Effect of Porosity and Copper Content on Copper Containing SAPO-34 for Removal of NOx

Abstract

In this thesis, hierarchical SAPO-34 with copper isomorphously substituted(H/CuSAPO-34) was attempted synthesised, by a hydrothermal method. As a step in the process, hierarchical SAPO-34 without copper(H/SAPO-34) was synthesised, also by a hydrothermal method. To evaluate the syntheses the following characterisation methods were employed: XRD, N2-physisorption, SEM, ICP-MS, FTIR, and XAS.

A modified version of the syntheses done by Kong et.al.1, where mesopores were generated by either cetyltrimethylammonium hydroxide(CTAOH) or glucose, yielded H/SAPO-34. The hierarchical nature of these samples was concluded based on comparison of N2-physisorption results of an analogue conventional SAPO-34 sample, also synthesised by a hydrothermal method. For H/SAPO-34 samples the mesopore volumes was close to 0.20cm3/g, which is significantly larger compared to the conventional counterpart, where the mesopore volume was 0.005cm3/g. The H/SAPO-34 samples had poor catalytic performance for MTH, which was due to abnormally rapid coke formation leading to deactivation.

For the synthesis of H/CuSAPO-34 a variety of structure directing agents(SDA). Based on N2-physisortpion results, syntheses using either cetyltrimethylammonium bromide(CTAB) or CTAOH were found to give rise to mesoporosity. The HC-SCR catalytic performance for H/CuSAPO-34 made with CTAOH was found to be worse compared to an analogue hydrothermally synthesised conventional SAPO-34(C/CuSAPO-34), also with copper attempted introduce by isomorphous substitution. Additionally, the catalytic activity window for HC-SCR was found at lower temperature with increasing copper content for H/CuSAPO-34 samples made with CTAOH. Form XAS analysis the presence of non-incorporated copper in H/CuSAPO-34 samples were observed, which means that copper is partially incorporated or not incorporated at all.