Biomass substrate-derived graphene-like N-doped porous carbon nanosheet-supported PtCo nanocatalyst for efficient and selective hydrogenation of unsaturated furanic aldehydes

Unsaturated furanic aldehydes are derived from lignocellulosic biomass resources and subsequently used to produce valuable chemicals. However, the highly efficient, selective hydrogenation of the biomass-derived unsaturated furan CO bond remains challenging. Here we report that graphene-like nitrogen doped porous carbon (GNPC) nanosheets are synthesized from carbon-rich, sustainable, and renewable biomass precursors (glucose, fructose and 5-hydroxymethylfurfural, HMF) with high surface areas, large pore volumes and narrow mesopores. GNPC derived from HMF is an excellent catalyst support for PtCo nanoparticles with ultrafine nanoparticles size and homogeneous distributions. This catalyst is highly efficient for hydrogenation of biomass-derived furan-based unsaturated aldehydes, with high yields, to the corresponding unsaturated alcohols under mild conditions. This design strategy should further allow the development of selective, simple, green heterogeneous catalysts for challenging chemical transformations.

Wood-converted porous carbon decorated with MIL-101(Fe) derivatives for promoting photo-Fenton degradation of ciprofloxacin

In response to the escalating concerns over antibiotics in aquatic environments, the photo-Fenton reaction has been spotlighted as a promising approach to address this issue. Herein, a novel heterogeneous photo-Fenton catalyst (Fe3O4/WPC) with magnetic recyclability was synthesized through a facile two-step process that included in situ growth and subsequent carbonization treatment. This catalyst was utilized to expedite the photocatalytic decomposition of ciprofloxacin (CIP) assisted by H2O2. Characterization results indicated the successful anchoring of MIL-101(Fe)-derived spindle-like Fe3O4 particles in the multi-channeled wood-converted porous carbon (WPC) scaffold. The as-synthesized hybrid photocatalysts, boasting a substantial specific surface area of 414.90 m2·g-1 and an excellent photocurrent density of 0.79 μA·cm-2, demonstrated superior photo-Fenton activity, accomplishing approximately 100% degradation of CIP within 120 min of ultraviolet-light exposure. This can be attributed to the existence of a heterojunction between Fe3O4 and WPC substrate that promotes the migration and enhances the efficient separation of photogenerated electron-hole pairs. Meanwhile, the Fe(III)/Fe(II) redox circulation and mesoporous wood carbon in the catalyst synergistically enhance the utilization of H2O and accelerate the formation of •OH radicals, leading to heightened degradation efficiency of CIP. Experiments utilizing chemical trapping techniques have demonstrated that •OH radicals are instrumental in the CIP degradation process. Furthermore, the study on reusability indicated that the efficiency in removing CIP remained at 89.5% even through five successive cycles, indicating the structural stability and excellent recyclability of Fe3O4/WPC. This research presented a novel pathway for designing magnetically reusable MOFs/wood-derived composites as photo-Fenton catalysts for actual wastewater treatment.

Polymer Supported Nitrogen-Bridged Symmetrical Binuclear Dioxidomolybdenum(VI) Complexes and Their Homogeneous Analogues as Potential Catalysts for Efficient Synthesis of 2-Amino-3-Cyano-4H-Chromenes/Pyrans

Reaction of 2-chloromethyl-1H-benzimidazole with known intermediates (i-iii), prepared from diaminoguanidine hydrochloride with salicylaldehyde, 5-bromosalicylaldehyde or 3,5-di-tert-butylsalicylaldehyde, in the presence of triethylamine (NEt3) led to the formation of benzimidazole appended new ligands, H4L1-H4L3 (I-III). The homogeneous nitrogen-bridged symmetrical binuclear complexes, [(MoVIO2)2(L1)(H2O)2] (1), [(MoVIO2)2(L2)(H2O)2] (2) and [(MoVIO2)2(L3)(MeOH)2] (3) have been isolated by reacting these ligands with [MoVIO2(acac)2] in a 1 : 2 molar ratio in refluxing methanol. Using 1 : 1 (ligand to Mo precursor) molar ratio under above reaction conditions resulted in the corresponding mononuclear complexes, [MoVIO2(H2L1)(MeOH)] (4), [MoVIO2(H2L2)(H2O)] (5) and [MoVIO2(H2L3)(MeOH)] (6). The binuclear heterogeneous compounds [(MoVIO2)2(L1)(DMF)2]@PS (PS-1), [(MoVIO2)2(L2)(DMF)2]@PS (PS-2) and [(MoVIO2)2(L3)(DMF)2]@PS (PS-3) have been obtained by immobilization of 1-3 onto chloromethylated polystyrene (PS) beads. All synthesized ligands, homogeneous as well as supported compounds have been characterized by elemental analyses and various spectroscopic methods. Single crystal X-ray diffraction study of complexes 1 and 3 confirms their nitrogen-bridged symmetrical binuclear structures while 4 is mononuclear. Heterogeneous compounds (PS-1-PS-3) have further been studied by microwave plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy along with energy dispersive spectroscopy. These compounds (homogeneous and heterogeneous) were explored for catalytic applications to one-pot multicomponent reactions (MCRs) for efficient synthesis of biologically active 2-amino-3-cyano-4H-chromenes/pyrans (21 examples). Optimising various reaction parameters helped in achieving as high as 97 % yields of products. Though, only half equivalent of the binuclear complexes (1-3) was required compared to mononuclear analogues (4-6) to achieve comparable yields, heterogeneous catalysts have an added advantage due to their stability and recyclability. Suitable reaction mechanism has also been proposed based on isolated intermediates.

Chloromethylation of Lignin as a Route to Functional Material with Catalytic Properties in Cross-Coupling and Click Reactions

We present a novel, greener chloromethylation procedure for organosolv aspen lignin under mild reaction conditions without Lewis acid as a catalyst and in acetic acid as a solvent. This synthetic protocol provides a reliable approach to chloromethylated lignin (CML) and means to obtain valuable lignin derivatives. The resulted CML was subsequently transformed into 1-methylimidazolium lignin (ImL), which effectively serves as a stabilizing agent for Pd/CuO nanoparticles (Pd/CuO-NPs). To evaluate the versatility of developed lignin-based catalyst, we investigate its performance in a series of carbon-carbon bond formation reactions, including Suzuki-Miyaura, Sonogashira, Heck reactions, and azide-alkyne cycloaddition (click) reaction. Remarkably, this catalyst exhibited a high degree of catalytic efficiency, resulting in reactions with yields ranging from average to excellent. The heterogeneous catalyst demonstrated outstanding recyclability, enabling its reuse for at least 10 consecutive reaction cycles, with yields consistently falling within the range of 42 % to 84 %. A continuous flow reactor cartridge prototype employing Lignin@Pd/CuO-NPs was developed, yielding results comparable to those achieved in batch reactions. The utilization of Lignin@Pd/CuO-NPs as a catalyst showcases its potential to facilitate diverse carbon-carbon bond formation reactions and underscores its promising recyclability, aligning with the green chemistry metrics and principles of sustainability in chemical processes.

