A surface science perspective on TiO2 photocatalysis

Recently sulfate radical-based advanced oxidation processes (SR-AOPs) attract increasing attention due to their capability and adaptability in decontamination. The couple of cobalt and peroxymonosulfate (PMS) is an efficient way to produce reactive sulfate radicals. This article reviews the state-of-the-art progress on various heterogeneous cobalt-based catalysts for PMS activation, including cobalt oxides, cobalt-ferrite and supported cobalt by diverse substrates. We summarize the intrinsic properties of these catalysts and their fundamental behaviors in PMS activation, as well as synthetic approaches. In addition, influencing factors and synergistic techniques of Co/PMS systems in organic degradation and possible environmental applications are also discussed. Finally, we propose perspectives on challenges related to cobalt-based catalysts, heterogeneous Co/PMS systems and their potential applications in practical environmental cleanup.

Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications

Photocatalytic oxidation for indoor air purification: a literature review

Trends in NOx abatement: A review

Permeability and diffusivity are critical parameters of tight reservoir rocks that determine their viability for commercial development. Current methods for measuring permeability and/or diffusivity may lead to erroneous results when applied to very tight rocks including gas shales, coal, and tight gas sands, as well as rocks considered as seals for nuclear waste repositories and strata for geological sequestration of CO2. The use of He as routinely applied to measure porosity, permeability, and diffusivity may result in non-systematic errors because of the molecular sieving effect of the fine pore structure to larger molecules such as reservoir gases. Utilizing gases with larger adsorption potentials than He, such as N2, and including all reservoir gases to measure porosity or permeability of rocks with high surface area is a viable alternative, but requires correcting for adsorption in the analyses. This study expands several approaches to measure permeability and diffusivity with considerations for gas adsorption, which has not been explicitly considered in previous studies. We present new models that explicitly correct for adsorption during pulse-decay measurements of core under reservoir conditions, as well as on crushed samples used to approximate permeability or diffusivity. We also present a method to determine permeability or diffusivity from on-site drill-core desorption test data as carried out to determine gas in place in coals or gas shales. Our new approach utilizes late-time data from experimental pressure-decay tests, which we show to be more reliable and theoretically (and practically) accurate than the early-time approach commonly used to estimate gas-transport properties.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1468-8123.2009.00244.x

Measurements of gas permeability and diffusivity of tight reservoir rocks: different approaches and their applications

Reaction activities of several developed catalysts for NO oxidation and NO x (NO + NO 2 ) reduction have been determined in a fixed bed differential reactor. Among all the catalysts tested, Co 3 O 4 based catalysts are the most active ones for both NO oxidation and NO x reduction reactions even at high space velocity (SV) and low temperature in the fast selective catalytic reduction (SCR) process. Over Co 3 O 4 catalyst, the effects of calcination temperatures, SO 2 concentration, optimum SV for 50% conversion of NO to NO 2 were determined. Also, Co 3 O 4 based catalysts (Co 3 O 4 -WO 3 ) exhibit significantly higher conversion than all the developed DeNO x catalysts (supported/unsupported) having maximum conversion of NO x even at lower temperature and higher SV since the mixed oxide Co-W nanocomposite is formed. In case of the fast SCR, N 2 O formation over Co 3 O 4 -WO 3 catalyst is far less than that over the other catalysts but the standard SCR produces high concentration of N 2 O over all the catalysts. The effect of SO 2 concentration on NO x reduction is found to be almost negligible may be due to the presence of WO 3 that resists SO 2 oxidation.

Co3O4 based catalysts for NO oxidation and NOx reduction in fast SCR process

Reaction kinetics of reduction and oxidation of metal oxides for hydrogen production

Hydrogen production from two-step steam methane reforming in a fluidized bed reactor

The effects of initial NO concentration, gas-residence time, reaction temperature and ultraviolet (UV) light intensity on the photocatalytic decomposition of NO have been determined in an annular flow-type and a modified two-dimensional fluidized-bed photoreactors. The decomposition of NO by photocatalysis increases with decreasing initial NO concentration and increasing gas-residence time. The reaction rate increases with increasing UV light intensity. The light transmission increases exponentially with the bed voidage at superficial gas velocity above 1.3 times the minimum fluidizing velocity ( U mf ) in the two-dimensional fluidized-bed photoreactor. In the two-dimensional fluidized-bed photoreactor, NO decomposition reaches >70% at the gas velocity of 2.5  U mf . A two-dimensional fluidized-bed photoreactor is an effective tool for high NO decomposition with efficient utilization of photon energy.

Sang Done Kim

Papers

Co3O4 based catalysts for NO oxidation and NOx reduction in fast SCR process

Reaction kinetics of reduction and oxidation of metal oxides for hydrogen production

Hydrogen production from two-step steam methane reforming in a fluidized bed reactor

Photocatalytic decomposition of NO by TiO2 particles

Trichloroethylene degradation by photocatalysis in annular flow and annulus fluidized bed photoreactors.