**1. Introduction**

288 Biodiesel – Feedstocks and Processing Technologies

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vibration for biodiesel production from soybean oil by Novozym 435. Process

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Rising world fuel prices, the growing demand for energy, and concerns about global warming are the key factors driving renewed interest in renewable energy sources and in bioenergy. Nowadays, the world energy demand has increased significantly due to the global industrialization and increase of population. As a result, the current limited reservoirs will soon be depleted at the current rate of consumption. So, the research in energy focuses on finding an alternative source of energy to the petroleum derived diesel.

India imported about 2/3rd of its petroleum requirement last year, which involved a cost of approximately Rs. 80,000 crores in foreign exchange. Even 5% replacement of petroleum fuel by bio-fuel can help India and save Rs. 4000 corers per year in foreign exchange. It is utmost important that the options for substitution of petroleum fuels be explored to control this import bill. Biodiesel is a suitable substitute for petroleum-derived diesel. It is biodegradable, almost sulfur less and a renewable fuel, though still not produced by environmentally friendly routes. This alternative fuel consists of methyl or ethyl esters, a result of either transesterification of triglycerides (TG) or esterification of free fatty acids (FFAs). Biodiesel fuel has become more attractive because of its environmental benefits, due to the fact that plants and vegetable oils and animal fats are renewable biomass sources.

Currently, most of the biodiesel comes up from transesterification of edible resources such as animal fats, vegetable oils, and even waste cooking oils, under alkaline catalysis conditions. However, the high consumption of catalysts, the formation of soaps, and the low yields, make biodiesel currently more expensive than petroleum-derived fuel. In addition, the plants from which the vegetable oils are produced capture more CO2 from the atmosphere than the amount that these oils release during their combustion [1].

The three basic routes to biodiesel production from oils and fats are Base catalyzed transesterification of the oil, Direct acid catalyzed transesterification of the oil and conversion of the oil to its fatty acids and then to biodiesel. Out of these three routes the major production of biodiesel is done with the base catalyzed reaction process.

Transesterification by Reactive Distillation for Synthesis and Characterization of Biodiesel 291

The Reactive distillation technology offers many benefits as well as restrictions over the conventional process of reaction followed by distillation or other separation approaches. Reducing capital cost, higher conversion, improving selectivity, lower energy consumption, the reduction or elimination of solvents in the process and voidance of azeotropes are a few of the potential advantages offered by Reactive distillation. Conversion can be increased far beyond what is expected by the equilibrium due to the continuous removal of reaction products from the reactive zone. This helps to reduce capital and investment costs and may be important for sustainable development due to a

Based on the applied separation technology, reactive distillation, reactive extraction, reactive adsorption and other combined processes have been distinguished. The combined simultaneous performance of chemical reaction and a multi-component distillation process is an alternative, which has been increasingly used for the large-scale production of relevant chemicals. The use of reactive distillation process can have several advantages such as reduced downstream processing, utilization of heat of reaction for evaporation of liquid phase, simple temperature control of reactor, possibility of influencing chemical equilibria by removal of products and limitations imposed by azeotropic mixture. Several commercially important processes in reactive distillation have been identified in some

Reactive section

Rectifying section

Stripping section

Reactive distillation has been successfully applied for the etherification reaction to produce fuel ethers such as methyl tert-butyl ether (MTBE), tert-amyl methyl ether(TAME) and ethyl tertbutyl ether (ETBE). These have been the model reactions for the studies in reactive distillation in the last two decades. A small number of industrial applications of reactive distillation have been around for many decades. Low chemical equilibrium constants can be overcome and high conversions achieved by the removal of products from the location

lower consumption of resources.[7]

The fig.1 represents the general configuration of reactive distillation.

Fig. 1. The general configuration of Reactive Distillation

Feed

recent reviews. [7]

where the reaction is occurring. [6]

The stoichiometric equation for transesterification reaction [9] in general can be represented as follows:


