Abstract:

NH₃ selective catalytic reduction (NH₃-SCR) can effectively remove nitrogen oxides (NO_x) from automobile exhaust. The development of low-cost catalysts with high activity at medium and low temperatures and environmentally friendly is the key to this technology. In this work, by utilizing cheap commercial organic structure guide agent morpholine as template, and copper amine complex (Cu-TEPA) as both Cu source and co-templating agent, a low-cost Cu-SAPO-34 molecular sieve was prepared by one-step hydrothermal synthesis method. It was found that with increasing the Si content, the crystallinity of Cu-SAPO-34 gradually decreases, and the acidic sites and Cu²⁺ ions gradually decrease. The NH₃-SCR performance of Cu-SAPO-34 with three different Si contents under different space velocities was systematically studied through fixed-bed experiments. The results show that under gas volumetric space velocity (GHSV=40000—120000 h^-1), Cu-SAPO-34 shows excellent SCR activity; when the SiO₂/Al₂O₃ molar ratio is 0.2, the prepared SCR catalyst, Cu-SAPO-34 has ideal low-temperature activity with the conversion of more than 90% and wide temperature window (225—425℃). This is attributed to the increase of Si addition, the crystallinity of Cu-SAPO-34 gradually decreases, and the precipitation of acidic sites and Cu²⁺ ions gradually decrease.

Key words: molecular sieves, co-templating agent, selective catalytic reduction, catalyst activation, Si contents

摘要：

NH₃选择性催化还原（NH₃-SCR）可以有效脱除机动车尾气中的氮氧化物（NO_x），开发在中低温下具有高活性且环境友好的低成本催化剂是该技术的关键。以廉价的商品吗啡啉为模板剂，新型络合物Cu-TEPA兼作Cu源和共模板剂，一步水热合成法制备出Cu-SAPO-34分子筛。发现随着Si含量增加，Cu-SAPO-34的结晶度逐渐降低，酸性位点和孤立Cu²⁺的数量逐渐减少。通过固定床实验系统研究了3种Si含量的Cu-SAPO-34在不同空速下的NH₃-SCR性能。结果表明，在气体体积空速（GHSV=40000~120000 h^-1）下，Cu-SAPO-34均表现出较优异的SCR活性；当SiO₂/Al₂O₃摩尔比为0.2时，具有理想的低温活性（转化率>90%）和较宽的温度窗口（225~425℃）。

关键词: 分子筛, 共模板剂, 选择性催化还原, 催化剂活性, Si含量