Prepn. of bridged clays for use as catalysts in petrochemical industry

摘要

Fluorine-contg. clay are synthesised in acid medium and then bridged by a process comprising: (A) contacting clay having exchangeable cations with a soln. of polycations to form a reaction mixt. contg. 1-200 g/l of the clay; (B) maintaining the temp. of the reaction mixt. at 15-100 deg C and allowing exchange to take place between the polycations and the exchangeable cations in the clay for 1 min. to 3 h.; and (C) separating the resulting prod. by filtration and washing it, the time for the sepn. being 20 sec. to 60 mins. per litre of the soln. contg. the suspended prod. to be separated. Pref. polycations are Keggin ions of formula (Al13O4(OH)24(H2O)12)7+, or polycations contg. at least one element chosen from Zr, Ti, Mo and V. Stage (A) may be carried out either by adding a soln. of the polycations to an aq. suspension of the clay, or by suspending the clay in a soln. of the polycations. Pref. the ratio R between the amt. of polycations multiplied by the charge on the polycation and the amt. of exchangeable cations present in the clay multiplied by their charge is between 0.5 and 10. The process may also comprise a fourth stage (D) in which the treated clay is first dried by heating in air at 30-150 deg C for 2-48 h and then calcined at 300-800 deg C for 1-10 h. The treatment process may be repeated successively 2-10 times.