Reusable Catalyst Research Articles

Synthesis and characterization of alumina supported molybdosilicic acid (SiMo12/Al2O3): Efficient solid acid catalyst for the synthesis of pyranopyrazole derivatives

A series of highly reusable heterogeneous catalysts (10-40 wt.% SiMo12/Al2O3), consisting of molybdosilicic acid (SiMo12) impregnated on alumina (Al2O3) support was synthesized by the wetness impregnation method. The physicochemical properties of synthesized catalyst were studied using FT-IR, XRD, SEM, EDX, TEM, BET and TG-DTA analysis techniques. The study proves that the synthesized SiMo12 catalyst efficiently incorporated on the surface of Al2O3. The catalytic activity of prepared catalyst was investigated for the synthesis of pyranopyrazole(6-amino-4-phenyl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5carbonitrile) via cyclocondensation reaction of aldehydes, malononitrile, hydrazine hydrate and ethyl-acetoacetate under solvent-free conditions. Among different catalysts, 30% SiMo12 supported on to Al2O3 showed the highest catalytic activity. High yield, shorter reaction time, operational simplicity, solvent-free conditions and reusability of the catalyst are the distinct features of this protocol.

Synthesis of tetrahydrobenzo[a]xanthene-11-ones by indium sulfide nanoparticles as green an efficient and reusable catalyst under solvent-free condition

In this work, tetrahydrobenzo[a]xanthene-11-ones are effectively synthesized without the need for solvents and in an environmentally safe manner by the use of indium sulfide (In2S3) nanoparticle as a catalyst. Indium sulfide (In2S3) nanoparticles were synthesized by the hydrothermal method, and X-ray diffraction pattern (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transition electron microscopy (TEM) were among the techniques used to characterize indium sulfide (In2S3) nanoparticles. The synthesis of tetrahydrobenzo[a]xanthene-11-ones was achieved in a single pot using a three-component reaction involving β-naphthol, dimedone, and aryl aldehyde. The resultant indium sulfide (In2S3) nanoparticles were produced without the need for a solvent and exhibited remarkable yields, as well as quick reaction times and reusable catalysts.

Polymer-Supported Heterogeneous Fenton Catalysts for the Environmental Remediation of Wastewater

Materials based on polymer hydrogels have demonstrated potential as innovative Fenton catalysts for treating water. However, developing these polymer-supported catalysts with robust stability presents a significant challenge. This paper explores the development and application of polymer-supported heterogeneous Fenton catalysts for the environmental remediation of wastewater, emphasizing the enhancement of metal incorporation into catalysts for improved efficiency. The study begins with an introduction to the heterogeneous Fenton process and its relevance to wastewater treatment. It further delves into the specifics of polymer-supported heterogeneous Fenton catalysts, focusing on iron oxide, copper complexes/nanoparticles, and ruthenium as key components. The synthesis methods employed to prepare these catalysts are discussed, highlighting the innovative approaches to achieve substantial metal incorporation. Operational parameters such as catalyst dosage, pollutant concentration, and the effect of pH on the process efficiency are thoroughly examined. The catalytic performance is evaluated, providing insights into the effectiveness of these catalysts in degrading pollutants. Recent developments in the field are reviewed, showcasing advancements in catalyst design and application. The study also addresses the stability and reusability of polymer-supported heterogeneous Fenton catalysts, critical factors for their practical application in environmental remediation. Environmental applications are explored, demonstrating the potential of these catalysts in addressing various pollutants. The Conclusions offers future perspectives, underlining the ongoing challenges and opportunities in the field, and the importance of further research to enhance the efficacy and sustainability of polymer-supported heterogeneous Fenton catalysts for wastewater treatment.

Selective Upcycling of Polyethylene over Ru/H-ZSM-5 Bifunctional Catalyst into High-Quality Liquid Fuel at Mild Conditions.

