The metal oxide catalyst was prepared by loading MnOx and FeOx on carbon nano-tubes (CNTs) with impregnation method. Then the catalyst was characterized by BET and XPS, and the effect of adding FeOx on MnOx/CNTs catalyst at the low-temperature selective catalytic reduction of NO with NH 3 was investigated. The results showed that the active components were loaded suc-cessfully and easily on the carriers by impregnation. The Mn-Fe/CNTs catalyst was chose 10% Fe(NO 3) 3 solution to impregnate Mn-Fe/CNTs. The species of active components loaded on the catalyst were Fe 2O 3. The different concentration of impregnant solution played an important role for NO conversion in SCR with NH 3. With the increase of the concentration of impregnant solution, the NO conversion of catalysts was increasing initially then decreasing.
NOx pollutants can cause lung irritation and inhibit the body’s ability to fight off diseases such as influenza and pneumonia. Long-term exposures to high concentrations of nitrogen dioxide can produce chronic damage to respiratory tract tissue that resembles the lung disease emphysema. The free radical then can react with organic compounds in the air to form nitrogenated organic compounds, some of which have been shown to be mutagenic and carcinogenic. Further high levels of NOx cause a variety of environmentally harmful effects such as acid rain and urban smog; they also contribute to the greenhouse effect. Therefore, it has become important to reduce the emission of nitrogen oxides from both stationary and mobile combustion technologies in order to keep the health of humans and protect environment.
Among various NOx emission control techniques, selective catalytic reduction (SCR) of NO with NH3 in the presence of excess oxygen has been proven to be the most effective which is widely used. It has been proved that the catalyst being prepared through supported metallic oxides are with good catalytic performance. Various metal oxide based catalysts have been shown to possess some potential for low temperature application, including Mn2O3, CeO2, V2O5, etc.. As a novel carbon material, carbon nanotubes (CNTs) have attracted much attention due to their unique electric, mechanical and structural characteristics. It has been widely studied in fields of high strength carbon fiber materials [
Therefore, it can be an issue deserved intensive study to make use of CNTs to study the low-temperature selective catalytic reduction of NO with NH3. This research prepared Mn/CNTs catalyst through supported manganese oxide, then adding iron oxide on the CNTs after purification. We have investigated the effect of adding FeOx on MnOx/CNTs catalyst at the low-temperature selective catalytic reduction of NO with NH3.
Immerse right amount of Mn/CNTs after purification in impregnating solution for 24 hours at room temperature, meanwhile, stir them with magnetic stirrer. Then, the end product of catalyst can be obtained after drying, cooling, grinding, and roasting the immersed catalyst.In the experiment, The ferric nitrate solution was choosed to prepare the two component catalyst.
We analyzed the catalysts characterizationby TEMand XPSof catalyst.Determine the TEM of catalyst by means of JEM-1200EX made in JEOL Ltd; XPS analysis can be carried out by making use of AXIS Ultra-type X-ray photoelectron spectroscopy made in England Kratos Company.
The catalytic activity tests were carried out in a fixed bed reactor made of stainless steel in the 150˚C ~ 300˚C range. The gas composition was 450 ppm NO, 500 ppm NH3, 5% O2 balanced by N2. The total flow rate was 500 ml∙min−1. The experimental apparatus of evaluation of the catalytic activity tests included sections of gas configuration, catalytic reaction and flue gas analysis, which was shown in
The surface morphology and microstructures of the catalysts can be observed directly by TEM.
The photographs of Mn/CNTs catalysts loaded with manganese oxides was in (1), (2) and (3) was photographs of the catalysts impregnated with different concentrations of ferric nitrate solution on Mn/CNTs catalysts. Metal oxide particles loaded on the CNTs was evenly on the surface of the carrier. Future researches should be worthy to be carried out to reveal the effect between the catalyst activity and the metal oxide particle dispersion. In addition, it can be seen that metal oxide particles supported on Mn/CNTs catalysts were relatively uniform and the agglomeration is smaller by adding ferric oxides, which improves the dispersion of the supported metal oxide particles.
It can be indicated from
decreasing. The NO conversion increased with increasing of impregnant concentration in the range of ratios from 5% to 10%. When the impregnant concentration continued to exceed 10%, the NO conversion decreased. For the impregnant concentration < 10%, the active sites provided by the catalyst surface was increased gradually. But excessive of impregnant concentration, the catalyst surface was overloaded with metal oxides, the surface area of the active substances on the catalyst surface decreased lead to the decease of the activity of the catalys.
The specific surface area of CNTs being the carrier of catalyst increased significantly after experiencing purification through nitration. Active components can load on the surface of CNTs with the augment of impregnation concentration of impregnating solution.
The species of active components loaded on the catalyst were MnO2 and Fe2O3. The different concentration of impregnant solution played an important role for NO conversion in SCR with NH3. With the increase of the concentration of impregnant solution, the NO conversion of catalysts was increasing initially then decreasing.
The author declares no conflicts of interest regarding the publication of this paper.
Ren, B.N. (2018) The Preparation of Mn-Fe/CNTs Catalyst at the Low-Temperature Selective Catalytic Reduction of NO with NH3. Journal of Materials Science and Chemical Engineering, 6, 33-38. https://doi.org/10.4236/msce.2018.612003