Catalyst Deactivation in the Abatement of Atmospheric Pollutants: Origin, Resistance, and Regeneration.

Catalyst deactivation is a complex phenomenon and identifying an appropriate deactivation model is a key effort in the catalytic industry and plays a significant role in catalyst design. Accurate determination of the catalyst deactivation model is essential for optimizing the catalytic process. Different mechanisms of catalyst deactivation by coke and metal deposition lead to different deactivation models for catalyst activity decay. In the rigorous mathematical models of the reactors, the reaction kinetics were coupled with the deactivation kinetic equation to evaluate the product distribution with respect to conversion time. Finally, selective and nonselective deactivation kinetic models were designed to identify catalyst deactivation through the propagation of heterogeneous chemical reactions. Therefore, the present review discusses the catalyst deactivation models designed for CO2 hydrogenation, Fischer-Tropsch, biofuels and fossil fuels, which can facilitate the efforts to better represent the catalyst activities in various catalytic systems.

This article presents a comprehensive examination of the combined catalytic conversion technology for nitrogen oxides (NOx) and volatile organic compounds (VOCs), which are the primary factors contributing to the formation of photochemical smog, ozone, and PM2.5. These pollutants present a significant threat to air quality and human health. The article examines the reaction mechanism and interaction between photocatalytic technology and NH3-SCR catalytic oxidation technology, highlighting the limitations of the existing techniques, including catalyst deactivation, selectivity issues, regeneration methods, and the environmental impacts of catalysts. Furthermore, the article anticipates prospective avenues for research, underscoring the necessity for the development of bifunctional catalysts capable of concurrently transforming NOx and VOCs across a broad temperature spectrum. The review encompasses a multitude of integrated catalytic techniques, including selective catalytic reduction (SCR), photocatalytic oxidation, low-temperature plasma catalytic technology, and biological purification technology. The article highlights the necessity for further research into catalyst design principles, structure–activity relationships, and performance evaluations in real industrial environments. This research is required to develop more efficient, economical, and environmentally friendly waste gas treatment technologies. The article concludes by outlining the importance of collaborative management strategies for VOC and NOx emissions and the potential of combined catalytic conversion technology in achieving these goals.

Smart Cities start with clean air, clean water, clean look, pleasant environment and energy savings. Data collected in a 12 month field study clearly demonstrate that photocatalytic technology (i.e. FN NANO) is a convenient, energy and cost efficient solution to the air pollution problem. New methodology to determine the depollution efficiency of urban structures on 3D printed objects inside a "City reactor" will be presented.Daylight energy activated photocatalytic surface shows a strong electron deficiency of 3.2eV (1), and have enough power to break down molecules of polluting compounds such as nitrogen oxides (2), ozone (3), organic volatile compounds, benzo-a-pyrene and other harmful pollutants.UV + TiO2 → TiO2 (h + e−) 3,2eV (1)NO (hv,TiO2)→(NO2)ads.+ H2O → NO3 − (2)2O3 + hv → 3O2 (3)Lab studies carried out over the past 15 years determine that facades painted with photocatalytic coating can easily compensate for emissions from the automobile traffic [1]. These lab data were confirmed by our long-term field study in real conditions of the polluted city of Prague (CR) and Milan (IT).Initially, there was a question, if the street mixture of pollutants will degrade on the photocatalytic surface with the same rate as the individual compounds in the lab [2,3]. Our study shows that photocatalytic degradation of pollutants in the real environment is even more efficient than the ISO 22197 based lab measurements. The highest efficiency we could measure with real air was 80% elimination of NOx. More importantly, the long-term average (12 months/all seasons) indicates 42% DeNOx efficiency. This study clearly demonstrates that photocatalysis can be used as an inexpensive coating technology to improve the quality of air in polluted cities.Our former studies showed high efficiency of the composite FN NANO coatings for removal of VOCs [4]. This was confirmed by measurements in the real conditions of the polluted cities of Prague and Milan. In addition, these studies demonstrated that concentrations of ozone are instantly converted into harmless molecules of oxygen on the photocatalytic surface [3]. The intensity of UV radiation determines the formation of ozone during the day, but the same radiation, in combination with the photocatalytic surface, is able to eliminate these ozone emissions. Relative air humidity does not impact the function of the photocatalytic coating in contrast to the layer of TiO2 photocatalytic standard Evonik P25 (Table 1). The initial concentration of ozone of 100 ppbv can be regularly found outdoors on sunny days.Table 1 Photocatalytic removal of ozone Relative humidity (%) FN NANO2 Conversion (%) P25 Conversion (%) 0 42 42 50 40 33 100 33 13 The photocatalytic surface not only cleans the air, but at the same time, it protects facades from UV radiation and soiling due to the self-cleaning properties of the photocatalytic coating. It prolongs facade life, and save money on maintenance and works as an giant air purifier.Some of these coatings have a significant cooling effect, measured by the Cool Roof Council, suitable for cooling of the heat islands (cities).Standard city model for prediction and mapping of spreading emissions was used to map disappearance of the nitrogen oxides pollutants. It provided valuable information on modeling and quantification of the street canyon photocatalytic air depollution. Over 10 % of elimination of pollutants was measured and can be expected in the street canyons [5].All these effects are efficient, inexhaustible and long lasting, presenting a new standard in the urban architecture and environmental planning.Keywords: FN NANO® photocatalytic coatings, self-cleaning coatings, decontamination, air cleaning, NOx, ozone, VOCs, BAP.Acknowledgements. This project was realized with the financial support from the Ministry of Industry and Trade of the Czech Republic (TRIO FV 40209)References[1] R. Zouzelka, J. Rathousky, Photocatalytic abatement of NOx pollutants in the air using commercial functional coating with porous morphology, Appl. Catal. B Environ. 217 (2017) 466–476.[2] Mikyskova, E., Martiniakova, I., Zouzelka, R. & Rathousky, J. (2022): Photocatalytic NOx abatement: The effect of high air-flow velocity, Environmental Technology & Innovation.[3] Zouzelka, R., Martiniakova, I., Muzikova, M., Mikyskova, E., & Rathousky, J. (2022): Photocatalytic Abatement of Ozone, VOC and NOx Pollutants in the Air Stream, Journal of Industrial and Engineering Chemistry[4] Namrata Pathaka, at el., Efficacy of photocatalysis and photolysis systems for the removal of ethylene under different storage conditions; Postharvest Biology and Technology 147 (2019) 68–77[5] Nosek at el.,The role of flow structures in the effective removal of NOx pollutants by a TiO2-based coating in a street canyon; Journal of Environmental Chemical Engineering 11 (2023) 109758 Figure 1

