TEMPERATURE-PROGRAMMED REDUCTION AND X-RAY PHOTOELECTRON-SPECTROSCOPY OF COPPER-OXIDE ON ALUMINA FOLLOWING EXPOSURE TO SULFUR-DIOXIDE AND OXYGEN

Sorbents/catalysts based on alumina-supported CuO were prepared by impregnation using a copper sulfate solution, activated under H2, and exposed to SO2 and O2. The subsequent reduction of those samples (before and after sulfation) was studied by temperature-programmed reduction (TPR) using H-2 or CH4 as the reducing gas. The reaction products were analyzed by mass spectrometry. In addition, chemical analysis for copper and sulfate, X-ray photoelectron spectroscopy, and Fourier transform infrared analyses were carried out. Prior to sulfation, sulfate impregnated as copper sulfate is transferred to the alumina to form aluminum sulfate. The TPR profile then corresponds to the reduction of CuO or CuAl2O4, followed by the reduction of Al2(SO4)3. Any residual CuSO4 is reduced to copper sulfide. After sulfation the sulfur to copper ratio achieved was usually greater than 2:1. In these circumstances the copper was present as CuSO4. This compound was reduced to form metallic copper and SO2, but some copper sulfide also formed. At higher temperatures Al2(SO4)3 was reduced as well as the copper sulfide formed at the lower temperatures. Methane is a less powerful reducing agent than hydrogen, but its utilization avoided the formation of copper sulfide.