Controlling size and acidity of SAPO-34 catalyst for efficient ethylene to propylene transformation

Acidity- and size-controlled SAPO-34 zeolites were prepared via a hydrothermal method by controlling the type and ratio of the structure-directing agents (SDA) such as tetraethylammonium hydroxide (TEAOH) and/or morpholine (MP). The SAPO-34 catalysts were applied and tested for their ability to convert ethylene to propylene (ETP) directly. The propylene formation from ethylene showed a volcano-type trend with a crystal size of 0.3–13 μm of the SAPO-34 zeolite by changing the ratio of TEAOH and MP. In addition, the propylene yield increased with an increase in the Si/(Si + P + Al) ratio from 0.042 to 0.105 and decreased at a Si/(Si + P + Al) ratio of 0.119. The results show that the proper size and acidity of the SAPO-34 catalyst with controlling the ratio of TEAOH and MP are required for an efficient ETP transformation process. The improved catalytic performance achieved while controlling the size and acidity may be related to number and strength of the active acid sites on the SAPO-34 zeolite.