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2 results on '"Enhanced hydrogen productions"'

1. Integrated catalytic adsorption steam gasification in a bubbling fluidized bed for enhanced H2 production : Perspective of design and pilot plant experiences

Author

Khan, Zakir, Yusup, Suzana, Ahmad, Murni M., Inayat, Abrar, Naqvi, Muhammad, Sheikh, Rizwan, Watson, Ian, Khan, Zakir, Yusup, Suzana, Ahmad, Murni M., Inayat, Abrar, Naqvi, Muhammad, Sheikh, Rizwan, and Watson, Ian

Abstract

It is important to build knowledge about the design of an integrated catalytic adsorption (ICA) steam gasification process in a bubbling fluidized bed, which can reduce CO2 content with enhanced hydrogen production. The value of this study is its presentation of detailed design considerations for the performance evaluation of an ICA system using palm oil waste as feedstock. The main advantage of using ICA gasification systems is the CO2 adsorption through a carbonation reaction (using CaO), which helps the water gas shift reaction to move forward. The activity of a catalyst improves steam methane reforming in parallel, which not only produces additional hydrogen but also releases CO to enhance the activity of the water gas shift reaction. The performance of the developed system has shown <1% of temperature variation inside the reactor, which suggested a positive role for exothermic reactions between reactive bed material (CaO) and CO2 in the product gas. The low pressure drop in the gasifier (100-130mbar) further strengthens the design strategy for the ICA gasification system for hydrogen production. Challenges encountered during the pilot plant operations, and their potential solutions, are discussed to optimize the operation, especially for downstream equipment and auxiliaries.

Published
2018
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2. Nanohybrid of titania/carbon nanotubes – nanohorns: A promising photocatalyst for enhanced hydrogen production under solar irradiation

Author

D. Praveen Kumar, Prathap Haridoss, Muthukonda Venkatakrishnan Shankar, M. MamathaKumari, and Valluri Durgakumari

Subjects
Multiwalled carbon nanotubes (MWCN), Carbon nanohorn, Single-walled carbon nanohorn, law.invention, chemistry.chemical_compound, Solar energy, Photogenerated charge carriers, law, Solar radiation, Water splitting, Reaction kinetics, Optical properties, Nanostructured materials, Condensed Matter Physics, Photo-stability, Fuel Technology, Photocatalysts, Catalyst activity, Photocatalysis, Single walled carbon nanohorns, Reaction rates, Materials science, Multiwalled carbon nanotube (MWCNTs), Energy Engineering and Power Technology, chemistry.chemical_element, Nanotechnology, Charge carriers, Carbon nanotube, Solar power generation, Catalysis, Single-walled carbon nanotubes (SWCN), Yarn, Light absorption, Enhanced hydrogen productions, Hydrogen production, Light reflection, Renewable Energy, Sustainability and the Environment, Crystal structure, Functionalized carbon nanotubes, Carbon, chemistry, Chemical engineering, Mixtures, Titanium dioxide, Nanohorns, Irradiation, Surface reactions
Abstract

Mixtures of straight and defect-free multiwalled carbon nanotubes (MWCNTs), single walled carbon nanohorns (SWCNHs), and multiwalled carbon nanohorns (MWCNHs) were prepared by the arc discharge method. Functionalized Carbon Nanotubes (FCNTs) composed of MWCNTs, MWCNHS and SWCNHs were obtained using acid functionalization process. TiO2/FCNTs (CTP) nanohybrid photocatalysts were obtained with different amounts of FCNTs (2-20 wt%), by wet impregnation method. The photocatalytic activity of both pristine TiO2 as well as the nanohybrids were studied in aqueous glycerol solution under solar irradiation. Reaction parameters such as amount of catalyst and amount of FCNTs in nanohybrids were optimized to ensure high rates of H2 production. With a relatively low amount of pristine TiO2, a high rate of H2 production of 2134 ?mol h-1 gcat -1 has been obtained and is likely due to several factors such as well dispersed catalyst, reduced particle-particle agglomeration, resulting in enhanced light absorption (less light shielding), improved separation of charge carriers and utilization for red-ox reactions. Even better results were obtained with the use of nanohybrid catalysts. The enhanced photocatalytic activities of the nanohybrid catalysts are ascribed to the synergetic effects of FCNTs that minimize light reflection which promotes enhanced solar light sensitization, good dispersion of the catalysts in the reaction solution, and improved surface-interface reactions of photogenerated charge carriers. In the present study 10 wt% FCNTs in nanohybrid (CTP-10) exhibited superior photocatalytic activity for H2 generation, nearly 3 times higher than that of pristine TiO2 catalyst. The CTP-10 photocatalyst exhibited photostability under the experimental conditions studied. The nanohybrid photocatalysts were characterized in order to confirm the crystal structure, morphology, surface chemical composition and optical properties. The present work demonstrates the unique beneficial photocatalytic properties of carbon nanotubes and nanohorn mixtures in nanohybrid photocatalysts, for enhanced H2 production. � 2014 Hydrogen Energy Publications, LLC.

Published
2015
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