Siddharth S. Ray

Cobalt phthalocyanine immobilized on graphene oxide: an efficient visible-active catalyst for the photoreduction of carbon dioxide.

New graphene oxide (GO)-tethered-Co(II) phthalocyanine complex [CoPc-GO] was synthesized by a stepwise procedure and demonstrated to be an efficient, cost-effective and recyclable photocatalyst for the reduction of carbon dioxide to produce methanol as the main product. The developed GO-immobilized CoPc was characterized by X-ray diffraction (XRD), FTIR, XPS, Raman, diffusion reflection UV/Vis spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). FTIR, XPS, Raman, UV/Vis and ICP-AES along with elemental analysis data showed that Co(II) -Pc complex was successfully grafted on GO. The prepared catalyst was used for the photocatalytic reduction of carbon dioxide by using water as a solvent and triethylamine as the sacrificial donor. Methanol was obtained as the major reaction product along with the formation of minor amount of CO (0.82 %). It was found that GO-grafted CoPc exhibited higher photocatalytic activity than homogeneous CoPc, as well as GO, and showed good recoverability without significant leaching during the reaction. Quantitative determination of methanol was done by GC flame-ionization detector (FID), and verification of product was done by NMR spectroscopy. The yield of methanol after 48 h of reaction by using GO-CoPc catalyst in the presence of sacrificial donor triethylamine was found to be 3781.8881 μmol g(-1)  cat., and the conversion rate was found to be 78.7893 μmol g(-1) cat. h(-1). After the photoreduction experiment, the catalyst was easily recovered by filtration and reused for the subsequent recycling experiment without significant change in the catalytic efficiency.

Visible light-induced surface initiated atom transfer radical polymerization of methyl methacrylate on titania/reduced graphene oxide nanocomposite

A novel visible light assisted photoredox catalyst system for surface initiated atom transfer radical polymerization (SI-ATRP) is developed for polymer growth on the surface of titania/reduced graphene oxide (TiO2/rGO) nanocomposites using tetrasulfonated copper(II) phthalocyanine (CuPcS) as catalyst at ambient temperature. The synthesized composite was initially treated with 3-aminopropyltrimethoxysilane (APTMS), and then functionalized with 2-bromoisobutyryl bromide (BIBB) moieties, serving as a surface initiator for ATRP. In the present method, TiO2/rGO acted as a photoactive material to reduce Cu(II) to a Cu(I) complex under visible light by a one-electron transfer process as well as a surface for ATRP initiator immobilization and gave polymer linked TiO2/rGO composites. These hybrid materials were found to show high dispersability in organic solvents.

Conventional and atom transfer radical copolymerization of n-octyl acrylate-styrene: chemoselectivity and monomer sequence distribution by 1H NMR

Abstract Octyl acrylate and styrene (OA–St) were copolymerized by conventional polymerization at 80 °C and atom transfer radical polymerizations at 130 °C in different feed ratios (0.1–0.9 mole fraction of OA) using benzoyl peroxide and cuprous chloride/2,2′-bipyridine/1-phenyl ethyl chloride respectively. Two linear (Fineman–Ross, Kelen–Tudos) methods and a nonlinear least-squares method were employed for determination of monomer reactivity ratios (rOA=0.30±0.02 and rSt=0.69±0.04). Integrated intensities of the three peaks observed in the 1 H NMR spectra of –OCH2 group (3.2–4.2 ppm) were used to determine the mole fraction of 111, 112 or 211 and 212 triad sequences in the copolymers. In addition, the rOA value was used for theoretical determination of mole fraction of these triad sequences. Well-agreed theoretical and experimental values helped us in determining most probable mole fractions of the triad sequences of monomers.

Microwave-assisted surface-initiated redox polymerization of acrylamide with functionalized graphene oxide for aqueous lubricant additive

A fast and efficient approach for the synthesis of nanocomposites of polyacrylamide-grafted-functionalized graphene oxide (FGO-PAM) through microwave-assisted surface initiated-redox polymerization (SI-RP) of acrylamide using functionalized graphene oxide and Ce(IV) ions as a redox couple in aqueous medium is reported. The nanocomposites are characterized by FT-IR, UV-Vis, Raman, XRD, TGA, FE-SEM, and HRTEM. These characterizations indicate a facile synthesis of macromolecular brushes of polyacrylamide on the surface of the graphene oxide. The high dispersion ability and composition ratio of the components facilitate the exploration and evaluation of the lubrication characteristics of this nanocomposite as an additive in an aqueous medium. The results showed a substantial reduction of the friction coefficient (46–55%) and improvement in anti-wear properties (13–37%), due to the formation of lubricating nanolayers of the nanocomposite between the two frictional surfaces, thus qualifying this nanocomposite as an aqueous lubricating additive for tribological application.

