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Rajaram Bal

Bio: Rajaram Bal is an academic researcher from Indian Institute of Petroleum. The author has contributed to research in topics: Catalysis & Syngas. The author has an hindex of 34, co-authored 138 publications receiving 3094 citations. Previous affiliations of Rajaram Bal include University of Tokyo & Academy of Scientific and Innovative Research.
Topics: Catalysis, Syngas, Benzene, Spinel, Selectivity


Papers
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TL;DR: In this article, a nickel-based catalyst with high activity at low temperature for partial oxidation of methane (POM) was synthesized by two-step preparation method, where Ni-nanoparticles supported on CeO2 nanoparticles were synthesized and a new procedure was developed where cetyltrimethylammonium bromide (CTAB) acted as morphology controlling agent and polyvinylpyrrolidone (PVP) as size controlling agent for nickel nanoparticles.
Abstract: The objective of the current study was to synthesize a nickel based catalyst with high activity at low temperature for partial oxidation of methane (POM). Ni-nanoparticles supported on CeO2 nanoparticles were synthesized by two step preparation method. First, 30–50 nm CeO2 was synthesized by solvo-thermal method and then Ni- nanoparticles were deposited over it following a newly developed procedure, where cetyltrimethylammonium bromide (CTAB) acted as morphology controlling agent and polyvinylpyrrolidone (PVP) as size controlling agent for nickel nanoparticles. The characterizations of synthesized catalysts were done by BET-Surface area, XRD, SEM, TEM, TPR, H2-chemisorpton, TGA and XPS analysis. The catalysts showed excellent coke resisting ability during POM and produces synthesis gas with H2/CO ratio almost 2. The catalyst activated methane at 400 °C with 10% methane conversion and converts methane almost completely at 800 °C. The catalyst showed above 98% methane conversion at 800 °C during 90 h of time on stream (TOS) reaction with H2/CO ratio 1.98. Average 5.5 nm Ni particles, use of CeO2 as a support played a very crucial role for methane activation at such lower temperature. The synergistic effect between small Ni-nanoparticles and CeO2 nanoparticles of Ni-CeO2 catalyst is the main reason for such activity. Detailed study of other reaction parameters like temperature, Ni loading, weight hourly space velocity (WHSV) was also carried out and reported.

163 citations

Journal ArticleDOI
TL;DR: In this paper, a catalytic partial oxidation of methane (CPO) to synthesis gas was performed over differently prepared CeO 2 supported nickel catalysts with 6-wt% Ni content.
Abstract: Catalytic partial oxidation of methane (CPO) to synthesis gas was performed over differently prepared CeO 2 supported nickel catalysts with 6 wt% Ni content. The samples were synthesized by microwave assisted procedures and by hydrothermal deposition procedure. Differences in the catalyst structural properties of the prepared catalysts were detected by XRD, TPR and XPS measurement. When tested at atmospheric pressure with feed gas mixture containing methane and oxygen in molecular ratio CH 4 /O 2 = 2, all the samples reached 98% conversion with CO selectivity values >95% in the 700–800 °C temperature range. The samples exhibited different behavior towards carbon formation during the tests. Moreover, according to XRD, XPS and TGA results, when the carbon was formed it did not cause catalyst deactivation. TPR profiles confirmed different degree of chemical interaction between NiO and CeO 2 support, depending on the preparation method. The building up or the easy removal of carbon during the CH 4 temperature programmed surface reaction (TPSR), substantiate the role of the CeO 2 lattice oxygen mobility, enhanced by metal-support interaction, in the removal of the deposited carbon through CO evolution. Structure-activity relationship established a close dependence of the CPO performance on the combination of NiO and CeO 2 crystallite sizes and the interaction between the two.

133 citations

Journal ArticleDOI
TL;DR: In this paper, a Ni-nanoparticles supported on MgO promoted nanocrytalline zinc oxide catalyst was prepared by hydrothermal method in presence of cationic surfactant cetyltrimethylammonium bromide.
Abstract: Ni-nanoparticles supported on MgO promoted nanocrytalline zinc oxide catalyst was prepared by hydrothermal method in presence of cationic surfactant cetyltrimethylammonium bromide. The catalyst showed very good activity for the reforming of methane with carbon dioxide to produce synthesis gas, where H 2 /CO ratio was almost 1 and the catalyst showed no deactivation for more than 100 h. The prepared catalyst was characterized using the analytical techniques like N 2 -physisorption studies, X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Temperature programmed desorption (TPD), Temperature programmed reduction (TPR), Temperature programmed oxidation (TPO), H 2 -chemisorpton, Thermo-gravimetric analysis (TGA), Inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), and Extended X-ray absorption fine structure (EXAFS). Transmission electron microscopy and H 2 -chemisorption analysis indicated that highly dispersed Ni nanoparticles with average size 5.7 nm, present on ZnO when MgO was added with the catalyst. The strong Ni–ZnO interaction was evidenced from TPR and EXAFS analysis. The presence of highly dispersed Ni nanoparticles and strong metal support interaction enhanced the reduction behaviour of the Ni-MgO/ZnO catalyst. The presence of MgO increased the adsorption behaviour of CO 2 , enhanced the dissociation of CO 2 and accelerated the carbon elimination.

