“…Titanium(IV) isopropoxide is regularly used, solely or in combination with TBT [ 28 , 29 , 60 , 68 , 77 , 93 , 97 , 100 ]. Zinc(II) acetate is also often used for the first step (Sb 2 O 3 is generally added for the polycondensation step) [ 30 , 31 , 34 , 35 , 36 , 48 , 58 , 59 , 102 ]. Dubois et al have synthesized a home-made titanium-silica complex that exhibited high catalytic activity [ 37 , 45 , 56 ].…”