Sinter resistant metal species in zeolites

A process for the preparation of a medium or large pore synthetic zeolite comprising:

• a. providing a synthesis mixture for forming the medium or large pore synthetic zeolite framework, the synthesis mixture comprising at least a source of Si, at least one catalytic metal precursor comprising a source of a catalytic metal selected from the group consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, Mo, W, Re, Co, Ni, Zn, Cr, Mn, Ce, Ga, Cu and combinations thereof, a source of at least one alkali metal or alkaline earth metal selected from the group consisting of Li, Na, K, Cs, Ca, Mg, Ba, Sr and combinations thereof, and a source of an additional extra-framework metal selected from the group consisting of Ga, Zn, Sn, Fe, Ti, Zr, Nb, Hf, Ta, Mo and combinations thereof, and wherein, if a trivalent metal element Y selected from Al, B, Ga, Fe and combinations thereof is present, the SiO2:Y2O3 ratio is greater than 200:1,
• b. heating said synthesis mixture under crystallization conditions to form crystals of said synthetic zeolite, and
• c. recovering said crystals of the medium or large pore synthetic zeolite from the synthesis mixture,
• wherein if a trivalent metal element Y selected from Al, B, Ga, Fe and combinations thereof is present in the medium or large pore synthetic zeolite, the SiO2:Y2O3 ratio is greater than 200:1,
• wherein the at least one catalytic metal is present on said crystals of the medium or large pore synthetic zeolite as catalytic metal particles, wherein at least 60% by number of said catalytic metal particles have a particle size of 2.0 nm or less, and wherein said crystals of the medium or large pore synthetic zeolite comprise at least 0.02 wt %, based on the weight of the medium or large pore synthetic zeolite, of the at least one catalytic metal, at least 0.005 wt %, based on the weight of the medium or large pore synthetic zeolite, of the at least one alkali metal or alkaline earth metal, and at least 0.01 wt %, based on a weight of the medium or large pore synthetic zeolite, of the at least one additional extra-framework metal, and
• wherein the medium or large pore synthetic zeolite is in as-synthesized form and further comprises a structure-directing agent.