This research focused on deriving kinetic mechanism, rate-limiting step and developed kinetic rate law specifically for biodiesel production catalyzed by green CaO nanocatalyst derived from waste muscle shell via thermal hydration-dehydration treatment. In addition, the CaO nanocatalyst preparation method via thermal hydration–dehydration related parameters (hydration duration, recalcination temperature, and recalcination duration) were investigated and optimized. The optimum conditions for the thermal hydration-dehydration treatment used to develop nano CaO catalyst were at 6 h hydration duration, 650 oC recalcination temperature and 3 h recalcination duration.
This thesis/dissertation entitled "CATALITIC ACTIVITY ENHANCEMENT OF NANO CALCIUM OXIDE CATALIST VIA THERMAL HYDRATION-DEHYDRATION TREATMENT FOR BIODIESEL PRODUCTION" was prepared by CHOOI CHEE YOONG and submitted as partial fulfillment of the requirements for the degree of engineering degree University. Tunku Abdul Rahman. It is hereby certified that CHOOI CHEE YOONG (ID No: 1806692) completed this thesis entitled "Catalytic Activity Enhancement Of Nano Calcium Oxide Catalyst Via Thermal Hydration-Dehydration Treatment For Biodiesel Production" under the supervision of Dr.
Background
World energy consumption
Problem Statement
According to Reddy et al. 2006) found low biodiesel conversions (about 2%) of biodiesel when the commercial CaO catalyst with low surface area (1 m2/g) was used in the process. Nanocatalyst can be developed using a top-down or bottom-up approach (Islam et al., 2007). Top-down approach refers to the bulk material where it is broken down into smaller particles by mechanical grinding (Schmidt, 2001), thermal degradation (Zhang et al., 2003) or chemical degradation (Garrigue et al., 2004) while bottom-up approach performed via reaction or agglomeration, such as the sol-gel method, template-guided, precipitation, and microemulsion.
In this study, nano-sized CaO catalyst will be prepared from waste muscle shells, and thermal hydration-dehydration technique is chosen to improve the thoroughness and surface area of the CaO catalyst, although bottom-up approach will provide uniform and well-defined structure on the catalyst (Zahmakiran et al. , 2011). This is because the thermal hydration-dehydration method exhibits the lowest operating costs compared to bottom-up methods, which require expensive chemical precursors and critical reaction conditions (Nadagouda et al., 2006).
Research Aims and Objectives
The catalytic performance of the nano CaO catalysts was compared based on the yield of biodiesel from the transesterification reaction of palm oil-based cooking oil. Finally, a kinetic mechanism for transesterification process catalyzed by nano CaO catalyst derived from waste muscle shells was developed and verified with experimental data. To derive the kinetic mechanism and subsequently formulate kinetic model for the transesterification reaction catalyzed by nano CaO catalyst for biodiesel production.
Scope of study
Commercialized biodiesel production
Catalyst for biodiesel production
- Homogeneous catalyst for biodiesel production
- Heterogeneous catalyst for biodiesel production
According to Yoo et al. 2010), a better yield of biodiesel was obtained as catalyst is applied during production. Among the catalysts, alkali and acid catalysts are most common compared to enzyme catalysts (Leung et al., 2010). Immune to free fatty acid and water content of the raw material (Lotero et al., 2005) and saponification reaction is inhibited.
Sensitive to the content of free fatty acids and the water content in the raw material (Lam et al., 2010). Saponification will occur simultaneously if the free fatty acid content exceeds 1%, leading to a low yield of biodiesel (Lam et al., 2010).
Current research trend of works
- Nano CaO
- Thermal decomposition of CaO
- Nano-CaO Preparation via Thermal-Hydration-Dehydration
- Factors related to thermal hydration-dehydration treatment
In addition, the number of active sites on the CaO surface depends on the calcination environment and temperature. However, prolonged calcination duration would cause sintering effects, which would reduce the catalyst surface area and cause a negative impact on the catalytic performance (Micic et al., 2015). The surface morphology and basicity of nano CaO catalysts depend on its precursor.
Therefore, there would be cracks on the surface of the sample when the particles expanded. This also indicated that the specific surface area of the catalyst (under BET analysis) decreased simultaneously.
