Molecular sieve precursors and synthesis of molecular sieves

Abstract

Molecular sieves, improved methods for their synthesis, and catalysts, systems and methods of using these molecular sieves as catalysts in a variety of processes such as abating pollutants in exhaust gases and conversion processes are described. The molecular sieves are made using a tailored colloid including an alumina source, a silica source and a structure directing agent.

What is claimed is: 
     
         1 . A process for the catalytic reduction of nitrogen oxides, the process comprising:
 contacting a gas comprising a nitrogen oxide with a zeolite, wherein the zeolite is prepared from a zeolite precursor comprising:
 a solution comprising colloidal particles, wherein each particle comprises alumina, silica, and a first structure directing agent; and the amounts of the alumina, silica, and the first structure directing agent are present in amount sufficient to form a zeolite having 8-ring pore openings and double-six ring secondary building units. 
   
     
     
         2 . The process of  claim 1 , wherein the nitrogen oxide comprises dinitrogen oxide (N 2 O), nitrogen monoxide (NO), dinitrogen trioxide (N 2 O 3 ), nitrogen dioxide (NO 2 ), dinitrogen tetroxide (N 2 O 4 ), dinitrogen pentoxide (N 2 O 5 ), or nitrogen peroxide (NO 3 ). 
     
     
         3 . The process of  claim 1 , wherein the zeolite is a molded catalyst. 
     
     
         4 . The process of  claim 3 , wherein the molded catalyst comprises a honeycomb carrier. 
     
     
         5 . The process of  claim 1 , wherein the gas comprises a waste gas stream. 
     
     
         6 . The process of  claim 1 , wherein the gas comprises a waste gas stream from a diesel engine. 
     
     
         7 . The process of  claim 1  which is carried out in the presence of ammonia or urea. 
     
     
         8 . The process of  claim 1 , wherein a ratio of the structure directing agent to the silica is less than about 0.07. 
     
     
         9 . The process of  claim 1 , wherein the first structure directing agent comprises an adamantyl-substituted compound. 
     
     
         10 . The process of  claim 1 , wherein the first structure directing agent comprises an adamantylammonium compound. 
     
     
         11 . The process of  claim 10 , wherein the first structure directing agent comprises trimethyl adamantylammonium cation. 
     
     
         12 . The process of  claim 1 , wherein the solution is stable at room temperature for at least 30 days. 
     
     
         13 . The process of  claim 1 , wherein the colloidal solution has a pH of less than 12. 
     
     
         14 . The process of  claim 1 , wherein the colloidal particles have a SiO 2  to Al 2 O 3  molar ratio from 10 to 1000. 
     
     
         15 . The process of  claim 1 , wherein the solution contains an additional metal selected from iron, copper, cerium, cobalt, platinum and combinations thereof. 
     
     
         16 . The process of  claim 1 , wherein the zeolite has a structure type that is AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, SAS, SAT, or SAV. 
     
     
         17 . The process of  claim 1 , wherein the zeolite has the CHA structure type. 
     
     
         18 . The process of  claim 1  having an aluminum-27 nuclear magnetic resonance (NMR) peak in the frequency shift range of 77-50 ppm with full width at half maximum of 100 to 2000 Hz. 
     
     
         19 . The process of  claim 1 , wherein the alumina is derived from aluminum chlorohydrate, to form the colloid particle.