Atmospheric pressure (AP) hydrogen cold plasma has been proved to be an efficient method for synthesizing supported metal catalysts. However, explosive hydrogen gas is generally required, and it is hard to be stored and transported. In this work, a safe AP alcohol cold plasma was developed and employed to reduce Deggusa P25 TiO2 supported metal (Au, Pd, Ag, Pt) ions with the assistance of methanol and ethanol instead of hydrogen gas. Obvious color changes are observed for the samples after AP alcohol cold plasma processing, and enhanced visible light absorption is detected according to the UV–vis diffuse reflectance spectra (UV–vis DRS). These indicate that AP alcohol cold plasma can reduce the noble metal ions into their metallic states, which are further confirmed by the results of X-ray photoelectron spectroscopy (XPS). Gold ions reduction is selected to further investigate the difference between AP alcohol and hydrogen cold plasma. The results reveal that gold ions can be reduced into metallic gold nanoparticles by AP cold plasma. Interestingly, compared to Au/P25-HP, the blueshift of the surface plasmon resonance (SPR) peaks for Au/P25-MP and Au/P25-EP is observed, attributing to the smaller size of gold nanoparticles (ca. 1.6 nm) and the influence of carbon species formed by alcohol dissociation during AP cold plasma. Optical emission spectroscopy (OES) is also used to diagnose the active species in AP cold plasma, and the mechanism of AP alcohol cold plasma for reducing the supported metal ions is discussed. AP alcohol cold plasma is proved to be an alternative safe method for synthesizing supported metal catalysts using methanol and ethanol instead of explosive hydrogen gas, and smaller size of metal nanoparticles can be obtained.

This study investigates the potential of isobutanol (iBuOH) as a reductant for the selective catalytic reduction (SCR) of NOx over 2 wt% Ag/Al2O3 between 150 and 550 °C and gas hourly space velocities (GHSV) between 10,000 and 35,000 h−1. The feed gas consists of 500 ppm NO, 5% H2O, 10% O2, and 375–1500 ppm iBuOH (C1:N ratios of 3–12); additionally, blends of 24 and 48% v/v iBuOH in gasoline are evaluated. Over 90% NOx conversion is achieved between 300 and 400 °C using pure iBuOH, including a 40% peak selectivity toward NH3 that could be utilized in a dual HC/NH3-SCR configuration. The iBuOH/gasoline blends are only able to achieve greater than 90% NOx conversion when operated at a GHSV of 10,000 h−1 and employing a C1:N ratio of 12. Iso-butyraldehyde and NO2 appear to function as intermediates in the iBuOH-SCR mechanism, which mirrors the mechanism observed for EtOH-SCR. In general, the performance of iBuOH in the SCR of NOx over a Ag/Al2O3 catalyst is comparable with that of EtOH, although EtOH/gasoline blends display higher NOx reduction than iBuOH/gasoline blends. The key parameter in employing alcohols in SCR appears to be the COH:N ratio rather than the C1:N ratio.

This special issue of Catalysis Today continues the tradition established since the 18th NAM in Cancun, 2003, of publishing the highlights coming from these catalytic after-treatment technologies sessions, where this volume contains 18 papers based on oral and poster presentations of the 23rd NAM, 2013. The guest editors would like to thank all of the catalyst scientists and engineers who presented in the Emission control sessions, and especially the authors who contributed to this special issue of Catalysis Today.