Heterogeneous Catalysis

All chemicals were purchased from Sigma-Aldrich and S.D Fine Chemicals, Pvt. Ltd. India and used as received. The particle size and morphology of the samples were studied using Philips TECNAI F12 FEI Transmission Electron Microscope (TEM). The X-ray powder diffraction (XRD) patterns were recorded on a Rigaku diffractometer with Cu K radiation. X-ray Photoelectron Spectra (XPS) were obtained using a PHI Quantera SXM (ULVAC-PHI), which was equipped with a monochromatic Al K X-ray source. The analysis area was defined by the X-ray beam, and the X-ray beam size was 1.5×0.1 mm at 60 W for both wide and high resolution spectra; the photoelectron take-off angle was 45 degrees. Wide spectra were obtained at a pass energy of 280 eV with 0.5 eV step and high resolution spectra were obtained at a pass energy of 26 eV with 0.1 eV step for C 1s and a pass energy of 55 eV with 0.1 eV step for N 1s and O 1s. The IR spectra of all compounds were recorded on a Perkin-Elmer, Spectrum GX FTIR spectrometer. The IR values are reported in reciprocal centimeters (cm -1 ). ESI mass spectra were recorded on a Finnigan LCQ Advantagemax spectrometer. High-resolution mass spectra (HRMS) were recorded on QSTAR XL Hybrid MS/MS mass spectrometer using ESI-QTOF mass spectrometry. All the glassware was dried before use.

This study presents a novel class of pseudohomogeneous catalysts (PHC) based on carbon quantum dots functionalized with terpyridine ligands (CQDs-Tpy) to immobilize and stabilize palladium nanoparticles (Pd NPs). Extensive characterization techniques clearly confirmed the successful stabilization of Pd NPs on CQDs-Tpy. The effectiveness of the catalyst was demonstrated in the selective aerobic oxidation of primary and secondary of benzylic alcohols to aldehydes in the absence of additives and phase transfer catalyst (PTC). Remarkably, the reactions predominantly yielded aldehydes without further oxidation to carboxylic acids. By employing low catalyst loadings (0.13 mol%), high conversions (up to 89%) and excellent selectivity (> 99%) of the aldehyde derivatives were achieved. Moreover, the CQDs-Tpy/Pd NPs catalyst displayed suitable catalytic activity and recyclability, offering potential economic advantages. This promising approach opens up new opportunities in the field of catalysis for designing subnanometric metal-based PHCs. The oxidation of alcohols is the efficient and significant reaction pathway for the achievement of the carbonylcontaining compounds. The carbonyl-containing compounds have always been dominant compounds because they have frequently been utilized as precursors in the synthesis of a plethora of high-value product . Despite the large number of undesirable environmental and economic effects continue to use stoichiometric oxidations such as Dess-Martin periodinane (DMP), Swern, Pfitzner-Moffatt, Corey-Kim, Jones, Collins, Oppenauer and pyridinium chlorochromate (PCC) reagents . Recent ideas on catalytic research led to the usage of environmentally benign oxidant such as molecular oxygen and hydrogen peroxide (H 2 O 2 ) in combination with active and selective recyclable catalysts based on transition-metal (such as Pd, Ru, Ir, Rh, Fe, Cu, Pt, Au, Ag, etc.,). These developments have paved the way for more sustainable oxidation reactions, addressing the drawbacks associated with traditional stoichiometric oxidations In recent years, substantial advancements have been achieved in the realm of developing cost-effective heterogeneous catalysts for selective oxidation, with a dedicated focus on the principles of green chemistry. Nevertheless, this field remains a captivating and extensively explored subject within the scientific literature, attracting significant attention and interest . Despite the introduction of catalytic systems with high activity and selectivity for this type of transformation, their industrial applications are hindered by issues related to recovery, recyclability, and environmental concerns. Furthermore, the complexity and cost of catalyst manufacturing, as well as the use of toxic and hazardous substances, restrict their widespread utilization in large-scale quantities. In light of these challenges, heterogeneous Pd catalysis emerges as a promising avenue of research to overcome these obstacles . In the past two decades, nanocatalysts have indeed played a pivotal role in advancing synthetic organic transformations. Heterostructure nanocatalysts are typically prepared by dispersing and stabilizing nano-scale

Binary materials composed of the oxides SiO2, TiO2 and N‐doped TiO2 and the Keggin heteropolyacid (PW12) were prepared and physicochemically characterized. They were used as catalysts and photocatalysts for the hydration of propene to 2‐propanol. The characterization of the samples, particularly the electron paramagnetic resonance (EPR) spectroscopy results and the acidity properties, were useful to explain the key role played by the PW12 in the composite materials in the thermal and photoassisted catalytic processes. The simultaneous presence of heat and UV light improved the activity of PW12 in the thermal process, and the binary materials showed better (photo)catalytic activities than that of the bare PW12 in almost all cases. For the first time, this work evidenced through EPR spectroscopy that the increase of reactivity under irradiation could be attributed to the ability of photoexcited PW12 to trap electrons, particularly if the PW12 is supported. Moreover, the effect of wate...

