Soybean Motor Oil

Download Soybean Motor Oil

Post on 21-Oct-2015

17 views

Category:

Documents

4 download

Embed Size (px)

DESCRIPTION

An article on Soybean Motor Oil

TRANSCRIPT

<ul><li><p>Journal of the Science of Food and Agriculture J Sci Food Agric 86:17691780 (2006)</p><p>ReviewPlant-oil-based lubricants and hydraulicfluidsManfred P SchneiderFB C Bergische Universitat Wuppertal, D-42097 Wuppertal, Germany</p><p>Abstract: It is estimated that, at present, approximately 50% of all lubricants sold worldwide end up in theenvironment via total loss applications, volatility, spills or accidents. More than 95% of these materials arecurrently mineral oil based. In view of their high ecotoxicity and low biodegradability, mineral oil-based lubricantsconstitute a considerable threat to the environment. In contrast,most lubricants and hydraulic fluids based on plantoils are rapidly and completely biodegradable and are of low ecotoxicity; moreover, lubricants based on plant oilsdisplay excellent tribological properties and generally have very high viscosity indices and flashpoints. However, inorder to compete with mineral-oil-based products, some of their inherent disadvantages must be corrected, suchas their sensitivity to hydrolysis and oxidative attack, and their behaviour at low temperatures. Various methodsto improve the undesirable properties of native plant oils will be discussed. In parallel, government regulationsthat encourage or enforce the use of bio-based fluids, at least in ecologically sensitive areas, will help to increasetheir market share. Using the numerous possibilities for selective breeding and/or chemical improvement of thedouble bond systems of natural fatty acids by increased R&amp;D, the major obstacles regarding the use of plant-basedraw materials for the production of lubricant base fluids can be overcome and bio-based fluids should expect afuture with increasing market shares. 2006 Society of Chemical Industry</p><p>Keywords: plant oils; high oleic sunflower oil; rapeseed (canola); oxidative attack; biodegradability; ecotoxicity;chemical modifications; additives; eco-labels; lubricants; hydraulic fluids</p><p>INTRODUCTION: LUBRICANTS AND THEENVIRONMENTThe environment must be protected against pollutionby lubricants and hydraulic fluids based on mineraloils. This is, of course, best done by preventingundesirable losses and by reclaiming and reusinglubricants. Alternatively, environmentally acceptablelubricants and hydraulic fluids should be usedwhenever and wherever possible. According toliterature reports, varying amounts of lubricants atpresent end up in the environment they disappear.It is claimed that in the EU alone in 1990 13%(661 106 L of a total of 4959 106 L) were lostin the environment.1,2 In the USA 32% (432 106gallons of 1351 106 gallons) of lubricating oils endedup in landfills or were dumped. It is claimed that50% of all lubricants sold worldwide end up inthe environment via total loss application (chainsawoils, two-stroke engines, concrete mould release oils,exhaust fumes in engines and metal cutting andforming processes) spillage and volatility.3 Estimatesfor the loss of hydraulic fluids are as high as7080%.4,5 Most problematic are uncontrolled lossesvia broken hydraulic hoses or accidents whereby largequantities of fluids escape into the environment.6 They</p><p>contaminate soil, surface-, ground- and drinking waterand also the air. In Table 1 the estimated amounts oflubricants used in Germany,7 the EU8 and worldwide9</p><p>are listed, together with the (estimated) losses.In contrast to mineral oils, lubricants and hydraulic</p><p>fluids based on plant oils are generally rapidlyand completely biodegradable and are also of lowecotoxicity. At present the use of pure native plantoils is limited to total loss applications (lubricantsfor chainsaws, concrete mould release oils) andthose with very low thermal stress. Hydraulic fluidsare of increasing importance for applications inenvironmentally sensitive areas where a potential totalloss could be encountered, such as excavators, earth-moving equipment and tractors, in agricultural andforestry applications and in fresh water (groundwater)sensitive areas.10,11 Mineral oils are toxic for mammals,fish and bacteria. Considering the sump capacities ofsuch machinery (up to 1000 L) the ecological impact isobvious as are the economics of the resulting clean-up operations.