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A simple model (Continuous Stirred-Tank Reactor) has been developed to predict the behavior of industrial ethylene oxychlorination fluidized beds operating in a turbulent regime. The approach showed good agreement both with results from industrial reactors and with those corresponding to the (Simple two phases-Plug bubble-Mixed flow emulsion approach) validated in the literature. For low flow rates, the use of the (Simple two phases - Plug bubble - Plug emulsion model) adapted to these conditions enabled us to highlight the location and extent of undesirable thermal hot spots for the process, and to propose actions to control them by acting on the temperature and/or on the feed gas flows. By comparing this model with the plug approach, the significant slowdown in ethylene conversion caused by resistance to mass transfer when feed flow rates are low is highlighted. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

The structure and performance stability of a Pt-based catalyst for propane dehydrogenation during its reaction–regeneration cycles is one of the key factors for its commercial application. A 0.3% Pt/Al2O3 catalyst with a sub-nanometric particle size was prepared and two different types of regeneration processes, long-term dichloroethane oxychlorination and a reaction–oxidation–oxychlorination cycle, were investigated on this catalyst. The fresh, sintered and regenerated catalyst was characterized by HAADF-STEM, CO-DRIFTS, XPS, CO chemisorption and N2 physisorption, and its catalytic performance for propane dehydrogenation was also tested. The results show that the catalysts tend to have a similar particle size, coordination environment and catalytic performance with the extension of the regeneration time or an increase in the number of cycles in the two regeneration processes, and a common steady state could be achieved on the catalysts. This indicates that structure of the catalyst tends to approach its equilibrium state in the regeneration process, during which the utilization efficiency of Pt is maximized by increasing the dispersion of Pt and its intrinsic activity, and the structural robustness is secured. The performance of the catalyst is comparable to that of a single-atom Pt/Al2O3 catalyst.

Abstract Fine constructing the chemical environment of the central metal is vital in developing efficient single‐atom catalysts (SACs). Herein, the atomically dispersed Cu on the N‐doped carbon is modulated by introducing CuP moiety to CuNC SAC. Through fine‐tuning with another heteroatom P, the Cu SAC shows the superior performance of ethylene oxychlorination. The Cu site activity of Cu‐NPC is four times higher than the P‐free Cu‐NC catalyst and 25 times higher than the Ce‐promoted CuCl2/Al2O3 catalyst in the long‐term test (>200 h). The selectivity of ethylene dichloride can be splendidly kept at ≈99%. Combined experimental and simulation studies provide a theoretical framework for the coordination of Cu, N, and P in the complex active center and its role in effectively catalyzing ethylene oxychlorination. It integrates the oxidation and chlorination reactions with superior catalytic performance and unrivaled ability of corrosive‐HCl resistance. The concept of fine constructing with another heteroatom is anticipated to provide with inspiration for rational catalyst design and expand the applications of carbon‐based SACs in heterogeneous catalysis.

β-halogenated enol esters and ethers are versatile building blocks in organic synthesis, which has attracted increasing attention. In this study, we report the facile trans-oxyiodination and oxychlorination of alkynes, leading to the direct construction of versatile halogenated enol esters and ethers. This transformation features an easy operation, optimal atomic economy, a strong functional group tolerance, broad substrate scope, and excellent trans-selectivity. Employing highly electrophilic bifunctional N–X (halogen) reagents was the key to achieving broad reaction generality. To our knowledge, this transformation represents the first oxyhalogenation system employing N–X (halogen) reagents as both oxylation and halogenation sources.

Acetylene hydrochlorination and ethylene oxychlorination are the two most common methods of producing vinyl chloride monomer (VCM), which has been linked to liver impairment, hepatocellular carcinoma (HCC), and angiosarcoma of the liver (ASL) in occupational settings. However, whether and how these impairments could be effectively improved from workplace root causes has yet to be discovered. This study aimed to evaluate whether improvements in protective measures in groups Y (408 subjects) and Z (349 subjects) could have an influential impact on the alleviation of liver impairment by comparing risk assessment levels under several semi-quantitative models and results from liver ultrasound detection and liver function tests before and after the improvement. Importantly, significant differences in constituent ratio involved in parameters among age, length of employment, weekly exposure time, smoking status, alcohol consumption, and sleeping quality were found between Y and Z before improvement took place in 2020 (P < 0.05 or P < 0.001), and population distribution by gender between Y and Z was in a large homogeneity with differences in age and length of employment. CSTE involves ore breaking, acetylene generation, steam stripping, outward processing, and welding maintenance, was disqualified in 2020 compared to OEL, and was said to have declined to meet OEL requirements by 2021. Further, a negative correction of fresh air requirement and ventilation air changing rate with ambient concentration toward hazards in Y was stronger in 2021 than in 2020. Significant differences in risk levels in Y between 2020 and 2021 were found as ore breaking, acetylene generation, steam stripping, outward processing, VCM polymerization, welding, and repairing, decreasing to relatively lower risk levels in 2021 from the original ones in 2020 only under the semi-quantitative comprehensive index model. Abnormal rates toward other hepatic symptoms decreased in the majority of positions after the improvement, as referred to by alterations such as ALT, AST, and GGT. Overall, the effect of improvements on protective measures effectively reduced positions' risk assessment levels through ventilation enhancement and airtight strengthening, which further affected abnormal rates toward other hepatic symptoms, and alterations such as ALT, AST, and GGT were much more significant in Y than effect in Z.

