Dehydration-hydrolysis processes and catalysts therefor
Crystalline zeolites having a FER framework type wherein the crystallites have a dimension in the c-axis of about 500 nanometers (nm) or less, a method for their preparation and a process for the co-production of acetic acid and dimethyl ether comprising the step of contacting methyl acetate and methanol in the presence of catalysts comprising the crystalline zeolites.
1. A crystalline zeolite having a FER framework type wherein the crystallites of the zeolite have a dimension in the c-axis of about 500 nanometers (nm) or less, a ratio of the dimension in the c-axis to the dimension in the b-axis being less than or equal to 3:1; and wherein 1 mol % to 60 mol % of the cation exchange capacity of the crystalline zeolite is occupied by cations of an alkali metal, said alkali metal being cesium.
2. The zeolite according to claim 1 wherein the crystallites have a dimension in the c-axis of about 350 nm or less.
3. The zeolite according to claim 2 wherein the crystallites have a dimension in the c-axis of about 50 nm to about 350 nm.
4. The zeolite according to claim 1 wherein the crystallites have a dimension in the c-axis of about 250 nm or less.
5. The zeolite according to claim 4 wherein at least 70% of the crystallites have a dimension in the c-axis of about 250 nm or less.
6. The zeolite according to claim 5 wherein the crystallites have a dimension in the c-axis of about 50 nm to about 250 nm.
7. The zeolite according to claim 1 wherein the crystallites have an oblong-like morphology.
8. The zeolite according to claim 1 wherein the zeolite has a mesopore volume of at least 0.1 cm 3 /g as measured by N 2 absorption.
9. The zeolite according to claim 8 wherein the mesopore volume is 0.1 to 0.2 cm 3 /g as measured by N 2 absorption.
10. The zeolite according to claim 1 wherein the zeolite is ferrierite.
11. The zeolite according to claim 5 wherein the zeolite has a mesopore volume of at least 0.1 cm 3 /g as measured by N 2 absorption.
12. The zeolite according to claim 11 wherein the zeolite is ferrierite.
13. The zeolite according to claim 1 wherein at least 70% of the crystallites have a dimension in the c-axis of about 250 nm or less.
14. The zeolite according to claim 13 , wherein 5 mol % to 50 mol % of the cation exchange capacity of the zeolite is occupied by cations of an alkali metal, said alkali metal being cesium.
15. The zeolite according to claim 1 wherein the zeolite is ZSM-35.
16. The zeolite according to claim 1 wherein 5 mol % to 50 mol % of the cation exchange capacity of the zeolite is occupied by cations of an alkali metal, said alkali metal being cesium.
17. The zeolite according to claim 1 wherein the ratio of the dimension in the c-axis to the dimension in the b-axis is less than or equal to 2:1.
18. A catalyst comprising the zeolite according to claim 1 and a refractory oxide binder.
19. A process for producing the crystalline zeolite according to claim 1 , the process comprising providing an aqueous synthesis mixture of silica, alumina, alkali metal ion and a saturated nitrogen-containing heterocyclic compound and heating said mixture under stirred conditions until zeolitic crystallites of the crystalline zeolite form.
20. The process of claim 19 , further comprising contacting the zeolitic crystallites with an aqueous solution of cesium ions.