This invention is directed to removing contaminants from an oxygenate-containing feedstream for an oxygenate to olefin reaction system. Oxygenate feeds used in the conversion of oxygenates to olefins, and which contain contaminants, are heated to form a vapor stream and a liquid stream. The heating is conducted so that a majority of the metalloaluminophosphate molecular sieve catalyst contaminants is contained in the liquid stream. The vapor stream is separated from the liquid stream, and the separated vapor stream is contacted with the metalloaluminophosphate molecular sieve catalyst to form olefin product. The heating of the feedstream and the separation of the vapor stream can be carried out in one or more stages.