Preparation of Adamantane Over Meso-H-Mordenite Zeolites

Desilicated mesoporous H-mordenites(HM)including template tetraethylammonium hydroxide with low Si/Al molar ratio were prepared by sequential acid and alkaline treatments.The physical chemical properties of these prepared catalysts were characterized by X-ray diffraction(XRD),liquid N2 adsorption-desorption,NH3 program temperature desorption(NH3-TPD)and scanning electron microscopy(SEM)techniques,and their catalytic performances were investigated in the preparation of adamantane(ADH)from endo-tetrahydrodicyclotadiene(endo-TCD)isomerization in a 100 mL stainless steel batch reactor equipped with a stirrer.The Si/Al molar ratio could be reached to 30.1 from 8.9 through acid treatment with 6mol/L HCl aqueous solution,and mesopores could be introduced into the structure of H-mordenite zeolite when the crystal morphology could be preserved by the following alkaline treatment with different concentrations of NaOH aqueous solutions.When the alkaline treatment concentration of NaOH aqueous solutions was 0.2mol/L,the prepared mesoporous HM-6H-0.2 zeolite showed higher catalytic performance than the HM series catalysts treated by other concentrations of NaOH solution,due to its appropriate acid properties and well diffusion properties.The influences of various reaction conditions on the catalytic performance of HM-6H-0.2 zeolite in ADH synthesis were discussed.The endo-TCD conversion of 98.5% and the ADH yield of 33.7% were obtained with the m(HM-6H-0.2)/m(endo-TCD)=0.6,reaction temperature of 260℃,reaction time of 6h.The catalytic activity of used catalyst could be recovered with the ADH yield of 28.5% after 5times reuse.