Investigating catalytic pathways: a comparative review of homogeneous and heterogeneous catalysis for 3-aroylimidazo[1,2-a]pyridine synthesis

3-aroylimidazo[1,2-a]pyridines represent a class of derivatives in the imidazo[1,2-a]pyridine family known for their important biological and pharmaceutical activities. Consequently, various methodologies have been designed to simplify the synthesis of this structure, with an emphasis on the use of cost-effective starting materials and environmentally friendly protocols. All the methods developed in recent years (from 2016 to 2023) rely on homogeneous or heterogeneous catalysts. Therefore, we aim to perform a comparative analysis between these two approaches, elucidating their respective advantages and limitations. The first part of this work focuses on techniques employing homogeneous catalysts, followed by the next section devoted to heterogeneous catalysts. This comprehensive review should be of substantial interest to researchers in the fields of organic and medicinal chemistry, as it provides a valuable resource for their research.

Developments in Titanium-Based Alkali and Alkaline Earth Metal Oxide Catalysts for Sustainable Biodiesel Production: A Review

Biodiesel represents a biodegradable, environmentally friendly, and renewable alternative to fossil fuels. Despite more than three decades of research, significant obstacles still hinder the widespread production of biodiesel. This current review elucidates both the potential and the existing challenges associated with homogeneous and heterogeneous catalysts in catalyzing biodiesel production, with a particular focus on alkali analogues, alkaline earth metal oxides, and titania-based catalysts. In particular, a comprehensive analysis is presented concerning alkali and alkaline earth-based titania (TiO2 ) catalysts. Among these, the alkaline earth metal oxides, including lithium, calcium, and strontium when combined with titanium-based catalysts, exhibit superior catalytic activity compared to other metal oxides, owing to their heightened basicity. Consequently, this review offers a thorough and up-to-date insight into the potential of titania-based heterogeneous catalysts for advancing biodiesel production.

A critical review on correlating active sites, oxidative species and degradation routes with persulfate-based antibiotics oxidation

At present, numerous heterogeneous catalysts have been synthesized to activate persulfate (PS) and produce various reactive species for antibiotic degradation from water. However, the systematic summary of the correlation among catalyst active sites, PS activation pathway and pollutant degradation has not been reported. This review summarized the effect of metal-based, carbon-based and metal-carbon composite catalysts on the degradation of antibiotics by activating PS. Metal and non-metal sites are conducive to inducing different oxidation pathways (SO₄^•-, ^•OH radical oxidation and ¹O₂ oxidation, mediated electron transfer, surface-bound reactive complexes and high-valent metal oxidation). SO₄^•- and ^•OH are easy to attack CH, S-N, CN bonds, CC double bonds and amino groups in antibiotics. ¹O₂ is more selective to the structure of the aniline ring and amino group, and also to attacking CS, CN and CH bonds. Surface-bound active species can cleave CC, SN, CS and CN bonds. Other non-radical pathways may also induce different antibiotic degradation routes due to differences in oxidation potential and electronic properties. This critical review clarified the functions of active sites in producing different reactive species for selective oxidation of antibiotics via featured pathways. The outcomes will provide valuable guidance of oriented-regulation of active sites in heterogeneous catalysts to produce on-demand reactive species toward high-efficiency removing antibiotics from water.

Recent advances in the removal of emerging contaminants from water by novel molecularly imprinted materials in advanced oxidation processes-A review

Recently, there has been a global focus on effectively treating emerging contaminants (ECs) in water bodies. Advanced oxidation processes (AOPs) are the primary technology used for ECs removal. However, the low concentrations of ECs make it difficult to overcome the interference of background substances in complex water quality, which limits the practical application of AOPs. To address this limitation, many researchers are developing new catalysts with preferential adsorption. Molecular imprinting technology (MIT) combined with conventional catalysts has been found to effectively enhance the selectivity of catalysts for the targeted catalytic degradation of pollutants. This review presents a comprehensive summary of the progress made in research on molecularly imprinted polymers (MIPs) in the selective oxidation of ECs in water. The preparation methods, principles, and control points of novel MIP catalysts are discussed. Furthermore, the performance and mechanism of the catalysts in photocatalytic oxidation, electrocatalytic oxidation, and persulfate activation are analyzed with examples. The possible ecotoxicological risks of MIP catalysts are also discussed. Finally, the challenges and prospects of applying MIP catalysts in AOP are presented along with proposed solutions. This review provides a better understanding of using MIP catalysts in AOPs to target the degradation of ECs.

Mononuclear ruthenium (II) complex covalently anchored on melem and g-C3N4 as efficient heterogeneous catalysts for chemical water oxidation

Ru-melem and Ru-C₃N₄ were synthesized by a simple and facile strategy to construct a novel covalently anchoring by introducing easily synthesized amide bond as a bridge connecting the Ru-terpy and melem or g-C₃N₄, respectively. The covalent anchoring of Ru complex on melem or C₃N₄ not only makes these materials exhibit water oxidation activity under Ce^IV-driven (Ce^IV = Ce(NH₄)₂(NO₃)₆) reaction condition, but also makes the obtained heterogeneous catalysts show higher catalytic activity than the corresponding homogeneous catalysts, which reveals that the covalent anchoring strategy of Ru complex is beneficial to improve the catalytic activity of homogeneous Ru catalysts. The synthetic method of hybrid catalysts offers an insightful strategy for enhancing water oxidation activity of molecular catalysts.

Graphene-based catalysts for biodiesel production: Characteristics and performance

Biodiesel is a promising alternative to reduce the dependency on fossil fuels. However, biodiesel's cost is still higher than its petroleum counterpart, hence its production process must be modified to make it economically viable. Microalgae are an alternative feedstock to replace agricultural crops for biodiesel production, and offer several advantages such as fast growth, use of non-arable land, growth in saline and wastewater, and high lipid yield. Unfortunately, biodiesel production from microalgae is very energy-intensive and costly, mainly due to the high energy consumption required for dewatering and drying. Therefore, utilizing wet microalgal biomass instead of dry biomass can be a promising solution to reduce the biodiesel production cost Furthermore, the use of heterogeneous catalysts offers high efficiency, recoverability, and reusability, and is therefore very promising from the economic and environmental perspectives. The unique characteristics of graphene-based nano-catalysts, such as their high surface area, two-dimensional structure, and functional groups, make them suitable candidates for biodiesel production. In this review, the use of graphene-based catalysts for biodiesel production is analyzed in depth, and their efficiency compared to other heterogeneous catalysts is scrutinized. Moreover, their recoverability, reusability, and economic feasibility are critically discussed, and their potential to produce biodiesel from wet microalgae is explored as a sustainable and cost-effective approach.

