The TPAD experiment generally follows these steps:
Pre-treatment: The catalyst sample is first pre-treated by heating it in a flow of an inert gas (e.g., nitrogen) to remove any impurities or pre-adsorbed species. Ammonia Adsorption: The sample is then exposed to a flow of ammonia gas at a low temperature (usually room temperature or below) to allow NH3 to adsorb onto the acid sites. Desorption: After adsorption, the temperature is gradually increased at a controlled rate. The desorbed ammonia is usually monitored by a thermal conductivity detector (TCD) or mass spectrometer (MS). Data Analysis: The resulting desorption profile (TPAD curve) is analyzed to determine the strength and density of acid sites.
