Evaluation of the use of silica extracted from industrial waste with an ultrasonic bath and modifications to the aging stage in the synthesis of ZSM-5 and its application in pyrolysis

• ZSM-5 zeolite was obtained from RHA without template. • The ultrasound was positive in the extraction and aging stages of the synthesis. • The use of ultrasound was essential to obtain ZSM-5 with a surface area of 278 m 2 /g. • The use of ultrasonically extracted silica influenced the synthesis of ZSM-5. • The application of ZU3 increased in the pyrolysis, increasing the gas phase production. Rice husk ash is an industrial residue composed essentially of silica that can be used as an alternative source of silica for the synthesis of ZSM-5 zeolite. This study aimed to obtain ZSM-5 zeolite without organic structure-directing agents, evaluating the use of silica extracted from industrial rice husks using an ultrasonic bath. The effect of ultrasound was also evaluated in the aging stage of the zeolite. The catalytic potential of the synthesized zeolite was measured in the pyrolysis of rice husks. XRF, XRD, BET, and SEM-EDS characterization were performed on the synthesized zeolites. It was possible to obtain the ZSM-5 zeolite under all the synthesis conditions studied. Still, the silica extraction method and the aging method were decisive for the formation of the crystalline phase and the surface area of the synthesized zeolite. The use of silica extracted with an ultrasonic bath promoted the most crystalline ZSM-5 phase in the samples and the highest surface areas. The ZU3 zeolite had the highest BET surface area of 277.5 m 2 /g, which was attributed to the use of ultrasound. The application of ZU3 zeolite increased the gas phase production in rice husk pyrolysis to 45 % due to its action in cracking reactions.