@article {42853, title = {Effective and selective oxidation of 2-butanol over Mn supported catalyst systems}, journal = {Applied Catalysis A-General}, volume = {525}, year = {2016}, month = {SEP}, pages = {237-246}, abstract = {

Oxidation of alcohols to their corresponding aldehydes/ketones is an important reaction in industries as well as in academic perspective. Selective oxidation (Selox) of alcohols like methanol, ethanol and propanol are well studied in literature; however, alcohols like butanol, pentanol, octanol is a challenging task. Selective oxidation of 2-butanol to methyl ethyl ketone (MEK) is an important reaction due to its wide range of applications. Herein, we demonstrated the selective oxidation of 2-butanol to MEK over Mn supported on different oxide supports. A series of MnxOy-Al2O3 (MA), MnxOy-CeO2 (MC), MnxOy-ZrO2 (MZ) and MnxOy-SiO2 (MS) catalysts were prepared by co-precipitation followed by hydrothermal method. As synthesised catalysts were characterised by various physico-chemical characterisation techniques. It was found that the presence of Mn3O4 species in MA and MZ catalysts is responsible for maximum catalytic activity towards 2-butanol oxidation. MA catalyst conferred a maximum 2-butanol conversion of 51\% and 88\% selectivity towards MEK. XPS analysis revealed that Mn in MA catalyst exists in +2 and +3 oxidation states and responsible for 2-butanol oxidation. Moreover it was found that the acidity of the catalyst also plays an important role in catalytic activity. (C) 2016 Published by Elsevier B.V.

}, doi = {10.1016/j.apcata.2016.08.005}, author = {Prabu, Kandasamy and Prabu, Marimuthu and Venugopal, Ashok Kumar and Venugopalan, Aswathy Thareparambil and Sandilya, W. V. Y. Sai and Gopinath, Chinnakonda S. and Raja, Thirumalaiswamy} } @article {45437, title = {Tuning the basicity of Cu-based mixed oxide catalysts towards the efficient conversion of glycerol to glycerol carbonate}, journal = {Molecular catalysis}, volume = {460}, year = {2018}, month = {DEC}, pages = {53-62}, type = {Article}, abstract = {A series of efficient and robust Cu based mixed oxides were synthesized by a simple co-precipitation method and utilized for the production of glycerol carbonate (GC) via transesterification of glycerol with dimethyl carbonate (DMC). The synthesized materials were characterized using XRD, UV-vis spectroscopy, SEM, TEM, N-2 sorption, CO2-TPD, and XPS. The addition of Cu on Mg/Al mixed oxides exhibits significant changes in its physicochemical properties and catalytic activity. The obtained mixed oxides showed remarkably high transesterification activity towards the efficient conversion of glycerol to GC under economical reaction conditions without using any solvent. Among all the catalysts employed, highest catalytic activity was observed over MAC-0.6 catalyst with glycerol conversion of 96.4\% and GC yield of 91.2\%. The improved catalytic performance was observed mainly due to the optimized catalyst molar ratio and strong surface basicity. The strong surface basic sites were greatly attributed to the incorporation of Cu2+ cations in the MgAl (O) periclase that efficiently catalyzed the transesterification of glycerol with DMC. Furthermore, the reported catalyst was robust and could be recycled for more than five times without any significant loss in its catalytic activity.}, issn = {2468-8231}, doi = {10.1016/j.mcat.2018.09.002}, author = {Manikandan, Marimuthu and Prabu, Marimuthu and Kumar, S. K. Ashok and Sangeetha, Palanivelu and Vijayaraghavan, Rajagopalan} } @article {46220, title = { Synthesis of biodiesel using the Mg/Al/Zn hydrotalcite/SBA-15 nanocomposite catalyst }, journal = {Acs Omega}, volume = {4}, year = {2019}, month = {FEB}, pages = {3500-3507}, type = {Article}, abstract = {

Biodiesel production is an enchanting and eccentric pathway for the reduction of use of fossil fuels and is procured from biologically available renewable sources such as oils and fats. A novel Mg/Al/Zn-based hydrotalcite/SBA-15 composite material having a high catalytic activity was developed and investigated for the transesterification of vegetable oil. The rationally developed composites were systematically characterized and assessed in the transesterification of soybean oil in the presence of methanol. The physicochemical evaluation of the nanocomposites demonstrated the influence of Zn in the textural characteristics, density of the basic sites, and successively the catalytic activity. The catalytic efficiency of the MAZ-x/SBA-15 composite could be linked with the basic site density determined by the temperature-programmed desorption of CO2. Among all the composites used, the MAZ-1/SBA-15 nanocomposite showed the highest activity for biodiesels, with a yield of around 90\% under economical reaction conditions. The catalytic studies conferred that the fatty acid methyl ester yield is significantly influenced by various experimental conditions such as the catalyst molar ratio, reaction temperature, pressure, and contact time. It was also found that the incorporation of hydrotalcite into SBA-15 pore channels can enhance the catalyst efficiency and stability of the nanocomposite. Moreover, under mild reaction conditions, a remarkably stable catalytic performance was achieved for more than 200 h of time on stream with no catalyst deactivation.

