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A heterogeneous catalyst NaOH–NaAlO2/γ-Al2O3 was prepared by supporting NaOH and NaAlO2 on γ-Al2O3, and it was further employed for the oxidative degradation of lignin. The influence of the oxidant, the molar ratio of NaOH to NaAlO2, and calcination temperature of the supported catalyst on the catalytic activity were investigated. Air was found to be an effective oxidant for lignin conversion in the presence of heterogeneous catalyst. The total yield of monophenolic compounds (MPCs) from dealkaline lignin was 13.0 %, which was obtained by using NaOH–NaAlO2/γ-Al2O3 calcinated at 550 °C as the catalyst with 2:3 M ratio of NaOH to NaAlO2 at 170 °C for 2.5 h in air. Vanillin and syringaldehyde were found to be the main products, giving yields of 6.7 and 2.9 %, respectively. The conversion of lignin derived from wheat straw was also carried out under the identical conditions. Wheat straw lignin also displayed considerable conversion to MPCs in the presence of NaOH–NaAlO2/γ-Al2O3, and the total yield of MPCs at 12.3 % was obtained at 180 °C. NaOH–NaAlO2/γ-Al2O3 was recovered by filtration after the reaction and reused without further treatment, and 11.0 % total yield of MPCs was obtained after four cycles. [ABSTRACT FROM AUTHOR]

Heterocyclic transformation of 2-ethoxycarbonyl-4H-3,1-benzoxazine-4-ones to new derivatives of tetracyclic quinazoline-4-ones has been investigated with MCM-41‐dtz‐Pd as a heterogeneous recoverable nanocatalyst under mild reaction conditions. [ABSTRACT FROM AUTHOR]

This work presents a superstructure for maximizing the annual profit of biodiesel production with Advanced Interactive Multidimensional Modeling System (AIMMS). The novelty features are the combination of pinch-based heat integration with a wide range of biodiesel feedstocks and the application of superstructure to evaluate the effect of uncertainties on the optimized design. The case study is a pilot refinery with the infeed capacity of 8000 tonnes feedstock per year. The biodiesel production route from tallow with reactive distillation technology and a heterogeneous acid catalyst has the highest total annual profit of 3.5 million USDs. The heating and cooling utilities can be reduced by 30 % with the heat integration. The result from the sensitivity analysis shows that the biodiesel and feedstock prices, and the production capacity have the most pronounced effects. From technical assessment, the reactive distillation process is the best choice for biodiesel production from different feedstocks. [ABSTRACT FROM AUTHOR]

Biodiesel, an important sustainable fuel used in the transportation sector, demands a stable, recyclable and green catalyst for its economical and environmentally benign production. A novel green heterogeneous acid catalyst was developed by extracting sodium silicate from bamboo leaf ash (BLA), using which SBA-16 (BLA) was synthesized and then impregnated with 10 wt% each of WO3 and ZrO2, characterized and evaluated for the transesterification of Ankol seed oil with methanol to biodiesel. XRD, SEM, TEM and pore size characterization indicated that impregnated WO3 and ZrO2 were present outside the mesopores of SBA-16 (BLA) as monoclinic phases, thus 3D cubic cage-like Im3m mesopores of SBA-16 were unaltered. NH3-TPD indicated the presence of acid sites of two distinct strengths, attributed to the Lewis and Brønsted acidity of WO3–ZrO2 impregnated into SBA-16 (BLA) and hence gave the highest biodiesel yield of 98 %. In contrast 10 wt% of WO3 and 10 wt% of ZrO2 separately impregnated into SBA-16 gave 65 and 57 % of biodiesel yield respectively, possibly due to the presence of Lewis acidity alone in them. Among the WO3(10 %)–ZrO2(10 %) impregnated mesoporous supports viz. SBA-16 (BLA), SBA-16 (synthesized using tetraethyl orthosilicate), SBA-15, MCM-41, MCM-48, KIT-6, FDU-5, and TUD-1, the highest biodiesel yield of 98 % was given by SBA-16 (BLA), attributed to its spherical morphology and strong interaction with WO3–ZrO2 as inferred from SEM and XPS characterizations respectively. From the effect of process parameters on the WO3(10 %)–ZrO2(10 %)/SBA-16 (BLA) catalyst, maximum biodiesel yield was obtained at the temperature of 65 °C, catalyst amount of 200 mg, methanol:oil weight ratio of 10:1 and reaction time of 3 h. Under these reaction conditions, it retained the same biodiesel yield for six recycles after regeneration every time, confirmed its catalytic stability and recyclability. [ABSTRACT FROM AUTHOR]

Manufacturing active and economical catalysts and using them in water treatment is one of the most important challenges facing researchers. Spent batteries signify a source of harmful materials when discarded without suitable treatment. In this work, a black paste as one of the main components of spent battery doped with different ratios of TiO2 nanocomposites (0, 1, 3, 7, and 10 %) were manufactured using the sol–gel method. The characterization of the paste@TiO2 nanocomposites has been investigated by SEM, XRD, DRS, FTIR, and BET analysis. The results show formation of anatase phase of TiO2 in all doped samples. While the XRD of black paste indicates the presence of Mn3O4 as a main phase. Photocatalytic properties of black paste@TiO2 nanocomposites have been investigated using Congo red dye. The results showed that the presence of TiO2 in the paste could increase the specific surface area and the composites' photocatalytic efficiency. A higher percentage of TiO2 (10 %) added to the black paste resulted in higher black paste@TiO2 nanocomposite catalytic activity. The experimental photodegradation data were found to be consistent with the Lagergren kinetics model. The recyclability of the photocatalysts was examined for reuse in the industrial sector. Signifying that the black paste dopped with 10 % of TiO2 (PTO4) photocatalyst in this study had high reusability. [ABSTRACT FROM AUTHOR]