Characterisation of catalyst
- Thermogravimetric analysis (TGA) for Calcite
- FTIR analysis of Treated CaO
- Surface Morphology Analysis via Scanning Electron Microscopy (SEM)
- Brunauer-Emmett-Teller (BET) analysis
- Basicity Analysis via Temperature Programmed Desorption (TPD)
According to Roschat et al. 2018), the diffractogram of commercial CaO showed the presence of impurities such as calcium carbonate and calcium hydroxide. According to Widayat et al. 2017), calcium carbonate and calcium hydroxide can be converted to CaO during the calcination process. A larger BET surface area indicates a higher basicity and catalytic efficiency of the CaO catalyst (Roschat et al., 2012).
This indicates that the surface area of the catalyst can affect the catalytic activity as well as the yield of biodiesel production (Viriya-empikul et al., 2012). According to Asikin-Mijan et al. 2016), with long hydration duration, the catalyst has higher basicity.
Kinetic study of transesterification process
Nevertheless, an excess of methanol is used in the reaction to maintain an advanced reaction (Darnoko et al., 2000). In addition, the activation energy and pre-exponential factor of biodiesel production can be investigated by varying the reaction temperature. If we plot the Arrhenius equation, the activation energy and the pre-exponential factor are 34.44 kJ mol-1 and 7.94 min-1, respectively.
1986) reported that the value of activation energy normally falls in the range of 33.6–84.0 kJ mol-1 for base-catalyzed transesterification reactions. Similar results were obtained by Maneerung et al. 2015) for the palm oil feedstock where the activation energy is 83.9 kJ mol-1 which also falls in the feasible range.
Kinetic study of CaO catalyst
- Eley-Rideal Kinetics
- Langmuir- Hinshelwood-Hougen-Watson (LHHW)
For Langmuir-Hinshelwood model, it assumed that both methanol and triglyceride were adsorbed on the adjacent active catalyst sites. In the first two steps, both methanol and triglyceride are adsorbed side by side on the catalyst surface, and then the adsorbed methanol (M) and triglyceride (TG) led to FAME and adsorbed diglyceride (DG).
Factors that affecting the biodiesel production
- Dosage of catalyst
- Reaction time
- Alcohol to oil molar ratio
According to Chen et al. 2016), the relationship between catalyst dosage and biodiesel yield was observed by changing the mass ratio of catalyst to palm oil from 2 to 9 wt%. Biodiesel yield increased proportionally with catalyst loading, and around 7 wt%, a decrease in biodiesel yield was detected even though the amount of catalyst was increased. It can be explained as the reaction mixture had become more viscous due to the high amount of catalyst, which indicates the increased mass transfer resistance in the heterogeneous reaction system (Bai et al., 2009).
Due to the reversibility of the transesterification reaction, a longer reaction time can shift the reaction path and decrease the biodiesel yield. The formation of biodiesel was significantly influenced by the reaction temperature, even though a CaO catalyst was present (Wen et al., 2010). The majority of researchers concluded that the optimum temperature for the transesterification reaction was 65 oC, which is the boiling point of methanol at atmospheric pressure (Kumar et al., 2012).
If the temperature exceeds 70 oC, a much lower biodiesel yield was obtained, the methanol will start to boil at 65 oC, the contact time between methanol and oil was reduced which led to the decrease in biodiesel yield (Zhao et al., 2013). . The oil can also be fully converted into biodiesel at 35 oC, however, an extended reaction time is required which was not feasible for industrial application (D. Kumar et al., 2013). For example, the transesterification reaction can be carried out at room temperature, but still 24 hours were required to complete the process (Reddy et al., 2006).
In addition, the excess methanol can compete with the product molecules to detach biodiesel molecules from the catalyst surface and regenerate the basic sites (Kaur et al., 2014). There is an optimal molar ratio between alcohol and oil as raw material where the reaction time for transesterification remains constant, even though the number of molar ratios was further increased (Granados et al., 2009). Still, the optimal ratio can be varied depending on the reaction. condition. According to Chen et al. 2016), the methanol to oil molar ratio ranged from 3:1 to 18:1, and the biodiesel yields show a gradual increase and then reach equilibrium at the optimal point, 9:1 for the treated CaO- catalyst.
Project Workflow
Catalyst preparation
Optimization of thermal hydration-dehydration treatment
The developed nano CaO catalysts were used to drive the transesterification of palm oil into biodiesel. The optimal catalytic performance of nano CaO catalyst was determined based on the biodiesel yield from the transesterification. The biodiesel yield was obtained by gas chromatography (GC) analysis and the catalytic performance of optimal nano CaO catalyst was compared with CaO catalyst.
