S.M. Javaid Zaidi

Synthesis of superacid-functionalized mesoporous nanocages with tunable pore diameters and their application in the synthesis of coumarins.

Here we demonstrate for the first time the preparation of a triflic acid (TFA)-functionalized mesoporous nanocage with tunable pore diameters by the wet impregnation method. The obtained materials have been unambiguously characterized by XRD, N(2) adsorption, FTIR spectroscopy, and NH(3) temperature-programmed desorption (TPD). From the characterization results, it has been found that the TFA molecules are firmly anchored on the surface of the mesoporous supports without affecting their acidity. We also demonstrate the effect of the pore and cage diameter of the KIT-5 supports on the loading of TFA molecules inside the pore channels. It has been found that the total acidity of the materials increases with an increase in the TFA loading on the support, whereas the acidity of the materials decreases with an increase in the pore diameter of the support. The acidity of the TFA-functionalized mesoporous nanocages is much higher than that of the zeolites and metal-substituted mesoporous acidic catalysts. The TFA-functionalized materials have also been employed as the catalysts for the synthesis of 7-hydroxy-4-methylcoumarin by means of the Pechmann reaction under solvent-free conditions. It has been found that the catalytic activity of the TFA-functionalized KIT-5 is much higher than that of zeolites and metal-substituted mesoporous catalytic materials in the synthesis of coumarin derivatives. The stability of the catalyst is extremely good and can be reused several times without much loss of activity in the above reaction.

Research Trends in Polymer Electrolyte Membranes for PEMFC

In this chapter research trends followed by various scientific groups for the development of polymeric membranes have been described and reviewed. Most notably, the developments made at Ballard Advanced Materials (BAM) and some of their results are discussed. In general three different approaches have been fol- lowed worldwide by various research groups for the development and conception of alternative membranes. These approaches include: (1) modifying perfluorinated ionomer membranes; (2) functionalization of aromatic hydrocarbon polymers/ membranes; and (3) composite membranes based on solid inorganic proton con- ducting materials and the organic polymer matrix or prepare acid-base blends and their composite to improve their water retention properties. The current trend is for the composite and hybrid membranes, which combines the properties of both the polymeric component and inorganic part. The most widely studied polymer after Nafion is the sulfonated polyether-ether ketone (SPEEK), as it has a high potential for commercialization. A number of research projects are currently undergoing dealing with the SPEEK polymer in various research labs.

KINETICS OF CATALYTIC OXIDATION OF AQUEOUS SODIUM SULFITE

A gas-lift bubble column was used to investigate the kinetics of the reaction between oxygen and aqueous solutions of sodium sulfite in the presence of cobalt sulfate catalyst. Reaction orders have been determined for the sulfite, catalyst, and oxygen under high and low oxygen partial-pressure conditions.

Perfluorinated Ionomer-Boron Phosphate Composite Membranes for Polymer Electrolyte Membrane Fuel Cell Applications

Composite membranes have been prepared from perfluorinated ionomer (10 wt % PFSA-H + solution) and boron phosphate (BPO 4 ). The contents of solid BPO 4 in the composite membrane varied from 10 to 50 wt %. The conductivityof the composite membranes measured both at room temperature and at higher temperatures was found to increase with the incorporation of boron phosphate particles into PFSA ionomer. The highest conductivity of 6.2 × 10 - 2 S/cm was found for the composite membrane containing 50% BPO 4 at 120°C. The membranes were characterized by X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy, which confirmed the presence of solid BPO 4 into the membranes. The morphology of the membranes showed the even distribution of BPO 4 particles into the composite membranes. These membranes have a strong potential to be considered for use in direct methanol fuel cells.

Fuel Cell Fundamentals

In this chapter fuel cell introduction and general concepts about fuel cell are presented. Types of fuel cell and their classification are given and desired properties of the polymeric membranes for use in PEMFC are described. At the end challenges facing the fuel cell industry and their future outlook are briefly discussed.

