Performance of Low‐temperature SCR of NO with NH₃ over MnOx/Ti‐based catalysts

Abstract

The effects of Mn loadings and precursors, catalyst preparation methods, incineration durations and temperatures, and the addition of Co and Ce on NO-reduction efficiency and selectivity (N 2 O formation) during the preparation of MnOx/Ti-based catalysts were studied by micropore-size analysis (XRD, XPS, SEM, and FTIR), while considering changeable parameters. Meanwhile, the performance of low-temperature SCR of NO with NH 3 over the designed catalysts was tested under various gas hourly space velocities (GHSVs), NH 3 /NO molar ratios, and contents of NO, NH 3 , O 2 , H 2 O, and SO 2 in a lab-scale reactor. Overall, the Mn(0.3)Ce(0.1)/Ti catalyst, which had high NO-reduction efficiency and selectivity (low N 2 O formation), was recommended, with the following preparation methods: ultrasonic impregnation; manganese acetate precursor; and incineration at 500 8C. Appropriate textural properties (high surface area and small pore and crystallite sizes), well-dispersed amorphous manganese (rather than crystalline) on the anatase surface (rather than rutile), abundant active sites, and long residence time are essential for high NO-reduction efficiency. In practice, NO-reduction efficiency decreased with increasing GHSV and the NH 3 and NO contents; however, it initially increased and then became saturated with an increasing NH 3 /NO molar ratio and O 2 content. Water deactivated the catalyst to a recoverable state, whereas SO 2 resulted in unrecoverable deactivation.

Investigation of deactivation effect of Au addition to Ce/TiO2 catalyst for selective catalytic reduction using real diesel engine exhaust samples at low temperature conditions

“…Selective catalytic reduction (SCR) is one of the most efficient methods to remove NO x in the emissions of diesel engine exhaust. [8][9][10][11] SCR can be classified as hydrocarbon-SCR (HC-SCR), oxygenated hydrocarbon-SCR (OHC-SCR), ammonia-SCR (NH 3 -SCR), hydrogen-SCR (H 2 -SCR), and urea-SCR according to the reductant. Among these, HC-SCR and OHC-SCR techniques have been considered as the most promising for NO x reduction due to their low cost, and being environmentally safe.…”

Research on the Impact of Carbon Tax on CO2Emissions of China’s Power Industry

“…erefore, the carbon tax should consider not only the impact on the environment, but also its economic effect. Like other types of taxes, carbon tax will also change the price signal, making resources deviate from the optimal allocation under the reference scheme, resulting in the loss of GDP [40].…”

Performance Evaluation of a Novel Thermal Power Plant Process with Low-Temperature Selective Catalytic Reduction

“…When SCR is installed at the front of the flue gas desulfurization (FGD) unit, problems occur with thermal fatigue of the catalyst and increases in the differential pressure of the boiler due to changes in the operating conditions. In addition, the catalyst may be damaged due to the deterioration of the quality of the coal [7]. Meanwhile, when installing the SCR unit at the rear of the FGD unit, as the desulfurization process is a wet reaction, there is a significant decrease in the temperature of the flue gas [6,8].…”

“…In a general boiler system, the exit temperature of the boiler system is~300-400 • C, which satisfies the operating range of the high-temperature SCR. However, in a low-temperature SCR unit, there is a risk of damaging the catalyst when exposed to these high temperatures and a problem associated with the NO x reduction rate when the temperature is too low [7,25]. Therefore, the inlet flue gas temperature of the low-temperature SCR should be controlled in the range of 150 to 200 • C to obtain economic efficiency and NO x reduction.…”