Patent ID: 7867766

Claim:
A method for measuring the active site concentration of a catalyst powder, comprising the steps: (a) providing a metal block having a cavity with a plurality of valved openings on the cavity circumference; (b) providing valving means for a first valved opening and preparing a cleaning gas therein; (c) providing pulsed valving means for a second valved opening and preparing a feed gas comprising at least one reactant and an inert gas therein; (d) providing a demountable sample tube, disposing at least the catalyst powder as a packed bed therein, and attaching it at the upstream end to the mouth of the cavity, wherein the number of active sites on the catalyst powder is less than 100 times the number of adsorbate fragments in the largest gas pulse that is sufficiently small to satisfy the condition for Knudsen flow whereby the response curve shape of each gas pulse of a different size is different; (e) providing gas removing means that is in communication with the downstream end of the sample tube; (f) providing a furnace that encloses the packed bed; (g) heating and cleaning the catalyst powder by a delivery of cleaning gas using the valving means and removing gas using the gas removing means; (h) stopping the delivery of cleaning gas and desorbing adsorbed gas from the catalyst powder by heating and removing gas using the gas removal means to provide a vacuum in the sample tube; (i) providing for the packed bed to be at an adsorption temperature, using the pulsed valving means to deliver a feed gas pulse into the sample tube, and removing gas using the gas removal means, wherein the feed gas pulse is sufficiently small so that the feed gas flows in Knudsen flow; (j) providing at least two gas concentration measuring means that are in communication with the downstream end of the sample tube, measuring the response curves of the inert gas and at least one reactant as they are removed, and using the area of the inert gas response curve to calculate the injected pulse size; (k) using a mathematical model and fitting at least the response curve of the reactant to extract the active site concentration on the catalyst powder, and (l) repeating steps (g) to (k) using a different pulse size in step (i), wherein the largest and smallest pulses differ by at least ten-fold.