Tuning the catalytic performance for the semi-hydrogenation of alkynols by selectively poisoning the active sites of Pd catalysts

2019 ◽  
Vol 21 (15) ◽  
pp. 4143-4151 ◽  
Author(s):  
Shanjun Mao ◽  
Bowen Zhao ◽  
Zhe Wang ◽  
Yutong Gong ◽  
Guofeng Lü ◽  
...  
Keyword(s):  
Active Sites ◽  
Catalytic Performance ◽  
Pd Catalysts ◽  
Fine Chemical

Semi-hydrogenation of alkynols to alkenols with Pd-based catalysts is of great significance in fine chemical industries.

The design and catalytic performance of molybdenum active sites on an MCM-41 framework for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

2019 ◽  
Vol 9 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Zhao-Meng Wang ◽  
Li-Juan Liu ◽  
Bo Xiang ◽  
Yue Wang ◽  
Ya-Jing Lyu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Aerobic Oxidation ◽  
Catalytic Performance ◽  
Mcm 41

The catalytic activity decreases as –(SiO)3Mo(OH)(O) > –(SiO)2Mo(O)2 > –(O)4–MoO.

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.

Structural/Texture Evolution During Facile Substitution of Ni into ZSM-5 Nanostructure vs. its Impregnation Dispersion Used in Selective Transformation of Methanol to Ethylene and Propylene

2020 ◽  
Vol 23 ◽  
Author(s):  
Parisa Sadeghpour ◽  
Mohammad Haghighi ◽  
Mehrdad Esmaeili
Keyword(s):  
High Temperature ◽  
Physicochemical Properties ◽  
Active Sites ◽  
Catalytic Performance ◽  
Fixed Bed Reactor ◽  
Light Olefins ◽  
Isomorphous Substitution ◽  
Impregnation Method ◽  
Hydrothermal Temperature ◽  
X Ray

Aim and Objective: Effect of two different modification methods for introducing Ni into ZSM-5 framework was investigated under high temperature synthesis conditions. The nickel successfully introduced into the MFI structures at different crystallization conditions to enhance the physicochemical properties and catalytic performance. Materials and Methods: A series of impregnated Ni/ZSM-5 and isomorphous substituted NiZSM-5 nanostructure catalysts were prepared hydrothermally at different high temperatures and within short times. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDX), Brunner, Emmett and Teller-Barrett, Joyner and Halenda (BET-BJH), Fourier transform infrared (FTIR) and Temperature-programmed desorption of ammonia (TPDNH3) were applied to investigate the physicochemical properties. Results: Although all the catalysts showed pure silica MFI–type nanosheets and coffin-like morphology, using the isomorphous substitution for Ni incorporation into the ZSM-5 framework led to the formation of materials with lower crystallinity, higher pore volume and stronger acidity compared to using impregnation method. Moreover, it was found that raising the hydrothermal temperature increased the crystallinity and enhanced more uniform incorporation of Ni atoms in the crystalline structure of catalysts. TPD-NH3 analysis demonstrated that high crystallization temperature and short crystallization time of NiZSM-5(350-0.5) resulted in fewer weak acid sites and medium acid strength. The MTO catalytic performance was tested in a fixed bed reactor at 460ºC and GHSV=10500 cm3 /gcat.h. A slightly different reaction pathway was proposed for the production of light olefins over impregnated Ni/ZSM-5 catalysts based on the role of NiO species. The enhanced methanol conversion for isomorphous substituted NiZSM-5 catalysts could be related to the most accessible active sites located inside the pores. Conclusion: The impregnated Ni/ZSM-5 catalyst prepared at low hydrothermal temperature showed the best catalytic performance, while the isomorphous substituted NiZSM-5 prepared at high temperature was found to be the active molecular sieve regarding the stability performance.

Efficient Production of Biodiesel Catalyzed by Acidic Nanoporous Carbon Materials：A Review

2020 ◽  
Vol 16 ◽  
Author(s):  
Anping Wang ◽  
Heng Zhang ◽  
Hu Li ◽  
Song Yang
Keyword(s):  
Pore Structure ◽  
Active Sites ◽  
Catalytic Performance ◽  
Nanoporous Carbon ◽  
Biodiesel Production ◽  
Efficient Production ◽  
Fossil Energy ◽  
Catalytic Materials ◽  
High Acid ◽  
Carbon Based

Background: With the gradual decrease of fossil energy, the development of alternatives to fossil energy has attracted more and more attention. Biodiesel is considered to be the most potent alternative to fossil energy, mainly due to its green, renewable and biodegradable advantages. The stable, efficient and reusable catalysts are undoubtedly the most critical in the preparation of biodiesel. Among them, nanoporous carbon-based acidic materials are very important biodiesel catalysts. Objective: The latest advances of acidic nanoporous carbon catalysts in biodiesel production was reviewed. Methods: Biodiesel is mainly synthesized by esterification and transesterification. Due to the important role of nanoporous carbon-based acidic materials in the catalytic preparation of biodiesel, we focused on the synthesis, physical and chemical properties, catalytic performance and reusability. Results: Acidic catalytic materials have a good catalytic performance for high acid value feedstocks. However, the preparation of biodiesel with acid catalyst requires relatively strict reaction conditions. The application of nanoporous acidic carbon-based materials, due to the support of carbon-based framework, makes the catalyst have good stability and unique pore structure, accelerates the reaction mass transfer speed and accelerates the reaction. Conclusion: Nanoporous carbon-based acidic catalysts have the advantages of suitable pore structure, high active sites, and high stability. In order to make these catalytic processes more efficient, environmentally friendly and low cost, it is an important research direction for the future biodiesel catalysts to develop new catalytic materials with high specific surface area, suitable pore size, high acid density, and excellent performance.

