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苯与丙烯在β分子筛上吸附行为的蒙特卡罗研究 总被引:1,自引:0,他引:1
采用巨正则统计系综蒙特卡罗模拟方法研究了β分子筛上苯与丙烯分子的吸附行为. 由分子筛内吸附质粒子云分布可知, 在100 kPa时, 丙烯在分子筛上的吸附量要远远大于苯的吸附量. 由吸附相互作用能分布来看, 苯与分子筛之间相互作用能比丙烯与分子筛之间的相互作用能更负, 这就使苯分子的吸附相对于丙烯分子稳定. 相对而言, 温度变化对丙烯吸附影响远大于对苯吸附的影响, 如100 kPa时, 温度由298 K升高至443 K导致丙烯分子吸附量明显减少, 由每8个晶胞吸附98个丙烯分子减少到80个; 而对苯分子吸附却没有显著的影响. β分子筛上存在着苯和丙烯的竞争吸附, 并且吸附分子之间存在相互作用使两者与分子筛之间的相互作用能分布改变. 在压力范围1×10-3~5.0 kPa, 不同温度下苯与丙烯在分子筛内吸附等温线的模拟结果表明, 在较高温度、较低压力下丙烯的吸附量要小于苯的吸附量. 相似文献
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C5烷烃分子在AlPO4-5分子筛中吸附的分子模拟研究 总被引:3,自引:0,他引:3
采用分子水平计算机模拟方法研究了环戊烷、正戊烷和2-甲基丁烷在AlPO4-5分子筛中的吸附,得到了有关吸附平衡常数、吸附热、吸附等温线以及平均势能等。结果表明,在373 K,2-甲基丁烷的饱和吸附量高于其他两种异构体;473 K,环戊烷的饱和吸附量高于其他两种异构体;573 K,在所测试的压力范围内,环戊烷的吸附量都高于其他两种异构体,2-甲基丁烷的吸附量高于正戊烷。C5烷烃分子在AlPO4-5中吸附量的不同是由于他们在分子筛中的排列方式不同而引起的。低吸附量时C5烷烃分子平均势能不随吸附量变化;高吸附量时平均势能随着吸附量的增加而降低;而2-甲基丁烷和环戊烷分子的平均势能变化更加明显。 相似文献
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研究了聚芳醚酮系列在1,2-二氯乙烷中的吸附,及溶剂与温度诱导结晶行为。得到60℃时的最大吸附量C∞及假扩散系数D为:PEEK,C∞=46%,D=3.10×10^-12m^2·s^-1;PEEKK,C∞=50%,D=6.57×10^-12m^2·s^-1;PEKK,C∞=55%,D=9.41×10^-12m^2·s^-1。实验表明,吸附及脱附行为均与分子链刚性或羰基含量有关,膜的分子链受溶剂作用而 相似文献
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硅胶自非极性溶剂中吸附苯甲酸 总被引:3,自引:0,他引:3
⑴测定了0℃、15℃和20℃时硅胶自四氯化碳中吸附苯甲酸的等温线,等温线为S型的,接近饱和溶液浓度时吸附量急剧上升。用BET二常数公式和D-R方程的类似形式处理了实验结果,最大吸附体积与夺胶比孔容一致。⑵测定了硅胶自四氯化碳-环己烷二元混合溶剂稀溶液中吸附苯甲酸的等温线(20℃)和各溶剂组成时苯甲酸饱和溶液浓度,等温线是Langmuir型的,吸附量与饱和溶液浓度间有直线关系,文中对所得结果给出了合 相似文献
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采用巨正则统计系综Monte Carlo模拟方法研究了不同温度、不同吸附方式下纯硅MCM-22型分子筛ITQ-1上苯与丙烯分子的吸附行为. 分子筛内吸附质粒子云分布模拟结果显示, 苯和丙烯主要吸附在超笼和十元环孔道内, 其中丙烯分子几乎充满了孔道内部大部分区域, 在链接超笼之间的十元环窗口也充满了丙烯分子, 而苯分子在超笼内和十元环孔道内的吸附却较为分散、均匀. 丙烯与分子筛之间相互作用能高于苯与分子筛之间的相互作用能, 使苯分子吸附相对丙烯分子更为稳定. 温度变化对分子筛上丙烯吸附远大于对苯吸附的影响, 100 kPa时温度由298 K升高至443 K导致丙烯分子吸附量迅速减少, 而对苯分子却没有显著的影响. ITQ-1分子筛上存在苯和丙烯分子的竞争吸附, 使两者吸附相互作用能最可几分布朝着折中方向移动. 苯与丙烯在分子筛内吸附等温线的模拟结果表明, 在温度较高、压力较低时, 丙烯的吸附量小于苯的吸附量. 相似文献
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采用本体聚合法,以甲基丙烯酸(MAA)为功能单体、三羟甲基丙烷三丙烯酸酯(TMPTA)为交联剂、尼莫地平为模板分子,制备了分子印迹聚合物。运用平衡结合实验,研究了印迹聚合物对尼莫地平、尼群地平、非洛地平药物分子的选择性识别能力。3种药物的静态吸附分配系数KD值分别为0.221 4、0.197 2、0.051 4。结果表明分子印迹聚合物对尼莫地平有较高的选择性。测定了不同温度下印迹聚合物的吸附等温曲线,表明吸附等温线为Ⅰ型吸附等温线,且随着温度的升高吸附量降低,说明吸附过程是放热过程。为了进一步研究印迹聚合物的吸附机理,进行了热力学性质的研究,测定了不同温度下吸附过程的熵变、焓变和吉布斯自由能变化,实验结果表明吸附是焓控制过程。 相似文献
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A. G. Krivenko N. S. Komarova L. N. Sviridova E. V. Stenina 《Russian Journal of Electrochemistry》2009,45(9):1064-1071
The effect of camphor adsorption on the differential capacitance of electrodes of nanostructured carbon of different morphology
(single-walled carbon nanotubes, filiform carbon, and columnar structures) in aqueous electrolyte solutions and also on the
electrochemical reactions in these systems is studied. It is shown that irrespective of the ac frequency, the differential
capacitance of the nanopaper and columnar electrodes increases 3–5-fold throughout the studied potential range. This experimental
fact is explained by the substantial increase in the electrode surface accessible for electrolyte, which is a manifestation
of the Rehbinder effect in electrochemistry. The revealed different kinds of effects of camphor adsorption layers formed at
the nanostructured carbon/electrolyte interface on the electron transfer processes are as follows: partial inhibition of both
the electron injection and the K3[Fe(CN)6] reduction; complete suppression of the reduction of sodium nitrate and nitrite; the absence of effects on the OH radical
reduction and solvated electron oxidation. 相似文献
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The consequences in a chemical reaction of the non-bonding interactions between molecules of one configuration on the one hand, and molecules of opposite configuration on the other hand are discussed. The reaction rates and product ratios in the reaction of a chiral compound depend upon the enantiomeric excess of the substrate. An antipodal interaction effect is observed in a phenol coupling reaction, a reductive camphor dimerization and a camphor reduction. 相似文献
