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The cationic interaction of binary metals in zeolite frameworks is a motivating field. The Isomorphous substitution of Ti and Ce in the framework of NaY zeolite has been achieved through post-synthesis treatment. Dealumination of the zeolite was accomplished by EDTA treatment, followed by the incorporation of three distinct ratios of Ce [(4.5–9) × 10−4 M] and Ti [(1.7–5.1) × 10−5 M] for decoration on the zeolite framework. This process was carried out in two steps based on their solubility in the corresponding solvents. The stability of the zeolite framework was assessed using metal loading. It was observed that as the amount of metals in the zeolite increased, the d spacing of the crystal lattice changed. Besides, certain metals were introduced at higher loading into the framework, while others acted as exchangeable cations in the extra-framework of the zeolite network. Spectroscopic studies were conducted to characterize the modified zeolite, and the catalysts were performed for their catalytic activity in the photodegradation of 4-NP. The optimum conditions were obtained with various parameters as: 0.01 g catalyst, 20 μL H2O2, 4-NP concentration: 3 × 10−4 M, pH = 5.5, and t = 120 min. In addition, the study of optimum conditions in the pH = 5 and isoelectric point = 5.5 indicated that the removal of 4-NP was achieved using both the absorption and photodegradation processes. The synthesized catalysts show good activity in the photodegradation process. This study also investigated the synergistic effect of Ce and Ti on photodegradation efficiency. The mineralization of 4-NP was confirmed by COD experiments, resulting in an efficiency of 68.76%. The catalyst was recoverable and maintained its catalytic activity after six runs. The kinetic of the reaction was obtained based on Hinshelwood's equation which was pseudo-first-order. In addition, the band gap of the catalyst was also calculated. This finding is particularly important because it indicates that the catalyst has the potential for industrial application and is cost-effectiveness. [ABSTRACT FROM AUTHOR]

Synthesizing organocatalysts is often a long and cost-intensive process, therefore, the recovery and reuse of the catalysts are particularly important to establish sustainable organocatalytic transformations. In this work, we demonstrate the synthesis, application, and recycling of a new lipophilic cinchona squaramide organocatalyst. The synthesized lipophilic organocatalyst was applied in Michael additions. The catalyst was utilized to promote the Michael addition of cyclohexyl Meldrum’s acid to 4-chloro-trans-β-nitrostyrene (quantitative yield, up to 96% ee). Moreover, 1 mol % of the catalyst was feasible to conduct the gram-scale preparation of baclofen precursor (89% yield, 96% ee). Finally, thanks to the lipophilic character of the catalyst, it was easily recycled after the reaction by replacing the non-polar reaction solvent with a polar solvent, acetonitrile, with 91–100% efficiency, and the catalyst was reused in five reaction cycles without the loss of activity and selectivity.

Herein we introduce a novel and reusable nanomagnetic copper catalyst (Fe3O4@SiO2-Imine/Thio-Cu(II)) constructed by immobilizing copper (II) complex on the surface of magnetic nanoparticles functionalized with Imine/Thio group. The structure of the as-constructed Fe3O4@SiO2-Imine/Thio-Cu(II) nanomaterial was well analyzed by a number of spectroscopic techniques including: FT-IR, SEM, TEM, EDX, XRD, VSM, AAS and ICP-OES. Experimental studies have well revealed that Fe3O4@SiO2-Imine/Thio-Cu(II) nanomaterial is an ecofriendly and efficient nanocatalyst for synthesis of 2,4,6-triaryl pyridines (82%–98%) via a C-N bond cleavage of benzylamines under aerobic oxidations in PEG at 120 °C. The grafting of the copper catalyst to the surface of magnetic nanoparticles has increased the catalytic activity of the material and also simplified catalyst recovery from the reaction mixture by an external magnet. The Fe3O4@SiO2-Imine/Thio-Cu(II) nanocatalyst was readily recovered by simple magnetic decantation and can be reused seven cycles without considerable loss in catalytic activity. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET), also known as polyester, is extensively utilized in the textile industry. The most commonly used chemical degradation method of PET is ethylene glycol (EG) glycolysis, which enables a closed-loop recovery process suitable for large-scale production. In this study, a new type of heterogeneous catalyst (Zn-MCM-41) was proposed for glycolysis of waste PET textiles, and their catalytic performance is much higher than other mesoporous zeolites. Under optimal reaction conditions, over Zn-MCM-41–25 (Si/Al molar ratio of 25) catalyst PET achieved a conversion ratio of 100 %, with bis-hydroxyethyl terephthalate (BHET) yield reaching 81.4 %. XPS results show that zinc is mainly presented as the state of Zn2+, resulting in excellent stability of the catalyst. HPLC and LCMS analyses were conducted on the products obtained from PET glycolysis, revealing that only a small amount of oligomers were generated during the process. These oligomers primarily consisted of dimer [BHET] 2 and trimer [BHET] 3. The Zn-MCM-41–25 catalyst also demonstrates exceptional performance in colored waste PET textiles glycolysis. Furthermore, we investigated the kinetics of PET glycolysis and determined it to follow first-order kinetics with an activation energy value of 210.03 kJ mol−1. Additionally, HPLC methods was established for analyzing glycolysis products and recovering catalysts using a simple filtration technique. The results demonstrate that even after five cycles, the catalyst maintains its high catalytic activity. [Display omitted] • Heterogeneous glycolysis catalyst with high efficiency and stability for waste PET textiles. • The proposed catalyst can be applied for both colorless and colored textiles. • BHET yield for colorless and colored PET glycolysis can achieve above 94 % and 91 %, respectively. • The potential mechanism of ester chain breaking over Zn2+ active center was proposed. [ABSTRACT FROM AUTHOR]

