粉煤灰基SAPO-34分子筛脱硝催化剂的合成及其脱硝性能

以内蒙准格尔电厂粉煤灰为原料，采用酸碱联合法，制备了粉煤灰基SAPO-34微孔分子筛。以SAPO-34分子筛为载体，以碳酸铵为铵盐、硝酸铜为铜源，采用离子交换法制备了不同Cu担载量的Cu-SAPO-34分子筛催化剂。在500℃、8% H₂O/N₂气氛下老化处理后，对催化剂的选择性催化还原脱硝性能和物理化学特性进行了测试分析。结果表明，SCR活性与Cu物种种类密切相关，位于离子交换位的孤立态的Cu²⁺是Cu-SAPO-34催化剂在NH₃-SCR反应中的主要活性中心，随着Cu担载量的增加，催化剂的低温SCR活性提高，而高温活性在Cu质量分数达到1.50%上达到最高而后降低。1.50 Cu-SAPO-34催化剂在空速高达200000h^-1、350~500℃范围内可达到80%以上的NO_x转化率，显示出较宽的脱硝温度窗口。文中指出该催化剂因更好的高温活性和抗烧结能力，相比钒钛系催化剂更适用于高温工况。这项工作开辟了燃煤电厂粉煤灰无害化处理用于制备SCR催化剂的新途径。

Preparation and performance of SAPO-34 based SCR catalyst derived from fly ash

A combined acid-alkali hydrothermal method was used to prepare SAPO-34 molecular sieves from the fly ash of a thermal power plant in Inner Mongolia Zhungeer(China). Cu-SAPO-34 catalysts were then prepared by impregnation of the fly-ash-derived SAPO-34 molecular sieves as the support, and using ammonium carbonate as the ammonium salt, and copper nitrate as the copper source. The prepared Cu-SAPO-34 catalysts were tested in the selective catalytic reduction of NH₃ (NH₃-SCR) after aging in 8% H₂O/N₂ at 500℃ and their physicochemical properties were characterized. The results showed that the SCR activity was closely related to the isolated Cu²⁺ at the ion exchange sites, which act as the main active center of the Cu-SAPO-34 catalyst in the NH₃-SCR reaction. The low temperature activity of the catalyst increased with the Cu content, while the high temperature activity also increased until the loading of Cu reached 1.50% and then decreased with further loading. The 1.50Cu-SAPO-34 catalyst having the highest isolated Cu²⁺ content showed a broad operation window (＞80%) between 300℃ and 500℃ under a GHSV of 200000h^-1. Compared with the vanadium-based catalyst, Cu-SAPO-34 catalyst is more suitable for high temperature. This work opens up new avenues for recycling the fly ash formed in coal-fired power plants and developing SCR catalysts for NO_x pollution control.