Catalytic wet oxidation of high-strength alcohol-distillery liquors

Abstract

This work demonstrated that the catalytic wet oxidation (CWO) of high-strength alcohol-distillery waste liquors is feasible. Two distillery liquors (TOC=10 500; 22 500 mg/l; COD=26 000; 50 000 mg/l) produced by alcohol fermentation of enzymatic hydrolyzates from steam- and ammonia-exploded timothy grass were treated in a batch stirred autoclave over three different catalysts, 1% Pt/Al 2O 3, Mn/Ce oxides, and Cu(II)-exchanged NaY zeolite. The temperature and oxygen partial pressure ranges were (453–523 K) and (0.5–2.5 MPa), respectively. Effects of temperature, oxygen partial pressure, TOC content, and type of catalyst on the removal of total organic carbon (TOC) were investigated. The CWO initial rates were found to be first-order with respect to TOC, and the activation energies ranged from 34 to 51 kJ/mol. The highest TOC removal was achieved with Mn/Ce oxides and Cu(II)/NaY catalysts. The catalysts were found to be very effective for short contact times, while for prolonged exposures coke laydown was shown to be the prime factor responsible for the loss of catalyst activity. The carbonaceous deposits were characterized by electron spectroscopy for chemical analysis (ESCA) and temperature-programmed oxidation (TPO).