Selective synthesis of 6,8-di-<i>t</i>-butylated flavan over Zn–Al containing mesoporous silica catalysts

Selvaraj, M.,Sinha, P. K.,Park, D.-W.,Kim, Il,Kawi, S.,Ha, C. S. The Royal Society of Chemistry 2012 Dalton Transactions Vol.41 No.46

<P>We demonstrate a much green synthesis method for highly selective synthesis of 6,8-di-<I>t</I>-butylated flavan (6,8-DTBF) by liquid phase alkylation of 2,4-di-<I>t</I>-butylphenol (2,4-DTBP) with cinnamyl alcohol (Cin-OH) over mesoporous Zn–Al–MCM-41 catalysts synthesized under direct basic hydrothermal method. The main alkylated product, 6,8-DTBF is importantly used as an intermediate in the manufacture of biosynthetic organic compounds. The recyclable mesoporous Zn–Al–MCM-41 catalysts have also been reused in this reaction to study their catalytic activities. The influences of various reaction parameters such as temperature, time, ratios of reactant (2,4-DTBP-to-Cin-OH) have been extensively investigated for the synthesis of 6,8-DTBF. In addition, dimethyl sulfoxide (DMSO) has also been used as a solvent in this catalytic reaction. The mesoporous Zn–Al–MCM-41(75) gives excellent catalytic activity with 6,8-DTBF selectivity (86.0%) and 2,4-DTBP conversion (63.1%), and these catalytic results have also compared with that obtained using other mesoporous and microporous catalysts. On the basis of catalytic activity obtained by using the all catalysts, the Zn–Al–MCM-41(75) catalyst is found to be a highly active, recyclable and eco-friendly heterogeneous catalyst in the liquid-phase alkylation of 2,4-DTBP.</P> <P>Graphic Abstract</P><P>Zn–Al–MCM-41(75) catalyst is found to be a highly active, recyclable and eco-friendly green catalyst in the liquid-phase alkylation of 2,4-DTBP. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2dt31409f'> </P>

Selective synthesis of vitamin K₃ over mesoporous NbSBA-15 catalysts synthesized by an efficient hydrothermal method

Selvaraj, M.,Park, D.-W.,Kim, I.,Kawi, S.,Ha, C. S. The Royal Society of Chemistry 2012 Dalton Transactions Vol.41 No.32

<P>Well hexagonally ordered NbSBA-15 catalysts synthesized by an efficient hydrothermal method were used, for the first time, for the selective synthesis of vitamin K<SUB>3</SUB> by liquid-phase oxidation of 2-methyl-1-naphthol (2MN1-OH) under various reaction conditions. The recyclable NbSBA-15 catalysts were also reused to find their catalytic activities. To investigate the leaching of non-framework niobium species on the surface of silica networks, the results of original and recyclable NbSBA-15 catalysts were correlated and compared. To find an optimum condition for the selective synthesis of vitamin K<SUB>3</SUB>, the washed NbSBA-15(2.2pH) was extensively used in this reaction with various reaction parameters such as temperature, time and ratios of reactant (2M1N-OH to H<SUB>2</SUB>O<SUB>2</SUB>), and the obtained results were also demonstrated. Additionally, the liquid-phase oxidation of 2M1N-OH was carried out with different solvents to find the best solvent with a good catalytic activity. Based on the all catalytic studies, the vitamin K<SUB>3</SUB> selectivity (97.3%) is higher in NbSBA-15(2.2pH) than that of other NbSBA-15 catalysts, and the NbSBA-15(2.2pH) is found to be a highly active and eco-friendly heterogeneous catalyst for the selective synthesis of vitamin K<SUB>3</SUB>.</P> <P>Graphic Abstract</P><P>Mesostructured NbSBA-15 catalysts were used, in novel green routes, for the synthesis of vitamin K<SUB>3</SUB> from 2-methyl-1-naphthol. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2dt31096a'> </P>

Disturbance Rejection of Interval Type-2 Fuzzy Systems Based on Equivalence-Input-Disturbance Approach

Selvaraj, P.,Sakthivel, R.,Kwon, O. M.,Muslim, M. ASME International 2017 Journal of Dynamic Systems, Measurement and Contro Vol.139 No.10

Highly active mesoporous chromium silicate catalysts in side-chain oxidation of alkylaromatics

Selvaraj, M.,Park, D.-W.,Kim, I.,Kawi, S.,Ha, C. S. The Royal Society of Chemistry 2012 Dalton Transactions Vol.41 No.46

<P>We approach a green method in the production of alkylaromatic ketones over hexagonally ordered mesoporous CrSBA-15 catalysts, which were used, in green routes, in the liquid-phase oxidation of alkylaromatics. A promising chemical treatment method was used with ammonium acetate solution to remove the toxic nature of non-framework chromium oxides deposited on the surface of calcined CrSBA-15(8), and the obtained green mesoporous CrSBA-15(8) catalyst was used to find its catalytic activity while the recyclability of mesoporous CrSBA-15 catalysts was also studied. Particularly, the mesoporous CrSBA-15 catalysts synthesized with a variety of chromium contents were extensively used in the production of acetophenone (AP&z.dbd;O) with various reaction parameters. On the basis of all catalytic results, the mesoporous CrSBA-15(8) catalyst produced a higher selectivity of alkylaromatic ketones (76–100%) as compared to other CrSBA-15 catalysts and was found to be a highly active, recyclable and promising heterogeneous catalyst for selective synthesis of alkylaromatic ketones.</P> <P>Graphic Abstract</P><P>Mesostructured green mesoporous CrSBA-15 catalyst has exceptional catalytic activity in oxidation of alkylaromatics. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2dt31571h'> </P>

