摘要:
The relationship of the structural organization and acid-base properties of the surface of phosphorus titanate oxides prepared from tetra-n-butoxytitanium and phosphorous esters with the catalytic activity and selectivity of these materials in ethylene glycol oxyethylation was studied. Single-phase phosphorus-containing oxides synthesized from 2-diethylamido-4-methyl-1,3,2-dioxophosphorinane and diphenyl(methano)phosphocane have strong surface aprotic acid sites and exhibit high catalytic activity with respect to oxyethylation and a record-breaking selectivity in the formation of the lower homolog, diethylene glycol. The last-mentioned fact is a consequence of the sieve effect exerted by the homogeneous porous structure of supermicropores (8-10 Angstrom) of the oxides. An increase in the concentration of the strong acid sites (greater than or equal to130 kJ mol(-1)) on the oxide surface enhances the catalytic activity. On the basis of the temperature programmed desorption of ammonia and CO2 and kinetic measurements, a concerted acid-base mechanism was proposed for the catalytic addition of ethylene oxide to ethylene glycol on the phosphorus-titanate surface.