Abstract: Applicants have prepared a novel zeolite identified as LZ-281. This zeolite has the framework topology of zeolite EMT. The LZ-281 zeolite is prepared by removing framework aluminum atoms from EMC-2 zeolite while simultaneously replacing the aluminum atoms with extraneous silicon atoms. This increases the SiO.sub.2 /Al.sub.2 O.sub.3 ratio versus the starting EMC-2 zeolite and results in the LZ-281 zeolite having increased thermal stability, increased number and/or strength of acid sites and increased activity in hydrocarbon processes requiring strong acid sites.

Abstract: Molecular sieve compositions have been synthesized which are resistant to the loss of framework atoms. Specifically, the molecular sieves of the invention have the empirical formulamA: (M.sub.w Al.sub.x Si.sub.y)O.sub.2where A is at least one rare earth metal, M is chromium or titanium and "m", "w", "x" and "y" are the mole fractions of A, M, Al and Si respectively. Applicants have discovered that the rare earth metals prevent loss of chromium and titanium from the framework and degradation of the molecular sieve. Along with the composition, a process for preparing the composition and processes using the composition are disclosed and claimed.