Cl Catalyst Research Articles

Important role of H2 spillover in asymmetric hydrogenation of quinolines in hybrid systems.

The phenomenon of hydrogen spillover usually involved in the hydrogenation reactions over supported metal catalysts has been seldom reported over molecular catalysts. Herein, we report the important role of hydrogen spillover in homogeneous hydrogenation with the asymmetric hydrogenation of quinolines as a model reaction. It is observed that the conversion of quinaldine over TsDPEN-Rh-Cp*-Cl catalyst is sharply increased by 2.1 folds in the presence of Ni/TiO2 and the ee value remained at the same level. The mechanism study shows that Ni/TiO2 is mainly used as H2 dissociation site, TsDPEN-Rh-Cp*-Cl is the active site to control the enantioselectivity of the product, and hydrogen spillover acts as a bridge between the two catalysts in the homogeneous and heterogeneous hybrid system. The hydrogen spillover makes it possible for heterogeneous catalysts and homogeneous organometallic complexes to cooperate, breaking the boundary between homogeneous and heterogeneous catalysis.

Negative impact of poly(acrylic acid) on proton conductivity of electrospun catalyst layers

The electrospun catalyst layers (E-spun CLs) have attracted great attention recently owing to their decent performance and durability compared to conventional coated CL fabricated by scrape coating. However, proton transport in E-spun CLs is poorly understood, hindering further performance improvements. We unravel herein that the high molecular weight (MW) polymer used to form nanofibers, usually Poly(acrylic acid) (PAA), is a key factor affecting the proton conductivity. Nuclear magnetic resonance (NMR) unravels strong interaction between the ionomer and PAA. The proton conductivity of ionomer membranes with varying PAA content under different ionomer volume fractions and relative humidity (RH) was quantitatively assessed using the four-probe electrochemical impedance spectroscopy (EIS). E-spun CL exhibited lower proton conductivity than coated CL or pseudo catalyst layer (PCL) at the same ionomer volume fraction due to the detrimental effects of PAA. The proton transport tortuosity of E-spun CL increased with RH, likely attributed to the significant swelling ratio of PAA. The proton transport tortuosity of E-spun CL displayed less sensitivity to the ionomer volume fraction, which can be attributed to the homogeneous distribution of the ionomer within the nanofibers. Our work implies that the key to enhancing proton conductivity of E-spun CLs is to remove PAA completely, or to replace PAA with alternatives that would not impair proton transport.

Cu (II)-catalyzed: synthesis of imidazole derivatives and evaluating their larvicidal, antimicrobial activities with DFT and molecular docking studies

This paper deals with the evaluation of novel imidazole molecules for their antimicrobial and larvicidal activities. A series of imidazole derivatives 1(a–f) and 2(a–e) were prepared by the Mannich base technique using a Cu(II) catalyst. The Cu(phen)Cl2 catalyst was found to be more effective than other methods. FTIR, elemental analyses, mass spectrometry, 1H NMR, and 13C NMR spectroscopy were performed to elucidate the structures of the synthesised compounds. Antimicrobial and larvicidal activities were investigated for all compounds. The antibacterial activity of compounds (2d) and (2a) were highly active in S.aureus (MIC: 0.25 μg/mL) and K.pneumoniae (MIC: 0.25 μg/mL) compared to ciprofloxacin. Compound (1c) was significantly more effective than clotrimazole in C.albicans (MIC: 0.25 μg/mL). Molecular docking studies of compound 2d showed a higher binding affinity for the 1BDD protein (− 3.4 kcal/mol) than ciprofloxacin (− 4.4 kcal/mol). Compound 1c had a higher binding affinity (− 6.0 kcal/mol) than clotrimazole (− 3.1 kcal/mol) with greater frontier molecular orbital energy and reactivity properties of compound 1c (∆E gap = 0.13 eV). The activity of compound 1a (LD50: 34.9 μg/mL) was more effective in the Culex quinquefasciatus than permethrin (LD50: 35.4 μg/mL) and its molecular docking binding affinity for 3OGN protein (− 6.1 kcal/mol). These newly synthesised compounds can act as lead molecules for the development of larvicides and antibiotic agents.