It has been known that plastics with undegradability and long half-times have caused serious environmental and ecological issues. Considering the devastating effects, the development of efficient plastic upcycling technologies with low energy consumption is absolutely imperative. Catalytic hydrogenolysis of single-use polyethylene over Ru-based catalysts to produce high-quality liquid fuel has been one of the current top priority strategies, but it is restricted by some tough challenges, such as the tendency towards methanation resulting from terminal C-C cleavage. Herein, we introduced Ru nanoparticles supported on hollow ZSM-5 zeolite (Ru/H-ZSM-5) for hydrocrackingof high-density polyethylene (HDPE) under mild reaction conditions. The implication of experimental results is that the 1Ru/H-ZSM-5 (~1wt% Ru) acted as an effective and reusable bifunctional catalyst providing higher conversion rate (84.30%) and liquid fuel (C5-C21) yield (62.77%). Detailed characterization demonstrated that the optimal performance in hydrocrackingof PE could be attributed to the moderate acidity and appropriate positively charged Ru species resulting from the metal-zeolite interaction. This work proposes a promising catalyst for plastic upcycling and reveals its structure-performance relationship, which has guiding significance for catalyst design to improve the yield of high-value liquid fuels.

Heterogeneous Porous Synergistic Photocatalysts for Organic Transformations.

Recent interest has surged in using heterogeneous carriers to boost synergistic photocatalysis for organic transformations. Heterogeneous catalysts not only facilitate synergistic enhancement of distinct catalytic centers compared to their homogeneous counterparts, but also allow for the easy recovery and reuse of catalysts. This mini-review summarizes recent advancements in developing heterogeneous carriers, including metal-organic frameworks, covalent-organic frameworks, porous organic polymers, and others, for synergistic catalytic reactions. The advantages of porous materials in heterogeneous catalysis originate from their ability to provide a high surface area, facilitate enhanced mass transport, offer a tunable chemical structure, ensure the stability of active species, and enable easy recovery and reuse of catalysts. Both photosensitizers and catalysts can be intricately incorporated into suitable porous carriers to create heterogeneous dual photocatalysts for organic transformations. Notably, experimental evidence from reported cases has shown that the catalytic efficacy of heterogeneous catalysts often surpasses that of their homogeneous analogues. This enhanced performance is attributed to the proximity and confinement effects provided by the porous nature of the carriers. It is expected that porous carriers will provide a versatile platform for integrating diverse catalysts, thus exhibiting superior performance across a range of organic transformations and appealing prospect for industrial applications.

Efficient synthesis of dihydropyranochromene derivatives via nanocopper immobilized on Zn/Cr-LDH functionalized with poly(p-phenylenediamine)

A new catalyst, poly(p-phenylenediamine) functionalized with copper nanoparticles stabilized on layered double hydroxide (LDH@poly(p-phenylenediamine)@CuI), was prepared. The structure of the new catalyst was identified and confirmed using different analyzes such as FESEM, EDX, XRD, TGA and elemental mapping. The efficiency of the mentioned catalyst was confirmed in the three-component one-pot synthesis of various derivatives of dihydropyrano[3,2-c]chromene in aqueous ethanol solvent. The structure of the synthesized products was confirmed using infrared spectrometry (FT-IR), nuclear magnetic resonance (1H NMR and 13C NMR) and Mass techniques. High yield of products, short reaction time, easy purification, reuse of catalyst, and the use of a soft reaction method can be considered as the main advantages of this method. Additionally, this catalyst was recycled four times without a significant loss of catalytic power.

A new protocol for the one-pot synthesis of α-aminophosphonates using hydroxyapatite-supported palladium as a solid and reusable catalyst

A new protocol for the one-pot synthesis of α-aminophosphonates using hydroxyapatite-supported palladium as a solid and reusable catalyst

Peroxymonosulfate activation by tin(IV) phosphate supported cobalt composite for acetaminophen degradation: Performance and mechanism