Keggin silicotungstic acid (HPS) catalyst was heterogenized by loading (10-40 wt.%) over zirconia support, and resulting catalysts were named as ESZN-1 (10 wt.%), ESZN-2 (20 wt.%), ESZN-3 (30 wt.%) and ESZN-4 (40 wt.%) respectively. After that, synthesized catalysts were characterized using several tools and techniques which revealed that the Keggin structure of parent HPS catalyst remained intact after heterogenization. Eventually, synthesized catalysts performance evaluation tests were performed for the production of ethyl levulinate from biomass-derived levulinic acid under microwave heating irradiations. Under optimum operating conditions, more than 90% LA conversion with 100% EL selectivity was obtained at 110 o C temperature in 30 minutes in the presence of 100 mg ESZN-4 in a solution containing levulinic acid and ethanol in 1:43 ratio. A kinetic study on LA conversion in the presence of ESZN-4 catalyst revealed a pseudo first order mechanism for ethyl levulinate synthesis.

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Microwave-assisted synthesis of 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) in the presence of tungsten disulfide has been studied for the first time. The catalyst was synthesized at 600 o C in a tubular furnace using elemental tungsten and sulfur to obtain multilayered flakes/sheets of the WS 2 . The textural and morphological properties of the synthesized WS 2 catalyst were characterized using XRD, Raman, SEM, SEM-EDX, TEM, TEM-EDX, HR-TEM, SAED and surface area analyzer which showed the formation of multiple two-dimensional layers of sheets/flakes type structure. Activity test of the catalyst in a microwave-assisted reaction resulted in 100% fructose conversion and 62% EMF yield for the experiment performed at 160 o C temperature in 15 minutes. A qualitative analysis of the product samples using GC-MS spectrometry showed the presence of several intermediate and byproducts based on which a mechanistic insight into the production of EMF from fructose has been proposed.

Ethyl levulinate (EL) synthesis from biorenewable feedstocks in the presence of metal salts and under nonmicrowave instant heating reaction environment has been studied. Initial screening suggested CuCl 2 and FeCl 3 as an efficient catalyst for EL synthesis from 5-hydroxymethylfurfural (HMF), thereby resulting into 47.5% and 43.3% EL yield respectively at 160 • C in 5 min. Interestingly, environmentally benign and widely available metal salt, AlCl 3 , was found to yield comparable EL (39.0%) when experiments were performed under identical reaction conditions. Therefore, further study was performed using AlCl 3 to estimate the effect of operating parameters and catalyst concentration over EL yield and HMF conversion. Thereafter, a comparative study on the effect of microwave vs non-microwave instant heating reaction environment has been done to develop a sustainable process for EL synthesis. Consequently, mechanistic insights on reactant conversion and product yield have been attempted to understand various pathways followed. Thereafter, effect of reaction temperature, catalyst loading, ethanol concentration and heating rates were explored. EL synthesis from HMF under instant heating reaction conditions in the presence of metal salts is reported for the first time. We anticipate that present work would be helpful in providing insights on effects of instant heating method and operating conditions for EL synthesis from HMF.

The state-resolved reactivity of CH 4 in its totally symmetric C-H stretch vibration ( 1 ) has been measured on a Ni(100) surface. Methane molecules were accelerated to kinetic energies of 49 and 63:5 kJ=mol in a molecular beam and vibrationally excited to 1 by stimulated Raman pumping before surface impact at normal incidence. The reactivity of the symmetric-stretch excited CH 4 is about an order of magnitude higher than that of methane excited to the antisymmetric stretch ( 3 ) reported by Juurlink et al. [Phys. Rev. Lett. 83, 868 (1999)] and is similar to that we have previously observed for the excitation of the first overtone (2 3 ). The difference between the state-resolved reactivity for 1 and 3 is consistent with predictions of a vibrationally adiabatic model of the methane reaction dynamics and indicates that statistical models cannot correctly describe the chemisorption of CH 4 on nickel.

The quantum state-resolved reactivity S0 of SiH4 on Si(100)-2×1 has been measured for the first time for two vibrationally excited Si–H stretch local mode states (|2000⟩ and |1100⟩) as well the ground state S0 as a function of translational energy En and surface temperature Ts. We observe evidence for both direct and precursor-mediated chemisorption pathways. As expected, increasing En (or Ts) decreases S0 for the precursor-mediated reaction and increases S0 for the direct chemisorption. However, vibrational excitation of the incident SiH4 increases S0 for both the direct and the precursor-mediated pathway with a higher S0 for the |2000⟩ state than for the |1100⟩ state, indicating a nonstatistical reaction mechanism.

