How are manganese oxide catalysts prepared for selective catalytic reduction?
How are manganese oxide catalysts prepared for selective catalytic reduction?
Manganese oxide catalysts prepared by a precipitation method with various precipitants were investigated for the low temperature selective catalytic reduction (SCR) of NOx with NH 3 in the presence of excess O 2.
How does Selective Catalytic Reduction ( SCR ) work?
The selective catalytic reduction (SCR) is a process in which a reducing agent, e.g. NH 3, reacts selectively with NOx to produce N 2 without consuming an excess O 2.
Which is the best catalyst for NH 3-scr?
Recently, we found that MnOx catalysts prepared by a simple precipitation method with sodium carbonate showed the high catalytic activity for low temperature NH 3 -SCR [19]. This catalyst also appeared to be stable in the presence of excess water vapor.
Which is the best catalyst for NOx reduction?
The active MnOx catalysts, precipitated with sodium carbonate and calcined in air at moderate temperatures such as 523 K and 623 K, have the high surface area, the abundant Mn 4+ species, and the high concentration of surface oxygen on the surface. The amorphous Mn 3 O 4 and Mn 2 O 3 were mainly present in this active catalyst.
What should the temperature of a SCR catalyst be?
A typical operating temperature window of SCR catalysts (e.g., V 2O 5/TiO 2) is about 250-450°C. The low temperature activity is insufficient for diesel engines operated at low loads. One of the methods to improve the low temperature performance of the catalyst is to increase the NO 2 content in the exhaust gas.
Which is the best reagent for selective catalytic reduction?
The outlet concentration from SCR on a utility boiler is rarely less than 0.04 lb/million British thermal units (MMBtu) [1].2In comparison, SNCR units typically achieve approximately 25 to 75 percent reduction efficiencies [5]. Either ammonia or urea may be used as the NO x reduction reagent in SCR systems.
What are the specification limits for metal reagents?
The objective of this guideline is to recommend maximum acceptable concentration limits for the residues of metal catalysts or metal reagents that may be present in pharmaceutical substances or in drug products. A pharmaceutical substance is defined here as a substance that is either an active pharmaceutical ingredient or an excipient.
When does ammonium sulfate foul the SCR catalyst?
At low exhaust temperatures, generally below 250°C, the fouling by ammonium sulfate may lead to a deactivation of the SCR catalyst [205]. The SCR process requires precise control of the ammonia injection rate. An insufficient injection may result in unacceptably low NOx conversions.
