Upgrading of sewage sludge-derived pyrolysis oil via hydrotreatment over NiMo-based catalysts

Abstract

Nowadays, sewage sludge is a hazardous, but valuable by-product of municipal wastewater treatment plants and so, perspective technologies in the frame of ongoing environmental agenda, including developing different approaches to obtain alternative fuels, are necessary.In the present paper, we have upgraded sewage sludge-derived pyrolysis oil by hydrotreatment over NiMoN/Al2O3 and NiMoPS/Al2O3 catalysts. The process with catalysts has been performed in a batch reactor at 350, 375, and 400 °C and under 7.7 MPa (25 °C) of an initial hydrogen partial pressure. A catalyst-free experiment was done at 375 °C for comparison.According to the obtained results, hydrotreatment of pyrolysis oil has led to relatively effective heteroatom removal, especially over NiMoPS/Al2O3 catalyst at 400 °C. Particularly, the most obvious was the decrease in the content of O-containing compounds. Besides, the used catalysts have accumulated Fe (in the form of FeNiS phase), Si, Ca and Cr elements, which could probably be produced by the erosion of stainless steel components of the setup during hydrotreatment. Such observations indicate the importance of developing effective catalysts for the target processes as well as selecting corresponding conditions and construction materials for further studying sewage sludge-derived pyrolysis oil.