Preparation and characterization of lithium orthosilicate sorbent for carbon dioxide removal
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Date
2015-10-01
Authors
Nurul Azrin Zubbri
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Abstract
Nowadays, the world is surviving the challenge of global warming and
climate change issues. So far, many efforts have been undertaken to mitigate CO2
emission among which is the use of solid sorbents for CO2 capture. Solid lithium
orthosilicate (Li4SiO4) is one of the sorbents used to capture CO2 at high
temperature. In this research, Li4SiO4 was synthesized by sol-gel method using
lithium nitrate (LiNO3) and silicon ethoxide (SiC8H20O4) as precursors. The
influences of Li:Si molar ratio (1-5), calcination temperature (600–800°C),
calcination time (1–8h) and H2O:Si molar ratio (1-5) were investigated during the
sorbent synthesis. The sorption capacity of the developed sorbent was evaluated
through CO2 capture tests performed using a Thermogravimetric Analyzer (TGA).
The calcination temperature (700-800ºC) and carbonation temperature (500-700ºC)
were varied during the carbonation test. The best sorbent with the highest CO2
sorption capacity was analyzed with XRD to confirm the appearance of Li4SiO4
species. The sorbent with highest CO2 sorption capacity was finally introduced to
some cyclic tests to study the durability of the sorbent through ten CO2 sorptiondesorption tests. The physicochemical properties of the developed sorbent before and after carbonation tests were investigated through SEM and XRD analyses. The results showed that the sorbent prepared with 1:1 molar ratio of Li:Si, 1:1 molar ratio
of H2O:Si and calcined at 700°C for 5h has the highest CO2 sorption capacity.
Calcination temperature of 800ºC and carbonation temperature of 700ºC were chosen
as the best values which resulted in the sorption capacity of 7.947 mmol CO2/g
sorbent which is 93% of the theoretical yield. Throughout ten cyclic process, CO2
sorption capacity of the sorbent dropped about 16.2% from the first to tenth cycle
which seems to be reasonable. Li4SiO4 was found to be a potential solid sorbent that
has high CO2 sorption capacity besides its stable cyclic performance.