Catalyst Recovery Research Articles

Sulfonated phenylamine ionic liquids as efficient phase-separation catalysts for the synthesis of trimethylolpropane triacrylate

PS3-PA with multi-SO3H exhibits excellent catalytic performance for the esterification of TMP with acrylic acidviahydrogen bond formation. The phase-separation behavior of PS3-PA plays an important role in catalyst recovery and stable reuse.

Highly efficient and recyclable chiral phosphine-functionalized polyether ionic liquids for asymmetric hydrogenation of β-keto esters.

Herein, based on the concept of integration of phosphine ligands and ionic liquids (ILs), a class of chiral phosphine-functionalized polyether ionic liquids (CPF-PILs) were synthesized by ion-exchange reaction between polyether imidazolium ILs and a phenyl-sulfonated (S)-(-)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) chiral diphosphine ligand, and employed in the Ru-catalyzed homogeneous asymmetric hydrogenation of β-keto esters. The resulting CPF-PILs combined the dual functions of the chiral phosphine ligand and ILs, allowing efficient recovery and recycling of the chiral catalysts using only a catalytic amount of CPF-PILs. The effects of various factors, including the chiral catalyst structure, solvent properties, reaction temperature, hydrogen pressure, and hydrobromic acid dosage, on catalytic performance were thoroughly investigated, as well as the cycling stability and universality of the chiral catalysts were examined. The findings of the present study demonstrated that, under optimal reaction conditions, the model substrate methyl acetoacetate underwent quantitative conversion to methyl β-hydroxybutyrate with a 97% enantiomeric excess (ee). The chiral catalyst used in this process can be recycled up to 12 times and showed good applicability to structurally various β-keto esters. The present study presents a novel approach for using ILs in asymmetric hydrogenation reactions in an environmentally friendly manner.

Facile one pot synthesis of 2-substituted benzimidazole derivatives under mild conditions by using engineered MgO@DFNS as heterogeneous catalyst.

Benzimidazole derivatives are considered as important heterocyclic motifs that show a wide range of pharmaceutical applications. In view of their wide-ranging bioactivities, it is imperative to direct research on the sustainable catalytic synthesis of benzimidazole. Therefore, herein, we report a novel approach for the synthesis of benzimidazole and its derivatives with engineered MgO supported on dendritic fibrous nano silica (MgO@DFNS) as a sustainable heterogeneous catalyst. The catalyst MgO@DFNS was thoroughly characterized to understand its physio-chemical properties using XRD, FE-SEM, XPS, FT-IR, zeta potential, HR-TEM, TGA, TPR and TPD. The obtained results suggested that the catalyst MgO@DFNS prepared well and have the desired characteristics in it. After the successful characterisation of the prepared catalyst MgO@DFNS, it was applied in the synthesis of benzimidazole derivatives via condensation of o-phenylenediamine, and various aromatic and aliphatic aldehydes under ambient temperature. The catalyst produced a clean reaction profile with excellent yields in a shorter time under the umbrella of green chemistry. The effect of reaction parameters such as the effect of time, catalyst dosage, loading of MgO, effect of solvents and effect of different homo and heterogeneous catalyst were also tested. Furthermore, to understand the scope of the catalyst different substituted diamines and substituted aldehydes were reacted and obtained desired products in good to efficient yield. In addition, a recyclability study was also conducted and it was observed that the catalyst could be recycled for up to six cycles without noticeable changes in the morphology and activity. We believe that the present methodology gave several advantages such as an eco-friendly method, easy work-up, good selectivity, high yields and quick recovery of catalyst. MgO@DFNS is highly stable for several cycles without significant loss of its activity, which possibly demonstrates its applicability at the industrial scale.

Recent advances in the application of magnetic nanocatalysts in multicomponent reactions.

Recently, the preparation and applications of magnetic nanostructures have attracted increasing attention in nanocatalysis studies, and magnetic nanoparticle (MNP) functionalized catalysts have been applied in important reactions such as Suzuki-Miyaura and Heck couplings. The modified nanocomposites demonstrate significant catalytic efficiency and excellent benefits in the context of catalyst recovery methods. This review discusses the recent modified magnetic nanocomposites in the field of catalytic applications along with the synthetic processes that are usually employed.

