Synthesis and characterization of K₂O-dolomite solid base catalysts for methyl ester production from palm oil
Biodiesel is one of the promising substitutes for petroleum-based diesel due to its numerous benefits. Generally, homogeneous catalysts are used in the methyl ester production, exhibiting better catalytic activity. However, this catalyst is associated with a number of shortcomings, these includes...
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| 主要作者: | |
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| 格式: | Thesis |
| 語言: | English |
| 出版: |
2020
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| 主題: | |
| 在線閱讀: | http://psasir.upm.edu.my/id/eprint/99305/1/YAHAYA%20MUHAMMAD%20%20UPM%20IR.pdf |
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| 總結: | Biodiesel is one of the promising substitutes for petroleum-based diesel due to its
numerous benefits. Generally, homogeneous catalysts are used in the methyl ester
production, exhibiting better catalytic activity. However, this catalyst is associated with
a number of shortcomings, these includes tedious in separation, generates a colossal
amount of wastewater and difficult to recover. These economic and environmental
drawbacks can be resolved with the help of heterogeneous catalysts, where they can be
reused repeatedly without any major loss in their catalytic activity, making the process
more economical and environmentally friendly. In this work, potassium oxide doped
dolomite (K2O-dolomite) catalysts were prepared by impregnation method with a
loading of 5, 10, 15 and 20 wt% K2O and labelled as 5 wt% K/D, 10 wt% K/D, 15 wt%
K/D, and 20 wt% K/D, respectively. The catalysts were calcined in a static air at 850 °C
for 3 hrs. X-ray diffraction (XRD) analysis of dolomite revealed the presence of calcium
oxide (CaO) and magnesium oxide (MgO) phases with high crystallinity, in which
intensity reduced after doped with varying concentrations of K2O. Scanning electron
microscope (SEM) revealed that as more K2O was doped on dolomite, the particles
became more agglomerated as opposed to a homogeneously small-sized particles on undoped
sample that lead to severe decrease of BET surface area from 19.0 m2/g in
dolomite to 1.3 m2/g in 20 wt% K/D. However, the high activity of the doped catalyst
was dictated by the high amount of basic site, as evidenced in Temperature Programmed
Desorption of carbon dioxide (TPD-CO2) which showed an increase in the capacity of
the basic site with an increased amount of K2O as in the case of 15 wt% K/D. Thermo
Gravimetry–Differential Thermal Gravimetry analysis (TG-DTG) of all the samples
showed a similar onset degradation temperatures with three decomposition signals.
Fourier Transmission infrared spectroscopy (FT-IR) confirmed the presence of CaO and
MgO which corroborated well with XRD results. The transesterification reaction was
optimized by Taguchi method involving four levels and five factors (reaction
temperature, reaction time, methanol to oil molar ratio, catalyst amount and K2O
loading). The results indicated that temperature is the most significant parameter
influencing the methyl ester yield, followed by methanol to oil molar ratio, catalyst
amount and K2O loading while reaction time was not a significant factor. The optimum conditions observed for maximum methyl ester yield of 98.7% were temperature 60 °C,
methanol to oil molar ratio 12:1, catalyst amount 1 wt.%, K2O loading 15 wt.% and
reaction time 1h. The 15 wt% K/D catalyst displayed the best catalytic performance due
to its highest total basicity content. The physicochemical properties of the produced
methyl ester were found to conform with the ASTM D6752 and EN1421 specification.
The catalyst can still possess a rather high methyl ester yield after reused for 6 cycles
with a negligible decrease in activity due to K+ ions leached into the product. Overall,
doping of K2O in the catalyst has significantly improved the catalytic activity in the
transesterification of palm oil. |
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