A process to make light olefins from an oxygen-containing, halogenide-containing or sulphur-containing organic feedstock is disclosed. The process includes contacting the feedstock in a primary reactor with a catalyst that includes a metalloaluminophosphate (MeAPO) molecular sieve to form a first reactor effluent that includes a light olefins and a heavy hydrocarbon fraction. The process further includes separating the light olefins from the heavy hydrocarbon fraction and contacting the heavy hydrocarbon fraction in a second reactor to convert the heavy hydrocarbon fraction to light olefins. The MeAPO molecular sieve is expressed by the formula HxMeyAlzPkO2 where y+z+k=1, x is less than or equal to y, y is from 0.0008 to 0.4, z is from 0.25 to 0.67, and k is from 0.2 to 0.67. The MeAPO molecular sieve has a predominantly plate crystal morphology where the width divided by the thickness is greater than or equal to 10.