A facile and novel synthesis of thirteen 2-amino-3-cyanopyridine derivatives 5(a–m) by a one-pot multicomponent reactions (MCRs) is described for the first time, starting from aromatic aldehydes, malononitrile, methyl ketones, or cyclohexanone and ammonium acetate in the presence of the nanostructured diphosphate Na2CaP2O7 (DIPH) at 80 °C under solvent-free conditions. These compounds were brought into existence in a short period with good to outstanding yields (84–94%). The diphosphate Na2CaP2O7 was synthesized and characterized by different techniques (FT-IR, XRD, SEM, and TEM) and used as an efficient, environmentally friendly, easy-to-handle, harmless, secure, and reusable catalyst. Our study was strengthened by combining five new pyrido[2,3-d]pyrimidine derivatives 6(b, c, g, h, j) by intermolecular cyclization of 2-amino-3-cyanopyridines 5(b, c, g, h, j) with formamide. The synthesized products were characterized by FT-IR, 1H NMR, and 13C NMR and by comparing measured melting points with known values reported in the literature. Gas chromatography/mass spectrometry was used to characterize the newly synthesized products and evaluate their purity. The operating conditions were optimized using a model reaction in which the catalyst amount, temperature, time, and solvent effect were evaluated. Antibacterial activity was tested against approved Gram-positive and Gram-negative strains for previously mentioned compounds. [ABSTRACT FROM AUTHOR]

Herein we introduce a novel and reusable nanomagnetic copper catalyst (Fe3O4@SiO2-Imine/Thio-Zn(OAc)2) constructed by immobilizing Zn (II) complex on the surface of magnetic nanoparticles functionalized with Imine/Thio group. The structure of the as-constructed Fe3O4@SiO2-Imine/Thio-Zn(OAc)2 nanomaterial was well analyzed by a number of spectroscopic techniques including: FT-IR, SEM, TEM, EDX, XRD, VSM, AAS and ICP-OES. Experimental studies have well revealed that Fe3O4@SiO2-Imine/Thio-Zn(OAc)2 nanomaterial is an ecofriendly and efficient nanocatalyst for synthesis of synthesis of nitriles via cyanation of aryl iodides. The grafting of the zinc catalyst to the surface of magnetic nanoparticles has increased the catalytic activity of the material and also simplified catalyst recovery from the reaction mixture by an external magnet. The Fe3O4@SiO2-Imine/Thio-Zn(OAc)2 nanocatalyst was readily recovered by simple magnetic decantation and can be reused seven cycles without considerable loss in catalytic activity. [ABSTRACT FROM AUTHOR]

As catalysis plays a significant role in the development of economical and sustainable chemical processes, increased attention is paid to the recovery and reuse of high-value catalysts. Although homogeneous catalysts are usually more active and selective than the heterogeneous ones, both catalyst recycling and product separation pose a challenge for developing industrially feasible methods. In this respect, membrane-supported recovery of organocatalysts represents a particularly useful tool and a valid option for organocatalytic asymmetric synthesis. However, catalyst leaching/degradation and a subsequent decrease in selectivity/conversion are significant drawbacks. As the effectivity of the membrane separation depends mainly on the size of the catalyst in contrast to the other solutes, molecular weight enlargement of small organocatalysts is usually necessary. In the last few years, several synthetic methodologies have been developed to facilitate their recovery by nanofiltration. With the aim of extending the possibilities for the membrane-supported recovery of organocatalysts further, this contribution presents a review of the existing synthetic approaches for the molecular weight enlargement of organocatalysts.

BACKGROUND: Transition metal catalysis has, over recent decades, developed into one of the most important methods of constructing molecules. However, although efficient in the construction of complex molecules, these catalysts can be expensive as they are often based upon second‐ and third‐row transition metals which have, for the most part, low terrestrial abundance. Present removal and recovery techniques for homogeneous catalysts tend, at best, to focus on recovering the metal center and to consider ligands as single‐use components. Recovery of the whole catalyst would be more beneficial from economic and environmental points of view. RESULTS: The integration of a membrane separation protocol with gold‐catalyzed carboxylative cyclization of propargylamine was investigated. Filtration conditions were identified in membrane screening experiments with the dinuclear catalyst [Au2Cl2(L)] (Au‐1) and the mononuclear catalyst [Au(IPr)Cl] (Au‐2). Recovery of the whole catalyst was then investigated. Catalyst Au‐1 proved unstable and led to metal recovery for reprocessing upon completion of the process. However, the membrane methodology does allow recovery of the catalyst within the reaction mixture which increases its efficiency. On the other hand, catalyst Au‐2 proved more stable and can be recovered along with its ancillary ligands. CONCLUSIONS: For both catalysts a membrane‐based recovery protocol was successfully demonstrated. This protocol was either internal or external in that the Au complex along with its ligands can be recovered after reaction. This initial work shows the possibility that ligands do not always need to be considered as single‐use components. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

[Display omitted] • Structured catalyst consisting of N doped carbon felt supported Pd NPs. • Surface oxygenated groups for introducing amine precursors of N dopants on carbon. • Pdδ+ interface between Pd NPs and carbon surface induced by coordination of pyridinic N to Pd precursors. • C=C bond hydrogenation enhanced by nonpolar surface and small NPs with high content of Pdδ+. • Easy recyclability for liquid-phase reaction due to monolith Pd/carbon catalyst. In this contribution, structured carbon tailored with various surface oxygen and nitrogen functionalities was synthesized using commercial carbon felt and further employed as support for Pd nanoparticles (NPs) in liquid-phase hydrogenation of α, β-unsaturated cinnamaldehyde. The surface oxygenated groups, generated by vapor acid treatment, play the role of exchange site for the selective introduction of the nitrogen-containing functional groups on the carbon support during amination step. The amine-group precursors can be converted into nitrogen-doping species after a high temperature annealing process. Such surface functionalized sites are actively involved in the metal-support interaction and provide anchoring sites for Pd NPs, thereby improving the hydrogenation activity and stability. We have found that the pyridinic N dopants coordinated by divalent Pd precursors along with charge transfer induce the formation of the partial positively charged Pdδ+ species on the metal NPs during reduction, consistent with the chemical shift observed in the N1s core level of N-doped carbon support. The trend of catalytic selectivity towards hydrocinnamaldehyde is closely correlated with the electronic structure of the active metal phase in addition to the particle size. Finally, the macroscopic shape of the carbon support enables an easy recovery of the catalyst from the liquid-phase media, hereby providing a strategy for the rational design of the monolith carbon supported catalysts. [ABSTRACT FROM AUTHOR]