The Nano-CrY zeolite synthesized and characterized by Fourier transfer infrared (FT-IR), X-ray diffraction (XRD),and Scanning electron microscopy (SEM).The result show that nano catalyst prepared with mainly particles size about 30-80 nm. The XRD show the structure of the zeolite does not collapse. This Nano-CrY zeolite has been used as new, and nontoxic catalyst for catalyzes of synthesis of 2-aryl-1H-benzothiazoles at mild condition. This procedure is simple, effective, inexpensive and green. The products were obtained in high yields and the catalyst is reusable. Since products were obtained by aqua work-up in good purity, complex purification methods are not necessary.

Nanoparticulate transition-metal phosphides remain an unexplored, though emerging area of interest on the materials landscape, due principally to their promising magnetic and catalytic properties. This review describes synthetic strategies for the formation of both supported and unsupported transition-metal phosphide nanoparticles, provides a summary of their relevant magnetic and catalytic properties, and indicates new directions for exploration.

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A series of supported copper catalysts at two different loadings (1 and 2 wt%) have been prepared by deposition precipitation on various supports including TiO 2 , ZnO, Al 2 O 3 and active carbon and submitted or not to reductive treatments to favor the increase in population of Cu(I). The samples have been characterized by textural measurements, electron microscopy and spectroscopic techniques including EPR and XPS, concluding the presence of dispersed copper oxides on the support with small particle size and contrasting prevalence of Cu(II) or Cu(I). The catalytic activity of all these catalysts for the C-N coupling of aniline and bromobenzene has been evaluated. A strong influence of the support, copper oxidation state, solvent, nature of the base was observed, the optimal conditions being the use of ZnO or TiO 2 as supports and toluene/dioxane as solvent and EtOK as base. t-C 5 H 11 OK as base in either THF or toluene give rise to the formation of t-C 5 H 11 phenyl ether in some extent. The catalyst undergoes deactivation during the reaction, but about 88% of the activity of the fresh sample could be regained by dioxane washings before reuse. XPS indicates that the most likely origin of catalyst deactivation is adsorption on the copper catalyst surface of KBr and inorganic salts formed as byproducts during the reaction.

During local spring, thin (nm thick) liquid, undercooled interfacial water could be present between the surface covering water ice and the minerals below, mainly by Van der Waals forces in Richardson crater at the southern circumpolar region at the outer ring-shaped area of Dark Dune Spots. Here the daytime max. temperature surpass the threshold limit of interfacial water formation around 180 K where H2O2 might decompose.

The effect of different ruthenium precursors on the structure and catalytic properties of the Ru/MgF 2 system was studied with such methods as IR, XPS, EPR and catalytic test reactions. The adsorption of probe molecules (CO and O 2 ) revealed a greater ability to transfer an electron from ruthenium in the case of samples obtained from Ru 3 (CO) 12 than in the case of samples obtained from RuCl 3 . Besides, metallic crystallites of different size were obtained depending on the precursor used. Namely, the average cluster size was 1.5 times smaller for carbonyl samples in comparison with chloride ones. Both series of preparations were active in redox or acid^base reactions. The activities of the carbonyl samples were higher than those of the chloride catalysts, particularly in reactions that require the presence of acid centers.

Bottom-up approaches to nanofabrication are of great interest because they can enable structural control while minimizing material waste and fabrication time. One new bottom-up nanofabrication method involves excitation of the surface plasmon resonance (SPR) of a Ag surface to drive deposition of sub-15 nm Au nanoparticles from MeAuPPh3. In this work we used density functional theory to investigate the role of the PPh3 ligands of the Au precursor and the effect of adsorbed solvent on the deposition process, and to elucidate the mechanism of Au nanoparticle deposition. In the absence of solvent, the calculated barrier to MeAuPPh3 dissociation on the bare surface is <20 kcal/mol, making it facile at room temperature. Once adsorbed on the surface, neighboring MeAu fragments undergo ethane elimination to produce Au adatoms that cluster into Au nanoparticles. However, if the sample is immersed in benzene, we predict that the monolayer of adsorbed solvent blocks the adsorption of MeAuP...

The reaction of an equimolar mixture of H2 and CO was studied over ZrOr at 350 to 45O"C, 35 atm total pressure, and varying residence times. The isosynthesis reaction mechanisms were studied by monitoring the incorporation of oxygenated compounds into the isosynthesis products. Propionaldehyde and [t3C]acetone, [i3C]isopropanol, and [W]methanol were added to the CO/Hz reactant stream. Their effect on the isosynthesis product distributions and on the isotopic distribution of the products was monitored as a function of oxygenate feed rate. Propionaldehyde, acetone, and methanol were found to incorporate into the isosynthesis products. The isotopic distribution of the products was used to support an isosynthesis reaction scheme that involves CO insertion into a bound aldehyde or ketone as the major chain growth step and a second chain growth step that involves condensation between methoxide and a surface bound enolate. Q 1988 Academic press, IK.

