Catalyst for epoxidation reactions and preparation thereof

A process for the manufacture of catalysts comprising amorphous titanium doped silica with pentahedrally coordinated titanium species, said process comprising the following steps:

• a) sol-gel-synthesis of a catalyst hydrogel-precursor, comprising the steps:
• i) adding water glass exhibiting a viscosity in the range of 400 to 600 mPa*s into an acid, thereby yielding silica gel exhibiting a residual water content, Xwa, in the range between Xw1 and Xw2;
• ii) removing impurities from said silica gel by washing the silica gel with an acidic aqueous solution, thereby yielding purified silica gel;
• iii) forming a catalyst hydrogel-precursor by either alternative a) or b) as follows:
• alternative a):
• doping said purified silica gel by contacting it with an acidic aqueous solution of a titanium salt, thereby yielding titanium-doped silica gel;
• and
• aging said titanium-doped silica gel by suspending the titanium-doped silica gel in an aging-solution for between 4 h and 6 h at a temperature between 60° C. and 90° C., wherein the liquid part of the suspension formed thereby exhibits a pH value of 5.5 to 7.5;
• thereby yielding the catalyst hydrogel-precursor having a titanium content, Xt, in the range between Xt1 and Xt2;
• alternative b):
• aging said purified silica gel by suspending it in an aging solution for between 4 h and 6 h at between 60° C. and 90° C., wherein the liquid part of the suspension formed thereby exhibits a pH value in the range of 5.5 to 7.5;
• thereby yielding aged, purified silica gel;
• and
• doping said aged, purified silica gel by contacting it with an acidic aqueous solution of a titanium salt;
• thereby yielding the catalyst hydrogel-precursor having a titanium content, Xt. in the range between Xt1 and Xt2;
• b) drying the catalyst hydrogel precursor to a residual water content, Xwb, of the dried catalyst hydrogel-precursor in a range between Xw3 and Xw4;
• c) calcining the dried catalyst hydrogel-precursor;
• wherein:
• Xw1=40 wt %, Xw2=60 wt %;
• Xt1=0.85 wt %, Xt2=1.9 wt %;
• Xw3=1 wt %, Xw4=7 wt %;
• the residual water content, Xwa and Xwb, is determined as the weight loss exhibited by a 100 g aliquot after drying at 200° C. for four hours in a drying cabinet under atmospheric conditions;
• the titanium content, Xt, of samples is determined by elemental analysis via optical emission spectrometry with inductively coupled plasma (ICP-OES);
• and
• the Ti content of solid materials is calculated on a dry-mass basis and corresponds to the content of elemental titanium.