Nitrous Oxide Formation over Zeolite-based Catalysts during Ammonia-SCR: The Effect of Framework Structure, Acidity, and Copper Content

The emission control of anthropogenic nitrous oxide (N2O), a by-product formed\ua0through fossil- and renewable fuel combustion, agricultural activities, and industrial\ua0chemical processes, has attracted large considerations due to its substantial contribution\ua0in global warming and ozone layer depletion. Selective catalytic reduction with\ua0ammonia (NH3-SCR) is the most prevailing technology for the abatement of nitrogen\ua0oxides (NOx) in the exhaust gases from lean-burn processes, with the possible formation\ua0of N2O. Therefore, the development of catalysts for efficient NOx reduction with\ua0no or minor N2O formation is of major importance. Hence, zeolite-based catalysts\ua0exchanged with copper have shown to be efficient catalysts for NOx reduction owing\ua0to their high catalytic performance under practical reaction conditions. This work\ua0aims to increase the understanding of the N2O formation during NH3-SCR, in particular\ua0studying the effect of different parameters, from zeolite framework structure,\ua0ammonia storage capacity of the zeolites, to Si/Al and Cu/Al molar ratios.\ua0Three different zeolites with varying pore sizes, from small to medium and large\ua0pore zeolites (SSZ-13, ZSM-5 and beta), were chosen to investigate their performance\ua0as SCR catalysts. A range of SSZ-13 samples with Si/Al molar ratios of 6, 12, and 24\ua0were prepared by hydrothermal crystallization, and exchanged with copper, Cu/Al=\ua00-0.4 molar ratios, to investigate the effect of the Si/Al and Cu/Al molar ratios on the\ua0ammonia storage capacity and the SCR performance of the samples. Furthermore,\ua0the role of the sample pretreatment on the SCR performance was investigated for the\ua0SSZ-13 sample with Si/Al= 12 molar ratio. The prepared samples were studied by\ua0flow reactor experiments and in situ diffuse reflectance infrared Fourier transform\ua0spectroscopy (DRIFTS) to evaluate the catalytic activity and selectivity, and to monitor\ua0the evolution of surface species during reaction.\ua0Copper ions as active sites in the zeolite catalyzing the SCR reaction by NO activation\ua0and formation of NO+ and/or surface nitrate species. During SCR, the nitrate\ua0species can subsequently react with NH3 and form ammonium nitrate (AN) as an\ua0intermediate, which partially contributes to N2O formation upon decomposition.\ua0In order to understand the system in more detail, we have investigated important\ua0factors such as Si/Al and Cu/Al molar ratio and temperature on the NH3 storage\ua0capacity of the samples based on SSZ-13. Temperature programmed desorption by\ua0NH3 (NH3-TPD) carried out to characterize the nature of the different acid sites in the\ua0zeolite. It is revealed that the samples with low Si/Al molar ratio provide higher NH3\ua0storage capacity, which increases with increasing Cu loading. After NH3-TPD, SCR\ua0experiments were subsequently performed resulting in higher NOx conversion and\ua0N2O formation by increasing the Cu content for all samples. Results from DRIFTS\ua0showing vibrational peaks associated with N2O in accordance with the flow reactor\ua0findings. Moreover, the role of pretreatment for the NH3-SCR performance was\ua0evaluated for the sample with Si/Al= 12, and the results show that the pretreatment\ua0in NH3 and NO, in the absence of O2, reveals higher low-temperature activity for\ua0standard SCR compared to the pretreatment including O2

A novel Chebyshev wavelet method for solving fractional-order optimal control problems

This thesis presents a numerical approach based on generalized fractional-order Chebyshev wavelets for solving fractional-order optimal control problems. The exact value of the Riemann– Liouville fractional integral operator of the generalized fractional-order Chebyshev wavelets is computed by applying the regularized beta function. We apply the given wavelets, the exact formula, and the collocation method to transform the studied problem into a new optimization problem. The convergence analysis of the proposed method is provided. The present method is extended for solving fractional-order, distributed-order, and variable-order optimal control problems. Illustrative examples are considered to show the advantage of this method in comparison with the existing methods in the literature

The manifestation of the political in the gendered society of Gilead in Margaret Atwood's The Testaments