CO2-Switchable Emulsification and Demulsification of Pickering Emulsion Stabilized by Zirconium-Based Metal–Organic Frameworks

Stimuli-responsive Pickering emulsions have aroused considerable amounts of attention recently because of their potential for on-demand demulsification. Metal–organic frameworks (MOFs) are promising emulsifiers for the construction of Pickering emulsions due to their ultrahigh specific surface area, tunable porosity, and designable structures. However, CO2-responsive zirconium-based MOF-stabilized Pickering emulsions have been rarely reported up to now. Herein, a new series of amine-functionalized UiO-66-O-APTES were developed via the covalent post-modification of UiO-66-OH with different amounts of (3-aminopropyl)triethoxysilane (APTES) and were then applied to construct CO2-switchable Pickering emulsions. It was shown that UiO-66-O-APTES could emulsify toluene and water well to form an emulsion even at the content of 0.1 wt %. Significantly, the Pickering emulsion could be reversibly demulsified and re-emulsified by alternate CO2 and N2 bubbling under constant pressure. Mechanism results revealed that the CO2-switchable phase transition based on the formation of hydrophilic ammonium salts resulting from the reaction of APTES with CO2, which lowered the wettability of particles, reduced emulsion stability, and resulted in emulsion breaking. After CO2 was removed, the Pickering emulsion could be rebuilt by the reverse reaction. By using this strategy, a controllable and highly effective CuI-catalyzed cycloaddition reaction has been achieved, and the coupling of efficient condensation, product separation, and recovery of MOF catalysts has been demonstrated to give rise to a sustainable reaction process.

Transformation of waste seed biomass of Cordia myxa into valuable bioenergy through membrane bioreactor using green nanoparticles of indium oxide

Depletion of non-renewable fuel has obliged researchers to seek out sustainable and environmentally friendly alternatives. Membranes have proven to be an effective technique in biofuel production for reaction, purification, and separation, with the ability to use both porous and non-porous membranes. It is demonstrated that a membrane-based sustainable and green production can result in a high degree of process intensification, whereas the recovery and repurposing of catalysts and alcohol are anticipated to increase the process economics. Therefore, in this study sustainable biodiesel was synthesized from inedible seed oil (37 wt%) of Cordia myxa using a membrane reactor. Transesterification was catalyzed by heterogenous nano-catalyst of indium oxide prepared with leaf extract of Boerhavia diffusa. Highest biodiesel yield of 95 wt% was achieved at methanol to oil molar ratio of 7:1, catalyst load 0.8 wt%, temperature 82.5 °C and time 180 min In2O3 nanoparticles exhibited reusability up to five successive transesterification rounds. The production of methyl esters was confirmed using Fourier-transform infrared spectroscopy and Nuclear Magnetic Resonance. The predominant fatty acid methyl ester detected in the biodiesel was 5, 8-octadecenoic acid. Biodiesel fuel qualities were determined to be comparable to worldwide ASTM D-6571 and EN-14214 standards. Finally, it was concluded that membrane technology can result in a highly intensified reaction process while efficient recovery of both nano catalysts and methanol increases the economics of transesterification and lead to sustainable production.

Inhibiting the Laydown of Polymeric Carbon and Simultaneously Promoting Its Facile Burn-Off during the Industrial-Scale Production of Hydrogen with Nickel-Based Catalysts: Insights from Ab Initio Calculations.