Ball-milling as effective and economical process for biodiesel production under Kraft lignin activated carbon stabilized potassium carbonate

Biodiesel is a typical renewable energy and the previous transesterification processes for biodiesel production mainly focus on thermocatalytic methods. In this paper, the ball-milling process was investigated into the biodiesel production under Kraft lignin activated carbon stabilized K₂CO₃. Biodiesel yield increased to 66 % after only 5 min and reached 100 % within 25 min under optimal ball-milling conditions (0.5 g of the catalyst; methanol/oil molar ratio 18:1; 195 g of ball-mill beads; 1400 rpm; 25 °C). The power demand between the thermocatalytic method and the ball-milling method was also compared. Based on the computation, the ball-milling method has lower power demand than the traditional method (38 vs 201 kWh·mol^-1). Therefore, the ball-milling method is an effective and economical process for biodiesel production.

Soluble porous organic cages as homogenizers and electron-acceptors for homogenization of heterogeneous alloy nanoparticle catalysts with enhanced catalytic activity

The creation of ultrafine alloy nanoparticles (<5 nm) that can maintain surface activity and avoid aggregation for heterogeneous catalysis has received much attention and is extremely challenging. Here, ultrafine PtRh alloy nanoparticles imprisoned by the cavities of reduced chiral covalent imine cage (PtRh@RCC3) are prepared successfully by an organic molecular cage (OMC) confinement strategy, while the soluble RCC3 can act as a homogenizer to homogenize the heterogeneous PtRh alloy in solution. Moreover, the X-ray absorption near-edge structure (XANES) results show that the RCC3 can act as an electron-acceptor to withdraw electrons from Pt, leading to the formation of higher valence Pt atoms, which is beneficial to improving the catalytic activity for the reduction of 4-nitrophenol. Attributed to the synergistic effect of Pt/Rh atoms and the unique function of the RCC3, the reaction rate constants of Pt₁Rh₁₆@RCC3 are 49.6, 8.2, and 5.5 times than those of the Pt₁Rh₁₆ bulk, Pt@RCC3 and Rh@RCC3, respectively. This work provides a feasible strategy to homogenize heterogeneous alloy nanoparticle catalysts in solution, showing huge potential for advanced catalytic application.

TiO2/C coated Co3O4 nanocages for peroxymonosulfate activation towards efficient degradation of organic pollutants

Developing new catalysts for efficient degradation of micropollutants in water is of significant importance in advanced oxidation processes (AOPs). Herein, TiO₂/C coated Co₃O₄ nanocages (Co₃O₄@TiO₂/C) were synthesized and their performance on micropollutants degradation was evaluated. Specifically, cobalt-based Zeolitic imidazolate framework (ZIF-67) coated by a thin layer of titanium species and polydopamine (PDA) was used as a precursor for the preparation of Co₃O₄@TiO₂/C by two-step calcination. The catalytic performance of peroxymonosulfate (PMS) activation towards the degradation of organic pollutants was investigated by using atrazine (ATZ) and Bisphenol A (BPA) as typical micropollutants. The efficiency and the effect of TiO₂/C shell on the as-synthesized catalyst were analyzed by comparing Co₃O₄ derived from ZIF-67 and Co₃O₄/C derived from ZIF-67/PDA. ATZ degradation results showed that the Co₃O₄@TiO₂/C catalyst was the most efficient for catalytic oxidation when 99.5% of ATZ was removed within 4 min, which is 57.5% and 74.6% faster than that of Co₃O₄@C and Co₃O₄, respectively. The enhanced performance of Co₃O₄@TiO₂/C is attributed to their unique nanocages structure and improved specific surface area. The catalysis mechanisms and ATZ degradation pathways were presented based on the results of electron paramagnetic resonance (EPR), XPS, and LC-MS analysis. Our results might have added to the design of heterogeneous catalysts of large surface area for efficient PMS activation in AOPs.

Porous aromatic frameworks with high Pd nanoparticles loading as efficient catalysts for the Suzuki coupling reaction

The development of efficient and recyclable heterogeneous Pd catalysts is an area of continuing attention due to their critical applications in organic synthesis and pharmaceutical production. In this study, two novel heterogeneous catalysts Pd@PAF-182 and Pd@PAF-183 were prepared by the immobilization/NaBH₄ reduction of PdCl₄^2- on hydrophilic cationic porous aromatic frameworks (PAF-182 and PAF-183), which were synthesized via a Yamamoto-type Ullmann coupling reaction from the corresponding aryl quaternary phosphonium salt monomer. Characterization by powder X-ray diffraction (PXRD), solid-state Cross-Polarization Magic-Angle-Spinning Nuclear Magnetic Resonance (CP/MAS NMR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) established the structures of the as-prepared catalysts. Inductively coupled plasma atomic emission spectrometry (ICP-AES) detection showed that the loading of Pd nanoparticles (Pd NPs) were 29.4 wt% for Pd@PAF-182 and 37.5 wt% for Pd@PAF-183, much higher than those of similar porous materials. Evaluation of the catalytic activity of the Pd@PAFs using Suzuki coupling as the model reaction demonstrated that as little as 0.12 mol% of Pd NPs could catalyze the Suzuki coupling with high efficiency, achieving yields up to 99% at 80 °C in 8 h. Recycling experiments also suggested that Pd@PAF-182 and Pd@PAF-183 maintained high catalytic activity with negligible leaching of Pd NPs after five cycles.

Recent progress of functional metal-organic framework materials for water treatment using sulfate radicals

Human health is being threatened by the ever-increasing water pollution. Sulfate radical (SO₄^•-)-based advanced oxidation processes (SR-AOPs) are rapidly being developed and gaining considerable attention due to their high oxidation potential and selectivity as a way to purify water by degrading organic contaminants in it. Among the catalytic materials that can activate the precursor to generate SO₄^•-, metal-organic frameworks (MOFs) are the most promising heterogeneous catalytic material in SR-AOPs because of their various structure possibilities, large surface area, ordered porous structure, and regular activation sites. Herein, an in-depth overview of MOFs and their derivatives for water purification with SR-AOPs is provided. The latest studies on pristine MOFs, MOF composites, and MOF derivatives (metal oxides, metal-carbon hybrids, and carbon materials) are summarized. The mechanisms of decomposition of pollutants in water via radical and non-radical pathways are also discussed. This review suggests future research directions for water purification through MOF-based SR-AOP.

