Deliverable. 4.5 Determination of desired lignin based fuel additive properties

Transcription

1 Ref. Ares(2017) /07/2017 Deliverable 4.5 Determination of desired lignin based fuel additive properties Version: 3 Due: 6 Completed Lead Beneficiary: Partners: Dissemination level: June PI WinGD, TOTAL Public This project has received funding from the European Union s Horizon 2020 research and innovation programme under grant agreement No

2 Contents Deliverable Description... 2 Desired lignin based fuel additive properties... 3 Benchmark... 3 Performance metrics... 4 Pre-screening... 8 Regulations Market demand Road Racing References P a g e 1 F A L C O N D e l i v e r a b l e

3 Deliverable Description Determination of desired lignin-based fuel additive properties; These concern the most critical properties with respect to practical applications, including octane number, viscosity, heating value, miscibility with fossil fuels and flashpoint. P a g e 2 F A L C O N D e l i v e r a b l e

4 Desired lignin based fuel additive properties Benchmark Some base fuels can also serve as fuel additive (ppm only), ethanol (EtOH) for example can also be used as an octane booster to increase octane number. Other examples are aromatic and oxygenated molecules. Such octane booster additives can be used in standard gasoline, racing fuel (competition) or avgas (aviation gasoline). In avgas there is an interest to replace lead, whereby hydrocarbon-based octane boosters without nitrogen could be particularly interesting. Today the regulation is oriented towards decreasing consumption, improvement of engine efficiency (for competition- and for standard fuel). MTBE and ETBE, as put forward in the FALCON proposal, are in fact not the best references for this project because they are incorporated at the refinery-level. EtOH, conversely, is blended outside the refinery. The same principle can be applied to molecules originating from lignin. EtOH has a very high octane number and is a great molecule if used alone. Incorporated in gasoline, its properties are not fully valorized because of a lack of incentives in the current commercial fuel regulation. Using EtOH is in fact more complicated than ETBE (because the mixture of gasoline and EtOH creates azeotropes having a high vapor pressure). More than ETBE, ethanol, has a very low heating value compared to gasoline. The Holy Grail would be a molecule as cheap as EtOH, but without its drawbacks. Accordingly, we should strive for lignin-derived compounds which have gasoline-like vapor pressures when mixed with gasoline and similar lower heating values. Alternative molecules are continuously looked for because known molecules such as EtOH, MeOH, toluene, ethylbenzene, xylenes are not always sufficient in terms of toxicity, boiling point and fuel system material compatibility. In the past, organo-metallic components were used as octane boosters, such as tetraethyl-pb, MMT (Manganese) and ferrocene. These will be likely to disappear. Pb is already forbidden for most applications and in most countries. Manganese is not recommended by the European Automobile Manufacturing Association (ACEA) in the World Wide Fuel Charter (WWFC) and limited to 2ppm by EN228, which is a norm for commercial gasoline. And ferrocene will be forbidden as of Taking all the above in consideration, ethanol is probably to best octane booster benchmark for our project. P a g e 3 F A L C O N D e l i v e r a b l e

5 Performance metrics Octane boosters primary directive is to improve the anti-knock quality of the gasoline it is blended into. Since the early 1930 s, fuel anti-knock quality, as measured in dedicated, specialized test engines, has been expressed in a RON and/or MON value. As is clear from the Table below, intake temperatures are relatively high and intake pressure is atmospheric. Table 1 RON and MON testing conditions (reprinted from [1]) Knock tendency can be determined experimentally at three levels of characterization: Test with a rapid compression machine or an Ignition Quality Tester (IQT) to measure auto-ignition delay (upstream characterization). Octane numbers (MON, RON) measurement with CFR engine (intermediate characterization) Test in a (single-cylinder) engine in real conditions (larger fuel quantities required) Spark ignition (SI) engine technology has come a long way since the invention of the engine type in As can be seen in Figure 1, the most profound changes in the past decades have been aimed at the process of the fuel and air delivery processes. P a g e 4 F A L C O N D e l i v e r a b l e

