One of the most crucial attributes of synthetic organic chemistry is to design organic reactions under the facets of green chemistry for the sustainable production of chemicals. Thus, due to the ...intensified environmental and safety concern, the need for new technologies for conducting chemical transformation has grown. In this regard, there is enormous interest in the use of heterogeneous catalysts as they generally avoid the generation of waste, require fewer toxic reagents, as well as entail easier separation and recycling of the catalyst. α,β-Unsaturated acids have been widely used in various industrial applications and have been identified as one of the most promising chemicals obtained
via
the Knoevenagel condensation reaction. This review aims to discuss the most pertinent heterogeneous catalytic systems such as zeolites, mesoporous silica, ionic liquids, metal oxides, and graphitic carbon nitride-based catalysts in the Knoevenagel reaction. Ultimately, this review focuses not only on the catalyst but also provides an overall idea and guide for the preparation of new catalysts with outstanding properties by looking at the chemical and engineering aspects such as the reaction conditions and the mechanisms.
One of the most crucial attributes of synthetic organic chemistry is to design organic reactions under the facets of green chemistry for the sustainable production of chemicals.
A viable hydrothermal technique has been explored for the synthesis of copper doped Zinc oxide nanoparticles (Cu-doped ZnO-NPs) based on the precursor's mixture of Copper-II chloride dihydrate ...(CuCl2.2H2O), Zinc chloride (ZnCl2), and potassium hydroxide (KOH). X-ray diffraction (XRD) reported the hexagonal wurtzite structure of the synthesized Cu-doped ZnO-NPs. The surface morphology is checked via field emission scanning electron microscopy (FE-SEM), whereas, the elemental compositions of the samples were confirmed by Raman, and X-ray photoelectron spectroscopy (XPS), respectively. The as-obtained ZnO-NPs and Cu-doped ZnO-NPs were then tested for their antibacterial activity against clinical isolates of Gram-positive (Staphylococcus aureus, Streptococcus pyogenes) and Gram-negative (Escherichia coli, Klebsiella pneumonia) bacteria via agar well diffusion method. The zone of inhibition (ZOI) for Cu-doped ZnO-NPs was found to be 24 and 19 mm against S. Aureus and S. pyogenes, and 18 and 11 mm against E. coli and K. pneumoniae, respectively. The synthesized Cu-doped ZnO-NPs can thus be found as a potential nano antibiotic against Gram-positive multi-drug resistant bacterial strains.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•A novel CNFs based Cu/ZrO2 catalyst for CO2 hydrogenation to methanol was investigated.•The efficiency of the catalyst was influenced by Cu content.•Efficient CO2 conversion recorded at relatively ...low reaction temperature.•N2O chemisorptions and activity data revealed the dependency of methanol synthesis rate on Cu surface area.
A series of novel bimetallic copper/zirconia carbon nanofibers supported catalysts with different Cu contents (5–25 wt%) were synthesized via deposition precipitation method. The physicochemical characterization of the calcined catalysts was carried out by X-ray diffraction, inductively coupled plasma optical emission spectroscopy, N2 adsorption–desorption, N2O chemisorption, temperature programmed reduction, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and temperature programmed CO2 desorption. Structure-reactivity correlation for catalytic hydrogenation of CO2 to methanol was discussed in details. Reaction studies revealed 15 wt% as optimum Cu concentration for CO2 conversion to methanol with CO2/H2 feed volume ratio of 1:3. Cu surface area was found to play a vital role in methanol synthesis rate. CO2 conversion was observed to be directly proportional to the number of total basic sites. A comparative study of this novel catalyst with the recently reported data revealed the better CO2 conversion at relatively low reaction temperature.
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•A novel Na-SiO2@TiO2 catalyst was synthesized by wet impregnation method.•Efficient yield of 98% was achieved under the temperate reaction conditions.•Kinetic plots recommended that ...the reaction pursue the pseudo 1st order kinetics.•The designed catalyst demonstrated the significant catalytic potency upto 5th run.
The novel Na-SiO2@TiO2 heterogeneous base catalyst was designed and successfully applied to the trans-esterification reaction of waste cooking oil for sustainable biodiesel production. The designed catalyst was characterized by SEM, XPS, FT-IR and BET before treatment, illustrated its suitability for the catalytic trans-esterification reaction. Moreover, the influence of reaction temperature, time, catalyst concentration and WCO:MeOH molar ratio on the catalytic activity were also investigated, resultant 98% biodiesel yield was achieved. The reusability test demonstrated that the Na-SiO2@TiO2 catalyst has noticeable catalytic potency up to 5 successive runs. Besides, the kinetics study explains that the reaction is kinetically controlled by pseudo 1st order. The Ea was found to be 21.65 kJ/mol. Similarly, the important thermodynamic parameters such as ΔH#, ΔS# and ΔG# were estimated to be 18.52 kJ.mol−1, −219.17 J.mol−1K−1and 92.59 kJ.mol−1respectively.
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Cobalt ferrite (CoFe2O4) was used as a catalyst for direct methane cracking. The reaction was accomplished in a fixed bed reactor at normal atmospheric pressure, while gas flow rate ...(20–50 mL/min) and reaction temperature (800–900 °C) were varied. The fresh CoFe2O4 morphology is sponge-like particle with inverse spinel structure as revealed from SEM and XRD results. The methane conversions and hydrogen formation rate were increased with reaction temperature, while catalyst stability and induction period decreased. Increases of gas flow rate > 20 mL/min led to a decrease the overall catalytic activity of CoFe2O4 for methane cracking. The XRD results of spent catalysts revealed that CoFe alloy was the active phase of methane cracking. TGA analysis showed that the largest amount of deposited carbon was 70.46 % at (20 mL/min, 900 °C), where it was 34.40 % at (50 mL/min, 800 °C). The deposited carbon has the shape of spherical carbon nanostructures and/or nano sprouts as observed with SEM. Raman data confirmed the graphitization type of the deposited carbon.