</p><p>Although it seems obvious that the increased useof rapidly biodegradable lubricants would be ofconsiderable ecological and economical advantage, thepresent market share of these materials is relatively</p><p> Correspondence to: Manfred P Schneider, FB C Bergische Universitat Wuppertal, D-42097 Wuppertal, GermanyE-mail: schneid@uni-wuppertal.deContract/grant sponsor: German Ministry of Agriculture (BVMEL)(Received 18 November 2005; accepted 31 March 2006)Published online 3 August 2006; DOI: 10.1002/jsfa.2559</p><p> 2006 Society of Chemical Industry. J Sci Food Agric 00225142/2006/$30.00</p></li><li><p>MP Schneider</p><p>Table 1. Consumed lubricants and (estimated) losses (in tons perannum)</p><p>Germany EU World</p><p>Amount consumed 1 000 000 5 000 000 3040 000 000Losses 400 000 2 500 000 20 000 000Losses in % 40 50 55</p><p>Table 2. Market share of bio-lubesa in Europe by geography for 2000and expected for 2006</p><p>Year Germany France UK BeneluxScand-inavia Italy</p><p>Switzer-land</p><p>Austria</p><p>2000 4.0 0.1 0.2 2.9 9.0 1.3 5.72006 15.1 0.3 0.4 4.9 10.8 2.0 8.4</p><p>a Biodegradable lubricants derived from renewable resources includingplants and animals.</p><p>small12 (2% in the EU and worldwide, with anestimated growth rate of 510%), as shown in Table 2for a selection of European countries.13 (It shouldbe noted that the Frost and Sullivan market surveyand prediction is probably overoptimistic and thata 10% increase per annum would be consideredalready a success by oil manufacturers. Increasesof 510% are in fact observed in reality; see alsoWhitby.14)</p><p>For hydraulic fluids this amount is increasing morerapidly, with estimates ranging from 25% to 75%.5,15</p><p>In order to increase this market share, the acceptabilitymust be improved. Technical performance, acceptableprice and ecological compatibility will constitute thebasis for future developments along these lines. Froman EU-sponsored study it seems that biolubricantsare already available for the majority of applicationsand that the technical performance is comparableand sometimes even better than for conventionallubricants. Furthermore, the price of mineral oil willcontinue to increase over the years to come and thepresent-day advantage of low cost for mineral oilproducts may be completely lost in a decade fromnow.16,17</p><p>PLANT-OIL-BASED LUBRICANTS ANDHYDRAULIC FLUIDS: PROPERTIESIn practical applications lubricants and hydraulicfluids have multiple functions. They are needed forlubrication, transmission of energy, protection againstcorrosion, wear (attrition) and heat removal.</p><p>Plant-based fluids meet these requirements ideally.They display:</p><p> excellent tribological properties (ester functions stickwell to metal surfaces);</p><p> lower friction coefficients than mineral-oil-basedfluids;</p><p> lower evaporation (Noack) up to 20% less thanmineral-oil-based fluids;</p><p> higher viscosity index (multi-range oils); excellent biodegradability; high flashpoints; low water pollution classification.</p><p>Their technical properties are thus largely com-parable with mineral-oil-based fluids. However, theyare thermally less stable than mineral oils, sensi-tive to hydrolysis and oxidative attack, and theirlow-temperature behaviour is frequently unsatisfac-tory properties which can be corrected by a numberof measures:</p><p> exchange of glycerol by other polyols, in particulartrimethylolpropane (TMP);</p><p> avoiding or modifying multiply unsaturated fattyacids;</p><p> suitable additivation.For the development of lubricants and hydraulic</p><p>fluids on the basis of renewable resources such asnative plant oils one will always have to make acompromise between the performance based on thechemical structure and the desired biodegradabilityand ecotoxicity. All lubricants and hydraulic fluids arecomposed of so-called base fluids and additives.