Sintering or agglomeration is formed in the process of the gasification of coal when fluxing K 2 CO 3 , which leading to the entire bed defluidization. In order to study the catalytic coal gasification reactivity and agglomeration properties in pressurized fluidized bed, Wangjiata raw coal, demineralized coal with HCl-HF treatment, and raw coal with different amounts of clay mineral addition were selected. The catalytic coal gasification reactivity, the agglomeration and sintering properties were studied. As well as water-soluble catalyst recovery from the gasification residue was also determined. The results show that for potassium-catalyzed steam gasification, not only coal ash content but also composition affected the gasification reactivity, agglomeration, and catalyst recovery. The carbon conversion increased varying degrees with increasing K 2 CO 3 loadings, K 2 CO 3 impregnated coal showed a high degree of agglomeration, and agglomeration increased with increasing K 2 CO 3 amount. Demineralized coal couldn't improve the agglomeration property. The addition of Clay mineral, was found to be very efficient in anti-sintering. However, compared with demineralized coal, the carbon conversion and water washing catalyst recoveries decreased obviously for those samples with the addition of clay minerals. The test verifies that part of potassium catalyst irreversibly reacted with coal ash to form relatively water-insoluble potassium compounds such as kaliophilite and sanidine. • Not only ash composition but also content of the ash affects gasification reactivity, agglomeration and catalyst recovery. • The addition of Clay mineral, was very efficient in anti-sintering in the pressurized bed gasifier. • The presence of KOH phase appears responsible for the agglomeration in the catalytic coal gasification gasifier. • Loading 15 wt% K 2 CO 3 and 5 wt% clay mineral can solve the agglomeration problem without reduce carbon conversion obviously. [ABSTRACT FROM AUTHOR]

Graphene, graphene oxide, reduced graphene oxide and their composites with various compounds/materials have high potential for substantial impact as cheap photocatalysts, which is essential to meet the demands of global activity, offering the advantage of utilizing "green" solar energy. Accordingly, graphene-based materials might help to reduce reliance on fossil fuel supplies and facile remediation routes to achieve clean environment and pure water. This review presents recent developments of graphene-based semiconductor photocatalysts, including novel composites with faceted particles, photonic crystals, and nanotubes/nanowires, where the enhancement of activity mechanism is associated with a synergistic effect resulting from the presence of graphene structure. Moreover, antimicrobial potential (highly needed these days), and facile recovery/reuse of photocatalysts by magnetic field have been addresses as very important issue for future commercialization. It is believed that graphene materials should be available soon in the market, especially because of constantly decreasing prices of graphene, vis response, excellent charge transfer ability, and thus high and broad photocatalytic activity against both organic pollutants and microorganisms. [ABSTRACT FROM AUTHOR]

Catalytic pyrolysis is a promising method for the resource utilization of wooden waste, and in-situ catalysis enhances the process and reduces treatment costs. The selection of catalysts is crucial, as their catalytic effect and service life directly impact treatment effectiveness and economic benefits. In this study, iron powder was utilized to examine its potential in in-situ catalytic pyrolysis of coated wooden boards. The results showed that some of the iron powder could compete for oxygen from lignin/ hemicellulose during the early pyrolysis stage, resulting in the formation of FeO and a decrease in CO 2. The formed FeO then promoted cellulose decomposition, reducing the pyrolysis activation energy by 26% ∼ 48%. Despite the addition of iron powder, no obvious impact was observed on the distribution of product yields. However, there are differences in the specific composition: the gas products showed a decrease of CO 2 by 26% and CH 4 by 13%, while the bio-oil showed an increase of phenol by 8%. This revealed that the iron powder primarily changed the energy barrier of the pyrolysis reaction. There was magnetic separation followed by particle size screening for the recovery of solid products. After separation, the recovery rate of iron powder was determined to be only 65.39%. Two kinds of char particles appeared in the separated products: magnetic (M3) and non-magnetic (NM). Approximately 44.45% of total Fe (from Fe powder and coating materials) contents and 73.62% of total Ti (main metal in the primary coating) were found in M3, while only 1.32% and 10.90% in NM, respectively. Interestingly, the distribution of elements Zn, Ba, and Mg was found to be opposite to that of Fe, which mainly distributed in NM and M2. It might be attributed to the primary coating on the M3 surface, which likely to help facilitated the adsorption of iron particles according to the combination of SEM/EDS and ICP-MS results. The adsorption competition effect of Fe and other metals resulted in significant differences in the distribution of metals on several char particles. [Display omitted] • Fe powder reduced the activated energy for pyrolysis by 26% ∼ 48%. • The addition of Fe powder slightly increased the generation of phenol. • Fe powder competed for oxygen from lignin/ hemicellulose to form FeO. • About 65% Fe powder was recovered via magnetic and size screening. • The presence of Fe powder had a repulsive effect on some metals like Zn and Ba. [ABSTRACT FROM AUTHOR]

The efficient reuse of homogeneous catalyst is important. Cation complex of [Ru(η6-p-cymene)(PPh3)(CH3CN) Cl]PF6 with different ligands was synthesized and characterized by infrared spectroscopy (IR), 1H-, 13C- and 31P-nuclear magnetic resonance spectroscopy (1H-, 13C- and 31P-NMR), element analysis (EA), and high resolution mass spectrometry (HR-MS). The complex was used as a catalyst for the hydrogen transfer reduction of carbonyl for the first time, presenting an excellent catalytic performance of 89%–98% conversion of acetophenone and its derivatives. The catalyst may be efficiently reused by the electro-adsorption of 10 times to one catalyst recovery. The cation [Ru] complex presented advantages of both homogeneous and heterogeneous catalysts.