Ni-Co loaded hemp-derived activated carbon (AC) catalyst is synthesized by the wet impregnation method for steam methane reforming (SMR) for hydrogen production. The monometallic and bimetallic metal ...(Co, Ni) catalysts were synthesized over activated AC with 5 wt% by the wet impregnation method and characterized by using various techniques. XRD and SEM results suggested that the catalysts with small metal crystallites promote a better dispersion of highly porous AC.The catalytic assessment of all synthesized catalysts for SMR was carried out in a thermal fixed bed reactor at 750 °C, WHSV 2000 mL CH
4
g
−1
h
−1
, and S/C of 2.0. The catalytic results showed that among all the investigated samples, monometallic cobalt catalyst (5% Co@AC) exhibited the best results in terms of CH
4
conversion (97.17%) and H
2
production (66.08%). While the 5% Ni@AC and 5% NiCo@AC show a CH
4
conversion of 90.28% and 92.52%, respectively, whereas the H
2
production was 61.02% and 65.89%.
A series of novel carbon nanofibers (CNFs) supported bimetallic copper/zirconia catalysts are synthesized by deposition precipitation method and calcined at different temperatures. Calcined catalysts ...are characterized by various techniques like X-ray diffraction, N sub(2) adsorption-desorption, N sub(2)O chemisorption, high resolution transmission electron microscopy, temperature programmed reduction, X-ray photo-electron spectroscopy and temperature programmed desorption (CO sub(2) & NH sub(3)). The structure-activity correlation is discussed in details. The results demonstrate 450 degreesC as optimum calcination temperature for methanol synthesis rate with CO sub(2)/H sub(2) feed volume ratio of 1:3. CO sub(2) conversion is found to be directly proportional to copper metallic surface area (S sub(Cu)), while a linear relationship is observed between methanol synthesis rate and fraction of dispersed Cu.
Cobalt (Co) doped zinc oxide (ZnO) microcrystals (MCs) are prepared by using the hydrothermal method from the precursor's mixture of zinc chloride (ZnCl
), cobalt-II chloride hexahydrate (CoCl
·6H
...O), and potassium hydroxide (KOH). The smooth round cylindrical morphologies of the synthesized microcrystals of Co-doped ZnO show an increase in absorption with the cobalt doping. The antibacterial activity of the as-obtained Co-doped ZnO-MCs was tested against the bacterial strains of gram-negative (
,
) and gram-positive bacteria (
,
) via the agar well diffusion method. The zones of inhibition (ZOI) for Co-doped ZnO-MCs against
and
were found to be 17 and 19 mm, and 15 and 16 mm against
and
, respectively. The prepared Co-doped ZnO-MCs were thus established as a probable antibacterial agent against gram-negative bacterial strains.
In the present study, hexagonal boron nitride (h-BN) was synthesized from boric acid and melamine by thermal annealing method in a nitrogen atmosphere. The pure h-BN was used as an efficient sorbent ...for the uptake of Cd2+ ions from the solution phase. The kinetics and sorption studies of metal ions onto the h-BN were carried out in batch adsorption experiments at different temperature, time, pH, sorbent dosage, and concentration of metal ions. The optimum pH for the removal of the Cd2+ ions was found to be pH 7. The effect of temperature showed that the process of Cd2+ sorption remained endothermic in the range of 298 K–328 K. The Lagergren's first and Ho's second kinetic models were tested to interpret the adsorption kinetic data, however the present data was explained well by Ho's model for kinetics. The thermodynamic perameters ΔG, ΔS and ΔH were determined using the available adsorption data at different temperatures. The physicochemical properties of the synthesized product were also characterized before and after adsorption by different analytical techniques like FT-IR, TGA, XRD and Point of Zero Charge (PZC). The morphology of the surface was analyzed with the help of Scanning Electron Microscopy. The h-BN proved to be an efficient adsorbent for the uptake of the Cd2+ ions from aqueous media.
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Owing to considerable energy constraints and global warming phenomenon, to find alternative sources of renewable and affordable energy has become a highly prerequisite in this current ...era. Use of sustainable technologies in this regard for renewable fuel retention applications has become more beneficial in encouraging the broad usage of clean energy. Conjugated microporous polymers (CMPs) are a distinct family of composites, that merge extensive the π-conjugation with microporous structure. The CMPs have been recognized as an essential subclass of porous composites, ever since their development in 2007. The CMPs have been developed with a number of distinct configurations and characteristics, which allows for the versatility of conjugated framework cellular implementations and mesoporous structure. The exploration of CMPs in sustainable fuel devices is crucial for the development of CMP-based composites and their use in sustainability and environmental design. Numerous network developing processes and synthesized building components provide a huge heterogeneity of CMPs with various characteristics and design patterns. As a consequence, CMPs have been employed here for cathode/anode materials for lithium ion batteries (LIBs), sodium/potassium LIBs, supercapacitors, fuel cell electrode for solar cell, hydrogen storage materials, photocatalytic hydrogen and oxygen production reaction (HER, OER), photocatalytic CO2 reduction and so on. Due to the large surface areas of these composites, the distinctive charge storage mechanisms found in CMPs are explored, and a synopsis of how CMPs might facilitate ultrafast in desirable variety is presented. In addition, an evaluation between CMPs and linear polymers is presented, which provides further assistance for the synthesis of active materials. The most significant shortcomings experienced by CMPs in the domains of energy production have been evaluated, and potential strategies, synthetic process with reactions, physiochemical properties along with morphology have been demonstrated. Thus, this review is intended to be an entertaining and motivating study in the scientific community of the energy storage experts.
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