Modeling and simulation of catalyst deactivation and regeneration cycles for propane dehydrogenation - comparison of different modeling approaches

An integrated dynamic model for reaction kinetics and catalyst deactivation in fixed bed reactors: skeletal isomerization of 1-pentene over ferrierite

Modeling of the Methanol Synthesis Catalyst Deactivation in a Spherical Bed Reactor: An Environmental Challenge

Modeling of catalyst deactivation

ABSTRACTThe performance of an ethylbenzene dehydrogenation industrial reactor was studied for about 800 days and a catalyst deactivation model was derived. The results showed that the proposed model can predict catalyst deactivation significantly better than standard models, with only 2.5% prediction error after 800 days of operation. Moreover, the optimal path for increasing the temperature of the styrene production reactor was introduced for the first time to maximize styrene production.

Recent advances in different catalysts for synergistic removal of NOx and VOCs: A minor review

Application of kinetics and computational fluid dynamics in pinene isomerization

Experiment and modeling of coke formation and catalyst deactivation in n-heptane catalytic cracking over HZSM-5 zeolites

A model of catalyst deactivation in the "Zeoforming" process was developed. The deactivation rate constants and activation energies were estimated. The role of adsorbed oligomers in the reaction and the deactivation kinetics were examined. The model is intended for further modeling and optimization of the process.

Modeling of catalyst deactivation in zeolite-catalyzed alkylation of isobutane with 2-butene

Applying new kinetic and deactivation models in simulation of a novel thermally coupled reactor in continuous catalytic regenerative naphtha process

In order to control the increasing ozone （O3） pollution in Hebi, Henan Province, clarifying the pollution characteristics of ozone and its precursors is vital. Therefore, we conducted a comprehensive analysis of O3 pollution utilizing the OFP-PMF-EKMA method combined with online hourly resolution monitoring data of conventional pollutants and volatile organic compounds （VOCs） in the summer of 2022 （June-September）. Ozone formation potential （OFP） was used to identify the key VOCs species, and the PMF model was used to identify the VOCs emission sources, whereas EKMA curves and scenario analysis were used to identify the main ozone control area in Hebi and to determine the reduction ratio of VOCs and NOx in a scientifically refined way. In 2022, Hebi had persistent O3 pollution, with the highest concentration in June. Conditions of high temperature, low humidity, and low atmospheric pressure contributed to the O3 accumulation. Aromatic and oxygenated volatile organic compounds （OVOCs） contributed significantly to the OFP and VOCs fraction, which were the dominant active substance and concentration dominant species. The results of the VOCs source analysis indicated that vehicle exhaust sources （25.3%） were the main source of atmospheric VOCs, followed by process sources （17.7%） and biomass combustion sources （17.6%）. Thus, emission sources associated with the combustion of fossil fuels and industrial production emissions were the most urgent sources of atmospheric VOCs to be controlled in Hebi. The O3 generation in Hebi occurred in the VOCs-sensitive zones, and the emission reduction results showed that a synergistic emission reduction of VOCs and nitrogen oxide （NOx） could effectively control O3 pollution with a 75% reduction in VOCs and a 10% reduction in NOx.