A CHA TYPE ZEOLITE AND THE METHOD OF SYNTHESISING SAID ZEOLITE
A hydrogen-form chabazite (CHA) zeolite having a SAR of from 8 to 35 with a ratio of the XRD peak intensity corresponding to [2 1 1] and [−1 1 1] reflection equal to or greater than 0.80. The CHA zeolite can be made by a method comprising: (i) forming a reaction gel comprising a precursor zeolite (e.g. FER), an organic structure directing agent (OSDA), sodium and/or potassium hydroxide and optionally a silica source, and (ii) heating the reaction gel to a temperature and for a duration suitable for the growth of the CHA zeolite. Suitable OSDAs for step (i) include N,N,N-trimethyl-1-adamantylammonium, N,N,N-dimethylethylcyclohexylam monium, trimethyl(cyclohexylmethyl) ammonium, tetraethylammonium, N-Ethyl-N,N-dimethylcyclohexanaminium, benzyltrimethyl ammonium, N,N,N-triethylcyclohexylammonium, N,N,N-trimethylcyclohexyl ammonium, N,N,N-diethylmethylcyclohexyl ammonium, trimethyl cyclohexyl ammonium, trimethyl phenyl ammonium and triethylmethyl ammonium.
1 . A hydrogen-form chabazite (CHA) zeolite having a SAR of from 8 to 35 with a ratio of the XRD peak intensity corresponding to [2 1 1] and [−1 1 1] reflection equal to or greater than 0.80.
2 . A hydrogen form CHA zeolite according to claim 1 having a SAR of from 8 to 17 with a ratio of the XRD peak intensity corresponding to [2 1 1] and [−1 1 1] reflection equal to or greater than 0.95.
3 . A hydrogen form CHA zeolite according to claim 1 having a SAR of from 17 to 24 with a ratio of the XRD peak intensity corresponding to [2 1 1] and [−1 1 1] reflection equal to or greater than 0.85.
4 . A hydrogen form CHA zeolite according to claim 1 having a SAR of from 24 to 34 with a ratio of the XRD peak intensity corresponding to [2 1 1] and [−1 1 1] reflection equal to or greater than 0.80.
5 . The hydrogen-form CHA zeolite according to claim 1 , wherein the CHA zeolite comprises uniform and non-aggregated cuboid crystals with an average size of from 1 to 10 pm.
6 . The hydrogen-form CHA zeolite according to claim 1 , wherein the CHA zeolite comprises uniform and non-aggregated conglomerate crystals.
7 . The hydrogen-form CHA zeolite according to claim 1 , wherein the CHA zeolite comprises a mixture of (a) uniform and non-aggregated cuboid crystals with an average size of from 1 to 10 pm and (b) uniform and non-aggregated conglomerate crystals.
8 . The hydrogen-form CHA zeolite according to claim 1 , wherein the zeolite has a crystallinity of greater than 90%.
9 . A method for the manufacture of a chabazite (CHA) zeolite having an SAR of from 8 to 35, the method comprising:
(i) forming a reaction gel comprising a precursor zeolite, an organic structure directing agent (OSDA), sodium and/or potassium hydroxide and optionally a silica source, and
(ii) heating the reaction gel to a temperature and for a duration suitable for the growth of the CHA zeolite.
10 . The method according to claim 9 , wherein the precursor zeolite is selected from FER, FAU, MFI, BEA and LTL.
11 . The method according to claim 9 , wherein the precursor zeolite is prepared from an organic structure directing agent-free synthesis gel or prepared from a synthesis gel which contains an organic structure directing agent.
12 . The method according to claim 9 , wherein the precursor zeolite is prepared by a process comprising:
(a) forming a reaction gel comprising an aluminium source, sodium and/or potassium hydroxide and a silica source,
(b) heating the reaction gel to a temperature and for a duration suitable for the growth of a FER zeolite, and optionally
(c) filtering and washing the resulting FER zeolite.
13 . The method according to claim 12 , wherein the reaction gel does not comprise an OSDA.
14 . The method according to claim 12 , wherein the FER zeolite product and associated mother liquor formed in step (b) is used directly, without separation of the FER zeolite from the mother liquor.
15 . The method according to claim 9 , wherein the OSDA used in step (i) is selected from one of more of the following: N,N,N-trimethyl-1-adamantylammonium, N,N,N-dimethylethylcyclohexylammonium, trimethyl(cyclohexylmethyl) ammonium, tetraethylammonium, N-Ethyl-N,N-dimethylcyclohexanaminium, benzyltrimethyl ammonium, N,N,N-triethylcyclohexylammonium, N,N,N-trimethylcyclohexyl ammonium, N,N,N-diethylmethylcyclohexyl ammonium, trimethyl cyclohexyl ammonium, trimethyl phenyl ammonium and triethylmethyl ammonium.
16 . The method according to claim 9 , wherein the reaction gel of step (i) does not comprise CHA seed crystals.
17 . The method according to claim 9 , wherein the temperature of step (ii) is from 100° C. to 200° C., preferably from 110° C. to 190° C.
18 . The method according to claim 9 , wherein the duration of step (ii) is at least 10 hours, preferably 20 to 60 hours.
19 . The method according to claim 9 for making a hydrogen-form chabazite (CHA) zeolite having a SAR of from 8 to 35 with a ratio of the XRD peak intensity corresponding to [2 1 1] and [−1 1] reflection equal to or greater than 0.80.
20 . A catalyst article for the treatment of an exhaust gas, the catalyst article comprising a hydrogen-form chabazite (CHA) zeolite having a SAR of from 8 to 35 with a ratio of the XRD peak intensity corresponding to [2 1 1] and [−1 1 1] reflection equal to greater than 0.80, or obtainable by the method according to claim 9 .
21 . A method for the treatment of an exhaust gas, the method comprising contacting an exhaust gas with the catalyst article according to claim 20 .
22 . A hydrogen-form chabazite (CHA) zeolite having SAR of from 8 to 35 formed by the method of claim 9 .