Mechanism of peroxymonosulfate activation and the utilization efficiency using hollow (Co, Mn)3O4 nanoreactor as an efficient catalyst for degradation of organic pollutants

Development of efficient catalysts for peroxymonosulfate (PMS) activation and further understanding its mechanism on organic pollutants degradation is of significant importance for advanced oxidation processes (AOPs). Herein, hollow (Co, Mn)₃O₄ catalysts were synthesized by calcination of Co, Mn containing metal-organic frameworks (MOFs) and further used to evaluate the effectiveness of organic pollutants (Bisphenol A (BPA), atrazine (ATZ), and diethyl phthalate (DEP)) degradation by PMS activation. The PMS utilization efficiency in (Co, Mn)₃O₄/PMS system (36.4%) was estimated to be 28.0% and 43.8% higher than that of Co₃O₄/PMS and Mn₅O₈/PMS system, respectively. Notably, the metal leaching in (Co, Mn)₃O₄/PMS system was significantly suppressed. The utilization efficiency also reveals an inverse proportionality relationship with BPA mineralization but decreases with increasing initial pH value. A synergy between oxides of Co and Mn was perceived to enhance PMS utilization efficiency and BPA degradation. The results indicate enhanced catalytic performance with (Co, Mn)₃O₄ compared to Co₃O₄ derived from Co-MOF and other reported catalysts, with 99% of BPA degradation within 4 min. The oxidation mechanism was then proposed based on the electron paramagnetic resonance (EPR) and XPS results. Our findings might have contributed to designing heterogeneous catalysts for efficient PMS utilization in AOPs.

Waste Ox bone based heterogeneous catalyst synthesis, characterization, utilization and reaction kinetics of biodiesel generation from Jatropha curcas oil

The present investigation has been carried out to utilize waste animal (Ox) bone for the progress of an innovative, low-budget, pollution free, and extremely resourceful heterogeneous catalyst synthesis for Jatropha curcas oil (JCO) conversion into biodiesel. The heterogeneous catalyst synthesized was characterized by its basic strength and subjected to spectroscopic (Fourier TransformInfrared and X-Ray Diffraction) and thermogravimetric analyses. Also, the physical properties of produced biodiesel were studied. The calcined Ox bone catalyst characterization distinctly showed that there was a tremendous catalytic activity for biodiesel synthesis. The kinetic study was accomplished employing a tri-necked RB flask furnished with a condenser and agitator. At the agitation speed of 500 rpm, 5% catalyst loading rate (w/w) of oil and 12:1 methanol-oil ratio (molar), biodiesel yields were tracked based on reaction time (1-4 h) and temperature (313-338 K). The temperature at 338 K was found to be optimal to obtain maximum (96.82%) biodiesel yield. Pseudo-first order kinetics was followed in the reaction. The energy required for the activation (E_a) was 38.55 kJ mol^-1 with a frequency factor (k_o) of 7.03 × 10⁶ h^-1. The reusability studies demonstrated that the calcined animal bone catalyst was much stable up to three cycles with >90% FAME yield, which was reduced significantly (P < 0.05) to 61% in the fourth cycle. The outcome of this investigation brought to light the possibilities of utilizing calcined Ox bone catalyst and JCO as low-cost and frequently obtainable discarded waste materials that can be used as feedstock for the commercial-scale generation of biodiesel to fulfill the prospective community demands.

Efficient removal of organic pollutants by a Co/N/S-doped yolk-shell carbon catalyst via peroxymonosulfate activation

Carbon-based catalysts with heteroatom doping and hollow structures are desired for advanced oxidation processes (AOPs). Herein, dual-shelled Co, N, and S codoped hollow carbon nanocages were developed by wrapping zeolitic imidazolate framework-67 (ZIF-67) with trithiocyanuric acid (TCA) and performing subsequent carbonization. The optimal composite catalyst (Co-NC-CoS) exhibited excellent catalytic performance toward different organic pollutants. Almost complete removal of 4-NP (60 mg/L^-1) was achieved within 20 min by 10 mg of catalyst and 0.2 g/L^-1 peroxymonosulfate (PMS). Moreover, the catalyst showed good stability and reusability. The effects of catalyst and PMS dose, pollutant concentration, pH and common anions were investigated, and reactive oxygen species (ROS) were studied by scavenger experiments and electron paramagnetic resonance (EPR) tests. The results show that multidoped atoms S, Co and N all contributed to the degradation system. Several lines of evidence suggested that S could change the catalytic process from Co³⁺/Co²⁺ to Co³⁺/Co²⁺/Co⁰ reduction due to its low redox potential. Degradation was achieved through both radical and nonradical pathways, where sulfate radicals (SO₄^·̶), hydroxyl radicals (^·OH) and singlet oxygen (¹O₂) were primary reactive species. Overall, this work may suggest that the novel multi heteroatom-doped catalysts with complex structures can be developed for environmental remediation.

Effective Heterogeneous Oxidative Desulfurization Catalyzed by H3 PMo9 W3 O40 @rht-MOF-1

With the increasingly strict standard for sulfur content in fuel, it is necessary to develop high-efficiency catalyst for extractive and catalytic oxidative desulfurization systems (ECODS). Herein, a series of three remarkable complexes H₃ PMo_(12-n) W_n O₄₀ @rht-MOF-1 (1 a, n=1; 2 a, n=2; 3 a, n=3) have been designed and prepared. Complexes 1 a, 2 a and 3 a were characterized by single-crystal X-ray diffraction and FT-IR, PXRD, SEM, N₂ adsorption-desorption isotherms, etc. Upon complex 3 a was applied as catalyst, it exhibited remarkably high catalytic activity in the ECODS reactions of aromatic sulfur compounds under optimal conditions. On the basis of its excellent heterogeneity, the catalyst could be recycled for nine consecutive cycles without significant losing of activity centers. Then, the reaction kinetics and mechanism were investigated and the activation energy have been calculated and discussed. Further, the complex 3 a is employed to catalyze the ODS of commercial diesel oil. As a result, the desulfurization efficiency reached 90%. These results provided important structure data for study the structure-property relationship and potential heterogeneous catalyst applied in ODS in industry.