The investigation describes detailed kinetic modelling of biodiesel synthesis catalysed by waste derived carbonaceous catalyst in a batch reactor. The modelling is conducted via three approaches i.e. power law equation, Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanism. Reversible and irreversible pathways with respect to triglycerides (TG) and fatty acid methyl esters (FAME) for first and second order reactions were considered for developing model equations. The kinetics of heterogeneous catalysis is studied using E-R and L-H mechanism to assess the exact rate controlling step by considering all the possible resistances offered by solid catalyst. The rate expressions for adsorption and desorption of individual reactant and product and surface chemical reaction were also developed. The influence of diffusional resistance offered by solid catalyst on conversion is also determined. The best fitted model is identified from calculated regression coefficients. The results revealed that glycerol desorption from catalyst surface given by E-R and L-H mechanisms is controlling the biodiesel synthesis process. The best suited model equation is considered for evaluating the kinetic parameters of the transesterification process. Thus, the study gives exact rate controlling step for heterogeneous catalysis to be used for reactor design and cost-effective production of biodiesel.

Highlights  Study of kinetics of soybean transesterification using methanol and cement kiln dust as a heterogeneous catalyst  Cement kiln dust characterization  Selection of best kinetic model and studying different mass transfer resistances during reaction in order to insure that the reaction is only kinetically controlled

According to the current consumption of world fossil-based oil, coal and natural gas used to produce energy, worldwide reserves of these fuels will be depleted in less than 10 decades. Therefore, new renewable energy sources have to be developed to overcome this problem. Biodiesel is one of these new sources; it is composed of methyl or ethyl esters produced from vegetable oil or animal fats and possesses fuel properties similar to diesel fuel. This paper presents a study of factors affecting biodiesel production using cement kiln dust (CKD), as heterogeneous catalyst, and determination of the optimum reaction conditions. This was achieved by using the factorial design and response surface methodology in conjunction with steepest ascent method in the range of this study. The optimum conditions were found to be: A reaction time of about 6 h, catalyst loading of 2% of oil mass and methanol to oil molar ratio of 15:1. Fixed mixing speed of 800 rpm and constant temperature of 65 °C were used in all experiments. After performing the optimization process, CKD leachability was studied in order to determine its stability and reusability.

Mesoporosity in ETS-10 titanosilicate was generated by postsynthesis treatment with hydrogen peroxide under microwave irradiation, resulting in an increased external surface area of the materials. The influence of mesopore content, external surface area, proton-exchange conditions, and solvent on the activity of the modified ETS-10 in the Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam under vapor-phase conditions was investigated. Protonated mesoporous ETS-10 was catalytically active and demonstrated improved performance with increasing external surface area.

The objective of this work is the development of a method for the catalytic conversion of biomass into liquid products, which could be further treated for the production of bio-fuels. Rapeseed cake was used as a source of biomass, while H-ZSM-5 and H-Beta zeolites were used as catalysts. The process was carried out at 400 °C, in a batch reactor with two configurations. In the first configuration, produced vapors were condensed and collected. In the second configuration, a fixed bed catalytic vapor upgrading section was added into the reactor. The conversion of the rapeseed cake resulted in the formation of two liquid phases (an organic and an aqueous phase), gases and a solid residue. The highest organic liquid phase yield was attained on H-ZSM-5 zeolite at the use of the vapor upgrading section. The aqueous phases contained a mixture of water-soluble substances, mainly N-heterocyclic compounds. The catalyst regeneration studies showed that H-ZSM-5 zeolite in both the reactor and the vapor upgrading section was more stable than H-Beta.

Linear, easily accessible alkyl and (hetero)aryl-substituted alkynyl allyl alcohols are readily and enantioselectively transformed into 2,7-dioxabicycloA C H T U N G T R E N N U N G [3.2.1]octanes by a sequential rhodiumcatalyzed process. Based on the initial cycloisomerization, the in situ generated rhodium(I)-BINAP complex enables a subsequent reduction with hydrogen and the transformation into bicyclic frameworks.