Then, the range of calcination temperature of waste muscle shells and calcination temperature of hydrated CaO was analyzed through Step 3: Characterization of the physical and chemical properties of.
Step 4: Deduce kinetic mechanism for the transesterification reaction catalyzed by optimized nano CaO catalyst
- Catalyst Preparation
- CaO catalyst prepared via calcination treatment
- Catalyst prepared via thermal hydration and dehydration method
- Optimization of thermal-hydration-dehydration treatment
- Transesterification reaction of palm oil
- Characterisation of catalyst
- Thermogravimetric & Differential Thermal Analyser (TGS/DTA)
- Fourier Transform Infrared (FT-IR)
- X-ray Diffraction (XRD)
- Scanning Electron Microscopy (SEM) and Energy Dispersive X- ray (EDX)
- Temperature Programmed Desorption (TPD)
- Brunauer-Emmett-Teller (BET) analysis
- High Resolution Transmission Electron Microscopy (HRTEM)
- Experimental work for verification of kinetic model
- Catalyst Characterization
- Thermogravimetric (TGA) analysis
- Fourier Transform Infrared (FT-IR) Analysis
- X-ray Diffraction (XRD) Analysis
- Scanning Electron Microscopy (SEM) analysis
- Energy Dispersive X-ray (EDX) Analysis
- Analysis on sintering effects
- Temperature Programmed Desorption (TPD) Analysis
- Brunauer-Emmett-Teller (BET) Analysis
- High Resolution Transmission Electron Microscopy (HRTEM) analysis
- Optimization of thermal hydration-dehydration treatment
- Effect of Hydration duration
- Effect of Recalcination temperature
- Effects of Recalcination duration
- Optimization study
- Comparison of optimized nano CaO catalyst (6_650_3) with literature
- Kinetic mechanism of transesterification reaction catalysed by optimized nano CaO catalyst
- Verification of kinetic equation with experimental data
- Activation energy and pre-exponential factor
- Conclusion
- Recommendation
The developed nano CaO catalyst prepared by means of thermal hydration-dehydration treatment was used to carry out the transesterification with palm oil as raw material. The catalytic performance of nano CaO catalyst prepared by thermal hydration-dehydration treatment was determined based on the biodiesel yield from the transesterification. CaO catalyst prepared via calcination method and nano CaO catalyst prepared by thermal hydration-dehydration treatment had the similar FT-IR spectra.
Nano CaO catalyst developed under different parameters (hydration duration, recalcination temperature and recalcination duration) was analyzed using XRD. As the hydration hour extended, the surface roughness and porosity of the nano CaO catalyst prepared by thermal hydration-dehydration treatment were increased. Four samples (waste cockle shell, CaO catalyst prepared by calcination method, hydrated CaO, and nano CaO catalyst prepared by thermal hydration-.
Likewise, the trace amount of the elements (magnesium, silicon and sodium) was not detected in hydrated CaO and nano CaO catalyst prepared by means of thermal hydration-dehydration treatment. The sintering effects can occur on the surface of the nano CaO catalyst prepared as the recalcination temperature increases (Smith et al., 2013). Similar to the recalcination temperature, sintering effects can occur on the surface of the nano CaO catalyst.
Multipoint BET sample (m2/g) Total pore volume (cm3/g) Average pore diameter (nm) Biodiesel yield (%) CaO catalyst prepared via. Nano CaO catalyst prepared by thermal hydration-dehydration treatment was successfully developed with particle size ranging from 1 to 100 nm. The reason for this phenomenon can be attributed to the sintering effects on the surface of the nano CaO catalyst prepared with thermal hydration-dehydration catalysts as the recalcination temperature increases (Smith et al., 2013).
This is because sintering effects occurred on the surface of the nano CaO catalyst prepared via hydration-dehydration heat treatment catalysts. In summary, the nano CaO catalyst was preferable as a relatively mild reaction condition (operating temperature, alcohol to oil molar ratio and catalyst loading). The kinetic mechanism of nano CaO catalyst prepared via hydration-dehydration heat treatment was deduced followed by kinetic model development.
Nano CaO catalyst was successfully developed from waste cockle shell via thermal hydration-dehydration treatment.
