Conversion of Y into SSZ-13 zeolite in the presence of tetraethylammonium hydroxide and ethylene-to-propylene reactions over SSZ-13 zeolites

Abstract

The conversion of Y-zeolites having a wide silica/alumina ratio (SAR, 5.2–80) into other zeolites was attempted using tetraethylammonium hydroxide (TEA-OH) as an organic structure directing agent (SDA). Depending on the SARs of the Y-zeolites, different zeolite phases, either pure or mixed, were obtained from the same reaction precursors (TEA-OH, Y zeolite, etc.) and conditions. To investigate the obtained phase selectivity and phase transformation, the effects of the reaction temperature and times were evaluated. The phase selectivity or transformation could be explained using the framework density or pore size of zeolites. Zeolites Y having SARs of 12 and 30 were also applied to examine the effects of alkali metal ions (AMIs; Li+, Na+, K+, and Cs+) on the conversion. The results showed that AMIs also have a dominant influence on the phase of the obtained zeolite, and Na+ was the most effective for the production of the SSZ-13 zeolite. The protonated SSZ-13 zeolites (obtained from zeolite Y with an SAR of 12 or 30) were employed in the direct conversion of ethylene-to-propylene (ETP). The results showed that these SSZ–13s were better or competitive in ETP against SSZ–13s synthesized from various organic SDAs or SSZ–13s prepared under SDA-free conditions. Therefore, TEA-OH can be suggested as a competitive SDA to synthesize SSZ-13 zeolites, especially for ETP, from Y zeolites.