• Temperature driven reversible biphasic solvent system was designed/optimised. • It was utilised for steroselective hydrogenation of MAA to (R) -MHB. • The reaction was catalysed by optically pure (R) -Ru-BINAP complex. • The reaction was performed in a microfluidic chip reactor. • The biphasic system utilised a mixture [N 14,222 ][Tf 2 N]/MeOH/H 2 O. Design of the reversible biphasic system for a practical use in asymmetric hydrogenation performed in a microfluidic chip reactor is reported. Methylacetoacetate (MAA) was transformed to (R) -methylhydroxybutyrate over optically pure (R) -Ru-BINAP as a model reaction. The study was an iteration towards the design, description and optimization of the temperature driven reversible biphasic system in the mixed [N R,222 ][Tf 2 N]/methanol/water phase by varying the parameter of the structure of the ionic molecule, starting from [NH 4 ][Tf 2 N] up to [N 14,222 ][Tf 2 N]. At temperatures, and other conditions providing high conversions and optical yields, the reaction mixture was monophasic. At lower temperatures, the mixture became biphasic for ionic liquids with long alkyl chains (namely [N 14,222 ][Tf 2 N]) due to their strong non-polar character. The formed ionic liquid phase accommodated the chiral Ru complex, the water/methanol phase the reaction products. After the reaction, when the mixture was cooled, over 90% of the catalytic complex was kept in the ionic liquid phase. Viscosity and density data were also discussed. It seems the reversible biphasic system offers a way to facilitate the separation of the chiral Ru-complex from the reaction mixture. Due to high sensitivity of the complex to handling conditions, its reuse still requires further optimization. [ABSTRACT FROM AUTHOR]

At 60–150 °C and 15–35 bar H2, two model reactions of levulinic acid (LA), hydrogenation and reductive amination with cyclohexylamine, were explored in a multiphase system composed of an aqueous solution of reactants, a hydrocarbon, and commercial 5 % Ru/C as a heterogeneous catalyst. By tuning the relative volume of the immiscible water/hydrocarbon phases and the concentration of the aqueous solution, a quantitative conversion of LA was achieved with formation of γ‐valerolactone or N‐(cyclohexylmethyl)pyrrolidone in >95 and 88 % selectivity, respectively. Additionally, the catalyst could be segregated in the hydrocarbon phase and recycled in an effective semi‐continuous protocol. Under such conditions, formic acid additive affected the reactivity of LA through a competitive adsorption on the catalyst surface. This effect was crucial to improve selectivity for the reductive amination process. The comparison of 5 % Ru/C with a series of carbon supports demonstrated that the segregation phenomenon in the hydrocarbon phase, never previously reported, was pH‐dependent and effective for samples displaying a moderate surface acidity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Structured catalyst consisting of oxygen functionalized graphite felt (OGF) supported highly dispersed Pd nanoparticles. • Abundant oxygenated groups decorated structural defects and porous structure on OGF. • Strong metal-support interaction from charge transfer at Pd-carbon interface in Pd/OGF. • Monolith Pd/OGF as efficient catalytic stirrer with easy recyclability for liquid-phase hydrogenation of cinnamaldehyde. Abstract Developing of both effective and stable noble metal nanoparticle (NPs) catalysts with easy catalyst-product recovery is still challenging in the liquid-phase catalytic processes. Here, we report on the synthesis of a hierarchical structured catalyst that consisted of oxygen functionalized graphite felt (OGF) support for liquid-phase processes. The monolith palladium-based catalyst was used as catalytic stirrer and displays excellent stability as well as complete recyclability for liquid-phase hydrogenation of α, β-unsaturated cinnamaldehyde. The surface defects decorated with abundant oxygenated groups as well as highly accessible porous structure generated from the acid treatment of carbon support, construct a bridge between Pd and support providing the charge transfer to alter the metal-support interactions. The electron-deficient high-valent Pdδδ+ species, formed on the metal NPs, and defects on the support help to enhance the Pd dispersion and resistance to sintering and/or aggregation during both catalyst preparation and cycling tests, leading to the high and stable hydrogen dissociative adsorption for hydrogenation process. [ABSTRACT FROM AUTHOR]

Graphical abstract Cyclodextrin-enhanced cinchona organocatalysis in a coiled tube continuous–flow reactor coupled with a nanofiltration recycle unit for asymmetric synthesis. Highlights • Cinchona-squaramide and -thiourea organocatalysts were anchored to cyclodextrins. • Cyclodextrin-anchored organocatalysts were in situ recovered via organic solvent nanofiltration. • Quantum chemical studies of the cyclodextrin–catalyst–reagents complex system. • Correlation between the enantiomeric excess and the Kamlet–Taft parameters. • Continuous catalysis–separation using coiled tube plug flow reactor coupled with nanofiltration. Abstract This work presents a cyclodextrin-enhanced organocatalytic method from molecular to process design. Cinchona-thiourea and -squaramide catalysts were covalently anchored to inherently large, stable and well-defined permethyl-β-cyclodextrins. The asymmetric catalysis was successfully demonstrated on the Michael reaction of 1,3-diketones and trans -β-nitrostyrene. Both emerging green and conventional solvents were screened for the asymmetric addition (up to 99% ee), and the Kamlet–Taft solvent parameters were correlated to the enantioselectivity. Quantum chemical modelling revealed that the catalyst anchoring resulted in favorable structural changes, and stronger intermolecular interactions between the catalyst and the reagents. Continuous organocatalysis was performed in coiled tube flow reactor coupled with a membrane separation unit, which allowed complete recovery of the catalyst and 50% solvent (2-MeTHF) recycling. The 100% conversion, 98% purity, 99% ee, 100% in-line catalyst recovery, and 80 g L−1 h−1 productivity makes it an attractive catalytic platform. [ABSTRACT FROM AUTHOR]

