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Nonlinear desorption activation energy from TPD curves: Analysis of the influence of initial values for the regression procedure
Author(s) -
Pirola Carlo,
Di Michele Alessandro
Publication year - 2020
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.23700
Subject(s) - desorption , activation energy , nonlinear regression , polynomial , thermal desorption spectroscopy , thermodynamics , nonlinear system , frequency factor , polynomial regression , energy (signal processing) , catalysis , curve fitting , function (biology) , mathematics , chemistry , regression analysis , materials science , mathematical analysis , adsorption , physics , statistics , organic chemistry , quantum mechanics , evolutionary biology , biology
Thermal programmed desorption (TPD) is a powerful technique for materials and catalysts characterization. By analyzing TPD curves, it is possible to calculate important parameters as the desorption activation energy, E d , that depends on the surface coverage ( θ ) by a nonlinear polynomial function, ie, E d θ = ∑ k = 0 N α k1 − θ k . The Polanyi‐Wigner equation, − dθ dT =A θ βθ n exp− E d θ RT , can be used as theoretical basis to calculate this parameter, by a fitting regression procedure starting from experimental TPD data. Different degrees (k) for this polynomial equation and different initial values of the frequency factor A ( θ ) were considered and discussed to obtain the univocal value of desorption energy. Three different Pt and Co based catalysts, suitable for hydrogenation reactions, have been considered as case studies for the application and validation of the proposed calculation procedure.