Amount Of Catalyst Research Articles

Catalysts review for hydrogen generation from sodium borohydride solutions and surviving ability of living beings in the long-time space flights

Hydrogen (H2), environmentally friendly effective energy carrier with the most advantageous combustion by-products, readily attained from borohydride (NaBH4) with higher hydrogen (H2) generation rates (HGRs) as safer than e other hydrates necessitating the use of various catalysts. The catalysts' performances are major factors in high HGR from NaBH4 regardless of hydrolysis or methanolysis reactions. The HGR is influenced by NaBH4 concentrations, reaction temperature, and the catalyst amounts. Nobel metals e.g., ruthenium (Ru), platinum (Pt), Rhodium (Rh) etc reported as highly effective catalysts for fast H2 production from NaBH4 solutions including ethanol, methanol, and ethylene glycol. Due to shortage and cost considerations of noble metals, transition metal-based catalysts e.g., cobalt (Co), nickel (Ni), and manganese (Mn) have gained great interest for H2 production from NaBH4 hydrolysis/alcoholysis. Metal nanoparticle-based catalysts, and their synthetic and natural polymer composites along with non-metallic catalyst including micro/nanogels, bulk hydrogels, cryogels, and polymeric ionic liquids (PILs) have been employed as catalysts in methanolysis/hydrolysis of NaBH4 to attain lower Ea and high HGR values. Therefore, in this review catalysts whether metal or non-metal used in H2 generation reactions will be surveyed, Moreover, space application of H2 energy systems with their commercial application for future use will be assessed.

Synergistic removal of tetracycline hydrochloride by nano-MnOx/NCF composite fiber (MNCs) catalysts via heterogeneous peroxymonosulfate (PMS) activation

Nnano-MnOx/NC composite fibers (MNCs) has been successfully prepared by the calcination treatment of Mn-Nitrilotriacetic acid (Mn-NTA) fibers precursor that are synthesized by hydrothermal method. The in-situ formed nano-MnOx is adhered to the N doped carbon nanofibers. The as-prepared MNCs fibers are employed as catalyst to decompose tetracyclines hydrochloride (TCH) by activating peroxymonosulfate. Compared with other MNCs catalyst, the synergistic effect of Mn3O4 and N-doping carbon in MNC-700 during the catalytic process endows MNC/PMS system with the superior mineralization capacity for TCH degradation with less amount of catalyst and PMS. Quenching experiments and EPR tests confirm that the oxidative degradation of TCH involves radical and non-radical route. Multiple reactive oxygen species (SO4−, OH, and 1O2) contribute to the degradation of TCH. Our research offers an effective strategy for the TCH degradation through PMS activation using the composite fibers of MnOx and N doped carbon.

Heterogeneization of Biodiesel Production by Simultaneous Esterification and Transesterification of Oleins

The production of biodiesel via simultaneous esterification and transesterification reactions of residual fats such as palm oleins, with variable TG and FFA composition, using methanol and methane sulfonic acid (MSA) or an acid carbon-based structured catalyst (SO3H-C) as homogeneous and heterogeneous catalysts respectively, has been investigated. The influence of various parameters, such as methanol to oil molar ratio, operating temperature, amount of catalyst, or nature and composition of the raw materials on the fatty acid methyl esters (FAME) yield was studied. It was determined that increasing the methanol to oil molar ratio resulted in an increase in the conversion of TG and FFA and a higher FAME yield; besides, reaction temperature has a strong effect. The best conditions tested to obtain the highest FAME yield (99.2%) was a methanol to oil molar ratio of 12:1, 120 °C (12 bar), a reaction time of at least 1 h, and 3% MSA as a homogeneous catalyst. The work demonstrated that an acidic solid catalyst, SO3H-C, homemade prepared, could be used as a heterogeneous catalyst in the simultaneous process under the optimized reaction conditions, achieving a complete esterification conversion with some limitations with respect to the transesterification reaction and a FAME yield close to 90.5%.

