An Overview of Photoreactors and Computational Modeling for the Intensification of Photocatalytic Processes in the Gas-Phase: State-of-Art
TL;DR: In this paper, a comprehensive review of the photoreactors for gas-phase reaction focusing on process intensification and recent computer simulations is provided, in which the state-of-the-art of photocatalytic air treatment providing examples such as the VOCs oxidation and NOx degradation.
Abstract: This article provides a comprehensive review of the photoreactors for gas-phase reaction focusing on process intensification and recent computer simulations. This review selected two photocatalytic gas-phase reactions, namely the oxidation of volatile organic compounds (VOCs) and the degradation of nitrogen oxides (NOx). It was also discussed two photocatalytic gas-phase reactions’ importance from a scientific and social perspective. Therefore, heterogeneous photocatalysis was applied, and it excelled itself as a promising technology for gas-phase reaction applications. However, despite the numerous advances in photocatalytic processes in recent times, there are still several challenges in their development for this technology to achieve high performance. Mass transfer and low quantum efficiency (photon transfer) are some of these challenges becoming a significant concern for the design of new photoreactors or the improvement of existing ones. Different types of photocatalytic reactors have already been designed, examined, and simulated, seeking to maximize the pollutant-catalyst contact (enhancing mass transfer) and to maximize the lighting efficiency throughout the catalyst surface (enhancing photon transfer). The process intensification has been highlighted in the development of photoreactors to ensure the improvement in mass and photons transfer. Here, we will address the monolithic photoreactors, photocatalytic membrane reactors, and photo-microreactors, in which each photoreactor has its advantages and drawbacks. CFD-based models, combined with the design of the photoreactors, are essential since they can successfully predict the performance of various geometric configurations and identify the limitations to the photon and the mass transfer with only validated virtual prototypes. From this perspective, this review presents the state-of-art of photocatalytic air treatment providing examples such as the VOCs oxidation and NOx degradation. Furthermore, this review also reports a literature exam of three different types of photoreactor designs presenting their advantages and limitations regarding the mass and the photons transfer focusing on photocatalytic process intensification. Also, it is presented a discussion of the recent applications of photocatalytic reactor modeling using computational fluid dynamics (CFD) for the gaseous pollutant degradation.
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TL;DR: In this paper , the chemical interactions between NO, O2, and N2 gas molecules and Cu-, Ag-, and Au-decorated germanene were investigated by using density functional theory simulations, and the potential applications as gas sensors or scavengers were addressed.
13 citations
TL;DR: In this article , a solution for the treatment of toxic gases based on a photocatalytic process using TiO2 coated on a cellulosic support, has been investigated, where cyclohexane was chosen as the reference for testing its removal efficiency via a continuous front flow reactor as type A anti-gas filters.
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TL;DR: In this article , a review of photocatalysis for air purification is presented, focusing on four main themes: air pollution is becoming a distinctly growing concern and the most pressing universal problem, with the multiplication of the human population and industrial enterprises, resulting in the generation of hazardous pollutants.
Abstract: Air pollution is becoming a distinctly growing concern and the most pressing universal problem as a result of increased energy consumption, with the multiplication of the human population and industrial enterprises, resulting in the generation of hazardous pollutants. Among these, carbon monoxide, nitrogen oxides, Volatile organic compounds, Semi volatile organic compounds, and other inorganic gases not only have an adverse impact on human health both outdoors and indoors, but have also substantially altered the global climate, resulting in several calamities around the world. Thus, the purification of air is a crucial matter to deal with. Photocatalytic oxidation is one of the most recent and promising technologies, and it has been the subject of numerous studies over the past two decades. Hence, the photocatalyst is the most reassuring aspirant due to its adequate bandgap and exquisite stability. The process of photocatalysis has provided many benefits to the atmosphere by removing pollutants. In this review, our work focuses on four main themes. Firstly, we briefly elaborated on the general mechanism of air pollutant degradation, followed by an overview of the typical TiO2 photocatalyst, which is the most researched photocatalyst for photocatalytic destruction of gaseous VOCs. The influence of operating parameters influencing the process of photocatalytic oxidation (such as mass transfer, light source and intensity, pollutant concentration, and relative humidity) was then summarized. Afterwards, the progress and drawbacks of some typical photoreactors (including monolithic reactors, microreactors, optical fiber reactors, and packed bed reactors) were described and differentiated. Lastly, the most noteworthy coverage is dedicated to different types of modification strategies aimed at ameliorating the performance of photocatalysts for degradation of air pollutants, which were proposed and addressed. In addition, the review winds up with a brief deliberation for more exploration into air purification photocatalysis.
10 citations
TL;DR: In this paper, the authors explored the combination of organic electrochemical synthesis and computational fluid dynamics (CFD) to perform a systematic theoretical investigation concerning the effect of different operational parameters on the performance of organic-aqueous Taylor flow in electrochemical microreactors.
7 citations
Cites methods from "An Overview of Photoreactors and Co..."
...In a previous study [41] we have used computational fluid dynamics (CFD), a powerful tool for simulating the coupled nonlinear phenomena taking place in micro-flow chemistry [42-48], to investigate the effect of mixing and charge transfer in gas–liquid microflow electro-organic transformations....