Synthesis of sulfur-containing polycarbonate block copolymers via Salen-metal catalyzed copolymerization of CO2, propylene oxide, and phthalic thioanhydride

Sulfur-containing ABA-type polycarbonate triblock copolymers were synthesized via sequential copolymerization of propylene oxide (PO) and carbon dioxide (CO2), followed by propylene oxide (PO) and phthalic thioanhydride (PTA) in the presence of water and Salen-Metal catalysts. The reaction was catalyzed using Salen-Co(III)-Cl/[PPN]Cl and Salen-Cr(III)-Cl/[PPN]Cl catalyst systems. The content of thioester units in the copolymer chain could be adjusted by varying the feed ratios of PTA. These triblock polymers displayed a higher refractive index, reaching up to 1.561.

Kinetic Modeling of Light Naphtha Hydroisomerization in an Industrial Universal Oil Products Penex™ Unit

Recently, the isomerization of light naphtha has been increasingly significant in assisting refiners in meeting sternness specifications for gasoline. Isomerization process provides refiners with the advantage of reducing sulfur, olefin, and benzene in the gasoline basin without significantly victimizing the octane. The mathematical modeling of a chemical reaction is a critical tool due to it can used to optimize the experimental data to estimate the optimum operating conditions for industrial reactors. This paper describes light naphtha isomerization reactions over a Pt/Al₂O₃-Cl catalyst at the Al-Dura Oil Refinery (Baghdad, Iraq) using a newly developed universal mathematical model. The proposed kinetic model involves 117 isomerization reactions and 90 cracking reactions to describe 52 real components graded from methane to n-octane. A Genetic Algorithm stochastic optimization technique applied in MATLAB R2020a software was employed to estimate the optimal set of kinetic parameters. The calculated activation energies for hydrocracking reactions was found to be higher than the other reactions because of hydrocracking reactions occur at higher range of temperatures. By benchmarking between the experimental and theoretical results for all 117 data sets, the mean absolute error was obtained to be 0.00360 for all 52 components. Also, a positive effect of increasing reaction temperatures was recognized on enhancing the research octane number (RON).

Homogeneous Electrocatalytic Reduction of CO2 by a CrN3O Complex: Electronic Coupling with a Redox-Active Terpyridine Fragment Favors Selectivity for CO.

Electrocatalyst design and optimization strategies continue to be an active area of research interest for the applied use of renewable energy resources. The electrocatalytic conversion of carbon dioxide (CO2) is an attractive approach in this context because of the added potential benefit of addressing its rising atmospheric concentrations. In previous experimental and computational studies, we have described the mechanism of the first molecular Cr complex capable of electrocatalytically reducing CO2 to carbon monoxide (CO) in the presence of an added proton donor, which contained a redox-active 2,2'-bipyridine (bpy) fragment, CrN2O2. The high selectivity for CO in the bpy-based system was dependent on a delocalized CrII(bpy•-) active state. Subsequently, we became interested in exploring how expanding the polypyridyl ligand core would impact the selectivity and activity during electrocatalytic CO2 reduction. Here, we report a new CrN3O catalyst, Cr(tpytbupho)Cl2 (1), where 2-(2,2':6',2″-terpyridin-6-yl)-4,6-di-tert-butylphenolate = [tpytbupho]-, which reduces CO2 to CO with almost quantitative selectivity via a different mechanism than our previously reported Cr(tbudhbpy)Cl(H2O) catalyst. Computational analyses indicate that, although the stoichiometry of both reactions is identical, changes in the observed rate law are the combined result of a decrease in the intrinsic ligand charge (L3X vs L2X2) and an increase in the ligand redox activity, which result in increased electronic coupling between the doubly reduced tpy fragment of the ligand and the CrII center. The strong electronic coupling enhances the rate of protonation and subsequent C-OH bond cleavage, resulting in CO2 binding becoming the rate-determining step, which is an uncommon mechanism during protic CO2 reduction.

Aerobic Baeyer‐Villiger Oxidation Catalyzed by Metal Corroles

AbstractMetal corrole catalyzed Baeyer‐Villiger oxidation reaction was successfully achieved for the first time. Among all tested Co, Mn, Fe and Cu complexes of 5, 10, 15‐Tris (pentafluorophenyl) corrole, Fe complex [Fe(tpfc)Cl] exhibited the best activity, and the highest yield was observed for six membered cyclic ketones. Preliminary results suggest that Fe(tpfc)Cl may act as an initiator for dehydrogenation of benzaldehyde to generate benzoyl radical, which will form peroxybenzoic acid under molecular oxygen atmosphere. The oxidation of Fe(tpfc)Cl catalyst by peroxybenzoic acid produces high‐valent iron‐oxo corrole intermediate. The iron‐oxo corrole is attacked by cyclohexanone to form a Criegee adduct, which will finally generate ϵ‐caprolactone product to finish the catalytic cycle. The 4 A‐MS additive may accelerate the production of perbenzoic acid and significantly improve the reaction yield.