Analysis of Reaction Conditions in Palmitic Acid Deoxygenation for Fuel Production

The development of effective catalytic systems for deoxygenation reactions is critical to the conversion of renewable feedstocks into sustainable fuels. In this work, the influence of various reaction parameters on the conversion of palmitic acid into alkanes, such as temperature, stirring rate, reaction time, H2 pressure, amount of catalyst and substrate concentration was evaluated using the commercial Co-Mo/Al2O3 catalyst. In parallel, bimetallic Co-Mo catalysts supported on carbon nanotubes (CNTs) were prepared and characterized using various techniques, and their catalytic performance was assessed under the optimized conditions. The results showed that palmitic acid can be efficiently converted at 350 °C for 6 h at 30 bar H2 pressure, stirring at 150 rpm and using 0.25 g of catalyst and 0.50 g of palmitic acid in 50 mL of n-decane. Under these conditions, a complete substrate conversion and yields of 89.4 and 4.8% of C16 and C15 were achieved. In addition, Co-Mo/CNTox presented a similar catalytic performance as the commercial one, with a final result of 90.9% yield in C16. These findings point out the potential of using Co-Mo/CNTox as a competitive alternative to liquid fuel production.

Microwave-assisted esterification of oleic acid using pyrrolidonium-based bronsted-acidic ionic liquids catalyst

Biodiesel is a liquid fuel obtained by the transesterification reaction of triglycerides and the esterification reaction of free fatty acids. In this study, pyrrolidonium-based Brønsted-acidic ionic liquids (ILs) were applied as catalysts for the production of biodiesel by microwave-assisted esterification of oleic acid with methanol. The effects of reaction temperature, catalyst amount, methanol/oleic acid molar ratio, and reaction time on the oleic acid conversion were investigated. Under optimal conditions, the results demonstrated that N-methyl-2-pyrrolidonium hydrogen sulfate (IL1) and 2-pyrrolidonium hydrogen sulfate (IL2) can achieve conversion rates exceeding 98 %. A comparative analysis with other IL catalysts showed the superior performance of pyrrolidonium-based ILs, especially in terms of Turn Over Frequency (TOF) values. To investigate the effects of different heating methods on the esterification of oleic acid, the esterification reaction was carried out using both conventional and microwave methods. The microwave method is more effective than the conventional method. The reusability of the IL catalyst was investigated, and the recovered catalyst showed excellent stability when it was reused for five consecutive runs without significant loss of activity.

A novel high-speed homogenizer assisted process intensification technique for biodiesel production using soya acid oil: Process optimization, kinetic and thermodynamic modelling

Acid oils, which are readily available and cost-effective, show promise as a feedstock for biodiesel synthesis. This study focuses on biodiesel production using soya acid oil having high free fatty acids (FFAs) content of 80.65 %. Biodiesel is produced from high-FFA soya acid oil by employing a novel high speed homogenizer technique through esterification process followed by neutralization step. The process variables affecting esterification reaction have been optimized through response surface methodology (RSM) based Box-Behnken Design (BBD) technique. A maximum FFA conversion of 98.06 % was found at a M:O molar proportion of 18.41:1, a process time of 84.62 min, a catalyst amount of 2.18 wt%, and a rotational speed of 14,100 RPM. The determined activation energy for esterification reaction using high speed homogenizer was 36.82 kJ/mol, which is 1.5 to 2 times lower compared to conventional techniques. Thermodynamic behaviour of esterification reaction was studied and analysed. The resulting biodiesel after the neutralization step meets the EN 14214 standard for conversion rate (minimum 96.5 %) and physicochemical properties, ensuring commercial viability.

