Efficient and controllable synthesis of zeolite Beta nanospheres and hollow-boxes using a temperature-sensitive bifunctional additive

Zeolite Beta nanospheres and hollow-boxes are successfully obtained through a simple one-pot hydrothermal crystallization route, using tetraethylammonium hydroxide (TEAOH) as the structure-directing agent (SDA) assisted with a temperature-sensitive bifunctional additive N-methyl-2-pyrrolidone (NMP). The influences of crystallization temperature, Si/Al ratio, and TEAOH content on the synthesis and physicochemical properties of zeolite Beta as well as the formation of hollow structure are investigated in detail. It reveals that the role of NMP changes from crystallization promoter (CP) to hollow-directing agent (HDA). And the acceleration effect of NMP decreases upon the crystallization temperature (120-160 degrees C) due to the decomposition of TEAOH. Meanwhile, high synthesis temperature (>= 180 degrees C), high Si/Al ratio (>= 30), and low TEAOH content (TEAOH/ SiO2 <= 0.2) may lead to the formation of undesired zeolites ZSM-5 and/or ZSM-12. The obtained Beta nanosphere and hollow-box catalysts exhibit excellent catalytic activity in the degradation of low-density polyethylene (LDPE) due to their high external surface area and acid density.

Automated summary

Zeolite Beta nanospheres and hollow-boxes were successfully synthesized using a simple hydrothermal method. The role of NMP changed with the variation of crystallization temperature and TEAOH content. Undesired zeolites may be formed under high synthesis temperature, high Si/ Al ratio, and low TEAOH content. The obtained catalysts exhibited excellent catalytic activity.