131 citations

Journal ArticleDOI
TL;DR: In this article, a new synthesis strategy was developed to prepare 2-5 nm metallic silver nanoparticles supported on tungsten oxide (WO3) nanorods with diameters between 30 and 40 nm, in the presence of cationic surfactant (cetyltrimethylammonium bromide: CTAB), capping agent (polyvinylpyrrolidone: PVP), and hydrazine.
Abstract: Propylene oxide (PO) is a versatile chemical intermediate, and by volume it is among the top 50 chemicals produced in the world. The catalytic conversion of propylene to PO by molecular oxygen with minimum waste production is of high significance from an academic as well as an industrial point of view. We have developed a new synthesis strategy to prepare 2–5 nm metallic silver nanoparticles (AgNPs) supported on tungsten oxide (WO3) nanorods with diameters between 30 and 40 nm, in the presence of cationic surfactant (cetyltrimethylammonium bromide: CTAB), capping agent (polyvinylpyrrolidone: PVP), and hydrazine. The synergy between the surface AgNPs and WO3 nanorods facilitates the dissociation of molecular oxygen on the metallic Ag surface to produce silver oxide, which then transfers its oxygen to the propylene to form PO selectively. The catalyst exhibits a PO production rate of 6.1 × 10–2 mol gcat–1 h–1, which is almost comparable with the industrial ethylene-to-ethylene oxide production rate.

108 citations


Cited by
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TL;DR: The "polymer chemistry" of g-C(3)N(4) is described, how band positions and bandgap can be varied by doping and copolymerization, and how the organic solid can be textured to make it an effective heterogenous catalyst.
Abstract: Polymeric graphitic carbon nitride materials (for simplicity: g-C(3)N(4)) have attracted much attention in recent years because of their similarity to graphene. They are composed of C, N, and some minor H content only. In contrast to graphenes, g-C(3)N(4) is a medium-bandgap semiconductor and in that role an effective photocatalyst and chemical catalyst for a broad variety of reactions. In this Review, we describe the "polymer chemistry" of this structure, how band positions and bandgap can be varied by doping and copolymerization, and how the organic solid can be textured to make it an effective heterogenous catalyst. g-C(3)N(4) and its modifications have a high thermal and chemical stability and can catalyze a number of "dream reactions", such as photochemical splitting of water, mild and selective oxidation reactions, and--as a coactive catalytic support--superactive hydrogenation reactions. As carbon nitride is metal-free as such, it also tolerates functional groups and is therefore suited for multipurpose applications in biomass conversion and sustainable chemistry.

2,735 citations

Journal ArticleDOI
TL;DR: This Review will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities in a unifying manner.
Abstract: Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

2,700 citations

Journal ArticleDOI
TL;DR: Pd on Modified Silica 159 4.5.1.
Abstract: 4.4. Pd on Modified Silica 159 4.5. Pd on Clay and Other Inorganic Materials 159 5. Stille, Fukuyama, and Negishi Reactions 159 5.1. Stille Reactions 159 5.1.1. Pd on Carbon (Pd/C) 159 5.1.2. Palladium on KF/Al2O3 159 5.1.3. Pd on Modified Silica (SiO2/TEG/Pd) 159 5.2. Fukuyama Reactions 159 5.2.1. Pd on Carbon (Pd/C) 159 5.2.2. Pd(OH)2 on Carbon (Perlman’s Catalyst) 160 5.3. Pd/C-Catalyzed Negishi Reactions 160 6. Ullmann-Type Coupling Reactions 161 6.1. Pd/C-Catalyzed Aryl−Aryl Coupling 161 6.2. Pd/C-Catalyzed Homocoupling of Vinyl Halides 162

1,900 citations

Journal ArticleDOI
TL;DR: A critical appraisal of different synthetic approaches to Cu and Cu-based nanoparticles and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications in catalysis.
Abstract: The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

1,823 citations

Journal ArticleDOI
TL;DR: A wide array of forms of palladium has been utilized as precatalysts for Heck and Suzuki coupling reactions over the last 15 years as mentioned in this paper, and there are now many suggestions in the literature that narrow the scope of types of precatalyst that may be considered true catalysts in these coupling reactions.
Abstract: A wide array of forms of palladium has been utilized as precatalysts for Heck and Suzuki coupling reactions over the last 15 years. Historically, nearly every form of palladium used has been described as the active catalytic species. However, recent research has begun to shed light on the in situ transformations that many palladium precatalysts undergo during and before the catalytic reaction, and there are now many suggestions in the literature that narrow the scope of types of palladium that may be considered true “catalysts” in these coupling reactions. In this work, for each type of precatalyst, the recent literature is summarized and the type(s) of palladium that are proposed to be truly active are enumerated. All forms of palladium, including discrete soluble palladium complexes, solid-supported metal ligand complexes, supported palladium nano- and macroparticles, soluble palladium nanoparticles, soluble ligand-free palladium, and palladium-exchanged oxides are considered and reviewed here. A considerable focus is placed on solid precatalysts and on evidence for and against catalysis by solid surfaces vs. soluble species when starting with various precatalysts. The review closes with a critical overview of various control experiments or tests that have been used by authors to assess the homogeneity or heterogeneity of catalyst systems.

1,737 citations