Synthesis of SSZ-13 zeolite in the presence of dimethylethylcyclohexyl ammonium ion and direct conversion of ethylene to propylene with the SSZ-13

Abstract

The conversion of Y zeolites having wide silica/alumina ratio (SAR, 5.1–80) into SSZ-13s was carried out in the presence of N,N,N-dimethylethylcyclohexylammonium (DMCHA) ion, as an organic structure directing agent (OSDA). SSZ-13 zeolites could be obtained from siliceous Y zeolites; however, another phase, analcime (ANA) was obtained when aluminous Y zeolites (SAR: 5.1–12) were converted. Sodium silicate was used not only to successfully convert the aluminous Y zeolites into SSZ-13s but also to increase the SAR of the obtained SSZ-13 zeolites. The synthesis of SSZ-13 with DMCHA was possible in the absence of any seed, which is advantageous in the viewpoint of both the expense and convenience of the synthesis. Moreover, the synthesized SSZ-13s were utilized in the direct conversion of ethylene-to-propylene (ETP). Moderately siliceous SSZ-13s (SAR: 18–24) showed better performance in ETP than aluminous or siliceous SSZ-13s. DMCHA-derived SSZ-13 was also competitive or better in ETP than SSZ-13s prepared with other reported templates including N,N,N-trimethyl-1-adamantanamine hydroxide (TMAda-OH). For example, the maximum propylene yield in ETP over SSZ-13s (with similar SAR of 15–19) prepared with choline chloride, tetraethylammonium hydroxide (TEA-OH), TMAda-OH, and DMCHA-Br were 51, 61, 65 and 68%, respectively. Based on the syntheses and ETP reactions, DMCHA ion can be recommended as a versatile/inexpensive OSDA for the conversion of Y (with wide SARs) into SSZ-13 zeolites which can be effective in ETP reaction. However, further work is required to understand the reason of the competitiveness of the DMCHA-derived SSZ-13 and the effect of the SAR on the propylene yield in ETP.