Natural gas storage on activated carbon modified by metal oxides

The surface of activated carbon has been modified with metal oxides in order to improve the adsorption capacity for methane. Three metal oxides were used: MgO, Fe₂O₃, and NiO. The results indicate that the adsorption capacity can be marginally improved by doping small amount of metal oxides. Excess loading of metal oxides would result in the blockage of pores and hence reduce the surface area. By modifying the surface with metal oxides, although the adsorption capacity of methane on activated carbon cannot be significantly improved, faster thermal diffusion was observed for the increase of desorption capacity.     

废活性炭微波加热法再生研究进展

论述了微波加热技术的特点,初步探讨了微波加热再生废活性炭的原理,综述了国内外微波再生废活性炭的研究进展。与传统加热技术相比较,微波加热再生废活性炭具有耗时短、产品质量好、能耗低、污染少等优点,并且微波加热再生废活性炭产品有更发达的孔隙结构,吸附性能较好。影响微波再生废活性炭的因素依次是微波功率、加热时间、活性炭吸附量。展望了微波加热再生废活性炭的发展方向。     

Preparation and modification of activated carbon fibres by microwave heating

Thermal treatment of activated carbon fibres (ACF) has been carried out using a microwave device, instead of a conventional furnace. The results show that microwave treatment affects the porosity of the ACFs, causing a reduction in micropore volume and micropore size. More importantly, the results also show that microwave treatment is a very effective method for modifying the surface chemistry of the ACFs with the production of pyrone groups, detected by FTIR. As a result very basic carbons, with points of zero charge approximately equal to 11, are readily obtained.     

等离子体法制备掺杂Ni碳材料的储氢性能

引言氢能是可再生的理想洁净能源,人类出于对环境的保护和化石燃料趋于短缺的考虑,太阳能和氢能的利用已是本世纪能源领域发展的必然趋势。特别是在燃料电池迅速发展并获得突破的今天,更安全、灵活和有效的氢能储藏技术的研究受到全球的广泛关注[1]。在吸附储氢材料中,碳质材料由于其质量轻、比表面积高和合适的结构引起了广泛的重视[2-10]。Yang等[11-12]发现在碳上掺杂过渡金属(Rh、Pt、     

微波加热核桃壳制取活性炭及孔结构表征

以核桃壳为原料,采用微波加热-水蒸汽活化法制备了活性炭。研究了微波功率、活化时间和水蒸汽流量等因素对吸附性能的影响。最佳工艺条件为：微波功率600 W、活化时间7 min、水蒸汽流量5 mL/min,活性炭产品的碘吸附值1076．57 mg/g,亚甲基蓝吸附值195 mg/g,得率25．11%。该工艺将常规加热方法的炭化和活化简化为一个过程,所需加热时间仅为传统方法的1/21,产品活性炭的亚甲基蓝吸附值为国家一级品标准的1．44倍。同时测定了该活性炭的氮吸附等温线,通过BET计算了活性炭的比表面积,并通过H—K方程和密度函数理论表征了活性炭的孔结构。结果表明,该活性炭为微孔型,BET 比表面积1 154．91 m~2/g,总孔体积0．564 9 mL/g,微孔占总孔体积(体积分数,下同) 79．86%,中孔体积分数19．97%,大孔占0．17%。     

微波加热再生废弃针剂用活性炭的性能

采用微波加热再生废弃针剂用活性炭, 通过响应曲面法中模型的优化设计和分析, 研究了再生过程中的3个影响因子(再生温度、再生时间以及物料厚度)对所再生活性炭亚甲基蓝值和得率的影响, 并通过方差分析(ANOVA)研究了各个实验因子或交互作用对活性炭性能的影响。得到实验优化工艺条件为:再生温度700℃, 再生时间18min, 物料厚度20mm, 所再生活性炭亚甲基蓝值和得率分别为187.5mg/g, 65.20 %。此外, 再生活性炭比表面积高达962m²/g, 总孔体积为1.02mL/g, 平均孔径为4.27nm。     

Effects of the microwave heating on the properties of gadolinium-doped cerium oxide prepared by polyol method

Gadolinium doped ceria (GDC) has received a lot of attention as possible electrolyte material for Intermediate-Temperature (500–800 °C) Solid Oxide Fuel Cells (IT-SOFC). Microwave heating has been recently considered in combination with precipitation for the production of oxide or non-oxide nano-powders. In this study, crystalline CeO₂ powders doped with different amount of gadolinium were successfully prepared by microwave-assisted polyol method under mild conditions and in one single step. The microwave heating was found to strongly influence the morphological properties of the powder especially for low gadolinium content. IR and thermal analyses helped to identify the major reaction path for the formation of the as-observed complex morphologies. Regardless to the morphology, the powders showed good densification behavior and expected electrochemical properties; Ce_0.9Gd_0.1O_1.95 exhibited the highest conductivity.     