Optimization of microwave-assisted biodiesel production using response surface methodology

Energy stands as the fuel of the human activities, and with finite fossil fuels, biodiesel has become a promising, eco-friendly alternative. Microwave technology is emerging as one of the most efficient biodiesel production methods. The primary goal of this work is to optimize the microwave-assisted production of biodiesel and improve its productivity using response surface methodology. A modified microwave oven with built-in stirring system and temperature measurement significantly reduces the reaction time compared to traditional thermoelectric heating. Numerous factors impact microwave-assisted biodiesel production, encompassing catalyst type and concentration, microwave power, reaction temperature, alcohol type, alcohol-to-oil molar ratio, water content, and stirring rate. Hence, acquiring a comprehensive understanding of how these variables affect the biodiesel production becomes imperative. Response surface methodology was utilized to improve the biodiesel microwave-assisted production yield of sunflower oil involving ethanol as alcohol and NaOH as catalyst. The impact of the ethanol-to-oil ratio, the catalyst amount and the reaction temperature on biodiesel production yield was investigated. Results demonstrated that the temperature had the most significant impact on biodiesel production, with an optimal temperature of 70 °C. The highest biodiesel yield, of 98.4%, was obtained at an alcohol-to-oil ratio of 6:1 and 2% by mass of sodium hydroxide.

Robust core−shell ZIF-67@PDB-Br as synergetic catalyst for chemical fixation of CO2 without co-catalysts

Metal-organic frameworks (MOFs) are widely studied for cycloaddition of CO2 as a heterogeneous catalyst, because of their potential Lewis acidic sites and adjustable porous structure. However, most of them exhibit good catalytic performance need the assistance of nucleophilic co-catalysts. Herein, a novel MOFs and porous organic polymers (POPs) hybrid catalyst, core-shell ZIF-67@PDB-Br, is constructed by a convenient synthetic strategy, which possesses abundant Lewis acidic sites, imidazole cations and nucleophilic centers and shows robust chemical and thermal stability. This material demonstrates high-efficient catalytic activities and recyclability in the cycloaddition of CO2 and propylene oxide without co-catalysts, the conversion and selectivity can reach 94.1 % and 99.0 %, respectively (100 °C, 1.0 MPa CO2 pressure). Furthermore, the effects of the temperature, pressure, amount of catalyst and thickness of POPs shell on the catalytic activity were investigated. This study provides a viable direction for the development of synergistic heterogeneous catalysts for fixation of CO2 without co-catalysts.

Homogeneous catalytic oxidation of thymol with dinuclear Cu(II)-2-phenyl propionate-bipyridine complex

A carboxylate-bridged dinuclear copper(II) complex, [Cu2(μ2-η2:η1(ppa)2(μ2-η1:η1 (ppa)bpy)2]·ClO4·H2O (ppa (C9H9OO) = 2-phenyl propionate, bpy = 2,2′-bipyridine), was prepared and its structure was determined by X-ray diffraction analysis. The octacoordinated Cu(II) dimer complex exhibits an asymmetric conformation, with the metal centers linked by two distinct modes of the carboxylate group. These include an asymmetric chelating bridging bidentate involving two ppa ligands and a syn-syn bidentate bridging mode involving one ppa ligand. The complex was employed as a catalyst for the oxidation of thymol, demonstrating a high degree of quantitative conversion and selectivity with TBHP across a range of solvents at moderate temperatures. The homogeneous catalytic system, comprising Cu(II)-2-phenyl propionate-bipyridine, tert-butylhydroperoxide (TBHP) as oxidant, and a polar aprotic solvent (acetonitrile or acetone), demonstrated high turnover numbers (TOF) in the absence of any additives. The impact of temperature, solvent, the ratio of thymol to TBHP, different oxidants and the quantity of catalyst on the catalytic activity and product selectivity was examined. Under optimized conditions, the maximum conversion of thymol (100 %) was obtained with 100 % selectivity to thymoquinone with TBHP after 35 min at the thymol to catalyst mole ratio of 267 (TOF = 449 h−1) in acetonitrile (MeCN) at 55 °C. Based on the available evidence, this activity and selectivity to thymoquinone represent the highest reported level of performance achieved by a homogeneously copper-catalysed process.

