介孔碳材料CMK-3及改性介孔碳材料N,O-CMK-3对药物的吸附和释放性能

以有序介孔碳材料CMK-3为碳骨架,通过硝酸(HNO₃)氧化并将三聚氰胺作为氮源采用热解技术成功制备了氮氧共掺杂介孔碳N,O-CMK-3,通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、N₂吸附-脱附、X射线光电子能谱(XPS)、拉曼光谱(Raman)和接触角测试对CMK-3和N,O-CMK-3材料的微观形貌、结构、组成及润湿性能进行了分析表征,测试了介孔碳材料对难溶性抗肿瘤药物羟基喜树碱(hydroxycamptothecin,HCPT)的吸附和释放性能。结果表明:经过改性后N,O-CMK-3的孔结构发生了变化,比表面积和孔体积减少,表面的含氮、氧官能团增加,介孔碳材料的表面润湿性得到改善,使得介孔碳材料的接触角由161.9°降低至138°。CMK-3和N,O-CMK-3对HCPT具有较好的吸附能力,饱和吸附量分别为811.11 mg g ^-1和805.93 mg g ^-1,介孔碳材料因具有纳米孔道结构提高了原料药羟基喜树碱的溶出度,负载于介孔碳材料后溶出率由22....     

有序介孔碳CMK-3微波负载NiO及其电容性能研究

微波法负载具有简便、快速、均匀的优点. 本文尝试以乙二醇为还原剂, Ni(Ac)₂为Ni源, 通过微波辐射负载及低温空气煅烧在CMK-3上形成NiO. 对样品进行X射线衍射(XRD)、透射电子显微镜(TEM)、N₂吸脱附等结构表征及循环伏安(CV)等电化学性能测试. 结果显示, 微波法并经低温空气煅烧后有序介孔碳CMK-3的小角XRD峰强度变弱、比表面积下降、孔容减小, 但却使其比电容从229.3 F/g提高到295.9 F/g, 大于文献报导中介孔碳负载MnO₂, RuO₂•xH₂O后的比电容值. 由此说明微波法是有效的负载方法, 具有较好的应用前景.     

载铜介孔碳CMK-3的制备及其对苯酚的吸附-催化氧化性能

通过一种简易的方法在介孔碳CMK-3的孔道内负载氧化铜粒子制备Cu/CMK-3复合物,利用粉末X射线衍射、氮气吸附-脱附、透射电镜等手段对其进行表征.结果表明,氧化铜均匀地分散在CMK-3孔道中,CMK-3在负载氧化铜后仍有较大的比表面积.考察了载铜CMK-3对水中苯酚的吸附和低温干法催化氧化苯酚性能.吸附和循环使用结果表明,Cu/CMK-3对水中苯酚具有较大的吸附量和良好的催化氧化效率.热重-质谱(TG-MS)联用测试结果表明,吸附的苯酚在180℃左右开始被催化氧化为CO2和水,此时不会造成苯酚的脱附和介孔碳CMK-3的烧蚀.     

有序介孔碳CMK-3负载离子液体催化CO2与环氧化物合成环状碳酸酯

采用有序介孔碳CMK-3为载体负载咪唑类离子液体制得CMK-3-IL催化剂,用X射线衍射(XRD)、透射电子显微镜(TEM)、N2吸附、热重分析和元素分析等手段表征了催化剂样品,并考察了CMK-3-IL催化剂催化CO2与环氧丙烷合成碳酸丙烯酯的反应性能。结果表明,离子液体被成功的负载到CMK-3载体上,CMK-3负载离子液体后孔道结构没有被破坏,但孔体积、孔径和比表面积均有所下降。催化实验表明,在120℃、2 MPa的条件下反应6 h,环氧丙烷转化率达到64%,碳酸丙烯酯选择性高达99%。     

A型沸石/活性炭复合材料的制备及甲烷/氮气吸附分离性能

以沥青和煤矸石为原料,经炭化、活化后获得型体活性炭材料(AC),并在此基础上进行水热晶化,研究晶化时间对复合材料中4A沸石的形成、孔结构和甲烷、氮气吸附性能的影响。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、77 K下的氮气吸附-脱附以及273 K下的CO_2吸附等温线对样品进行表征,结果表明水热晶化后,复合材料中的硅铝形成立方结构的4A沸石,出现了0.45~0.6 nm的微孔,微孔孔容增加,并伴有少量的中孔和大孔。复合材料在298 K下的甲烷(CH_4)和氮气(N_2)吸附等温线的结果表明,晶化时间6 h的复合材料AC-2的甲烷吸附量被提高至10.8 m L/g,并保持较高的CH4/N2平衡分离比(3.7)。     

甲烷在AFS型分子筛中的吸附模拟

采用巨正则系综蒙特卡罗(GCMC)方法模拟了甲烷分子在AFS型分子筛中的吸附量, 并和Dvren等人(Langmuir, 2004, 20: 2683)设计的金属有机骨架中的甲烷吸附量进行比较, 发现AFS型沸石分子筛对甲烷分子有很好的吸附性能, AFS型分子筛是中低压吸附储存天然气系统中的一种比较理想的吸附剂. 采用Dubinin Asakhov(DA)微孔分析方法, 分析了沸石结构对甲烷储量大小的影响, 总结了影响甲烷储量大小的物理因素.     

