Synthesis of ZSM-type zeolites from biowaste gasification ashes

Biowaste is one of the typical types of domestic energy sources. Most of these biomass materials contain a high amount of organic volatiles. Gasification ashes of these biowastes containing 70-87% amorphous silica would make the biowaste ash utilization systems highly economically and environmentally attractive. Zeolite ZSM-5 or ZSM-48 with a high crystallinity was synthesized from a reaction mixture containing a silica source from mixed gasification ashes, containing 70-87% amorphous silica, of agricultural biowastes, such as sugar cane bagasse, sugar cane leaf, rice straw, and corn leaf. The ashes obtained from the biowastes by gasification at low temperatures contained amorphous silica, while ash formed at a higher temperature (> 923 K) contained mostly crystalline silica. For the synthesis of zeolite ZSM-5 or ZSM-48 with silica from biowaste gasification wastes, relatively lesser NaOH (NaBr) or greater silica content in the initial mixture of hydrogel was required compared to the synthesis of the ZSM-5 type zeolites by using silica mainly from the chemical sources. Pure ZSM-5 or ZSM-48 could be obtained only with a Si/Al ratio of > 60:1 or > 350:1, respectively.