کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
62231 47628 2009 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
A general method for determining the role of spectroscopically observed species in reaction mechanisms: Analysis of coverage transients (ACT)
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
پیش نمایش صفحه اول مقاله
A general method for determining the role of spectroscopically observed species in reaction mechanisms: Analysis of coverage transients (ACT)
چکیده انگلیسی

A kinetic method is described to determine the role of adsorbed intermediates in heterogeneous reaction mechanisms. The method, denoted as analysis of coverage transients (ACT), involves comparing the time response of a spectroscopically observed species in an inert gas and a reactive gas to differentiate between adsorption–desorption processes and reaction. The method is applied in a kinetic study of pyridine hydrodenitrogenation (HDN) on a 12.2 wt% silica-supported nickel phosphide (Ni2P/SiO2) catalyst at 423 K and atmospheric pressure. In situ Fourier transform infrared spectroscopy (FTIR) measurements of pyridine adsorbed on Ni2P revealed the formation of a pyridinium surface intermediate. The concentration of the pyridinium intermediate increased with pyridine partial pressure and decreased in the presence of hydrogen, suggesting that it was a reaction intermediate. However, transient and steady-state kinetic measurements showed that the rate of reaction of the intermediate did not correspond to the overall reaction rate, and it is concluded that the pyridinium intermediate is not directly involved in the HDN reaction of pyridine over Ni2P. The studies demonstrate that mere observation of an adsorbed surface species at reaction conditions is not sufficient to prove that it is a reaction intermediate. The ACT method has potential as it can be used with any type of spectroscopy, as long as the surface coverage can be calibrated.

The transient reaction rate of a pyridinium species did not correspond to the overall reaction rate, demonstrating that mere observation of an adsorbed species is not sufficient to prove it is a reaction intermediate.Figure optionsDownload high-quality image (99 K)Download as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 263, Issue 2, 25 April 2009, Pages 359–371
نویسندگان
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