Temperature-Programmed Desorption

temperature

time

reaction order

0

1

2

activation energy /kJ

150

coverage

0.5

heating rates K

-1

s

β = 1

β = 3

β = 10

Catalytic mechanisms and desorption from solids are studied using temperature-programmed desorption. In such a measurement, a molecule is adsorbed on a solid surface, the temperature is ramped linearly with time, and the rate of desorption is measured, usually with a mass spectrometer. This is essentially a small batch reactor whose temperature increases linearly with time. This Demonstration shows temperature-programmed desorption curves for three heating rates (1, 3, and 10 K/s). Changing heating rate is often used to determine heats of desorption. You can change the order of reaction, activation energy, and coverage. The rate of desorption is plotted either as a function of time or as a function of temperature.