Let’s Do It Creatively ... and Environmentally with Renewable Energy (CERE)”. A Review of Dimethylfuran : A potential renewable biological fuel by Krzysztof Bahrynowski and Eloise Renouf Recently, this compound has been proposed as a potential biofuel, developed by a team of 4 American searchers from Wisconsin-Madison University, let by the Professor James Dumesic. They reported on the 21st of June 2007 (Roman-Leshkov et al., 2007) that this molecule can be produced rapidly and efficiently from the conversion of fructose (Figure 1), found abundantly in the plants, particularly in fruits and some root vegetable s . Fig.1: Simplified representation of the conversion of Fructose into DMF (Heiden & Rauchfuss, 2007). This reaction consists of a two-steps catalytic biomass-to-liquid process (Figure 2), via 5-hydroxymethylfurfural (HMF). The first step consists of converting fructose to HMF by dehydration in a biphasic reactor, by the removal of three oxygen atoms, using an acid catalyst in water, in the presence of solvents with a low boiling point (Figure 3, R1). These solvents are also excellent fuel components, which eliminates the need for expensive separation steps to produce the final liquid fuel mixture. Under the action of these solvents, the HMF is extracted from water. Even if various solvents can generate HMF, the team found that the use of 1-butanol as a solvent is advantageous for biomass application because it can be produced by the fermentation of biomass-derived carbohydrates. Furthermore, 1-butanol is inert in the hydrogenolysis step of the process. This reaction had been previously done by other research groups, but Dumesic’s team brought some improvements to make the HMF easier to extract and raise the production so as HMF can be produced in high yields. For instance, they added NaCl in the aqueous phase so as to decrease the formation of impurities and to improve the extraction of HMF from water without using high boiling point solvents. Recently, a new process for this step has been developed, using chromium chloride (CrCl3·6H2O) and boric acid (B(OH)3) as double catalysts in ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), which show a better efficiency (Hu et al., 2012). The results showed that the highest HMF yield of 78.8% was achieved at 120⁰C for only 30 min. After the extraction of HMF, [BMIM]Cl and CrCl3·6H2O/B(OH)3 could be easily recycled with stable activity, after five successive runs. Tetraethyl ammonium chloride (TEAC) was also found to be a good solvent for HMF formation. Then, the extracting solvent containing HMF undergoes a purification step, with evaporation (Figure 3, E1). The water, the NaCl, the fraction of 1-butanol that evaporates, and 58% of HCl are recovered and recycled back into the biphasic reactor, while the purified liquid stream containing HMF and 1-butanol is sent for the second step of the process.
The next step is the conversion of HMF to DMF by hydrogenolysis of C-O bonds over a copper-based catalyst (Figure 3, R2). The normal boiling point of HMF is too high for it to be used as fuel, so the HMF extracted by the organic phase of the biphasic reactor has to be converted into DMF. A catalyst allows a thermal stability during the reaction and the copper catalyst is often used as a low temperature shit catalyst, because it is more active at lower temperatures. This reaction removes two oxygen atoms from the HMF, which leads to the diminution of the boiling point and makes it suitable as a transportation fuel, and involves two intermediates: 2-methyl,5-hydroxymethylfuran and 2-methylfuran (4 and 5 in Figure 2). Species 6, produced by way of 7, is a hydrogenolysis by-product that also posses excellent fuel quality. However, for this second step, the salt can diminish the production of DMF because of the interaction between chloride ions (introduced during the dehydration step and not completely removed during the evaporation step) and the conventional copper chromite (CuCrO4) catalyst. Indeed, when the (CuCrO4) catalyst is used, in a 1-butanol solution containing 1.6mmol-1 of NaCL, only a 6% yield of DMF is obtained. So the team developed a carbon-supported copper-ruthenium catalyst (CuRu/C), with a superior performance and a chloride resistance. The carbon-supported ruthenium catalyst is resistant to deactivation in the presence of chloride ions. Because copper and ruthenium are immiscible, and copper has a lower surface energy than ruthenium, their mixture creates a two-phase system in which the copper phase coats the surface of the ruthenium phase. Accordingly, the team hypothesized that a CuRu/C catalyst may exhibit copper-like hydrogenolysis behaviour combined with ruthenium-like chlorine resistance. With this catalyst, the team obtained a 61% yield of DMF. To end this step, DMF has to be separated from the solvent and the reaction intermediates (Figure 3, S1). The more volatile components (such as DMF and water) can be separated from the solvent and the intermediates. On condensation, the hydrophobic products of DMF separate spontaneously from water . Fig. 2: The rationale for converting carbohydrates to DMF (Roman-Leshkov et al., 2007) Figure 3: Schematic diagram of the process for conversion of fructose to DMF (Roman-Leshkov et al., 2007). A few months later, another study improved the HMF’s production, without the need for acid catalysts (Zhao et al., 2007). This new method allows reducing the production costs, and also includes glucose as a potential feedstock for HMF. Furthermore, Mascal reported that cellulose itself can be converted into furanic products (Mascal & Nikitin, 2008).
