3D-printed zeolite with combined structure for xylene isomerization

Para-xylene (PX) is an important material for the production of polyester fibers and resins; it is widely used in fuel and medical fields. To alleviate the low strength and unsatisfactory mass-transfer performance of conventional catalysts during xylene isomerization, a combined-structure catalyst is fabricated using three-dimensional (3D) printing technology. In this study, a catalyst ink formulation and preparation method suitable for 3D printing is designed, and a wet ball-milling process is adopted to improve the stability of the ink during 3D printing. The mass-transfer performance of the structured catalysts are investigated via computational fluid dynamics simulation; thus, combined-structure catalysts with high diffusivity and high specific surface area are realized. Compressive strength tests and xylene isomerization reaction experiments are conducted on the three-dimensionally printed catalysts and extrudates. Compared with the extrudates, the three-dimensionally printed catalyst exhibits higher mechanical strength and better catalytic performance. Among the structured catalysts, the combined linear-staggered/wave-vertical (LS/WV) catalyst demonstrates the best overall performance with a PX concentration in xylene of 22.89% and a high ethylbenzene conversion of 36.70%, which is approximately 21.68% higher than the extrudates.