Promoted catalytic hydrodechlorination for deep degradation of chlorophenols over Rh-La/SiO2 catalyst

Deep degradation of chlorophenols (CPs) into safe and ecofriendly cyclohexanol during catalytic hydrodechlorination (HDC), shows important practical significance and attractive prospect in the treatment of wastewater containing chlorophenols. An efficient Rh-La/SiO₂ catalyst was developed, by employing La as promoter. The presence of La in catalyst promoted catalytic performance of HDC significantly. Characterization results revealed that the interaction occurred between Rh and La in Rh-La/SiO₂ catalyst. This interaction accompanied with the high dispersion and finely particle size of active Rh, and generation of abundant Rh sites neighboring La atom. Kinetic study illustrated that Rh-La(1:1)/SiO₂ catalyst possessed the fastest kinetic constants, and minimized the apparent activation energies of 4-CP, phenol and cyclohexanone greatly. Complete degradation of 4-CP with a very high yield of cyclohexanol (> 98%) can be achieved at room temperature, making Rh-La(1:1)/SiO₂ catalyst to be a promising candidate for deep degradation of CPs during HDC and other Rh catalyzed hydrogenation reactions.

Nanoferrites heterogeneous catalysts for biodiesel production from soybean and canola oil: a review

Fossil fuel depletion and pollution are calling for alternative, renewable energies such as biofuels. Actual challenges include the design of efficient processes and catalysts to convert various feedstocks into biofuels. Here, we review nanoferrites heterogeneous catalysts to produce biodiesel from soybean and canola oil. For that, transesterification is the main synthesis route and offers simplicity, cost-effectiveness, better process control, and high conversion yield. Catalysis with nanoferrites and composites allow to obtain yields higher than 95% conversion with less than 5.0 wt.% of catalyst loading at 80 °C in 1-2 h. More than 90% conversion yields can be achieved with a moderate alcohol/oil molar ratio, i.e., between 12:1 to 16:1. Catalyst recovery is easy due to the magnetic properties of nanoferrite, which can be effectively reused up to 4 times with less than 10% loss of catalytic efficiency.

Degradation of fluoroquinolones in homogeneous and heterogeneous photo-Fenton processes: A review

Fluoroquinolone antibiotics are frequently detected in the environment causing potential hazards to ecological and human health. Inadequate removal efficiencies were reported for fluoroquinolones during conventional wastewater treatment processes whereas the application of photo-Fenton reactions has attracted much attention due to their high reaction rate. This article summarizes the recent proceedings on homogeneous and heterogeneous photo-Fenton degradation of fluoroquinolones. Degradation efficiencies of fluoroquinolones were discussed as well as rate constants for a distinct comparison. The influences of initial fluoroquinolone concentration, H₂O₂, Fe²⁺, pH and temperature were also investigated on homogeneous photo-Fenton degradation of fluoroquinolones. The currently applied heterogenous catalysts were considered including iron oxides catalysts, iron-based composite catalysts and iron-based semiconductor. In addition, the degradation pathways for typical fluoroquinolones were proposed with the products identified in the literature. The results indicated the better performance with the aid of heterogeneous catalysts due to the generation of more active species. Intermediate products at smaller molecular weight were obtained through various types of pathways under heterogeneous photo-Fenton degradation of fluoroquinolones, implying a practical application with biological treatment processes for fully mineralization.

Recent advances in waste water treatment through transition metal sulfides-based advanced oxidation processes

With the ever-growing water pollution issues, advanced oxidation processes (AOPs) have received growing attention due to their high efficiency in the removal of refractory organic pollutants. Transition metal sulfides (TMSs), with excellent optical, electrical, and catalytical performance, are of great interest as heterogeneous catalysts. These TMSs-based heterogeneous catalysts have been demonstrated to becapable and adaptable in water purification through advanced oxidation processes. The aim of this review is to conduct an exhaustive analysis and summary of recent progress in the application of TMSs-based AOPs for water decontamination. Firstly, the commonly used tuning strategies for TMSs-based catalysts are concisely introduced, including artificial size and shape control, composition control, doping, and heterostructure manufacturing. Then, a comprehensive overview of the current state-of-the-art progress on TMSs-based AOPs (i.e., Fenton-like oxidation, photocatalytic oxidation, and electro chemical oxidation processes) for wastewater treatment is discussed in detail, with an emphasis on their catalytic performance and involved mechanism. In addition, influencing factors of water chemistry, namely, pH, temperature, dissolved oxygen, inorganic species, and natural organic matter on the catalytic performance of established AOPs are analyzed. Furthermore, the reusability and stability of TMSs-based catalysts in these AOPs are also outlined. Finally, current challenges and future perspectives related to TMSs-based catalysts and their applications for AOPs wastewater treatment are proposed. It is expected that this review would shed some light on the future development of TMSs-based AOPs towards water purification.

Diyne-linked and fully π-conjugated polymetalloporphyrin nanosheets for outstanding heterogeneous catalysis

Two-dimensional, ultrathin, robust, and fully π-conjugated organic nanomaterials are highly desirable for application in various fields due to their unique photoelectric characteristics and great number of exposed active sites. However, such matters combining excellent stability, full π-conjugation and adjustability are rare, which has become a bottleneck for their practical application. Herein, we present a novel kind of diyne-linked polymetalloporphyrin nanosheet featuring permanent porosity and full π-conjugation, which exhibits a high-aspect-ratio, outstanding stability and convenient tailoring for electronic structures. Importantly, the novel nanosheets with monodisperse nickel atoms were found to be outstanding heterogeneous catalyst with unprecedented catalytic activity and selectivity for 4-nitrophenol reduction to 4-aminophenol under mild conditions. The findings recommend that diyne-linked polymetalloporphyrin nanosheets may offer new platforms for the conversion of photoelectricity and energy in the future.

A review on multicomponent reactions catalysed by zero-dimensional/one-dimensional titanium dioxide (TiO2) nanomaterials: Promising green methodologies in organic chemistry

Heterogeneous catalysis has currently become an emerging tool for the design and development of sustainable manufacturing processes in order to obtain advanced intermediates, fine chemicals, and bioactive molecules. This field has been considered efficient and eco-friendly, as it investigates the utilization of non-hazardous metals for atom-economical reactions. Nanomaterials have created a significant impact on scientific and engineering advancements due to their tunable properties with superior performance over their massive counterparts. Due to the increased demand for heterogeneous catalysts in industries and academia, different transition metal oxides have been made into substantial nanostructures. Among them, titanium dioxide (TiO₂) nanomaterials have received more attention on account of their chemical stability, low cost, dual acid-base properties, good oxidation rate and refractive index. Different modifications of TiO₂ extend their applications as active catalysts or catalyst supports in diverse catalytic processes, such as photovoltaics, lithium batteries, pigments and others. One-dimensional (1-D) TiO₂ nanostructures such as nanotubes, nanowires and nanorods have achieved greater importance owing to the unique properties of improved porosity, decreased inter-crystalline contacts, large surface-to-volume ratio, superior dispersibility, amplified accessibility of hydroxyl (-OH) groups and presence of good concentrations of Brønsted/Lewis acid sites. Since the discovery, 1-D TiO₂ nanostructures have served good photocatalytic applications, but were less explored in organic transformations. While many articles and reviews have covered the applications of 0-D and 1-D TiO₂ nanostructured materials (NSMs) in photoelectrochemical reactions and solar cells, there are other interesting applications of these as well. In contrast to the conventional multi-step processes that utilise the stepwise formation of individual bonds, one-pot conversions based on multicomponent reactions (MCRs) have acquired much significance in contemporary organic synthesis. This paper presents a critical review on history, classification, design and synthetic utility of titania-based nanostructures, which could be used as robust solid-acid catalysts and catalyst supports for MCRs. Further, to put ideas into perspective, the introduction and applications of MCRs for various organic transformations have been discussed.