}, doi = {10.1021/acsomega.8b02547}, author = {Prabu, Marimuthu and Manikandan, Marimuthu and Kandasamy, Prabu and Kalaivani, P. R. and Rajendiran, Nagappan and Raja, Thirumalaiswamy} } @article {48074, title = {Comparative investigation on the catalytic performance of HT/SBA-15 and SBA-15/HT composites for the isomerization of glucose to fructose}, journal = {Materials Science and Engineering B-Advanced Functional Solid-State Materials}, volume = {286}, year = {2022}, month = {DEC}, pages = {116052}, type = {Article}, abstract = {

Hydrotalcites (HT) have a broad spectrum of applications as prosperous heterogeneous catalysts for diverse chemical transformations. The catalytic activity of HT-based materials can be tailored by introducing siliceous material into the internal or external framework. The surface modification of the HT framework with silica mesostructures leads to the formation of versatile Lewis base, Bronsted base and redox catalytic active sites. This work presents the comparative evaluation of the catalytic performance of HT/SBA-15 and SBA-15/HT composites for the isomerization of glucose to fructose using 1-butanol as a solvent. The composites with different external morphology were prepared by a modified template-assisted hydrothermal method, using different HT to SBA-15 proportions. The textural and morphological characterization results conferred the efficiency of the employed post-synthetic intercalation strategy to achieve the successful formation of HT/SBA-15 and SBA-15/HT composites. With optimal HT loading and surface basicity, the HTS-3 composite demonstrated the highest catalytic performance, resulting in good glucose conversions (54 \%) with improved selectivity (\>83 \%). The observed high reactivity could be mainly attributed to the extensive dispersion of HT particles on the SBA-15 component, which contributes to a significant increase in textural properties and surface basicity. Furthermore, special attention is devoted to addressing such reactivity phenomena as active site selectivity, catalyst multifunctionality and multisite reactivity commonly encountered in mesoporous catalysis.

}, keywords = {composites, glucose, hydrotalcite, isomerization, SBA-15}, issn = {0921-5107}, doi = {10.1016/j.mseb.2022.116052}, author = {Manikandan, Marimuthu and Arjunan, Ayyappan and Prabu, Marimuthu and Raja, Thirumalaiswamy and Sangeetha, Palanivelu} } @article {48076, title = {Green synthesis of cyclohexanone to adipic acid over Fe-W oxides incorporated mesoporous carbon support}, journal = {Catalysis Communications}, volume = {168}, year = {2022}, month = {AUG}, pages = {106466}, type = {Article}, abstract = {

We have prepared iron and tungsten oxides incorporated mesoporous carbon (MC) catalysts using a simple hydrothermal methodology with different carbon sources, and the catalytic performance was investigated for cyclohexanone oxidation. An adequate amount of metal oxide loading has displayed a key role in the selective catalyst for adipic acid (AA) synthesis. The MC catalyst has shown its prime activity under the influence of redox properties of W5+/W6+ and Fe2+/Fe3+ as promoters. The 10\%Fe 90\%W-MC fructose as a carbon source catalyst has provided its best selectivity of 87\% for AA at 120 ?C.

}, keywords = {Adipic Acid, Liquid phase oxidation, mesoporous carbon, Redox center}, issn = {1566-7367}, doi = {10.1016/j.catcom.2022.106466}, author = {Mekala, Siva Prasad and Prabu, Marimuthu and Gawali, Sheetal Datta and Gopakumar, Karthik and Gogoi, Pranjal and Bhatkar, Akash Ravindra and Mohapatra, Gourab and Unnikrishanan, Eeswar and Raja, Thirumalaiswamy} } @article {48217, title = {Synthesis and crystal structures of Mn(II) and Co(II) complexes as catalysts for oxidation of cyclohexanone}, journal = {Inorganics}, volume = {10}, year = {2022}, month = {JUL}, pages = {100}, type = {Article}, abstract = {