The structure and performance stability of a Pt-based catalyst for propane dehydrogenation during its reaction–regeneration cycles is one of the key factors for its commercial application. A 0.3% Pt/Al2O3 catalyst with a sub-nanometric particle size was prepared and two different types of regeneration processes, long-term dichloroethane oxychlorination and a reaction–oxidation–oxychlorination cycle, were investigated on this catalyst. The fresh, sintered and regenerated catalyst was characterized by HAADF-STEM, CO-DRIFTS, XPS, CO chemisorption and N2 physisorption, and its catalytic performance for propane dehydrogenation was also tested. The results show that the catalysts tend to have a similar particle size, coordination environment and catalytic performance with the extension of the regeneration time or an increase in the number of cycles in the two regeneration processes, and a common steady state could be achieved on the catalysts. This indicates that structure of the catalyst tends to approach its equilibrium state in the regeneration process, during which the utilization efficiency of Pt is maximized by increasing the dispersion of Pt and its intrinsic activity, and the structural robustness is secured. The performance of the catalyst is comparable to that of a single-atom Pt/Al2O3 catalyst. [ABSTRACT FROM AUTHOR]

A simple model (Continuous Stirred-Tank Reactor) has been developed to predict the behavior of industrial ethylene oxychlorination fluidized beds operating in a turbulent regime. The approach showed good agreement both with results from industrial reactors and with those corresponding to the (Simple two phases-Plug bubble-Mixed flow emulsion approach) validated in the literature. For low flow rates, the use of the (Simple two phases - Plug bubble - Plug emulsion model) adapted to these conditions enabled us to highlight the location and extent of undesirable thermal hot spots for the process, and to propose actions to control them by acting on the temperature and/or on the feed gas flows. By comparing this model with the plug approach, the significant slowdown in ethylene conversion caused by resistance to mass transfer when feed flow rates are low is highlighted. [ABSTRACT FROM AUTHOR]

Herein we report an additive-free protocol for the facile synthesis of α,α-dichloroketones and α-chlorohydrins from various aryl terminal, diaryl internal, and aliphatic terminal alkynes and alkenes, respectively. The commercially available tert -butyl hypochlorite ( t BuOCl) was employed as a suitable chlorinating reagent, being accompanied by the less harmful t BuOH as the by-product. In addition, the oxygen atoms in the products came from water rather than molecular oxygen, based on the 18 O-labelling experiments. Meanwhile, the diastereoselectivity of the Z - and the corresponding E -alkenes has been compared and rationalized. Using a group of control experiments, the possible mechanisms have been proposed as the initial electrophilic chlorination of unsaturated C-C bonds in a Markovnikov-addition manner in general followed by a nucleophilic addition with water. This work simplified the oxychlorination method with a mild chlorine source and a green oxygen source under ambient conditions.

The main patterns of oxidative chlorination (oxychlorination) with such unsaturated hydrocarbons as propylene, acetylene, 1,3-butadiene, and benzene are considered. It is shown that when the processes are conducted in the gas phase, having heterogeneous copper or palladium based catalysts in the system is preferable. It is shown that palladium in a catalyst promotes processes of substitutive oxychlorination. Stagewise schemes of reactions are given for processes of propylene, acetylene, and benzene oxychlorination along with corresponding kinetic equations. Applied aspects of the above processes are discussed. [ABSTRACT FROM AUTHOR]

β-halogenated enol esters and ethers are versatile building blocks in organic synthesis, which has attracted increasing attention. In this study, we report the facile trans -oxyiodination and oxychlorination of alkynes, leading to the direct construction of versatile halogenated enol esters and ethers. This transformation features an easy operation, optimal atomic economy, a strong functional group tolerance, broad substrate scope, and excellent trans-selectivity. Employing highly electrophilic bifunctional N-X (halogen) reagents was the key to achieving broad reaction generality. To our knowledge, this transformation represents the first oxyhalogenation system employing N-X (halogen) reagents as both oxylation and halogenation sources.

