Astam K. Patra

Self-assembled mesoporous γ-Al2O3 spherical nanoparticles and their efficiency for the removal of arsenic from water.

We report a highly efficient synthetic strategy for self-assembled mesoporous γ-Al(2)O(3) materials using sodium salicylate as template. The mesoporous γ-Al(2)O(3) samples synthesized following this strategy have high surface areas (231-497 m(2)g(-1)), consist of crystalline tiny spherical nanoparticles of dimensions ca. 2-10nm and showed high affinity for the adsorption of arsenic from the contaminated aqueous solutions. Efficient synthesis strategy, exceptionally high surface area and high adsorption efficiency of these mesoporous γ-Al(2)O(3) materials for the dissolved arsenic from the contaminated aqueous solutions (in the form of oxyanions of arsenic) could find potential utility in the purification of polluted water.

Efficient Solid Acid Catalyst Containing Lewis and Brønsted Acid Sites for the Production of Furfurals

Self-assembled nanoparticulates of porous sulfonated carbonaceous TiO2 material that contain Brønsted and Lewis acidic sites were prepared by a one-pot synthesis method. The material was characterized by XRD, FTIR spectroscopy, NH3 temperature-programmed desorption, pyridine FTIR spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, N2 -sorption, atomic absorbance spectroscopy, and inductively coupled plasma optical emission spectroscopy. The carbonaceous heterogeneous catalyst (Glu-TsOH-Ti) with a Brønsted-to-Lewis acid density ratio of 1.2 and more accessible acid sites was effective to produce 5-hydroxymethylfurfural and furfural from biomass-derived mono- and disaccharides and xylose in a biphasic solvent that comprised water and biorenewable methyltetrahydrofuran. The catalyst was recycled in four consecutive cycles with a total loss of only 3 % activity. Thus, Glu-TsOH-Ti, which contains isomerization and dehydration catalytic sites and is based on a cheap and biorenewable carbon support, is a sustainable catalyst for the production of furfurals, platform chemicals for biofuels and chemicals.

Synthesis of 5‐Hydroxymethylfurural from Carbohydrates using Large‐Pore Mesoporous Tin Phosphate

A large-pore mesoporous tin phosphate (LPSnP-1) material has been synthesized hydrothermally by using Pluronic P123 as the structure-directing agent. The material is composed of aggregated nanoparticles of 10-15 nm in diameter and has a BET surface area of 216 m(2)  g(-1) with an average pore diameter of 10.4 nm. This pore diameter is twice as large as that of mesoporous tin phosphate materials synthesized through the surfactant-templating pathways reported previously. LPSnP-1 shows excellent catalytic activity for the conversion of fructose, glucose, sucrose, cellobiose, and cellulose to 5-hydroxymethylfurfural (HMF) in a water/methyl isobutyl ketone biphasic solvent to give maximum yields of HMF of 77, 50, 51, 39, and 32 mol %, respectively, under microwave-assisted heating at 423 K. Under comparable reaction conditions, LPSnP-1 gives 12 % more HMF yield than a small-pore mesoporous tin phosphate catalyst that has an identical framework composition. This confirms the beneficial role of large mesopores and nanoscale particle morphology in catalytic reactions that involve bulky natural carbohydrate molecules.

Hierarchically porous titanium phosphate nanoparticles: an efficient solid acid catalyst for microwave assisted conversion of biomass and carbohydrates into 5-hydroxymethylfurfural

A new hierarchical macro/mesoporous titanium phosphate MTiP-1 has been synthesized through a slow evaporation method by using titanium isopropoxide and orthophosphoric acid as inorganic sources and pluronic P123 as the structure directing agent. Powder X-ray diffraction, FT-IR and electron dispersive spectroscopy (EDS) were used to analyze the framework, structure and composition of the material. The N2 adsorption/desorption isotherm of this material is of type IV, which is characteristic of a mesoporous material and it shows a Brunauer–Emmett–Teller (BET) surface area of 193 m2 g−1 together with an average pore dimension of ca. 7 nm. From scanning electron microscopic (SEM) images it is seen that there is hierarchical porosity in MTiP-1 and the mesoporosity of this material arises due to self-aggregation of tiny spherical particles of dimension ca. 15–20 nm. Transmission electron microscopic (TEM) images show the existence of randomly distributed mesopores in the material. This MTiP-1 material shows very good catalytic activity in the microwave assisted conversion of biomass and carbohydrates into 5-hydroxymethylfurfural (HMF). The catalytic reactions are carried out in different solvents like water, water–methylisobutyl ketone (MIBK), MIBK and dimethylacetamide (DMA)–LiCl. MTiP-1 also catalyzes the direct conversion of cellulose substrates and lignocellulosic biomass, sugarcane bagasse, into HMF.

