Patent ID: 7309806

Claim:
A method of protecting activated metalloaluminophosphate molecular sieve from loss of catalytic activity, comprising contacting the activated metalloaluminophosphate molecular sieve with a gas containing water at a temperature and water partial pressure effective to maintain a predetermined catalytic activity index and stopping contact of the activated metalloaluminophosphate molecular sieve with the gas and contacting with an oxygenate to form an olefin product, wherein the catalytic activity index is represented by the formula: CAI =exp( f ( T )* f ( PP water ) n *alpha* t ) wherein t=time of contact of catalyst with water (hours) T=temperature at contact (° C.) PP water =Partial Pressure of water in contact gas (psia) alpha=−0.071 n=3.5 f(T)=exp(ea(1/(T+273)−1/(T o +273))) ea=−5500° K T o =200° C. f(PP water )=(26.2*PP water /P sat +1.14)*0.175, for T≧180° C. (453° K) f(PP water )=((26.2+0.272*(180−T))*PP water /P sat +1.14)*0.175, for 180° C. (453° K)>T≧150° C. (433° K) P sat =Saturation pressure of water at T (psia).