Rare earth stabilized Cr/Ti substituted molecular sieves

A molecular sieve having a three-dimensional microporous framework structure which has a unit empirical formula on an anhydrous basis of:

• nA:
• (Al.sub.u Si.sub.v M.sub.w ›!.sub.z1)O.sub.2
• where A is at least one rare earth metal, "n" is the mole fraction of A and varies from about 0.01 to about (w+u), M is chromium or titanium, "u" is the mole fraction of aluminum and ranges from about 0.01 to about 0.49, "v" is the mole fraction of silicon and varies from about 0.50 to about 0.98, "w" is the mole fraction of M and varies from about 0.01 to about 0.49, ›! is framework defect sites and "z1" is the mole fraction of defect sites in the framework and ranges from greater than zero to about 0.2 characterized in that the aluminum, silicon and M are present as tetrahedral oxide units in the framework structure and the molecular sieve has the x-ray diffraction pattern characteristic of zeolite Y, erionite, mordenite, zeolite L, offertite, chabazite, ZSM-5, LZ-105, zeolite omega or zeolite beta.

A process for preparing a molecular sieve having a three-dimensional microporous framework structure which has an empirical formula on an anhydrous basis of:

• mA:
• (M.sub.w Al.sub.x Si.sub.y)O.sub.2
• where A is at least one rare earth metal, "m" is the mole fraction of A and varies from about 0.01 to about (w+x), M is chromium or titanium, "w", "x", and "y" are the mole fractions of M, aluminum and silicon, respectively, present as framework tetrahedral oxide units and "w" has a value of about 0.01 to about 0.49, "x" has a value of about 0.01 to about 0.49 and "y" has a value of about 0.50 to about 0.98, said molecular sieve characterized in that it has the x-ray diffraction pattern characteristic of zeolite Y, erionite, mordenite, zeolite L, offertite, chabazite, ZSM-5, LZ-105, zeolite omega or zeolite beta, the process comprising contacting a crystalline zeolite Y having a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of at least 3 with a fluoro salt of M at a pH of about 3 to about 7, whereby framework aluminum atoms of the zeolite are removed and replaced by extraneous M atoms, contacting the M substituted molecular sieve with an aqueous solution containing at least one rare earth salt at ion exchange conditions to provide said molecular sieve.

A hydrocarbon conversion process comprising contacting a hydrocarbon with a catalyst at hydrocarbon conversion conditions to give a converted product, the catalyst comprising a molecular sieve having a three-dimensional microporous framework structure which has an empirical formula on an anhydrous basis of:

• mA:
• (M.sub.w Al.sub.x Si.sub.y)O.sub.2
• where A is at least one rare earth metal, "m" is the mole fraction of A and varies from about 0.01 to about (w+x), M is chromium or titanium, "w", "x", and "y" are the mole fractions of M, aluminum and silicon, respectively, present as framework tetrahedral oxide units and "w" has a value of about 0.01 to about 0.49, "x" has a value of about 0.01 to about 0.49 and "y" has a value of about 0.50 to about 0.98, said molecular sieve characterized in that it has the x-ray diffraction pattern characteristic of zeolite Y, erionite, mordenite, zeolite L, offertite, chabazite, ZSM-5, LZ-105, zeolite omega or zeolite beta.