Pd/SAPO-41 Bifunctional Catalysts with Enhanced Pd Dispersion Prepared by Ultrasonic-Assisted Impregnation: High Selectivity for n-Hexadecane Hydroisomerization

2020 ◽  
Vol 93 (4) ◽  
pp. 502-511 ◽  
Author(s):  
Guozhi Jia ◽  
A. L. Maximov ◽  
Wei Wang ◽  
Xuefeng Bai ◽  
Xiaomeng Wei ◽  
...  
Keyword(s):  
High Selectivity ◽  
Bifunctional Catalysts ◽  
Pd Dispersion ◽  
Ultrasonic Assisted

scholarly journals Hydrogenative Ring-Rearrangement of Furfural to Cyclopentanone over Pd/UiO-66-NO2 with Tunable Missing-Linker Defects

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5736
Author(s):  
Chunhua Wang ◽  
Zhiquan Yu ◽  
Yuhao Yang ◽  
Zhichao Sun ◽  
Yao Wang ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
High Selectivity ◽  
Reaction System ◽  
Pd Nanoparticles ◽  
Catalytic Performance ◽  
Lewis Acidity ◽  
Bifunctional Catalysts ◽  
Defect Sites ◽  
Highly Dispersed ◽  
Key Factor

Upgrading furfural (FAL) to cyclopentanone (CPO) is of great importance for the synthesis of high-value chemicals and biomass utilization. The hydrogenative ring-rearrangement of FAL is catalyzed by metal-acid bifunctional catalysts. The Lewis acidity is a key factor in promoting the rearrangement of furan rings and achieving a high selectivity to CPO. In this work, highly dispersed Pd nanoparticles were successfully encapsulated into the cavities of a Zr based MOF, UiO-66-NO2, by impregnation using a double-solvent method (DSM) followed by H2 reduction. The obtained Pd/UiO-66-NO2 catalyst showed a significantly better catalytic performance in the aforementioned reaction than the Pd/UiO-66 catalyst due to the higher Lewis acidity of the support. Moreover, by using a thermal treatment. The Lewis acidity can be further increased through the creating of missing-linker defects. The resulting defective Pd/UiO-66-NO2 exhibited the highest CPO selectivity and FAL conversion of 96.6% and 98.9%, respectively. In addition, the catalyst was able to maintain a high activity and stability after four consecutive runs. The current study not only provides an efficient catalytic reaction system for the hydrogenative ring-rearrangement of furfural to cyclopentanone but also emphasizes the importance of defect sites.

scholarly journals Promoting Light Hydrocarbons Yield by Catalytic Hydrodechlorination of Residual Chloromethanes Using Palladium Supported on Zeolite Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 199 ◽  
Author(s):  
Carlos Fernandez-Ruiz ◽  
Jorge Bedia ◽  
Javier Mario Grau ◽  
Ana Clara Romero ◽  
Daniel Rodríguez ◽  
...  
Keyword(s):  
Surface Properties ◽  
High Selectivity ◽  
Surface Acidity ◽  
Zeolite Catalysts ◽  
Ionic Exchange ◽  
Light Hydrocarbons ◽  
Reaction Conditions ◽  
Catalytic Hydrodechlorination ◽  
Pd Dispersion ◽  
Zeolite Supports

Gas catalytic hydrodechlorination (HDC) of trichloromethane (TCM) and dichloromethane (DCM) was analyzed using Pd (1 wt.%) on different zeolites as catalysts. The aim of this study was to know the surface properties of the catalysts and reaction conditions that promote the yield to light hydrocarbons in this reaction. Five different zeolite supports were used from three commercial zeolites (KL, L-type; NaY, Faujasite; H-MOR, Mordenite). KL and NaY were submitted to ionic exchange treatments in order to increase their acidity and analyze the effect of the acidity in the activity and selectivity of the HDC reaction. Exchanged zeolites (HL and HY) showed the highest Pd dispersion due to their higher surface acidity. The best TCM/DCM conversion and selectivity to light hydrocarbons was obtained using the two non-exchanged zeolite-catalysts, KL and NaY. Low surface acidity seems to be the key aspect to promote the formation of light hydrocarbons. The formation of these products is favored at high reaction temperatures and low H2: chloromethane ratios. KL showed the highest selectivity to olefins (60%), although with a lower dechlorination degree. Non-exchanged NaY catalyst showed high selectivity to paraffins (70% and 95% for the HDC of DCM and TCM, respectively).

Direct and selective hydrogenation of CO2 to ethylene and propene by bifunctional catalysts

2017 ◽  
Vol 7 (23) ◽  
pp. 5602-5607 ◽  
Author(s):  
Jiajian Gao ◽  
Chunmiao Jia ◽  
Bin Liu
Keyword(s):  
Selective Hydrogenation ◽  
High Selectivity ◽  
Bifunctional Catalyst ◽  
Bifunctional Catalysts ◽  
Hydrogenation Of Co2 ◽  
Synthesis Of Methanol

A bifunctional catalyst was designed to directly and selectively hydrogenate CO2 to ethylene and propene with a high selectivity of 80–90% in hydrocarbons by combining the synthesis of methanol and methanol-to-olefins processes.