Thiadiazolopyrimidines as Acid Corrosion Inhibitors for Mild Steel

( S. Chitra ),( K. Parameswari ),( M. Vidhya ),( M. Kalishwari ),( A. Selvaraj ) 한국부식방식학회(구 한국부식학회) 2011 Corrosion Science and Technology Vol.10 No.1

The inhibitive action of thiadiazolopyrimidines on mild steel in 1 M H2SO4 has been studied using weight loss, gasometric studies and electrochemical polarization and AC impedance measurements. The effect of temperature on the corrosion behaviour of mild steel in 1 M H2SO4 with optimum concentration of inhibitors was studied in the temperature ranging from 313-333K The adsorption of the inhibitor on the surface of mild steel was found to be exothermic, spontaneous and followed the mechanism of physisorption. The adsorption of these compounds on mild steel surface was found to obey Langmuir adsorption isotherm. The protective film formed on the surface of mild steel by the adsorption of inhibitor in 1 M H2SO4 solution was confirmed by optical microscopic technique. Synergistic effect of halide ions on mild steel in 1 M H2SO4 was studied by weight loss technique.

Disturbance and uncertainty rejection performance for fractional-order complex dynamical networks

Selvaraj, P.,Kwon, O.M.,Sakthivel, R. Elsevier 2019 Neural networks Vol.112 No.-

<P><B>Abstract</B></P> <P>This paper investigates the synchronization issue for a family of time-delayed fractional-order complex dynamical networks (FCDNs) with time delay, unknown bounded uncertainty and disturbance. A novel fractional uncertainty and disturbance estimator (FUDE) based feedback control strategy is proposed to not only synchronize the considered FCDNs but also guaranteeing the precise rejection of unmodelled system uncertainty and external disturbance. Especially, in FUDE-based approach, model uncertainties and external disturbance are integrated as a lumped disturbance and it does not require a completely known system model or a disturbance model. On the other hand, the design algorithm for the proposed control strategy is based on the state-space framework, rather than frequency-based design methodologies in the literature, which helps for predominant comprehension of the inner system behaviour. Also, by the temperance of Lyapunov stability theory and fractional calculus, a set of adequate conditions in the linear matrix inequality framework is obtained, which guarantees the robust synchronization of the closed-loop system. Furthermore, an iterative optimization algorithm is proposed to improve control robustness against the external disturbance and model uncertainties. Finally, two numerical illustrations including financial network model, where the influence of adjustment of macro-economic policies in the entire financial system are given to exhibit the rightness and important features of the acquired theoretical results.</P>

Schiff Bases as Anticorrosive Additives for Mild Steel Corrosion in Acid Media

M. Abirami,S. Sasikala,S. Chitra,K. Parameswari,A. Selvaraj 한국부식방식학회(구 한국부식학회) 2009 Corrosion Science and Technology Vol.8 No.1

Finite-time synchronization of stochastic coupled neural networks subject to Markovian switching and input saturation

Selvaraj, P.,Sakthivel, R.,Kwon, O.M. Elsevier 2018 Neural networks Vol.105 No.-

<P><B>Abstract</B></P> <P>This paper addresses the problem of finite-time synchronization of stochastic coupled neural networks (SCNNs) subject to Markovian switching, mixed time delay, and actuator saturation. In addition, coupling strengths of the SCNNs are characterized by mutually independent random variables. By utilizing a simple linear transformation, the problem of stochastic finite-time synchronization of SCNNs is converted into a mean-square finite-time stabilization problem of an error system. By choosing a suitable mode dependent switched Lyapunov–Krasovskii functional, a new set of sufficient conditions is derived to guarantee the finite-time stability of the error system. Subsequently, with the help of anti-windup control scheme, the actuator saturation risks could be mitigated. Moreover, the derived conditions help to optimize estimation of the domain of attraction by enlarging the contractively invariant set. Furthermore, simulations are conducted to exhibit the efficiency of proposed control scheme.</P>

Synchronization of fractional-order complex dynamical network with random coupling delay, actuator faults and saturation

Selvaraj, P.,Sakthivel, R.,Kwon, O. M. Springer-Verlag 2018 Nonlinear dynamics Vol.94 No.4

Characterization of Plant-Growth Promoting Diazotrophic Bacteria Isolated from Field Grown Chinese Cabbage under Different Fertilization Conditions

임우종,Selvaraj Poonguzhali,마드하이안,Pitchai Palaniappan,M. A. Siddikee,사동민 한국미생물학회 2009 The journal of microbiology Vol.47 No.2

Diazotrophic bacteria isolated from the rhizosphere of Chinese cabbage were assessed for other plant growth promoting characteristics viz., production of IAA, ethylene, ACC deaminase, phosphate solubilization, and gnotobiotic root elongation. Their effect on inoculation to Chinese cabbage was also observed under growth chamber conditions. A total of 19 strains that showed higher nitrogenase activity identified by 16S rRNA gene sequence analysis were found to be the members of the genera Pseudomonas and Agrobacterium belonging to α- and γ-Proteobacteria groups. These strains were also efficient in producing IAA and ACC deaminase though they produced low levels of ethylene and no phosphate solubilization. In addition, inoculation of selected diazotrophic bacterial strains significantly increased seedling length, dry weight, and total nitrogen when compared to uninoculated control. The colonization of crop plants by diazotrophic bacteria can be affected by many biotic and abiotic factors, and further studies are oriented towards investigating the factors that could influence the establishment of a selected bacterial community.