Layered double hydroxides as heterogeneous catalyst systems in the cross-coupling reactions: an overview

Layered double hydroxides (LDHs) are recognized as two-dimensional (2D) clay materials, which comprise the interlayer anions and host layers with a positive charge (brucite-like M(OH)₆ octahedral). They have been used as effective and eco-friendly heterogeneous catalytic systems in cross-coupling reactions. In this review, we try to underscore the applications of (LDHs) as an efficient and green catalyst in some important name reactions, namely Suzuki, Heck, Sonogashira, and Ullmann cross-coupling reactions leading to carbon-carbon bond formations.

Synthesis and catalytic utilization of bimetallic systems for wastewater remediation: A review

The environment is affected by agricultural, domestic, and industrial activities that lead to drastic problems such as global warming and wastewater generation. Wastewater pollution is of public concern, making the treatment of persistent pollutants in water and wastewater highly imperative. Several conventional treatment technologies (physicochemical processes, biological degradation, and oxidative processes) have been applied to water and wastewater remediation, but each has numerous limitations. To address this issue, treatment using bimetallic systems has been extensively studied. This study reviews existing research on various synthesis methods for the preparation of bimetallic catalysts and their catalytic application to the treatment of organic (dyes, phenol and its derivatives, and chlorinated organic compounds) and inorganic pollutants (nitrate and hexavalent chromium) from water and wastewater. The reaction mechanisms, removal efficiencies, operating conditions, and research progress are also presented. The results reveal that Fe-based bimetallic catalysts are one of the most efficient heterogeneous catalysts for the treatment of organic and inorganic contamination. Furthermore, the roles and performances of bimetallic catalysts in the removal of these environmental contaminants are different.

Transition metal catalysts for the bioorthogonal synthesis of bioactive agents

The incorporation of abiotic transition metal catalysis into the chemical biology space has significantly expanded the tool kit of bioorthogonal chemistries accessible for cell culture and in vivo applications. A rich variety of homogeneous and heterogeneous catalysts has shown functional compatibility with physiological conditions and biostability in complex environs, enabling their exploitation as extracellular or intracellular factories of bioactive agents. Current trends in the field are focusing on investigating new metals and sophisticated catalytic devices and toward more applied activities, such as the integration of subcellular, cell- and site-targeting capabilities or the exploration of novel biomedical applications. We present herein an overview of the latest advances in the field, highlighting the increasing role of transition metals for the controlled release of therapeutics.

Insights to the oxidative desulfurization process of fossil fuels over organic and inorganic heterogeneous catalysts: advantages and issues

Strict environmental laws have been put in place around the world to reduce the amount of sulfur in the fuel to reduce the emissions of harmful gases from fuel combustion and improve air quality. Therefore, extensive researches have been undertaken to devise effective processes or to improve the desulfurization processes. Among the desulfurization processes, the oxidative desulfurization (ODS) process is a promising method to achieve very low and near-zero sulfur content of the fuel. In this process, sulfur compounds are converted to the corresponding sulfone by a catalyst and in the presence of an oxidant. The obtained compounds by polar solvents or adsorbents are removed from the fuel. In recent decades, extensive studies have been carried out on the catalysts used in the oxidative desulfurization process. In this review, a comprehensive survey has been performed on heterogeneous catalysts used in the oxidative desulfurization process. According to the reported researches, the heterogeneous catalysts used can be divided into five groups: ionic liquids, carbon materials, polyoxometalates, transition metal oxides stabilized on porous solid substrates, and metal-organic frameworks. The proposed mechanisms with different catalysts have also been studied in this work.

Silica bonded N-(propylcarbamoyl)sulfamic acid (SBPCSA) as a highly efficient and recyclable solid catalyst for the synthesis of Benzylidene Acrylate derivatives: Docking and reverse docking integrated approach of network pharmacology

A green approach has been developed for the synthesis of a series of benzylidene acrylate 3(a-p) from differently substituted aromatic/heterocyclic aldehydes and ethyl cyanoacetate in excellent yields (90-98%), and employing silica bonded N-(Propylcarbamoyl)sulfamic acid as a recyclable catalyst under solvent-free condition. The molecular structure of compounds 3b, 3d and 3i were well supported by single-crystal X-ray crystallographic analysis. The present protocol bears wide substrate tolerance and is believed to be more practical, efficient, eco-friendly, and compatible as compared to existing methods. In-silico approaches were implemented to find the biochemical and physiological effects, toxicity, and biological profiles of the synthesized compounds to determine the expected biological nature and confirm a drug-like compound. A molecular docking study of the expected biologically active compound was performed to know the hypothetically binding mode with the receptor. Also, reverse docking is applied to recognize receptors from unknown protein targets for drug-like compounds to explain poly-pharmacology and binding postures with different receptors.

Data on the synthesis and characterizations of carboxylated carbon-based catalyst from eucalyptus as efficient and reusable catalysts for hydrolysis of eucalyptus

The presented article reports the preparation and characterization of heterogeneous carbon catalyst enriched with carboxylic group denoted as (ECS) from Eucalyptus as an efficient catalyst for the hydrolysis of woody Eucalyptus biomass. The fabrication process is based on the ball milling of Eucalyptus as a carbon source in the presence of dry ice as an oxidizing agent followed by acidification with the assistance of hydrochloric acid. The data are including the schematic for the full synthesis steps and characterization tools in addition to the thermogravimetric analysis and proton nuclear magnetic resonance analysis for the ECS catalyst. Meanwhile, the catalytic performance of ECS catalyst towards the hydrolysis of Eucalyptus was measured under different temperatures ranged from 160  to 200 °C. The ECS catalyst allowed the selective hydrolysis of Eucalyptus to glucose and xylose, as proved by high-performance liquid chromatography. The data herein are associated with the article entitled " Unveiling one-pot fabrication of scalable and reusable carboxylated heterogeneous carbon-based catalyst from Eucalyptus plant with the assistance of dry Ice for selective hydrolysis of Eucalyptus Biomass'' [1].

