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Abstract: Synthesis of a multicomponent (K, Zn-doped) cobalt spinel deN2O catalyst developed in a laboratory was extended to a pilot scale. The optimal composition and morphology of the prototype catalyst elucidated in the laboratory conditions were successfully reproduced upon large scale synthesis and shaping. Tuning of the catalyst properties was guided by in situ work function measurements in conjunction with the TPRS tests of N2O decomposition including the effect of water and oxygen inhibitors. In the pilot tests the engineered catalyst exhibited high performance (conversion >95% below 350°C) in N2O removal from the real tail gases of the nitric plant for at least 20 days. [Copyright &y& Elsevier]

Catalytic high temperature decomposition (secondary abatement) of nitrous oxide over calcium aluminate 12CaO · 7Al2O3 (mayenite) was studied in the model laboratory tests (TPSR) and pilot units (steady-state) using the real feed. X-ray diffraction (XRD), scanning electron microscopy (SEM), N2-sorption (BET), electron paramagnetic resonance (EPR) and Raman spectroscopies were used to characterize the synthesized material. The catalyst exhibited high efficiency and selectivity in N2O removal, reaching practically 100% conversion at 1150 K without appreciable total losses of NO x . Owing to its high thermal stability and resistivity to sintering and low cost of production raw materials, mayenite was found to be a promising catalyst for economically appealing secondary abatement of nitrous oxide in nitric acid plants. [ABSTRACT FROM AUTHOR]

Different variants for abatement of N2O emission from nitric acid plants with the use of catalysts developed at Łukasiewicz-INS were analyzed. Activity tests on a pilot scale confirmed the high activity of the studied catalysts. A two-stage catalytic abatement of N2O emission in nitric acid plants was proposed: by high-temperature decomposition in the nitrous gases stream (HT-deN2O) and low-temperature decomposition in the tail gas stream (LT-deN2O). The selection of the optimal variant for abatement of N2O emission depends on the individual characteristics of the nitric acid plant: ammonia oxidation parameters, construction of ammonia oxidation reactor and temperature of the tail gas upstream of the expansion turbine. It was shown that the combination of both deN2O technologies, taking into account their technological constraints (dimensions of the catalyst bed), allows for a greater abatement of N2O emission, than the use of only one technology. This solution may be economically advantageous regarding the high prices of CO2 emission allowances. [ABSTRACT FROM AUTHOR]

In this paper, the design of experiments and response surface methodology were proposed to study ammonia oxidation process. The following independent variables were selected: the reactor's load, the temperature of reaction and the number of catalytic gauzes, whereas ammonia oxidation efficiency and N2O concentration in nitrous gases were assumed as dependent variables (response). Based on the achieved results, statistically significant mathematical models were developed which describe the effect of independent variables on the analysed responses. In case of ammonia oxidation efficiency, its achieved value depends on the reactor's load and the number of catalytic gauzes, whereas the temperature in the studied range (870–910 °C) has no effect on this dependent variable. The concentration of nitrous oxide in nitrous gases depends on all three parameters. The developed models were used for the multi-criteria optimization with the application of desirability function. Sets of parameters were achieved for which optimization assumptions were met: maximization of ammonia oxidation efficiency and minimization of the N2O amount being formed in the reaction. [ABSTRACT FROM AUTHOR]

A series of monolithic catalysts with the 0.3 wt.% loading of the (Co,Zn)Co 2 O 4 spinel active phase dispersed on bare and ceria and zincite washcoated cordierite substrates was prepared by impregnation method: (Co,Zn)Co 2 O 4 /cordierite, (Co,Zn)Co 2 O 4 /ZnO/cordierite and (Co,Zn)Co 2 O 4 /CeO 2 /cordierite. The catalysts were thoroughly characterized (XRD, RS, SEM/TEM/EDX, XRF), and their catalytic deN 2 O activity was investigated using model gas mixture (2000 ppm N 2 O/N 2 ), and tail gases (1400 ± 50 ppm N 2 O, 900 ± 100 ppm NO x , 0.8 ± 0.2 vol.% H 2 O, 2.0 ± 0.2 vol.% O 2 ) of the nitric acid pilot plant. The reported data points correspond to the measurements performed at possibly the closest tail gas composition. Morphological SEM analysis of the monolith cross-sections indicated the segregation of both ZnO and CeO 2 washcoats in the form of islands covered by the (Co,Zn)Co 2 O 4 active phase. The catalytic tests revealed that the monolithic catalysts exhibit high catalytic deN 2 O activity, reaching X > 96% at 400 °C (model gas) and 450 °C (tail gases) for the best (Co,Zn)Co 2 O 4 /CeO 2 /cordierite system. It was also found that the specific reaction rate per cobalt spinel weight loading for the monolithic catalysts is even two orders of magnitude higher than in the case of the optimized bulk spinel phase. Yet, the beneficial effect of ceria, dominant in the model gas mixture, is largely dumped in tail gases at low temperature. It is however restored above 400 °C, when the poisoning H 2 O and NO x molecules are desorbed. [ABSTRACT FROM AUTHOR]

The influence of Zn and K promoters on N2O decomposition over Co3O4 was investigated by work function measurement and temperature-programmed surface reaction. The beneficial effect of the promoters resulting in spectacular decrease in the temperature of 50% conversion by 200 °C was found to be essentially of electronic origin. The strong correlation between the catalyst work function and deN2O activity allowed for the optimization of the doping level of both additives. The pilot plant tests in real nitric acid tail gases revealed that the optimized double promoted (Zn, K) cobalt spinel catalyst maintained its remarkable activity in N2O decomposition (conversion >95% at the target temperature of 350 °C) for more than 60 h. [ABSTRACT FROM AUTHOR]