Le genre représente l'un des sujets les plus populaires dans les discussions sur les romans de Margaret Atwood. Les Testaments, le roman le plus récent d'Atwood, n’est pas d’exception. La plupart de ces études, cependant, sont dépourvues d'une étude politique dédiée analysant les systèmes et les gouvernements et leur rôle dans la création de la condition actuelle. Par conséquent, le but de cette étude est d'adopter une approche différente et de se concentrer sur le régime de Gilead en tant que système politique et de l'analyser sous le prisme d'une théorie politique dédiée. En choisissant le politique plutôt que le politique, cette recherche peut aller au-delà de l'action et enquêter sur l’incitation et le principal moteur des actions du régime de Gilead, qui ne sont pas nécessairement sexospécifiques. La recherche actuelle se concentre sur le concept de politique de Carl Schmitt et analyse les relations ami-ennemi et les raisons de sa production telles qu'elles se manifestent dans le roman. Étant donné que la théorie de Schmitt ne suffit pas à couvrir les compréhensions multidimensionnelles et radicalement différentes du politique, la lecture des Testaments basée sur la définition du terme de Hannah Arendt est nécessaire. La définition d'Arendt se concentre sur le politique comme une force de manipulation et un contrat partagé entre les individus. Elle distingue le social et le politique et explique la fonction du politique dans l'espace public et privé. Bien que le genre ne soit pas une priorité absolue pour lire Les Testaments dans cette recherche, il est également discuté en fonction de ses relations avec le politique. Les résultats indiquent que, pour Gilead, le maintien du pouvoir et de la sécurité, ainsi que la manipulation de l'espace privé pour garantir la souveraineté, importent plus que le genre. De plus, le roman, tout en discutant des horreurs genrées du régime religieux de Gilead, tente d'attirer notre attention sur l'importance d'étudier les gouvernements plutôt que les sociétés et les discours seuls. Mots-clés : politique, souveraineté, espace public, espace privé, ami, ennemiGender represents one of the most popular topics in discussions of Margaret Atwood’s novels. The Testaments, Atwood’s most recent novel, is no exception. Most of these studies, however, are devoid of a dedicated political study that analyzes the systems and governments and their role in creating the present condition. Hence, the purpose of this study is to take a different approach and focus on the Gilead regime as a political system and analyze it through the lens of dedicated political theory. By choosing the political instead of political, this research can move beyond the action and investigate the incentives and the main driving force behind the actions of Gilead’s regime, which are not necessarily gender-oriented. The present research focuses on Carl Schmitt’s concept of the political and analyzes friend-enemy relationships and the reasons behind its production as manifested in the novel. Since Schmitt’s theory is not enough to cover the multi-dimensional and drastically different understandings about the political, reading The Testaments based on Hannah Arendt’s definition of the term is necessary. Arendt’s definition focuses on the political as a manipulative force and a shared contract between the individuals. She distinguishes the social and the political and explains the function of the political in the public and private space. While gender is not a top priority to read The Testaments in this research, it is also discussed based on its relations to the political. The results indicate that, for Gilead, sustaining power and security, as well as the manipulation of private space for securing sovereignty, matters more than gender. Furthermore, the novel, while discussing the gendered horrors of Gilead’s religious regime, tries to attract our attention to the importance of studying governments rather than societies and discourses alone. Keywords: the political, sovereignty, public space, private space, friend, enem

Enhanced Solar Photocatalytic Hydrogen Generation and Water Treatment Using Hetero-Structure Photocatalysts