A process for obtaining ethyl levulinate through the direct esterification of levulinic acid and ethanol using AlCl3·6H2O as a catalyst was investigated. AlCl3·6H2O was very active in promoting the reaction and, the correspondent kinetic and thermodynamic data were determined. The reaction followed a homogeneous second-order reversible reaction model: in the temperature range of 318–348 K, Ea was 56.3 kJ·K−1·mol−1, whereas Keq was in the field 2.37–3.31. The activity of AlCl3·6H2O was comparable to that of conventional mineral acids. Besides, AlCl3·6H2O also induced a separation of phases in which ethyl levulinate resulted mainly (>98 wt%) dissolved into the organic upper layer, well separated by most of the co-formed water, which decanted in the bottom. The catalyst resulted wholly dissolved into the aqueous phase (>95 wt%), allowing at the end of a reaction cycle, complete recovery, and possible reuse for several runs. With the increase of the AlCl3·6H2O content (from 1 to 5 mol%), the reaction proceeded fast, and the phases’ separation improved. Such a behavior eventually results in an intensification of processes of reaction and separation of products and catalyst in a single step. The use of AlCl3·6H2O leads to a significant reduction of energy consumed for the final achievement of ethyl levulinate, and a simplification of line-processes can be achieved.

Highlights • Sodium recovery with water leaching was low due to the formation of NaAlSiO 4. • The synchronous recovery of sodium and alumina from NCGA is feasible. • The formation of Na 2 CaSiO 4 accounts for the low sodium recovery with Ca-calcination. • The combination of water leaching and alumina extraction can improve sodium recovery. Abstract The catalyst recovery from Na 2 CO 3 -catalyzed steam gasification ash of Sunjiahao (SJH) high-aluminium coal char was investigated using water leaching method combined with extracting alumina by means of Ca(OH) 2 thermal activation. The recovery efficiency of sodium catalyst from Na 2 CO 3 -catalyzed gasification ash (NCGA) with single water leaching method was as low as 39.5 wt%, which resulted from the formation of water insoluble sodium aluminosilicate during Na 2 CO 3 -catalyzed gasification. In order to improve sodium recovery, the water-washed NCGA was activated by means of Ca(OH) 2 thermal activation for simultaneous recovery of sodium and alumina. The recovery efficiency of sodium from the water insoluble sodium aluminosilicate is 63.6 wt%, thus the total sodium recovery can be remarkably improved and reach 72 wt%. Meanwhile, the extraction efficiency of alumina from NCGA can reach 88.46 wt%. The low sodium recovery with Ca(OH) 2 thermal activation is attributed to the formation of Na 2 CaSiO 4 during Ca(OH) 2 calcination. Extracting alumina process from NCGA of SJH high-aluminium coal can effectively promote the recovery of sodium catalyst and the process economy. [ABSTRACT FROM AUTHOR]

Abstract In this paper we combine two operando methods, Raman spectroscopy and X-ray absorption spectroscopy (XAS), in order to probe reduced graphene-oxide supported tinIV oxide nanoparticles ( SnO 2 NPs @ rGO) as they are being used to catalyse CO 2 electroreduction. To achieve high reaction rates it is necessary to apply sufficiently cathodic electrode potentials. Under such conditions, however, not only CO 2 is reduced electrochemically, but also the catalyst particles may be transformed from the initial SnIV state to SnII or, in an extreme case, to metallic Sn. While SnII species still favour CO 2 electroreduction, yielding formate as a primary product, on metallic Sn CO 2 reduction is disfavoured with respect to the competing hydrogen evolution reaction (HER). We show that operando XAS, a robust technique yielding information averaged over a large surface area and a relatively large thickness of the catalyst layer, is a very expedient method able to detect the reduction of SnO 2 NPs @ rGO to metallic Sn. XAS can thus be used to establish an optimum potential for the electroreduction in practical electrolysing cells. It takes, however, a complementary method offered by operando Raman spectroscopy, having greater sensitivity at the catalyst/electrolyte solution interface, to probe reduction intermediates such as the SnII state, which remain undetectable for ex situ methods. As it is shown in the paper, Raman spectroscopy may also find further use when investigating the recovery of catalyst particles following exposure to extreme reducing conditions. Graphical abstract fx1 Highlights • SnO 2 NP catalysts of CO 2 electroreduction were probed by two operando spectroscopies. • At cathodic potentials, SnIV is transformed to SnII or, in an extreme case, to Sn. • On SnII, the reduction of CO 2 to formate is preferred; Sn favours hydrogen evolution. • Operando XAS and Raman give complementary information on the degradation of SnO 2 NPs. • Catalyst recovery is studied, and safe operating conditions are established by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Two new pyridine-based asymmetric bifunctional organocatalysts containing one or two camphorsulfonamide units were synthesized. Asymmetric Michael addition of pentane-2,4-dione to β-nitrostyrene was catalyzed by these organocatalysts. During our experiments, influence of the solvent and temperature on the yield and enantioselectivity was studied. Using monocamphorsulfonamide derivative the S enantiomer of the corresponding Michael adduct was gained with moderate yield (up to 51 %) and low enantiomeric excess (up to 18 %). Organic solvent nanofiltration was successfully applied for the recovery of these organocatalysts. Furthermore, pyridine camphorsulfonamide was reduced to its piperidine derivative. Using piperidine monosulfonamide derivative racemic Michael adduct was obtained with excellent yield (up to 89 %). Beside its organocatalytic relevance, piperidine monosulfonamide derivative may also possess biological activity. [ABSTRACT FROM AUTHOR]

