The Effect of Branched‐Chain Fatty Acid Alkyl Esters on the Cold‐Flow Properties of Biodiesel

Abstract

Biodiesel (fatty acid methyl esters [FAME]) is produced from various fats, oils, and greases (FOG) using catalytic transesterification with methanol. These fuels have poor cold-flow properties depending on the fatty acid (FA) composition of the parent FOG. Improving the coldflow properties of biodiesel will enhance its prospects for use during cooler months in moderate temperature climates. This work is a study on the use of skeletally branchedchain alkyl esters (BCAE) composed of the isopropyl, nbutyl, and 2-ethylhexyl esters of iso-oleic acid isomers (iPr-iOL, nBu-iOL, and 2EH-iOL). These BCAE additives were tested in blends with linear-FAME (L-FAME) derived from soybean oil (SME), lard (LME), tallow (TME), and sewage scum grease (SGME). Binary L-FAME/SME admixtures were also studied. Admixtures were tested for the effects of the additives on cloud point (CP), pour point (PP), and kinematic viscosities at standard (ν 40 = 40 C) and low temperatures (T L ) = CP + 5 C (ν L ). Although the BCAE additives were more effective than SME, relatively large additive concentrations (y Add ) were needed to depress CP and PP by more than 2 C. Admixtures with high concentrations of BCAE additive had ν 40 > 6.0 mm 2 s −1 , the maximum limit in ASTM fuel specification D 6751. While the iPr-iOL and nBu-iOL additives may be blended at concentrations up to y Add = 0.50, 2EH-iOL should not exceed y Add = 0.28 in LME, 0.31 in SGME, 0.35 in TME, or 0.41 in SME to avoid driving the admixture out of specification. Some anomalies observed in the results at low y Add for SGME/BCAE admixtures were speculated to have been affected by the low-temperature rheology of SGME. KeywordsAdmixture Á Branched-chain alkyl esters Á Cloud point Á Kinematic viscosity Á Additive mass fraction Á Pour point J Am Oil Chem Soc (2019) 96: 805-823. Scheme 1 Molecular structures of linear-fatty acid methyl ester (L-FAME), skeletally branched-chain-fatty acid methyl ester (BC-FAME) and skeletally branched-chain alkyl esters (BCAE) 807 J Am Oil Chem Soc J Am Oil Chem Soc (2019) 96: 805-823

Synthesis of Dimer Acid 2‐Ethylhexyl Esters and their Physicochemical Properties as Biolubricant Base Stock and their Potential as Additive in Commercial Base Oils

“…Consequently, the addition of 1% (w/w) C52‐DA 2‐EH esters 1 or 2 lowered the PP of HOSuO from −18.8 to −21.0 °C. Contrary to the results of the biodiesel–BCAE blend study (Dunn et al, 2019), the PP of the base oil C52‐DA 2‐EH ester blends were not affected by C52‐DA 2‐EH ester concentrations above 1% (w/w).…”

“…In repeated CP determinations, the CP of HOSuO increased at 1% (w/w) blend concentration of both C52‐DA 2‐EH esters. Similar to previous observations (Dunn et al, 2019), this phenomenon may be attributed to the diffusion of high melting components in HOSuO, resulting in accelerated crystal formation and, thereby, initially increasing the CP. As can be seen in Fig.…”

“…Previous reports (Dunn et al, 2015, 2019) have shown that branched‐chain fatty acid alkyl esters (BCAE) improved the cold flow properties of biodiesel by decreasing the PP with increasing BCAE concentration in the blend. In this study, blends of C52‐DA 2‐EH esters in HOSuO were investigated for their cold flow properties relative to the neat base oil (Fig.…”

Valorization of Food Loss and Wastes: Feedstocks for Biofuels and Valuable Chemicals

“…Substantial progress in the development of industrial and consumer goods based from biorefineries includes broad based biolubricants base oils containing furan ring and branched chain alkanes from oleic acid, milkweed oil, cotton seed oil, canola oil ricinoleic acid from soybean bean. Chemical and enzymatic modification of these renewable materials have led to commercial production of renewable lubricant base oil, cold flow imoprover additives, "green diesel, " surface active agents and rusty and corrosion inhibitors (Adhvaryu et al, 2000;Seo et al, 2012;Yasa et al, 2017;Dunn et al, 2019;Liu et al, 2019).…”

Polymer Cold-Flow Improvers for Biodiesel

“…Low molecular weight (MW) CFIs have been well-represented in the literature, and relatively high efficiency was demonstrated by ethanol as diluent [ 44 ], hydroxyacetone, solketal, glycerol formal [ 45 ], ozonized vegetable oil [ 46 ], triacetin [ 47 , 48 ], dimethyl azelate [ 48 ], branched esters of FA [ 49 , 50 ], monoglycerides as emulsifiers [ 51 ], mannosylerythritol lipid-A [ 52 ], branched diesters [ 53 , 54 ] and other compounds [ 6 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. However, it is difficult to find a balance between the effect of the additives and the result of blending: actually, appreciable percentages of low MW additives were acting as a component of binary/ternary mixtures, which naturally have lower crystallization points [ 44 , 55 , 56 ].…”