Self-assembly of mesoporous TiO2 nanospheres viaaspartic acid templating pathway and its catalytic application for 5-hydroxymethyl-furfural synthesis

Self-assembled mesoporous TiO2 nanoparticulate material with well-defined nanospherical morphologies was prepared by using DL-aspartic acid as a template. Powder XRD, TEM and SEM techniques were used to characterize the TiO2 nanoparticles. The presence of high acid density in the mesoporous TiO2 was confirmed by pyridine-IR and NH3-TPD studies. This new mesoporous TiO2 nanomaterial efficiently catalyzed the dehydration of D-fructose and D-glucose into 5-hydroxymethylfurfural in DMA-LiCl solvent under microwave assisted heating. The acidic sites of the TiO2 nanomaterial were responsible for the dehydration reaction which produced a maximum 82.3% HMF.

Self-assembled mesoporous TiO2 spherical nanoparticles by a new templating pathway and its enhanced photoconductivity in the presence of an organic dye

The supramolecular assembly of ionic/non-ionic surfactants has been extensively employed as a template or structure directing agent (SDA) in the synthesis of a large variety of mesoporous materials over the past one and a half decades. Herein, we report the first highly efficient synthesis strategy for self-assembled mesoporous TiO2 materials with well-defined crystal morphologies using sodium salicylate as a template. Mesoporous TiO2 nanoparticles showed a drastically enhanced photoelectrochemical response under visible light irradiation after entrapping a photosensitizer molecule (dye) inside the mesopores. The efficient synthesis strategy and enhanced photoresponse of these mesoporous TiO2 materials could facilitate the design of other porous semiconductor oxides and their applications in photon-to-electron conversion processes.

Self-Assembled TiO2 Nanospheres By Using a Biopolymer as a Template and Its Optoelectronic Application

Self-assembled TiO(2) nanoparticulate materials with well-defined spherical morphologies were synthesized by using a biopolymer sodium alginate as a template under different synthesis conditions. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) techniques were used to characterize the TiO(2) nanoparticles. N(2) sorption analysis revealed the moderately good surface area (124.0 m(2) g(-1)) and pore volume (0.44 cm(3) g(-1)) of these TiO(2) nanoparticles. The biopolymer templating pathway leads to good-quality self-assembled TiO(2) nanoparticles with dimensions of ca. 10-12 nm within the synthesis temperature range of 0-60 °C. These porous TiO(2) nanomaterials showed high photogenerated current in the presence of a dye (Rose Bengal), used as a sensitizer for several photo on/off cycles.

Hybrid porous tin(IV) phosphonate: an efficient catalyst for adipic acid synthesis and a very good adsorbent for CO2 uptake.

A new porous organic-inorganic hybrid tin phosphonate material has been synthesized hydrothermally, which shows a Brunauer-Emmett-Teller surface area of 723 m(2) g(-1) and it adsorbs 4.8 mmol g(-1) CO(2) at 273 K and 5 bar pressure. The material also shows remarkable catalytic activity in one-pot liquid phase oxidation of cyclohexanone to adipic acid under eco-friendly conditions.

Template-Free Synthesis of a Porous Organic–inorganic Hybrid Tin(IV) Phosphonate and Its High Catalytic Activity for Esterification of Free Fatty Acids

Here we have synthesized an organic-inorganic hybrid mesoporous tin phosphonate monolith (MLSnP-1) with crystalline pore walls by a template-free sol-gel route. N2 sorption analysis shows Brunauer-Emmett-Teller (BET) surface area of 347 m2 g(-1). Wide-angle powder X-ray diffraction (PXRD) pattern shows few broad diffraction peaks indicating crystalline pore wall of the material. High-resolution transmission electron microscopic (HR TEM) image further reveals the crystal fringes on the pore wall. Framework bonding and local environment around phosphorus and carbon were examined by Fourier transform infrared (FT IR) spectroscopy and solid-state MAS NMR spectroscopy. The material exhibits remarkable catalytic activity for esterification of long chain fatty acids under mild reaction conditions at room temperature.

Synthesis of Hierarchical Mesoporous Mn–MFI Zeolite Nanoparticles: A Unique Architecture of Heterogeneous Catalyst for the Aerobic Oxidation of Thiols to Disulfides

An efficient procedure for aerobic oxidation of thiols to disulfides catalyzed by new self‐assembled hierarchical mesoporous Mn–MFI in the presence of air under solvent‐free conditions as well as in aqueous medium is reported. The mesoporosity and Mn4+ loading, together with a highly crystalline microporous pore wall structure of the MFI framework were achieved through a newly designed hydrothermal process. This hydrothermal approach leads to hierarchical self‐assembled mesoporous zeolite structures through isomorphous substitution of Si by Mn and Al. It is shown that Mn‐containing mesoporous zeolites are capable to form disulfide bonds from thiols in the presence of air. The zeolitic materials were characterized by XRD, field‐emission scanning electron microscopy, high‐resolution TEM, X‐ray photoelectron spectroscopy, 29Si NMR, 27Al NMR, and EPR spectroscopy, as well as AAS analysis and N2 sorption studies. N2 sorption analysis revealed high surface areas and narrow pore size distributions (1.2–6.0 nm) for different samples. The mesoporous Mn–ZSM‐5 acted as an efficient heterogeneous catalyst with maximum catalytic activity in the benzenethiol conversion to diphenyldithiol.