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TL;DR: A review of the research and development on photocatalytic oxidation (PCO) of VOCs, with emphasis on recent catalyst's immobilization and reactor designs in detail is presented in this article .
Abstract: Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy efficiency, and high mineralization efficiency under ambient conditions. However, the practical applications of this technology are limited, despite considerable research efforts in recent decades. Until now, most of the works were carried out in the laboratory and focused on exploring new catalytic materials. Only a few works involved the immobilization of catalysts and the design of reactors for practical applications. Therefore, this review systematically summarizes the research and development on photocatalytic oxidation (PCO) of VOCs, with emphasis on recent catalyst's immobilization and reactor designs in detail. First, different types of photocatalytic materials and the mechanisms for PCO of VOCs are briefly discussed. Then, both the catalyst's immobilization techniques and reactor designs are reviewed in detail. Finally, the existing challenges and future perspectives for PCO of VOCs are proposed. This work aims to provide updated information and research inspirations for the commercialization of this technology in the future.
7 citations
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4,241 citations
TL;DR: The number of people exposed to environmental tobacco smoke in California seems to have decreased over the same time period, where exposure is determined by the reported time spent with a smoker.
Abstract: Because human activities impact the timing, location, and degree of pollutant exposure, they play a key role in explaining exposure variation. This fact has motivated the collection of activity pattern data for their specific use in exposure assessments. The largest of these recent efforts is the National Human Activity Pattern Survey (NHAPS), a 2-year probability-based telephone survey ( n=9386) of exposure-related human activities in the United States (U.S.) sponsored by the U.S. Environmental Protection Agency (EPA). The primary purpose of NHAPS was to provide comprehensive and current exposure information over broad geographical and temporal scales, particularly for use in probabilistic population exposure models. NHAPS was conducted on a virtually daily basis from late September 1992 through September 1994 by the University of Maryland's Survey Research Center using a computer-assisted telephone interview instrument (CATI) to collect 24-h retrospective diaries and answers to a number of personal and exposure-related questions from each respondent. The resulting diary records contain beginning and ending times for each distinct combination of location and activity occurring on the diary day (i.e., each microenvironment). Between 340 and 1713 respondents of all ages were interviewed in each of the 10 EPA regions across the 48 contiguous states. Interviews were completed in 63% of the households contacted. NHAPS respondents reported spending an average of 87% of their time in enclosed buildings and about 6% of their time in enclosed vehicles. These proportions are fairly constant across the various regions of the U.S. and Canada and for the California population between the late 1980s, when the California Air Resources Board (CARB) sponsored a state-wide activity pattern study, and the mid-1990s, when NHAPS was conducted. However, the number of people exposed to environmental tobacco smoke (ETS) in California seems to have decreased over the same time period, where exposure is determined by the reported time spent with a smoker. In both California and the entire nation, the most time spent exposed to ETS was reported to take place in residential locations.
3,400 citations
TL;DR: In this article, a review of recent developments in the area of TiO 2 photocatalysis research, in terms of new materials from a structural design perspective, has been summarized.
Abstract: TiO 2 photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including self-cleaning surfaces, air and water purification systems, sterilization, hydrogen evolution, and photoelectrochemical conversion. The development of new materials, however, is strongly required to provide enhanced performances with respect to the photocatalytic properties and to find new uses for TiO 2 photocatalysis. In this review, recent developments in the area of TiO 2 photocatalysis research, in terms of new materials from a structural design perspective, have been summarized. The dimensionality associated with the structure of a TiO 2 material can affect its properties and functions, including its photocatalytic performance, and also more specifically its surface area, adsorption, reflectance, adhesion, and carrier transportation properties. We provide a brief introduction to the current situation in TiO 2 photocatalysis, and describe structurally controlled TiO 2 photocatalysts which can be classified into zero-, one-, two-, and three-dimensional structures. Furthermore, novel applications of TiO 2 surfaces for the fabrication of wettability patterns and for printing are discussed.
2,733 citations
TL;DR: In this article, the basic fundamental principles are described as well as the influence of the main parameters governing the kinetics (mass of catalyst, wavelength, initial concentration, temperature and radiant flux).
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TL;DR: This Review aims to address the lack of attention given to microstructured reaction techniques in organic chemistry by providing an overview of the chemistry in microstructures, grouped into liquid-phase, gas- phase, and gas-liquid reactions.
Abstract: The application of microstructured reactors in the chemical process industry has gained significant importance in recent years. Companies that offer not only microstructured reactors, but also entire chemical process plants and services relating to them, are already in existence. In addition, many institutes and universities are active within this field, and process-engineering-oriented reviews and a specialized book are available. Microstructured systems can be applied with particular success in the investigation of highly exothermic and fast reactions. Often the presence of temperature-induced side reactions can be significantly reduced through isothermal operations. Although microstructured reaction techniques have been shown to optimize many synthetic procedures, they have not yet received the attention they deserve in organic chemistry. For this reason, this Review aims to address this by providing an overview of the chemistry in microstructured reactors, grouped into liquid-phase, gas-phase, and gas-liquid reactions.
1,163 citations