Complete mineralization of acetic acid using catalytic ozonation with a high energy efficiency enhanced by MnO2/γ-Al2O3

The complete mineralization of acetic acid in a biodegradation process is difficult due to the α-position methyl on the carboxyl group of acetic acid. This study explores the complete oxidation of acetic acid by catalytic ozonation. Metal oxides of MnO2, Co3O4, Fe3O4, and CeO2 loaded on γ-Al2O3 power were used as the catalysts. The experimental results showed that MnO2/γ-Al2O3 catalyst had the best mineralization performance for acetic acid. Typically, the mineralization of acetic acid is as high as 88.4% after 300 min ozonation of 100 mL of 1.0 g L‒1 acetic acid catalysed by 3.0 g 1.0wt.% MnO2/γ-Al2O3 catalyst powder with an energy efficiency of 15 g kWh‒1. However, without a catalyst, the mineralization of acetic acid is only 33.2% with an energy efficiency of 5.1 g kWh−1. The effects of MnO2 loading, catalyst dosage, acetic acid concentration, O3 concentration, ozonation temperature, and initial pH value of the acetic acid solution were systematically investigated. Radical quenchers and in-situ DRIFTS analyses indicated that •OH radical and reactive oxygen species on catalyst surface played an important role in the ozonation of acetic acid to CO2 and H2O. The mechanism of acetic acid oxidation on MnO2/γ-Al2O3 is proposed.

Block catalytic system for neutralization of carbon monoxide based on aerated concrete

The paper presents the results of a study of catalysts for the conversion of carbon monoxide based on aerated concrete, modified with magnetite and chromium ferrite separately and in aggregate. It was found that at a consumption of 100 g of catalyst powder per 1 dm3 of a typical mixture for producing aerated concrete and obtaining blocks of modified aerated concrete according to the traditional technology, their efficiency is 70-85% at 400 °C and decreases to 9-13% at 200 °C. In terms of strength and physicochemical properties, aerated concrete samples differ little from standard ones, and in some cases even exceed them. The proposed method for fixing catalyst particles in blocks of aerated concrete makes it possible to build fundamentally new schemes for neutralizing carbon monoxide when placing modified blocks directly at the loading of electrode raw materials in furnaces. This greatly simplifies the conversion process and its control system.

High-Performance 3D Semiconductor-Based Heterostructure Photocatalyst in Sustained Control of Harmful Gas-Phase Pollutants Under Visible-Light Illumination

Herein, a highly efficient three-dimensional (3D) semiconductor-based heterostructure photocatalyst (i.e., WO3–g-C3N4 monolithic architecture; WOCNM) was developed by immobilizing a WO3–g-C3N4 heterostructure powder on a melamine foam (MF) framework. Subsequently, the sustained control of two harmful model gas-phase pollutants (i.e., n-butanol and o-xylene) over WOCNM and selected monolithic counterparts (i.e., MF-supported WO3 monolith and MF-supported g-C3N4 monolith) was investigated under visible-light irradiation. WOCNM exhibited higher photocatalytic capabilities in the sustained control of the two model pollutants than those of individual WO3 and g-C3N4 monoliths because the WO3–g-C3N4 heterojunction enhanced its charge-separation ability. Notably, WOCNM exhibited highly efficient photocatalytic capabilities in the sustained control of n-butanol (up to 97%) and o-xylene (up to 86%). Moreover, no noticeable changes were observed in the WOCNM photocatalytic capability after the final run of successive applications. The fresh and successively used WOCNMs were nearly identical, and the photocatalyst powder was not observed in the reaction chamber after its successive application. As a result, WOCNM was a highly efficient and stable 3D heterostructure photocatalyst for the sustained control of gas-phase n-butanol and o-xylene, without significant catalyst powder loss. Promisingly, this study will expedite the future development of 3D photocatalysts for the sustained control of harmful gas-phase pollutants.

Preparation of catalyst as Au doped Mn1Co9Ox/ceramic system for total oxidation of CO

In this paper, the Au doped Mn1Co9Ox was investigated for total oxidation of CO. The sol-gel method was applied to prepare this catalyst and some modern analysis methods as XRD, EPR, TPx, SEM were utilized to characterize its properties. The XRD patterns showed only Co3O4 phase without any peaks belonging to Mn or Au. However, the presence of Au and Mn was confirmed by EPR and O2-TPD results. With the aim to further apply catalyst in reality, the Au doped Mn1Co9Ox was deposited on ceramic by sol-gel, wet impregnation. The SEM images displayed the successful coating of active phase on substrate. However, the complete catalyst system didn’t have the high activity in total CO oxidation like the catalyst powder because of large agglomerations on coatings.

Reaction Kinetics of One-Pot Xylan Conversion to Xylitol via Precious Metal Catalyst

The hydrolytic hydrogenation of xylan to xylitol by a one-pot process was studied in detail in a batch reactor. The reaction was catalyzed by a combination of diluted sulfuric acid and precious metal Ru on carbon powder. Process parameters were varied between 120–150°C, while maintaining constant hydrogen pressure at 20 bar and an acid concentration equivalent to pH 2. The xylan solution consisted of 1 wt% beechwood powder (Carl Roth, >90%) in deionized water. Sulfuric acid was added to the solution until pH two was reached, then the 0.3 wt% catalyst powder (5% Ru on Act. C) was added and the solution was put into the batch reactor. The first approach of kinetic modeling began with conventional first-order kinetics and compared this to a more complex model based on Langmuir–Hinshelwood kinetics. The xylan and xylitol data reached a good fit. However, the modeling results also showed that the rate-limiting step of xylose-formation was still not represented in a satisfactory manner. Therefore, the model was adapted and developed further. The advanced model finally showed a good fit with the intermediate product xylose and the target product xylitol. The overall modeling methods and results are presented and discussed.

CO Catalytic Oxidation Performances of Pd-Doped BaCeO3

A series of palladium doped barium-based cerium (BaCe1-xPdxO3-δ) catalysts were prepared by the sol–gel method. The catalytic properties of BaCe1-xPdxO3-δ for the oxidation of carbon monoxide were studied. The results show that Pd doping can effectively inhibit the crystal size of catalyst powder, and the specific surface area of the catalyst increases with the increase of doping ratio. Palladium doping significantly improved the catalytic activity of barium ceric acid-based catalyst for CO oxidation. BaCe0.96Pd0.04O3-δ had the best catalytic activity for CO oxidation. After calcination at high temperature, the BaCeO3 perovskite is stable.