Boosted Hydrodeoxygenation of Lignin-Derived Phenolics to Cycloalkanes with a Complex Copper Acid Catalyst

2021 ◽  
Author(s):  
Xiangchen Kong ◽  
Chao Liu ◽  
Baolong Wang ◽  
Weicong Xu ◽  
Yuyang Fan ◽  
...  
Keyword(s):  
Acid Catalyst ◽  
Complex Copper

Method of complex copper-zinc ore typification using neural network models

2020 ◽  
Vol 5 ◽  
pp. 140-147 ◽  
Author(s):  
T.N. Aleksandrova ◽  
◽  
E.K. Ushakov ◽  
A.V. Orlova ◽  
◽  
...  
Keyword(s):  
Neural Network ◽  
Network Models ◽  
Neural Network Models ◽  
Copper Zinc ◽  
Complex Copper

Proton Acidity and Proton Mobility in ECR-40, a Silicoaluminophosphate That Violates Löwenstein’s Rule

2019 ◽  
Author(s):  
Michael Fischer
Keyword(s):  
Density Functional ◽  
Water Clusters ◽  
Computational Study ◽  
Acid Catalyst ◽  
Ab Initio Molecular Dynamics ◽  
Brønsted Acidity ◽  
Hydrothermal Route ◽  
Proton Mobility ◽  
Brönsted Acidity ◽  
A Minor

<p>The silicoaluminophosphate zeotype ECR-40, which has the MEI topology, contains linkages of AlO<sub>4</sub> tetrahedra via a common oxygen atom, thereby violating the famous “Löwenstein’s rule”. Due to the proven existence of Al-O-Al linkages in this material, it constitutes an ideal model system to study the acidity and mobility of protons associated with such unusual linkages. In addition, their properties can be directly compared to those of protons associated with more common Si-O-Al linkages, which are also present in ECR-40. In this work, static density functional theory (DFT) calculations including a dispersion correction were employed to study the preferred proton sites as well as the Brønsted acidity of the framework protons, followed by DFT-based ab-initio molecular dynamics (AIMD) to investigate the proton mobility in guest-free and hydrated ECR-40. Initially, two different proton arrangements were compared, one containing both H[O6] protons associated with Al-O-Al linkages and H[O10] protons at Si-O-Al linkages, the other one containing only H[O10] protons. The former model was found to be thermodynamically favoured, as a removal of protons from the Al-O-Al linkages causes a local accumulation of negative charge. Calculations of the deprotonation energy showed a moderately higher Brønsted acidity of the H[O10] protons, at variance with previous empirical explanations, which attributed the exceptional performance of ECR-40 as acid catalyst to the presence of Al‑O‑Al linkages. The AIMD simulations (<i>T</i> = 298 K) delivered no appreciable proton mobility for guest-free ECR-40 and for low levels of hydration (one H<sub>2</sub>O per framework proton). Under saturation conditions, framework deprotonation occurred, leading to the formation of protonated water clusters in the pores. Pronounced differences between the two types of framework protons were observed: While the H[O10] protons were always removed from the Si-O-Al linkages, the Al-O-Al linkages remained mostly protonated, but deprotonation did occur to a minor extent. The observation of a degree of framework deprotonation of Al-O-Al linkages differs from the findings reported in a recent computational study of hydrated aluminosilicate zeolites with such linkages (Heard et al., <i>Chem. Sci.</i> <b>2019</b>, <i>10</i>, 5705), pointing to an influence of the overall framework composition. Further inspection of the AIMD results showed that a coordination of water molecules to framework Al atoms occurred in many cases, especially in the vicinity of the Al-O-Al linkages, sometimes resulting in a pronounced modification of the linkages through additional bridging oxygen atoms. Given the changes in the local structure, it can be expected that such modified linkages are especially prone to break upon dehydration. Thus, in addition to elucidating the deprotonation behaviour of protons associated with different types of linkages, the calculations also provide insights into possible reasons for the instability of Al-O-Al linkages, clarifying why Löwenstein’s rule is mostly obeyed in materials that are formed via a hydrothermal route.</p>

Computationally-Guided Investigation of Dual Amine/pi Lewis Acid Catalysts for Direct Additions of Aldehydes and Ketones to Unactivated Alkenes and Alkynes

