scholarly journals Intensification of Catalytic Processes through the Pellet Structuring: Steady-State Properties of a Bifunctional Catalyst Pellet Applied to Generic Chemical Reactions and the Direct Synthesis of DME

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1020 ◽  
Author(s):  
Katarzyna Bizon ◽  
Krzysztof Skrzypek-Markiewicz ◽  
Dominik Pędzich ◽  
Natalia Reczek
Keyword(s):  
Chemical Reactions ◽  
Active Sites ◽  
Direct Synthesis ◽  
Fixed Bed ◽  
Product Yield ◽  
Bifunctional Catalyst ◽  
Active Centers ◽  
Entire Volume ◽  
Catalyst Pellet ◽  
Real Process

Structuring of different types of catalytic active centers at a single-pellet level appears to be a promising and powerful tool for integration and intensification of multistep solid-catalyzed chemical reactions. However, the enhancement in the product yield and selectivity strongly depends on the proper choice of the distribution of different catalysts within the pellet. To demonstrate potential benefits from properly designed catalyst pellet, numerical studies were conducted with the aid of the mathematical model of a single spherical bifunctional catalyst pellet. The analysis was performed both for a system of two generic chemical reactions and for a real process, i.e., direct synthesis of dimethyl ether (DME) from synthesis gas via methanol. Evaluation of the pellet performance was done for three arrangements of the catalytic active sites within the pellet, i.e., a uniform distribution of two types of catalytic active centers in the entire volume of the pellet, and two core–shell structures. It was demonstrated that, especially for the larger pellets typical for fixed-bed applications, the product yield might be significantly improved by selecting proper catalyst arrangements within the pellet.

Nanoreactors: properties, applications and characterization

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Rahmad Syah ◽  
Marziah Zahar ◽  
Ehsan Kianfar
Keyword(s):  
Chemical Reactions ◽  
Active Sites ◽  
Extended Period ◽  
Chemical Reactor ◽  
Chemical Processes ◽  
Metal Species ◽  
Limited Area ◽  
Active Centers ◽  
Chemical Structures ◽  
Wide Range

Abstract Nanoreactors are a type of chemical reactor that is used mostly in nanotechnology and nanobiotechnology. These unique reactors are critical to the operation of a nano foundry, which is essentially a foundry that produces goods on a nanoscale. Active sites, such as transitional metal species, can also be added to nanoreactors. In this situation, the NR’s limited area might impact reaction rate and mechanism by increasing the contacts between reactants and active sites and changing the concentration of the reactant at the active site. Immobilization of chiral active centers inside porous materials has received a lot of interest in this context, and there have been a lot of publications proving the benefits of nano space confinement in chemical processes. The specific mechanism in which enantioselectivities are strengthened has been clarified using molecular dynamics simulations. Nanoreactors are nanometer-sized chambers with the potential to improve chemical conversions by shielding catalysts from external effects and encapsulating reactors and catalysts in a tiny space for an extended period of time. Natural and synthetic nanoreactors are the two types of nanoreactors that can be found in general. The first group has a more selective function while also having a more complicated structure, whereas the second group has more variation and a simpler structure. Synthetic nanoreactors have so far been made with a variety of molecules and large types of molecules. The space inside the nanoreactors is a good environment for the production of various nanostructures, in addition to a wide range of chemical reactions. When chemical reactions are carried out in confined spaces with nanometer dimensions and micrometer volumes, the kinetics and the entire process path are altered. Nanoreactors are restricted areas used to execute specialized chemical processes. In the cells of living organisms, numerous simultaneous reactions are based on the same concept. As a result, various biological and chemical structures with nanoreactor characteristics are used in this strategy.

scholarly journals Enhancement of the Direct Synthesis of Dimethyl Ether (DME) from Synthesis Gas by Macro- and Microstructuring of the Catalytic Bed

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 852
Author(s):  
Katarzyna Bizon ◽  
Krzysztof Skrzypek-Markiewicz ◽  
Gaetano Continillo
Keyword(s):  
Dimethyl Ether ◽  
Direct Synthesis ◽  
Bifunctional Catalyst ◽  
Physical Mixture ◽  
Fixed Bed Reactor ◽  
Synthesis Process ◽  
Active Centers ◽  
Heterogeneous Model ◽  
Catalyst Pellets ◽  
Synthesis Of Dimethyl Ether

This work reports on a modelling study of the influence of the distribution of metallic and acidic active centers within a catalytic fixed-bed reactor for the direct synthesis of dimethyl ether (DME), conducted to demonstrate the potential of reactor-level and pellet-level structuring of catalytic active centers in process integration and intensification. To account for the pellet structure, the analysis was performed with the aid of a heterogeneous model considering both interphase and intrapellet mass transport resistances. The study evaluated, in terms of DME and methanol yield and selectivity, the performance of a tubular reactor loaded with a physical mixture of monofunctional catalyst pellets or structured bifunctional catalyst pellets with different arrangements of the catalytic centers. It was confirmed that bifunctional catalysts overperform significantly a physical mixture of monofunctional particles. Moreover, it was shown that the internal structure of a bifunctional catalyst pellet is an important feature that deserves to be exploited deeper, in view of further intensification of the DME synthesis process to be achieved with a better reactor design.

