Fast Colorimetric Assay for Screening NSR Catalyst

Abstract

The NSR (NOx storage and reduction) technology is one of the most promising methods for removing NOx from next-generation lean-burn and diesel engines. Three major drawbacks, including the low temperature activity, the catalyst sulfur tolerance and the use of the large amount of the noble metals for the commercial application of NSR catalytic system, may be resolved by the development of a better catalytic system through a fast assay method in line with the combinatorial chemistry technique. The colorimetric method is the most effective way for screening a large number of the catalyst samples at once, although an appropriate dye for revealing the color specific to NOx should be examined in advance. A knowledgebased colorimetric methodology for screening a better NSR catalyst by combinatorial approach has been developed and validated by the experimental results determined by means of traditional, time-consuming techniques such as TPD.

Effect of Hydrocarbon on DeNOx Performance of Selective Catalytic Reduction by a Combined Reductant over Cu-Containing Zeolite Catalysts

“…Adsorption and oxidation of NO on the catalyst surface were investigated using in situ FT-IR along with sequential addition of 6000 ppm of C 1 of the mixed HCs, 500 ppm of NO, and 5% O 2 to the feed stream to a diffuse reflectance infrared Fourier transform (DRIFT) sample cell containing the catalyst powder (30 mg) heated at 230 °C, after pretreatment with a 100 cm 3 / min He flow at 500 °C for 30 min. The total gas flow rate was maintained at 100 cm 3 /min during the adsorption and A colorimetric assay technique was also newly adopted to directly determine the amount of nitrates formed by the oxidation of NO on the catalyst surface, 19 4 show the conversions of NO and NH 3 over Cu zeolite catalysts as a function of the reaction temperature during the SCR reaction in a feed gas stream including NH 3 and HCs (mixed or individual HCs) as primary reductants. The formation of N 2 O and NO 2 was negligible during the NH 3 /SCR without HCs, indicating high N 2 selectivity of the Cu zeolite catalysts examined in the present study.…”

“…Indeed, gaseous NO 2 over Cu zeolites was not observed during the NO oxidation experiment in the presence of HCs, due to the immediate reduction of NO 2 to NO via the reaction of NO 2 with HCs (Figures S3 and S4). To overcome these difficulties, a state of the art technique, a colorimetric assay method, has been adopted and employed for the present study, 19 in order to directly quantify the amount of nitrate/ nitrite species formed on the catalyst surface by the NO oxidation with or without HCs in the feed gas stream.…”

“…A colorimetric assay technique was also newly adopted to directly determine the amount of nitrates formed by the oxidation of NO on the catalyst surface, since surface IR and other techniques were not suitable for an accurate quantification of surface nitrates. Reaction feed gases containing 500 ppm of NO, 5% O 2 , 10% H 2 O, and N 2 balance with or without 6000 ppm of C 1 of the mixed HCs were introduced to three parallel stainless steel reactors (3/8 in.…”

“…After the NO oxidation reaction with or without HCs, the catalysts were collected and dissolved in distilled water for the extraction of NOx species adsorbed on the catalysts in the form of anionic NO 2 − and/or NO 3 − . The amounts of the extracted NO 2− and/or NO 3 − dyed by Griess reagent were quantified via a colorimetric assay in an automatic continuous-flow system (Bran+Luebbe, autoanalyzer III Digital Colorimeter) 19.…”

Synthesis of Pt/K2CO3/MgAlOx–reduced graphene oxide hybrids as promising NOx storage–reduction catalysts with superior catalytic performance

“…For the NO x emission control from automobile exhausts, three–way catalysts are highly efficient when the engines work at stoichiometric air/fuel ratio (A/F = 14.7). However, their efficiency diminishes severely in the presence of an excess of oxygen45678. Thus, up to now, the NO x abatement for lean–burn engine emissions is still widely recognized as one of the most challenging problems91011.…”