EFFECT OF ACID TREATMENT ON THE STRUCTURE AND ACIDITY OF BETA-ZEOLITE

The effect oi acid treatment on the structure and acidity of beta zeol ite was investigated. It was found that beta zeolite is easily dealumi nated by acid treatment, but it can resist 5 mol/L HCl solution. The d egree of dealumination is higher than 80% in the 5 mol/L HCl solution. In the acid solution the stability of polymorph (A) is less than that of (B). The chiral of beta zeolite can be modified by acid treatment. The results of adsorption, NH3-TPD and pyridine-IR show that the pore volume does not change obviously, the acid strength of sample changes with acid treatment and reaches its maximum in the sample with the Si /Al of 38.8. L acid is the main acid sites on the surface and increase s with increasing the value of Si/Al ratio.