Rajesh S. Somani

Nanoclays for polymer nanocomposites, paints, inks, greases and cosmetics formulations, drug delivery vehicle and waste water treatment

An overview of nanoclays or organically modified layered silicates (organoclays) is presented with emphasis placed on the use of nanoclays as the reinforcement phase in polymer matrices for preparation of polymer/layered silicates nanocomposites, rheological modifier for paints, inks and greases, drug delivery vehicle for controlled release of therapeutic agents, and nanoclays for industrial waste water as well as potable water treatment to make further step into green environment. A little amount of nanoclay can alter the entire properties of polymers, paints, inks and greases to a great extent by dispersing 1nm thick layered silicate throughout the matrices. The flexibility of interlayer spacing of layered silicates accommodates therapeutic agents which can later on be released to damaged cell. Because the release of drugs in drug-intercalated layered materials is controllable, these new materials have a great potential as a delivery host in the pharmaceutical field. The problem of clean water can be solved by treating industrial and municipal waste water with organoclays in combination with other sorbents like activated carbon and alum. Organoclays have proven to be superior to any other water treatment technology in applications where the water to be treated contains substantial amounts of oil and grease or humic acid.

A low temperature bottom-up approach for the synthesis of few layered graphene nanosheets via C–C bond formation using a modified Ullmann reaction

A low temperature, single-pot, bottom-up approach for the synthesis of few layered graphene sheets using the modified Ullmann reaction is reported. The synthesis protocol involved a solvothermal technique under an autogenic pressure of chloroform, which was used as the carbon source. Scanning and transmission electron microscopy revealed the formation of randomly aggregated, thin, crumpled graphene sheets with a thickness of ∼2 nm. Solid state 13C nuclear magnetic resonance and Fourier transform infrared spectroscopy showed that the prepared graphene sheets have copious surface functionality. The possible growth mechanism for the formation of graphene sheets is proposed based on an analysis of the intermediate products by gas chromatography coupled with mass spectroscopy. The growth of few layered graphene sheets proceeded through addition and cyclization reactions of different chloroalkene intermediate products formed by the addition reaction of chloroform molecules, and not by the chain polymerization of chloroform molecules.

Synthesis of aluminium triflate-grafted MCM-41 as a water-tolerant acid catalyst for the ketalization of glycerol with acetone

An aluminium triflate covalently grafted over MCM-41 (Al(TF)–MS catalyst) was synthesized by a novel route, aiming to generate enhanced surface acidity as compared to aluminosilicates and water-tolerant mesoporous solid acid catalysts for reactions producing water as a co-product. The synthesis strategy involves an equimolar reaction of triflic acid and aluminium isopropoxide, followed by treatment with MCM-41. The direct treatment of triflic acid with Al-grafted MCM-41 (Al–MCM-41) was also attempted to synthesize silica-supported aluminium triflate. The MCM-41-supported aluminium triflate and triflic acid were synthesized as standard samples for comparison. The catalytic potentials of the samples were studied for the ketalization of glycerol with acetone into solketal. The TGA and 27Al MAS NMR studies revealed the formation of aluminium triflate species on the silica surface in the Al(TF)–MS sample. The covalent grafting of the aluminium triflate species in the Al(TF)–MS sample was confirmed from catalysis and reusability tests, showing the stability of the aluminium triflate species against hydrolysis by water produced during the reaction. The solvent-free and selective conversion of glycerol to solketal at room temperature and the simple reusability of spent catalyst without any regeneration are some attractive features of Al(TF)–MS, making it a suitable catalyst for solketal synthesis.

A dechlorination pathway for synthesis of horn shaped carbon nanotubes and its adsorption properties for CO2, CH4, CO and N2

Using metallic copper as reductant and tetrachloroethylene as carbon precursor, a simple, low temperature solvothermal method for the synthesis of horn shaped carbon nanotubes is reported. The detail study of reaction parameters such as temperature, time, carbon precursor amount, type and catalyst proportion has been carried out to optimize the conditions wherein that the copper metal (10 g) mediated reduction of tetrachloroethylene (25 mL) at 200°C for 5h resulted in the horn shaped carbon nanotubes with high yield and structural selectivity. The adsorption properties of horn shaped carbon nanotubes were investigated for carbon dioxide, methane, carbon monoxide and nitrogen as adsorbate by volumetric measurements up to 850 mm Hg. The prepared horn shaped carbon nanotubes showed good adsorption capacity for CO(2) (45 cm(3)/g) and CO (17 cm(3)/g), at 303 K and 850 mm Hg pressure, with high equilibrium selectivity (73.3 for CO(2) and 110.7 for CO at 318 K) and capacity selectivity (9.1 for CO(2) and 3.1 for CO at 850 mm Hg and 318 K) over nitrogen which provides the tool for the separation of CO(2) from its mixture with nitrogen observed in flue gas of thermal power plants and boilers, as well as with CO such as syngas.