介孔碳CMK-3对苯酚的吸附动力学和热力学研究

研究了介孔碳CMK-3对苯酚的吸附性能, 与传统商用活性碳(CAC)进行了比较, 结果表明, CMK-3比CAC的吸附量大、吸附速率快、达到平衡时间短, 是一种较好的吸附剂. 同时探讨了介孔碳CMK-3对苯酚的吸附热力学和动力学特征. CMK-3对苯酚的吸附行为可用Langmuir和Freundlich等温式进行描述, 相关性都较好, 但更符合Freundlich经验公式. 分别采用模拟一阶反应和二阶反应模型考察了吸附动力学, 并计算了这些动力学模型的速率常数. 模拟二级反应模型和实验数据之间有较好的相关性. 分别计算了热力学参数ΔG0, ΔS0和ΔH0, 结果表明, CMK-3对苯酚的吸附过程是吸热和自发的.     

应用基于第一性原理的分子模拟方法预测小分子在多孔材料中的吸附

分子在多孔材料中的吸附在工业中有着重要的应用．计算化学的发展和应用使得对多孔材料中小分子的吸附研究进入了一个新阶段．从第一性原理出发,在MP2高精度量子化学计算基础上推导小分子与多孔材料相互作用的分子力场,运用巨正则系综的蒙特卡罗模拟,研究小分子在多孔材料的吸附和脱附过程．以具有代表性的沸石分子筛ZSM-5和储氢材料MOF-5为对象,应用上述方法分别研究氨气分子和氢气分子在两种材料中的吸附,进而讨论沸石的酸性和MOF-5的储氢性能,计算得到的结果和实验数据高度吻合．     

短链烷烃二元混合物在分子筛上吸附分离的分子模拟

用巨正则是系综Monte Carlo(GCMC)与构型偏倚(CBMC)相结合的方法模拟了 MFI分子筛对甲烷-丙烷、乙烷-丙烷体系(300K，345kPa)的吸附平衡，模拟结果与 文献实验结果相吻合，分别模拟了FER，ISV，MEL，MFI，MOR，TON等六种分子筛对 甲烷－丙烷、乙烷－丙烷体系（300K，345kPa）的吸附，得出甲烷－丙烷体系中分 子筛对较长链烷烃的选择性大小顺序（气相乙烷摩尔分数为0.5时）为ISV＞MEI＞ MEL＞FER＞TON＞MOR,对乙烷－丙烷体系选择性大小顺序（气相乙烷摩尔分数为0. 5时）为ISV＞MOR＞MFI＞FER＞MEL＞TON. MOR型分子筛对两个不同体系的吸附行为 表现出明显的不同，两个体中ISV的吸附量均最大，MFI，MEL，FER次之，此三种分 子筛具有相拟的吸附量，MOR和TON型分子筛吸附量较低。     

有序介孔炭负载铜基催化剂Cu/CMK-3用于气相甲醇氧化羰基化反应

通过纳米浇铸法合成了有序介孔炭CMK-3,再通过浸渍法制备了Cu/CMK-3催化剂,并将其用于气相甲醇氧化羰基化反应。N2吸附-脱附测试、X射线衍射(XRD)以及透射电镜(TEM)的表征结果表明,Cu/CMK-3具有序介孔结构,活性Cu物种均匀分散于CMK-3的表面及孔道中,粒径为10~20 nm,远小于相同条件下制备的铜/活性炭(Cu/AC)催化剂。固定床反应器的活性评价结果显示450℃下制备的Cu/CMK-3催化活性最高,反应10 h内碳酸二甲酯(DMC)的时空收率(STY)达到286 mg·g^-1·h^-1,选择性为76%。长周期活性评价结果表明Cu/CMK-3稳定性较相同条件下制备的Cu/AC有大幅提高,50 h内DMC的STY降低了20%,75 h内降低了28%。     

A computational study of CO2, N2, and CH4 adsorption in zeolites

The adsorption properties of CO₂, N₂ and CH₄ in all-silica zeolites were studied using molecular simulations. Adsorption isotherms for single components in MFI were both measured and computed showing good agreement. In addition simulations in other all silica structures were performed for a wide range of pressures and temperatures and for single components as well as binary and ternary mixtures with varying bulk compositions. The adsorption selectivity was analyzed for mixtures with bulk composition of 50:50 CO₂/CH₄, 50:50 CO₂/N₂, 10:90 CO₂/N₂ and 5:90:5 CO₂/N₂/CH₄ in MFI, MOR, ISV, ITE, CHA and DDR showing high selectivity of adsorption of CO₂ over N₂ and CH₄ that varies with the type of crystal and with the mixture bulk composition.     