This article presents an overview of some of the available research studies of MOFs as catalysts. Catalytic studies of magnetic iron oxide nanoparticles with modified surfaces, MOFs with precious metals such as palladium, platinum, and silver, with zirconium, hafnium, copper, alkaline earth metals, lanthanides are generalized. The studies of the catalytic activity of micro- and mesoporous MOF structures are described. [ABSTRACT FROM AUTHOR]

Composite heterogeneous catalysts of ferrous and manganese oxalate (FeC2O4/MnC2O4) were prepared via simple chemical co-precipitation. The catalytic performance was evaluated by determining the degradation efficiency of rhodamine B (RhB). Under optimum conditions, 6-1FeMn showed the best catalytic performance, and the degradation efficiency exceeded 95 % within 2 min, which was 1.4 times more than ferrous oxalate. Under a wide pH range (1–8), 6-1FeMn showed high degradation efficiency for RhB with good recyclability and reusability. By characterizing the catalysts before and after the reaction and analyzing the degradation process, a possible mechanism was proposed: Mn2+ and Fe2+ synergistically catalyzed and produced a large number of hydroxyl radicals (·OH) by forming a composite active site for efficient reactivation. Mn3+ accelerated the transfer between Fe2+ and Fe3+. In addition, C2O42− reactivated the active site in situ and enhanced the catalytic properties. This study provides new insight into the catalytic degradation of organic dyes using composite heterogeneous Fenton catalysts. [ABSTRACT FROM AUTHOR]

Mesoporous materials (MMs) in the Santa Barbara Amorphous (SBA) family can be used as catalysts or support materials (SMs) for catalysts because they have controllable pore structure, thermal and chemical stability, and their surface properties can be modified easily depending on the desired reaction type. Surfactant (Pluronic p123; it is a symmetric triblock copolymer comprising poly and its chemical formula; HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H), a silica source (such as Tetraethyl orthosilicate: TEOS; SiC8H20O4), and a solvent are used in the synthesis of the SBA family (SBA-15). The SBA-15 was given with the hydrothermal method (HM) a catalyst feature by loading the active substance at a rate of 10, 25 % (cadmium/silica) by mass. Esterification reactions (ERs) were carried out with Cd-SBA-15 (Cd/Si: 10–25 %) catalyst at a feed rate of 1/2 (methanol/acetic acid), in the presence of 0.4 g catalyst, at a reaction temperature of 373 K and for 6–48 h. After 48 h, the catalytic activity (CA) values were obtained as 65 and 68 %, respectively. The re-usability of the catalysts was repeated two times under the same experimental conditions. It was observed that the catalysts maintained their catalytic activity of 73.35 and 68.72 % (3 × 48 h). In addition, the limited effect of catalyst amount on acetic acid conversion was investigated by Response Surface Methodology, and Historical Data Design. Moreover, k1, k2, equilibrium constant and activation energy values were calculated using the pseudo-homogeneous kinetic model. The physical features of the catalysts were investigated by BET, XRD, FTIR, DRIFT, SEM/EDX, and MAPPING analysis methods. [ABSTRACT FROM AUTHOR]

Palladium nanostructures are interesting heterogeneous catalysts because of their high catalytic activity in a vast range of highly relevant reactions such as cross couplings, dehalogenations, and nitro-to-amine reductions. In the latter case, the catalyst Pd@GW (palladium on glass wool) shows exceptional performance and durability in reducing nitrobenzene to aniline under ambient conditions in aqueous solutions. To enhance our understanding, we use a combination of optical and electron microscopy, in-flow single molecule fluorescence, and bench chemistry combined with a fluorogenic system to develop an intimate understanding of Pd@GW in nitro-to-amine reductions. We fully characterize our catalyst in situ using advanced microscopy techniques, providing deep insights into its catalytic performance. We also explore Pd cluster migration on the surface of the support under flow conditions, providing insights into the mechanism of catalysis. We show that even under flow, Pd migration from anchoring sites seems to be minimal over 4 h, with the catalyst stability assisted by APTES anchoring. [ABSTRACT FROM AUTHOR]

As biodiesel (BD)/Fatty Acid Alkyl Esters (FAAE) is derived from vegetable oils and animal fats, it is a cost-effective alternative fuel that could complement diesel. The BD is processed from different catalytic routes of esterification and transesterification through homogeneous (alkaline and acid), heterogeneous and enzymatic catalysis. However, heterogeneous catalysts and biocatalysts play an essential role towards a sustainable alternative to homogeneous catalysts applied in biodiesel production. The main drawback is the supporting material. To overcome this, currently, Metal-Organic Frameworks (MOFs) have gained significant interest as supports for catalysts due to their extremely high surface area and numerous binding sites. This review focuses on the advantages of using various MOFs structures as supports for heterogeneous catalysts and biocatalysts for the eco-friendly biodiesel production process. The characteristics of these materials and their fabrication synthesis are briefly discussed. Moreover, we address in a general way basic items ranging from biodiesel synthesis to applied catalysts, giving great importance to the enzymatic part, mainly to the catalytic mechanism in esterification/transesterification reactions. We provide a summary with recommendations based on the limiting factors. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) are currently gaining considerable attention as heterogeneous catalysts. Since the functionality of the framework and the pore size of the MOFs can be adjusted over a wide range for various catalytic reactions, the usage of these materials as solid catalysts is attractive. One of the preferred catalytic mesoMOFs is MIL-101 (MIL: Material of Institute Lavoisier) family which has been mainly investigated. The large surface area, high pore volumes, and acceptable solvent/thermal stability (MIL-101(Cr) up to 300 °C) have led the MIL-101 family to be considered an ideal and widespread MOF for use as a great heterogeneous catalyst or solid support for a variety of reactions. The objective of this review is to present recent research on the use of the MIL-101 family for heterogeneous catalysis in gas and liquid phase reactions. [ABSTRACT FROM AUTHOR]

