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Title: Carbon structures and Mg-based materials for gas sorption
Author: Tian, Mi
ISNI:       0000 0004 5352 0931
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2014
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Hydrogen is an alternative energy carrier for both mobile and stationary applications, which can effectively alleviate greenhouse gas emissions and reduce dependence on fossil fuels. The other promising approach in reducing greenhouse gas emissions is carbon capture. Mg-based materials have been considered as a promising hydrogen storage system due to their high hydrogen capacity (up to 7.6 wt.%), high abundance, low cost and lightweight. Different carbon structures have also drawn considerable interests for hydrogen storage and carbon capture. In this research, the nanostructured carbon was produced in a cold plasma reactor designed in-house as additives for improving hydrogen storage properties of Mg-based materials and CO2 storage of MgO. The effects of the plasma reactor’s flow rate, temperature and power were evaluated for the formation of the carbon structures. TEM shows that the carbon consists of spherical particles of 40.8±8.7 nm in diameter and graphene sheets. Further thermal treatment of the plasma carbon was carried out to enhance the surface area. The treatment conditions were optimized through response surface methodology (RSM). The effects of the treatment temperature, time and pressure on BET surface area and yield were studied. The predicted BET surface area and yield by RSM were found to agree with the experimental values. The optimum treatment conditions for the plasma carbon (PC) were found to be: temperature = 950°C and time = 120 min, pressure = 100 kPaCO2 gas flow. The optimized PC was mixed as an additive with 20h-milled MgH2/TiC for improvement of hydrogen storage properties. RSM optimized the mixing time and the content of PC in the (MgH2/TiC + PC) composite. The results demonstrated that both mixing time and the content of plasma carbon (PC) significantly affected the hydrogen storage properties. The effects of the PC, activated carbon (AC) and carbon nanotubes (CNTs) on hydrogen storage properties of MgH2/TiC were studied. PC, AC and CNTs showed positive effects on reducing hydrogen desorption temperature and improving the adsorption kinetics of the 20h-milled MgH2/TiC. PC shows the best effect due to its unique structure. The mechanism of the effects of the three carbon structures on hydrogen storage was discussed. ABSTRACT II The optimized PC was also mixed with MgO, both by ball milling and chemical coprecipitation methods to form porous carbon supported MgO for CO2 storage and separation. The results indicated that the chemically synthesized MgO+PC calcined at 800 °C (referred to as MgO/PC-800) showed the most promising CO2 storage capacity up to 6.16 mmol/g at 25 °C and 1500 kPa CO2 pressure. The introduction of PC improves the CO2 adsorption capacity of the chemical synthesized MgO due to improved surface area. The dual-site Langmuir (DSL) model was employed to predict adsorption equilibria of CO2/H2 gas mixtures, which well simulated the behaviors of pure CO2 adsorption and H2 adsorption, and can be used to predict the binary CO2/H2 gas mixture separation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available