Metal-substituted beta zeolite and method for producing same
The purpose of the present invention is to provide a metal-substituted beta zeolite that exhibits a more excellent catalytic performance than conventional one, and a method for producing the same. The present invention provides a metal-substituted beta zeolite by subjecting an alkali metal-form beta zeolite produced without using an organic structure-directing agent to ion exchange with ammonium ion and then, using a filter cake procedure, to ion exchange with copper ion or iron(II) ion. The present invention also provides a metal-substituted beta zeolite which has been ion exchanged with copper ion or iron(II) ion and in which the amount of Lewis acid sites is greater than the amount of Bronsted acid sites when the amount of Bronsted acid sites and the amount of Lewis acid sites are measured by ammonia infrared-mass spectroscopy temperature-programmed desorption on the as-produced state.
1. A metal-substituted beta zeolite comprising a product produced by a process comprising: subjecting, to ion exchange with ammonium ions, a beta zeolite of an alkali metal type produced without using any organic structure-directing agent; and then subjecting the zeolite to ion exchange with copper or iron(II) ions by a filter cake method.
2. A metal-substituted beta zeolite having undergone ion exchange with copper ions and having a Lewis acid site amount larger than a Bronsted acid site amount when the Lewis acid site amount and the Bronsted acid site amount of the zeolite in an as-produced state are measured by an ammonia infrared-mass spectrometry/temperature-programmed desorption method.
3. The metal-substituted beta zeolite according to claim 1 , which has undergone ion exchange with copper ions and has substantially no hexacoordinated-Al-derived peak observed when the zeolite is subjected to 27 Al MAS NMR spectroscopy at 600 MHz.
4. The metal-substituted beta zeolite according to claim 1 , which has an M/Al molar ratio of 0.3 or more and 1 or less, wherein M is Fe or Cu.
5. The metal-substituted beta zeolite according to claim 1 , which has a total of Bronsted acid site amount and Lewis acid site amount of 0.5 mol or more and 3.5 mol or less per 1 kg of the metal-substituted beta zeolite when the Lewis acid site amount and the Bronsted acid site amount of the zeolite in an as-produced state are measured by an ammonia infrared-mass spectrometry/temperature-programmed desorption method after ion exchange with copper ions.
6. A method for producing a metal-substituted beta zeolite, comprising: exchanging alkali metal ions in a beta zeolite of an alkali metal type produced without using any organic structure-directing agent, with ammonium ions so that an ammonium-substituted beta zeolite is obtained; and allowing a copper ion- or iron(II) ion-containing aqueous solution to pass through a cake of the ammonium-substituted beta zeolite to exchange ammonium ions in the ammonium-substituted beta zeolite for copper or iron(II) ions.
7. The method for producing a metal-substituted beta zeolite according to claim 6 , wherein the copper ion- or iron(II) ion-containing aqueous solution has a copper or iron(II) ion concentration of 0.3 mol/L or less.
8. The process for producing a metal-substituted beta zeolite according to claim 6 , wherein the alkali metal ions in the alkali metal-substituted beta zeolite are exchanged for ammonium ions by allowing an ammonium ion-containing aqueous solution with a pH of 6.5 or more and 7.5 or less to pass through a cake of the alkali metal-substituted beta zeolite.