This paper presents a computational study of the mechanistic models for the laydown of carbon species on nickel surface facets and the burn-off models for their gasification mechanism in methane steam reforming based on density functional theory. Insights into catalyst design strategies for achieving the simultaneous inhibition of the laydown of polymeric carbon and the promotion of its burn-off are obtained by investigating the influence of single atom dopants on nickel surfaces. The effects of single atom dopants on adsorption energies are determined at both low and high carbon coverages on nickel and used to introduce appropriate thermodynamic descriptors of the associated surface reactions. It is found that the critical size of the nucleating polymeric carbon adatom contains three atoms, i.e., C3. The results show that the burn-off reaction of a polymeric carbon species is thermodynamically limited and hard to promote when the deposited carbon cluster grows beyond a critical size, C4. The introduction of single atom dopants into nickel surfaces is found to modify the structural stability and adsorption energies of carbon adatom species, as well as the free energy profiles of surface reactions for the burn-off reactions when CH4, H2O, H2, and CO species react to form hydrogen. The results reveal that materials development strategies that modify the sub-surface of the catalyst with potassium, strontium, or barium will inhibit carbon nucleation and promote burn-off, while surface doping with niobium, tungsten, or molybdenum will promote the laydown of polymeric carbon. This study provides underpinning insights into the reaction mechanisms for the coking of a nickel catalyst and the gasification routes that are possible for the recovery of a nickel catalyst during the steam reforming of methane for large-scale production of hydrogen.

Recycling and reuse performance of cobalt catalyst for coal hydrogasification

Hydrogasification (C + H2 → CH4) is a crucial reaction for obtaining CH4 from coal or biomass. However, the reaction is sluggish in the absence of a suitable catalyst. Cobalt is more catalytically active than iron, nickel, and alkali metals, but is expensive. To improve the process economy, catalyst recycling was investigated with a focus on cobalt and calcium (Co–Ca) catalyzed coal hydrogasification. The results revealed that Co existed as metallic state in the gasified residue, and it was strongly associated with Ca compounds. Co–Ca as nitrate and acetate exhibited significantly higher activity than that of chloride and sulfate. Nitrate acid (HNO3) can effectively leach Co and Ca from the residue, as the leaching efficiencies of Co and Ca exceeded 99.7 % and 98.0 %, respectively. Additionally, seventeen mineral impurity elements were extracted from the residue. With repeated recycling, the majority of impurities accumulated in the recovered catalyst and exhibited distinct effects on its activity. Al impurity demonstrated its ability to significantly lower the Co–Ca activity, whereas Fe, K, Na, Mg, P, and S could not. Because impurities inhibited Co reducibility, the catalytic performance of recovered Co–Ca decreased with each recycling. Inspired by the results, the proposed HNO3 leaching procedure was optimized using two-step precipitations for impurities removal, and a high activity of recovered catalyst was achieved. This study provides some insights into the recovery, deactivation, and regeneration of cobalt catalyst employed for coal or biomass hydrogasification.

Computational investigation of functionalized carbenes on dinitrogen activation

Activation of the dinitrogen triple bond is a crucial step in the overall fixation of atmospheric nitrogen into usable forms for industrial and biological applications. Current synthetic catalysts incorporate metal ions to facilitate the activation and cleavage of dinitrogen. The high price of metal-based catalysts and the challenge of catalyst recovery during industrial catalytic processes has led to increasing interest in metal-free catalysts. One step toward metal-free catalysis is the use of frustrated Lewis pairs (FLPs). In this study, we have examined 18 functionalized carbenes as FLPs to elucidate the influence of steric and electronic effects on the activation of dinitrogen. To test the effects of functionalization on dinitrogen activation, we have performed density functional theory (DFT), multireference, non and extended transition state-natural orbital for chemical valence (ETS-NOCV) calculations. Our results suggest that functional groups which introduce strong electron-withdrawing effects and/or engage in extended π/π* systems lead to the lowering of the dissociation energy of the dinitrogen bond, which further contributes to greater nitrogen activation. We conjecture that these effects are due to enhanced back-bonding capability of the p orbital of the carbene carbon atoms to the adjacent nitrogen atoms (increasing Lewis basicity of the carbene carbon atom) and enhanced stability of dissociated products. Our concluding remarks include opportunities to extend this activation study to explore the entire catalytic cycle with promising functionalized carbenes for experimental evaluation.