Recent advances of SBA-15-based composites as the heterogeneous catalysts in water decontamination: A mini-review

As an emerging class of silica-based mesoporous materials with incorporation of active components (e.g., transition metals/metal oxides and nanocarbons), SBA-15-based composites (X@SBA-15) have been attracting increasing attention in the field of water treatment owing to their unique characteristics and excellent remediation performance. This paper reviews recent advances in catalytic applications of X@SBA-15 to remove organic contaminants from water. Emphasis is made on the use of X@SBA-15 in four advanced oxidation processes (AOPs) (i.e., photocatalysis, Fenton-like oxidation, catalytic ozonation, and sulfate radical-based oxidation). Impregnation and hydrothermal methods are two most widely used synthetic approaches to combine the active composites with SBA-15, obtaining a synergistic effect with significant improvement in their individual catalytic activity for pollution remediation. The enhanced generation of highly reactive hydroxyl radicals from the surface of X@SBA-15 was widely recognized as being responsible for water decontamination using these AOPs, while sulfate radicals were also involved during activation of persulfate or peroxymonosulfate. Especially, X@SBA-15 could significantly enhance the light harvest and reduce the recombination of photo-induced electrons and holes during photocatalytic treatment, which also played the critical role in oxidizing the organics. The superior catalytic performance of X@SBA-15 without leaching metal ions during successive runs demonstrated the excellent reusability and structural stability. Together with the reduced toxicity of the treated solutions and the cost-effective characteristics of X@SBA-15 nanohybrids reported in the published literature, their great potential as the efficient and environmentally friendly heterogeneous catalysts in a real use scenario is suggested. Finally, the future perspectives on the development and practical utilization of X@SBA-15 are addressed.

Advances in nano-catalysts based biodiesel production from non-food feedstocks

This paper aims to examine the influence of various catalysts on biodiesel production, especially from non-food feedstocks with an ambition to optimize the catalytic biodiesel production. Homogenous acid catalysts are mainly used in biodiesel production, but they cannot be recovered and demand costly fuel purification as being corrosive. Similarly, enzyme catalysts are expensive in industrial-scale production of biodiesel. However, heterogeneous catalysts simplify the easy separation of product and by-products from the catalyst along with catalyst reusability and reduction of waste. Solid acid and base catalysts offer more advantages due to their non-toxicity, high surface area, reusability, higher stability, and the simplicity of purification. Solid base catalysts yield better activity than solid acid catalysts, however, they cannot esterify large amounts of free fatty acids (FFAs) in non-food feedstocks. The solid acid catalysts have the added advantages of being more tolerant to high amounts of FFAs and being able to simultaneously esterify FFAs and transesterify triglycerides in cheap feedstocks like waste cooking oil. Recently, an array of inorganic, organic and polymeric solid acid and nanomaterial-based catalysts have been developed using cheap feedstocks. However, the issues of low reactivity, small pore sizes, low stabilities, long reaction times, and high reaction temperatures still need to be solved. The developments of producing efficient, cheap, durable, and stable solid acid and nanomaterial-based catalysts have been critically reviewed in this study. Furthermore, the challenges and future perspectives of production of biodiesel and its industry growth have also been discussed.

Selective ultrasonic assisted synthesis of iron oxide mesoporous structures based on sulfonated melamine formaldehyde and survey of nanorod/sphere, sphere and core/shell on their catalysts properties for the Biginelli reaction

Sulfonated melamine-formaldehyde including iron oxide nanoparticles were synthesized by sulfonation of melamine-formaldehyde and then Fe₃O₄ nanoparticles were bounded onto the surface of sulfonated melamine-formaldehyde (SMF). Two different iron oxide nanostructures including nanorods/spheres and nanospheres on sulfonated melamine-formaldehyde (SMF/Fe₃O₄) were obtained only by modifying the time of radiation from 4 to 8 h in our synthetic method. Furthermore core/shell (Fe₃O₄@SMF) was prepared by entrapping Fe₃O₄ magnetic nanoparticles as the core and sulfonated melamine-formaldehyde as the outer shell. The prepared components were characterized via, Fourier transform infrared spectroscopy (FT-IR), titration, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis, Barret-Joyner-Halenda (BJH) analysis, vibrating sample magnetometer (VSM), energy-dispersive X-ray (EDX) spectroscopy, and thermal gravimetric analysis (TGA). According to obtained results, the synthesized products had a thermal stability near 180 °C, particle-size distribution around of 20-140 nm and surface area between 6 and 10 m²/g. In this study, vapor was used as a heat source. These effective and magnetically recoverable catalysts were employed for the synthesis of numerous 3,4-dihydropyrimidin-2(1H)-ones by utilizing aldehydes, ethylacetoacetate and urea. Functional easiness, excellent yields, short reaction time, the simplicity of work-up or filter, and thermal stability of these catalysts created them as appropriate heterogeneous systems and acceptable alternative to different heterogeneous catalysts.

Premodified Surface Method to Obtain Ultra-Highly Dispersed Metals and their 3D Structure Control on an Oxide Single-Crystal Surface

Precise control of the three-dimensional (3D) structure of highly dispersed metal species such as metal complexes and clusters attached to an oxide surface has been important for the development of next-generation high-performance heterogeneous catalysts. However, this is not easily achieved for the following reasons. (1) Metal species are easily aggregated on an oxide surface, which makes it difficult to control their size and orientation definitely. (2) Determination of the 3D structure of the metal species on an oxide powder surface is hardly possible. To overcome these difficulties, we have developed the premodified surface method, where prior to metal deposition, the oxide surface is premodified with a functional organic molecule that can strongly coordinate to a metal atom. This method has successfully provided a single metal dispersion on an oxide single-crystal surface with the 3D structure precisely determined by polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). Here we describe our recent results on ultra-high dispersions of various metal atoms on TiO₂ (110) surfaces premodified with mercapto compounds, and show the possibility of fine tuning and orientation control of the surface metal 3D structures.

