On the effects of K and La co-promotion on CuCl2/γ-Al2O3 catalysts for the oxychlorination of ethylene

Baidoo, Martina Francisca; Fenes, Endre; Rout, Kumar Ranjan; Fuglerud, Terje; Chen, D.

doi:10.1016/j.cattod.2017.06.040

Cited by 20 publications

(34 citation statements)

References 27 publications

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“…The high stability is due to the high concentration of CuCl 2 , which is resulted from the fast oxidation rate of CuCl. This is in good agreement with the previous reports that when the catalyst is doped with KCl, the CuCl oxidation rate can be greatly enhanced and the RDS changed from the oxidation to the reduction step. ,, Furthermore, the reaction rate is quite close to the predicted by the intersection point shown in Figure f, which shows that rate diagram is a reliable method for kinetic studies for the analysis of the activity and the evolution of CuCl 2 concentration. It further proves that the high CuCl 2 concentration can benefit the stability of the ethylene oxychlorination catalyst, and it can be achieved by adding certain promoters through enhancing the oxidation rate of CuCl.…”

Section: Results and Discussionsupporting

confidence: 92%

“…In our previous reports, we have systematically studied the CuCl 2 /γ-Al 2 O 3 -based catalyst in the ethylene oxychlorination process using ultraviolet–visible and near-infrared spectroscopy (UV–vis–NIR), and the concentration of CuCl 2 can be quantified under steady-state reaction conditions. ,,, This method was mainly based on the d–d transition, and the absorption intensity is proportional to the amount of CuCl 2 since no absorption can be observed on CuCl in the near-IR region (a wavelength of 793 nm was chosen for analysis). Although this single-wavelength analysis of UV–vis–NIR spectroscopy has been successfully applied in operando kinetic study of ethylene oxychlorination, the following challenges remain: the Cu oxidation state in both CuCl 2 and Cu 2 OCl 2 is +2, and it cannot be distinguished only in the d–d transition region; the surface intermediate such as CuCl 2 with Cl vacancies cannot be detected and analyzed; large datasets of spectroscopy were collected with time in reactions; and treatment of the large datasets by scan to scan becomes a highly time-consuming task.…”

Section: Introductionmentioning

confidence: 99%

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Insights of the Dynamic Copper Active Sites in Ethylene Oxychlorination Studied by the Multivariate UV–vis–NIR Resolution Kinetic Approach

Gopakumar

Zhang

et al. 2021

Ind. Eng. Chem. Res.

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Monitoring and simulating the events occurring on the catalysts under the real reaction conditions has significant meaning for elucidating the dynamic changes of the active sites during the reactions and for a better understanding of the reaction mechanisms. Herein, we use the operando ultraviolet–visible and near-infrared (UV–vis–NIR) spectroscopy to study the CuCl2/γ-Al2O3-based catalyst in ethylene oxychlorination, one of the most important processes for producing vinyl chloride in the industry, to elucidate the dynamic changes of the copper active sites. The full spectra of Cu species such as CuCl2, CuCl2 with vacancies, CuCl, and Cu2OCl2 were detected and identified for the first time, and their transient changes and contribution in the reduction, oxidation, and hydrochlorination steps as well as at the steady-state operation in the catalytic cycle can be accurately “imaged” by resolving the UV–vis–NIR spectra dataset using the multivariate curve resolution (MCR) analysis. The distribution and changes of the Cu species are correlated to the catalytic activity, selectivity, and stability. The time-resolved spectra and their correlation with the catalytic performance provide better insights into the dynamic nature of the active sites and their role in the Mars–van Krevelen-type reaction. This method is expected to be exploited to analyze the dynamics of the active sites and kinetic studies in other catalytic redox systems.

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Section: Results and Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Insights of the Dynamic Copper Active Sites in Ethylene Oxychlorination Studied by the Multivariate UV–vis–NIR Resolution Kinetic Approach

Gopakumar

Zhang

et al. 2021

Ind. Eng. Chem. Res.

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Section: Cu-based Catalysts For Ethylene Oxychlorinationmentioning

confidence: 92%

“…Recently, the three-step MvK mechanism was further demonstrated and confirmed by a study of three individual steps using a combined UV–vis-NIR and mass spectroscopy (MS), where the evolution of the number of CuCl 2 with time was investigated. ,, The Kubelka–Munk function (KMF) at 793 nm is sensitive to the d–d transition band of CuCl 2 . CuCl with the electronic configuration of 3d 10 does not exhibit a d–d band transition.…”

Section: Cu-based Catalysts For Ethylene Oxychlorinationmentioning

confidence: 99%

Critical Review of Catalysis for Ethylene Oxychlorination

Wang

et al. 2020

ACS Catal.

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Ethylene oxychlorination is the key technology in vinyl chloride (VCM, the monomer of PVC, polyvinyl chloride) production to close the chlorine loop by consuming the HCl released from the former cracking step. Due to the high demand for PVC, this leads to ethylene oxychlorination being one of the most important processes in the industry. This Review covers an indepth analysis of the dynamic nature of active sites for the main and side reactions involved in ethylene oxychlorination, featuring the findings and viewpoints from the dynamic kinetics study and analysis under industrial operating conditions. A unified picture of the mechanism of the surface reactions, and the effect of supports and promoters, has been presented based on the decoupled redoxcycle experiments, which leads to a significantly better understanding of the mechanism and provides valuable guidelines for effective catalyst design. Operando techniques and kinetic tools of the rate-diagram, as well as their application to the study of the redox-cycle in ethylene oxychlorination and kinetic models on both the main product and byproduct, are also reviewed. Perspectives on challenges and new process development and future research focus for better study of the VCM production chemistry are also proposed.

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“…(3)], CuCl 2 was reduced by C 2 H 4 [10] . The ethylene conversion and the accumulative removed Cl from CuCl 2 was measured as a function of time [8d,9,11] . Only EDC and no CO x were detected as the product.…”

Section: Transient Kinetics Of the Reduction Of Cucl2mentioning

confidence: 99%

Prediction and Tuning of the Defects in the Redox Catalysts: Ethylene Oxychlorination

Fenes

et al. 2020

ChemCatChem

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The defect plays a significant role in tuning the electronic structure of metal compounds such as oxides, chlorides, sulfides and nitrides, which is frequently used to explain the enhanced catalytic activity. However, the dynamic change of defect relating to the oxidation state change during the reaction is rarely addressed, and it is still not able to be appropriately predicted since the kinetic modeling of the redox reaction involving the in‐situ formation of defects is challenged by the dynamic evolution of the active sites and the complex kinetic phenomena. Here, for the first time, we present a general method to build a new kinetic model of the redox reaction cycle by combined kinetics of reduction‐ and oxidation steps to predict the time and spatially resolved formation of defects of solid catalysts and the reaction products in ethylene oxychlorination on CuCl2/Al2O3 catalyst. The defect concentration can be tuned by manipulating the relative rates of the reduction‐ and oxidation steps.

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On the effects of K and La co-promotion on CuCl2/γ-Al2O3 catalysts for the oxychlorination of ethylene

Cited by 20 publications

References 27 publications

Insights of the Dynamic Copper Active Sites in Ethylene Oxychlorination Studied by the Multivariate UV–vis–NIR Resolution Kinetic Approach

Insights of the Dynamic Copper Active Sites in Ethylene Oxychlorination Studied by the Multivariate UV–vis–NIR Resolution Kinetic Approach

Critical Review of Catalysis for Ethylene Oxychlorination

Prediction and Tuning of the Defects in the Redox Catalysts: Ethylene Oxychlorination

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