Structure-Activity Relationship of Gold Catalysts on Alumina Supported Cu-Ce Oxides for CO and Volatile Organic Compound Oxidation

Year: 2017 Volume: 11 Issue: 7 491 - 496 Pages

• Authors:
• Tatyana T. Tabakova
• Elitsa N. Kolentsova
• Dimitar Y. Dimitrov
• Krasimir I. Ivanov
• Yordanka G. Karakirova
• Petya Cv. Petrova
• Georgi V. Avdeev

Abstract: The catalytic oxidation of CO and volatile organic compounds (VOCs) is considered as one of the most efficient ways to reduce harmful emissions from various chemical industries. The effectiveness of gold-based catalysts for many reactions of environmental significance was proven during the past three decades. The aim of this work was to combine the favorable features of Au and Cu-Ce mixed oxides in the design of new catalytic materials of improved efficiency and economic viability for removal of air pollutants in waste gases from formaldehyde production. Supported oxides of copper and cerium with Cu: Ce molar ratio 2:1 and 1:5 were prepared by wet impregnation of g-alumina. Gold (2 wt.%) catalysts were synthesized by a deposition-precipitation method. Catalysts characterization was carried out by texture measurements, powder X-ray diffraction, temperature programmed reduction and electron paramagnetic resonance spectroscopy. The catalytic activity in the oxidation of CO, CH3OH and (CH3)2O was measured using continuous flow equipment with fixed bed reactor. Both Cu-Ce/alumina samples demonstrated similar catalytic behavior. The addition of gold caused significant enhancement of CO and methanol oxidation activity (100 % degree of CO and CH3OH conversion at about 60 and 140 oC, respectively). The composition of Cu-Ce mixed oxides affected the performance of gold-based samples considerably. Gold catalyst on Cu-Ce/γ-Al2O3 1:5 exhibited higher activity for CO and CH3OH oxidation in comparison with Au on Cu-Ce/γ-Al2O3 2:1. The better performance of Au/Cu-Ce 1:5 was related to the availability of highly dispersed gold particles and copper oxide clusters in close contact with ceria.

• Keywords:
• CO and VOCs oxidation
• copper oxide
• ceria
• gold catalysts.

Alumina Supported Cu-Mn-La Catalysts for CO and VOCs Oxidation

Year: 2016 Volume: 10 Issue: 7 912 - 921 Pages

• Authors:
• Elitsa N. Kolentsova
• Dimitar Y. Dimitrov
• Petya Cv. Petrova
• Georgi V. Avdeev
• Diana D. Nihtianova
• Krasimir I. Ivanov
• Tatyana T. Tabakova

Abstract: Recently, copper and manganese-containing systems are recognized as active and selective catalysts in many oxidation reactions. The main idea of this study is to obtain more information about γ-Al2O3 supported Cu-La catalysts and to evaluate their activity to simultaneous oxidation of CO, CH3OH and dimethyl ether (DME). The catalysts were synthesized by impregnation of support with a mixed aqueous solution of nitrates of copper, manganese and lanthanum under different conditions. XRD, HRTEM/EDS, TPR and thermal analysis were performed to investigate catalysts’ bulk and surface properties. The texture characteristics were determined by Quantachrome Instruments NOVA 1200e specific surface area and pore analyzer. The catalytic measurements of single compounds oxidation were carried out on continuous flow equipment with a four-channel isothermal stainless steel reactor in a wide temperature range. On the basis of XRD analysis and HRTEM/EDS, it was concluded that the active component of the mixed Cu-Mn-La/γ–alumina catalysts strongly depends on the Cu/Mn molar ratio and consisted of at least four compounds – CuO, La2O3, MnO2 and Cu1.5Mn1.5O4. A homogeneous distribution of the active component on the carrier surface was found. The chemical composition strongly influenced catalytic properties. This influence was quite variable with regards to the different processes.

• Keywords:
• Supported copper-manganese-lanthanum catalysts.