Ni/PiNe Heterogeneous Catalyst from Biomass Waste: Low-Loading, Ligand-Free Suzuki-Miyaura Cross-Coupling.

An efficient Ni-based heterogeneous catalyst from pine needles urban waste valorization was designed and developed with a resource recycling strategy. The Ni/PiNe catalyst was fully characterized and tested in the Suzuki-Miyaura coupling under microwave irradiation. Although Ni is a promising candidate for replacing Pd-based catalytic systems, it generally requires a high catalyst amount and the exploitation of ligands and additives to enhance the reaction rate. On the contrary, with our new Ni/PiNe, 30 different products were efficiently synthesized with an isolated yield of up to 93%, using a very low catalyst amount and in the absence of ligands. Furthermore, the Ni/PiNe catalyst also showed good durability for consecutive cycles and an impressive TON value (1140). In addition to the catalytic efficiency in short reaction time and to the stability and durability under MW irradiation, the Ni/PiNe allowed for further optimization, achieving a low E-factor value (14.0), thus highlighting the potential in further reducing the waste and costs associated to the process.

Methanol steam reforming using Ce and La modified low-Cu catalysts for On-board hydrogen production

Methanol steam reforming (MSR) combined with simultaneous hydrogen purification using palladium membranes offers an advanced method for on-board hydrogen utilization in fuel cell vehicles. However, commercial Cu-Zn-Al catalysts typically operate around 300 °C, significantly lower than palladium membranes. In this study, a series of γ-Al2O3 supported and CeO2 and La2O3 modified low-copper catalysts (n%Cu-CL-Al, n% = 2∼6 wt.%) were synthesized and compared with a commercial 45 %Cu-Zn-Al catalyst at 1.1 MPa. The Cu-CL-Al catalysts exhibited higher hydrogen yields (Y [H2]) at temperatures above 400 °C. This performance is attributed to a limited reverse water-gas shift (R-WGS) reaction, facilitated by the strong CO2 absorption properties of rare earth oxides. During long-term stability tests, the activity of the 4 %Cu-CL-Al catalyst significantly decreased after 50 h but rapidly recovered upon oxygen introduction. As no significant carbon deposition was observed on the catalyst surface, and nearly all Cu species in the used catalyst were reduced to Cu0, suggesting that deactivation was due to the over-reduction of Cu species by the generated H2. The presence of O2 accelerated the oxidation rate of Cu0, maintaining an appropriate Cu0/Cu+ ratio for MSR reaction. At 450 °C, Y [H2] was constrained only by the equilibrium of R-WGS reaction, independent of the Cu loading and contact time. This indicates that for on-board hydrogen production using Cu-based catalysts, it is crucial to regulate Cu loading and catalyst quantity to achieve Y [H2] that surpass the equilibrium limit of the chemical reaction.

Preparation of Bi self-doped BiOBr by microwave solvothermal method and its degradation of oxytetracycline

Using a microwave solvothermal technique, the Bi/BiOBr photocatalyst was effectively synthesized in this article. Oxytetracycline (OTC) was used as a simulated pollutant to assess the photocatalytic efficacy of Bi/BiOBr. Inorganic salt operation parameters, beginning concentration, and the amount of catalyst all have an impact on how effectively Bi/BiOBr degrades on OTC, according to the results of photocatalytic degradation experiments. Additionally, the catalyst exhibits some degrading activity toward moxifloxacin and sulfadiazine, supporting its broad-spectrum properties. The free radical quenching experiment proved that the Bi/BiOBr photodegradation system is heavily dependent on h+ and •O2 −, and •OH This study offers a fresh approach to creating effective solar-powered catalysts for the treatment of water contamination.