微波加热CO2活化法制备生物质活性炭及其脱硫性能研究

以富含含氮官能团的大豆秸秆为原料前体,结合微波加热的特殊优势,将微波加热技术应用于大豆秸秆热解和活化工艺。以热解固体产物为活化原料,以CO₂为活化剂进行活性炭制备研究,以期制备出高脱硫性能的生物质活性炭。首先通过正交实验设计及极差分析得出最优活化水平,再通过单因素实验法考察微波功率、CO₂流量和活化时间对活性炭产率、孔隙结构以及脱硫性能的影响。对比分析选出最佳活化条件为微波功率900 W,CO₂流量0.10 L/min,活化时间20 min。在此条件下活性炭产率为76.3%（质量）,SO₂饱和吸附容量为112.56 mg/g,比表面积为466.28 m²/g。相比热解炭,活性炭的比表面积更大,孔隙更加丰富,脱硫性能显著提高。     

Study on preparation and desulfurization characteristics of biomass activated carbon by microwave heating CO2 activation method

Taking soybean straw rich in nitrogen-containing functional groups as the raw material precursor, combined with the special advantages of microwave heating, microwave heating technology is applied to the pyrolysis and activation process of soybean straw. The pyrolysis solid product is used as the activation raw material, and CO₂ is used as the activator to study the preparation of activated carbon, in order to prepare the biomass activated carbon with high desulfurization performance. First, the optimal activation level was obtained by orthogonal experimental design and range analysis. Then, the effects of microwave power, CO₂ flow rate and activation time on the yield, pore structure and desulfurization performance of activated carbon were investigated by single factor experiment. The optimal activation conditions were selected by comparative analysis: microwave power 900 W, CO₂ flow rate 0.10 L/min, activation time 20 min. Under these conditions, the yield of activated carbon is 76.3%(mass), the SO₂ adsorbance quantity is 112.56 mg/g, specific surface area is 466.28 m²/g. Compared with pyrolytic carbon, activated carbon has larger specific surface area and more abundant pores and significantly improved desulfurization performance.     

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.     

真空微波加热对松木屑制备活性炭产率及吸附性能的影响

为探究真空度和微波辐射对松木屑制备活性炭的可行性,采用自制的真空微波辐射集成装置对松木屑进行处理,根据处理前后样品的质量比、碘吸附值、表面形貌显微扫描结果及表面官能团分布的红外光谱数据,分析微波辐射时间、辐射功率、真空度三个关键因素对松木屑活性炭产率和吸附性能的影响及其作用机理。结果表明,在真空度为-0.08 MPa,辐射功率为630 W,辐射时间为8 min时制备出的松木屑活性炭产率(49.25%)和吸附能力(碘吸附值958.33 mg/g)最佳。     

Hydrogen storage in carbon nanotubes modified by microwave plasma etching and Pd decoration

Microwave plasma etching and Pd decoration methods were employed for the modification of carbon nanotubes (CNTs). The defects on the nanotube wall increased after the etching process as determined from HRTEM observation and Raman measurement. The defects supplied more hydrogen accesses to the interlayers and hollow interiors of CNTs. The results of hydrogen uptake measurements showed that the etched CNTs had higher hydrogen storage capability than that of the original sample at ambient temperature and pressure of 10.728 MPa. Furthermore, the CNTs decorated with Pd showed a hydrogen storage capability of 4.5 wt.%, about three times higher than that of the non-decorated samples. The hydrogen uptake mechanism of the modified CNTs was discussed.     

微波辐射法制备活性氧化镁除氟剂的实验研究

采用微波辐射法制备饮用水除氟用粉末吸附剂.以碱式碳酸镁为原料,在原料中掺加活性炭以强化微波加热效率,制备条件为:掺加活性炭与碱式碳酸镁的质量比为(5～7):8,煅烧温度高于450 ℃,微波功率在0.5～2.0 kW,煅烧时间在20 min以上.在原水pH为5～9时,含活性炭的活性氧化镁粉末除氟剂的静态除氟容量为13.11～13.29 mg/g.产物的XRD和SEM分析结果表明,碱式碳酸镁分解完全,活性氧化镁为松散片状结构.     