Derivatizing L-histidine to develop a novel additive for a polyol-based biolubricant

Two novel histidine Schiff base esters, HSE-A and HSE-B, were synthesized using a two-step reaction. The synthesized compounds were characterized using carbon, hydrogen, nitrogen analysis, Fourier-transform infrared and nuclear magnetic resonance spectroscopy. The antioxidant and anticorrosion properties of these additives were assessed using the universal oxidation test (IP-306) and standard accelerated corrosion testing procedure, which revealed that both additives have good antioxidant and anticorrosion properties. Lubricity test carried out in a four-ball test machine indicated that both additives could reduce wear when compared with the pure polyol base oil. Overall, the HSE-A additive is more effective than the HSE-B additive as an antioxidant/antiwear/anticorrosion biolubricant additive.

Development of new ecofriendly detergent/dispersant/antioxidant/antiwear additives from L-histidine for biolubricant applications

Two novel overbased Ca salts of histidine Schiff base esters Ca-HDS-L and Ca-HDS-M were synthesized following a three-step reaction sequence. The histidine Schiff base (HDS) was synthesized first by imine coupling of histidine with salicylaldehyde. Then its phenolic group was esterified using lauroyl chloride and myristoyl chloride to obtain HDS-L and HDS-M, respectively. Finally in the third step, their respective overbased salts Ca-HDS-L and Ca-HDS-M were synthesized by reaction with Ca(OH)2. All the synthesized compounds were characterized using FT-IR, NMR, CHN and TG analysis. Panel coker federal test (FTM 3462), blotter spot test (ASTM D7899), universal oxidation test (IP-306) and four ball test (ASTM 4172A) were used for the evaluation of detergent, dispersant, antioxidant and antiwear activity, respectively, of the synthesized additives in polyol base oil. Both the additives are active but overall Ca-HDS-L is more effective as detergent and dispersant while Ca-HDS-M is more effective as antioxidant and antiwear multifunctional biolubricant additive.

Ex situ Cu(0) nanoparticle mediated SET-LRP of methyl methacrylate/styrene-methyl methacrylate in a biphasic toluene–water system

The present paper described the first successful use of ex situ copper(0) nanoparticles as an efficient catalyst vis-a-vis using toluene as an effective solvent when doped with water for SET-LRP. Copper(0) nanoparticles (Cu(0) nanoparticles) of ∼5 nm were used as a catalyst with different nitrogen(N)-ligands for the single-electron transfer mediated LRP (SET-LRP) of methyl methacrylate (MMA) using a biphasic water–toluene system as the reaction media. The polymerization was studied by varying the catalyst concentration (0.15 ppm to 28.5 ppm) as well as by varying the mole ratios of monomer, initiator and N-ligands such as N,N,N′,N′′,N′′′-pentamethyldiethylene-triamine (PMDETA), N,N,N′,N′-tetramethyl-1,6-hexanediamine(TMHDA), N,N,N′,N′-tetramethylethylenediamine (TMEDA) and N,N-dimethylhexadecylamine (DMHA). Among the various N-ligands studied PMDETA provided best control over molecular weight while TMHDA gave worst control resulting in a polydispersity of 1.15 and 2.11, respectively at high monomer conversion. The rate of polymerization (kappp) of MMA using Cu(0) nanoparticles/PMDETA at 25 °C and 70 °C was found to be 0.00076 min−1 and 0.0048 min−1, respectively. Under these polymerization conditions, the reactivity ratio of MMA and styrene (St) was found to be 0.41 and 0.23 at 70 °C, respectively.

