The deactivation of a ZnO doped ZrO(2)–SiO(2) catalyst in the conversion of ethanol/acetaldehyde to 1,3-butadiene

A deactivation study on the ethanol/acetaldehyde conversion to 1,3-butadiene over a ZnO promoted ZrO(2)–SiO(2) catalyst prepared by a sol–gel method was performed. The samples were characterized by N(2) adsorption–desorption isotherms, scanning electron microscopy (SEM), NH(3) temperature programmed desorption (NH(3)-TPD), X-ray powder diffraction characterization (XRD), thermogravimetric analyses (TGA), Fourier transform infrared resonance (FT-IR), (13)C magic-angle spinning nuclear magnetic resonance ((13)C NMR) and X-ray photoelectron spectroscopy (XPS). The pore structure characteristics and surface acidity of Zn(0.5)–Zr–Si catalysts were largely decreased with time-on-stream and no crystal structure was formed in the used catalyst, indicating that the deactivation was caused by carbon deposition. Two main types of carbon deposition were formed, namely low-temperature carbon deposition with the oxidation temperature of around 400 °C and high-temperature carbon deposition with the oxidation temperature of 526 °C. The carbon species were mainly composed of graphitized carbon, amorphous carbon, carbon in C–O bonds and carbonyls. The deactivated catalyst could be regenerated by a simple oxidation process in air. Adding a certain amount of water into the feed had a positive effect on reducing the carbon deposition.