Hydrogenation velocity

To study whether acoustic irradiation might have a beneficial effect on the hydrogenation velocity, or on the obtained selectivity to the desired products, a series of experiments with on-line unltrasonic treatment of the reaction mixture was performed. 

Hydrogenation experiments confirmed that the commercial catalysts studied, i.e. silica-supported NiCr was able to hydrogenate the aldol selectively to triol. The comparison of methanolic and water solvents revealed that the absence of methanol increased the total hydrogenation velocity, especially when the starting mixture contained high quantities of formaldehyde. The experimental data produced with NiCr were reasonably well described by the kinetics model, which account for competitive adsorption of reagents, surface reactions and the inhibitory effect of formaldehyde. 

Preliminary results from a much more complex CMD simulation of liquid water have recently been obtained. Shown in Fig. 11 are the quantum and classical hydrogen velocity correlation functions computed, in the former case, by CMD and, in the latter case, by classical MD. This... 

Figure 11. Classical and quantum hydrogen velocity time correlation function for liquid water at 300 K. The classical result is obtained from classical MD and the quantum result is from CMD. The difference between the classical and quantum results is due primarily to the large zero-point energy in the O—H bonds. The simulation consisted of 125 periodically replicated flexible water molecules represented by site-site point-charge Coulomb and 0-0 Lennard-Jones interactions [47],...

In what follows, the model formulations are firstly described in Section 12.2 and Section 12.3. In Section 12.4, modeling results including model validation through comparisons with previous experimental data in the literature, and analyses on distributions of hydrogen, velocity, species, current density, and potential in the cell are shown and discussed. Conclusions from the study are finally summarized in Section 12.5. It should be mentioned that all computations carried out in the study are under steady-state assumption, though the equations are derived in a time-dependent form. 

Aqueous hydrogen fluoride of greater than 60% maybe handled in steel up to 38°C, provided velocities are kept low (<0.3 m/s) and iron pickup in the process stream is acceptable. Otherwise, mbber or polytetrafluoroethylene (PTFE) linings are used. For all appHcations, PTFE or PTEE-lined materials are suitable up to the maximum use temperature of 200°C. PTEE is also the material of choice for gasketing. AHoy 20 or Monel is typically used for valve and pump appHcations. Materials unacceptable for use in HE include cast iron, type 400 stainless steel, hardened steels, titanium, glass, and siHcate ceramics. 

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