Effect of catalyst layer designs for high-performance and durable anion-exchange membrane water electrolysis

Development of anode design is crucial for highly efficient and durable anion-exchange membrane water electrolysis (AEMWE) as the kinetic of oxygen evolution reaction (OER) is sluggish. In this study, a macroporous catalyst layer (macroporous_CL) was proposed as an anode design for AEMWE to enhance the catalyst utilization. A macroporous_CL contains pores of two main size ranges: hundreds of nanometers and hundreds of micrometers. It is prepared using a spraying method to form nanometer-sized pores. The use of a stainless-steel (SUS) porous transport layer (PTL) as the substrate of the spraying method produces micrometer-sized macropores. In an investigation of the effects of the macroporous_CL and conventional catalyst layer (plain_CL) on AEMWE using two different kinds of oxygen evolution reaction (OER) catalysts, the macroporous_CL exhibited higher performance with lower ohmic and charge-transfer resistances compared to the plain_CL. This performance enhancement was attributed to the improved catalyst utilization and electron transport. Also, the macroporous_CL showed better durability compared to the plain_CL. Therefore, the macroporous_CL has been considered as an alternative anode design for AEMWE.

Synergism between iron porphyrin and dicationic ionic liquids: tandem CO2 electroreduction-carbonylation reactions.

Here, we report a simple procedure that drastically reduces the electrochemical E(FeI/Fe0) and E0cat of the commercially available iron(III) tetraphenylporphyrin chloride (FeIIITPP·Cl) catalyst via a synergetic effect with the imidazolium dications of the ionic liquid electrolyte. This procedure enhanced the performance of catalytic systems in the electrochemical production of CO and enabled us to perform different tandem CO2 reduction-carbonylation reactions under mild conditions.

Mesoporous silica nanospheres supported atomically precise palladium nanocluster: Highly efficient and recyclable catalysts in the reduction of 4‐nitrophenol and Heck reactions

AbstractAtomically precise palladium nanoclusters show great potential applications in the field of catalysis owing to its ultrasmall size and precise structure. This work, we report the mesoporous silica nanoparticles (MSNs) supported [Pd3Cl(PPh3)3(PPh2)2]Cl catalysts (denoted as Pd3Cl/MSNs) for the reduction of 4‐nitrophenol and Heck coupling reactions of iodobenzene and styrenes. High uniform MSNs, with average diameter ≈110 nm, were prepared by sol–gel method, followed by Pd nanoclusters immobilization into the pore of MSNs. The MSNs supported Pd nanoclusters were well characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT‐IR), and diffuse reflectance optical spectrum. The results indicated that Pd3Cl nanoclusters after immobilized into the pores of MSNs are intact and possess good dispersibility. The catalytic performance of as‐prepared nanocomposites was evaluated by the reduction of 4‐nitrophenol and Heck reactions. The 4‐nitrophenol could be completely conversion to 4‐aminophenol within 6 min. Meanwhile, the as‐prepared Pd3Cl/MSNs exhibit excellent catalytic performance in the Heck reactions between iodobenzenes and styrenes. The high catalytic activity of Pd3Cl/MSNs could be attributed to the large surface area and unique geometric structure of as‐prepared Pd nanoclusters. More importantly, the catalysts could be easily recycled by centrifugation and shows excellent reusability.

MerDABCO-SO3H]Cl catalyzed synthesis, antimicrobial and antioxidant evaluation and molecular docking study of pyrazolopyranopyrimidines

Sulfonic acid functionalized 1,4-diazabicyclo[2.2.2]octane supported on Merrifield resin, [MerDABCO-SO3H]Cl catalyst was prepared and explored in one-pot four-component reaction of ethyl acetoacetate, hydrazine hydrate, aryl aldehyde and barbituric acid for the synthesis of pyrazolopyranopyrimidines with excellent yields. The catalyst could be easily recovered and reused for four cycles without significant decrease in catalytic activity. The antimicrobial and invitro antioxidant activities of the synthesized pyrazolopyranopyrimidines were found to be promising and antioxidant activities are supported by molecular docking studies.

ESI-MS Analysis of Thiol-yne Click Reaction in Petroleum Medium.