Abstract: Despite the high efficiency and broad scope of chiral iridium(N,P ligand) complexes as catalysts for asymmetric hydrogenation, the problem of catalyst recovery and recycling has so far attracted little attention. We have found that at the end of a hydrogenation reaction, iridium(N,P ligand) catalysts form dimeric Ir(III) dihydride complexes, which can be converted back to the original precatalysts by addition of COD. Based on these findings, a practically simple protocol for catalyst recovery was devised. The recovered complexes showed essentially the same reactivity and enantioselectivity as the original catalysts. Especially large‐scale applications and hydrogenations of less reactive substrates that require high catalyst loadings will benefit from this protocol that allows recovery and reuse of expensive iridium complexes. [ABSTRACT FROM AUTHOR]

Abstract: A new type of composite material involving the in situ immobilization of tin oxide nanoparticles (SnO2‐NPs) within a monolithic metal–organic framework (MOF), the zeolitic imidazolate framework (ZIF)‐8 is presented. SnO2@monoZIF‐8 exploits the mechanical properties, structural resilience, and high density of a monolithic MOF, while leveraging the photocatalytic action of the nanoparticles. The composite displays outstanding photocatalytic properties and represents a critical advance in the field of treating toxic effluents and is a vital validation for commercial application. Crucially, full retention of catalytic activity is observed after ten catalytic cycles. [ABSTRACT FROM AUTHOR]

The efficient reuse of homogeneous catalyst is important. Cation complex of [Ru(η6-p-cymene)(PPh3)(CH3CN) Cl]PF6 with different ligands was synthesized and characterized by infrared spectroscopy (IR), ¹H-, 13C- and 31Pnuclear magnetic resonance spectroscopy (¹H-, 13C- and 31P-NMR), element analysis (EA), and high resolution mass spectrometry (HR-MS). The complex was used as a catalyst for the hydrogen transfer reduction of carbonyl for the first time, presenting an excellent catalytic performance of 89%-98% conversion of acetophenone and its derivatives. The catalyst may be efficiently reused by the electro-adsorption of 10 times to one catalyst recovery. The cation [Ru] complex presented advantages of both homogeneous and heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A unique Pd&Cu@Al catalyst was easily fabricated just by immersing commercial aluminum foil in a mixed xylene solution of PdCl 2 and CuCl 2. The catalyst fabrication process led to aluminum oxide coatings in situ, which supported the metal nanoparticles and enhanced their catalytic activities for the phosphine-free Heck reaction of aryl halides and styrenes with high turnover number (TON) up to 3.9 × 105. The reaction can be scaled up to at least 100 mmol and has been applied in modification of drug Lapatinib 's intermediate with low metal residue. This novel catalyst is of good application potential in industrial production because it was extremely easy to be recycled, in regardless of the generation of the insoluble impurities or tars during the reaction processes. [ABSTRACT FROM AUTHOR]

Hydrogenated nitrile butadiene rubber (H-NBR), which is obtained by the selective hydrogenation of nitrile butadiene rubber (NBR), has attracted great interests in many industrial fields. However, the recovery of the catalyst remains a challenge in the homogeneous catalytic hydrogenation of NBR, restricting its industrial production. In the present work, ureido-modified macroporous hollow silica microspheres were designed for the recovery of the Rh-based catalyst, with Wilkinson's catalyst (RhCl(P(C 6 H 5 ) 3 ) 3 ) as an example, in the homogeneous catalytic hydrogenation of NBR. After the effects of the adsorbent loading, adsorption parameters (temperature, agitating speed and time), and separation condition (centrifugal speed and time) on the Rh recovery rate were optimized in detail, a maximum Rh recovery rate of 92.2% was achieved. [ABSTRACT FROM AUTHOR]

Three methods have been used for synthesis of pyrazolopyranopyrimidines, 3-methyl-4-aryl-4,5-dihydro-1H-pyrano[2,3-c]pyrazol-6-ones, and 1,6-diamino-2-oxo-1,2,3,4-tetrahydropyridine-3,5-dicarbonitrile derivatives via four-component reactions under solvent-free conditions. Silica-bonded 5-n-propyl-octahydro-pyrimido[1,2-a]azepiniumchloride (SB-DBU+Cl−), silica-bonded n-propyl-4-aza-1-azoniabicyclo[2.2.2]octane chloride (SB-DABCO+Cl−), and nano silica-bonded 5-n-propyl-octahydro-pyrimido[1,2-a]azepinium chloride (NSB-DBU+Cl−) as silica-supported ionic liquids catalyzed these reactions. These green, heterogeneous catalysts are separated from the reactions by simple filtration. The catalysts were recovered for at least four times without significant loss of their catalytic activities. [ABSTRACT FROM AUTHOR]

