共查询到18条相似文献,搜索用时 171 毫秒
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《化工学报》2017,(9)
为提高非定域密度泛函理论(NLDFT)预测活性炭孔径分布(PSD)的精度,考虑了活性炭孔壁面晶体粗糙度对结果的影响。在传统NLDFT基础上,结合吸附壁面碳原子的密度分布,推导出改进NLDFT,预测了氩在光滑及具粗糙碳晶体表面的吸附平衡,并根据87.3 K、氩在活性炭上的吸附平衡数据,在由两种NLDFT确定了不同孔径的理论等温线核后,由寻优函数确定活性炭在0.35~12 nm区间的PSD。结果表明,以改进的NLDFT预测活性炭的PSD时,确定的活性炭孔径呈连续分布,预测平衡数据的相对误差小于10%;传统NLDFT确定的孔径在1 nm处出现断点,最大的预测相对误差范围达45%。改进NLDFT能较准确预测氩在具有粗糙晶体碳表面活性炭的PSD。 相似文献
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借助Materials Studio软件建立了0.902nm、1.997nm、3.000nm、4.000nm孔径的活性炭狭缝孔模型,采用巨正则蒙特卡洛模拟(Grand Canonical Monte Carlo)的模拟方法计算了其对挥发性有机物(VOCs,如异己烷、苯、甲苯、丙酮和甲醇)的吸附数据,考察了活性炭孔径的变化对VOCs吸附性能的影响,并对实际应用进行指导。模拟结果显示:活性炭对VOCs的吸附受孔径和吸附能的共同影响,在293.15K、各物质饱和蒸气压p0下,随着孔径的增大,吸附质吸附剂之间的亲和力呈下降趋势。活性炭孔径由0.902nm增加到4.000nm对异己烷、苯、甲苯的饱和吸附量逐渐增大,而4.000nm孔径活性炭对丙酮饱和吸附量小于3.000nm孔径活性炭,3.000nm、4.000nm孔径活性炭对甲醇饱和吸附量小于1.997nm孔径活性炭。在工业废气VOCs吸附回收中选择0.902~1.997nm孔径活性炭能够达到最佳效果。 相似文献
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水蒸气活化法制备椰壳活性炭的孔结构特征 总被引:2,自引:0,他引:2
以农林废弃物椰壳在600℃炭化2h后的炭化料为原料,以水蒸气为活化剂,研究了活化温度、活化时间、水蒸气用量对活性炭的比表面积、微孔容积和收率等的影响。结果表明:椰壳炭化料的比表面积仅为185m^2/g,且以中孔为主。在活化过程中,通过提高活化温度和水蒸气用量缩短了活化时间,扩宽了孔径;当水蒸气用量和活化温度较为适宜时,延长活化时间,有利于微孔的形成。活性炭的比表面积、总孔容积、微孔容积可达:1465m^2/g,0.9703cm^3/g,0.7519cm^2/g。并通过非定域密度函数理论(NLDFT)对活性炭的孔径分布进行了表征。 相似文献
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以杏壳活性炭(AC)为原料,系统地研究了改性剂(硝酸银、硝酸铜、双氧水-硝酸铜)、改性条件(AC粒度、浸渍时间、焙烧时间、焙烧温度)对改性活性炭吸附乙烯性能的影响。采用ESEM-EDS、FT-IR、XPS等手段对改性活性炭的结构、表面化学成分等进行分析,并初步探讨了改性活性炭吸附乙烯的机理。研究结果表明用15%双氧水先氧化预处理后再用2%硝酸铜作改性剂时活性炭改性效果最好;活性炭改性时,活性炭粒度、焙烧时间和焙烧温度对改性活性炭乙烯吸附性能的影响较大,而浸渍时间的影响较小。在15%双氧水氧化预处理、改性剂为2%硝酸铜、活性炭粒径0.38~0.83 mm、浸渍时间6 h、焙烧温度400℃、焙烧时间4 h条件下制得改性活性炭(H2O2-Cu-AC)对乙烯的吸附量为0.163 g/g,比AC(0.069 g/g)提高了136.23%;H2O2-Cu-AC中活性组分铜能相对均匀地分散在活性炭的表面和孔隙内部,改性剂引起了活性炭孔隙结构和表面官能团的变化,比表面积由AC的1 047.50 m2/g下降到1 012.65 m2/g,总孔容积由AC的0.467 1 cm3/g下降到0.434 7 cm3/g,孔径向较宽方向分布,其中< 10 nm的孔径分布占比由58.16%下降到53.95%,10~20 nm的孔径分布占比由18.01%上升到19.10%,>20 nm的孔径分布占比由23.83%上升到26.94%。其含氧官能团增加,C1、C3、C5降低,其中,C1峰面积占比由77.468%降低到76.827%,C3峰面积占比由6.684%降低到5.675%,C5峰面积占比由0.844%降低到0.749%;C2、C4增加,其中C2峰面积占比由13.514%增加到15.225%,C4峰面积占比由1.490%增加到1.524%。 相似文献
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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。 相似文献
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Quenched solid density functional theory and pore size analysis of micro-mesoporous carbons 总被引:1,自引:0,他引:1
We present a new model of adsorption on micro-mesoporous carbons based on the quenched solid density functional theory (QSDFT). QSDFT quantitatively accounts for the surface geometrical inhomogeneity in terms of the roughness parameter. We developed the QSDFT models for pore size distribution calculations in the range of pore widths from 0.4 to 35 nm from nitrogen at 77.4 K and argon at 87.3 K adsorption isotherms. The QSDFT model improves significantly the method of adsorption porosimetry: the pore size distribution (PSD) functions do not possess gaps in the regions of ∼1 nm and ∼2 nm, which are typical artifacts of the standard non-local density functional theory (NLDFT) model that treats the pore walls as homogeneous graphite-like plane surfaces. The advantages of the QSDFT method are demonstrated on various carbons, including activated carbons fibers, coal based granular carbon, water purification adsorbents, and mirco-mesoporous carbon CMK-1 templated on MCM-48 silica. The results of PSD calculations from nitrogen and argon are consistent, however, argon adsorption provides a better resolution of micropore sizes at low vapor pressures than nitrogen adsorption. 相似文献
