scholarly journals Carbon Molecular Sieve Supported Pd Catalyzed Hydrogenation of Cinnamaldehyde in Alkaline Medium

2021 ◽  
Vol 33 (4) ◽  
pp. 846-852
Author(s):  
Racharla Krishna ◽  
Chowdam Ramakrishna ◽  
Bijendra Saini ◽  
Thakkallapalli Gopi ◽  
Gujarathi Swetha ◽  
...  
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Active Sites ◽  
Organic Medium ◽  
Fine Chemicals ◽  
Carbon Molecular Sieve ◽  
Activity Data ◽  
Cinnamaldehyde Hydrogenation ◽  
Supported Pd

Synthesis of various fine chemicals and pharmaceuticals are regulated through selective hydrogenation of α,β-unsaturated aldehydes. Hydrocinnamaldehyde is one of the important compounds in perfumery and flavouring industries. It is highly precarious and challenging to control the product selectivity as well as conversion in cinnamaldehyde hydrogenation. In this study, an effective hydrogenation of cinnamaldehyde was attained in presence of aqueous-protic organic medium by utilizing Pd/CMS and other additives of alkali such as K2CO3. The Pd/CMS catalyst along with alkali media catalyzed the hydrogenation of C=C selectively in cinnamaldehyde in order to form hydrocinnamaldehyde with 100% conversion rate. Additionally, the parallel hydrogenation of C=O and C=C bonds in cinnamaldehyde takes place in absence of media. The C=O bond reduction in cinnamaldehyde can be restricted through K2CO3 addition to aqueous-protic solution. The active sites of palladium were found to be uniform and analyzed using HRTEM data. Based on the mechanism involved in micropores of carbon molecular sieves, the key role of promoter is associated with hydrogenation of cinnamaldehyde. The catalytic criterion was appropriate with the acquired activity data.

scholarly journals Envisioned role of slit bypass pores in physical aging of carbon molecular sieve membranes

Carbon ◽  
2020 ◽  
Vol 157 ◽  
pp. 385-394 ◽  
Author(s):  
Samuel S. Hays ◽  
Oishi Sanyal ◽  
Nicholas E. León ◽  
Pezhman Arab ◽  
William J. Koros
Keyword(s):  
Molecular Sieve ◽  
Physical Aging ◽  
Carbon Molecular Sieve

Effect of fixed carbon molecular sieve (CMS) loading and various di-ethanolamine (DEA) concentrations on the performance of a mixed matrix membrane for CO2/CH4 separation

RSC Advances ◽  
2015 ◽  
Vol 5 (75) ◽  
pp. 60814-60822 ◽  
Author(s):  
Rizwan Nasir ◽  
Hilmi Mukhtar ◽  
Zakaria Man ◽  
Maizatul Shima Shaharun ◽  
Mohamad Zailani Abu Bakar
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Mixed Matrix Membranes ◽  
Inorganic Filler ◽  
Mixed Matrix Membrane ◽  
Mixed Matrix ◽  
Fixed Carbon ◽  
Carbon Molecular Sieve ◽  
Carbon Molecular Sieves ◽  
The Third

Polyethersulfone (PES) as a polymer along with carbon molecular sieves (CMS) as an inorganic filler and di-ethanolamine (DEA) as the third component were used to fabricate amine mixed matrix membranes (A3Ms).

scholarly journals Nanopowder-Supported Ultra-Low Content Co–Rh Bimetallic Catalysts for Hydroformylation of Monoformyltricyclodecenes to Value-Added Fine Chemicals

2018 ◽  
Vol 43 (3-4) ◽  
pp. 254-261
Author(s):  
Chengyang Li ◽  
Libo Zhang ◽  
Yubo Ma ◽  
Tianfu Wang
Keyword(s):  
Reaction Temperature ◽  
Bimetallic Catalysts ◽  
Active Sites ◽  
Value Added ◽  
Catalytic Performance ◽  
Fine Chemicals ◽  
Co Catalysts ◽  
Incipient Wetness ◽  
Incipient Wetness Method

The hydroformylation of monoformyltricyclodecenes (MFTD) to diformyltricyclodecanes (DFTD) was studied systematically. A series of 0.006 wt% Rh–0.006 wt% Co catalysts supported on commercially available nanopowders such as Al2O3, ZnO, TiO2 and CeO2 was prepared by the incipient wetness method and used to catalyse the hydroformylation of MFTD to DFTD. The 0.006 wt% Rh–0.006 wt% Co/ZnO catalyst showed the highest catalytic performance among the catalysts investigated, thus 41.8% DFTD yield with 100% DFTD selectivity could be achieved. This suggested that there may be a key role of the carrier on the catalytic performance in MFTD hydroformylation. Furthermore, the kinetic profiles for MFTD hydroformylation over the 0.006 wt% Rh–0.030 wt% Co/ZnO catalyst have been examined systematically to explore the effect of reaction temperature on the catalytic performance. These results collectively suggested that a particular reaction temperature might benefit MFTD hydroformylation. There may be some agglomeration of the active sites at higher reaction temperatures.

