scholarly journals Structure-Catalytic Properties Relationship in Friedel Crafts Alkylation Reaction for MCM-36-Type Zeolites Obtained by Isopropanol-Assisted Pillaring

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 299
Author(s):  
Karolina Ogorzały ◽  
Agnieszka Węgrzyn ◽  
Aleksandra Korzeniowska ◽  
Andrzej Sławek ◽  
Andrzej Kowalczyk ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Acid Sites ◽  
Alkylation Reaction ◽  
High Catalytic Activity ◽  
Large Molecules ◽  
External Acid Sites ◽  
Hierarchical Porous ◽  
Acid Centers ◽  
Ir Study

MWW type zeolites are characterized by the presence of zeolitic layers of 2.5 nm thickness, containing 10-member ring sinusoidal channels inside and supercavities with 12-member ring openings located on their surfaces. Expansion and pillaring of layered zeolites increase the access to active sites and can enable or facilitate catalytic activity towards larger reactant molecules. This goal is explored in this work reporting the pillaring of layered zeolite MCM-56 with MWW topology by tetraethylorthosilicate (TEOS) treatment with the assistance of isopropanol, aimed at obtaining hierarchical micro-mesoporous systems. MCM-56 (Si/Al = 12) was synthesized with hexamethyleneimine as a structure-directing and aniline as a structure-promoting agent. Hierarchical porous systems were obtained using two different pillaring methods: (1) with TEOS only and (2) with TEOS mixed with isopropanol. The MWW framework was preserved during swelling/pillaring in both methods. Pillared zeolites obtained via alcohol-assisted pillaring possessed unique intermediate micro-mesopores with the size of about 2 nm. IR study revealed a decrease in the concentration of accessible acid centers upon pillaring. However, the fraction of acid sites on the external surface, accessible for adsorption of large molecules, increased by up to 90%. Catalytic activity was evaluated in the Friedel-Crafts alkylation of mesitylene with benzyl alcohol. Pillaring resulted in reduction of the acid site concentrations, but the materials retained high catalytic activity. Pillaring in the presence of alcohol produced increased turnover frequency values based on the concentrations of the external acid sites.

scholarly journals Hollow MFI Zeolite Supported Pt Catalysts for Highly Selective and Stable Hydrodeoxygenation of Guaiacol to Cycloalkanes

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 362 ◽  
Author(s):  
Xiaopo Niu ◽  
Fuxiang Feng ◽  
Gang Yuan ◽  
Xiangwen Zhang ◽  
Qingfa Wang
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Acid Sites ◽  
Pt Catalyst ◽  
Pt Catalysts ◽  
Mfi Zeolite ◽  
Long Term Stability ◽  
Supported Pt Catalysts ◽  
Hierarchical Porous ◽  
Ft Ir

Hollow Silicalite-1 and ZSM-5 zeolites with hierarchical porous shells have been synthesized by using a dissolution-recrystallization method. The morphology, structure, and acidity of these zeolites supported Pt catalysts were characterized by XRD, FT-IR, MAS-SSNMR, FE-SEM, FE-TEM, N2-BET, XPS, NH3-TPD, and CO pulse chemisorption. Compared to the conventional ZSM-5 supported Pt catalyst, the special structure in hollow ZSM-5 zeolite significantly promotes the dispersion of metallic Pt and the synergistic effect between metal active sites and acid sites. These boost the catalytic activity, selectivity of guaiacol hydrodeoxygenation toward cycloalkanes and long-term stability over the Pt/hollow ZSM-5 catalyst combined with improved mass transfer of products and reactants derived from the hierarchical hollow porous structure. Moreover, the Pt/hollow ZSM-5 catalyst exhibits excellent low temperature catalytic activity to completely transform guaiacol into cycloalkanes with the cyclohexane selectivity of more than 93% at 220 °C, suggesting that hollow ZSM-5 zeolite is a promising support for upgrading of bio-oils.

scholarly journals CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131 ◽  
Author(s):  
Rola Mohammad Al Soubaihi ◽  
Khaled Mohammad Saoud ◽  
Myo Tay Zar Myint ◽  
Mats A. Göthelid ◽  
Joydeep Dutta
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Active Sites ◽  
Bond Activation ◽  
Dissociative Adsorption ◽  
High Catalytic Activity ◽  
Good Catalytic Activity ◽  
Pretreatment Conditions ◽  
Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

Facile preparation of a hierarchically porous metal–organic nanocomposite with excellent catalytic performance