Highly efficient and recyclable novel spindles Fe2O3@SiO2/In2O3 nanomagnetic catalyst designed for green synthesis of azomethine compounds

A novel and reusable nanomagnetic catalyst, Fe2O3@SiO2/In2O3, was synthesized by a facile chemical approach in three successive steps. The nanocatalyst was characterized by FT-IR, XRD, SEM, EDX, TEM, and VSM. The XRD pattern displays the characteristic peaks of Fe2O3 and SiO2, accompanied by new peaks assigned to different planes of In2O3 that confirm the formation of In2O3 on the surface of Fe2O3@SiO2 core/shell spindles. The TEM micrographs show spindle-like particles of Fe2O3 covered with SiO2 shell, and the In2O3 nanoparticles in an average diameter of 20 nm are hung on the surface of the Fe2O3@SiO2. The nanomagnetic catalyst Fe2O3@SiO2/In2O3 was used for the transformation of the (4-nitrophenyl)-1-phenyl-1H-pyrazole-5-amine, and chalcones derivatives, into valuable azomethine compounds of 3-(substituted)-1-(pyridine-2-yl)allylidene)-3-(4-nitrophenyl)-1-phenyl-1H-pyrazole-5-amine with high rate and efficient catalyst recovery. The yield obtained through the catalytic route reached 90–95% in shorter reaction times compared with uncatalyzed reaction method.Graphical abstract

TITANIUM DIOXIDE SOL-GEL/ZINC OXIDE POWDER-COATED CLAY BEADS IN PHOTOCATALYTIC REACTOR

Catalyst Immobilization methods are important for providing better recovery of catalyst in photocatalytic treatment. The aim is to characterize and evaluate the photocatalytic performance of TiO2/ZnO-coated clay beads. The titanium dioxide/zinc oxide (TiO2/ZnO)-coated clay beads were prepared via the sol-gel process. Various ZnO powder ratios gave different TiO2/ZnO composites sol. Four layers of TiO2/ZnO sol were coated on clay beads and dried in the oven at 100°C for 30 min. The coated clay beads were calcined at 500°C for one hour for every two layers. Characterization of coated clay beads was done using a scanning electron microscope and energy dispersive spectroscopy. The increased surface area on small agglomeration and optimum loading of ZnO (5 g) resulted in the highest degradation efficiency recorded at 86.57%. An effective catalyst immobilization achieved a good recycling performance on clay beads. Degradation rate data were presented by pseudo-first-order kinetics. It was observed that the average degradation rate for TiO2/5 g ZnO is 0.00836 min–1. The actual results in this work can be applied as a guideline for the preparation of TiO2/ZnO-coated clay beads with high photocatalytic performance.

Photocatalytic activity of Co3O4@C enhanced by induction of amorphous cobalt-based MOF

A series of Co3O4@C-N (N = 1, 2, 3) composite photocatalysts were prepared by simple agitation and pyrolysis for degradation of organic dyes. The hollow macroscopic spherical structure of Co3O4@C-2 was constructed by adjusting the pyrolysis time. Compared with pure Co3O4, the carbon composite Co3O4@C-2 significantly enhanced light absorption in the UV and visible range, improved the electron transport efficiency and prevented the necessary photoexcited electron-hole pair recombination. Hence, the photocatalytic degradation rate of methylene blue (MB, 20 mg/L) reached 100% in 120 min under UV–vis light irradiation. Under the coupling of Co3O4 and graphitized carbon, Co3O4@C-2 obtained high structural stability, good reusability and low biotoxicity. Scavenging experiments and ESR test showed that •O2- radical was the active species for MB removal. After six cycles of tests, the photocatalytic efficiency of Co3O4@C-2 remained at 90.42%. The macroscopic spherical structure Co3O4@C-2 effectively avoids the problem of dispersion and recovery of powder catalyst, which also paves a path for the designing of candidate commercial photocatalyst with high efficiency and low consumption.