</p><p>BASE FLUIDSNative oilsThese are triglycerides, esters composed of variousnatural fatty acids and glycerol. The most importantfatty acids contained in plant oils are unsaturatedmolecules such as oleic acid (C18:1), linoleic acid(C18:2) and linolenic acid (C18:3), as well as(saturated) palmitic acid (C16:0) and stearic acid(C18:0). At present, the most important sources fornative oils are rapeseed (canola), sunflower (variousqualities) and soybean. The fatty acid compositions ofpotential plant oils are summarized in Fig. 1.18</p><p>The structures of fatty acids both chain lengthand degree of unsaturation are directly related totheir operational stabilities and lubricant propertiessuch as viscosity, viscosity index and low-temperaturebehaviour (e.g. pour point). Thus the oxidativestability of native oils increases with decreasingamounts of polyunsaturated acids (compare oxidativeattack below). Since at least one cis- (Z) doublebond is essential for the required low-temperaturebehaviour, a high content of oleic acid is optimal.The best compromise at present among the abovefactors is high oleic sunflower oil (HOSO) with 90%oleic acid </p></li><li><p>Plant-oil-based lubricants and hydraulic fluids</p><p>0</p><p>10</p><p>20</p><p>30</p><p>40</p><p>50</p><p>60</p><p>70</p><p>80</p><p>90</p><p>100</p><p>C16:0 C18:0 C18:1 C18:2 C18:3Fatty Acids</p><p>[%]</p><p>safflower oil</p><p>high-oleic safflower oilhigh-linoleic safflower oil</p><p>sunlower oil</p><p>sunflower oil (80%)sunflower oil (90%)rapeseed oilsoybean oil</p><p>high-oleic soybean oil</p><p>corn oil</p><p>cottonseed oil</p><p>Figure 1. Fatty acid composition of various vegetable oils (worldwide).</p><p>present time we have two options: (a) to providesufficient quantities of native oils with a high contentof oleic acid by breeding or GMOs; or (b) to modifyrapeseed oil (canola) or soybean oil by a variety ofchemical measures (see below).</p><p>Synthetic estersNative oils, i.e. triglycerides, contain glycerol as thealcohol component. They are inherently sensitivetowards hydrolysis and thermal degradation. Muchimproved performance is achieved in products wherethe glycerol has been replaced by other polyols such astrimethylolpropane (TMP),19 neopentyl glycol (NPG)or pentaerythritol (PE)20,21 (Fig. 2).</p><p>Some of these esters display extraordinary thermalstabilities. NPG esters are used as lubricants in jetengines. Several of such derivatives are used underarctic conditions. PE derivatives of carboxylic acidsC5 C9 are employed in modern gas turbine engines.TMP esters of oleic acid are among the most widelyapplied materials for hydraulic fluids at present. Thesebio-based esters show very good biodegradability,moderate oxidative stability and have a moderate pricelevel. They are generally of high viscosity and displaygood shear stability. With some additivation they arethe optimal choice for medium to heavy applications. Asubgroup of these materials is called complex or oligoesters, resulting from the above polyols and mixturesof mono-, di- and tricarboxylic acids (for an examplesee Bondioli et al.22) (Fig. 3).</p><p>Ester of trimethylolpropane Ester of pentaerythritol Ester of neopentylglycol</p><p>O O</p><p>O</p><p>O O</p><p>OOR</p><p>R</p><p>R</p><p>RR</p><p>R</p><p>R</p><p>O</p><p>OO</p><p>O O</p><p>OO</p><p>R O R</p><p>O O</p><p>O</p><p>Figure 2. Esters of trimethylolpropane (TMP), pentaerythritol (PE) andneopentylglycol (NPG).</p><p>O</p><p>O</p><p>O R3R1</p><p>O</p><p>OO</p><p>OR2O</p><p>n</p><p>Figure 3. An oligo- or complex ester (schematic).