Among different approaches to overcome current environmental concerns, heterogeneous photocatalysis is recognized as a promising one. While there are various applications of photocatalysis including water splitting and water treatment, the overall efficiency of this process is still fairly low due to the two dominant drawbacks of current semiconductors, namely wide band gap and fast recombination of photo-generated charges, which restrict the photocatalytic reactions. Designing a hybrid photocatalyst composed of semiconductor hetero-junctions is a viable approach to address these challenges. The objective of this research project is developing efficient photocatalysts via simple and practical synthesis methods in order to enhance the solar photocatalytic water splitting and water treatment. In this regard, hetero-structure photocatalysts from various groups are synthesized and characterized. Furthermore, the performance of such photocatalysts for photocatalytic reactions are evaluated and compared with single semiconductors. The experiments presented in this study use solar simulator as the light source. Platinum is loaded on TiO2 photocatalyst by solar photo-deposition method. Pt/TiO2 as a metal-semiconductor hetero-structure is used for sacrificial photocatalytic hydrogen generation and Formaldehyde acts as sacrificial agent. The performance of the Pt loaded TiO2 is shown to be superior to that of the pure TiO2. Furthermore, a detailed parametric study is carried out on photocatalytic hydrogen generation using Pt/TiO2 and formaldehyde and it is shown that the solution pH, platinum content (wt %) on TiO2, catalyst concentration, light intensity, and initial formaldehyde concentration all affect the process. In order to study the performance of a noble-metal-free-co-catalyst-semiconductor hetero-structure for photocatalytic hydrogen generation, molybdenum sulfide is grown on TiO2 by applying the in-situ solar photo-deposition method in a dye-sensitized photocatalytic system. It is observed that the presence of molybdenum sulfide in the system improves the solar photocatalytic hydrogen generation. A systematic statistical analysis is performed to investigate the effect of different reaction parameters as well as their interaction effects and to maximize the hydrogen generation under solar light irradiation. Graphene-based TiO2 and ZnO are synthesized by hydrothermal method and their performances for photocatalytic water treatment are studied. Optical and structural properties of the composites are obtained using XRD, XPS, Raman spectroscopy, UV-vis spectroscopy, TEM, and SEM. Due to the beneficial effects of graphene, using the two composites results in better degradation of photocatalytic phenol. The parametric study for optimizing the reaction conditions is also presented. The study conducted in this research thesis establishes that the efficiency of solar photocatalytic is greatly enhanced by using a hybrid photocatalyst, since such photocatalyst can significantly suppress the recombination of photo-generated charge carries and absorb the wider range of solar light

A Corpus-driven Food Science and Technology Academic Word List

The overarching goal of this study was to create a list of the most frequently occurring academic words in Food Science and Technology (FST). To this end, a 4,652,444-word corpus called Food Science and Technology Research Articles (FSTRA), which included 1,421 research articles (RAs) randomly selected from 38 journals across five sub-disciplines in FST, was developed. Frequency and range-based criteria were used to develop Food Science and Technology Academic Word list (FSTAWL). Word families had to occur in more than 19 journals, and they had to recur at least 134 times in the whole corpus. The computer programme RANGE was used to analyse the data. The results of frequency and range-based analysis showed that 1,090 academic words met the criteria of the study and constituted FSTAWL. The results also revealed that these words accounted for 13% of the coverage in the FSTRA.  FSTAWL provides food science and technology non-native English learners who need to read a large number of RAs and to publish FST RAs in the English journals with a useful list of the most frequently used academic words, helping them to strengthen their academic reading and writing proficiency. The findings echo calls for creating more discipline-specific word lists to cater for the needs of specialized learner populations, providing implications for materials producers  as well as explicit teaching of academic words

Synthesis and characterization of Ni(II) and Cu(II) complexes based on quercetin Schiff base and using them as heterogeneous catalysts in Henry reaction

136-143Quercetin is a dietary flavonoid, which with its specialized structure can form Schiff bases and their metal complexes. Schiff base ligand has been synthesized through the condensation of quercetin and ethanolamine. In this paper, two new metal complexes involving the Schiff base ligand have been prepared by a simple method at room temperature. SBL-Cu and SBL-Ni have been characterized by elemental analysis, ICP, UV-visible, and FT-IR studies. The activity of the synthesized complexes as a heterogeneous catalyst has been assessed in Henry reaction. The complexes have shown high catalytic performance in Henry reaction. However, SBL-Cu had better catalytic activity than SBL-Ni. These catalysts can be recycled and reused five times without a significant reduction in the activity. A series of benzaldehyde derivatives have been applied in the optimized Henry reaction to investigate the effect of the substituent group on the yield of the reaction. As expected, benzaldehydes containing electron-withdrawing group have a higher yield in Henry reaction

N2O Formation during NH3-SCR over Different Zeolite Frameworks: Effect of Framework Structure, Copper Species, and Water

