Lipid feedstock

However, acids can simultaneously catalyze both esterification and transesterification, therefore they can directly produce biodiesel from low-cost lipid feedstocks. 

Compared to the base-catalyzed synthesis of biodiesel, fewer studies have dealt with the subject of acid-catalyzed transesterification of lipid feedstocks. Among acid catalysts, sulfuric acid has been the most widely studied. In the previously mentioned work of Freedman et al., the authors examined the transesterification kinetics of soybean oil with butanol using sulfuric acid. The three reaction regimes observed (in accordance with reaction rate) for base-catalyzed reactions were also observed here. A large molar ratio of alcohol-to-oil, 30 1, was required in this system in order to carry out the reaction in a reasonable time. As expected, transesterification followed pseudo-first-order kinetics for the forward reactions (Figure 2), while reverse reactions showed second-order kinetics. 

Feedstock (1) Lipid feedstocks with high free fatty acid contents ... 

The lipid feedstock may contain variable proportions of free fatty acids (FFA), which should be converted in esters before transesterification. Otherwise, the formation of soaps occurs by reaction with the hydroxide catalyst, as follows ... 

Kinetic experiments have been reported in literature for the treatment of different types of lipidic feedstock with methanol, such as for soybean [16, 33], rapeseed [25] and sunflower oil [1, 36]. The aim is to optimize the reaction conditions, namely the amount of catalyst, the excess of methanol and the reaction temperature. The results depend largely on the composition of the raw materials, but some trends can be distinguished ... 

Most often, the rates for feedstock destruction in anaerobic digestion systems are based upon biogas production or reduction of total solids (TS) or volatile solids (VS) added to the system. Available data for analyses conducted on the specific polymers in the anaerobic digester feed are summarized in Table II. The information indicates a rapid rate of hydrolysis for hemicellulose and lipids. The rates and extent of cellulose degradation vary dramatically and are different with respect to the MSW feedstock based on the source and processing of the paper and cardboard products (42). Rates for protein hydrolysis are particularly difficult to accurately determine due the biotransformation of feed protein into microbial biomass, which is representative of protein in the effluent of the anaerobic digestion system. 

Betahistine (84), a vasodilator based on the readily available feedstock a-picoline, can be synthesized by a very lengthy process (75MI20904). A shorter route employing the commercially available 2-pyridylethanol has also been described (77CZ389). Reaction of (6-hydroxymethyl-2-pyridyl)methanol with methyl isocyanate, or its bis(phenylcarbonate) with methylamine (66JAP6622185), affords anginin (85), a compound used to reduce lipids and cholesterol levels in the blood. Esterification of 2-pyridylmethanol with ibuprofen... 

Macromolecular biomass composition is of obvious interest when the biomass itself is the product, such as algal biomass in [18], or for production of singlecell protein, for e.g. animal feedstock. Moreover, for a precise metabolic flux analysis, changes in biomass composition should be taken in account. For example, Henriksen et al. [19] observed with E. coli under different growth rates, that the levels of DNA and lipids were relatively constant, whereas the proteins and stable RNA levels increased with the specific growth rate and the total amount of carbohydrates decreased. 

Biomass can be divided mainly into three compound classes - namely, lignocellulose, lipids, and proteins. These may come from different feedstocks and may differ in composition but should need only different steps in preprocessing to obtain a... 

TABLE 1.3. Cold flow properties of biodiesel (B100) derived from various feedstock lipids and alcohols.2... 

For edible applications, lipids are often used intact. For such uses, the whole fats and oils are subjected to hydrogenation. For industrial uses, lipids are the feedstocks for free fatty acid production. When firmer fractions are needed for industrial applications, the free fatty acids obtained by lipid hydrolysis are subjected to... 

Considerable recent research has defined conditions for successful use of lipases and other enzymes in numerous lipid modification reactions, including a variety of types of interesterifications (69, 71, 76). For edible applications to date, they have been employed at industrial scales for the production of (1) cocoa butter substitutes, for which disaturated, monounsaturated acylglycerols with the unsaturated fatty acid in the sn-2 position are desired (77) (2) to produce human milkfat analogues, where 2-palmitoyl acylglycerols are desired (77) (3) in the synthesis of 1,3- di-acylglycerols (78) and in the production of diacylglycerols for edible applications. These reactions employ vegetable oils as feedstocks. 

As animal fats are a potential feedstock for biodiesel production, Cummins et al. (142) assessed the danger of a human contracting CJD as a result of the use of tallow as a fuel in diesel engines. They concluded that the risk was several orders of magnitude less than the rate of spontaneous appearance of CJD. Thus, scientific analysis indicates that processed (i.e., rendered) animal fat is not an agent of transmission of BSE. Nonetheless, especially in the United Kingdom, the public remains skeptical. This has in some cases led to less use of animal fats in feed applications. Especially in the United Kingdom, the BSE epidemic has reduced the amount of domestically available tallow (because of condemnation) and increased the use of other lipids in place of animal fats. 

Selected thermochemical syntheses are discussed here to show how the structural characteristics of biomass components can affect the methods chosen to manufacture a few specific commodity chemicals. The main components of biomass, the pentoses and hexoses from the polysaccharides and the lignins, lipids, and proteins, are examined as potential feedstocks. 

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