Co-Ag alloy protected by nitrogen doped carbon as highly efficient and chemoselective catalysts for the hydrogenation of halogenated nitrobenzenes

The design of lower-cost alternative heterogeneous catalysts for the hydrogenation of halogenated nitrobenzenes using green method to synthesize the corresponding anilines is highly desirable. In this study, Ag was incorporated into the Co-MOFs during the growing process (Co-Ag(n)-MOFs), and then followed the carbothermal reduction process without any additional procedures, we synthesized a series of Co-Ag(n)@NCs. The self-supported catalysts exhibited excellent and stable catalytic performances for the chemoselective hydrogenation of halogenated nitrobenzenes without obvious dehalogenation. The Co-Ag bimetallic alloy nanoparticles were well-dispersed and protected from aggregation and leaching by the porous nitrogen doped carbon. Besides, either hydrazine hydrate (N₂H₄·H₂O, generating byproducts N₂ and H₂O) or H₂ could be used as green reducing agent with excellent selectivity towards synthesizing the corresponding anilines. And when the Co/Ag content ratio was approximate 1:1, the Co-Ag(1:1)@NC showed the best catalytic performance. Moreover, the Co-Ag(1:1)@NC could be efficiently recovered by using an external magnetic force and reused without obvious decrease of catalytic activity. Thus, such highly efficient, inexpensive, stable and magnetically recyclable catalysts could show great potentials in practical applications for many important reactions.

Synthesis of Supported Bimetal Catalysts using Galvanic Deposition Method

Supported bimetallic catalysts have been studied because of their enhanced catalytic properties due to metal-metal interactions compared with monometallic catalysts. We focused on galvanic deposition (GD) as a bimetallization method, which achieves well-defined metal-metal interfaces by exchanging heterogeneous metals with different ionisation tendencies. We have developed Ni@Ag/SiO₂ catalysts for CO oxidation, Co@Ru/Al₂ O₃ catalysts for automotive three-way reactions and Pd-Co/Al₂ O₃ catalysts for methane combustion by using the GD method. In all cases, the catalysts prepared by the GD method showed higher catalytic activity than the corresponding monometallic and bimetallic catalysts prepared by the conventional co-impregnation method. The GD method provides contact between noble and base metals to improve the electronic state, surface structure and reducibility of noble metals.

Emerging trends in photodegradation of petrochemical wastes: a review

Various human activities like mining and extraction of mineral oils have been used for the modernization of society and well-beings. However, the by-products such as petrochemical wastes generated from such industries are carcinogenic and toxic, which had increased environmental pollution and risks to human health several folds. Various methods such as physical, chemical and biological methods have been used to degrade these pollutants from wastewater. Advance oxidation processes (AOPs) are evolving techniques for efficient sequestration of chemically stable and less biodegradable organic pollutants. In the present review, photocatalytic degradation of petrochemical wastes containing monoaromatic and poly-aromatic hydrocarbons has been studied using various heterogeneous photocatalysts (such as TiO₂, ZnO and CdS. The present article seeks to offer a scientific and technical overview of the current trend in the use of the photocatalyst for remediation and degradation of petrochemical waste depending upon the recent advances in photodegradation of petrochemical research using bibliometric analysis. We further outlined the effect of various heterogeneous catalysts and their ecotoxicity, various degradation pathways of petrochemical wastes, the key regulatory parameters and the reactors used. A critical analysis of the available literature revealed that TiO₂ is widely reported in the degradation processes along with other semiconductors/nanomaterials in visible and UV light irradiation. Further, various degradation studies have been carried out at laboratory scale in the presence of UV light. However, further elaborative research is needed for successful application of the laboratory scale techniques to pilot-scale operation and to develop environmental friendly catalysts which support the sustainable treatment technology with the "zero concept" of industrial wastewater. Nevertheless, there is a need to develop more effective methods which consume less energy and are more efficient in pilot scale for the demineralization of pollutant.

One-pot sonochemical synthesis of 1,3-thiazolidin-4-ones using nano-CdZr4(PO4)6 as a robust heterogeneous catalyst

An efficient three-component synthesis of 1,3-thiazolidin-4-ones is described by one-pot condensation of aldehydes, aniline and thioglycolic acid with nano-CdZr4(PO4)6 as a robust heterogeneous catalyst under ultrasonic irradiation. Use of simple and readily available starting materials, experimental simplicity, applying the sonochemical methodology as an efficient method and innocuous means of activation in synthetic chemistry are some advantages of this protocol.

Highly Stable Bimetallic AuIr/TiO₂ Catalyst: Physical Origins of the Intrinsic High Stability against Sintering

It has been a long-lived research topic in the field of heterogeneous catalysts to find a way of stabilizing supported gold catalyst against sintering. Herein, we report highly stable AuIr bimetallic nanoparticles on TiO2 synthesized by sequential deposition-precipitation. To reveal the physical origin of the high stability of AuIr/TiO2, we used aberration-corrected scanning transmission electron microscopy (STEM), STEM-tomography, and density functional theory (DFT) calculations. Three-dimensional structures of AuIr/TiO2 obtained by STEM-tomography indicate that AuIr nanoparticles on TiO2 have intrinsically lower free energy and less driving force for sintering than Au nanoparticles. DFT calculations on segregation behavior of AuIr slabs on TiO2 showed that the presence of Ir near the TiO2 surface increases the adhesion energy of the bimetallic slabs to the TiO2 and the attractive interactions between Ir and TiO2 lead to higher stability of AuIr nanoparticles as compared to Au nanoparticles.

Synthesis of biodiesel from pongamia oil using heterogeneous ion-exchange resin catalyst

Biodiesel is a clean-burning renewable substitute fuel for petroleum. Biodiesel could be effectively produced by transesterification reaction of triglycerides of vegetable oils with short-chain alcohols in the presence of homogeneous or heterogeneous catalysts. Conventionally, biodiesel manufacturing processes employ strong acids or bases as catalysts. But, separation of the catalyst and the by-product glycerol from the product ester is too expensive to justify the product use as an automobile fuel. Hence heterogeneous catalysts are preferred. In this study, transesterification of pongamia oil with ethanol was performed using a solid ion-exchange resin catalyst. It is a macro porous strongly basic anion exchange resin. The process parameters affecting the ethyl ester yield were investigated. The reaction conditions were optimized for the maximum yield of fatty acid ethyl ester (FAEE) of pongamia oil. The properties of FAEE were compared with accepted standards of biodiesel. Engine performance was also studied with pongamia oil diesel blend and engine emission characteristics were observed.

Catalytic performance of carbon nanotubes in H2O2 decomposition: experimental and quantum chemical study

The catalytic performance of multi-walled carbon nanotubes (MWCNTs) with different surface chemistry was studied in the decomposition reaction of H2O2 at various values of pH and temperature. A comparative analysis of experimental and quantum chemical calculation results is given. It has been shown that both the lowest calculated activation energy (∼18.9 kJ/mol) and the highest rate constant correspond to the N-containing CNT. The calculated chemisorption energy values correlate with the operation stability of MWCNTs. Based on the proposed quantum chemical model it was found that the catalytic activity of carbon materials in electron transfer reactions is controlled by their electron donor capability.