Specifications, biodiesel

The traditional catalyst used for esterification of acids to methyl esters is sulfuric acid. Homogeneous sulfuric acid catalysis has many downsides. When using sulfuric acid, much capital expense is required for Hastalloy and/or other specialty metals of construction. Homogeneous catalysis results in the contamination of the product by sulfur containing species. Therefore, neutralization and removal of acid is required to meet biodiesel specifications and to protect the downstream transesterification reactor. Inevitably, when using sulfuric acid, organic sulfur compounds will be produced. These products will cause the resultant biodiesel to fail specification tests. 

The term energy crop can be used both for biomass crops that simply provide high output of biomass per hectare for low inputs, and for those that provide specific products that can be converted into other biofuels such as sugar or starch for bioethanol by fermentation, or into vegetable oil for biodiesel by transesterificatiou... 

Biodiesel may be chemically represented as a mixture of fatty acid methyl esters (FAMEs). It is a naturally derived liquid fuel, produced from renewable sources which, in compliance with appropriate specification parameters, may be used in place of diesel fuel both for internal combustion engines and for producing heat in boilers. 

Moreover, European regulations in 2005 restricted the sulfur content in diesel fuel to SOmgkg. Sulfur organic compounds are known to provide diesel fuel with a lubricity that will disappear as the regulations take effect. Addition of biodiesel at a level of 1-2% to diesel blends has the effect of restoring lubricity through an antiwear action on engine injection systems, which is specific for polar molecules. 

Biodiesel from reactor 1 Biodiesel from reactor 2 European specification... 

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. 

Crude biodiesel is initially purified by thoroughly washing the ester phase with water or by neutralization with a polyprotic mineral acid to eliminate base catalyst residues. Next, in a settling tank, an aqueous phase, salt precipitates, and biodiesel are separated. Another water washing step follows to further remove polar compounds that might still be present in the biodiesel product. Finally, the biodiesel is vacuum distillated at moderate-to-high temperatures (around 190-270°C) to comply with ASTM specifications (99.6% or purer). ... 

The American Society for Testing and Materials (ASTM) initiated a Biodiesel Task Force in June 1994 to develop a specification for vegetable ester fuels for use in diesel-engine-powered vehicles. When completed, this specification for vegetable ester fuels will be the analog of ASTM D 975, the specification for petroleum-based diesel fuel. 

However, one of the limitations of using biodiesel fuel for diesel engines is higher cold flow properties compared with petroleum diesel fuel (4). Cold properties consist of cloud point, pour point, and cold filter plugging point. The cloud point is a temperature at which the fuel starts to thicken and cloud, the pour point is a temperature at which the fuel thickens and no longer pours, and the cold filter plugging point is the lowest temperature at which fuel still flows through a specific filter. These... 

Table 14.4 Specification of biodiesel following the german norm DIN EN 14214.

The quality of biodiesel is regulated by standards. The most important regards the content of free and bound glycerol. This cannot be modified by effective separation techniques. Therefore, the major element in design should be to obtain a composition of the mixture leaving the reaction system capable of matching the biodiesel specifications. This is difficult to achieve in view of the variety of raw materials. 

Grade = petrodiesel grade according to ASTM fuel specification D 975 Ratio = blend ratio where B0 = 0vol% biodiesel, B10 = 10%, B20 = 20% and B30 = 30%. See Table 1.3 for other abbreviations. 

Shrestha et al (2005) conducted a study in which SME, mustard seed oil methyl and ethyl esters and used peanut oil methyl esters were blended (B0, B5 and B10) with No. 2 petrodiesel and treated with six commercial petrodiesel CFI additives. It was found that at 100, 200, and 300% of the specified loading rate, CP and PP were reduced by an average of 2.2 °C and 14.1 °C, respectively. Mustard seed oil ethyl esters exhibited the highest average reduction in CP and PP and SME exhibited the lowest, as shown by Table 1.9 for CP. Furthermore, a significant decrease in CP was noticed when additive concentration was increased from 100% of the specified loading rate to 200% however, the difference between 200% and 300% was not significant. The authors conclude that the effect of fuel additive is not only different for different feedstocks but also some fuel additives worked better for a specific blend of biodiesel with No. 2 petrodiesel. 

Two reports in the patent literature claim the invention of CFI additives specifically designed to improve the cold weather performance of biodiesel (Scherer and Souchik, 2001 Scherer et al, 2001). Block copolymers of long-chain alkyl methacrylates and acrylates were effective as PPD and flow improv-... 

The Biodiesel Stability (BIOSTAB) project, supported by the European Commission, was initiated in 2001 to establish clear criteria and analytical methods for the monitoring biodiesel fuel stability (Various, 2003 Prankl, 2002). The resulting unified method, EN 14112 (Anon., 2003c) established a means for measuring oxidative stability utilizing the Rancimat or oxidation stability instruments. This test method was essentially developed from standards employed in the fats and oils industry to measure isothermally the induction period for oxidation of fatty derivatives. At present, both biodiesel fuel standards ASTM D 6751 (Anon., 2007a) and EN 14214 (Anon., 2003b) include an oxidative stability specification based on measurement by method EN 14112. 

Anon. 2007a. D 6751-06b Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels. In Annual Book of ASTM Standards (05.04). West Conshohocken PA ASTM International. 

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