Support structures of various materials are used to enhance the performance of catalytic process chemistry. Typically, fixed bed supports contain regular channels enabling high throughput because of the low pressure drop that accompanies high flow rates. However, many fixed bed supports have a low surface-area-to-volume ratio resulting in poor contact between the substrates and catalyst. Three dimensional polymer printing (3dP) can be used to overcome these disadvantages by offering precise control over key design parameters of the fixed bed, including total bed surface area, as well as accommodating system integration features that are compatible with continuous flow chemistry. Additionally, 3dP allows for optimization of the catalytic process based on extrinsic constraints (e.g. operating pressure) and digital design features. These design parameters together with the physicochemical characterization and optimization of catalyst loading can be tuned to prepare customizable reactors based on objectives for substrate conversion and desired throughput. Using a Suzuki (carbon–carbon) cross-coupling reaction catalyzed by palladium, we demonstrate our integrated approach. We discuss key elements of our strategy including the rational design of hydrodynamics, immobilization of the heterogeneous catalyst, and substrate conversion. This hybrid digital-physical approach enables a range of pharmaceutical process chemistries spanning discovery to manufacturing scale. [ABSTRACT FROM AUTHOR]

In this study, oxidative desulfurization was performed on simulated oil fraction consist of 1000 ppm dibenzothiophene. Cobalt supported on natural zeolite of Kaolin has been used as heterogeneous catalysts. 10% Co/metaKaolin with hydrogen peroxide as oxidant and acetonitrile as extraction solvent have shown excellent performance on desulfurization. Response surface methodology in experimental design and its subset Box–Benken was used to evaluate the performance of the selected catalyst in different operating conditions such as temperature, oxidant to sulfur molar ratio, time and catalyst amount. Also, optimum conditions was obtained are equal to 60 °C, O/S molar ratio (10.8 mol/mol), time (46 min) and catalyst amount 0.04 g with 97.1% sulfur removal. Oxidative desulfurization of model oil containing 1000 ppm of each sulfur component benzothiophene and thiophene was also tested at the optimum conditions, Oxidative desulfurization yield was ordered as DBT > BT > Th. In addition, after four steps consecutive recycle under optimum conditions oxidative desulfurization capacity of 10% Co/metaKaolin catalyst decreased from 97% to 92%, which is still high desulfurization capability. Finally, the performance of 10% Co/metaKaolin catalyst in oxidative desulfurization was evaluated for real oil fractions, gasoline and gasoil that was provided from regional oil refinery with sulfur content of 286 ppm and 7900 ppm, respectively. At the optimum conditions of operating variables desulfurization yield was 58% and 79% of total sulfur removal for gasoline and gasoil respectively with no significant changes in fuels properties. [ABSTRACT FROM AUTHOR]

Microreactors are small in size with significant heat and mass transfer. Performic acid (PFA) is an important organic compound. It has broad applications in food, oil and chemical industries because of its oxidizing properties. In the present work PFA is produced in a continuous flow Teflon spiral capillary microreactor. The PFA is produced with and without a heterogeneous catalyst. The formic acid (FA) and hydrogen peroxide (HP) are the reactants to produce the PFA. It is a reversible reaction. The aim of the present work to monitor the consequence of hydrogen peroxide concentration, temperature and heterogeneous catalyst (Amberlite) for conversion of the FA. The experimental results showed that the formation of the PFA is effected with increase in hydrogen peroxide concentration, percentage of catalyst and temperature. The PFA formed within short residence time by the use of solid catalyst. The heterogeneous catalysts are better in decreasing corrosion and segregation of the catalyst compared to homogeneous catalysts. The best conditions for the PFA synthesis reaction were noted that 10 min residence time, 30 w/v% of HP, 6 wt% of catalyst concentration based on formic acid and 30 °C. Hence, the maximum concentration of the PFA was recorded 2.8 mol/L (XFA = 39.4%) [ABSTRACT FROM AUTHOR]

Biodiesel is a promising clean energy supply that can be made from sustainable and low-grade fuels using a variety of methods. Transesterification is one of the processes that can occur in the manifestation of an effective catalyst. The catalyst may be homogeneous or heterogeneous in nature. This article reviews on the formation of biodiesel from various sources of waste oils using heterogeneous nanocatalysts. The manufacture of biodiesel using homogeneous and heterogeneous catalysis had been extensively studied, and new heterogeneous catalysts are constantly being examined. In general, homogeneous catalysts are effective at remodeling biodiesel with low free fatty acid (FFA) and single-origin feedstock having water. Heterogeneous catalysts, instead have higher interest, a wider scope of selectivity, better FFA, and better water adaptability. These properties are regulated by the number and intensity of active basic or acid sites. In order to achieve a viable alternative to conventional homogeneous catalysts for biodiesel processing, heterogeneous catalysts made from waste and biocatalysts are needed. Nanocatalysts have recently attracted interest due to their high catalytic performance under favorable operating conditions. This review evaluates the usage of heterogeneous nanocatalysts for the production of biodiesel from different sources of waste oil and the factors effecting the process of biodiesel production. [ABSTRACT FROM AUTHOR]