CO2 Electroreduction on Carbon-Based Electrodes Functionalized with Molecular Organometallic Complexes—A Mini Review

Heterogeneous electrochemical CO2 reduction has potential advantages with respect to the homogeneous counterpart due to the easier recovery of products and catalysts, the relatively small amounts of catalyst necessary for efficient electrolysis, the longer lifetime of the catalysts, and the elimination of solubility problems. Unfortunately, several disadvantages are also present, including the difficulty of designing the optimized and best-performing catalysts by the appropriate choice of the ligands as well as a larger heterogeneity in the nature of the catalytic site that introduces differences in the mechanistic pathway and in electrogenerated products. The advantages of homogeneous and heterogeneous systems can be preserved by anchoring intact organometallic molecules on the electrode surface with the aim of increasing the dispersion of active components at a molecular level and facilitating the electron transfer to the electrocatalyst. Electrode functionalization can be obtained by non-covalent or covalent interactions and by direct electropolymerization on the electrode surface. A critical overview covering the very recent literature on CO2 electroreduction by intact organometallic complexes attached to the electrode is summarized herein, and particular attention is given to their catalytic performances. We hope this mini review can provide new insights into the development of more efficient CO2 electrocatalysts for real-life applications.

Developing an adaptive catalyst for an FCC reactor using a CFD RSM, CFD DPM, and CFD DDPM–EM approach

Cyclone separators, which have an important role in the recovery of catalysts, constituted one of the aims of the study. In the work to be done, the pressure drop occurring during the fcc reaction is also calculated using the Ergun equation and it is aimed to provide the same value in a cyclone separator. In this study, which was presented for the first time in the literature, the best working conditions were determined by simulating the pressure drop in the cyclone separator modeled by using the various catalyst types namely NiMo/ASA–Al2O3, NiMo/p–Al2O3, NiMo/Y–Al2O3, Co-Mo, HZSM-5 zeolite, HY zeolite, pAl2O3, ASA-Al2O3, Y-Al2O3 determined from the literature in the Ergun equation. Among them, NiMo/ASA Al2O3, Co-Mo, HY zeolite, and ASA-Al2O3 were determined as the best catalyst for producing diesel from high oil fractions. Unlike previous studies, the condition that the cyclone separator modeled cleans the catalyst with maximum efficiency also determines the condition that provides low catalyst porosity in the determination of the catalyst type to be determined in diesel production. Due to the accuracy between the calculated and the predicted pressure drop results (about 1,8%), HY zeolite is the best catalyst for cyclone separator geometry. It is widely used to convert high molecular weight hydrocarbon fractions, the high boiling point of petroleum crude oils into olefinic gases, more valuable gasoline, and other products. The purpose of the FCC unit is to increase the refinery conversion and white product yield by converting heavy vacuum gas oil (HVGO) into light hydrocarbons at high temperatures with the aid of fluid catalysis. These two zones (reactor and regenerator) are placed as two different pressure vessels. For these two different systems to work in harmony with each other, unlike in previous studies, the “dense discreet phase-Eularian” approach was used in the modeling of the catalytic unit and the “discreet phase” approach was used in the modeling of the cyclone separator. The values required for both processes to work together have been determined approximately.

Recent Developments on Processes for Recovery of Rhodium Metal from Spent Catalysts

Rhodium (Rh) catalyst has played an indispensable role in many important industrial and technological applications due to its unique and valuable properties. Currently, Rh is considered as a strategic or critical metal as the scarce high-quality purity can only be supplemented by refining coarse ores with low content (2–10 ppm) and is far from meeting the fast-growing market demand. Nowadays, exploring new prospects has already become an urgent issue because of the gradual depletion of Rh resources, incidental pressure on environmental protection, and high market prices. Since waste catalyst materials, industrial equipment, and electronic instruments contain Rh with a higher concentration than that of natural minerals, recovering Rh from scrap not only offers an additional source to satisfy market demand but also reduces the risk of ore over-exploitation. Therefore, the recovery of Rh-based catalysts from scrap is of great significance. This review provides an overview of the Rh metal recovery from spent catalysts. The characteristics, advantages and disadvantages of several current recovery processes, including pyrometallurgy, hydrometallurgy, and biosorption technology, are presented and compared. Among them, the hydrometallurgical process is commonly used for Rh recovery from auto catalysts due to its technological simplicity, low cost, and short processing time, but the overall recovery rate is low due to its high remnant Rh within the insoluble residue and the unstable leaching. In contrast, higher Rh recovery and less effluent discharge can be ensured by a pyrometallurgical process which therefore is widely employed in industry to extract precious metals from spent catalysts. However, the related procedure is quite complex, leading to an expensive hardware investment, high energy consumption, long recovery cycles, and inevitable difficulties in controlling contamination in practice. Compared to conventional recovery methods, the biosorption process is considered to be a cost-effective biological route for Rh recovery owing to its intrinsic merits, e.g., low operation costs, small volume, and low amount of chemicals and biological sludge to be treated. Finally, we summarize the challenges and prospect of these three recovery processes in the hope that the community can gain more meaningful and comprehensive insights into Rh recovery.