scholarly journals Degradation of hydroxypropyl guar gum at wide pH range by a heterogeneous Fenton-like process using bentonite-supported Cu(0)

2020 ◽  
Vol 82 (8) ◽  
pp. 1635-1642
Author(s):  
Ling Zhou ◽  
Zhongying Xu ◽  
Jie Zhang ◽  
Zhifang Zhang ◽  
Ying Tang
Keyword(s):  
Active Sites ◽  
Guar Gum ◽  
Heterogeneous Reaction ◽  
Removal Rate ◽  
Catalytic Performance ◽  
High Dispersion ◽  
Application Process ◽  
Experimental Conditions ◽  
Hydroxypropyl Guar ◽  
Hydroxypropyl Guar Gum

Abstract To seek for efficient Fenton-like oxidation processing for treatment of waste fracturing fluid containing hydroxypropyl guar gum (HPGG), in heterogeneous reaction, five bentonite-supported zero-valent metal catalysts were prepared by liquid-phase reduction. The results showed that the bentonite-supported zero-valent copper exhibited best catalytic performance, attributed to the high dispersion of active sites of zero-valent copper. The effects of the most relevant operating factors (H2O2 concentration, catalyst dosage, temperature and pH) were evaluated in detail. Moreover, the chemical oxygen demand removal rate of HPGG can achieve 76% when the reaction time was selected at 45 min under optimal experimental conditions. The stability evaluation showed that the catalytic performance was almost unaffected after the catalyst was recycled and used once more showing the good stability of the bentonite-supported zero-valent copper in the application process.

Valence variation of phase-pure M1 MoVNbTe oxide by plasma treatment for improved catalytic performance in oxidative dehydrogenation of ethane

RSC Advances ◽  
2015 ◽  
Vol 5 (111) ◽  
pp. 91295-91301 ◽  
Author(s):  
Xin Chen ◽  
Qianli Yang ◽  
Bozhao Chu ◽  
Hang An ◽  
Yi Cheng
Keyword(s):  
Surface Modification ◽  
Metal Oxide ◽  
Plasma Treatment ◽  
Oxidative Dehydrogenation ◽  
Oxidation State ◽  
Active Sites ◽  
Oxygen Plasma ◽  
Catalyst Surface ◽  
Catalytic Performance ◽  
Phase Pure

This work presents a new method of catalyst surface modification by using oxygen plasma to change the oxidation state of active sites in metal oxide catalysts.

Fast identification of stability of atomically dispersed bi-atom catalysts by a structure descriptor-based model

2022 ◽  
Author(s):  
Danyang LI ◽  
Haoxiang Xu ◽  
Jiqin Zhu ◽  
Dapeng Cao
Keyword(s):  
Synergistic Effect ◽  
Active Sites ◽  
Catalytic Performance ◽  
Fast Identification ◽  
Structure Descriptor

Atomically dispersed bi-atom catalysts (BACs) exhibit remarkable catalytic performance in a variety of reactions due to the adjacent coordination-unsaturated metal active sites, as well as interatomic synergistic effect. However, high-efficiently...

scholarly journals A Zirconium Metal-Organic Framework with SOC Topological Net for Catalytic Peptide Bond Hydrolysis

2021 ◽  
Author(s):  
Sujing Wang ◽  
Antoine Tissot ◽  
Guillaume Maurin ◽  
Tatjana Parac-Vogt ◽  
Christian Serre ◽  
...  
Keyword(s):  
Active Sites ◽  
Metal Organic Framework ◽  
Cost Effective ◽  
Peptide Bond ◽  
Catalytic Performance ◽  
Wide Range ◽  
Horse Heart Myoglobin ◽  
Metal Organic ◽  
Effective Synthesis ◽  
Organic Framework

<div>The discovery of nanozymes for selective cleavage of proteins would boost the emerging areas of modern proteomics, however, the development of efficient and reusable artificial catalysts for peptide bond hydrolysis is challenging. Here we report the detailed catalytic properties of a microporous zirconium carboxylate metal-organic framework, MIP-201, in promoting peptide bond hydrolysis in a simple dipeptide, as well as in horse-heart myoglobin (Mb) protein that consists of 153 amino acids. We demonstrate that MIP-201 features an excellent catalytic activity and selectivity, a good tolerance toward reaction conditions covering a wide range of different pH values, and importantly, an exceptional recycling ability associated with easy regeneration process. Taking into account the excellent catalytic performance of MIP-201 and its other advantages such as 6-connected Zr6 cluster active sites, the green, scalable and cost-effective synthesis, and an outstanding chemical and architectural stability, our finding suggests that MIP-201 may be a promising and practical alternative to the current commercially available catalysts for peptide bond hydrolysis.</div>

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