Tin(IV) phosphate-supported cobalt composite (Co-SnP) was prepared and employed as a heterogeneous activator of peroxymonosulfate (PMS) for acetaminophen (APAP) degradation. The results indicated that almost all APAP (5 mg L−1) was eliminated by PMS (0.5 mM) assisted with Co-SnP (0.2 g L−1) in an initial pH range of 7–9 within 15 min, mainly owing to the role of OH and SO4−, with contributions of 59.7 % and 39.6 %, respectively. The rate constant (k) value increased gradually with the increase in catalyst dosage and PMS concentration. APAP degradation was suppressed by Cl−, HCO3− and humic acid but promoted by NO3−. The Co-SnP/PMS system exhibited strong oxidation ability toward APAP in real water matrices and toward other organic pollutants (rhodamine B, phenacetin, bisphenol A, and sulfisoxazole), indicating the outstanding catalytic performance of Co-SnP for PMS activation. Furthermore, the superior stability and reusability of the Co-SnP catalyst were confirmed through four consecutive uses. Finally, the intermediates of APAP degradation were identified and the APAP degradation pathways were proposed. This work demonstrates the potential application of the Co-SnP/PMS system in the elimination of organic pollutants from water and provides a novel avenue for the recovery and utilization of phosphorus and cobalt ions in wastewater.

Synthesis of Pyrano[2,3-d]Pyrimidine Diones Catalyzed by Cobalt-Doped Iron Tartrate Nanomaterial: A Sustainable and Efficient Approach

Synthesis of Pyrano[2,3-d]Pyrimidine Diones Catalyzed by Cobalt-Doped Iron Tartrate Nanomaterial: A Sustainable and Efficient Approach

Sustainable upgrading of crude glycerol via ultrasound-reinforced bio-refinery process with oxygen–nitrogen subsistence: Co-application of reusable heterogeneous catalyst

Selective/rapid production of value-added glyceryl triacetate (GT) from catalytic transformation of crude glycerol (CG) derived from biodiesel production procedure was systematically investigated using ultrasound-reinforced bio-refinery process with environmental friendliness. Interestingly, the tartaric-magnetic mesoporous alumina (TMMA) was synthesized via hydrothermal aluminization, calcination and functionalization, further applied as an active catalyst for CG acetylation under nitrogen and/or oxygen subsistence. The operative parameters for selective synthesis of GT derived optimization process were in the sequence of TMMA loading amount > ultrasonic level > acetylation time. The GT selectivity and activation energy derived from catalytic acetylation of CG using ultrasonic system were 97.78 % and 44.38 kJ/mol while traditional system were 52.51 % and 60.66 kJ/mol. For catalytic comparison, TMMA catalyst presented better turnover rate of CG transformation than that of marketable catalysts. Moreover, TMMA catalyst could be reused for 15 cycles without notable changing in physicochemical properties such as surface area and acidity which was contributed under oxygen subsistence by oxidative degradation, leading to long-term durability of catalytic performance and long-term repression of polymeric formation. The sustainable application of O2 molecular could perfectly restrain hard polymeric deposition on TMMA structure, leading to facile separation after complete acetylation. This work anticipated that specific integration between TMMA with CG acetylation can be further co-applied for practical process of biodiesel production using ultrasound-reinforced bio-refinery process.

Enhancing the catalytic activity of Pd nanoparticles in the hydrolysis of ethylenediamine-bisborane through sulfonation of graphene oxide as a solid support

Ethylenediamine-bisborane (EDB), with its high hydrogen storage capacity, has been in the limelight among researchers. In this study, a new catalytic hybrid material (Pd@rGO-SO3H), comprising sulfonated reduced graphene oxide (rGO-SO3H) and palladium (Pd), was developed. This material serves as a highly efficient and reusable catalyst in the hydrogen production from EDB hydrolysis. The synthesized EDB, rGO-SO3H, and Pd@rGO-SO3H were characterized using ICP-OES, PXRD, XPS, SEM, TEM, and TEM/EDX tools. The initial TOF value of the Pd@rGO-SO3H catalyst in hydrogen production from EDB hydrolysis was calculated as 136 min−1. This TOF value was found to be remarkably high compared to related studies in the literature. The reusability performance of Pd@rGO-SO3H was observed to be quite stable. Finally, activation parameters, such as activation energy (Ea), activation enthalpy (ΔH#), and activation entropy (ΔS#) for the hydrolysis reaction, were calculated by conducting catalytic reactions at different temperatures using relevant equations.

