Structures of hydrate complexes (H2O)xCN–(H2O)y , where x + y = 1–5 are optimized by the density functional method in the B3LYP version. It is shown that the nearest hydration sphere of the cyanide ion comprises four water molecules directly linked to the ion by hydrogen bonds. The chemical enthalpy of the hydration of the cyanide ion is calculated in the reactive-field continuum models (PCM and SCIPCM) and in other nonelectrostatic interactions. The calculation takes into account the electrostatic interaction between the hydrate complex and the solvent's dielectric surrounding. Calculation results are in good agreement with experiment. 相似文献
Metal ion exchanged montmorillonites (AlM & CrM) and metal oxide pillared montmorillonite (AlPM & CrPM) were prepared and characterized with XRD, FT‐IR, nitrogen adsorption and TPD of ammonia. The pillaring process results in a remarkable increase of interlayer distance, surface area and acid amount of the catalyst. However, increasing the calcined temperature causes reverse effects for the CrPM catalyst. The acid amount decreases in the order of CrPM200 < CrPM300 < AlPM500 < CrM < CrPM400 ≥ CrPM500 ≥ AlM. In the dehydration of 2‐propanol to propene, the reaction follows first order kinetics and the apparent rate constant is related to the catalyst acid amount. Compensation effect occurs in this reaction over the series of catalysts. 相似文献
Vapor‐phase aldol condensation of n‐butyraldehyde to 2‐ethyl‐2‐hexenal was studied at 1 atm and 150～ 300°C in a fixed‐bed, integral‐flow reactor by using NaX, KX, γ‐Al2O3 and Na/NaOH/γ‐Al2CO3 catalysts. Ion exchange of NaX zeolite with potassium acetate solution results in a decrease of crystallinity and apparent lowering of surface area, whereas the basic strength is enhanced. Treatment of γ‐Al2O3 with NaOH and Na causes a large decrease of the surface area but strong enhancement of the catalyst basicity. The catalytic activity on the basis of unit surface area is in the order Na/NaOH/γ‐Al2O3 < KXU < KXW < NaX >γ‐Al2O3, in accordance with the relative catalyst basic strength. The molar ratio of trimeric to dimeric products increases with increasing the reaction temperature and the catalyst basic strength except for Na/NaOH/γ‐Al2O3. Very high selectivity of 2‐ethyl‐2‐hexenal (>98.5%) was observed for reactions over NaX zeolite at 150°C. Based on the FT‐IR and the catalytic results, the reaction paths are proposed as follows: self‐aldol condensation of n‐butyraldehyde, followed by dehydration produces 2‐ethyl‐2‐hexenal, which then reacts with n‐butyraldehyde and successively dehydrates to 2,4‐diethyl‐2,4‐octadienal and 1,3,5‐triethylbenzene. For the reaction over NaX, the calculated Arrhenius frequency factor and activation energy are 314 mol/g·h and 32.6 kJ/mol, respectively. 相似文献
Complex micelles with a P4VP core surrounded by a mixed PNIPAM/PEG shell were prepared by comicellization of PNIPAM93‐b‐P4VP58 and PEG114‐b‐P4VP58 in aqueous solutions. Increasing the temperature above the LCST of the PNIPAM induced a phase separation of the mixed shell due to the collapse of the PNIPAM block. The morphology of the collapsed PNIPAM was dependent on the composition of the mixed shell; a lower content of the PNIPAM resulted in separately distributed domains on the surface of the P4VP core, while a higher content of the PNIPAM led to the formation of continuous membrane around the P4VP core. When the continuous membrane was formed, the hydrophilic PEG block could connect the inner P4VP core and the outer milieu to form channels across the PNIPAM membrane for water and other small molecules to pass through.
using the isospin–and momentum–dependent transport model, for three different symmetry energies, we have calculated the π–/π+ ratio as a function of time and tranverse–momentum in central 132sn+124 sn collision at e_beam/A=400mev. the results show that the π–/π+ ratios is very sensitive to the stiffness of the symmetry energy. thus we can probe the stiffness of the symmetry energy at high densities by using the π–/π+ ratio at different time or transverse momentum more accurately than before. comparing experimental data with the calculations will reveal crucial information about the stiffness of the symmetry energy more accurately.hadronic transport model, symmetry energy, π–/π+ ratio 相似文献
