY-6AC和Ca(Ⅱ)/SY-6AC的脱附活化能高于其在原始活性炭上的脱附活化能,而它在 Ag(Ⅰ)/SY-6AC的脱附活化能低于在原始活性炭上的脱附活化能。根据软硬酸碱理论分类,二氯甲烷属硬碱,当活性炭表面分别负载了硬酸类金属离子Al³⁺、Li⁺、Mg²⁺、Fe³⁺和Ca²⁺,则增大了表面局部硬酸度,提高了对二氯甲烷的吸附能力; Ag⁺ 属软酸,当活性炭表面负载了Ag⁺,则降低了活性炭表面局部硬酸度,从而降低了对二氯甲烷的吸附能力。     

中高温环境下VOCs在活性炭上的吸附性能研究

选用3种商用活性炭及其分别经HCl溶液和KOH溶液浸渍改性的商用活性炭,研究中高温烟气环境下,反应空速、吸附温度对挥发性有机物（VOCs）吸附性能的影响,以及VOCs种类、吸附剂特性等与VOCs吸脱附效果的关系。研究发现：空速对吸附穿透时间影响较大,但对饱和吸附量影响不显著。吸附温度与VOCs浓度对饱和吸附量存在较大影响,150℃时甲苯的饱和吸附量仅能达到90℃时的40％。高沸点吸附质更易被吸附,更难被脱附。     

活性炭吸附法在挥发性有机物治理中的应用研究进展

挥发性有机化合物(VOCs)是一类重要的大气污染物,其所带来的环境污染问题已经引起全世界的关注.活性炭吸附法是治理VOCs污染的有效手段.本文从介绍VOCs治理技术出发,简述了活性炭吸附法在VOCs治理中的使用现状,概括了活性炭吸附法治理VOCs的工艺技术和存在问题,指出变温-变压吸附、变电吸附以其高效节能环保的优点,在VOCs治理中具有较好的发展前景.分析了活性炭表面化学性质、吸附质的物性、操作条件对活性炭吸附法治理VOCs的影响,为VOCs治理专用活性炭的改进和新产品的开发,提供了理论依据.在总结现有研究进展的基础上,预测了活性炭吸附法治理VOCs技术的发展趋势,提出对工艺的改进以及与其他VOCs废气处理技术的耦合使用,针对不同VOCs排放场所开发不同活性炭品种和VOCs回收装置将是以后研究的重要方向.     

改性活性碳纤维对苯胺吸附特性分析

开展了等离子体改性活性碳纤维对苯胺吸附性能的理论和实验研究。通过改变等离子体改性功率和改性时间,探寻最佳改性条件;采用BET、XPS、FTIR、热重测试对改性前后活性碳纤维理化特性进行了表征分析。结果表明,在等离子改性功率为22W,时间为3min时为最佳改性条件;改性后的活性碳纤维对水溶液中苯胺的去除率可达79.3%,去除率提高了8%。微观上等离子体改性使得活性碳纤维表面含氧官能团含量增加,增强对溶液中苯胺的吸附效果。吸附实验结果表明,改性前后活性碳纤维对苯胺的吸附在溶液pH为6时,吸附效果最佳;但达到同一去除率时改性活性碳纤维的速度更快,并且平衡吸附容量也更大。采用准一级和准二级动力学模型对该吸附过程进行描述,其改性前后均用准二级动力学拟合效果更好,表明活性碳纤维结构的特殊性使其对苯胺的吸附以化学吸附为主。活性碳纤维的等离子体改性提高了其对水溶液中苯胺的吸附速度和容量,增强去除效果降低了苯胺对环境的危害。     

Performance analysis of activated carbon + HFC-134a adsorption coolers

The purpose of this paper is to present the results of performance analysis of a heat driven continuous vapor adsorption refrigerator with activated carbon as the adsorbent and 1,1,1,2-tetrafluoroethane (HFC-134a) as the refrigerant. A set of four adsorption cells takes on the role of the mechanical compressor in the conventional vapor compression refrigeration (VCR) system. Three specimens of activated charcoal under various packing densities were investigated. A parametric analysis was carried out with several evaporating, condensing/adsorbing and desorbing temperatures which are typical operating conditions catered to by HFC-134a. A new integrated relative performance evaluation scheme is proposed. It uses the maximum cycle uptake difference as a factor against which the coefficient of performance (COP) and exergetic efficiency are evaluated. It is shown that there is an optimal set of operating conditions wherein the exergetic efficiency is the maximum. A major part of the thermal energy input is for sensible heating of the compressor body.     

