Absence Of Catalyst Research Articles

A Landscape of Lignocellulosic Biopolymer Transformations into Valuable Molecules by Heterogeneous Catalysis in C'Durable Team at IRCELYON.

This review article highlights part of the research activity of the C’Durable team at IRCELYON in the field of sustainable chemistry. This review presents a landscape of the work performed on the valorization of lignocellulosic biopolymers. These studies intend to transform cellulose, hemicellulose and lignin into valuable molecules. The methodology usually consists in evaluating the behavior of the biopolymers in the absence of catalyst under various conditions (solvent, temperature), and then to assess the influence of a catalyst, most often a heterogeneous catalyst, on the reactivity. The most significant results obtained on the upgrading of cellulose and lignin, which have been mainly investigated in the team, will be presented with an opening on studies involving raw lignocellulose.

Molten Ga-Pd alloy catalyzed interfacial growth of graphene on dielectric substrates

Direct growth of graphene on insulating substrate is highly desired for practical applications in two-dimensional electronics and optoelectronics. However, the controllable synthesis of large scale graphene films on dielectrics is still limited in thickness and crystallinity by the absence of catalyst. Here we develop a transfer-free method to synthesize continuous graphene films on various insulating substrates by using molten Ga-Pd alloy and silicon carbide (SiC) as catalyst and carbon source. The catalytic Ga-Pd alloy induces the decomposition of SiC bonds and promotes the formation of C-C sp2 at relatively low temperature around 1000 °C. The suitable carbon solubility of Ga-Pd alloy could also promote the fabrication of few-layer graphene films on the interface between alloy and SiC substrate as well as the upper surface of alloy. Furthermore, this strategy could be extended to the interfacial growth of graphene on other dielectrics by simply placing the substrate face down to the surface of molten alloy. The progress of this work may help to understand the mechanism of molten Ga-Pd alloy catalyzed interfacial growth of transfer-free graphene and benefit the application of graphene-based electronics and photonics in the future.

Recycling Thermoset Epoxy Resin Using Alkyl-Methyl-Imidazolium Ionic Liquids as Green Solvents.

Herein, a solvent-based green recycling procedure is reported for recycling thermoset epoxy resins (TERs) and carbon fiber reinforced epoxy composites (CFRECs) employing ionic liquids (ILs) and alcohols under mild conditions. With melting points less than 100 °C, ILs are defined as organic salts, typically composed of bulky cations with organic or inorganic counteranions. As a result of their unique physical properties such as low vapor pressure, relatively high thermal stability, and multifunctional tunability, these solvents are often classified as “green solvents” as compared to traditional organic solvents. In this study, swelling and dissolution of TER are evaluated in the presence of pure alkyl-methyl-imidazolium ILs, alcohols, and various mixtures of these co-solvents to determine their swelling and depolymerization capacity at mild temperatures in the absence of catalysts. In these studies, three ILs with different alkyl lengths were evaluated: 1-butyl-3-methyl imidazolium chloride ([BMIm][Cl]), 1-hexyl-3-methyl imidazolium bromide ([HMIm][Br]), and 1-octyl-3-methyl imidazolium bromide ([OMIm][Br]) along with two alcohols: ethylene glycol (EG) and glycerol (Gly). The highest swelling capacity of TER at 150 °C was achieved by a combination of [BMIm][Cl] and EG. In addition, swelling and dissolution of TER were evaluated in the presence of several anion variants of 1-butyl-3-methyl-imidazolium ILs with EG. Complete dissolution of both TERs and CFRECs was achieved in 150 min (2.5 h) at 150 °C under atmospheric pressure. Finally, recovery and reuse of the recycled monomer after dissolution were examined. Recovered epoxy monomers employed to synthesize a recycled TER exhibited similar mechanical properties to the parent TER. In addition, it was demonstrated that carbon fibers could be successfully recovered from CFREC using the recycling method detailed in this manuscript.

Reported Catalytic Hydrofunctionalizations that Proceed in the Absence of Catalysts: The Importance of Control Experiments

The enlarged landscape of catalysis lies in the heart of chemistry. As the journey has set a milestone in organic synthesis, its darker side has not entered into the limelight. Studies disclose that the reported reactions by using catalysts were also attainable in the absence of catalysts in many cases. This article presents a literature collection that includes the significance of control experiments in hydrofunctionalization reactions. Systematic analysis reveals that the catalysts are ambiguous and might be unessential in chemical reactions enlisted here.