Recent trends in synthetic strategies using magnetic nanostructures as green catalysts in synthesis of pyran analogues

In recent years, magnetic nanoparticles and nanocomposites play an important role as a nanocatalyst in the creation of a wide range of bioactive heterocycles with extraordinarily high activity and selectivity, low energy consumption, and extended life. Among all heterocycles, many natural products, pharmaceuticals, and bioactive compounds contain pyran scaffolds which have a wide range of uses in biomedical research, industry, and medicine. Additionally, these are also widely used in the synthesis of novel heterocyclic systems as precursors. This study focused on recent advances in the last 5 years in using various magnetic recoverable and recycled nanoparticles and nanocomposites to synthesize pyran derivatives and their pharmacological activity. This article has been classified into three subsections: (i) MNPs‐metal nanocomposite catalyzed reactions, (ii) MNPs‐organic based nanocomposite catalyzed reactions, and (iii) MNPs‐ionic liquid nanocomposite catalyzed reactions and (iv) MNPs‐acid based nanocomposite to describe catalytic efficiency of magnetic nanocomposites for the synthesis of pyran derivatives. A comparative study of nanocomposites and different approaches for green synthesis of pyrans by highlighting the advantages and disadvantages along with catalyst recovery and recyclability has been mentioned, which will help scientists to probe and stimulate the study of these scaffolds.

Cu-α-diimine Compounds Encapsulated in Porous Materials as Catalysts for Electrophilic Amination of Aromatic C-H Bonds.

Electrophilic amination has emerged as a more environmentally benign approach to construct arene C-N bonds. However, heterogeneous catalysts remain largely unexplored in this area, even though their use could facilitate product purification and catalyst recovery. Here we investigate strategies to heterogenize a Cu(2,2'-bipyridine) catalyst for the amination of arenes lacking a directing group with hydroxylamine-O-sulfonic acid (HOSA). Besides immobilization of Cu on a metal-organic framework (MOF) or covalent organic framework (COF) with embedded 2,2'-bipyridines, a ship-in-a-bottle approach was followed in which the Cu complex is encapsulated in the pores of a zeolite. Recyclability and hot centrifugation tests show that zeolite Beta-entrapped CuII(2,2'-bipyridine) is superior in terms of stability. With N-methylmorpholine as a weakly coordinating, weak base, simple arenes, such as mesitylene, could be aminated with yields up to 59%, corresponding to a catalyst TON of 24. The zeolite could be used in three consecutive runs without a decrease in activity. Characterization of the catalyst by EPR and XAS showed that the active catalytic complex consisted of a site-isolated CuII species with one 2,2'-bipyridine ligand.

Magnetically separable ZnFe2O4 grafted g-C3N4/rGO ternary nanocomposites for enhanced photo-Fenton catalytic activity under visible light