Adsorption of carbon monoxide, methane and nitrogen on alkaline earth metal ion exchanged zeolite-X: structure, cation position and adsorption relationship†

Development of zeolite based adsorbents with high adsorption capacity and selectivity is the key requirement for efficient and economic separation processes. However, less attention has been given so far towards understanding the mechanism of adsorption on the zeolites. In the present study adsorption of carbon monoxide, methane and nitrogen on zeolite-X exchanged with magnesium, calcium, strontium and barium cations was carried out using a volumetric gas adsorption method. Calcium, strontium, and barium ion exchanged zeolite-X shows increase in carbon monoxide, methane and nitrogen adsorption capacity. Strontium exchanged zeolite-X shows carbon monoxide adsorption capacity of 28.4 molecules per unit cell and calcium exchanged zeolite-X shows methane and nitrogen adsorption capacity of 18.8 and 13.8 molecules per unit cell, respectively at 303 K and 760 mm Hg pressure, maximum among the alkaline earth metal ion exchanged zeolite-X samples. However, barium exchanged zeolite-X shows methane/nitrogen selectivity of 1.78, maximum among the studied samples. The initial heat of adsorption for carbon monoxide, methane and nitrogen increases on calcium, strontium and barium ion exchange, and decreases with increase in the size of the cations due to decrease in the electrostatic interactions. However, magnesium exchanged zeolite-X shows decrease in the heat of adsorption. The significant decrease in adsorption capacity and heats of adsorption on magnesium ion exchange is due to the migration of small size magnesium ions inside the sodalite cages (I′ and II′) and D6R (site I) from the super cage (site II, III and III′) during activation, where cations are not accessible for adsorption. The change in adsorption capacity, selectivity and heats of adsorption for alkaline earth metal ion exchanged zeolite-X is discussed in terms of the size, location, and effective charges on the extra-framework cations present in the zeolite cavity and the subsequent electrostatic interactions between the adsorbed molecules and the extra-framework cations.

Eco-friendly, catalyst-free synthesis of highly pure carbon spheres using vegetable oils as a renewable source and their application as a template for ZnO and MgO hollow spheres

Herein we report the eco-friendly and catalyst-free single step synthesis of solid carbon spheres, 1–10 μm in diameter, using vegetable oils derived from different bio-resources as the carbon source. The surface functionality of the synthesized carbon spheres was examined by Fourier transform infrared and charge polarized magic angle spinning nuclear magnetic resonance spectroscopy. The resulting carbon spheres were 100% pure, i.e. free of metal impurities, carbon soot and other structures; and do not require post treatments, such as extraction and purification. A detailed study showed that the synthesis of the carbon spheres proceeds through the formation and self-condensation of aromatic hydrocarbons generated from the oil precursor under autogenic pressure. The carbon spheres were used further as a template for the synthesis of nano crystalline ZnO and MgO hollow spheres.

A density functional theory study on the interaction of hydrogen molecule with MOF-177

The binding energies of H2 molecule with metal-organic framework MOF-177 clusters at various possible interaction sites have been calculated using density functional theory. The binding energy of adsorbed H2 molecule in MOF-177 was investigated, with the consideration of the favourable adsorption sites and the orientations at the inorganic cluster Zn4O and organic linker (1,3,5-benzenetribenzoate) in order to evaluate the role of these two principal components in MOF for H2 adsorption. Our results showed that both the inorganic connector and the organic linker play an important role in the H2 adsorption. The binding energy calculated for the inorganic cluster is 2.96–4.50 kJ mol− 1 and for the organic linker is 2.6–3.8 kJ mol− 1.

Preparation, characterization and hydrogen sorption study of MIL-101(Cr) pellets

The paper discusses the bulk (25 g/batch) synthesis of MIL-101(Cr) using acetic acid and its pelletization as hydrogen storage material for on-board automotive applications. The synthesized material was moulded into a shaped body (a pellet) using binders such as sodium salt of carboxy methyl cellulose (Na-CMC), starch (ST) and polyvinyl alcohol (PVA) as well as a pellet without binder. Pellets were prepared using an hydraulic press by applying different pressures (5, 10 and 15 tonnes; where 1 tonne per square metre = 9.80665 kPa). The research team investigated the effect of compression pressure on the pellet properties and also its hydrogen adsorption capacity. The surface area and micropore volume decreased with the increase of compression pressure. The Dubinin-Radushkevich (DR) equation was used to calculate micropore volume. The maximum hydrogen storage capacity obtained is 2.54 wt.% at temperature of 77 Kelvin (K) using 10% PVA as a binder at 10 tonnes compression pressure. MIL-101(Cr) pellets prepared without binder, compressed at 10 tonnes pressure, showed 3.10 wt.% hydrogen storage capacity at the temperature of 77 K.

Greenhouse Gas Adsorptivity of Horn-Shaped Carbon Nanotubes over Nitrogen: Equilibrium Study

The synthesis of horn-shaped carbon nanotubes using carbon tetrachloride as carbon source was carried out by solvothermal method at 200°C for 2 h. The scanning and transmission electron microscopic characterization of the obtained product showed the formation of horn-shaped carbon nanotubes with irregular wall structure having inner diameter of ∼105 nm and length of ∼1 µm. The equilibrium gas adsorption properties of horn-shaped carbon nanotubes derived from carbon tetrachloride were successfully investigated for CO2, CH4, and N2 at 288, 303, and 318 K. Horn-shaped carbon nanotubes possess better CO2 adsorption capacity (2.53 mmol/g) with high capacity selectivity (14.7) and equilibrium selectivity (59.1) over N2 at 288 K. The detailed adsorption study with estimation of physical parameters such as Henrys constant and heat of adsorption identifies the horn-shaped carbon nanotubes as a potential adsorbent material in the field of CO2 storage and separation.