A review of role of cathodes in the performance of microbial fuel cells

• The material of cathodes significantly improves the power density as well as the electrochemical performance due to higher oxidation reduction reaction (ORR). • The performance of cathodes can be improved by using an appropriate catalyst loading. • The anode material and the experimental conditions has a significant impact on the performance of cathode. • The air-cathodes prove to provide better performance due to its four-electron reduction pathway owing to the catalytic activity at the cathode surface as compared to the other types of cathodes especially when the metal complexes such as Fe–N 4 (catalyst) are embedded with other materials like activated carbon significantly improve the performance of the air–cathode. Cathodes play an essential role in evaluating the performance such as power density and especially the cost of microbial fuel cells (MFCs). Various types of cathodes such as air–cathode, aqueous air–cathode and bio-cathodes are used for MFCs in presence and absence of catalysts. The performance of these cathodes is differentiated in terms of their electrochemical performance, polarization and (or) power density. The material of cathodes significantly improves the power density as well as the electrochemical performance due to higher oxidation reduction reaction (ORR). The performance of cathodes can be improved by using an appropriate catalyst loading. This study reports the use of various cathodes such as air–cathode, aqueous air–cathode, and bio-cathode and their performance in terms of polarization and power density, and electrochemical performance (such as Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS)). Studies suggest that the air-cathodes provide better performance as compared to the other types of cathodes. Furthermore, the metal complexes such as Fe–N 4 (catalyst) when embedded with other materials like activated carbon significantly improve the performance of the air–cathode.

Ultrasonic-assisted degradation of a methylene blue using CuCo2O4 as a heterogeneous Fenton-like catalyst

In this study, a copper cobaltite nanostructure was prepared as a non-ferrous heterogeneous Fenton catalyst using a one-step solvothermal method. The prepared nanocatalyst was characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), infrared spectroscopy (FT-IR) and energy-dispersive X-ray spectroscopy (EDS). The prepared CuCo2O4 exhibited outstanding activity for the degradation of methylene blue (MB) in aqueous solutions under ultrasonic irradiations. The degradation efficiency of MB was only 27.4 % in the absence of catalyst, whereas it reached more than 95.0 % in the presence of the CuCo2O4 after 60 min of ultrasonic irradiation. The trapping experiments with two radical scavengers (tert-butanol and chloroform) showed that both hydroxyl and superoxide radicals are generated during the decomposition of H2O2 and played important roles in oxidation of MB. The prepared nanocatalyst demonstrated good catalytic stability over three successive runs, without any remarkable decrease in catalytic activity.

Quantitative insights on de/repolymerization and deoxygenation of lignin in subcritical water

The objective of the study was to investigate alkali lignin polymerization/depolymerization pathways in subcritical water (SW) without additives. Following a SW treatment at 200, 250, 275 and 300 °C, the products were subjected to a comprehensive suite of analyses addressing the product speciation and molecular weight (MW) distribution. The MW reduction (1.4 times) in the solid products following the SW treatment indicated a surprisingly reduced impact of cross-linking/repolymerization at 300 °C and lower temperatures. This was further confirmed by thermal carbon analysis (TCA) showing a reduction in pyrolytic charring after the SW treatment. The TD-Py gas chromatography analysis of the SW treated lignin indicated that the solid residue is less oxygenated than the initial lignin (23 vs. 29% as confirmed by elemental analysis). Thus, deoxygenation rather than re-polymerization appears to be the main process route in the absence of catalysts within the temperature range considered.