Sulfonated Poly(Ether Ether Ketone) (SPEEK): A Promising Membrane Material for Polymer Electrolyte Fuel Cell

Nafion has been the material of choice for polymer electrolyte membrane fuel cells (PEMFCs), but during the last two decades, considerable efforts have been made to find an alternative with similar or better physicochemical properties and with lower manufacturing cost. Developments over the last two decades have resulted to some novel membrane materials with improved properties. Among the materials researched and developed, sulfonated poly(ether ether ketone) (SPEEK) has been the most promising and has the potential for commercialization. In this chapter, the properties of SPEEK and its characteristics are discussed.

Factors influencing the performance of naphtha hydro-desulfurization catalysts

Abstract The performance of the two CoMo catalysts was evaluated for hydrodesulfurization of two Saudi naphthas in a bench-scale unit under Industrial conditions. Various types of sulfur compounds in the naphtha feed stocks and products were determined by chemical analysis and gas chromatography. The results show that the product sulfur decreased with increasing temperature down to a minimum, followed by an increase at higher temperatures. This increase was attributed to the occurrence of H2S-alkene recombination reaction leading to the formation of mercaptans. The effect of increasing the space velocity was to slightly increase product sulfur, while the hydrogen gas rate had an insignificant effect. The product sulfur for the two catalysts was below 1 ppm in the temperature range 280–350°C. However, one catalyst was selected based on its superior HDS performance attributed to higher concentrations of molybdenum, cobalt and phosphorus oxides.

Application of titanium dioxide (TiO 2) based photocatalytic nanomaterials in solar and hydrogen energy: A short review

Tremendous amount of research work is going on Titanium dioxide (TiO2) based materials. These materials have many useful applications in our scientific and daily life and it ranges from photovoltaics to photocatalysis to photo-electrochromics, sensors etc.. All these applications can be divided into two broad categories such as environmental (photocatalysis and sensing) and energy (photovoltaics, water splitting, photo-/electrochromics, and hydrogen storage). Synthesis of TiO2 nanoparticles with specific size and structural phase is crucial, for solar sell application. Monodispersed spherical colloids with minimum size variation (5% or less) is essential for the fabrication of photonic crystals. When sensitized with organic dyes or inorganic narrow band gap semiconductors, TiO2 can absorb light into the visible light region and convert solar energy into electrical energy for solar cell applications. TiO2 nanomaterials also have been widely studied for water splitting and hydrogen production due to their suitable electronic band structure given the redox potential of water. Again nanostructured TiO2 has extensively been studied for hydrogen storage with good storage capacity and easy releasing procedure. All these issues and related finding will be discussed in this review.

Removal of Acid gases from Natural Gas Streams by Membrane Technology

Publisher Summary Membrane technology has a strong potential and promise for the removal of acid gases from natural gas. A number of studies have demonstrated the use of membrane processes for natural gas purification as feasible, economical, and environmental friendly. Membrane-base gas separations are getting popular due to the environmental and economic advantages. It can be used for the natural gas purification to remove acid gas such as CO2 and H2S. It competes directly against amine absorption process for removal of carbon dioxide. Even though there are a large number of other potential applications for gas separation using polymeric membranes, only few of them have been adopted in practice. Progress in gas separation studies using membranes was greatly accelerated and this technique has emerged as a commercially viable method in the 1980s due to the development and refinement of novel synthetic polymers. Since then, progress has been made continuously in improving membrane formation processes, chemical and physical structures and different modular configurations for specific end applications. In order to ensure the performance of a membrane, the scientific factors, such as processing of new materials and behavior of membranes with respect to various feed mixtures under practically realistic operating conditions must be considered.

Overview of Conversion of Greenhouse Gas Carbon dioxide to Hydrocarbons

Publisher Summary Carbon dioxide is a greenhouse gas and the concentration of CO2 in the atmosphere has increased significantly since the beginning of the industrial revolution. There are three main sources of CO2 emissions: stationary, mobile and natural sources. Conversion of green house gas carbon dioxide to abate global warming is of interest to save the planet from the catastrophe. Carbon dioxide can be used for the synthesis of important petrochemicals like methanol, ethylene etc. Various aspects of CO2 conversion have been extensively studied in both aqueous and non-aqueous medium. The process requires an efficient catalyst and energy and strongly depends on electrocatalyst used for the reduction products. Both in aqueous and non-aqueous environments and at higher over potentials the selectivity towards desired products is still relatively low. The major limitation is the low solubility of carbon dioxide in electrolyte and high over potential at which this reaction proceeds.