Selective oxidation of aniline into azoxybenzene catalyzed by Nb-peroxo@iron oxides at room temperature

2020 ◽  
Vol 44 (21) ◽  
pp. 8710-8717
Author(s):  
André L. D. Lima ◽  
Humberto V. Fajardo ◽  
André E. Nogueira ◽  
Márcio C. Pereira ◽  
Luiz C. A. Oliveira ◽  
...  
Keyword(s):  
Iron Oxides ◽  
Selective Oxidation ◽  
Room Temperature ◽  
High Selectivity

Nb-peroxo@iron oxides show high selectivity and activity in aniline conversion to azoxybenzene.

10-step Synthesis of 20-nor-Salvinorin A by Dynamic Strategic Bond Analysis

2017 ◽  
Author(s):  
Jeremy Roach ◽  
Yusuke Sasano ◽  
Cullen Schmid ◽  
Saheem Zaidi ◽  
Vsevolod Katritch ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Opioid Receptors ◽  
Structural Modification ◽  
High Selectivity ◽  
Therapeutic Potential ◽  
Salvinorin A ◽  
High Affinity ◽  
Plant Metabolite ◽  
Complex Architecture ◽  
Property Modification

Salvinorin A (SalA) is a plant metabolite that agonizes the human <i>kappa</i>-opioid receptor (κ-OR) with high affinity and high selectivity over <i>mu- </i>and <i>delta-</i>opioid receptors. Its therapeutic potential has stimulated extensive semi-synthetic studies and total synthesis campaigns. However, structural modification of SalA has been complicated by its instability, and efficient total synthesis has been frustrated by its dense, complex architecture. Treatment of strategic bonds in SalA as dynamic and dependent on structural perturbation enabled the identification of an efficient retrosynthetic pathway. Here we show that deletion of C20 simultaneously stabilizes the SalA skeleton, simplifies its synthesis and retains its high affinity and selectivity for the κ-OR. The resulting 10-step synthesis now opens the SalA scaffold to deep-seated property modification.

The Stabilizing Effect of Pre-Equilibria: A Trifluoromethyl Complex as CF2 Reservoir in Catalytic Olefin Difluorocarbenation

2020 ◽  
Author(s):  
Thomas Louis-Goff ◽  
Huu Vinh Trinh ◽  
Eileen Chen ◽  
Arnold L. Rheingold ◽  
Christian Ehm ◽  
...  
Keyword(s):  
High Selectivity ◽  
Side Reactions ◽  
Theoretical Studies ◽  
Attractive Feature ◽  
Catalyst Recovery ◽  
Wide Range ◽  
Stabilizing Effect ◽  
Experimental And Theoretical Studies

A new, efficient, catalytic difluorocarbenation of olefins to give 1,1-difluorocyclopropanes is presented. The catalyst, an organobismuth complex, uses TMSCF<sub>3</sub> as a stoichiometric difluorocarbene source. We demonstrate both the viability and robustness of this reaction over a wide range of alkenes and alkynes, including electron-poor alkenes, to generate the corresponding 1,1-difluorocyclopropanes and 1,1-difluorocyclopropenes. Ease of catalyst recovery from the reaction mixture is another attractive feature of this method. In depth experimental and theoretical studies showed that the key difluorocarbene-generating step proceeds through a bismuth non-redox synchronous mechanism generating a highly reactive free CF<sub>2</sub> in an endergonic pre-equilibrium. It is the reversibility when generating the difluorocarbene that accounts for the high selectivity, while minimizing CF<sub>2</sub>-recombination side-reactions.

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

Deprocessing Methodologies for Detection of IBC and Cell-to-Cell Shorts in Submicron DRAM

2012 ◽  
Author(s):  
Ramachandra Chitakudige ◽  
Sarat Kumar Dash ◽  
A.M. Khan
Keyword(s):  
High Selectivity ◽  
Electron Cyclotron Resonance ◽  
Random Access ◽  
Random Access Memory ◽  
Access Memory ◽  
Plasma System ◽  
Poly Silicon ◽  
Hazardous Gases ◽  
Wet Etch ◽  
Resonance Plasma

Abstract Detection of both Insufficient Buried Contact (IBC) and cell-to-cell short defects is quite a challenging task for failure analysis in submicron Dynamic Random Access Memory (DRAM) devices. A combination of a well-controlled wet etch and high selectivity poly silicon etch is a key requirement in the deprocessing of DRAM for detection of these types of failures. High selectivity poly silicon etch methods have been reported using complicated system such as ECR (Electron Cyclotron Resonance) Plasma system. The fact that these systems use hazardous gases like Cl2, HBr, and SF6 motivates the search for safer alternative deprocessing chemistries. The present work describes high selectivity poly silicon etch using simple Reactive Ion Etch (RIE) plasma system using less hazardous gases such as CF4, O2 etc. A combination of controlled wet etch and high selectivity poly silicon etch have been used to detect both IBC and cell-to-cell shorts in submicron DRAMs.

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