Treatment of hormones in wastewater from the pharmaceutical industry by continuous flow supercritical water technology

Hormones are bioactive, ubiquitous, and persistent organic molecules that demand effective treatment when released in the environment. However, most conventional treatments are inefficient or not suitable for large-scale applications. This study describes the use of supercritical water (SCW) technology in the degradation of hormones in wastewater from the pharmaceutical industry. Initially, the treatment was developed with synthetic wastewater (SW) containing hormone prepared from commercial desogestrel pills and, later, with real industrial wastewater (IW). All the experimental tests were conducted in a continuous flow reactor in the absence of catalysts. Both liquid and gas phases generated during the process were analyzed by instrumental techniques. The liquid phase was characterized by total organic carbon (TOC), chemical oxygen demand (COD), high-performance liquid chromatography (HPLC), and phytotoxicity assays. The gas phase was characterized by gas chromatography (GC). TOC reductions of SW and IW samples, both treated at 700 °C and feed flow rate of 10 mL min−1 were 87.2% and 88.4%, respectively. Phytotoxicity assays indicated a significant reduction in the toxicity of the IW treated at 700 °C. Thus, considering the gas production, especially hydrogen, and the high toxicity mitigation, the IW treatment via SCW is quite promising.

Morphological and thermal characterization of an immiscible catalyzed polymer blends (PC/PET)

The aim is to study the reactive compatibilization of two immiscible thermoplastic polyesters, namely polycarbonate (PC) and poly (ethylene terephthalate) (PET), by transesterification reactions through melt compounding. For this, a catalyst, which is hydrated samarium acetylacetonate (Sm(acac)3), is incorporated with concentrations of 0.10, 0.15 and 0.20 phr into the 70PC/30PET mixture. The characterization of the PC/PET blends by differential scanning calorimetry (DSC) revealed that, the transesterification reactions in the absence of catalyst are undetectable or practically impossible; however, by increasing the catalyst concentration, significant variations are noticed on the thermal properties. These modifications, due to the interfacial reactions between the two phases of the system, were also evidenced by variations in morphological properties observed after the study of atomic force microscopy (AFM).

Study on pressurized upgradation of pyrolysis oil for high-value liquid products.

Upgradation of pyrolysis oil is a key process to achieve high-quality biofuel. In this study, the effects of different Ar pressures and H2/Ar ratios in the presence and absence of catalysts on deoxygenation of pyrolysis oil were investigated by autoclaving. When the initial pressure of the reaction is 6MPa and without catalyst addition, the content of carboxylic acid decreases from 51.52 to 41.54%, whereas with the addition of catalyst (10 % Ni/C), the deoxygenation and hydrocarbon content in the product were significantly improved. Hence, 6 MPa was found to be optimum and above which failed to induce such useful changes but can lead to lower high heating value (HHV). However, the presence of hydrogen affects the content of alkanes and olefins in the product.

Oxidative depolymerization of lignin using nitric acid under ambient conditions

In this work, we demonstrated an innovative and cost-effective strategy to produce high- value depolymerized kraft lignin (DKL) from softwood kraft lignin (SKL) and hardwood kraft lignin (HKL). The depolymerization of kraft lignin was successfully achieved by an oxidative approach using nitric acid under ambient conditions (room temperature and pressure). This novel approach has the following features: ambient process conditions, no heat required, absence of catalysts or organic solvents, and no further purification process being required. The obtained DKL products were characterized extensively by gel permeation chromatography with ultraviolet detector (GPC-UV), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS), potentiometric titration and elemental analysis. Treatment of SKL or HKL at a KL/nitric acid (HNO3) mass ratio of 1:4 (w/w) at room temperature for 84 h resulted in DKL products with a weight-average molecular weight (Mw) of 1350 Da, much lower than that of the original lignins. In addition, the DKL products displayed a significant increase in carboxylic acid group content, a high solubility in water at low pH and, significantly lower decomposition temperatures compared to the original lignins. It was confirmed that nitration of the lignin structure occurred during nitric acid-oxidative depolymerization, as evidenced by the presence of 5% nitrogen (N) content in the DKL products.

A Comparison Study of the Metal Oxide Catalysts for the Conversion of Used Cooking Oil into High Grade Chemicals