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The circular dichroism spectra of copper(II) complexes with hydroxymethylene camphor, hydroxymethylene menthone, and trifluoroacetyl camphor as well as of mixed-ligand complexes with acetylacetone have been studied in different solvents at different temperatures. The changes observed in the spectra are attributed to a strong coordination of the solvent molecules in axial positions of square-planar complexes. It has been shown that the contributions of two ligands to the net spectrum of circular dichroism are additive and that the absorption spectra of the complexes do not depend on the optical configuration of the ligands. The conclusion has been drawn that no noticeable inter-ligand interactions exist in the complex and no enantioselective effects are exhibited. 相似文献
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The adsorption behaviors of amino acids in short chain peptides were examined. Each amino acid, aliphatic or charged, was inserted between the two tryptophans of a peptide, GWWG. The capacity factors of these peptides on an Ocytl-Sepharose column were measured. The adsorption enthalpies, entropies, and the number of repelled water molecules after adsorption were estimated to analyze the contribution of each different amino acid to its hydrophobic adsorption. The peptides inserted with aliphatic amino acids owned the highest capacity factors but released the least amount of adsorption heat among all the peptides under examination. It was found that the hydrophobic contribution of aliphatic amino acids was derived from the entropy gain by repelling the ordered water surrounding them. The insertion of negatively charged amino acids greatly reduced the capacity factors but still repelled a significant number of water molecules after adsorption. This indicated that the water molecules surrounding ionic amino acids were not orderly aligned. The dehydration cost energy but the water repelling did not offer enough entropy to drive the adsorption. Subsequently, lower retention was obtained from the peptides inserted with negatively charged ionic amino acids. The insertion of lysine increased the adsorption enthalpy but repelled no water molecules after adsorption. It was speculated that the inserted lysine still interacted with hydrophobic ligands but disturbed the interaction between ligands and adjacent tryptophans. Therefore, the adsorption enthalpy increased and the capacity factors decreased. Different amino acids contributed to hydrophobic interaction in different ways. The simultaneous analysis of capacity factor, adsorption enthalpy, adsorption entropy, and the number of repelled water molecules facilitated the understanding of the adsorption processes. 相似文献
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M. I. Volkova-Gugeshashvili A. G. Volkov V. S. Markin 《Russian Journal of Electrochemistry》2006,42(10):1073-1078
The thermodynamics of adsorption of amphiphilic surface-active compounds at the interface between two immiscible liquids is
considered. At the interface, these molecules are supposed to replace a few of the adsorbed molecules of both solvents. Classical
isotherms of adsorption (Frumkin, Frumkin-Damaskin, Langmuir, Henry) were based on the model of non-penetrable interface,
where an adsorbate can substitute only molecules of one solvent. At the interface between two immiscible electrolytes, nonpolar
oil/water interfaces, and liquid membranes amphiphilic molecules can substitute molecules of both solvent and classic isotherms
cannot be used. The generalization of Frumkin isotherm for permeable and non-permeable interfaces, known as the Markin-Volkov
isotherm, gives the possibility to analyze adsorption in a general case. The adsorption isotherms of pentafluorobenzoic acid
at the octane/water interface at different pHs were measured by the drop-weight method. The thermodynamic parameters of pentafluorobenzoic