RSC Advances ◽  
2016 ◽  
Vol 6 (99) ◽  
pp. 97399-97403 ◽  
Author(s):  
Rui Kuang ◽  
Luyi Zheng ◽  
Ethan Cottrill ◽  
Ning Pan ◽  
Yanhui Chi ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Aging Process ◽  
Porous Metal ◽  
Catalytic Performance ◽  
High Catalytic Activity ◽  
Hierarchically Porous ◽  
Hierarchical Porous ◽  
Metal Organic ◽  
Facile Preparation ◽  
Excellent Catalytic Performance

A hierarchical porous MOF nanocrystal, hpCuL (L = 2,4,6-tris(3,5-dicarboxylatephenylamino)-1,3,5-triazine) was prepared via a facile gel-aging process. This nanocomposite exhibits high catalytic activity and stability for the reduction of 4-nitrophenol.

scholarly journals New gold standard: weakly capped infant Au nanoclusters with record high catalytic activity for 4-nitrophenol reduction and hydrogen generation from an ammonia borane–sodium borohydride mixture

2020 ◽  
Vol 2 (11) ◽  
pp. 5384-5395
Author(s):  
Dinabandhu Patra ◽  
Srinivasa Rao Nalluri ◽  
Hui Ru Tan ◽  
Mohammad S. M. Saifullah ◽  
Ramakrishnan Ganesan ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Citric Acid ◽  
Solid State ◽  
Gold Standard ◽  
Active Sites ◽  
Hydrogen Generation ◽  
High Catalytic Activity ◽  
Au Nanoclusters ◽  
Nitrophenol Reduction ◽  
Rapid Dissolution

Active sites are preserved in the citric acid-capped Au nanoclusters prepared in solid state. In water, the rapid dissolution of citric acid allows the reactants to easily access the active sites of infant Au nanoclusters leading to faster catalysis.

Preparation, characterization and catalytic properties of yttrium-zirconium-pillared montmorillonite and their application in supported Ce catalysts

Clay Minerals ◽  
2015 ◽  
Vol 50 (2) ◽  
pp. 211-219 ◽  
Author(s):  
Bo Xue ◽  
Hongmei Guo ◽  
Lujie Liu ◽  
Min Chen
Keyword(s):  
Catalytic Activity ◽  
Ethyl Acetate ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Active Sites ◽  
Industrial Applications ◽  
High Catalytic Activity ◽  
Total Oxidation ◽  
Pillared Montmorillonite

AbstractA new yttrium-zirconium-pillared montmorillonite (Y-Zr-MMT), was synthesized, characterized and used as a Ce catalyst support. The Y-Zr-MMT is a good support for dispersing cerium active sites and it is responsible for the high activity in the total oxidation of acetone, toluene and ethyl acetate. The Y-Zr-MMT shows greater advantages than the conventional alumina/cordierite honeycomb supports such as large specific surface area, lower cost and easier preparation. Catalytic tests demonstrated that Ce/Y-Zr-MMT (Ce loading 8.0%) was the most active, with the total oxidation of acetone, toluene and ethyl acetate being achieved at 220, 300 and 220°C, respectively. The catalyst displayed better activity for the oxidation of acetone and ethyl acetate than a conventional, supported Pd-catalyst under similar conditions. The special structure of the yttrium-doped zirconium-pillared montmorillonite can strengthen the interaction between the CeO2 and Zr-MMT support and improve the dispersion of the Ce particles, which enhances the catalytic activity for the oxidation of VOCs. The new catalyst, 8.0%Ce/Y-Zr-MMT, could be promising for industrial applications due to its high catalytic activity and low cost. The support and the catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET specific surface area measurements.

scholarly journals Biodiesel Production over Niobium-Containing Catalysts: A Review

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5506
Author(s):  
Daniel Carreira Batalha ◽  
Márcio José da Silva
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Raw Materials ◽  
Catalytic Performance ◽  
High Specific Surface Area ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Main Reaction ◽  
High Catalytic Activity

Nowadays, the synthesis of biofuels from renewable raw materials is very popular. Among the various challenges involved in improving these processes, environmentally benign catalysts compatible with an inexpensive feedstock have become more important. Herein, we report the recent advances achieved in the development of Niobium-containing heterogeneous catalysts as well as their use in routes to produce biodiesel. The efficiency of different Niobium catalysts in esterification and transesterification reactions of lipids and oleaginous raw materials was evaluated, considering the effect of main reaction parameters such as temperature, time, catalyst load, and oil:alcohol molar ratio on the biodiesel yield. The catalytic performance of Niobium compounds was discussed considering the characterization data obtained by different techniques, including NH3-TPD, BET, and Pyr-FT-IR analysis. The high catalytic activity is attributed to its inherent properties, such as the active sites distribution over a high specific surface area, strength of acidity, nature, amount of acidic sites, and inherent mesoporosity. On top of this, recycling experiments have proven that most Niobium catalysts are stable and can be repeatedly used with consistent catalytic activity.