Petroleum contains a large number of heteroatomic compounds, but today, most of them are not efficiently utilized. The constant development of the sustainability concept recalls for rethinking the usage of fossil resources with improved chemical utility. In order to initiate research aimed at involving active petroleum compounds in chemical transformations, a new analytical method for product detection is needed. Here, we study the click reaction of thiols with alkynes, leading to the formation of α-vinyl sulfides directly in the petroleum environment. The reaction was carried out using an (IMes)Pd(acac)Cl catalyst, which demonstrated tolerance to petroleum components. In this study, the concentration of thiols ranged from 1 M to 0.01 M (from 8% to 0.1%). To detect products at low concentrations, a special alkyne labeled with an imidazole moiety was used. This approach made it possible to observe the formation of vinyl sulfides by electrospray ionization mass spectrometry (ESI-MS), which provides an opportunity for further optimization of the reaction conditions and future developments for the direct involvement of oil components in chemical reactions.

Microwave assisted synthesis of phenanthridine derivatives via Suzuki coupling and condensation

One-pot synthesis of phenanthridine derivatives using appropriately substituted aromatic ortho-bromo N-tosylhydrazones and 2′-aminobenzeneboronic acid pinacol esters is described. In the presence of Pd(amphos)Cl2 catalyst, tosylhydrazone precursors undergo a Suzuki cross-coupling reaction with 2′-aminobenzeneboronic acid pinacol ester derivatives followed by intramolecular condensation to form the corresponding phenanthridines derivatives in one step.

Kinetic modelling of Pt/γ-Al2O3–Cl catalysts formulation changes in n-heptane reforming

A common n-heptane reforming lumped kinetic model based on linear free energy relationships was developed on experimental data acquired over 19 Pt/γ-Al2O3–Cl catalysts presenting different formulations and support crystallite morphologies.

Fesipmim]Cl as highly efficient and reusable catalyst for solventless synthesis of dihydropyridine derivatives through Hantzsch reaction

In the present investigation, magnetic ferrite nanoparticles (ferrite NPs) were synthesized and coated with silica (ferrite@SiO2NPs) by using the sol-gel method. After that, silica propylmethylimidazolium chloride ionic liquid [Sipmim]Cl was prepared and linked with the above-prepared ferrite@SiO2NPs to synthesize ferrite silica propylmethylimidazolium chloride [Fesipmim]Cl catalyst. The formation of [Fesipmim]Cl catalyst was confirmed by Fourier-transform infrared (FT-IR) spectroscopy analysis. X-ray diffraction (XRD) analysis confirmed the structure of ferrite NPs and ferrite@SiO2 NPs. Transmission electron microscopy (TEM) evidenced the successful formation of ferrite NPs and ferrite@SiO2 NPs. Scanning electron microscopy (SEM) results revealed the change in morphology of ferrite NPs, ferrite@SiO2NPs and [Fesipmim]Cl. The magnetic properties of [Fesipmim]Cl catalyst were measured by vibrating sample magnetometer (VSM). The efficiency of the [Fesipmim]Cl catalyst was checked by using it for the synthesis of different derivatives of dihydropyridine through Hantzsch reaction via a three-component coupling reaction of substituted benzaldehydes, ethyl/ methyl acetoacetate and ammonium acetate. The formation and structures of all the synthesized compounds were confirmed by FT-IR, 1HNMR, 13C NMR spectral analyses. The reusability of the catalyst [Fesipmim]Cl was checked up to seven cycles and found to have excellent activity up to five cycles.

Non Monotonous Product Distribution Dependence on Pt/γ‐Al2O3−Cl Catalysts Formulation in n‐Heptane Reforming.

AbstractThe synthesis of 19 carefully selected Pt/γ‐Al2O3−Cl formulations was followed by high‐throughput catalytic testing in order to unravel the effect of an active phase formulation change on n‐heptane reforming performances. Pt/γ‐Al2O3−Cl catalysts were prepared with different Pt (0.3–1 %wt) and Cl (0.1–1.4 %wt) contents and using two γ‐Al2O3 supports so that both sites concentrations and sites locations at the crystallite surface vary among the catalyst pool. Catalytic tests were conducted in mild conditions for a comparison of catalysts in kinetic regime. Results show that Pt and Cl concentrations control the competition between hydroisomerisation, hydrogenolysis and hydrocracking pathways. Aromatisation, on the contrary, is poorly affected by formulation changes. Non‐monotonous trends linking Pt/Cl ratio to isomerisation selectivity are found for both γ‐Al2O3 supports. This study provides new insights for the description of bi‐functional transformations in catalytic naphtha reforming.