Cracking of edible oils occurs at high temperature and forms valued low molecular weight chemical species. The aim of the current study was to find a catalyst which can break these heavy molecules at the lower ranges of temperatures. From the analysis prospective, the non-condensable hydrocarbons (gaseous product species) were not determined and reactions study was carried out in a batch reactor. There was no evident conversion up to a temperature of 450 °C in the absence of catalyst whereas the reaction mixture was left inside a batch reactor for a long duration of an hour. Reaction parameters, such as catalyst types (ZnO and Al2O3), amount of catalyst, reaction temperature, residence or holding time, and heating rate to reach a reaction temperature were systematically examined. Powdered form of catalyst samples (ZnO and Al2O3) were characterized by using XRD, EDX, and Nitrogen adsorption isotherms. Temperatures studied over ZnO catalyst were 400 °C, 425 °C, 450 °C, 475 °C, and 500 °C. The maximum oil conversion was 81 % at a temperature of 450 °C. We observed that the conversion increases from 400 °C to 450 °C, whereas above 450 °C it starts to decrease. However, in comparison to ZnO catalyst the reaction rate was much higher over the Al2O3, i.e. a considerable conversion occurred at lower ranges of temperatures. Thus here a different set of temperatures (330 °C, 370 °C, 390 °C, 410 °C, and 430°C) were used. When reacting for an hour at a temperature of 390 °C, and in the presence of 8 wt.% of Al2O3 (same catalyst mass was used in ZnO reacting system) the conversion reached to 71 %. Above 390 °C the conversion decreased. Over both tested metal oxide catalysts the caloric value, density, flash point, and kinematic viscosity of the liquid product species were similar to petro fuels. The XRD and EDX signature of the catalyst samples corresponds to the standard ZnO and Al2O3 patterns. Finally, when compared to ZnO the better activity over the Al2O3 (higher conversion at lower temperature) catalyst can be linked with a high external surface area.

One‐pot synthesis of new functionalized 4H‐chromen‐4‐ylidene derivatives

AbstractA simple synthesis of new series of functionalized chromene derivatives through an efficient, one‐pot, multicomponent reaction of nitroketene N,S‐acetals, salicylaldehydes, and cyanoacetohydrazide in ethanol at ambient temperature in good to high yields is reported. This novel efficient method has the advantages of mild reaction conditions, absence of catalyst, simple work‐up, and the non‐chromatographic purification of products.

Thermal Healing of Copolyacrylate Elastomer Based on Catalyst‐Free Transketalization

AbstractCopolyacrylate can heal via dynamic covalent bonds when it is exposed to external stimuli, such as pH value, ionic strength, humidity, and light, but the incorporation of dynamic covalent bonds will result in a decrease in the thermal stability of materials. It is still a great challenge to design a healable copolyacrylate with high thermal stability. The transketalization is confirmed by the reaction of model compounds including acetophenone glycerol ketal (AGK) and ethylene glycol (EG) in the absence of catalyst. The copolyacrylate elastomers are prepared by copolymerization of methyl methacrylate (MMA), butyl acrylate (BA), 2,3‐dihydroxypropyl methacrylate (DHPMA), and ketal‐containing diacrylate as a cross‐linking agent. The results show that the ketal‐containing copolyacrylate (KCPA) can achieve a 96% of healing efficiency at 120 °C, meanwhile, it has high thermal stability. The healing of copolyacrylate elastomers originates from the transketalization between ketal and o‐dihydroxyl groups, which is confirmed by comparison with those of the ketal‐free control samples. The study will expand the scope of self‐healing polymers based on dynamic covalent bonds.

Direct synthesis of sulfinic esters via ultrasound accelerated tandem reaction of thiols and alcohols with N-bromosuccinimide

The direct transformation of various thiols and simple alcohols with N-bromosuccinimide into sulfinic esters has been investigated by using different categories of base/acidic catalysts as well as co-solvents under varied reaction conditions. The reaction was found out to afford the sulfinic esters with high yields in the absence of catalysts, especially within the shorter time under the acceleration of ultrasonic irradiation than under the longer-lasting conventional stirring conditions.

Squeezing Out the Catalysts: A Sustainable Approach to Disulfide Bond Exchange in Aryl Disulfides

High-pressure conditions can be considered as an alternative, environmentally responsible way for the equilibrium reactions, such as disulfide exchange. This approach is capable of eliminating the catalysts or stimuli, such as reducing agents, strong bases, ultraviolet light, or ultrasound. The exchange of aryl disulfides in the absence of catalysts or other stimuli has been systematically studied. The effects of pressure in the range between 100 and 400 MPa, accessible in large-scale technological installations, have been tested for promoting exchange reactions between various homodimeric aryl disulfides. For the optimized conditions, 100% yields of the heterodimer in pure single-crystal form were obtained. The reactions were performed in a diamond anvil cell, as well as in a hydraulic piston-and-cylinder press, and the products were characterized by X-ray diffraction, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The prominent role of high-entropy states, not attainable under ambient conditions, as well as the high-entropy nucleation, kinetic crystallization, and other effects associated with the high-pressure environment, has been demonstrated. These entropy-driven reactions represent an efficient, environmentally friendly, one-pot method for obtaining pure crystalline heterodimeric disulfides.