scholarly journals Pore Structure Alteration of a Carbon Molecular Sieve for the Separation of Hydrogen Sulfide from Methane by Adsorption

1993 ◽  
Vol 10 (1-4) ◽  
pp. 193-201 ◽  
Author(s):  
Z.J. Pan ◽  
S.G. Chen ◽  
J. Tang ◽  
R.T. Yang
Keyword(s):  
Natural Gas ◽  
Pore Structure ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Carbon Deposition ◽  
Important Variable ◽  
Equilibrium Adsorption ◽  
Carbon Molecular Sieve ◽  
Natural Gas Desulfurization ◽  
Kinetic Selectivity

The equilibrium adsorption of H2S is substantially stronger than that of CH4 on carbons, including carbon molecular sieve (CMS). A carbon molecular sieve with a proper pore structure can provide a kinetic selectivity for H2S over CH4, thus further enhancing the overall selectivity (equilibrium plus kinetic) for H2S and providing the basis of natural gas desulfurization by adsorption. Kinetic selectivity requires a unique pore structure due to the small difference in the molecular dimensions of H2S and CH4 (~0.2 Å). Equilibrium and diffusion rate data for CH4 and H2S at 25°C have been measured in three commercial carbon molecular sieves: Bergbau Forschung CMS, Takeda CMS 3A and Takeda CMS 5A. The pores are either too small (in the two former carbons) or too large (in CMS 5A) for H2S/CH4 separation. Alterations to the pore structure either by controlled oxidation or carbon deposition by pyrolysis have been studied. Optimal results were obtained by pyrolysis of propylene on CMS 5A under the following conditions: 0.05 atm, 700°C, 5 min, weight gain of 0.67%. The resulting carbon molecular sieve retained the high equilibrium adsorption capacities while yielding a diffusion time constant ratio for H2S/CH4 of 8.2. This carbon is suitable for natural gas desulfurization by adsorption processes such as pressure swing adsorption. Temperature was the most important variable in pore structure alteration by carbon deposition. Under the optimal pyrolysis conditions, carbon was only deposited near the pore entrances.

The Effect of Type of Acid Sites in Molecular Sieves on Activity and Selectivity in Acylation Reactions

2007 ◽  
Vol 72 (5-6) ◽  
pp. 728-746 ◽  
Author(s):  
Martina Bejblová ◽  
Josef Vlk ◽  
Dana Procházková ◽  
Helena Šiklová ◽  
Jiří Čejka
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Acid Sites ◽  
Acid Strength ◽  
Zeolite Beta ◽  
Mesoporous Molecular Sieves ◽  
Lewis Acid Sites ◽  
Mcm 41 ◽  
Acylation Reactions

The role of the type of acid site (Broensted vs. Lewis) on the activity and selectivity of molecular sieve catalysts was investigated in ferrocene and toluene acylation. H-, Zn-, Fe-, Al- and La-forms of zeolite Beta, USY and mesoporous molecular sieves (Al)MCM-41, (Al)SBA-15 were tested. It was observed that addition of metal cations acting as Lewis acid sites can increase the acidity of various molecular sieve catalysts. No general relationship between the type of cation and conversion of individual substrate was found. While the highest activity in ferrocene acylation was observed after addition of Zn, in the case of toluene acylation Al-forms of catalysts were the most active. The results indicate that the acid strength of cationic Lewis sites controls their activity in acylation reactions.

Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said
Keyword(s):  
Active Sites ◽  
Isopropyl Alcohol ◽  
Oxide Catalyst ◽  
Flow System ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalyst Composition ◽  
Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

Geometric Factor in Skeletal Reactions of 2-Methylpentane on Stepped Surfaces of Platinum Catalyst

1992 ◽  
Vol 57 (10) ◽  
pp. 2012-2020
Author(s):  
Vladimír Hejtmánek
Keyword(s):  
Active Sites ◽  
Platinum Catalyst ◽  
Point Of View ◽  
Geometric Factor ◽  
Published Data ◽  
Stepped Surfaces ◽  
Geometric Conditions ◽  
Surface Intermediates ◽  
Isomerization Mechanism

The role of geometric factor in the course of skeletal reactions (isomerization, hydrogenolysis) of 2-methylpentane on stepped (119), (557) and reconstructed R(557) surfaces of single crystals of platinum was evaluated with computer designed models. These calculations were compared with reported experimental data. It was found by analysis of geometric conditions that there are accessible active ensembles on double step of the reconstructed R(557) surface. In addition, these active sites are unsaturated in their coordination sphere and thus catalytically effective. This finding is consistent with published data, confirming higher catalytic activity of this surface. The various pathways of Bond Shift isomerization mechanism of 2-methylpentane from the point of view of steric demands of surface intermediates on differently located ensembles are discussed, too.

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