Ternary nanocomposites (TNCs) comprising layered functional materials with favorable band edge positions have been strategically employed to suppress the photogenerated carrier recombination and augment photocatalytic performance by harnessing the entire UV–visible–near infrared broadband spectrum. Utilizing the intrinsic magnetic properties of the co-catalysts, a series of easily separable and recyclable g-C3N4/rGO/ZnFe2O4 (CNGZF) TNCs were developed by modulating g-C3N4 mass fraction. The heterogeneous photo-Fenton performances of the TNCs were evaluated in the discoloration of methylene blue with/ or without H2O2 under visible light. The photocatalytic efficacy of TNCs with a mass ratio of 2:1:1 (i.e., 2-CNGZF) surpasses the individual merits of their counterparts, g-C3N4 and ZnFe2O4 by 11.08 and 2.91 times, respectively, and binary composite CNZF (g-C3N4/ZnFe2O4) by 2.34 times in dye degradation. In the presence of H2O2, the highest removal efficiencies of more than 93% (k = 0.0442 min−1) and 97% (k = 0.1922 min−1) were achieved within 60 min and 20 min under artificial visible light and solar irradiation, respectively. Controlling various operational parameters of the reaction medium, a remarkable improvement in the rate constant up to 0.229 min−1 was obtained for 15 mg of catalysts loading using an H2O2 concentration of 0.15 M at pH 7. The enhanced photocatalytic performances are corroborated by a large number of induced active sites, resulting from special dimension effects of the layered nanosheets, broadband absorption capabilities of the co-catalysts, and accelerated electron migration through the metallic counterparts. Electrochemical impedance spectroscopy measurements further confirm the lower interfacial charge transfer resistance and prolonged lifetime of electrons in the TNCs. Furthermore, the moderate magnetic properties of the co-catalysts ease the catalyst recovery process, exhibiting excellent stability and durability even after recycling up to four successive runs.

Highly active Mn-Cu bimetallic oxide catalyst assembled as 3D-printed monolithic agitating paddles for advanced oxidation process

Catalytically agitating paddles are essential to perform liquid-solid heterogeneous catalytic reactions on an industrial scale due to the improved mass transfer and easy catalyst recovery. Herein, bimetallic oxides were formed after the calcination of nanomaterials derived from metal-organic frameworks (MOFs). Particularly, Mn(M)-BTC nanomaterials were synthesized by self-assembly of Mn2+ ions (mixed with various dopants such as Cu2+, Ce3+, or Fe2+) and H3BTC ligands in a mixed solvent of ethanol and water. It was found that in the powdery form, the Mn-Cu oxide derivate exhibited the highest degradation rate in the catalytic wet peroxide oxidation process (CWPO process), which was significantly higher than that of single metal oxide as well as Mn-Fe and Mn-Ce oxide derivates. The reason was caused by the synergistic effect between Mn-Cu promoted the formation of Mn3+ and Cu+ species to boost the CWPO reaction. Furthermore, the obtained Mn-Cu powdery catalysts were 3D-printed to obtain monolithic agitating paddles with different geometries, which were then mounted on a central shaft in the stirred reactor. An advanced oxidation process was used to investigate the effect of 3D patterns on the degradation efficiency of various organic dyes. It was discovered that the 3D-printed grid with higher cell density (484 cpsi) had better liquid mixing efficiency and thus better catalytic performance, which could be repeatedly used more than seven times. Additionally, the numerical simulation analysis (computational fluid dynamics) revealed a good mixing efficiency and improved mass transfer in the entire reactor equipped with the designed monolithic agitating impellers.

Magnetic MCR-Functionalized Graphene Oxide Complexed with Copper Nano-Particles: An Efficient and Recyclable Nanocatalyst for Ullmann C–N Coupling Reaction

In this study, we report the synthesis of Cu nanoparticle modified dithiocarbamate (DTC)-functionalized magnetic graphene oxide (GO) nanocatalyst through a one-pot three component reaction. It has an excellent affinity for copper nanoparticles due to its DTC ligand amide motif. The structure of the synthesized catalysts was confirmed by using FT-IR, TGA, CHNS, SEM, XRD, EDS mapping, and ICP. The catalytic activity of the synthesized nanocatalyst was investigated in Ullmann cross-coupling reaction for the synthesis of N-aryl amines, which resulted in high reaction yields, easy workup, and short reaction times. The catalyst is separated easily by a magnetic field and can be reused for at least five successive runs without significant loss of catalytic activity. The nature of the supported DTC on the GO’s surface improved the catalytic activity of the graphene, provided homogeneity to the catalyst, and enhanced the capability of coordination with copper ions. Facile catalyst recovery and reusability, simple setup procedure, generality of the method and high turnover number (TON) make this procedure an environmentally benign approach for preparing the titled compounds. Based on the findings of this study, it appears that the catalytic system introduced can be used to prepare other beneficial heterocyclic compounds.