CARBON STRUCTURES AND Mg-BASED MATERIALS FOR GAS SORPTION

Tian, Mi (2014) CARBON STRUCTURES AND Mg-BASED MATERIALS FOR GAS SORPTION. Doctoral thesis, University of East Anglia.

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Abstract

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. Mgbased
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
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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.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Mia Reeves
Date Deposited: 17 Oct 2014 11:58
Last Modified: 17 Oct 2014 11:58
URI: https://ueaeprints.uea.ac.uk/id/eprint/50552
DOI:

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