The energy demands of the world are increasing day by day at a substantial rate with increase in the world’s population. This high energy demand mainly depends on fossil fuel resources because they are the major contributors of energy and thus power generation. But, they are unsustainable sources because of their dwindling reserves and depleting nature. Also, its usage creates environmental pollution. The fossil fuel combustion causes the release of greenhouse gases into the atmosphere, which are responsible for global warming. This is able to threaten both human beings and the environment. As a result of this, researchers are giving more attention for the search of alternative fuels which can fully replace the fossil fuels and can be produced from renewable feedstocks. Biofuels are renewable solutions to replace the ever dwindling energy reserves and environmentally pollutant fossil liquid fuels when they are produced from low cost sustainable feedstocks. Biodiesel is one of the environmental friendly, sustainable and renewable energy resources among the family of alternative fuels. It is a clean and ecofriendly fuel compared to the fossil fuel. Because of its renewability and better combustion nature it is known as a substitute for petroleum derived diesel fuel. Thus, they are believed to be the future fuels for the transportation sector instead of the polluting fossil fuels.
Generally, biodiesel is produced from vegetable oil, algal oil or animal fat as feed stock through a homogeneous or heterogeneous catalytic process called transesterification. The alcohols utilized for transesterification process are generally methanol, ethanol, propanol, butanol, etc. Most frequently used alcohols are methanol and ethanol. Due to the low cost, physical and chemical advantages methanol is commonly employed. Among the catalytic processes that are used in the production of biodiesel, heterogeneously catalyzed processes are often considered to be inherently green due to the following features: easier separation and purification of biodiesel from glycerol thereby reducing the process steps, cost effective and reusable nature of catalyst. The activity of the solid catalyst determines the effectiveness of the heterogeneous catalytic reaction. The heterogeneous catalysts are potentially low cost and can solve many of the problems encountered in homogeneous catalysts. The conversion of triglycerides into methyl ester and glycerol takes place slowly but the biodiesel is produced in a very feasible economic way when it follows the heterogeneous catalytic reaction. Base and acid are two types of heterogeneous catalysts used for biodiesel production. Most of them prefer solid base catalysts since it is found to be more active than acid catalyst in the sense that it requires lower reaction time and temperature. Researchers are focusing more on heterogeneous base catalysis as a promising way to produce biodiesel since it follows a green route for the conversion of biomass into biodiesel. The development of new and cost effective heterogeneous catalyst for transesterification of low cost vegetable oils can decrease the total production cost of biodiesel. The goals of green chemistry have to be achieved for the environmental protection as well as sustainable development. The utilization of cost effective renewable energy resources and the development of eco-friendly reusable heterogeneous catalysts together solves many of the issues regarding the biodiesel production process. In the present investigation, we have developed different heterogeneous catalysts and they are used in the transesterification reaction of vegetable oils that are produced from renewable resources for the production of biodiesel. Thus, the present investigation can make the biodiesel industry cost effective and greener.
The present investigation had developed different heterogeneous catalysts by employing alkali metal sources and different precursor materials. The developed catalysts are, sodium aluminates, lithium silicates, Na loaded CeO2 catalysts, sodium titanate and sodium silicates. Sodium aluminate is prepared from waste aluminium foils following an easy and low cost method. The crystalline NaAlO2 showed high efficiency in the production of biodiesel from jatropha curcas oil. Lithium silicate prepared by a simple method of impregnation shows excellent activity in the transesterification reaction of waste cooking oil. Ceria is prepared via a simple and inexpensive method and NaOH is incorporated to the ceria support by the impregnation method to develop a novel Na/CeO2 catalyst which is highly active in the methanolysis of waste cooking oil for the production of biodiesel. Porous titania is prepared by sol-gel method using a surfactant and the developed titania is used as the precursor material for the preparation of sodium titanate nanotubes. The sodium titanate exhibits outstanding performance in the transesterification of waste cooking oil. Sodium silicate is prepared from silica and NaOH and had employed the catalytic activity in the transesterification reaction of waste cooking oil.