Process for preparing molecular sieves via continuous addition of nutrients

A process for synthesizing a molecular sieve having a three dimensional microporous framework structure and a framework composition represented by an empirical formula of:

• (ElwAlxPy′Siz)O2
• where El, Al, P and Si are framework elements present as tetrahedral oxide units, “w” is the mole fraction of El and has a value from 0 to about 0.5, “x” is the mole fraction of Al and has a value from 0 to about 0.5, y′ is the mole fraction of P and has a value from greater than 0 to about 0.5, and “z” is the mole fraction of Si and has a value from 0 to about 0.98, w+x+y′+z=1, the process comprising forming a reaction mixture comprising reactive sources of the framework elements and R, where R is an organic templating agent selected from the group consisting of quaternary ammonium cations, amines and mixtures thereof:
• the reaction mixture having a composition expressed in terms of the mole ratios of the oxides of:
• b′R:
• c′El2O3:
• d′Al2O3:
• e′P2O5:
• fSiO2:
• gH2O
• where b′/e′ has a value from about 0.4 to about 7, c′/e″ has a value from 0 to about 0.5, d′/e′ has a value from about 0.2 to about 1.6, f/e′ has a value from 0 to about 3.6, g/e′ has a value from about 4 to about 200;
• reacting the reaction mixture at reaction conditions which include a temperature of about 50° C. to about 250° C. for a period of about 1 hour to about 48 hours to at least partially crystallize molecular sieve seed crystals and provide a seed crystal slurry;
• adding to the seed slurry, at growing conditions, nutrients (sources) to provide framework elements of the seed crystals thereby growing the seed crystals;
• carrying out the addition at a rate that essentially equals the crystal growth rate and for a time sufficient to produce the molecular sieve.

A process for synthesizing a microporous molecular sieve having a three dimensional structure comprising a core molecular sieve and an outer molecular sieve, both molecular sieves having the same framework structure, the core molecular sieve having a composition represented by an empirical formula of:

• (AlxS1−x)O2
• where Al and Si are framework elements, present as tetrahedral oxide units, and “x” has a value from 0 to about 0.5;
• the process comprising forming a reaction mixture comprising reactive sources of the framework elements, M and optionally R, where M is selected from the group consisting of alkali metals, alkaline earth metals and mixtures thereof, R is an organic templating agent selected from the group consisting of quaternary ammonium cations, amines and mixtures thereof;
• the reaction mixture having a composition expressed in terms of mole ratios of the oxides of:
• aM2/nO:bR:Al2O3:cSiO2:dH2O
• where “a/c” has a value from 0 to about 4, “n” is the valence of M and has a value from about 1 to about 2, “b/c” has a value from 0 to about 4, “d/c” has a value of about 2 to about 200, and reacting the reaction mixture at reaction conditions which include a temperature of about 50° C. to about 200° C. for a period of about 4 hours to about 14 days to at least partially crystallize molecular sieve seed crystals and provide a seed crystal slurry;
• adding to the slurry nutrients to provide framework elements, thereby growing an outer molecular sieve over the seed crystals, the outer molecular sieve having the same framework structure as the core molecular sieve but the core and outer molecular sieve differing by at least one framework element, the outer molecular sieve having a composition represented by the empirical formula:
• (ElwAlxPySiz)O2
• where El, Al, P and Si are framework elements present as tetrahedral oxide units, “w” is the mole fraction of El and has a value from 0 to about 0.5, “x” is the mole fraction of Al and has a value from 0 to about 0.5, “y” is the mole fraction of P and has a value from 0 to about 0.5, and “z” is the mole fraction of Si and has a value from 0 to about 1, w+x+y+z=1 and “y” and “z” are not simultaneously zero;
• carrying out the addition at a rate that essentially equals the growth rate of the outer molecular sieve and for a time sufficient to produce the molecular sieve.

A process for synthesizing a microporous molecular sieve having a three dimensional structure comprising a core molecular sieve and an outer molecular sieve, both molecular sieves having the same framework structure, the core molecular sieve having a composition represented by an empirical formula of:

• (ElwAlxPy′Siz)O2
• where El, Al, P and Si are framework elements present as tetrahedral oxide units, “w” is the mole fraction of El and has a value from 0 to about 0.5, “x” is the mole fraction of Al and has a value from 0 to about 0.5, y′ is the mole fraction of P and has a value from greater than 0 to about 0.5, and “z” is the mole fraction of Si and has a value from 0 to about 0.98, w+x+y′+z=1, the process comprising forming a reaction mixture comprising reactive sources of the framework elements and R, where R is an organic templating agent selected from the group consisting of quaternary ammonium cations, amines and mixtures thereof, the reaction mixture having a composition expressed in terms of the mole ratios of the oxides of:
• b′R:c′El2O3:d′Al2O3:e′P2O5:fSiO2:gH2O
• where “b′/e′” has a value from about 0.4 to about 7, “c′/e″” has a value from 0 to about 0.5, “d′/e′” has a value from 0 to about 1.6, “f/e′” has a value from 0 to about 3.6, “g/e′” has a value from about 4 to about 200;
• reacting the reaction mixture at reaction conditions which include a temperature of about 50° C. to about 250° C. for a period of about 1 hour to about 48 hours to at least partially crystallize molecular sieve seed crystals and provide a seed crystal slurry;
• adding to the slurry at growing conditions nutrients to provide framework elements thereby growing an outer molecular sieve over the crystals, the outer molecular sieve having the same framework structure as the core molecular sieve, but the core and outer molecular sieve differing by at least one framework element, the outer molecular sieve having a composition represented by the empirical formula:
• (ElwAlxPySiz)O2
• where El, Al, P and Si are framework elements present as tetrahedral oxide units, “w” is the mole fraction of El and has a value from 0 to about 0.5, “x” is the mole fraction of Al and has a value from 0 to about 0.5, “y” is the mole fraction of P and has a value from 0 to about 0.5, and “z” is the mole fraction of Si and has a value from 0 to about 1, w+x+y+z=1 and “y” and “z” are not simultaneously zero;
• carrying out the addition at a rate that essentially equals the growth rate of the outer molecular sieve and for a time sufficient to produce the molecular sieve.