</p><p>DiestersOnly partly or to a lesser degree derived fromrenewable resources are synthetic diesters preparedfrom dicarboxylic acids and monovalent alcohols. Theemployed dicarboxylic acids can be derived either fromnatural sources such as azelaic acid (ozonolysis of oleicacid), sebacic acid or dimeric fatty acid, isostearicacid or from purely petrochemical sources such asadipic acid or maleic acid. The alcohols are generallybranched for better low-temperature performancesuch as 2-ethylhexanol (isooctanol), isodecanol orguerbet alcohols (Fig. 4). Also branched fatty acids,e.g. 12-hydroxystearic acid (derived from rhizinoleicacid), can be employed.</p><p>O</p><p>O</p><p>O</p><p>O</p><p>H H</p><p>HO OH HO</p><p>O O</p><p>O</p><p>O</p><p>O</p><p>O</p><p>+ 2</p><p>Figure 4. Diesters from adipic and maleic acids and 2-ethylhexanol.</p><p>J Sci Food Agric 86:17691780 (2006) 1771DOI: 10.1002/jsfa</p></li><li><p>MP Schneider</p><p>Base fluids: structure and propertiesThere is a definite relationship between the structureof the molecules and their properties such as viscosity,viscosity index (VI), low-temperature performancesuch as pour point and the oxidative stability.Viscosity of the base fluid generally increases with</p><p>the chain length of the carboxylic acid and the alcohol.However, if polyols are employed the viscosity alsodepends on the number of hydroxy functions present,and base fluids with identical fatty acid residues wouldshow the following series of viscosities depending onthe employed polyol:</p><p>PE (40) &gt; TMP (27) &gt; Glycerol (20) &gt; NPG (12)</p><p>Viscosity index describes the dependence of viscosityon the temperature. A high viscosity index meansthat there is little change over a wide temperaturerange. It increases with increasing chain length ofcarboxylic acid and alcohol, while branching in eitherthe carboxylic acid or the alcohol results in a loweringof the viscosity index. Base oils based on natural fattyacids in general are known for their high viscosityindices and can be considered multi-range oils.Good low-temperature properties require a low con-</p><p>tent in saturated fatty acids (C16:0 and C18:0) and/orshortening of the chain length. In contrast, unsaturatedfatty acids display excellent low-temperature proper-ties. Thus, the pour points of simple esters derivedfrom saturated and unsaturated fatty acids of iden-tical carbon atom number are dramatically different(Fig. 5).</p><p>-40-20</p><p>020406080</p><p>100</p><p>6:0 8:0 10:0 12:0 14:0 16:0 18:0 18:1 18:2 18:3Fatty acid</p><p>Pour</p><p>poin</p><p>t [C]</p><p>Figure 5. Dependence of pour point on fatty acid structure.</p><p>Also, the pour point is lowered (improved) withincreasing branching and shortening of the chainlength.Oxidative stability requires a low content in polyun-</p><p>saturated fatty acids (C18:2 and C18:3), while onedouble bond such as in oleic acid (C18:1) is essen-tial for good low-temperature properties and doesnot negatively influence the oxidative stability (seebelow). Fully saturated esters exhibit excellent oxida-tive stability,23,24 while partially unsaturated systemsneed improvement for applications in automotive(engine, transmission fluids), diesel and industrial(hydraulic, compressor) lubricants.</p><p>Fully saturated diesters in general show good low-temperature performance (branched alcohol) and ahigh viscositytemperature index. By adjusting thechain length of the dicarboxylic acid the viscositycan be modified. These oils are highly stable towardsoxidation (saturated compounds).Hydrolytic stability is strongly dependent on the ester</p><p>structure. In general, saturated esters with straight-chain components are more stable than unsaturated orbranched equivalents. The most stable derivatives aresaturated dicarboxylic esters. This is usually attributedto steric effects although there is some debate over this.</p><p>Base fluids: chemical structure and performanceAs already pointed out above, native plant oils(triglycerides) are sensitive towards hydrolysis, thermaldegradation by...</p></li></ul>