Synthesis of Cu-SSZ-13 from zeolite analcime derived from solid waste and natural minerals for selective catalytic reduction of NO

Zeolites contribute significantly to the fields of chemical engineering, pharmaceuticals, and environmental protection. However, their synthesis usually involves chemicals for which reason the development of low-cost and eco-friendly synthesis methods is important. In this study, two solid wastes (coal fly ash, gasification slag) and one mineral (kaolin) were used as Si and Al sources, while diatomite was added as an auxiliary Si source, to synthesize the zeolite analcime via a hydrothermal method. The obtained analcime was upgraded, resulting in high purity and a high Si/Al molar ratio. The upgraded analcime was used to synthesize Cu-SSZ-13 catalysts by the inter-zeolite transformation method. By comparing the primary products synthesized from different raw materials, it was found that the appropriate Si/Al molar ratio and fewer impurities are key factors for the crystallinity of the resulting product. In addition, the zeolite SSZ-13 synthesized from the upgraded analcime had a higher utilization rate of Al element and smaller sizes. The Cu-SSZ-13 catalyst synthesized with the addition of diatomite (route 2) exhibited a high conversion of NO and selectivity to N2. The as-synthesized Cu-SSZ-13 catalyst had more isolated Cu2+ species and acidic sites, possibly due to the high Al content. This work provides a method for the modification of zeolites based on solid waste and minerals for use in wider applications.