Biodiesel homogeneous process

Experiments showed that high methyl ester yields can be achieved with solid bases and super acids under moderate reaction conditions. The solid bases were more effective catalysts than the solid super acids. High stability can be achieved by an ordinary inexpensive preparation process, and the catalyst can be separated easily from the reaction products in the heterogeneous catalysis process. The costly catalyst removal process can be avoided compared with the homogeneous process. Therefore, the heterogeneous process using a solid catalyst should be more economical for biodiesel production. 

Baroi, C., Dalai, A.K., 2015. Process sustainabihty of biodiesel production process from green seed canola oil using homogeneous and heterogeneous acid catalysts. Fuel Processing Technology 133, 105—119. 

Biodiesel is a mixture of methyl esters of fatty acids and is produced from vegetable oils by transesterification with methanol (Fig. 10.1). For every three moles of methyl esters one mole of glycerol is produced as a by-product, which is roughly 10 wt.% of the total product. Transesterification is usually catalyzed with base catalysts but there are also processes with acid catalysts. The base catalysts are the hydroxides and alkoxides of alkaline and alkaline earth metals. The acid catalysts are hydrochloride, sulfuric or sulfonic acid. Some metal-based catalysts can also be exploited, such as titanium alcoholates or oxides of tin, magnesium and zinc. All these catalyst acts as homogeneous catalysts and need to be removed from the product [16, 17]. The advantages of biodiesel as fuel are transportability, heat content (80% of diesel fuel), ready availability and renewability. The... 

Recently, two processes for biodiesel production from crude tall oil have been proposed [48, 49]. They rely on the use of a homogeneous acid catalyst or of an acyl halide for the esterification reaction, but no information was given on the properties of the fuel obtained, particularly concerning the oxidative stability and conformity with European specification EN 14214 2003 for IV. 

Even though the base-catalyzed process seems operator friendly and economically possible, it suffers from a key limitation only refined oils and pretreated fats with low concentrations of FFAs be used to produce biodiesel using homogeneous base catalysts. FFAs can react with the base catalyst giving... 

Existing Problems with Homogeneous Catalysts. - The use of homogeneous catalysts involved in biodiesel synthesis currently presents separation and catalyst recovery issues. For instance, process methodologies using homogeneous... 

In homogeneous catalysis, the catalyst is in the same phase as the reactants and products. Here we will concentrate on homogeneous catalysis in the liquid phase. In the classic case, the reactant (also called the substrate) molecules and the catalyst are reacted in a solvent. For example, the transesterification of fatty acid triglycerides with methanol (Figure 1.10) is catalyzed by hydroxide (OH-) ions. This is an important process for making fatty acid methyl esters which are then used as biodiesel. 

Conventional industrial biodiesel processes are based on homogeneous alkaline catalysts. Sodium hydroxide or sodium methylate are the most often used catalyst in... 

In all cases, for batch homogeneous biodiesel processes, the neutralization step leads to the formation of salts, carried in the glycerol phase, but which need to be disposed of Glycerol from homogeneous biodiesel processes can to some extent be considered as a waste stream. 

Homogeneous biodiesel process Heterogeneous biodiesel process... 

The alkali process for biodiesel production can achieve high purity and yield of biodiesel in a short time. However, vegetable oils high in free fatty acids result in the production of soap and the loss of catalyst in the alkali process. To overcome this, the free tatty acids should be removed before the transesterification reaction. Because a homogeneous acid catalyst like sulfuric acid can not be recovered and is toxic, a heterogeneous acid catalyst can be used for the esterification of free fatty acids. Solid catalysts can be easily recovered after the reaction and reused [10-12]. 

Figure 10. A simplified block flow diagram of the homogeneous acid solid-catalyzed process for the production of biodiesel [23].

One of the chemical treatments of triglycerides of different vegetable and algae oils and animal fats produces the biofuel known as biodiesel. This development was based on the knowledge of the catalytic processes as well as on the evolution of instrumental techniques, which permitted the elucidation of the esterification mechanisms and consequently, the study of transesterification. Homogeneous and heterogeneous processes were studied focusing on basic, acid, and enzymatic catalysis [13, 15, 16, 22-36], Usually,... 

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