Must the Best Laboratory Prepared Catalyst Also Be the Best in an Operational Application?

Abstract

Three cobalt mixed oxide deN2O catalysts, with optimal content of alkali metals (K, Cs), were prepared on a large scale, shaped into tablets, and tested in a pilot plant reactor connected to the bypassed tail gas from the nitric production plant, downstream from the selective catalytic reduction of NOx by ammonia (SCR NOx/NH3) catalyst. High efficiency in N2O removal (N2O conversion of 75–90% at 450 °C, VHSV = 11,000 m3 mbed−3 h−1) was achieved. However, a different activity order of the commercially prepared catalyst tablets compared to the laboratory prepared catalyst grains was observed. Catalytic experiments in the kinetic regime using laboratory and commercial prepared catalysts and characterization methods (XRD, TPR-H2, physisorption, and chemical analysis) were utilized to explain this phenomenon. Experimentally determined internal effectiveness factors and their general dependency on kinetic constants were evaluated to discuss the relationship between the catalyst activity in the kinetic regime and the internal diffusion limitation in catalyst tablets as well as their morphology. The theoretical N2O conversion as a function of the intrinsic kinetic constants and diffusion rate, expressed as effective diffusion coefficients, was evaluated to estimate the final catalyst performance on a large scale and to answer the question of the above article title.

How Loading of Co3O4-Cs on an Open-Cell Foam Influences N2O Decomposition

“…Elimination of nitrous oxide (N 2 O), a strong greenhouse gas with high global warming potential and dominant stratospheric-ozone-depleting substance, represents a goal of many researchers from both environmental and economic points of view. , High catalytic activity was observed over alkali metals modified Co 3 O 4 even in the presence of oxygen, water vapor, and NO x . − − However, the formation of Co 3 O 4 into tablets leads to a catalyst with low mechanical strength and ineffective utilization of cobalt due to mass transfer limitations in the pellets . Therefore, different supports were studied as carriers of cobalt mixed oxide catalysts: monoliths, , sieves , tablets, and foams. , We have previously published (i) a comparison of different deposition methods of Co 3 O 4 and Co 4 MnAlO x active phase on the SiC foam, (ii) the effect of the ceramic foam composition on the activity of Cs/Co 3 O 4 for N 2 O decomposition, and (iii) the effect of the washcoat on the activity of Cs/Co 3 O 4 for N 2 O decomposition .…”

“…4−94−9 However, the formation of Co 3 O 4 into tablets leads to a catalyst with low mechanical strength and ineffective utilization of cobalt due to mass transfer limitations in the pellets. 5 Therefore, different supports were studied as carriers of cobalt mixed oxide catalysts: monoliths, 10,11 sieves 12,13 tablets, 14 and foams. 15,16 We have previously published (i) a comparison of different deposition methods of Co 3 O 4 and Co 4 MnAlO x active phase on the SiC foam, 15 (ii) the effect of the ceramic foam composition on the activity of Cs/Co 3 O 4 for N 2 O decomposition, 16 and (iii) the effect of the washcoat on the activity of Cs/Co 3 O 4 for N 2 O decomposition.…”

Erratum: Obalová, L.; Klegova, A.; Matějová, L.; Pacultová, K.; Fridrichová, D. Must the Best Laboratory Prepared Catalyst Also Be the Best in an Operational Application? Catalysts 2019, 9, 160

“…The authors wish to make the following erratum to this paper [1]: There is one mistake in this article [ The authors would like to apologize for any inconvenience caused to the readers by these changes. The manuscript will be updated and the original will remain online on the article webpage https://www.mdpi.com/2073-4344/9/2/160.…”