Alumina silicate zeolite-type material having prolonged acid strength for use as a catalyst in selective catalytic reduction and process of making thereof
The present disclosure generally provides novel STT-type zeolite materials called PIDC-120501, PIDC-120502, and PIDC-120805/120806 or PIDC-type zeolites and a method of making these zeolites. The present disclosure also provides for the use of these zeolite materials as a catalyst and a method of preparing said catalyst. The PIDC-type zeolites or STT-type zeolite materials may be used as a catalyst, such as in Selective Catalytic Reduction (SCR) applications.
1. A crystalline, modified STT-type zeolite material for use as a catalyst, the modified STT-type zeolite material comprising a mole ratio ranging from 19:1 up to 50:1 of an oxide of a tetravalent element to an oxide of a trivalent element, and having peaks in an x-ray diffraction pattern with a 2 theta degree at 8.22, 9.68, 14.51, 15.55, 17.9, 18.58, 19.3, 19.66, 21.5, and 27.4 attributed to the presence of an SSZ-23 zeolite phase and the other peaks in the x-ray diffraction pattern being attributed to the presence of an SSZ-13 zeolite phase;
wherein the peak intensities in the x-ray diffraction pattern for the peaks attributed to the SSZ-13 zeolite phase are greater than the peak intensities of the peaks attributed to the SSZ-23 zeolite phase.
2. The modified STT-type zeolite material of claim 1 , wherein the mole ratio of the oxide of the tetravalent element to the oxide of the trivalent element is about 28:1.
3. The modified STT-type zeolite material of claim 1 , wherein the zeolite-type material further includes a metal selected as one from the group of copper, iron, cobalt, zirconium, titanium, and a mixture thereof;
wherein the metal containing zeolite-type material functions as a catalyst in a selective catalytic reduction (SCR) reaction.
4. The modified STT-type zeolite material of claim 3 , wherein the metal present in the catalyst ranges from 0.3 to 10.0%, based on the total weight of the zeolite catalyst.
5. The modified STT-type zeolite material of claim 3 , wherein the catalyst contains ion-exchanged metal Cu, Fe, Co, Zr, or Ti, sufficient to maintain NO x conversion performance in an exhaust gas stream containing nitrogen oxides;
wherein the NO x conversion performance of the fresh catalyst at about 500° C. is about 70%.
6. The modified STT-type zeolite material of claim 5 , wherein the catalyst is hydrothermally aged and the NO x conversion performance of the hydrothermally aged catalyst at about 200° C. is 30%.
7. The modified STT-type zeolite material of claim 3 , wherein the metal containing zeolite-type material is deposited onto a honeycomb structure, a metal substrate or a formed extrudate.
8. The modified STT-type zeolite material of claim 1 , wherein the zeolite-type material is characterized by ammonia temperature desorption and n-propylamine temperature desorption that is at least 1.4 and 2.0, respectively, times greater than the corresponding desorption of a SSZ-13 zeolite.
9. The modified STT-type zeolite material of claim 8 , wherein the zeolite-type material is hydrothermally aged and the hydrothermally aged zeolite-type material is characterized by ammonia temperature desorption and n-propylamine temperature desorption that is at least 1.5 and 6.5, respectively, times greater than the corresponding desorption of a SSZ-13 zeolite.
10. The modified STT-type zeolite material of claim 1 , wherein the zeolite-type material is characterized by Broensted acid sites that are stronger and present in a greater number than such sites in a SSZ-13 zeolite;
wherein the Broensted acid sites results in the zeolite-type material exhibiting greater than a 50% increase in n-propylamine temperature desorption over the SSZ-13 zeolite.
11. A method of preparing a metal containing catalyst, the method comprising the steps of:
providing a modified SST-type zeolite according to claim 1 ;
dealuminating a modified SST-type zeolite with nitric acid, the modified SST-type zeolite comprising cubic particles of an SSZ-13 zeolite structure co-crystallized with spherical shape particles of an SSZ-23 zeolite structure;
impregnating or ion-exchanging the dealuminated zeolite with an aqueous metal salt solution; and
incorporating a metal selected as one from the group of Cu, Fe, Co, Zr, Ti, or a mixture thereof into the framework sites of dealuminated zeolite.
12. The method of claim 11 , wherein the catalyst incorporates the metal in the framework in an amount sufficient to maintain NO x conversion performance in an exhaust gas stream containing nitrogen oxides.
13. The method of claim 11 , wherein the method further comprises depositing the catalyst onto a honeycomb substrate, a metal substrate or an extruded substrate.
14. The method of claim 13 , wherein the honeycomb substrate comprises a wall flow substrate.
15. The method of claim 11 , the method further comprising preparing the modified STT-type zeolite, said modified STT-type zeolite being prepared by
forming an aqueous reaction mixture comprising a source of the oxide of tetravalent element; a source of the oxide of the trivalent element; a source of alkali metal; and an organic structure directing agent wherein at least a portion of which is N,N,N-trimethyl-1-adamantamonium hydroxide;
maintaining the aqueous mixture under crystallization conditions sufficient to crystallize crystals of a zeolite type material having an x-ray diffraction pattern as provided in FIG. 2 ; and
recovering the zeolite crystals.
16. The method of claim 15 , wherein the source of the tetravalent element oxide is fumed silica with a water content of about 2 wt. %.
17. The method of claim 15 , wherein the source of trivalent element oxide is aluminum trihydroxide.
18. The method of claim 15 , wherein the alkali metal cation balances the valence electrons charges in the crystalline zeolite-type material.
19. The method of claim 15 , wherein the method further comprises heating the zeolite to a temperature of at least 150° C.