The work that has been carried out on microwave irradiation applied in catalyst preparation for drying, calcination or postsynthesis methods, and as a heating source for the Fischer–Tropsch reaction has been reviewed. It has been found that microwave irradiation can, in some cases, greatly enhance the performance of heterogeneous catalyst systems for Fischer–Tropsch synthesis. We have also summarized the advantages and drawbacks of using microwave irradiation in Fischer–Tropsch catalyst preparation and postsynthesis, and identified opportunities for future investigation. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the performance of nano-γ-Fe2O3–SO3H catalyst in the Biginelli reaction and synthesized 3,4-dihydropyrimidine-2-(1H)-ones. This reaction was carried out under solvent-free and ultrasonic irradiation conditions and belonged to one-pot multicomponent reactions (MCRs) with an adopted aromatic aldehyde, ethyl acetoacetate, and urea as starting materials for the beginning of the reaction. The synthesized materials were efficient in synthesizing 3,4-dihydropyrimidine-2-(1H)-ones via the Biginelli reaction under reaction conditions. Thus, the advantages of using nano-γ-Fe2O3–SO3H in the Biginelli reaction are short reaction time, high efficiency, green method, solvent free, and cost-effective. Furthermore, nano-γ-Fe2O3–SO3H as a heterogeneous catalyst can be recycled five times without significantly reducing catalytic activity. [ABSTRACT FROM AUTHOR]

This study focusses on the production of biodiesel by reacting the heterogeneous based nano-catalysts with used cooking oil in the presence of methanol. The CZO nanoparticles (NPs) were synthesized by co-precipitation method and characterized by different techniques. Biodiesel was characterized by the gas chromatograph (GC) and Fourier Transform Infra-red Spectroscopy (FTIR). Optimum conditions for the maximum biodiesel yield (90%) were 0.2% (w/w) catalyst dose, 3:1 methanol to oil ratio, 50 °C reaction temperature, 150 min reaction time and 136 rpm stirring speed. The kinetic modeling and the thermodynamic factors like enthalpy (ΔH), activation energy (Ea), entropy (ΔS) and free energy (ΔG) were operated on all the data. Mean and standard deviation was used for analysis of data. The results indicate the maximum biodiesel yield under the optimum reaction conditions, which is promising to reduce the pollution such as air pollution and greenhouse effect for sustainable environmetal development. [ABSTRACT FROM AUTHOR]

MIL-125(Ti) metal–organic framework-derived nanoporous titanium dioxide–heteropoly acid (PW–TiO2) have been synthesized by a facile hydrothermal approach and subsequent calcination, and the PW–TiO2 catalysts were investigated using various characterization technologies including FTIR, XRD, SEM, TEM, N2-physisorption, and NH3-TPD. Further, we investigated the use of PW–TiO2 composites as heterogeneous acid catalysts for the catalytic esterification of oleic acid. Among all series of catalysts, the calcined PW–TiO2 at a temperature of 350°C showed excellent activity with a high conversion of 90.5% at 160°C for 4 h. More importantly, the catalyst could be simply separated via centrifugation and reused for six cycles and shows a relatively high conversion of 74.8%. [ABSTRACT FROM AUTHOR]

The synergistic relationship between the reactor and the catalysts has gained immense popularity in the field of Chemical Engineering due to their wide application. Catalytic processes have evolved over the decades from expensive commercial catalysts to low-cost solid waste catalysts for the sustainable development and reduction of their impacts on the environment. This alternative use of solid waste can greatly decrease the cost of wastewater treatment and addresses solid wastes issues. Bauxite Residue (BR) is one such waste from alumina-based industries with excellent catalytic properties. The fluid dynamics of fluidized bed technology improves profoundly the hydrodynamics and mass transfer of the heterogeneous Fenton process. This paper presents the preparation of the catalyst with minimum processing effort. It was characterized and factors affecting the degradation efficiency of synthetic dye wastewater were investigated. The optimum conditions for the eosin yellow dye were observed at a pH of five, oxidant concentration of 30 mM, catalyst dosage of 4 g/L. The removal efficiency at these optimum conditions was observed to be 91%. The residence time distribution (RTD) study was aimed to determine the behavior of the reactor using the mean residence time, variance, and dispersion number for the fluidized bed reactor. [ABSTRACT FROM AUTHOR]

Nano-magnetite-supported sulfated polyethylene glycol (Fe3O4@PEG-SO3H) was prepared, characterized and utilized as a magnetically recoverable heterogeneous catalyst for the one-pot, three-component reaction of 2-aminobenzothiazole, aldehydes and 2-naphthol/isatoic anhydride resulting in efficient formation of 1-(benzothiazolylamino)arylmethyl-2-naphthol or dihydroquinazolinones derivatives. The significant features of this method include green conditions, operational simplicity, minimizing production of chemical waste, shorter reaction times and good to high yields. In addition, the nanocatalyst can easily be separated from the reaction mixture by application of a magnetic field and reused without significant deterioration in its catalytic activity. [ABSTRACT FROM AUTHOR]

Among the synthetic strategies commonly used for supporting a metal complex onto an organic polymer in order to obtain an heterogenous catalyst, a valid choice is to synthesize a metal containing monomer (MCM), which can subsequently be subjected to polymerization with suitable comonomers and crosslinkers, achieving a supported transition metal catalyst as a metal-containing polymer (MCP). In this context, during the last two decades, we explored the use of 2-(acetoacetoxy)ethyl methacrylate (HAAEMA) as a ligand to prepare several MCMs for the relevant MCPs. In this review we summarize and discuss our developments in the studies of the catalytic activity of these “hybrid” catalysts. These catalysts have demonstrated high efficiency and/or excellent selectivity in several kinds of chemical reactions and very often they could be recovered and reused in multiple cycles maintaining their activity and selectivity without suffering from appreciable metal leaching.