Expanded corn starch a novel material as macroinitiator/solid support in SI and AGET ATRP: GMA polymerization

Here we have shown the use of expanded corn starch (ECS) as an effective macro-initiator in Surface Initiated Atom Transfer Radical Polymerization (SI-ATRP) as well as a solid support in catalytic system for Activators Generated by Electron Transfer-Atom Transfer Radical Polymerization (AGET ATRP) for poly-glycidyl methacrylate (PGMA) with reasonably narrow polydispersity (PDI: 1.3–1.6). ECS having characteristic V type crystallinity imparts high surface area (~50 m2g−1), pore volume (0.43 cm3g−1) and high thermal stability enabling it as a better material over CS for use in ATRP. Also, catalytic system in AGET ATRP based on ECS can be recycled for several times without substantial loss of activity. Thus, ECS proves to be a versatile material that can be used in different ways in ATRP leading to polymers/polymer-hybrids with controlled molecular weight.

Capacity of thiourea Schiff base esters as multifunctional additives: synthesis, characterization and performance evaluation in polyol

A novel thiourea Schiff base ester TSBE was synthesized following a two step reaction. At first, thiourea and salicylaldehyde were reacted in ethanol to obtain thiourea Schiff base TSB. In the second step, esterification of TSB was done with lauroyl chloride catalyzed by 4-(dimethylamino)pyridine (DMAP) in N,N-dimethylacetamide (DMAc) solvent to obtain the final product TSBE. The synthesized compounds were characterized using CHN analysis, FT-IR and NMR. The antioxidant properties of this additive were assessed via the universal oxidation test (IP-306) and rotary bomb oxidation test (ASTM D2272) while antifriction and antiwear properties were evaluated in terms of the average friction coefficient and average wear scar diameter respectively by doing the four ball test (ASTM D4172). Studies revealed that TSBE had good antioxidant properties. Tests carried out by a four ball test machine indicated that the additive TSBE could reduce the friction to 45.6% and wear to ∼20% when compared with the pure polyol base oil.

Chapter 12 NMR studies of FCC feeds, catalysts and coke

Abstract NMR has become an indispensable tool for characterizing a variety of complex materials, includingheavy petroleum fractions, catalysts and coke. Determination of average molecular parameter by NMR is useful for the analysis of complex hydrocarbons like coal liquids, heavy oils, synthetic oils and high boiling petroleum fractions. This not only gives a brief idea of the molecules present but can also be used for prediction of crackability and coking tendency of the feedstock under a particular condition of operation. Although solid state NMR has not attained the resolution as of liquids, it has been proved as a better technique for molecular level characterization particularly in catalysis. This is because of the use of magic angel spinning, cross polarization (CP) and heteronuclear decoupling techniques in conjunction with routine and sophisticated solid experiments. In this chapter, NMR has been used to study the feeds, catalysts and coke of the FCC process of refining industries. Fluid catalytic cracking (FCC) feeds from two Indian refineries are structurally characterized by inverse gated decoupled 13C and distortionless enhancement by polarization transfer (DEPT) NMR methods. Detailed structural analyses are completely supported by a range of NMR information including chemical shifts of 1H and 13C, CHn type distributions and 1H-13C connectivities from 2D HETCOR NMR. The average structural parameters obtained from NMR analysis give a brief idea about the nature of feeds used in the FCC units. 29Si MAS, 27Al MAS and 27Al 3QMAS NMR methods are employed to study the structure of fresh and spent catalyst obtained after stripping. Other analytical techniques like HPLC, microcalorimetry, XRD, TGA, IR are used to compliment or augment the inferences obtained from NMR. The changes in structure of catalyst are described in terms of framework Si/Al ratio, the relative distribution of various acid sites (different framework Si atoms) and the changes in their relative populations and changes in unit cell sizes. The variations in structure of two catalysts are correlated in terms of their quadrupolar coupling constant values at the site of octahedral and tetrahedral Al nuclei obtained from the MQMAS studies. The soluble and insoluble coke concentrates are extracted from the spent FCC catalysts by chemical methods and are studied by different NMR techniques. Conventional 1H and 13C NMR is used to derive the average structure of soluble coke. Quantitative data about the insoluble coke aromaticity are obtained from solid state13C SHPE/MAS NMR. The information of protonated and non-protonated carbons are obtained from Dipolar Dephasing (DD) experiments in combination with SHPE/MAS. The compositional variation in the feed and changes in catalyst properties are used to explain the nature and structural differences of the coke.