Microwave-assisted catalytic technology for sustainable production of valuable chemicals from plastic waste with enhanced catalyst reusability

High energy consumption and catalyst deactivation hinder thermal plastic waste decomposition for chemical production. This study employs a microwave-assisted catalytic process with Ru/ZSM-5 as the catalyst for polyethylene waste. At 300 °C under the first cycle of microwave heating, gas yield reaches 90 wt%, with 23 wt% aromatics selectivity and 30 wt% light olefins selectivity. In the first cycle of thermal heating, gas yield is 72 wt%, with 67 wt% alkanes and 32 wt% light olefins selectivity. In microwave cycle reactions, gas yield remains around 88 wt% through seven cycles over the spent catalyst (without regeneration), shifting product composition to 80 wt% light olefins in the 7th cycle. In contrast, in thermal cycle reactions, catalyst activity is lost after one cycle, and gas yield drops from 72 wt% to 45 wt%. Microwave-assisted catalytic technology shows potential for economically producing valuable chemicals from plastic waste, as lower reaction temperature and high catalyst reusability.

Copper(II) Ions Originating from CuBTC MOF Act as a Soluble Catalyst in the Friedländer Synthesis.

The copper-based metal-organic framework (MOF), CuBTC (where H3BTC = benzene-1,3,5-tricarboxylate), has been reported as a reusable heterogeneous catalyst for the Friedländer synthesis of substituted quinolines, which are desirable targets in the pharmaceutical industry. Because of this application, we further investigated the CuBTC-catalyzed Friedländer synthesis of 3-acetyl-2-methyl-4-phenylquinoline. CuBTC was synthesized in-house and used as a catalyst for the Friedländer synthesis. Fresh and used CuBTC were analyzed using scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), and X-ray photoelectron spectroscopy (XPS). The used CuBTC shows structural breakdown in pXRD patterns and SEM images. Despite the structural breakdown, the desired product, 3-acetyl-2-methyl-4-phenylquinoline, is still produced in a moderate yield (76.3% ± 0.2), as confirmed via time-of-flight mass spectrometry and nuclear magnetic resonance spectroscopy. Inductively coupled plasma atomic emission spectroscopy of the recovered supernatant solution indicates the presence of copper(II) ions in solution. Thus, we hypothesized that the standard Friedländer conditions may degrade the CuBTC framework, resulting in copper(II) ions in solution. Control experiments with copper(II) from Cu(NO3)2·3H2O catalyzes the Friedländer reaction in yields (75.6% ± 0.1) equal to that of the CuBTC MOF. Overall, our findings suggest that CuBTC acts as a copper(II) source, and the copper(II) ions originating from the CuBTC MOF are responsible for the observed catalysis.

Rapidly solidified Al-Cu-Co quasicrystalline alloy: microstructure and catalytic properties

This study presents the characterisation and evaluation of the catalytic potential of an alloy with a composition referring to the quasicrystal from the Al-Cu-Co system. The material was synthesised through a melt-spinning process, providing rapid solidification conditions and a favourable material form of thin ribbons. Microstructural and chemical analyses were performed using scanning electron microscopy, X-ray diffraction and transmission electron microscopy methods. The obtained results confirmed the presence of a major phase which was a decagonal quasicrystal in the form of globular grains and additional crystalline phases occurring along the grain boundaries. The catalytic potential of the materials was explored using phenylacetylene hydrogenation. The catalyst, obtained by pulverising the ribbons, demonstrated catalytic activity with over 40% phenylacetylene conversion and selectivity exceeding 60% for styrene production under mild reaction conditions. The recovered catalyst displayed a stable phase composition, as confirmed by X-ray diffraction, and unchanged morphology, indicating the possibility of catalyst reuse for subsequent reaction cycles. The presented results provide insight into the experimental verification of the catalytic properties of the developed environmentally friendly catalysts.