The global demand on adipic usage in the production of plasticizers and synthetic polyamide is increasing. In line with the search for an efficient and energy-conserving way to isolate adipic acid (AA) in good yields, this paper introduces the oxidization of cyclohexanone utilizing two new coordination compounds, [Mn(2,6-pydc)(2)](imi) (1) and [Co(H(2)pza)(2)(H2O)(2)(NO3)].NO3 (2), as catalysts. Compounds 1 and 2 were synthesized by room temperature and refluxing methods, and characterized by spectral analyses (IR and UV-Vis.), SEM, BET, TGA, elemental, and X-ray crystallography. The single crystal structure of compound 1 revealed that pyridinedicarboxylate (2,6-pydc) and imidazole (imi) moieties were coordinated to the Mn(II) atom through imine nitrogen and deprotonated oxygen atoms, to form an undistorted octahedral coordination geometry with the N2O4 donor set. The axial and equatorial planes containing O2, O4, O5, and O7 atoms were from two adjacent 2,6-pydc ligands which formed the unidendate donor ligand; imi, on the other hand, acted as a bidendate donor ligand. For compound 2, the Co(II) atom was being coordinated by two pyrazinamide (H(2)pza) moieties, which acted as an unidendate donor ligand; two water molecules occupying the axial position, and one nitrate molecule occupying the apical position, were within the coordination sphere; a nitrate molecule was disordered outside the coordination sphere. The distance, 4.658 angstrom, between the Co1 atom and the N8 atom of the uncoordinated nitrate molecule, was within the range reported elsewhere. Cyclohexanone peroxidation experiments revealed that compound 1 exhibited unique catalytic performance by giving a 72.8\% yield in adipic acid, in comparison to the 71.3\% yield obtained with compound 2. The yields in AA were maintained by way of recyclability evaluation. The reaction kinetics of compound 2 gave less activation energy, E-a 2938 J mol(-1), while the thermodynamic parameters indicated that the chemical reactivity of cyclohexanone on the active surfaces of compounds 1 and 2 was via monolayer physisorption.

}, keywords = {cobalt, Complexes, cyclohexanone, Imidazole, managanese, Oxidation, pyrazinamide, pyridinedicarboxylate}, doi = {10.3390/inorganics10070100}, author = {Tella, Adedibu C. and Isaac, Aaron Y. and Clayton, Hadley S. and Ogunlaja, Adeniyi S. and Venugopalan, Aswathy T. and Prabu, Marimuthu and Thirumalaiswamy, Raja} } @article {48765, title = {MnXWO4 nanostructure-based catalysts for single-step oxidation of cyclohexane and methane to oxygenates}, journal = {ACS Applied Nano Materials}, volume = {6}, year = {2023}, month = {APR}, pages = {7245-7258}, type = {Article}, abstract = {

Activation of the C-H bond in cyclohexane (CYH) and methane is a crucial step to obtain desirable oxygenated products using nanostructured catalyst and is a great challenge and an efficient route to mitigate the inauspicious effects of climate change. The active sites were identified using XRD, HR-TEM, SEM, N2 sorption analysis, TPR, Raman, XPS, TGA, in situ DRIFT, XAS, etc. In optimal reaction conditions, 46\% of CYH was converted into adipic acid (AA) on MnxWO4 nanostructures within 6 h. The recyclability test confirmed the catalyst heterogeneity, which revealed no appreciable loss of catalytic activity even after three consecutive reactions. In situ DRIFT study reveals that CYH is oxidized to cyclohexanone and cyclohexanol (KA oil) and is further oxidized to AA via carboxylate intermediates. DFT studies disclosed that MnOx species are responsible for the C-H activation of CYH, and the Mn2+/Mn3+ redox centers play a vital role in the absorption of KA oil to form AA. Herein, we demonstrated the significant role of the {\textquoteleft}{\textquoteleft}MnOx{\textquoteright}{\textquoteright} species and that adequate Lewis and Bronsted acidic sites, redox centers of (Mn2+/Mn3+), and lattice oxygen are accountable for the CYH conversion toward the AA. Additionally, we have reported the oxidation of methane to methanol (146 mu mole per gram of catalyst) in the presence of water at 75 degrees C without over-oxidation products.