Although gold is the most inert of all metallic elements, it has interesting properties as a heterogeneous catalyst. There are a number of curious aspects to catalysis by gold that are currently attracting academic investigation, while the observation that gold-based catalysts are active at room temperature and below is driving considerable industrial interest. However, much is still not understood about these catalysts and, for example, apparently similar preparation techniques result in activities of hugely varying magnitude. In the present paper we assess the known phenomenology of heterogeneous catalysis by gold, with particular reference to the material properties of the individual nano-particles of catalyst and the many disagreements in the literature. Even the structure of the nano-particles is uncertain, with claims being made for truncated octahedra, cub-octahedra, icosahedra, various kinds of decahedra, and amorphous structures. As far as uncertainty concerning the mechanism of catalysis is concerned, we show that the situation has not yet been resolved, with evidence that catalysis can proceed even in the absence of either a discrete particulate morphology or an oxide support. One possibility is that more than one mechanism applies. Alternatively, the explanation may be that the activity of gold as a catalyst is determined only by the availability of surface gold atoms with low coordination numbers and an associated electron density suitable for whatever reaction is being catalysed. In this case, the role of the oxide support and of gold particle size and structure is indirect, and they would serve mainly to modulate the specific surface area of the gold, and the electronic configuration of its surface atoms.

A oxidação de substratos orgânicos é uma importante classe de reações explorada visando a produção de insumos industriais tais como epóxidos, álcoois e cetonas. As metaloporfirinas são compostos com reconhecida atividade catalítica que mimetizam processos de oxidação que ocorrem em seres vivos. A sua imobilização em diferentes sólidos robustos e inertes permite a recuperação e reuso do catalisador em processos catalíticos heterogêneos. Hidróxidos duplos lamelares (LDHs) são materiais inorgânicos constituídos de hidróxidos de metais di e trivalentes, resultando em lamelas bidimensionais carregadas positivamente. Neste trabalho reportamos a preparação de catalisadores baseados na imobilização de ferroporfirina (FeP) em LDH macroporoso (LDHM) obtido pelo método de co-precipitação usando poliestireno como template, reconstrução de óxidos e esfoliação (LDHME). A imobilização da FeP no LDH intercalado com ânions nitrato obtido pelo método de co-precipitação também é reportada. Os sólidos obtidos foram caracterizados e investigados como catalisadores na oxidação do cicloocteno e cicloexano. The oxidation of organic substrates via catalytic routes is an important class of reactions to produce industrial input materials such as epoxides, alcohols, and ketones. Metalloporphyrins display recognized catalytic activity that mimics oxidation processes in living organisms. Their immobilization in different inert supports allows their recovery and reuse in heterogeneous catalytic processes. Layered double hydroxides (LDHs) are inorganic materials consisting of di-and trivalent metal hydroxides that afford bidimensional positively charged layers. This work reports on the preparation of the solid based on macroporous LDHs (LDHMs) by the co-precipitation method, which involved the use of polystyrene as template, oxides reconstruction, and exfoliation, to furnish LDHME. We also describe the immobilization of an iron(III) porphyrin (FeP) in LDHME and in LDH intercalated with nitrate anions, obtained by the co-precipitation method. Application of the immobilized catalysts in (Z)-cyclooctene and cyclohexane oxidation will help to assess their catalytic activity.

One pot condensation of ethyl acetoacetate or methyl acetoacetate with various para and ortho substituted aromatic aldehydes and urea or thiourea by tin(IV) chloride affords twenty-one different substituted 3,4-dihydropyrimidin-2-(1H)ones. Tin(IV) chloride has emerged as a powerful catalyst for the preparation of 3,4-dihydropyrimidin-2-(1H)-ones under simple and mild conditions. It is compatible with a wide variety of substituents in the aromatic aldehyde. Substituents at para position in aldehyde are more effective than the substituents at ortho position. Both the β-ketoesters, and urea or thiourea are equally effective towards an efficient 3,4-dihydropyrimidin-2-(1H)-one synthesis.

In this review, the most recent advances (2014)(2015)(2016) on the synthesis of new polymer-supported catalysts are reported, focusing the attention on the synthetic strategies developed for their preparation. The polymer-supported catalysts examined will be organic-based polymers and organic-inorganic hybrids and will include, among others, polystyrenes, poly-ionic liquids, chiral ionic polymers, dendrimers, carbon nanotubes, as well as silica and halloysite-based catalysts. Selected examples will show the synthesis and application in the field of organocatalysis and metal-based catalysis both for non-asymmetric and asymmetric transformations.

Starting from 3,5‐dimethoxybenzaldehyde, some functionalized 2,3,4‐trisubstituted tricyclic 4,5‐cycloalkyl‐fused and 6‐modified chromans could be prepared via ortho‐quinone methides (o‐QMs)/hetero‐Diels–Alder (HDA) reactions of the appropriate precursors. The bromide at C6 served as a handle for introducing other substituents through palladium‐catalyzed cross‐coupling reactions and other functional‐group transformations. Moderate to high yields (up to 80 %) and diastereoselectivities (up to >99:1) could be obtained under [PtCl4] catalysis. The preferred endo transition state during the cycloaddition reaction played an important role in governing the stereochemical outcomes at C2C3C4. The configurationally fixed E geometry of the bicyclic o‐QMs influenced the cycloaddition reactions to favor the C2C4 cis relationship.

