Wang Yunzheng, Han Jinfeng, Chen Mengyang, Lv Wenting, Meng Pengtong, Gao Wei, Meng Xiangju, Fan Weibin, Xu Jun, Yan Wenfu, Yu Jihong
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China.
Shanxi Normal University, Taiyuan, 030000, P. R. China.
Angew Chem Int Ed Engl. 2023 Aug 7;62(32):e202306174. doi: 10.1002/anie.202306174. Epub 2023 Jun 28.
Cu-exchanged low-silica CHA zeolites (Si/Al≤4) synthesized without organic templates are promising candidate catalysts for ammonia selective catalytic reduction of nitrogen oxides (NH -SCR), but their practical application is restricted due to the low hydrothermal stability. Here, inspired by the transcription from duplex DNA to RNA, we synthesized Al pairs enriched low-silica CHA zeolite (CHA-SPAEI, Si/Al=3.7) by using silicoaluminophosphate (SAPO) featured by strict alternation of -Al-O-P(Si)-O-Al-O- tetrahedra as seed. The proportion of Al pairs in CHA-SPAEI is 78 %, which is much higher than that in the conventional low-silica CHA (CHA-LS, 52 %). After hydrothermal ageing at 800 °C for 6 h, Cu-exchanged CHA-SPAEI shows NO conversion above 90 % within 225-500 °C under a gas hourly space velocity of 200,000 h , which is much better than that of Cu-exchanged CHA-LS. The spatial close proximity of Al pairs in CHA-SPAEI is confirmed by the Al double-quantum single-quantum two-dimensional NMR analyses. The strict -P(Si)-O-Al-O-P(Si)-O- sequence in the fragments from the dissolution of SAPO seed promotes the Al pairs with the -Al-O-Si-O-Al-O- sequence via a transcription process. The utilization of aluminophosphate-based zeolites as seeds opens up a new avenue for the regulation of the Al distribution in zeolites.
无有机模板合成的铜交换低硅CHA沸石（Si/Al≤4）是氨选择性催化还原氮氧化物（NH₃-SCR）的有前景的候选催化剂，但由于水热稳定性低，其实际应用受到限制。在此，受双链DNA转录为RNA的启发，我们以具有严格交替的 -Al-O-P(Si)-O-Al-O- 四面体特征的硅铝磷酸盐（SAPO）为晶种，合成了富铝对低硅CHA沸石（CHA-SPAEI，Si/Al = 3.7）。CHA-SPAEI中铝对的比例为78%，远高于传统低硅CHA（CHA-LS，52%）。在800℃水热老化6小时后，铜交换的CHA-SPAEI在200,000 h⁻¹的气体时空速下，在225 - 500℃范围内NO转化率高于90%，远优于铜交换的CHA-LS。通过²⁷Al双量子单量子二维核磁共振分析证实了CHA-SPAEI中铝对的空间紧密相邻。SAPO晶种溶解片段中严格的 -P(Si)-O-Al-O-P(Si)-O- 序列通过转录过程促进了具有 -Al-O-Si-O-Al-O- 序列的铝对。以铝磷酸盐基沸石为晶种的利用为调控沸石中铝分布开辟了一条新途径。