This review summarizes Russian developments on the most important industrial processes of hydrocarbon feedstock refining according to the data of the last 15–20 years on the kinetics of deactivation of heterogeneous and liquid-phase catalysts under non-stationary conditions. The methodological aspects of the creation and application of kinetic models for the deactivation of heterogeneous and liquid-phase catalysts under non-stationary conditions are considered. It is shown that high efficiency of catalytic technologies is ensured by regulation of hydrodynamic and thermal conditions of industrial processes of gasoline reforming, alkane dehydrogenation, alkylation of benzene with higher alkenes and catalytic dewaxing using kinetic models, which take into account catalyst deactivation. [ABSTRACT FROM AUTHOR]

To reveal the catalytic potential of abandoned naturally occurring material, we synthesized titania-termite hill composite (Ti-THC) via an incipient wetness impregnation route, characterized by various techniques and tested as a catalyst for transesterification of waste frying oil (WFO). The reusability of the prepared catalyst was also studied to evaluate its stability. The effects of reaction process parameters, such as temperature, time, catalyst loading and methanol/WFO molar ratio on fatty acid methyl ester (FAME) yield, were investigated using a central composite design approach. SEM result revealed pores formation on the catalyst surface, while XRD and EDX analyses confirmed successful insertion of titania into the aluminosilicate layer of the termite hill. The maximum FAME yield of 90.78% was obtained at optimum experimental conditions of 71.16 °C reaction temperature, 2.12 h reaction time, 1.03 wt.% catalyst loading and 9.96:1 methanol/WFO molar ratio. The catalyst still maintained its better stability after being reused for three reaction cycles. [ABSTRACT FROM AUTHOR]

In order to meet the stringent environmental and industrial legislation on fuel specifications, sulfur compounds have to be removed efficiently from fuels. The requirement to produce ultralow-sulfur fuels (S < 10 ppm) has stimulated many works in the area of conventional hydro-desulfurization (HDS) method. Oxidative desulfurization (ODS), as an alternative or complementary technology to HDS for deep desulfurization, is conducted with high selectivity and reactivity to sterically hindered S compounds under mild reaction conditions. In the ODS process, using an appropriate oxidant in the presence of a catalyst, organic sulfur compounds can be oxidized selectively to their corresponding sulfoxides and sulfones, which can be easily removed by different separation methods. Having great catalytic characteristics, polyoxometalate materials have been utilized as a vital class of catalysts for deep desulfurization of fuels. In the past few decades, ODS of fuels using polyoxometalate as catalyst has drawn much attention, and various studies have been carried out in this area. Here, we give a critical review for the removal of sulfur compounds from liquid fuels (mostly from diesel and model fuels) by ODS via homogeneous and heterogeneous polyoxometalate catalysts. [ABSTRACT FROM AUTHOR]

One of the essential themes in modern catalysis is that of bridging the gap between its homogeneous and heterogeneous counterparts to combine their individual advantages and overcome shortcomings. One more incentive can now be added to the list, namely the ability of transition metal complexes to provide strong nuclear magnetic resonance (NMR) signal enhancement upon their use in homogeneous hydrogenations of unsaturated compounds with parahydrogen in solution. The addition of both H atoms of a parahydrogen molecule to the same substrate, a prerequisite for such effects, is implemented naturally with metal complexes that operate via the formation of a dihydride intermediate, but not with most heterogeneous catalysts. Despite that, it has been demonstrated in recent years that various types of heterogeneous catalysts are able to perform the required pairwise H2 addition at least to some extent. This has opened a major gateway for developing highly sensitive and informative tools for mechanistic studies of heterogeneous hydrogenations and other processes involving H2. Besides, production of catalyst-free fluids with NMR signals enhanced by 3-4 orders of magnitude is essential for modern applications of magnetic resonance imaging (MRI), including biomedical research and practice. The ongoing efforts to design heterogeneous catalysts which can implement the homogeneous (pairwise) hydrogenation mechanism are reported. [ABSTRACT FROM AUTHOR]

The synthesis of monoglycerides by the transesterification of triglycerides with glycerol was studied using zinc glycerolate as a heterogeneous catalyst. The effect of the operating variables on the triglyceride conversion and monoglyceride yield was evaluated. The maximum values of triglyceride conversion and monoglyceride yield reached at 2-hour reaction time were 83 and 49 %, respectively. These values were obtained at 240 °C with 3 % catalyst loading and glycerol/oil molar ratio of 6. When the molar ratio of the reactants was increased, the triglyceride conversion and monoglyceride yield achieved an optimum value. This behavior was related with a competitive adsorption of the reagents. It was possible to reuse the catalyst without significant changes in activity. [ABSTRACT FROM AUTHOR]

A simple and rapid method for the preparation of benzopyranophenazines is presented, involving a one-pot four-component reaction of hydroxynaphthoquinone, o-phenylenediamine, benzaldehydes, and malononitrile with nano-Fe3O4@chitosan as an efficient heterogeneous solid acid catalyst under reflux conditions in ethanol. The catalyst is characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), magnetic susceptibility measurements, energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared (FT-IR) spectroscopy. Atom economy, high catalytic activity, a wide range of products, excellent yields in short reaction times, and low catalyst loading are some of the important features of this method. [ABSTRACT FROM AUTHOR]