2020 ◽  
Author(s):  
Eric Greve ◽  
Jacob D. Porter ◽  
Chris Dockendorff
Keyword(s):  
Lewis Acid ◽  
Density Functional ◽  
Acid Catalyst ◽  
Metal Catalyst ◽  
Catalyst Poisoning ◽  
Lewis Acid Catalysts ◽  
Metal Ligands ◽  
Aldehydes And Ketones ◽  
Lewis Acid Catalyst ◽  
Catalyst Systems

Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare and not presently of significant synthetic utility, likely due to undesired coordination of enamine intermediates to the metal catalyst. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of aldehyde/ketones to alkenes/alkynes. Density Functional Theory (DFT) calculations were performed that suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined with MacMillan’s imidazolidinone organocatalyst for aldehyde/ketone activation to facilitate desirable C-C bond formations, and certain reactions were calculated to be more exergonic than catalyst poisoning pathways. As calculated, preformed enamines generated from the MacMillan imidazolidinone did not displace ethylene from a biscationic (<i>t</i>-Bu)PyBOX-Pt<sup>2+</sup>complex, but neither were the desired C-C bond formations observed under several different conditions.

Computationally-Guided Investigation of Dual Amine/pi Lewis Acid Catalysts for Direct Additions of Aldehydes and Ketones to Unactivated Alkenes and Alkynes

2020 ◽  
Author(s):  
Eric Greve ◽  
Jacob D. Porter ◽  
Chris Dockendorff
Keyword(s):  
Lewis Acid ◽  
Density Functional ◽  
Acid Catalyst ◽  
Metal Catalyst ◽  
Catalyst Poisoning ◽  
Lewis Acid Catalysts ◽  
Metal Ligands ◽  
Aldehydes And Ketones ◽  
Lewis Acid Catalyst ◽  
Catalyst Systems

Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare and not presently of significant synthetic utility, likely due to undesired coordination of enamine intermediates to the metal catalyst. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of aldehyde/ketones to alkenes/alkynes. Density Functional Theory (DFT) calculations were performed that suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined with MacMillan’s imidazolidinone organocatalyst for aldehyde/ketone activation to facilitate desirable C-C bond formations, and certain reactions were calculated to be more exergonic than catalyst poisoning pathways. As calculated, preformed enamines generated from the MacMillan imidazolidinone did not displace ethylene from a biscationic (<i>t</i>-Bu)PyBOX-Pt<sup>2+</sup>complex, but neither were the desired C-C bond formations observed under several different conditions.

SO3H-functionalized Zeolite-Y as an Efficient Nanocatalyst for the Synthesis of Nbenzimidazole- 2-aryl-4-thiazolidinones and tri-substituted Imidazoles

2020 ◽  
Vol 17 (2) ◽  
pp. 117-130 ◽  
Author(s):  
Mehdi Kalhor ◽  
Zohre Zarnegar ◽  
Zahra Seyedzade ◽  
Soodabeh Banibairami
Keyword(s):  
Zeolite Y ◽  
Internal Standard ◽  
Acid Catalyst ◽  
Aromatic Aldehydes ◽  
Reaction Rates ◽  
Ambient Conditions ◽  
Catalytic Method ◽  
Efficient Catalyst ◽  
Bet Analysis ◽  
Ft Ir

Background: SO3H-functionalized zeolite-Y was prepared and used as a catalyst for the synthesis of 2-aryl-N-benzimidazole-4-thiazolidinones and tri-substituted imidazoles at ambient conditions. Objective: The goals of this catalytic method include excellent yields and high purity, inexpensive procedure and ease of product isolation, the use of nontoxic and heterogeneous acid catalyst, shorter reaction times and milder conditions. Materials and Methods: NMR spectra were recorded on Brucker spectrophotometer using Me4Si as internal standard. Mass spectra were recorded on an Agilent Technology 5975C VL MSD with tripe-axis detector. FTIR spectra were obtained with KBr disc on a galaxy series FT-IR 5000 spectrometer. The surface morphology of nanostructures was analyzed by FE-SEM (EVO LS 10, Zeiss, Carl Zeiss, Germany). BET analysis were measured at 196 °C by a Japan Belsorb II system after the samples were vacuum dried at 150°C overnight. Results: The NSZ was characterized by FT-IR, FESEM, EDX, XRF, and BET. The catalytic activity of NSZ was investigated for synthesis of 1,3-tiazolidin-4-ones in H2O/Acetone at room temperature. Moreover, NSZ was used for synthesis of tri-substituted imidazoles at 60 °C via solvent-free condensation. Different kinds of aromatic aldehydes were converted to the corresponding of products with good to excellent yields. Conclusion: Sulfonated zeolite-Y was as an efficient catalyst for the preparation of N-benzimidazole-2-aryl-1,3- thiazolidin-4-ones and 2,4,5-triaryl-1H-imidazoles. High reaction rates, elimination toxic solvent, simple experimental procedure and reusability of the catalyst are the important features of this protocol.