Selective Reduction of CO2 to CO by a Molecular Re(ethynyl-bpy)(CO)3Cl Catalyst and Attachment to Carbon Electrode Surfaces

The catalytic properties of Re(ethynyl-bpy)(CO)3Cl and Re(vinyl-bpy)(CO)3Cl were studied and compared with those of the previously reported Re(tBu-bpy))CO)3Cl. As a molecular catalyst, Re(ethynyl-bpy)(CO)3Cl reduces CO2 to CO with lower overpotential (η ≈ 0.525 V), higher selectivity for CO (FE 96%), and higher reaction rate (Icat/Ip = 27) compared to similar catalysts reported to date. The catalyst undergoes electropolymerization at the surface of a glassy carbon electrode in dry acetonitrile solution, creating a polymer film that is electroactive under a CO2 atmosphere. In the presence of trifluoroethanol (TFE) (pKa 35.4, MeCN) these films exhibit high efficiencies for CO (FECO 97%). On the basis of preliminary studies, these electrodes show promise as heterogeneous electrocatalysts. Further optimization and understanding of deactivation pathways will be required to make these systems practical. The ethynyl functionalized Re(ethynyl-bpy)(CO)3Cl catalyst also can be attached to graphitic carbon electrodes through the “click” reaction. This represents the first example of attachment of a CO2 reduction catalyst to an electrode surface by “click” chemistry.

β-Cyclodextrin functionalization of metal-organic framework MOF-235 with excellent chemiluminescence activity for sensitive glucose biosensing

Herein, we developed a new CL method for the detection of glucose, exhibiting high sensitivity, low limit of detection, good stability and reliability for analysis of real biological samples. The MOF-235/β-cyclodextrin (β-CD) hybrids were facilely prepared by a simple method, and characterized by XRD, TGA, FT-IR and SEM. The as-prepared hybrids exhibited highly catalytic activity for the hydrogen peroxide-luminol system, and gave more than 30-fold enhancement in CL response as compared with that of hydrogen peroxide-luminol system, thus could be used for sensitive detection of H2O2 and glucose. The excellent catalytic performance of the MOF-235/β-CD hybrids is ascribed to the large surface area of MOF-235 as well as the synergistic effect between β-CD and MOF-235. The proposed sensing strategy coupled with CL detection method showed low detection limits of 5 nM and 10 nM for H2O2 and glucose, respectively. Successful application of the MOF-235/β-CD hybrid in CL assay of glucose in real human serum samples is demonstrated as an efficient catalyst for sensitive chemiluminescence-based analyses. The success of this work favors to facilitate the future development in CL catalysts via MOF functionalization.

Aminocarbonylation of N-Containing Heterocycles with Aromatic Amines Using Mo(CO)6

We describe herein the palladium-catalyzed aminocarbonylation of nitrogen-containing heterocycles with aniline derivatives using molybdenum hexacarbonyl as a CO solid source, expanding the scope of the limited examples. This method is compatible with a variety of substitutions on the aniline moiety. The simple reaction conditions include easily available Pd(dppf)Cl2 catalyst, DBU as base in DMF at 120 °C for 3 hours in sealed tube thereby leading to the isolation of 21 compounds with yields ranging from 18 to 82%. We also show that double aminocarbonylation reactions are possible in satisfactory yields regarding both coupling partners.

Structural behaviour of copper chloride catalysts during the chlorination of CO to phosgene.

The interaction of CO with an attapulgite-supported Cu(ii)Cl2 catalyst has been examined in a micro-reactor arrangement. CO exposure to the dried, as-received catalyst at elevated temperatures leads to the formation of CO2 as the only identifiable product. However, phosgene production can be induced by using a catalyst pre-treatment where the supported Cu(ii)Cl2 sample is exposed to a diluted stream of chlorine. Subsequent CO exposure at ∼370 °C then leads to phosgene production. In order to investigate the origins of this atypical set of reaction characteristics, a series of X-ray absorption experiments were performed that were supplemented by DFT calculations. XANES measurements establish that at the elevated temperatures connected with phosgene formation, the catalyst is comprised of Cu+ and a small amount of Cu2+. Moreover, the data show that unique to the chlorine pre-treated sample, CO exposure at elevated temperature results in a short-lived oxidation of the copper. On the basis of calculated CO adsorption energies, DFT calculations indicate that a mixed Cu+/Cu2+ catalyst is required to support CO chemisorption.