A simple and rapid method for the preparation of benzopyranophenazines is presented, involving a one-pot four-component reaction of hydroxynaphthoquinone, o-phenylenediamine, benzaldehydes, and malononitrile with nano-Fe3O4@chitosan as an efficient heterogeneous solid acid catalyst under reflux conditions in ethanol. The catalyst is characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), magnetic susceptibility measurements, energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared (FT-IR) spectroscopy. Atom economy, high catalytic activity, a wide range of products, excellent yields in short reaction times, and low catalyst loading are some of the important features of this method. [ABSTRACT FROM AUTHOR]

Coupling of second and first order reactions in one pot fashion through a cascade process is an often encountered process. Consecutive reactions of this type are considered and selectivity analysis is performed demonstrating dependence of selectivity pattern on reaction parameters. [ABSTRACT FROM AUTHOR]

The effect of the metal-support interaction (MSI) has been discussed for several types of catalytic systems comprising metal nanoparticles (Ni, Pd, Au, Fe) on oxide and carbon supports, showing promising catalytic properties in hydrogenation of unsaturated C–C bonds, hydrodechlorination (HDC) of chlorinated organic molecules and CO total oxidation. The MSI of a different strength, from the redistribution of the electron density of nanoparticles (NPs) to the chemical interactions, is determined by the composition of the support and the active site, the method of active metal deposition, calcination temperature, particle size etc. The types of MSI considered in this review include: (1) the interaction of the active metal (Me) NPs with alumina and modified zirconia to form several oxidation states of Me in the composition of surface or bulk chemical compounds with a support; (2) the influence of oxide (alumina, silica) or carbon (highly oriented pyrolytic graphite, Sibunit) supports on the formation of active sites in the catalysts with ultra-low Me loading prepared by deposition of pre-formed metal NPs produced by laser electrodispersion (LED) or as colloidal dispersion; (3) the anchoring of Me NPs on the surface of carbon supports (nanodiamonds and carbon nanotubes) directly with a support surface, e.g. through surface defects, or through surface functional groups; (4) 'reverse' MSI in the Me@C composites, consisting of metal NPs, covered with the defected graphene layers or immersed into carbon matrix. It is demonstrated on the example of LED systems, that oxidation of metal under MSI is less significant in carbon-supported systems than in oxide-supported ones, but charge effects can play a noticeable role for both types of supports. Different ways of MSI tuning provide the possibilities to achieve the optimal Men+/Me0 ratio in the catalysts for HDC of mono- and polychlorinated organic molecules, including persistent organic pollutants. One of these ways is tuning the composition of functional groups on the surface of nanodiamonds and carbon nanotubes by additional treatments to achieve the desirable metal anchoring, the optimal metal NPs size and the improved catalytic properties. Unusual type of MSI is represented by the activation of thin graphene shell of Me@C composites by the presence of defects in the shell and a transition metal (Ni, Fe) in subsurface layer. This effect allows H2 activation that is a significant step in many industrially important reactions. The selectivity and activity of such systems can be intentionally changed by varying the nature of metal and reaction temperature. Significant attention has been given in the review to the novel catalytic systems described in the previous works of the authors. [ABSTRACT FROM AUTHOR]

Highly effective tungsten-based carbon nanotubes (W/CNT) were synthesized and used as a heterogeneous catalyst for the oxidation of dibenzothiophene (DBT) with the oxidant H2O2. The obtained materials were characterized by modern methods. The Langmuir–Hinshelwood kinetics model described the precursor mechanism of the reaction well through an intermediate compound. The low activation energy showed that the reaction was mainly controlled by diffusion. The positive activation enthalpy proved the endothermic nature of the activation process, and this process did not alter the inside structure of the catalyst. The thermodynamic parameters of the reaction were determined, which implied that the oxidation was endothermic and spontaneous at 303 K. The more negative values of the Gibbs free energy from 283 to 323 K confirmed that the reaction was more favorable at high temperatures. The stability and activity of catalyst were retained after three reaction cycles. [ABSTRACT FROM AUTHOR]

The reduced availability of propylene and C4 products from steam crackers continues to provoke on-purpose technologies for light olefins such that almost 30% of propylene in 2025 is predicted to be supplied from unconventional sources. Furthermore, the recent discoveries of natural gas reservoirs have urged interest in the conversion of surplus alkanes and alkenes, especially ethane and ethylene. The direct conversion of ethylene to propylene or a combination of value-added chemicals, including butylenes and oligomers in the range of gasoline and diesel fuel, provides the capability of responding to the fluctuations in the balance between supply and demand of the main petrochemicals. A comprehensive review of heterogeneous catalysts for the gas-phase conversion pathways is presented here in terms of catalytic performances (ethylene conversion and product selectivities), productivities, lifetimes, active sites, physicochemical properties, mechanisms, influence of operating conditions, deactivation and some unresolved/less-advanced aspects of the field. The addressed catalysts cover both zeolitic materials and transition metals, such as tungsten, molybdenum, rhenium and nickel. Efforts in both experimental and theoretical studies are taken into account. Aside from the potential fields of progress, the review reveals very promising performances for the emerging technologies to produce propylene, a mixture of propylene and butenes, or a liquid fuel from ethylene. [ABSTRACT FROM AUTHOR]