Selective Hydrogenation of Aldehydes under Syngas Using CeO2-Supported Au Nanoparticle Catalyst.

Chemoselective hydrogenation of aldehydes to alcohols is of importance in synthetic chemistry. Here, we report a reusable CeO2-supported Au nanoparticle catalyst for the selective hydrogenation of aldehydes using syngas as the hydrogen source for which CO in syngas works as a site blocker to prevent side reactions. In particular, the hydrogenation of aldehydes with an easily reducible alkene, alkyne, or halogen moiety under syngas gave the corresponding alcohols with high selectivity, while the hydrogenation under pure hydrogen resulted in overreduction or dehalogenation. Of particular interest is that CO works as a site blocker but does not affect the hydrogenation rate significantly. A potential application of the present catalyst system was demonstrated by the conversion of terminal alkenes to alcohols via a one-pot hydroformylation/hydrogenation sequence.

Preparation of biodiesel by transesterification of castor oil catalyzed by flaky halloysite supported ZnO/SnO2 heterojunction photocatalyst

Biodiesel belongs to renewable energy and is a potential substitute for petrochemical diesel. In this study, ZnO/SnO2@halloysite heterojunction photocatalyst was prepared by loading semiconductor zinc oxide and tin dioxide on layered kaolin by the improved wet calcination method, which was used to photocatalytic the transesterification of castor oil and ethanol to produce biodiesel. TG-DTG, BET, XRD, UV–vis and SEM-EDS were used to characterize the composition, specific surface area, light absorption characteristics and photocatalytic performance of the samples. The reaction conditions were optimized by the Taguchi method. The optimum reaction conditions were as follows: catalyst dosage 4 wt%, molar ratio of ethanol to oil 12:1, reaction temperature 75 °C. After 2 h, the yield of biodiesel was 96.75 %. In the study of catalyst reusability, the yield of biodiesel is still above 85 % after being reused for 5 times. The kinetics of photocatalytic transesterification was studied, and the results accorded with quasi-first-order kinetics. The activation energy was 75.02 kJ/mol. Lastly, an eight-step reaction mechanism of photocatalytic transesterification was proposed. The prepared castor oil biodiesel can be prepared into B20 biodiesel through additives or mixing to meet ASTM D6751 and EN 14214 standards.

One–Pot Three–Component Synthesis of 2,4,5–Triaryl Imidazoles using Fe3O4@BisImid−CuBr Nanocomposite as an Ecofriendly and Efficient Magnetically Reusable Catalyst

AbstractImidazoles are one of the keys of N‐heterocycle molecules that exist in the structure of many biomolecules. In this research project, we reported that Fe3O4@BisImid−CuBr nanocomposite is an attractive and efficient nanomagnetic catalyst to afford 2,4,5–triaryl imidazoles through reactions of 1,2–diketones and aldehydes in the presence of NH4OAc under ecofriendly conditions. The Fe3O4@BisImid−CuBr nanocomposite was readily fabricated by a simple method from available reagents and its structure was analyzed by spectroscopic techniques. SEM and TEM images affirmed the formation of particles in spherical shape and nanometer–size. Under this methodology, a diverse library of triaryl imidazoles were afforded with high yields in water. This synthetic methodology has significant features such as (a) high yields and high purity of the products (b) suitable reaction time (c) use of magnetic reusable nanocatalyst (d) high reusability of Fe3O4@BisImid−CuBr nanocatalyst and the performance of reactions in aqueous medium.