The formation characteristics of N2O were investigated with respect to copper-functionalized zeolites, i.e., Cu/SSZ-13 (CHA), Cu/ZSM-5 (MFI), and Cu/BEA (BEA) and compared with the corresponding zeolites in the H form as references to elucidate the effect of the framework structure, copper addition, and water. Temperature-programmed reduction with hydrogen showed that the CHA framework has a higher concentration of Cu2+ (Z2Cu) compared to MFI and BEA. The characterizations and catalyst activity results highlight that CHA has a framework structure that favors high formation of ammonium nitrate (AN) in comparison with MFI and BEA. Moreover, AN formation and decomposition were found to be promoted in the presence of Cu species. On the contrary, lower N2O formation was observed from Cu/CHA during standard and fast SCR reactions, which is proposed to be due to highly stabilized AN inside the zeolite cages. On the other hand, significant amounts of N2O were released during heating due to decomposition of AN, implying pros and cons of AN stability for Cu/CHA with possible uncontrolled N2O formation during transient conditions. Additionally, important effects of water were found, where water hinders AN formation and increases the selectivity for decomposition to NO2 instead of N2O. Thus, less available AN forming N2O was observed in the presence of water. This was also observed in fast SCR conditions where all Cu/zeolites exhibited lower continuous N2O formation in the presence of water

In situ DRIFT studies on N2O formation over Cu-functionalized zeolites during ammonia-SCR

The influence of the zeolite framework structure on the formation of N2O during ammonia-SCR of NOx was studied for three different copper-functionalized zeolite samples, namely Cu-SSZ-13 (CHA), Cu-ZSM-5 (MFI), and Cu-BEA (BEA). The evolution of surface species during the SCR reaction at different temperatures was monitored with step-response experiments using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at different reaction conditions. Also, density functional theory (DFT) calculations were performed to assist the interpretation of the experimental results. The DRIFTS results indicate that NO+ and nitrate species are the main products formed during NO oxidation, and NO appears to adsorb on both Cu-Lewis and Al-Lewis acid sites. The DFT calculations for NO adsorption on the SSZ-13 sample reveal adsorption at Bronsted acid sites with similar adsorption energies but with a slight difference in NO+ stretching vibrations in the DRIFT spectra. Within the standard SCR reaction, in the O-H stretching region, the number of NH3 molecules adsorbed on the Bronsted acid sites is higher for the small-pore size sample compared to the medium- and large-pore zeolites. The obtained DRIFTS results for nitrate species are supported by DFT calculations by simulating the IR spectra of mobile and framework bound nitrate species, which both have a signature at 1604 cm(-1) associated with the O-N bond on NO3-. It is revealed that N2O is produced in a higher amount at lower temperatures for all three samples irrespective of the NO/NO2 ratio. Furthermore, the obtained results from both DRIFTS studies and flow reactor experiments show the higher formation of N2O for the large-pore zeolite compared to the medium- and small-pore zeolite

Does Serum Chloride Level Affect the Outcomes in Children Admitted to the Pediatric Intensive Care Unit?

Background: Serum chloride disorders are common in critically ill patients and appear to be associated with worse outcomes in patients. However, less attention has been paid to the amount of chloride in critically ill patients.  This study aims to determine the frequency of serum chloride disorders and their possible association with disease outcomes in all children admitted to the pediatric intensive care unit (PICU). Methods: This prospective study was performed on all patients admitted to the PICU of Akbar Children Hospital, Mashhad, Iran, from April 2019 to April 2020. Serum chloride levels were recorded daily on the first, second, and third days of the PICU stay. Statistical analyses were carried out using SPSS software (Version 24, SPSS Inc., Chicago, IL, USA) through one-way analysis of variance test, and Chi-square test in the significance level of α=0.05. Results: In this study, no significant relationship was observed between serum chloride levels and patients’ final status (P≥0.05). Serum Chloride level on the first day of PICU admission was significantly correlated with the length of PICU stay (r= 0.258, P= 0.029). There was no significant relationship between serum chloride levels and the patients’ need for mechanical ventilation on any of the three days (P≥0.05). Conclusions: According to the results, serum chloride level can be considered as an indicator of the length of the PICU stay

Immobilization of Laccase in Alginate-Gelatin Mixed Gel and Decolorization of Synthetic Dyes

Alginate-gelatin mixed gel was applied to immobilized laccase for decolorization of some synthetic dyes including crystal violet. The immobilization procedure was accomplished by adding alginate to a gelatin solution containing the enzyme and the subsequent dropwise addition of the mixture into a stirred CaCl2 solution. The obtained data showed that both immobilized and free enzymes acted optimally at 50°C for removal of crystal violet, but the entrapped enzyme showed higher thermal stability compared to the free enzyme. The immobilized enzyme represented optimum decolorization at pH 8. Reusability of the entrapped laccase was also studied and the results showed that ca. 85% activity was retained after five successive cycles. The best removal condition was applied for decolorization of seven other synthetic dyes. Results showed that the maximum and minimum dye removal was related to amido black 10B and eosin, respectively