Selective and mild sulfoxidation of 2-sulfylbenzothiazole using hydroperoxides derived from cyclohexanone in the absence of catalyst

Alkyl hydroperoxides derived from cyclohexanone are attractive oxidants because they are easily available, more reactive than TBHP but much less acidic than m-CPBA. Wherein 1,1′-peroxybis(1-hydroperoxycyclohexane) (C) can be generated by the current simply method and displays the excellent reactivity and selectivity based on oxidative reactions of various benzothiazolyl sulfides substituted by different function groups. The research found that the reactions can be performed in the absence of catalyst and under very mild conditions optimized. Yields of sulfoxides is higher than 90%, no or a little reaction happened at the proximal double bond、 N and S atoms in the benzothiazolyl moiety. Phenyl sulfide as the substrates was also examined for the reaction scope test. The results show that they were uniquely and completely oxidized to sulfoxides in 1 h. A mild, environmentally friendly, catalyst-free aryl sulfide sulfoxidation method has been developed.

Characterization of liquid products obtained from catalytic co-cracking of polypropylene waste and residual fuel oil

The characterization of the liquid yield resulting from the co-cracking of Polypropylene extrusion grade and Residual fuel oil was carried out using analysis techniques like Gel Permeation chromatography, Ultimate, Calorimetry, and Fourier-transform infrared spectroscopy analysis technique. The resulting product of liquid yield from the co-cracking of the two feedstocks in presence of catalyst Zeolite Socony Mobil–5 was observed to have high calorific values of 44.084 MJ/Kg comparable values to that of the commercial diesel and therefore, has the potential to be used as source of renewable fuel energy. The addition of catalyst and temperature has been found to have positive synergistic effect on the heating value of the liquid product. The Fourier-transform infrared spectroscopy spectrum obtained from the co-cracking of Residual fuel oil and Polypropylene extrusion grade both in the presence and absence of catalyst was observed to be a mixed spectrum of their individual component and addition of catalyst had an insignificant effect on the properties of the resulting liquid except in the calorific values which were increased. The spectrum shows that the liquid product was dominated by the presence of alkanes and alkenes compounds.

Retraction of "Enantioselective Organocatalytic Hantzsch Synthesis of Polyhydroquinolines".

The following changes were made to the revised Supporting Information document submitted with this correction: (1) All data referring to compound 4o has been removed. (2) HPLC traces for 4a, 4d, 4h, and 4n have been replaced with less ambiguous choices, pp 43−47. (3) Clarification of the method to confirm peak identities is now included, p 48. (4) Confirmation of peak identities is now included for compounds 4a, 4d, 4h, 4k, 4l, and 4n, pp 48−50. (5) Missing retention times for compounds 4a and 4g have been added on p 42. (6) H NMR peaks have been added for compounds 4k and 4j. These were missing in the original document, p 5. (7) The new Supplemental Figure 1 has been added (p 2), which shows that the Hantzsch reaction to produce compound 4b does not proceed in the absence of catalyst. We previously neglected to include this important data. This material is available free of charge via the Internet at http://pubs.acs.org.

Prebiotic Route to Thymine from Formamide—A Combined Experimental–Theoretical Study

Synthesis of RNA nucleobases from formamide is one of the recurring topics of prebiotic chemistry research. Earlier reports suggest that thymine, the substitute for uracil in DNA, may also be synthesized from formamide in the presence of catalysts enabling conversion of formamide to formaldehyde. In the current paper, we show that to a lesser extent conversion of uracil to thymine may occur even in the absence of catalysts. This is enabled by the presence of formic acid in the reaction mixture that forms as the hydrolysis product of formamide. Under the reaction conditions of our study, the disproportionation of formic acid may produce formaldehyde that hydroxymethylates uracil in the first step of the conversion process. The experiments are supplemented by quantum chemical modeling of the reaction pathway, supporting the plausibility of the mechanism suggested by Saladino and coworkers.