The ZSM-5 samples prepared by different synthesis routes have different acid properties. The surface acid properties of four ZSM-5 samples were investigated by NH3-TPD and pyridine FT-IR experiments. As shown in Fig. 9, all ZSM-5 samples have two NH3desorption peaks at 186-189 ℃ and 387-405 ℃, which correspond to weak acid sites and strong surface acid sites, respectively [44]. The acid amount and acid strength of samples are reflected by peak area and peak position of the TPD profile, respectively [45]. As shown in Table 3, acid amount and strong surface acid strength of ZSM5-RS and ZSM5-RD increase significantly compared with ZSM5-SS and ZSM5-SD. Moreover, the desorption temperature of ammonia from the strong acid sites shifted to higher temperatures as inducing RPB in the premix process, which indicates the increase of Al content in extra-framework positions [34]. In comparison with ZSM5-SS, the acid amount and acid strength of ZSM5-SD have a slight growth. A possible reason is that the enhancement of micromixing in the STR affects the acid properties of zeolites in the crystallization process.