scholarly journals Modification of Coal Char-loaded TiO2 by Sulfonation and Alkylsilylation to Enhance Catalytic Activity in Styrene Oxidation with Hydrogen Peroxide as Oxidant

2017 ◽  
Vol 12 (1) ◽  
pp. 55 ◽  
Author(s):  
Mukhamad Nurhadi
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Active Sites ◽  
Catalyst Particle ◽  
Local Environment ◽  
Coal Char ◽  
Low Rank ◽  
High Catalytic Activity ◽  
Styrene Oxidation ◽  
Aqueous Hydrogen Peroxide

<p>The modified coal char from low-rank coal by sulfonation, titanium impregnation and followed by alkyl silylation possesses high catalytic activity in styrene oxidation. The surface of coal char was undergone several steps as such: modification using concentrated sulfuric acid in the sulfonation process, impregnation of 500 mmol titanium(IV) isopropoxide and followed by alkyl silylation of n-octadecyltriclorosilane (OTS). The catalysts were characterized by X-ray diffraction (XRD), IR spectroscopy, nitrogen adsorption, and hydrophobicity. The catalytic activity of the catalysts has been examined in the liquid phase styrene oxidation by using aqueous hydrogen peroxide as oxidant. The catalytic study showed the alkyl silylation could enhance the catalytic activity of Ti-SO<sub>3</sub>H/CC-600(2.0). High catalytic activity and reusability of the o-Ti-SO<sub>3</sub>H/CC-600(2.0) were related to the modification of local environment of titanium active sites and the enhancement the hydrophobicity of catalyst particle by alkyl silylation. Copyright © 2017 BCREC GROUP. All rights reserved</p><p><em>Received: 24<sup>th</sup> May 2016; Revised: 11<sup>st</sup> October 2016; Accepted: 18<sup>th</sup> October 2016</em></p><p><strong>How to Cite:</strong> Nurhadi, M. (2017). Modification of Coal Char-loaded TiO<sub>2</sub> by Sulfonation and Alkylsilylation to Enhance Catalytic Activity in Styrene Oxidation with Hydrogen Peroxide as Oxidant. <em>Bulletin of Chemical Reaction Engineering &amp; Catalysis</em>, 12 (1): 55-61 (doi:10.9767/bcrec.12.1.501.55-61)</p><p><strong>Permalink/DOI</strong>: http://dx.doi.org/10.9767/bcrec.12.1.501.55-61</p><p> </p>

Template-directed approach to two-dimensional molybdenum phosphide–carbon nanocomposites with high catalytic activities in the hydrogen evolution reaction

2016 ◽  
Vol 40 (7) ◽  
pp. 6015-6021 ◽  
Author(s):  
Zhaoquan Yao ◽  
Yuezeng Su ◽  
Chenbao Lu ◽  
Chongqing Yang ◽  
Zhixiao Xu ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Catalytic Activity ◽  
Hydrogen Evolution Reaction ◽  
Active Sites ◽  
High Catalytic Activity ◽  
Two Dimensional ◽  
Carbon Nanocomposites ◽  
Carbon Nanosheets ◽  
Catalytic Activities ◽  
Molybdenum Phosphide

MoP-embedded 2D N-doped porous carbon nanosheets, with excellent electrical conductivity and abundant active sites, achieved high catalytic activity in the HER.

scholarly journals One-pot conversion of dihydroxyacetone into ethyl lactate by Zr-based catalysts

RSC Advances ◽  
2021 ◽  
Vol 11 (18) ◽  
pp. 10935-10940
Author(s):  
Junjun Shi ◽  
Fukun Li ◽  
Jie Zhang ◽  
Ning Li ◽  
Xingmin Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Synergistic Effect ◽  
Active Sites ◽  
Ethyl Lactate ◽  
High Catalytic Activity ◽  
One Pot

An eco-friendly strategy for efficiently converting dihydroxyacetone to ethyl lactate in one-pot is proposed. The synergistic effect among acid and basic active sites contributes to the high catalytic activity.

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