This study deals with the photocatalytic treatment of saccharin (SAC) and bisphenol-A (BPA) under UV irradiation. For this purpose, novel submicronic anatase-rutile nanocomposite particles with tuned phase ratio, produced by thermohydrolysis of acidic Ti(IV) solutions in the presence of controlled amounts of Sn(IV), were used. These catalysts were then assessed regarding their efficiency to degrade SAC or BPA, which are contaminants of increased environmental and health concern. The effect of various operating conditions, such as the anatase-rutile ratio (100:0, 85:15, 70:30), catalyst concentration (50-600 mg/L) and solute concentration (3-10 mg/L) was investigated. Furthermore, catalyst reuse -an important but little studied aspect- was assessed. Anatase-rutile nanocomposites were successfully prepared presenting good crystallinity and surface quality. Their activity was about the same for removing SAC or BPA from water. It was found that photocatalytic performance was increased with catalyst loading up to 400 mg/L. A further increase to 600 mg/L did not significantly enhance BPA removal, thus associating this tendency with screening effects. Also, photocatalytic efficiency was increased with initial solute concentration decrease. Organics degradation followed a pseudo-first order kinetic rate in terms of both SAC and BPA removal. The reproducibility of catalyst activity was assessed in three successive reuse cycles, where the removal percentage of initially 5 mg/L SAC was maintained as high as 70% at the end of the 3rd cycle, in the presence of initially 400 mg/L anatase catalyst, and after 90 min of treatment. Finally, additional experimental runs were carried out with ultrasound cleaning (US) being applied to the reactant mixture at the beginning of each reuse cycle, but it was found to have no significant effect on treatment efficiency. [ABSTRACT FROM AUTHOR]

In this study, after conducting K 2 CO 3 -catalyzed steam gasification in a bench-scale bubbling fluidized bed reactor, the bench-scale recovery process of potassium catalyst was investigated by changing washing methods and operating parameters. The optimal potassium catalyst recovery efficiency ( η K ) from MSJ gasified residue was 87.62%, achieved by utilizing a combined washing method in which the first wash was performed with N 2 limewater (0.25 mol ratio of Ca/K) and the last two washes were with CO 2 water. The recovered potassium catalyst was re-loaded with MSJ coal and then was utilized for conducting the catalytic steam gasification in a lab-scale fixed bed reactor, in order to evaluate the performance of the recovered potassium catalyst from both experimental and kinetic aspects. Compared with the results obtained from fresh K 2 CO 3 , not only the trends of carbon conversion ( X C ) were similar at each gasifying temperature, but also there was no obvious difference in volume percentage of gases produced. When the random pore model (RPM) was adopted, both reaction rate constant ( k RPM ) and activation energy ( Ea ) remained similar. In addition, the lifecycle of the recovered potassium catalyst was studied. Finally, it can be concluded that the potassium catalyst was effectively and efficiently recovered from gasified residue and the recovered potassium catalyst had the same catalytic activity as fresh K 2 CO 3 , promoting the commercialization and development of the catalytic gasification process. [ABSTRACT FROM AUTHOR]

The prevalence of homogeneous catalysts, to produce high value commodities in the surfactant and detergent range by upgrading inter alia syngas and short chain olefins, through metathesis, hydroformylation and hydrogeneration, is hampered by the expensive, waste generating and destructive thermal separation methods required for the recovery of these catalysts. By using the membrane technology of organic solvent nanofiltration (OSN), the successful recovery of two commercially available homogeneous catalysts, the rhodium-based complex, HRh(CO)(PPh 3 ) 3 , and the cobalt-based complex, Co(C 5 H 7 O 2 ) 3 , from the solvents representative of the hydroformylation and hydrogenation reactions, with the STARMEM 240 membrane, was performed. The energy-efficiency of OSN for homogeneous catalyst recovery, commonly alluded to in literature, was investigated by performing a technological evaluation between OSN and a conventional downstream recovery process such as distillation. It was found that, using the ST-240 membrane, catalyst concentrations in the permeate stream can be successfully reduced to near negligible amounts (<5 ppm), similar to that of distillation but with significant energy and cost savings of up to 85% and 75%, respectively, for the different reaction systems. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticle (MNP)-supported catalysis is a new method to facilitate catalyst separation and reuse. This technique has recently been introduced for organocatalysis. MNP-supported organocatalysts have been evaluated for their activity, selectivity, and recyclability in a range of chemical transformations, especially for asymmetric synthesis. The synthesis and application of Fe3O4 MNP-supported organocatalysis are highlighted in this short review article.

Organic solvent nanofiltration is a convenient method for the recovery of homogeneous transition metal catalysts. The long chain olefin 1-dodecene is hydroformylated continuously, and the commercially available catalyst complex is separated efficiently using a commercially available nanofiltration membrane. An advantage of this method is that both reaction and separation take place in a single liquid phase. Only continuous operation shows interactions of reaction and separation in the long run. Low energy demand, high scalability as well as transferability to other reactions make this method promising for new industrial applications. [ABSTRACT FROM AUTHOR]

The catalyst recovery process was investigated utilizing different washing methods and operating conditions after potassium-catalyzed steam gasification. During potassium-catalyzed steam gasification, the H 2 yield and carbon conversion (X C ) could reach 101.18 g/kg-coal and 73.39%, respectively, when utilizing Lanna clean coal as a sample; the potassium compounds mainly existed in three forms: KAlSiO 4 , KHCO 3 , and K 2 SO 4 . In the catalyst recovery process, the highest recovery efficiency of potassium (η K ) on Lanna raw coal and clean coal gasified residue reached 92.14% after six limewater washings and 93.37% after three limewater washings, respectively. When utilizing the combined washing method for the Lanna clean coal gasified residue, the recovered catalyst showed a longer catalyst reuse lifetime even though the recovery efficiency of potassium (η K ) only reached 89.42%, which was 4% lower than that obtained after three limewater washings. [ABSTRACT FROM AUTHOR]

