Large-pored molecular sieves containing at least one octahedral site comprising titanium and at least silicon as a tetrahedral site

A crystalline molecular sieve having a pore size of at least 8 Angstrom units and having a composition consisting of in terms of mole ratios of oxide as follows:

• a (1.0.+-.0.25)M.sub.2/n O:XO.sub..alpha. :dZO.sub..beta. :0-100 H.sub.2 O
• wherein X is octahedrally coordinated titanium alone or a mixture of octahedrally coordinated titanium and another octahedrally coordinated metal selected from the group consisting of arsenic, cobalt, chromium, copper, iron, germanium, hafnium, magnesium, manganese, molybdenum, niobium, nickel, antimony, tin, uranium, vanadium, yttrium, zinc, zirconium, lanthanium, an actinide and a lanthanide and mixtures thereof;
• Z is silicon and another metal selected from the group consisting of aluminum, arsenic, bismuth, boron, beryllium, cobalt, chromium, copper, iron, gallium, germanium, indium, lead, magnesium, manganese, molybdenum, niobium, nickel, antimony, tin, titanium, vanadium, tungsten, zinc, and mixtures thereof;
• M is at least one cation of valence n;
• .alpha. is 1/2 the valence of X;
• .beta. is 1/2 the valence of Z;
• d is 2-100;
• a is equal to 1/2 the charge provided by the total of X and Z with the proviso that when X is solely titanium, Z cannot be solely silicon or silicon plus aluminum.