In the article, the thermodynamics of the oxychlorination processes of ethylene in the presence of oxygen under the influence of hydrogen chloride were studied and the mechanism of the oxychlorination reaction was proposed. Kinetic equations describing the rate of formation of 1,2-dichloroethane and carbon dioxide were proposed based on the study of the mechanism of the process. The laws of formation of complete oxidation products of oxychlorination of ethylene with hydrogen chloride in the presence of oxygen in the presence of catalysts obtained for the oxychlorination reaction of ethylene with hydrogen chloride in the presence of oxygen were studied in a fluidized bed reactor designed for the oxychlorination reaction of ethylene in the presence of oxygen under the influence of hydrogen chloride. The temperature range is 210-240 ℃, the linear velocity of gases is 5.5-7 cm/sec, and the contact time of the oxychlorination reaction of conditioned ethylene with hydrogen chloride in the presence of oxygen is 8.5-9.5 sec. The ethylene oxychlorination reactor consists of a 32.5 m column apparatus with a diameter of 3.5 m. The operating modes of the reactor designed for the oxychlorination of ethylene under the influence of hydrogen chloride in the presence of oxygen were determined, and the material and heat balance of the reactor designed to carry out the oxychlorination reaction was calculated. The purpose of the work is to study the thermodynamic and kinetic laws of the oxychlorination processes of ethylene under the influence of hydrogen chloride in the presence of oxygen and to create a technology for obtaining vinyl chloride.

Fine constructing the chemical environment of the central metal is vital in developing efficient single-atom catalysts (SACs). Herein, the atomically dispersed Cu on the N-doped carbon is modulated by introducing Cu-P moiety to Cu-N-C SAC. Through fine-tuning with another heteroatom P, the Cu SAC shows the superior performance of ethylene oxychlorination. The Cu site activity of Cu-NPC is four times higher than the P-free Cu-NC catalyst and 25 times higher than the Ce-promoted CuCl2/Al2O3 catalyst in the long-term test (>200 h). The selectivity of ethylene dichloride can be splendidly kept at ≈99%. Combined experimental and simulation studies provide a theoretical framework for the coordination of Cu, N, and P in the complex active center and its role in effectively catalyzing ethylene oxychlorination. It integrates the oxidation and chlorination reactions with superior catalytic performance and unrivaled ability of corrosive-HCl resistance. The concept of fine constructing with another heteroatom is anticipated to provide with inspiration for rational catalyst design and expand the applications of carbon-based SACs in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Methane oxychlorination (MOC) is a promising reaction for the production of liquefied methane derivatives. Even though catalyst design is still in its early stages, the general trend is that benchmark catalyst materials have a redox-active site, with, e.g., Cu 2+ , Ce 4+ , and Pd 2+ as prominent showcase examples. However, with the identification of nonreducible LaOCl moiety as an active center for MOC, it was demonstrated that a redox-active couple is not a requirement to establish a high activity. In this work, we show that Mg 2+ -Al 3+ -based mixed-metal oxide (MMO) materials are highly active and stable MOC catalysts. The synergistic interaction between Mg 2+ and Al 3+ could be exploited due to the fact that a homogeneous distribution of the chemical elements was achieved. This interaction was found to be crucial for the unexpectedly high MOC activity, as reference MgO and γ-Al 2 O 3 materials did not show any significant activity. Operando Raman spectroscopy revealed that Mg 2+ acted as a chlorine buffer and subsequently as a chlorinating agent for Al 3+ , which was the active metal center in the methane activation step. The addition of the redox-active Eu 3+ to the nonreducible Mg 2+ -Al 3+ MMO catalyst enabled further tuning of the catalytic performance and made the EuMg 3 Al MMO catalyst one of the most active MOC catalyst materials reported so far. Combined operando Raman/luminescence spectroscopy revealed that the chlorination behavior of Mg 2+ and Eu 3+ was correlated, suggesting that Mg 2+ also acted as a chlorinating agent for Eu 3+ . These results indicate that both redox activity and synergistic effects between Eu, Mg, and Al are required to obtain high catalytic performance. The importance of elemental synergy and redox properties is expected to be translatable to the oxychlorination of other hydrocarbons, such as light alkanes, due to large similarities in catalytic chemistry., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)