Starting from 3,5-dimethoxybenzaldehyde, some functionalized 2,3,4-trisubstituted tricyclic 4,5-cycloalkylfused and 6-modified chromans could be prepared via ortho-quinone methides (o-QMs)/hetero-Diels-Alder (HDA) reactions of the appropriate precursors. The bromide at C6 served as a handle for introducing other substituents through palladium-catalyzed cross-coupling reactions and other functional-group transformations. Moderate to high yields (up to 80 %) and diastereoselectivities (up to > 99:1) could be obtained under [PtCl 4 ] catalysis. The preferred endo transition state during the cycloaddition reaction played an important role in governing the stereochemical outcomes at C2ÀC3ÀC4. The configurationally fixed E geometry of the bicyclic o-QMs influenced the cycloaddition reactions to favor the C2ÀC4 cis relationship.

NiMo catalysts supported on mesoporous MCM-41 type materials shaped with binder were tested for activity in the hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and the diesel fuel fraction (0.92 wt% of sulfur). The aim of the investigation was to evaluate the effect of ion exchange with protons of Al-or Ti-substituted MCM-41 mesoporous supports. The subjected catalytic systems were NiMo/HAlMCM-41 and NiMo/HTiMCM-41, and for comparison purposes NiMo/AlMCM-41 and NiMo/TiMCM-41. The samples were characterized by N 2 sorption (at 77 K), XRD, TEM, XPS, SEM and Py-IR. It was found that the functionalization of AlMCM-41 and TiMCM-41 with protons increased the conversion of 4,6-DMDBT and the pseudo-first-order rate constant. Correspondingly, 4,6-DMDBT HDS reactions over the NiMo/HTiMCM-41 catalyst proceeded to a similar extent via hydrogenation and direct desulfurization, whereas over the NiMo/HAlMCM-41 they proceeded mainly via direct desulfurization. Furthermore, the ion-exchanged catalysts displayed two-fold higher efficiency in direct desulfurization than their non-modified counterparts. The NiMo/HTiMCM-41 catalyst exhibited the highest catalytic efficiency in the HDS of 4,6-DMDBT and the diesel oil fraction. The high activity of the NiMo/HTiMCM-41 catalyst is mainly attributed to its appropriate acidity, as well as the metal-support interaction providing both the high dispersion of the active phase and the desirable multilayered stacking morphology of the active phase slabs.

Vanadium modified mesocellular silica foams (MCF) materials (V content ca. 3 and 5 wt%) prepared by the impregnation method show mainly isolated or low-polymeric VO x species, which was confirmed by means of Raman spectroscopy and DR UV-Vis. Textural measurements, and also XRD and TEM results indicate that the characteristic mesocellular structural features of MCFs are preserved after vanadium incorporation. The MCF-supported vanadia catalysts exhibit much higher propene conversion and propene oxide productivity when compared to vanadium modified mesoporous silicas of 2D structure, demonstrating that apart from the presence of highly dispersed isolated vanadium species, internal molecular transport within three-dimensional ultra large pores of MCF materials also plays an important role in gas-phase propene epoxidation.

Raman microscopy has been applied to characterize physical and chemical mixtures of mixed metal oxides. The obtained Raman mapping data were first subjected to singular value decomposition to obtain the right singular vectors, and the right singular vectors were then subjected to bandtarget entropy minimization (BTEM) to recover the pure component spectra of the observed species present in the sample. Subsequently, these resolved pure component spectral information was used to differentiate the physical and chemical mixtures. In addition, BTEM is also able to recover the pure component spectra of both unstable compound and its degradation product due to laser irradiation. In current study, the physical mixture of Mn 2 O 3 and Co 3 O 4 , and the chemical mixture of CoMn 2 O 4 spinel oxide were investigated.

The rising concentration of plastics due to extensive disposal and inefficient recycling of plastic waste poses an imminent and critical threat to the environment and ecological systems. Photocatalytic reforming of plastic derivatives to value-added chemicals under ambient conditions proceeds at lower oxidation potential which galvanizes the hydrogen evolution. We report the synthesis of a narrow band gap NCN-functionalized O-bridged carbon nitride (MC) through condensation polymerization of hydrogen-bonded melem (M)-cyameluric acid (C) macromolecular aggregate. The MC scaffold hosts well-dispersed Ir single atom (MCIrSA) sites which catalyze oxidative photoreforming of alkali-treated polylactic acid (PLA) and polyethylene terephthalate (PET) derivatives to produce H2 at a rate of 147.5 and 29.58 μmol g−1cat h−1 under AM1.5G irradiation. Solid-state electron paramagnetic resonance (EPR) and time-resolved photoluminescence (TRPL) reveals efficient charge carrier generation and separation in MCIrSA. X-ray absorption spectroscopy (XAS) and Bader charge analysis reveal undercoordinated IrN2O2 SA sites pinned in C6N7 moieties leading to efficient hole quenching. The liquid phase EPR, in situ FTIR and density functional theory (DFT) studies validate the facile generation of •OH radicals due to the evolution of O-Ir-OH transient species with weak Ir--OH desorption energy barrier.

