Synthesis, characterization, and catalytic application of hierarchical nano-ZSM-5 zeolite

Preparation of a High-Silicon ZSM-5 Molecular Sieve Using Only Coal Gangue as the Silicon and Aluminum Sources

The traditional preparation of ZSM-5 molecular sieves relies on chemical reagents to provide silicon and aluminum sources, which are limited as raw materials and cannot be commonly used in production practice. Using coal gangue as the raw material and using medium-temperature chlorination roasting and the pressure acid leaching process to control the silicon-aluminum ratio [n(Si/Al)] of coal gangue, a ZSM-5 molecular sieve was prepared using the alkali melting hydrothermal method. The pressure acid leaching process solved the limitation that kaolinite and mica cannot simultaneously be activated. Under optimal conditions, the n(Si/Al) of the coal gangue increased from 6.23 to 26.14 and complied with the requirements for the synthesis n(Si/Al) of a ZSM-5 molecular sieve. The effect of n(Si/Al) on the preparation of the ZSM-5 molecular sieve was studied. Finally, spherical granular ZSM-5 molecular sieve material with a microporous specific surface area of 169.6329 m²/g, an average pore diameter of 0.6285 nm, and a pore volume of 0.0988 cm³/g was prepared. Providing ideas for the high-value utilization of coal gangue, it is significant for solving the problem of coal gangue solid waste, as well as the problem of ZSM-5 molecular sieve feed stock.

Effects of a Cellulose Aerogel Template on the Preparation and Adsorption Properties of Coal Gangue-Based Multistage Porous ZSM-5

In this study, a ZSM-5/CLCA molecular sieve was prepared by the hydrothermal method using coal gangue as the raw material and cellulose aerogel (CLCA) as the green templating agent, which not only reduces the cost of traditional molecular preparation but also improves the comprehensive resource utilization rate of coal gangue. Through a series of characterization methods (XRD, SEM, FT-IR, TEM, TG, and BET), the crystal form, morphology, and specific surface area of the prepared sample were tested and analyzed. The performance of the adsorption process of malachite green (MG) solution was analyzed by adsorption kinetics and adsorption isotherm. The results show that the synthesized zeolite molecular sieve and the commercial zeolite molecular sieve are highly consistent. At a crystallization time of 16 h, a crystallization temperature of 180 °C, and an additive amount of cellulose aerogel of 0.6 g, the adsorption capacity of ZSM-5/CLCA for MG was up to 136.5 mg/g, much higher than that of commercially available ZSM-5. This provides an idea for the green preparation of gangue-based zeolite molecular sieves to remove organic pollutants from water. Moreover, the process of adsorbing MG on the multistage porous molecular sieve, which is spontaneous, conforms to the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model.