Effect of catalysts on the formation of titanium hydride under hydrogen atmopshere
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Date
2018-06
Authors
Wong, Jia Ying
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Abstract
The research objective is to produce titanium hydride (TiH2) from the reaction
between magnesium Hydride (MgH2) and titanium tetrachloride (TiCl4) under hydrogen
atmosphere using catalysts such as nickel (Ni), ammonium chloride (NH4Cl) and calcium
fluoride (CaF2). The experiment was performed by design of experiment (DOE). The
parameters involved were reaction temperature (300 to 400 'C), reaction time (60 to 120
minutes) and molar ratio of Ni to NH4Cl (0.1 to 0.3) while the responses were percentage of
weight gain and degree of dehydriding. Various characterization method had been carried
out such as X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy
(FESEM),Energy Dispersive X-Ray Spectroscopy (EDS), Fourier-transform infrared
spectroscopy (FTIR), CHNS elemental analysis and Inductively Coupled Plasma Optical
Emission Spectrometry (ICP-OES). From the experimental results, the high percentage of
weight gain of 17 % was achieved at the reaction temperature of 400 'C, 60 minutes of
reaction time and molar ratio of Ni to NH4Cl of 0.5 while highest degree of dehydriding of
79.85% was obtained when reaction temperature was 300 'C, reaction time was 120
minutes and molar ratio of Ni to NH4Cl was 1.5. The DOE analysis showed that reaction
time was the most significant parameter, followed by reaction temperature and molar ratio
of Ni to NH4Cl. The main compound formed after the reaction was magnesium nickel instead
of titanium hydride because the amount of the nickel catalyst used was large while the
amount of titanium tetrachloride gas flow inside the tube furnace was too little. Besides, the
existence of reverse reaction and high reaction temperature caused the desorption of
magnesium hydride by nickel under hydrogen atmosphere, forming magnesium nickel. From
the simulation results, the isothermal and non-isothermal Shrinking Core Model (SCM) were
used to study the reaction. Both isothermal and non-isothermal shrinking core model
showed similar trend and significant closeness to the experimental result within reaction time
of 60 minutes.