Study of properties and Performance of Biodiesel in C.I. engine produced from Waste Cooking Oil using Heterogeneous Catalyst

Abstract

The world is dependent on fossil fuels for more than a century. In recent years exponential growth in industrialization and world population has increased the demand for the energy. Approximately 80% energy need is fulfilled by the fossil fuels. A major part, nearly 57% from it is utilized by the transport sector. From present scenario there is a huge gap between world energy requirement and energy demand. Therefore, world is facing twin crises of depleting fossil fuel reserves and environmental degradation. This fast diminishing of fossil fuel reserves has adversely affected the world oil supply which increased the oil price. This fluctuation in increasing petroleum prices, limited fossil fuel reserves and environmental degradation escalated the search for substitute for fossil fuels especially in transport sectors. Due to these reasons liquid fuels such as biodiesel is in lime light and become more attractive because of environmental benefits.

Chemically biodiesel is defined as the mixture of long chain fatty acids and is typically produced from non-toxic biological resources such as vegetable oils, animal fats or waste cooking oils. Compared to traditional diesel fuel, biodiesel is technically and economically more competitive due to its renewability, biodegradability, liquid nature-portability, low emission profiles, high flash point and lower sulfur and aromatic content. Biodiesel has properties very similar to conventional diesel and can be run on diesel engine without any major modification in it.

Generally the biodiesel production comprises of transesterification of vegetable oil (edible or non-edible oils) in presence of homogeneous base or acid catalysts. Sodium hydroxides (NaOH), potassium hydroxide (KOH) are homogeneous base catalysts and are widely used for biodiesel production. The merits of homogeneous catalyst are that it possesses high conversion rate under mild reaction conditions and the reaction completes in one hour. However, transesterification in the presence of base catalysts associates several drawbacks viz. non-reusability, formation of the catalyst contaminated biodiesel and glycerol, deactivation by free fatty acid (FFA) and moisture content. These limiting factors of homogenous catalysts can be overcome by using heterogeneous catalysts instead of homogeneous catalysts.

Utilization of these catalysts offers some advantages such as easy catalyst separation from reaction mixture or final product, reusability and regenerability of the catalyst. In addition to this, these catalysts are less sensitive to water which makes them even more attractive for biodiesel production from a variety of feedstocks. There is large number of heterogeneous catalysts such as metal oxides, alkaline earth metal oxides, transition metal oxides, ion exchange resins, sulfated oxides, carbon based heterogeneous catalysts, enzyme supported catalysts that have been reported in literature for biodiesel production.

Among the reported literature of these catalysts, vast study has been done on different metal oxide for biodiesel production. Among the different metal oxides reported, the most popular metal oxide was found to be calcium oxide which was due to its easy availability, low price, low toxicity and high catalytic activity. Moreover, calcium oxide can be prepared from the waste matters consisting of calcium carbonate, such as mollusk shells, egg shells. The use of the waste matters is not only effective in enhancing the cost advantage of CaO catalyst but is also related to recycle of the naturally available mineral resources.

This study is focused on biodiesel production from waste cooking oil using zinc doped calcium oxide as heterogeneous catalyst and its operational characteristics on VCR compression ignition engine. The optimum experimental conditions were methanol/oil molar ratio 12:1 with 5wt.% zinc doped calcium oxide, temperature of 65°C and 140 min provided yield above 98% methyl esters.

The fuel properties of the produced biodiesel such as the calorific value, flash point and density were examined and compared to conventional diesel. The properties of produced biodiesel and their blend for different ratios (B20, B40, B60, B80 and B100) were comparable with properties of diesel oil and ASTM biodiesel standards. Tests had been conducted on CI engine which runs at a constant speed of 1500 rpm, injection pressure of 200bar, compression ratio 15:1 and 17.5, and varying engine load. The performance parameters include brake thermal efficiency, brake specific energy consumption and emissions parameters such as carbon monoxide (CO), hydrocarbon (HC), oxides of nitrogen (NOx) and smoke opacity varying with engine load (BP). Diesel engine’s thermal performance and emission parameters such as CO, HC, and NOx on different biodiesel blends demonstrated that biodiesel produced from waste cooking oil using heterogeneous catalyst was suitable to be used as diesel oil blends and had lesser emissions as compared to conventional diesel.