6 Figure 1 Trends in U.S. light dusty SI engine technology (reprinted from [2]) Importantly, the transition from carburetors to port fuel injection (PFI) and later to direct injection (DI) has manifested in ever-cooler intake temperatures. These have come down from C (heated carburetors) to roughly 50 C (PFI). Owing to evaporative cooling effects, intake temperatures in DI engines tend to be lower still. Another trend, particularly the last decade, is downsizing. To obtain similar engine characteristics turbocharging is used. When intercooling is applied, heat is extracted from the intake air. As a result, the atmospheric pressure equivalent temperature can even fall below the freezing point. A consequence of these developments is that MON and even RON testing conditions are no longer representative for modern SI engine operation. This means that a new performance metric is long overdue. The most cited alternative octane rating method is the so-called Octane Index (OI), introduced in 2001 by Gautam Kalghatgi from Shell Global Solutions [3]. As is clear from his equations, shown below, RON requires several correction parameters, being K and S. What still remains the same, however, is that, akin to what is desired for RON and MON in the fuel specifications, the higher the value of OI the better for the engine performance. P a g e 5 F A L C O N D e l i v e r a b l e

7 The first parameter, K, relates to the state of the art with respect to SI engine technology. More specifically, it is a function of charge temperature relative to pressure and engine speed. In literature, the prevailing temperature at 15 bar compression, Tcomb15, is often used to estimate K. By definition, K is 0 and 1 for RON and MON conditions, respectively. As can be observed in Figure 2, the value of this parameter decreases with Tcomb15. In other words, as temperatures fall relative to pressure, as might be expected when turbocharging, intercooling and DI is applied, K moves down from MON to RON to so-called beyond RON territory. Shown in Table 2, K values are indeed trending lower. More importantly still, K appears firmly in negative territory. The impact of this becomes clear when we move to the second correction factor S. S is a measure of fuel sensitivity; in this case of anti-knock quality to (relative) temperature. When K was still positive, as was the case for most of the 20 th century, the OI equation would suggest that S should be as low as possible for any given RON. Now, with a negative K, highly sensitive fuels yield the higher OI for any given RON. P a g e 6 F A L C O N D e l i v e r a b l e

8 Figure 2 Impact of relative charge temperature on K (reprinted from [1]) Table 2 Evolution of K since 2001 (reprinted from [1]) P a g e 7 F A L C O N D e l i v e r a b l e

9 By definition, S is zero for the paraffins iso-octane and n-heptane. It would go too far here to discuss the chemical causalities and subtleties that ultimately determine S. For now, it is sufficient to say that nonparaffinic compounds, such as oxygenates, aromatics and olefinic compounds, tend to have higher S values compared to paraffins (Table 3). Table 3 OI for various octane boosters as a function of K (reprinted from [1]) Modern turbocharged and direct injected SI engines will thus benefit most from octane boosters that not only possess a high RON, but are also highly sensitive. This conclusion is not only applicable for road going vehicles, but, increasingly, also of importance to the racing world. In Formula 1, for example, a 1.6 liter turbocharged SI engine has become the standard. Apart from these anti-knock quality criteria, the octane boosters should also have a gasoline-like volatility behavior and heating value. In addition, the compounds in question should not be toxic. Pre-screening In a recent book on novel biofuel candidates [3], a whole chapter, titled Benzenoids (pp ), is devoted to lignin derived fuel compounds. The relevant fuel characteristics of aromatic oxygenates treated herein have been summarized in Figure 3 and Table 4. It is clear that aromatics with a single oxygen functionality are to be preferred over those that harbor two (e.g., guaiacol). Not only is more than one P a g e 8 F A L C O N D e l i v e r a b l e

10 oxygen functionality detrimental to anti-knock quality, it also decreases the heating value and increases the boiling point. Benchmarked against ethanol, single oxygen group aromatics have (on average) a slightly lower positive impact on anti-knock quality, but tend to have a gasoline like heating value without its toxicity. Figure 3 Prescreening of lignin model compounds as octane boosters. NB all compounds have been blended to EN228 gasoline at 10 vol.-% (based on data from [3]) P a g e 9 F A L C O N D e l i v e r a b l e

11 Table 4 Prescreening of lignin model compounds as octane boosters (based on data from [3]) Neat compound Boiling point HHV Toxicity - K MJ/l - Anisole ,8 FDA approved food flavorant Benzaldehyde ,6 FDA approved food flavorant Benzyl alcohol ,1 FDA approved food flavorant 2-phenylethanol ,5 FDA approved food flavorant Acetophenone ,5 FDA approved food flavorant Cinnamaldehyde ,9 FDA approved food flavorant Guaiacol ,1 FDA approved food flavorant Ethanol ,4 Carcinogenic when metabolized to acetaldehyde Gasoline - 33,1 Carcinogenic MTBE ,1 Not classifiable or potentially Carcinogenic ETBE ,9 Not classifiable or potentially Carcinogenic Regulations To introduce a molecule on the market, it needs to be compatible with EN 228 (Automotive fuels Unleaded petrol Requirements and test methods) when mixed with gasoline. Specific regulations can be put in place, for example, EN15376 for EtOH (Automotive fuels Ethanol as a blending component for petrol Requirements and test methods). The main incentives for bio components incorporation are predominantly regulations. Market demand Road Recent market data suggests that while the price differential is increasing between regular and premium gasoline, demand for the latter has fallen from 30 % of retail sales in the 1980 s to roughly 10 %, where it has plateaued over the past 10 years (figure 4. In Europe there would to be no need (yet) because RON 98 is already available (car manufacturers do not valorize RON 98 today). On the other hand, in Germany at least, all Shell stations offer V-Power Racing 100, rated at 100 RON. This in stark contrast to many developing countries, where there is even a resistance to increase RON. Moreover, with the upcoming P a g e 10 F A L C O N D e l i v e r a b l e

12 organometallic octane booster ban as planned in Africa for 2018, there is a risk of a falling RON like previously happened to both China and earlier in Europe. Figure 4 Demand and pricing trends for premium gasoline in the US (reprinted from [2]) P a g e 11 F A L C O N D e l i v e r a b l e

13 Racing For racing fuels, the objective is to increase octane number to improve the fuel resistance to knocking. RON target is between 105 and 110. Metals are forbidden, there is a maximal Nitrogen (N) content acceptable. For oxygenated-components, above 1%, there is a constraint for mono-alcohol or mono-ester and boiling point needs to be below 210 C. Adding oxygenated compounds increases fuel consumption. Bio-sourced mono-aromatics can be interesting, 10 carbon atoms would be the limit for gasoline cut: the heaviest component used currently is mesitylene; if alkyl groups are present on the aromatic ring, it is better to favor methyl or ethyl groups. The time scale is very short for F1: only a few weeks to develop a new fuel; for other competitions it is up to 1 year. Therefore it is mandatory to bring novelty and to be reactive. For competition sector, price is at least twice the price of standard fuel. P a g e 12 F A L C O N D e l i v e r a b l e

14 References [1] Boot, M. D., Tian, M., Hensen, E. J., & Sarathy, S. M. (2017). Impact of fuel molecular structure on autoignition behavior Design rules for future high performance gasolines. Progress in Energy and Combustion Science, 60, [2] Splitter, D., Pawlowski, A., & Wagner, R. (2016). A historical analysis of the co-evolution of gasoline octane number and spark-ignition engines. Frontiers in Mechanical Engineering, 1, 16. [3] Boot, M. (2016). Biofuels from lignocellulosic biomass: innovations beyond bioethanol. John Wiley & Sons. P a g e 13 F A L C O N D e l i v e r a b l e