acid (PFBA) adsorption at octane/water interface were determined. From the measurements of PFBA adsorption, the structure
of the octane/water interface was determined. Substitution of one adsorbed octane molecule requires approximately three adsorbed
PFBA molecules. This result shows that the orientation of solvent molecules at the interface is different from the bulk. Adsorbed
octane molecules have a lateral orientation with respect to the interface. Gibbs free energy of adsorption equilibrium and
thermodynamic parameters of PFBA adsorption show that the adsorption of PFBA at the octane/water interface is accompanied
by a reduction in the attraction between adsorbed PFBA molecules as the pH decreases to the acidic region.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 10, pp. 1194–1200.
The text was submitted by the authors in English. 相似文献
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An atomic force microscope was used to observe the adsorption of phospholipid molecules(phospha-tidylcholine, PC) on the mica substrate.The film-formation by PC molecules adsorption spontaneously on the specific substrate has been proved. It is revealed that the evident differences of morphology exist among different sampler with different concentrations of PC/decane solutions. different adsorption times, etc.The effect of tip-induced change in size of domains formed by adsorption of PC molecules on the substrate during the AFM scanning was observed. 相似文献
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Wei Liu Yuxi Zhang Shui Wang Lisen Bai Yanhui Deng Jingzhong Tao 《Molecules (Basel, Switzerland)》2021,26(17)
Polymeric adsorbents with different properties were synthesized via suspension polymerization. Equilibrium and kinetics experiments were then performed to verify the adsorption capacities of the resins for molecules of various sizes. The adsorption of small molecules reached equilibrium more quickly than the adsorption of large molecules. Furthermore, the resins with small pores are easy to lower their adsorption capacities for large molecules because of the pore blockage effect. After amination, the specific surface areas of the resins decreased. The average pore diameter decreased when the resin was modified with either primary or tertiary amines, but the pore diameter increased when the resin was modified with secondary amines. The phenol adsorption capacities of the amine-modified resins were reduced because of the decreased specific area. The amine-modified resins could more efficiently adsorb reactive brilliant blue 4 owing to the presence of polar functional groups. 相似文献
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Wu D Fang Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(8-9):1845-1852
Surface-enhanced Raman scattering (SERS) spectra of a series of n-hydroxybenzoic acids (n-HBA, n = P, M and O) adsorbed on the silver nano-particles were studied, respectively, in the silver colloidal solution and on the dried silver-coated filter paper. On the same substrate, the different molecules' SERS spectra were different, while on the different substrates the same molecules' SERS spectra were also different. Significant changes were found in the SERS spectra of PHBA molecules adsorbed on the two substrates, and the changes found in MHBA's spectra on two substrates were next to PHBA's, while almost no changes were found in the spectra of OHBA molecules. Moreover, it was found, on the filter paper, that the SERS spectra of the same molecules would change with the coverage density of the silver nano-particles. The analyses showed that the origins of these changes were the different adsorption behavior of molecules adsorbed on the silver nano-particles. Because in these three molecules the relative positions of the carboxyls and hydroxyls on the benzenes are different, the adsorption behaviors of these three molecules adsorbed on the silver surfaces are also different. The experimental results suggest that the surface characteristic of the substrate and the surface configuration of the adsorbate could exert a great influence on the adsorption behavior of the adsorbates on the substrates. 相似文献
