A CATALYTIC METHOD FOR THE QUANTITATIVE-EVALUATION OF CRYSTALLINITIES OF ZSM-5 ZEOLITE PREPARATIONS

For a series of ZSM-5 zeolites, in which the aluminum contents range from 0.2-1.7% by mass, it is shown that the catalytic activity in terms of n-hexane cracking is proportional to the amount of aluminum in the samples. Amorphous silica-alumina, on the other hand, exhibits extremely low activity in terms of this catalytic test reaction (CTR). The use of this CTR for the determination of the amount of zeolitic aluminum in ZSM-5 samples has therefore been examined as a means of evaluating % crystallinity. The catalytic results are then compared with those from XRD analysis where use was made of three different sets of peaks in the diffractograms. The summation of the intensities of the peaks between 22 and 25-degrees 2-thea and, to a slightly lesser extent, the intensity of the peak at 23.1-degrees 2-theta were found to be in closer agreement with the CTR results. It is further demonstrated that this CTR can be used to monitor the extent of crystallization of batches of ZSM-5 zeolites. Elemental analyses for aluminum were also found to be useful in this regard.