Mixed oxide compositions and process for preparing isoolefins
View Patent ↗The present invention relates to mixed oxide compositions, to the use thereof as a catalyst for cleavage of alkyl tert-alkyl ethers or tertiary alcohols, and to a process for cleaving alkyl tert-alkyl ethers or tertiary alcohols to isoolefins and alcohol or water.
1. A process, comprising:
cleaving a starting compound of formula II:
to isoolefins of formula I:
and a compound of formula III:
R—OH III
in the presence of a catalyst,
wherein
R is H or an alkyl radical having one carbon atom or two carbon atoms,
R1 is H, or a methyl or ethyl radical, and
R2 and R3 are each independently a methyl or ethyl radical, and
wherein the catalyst comprises a silicon-aluminium mixed oxide powder, present predominantly or completely as aggregated primary particles, and
an alkali metal or alkaline earth metal oxide,
wherein a weight ratio (Al 2 O 3 /SiO 2 ) gt in the primary particles is from 0.002 to 0.05,
a weight ratio (Al 2 O 3 /SiO 2 ) surface of the primary particles in a layer close to a surface and having a thickness of approximately 5 nm is less than in the primary particles overall and
a BET surface area of the primary particles is from 50 to 250 m 2 /g.
2. The process according to claim 1 , wherein the starting compound is methyl tert-butyl ether.
3. The process according to claim 1 , wherein the starting compound is tert-butyl alcohol.
4. The process according to claim 3 , wherein the starting compound is tert-butanol in an azeotropic mixture with water.
5. The process according to claim 1 , wherein the cleaving is at a temperature of from 110 to 450° C.
6. The process according to claim 1 , wherein the cleaving is at a pressure of from 0.1 to 2 MPa(abs).
7. A process, comprising:
cleaving a starting compound of formula II:
to isoolefins of formula I:
—R 2
and a compound of formula III:
R—OH III
in the presence of a catalyst,
wherein R is H or an alkyl radical having one carbon atom or two carbon atoms,
R1 is H, or a methyl or ethyl radical, and
R2 and R3 are each independently a methyl or ethyl radical, and
wherein the catalyst comprises:
a silicon-aluminium mixed oxide powder, present predominantly or completely as aggregated primary particles,
wherein a weight ratio (Al 2 O 3 /SiO 2 ) nt in the primary particles is from 0.002 to 0.05,
a weight ratio (Al 2 O 3 /SiO 2 ) surface of the primary particles in a layer close to a surface and having a thickness of approximately 5 nm is less titan in the primary particles overall,
a BET surface area of the primary particles is from 50 to 250 m 2 /g, and
the composition is obtained by a process comprising treating with acidic aqueous solution, wherein a pH is within a range from 0 to 6.