A synthetic polymer selective for paraoxon was prepared by a molecular surface imprinting technique. We have combined molecular imprinting with the ability of histidine to chelate metal ions to create active centrum of phosphotriesterase on microbead surfaces. For this purpose, methacryloyl-histidine-copper(II) [MAH-Cu(II)] and methacryloyl-histidine-copper(II)-paraoxon [MAH-Cu(II)-paraoxon] metal chelating monomers were synthesized; paraoxon imprinted polymers were produced and the binding characteristics of the polymers were evaluated. The optimum pH was determined applying different pH values and the hydrolytic activity of phosphotriesterase was evaluated in the framework of Micheaelis-Menten kinetics. In addition, the values of maximal rate: V m (4.58 Â 10 À2 mM/min) and Micheaelis-Menten constant, K m (1.28 Â 10 À3 M), were obtained from Lineweaver-Burk plots for the imprinted polymeric catalyst.

Polymer-silica hybrid support (SA-2-AMPS-SiO 2 ) was synthesized and Co (II), Cu (II) metals were loaded over hybrid support by incipient impregnation technique. Oxidation of ethylbenzene was carried out for testing catalytic activity of catalysts at different reaction conditions i.e. the mole ratio of ethylbenzene to TBHP and reaction temperature. The main oxidation product was acetophenone along with benzaldehyde as the minor product and the highest ethylbenzene conversion (83.65 %) was attained at a 1:4 mol ratio of ethylbenzene to TBHP and temperature at 100 °C. The reusability of the catalysts was also determined and results showed that they can be easily reused three times without much loss in their structural and catalytic properties.

Polymer-silica hybrid support (SA-2-AMPS-SiO 2 ) was synthesized and Co (II), Cu (II) metals were loaded over hybrid support by incipient impregnation technique. Oxidation of ethylbenzene was carried out for testing catalytic activity of catalysts at different reaction conditions i.e. the mole ratio of ethylbenzene to TBHP and reaction temperature. The main oxidation product was acetophenone along with benzaldehyde as the minor product and the highest ethylbenzene conversion (83.65 %) was attained at a 1:4 mol ratio of ethylbenzene to TBHP and temperature at 100 °C. The reusability of the catalysts was also determined and results showed that they can be easily reused three times without much loss in their structural and catalytic properties.

Deep hydrodesulfurization (HDS) was investigated over amorphous silicaalumina (ASA), produced using various synthetic methods as supports for NiMo catalysts, in single and dual catalytic bed systems. NiMoS active components supported on ASA-2 (ASA from synthetic method 2) achieved S levels of 4.5 and 3.0 ppm at 345 and 360°C, respectively, in single catalytic beds, which was the highest HDS reactivity. Dual catalytic beds were introduced to inhibit excess hydro-cracking of C species in gas oil. For the dual catalytic combination of LX6 (commercial catalyst for reactive S species) and NMASA-2 (NiMoS supported on ASA-2), the S levels were 5.4 and 2 ppm at 345 and 360°C, respectively, indicating that the performance was enhanced at higher temperatures, likely due to improved activity for refractory S species. The increased reactivity for HDS over NMASA-2 was related to the strong acidity of this support due to tetrahedrally-coordinated Al species. In addition, the smaller homogeneous particle size of the support influenced the HDS catalytic performance. Moreover, weaker interactions between the Mo and ASA-2 in NMASA-2 improved the HDS reactivity, as confirmed by laser Raman spectroscopy.

This study introduces a novel composite catalyst formed by anchoring delta iron oxyhydroxide (δ-FeOOH) onto pyrolyzed Pili nutshell biochar via a room temperature coprecipitation technique, marking the first application of Pili nutshell waste in advanced oxidation processes for wastewater treatment. This innovative methodology enhances catalyst dispersion and stability, facilitating the activation of peroxymonosulfate (PMS) to generate reactive sulfate radicals (SO4•-) for the degradation of methylene blue (MB), a thiazine dye commonly used in the medical field and the dye industry. Different techniques have been used to characterize synthesized composites in terms of their morphology, elemental composition, surface functional groups, and crystalline phase structure. The system achieved a maximum MB degradation efficiency of 90.88% within 30 min at pH 6.0 when low dosages of PMS and the δ-FeOOH/biochar composite were used, following pseudo-first-order degradation kinetics. Radical scavenging experiments confirmed that SO4•- radicals were primarily responsible for the degradation process. Notably, the composite maintained over 70% removal efficiency after four reuse cycles, indicating its potential for sustainable and cost-effective wastewater treatment. This research highlights the effectiveness of the δ-FeOOH/biochar/PMS system as a promising solution for treating MB-laden wastewater, contributing to environmental sustainability and waste valorization.

