PRODUCTION OF CATALYSTS BASED ON BORON ZEOLITES
The process described here has made it possible to obtain boron-containing silicates having a zeolitic structure which display negligible DME and C 8 selectivities combined with high activities when used as catalysts for the dissociation of MTBE.
1 . A process for producing a catalyst based on boron-containing silicates having a zeolitic structure, which comprises:
a) providing an aqueous suspension containing at least one boron-containing silicate having a zeolitic structure,
b) adding acid to set a pH in the range from 1 to 5,
c) stirring the suspension,
d) isolating the solid obtained,
e) optionally, washing the solid,
f) calcining the solid.
2 . The process according to claim 1 , wherein the at least one boron-containing silicate has a zeolitic structure of an MFI type.
3 . The process according to claim 1 , wherein the silicate present in the suspension has a molar ratio of SiO 2 /B 2 O 3 in the range from 2 to 4.
4 . The process according to claim 1 , wherein the silicate present in the suspension has an aluminium content of less than 0.1% by weight.
5 . The process according to claim 1 , wherein the silicate present in the suspension has, at least after addition of the acid, a boron content of less than 1% by weight.
6 . The process according to claim 1 , wherein the silicate in step a) has a surface area measured by the BET method ranging from 300 m 2 /g to 500 m 2 /g.
7 . The process according to claim 1 , wherein the setting of the pH in step b) is effected by addition of hydrochloric acid.
8 . The process according to claim 1 , wherein the setting of the pH in step b) is effected by addition of phosphoric acid.
9 . The process according to claim 1 , wherein the stirring of the suspension in step c) is carried out at not more than 80° C.
10 . The process according to claim 9 , wherein the stirring of the suspension in step c) is carried out at not more than 25° C.
11 . The process according to claim 1 , wherein the stirring of the suspension in step c) is carried out for a period of at least 24 hours.
12 . The process according to claim 1 , wherein isolation of the solid in step d) is carried out by vacuum filtration or by superatmospheric pressure filtration.
13 . The process according to claim 1 , wherein the solid is washed with water in step e).
14 . The process according to claim 1 , wherein calcination of the solid in step f) is carried out at a temperature of not more than 500° C.
15 . The process according to claim 1 , wherein the calcination of the solid in step 0 is carried out in a nitrogen-containing atmosphere.
16 . The process according to claim 1 , wherein the solid obtained in step 0 is washed with water and step f) is subsequently repeated.
17 . The process according to claim 1 , wherein the calcined solid is treated with methanol.
18 . A catalyst comprising a boron-containing silicate which has a zeolitic structure that can be obtained by a process according to claim 1 .
19 . The catalyst according to claim 18 , wherein the zeolitic structure is of an MFI type.
20 . The catalyst according to claim 18 , which has a proportion of boron less than 1% by weight.