Composite hierarchical zeolite catalyst for heavy reformate conversion to xylenes
A method of producing a hierarchical zeolite composite catalyst is provided. The method includes dissolving, in an alkaline solution and in the presence of a surfactant, a catalyst precursor comprising mesoporous zeolite to yield a dissolved zeolite solution, where the mesoporous zeolite comprises large pore ZSM-12 and medium pore ZSM-5. The method also includes condensing the dissolved zeolite solution to yield a solid zeolite composite from the dissolved zeolite solution and heating the solid zeolite composite to remove the surfactant. The method further includes impregnating the solid zeolite composite with one or more active metals selected from the group consisting of platinum, rhenium, rhodium, molybdenum, nickel, tungsten, chromium, ruthenium, gold, and combinations thereof to yield impregnated solid zeolite composite and calcining the impregnated solid zeolite composite to produce the hierarchical zeolite composite catalyst. The hierarchical zeolite composite catalyst has a mesostructure comprising at least one disordered mesophase and at least one ordered mesophase.
1. A method of producing a hierarchical zeolite composite catalyst comprising:
dissolving, in an alkaline solution and in the presence of a surfactant, a catalyst precursor comprising zeolite while heating, stirring, or both to yield a dissolved zeolite solution, where the zeolite comprises ZSM-12 having a SiO 2 /Al 2 O 3 ratio of 20 to 300 and ZSM-5 having a SiO 2 /Al 2 O 3 ratio of 5 to 500, where a ratio of ZSM-12 to ZSM-5 is 1:1 to 5:1 by weight and where the alkaline solution is a 0.1 to 0.6 M NaOH solution;
condensing the dissolved zeolite solution to yield a solid zeolite composite from the dissolved zeolite solution, where condensing the dissolved zeolite solution comprises:
adjusting a pH of the dissolved zeolite solution; and
aging the pH adjusted dissolved zeolite solution;
heating the solid zeolite composite to remove the surfactant;
impregnating the solid zeolite composite with one or more active metals selected from the group consisting of platinum, rhenium, rhodium, molybdenum, nickel, tungsten, chromium, ruthenium, gold, and combinations thereof to yield impregnated solid zeolite composite; and
calcining the impregnated solid zeolite composite to produce the hierarchical zeolite composite catalyst, where the hierarchical zeolite composite catalyst has a mesostructure comprising at least one disordered mesophase and at least one ordered mesophase.
2. The method of claim 1 further comprising extruding the solid zeolite composite with binder.
3. The method of claim 2 where the binder is an alumina based binder.
4. The method of claim 1 where the ordered mesophase is a hexagonal mesophase.
5. The method of claim 1 where the aging involves maintaining the pH adjusted dissolved zeolite solution at a temperature of 75 to 125° C. for a duration of 12 to 48 hours.
6. The method of claim 1 where the ZSM-12 has a SiO 2 /Al 2 O 3 molar ratio 60 to 100 and the ZSM-5 has a SiO 2 /Al 2 O 3 molar ratio of 20 to 75.
7. The method of claim 1 where the ratio of ZSM-12 to ZSM-5 is 3:1 by weight.
8. The method of claim 1 further comprising ion exchanging the solid zeolite composite.
9. The method of claim 1 where the surfactant is cetyltrimethyl ammonium bromide and the dissolved zeolite solution comprises 1 to 8 wt. % of the cetyltrimethyl ammonium bromide.
10. The method of claim 1 where the adjusting of the pH is performed by an acidic solution to adjust the pH to less than 9.
11. The method of claim 1 where the zeolite composite catalyst has a pore volume ranging from 0.2 to 3.0 cm 3 /g.
12. The method of claim 1 where a molar ratio of silica to alumina in the zeolite composite catalyst is from 20 to 500.
13. The method of claim 1 where the active metals comprises 0.01 to 6.0 wt. % of the impregnated solid zeolite composite.