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Markin VS Volkova-Gugeshashvili MI Volkov AG 《The journal of physical chemistry. B》2006,110(23):11415-11420
The thermodynamics of adsorption of amphiphilic surface-active compounds at the interface between two immiscible liquids is considered. At the interface, these molecules are supposed to replace a few of the adsorbed molecules of both solvents. Classical isotherms of adsorption (Frumkin, Langmuir, Henry) were based on the model of nonpenetrable interface, where an adsorbate can substitute only molecules of one solvent. However, at the interface between two immiscible electrolytes, like nonpolar oil-water interfaces, or liquid membrane amphiphilic molecules can substitute molecules of both solvents; therefore, classical isotherms are not applicable in these cases. The generalization of Langmuir and Frumkin isotherms for permeable and nonpermeable interfaces, known as the Markin-Volkov (MV) isotherm, gives the possibility to analyze adsorption and the interfacial structure in a general case. In the present paper, the adsorption isotherms of pentafluorobenzoic acid at the octane-water interface at various pH were measured by the drop-weight method. The thermodynamic parameters of pentafluorobenzoic acid (PFBA) adsorption at the octane-water interface were found. From the measurements of PFBA adsorption, the structure of the octane-water interface was determined. Substitution of one adsorbed octane molecule requires approximately three adsorbed PFBA molecules. This result shows that the orientation of solvent molecules at the interface is different from the bulk solution. Adsorbed octane molecules have a lateral orientation with respect to the interface. Gibbs free energy of adsorption equilibrium and thermodynamic parameters of PFBA adsorption show that the adsorption of PFBA at the octane-water interface is accompanied by a reduction in the attraction between adsorbed PFBA molecules as the pH decreases to the acidic region. 相似文献
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Tewodros Asefa Amy N. Otuonye Gang Wang Elizabeth A. Blair Rajyalakshmi Vathyam Kelley Denton 《Adsorption》2009,15(3):287-299
A series of mesoporous nanosphere materials that are functionalized with various terminal and bridging organic groups were
synthesized. They have improved adsorption capacity and different release properties for drug and small molecules. The materials
contained terminal vinyl, 3-mercaptopropyl, 3-aminopropyl, and secondary amine functional groups and bridging ethane, ethene,
and benzene groups within their mesopore channel walls. The samples containing mercaptopropyl and vinyl groups showed greater
adsorption capacity and better controlled release behavior for rhodamine 6G molecules. On the other hand, mesoporous matrices
containing amine functional groups showed higher adsorption capacity and better release properties for ibuprofen molecules.
Further studies revealed that the bridging organic groups in the mesopore channel walls also improved the adsorption capacity
and release properties of the materials compared to the corresponding samples containing no bridging organic groups. Such
improved adsorption and controlled release properties of molecules by simple changes of functional groups on mesoporous materials
are important for the development of nanomaterial drug delivery vehicles and for controlled release of drugs over long time
periods at specific targeted sites in the body. By judicious choice of organic groups and by systematic design and synthetic
approaches, nanoporous materials having different adsorption capacity and release properties for many other drug molecules
can also be achieved. 相似文献