Process for preparing a modified zeolite Y which process comprises subjecting zeolite Y having a silica to alumina molar ratio of at least 10 to calcination at a temperature of from 700 to 1000° C. wherein (i) the steam partial pressure is at most 0.06 bar at a temperature of from 700 to 800° C., (ii) the steam partial pressure is at most 0.08 bar at a temperature of from 800 to 850° C., (iii) the steam partial pressure is at least 0.03 bar at a temperature of from 850 to 900° C., and (iv) the steam partial pressure is at least 0.05 bar at a temperature of from 900 to 950° C. and (v) the steam partial pressure is at least 0.07 bar at a temperature of from 950 to 1000° C., a modified zeolite Y obtainable by such process, zeolite Y having a silica to alumina molar ratio of at least 10, the infrared spectrum of which has a peak at 3700 cm −1 but substantially no peaks at 3605 and 3670 cm −1 and zeolite Y having a silica to alumina molar ratio of at least 10, which zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 20 micromole/gram.
1. A process for preparing a modified zeolite Y which process comprises subjecting zeolite Y having a silica to alumina molar ratio of at least 10 to calcination at a temperature of from 700° C. to 1000° C. wherein (i) the steam partial pressure is at most 0.06 bar at a temperature of from greater than 700° C. to less than 800° C., (ii) the steam partial pressure is at most 0.08 bar at a temperature of from greater than 800° C. to less than 850° C., (iii) the steam partial pressure is at least 0.03 bar at a temperature of from greater than 850° C. to less than 900° C., and (iv) the steam partial pressure is at least 0.05 bar at a temperature of from greater than 900° C. to less than 950° C. or (v) the steam partial pressure is at least 0.07 bar at a temperature of from greater than 950° C. to less than 1000° C.
2. A process according to claim 1 , in which process the zeolite Y has a silica to alumina molar ratio of more than 10.
3. A process according to claim 2 , in which process the calcination is carried out during a time of from 20 minutes to 5 hours.
4. A process according to claim 3 , in which process the zeolite Y before calcination has a bulk silica to alumina molar ratio of greater than 13, a unit cell size in the range of from 24.10 to 24.40 Å, and a surface area of at least 875 m 2 /g.
5. The process of claim 1 wherein the modified zeolite Y has a silica to alumina molar ratio of at least 10, the infrared spectrum of which has a peak at 3700 cm −1 but substantially no peak at 3670 cm −1 .
6. A process according to claim 1 , in which process the zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 20 micromole/gram.
7. A process according to claim 6 , in which process the zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 10 micromole/gram.
8. A modified zeolite Y prepared by subjecting zeolite Y having a silica to alumina molar ratio of at least 10 to calcination at a temperature of from 700° C. to 1000° C. wherein (i) the steam partial pressure is at most 0.06 bar at a temperature of from greater than 700° C. to less than 800° C., (ii) the steam partial pressure is at most 0.08 bar at a temperature of from greater than 800° C. to less than 850° C., (iii) the steam partial pressure is at least 0.03 bar at a temperature of from greater than 850° C. to less than 900° C., and (iv) the steam partial pressure is at least 0.05 bar at a temperature of from greater than 900° C. to less than 950° C. or (v) the steam partial pressure is at least 0.07 bar at a temperature of from greater than 950° C. to less than 1000° C.
9. The modified zeolite Y of claim 8 wherein the zeolite Y has a silica to alumina molar ratio of more than 10.
10. The modified zeolite Y of claim 9 , wherein the calcination of the zeolite Y is carried out during a time of from 20 minutes to 5 hours.
11. The modified zeolite Y of claim 10 , wherein the zeolite Y before calcination has a bulk silica to alumina molar ratio of greater than 13, a unit cell size in the range of from 24.10 to 24.40 Å, and a surface area of at least 875 m 2 /g.
12. A zeolite Y having a silica to alumina molar ratio of at least 10, the infrared spectrum of which has a peak at 3700 cm −1 but substantially no peak at 3670 cm −1 .
13. A zeolite Y having a silica to alumina molar ratio of at least 10, which zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 20 micromole/gram.
14. The zeolite Y according to claim 13 , which zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 10 micromole/gram.
15. The modified zeolite Y of claim 8 having a silica to alumina molar ratio of at least 10, wherein the infrared spectrum of which has a peak at 3700 cm −1 but substantially no peak at 3670 cm −1 .
16. A process according to claim 8 , in which process the zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 20 micromole/gram.
17. A process according to claim 16 , in which process the zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 10 micromole/gram.
18. A method of using a zeolite, wherein a modified zeolite Y prepared by subjecting zeolite Y having a silica to alumina molar ratio of at least 10 to calcination at a temperature of from 700° C. to 1000° C. wherein (i) the steam partial pressure is at most 0.06 bar at a temperature of from greater than 700° C. to less than 800° C., (ii) the steam partial pressure is at most 0.08 bar at a temperature of from greater than 800° C. to less than 850° C., (iii) the steam partial pressure is at least 0.03 bar at a temperature of from greater than 850° C. to less than 900° C., and (iv) the steam partial pressure is at least 0.05 bar at a temperature of from greater than 900° C. to less than 950° C. or (v) the steam partial pressure is at least 0.07 bar at a temperature of from greater than 950° C. to less than 1000° C. is used as an adsorbent.
19. The modified zeolite Y of claim 18 wherein the zeolite Y has a silica to alumina molar ratio of more than 10.
20. The modified zeolite Y of claim 19 , wherein the calcination of the zeolite Y is carried out during a time of from 20 minutes to 5 hours.
21. The modified zeolite Y of claim 20 , wherein the zeolite Y before calcination has a bulk silica to alumina molar ratio of greater than 13, a unit cell size in the range of from 24.10 to 24.40 Å, and a surface area of at least 875 m 2 /g.
22. A method of using a zeolite, wherein a modified zeolite Y having a silica to alumina molar ratio of at least 10, the infrared spectrum of which has a peak at 3700 cm −1 but substantially no peak at 3670 cm −1 is used as an adsorbent.
23. A method of using a zeolite, wherein a modified zeolite Y having a silica to alumina molar ratio of at least 10, which zeolite Y has an acidity as measured by exchange with perdeuterated benzene of at most 20 micromole/gram is used as an adsorbent.