Maintaining molecular sieve catalytic activity under water vapor conditions

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 products wherein the catalytic activity index is represented by the formula:

• CAI=exp(f(T)*f(PPwater)n*alpha*t)
• wherein
• t=time of contact of catalyst with water (hours)
• T=temperature at contact (° C.)
• PPwater=Partial Pressure of water in contact gas (psia)
• alpha=−0.071
• n=3.5
• f(T)=exp(ea(1/(T+273)−1/(To+273)))
• ea=−5500° K
• To=200° C.
• f(PPwater)=(26.2*PPwater/Psat+1.14)*0.175, for T≧180° C. (453° K)
• f(PPwater)=((26.2+0.272*(180−T))*PPwater/Psat+1.14)*0.175, for 180° C. (453° K)>T≧150° C. (433° K)
• Psat=Saturation pressure of water at T (psia).

A process for converting oxygenate to an olefin product, the process comprising the steps of:

• a) loading an activated metalloaluminophosphate molecular sieve into a reaction system;
• b) contacting the activated metalloaluminophosphate molecular sieve loaded into the reaction system with a gas containing water at conditions effective to maintain the activated sieve at an ethylene or propylene selectivity effective to convert an oxygenate feed to an olefin product, wherein the olefin product contains greater than 50 weight percent olefin, based on total weight of hydrocarbon produced;
• and
• c) contacting the water-contacted sieve with an oxygenate feed to form the olefin product.

A method of activating metalloaluminophosphate molecular sieve, the method comprising the steps of:

• a) providing a metalloaluminophosphate molecular sieve containing template;
• b) calcining the metalloaluminophosphate molecular sieve in a calcination unit to remove the template;
• c) sweeping gas through the calcination unit to cool the calcined metalloaluminophosphate molecular sieve, while maintaining the calcined metalloaluminophosphate molecular sieve at a catalytic activity index of at least 0.7, wherein the gas has a relative water pressure of at least 0.0001 and contacts the activated molecular sieve at a temperature less than water critical temperature;
• and
• d) removing the activated metalloaluminophosphate molecular sieve from the calcination unit and contacting the removed molecular sieve with an oxygenate to form an olefin product.

A method of shutting-down an olefin forming reaction system, comprising the steps of:

• a) contacting an activated metalloaluminophosphate molecular sieve in a reaction system with an oxygenate to form an olefin product;
• b) stopping contact of the activated metalloaluminophosphate molecular sieve with the oxygenate;
• and
• c) sweeping gas through the reaction system to cool down the system, wherein the activated metalloaluminophosphate molecular sieve is maintained at a catalytic activity index of at least 0.7 while the system is at a temperature less than water critical temperature.