Research On Recycle And Utilization Of The Mother Liquor Of SAPO-34

The development of molecular sieve catalyst is the core part of methanol to olefins technology, and the SAPO-34 molecular sieve catalyst become dominant in the MTO reaction catalysts because of its good catalytic selectivity and hydrothermal stability. At present, the synthesis of SAPO-34 is given priority to the hydrothermal synthesis method, however, its raw material utilization ratio is low, and the mother liquor formed after the isolation of molecular sieve contains too much unreacted raw materials and the water contains a large amount of organic template agent. The direct emission of Mother liquor, on the one hand, causes a waste of raw material, on the other hand, can cause a great pollution to the environment. So the recycle for the mother liquor of synthesis is gaining wide attention.This paper describes researches on the recycling of crystallization mother liquor of SAPO-34 molecular sieve in three steps gradually. The molecular sieve catalyst microsphere is synthesized by adding to the mother liquor the corresponding silicon source?the calcined kaolin?, aluminum?Pseudoboemite? and phosphorus?phosphoric acid? sources, as well as other raw materials such as the substrate materials, binder and pore former, and then by spraying. The calcined microsphere material is mixed with template agent and water, and then the mixture is directly in-situ crystallized to form the SAPO-34 molecular sieve catalyst. At the same time, the influences of different synthetic process conditions on the SAPO-34 molecular sieve catalyst are examined in all parts of the experiment:spray forming microsphere roasting time, crystallization temperature, crystallization time, the ratio of different materials, namely the ammonia amount of template agent to water. The result shows that SAPO-34 molecular sieves and catalysts can also be synthesized by changing the corresponding technological conditions and the proportion of ingredients.Based on the first three synthesis experiment steps, investigation is given to the influence of material changes of silicon source?Silica Sol?silicon oxide?tetraethyl orthosilicate?the calcined kaolin?, phosphorus source?phosphoric acid?ammonium dihydrogen phosphates?, aluminum source?Pseudoboemite?silica?alumina sol? and template agent?triethylamine? morpholine?ethylamine?diethylamie?N-propyl amine?on the synthesis of SAPO-34 molecular sieve catalyst. Researches show that the qualified SAPO-34 molecular sieve catalysts can also be synthesized by altering the corresponding technological conditions and the proportion of ingredients, even after raw materials change.Finally, the evaluation experiment is conducted on the compact fixed fluidized bed evaluation device of our company. Reaction conditions are:catalyst inventory 5 g, WSHV 4h^-1, reaction temperature 480 ?, pressure 0.1 MPa. The used catalyst are the fresh catalyst of SAPO-34 prepared by reusing the mother liquor and the regenerated catalyst under 620 ?. Results show that these catalysts display comparable performances with those catalysts produced through conventional proportions and processes.