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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. 相似文献
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CO_2活化制备椰壳基活性炭 总被引:6,自引:1,他引:6
以600℃下炭化2h后的椰壳炭化料为原料,通过CO2活化制备椰壳基活性炭,研究了活化温度、活化时间、CO2流量对活性炭得率及其吸附性能的影响。同时测定了该活性炭的N2吸附等温线,通过非定域化密度函数理论表征活性炭孔径分布。在适宜的工艺条件,所制备活性炭的得率为24%,碘吸附值为1428mg/g,其比表面积、总孔容积、微孔容积分别可达:1653m2/g,1.045cm3/g,0.8582cm3/g,且以2nm以下的微孔为主,产品性能达到了双层电容器专用活性炭(LY/T1617—2004)标准。 相似文献
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采用容积法测定了CO2在两种炭分子筛(CMS-200A、CMS-200B)上的吸附等温线,温度为273K、相对压力为0.000001~0.9。通过HK模型和D-R方程对吸附平衡数据进行分析,计算得到了两种炭分子筛的孔径分布。结果表明:两者的孔径分布主要在0.35~0.8nm之间,CMS-200B的平均孔径略大于CMS-200A。HK模型和D-R方程两种方法均可以反映出两种炭分子筛孔径分布的差异,且计算得到的结论是一致的。 相似文献
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《Carbon》2013
In this work, we show that the standard slit pore model widely used for the characterization of activated carbons may be improved by introducing structural and/or energetical heterogeneity to the surface of pore walls. The existing one dimensional slit pore model assumes graphite-like energetically uniform pore walls. As a result of this assumption adsorption isotherms calculated by the non local density functional theory (NLDFT) do not fit accurately the experimental N2 data measured for real activated carbons. Assuming a graphene-based structural framework for activated carbons and using a 2D-NLDFT treatment of the fluid density in the pores we consider two options for model pores: energetically heterogeneous (EH) and geometrically corrugated (GC). For testing, we applied these two models to the pore size analysis of porous carbons that were giving poor results of the analysis with the standard slit model. We found that the typical artifacts of the homogeneous slit pore model were eliminated. Also, the agreement of the new models with experimental data was significantly better than that of the standard slit model. 相似文献
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The structural properties of combustion-chamber deposits (CCDs) are studied by combining molecular simulation of adsorption in a set of model pores with experimental adsorption measurements, using ethane as the adsorptive. The implemented approach is a modification of the common method used to determine the pore size distribution (PSD) of manufactured carbon adsorbents, changed in order to take into account the higher degree of chemical and physical heterogeneity of CCDs. The realism of the PSD obtained is demonstrated by accurately predicting adsorption under a range of conditions. The general applicability of the method is tested by transferring a characteristic parameter of CCDs (and different from the corresponding parameter in manufactured carbon adsorbents) from one sample to another. 相似文献