Catalytic Resonance Theory: Parallel Reaction Pathway Control

2019 ◽  
Author(s):  
M. Alexander Ardagh ◽  
Manish Shetty ◽  
Anatoliy Kuznetsov ◽  
Qi Zhang ◽  
Phillip Christopher ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Active Site ◽  
Active Sites ◽  
Reaction Pathway ◽  
Control Strategies ◽  
Oscillation Amplitude ◽  
Catalytic Performance ◽  
Parallel Reaction ◽  
Resonance Theory ◽  
Static Conditions

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site is achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10<sup>-6</sup> < f < 10<sup>4</sup> Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

scholarly journals Synergistic Effect of Alkali Na and K Promoter on Fe-Co-Cu-Al Catalysts for CO2 Hydrogenation to Light Hydrocarbons

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 735
Author(s):  
Yuhao Zheng ◽  
Chenghua Xu ◽  
Xia Zhang ◽  
Qiong Wu ◽  
Jie Liu
Keyword(s):  
Synergistic Effect ◽  
Active Sites ◽  
Intermediate Formation ◽  
Active Phase ◽  
Dissociative Adsorption ◽  
Co2 Hydrogenation ◽  
Chain Growth ◽  
Co2 Conversion ◽  
Light Hydrocarbons ◽  
Active Centers

Alkali metal K- and/or Na-promoted FeCoCuAl catalysts were synthesized by precipitation and impregnation, and their physicochemical and catalytic performance for CO2 hydrogenation to light hydrocarbons was also investigated in the present work. The results indicate that Na and/or K introduction leads to the formation of active phase metallic Fe and Fe-Co crystals in the order Na < K < K-Na. The simultaneous introduction of Na and K causes a synergistic effect on increasing the basicity and electron-rich property, promoting the formation of active sites Fe@Cu and Fe-Co@Cu with Cu0 as a crystal core. These effects are advantageous to H2 dissociative adsorption and CO2 activation, giving a high CO2 conversion with hydrogenation. Moreover, electron-rich Fe@Cu (110) and Fe-Co@Cu (200) provide active centers for further H2 dissociative adsorption and O-C-Fe intermediate formation after adsorption of CO produced by RWGS. It is beneficial for carbon chain growth in C2+ hydrocarbons, including olefins and alkanes. FeCoCuAl simultaneously modified by K-Na exhibits the highest CO2 conversion and C2+ selectivity of 52.87 mol% and 89.70 mol%, respectively.

Tailoring the Co4+/Co3+ active sites in single perovskite as a bifunctional catalyst for oxygen electrode reactions "

2021 ◽  
Author(s):  
Song-Jeng Isaac Huang ◽  
Adil Muneeb ◽  
Sabhapathy Palani ◽  
Anjaiah Sheelam ◽  
Bayikadi Khasimsaheb ◽  
...  
Keyword(s):  
Oxygen Evolution Reaction ◽  
Precious Metal ◽  
Active Sites ◽  
Low Cost ◽  
Bifunctional Catalyst ◽  
Oxygen Electrode ◽  
Reduction Reaction ◽  
New Class ◽  
Electrode Reactions ◽  
Energy Conversion Devices

Developing a non-precious metal electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is desirable for low-cost energy conversion devices. Herein, we designed and developed a new class...

Active sites-enriched carbon matrix enables efficient triiodide reduction in dye-sensitized solar cells: An understanding of the active centers

Nano Energy ◽  
2018 ◽  
Vol 54 ◽  
pp. 138-147 ◽  
Author(s):  
Xiangtong Meng ◽  
Chang Yu ◽  
Xuepeng Zhang ◽  
Longlong Huang ◽  
Matthew Rager ◽  
...  
Keyword(s):  
Solar Cells ◽  
Active Sites ◽  
Dye Sensitized Solar Cells ◽  
Carbon Matrix ◽  
Active Centers ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

scholarly journals Heterogeneous Catalytic Synthesis of 2-Methylbenzimidazole from 2-Nitroaniline and Ethanol Over Mg Modified Cu-Pd/γ-Al2O3