石墨烯/纳米管复合结构吸附分离CO2/CH4混合物的分子模拟

采用巨正则蒙特卡洛(GCMC)及分子动力学(MD)方法探讨了石墨烯/碳纳米管三维骨架结构(GNHS)对等摩尔CO₂/CH₄二元混合物的吸附分离性能. 模拟结果表明CO₂比CH₄更易吸附于GNHS中, GNHS与(6, 6)SWCNT (单壁碳纳米管)相比具有更高的分离性能. 随着温度升高, CO₂的吸附量快速降低, 而CH₄的吸附量则呈现出先升高后降低的趋势. 最后采用分子动力学方法计算了CO₂与CH₄的自扩散系数及停留时间等动力学相关参数, 发现CO₂在GNHS内扩散的阻力更大. 而各组分在吸附剂外部吸附层内的扩散过程对混合物的分离也存在一定影响.     

Adsorption of carbon dioxide of 1-site and 3-site models in pillared clays: a Gibbs ensemble Monte Carlo simulation

Adsorption behavior of carbon dioxide confined in pillared clays is analyzed by using constant pressure Gibbs ensemble Monte Carlo (GEMC) method. In our simulation, 1-site and 3-site models are used to represent carbon dioxide. At the 1-site model, carbon dioxide is described as a Lennard-Jones (LJ) sphere, while at the 3-site model, carbon dioxide is modeled as a three-sites linear chain represented by EPM2 potential considering the quadrapolar effect. The potential model from Yi et al. for pillared clays is used to emphasize its quasi two-dimensional structure. Comparing the calculated results from the 1-site and the 3-site models at T=228.15 and 258.15 K, we observe that the adsorption amount from the two models is the same basically. However, the local density presents a significant difference, because the shoulder in the main peak near the wall from 3-site model can reflect the orientation of carbon dioxide. Accordingly, in the systematical investigation to explore the effect of porosity and pore width on the adsorption of carbon dioxide in pillared clays, the 3-site model was only used. We observe that for a narrow pore of H=1.02 nm, each isotherm shape displays type I curve, suggesting that it is not inflected by the porosity. However, for the larger pores of H=1.70 and H=2.38 nm, the increase of the porosity alters the shape of adsorption isotherms from a simple linear relation to the first order jump, indicating that the porosity is of very important factor to affect adsorption and phase behavior of fluids confined in pillared clays. The excess adsorptions of carbon dioxide at supercritical temperatures of T=323.15 and 348.15 K are also investigated. We find that the maximum exists for each excess isotherm, and the optimal pressure corresponding to the maximum increases with the pore width. However, the porosity has no significant effect on the optimal pressure.     

Separation of H2O/CO2 Mixtures with Layered Adsorption Method for Greenhouse Gas Control

Multiple-layered vacuum swing adsorption technique was used and investigated in order to effectively keep the feed gas that flows into zeolite 13X zone being dry and keep the CAPEX down(not adding pre-treatment equipment). Activated carbon fiber(ACF) and alumina CDX were laid at the lower parts of the column as pre-layers to selectively adsorb moisture. Zeolite 13X was laid on the top of those two adsorbents as the main layer to capture CO₂. Systematic cyclic experiments show that water vapor was successfully contained within the ACF and CDX layers at cyclic steady states. It was also found that ultimate vacuum pressure played a decisive factor for stabilizing the water front, and achieving good CO₂ purity and recovery. The findings also reveal the pathway for large-scale CO₂ capture process.     

Separation of CO2/CH4 and CH4/N2 mixtures using MOF-5 and Cu3(BTC)2

In this paper we used MOF-5 and Cu₃(BTC)₂ to separate CO₂/CH₄ and CH₄/N₂ mixtures under dynamic conditions. Both materials were synthesized and pelletized, thus allowing for a meaningful characterization in view of process scale-up. The materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). By performing breakthrough experiments, we found that Cu₃(BTC)₂ separated CO₂/CH₄ slightly better than MOF-5. Because the crystal structure of Cu₃(BTC)₂ includes unsaturated accessible metal sites formed via dehydration, it predominantly interacted with CO₂ molecules and more easily captured them. Conversely, MOF-5 with a suitable pore size separated CH₄/N₂ more efficiently in our breakthrough test.     

Large‐Scale Screening and Design of Metal–Organic Frameworks for CH4/N2 Separation

CH₄/N₂ separation is one of the great challenges in gas separation, which is of scientific and practical importance, such as in the upgrading of unconventional natural gas. Unfortunately, the separation performance is still quite low so far mainly due to their very close physical properties. In this work, a high‐throughput computational screening method was performed to develop metal–organic frameworks (MOFs) for efficient CH₄/N₂ separation. General designing rules as well as the correlation between selectivity and our proposed adsorbility (AD) parameter were obtained by carrying out systematic GCMC simulations of the existing 5109 CoRE MOFs. With the aid of this information, five virtual MOFs were screened out from the large database with 303 991 generated MOFs constructed in our previous work, exhibiting much higher selectivities than all the reported values. Among them, the selectivity of Zn‐PYZ‐BPY‐1 can reach over 29.0, about 2.4 times of the highest value reported in the literature. These results may not only suggest promising candidates for CH₄/N₂ separation but also provide useful information for large screening of MOFs for other specific separation mixtures.