An Efficient Synthesis of 2-Substituted Quinazolin-4(3H)-ones by Using Recyclable Wang Resin Supported Sulfonic Acid Catalyst

2020 ◽  
Vol 17 ◽  
Author(s):  
Kalyani K. ◽  
Srinivasa Reddy Kallam
Keyword(s):  
Sulfonic Acid ◽  
Functional Group ◽  
Acid Catalyst ◽  
Sulphonic Acid ◽  
Isatoic Anhydride ◽  
Efficient Synthesis ◽  
Wang Resin ◽  
Polymer Supported ◽  
High Yields

Abstract:: An efficient synthesis of 2-substituted Quinazolin-4(3H)-ones has been developed from isatoic anhydride with various amidoximes by using recyclable polymer supported sulphonic acid catalyst. Excellent functional group compatibil-ity and high yields are the important features of this protocol.

Synthesis and Characterization of Heterogeneous Solid Acid Catalyst from Alstonia Scolaris Stalks for Biodiesel Production using Waste Cooking Oil

2020 ◽  
Vol 10 ◽  
Author(s):  
Charishma Venkata Sai Anne ◽  
Karthikeyan S. ◽  
Arun C.
Keyword(s):  
Reaction Time ◽  
Solid Acid ◽  
Solid Acid Catalyst ◽  
Acid Catalyst ◽  
Waste Cooking Oil ◽  
Biodiesel Production ◽  
Wood Biomass ◽  
Waste Wood ◽  
X Ray ◽  
Cooking Oil

Background: Waste biomass derived reusable heterogeneous acid based catalysts are more suitable to overcome the problems associated with homogeneous catalysts. The use of agricultural biomass as catalyst for transesterification process is more economical and it reduces the overall production cost of biodiesel. The identification of an appropriate suitable catalyst for effective transesterification will be a landmark in biofuel sector Objective: In the present investigation, waste wood biomass was used to prepare a low cost sulfonated solid acid catalyst for the production of biodiesel using waste cooking oil. Methods: The pretreated wood biomass was first calcined then sulfonated with H2SO4. The catalyst was characterized by various analyses such as, Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray diffraction (XRD). The central composite design (CCD) based response surface methodology (RSM) was applied to study the influence of individual process variables such as temperature, catalyst load, methanol to oil molar ration and reaction time on biodiesel yield. Results: The obtained optimized conditions are as follows: temperature (165 ˚C), catalyst loading (1.625 wt%), methanol to oil molar ratio (15:1) and reaction time (143 min) with a maximum biodiesel yield of 95 %. The Gas chromatographymass spectrometry (GC-MS) analysis of biodiesel produced from waste cooking oil was showed that it has a mixture of both monounsaturated and saturated methyl esters. Conclusion: Thus the waste wood biomass derived heterogeneous catalyst for the transesterification process of waste cooking oil can be applied for sustainable biodiesel production by adding an additional value for the waste materials and also eliminating the disposable problem of waste oils.

scholarly journals Acylation of isobutylbenzene with acetic anhydride on AlKIT-6 mesoporous acid catalyst

2021 ◽  
Vol 4 ◽  
pp. 128-135
Author(s):  
Prabhu Azhagapillai ◽  
Balachandran Sundaravel ◽  
Muthusamy P. Pachamuthu
Keyword(s):  
Acetic Anhydride ◽  
Acid Catalyst
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