* The profile is defined as; initial temperature/time → final temperature/time
The XRD patterns of synthesized membranes listed in Table 5 are shown in Fig. 7. These patterns indicate high crystallinity of zeolite ZSM-5 formed on the surface of tubular alumina supports. As expected, starting the synthesis at low temperature reinforces the nucleation reactions against the crystal growth reactions. So, a larger number of nuclei are produced. In the following, increasing temperature, immediately, shifts the dominant reactions from nucleation to growth reactions. So, at the end of synthesis, a larger number of smaller crystals compared to those formed in isothermal synthesis, are produced. It may also reduce the thickness of the zeolite layer, but, produce a more integrated and uniform layer with eliminated inter-crystalline gaps. The results confirm that for a constant total synthesis time, the longer the exposure time to higher temperatures, the higher the crystallinity, the thicker the zeolite layer, and less inter-crystalline gaps.