Influence of Ag-concentration on TiO2-supported catalysts for photocatalytic degradation of microplastics PA66 in marine

Over the past few years, microplastics pollution in marine environments has become a global concern. In this study, a series of silver-doped titanium dioxide (Ag/TiO2) photocatalysts were prepared by the photo-assisted deposition method as an alternative approach for the rapid removal of microplastics particles from aqueous media, specifically polyamide 66 (PA66), the major type of microplastics in marine. The physicochemical and optical properties of photocatalysts were analyzed by Scanning Electron Microscopy (SEM), X-ray Energy Dispersion Spectrum (EDS), X-ray Diffraction (XRD), Photoluminescence Spectroscopy (PL), and Ultraviolet-visible Diffuse Reflectance Spectroscopy (UV–vis DRS). The characterization results of the photocatalysts indicated that the appropriate loading of Ag on TiO2 significantly enhanced the optical properties of the catalysts. Specifically, 1.5 % Ag/TiO2 (AT1.5) exhibited the best light absorption performance and the lowest bandgap value, effectively suppressing the recombination of photogenerated electron-hole pairs. Furthermore, a series of photocatalytic degradation experiments confirmed that AT1.5 exhibited optimal performance in degrading PA66. Under UVA irradiation for 4 hours, the photocatalytic degradation of PA66 by AT1.5 resulted in a mass loss of 58.9 %. The degradation rate of PA66 increased with the amount of catalyst. When the mass ratio of AT1.5 to PA66 was 3:1, PA66 experienced 100 % mass loss after 4 hours of UVA exposure. Finally, through qualitative analysis, this study proposed the possible pathways and mechanisms for the photocatalytic degradation of PA66 by Ag/TiO2. Despite the challenges posed by microplastics pollution to marine ecosystems, this research provides a rapid and effective degradation method.

Etherification of isoamyl alcohol using Amberlyst®15 as an acid catalyst

The present work reports on the production of di-isoamyl ether from the etherification of isoamyl alcohol, using the sulphonic resin Amberlyst®-15 (A-15) as a catalyst. Parameters such as temperature, reaction time and amount of catalyst were studied. Although the etherification reaction shows low conversions (9-18%), when glycerol is added to the reaction medium and an external pressure to the reaction system (3.5 atm), the conversion increases up to 40% and a yield up to 100% can be obtained towards di-isoamyl ether.

Tailoring of Novel Ru (III) and Cr (III) Salen Complexes as Catalysts for a Sustainable and Green Synthesis of Dihydro‐tetrazolo [1,5‐a] thiazolo [4,5‐d] pyrimidin‐6‐yl morpholine: Experimental and Theoretical Approaches

ABSTRACTTwo novel Cr (III) and Ru (III) salen complexes based on {3,4‐Bis‐[(5‐chloro‐2‐hydroxy‐benzylidene)‐amino]‐phenyl}‐phenyl‐methanone ligand (CSAB) were synthesized. The complexes were characterized using various spectral and analytical methods. The catalytic performance of the CSAB complexes was investigated via a four‐component condensation reaction involving aromatic aldehydes, rhodamine, morpholine, and 5‐aminotetrazole under mild, environmentally friendly conditions. Different Lewis acids, bases, ionic liquid catalysts, solvents, and catalyst amounts were assessed to optimize the reaction parameters. Both catalyst systems demonstrated robust catalytic activity under strictly managed conditions, with the heterogeneous catalyst CSAB‐Ru showing superior efficacy compared to the homogeneous CSAB‐Cr catalyst. The study confirmed the catalytic capabilities of both complexes and evaluated their recyclability and reusability. The heterogeneous catalyst (CSAB‐Ru) could be reused seven times, whereas the homogeneous catalyst (CSAB‐Cr) could be recycled four times. Both complexes demonstrated strong catalytic activity and selectivity, resulting in high product yields. The study provides insights into the synthetic applications of novel CSAB complexes, highlighting their potential in organic transformations. It emphasizes their ease of use, safety, stability, component availability, quick reaction times, and high yields, making them promising for future industrial applications.