Due to increasing concerns about global warming and dwindling oil supplies, the world’s attention is turning to green processes that use sustainable and environmentally friendly feedstock to produce renewable energy such as biofuels. Among them, biodiesel, which is made from nontoxic, biodegradable, renewable sources such as refined and used vegetable oils and animal fats, is a renewable substitute fuel for petroleum diesel fuel. Biodiesel is produced by transesterification in which oil or fat is reacted with short chain alcohol in the presence of a catalyst. The process of transesterification is affected by the mode of reaction, molar ratio of alcohol to oil, type of alcohol, nature and amount of catalysts, reaction time, and temperature. Various studies have been carried out using different oils as the raw material; different alcohols (methanol, ethanol, butanol); different catalysts; notably homogeneous catalysts such as sodium hydroxide, potassium hydroxide, sulfuric acid, and supercritical fluids; or, in some cases, enzymes such as lipases. This article focuses on the application of heterogeneous catalysts for biodiesel production because of their environmental and economic advantages. This review contains a detailed discussion on the advantages and feasibility of catalysts for biodiesel production, which are both environmentally and economically viable as compared to conventional homogeneous catalysts. The classification of catalysts into different categories based on a catalyst’s activity, feasibility, and lifetime is also briefly discussed. Furthermore, recommendations have been made for the most suitable catalyst (bifunctional catalyst) for low-cost oils to valuable biodiesel and the challenges faced by the biodiesel industry with some possible solutions. [ABSTRACT FROM AUTHOR]

Heterogeneous catalysts play an important role in the chemical industry and are also of critical importance in the general well-being of society in the 21st century. Increasing demands are being placed on catalyst performance in a number of areas such as activity, selectivity, longevity, and cost. Conventional approaches to improving catalytic performance are becoming exhausted, and novel ways of generating the increased performance are being sought. The utilization of cold plasmas has opened great opportunities for modification of catalysts, thanks to their room-temperature operations with reduced energy combustion, shortened duration, and undestroyed bulk structure. In this review, we present an assessment of the modification of catalysts by cold plasmas, with emphasis on particle sizes, dispersion of nanoparticles, distribution of elements, electronic properties, acid-base properties, surface functional groups, and metal-support interaction. Moreover, challenges and perspectives are also presented for the further modification of catalysts by cold plasmas and broadening their practical applications. [ABSTRACT FROM AUTHOR]

The title compounds were synthesized by a three-component reaction of 4-hydroxycoumarin, aromatic amines and α,β-epoxy ketones, catalyzed by ZnOZnAl 2O4 nanocomposite. [ABSTRACT FROM AUTHOR]

In the present study, we have investigated the counter-ion effect on the thermodynamics of Cr(III) sorption by macroporous resin Amberlyst-15. The exchange reaction was studied as a function of concentration of Cr(III) and nature of counter-ions at different temperatures. It was observed that nature of counter- ions have a profound effect on the exchange of Cr(III) ions. The selectivity of Amberlyst-15 towards metal ion sorption follows the order univalent > divalent > trivalent forms. This trend can be associated to the electrostatic interaction of ions with the functional sites of the resin. The equilibrium pH values (pHeq) were observed to decrease with Cr3+/H+ exchange whereas an increase in pHeq was detected during the exchange of Cr3+/Li+, Cr3+/Na+, Cr3+/Ca2+ and Cr3+/Al3+. Different adsorption models such as Dubinin-Radushkevich (D-R) and Langmuir were employed to analyze the sorption data. The maximum exchange capacities (Xm) and binding energy constants (Kb) values were determined by using the Langmuir model. The values of both ∆Hº and ∆Sº were found positive inferring that the exchange process is endothermic accompanied by the dehydration of Cr(III) ions. The thermodynamic parameters revealed that the mechanism of Cr(III) sorption for all the counter ions is entropy driven ion exchange. [ABSTRACT FROM AUTHOR]

A composite catalytic membrane (CCM), as a heterogeneous catalyst, was prepared from sulfonated polyethersulfone (SPES) and polyethersulfone (PES) impregnating polyphenylene sulfide (PPS) non-woven fabric by solvent evaporation method, which was employed to produce butyl acetate from continuous esterification of acetic acid with n-butyl alcohol in a flow-through mode. The pervaporation-assisted esterification was also carried out to promote forward reaction of the esterification through online removing the water produced. The results showed that the n-butyl alcohol conversion was over 95.0 % at the reaction temperature of 363 K, the initial acetic acid/n-butyl alcohol molar ratio of 4:1 and the residence time of 4,000 s in single flow-through mode. In the pervaporation-assisted esterification, an obvious enhancement in conversion was achieved compared with the esterification without pervaporation. And the CCMs presented a good catalytic activity and stability. [ABSTRACT FROM AUTHOR]

Researchers normally consider MgO as a promising high-surface-area heterogeneous catalyst support, additive, and promoter for many kinds of chemical reactions due to its certain properties, including stoichiometry and composition, cation valence, redox properties, acid-base character, and crystal and electronic structure. The presence of MgO as a support catalyst also modifies the electronic state of the overall catalytic performance by electron transfer between the native catalyst and MgO as support. The influence is clarified by alteration of acid-base properties of the catalyst-supported MgO. Meanwhile, the method, chemical composition, and condition in the preparation of MgO are the important factors affecting its surface and catalytic properties. Therefore, MgO with a high surface area and nanocrystalline structure has encouraging applications for some reactions, including as dry reforming, dehydrohalogenation, oxidative dehydrogenation of butane, nonoxidative dehydrogenation of ethylbenzene, decomposition of CCl4, oxidative coupling of methane, hydrodesulfurization reactions, methane dimerization, and water gas shift reaction oxidation of CO by O2 and ISO-propane conversion. This review highlights the synthesis and the role of MgO as a support catalyst and focuses on the design of better selective, energy-saving, durable, intrinsically clean, and safer catalytic processes. [ABSTRACT FROM AUTHOR]

