Manganese cluster induce the control synthesis of RHO- and CHA-type silicoaluminaphosphates for dimethylether to light olefin conversion

RHO- and CHA-type silicoaluminaphosphates have played an essential role in the global olefin production, e.g., dimethylether to light olefin process (DTO). In this work, we report a simple synthetic protocol to selectively acquire pure RHO and SAPO-34 and RHO&SAPO-34 silicoaluminaphosphates, which is controllable mediated by the thiolate-capped manganese cluster additives. These prepared silicoaluminaphosphates are well characterized by powder X-ray diffraction (XRD), ammonia-temperature programmed desorption (NH3-TPD), and as well as N-2-physical adsorption. They are investigated in the DTO catalysis. The selectivity for the C2-4= light olefins over the RHO&SAPO-34 catalysts is up to 90.2%, which is much higher than these over the RHO (65.5%) and SAPO-34 (69.0%) silicoaluminaphosphates. Especially, the selectivity for ethylene is two times of these over RHO and SAPO-34. It is beneficial to selectively give rise to ethylene by the dual cycle hydrocarbon-pool mechanism in the DTO reactions, as the RHO&SAPO-34 showed much stronger acidic density, both in the strong acidic sites (0.966 mmol g(-1)) and weak acidic sites (0.575 mmol g(-1)), than the RHO and SAPO-34. Finally, the RHO&SAPO-34 also performs longer lifetime and durability (ca. 4.5 h) than the corresponding SAPO-34 and RHO silicoaluminaphosphates (ca. 1 h and 4 h), which is mainly due to slow formation of the carbon deposition over its strong acid density.