Biodiesel/petrodiesel blends

TABLE 1.4. Cold flow properties of biodiesel/petrodiesel blends."... 

Eberlin, L.S., Abdelnur, P.V., Passero, A., de Sa, G.F., Daroda, R.J., de Souza, V, Eberlin, M.N. (2009) Analysis of biodiesel and biodiesel-petrodiesel blends by high performance thin layer chromatography combined with easy ambient sonic-spray ionization mass spectrometry. Analyst, 134,1652-1657. 

These samples are mustard biodiesel-petrodiesel blends at 1% biodiesel. 

Many studies on the performances and emissions of compression ignition engines, fueled with pme biodiesel and blends with diesel fuel, have been conducted and are reported in the literature (Laforgia and Ardito, 1994). Fuel characterization data show some similarities and differences between biodiesel and petrodiesel fuels. The sulfur content of petrodiesel is 20 to 50 times that of biodiesel. Biodiesel has demonstrated a number of promising characteristics, including reduction of exhaust emissions. 

MEE = mustard seed oil ethyl esters MME = mustard seed oil methyl esters UPEME = used peanut oil methyl esters B5 = 5vol% biodiesel in No. 2 petrodiesel blends B20 and B100 are defined in Tables 1.4 and 1.6. See Tables 1.2 and 1.3 for other abbreviations. 

The biodiesel can be used alone or blended, as B20 in 20wt% with petrodiesel. As shown in Table 14.2, the biodiesel has remarkable combustion properties reflected in a drastic reduction of all emissions, excepting for a small increase in NO. Over a life cycle the C02 reduction is about 65% [13]. 

With respect to viscosity, which controls the fuel injection, the biodiesel shows somewhat higher values compared with petrodiesel, but this can be kept under 5 mm2/s by controlling the feedstock composition or by blending. 

Blending petrodiesel with SME significantly increases CP and PP at relatively low blend ratios (vol% SME) in No. 1 petrodiesel fuel and jet fuel (Dunn, 2001 Dunn and Bagby, 1995). For blends in No. 2 petrodiesel, increasing blend ratio increases CP and PP linearly (R2 = 0.99 and 0.96). Blending petrodiesel with SME also increases CFPP and LTFT (Dunn and Bagby, 1995). Similar results were reported for blends with biodiesel derived from coconut oil, rapeseed oil, tallow and waste grease (see Table 1.4). 

Nearly linear correlations for CFPP versus CP and LTFT versus CP were reported for neat biodiesel and its blends with petrodiesel (Dunn and Bagby, 1995,1996 Dunn et al., 1996). For LTFT, the correlation was essentially LIFT CP, suggesting the labor- and time-intensive LTFT test could be spared by simply measuring CP. A major conclusion from these studies was that development of approaches to improve cold flow properties of biodiesel should focus on technologies that decrease CP. 

Many approaches for improving the cold flow properties of biodiesel have been explored. These include blending with petrodiesel, transesterification with medium or branched-chain alcohols instead of methanol or ethanol, crystallization fractionation, and treatment with cold flow improver (CFI) additives. 

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. 

Effects of six commercial petrodiesel CFI additives on SME and its blends with No. 1 and No. 2 petrodiesel were studied previously (Dunn and Bagby, 1996 Dunn et al., 1996). Results from these studies are summarized in Table 1.6. These petrodiesel CFI additives decreased PP by up to 18-20°C for B30 blends in No. 1 petrodiesel and B20 blends in No. 2 petrodiesel. Similarly, these additives decreased PP of neat SME ( B100 ) by as much as 6°C. When applied to unblended petrodiesel ( BO ), these additives reduced PP by 7°C for No. 1 petrodiesel and by 23°C for No. 2 petrodiesel (Dunn et al., 1996). These results suggested that mechanisms associated with crystalline growth and agglomeration in neat biodiesel were similar to those for petrodiesel (Dunn and Bagby, 1996 Dunn et al., 1996). 

In contrast to the PP data listed in Table 1.6, none of the CFI additives greatly affected CP of SME or its blends with No. 1 or No. 2 petrodiesel. In terms of wax crystallization, CFI additives designed for treating petrodiesel did not selectively modify crystal nucleation in biodiesel (Dunn et al., 1996). 

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. 

TABLE 1.9. CP depression at manufacturer s recommended additive loading for biodiesel from various feedstocks and blend levels in low-sulfiir (500ppm) No. 2 petrodiesel."... 

Results related to those discussed above (Knothe and Steidley, 2005b) are available in the literature (Hu et al., 2005 Hillion et al, 1999). The results in these publications do not agree on all aspects, however, there is agreement that low-level contaminants significantly affect biodiesel lubricity and its low-level blends with petrodiesel. 

It has been shown that when fatty acid methyl esters are pyrolysed over activated alumina at 400 C at a weight-hourly space velocity of 0.45, they are completely deoxygenated to form linear hydrocarbons. These are completely compatible with petrodiesel with which they can be blended in all proportions. Because the blending of biodiesel with petrodiesel is one strategy for addressing the CFPP, the pyrolytic deoxygenation offers several options for the use of waste fats and oils as biodiesel precursors. 

Stability tests developed for petrodiesel fuels reportedly are not suitable for biodiesel or biodiesel blends with petrodiesel (Canakci et al., 1999 Stavinoha Howell, 1999 Westbrook Stavinoha, 2003), however, appropriate modification may render them useful. Another study (Bondioli et al., 2003) states that the petrodiesel method ASTM D4625 (Standard Test Method for Distillate Fuel Storage Stability at 43°C (110°F) is suitable but not fast. 

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