Behavior of phenol adsorption on thermal modified activated carbon

Adsorption process is acknowledged as an effective option for phenolic wastewater treatment. In this work, the activated carbon(AC) samples after thermal modification were prepared by using muffle furnace. The phenol adsorption kinetics and equilibrium measurements were carried out under static conditions at temperature ranging from 25 to 55 °C. The test results show that the thermal modification can enhance phenol adsorption on AC samples. The porous structure and surface chemistry analyses indicate that the decay in pore morphology and decrease of total oxygen-containing functional groups are found for the thermal modified AC samples. Thus, it can be further inferred that the decrease of total oxygen-containing functional groups on the modified AC samples is the main reason for the enhanced phenol adsorption capacity. For both the raw sample and the optimum modified AC sample at 900 °C, the pseudo-second order kinetics and Langmuir models are found to fit the experimental data very well. The maximum phenol adsorption capacity of the optimum modified AC sample can reach144.93 mg·g-1which is higher than that of the raw sample, i.e. 119.53 mg·g-1. Adsorption thermodynamics analysis confirms that the phenol adsorption on the optimum modified AC sample is an exothermic process and mainly via physical adsorption.     

浸渍法改性活性炭纤维吸附一氧化氮的研究

采用不同浓度的硝酸铁溶液在不同的处理温度和时间下,浸渍聚丙烯腈基活性炭纤维(PANACF), 用正交实验法分析影响改性PAN-ACF吸附一氧化氮转化率的主要因素。实验结果表明,浸渍液的初 始浓度是影响一氧化氮吸附转化率的主要因素。在初始浓度为0.1-0.14mol／L时,吸附转化率达到最大 值70％左右,吸附温度和吸附时间对吸附转化率影响不大。通过扫描电镜观察,铁离子不规则分布在PANACF 表面。     

Nitrogen and hydrogen adsorption of activated carbon fibers modified by fluorination

In this study, activated carbon fibers (ACFs) were surface modified with fluorine and mixed oxygen and fluorine gas to investigate the relationship between changes in surface properties by nitrogen and hydrogen adsorption capacity. The changes in surface properties of modified activated carbon fibers were investigated using X-ray photoelectron spectroscopy (XPS) and compared before and after surface treatment. The specific surface area and pore structures were characterized by the nitrogen adsorption isotherm at liquid nitrogen temperature. Hydrogen adsorption isotherms were obtained at 77 K and 1 bar by a volumetric method. The hydrogen adsorption capacity of fluorinated activated carbon fibers was the smallest of all samples. However, the bulk density in this sample was largest. This result could be explained by virial coefficients. The interaction of hydrogen-surface carbon increased with fluorination as the first virial coefficient. Also, the best fit adsorption model was found to explain the adsorption mechanism using a nonlinear curve fit. According to the goodness-of-fit, the Langmuir–Freundlich isotherm model was in good agreement with experimental data from this study.     

HFC-134a反应器的设计

大直径不带法兰的立式列管固定床HFC-134a反应器材料和加热方式的选择,以及各主要部件结构的设计特点。     

Synthesis of HFC-134a by isomerization and hydrogenation

For the preparation of HFC-134a, the isomerization of CFC-114 and the hydrogenation of CFC-114a were investigated. Both reactions were catalyzed by AlC₃ and supported Pd catalysts, respectively. For the comparison purpose, the isomerization of CFC-113 was carried out also. With virgin AICI₃ catalyst, both isomerization reactions proceeded after a certain induction period probably because the catalyst needed the activation by the halogen exchange. The catalyst deactivated gradually with the time on stream. However, the deactivation rate could be reduced by removing impurities from the reactants. Isomerization rate of CFC-114 was much slower than that of CFC-113. Palladium supported on carbon catalyzed the hydrogenation reaction quite selectively while the selectivity declined when the support was replaced with different supports. The catalytic activity and selectivity to desired products increased in the following order. Pd/kieselguhr Pd/silica-alumina ≅Pd/silica gel Pd/TiO₂Pd/Al₂O₃Pd/C     

Characterization of activated carbon fibers using argon adsorption

In this paper, we present results of the internal structure (pore size and pore wall thickness distributions) of a series of activated carbon fibers with different degrees of burn-off, determined from interpretation of argon adsorption data at 87 K using infinite and finite wall thickness models. The latter approach has recently been developed in our laboratory. The results show that while the low bun-off samples have nearly uniform pore size (<0.6 nm), the pore size distribution of the high burn-off samples becomes broader, with a significant increase in proportion of larger pores. The results of pore wall thickness distribution are generally consistent with development of porosity with increasing degree of burn-off. Further they show good correspondence with X-ray diffraction.     

聚甲基丙烯酸改性活性炭的制备及其吸附高氯酸铵的研究

通过表面引发接枝聚合将甲基丙烯酸接枝聚合到活性炭表面,用于处理高氯酸铵污染水的研究。结果表明,改性活性炭吸水率明显提高,高氯酸铵吸附量2. 28 mg/g,吸附平衡时间10 min。与活性炭相比,吸附量提高了2. 2倍,吸附平衡时间降低了60%。