A Heterogeneous Phosphomolybdate Nanocatalyst Utilizes Vitamin B1 to Promote Solvent‐Free H2O2 Sulfoxidation Selectivity

ABSTRACTCatalyst design and fabrication with safe and affordable components and methods is a high‐value‐added business. In this work, a vitamin‐based hybrid nanomaterial (PMoB1) is prepared by simple stirring of thiamine hydrochloride (vitamin B1, VB1) as an inexpensive commercially available biologically active compound with phosphomolybdic acid (PMo12) in acidic aqueous solution to catalyze selective oxidation of sulfides using aqueous H2O2. A small amount of this heterogeneous catalyst drives rapidly the sulfoxidation reaction under mild and solvent‐free conditions facilitating the product separation and reducing significantly the environmental impacts. The main factors of the catalytic reaction were optimized by the central composite design (CCD) method. The solid catalyst tolerates a wide range of pH and retained its structural integrity even at alkaline solution (pH = 11). PMoB1 composed of two VB1 and one PMo12 was found to be partially reduced based on 13P NMR and UV–Vis spectra. An amorphous structure with aggregated nanoparticles with sizes ranging between 50 and 70 nm and a specific surface area of 35 m2/g are important reasons for enhanced catalytic activity and selectivity. Nevertheless, non‐covalent interactions such as hydrogen bonding and the π–π stacking can also significantly affect the catalyst performance. Given the scavenging tests and spectral evidences, a non‐radical mechanism involving peroxo species is postulated. The catalysis is shown to be truly heterogeneous while the solid catalyst largely maintains its structural integrity during the recycling test.

Establishing robust ZnO-sodium alginate nanocomposite for dye wastewater treatment: characterization, RSM methodology, and mechanism evaluation.

In today's world, water is a highly valued resource, and enhancing the quality of this natural endowment is a significant concern and a worldwide endeavor. This study sought to purify real wastewater and water tainted with methylene blue (MB) by immobilizing ZnO nanoparticles onto an alginate matrix using a straightforward approach and a three-dimensional structure. After analyzing the impact of , it was determined that 93.84% of MB was successfully removed (time = 120 min, dye concentration = 15 mg/L, catalyst amount = 2.5 g). The effects of inorganic ions and water types were investigated to simulate real wastewater conditions, and the catalyst performed satisfactorily. Alginate played a significant role in selectively removing dye, and the catalyst effectively removed 80.36% of MB and, in contrast, 20% of methyl orange (MO). The practical application of the catalyst was evaluated in textile wastewater treatment, and the catalyst showed satisfactory performance. An average 2.49% reduction in dye removal was observed after five stages of using the catalyst, demonstrating the beads' excellent stability. The composites were subjected to free radical trapping experiments to ascertain the active species. According to the results, and acted as the main reaction species in the degradation of MB. At the end, the synergistic mechanism of adsorption and degradation in MB removal was presented.

Conversion Single Reagent of n-Propanol to 1,1-Dipropoxypropane Using Cr/Activated Carbon Catalyst

Synthesis of 1,1–dipropoxypropane from a single reagent of n-propanol using Cr/Activated Carbon (Cr/AC) as a catalyst has been done. Activated carbon (AC) was prepared by activating coconut shell carbon at 650 °C in the atmosphere of N2 at a flow rate of 20 mL/min for 4 h, and then it was washed using acetone in a Soxhlet for 15 rounds, washed three times by 1.0 M HCl, and finally, it was sieved at 60–80 mesh. Metal content was analyzed using atomic absorption spectroscopy (AAS) and represented by Na, Ca, and Fe. The AC was impregnated with Cr (VI) solution and reduced with H2 at 650 °C. The acidity of the Cr catalyst was determined by the adsorption of ammonia. Optimation of n-propanol conversion to 1,1-dipropoxypropane using Cr/AC catalyst in the atmosphere of N2 was conducted in an oven using variations of temperature of 450, 500, and 550 °C, amount of catalyst of 5, 10, and 15 g, and flow rate of alcohol of 0.10, 0.50, and 0.90 mL/min. The conversions of 1,1-dipropoxypropane were analyzed by GC-MS and 1H-NMR. The results showed that the AC's metal content significantly decreased after washing with acetone and 1.0 M HCl. The AC and Cr/AC had 2.49 and 8.27 mmol/g acidity, respectively. The highest product of 1,1-dipropoxypropane of 65.0% was reached at 450 °C using a 5 g catalyst at a flow rate of the alcohol 0.10 mL/min.

