Microwave pyrolysis of oil palm shell for supercapacitor applications / Manoj Tripathi
In the present work, a carbonaceous, porous oil palm shell (OPS) char with high thermal stability and low thermal conductivity has been synthesized using microwave pyrolysis technique. In comparison with conventional heating, microwave heating provides a rapid and uniform heating without sufferin...
| Main Author: | |
|---|---|
| Format: | Thesis |
| Published: |
2016
|
| Subjects: | |
| Online Access: | http://studentsrepo.um.edu.my/7011/ http://studentsrepo.um.edu.my/7011/4/manoj2.pdf |
| Summary: | In the present work, a carbonaceous, porous oil palm shell (OPS) char with high thermal
stability and low thermal conductivity has been synthesized using microwave pyrolysis
technique. In comparison with conventional heating, microwave heating provides a rapid
and uniform heating without suffering from high energy loss during the heating process.
Process parameters such as microwave power, radiation time and N2 flow rate have been
investigated and found to have a significant effect on the yield and BET surface area of
OPS char. Central Composite Design (CCD) technique of Response Surface Methodology
(RSM) is used to conduct the optimization study so as to get the optimized process
conditions for the maximized yield and BET surface area of OPS char.
Thermal, structural, elemental, compositional and dielectric characterization of the
OPS char is carried out to check its utility as electrode material. Large BET surface area
(265.9 m2/g) and porous nature (pore volume 1.28 cm3/g) of OPS char is helpful in the
charge storage application. Furthermore, surface area analysis of OPS char has also
revealed that microwave pyrolysis process has developed the micro pores within the OPS
char which are clearly seen in the SEM images of OPS char. Thermogravimetric analysis
showed that OPS char has a higher thermal stability temperature (355 °C) as compared to
OPS (270 °C). OPS char is found to have a high carbon content (59.42 wt. %). Dielectric
properties are found to be largely dependent upon microwave frequency and as well as on
temperature. Dielectric characterization of OPS shows that penetration depth of microwave
radiation with frequency 2450 MHz is lower than that of 915 MHz frequency by 11.6 %
which imply that microwave radiation with frequency 2450 MHz are more suitable for the
thermal treatment of OPS. OPS char is seen to have lower thermal conductivity and thermal diffusivity as compared to OPS (0.169 W/m-K & 0.124 mm2/s respectively for OPS char as
compared to 0.199 W/m-K & 0.142 mm2/s respectively for OPS). Low thermal
conductivity and thermal diffusivity suggests OPS char to be a good insulating material.
Specific heat capacity of OPS char is higher than that of OPS. Based on all these results it
is found that the synthesized OPS char has a large BET surface area, high carbon content,
porous nature, higher thermal stability, low thermal conductivity along with high specific
heat capacity. These properties are appropriate for its consideration as an electrode
material.
OPS char derived electrode is prepared and its charge storage capacity is
determined using cyclic voltammetry. Specific capacitance of OPS char electrode is found
to be 203.30 F/g which is comparable to the other biomass/ agricultural waste based char
materials. Economically, it looks very attractive that by considering the OPS char synthesis
cost to be $100/MT it is possible to reduce the charge storage cost to less than 0.0005
cent/F using its specific capacitance to be 203.30 F/g. Based on all the above mentioned
results we propose that the OPS char synthesized in the optimized process conditions using
the microwave pyrolysis has the potential to be considered as a supercapacitor electrode
material |
|---|