SiO2Al2O3 ratios of ZSM—5 crystals measured by electron microprobe and X-ray diffraction

Abstract An X-ray diffraction technique has been developed for estimating the SiO 2 Al 2 O 3 ratio in ZSM—5 crystals with ratios varying from 30 to 150. The 26 value in degrees for the (10, 0, 0; 804) peak minus the 2θ value for the (0, 10, 0) peak is used for the measurement. Both bulk and electron microprobe analyses of individual crystals were used to check the composition of the crystals. Similar Δ2θ values were obtained with NH 4 + , Na + , and H + as exchangeable cations. After the crystals were used as catalysts, their Δ2θ values decreased, indicating a decrease in the a axis of approximately 0.05 A and an increase in the b axis of approximately 0.05 A. Two possible causes of these shifts are changes in the SiO 2 Al 2 O 3 ratio of the ZSM—5 framework, or filling of the pores of the zeolite.