}, keywords = {Adipic Acid, C-H bond activation, Cyclohexane oxidation, methane activation, MnOx chain, Redox center}, doi = {10.1021/acsanm.3c00319}, author = {Prabu, Marimuthu and Manikandan, Marimuthu and Samal, Pragnya Paramita and Gurrala, Lakshmi Prasad and Mekala, Siva Prasad and Archana, Ramakrishnan and Nayak, Chandrani and Bhattacharyya, D. and Jha, S. N. and Krishnamurty, Sailaja and Raja, Thirumalaiswamy} } @article {48313, title = {Nitric acid free cyclohexane to adipic acid production using nickel and vanadium incorporated AlPO-5 molecular sieve}, journal = {Molecular Catalysis}, volume = {540}, year = {2023}, month = {APR }, pages = {113051}, type = {Article}, abstract = {

Rationally designing a stable and sustainable metal oxide supported over the molecular sieve catalysts for oxidizing cyclohexane (CYH) to adipic acid (AA) is vital in industrial applications. The in-situ hydrothermal synthesis method successfully incorporated vanadium and nickel into the aluminium phosphate-5 (AlPO-5) molecular sieves (MFI structure). The XPS and NH3 TPD analysis disclosed that the addition of Ni into V-AlPO-5 stabilizes the ratio of V4+/V5+, creating strong acidic sites and the formation of NiOOH, which are a vital role for the selective CYH oxidation to AA. An in-situ DRIFT study reveals that nickel takes part in the formation of dicarboxylate ions as an intermediate to form AA. Our catalytic studies profoundly suggested that the Ni0.1V0.2AlPO-5 catalyst used for CYH oxidation gives better selectivity towards AA (53\%) in the presence of oxygen at an appropriate amount of solvent without an initiator or promoter within a short time (3h).

}, keywords = {Adipic Acid, Cyclohexane oxidation, In situ DRIFT, NiOOH, NiVAlPO-5, Ratios ofV4+, V5+}, issn = {2468-8231}, doi = {10.1016/j.mcat.2023.113051}, author = {Prabu, Marimuthu and Sharma, Shweta and Raja, Abhishekram and Archana, Ramakrishnan and Samruddhi, Mane and Raja, Thirumalaiswamy} } @article {49388, title = {Temperature-controlled hydrothermal synthesis of α-MnO2 nanorods for catalytic oxidation of cyclohexanone}, journal = {CHEMPLUSCHEM}, volume = {89}, year = {2024}, month = {JUL}, type = {Journal Article}, keywords = {Adipic Acid, conversion, MANGANESE OXIDES}, issn = {2192-6506}, doi = {10.1002/cplu.202300589}, author = {Jha, Ratnesh Kumar and Manikandan, Marimuthu and Prabu, Marimuthu and Vineeth, Nidhi R. and Dharmalingam, Praveen and Archana, Ramakrishnan and Harsha, Murudappa and Shankar, Sonu Ram and Bhatte, Kushal and Raja, Thirumalaiswamy} } @article {49587, title = {Deciphering the intricate mechanisms behind the selective oxidation of methane to C1 and C2 oxygenates over FeAu/γ-Al2O3 catalysts}, journal = {Chemical Engineering Journal}, volume = {512}, year = {2025}, month = {MAY}, pages = {162510}, type = {Article}, abstract = {

In this work, we demonstrate an eco-benign synthesis protocol for preparing gold nanoparticles and the role of the strong interaction between gold nanoparticles and iron oxide in FeAu/gamma-Al2O3 catalysts that render it an anionic (Au delta-) character while tailoring them in a smaller size. The multifunctional FeAu/gamma-Al2O3 catalyst selectively produces ethanol (95 \% selectivity, similar to 240 mu mol(-1) cat) at a mild temperature of 75 degrees C without the addition of co-reactants during liquid phase methane oxidation with molecular oxygen. Conversely, Au/gamma-Al2O3 and Fe/gamma-Al2O3 catalysts exhibited high selectivity for CH3OH and HCHO. A high dispersion accompanied by strong electronic interaction between the Au delta{\textendash}FeOx, as corroborated by diverse techniques, enables methane activation across the interface and coupling on the gold nanoparticles, which are responsible for the markedly improved formation of ethanol. Furthermore, in situ DRIFTS studies and DFT investigations point to a reaction mechanism of coupling of CH2OH and CH3 intermediates as the most likely route for ethanol formation.

}, keywords = {Anionic gold catalysts, Au-FeOx synergism, C-H bond activation, Ethanol, Methane oxidation, Methanol}, issn = {1385-8947}, doi = {10.1016/j.cej.2025.162510}, author = {Prabu, Marimuthu and Manikandan, Marimuthu and Rengam, B. Sathya Sai and Ramakrishnan, Archana and Raja, Abhishekram and Urkude, Rajashri R. and Ghosh, Biplab and Varghese, Jithin John and Raja, Thirumalaiswamy} }