表面改性活性炭吸附CS2及微波场中再生的研究

利用浸渍法探讨氧化物和含氮物质表面改性活性炭对CS2吸附性能的影响,通过boehm滴定和FT-IR分析结果证明:双氧水改性使活性炭表面碱性基团数增多,CS2动态吸附量增大;氨水和乙二胺改性活性炭,其表面碱性基团数增多,并引入含氮官能团,提高了CS2吸附容量。建立微波再生正交实验,确定微波再生最优实验条件:微波功率110 W、辐射时间2 min、载气流量250 mL/min时,活性炭再生综合率最大。对改性活性炭进行TG-DSC热分析,为活性炭微波热再生提供可靠参考依据。实验结果证明:双氧水、氨水、乙二胺改性可提高活性炭综合再生恢复率,硝酸改性对活性炭再生不利。     

Preparation of activated carbon from phenolic resin by KOH chemical activation under microwave heating

Microwave irradiation was used as a heat source in the preparation of activated carbon (AC) from phenolic resin by potassium hydroxide chemical activation. The input microwave power was varied from 0.26 to 0.52 kW, while weight ratios of KOH to phenolic resin, R, were changed from 2 to 6. For a comparison, phenolic resin was also activated at R = 4 using electric furnace heating. During microwave irradiation of KOH and KOH/phenolic resin mixtures, the sample temperatures increased rapidly, which proved that activated carbon was prepared from the mixture under microwave irradiation. The most developed porosity of AC was obtained at R = 4 with a microwave power of 0.39 kW, and the activated carbon was characterized by high mesopore ratio. The development of mesopores under microwave heating was attributed to the rapid heating of the sample in contrast to slow electric furnace heating. The possibility of using the AC as a desiccant humidity conditioner was confirmed in terms of its effective water adsorptivity.     

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。     

Ethanol sensing properties of tungsten oxide nanorods prepared by microwave hydrothermal method

Tungsten oxide nanorods have been prepared by a simple microwave hydrothermal (MH) method via Na₂SO₄ as structure-directing agent at 180 °C for 20 min. The structure and morphology of the products are characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The obtained nanorods are about 20–50 nm in diameter and several micrometers in length. The ethanol sensing property of as-prepared tungsten oxide nanorods is studied at ethanol concentration of 10–1000 ppm and working temperature of 370–500 °C. It was found that the sensitivity depended on the working temperatures and also ethanol concentration. The results show that the tungsten oxide nanorods can be used to fabricate high performance ethanol sensors.     

环氧化合物法制备金属氧化物气凝胶研究进展

环氧化合物法作为一种新的溶胶-凝胶制备金属氧化物气凝胶的方法近年来得到了长足发展。综述了环氧化合物法制备不同价态金属氧化物气凝胶的研究进展,并阐述了其在溶胶-凝胶过程中的作用机理     

Methane aromatization using Mo-based catalysts prepared by microwave heating

Mo/HZSM-5 and Cu–Mo/HZSM-5 catalysts for the non-oxidative aromatization of methane have been prepared by microwave heating method. The effects of Mo loading, the molar ratio of Cu/Mo and preparation method on the catalytic performance of catalysts were studied. The results were compared with those for the methane aromatization over catalysts prepared by conventional heating. Both two kinds of catalysts have the maximum methane conversion when the Mo loading is 6%. The catalysts prepared by microwave heating exhibited higher selectivity to benzene than that prepared by conventional heating. The addition of metal Cu to Mo/HZSM-5 catalyst prepared by microwave heating enhanced the lifetime of catalyst, and gave rise to a little increase in methane conversion. The molar ratio of Cu/Mo influenced the methane conversion, and the maximum value was attained when Cu/Mo = 0.05, whereas no significant influence on the benzene selectivity was observed with the increase molar ratio of Cu/Mo. N₂ adsorption results showed that the catalysts prepared by microwave heating have the larger surface area and the similar pore volume compared with the catalysts prepared by conventional heating. This fact revealed that the more Mo species located on the outer surface of catalysts prepared by microwave heating is the main reason why they have better catalytic performance. XRD analysis indicated that the Mo species are highly dispersed on HZSM-5 zeolite. The addition of Cu influenced the dispersion. The actual active phase Mo₂C can be identified on the catalyst surface after reaction. TEM analysis revealed the carbonaceous deposition to have the form of carbon nanotube after reaction, with a uniform size range of 10–20 nm. TG analysis indicated that carbonaceous deposition on the catalysts prepared by microwave heating is lower than that by conventional heating, and the metal Cu further prompts the stability of catalyst. Most of the carbonaceous deposition on catalysts prepared by microwave heating is formed at low temperature and it is easy to burn-off. Coke accumulation at high temperature is the main reason of catalyst deactivation. The carbonaceous deposition formed on the catalysts for non-oxidative aromatization of methane is different from those formed on the catalysts for partial oxidation of methane.