2) Advantages: The awareness of global warming and of the necessity to decrease the use of fossil fuel reserves, which are exhaustible, lead the searchers to develop new sources of energy which can be more sustainable. Concerning the fuels, the only renewable liquid fuel used nowadays is the Ethanol (formula CH3OCH3), but its production is limited by several factors as its low energy density, a high volatility, and a potential contamination by the absorption of water from the atmosphere so it requires an energy-intensive distillation process to separate the fuel from water. All these factors contribute to the fact that this production is not enough profitable therefore it is necessary to develop fuels from other sources. Compared to Ethanol, DMF is chemically stable, has a higher energetic efficiency (by 40%) using the same raw material, a higher boiling point (14°C more) which make it less volatile and more practical for transportation and is not soluble in water, so it doesn’t absorb moisture from the atmosphere and it makes it easier to store. By the creation of DMF, we can transform an important amount of biomass into a liquid fuel usable for the transport, and probably decrease the use of petroleum-based gasoline. In fact, they share very similar physicochemical properties, even more than with Ethanol, so DMF can be a better substitute. Table 1: Main properties of DMF, benchmarked with ethanol and gasoline
Dimethylfuran is a heterocyclic compound, formula (CH3)2C4H2O. This is a derivative from furan, with methyl substitutions. This substance has a caramel odour and is often used for food flavourings. POTENTIAL AS A BIOFUEL: 1) Production: (ng et al., 2011).
In the Dumesic study, the team conducted some experiments in order to compare the performances of DMF against Ethanol and gasoline. To do it, they used a single-cylinder gasoline direct-injection (GDI) research engine. The first results are very promising for DMF as a new biofuel: in fact, the combustion performance is similar to commercial gasoline, and the regulated emissions are comparable. Ethanol production creates 1.1 units of energy for every unit of energy consumed. This DMF process creates 2.2 units of energy for every unit of energy consumed. So DMF surpasses Ethanol in terms of resource efficiency, from production through processing. These results have been confirmed by another team, from University of Birmingham, let by Professor Hongming Xu; the preliminary results show that DMF can be used in spark-ignition engines without any modifications, and it presents very similar characteristics concerning the combustion and emissions (The Midlands Energy Consortium, 2012). Comparing to Ethanol, DMF allows a lower consumption, but the emission levels are the same. Other works were conducted to evaluate the engine performance and regulated emissions. As DMF is a new biofuel candidate, it is important to analyse the products of combustion. In a study (Guohong et al., 2011), is was a question of discussing the emissions of carbon monoxide (CO), nitrogen oxides (NOx), total hydrocarbons (THC) and CO2 emitted according to the fuel used. The CO emissions are lower with both biofuels compared to gasoline because of a greater oxidation of the hydrogen and carbon molecules. Ethanol produces the lowest CO emissions, due to higher combustion efficiency and oxygen content. This study also revealed that both biofuels produce higher CO2 emissions than gasoline; however they both have the benefit of consuming the CO2 in the atmosphere during their production, which would help to offset the increase in the engine-out emissions. The level of NOx were a bit higher with DMF than with both Ethanol and gasoline, because of a higher combustion temperature, which can represent an major issue because NOx is 20 times more toxic than CO that is why it is one of the most concerning engine-out emissions. But the NOx emissions with DMF would be reduced through the catalytic converter. Ultimately, the results of the whole study reveal that the engine-out emissions with DMF are similar to those with gasoline. Work is ongoing and more results are needed about the emissions, but these results seem promising. For DMF’s production, we can use the non-food biomass coming from food crops (for instance the inedible residues of maize production) to produce DMF as a second generation biofuel, and in this way reduce the competition with agriculture over land capacity. Contrary to first generation biofuel technologies (bio-Ethanol) which is criticised because it uses edible resources (production of biofuels is made to the detriment of the food production), second generation biofuel technologies can be manufactured from various types of biomass, even inedible. Since 2011, both Columbian and Ecuadorian governments suggest to use bananas to produce DMF: indeed, in Colombia, around 120.000 tons of surpluses are lost every year due to damage, overproduction or inadequate maturity. Banana fruit is mainly composed of starch and has cellulose in the skin, which can be hydrolysed to produce glucose, that can be transformed into HMF and then into DMF. Other wastes from banana crops as stalks, rich in cellulose, could be transformed into glucose monomers, then into HMF and into DMF. It could be an alternative process that adds value to wastes generated in the banana industry. Using only the inedible parts of plants and crop wastes, the biofuels with cellulose should allow of produce at the same time food and energy, on the same cultivated surface. Another advantage with the DMF is that the potential application, market and demand will be the same as Ethanol, so it is possible to develop a new more efficient biofuel without spending more money or needing to develop particular technologies. It is also possible to intend using it as jet fuel or aviation fuel for a future development. 