A series of dinuclear and mononuclear oxovanadium(V) complexes containing tridentate Schiff base ligands derived from pyridoxal and appropriate thiosemicarbazide or hydrazide are reported. The compounds were characterised by elemental analysis, thermogravimetric analysis, IR and NMR spectroscopy. The molecular structure of the dioxido-vanadium(V) complex [VO 2 (HL 5 )]·MeOH·H 2 O (H 2 L 5 = pyridoxal benzhydrazido ligand), determined by X-ray crystallography, reveals an unexpected distorted trigonal bipyramidal arrangement of the VO 2 moiety. A DFT study of this molecule and of the related [VO 2 (H 2 L 5 )] complex of V IV reveals a moderate effect of the oxidation state change on the bond distances and angles, pointing to solvation as the cause of the structural distortion. All complexes were tested as (pre) catalysts for olefin epoxidation by aqueous tert -butylhydroxyperoxide (TBHP) under solvent-free conditions. Low vanadium loadings (0.05% vs . olefin) resulted in good cyclooctene conversions and TOFs. The lifetime of one catalyst was explored through repeated runs with recovery/recycling. DFT calculations have also addressed the olefin epoxidation mechanism, which reveals the possible direct O atom transfer from the activated tert -butoxido ( t BuOO – ) ligand, without the need to generate a peroxido (O 2 2– ) ligand. [ABSTRACT FROM AUTHOR]

A simple, green and environmentally benign procedure was developed for the synthesis of 2,3-dihydro-2-phenylquinazolin-4(1 H)-ones using catalytic amounts of succinimide- N-sulfonic acid via the cyclocondensation of 2-aminobenzamide with an aldehyde. The present methodology offers several advantages such as high yields, simple procedure, low cost, short reaction times, mild reaction conditions, and use of a reusable catalyst. [ABSTRACT FROM AUTHOR]

A whole set of 'green' nano-processes providing hydrogenated PMMA-PS-NBR tri-layer core-shell nanostructured high performance rubbers was developed in this research, which involved the synthesis of diene elastomers as the substrate, followed by the catalytic hydrogenation reaction, and finally catalyst recovery. This study may contribute to the development of hydrogenated high performance elastomers in latex form and recovery of catalyst from the polymer matrix. [ABSTRACT FROM AUTHOR]

Three different chelating ligands were used to separate Wilkinson's catalyst from HNBR nanoparticles in latices. N, N, N′, N′, N′′-pentamethyldiethylenetriamine was found to be very effective in removing the catalyst. HNBR particle size and the extraction temperature on catalyst removal were investigated. The mechanism involved in the separation process was elucidated. This study promotes the possible commercialization of the green latex direct hydrogenation technique. [ABSTRACT FROM AUTHOR]

BACKGROUND: In spite of its efficiency and versatility, examples of the use of N-hydroxyphthalimide (NHPI) as catalyst for oxidations at industrial scale are scant, mainly due to the lack of methodologies for the recovery and reuse of the catalyst. This paper reports a step by step investigation of the aerobic oxidation of cumene (CU), in order to verify the usability of NHPI catalysis in industrial processes. RESULTS:CUis oxidized to the corresponding cumyl hydroperoxide (CHP) at 70°C in the presence of a polar co-solvent and1%of NHPI with good conversion (>30%) and almost complete selectivity (>90%), without requiring the use of additional initiators. The catalyst is recovered at the end of the oxidation process by removal of polar co-solvent, with consequent precipitation of NHPI. The resulting filtered mixture is treated with non-basic supports, which are capable of adsorbing the residual NHPI by physical interaction. Finally, the adsorbing solids can be regenerated by washing with a polar solvent, allowing the recovery of residual catalyst. CONCLUSION: We provide evidence for the feasibility of the use of NHPI catalysis for industrial applications by investigating the case study of CU oxidation. The process can be performed under mild conditions without requiring the use of sacrificial initiators. The effect of temperature and composition in the NHPI precipitation step is investigated. The performances of basic and non-basic adsorbing beds during the recovery of residual NHPI are compared. The results obtained indicate that the recovery and recycling of the unaltered catalyst is possible without affecting, at the same time, the nature of cumyl hydroperoxide. [ABSTRACT FROM AUTHOR]

The development of heterogeneous catalytic processes is highly desirable in order to overcome some drawbacks of homogeneous catalysts, such as the separation and recycling of these catalysts. In this work, we report that Jacobsen type catalysts are efficient and selective for the oxidation of R-(+)-limonene to its corresponding diepoxides using in situ generated dimethyldioxirane (DMD) as oxidant. It was demonstrated that the solid NaHCO3 addition to the initial reaction mixture, improves the catalytic activity. Additionally, catalyst samples can be recovered and reused at least twice without significant loss of its initial catalytic activity. [ABSTRACT FROM AUTHOR]

A convenient approach to the synthesis of 2-amino-4,6-diphenylnicotinonitriles via four-component reaction of aromatic aldehydes, acetophenone derivatives, malononitrile and ammonium acetate is described. The reactions were done in water as solvent using cellulose sulfuric acid as catalyst. This simple protocol offer advantages such as shorter reaction times, simple work-up procedure, excellent yields and catalyst recovery. [ABSTRACT FROM AUTHOR]

DFT (B3LYP-D) calculations have been used to better understand the origin of the recovered Hoveyda-Grubbs derivative catalysts after ring-closing diene or enyne metathesis reactions. For that, we have considered the activation process of five different Hoveyda-Grubbs precursors in the reaction with models of usual diene and enyne reactants as well as the potential precursor regeneration through the release/return mechanism. The results show that, regardless of the nature of the initial precursor, the activation process needs to overcome relatively high energy barriers, which is in agreement with a relatively slow process. The precursor regeneration process is in all cases exergonic and it presents low energy barriers, particularly when compared to those of the activation process. This indicates that the precursor regeneration should always be feasible, unlike the moderate recoveries sometimes observed experimentally, which suggests that other competitive processes that hinder recovery should take place. Indeed, calculations presented in this work show that the reactions between the more abundant olefinic products and the active carbenes usually require lower energy barriers than those that regenerate the initial precatalyst, which could prevent precursor regeneration. On the other hand, varying the precursor concentration with time obtained from the computed energy barriers shows that, under the reaction conditions, the precursor activation is incomplete, thereby suggesting that the origin of the recovered catalyst probably arises from incomplete precursor activation. [ABSTRACT FROM AUTHOR]