Investigation of regeneration cycles with different catalysts on steam gasification of biomass

In this work, agricultural biomass waste was gasified in a two-zone tubular reactor in the presence of steam. Firstly, during preliminary experiments the effect of temperature in the 1st and 2nd reactor zone, as well as the influence of catalysts and steam/raw material ratio was investigated, then the reusability of catalysts was also studied during ten regeneration cycles. Based on the preliminary results, in the 1st reactor zone a lower temperature was used (400 °C), where the yield of carbon dioxide was ∼55 %, which has a positive effect on numerous reactions, also it can be converted to carbon monoxide with proper catalysts with in-situ process. Regarding the temperature, it is important to be mentioned that a significant difference was observed in the yield of synthesis gas at 700 °C thus, the experiments were carried out using 700 °C in the 2nd reactor zone. A natural (Clinoptilolite) and a synthetic zeolite (ZSM-5), a mesoporous alumina (Al2O3) and a carbon dioxide capturing carrier (CaO) were selected and impregnated with nickel for further use and for enhancing the yield of synthesis gas and hydrogen during the gasification process. The utilization of catalysts helped the in-situ reduction of carbon dioxide while their performance in the gasification process during the regeneration cycles was also investigated. Henceforward, the tested Ni/ZSM-5, Ni/Al2O3 and Ni/Clinoptilolite, reduced the amount of carbon monoxide from the 5th regeneration cycles, while the amount carbon dioxide with the four mentioned catalysts was decreased by 15–35 mmol/g raw material, compared to the results obtained during thermal degradation.

Continuous-flow hydrogenation of cinnamaldehyde over catalysts derived from modified CoAl4 layered double hydroxides incorporating Mn, Ni, Cu and Zn ions

Series of CoxM1-xAl4 layered triple hydroxides, LTHs were prepared as catalyst precursors for hydrogenation of biomass compound cinnamaldehyde under flow and batch reaction conditions. To this end, we have successfully extended the eco-friendly family of Al-rich layered double hydroxides (LDHs) by synthesizing MnAl4-LDHs, furthermore Co3Al-, Co2Al-LDHs were also exploited. Both the magnetic Co-rich and Al-rich reduced forms behaved as robust, efficient and reusable catalysts with significantly different selectivities correlated with their acid-base properties. Al-rich solids showed increased acidity and lower basicity resulting in high hydrocinnamaldehyde selectivity (∼75 %), while the Co-rich catalysts attested enhanced hydrocinnamyl alcohol production (∼80 % selectivity) due to their low acidity and high basicity (mapped by NH3/CO2 temperature programmed desorption tests). Incorporation of Mn, Ni, Cu and Zn ions generally decreased the total acidity of Al-rich catalysts, while their Lewis basicity largely increased: the highest was found for Mn, resulting in activity similar to that of Co-rich catalysts.

Hexanoic acid upgrading into hexyl hexanoate: An efficient way to obtain a new sustainable biofuel

Hexyl hexanoate emerges as a promising candidate for integration into diesel fuel blends. To achieve a green synthesis of hexyl hexanoate, a straightforward process was proposed, utilizing hexanoic acid and hydrogen as reactants, both potentially obtainable from renewable sources. 5 % Ru/C, 5 % Pt/C and 10 % Pd/C were tested for the hydrogenation/esterification of hexanoic acid. Among these, 10 % Pd/C proved to be the most effective catalyst: after a 6-hour reaction at 573 K under 20 bar of H2, hexanoic acid exhibited a partial conversion (84.7 %) into a mixture of hexyl hexanoate, water, hexanoic acid, and 1-hexanol (58.7 %, 12.9 %, 14.9 %, and 13.5 % wt, respectively), resulting in a hexyl hexanoate yield of 69.8 %. Following the removal of 10 % Pd/C, the addition of AlCl3·6H2O to the reaction mixture was considered for enhancing hexyl hexanoate production, through further conversion of previously unreacted hexanoic acid and 1-hexanol. A remarkable increase in hexanoic acid conversion (94.2 %) and hexyl hexanoate yield (from 69.8 % to 88.8 %) was achieved, along with an increase in the hexyl hexanoate purity of the final product (86.8 %). An efficient, clean, and resource-saving synthesis of hexyl hexanoate from hexanoic acid was achieved, supported by the recoverability and reusability of both catalysts, boding well for an effective and widespread use of such ester in diesel fuel blends.