3) Limitations: Even if DMF presents a huge long-term potential, its production face a lot of political or regulatory hurdles, at least for the immediate future. More research needs to be conducted before the commercialisation: · Safety issues must be examined. · Environmental health impact has to be thoroughly tested. · Neither IARC (International Agency for Research on Cancer) nor NTP (National Toxicology Program) has evaluated DMF’s human carcinogenicity (“No component of this product present at levels greater than or equal to 0.1% is identified as probable, possible or confirmed human carcinogen by IARC”, Sigma-Aldrich Safety data sheet, 2012). The little available information suggests that DMF is similar to other current fuel components. · It is well known that DMF’s blood concentration can be used as a biomarker for smoking because levels of DMF in the blood generally increase with the number of cigarettes smoked per day, and are generally undetectable in the blood of non-smoking adults (Ashley, 1996). In this kind of biomonitoring studies, if some DMF is found in the blood, it does not mean that the level can cause adverse health effects, there is no evidence for this at the moment. However, biomonitoring data can help scientists to conduct research on exposure and health effects. · Toxicology has to be well understood; we can’t state that the hazards posed are acceptable comparing to other liquid fuel components… Conclusion: Since 2007, very little papers were published about DMF concerning the health and environmental effects, which can only suggest commercial interest in production. It might take 5 to 10 years before this fuel is available as it has to pass food and toxicology tests. At the moment, it is intended to use a lot of various sources to produce biofuels, as surpluses of beer or whisky production, or coffee grounds, or willow, or eucalyptus for the aviation. A third generation biofuel technology is also studied, using algae, which could be 30 to 100 times more efficient than terrestrial oilseed, because of a higher photosynthesis rate and a better CO2 concentration. This biofuel can be produced with higher yields, making possible mass production without massive deforestation or competition with food crops.
The biofuel industry is at an early stage of its evolution. However, it is developing fast and it appears that it can represent an important contribution to the future alternative energy production.
Reference Ashley D L; Bonin M A; Hamar B; Mcgeehin M . (1996). “Using the blood concentration of 2,5-dimethylfuran as a marker for smoking.” International archives of occupational and environmental health / 68(3):183-7 Guohong, T., Ritchie, D., and Hongming, X. (2011). DMF - A New Biofuel Candidate, Biofuel Production-Recent Developments and Prospects, Dr. Marco Aurelio Dos Santos Bernardes (Ed.), ISBN: 978-953-307-478-8, InTech, Available from: http://www.intechopen.com/books/biofuel-production-recent-developments-and-prospects/dmf-a-new-biofuel-candidate(consulted on May 2012). Heiden, Z. M., Rauchfuss, T. B. (2007). "Homogeneous Catalytic Hydrogenation of Dioxygen: a Step Toward an Organometallic Fuel Cell?” 129, 14303-14310. Hu, L., Sun, Y., Lin, L., Liu, S. (2012) “Catalytic conversion of glucose into 5-hydroxymethylfurfural using double catalysts in ionic liquid”. Journal of the Taiwan Institute of Chemical Engineers, In Press, Corrected Proof, Available online 16 May 2012. Mascal, M., Nikitin, E.B. (2008). "Direct High-Yield Conversion of Cellulose into Biofuel." Angewandte Chemie Internation Edition 47: 7924-7926. Roman-Leshkov, Y., Barrett, C.J., Liu, Z.Y. and Dumesic, J.A. (2007). "Production of dimethylfuran for liquid fuels from biomass-derived carbohydrates." Nature 447: 982-986. Sigma-Aldrich Savety data sheet, 2,5-Dimethylfuran http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=GB&language=en&productNumber=177717&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2FALDRICH%2F177717%3Flang%3Den(consulted on May 2012). The Midlands Energy Consortium – Impact of biofuels on engine performance http://www.midlandsenergyconsortium.org/Case%20Studies/engine%20performance%20and%20biofuels%201.pdf(consulted on May 2012). Zhao, H., Holladay, J.E., Brown, H. and Zhang, Z.C. (2007). "Metal Chlorides in Ionic Liquid Sovlents Convert Sugars to 5-Hydroxymethylfuran." Science 5831: 1597-1600. |
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