Prepn. of coatings of spinel - by hydrolysing magnesium aluminium-alkoxide in presence of water, peptising suspension with acid, ageing suspension, coating substrate with resulting colloidal soln., drying and calcining

摘要

Prepn. of coatings of spinel (MgOAl2O3, MgAl2O4) (I) comprises: (i) hydrolysing a mixed alkoxide (Mg-Al-double alkoxide) of formula MgAl2(OR)8 or Mg(Al(OR)4)2, where R = identical or different branched or linear 1-10 pref. 3-4C alkyl; opt. in the presence of a solvent and/or catalyst and opt. under the addn. of additives, by the action of water, of moisture or of water-contg. solvent with at least enough water for complete hydrolysis of the hydrolysable gps.; (ii) peptising the resulting Mg-Al-hydroxide-suspension with an acid; (iii) aging the suspension to form a colloidal Mg-Al-hydroxide soln.; (iv) coating of a substrate with the colloidal Mg-Ag-hydroxide soln.; (v) drying and calcining the spinel-coated substrate. USE/ADVANTAGE - (I) are used in the coating of microporous substrates for the mfr. of ultrafiltration- or gas sepn. membranes and in the mfr. of substrate-less coatings by coating of a substrate with a thick layer of the colloidal soln. and removal of it from the substrate after drying. They are also used to coat substrates for the prepn. of substrate materials for catalyst, indicators or enzymes. The spinel particles have a narrow grain size distribution and their size can be controlled. They are arranged regularly within the coating so that the pores between them have a narrow pore-radius distribu