The mechanisms involving the nanoparticle surfaces in catalytic reactions are more difficult to elucidate due to the nanoparticle surface unevenness, size distributions, and morphological irregularity. True surface area and particle sizes determination are key aspects of the activity of metal nanoparticle catalysts. Here we report on the organothiol adsorption-based technique for the determination of specific surface area of Cu nanoparticles, and their resultant sizes on ␥-Al 2 O 3 supports. Quantification of ligand packing density on copper nanoparticles is also reported. The concentration of the probe ligand, 2-mercaptobenzimidazole (2-MBI) before and after immersion of supported copper catalysts was determined by ultraviolet-visible spectrometry (UV-vis). The amount of ligand adsorbed was found to be proportional to the copper nanoparticles surface area. Atomic absorption spectrometry (AAS), N 2physisorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used for the characterization of the catalysts. A fair agreement was found between particle sizes obtained from ligand adsorption and TEM methods. The catalytic activity of the copper nanoparticles related to their inherent surface area was evaluated using the model reaction of the oxidation of morin by hydrogen peroxide.

Polystyrene-supported quaternized ammonium salt catalysts (PS-alkyl-AX) were synthesized and characterized by various physicochemical analytic methods such as EA, FT-IR, XPS, and SEM. The reactivity of the catalysts was investigated for the synthesis of allyl glycidyl carbonate from CO 2 and allyl glycidyl ether under mild reaction conditions. The PS-alkyl-AX catalysts showed good catalytic activity without using any solvent due to the synergistic effect of NH functional group and quaternary ammonium salt structure. Theoretical studies using density functional theory (DFT) was applied to investigate the reaction mechanism. The PS-hexyl-MeI catalyst was readily recoverable and reusable in subsequent reaction cycles without a significant loss in its activity.

Catalyst leaching is a major impediment to the development of commercially-viable processes conducted in a liquid-phase. To date, there is no reliable technique that can accurately identify the extent and dynamics of the leaching process in a quantitative manner. In this work, a tandem flow-reactor system has been developed, which allowed us to distinguish between surface-catalyzed reactions from those occurring in solution by com-paring%conversion at the exit of each reactor (S1, S2) corresponding to predominance of heterogeneous/ homogeneous reactions (spatial) and two different residence times (temporal). A multiscale model is subsequently established to quantify the two types of reaction rate and simulate the catalyst leaching from a crosscoupling catalyst, PdEncat™ 30; including: (1) a multi-particle sizes model for catalyst scale; and (2) a dispersion model for reactor scale. The results show that catalyst leaching occurs via more than one process, and that the homogeneous Pd-catalyst (leached from the immobilized catalyst and dissolved in the flow) dominates the reaction and possesses a much higher activity than the heterogeneous (immobilized) Pd-catalyst. Additionally, the change of leached Pd stream inside reactors can be predicted along with the axial direction and the reaction time through the reactor-scale dispersion model.

Oxidation of phenol in aqueous media by electro-Fenton process using carbon felt cathode has been studied. The salts of iron, cobalt, manganese, and copper were used to provide the metal cations as catalyst of Fenton reaction to produce hydroxyl radicals. 10 À4 M of soluble iron(II) sulfate salt supplied the optimum catalytic condition, allowing to remove 100% of total organic carbon (TOC) of aqueous phenol solutions. The main reaction intermediates formed during electro-Fenton treatment were identified as hydroquinone, p-benzoquinone, and catechol. Carboxylic acids such as maleic, fumaric, succinic, glyoxylic, oxalic, and formic were predominantly identified as end products, before complete mineralization. The absolute rate constant of phenol degradation by hydroxyl radicals was obtained in acid medium (2.5 < pH < 3.0), being equal to (2.62 AE 0.23) Â 10 9 M À1 s À1 . Experiments with electro-Fenton oxidation of each aromatic intermediate allowed to propose a complete mineralization pathway.

Cerium (IV) sulfate tetrahydrate, Ce(SO4)2•4H2O, is a novel inorganic solid acidic catalyst that efficiently catalyzes the synthesis of 2,3-dihydroquinazolin-4(1H)-ones via the one-pot threecomponent reaction of isatoic anhydride, aromatic aldehydes, and a nitrogen source (ammonium acetate, ammonium carbonate, ammonium chloride, or methylamine) under solvent-free conditions. The desired products are obtained in short reaction time with high yields. The catalyst is inexpensive and readily available and can be recovered conveniently and reused such that considerable catalytic activity can still be achieved after the fifth run. Easy work-up and avoiding the use of harmful organic solvents are other advantages of this simple procedure.