利用含有模板剂的SAPO-34分子筛制备高效铜基催化剂

氮氧化物污染已经成为一个严重的环境问题。利用分子筛催化剂进行选择性催化还原(SCR)处理氮氧化物是最有效的方法之一。为了降低现有催化剂的制备成本, 本工作直接利用含有模板剂的分子筛浆料为原料, 通过预处理、离子交换及一次焙烧的方法制备Cu-SAPO-34催化剂。采用XRD、BET、TG、ICP、XPS、SEM、TPR、TPD及NH₃-SCR等对制备的Cu-SAPO-34样品进行表征, 并对离子交换过程中的pH条件进行了优化。研究结果表明: 利用含模板剂的分子筛浆料制备得到催化剂含有2.43% Cu、立方晶型完整、酸性较强以及催化还原性能优秀。在200~450℃下, NO转化率超过80%, 并且在300℃时转化率达到最高97.8%。与使用商品化SAPO-34制备的催化剂相比, 两者具有相似的微观结构和SCR性能。SAPO-34分子筛中少量模板剂的存在对最终制备得到的Cu-SAPO-34催化剂的性能影响很小。因此采用含有模板剂的分子筛浆料制备高效Cu-SAPO-34催化剂是可行的。

Preparation of High-performance Cu-SAPO-34 Catalysts without Removal of Templating Agents

The pollution of nitrogen oxides has become a serious environmental problem. Selective catalytic reduction (SCR) with zeolites is one of the most effective ways to remove nitrogen oxides. To reduce the cost of the catalysts’ preparation, a facile fabrication method of high-performance Cu-SAPO-34 catalysts without removal of templating agents was proposed. Zeolite slurry containing templating agents was directly applied as a raw material to prepare the Cu-SAPO-34 catalyst followed by pretreatment, ion exchange and one-time calcination. As prepared catalysts were systematically investigated by XRD, BET, TG, ICP, XPS, SEM, TPR, TPD, and NH₃-SCR. In the ion exchange process, different pH conditions were studied and optimized. The optimized catalyst with Cu content of 2.43% performed a cubic crystal, high acidity and catalytic activity. The NO conversion rate was more than 80% in the range of 200~450℃, and the highest value was 97.8% obtained at 300℃. Compared with the catalyst prepared from commercial SAPO-34, the as-prepared Cu-SAPO-34 catalysts without removal of templating agents exhibited similar microstructure and catalytic performance. These results indicate that the presence of a small amount of templating agent in the SAPO-34 zeolites makes no difference to fabricate high-performance Cu-SAPO-34 catalysts. It is a feasible method to prepare high-performance Cu-SAPO-34 catalysts without removal of templating agents.