In the past few years, there have been many researches on the use of different types of homogenous catalyst for the degradation of textile wastewater in conventional advanced oxidation processes (AOPs). However, homogenous AOPs suffer from few limitations, including large consumption of chemicals, acidic pH, high cost of hydrogen peroxide, generation of iron sludge, and necessity of post-treatment. Therefore, recently, there have been more researches that focus on improving the performance of conventional AOPs using heterogeneous catalysts such as titanium dioxide, nanomaterials, metal oxides, zeolite, hematite, goethite, magnetite, and activated carbon (AC). Besides, different supports such as AC that have been incorporated with transition metals and clays have been proven to have excellent catalytic activity in AOPs. This paper presents a comprehensive review of advances and prospects of catalytic AOPs for the decontamination of a wide range of synthetic and real textile wastewater. This review provides an up-to-date critical review of the information on the degradation of various textile dyes by a wide range of heterogeneous catalysts and adsorbents. The future challenges of AOPs, including chemical consumption, toxicity assessment, reactor design, and limitation of catalysts, are discussed in this paper. In addition, this paper also discusses the presence of ions, generation of by-products, and industrial applications of AOPs. Special emphasis is given to recent studies and large-scale combination of AOPs for wastewater treatment. This review paper concludes that more studies are needed for the kinetics, reactor design, and modeling of hybrid AOPs and the production of their corresponding intermediate products and secondary pollutants. A better economic model should also be developed to predict the cost of AOPs, as the treatment cost varies with dyes and textile effluents. [ABSTRACT FROM AUTHOR]

The amount of waste generated in cashew nut processing factories has caused serious problems for a long time. However, this situation is about to change because they are being turned into an opportunity by a variety of bio-based chemicals. Todate, cashew nut shells (CNS) have proven to be among the most versatile renewable resource as they produce cashew nut shell liquid (CNSL). CNSL which is a dark reddish brown viscous liquid (ca. 30-35 wt%) is extracted from the soft honeycomb of the CNS. The shells have been regarded as a by-product of the cashew industry though now it is a cheaper source of natural unsaturated phenols. CNSL offers a multitude of interesting possibilities for the synthesis of speciality chemicals, high value products and polymers. Our recent research efforts have demonstrated that its constituents can be transformed into diverse functional chemicals. This paper reports some key results on how cashew nut shells (an agro waste from cashew nut processing factories) have been employed to produce several functional materials and chemicals. The materials that are highlighted include the synthesis of 3-propylphenol from cardanol and anacardic acid, some polymers prepared from CNSL components, heterogeneous catalysts prepared using CNSL as a templating agent and anacardic acid capped chalcogenide nanoparticles. [ABSTRACT FROM AUTHOR]

In this work, electrochemical studies on the seven-coordinate iron complex (FeIII/IIdapsox), a functional model for the superoxide dismutase enzyme (SOD mimetic), were performed in an aqueous solution over the pH range 1-12 (with and without buffers) to conceive the underlying heterogeneous proton-coupled electron transfer (PCET) processes of various complex species. The thermodynamics of the corresponding proton transfer, electron transfer, and PCET processes have been evaluated as well as the kinetics of related heterogeneous electrode reactions of all complex species in solution. Measurements in D2O have also been carried out for selected redox couples to assess a possible kinetic isotope effect (KIE). In the case of a two-proton one-electron transfer process in the absence of a buffer, the KIE was found to be 4.8, whereas in the case of a one-proton one-electron transfer process in buffered solutions, an inverse KIE was observed. The overall data suggest the operation of a concerted PCET mechanism for the two-proton one-electron transfer process, whereas involvement of an H-bonded precursor adduct formed between the buffer components, and the complex species within a one-proton one-electron transfer mechanism is feasible. These results shed light on both the enzymatic and the mimetic SOD mechanisms, speaking in favor of the two-proton one-electron transfer process as a desirable mechanism for efficient catalytic superoxide dismutation. [ABSTRACT FROM AUTHOR]

A number of heterogeneous acid type catalysts of silica-alumina nature, which are proposed to be used for petrochemistry by-product oligomerization, have been investigated. Particularly, such key indicators as active site concentration and strength have been determined. These parameters have been determined by the method based on potentiometric titration that is relatively seldom used in heterogeneous catalysis. The number of active site types present in investigated catalysts, as well as concentrations of each type of site, has been determined by mathematical processing of potentiometric titration data. The sequence of mathematical processing of titration data is described. The relationship between the properties of the investigated catalysts and their effectiveness in heterogeneous catalytic cooligomerization of the C fraction of liquid products of diesel fuel pyrolysis has been analyzed. The relationships between yields achieved in the presence of various catalysts and the properties of these catalysts have been defined. Namely, it was determined that the product yield is almost proportional to the active site's concentration of the catalysts (activated clay materials). The relationship between the strength of active sites and average molecular weight of the cooligomers has been found. The causes of obtained regularities have been analyzed and explained. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Molecular transformations using Au, Pd, and Cu nanoporous skeleton catalysts and the reactivity difference between those catalysts and the corresponding well-known homo-geneous molecular catalysts are described. Nanoporous skeleton catalysts (e.g., PdNPore) can be fabricated through dealloying of the corresponding Pd-containing alloy PdxM1yM2z. [ABSTRACT FROM AUTHOR]

The article offers information on a couple of chemical engineering studies, published within the issue, including "Heterogeneous Catalysts for Gas-Phase Conversion of Ethylene to Higher Olefins" and " Synthesis of Organophosphorus Compounds Using Ionic Liquids."