Catalysts ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 8 ◽  
Author(s):  
Feng Feng ◽  
Yaqin Deng ◽  
Zheng Cheng ◽  
Xiaoliang Xu ◽  
Qunfeng Zhang ◽  
...  
Keyword(s):  
Active Sites ◽  
Hydrogen Transfer ◽  
High Efficiency ◽  
Simple Procedure ◽  
Direct Synthesis ◽  
Reaction System ◽  
Simple Method ◽  
Heterogeneous Catalytic ◽  
Coupled Reaction ◽  
Al2o3 Catalyst

The direct synthesis of benzimidazoles from 2-nitroaniline and ethanol over Cu-Pd/γ-Al2O3 catalysts has the advantages of requiring easily available starting materials, having high efficiency, and a simple procedure. The modification by Mg of the Cu-Pd/γ-Al2O3 catalyst could improve the catalytic activity significantly. The addition of Mg to the Cu-Pd/γ-Al2O3 catalyst could maintain and promote the formation of CuPd alloy active sites. Meanwhile, the basicity of the support was enhanced appropriately by Mg, which generated more basic sites (Al-Oδ−) to accelerate the dehydrogenation of alcohol and increased the rate of the whole coupled reaction. The 2-nitroaniline was completely converted over Cu-Pd/(Mg)γ-Al2O3 after reacting for six hours, and the yield of 2-methylbenzimidazole was 98.8%. The results of this work provide a simple method to develop a more efficient catalyst for the “alcohol-dehydrogenation, hydrogen transfer and hydrogenation” coupled reaction system.

On efficiency of vanadium-oxide promoter in cobalt Fischer – Tropsch catalysts

2021 ◽  
Vol 1 (1-2) ◽  
pp. 15
Author(s):  
Elham Yaghoobpour ◽  
Yahya Zamani ◽  
Saeed Zarrinpashne ◽  
Akbar Zamaniyan
Keyword(s):  
Vanadium Oxide ◽  
Active Sites ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bet Surface Area ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Fischer Tropsch ◽  
Co Conversion ◽  
Loading Amount

Promoters and their loading amount have crucial roles in cobalt Fischer – Tropsch catalysts. In this regard, the effects of vanadium oxide (V2O5) as a proposed promoter for Co catalyst supported on TiO2 have been investigated. Three catalysts with 0, 1, and 3 wt.% of V2O5 promoter loading are prepared by the incipient wetness impregnation method, and characterized by the BET surface area analyzer, XRD, H2-TPR, and TEM techniques. The fixed-bed reactor was employed for their evaluations. It was found that the catalyst containing 1 wt.% V2O5 has the best performance among the evaluated catalysts, demonstrating remarkable selectivity: 92 % C5+ and 5.7 % CH4, together with preserving the amount of CO conversion compared to the unpromoted catalyst. Furthermore, it is reported that the excess addition of V2O5 promoter (> 1 wt.%) in the introduced catalyst leads to the detrimental effect on the CO conversion and C5+ selectivity, mainly owing to diminished active sites by V2O5 loading.

scholarly journals Hierarchical H-ZSM5 zeolites based on natural kaolinite as a high-performance catalyst for methanol to aromatic hydrocarbons conversion

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ahmad Asghari ◽  
Mohammadreza Khanmohammadi Khorrami ◽  
Sayed Habib Kazemi
Keyword(s):  
Pore Size ◽  
Aromatic Hydrocarbons ◽  
High Performance ◽  
Low Cost ◽  
Direct Synthesis ◽  
Fixed Bed ◽  
Methanol Conversion ◽  
Catalytic Performance ◽  
Fixed Bed Reactor ◽  
Good Prospect

AbstractThe present work introduces a good prospect for the development of hierarchical catalysts with excellent catalytic performance in the methanol to aromatic hydrocarbons conversion (MTA) process. Hierarchical H-ZSM5 zeolites, with a tailored pore size and different Si/Al ratios, were synthesized directly using natural kaolin clay as a low-cost silica and aluminium resource. Further explored for the direct synthesis of hierarchical HZSM-5 structures was the steam assisted conversion (SAC) with a cost-effective and green affordable saccharide source of high fructose corn syrup (HFCS), as a secondary mesopore agent. The fabricated zeolites exhibiting good crystallinity, 2D and 3D nanostructures, high specific surface area, tailored pore size, and tunable acidity. Finally, the catalyst performance in the conversion of methanol to aromatic hydrocarbons was tested in a fixed bed reactor. The synthesized H-ZSM5 catalysts exhibited superior methanol conversion (over 100 h up to 90%) and selectivity (over 85%) in the methanol conversion to aromatic hydrocarbon products.

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