Enhancing photocatalytic degradation of beta-blocker drugs using TiO2 NPs/zeolite and ZnO NPs/zeolite as photocatalysts: optimization and kinetic investigations

This study delves into the development and optimization of photocatalysts, namely ZnO NPs/Zeolite and TiO2 NPs/Zeolite, for the degradation of two beta-blocker drugs, including Atenolol (AT) and Metoprolol (ME). Structural and morphological analyses of the catalysts were conducted, and optimal conditions for drug degradation were determined using a Box-Behnken design. The results underscored the significant influence of pH, catalyst amount, drug concentration, and H2O2 concentration on the degradation process using ZnO NPs/Zeolite and TiO2 NPs/Zeolite as the catalysts. The optimal values of drug concentration, pH, catalyst amount, and H2O2 concentration, were determined to be 32 and 33 mg L−1, 4.2 and 4.6, 428 and 386 mg, and 2.6 and 2.5 mM utilizing ZnO NPs/Zeolite and TiO2 NPs/Zeolite as the catalyst, respectively. Following optimization, the kinetics of the photodegradation process were investigated, revealing promising rates and half-life times for both drugs. The pseudo-first-order rate constants for Atenolol and Metoprolol degradation were 0.064 ± 0.007 min−1 and 0.065 ± 0.004 min−1 with ZnO NPs/Zeolite and 0.071 ± 0.007 min−1 and 0.071 ± 0.006 min−1 with TiO2 NPs/Zeolite, respectively. Furthermore, ZnO NPs/Zeolite and TiO2 NPs/Zeolite demonstrated reusability up to 5 and 6 times, respectively, without significant activity loss. The comparative analysis highlighted the superior performance of TiO2 NPs/Zeolite over ZnO NPs/Zeolite, attributed to lower consumption, shorter degradation time, improved reusability, and compatibility with milder acidic conditions. Overall, the research showcases the potential of ZnO NPs/Zeolite and TiO2 NPs/Zeolite as an effective and sustainable solution for removing Metoprolol and Atenolol contaminants.

Divergent Annulations of 5,6‐Dihydro‐4H‐1,2‐Oxazine N‐Oxides and Enol Diazoacetates for the Switchable Chemoselective Synthesis of Fused 1,2‐Oxazine Derivatives

AbstractReactions of 5,6‐dihydro‐4H‐1,2‐oxazine N‐oxides with enol diazoacetates were studied. A particular reaction path depends on the amount of catalyst and the order of the addition of the substrates. Use of Rh2(Oct)4 (2 mol.%) leads to chemoselective [3+3]‐annulation producing 1,2‐oxazine‐fused 1,2‐oxazine derivatives. With lower catalyst loadings (0.03 mol.%) enol diazoacetates are converted to cyclopropene derivatives, which in situ react with 1,2‐oxazine N‐oxides via tandem [3+2]‐cycloaddition‐rearrangement producing oxazine‐fused aziridines. Both transformations showed a wide substrate scope and produced target products with good yields and diastereoselectivity, thus allowing selective preparation of these rare heterocyclic systems. A mechanistic rationale for observed chemo‐ and stereo‐ selectivities was proposed.