Effect of Structure-Directing Agents on FAU–CHA Interzeolite Conversion and Preparation of High Pervaporation Performance CHA Zeolite Membranes for the Dehydration of Acetic Acid Solution

Abstract

FAU–CHA interzeolite conversions were investigated in the presence of benzyltrimethylammonium hydroxide (BTMAOH) and 1-adamantyltrimethylammonium hydroxide (AdaTMOH) as organic structure-directing agents (OSDAs). AdaTMOH was well able to both decompose/dissolve the starting FAU-type zeolites into locally ordered aluminosilicate species (nanoparts) and transform them into CHA-type zeolites. In contrast, although BTMAOH did not show such high performance in the decomposition and transformation as compared to AdaTMOH, the obtained CHA-type zeolites exhibited higher acid stability. Next, the application of the highly acid-resistant CHA-type zeolites to membranes was investigated. The CHA zeolite membrane prepared on the outer surface of a porous α-alumina tube by FAU–CHA interzeolite conversion demonstrated excellent pervaporation performance in the dehydration of acetic acid aqueous solution. A high permeate flux of ca. 8 kg m−2 h−1 with a high separation factor of ca. 2500 was maintained during long-term (1700 h) testing.

Building Zeolites from Precrystallized Units: Nanoscale Architecture

“…Reviews mixtures of water and acetic acid ( Figure 12). [64] Sano and coworkers described that adjusting the Si/Al ratio of the starting FAUi nc ombination with the use of BzTMA as the OSDA allows the crystal sizes of the resultant CHA to be reduced to the nanometer scale (ca. 100 nm), particularly when the Si/Al ratios of the initial FAUw ere fixed between 35-60.…”

“…Further addition of crystals of CHA to the synthesis gel as seeds permits broadening of the Si/Al ratio (13.4–21.5) and shortening of the crystallization time . Moreover, the CHA obtained through this method showed higher resistance to acid treatment than the conventional SSZ‐13, thus providing excellent separation capabilities for feeds containing mixtures of water and acetic acid (Figure ) . Sano and co‐workers described that adjusting the Si/Al ratio of the starting FAU in combination with the use of BzTMA as the OSDA allows the crystal sizes of the resultant CHA to be reduced to the nanometer scale (ca.…”

“…Reproducedf rom Ref [64]. Right:Long-term testing of aCHA zeolite membrane for the dehydration of acetic acid solution (50 wt %CH 3 COOH/H 2 O).…”

“…Right:Long-term testing of aCHA zeolite membrane for the dehydration of acetic acid solution (50 wt %CH 3 COOH/H 2 O). Reproducedf rom Ref [64]. with permission from the Chemical Society of Japan.…”

Synthesis of high-silica AEI zeolites with enhanced thermal stability by hydrothermal conversion of FAU zeolites, and their activity in the selective catalytic reduction of NOx with NH3

“…[7][8][9][10] The AEI zeolite has a three-dimensional pore system with large cages that are accessible via 8-ring windows that measure around 3.8Å Â 3.8Å; its cage structure is similar to that of the CHA zeolite. However, the high-silica AEI zeolite SSZ-39 has only been synthesized by using expensive cyclic and polycyclic quaternized amine molecules such as the 1,1,3,5-tetramethylpiperidinium cation as a structure-directing agent (SDA).…”