Siow Hwa Teo

Hydrothermal effect on synthesis, characterization and catalytic properties of calcium methoxide for biodiesel production from crude Jatropha curcas

Hydrothermal synthesis is a well-suited approach for preparing bulk metal catalysts with high purity as it is cost-effective and easy to control in terms of temperature and time. In the current study, an effective catalyst for transesterification of high fatty acid content of crude Jatropha curcas oil (JCO) was appraised. Calcium methoxide (Ca(OCH3)2) has been successfully synthesized via a green and economical hydrothermal process at different synthesis times. CaO was used as a precursor as it is abundant, inexpensive and environmentally friendly. Ca(OCH3)2 can form on the surface of CaO and its active basic surface is very well developed. This facile experimental strategy without any surfactant or template produced porous Ca(OCH3)2 with a high surface area and high basicity, which leads to a superior catalytic reaction and is a promising alternative for short-reaction-time solid-based catalysts in biodiesel production in terms of excellent transesterification performance and long durability. The performance of synthesized Ca(OCH3)2 was examined by characterizing it using analytical techniques such as TG-DTA, XRD, BET, FT-IR, TEM and SEM. Ca(OCH3)2 catalysts had three types of morphologies, i.e. (a) irregular round shape particles, (b) a well arrangement of plate-like structures with rough surface and (c) a cluster of tiny plate-like architectures with smooth surfaces. The correlation between synthesis time, surface area and morphology of catalysts and the biodiesel yield was studied. Ca(OCH3)2 was able to maintain the FAME content above 86% after a fifth cycle, at optimum reaction conditions of 2 h reaction time, 12:1 methanol/oil molar ratio, 2 wt% catalyst loading and 65 °C reaction temperature. Ca(OCH3)2 is a solid heterogeneous catalyst for the transesterification reaction of non-edible Jatropha curcas oil for biodiesel production. The catalyst can be separated easily from the reaction mixture and reused to give a consistent transesterification activity.

Enhancing the sorption performance of surfactant-assisted CaO nanoparticles

Microsized calcium oxide prepared via precipitation and thermal decomposition of calcium carbonates has been widely used in industrial hydrogen production and biomass gasification processes to remove CO2 from the reactors. One of the most interesting perspectives in catalysis is the development of nano-sized, high performance, low cost catalysts. However, due to the high cost of nano-sized calcium oxide (CaO), it is critically important to develop new techniques that overcome this challenge. The main goal of this study was to prepare zwitterionic surfactant (BS-12) modified nano calcium oxide sorbents. Ctenocardia fornicata shell was used as the precursor for nano CaO, as it is cheap and easily available. The effect of BS-12 on the physico-chemical properties and the performance of the nano CaO sorbent for CO2 capture were investigated. Thermo gravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), X-ray fluorescence (XRF), N2 adsorption–desorption (BET) measurements, transmission electron microscopy (TEM), zeta potential and temperature programmed desorption (TPD-CO2) studies were used for the characterization of the prepared nano-sized CaO particles. The results showed that BS-12 modified nano CaO exhibited the best performance for CO2 capture. The particle size and morphology of CaO varied from rod shape (45–33 nm) to cubic (13–23 nm) by changing the operating variables. A suggested mechanism for nanoparticle formation in the presence of BS-12 is also discussed.

Heterogeneous catalysis of transesterification of jatropha curcas oil over calcium–cerium bimetallic oxide catalyst

A series of heterogeneous basic catalysts (mixed oxides of Ca and Ce) with different molar ratios were synthesized via a conventional co-precipitation process using a highly alkaline carbonate salt. Moreover, investigation was conducted batchwise for the transesterification of crude Jatropha curcas oil (JCO) with methanol at 65 °C and 1 atm pressure. The bimetallic oxides possess high thermal stability, since X-ray diffraction (XRD) proved that the crystalline phases present in mixed oxide catalysts were preserved well as pure oxide even up to 900 °C. The co-precipitation synthesis method provided better interaction between vacancies created by the substitution of calcium (Ca) and cerium (Ce) at pH 11. Moreover, the combination of Ca and Ce reduced the temperature maxima and increased the basicity of catalysts, which exhibited better catalytic activity compared with bulk catalysts (CaO and CeO2). The influences of the Ca/Ce atomic ratio in the mixed oxide catalyst, methanol–oil molar ratio, catalyst amount and reaction time on the fatty acid methyl ester (FAME) content were studied. The suitable molar ratio of Ca-to-Ce was 1, and with the optimum conditions of 4 wt% catalyst dosage and 15% methanol–oil molar ratio, a fatty acid methyl ester (FAME) content of 95% was achieved over CaO–CeO2 catalyst at 65 °C. Moreover, the CaO–CeO2 catalyst shows substantial chemical stability and could be reused at least 4 times without major loss in its catalytic activity.

Biodiesel synthesis from photoautotrophic cultivated oleoginous microalgae using a sand dollar catalyst

The aim of this study was to synthesize a calcined sand dollar (CSD), Clypeaster reticulatus as a green mixed oxide CaO–MgO solid catalyst through a thermal degradation method for transesterification of Nannochloropsis oculata (N. oculata) microalgae derived crude oil. The catalysts characterizations were carried out by TG/DTA, XRD, FTIR, TPD-CO2, SEM and ICP–AES analysis, respectively. Formation of binary phase solid oxides i.e. CaO and MgO were confirmed at a calcination temperature of 800 °C. The effect of the reaction parameters i.e. catalyst amount, methanol/oil molar ratio, reaction temperature and time were evaluated for the transesterification reaction. The photoautotrophic microalgae propagation produced lipids with 25.8 ± 4.5% of total lipids, 18.5 ± 1.8% of crude lipids and 12.8 ± 2.6% of neutral lipids, respectively. Interestingly, the produced N. oculata biodiesel using this process revealed an insignificant change in FAME composition, which comprised mostly C16:0 and C16:1, similar to conventional biodiesel. Under the conditions tested, the catalyst showed a 90% yield of fatty acid methyl ester (FAME) at ideal reaction variables of 3 wt% of catalyst loading, 60 °C, 30:1 of methanol/oil, and 3 h reaction time.

Seeded Growth Route to Noble Calcium Carbonate Nanocrystal

A solution-phase route has been considered as the most promising route to synthesize noble nanostructures. A majority of their synthesis approaches of calcium carbonate (CaCO3) are based on either using fungi or the CO2 bubbling methods. Here, we approached the preparation of nano-precipitated calcium carbonate single crystal from salmacis sphaeroides in the presence of zwitterionic or cationic biosurfactants without external source of CO2. The calcium carbonate crystals were rhombohedron structure and regularly shaped with side dimension ranging from 33–41 nm. The high degree of morphological control of CaCO3 nanocrystals suggested that surfactants are capable of strongly interacting with the CaCO3 surface and control the nucleation and growth direction of calcium carbonate nanocrystals. Finally, the mechanism of formation of nanocrystals in light of proposed routes was also discussed.