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Cite This: Energy Fuels XXXX, XXX, XXX−XXX
Two-Step Sequence of Acetalization and Hydrogenation for Synthesis of Diesel Fuel Additives from Furfural and Diols Anil Patil, Suhas Shinde, Sanjay Kamble, and Chandrashekhar V. Rode* Chemical Engineering and Process Development Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
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S Supporting Information *
ABSTRACT: Acetalization of diols with furfural and subsequent hydrogenation of acetal products provided potential fuel additives that could be blended into commercial diesel. Glycerol could be an interesting polyol for acetalization with furfural due to its low cost, and it is produced as a byproduct in very large amount in the process of biodiesel production. In this work, glycerol acetalization with furfural has been selected as a model reaction. Acetalization reaction was performed under neat conditions (solventless) with 1:1 molar ratio of furfural and glycerol at room temperature over various acid catalysts, including homogeneous and heterogeneous acids. Among several catalysts, Zr-Mont, a heterogeneous solid acid having controlled acidity, gave as high as 78% isolated yield of acetal products. Interestingly, acetal products can be isolated in pure form by performing extraction using cyclohexane that enables selective extraction of product, and unreacted glycerol and furfural were left in aqueous phase, which can be recycled. Further, to make fuel components from isolated acetal product of glycerol and furfural, hydrogenation was performed over a series of supported noble-metal catalysts under low H2 pressure at room temperature. Among them, 5% Pd/C showed very high activity for ring hydrogenation that resulted in high yield of hydrogenation products. However, hydrogenated product contains free hydroxyl group that needs to be subsequently etherified or acetylated. Interestingly, etherified derivative was obtained in high yield compared to acetylated derivative. In addition, several other diols were treated with furfural and their products were subsequently hydrogenated over 5% Pd/C under very low H2 pressure. The properties of resulting compounds were investigated so as to find most suitable candidates as additives to commercial diesel. forestry residues.4,5 Furfural market price is ∼1500 USD/ tonne.6 Dehydration of C5 sugars can yield furfural, which has a wide range of industrial applications ranging from solvents to resins and fuel additives.7 Among various options, acetalization of glycerol with furfural provides a mixture of two isomeric products, (2-(furan-2-yl)1,3-dioxolan-4-yl) methanol and 2-(furan-2-yl)-1,3-dioxan-5ol, which are realized as potential fuel additives. Wegenhart et al. reported valorization of furfural with crude glycerol using simple Lewis acid salts or acidic solids as catalysts at 100 °C with up to 90% yield.8 Further modifications of the acetal products have also been explored, which include furan ring hydrogenation and acetylation of free hydroxyls. These modified acetal derivatives showed improved properties as fuel components. Mallesham and co-workers synthesized valuable acetal product from glycerol and furfural using SO42−/MoO3- and SO42−/WO3-promoted SnO2-based solid acids.9 SO42−/SnO2 showed superior catalytic activity by achieving optimum glycerol conversions of ∼98 and 99% with acetone and furfural, respectively. In the subsequent work of the same group, molybdenum- and tungsten-promoted SnO2 solid acids (wet impregnation) were reported, particularly Mo6+-doped SnO2 catalyst exhibited excellent catalytic performance in terms of both glycerol conversion and selectivity of the products.10
1. INTRODUCTION The phenomenal growth in living standards which will be continued for next few decades, particularly in developing nations, has resulted in an exponential rise in demand for fuels and chemicals. U.S. energy authorities have predicted 38% increase in the consumption of world petroleum and other liquid fuels by 2040 and 92% of the global liquid fuel demand is for the transportation and industrial sectors. Indeed, to satisfy the need of fuels and chemicals, society is largely relied on petroleum supply that has a threat of diminishing in the near future and more importantly associated with a serious concern of global warming by generation of greenhouse gases.1 From both these perspectives, biomass is one of the best alternatives having low carbon footprint due to its renewable nature. Nevertheless, structural and chemical complexities of lignocellulosic biomass necessitate to employ various pretreatment steps to convert it into downstream fuels and chemicals. The multistep pretreatment processes include gasification, pyrolysis/liquefaction, and hydrolysis. Gasification is well suited for the production of fuels, whereas pyrolysis/ liquefaction and hydrolysis provide attractive paths for the production of sugar monomers and their dehydration products such as furfural and HMF, which can be subsequently upgraded to useful chemicals and/or fuels for the transportation sector. Furfural is the most common industrial chemical derived from lignocellulosic biomass, with an annual production volume of >200 000 tonnes.2,3 Recently, furfural production has become exclusively based on the acid-catalyzed conversion of pentosane sugars present in agricultural and © XXXX American Chemical Society
Received: May 22, 2019 Revised: July 18, 2019 Published: July 23, 2019 A
DOI: 10.1021/acs.energyfuels.9b01640 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels Scheme 1. Valorization of Furfural with Diols to Fuel Additives
In this work, we have investigated featured Zr-Mont as a solid acid catalyst having controlled acidity for acetalization of glycerol with furfural in 1:1 molar ratio at room temperature. Use of cyclohexane as a suitable extractant enables easy isolation of pure acetal products in high yield that avoided critical workup and purification processes. In addition, the unreacted starting materials have been dried and reused successfully. To make suitable as diesel fuel additives, the respective acetal products (mixture of 1 and 2) need to undergo furan ring hydrogenation and derivatize the free hydroxyl group. Furan ring hydrogenation was also carried out over different noble-metal catalysts under low H2 pressure at room temperature. The catalytic activity of Zr-Mont catalyst was also evaluated for several other diols with furfural, and the resultant acetal products were hydrogenated over 5% Pd/C catalyst. The applicability of novel hydrogenated acetal
compounds as fuel additives to commercial-grade diesel is also investigated. A general overview of this entire work is shown in Scheme 1.
2. EXPERIMENTAL SECTION 2.1. Materials. Solvents such as N,N-dimethylformamide, dichloromethane, acetone, 1,4-dioxane, ethylene glycol, dimethyl sulfoxide, cyclohexane, and acetonitrile were purchased from Thomas Baker, India. Acetic anhydride was purchased from S.D. Fine Chem. n-Butyl bromide was purchased from Alfa Aesar. Triethylamine, sodium hydroxide, and K2CO3 were purchased from Thomas Baker. Furfural, montmorillonite clay, 5% Pd/C, 1,3-propanediol, 1,4butanediol, 1,5-pentanediol, 1,2-pentanediol, 1,2-propanediol, and 1,5-pentanediol were purchased from Sigma-Aldrich. Commercialgrade diesel was obtained from Hindustan Petroleum, India. 2.2. Acetalization of Glycerol and Furfural. In a typical reaction, a round-bottom flask containing a mixture of furfural (2 g, 0.021 mol), glycerol (1.91 g, 0.021 mol), and catalyst (10 mol % B
DOI: 10.1021/acs.energyfuels.9b01640 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels liquid acid or 0.2 g of solid acid) was stirred at room temperature for 4 h. The reaction was monitored by using thin-layer chromatography, which was visualized by charring in 2,4-dinitrophenylhydrazine stain. Samples were withdrawn after specific time interval and analyzed using high-performance liquid chromatography (HPLC) for the conversion of starting material. After specific period of time, the reaction mass was diluted with water (10 mL) and extracted with cyclohexane (50 mL × 3). Collected cyclohexane layers was dried over anhydrous Na2SO4 and evaporated under reduced pressure to afford pure products as a mixture of (2-(furan-2-yl)-1,3-dioxolan-4-yl) methanol and 2-(furan-2-yl)-1,3-dioxan-5-ol, each with a Z and E isomer with varying ratios. Aqueous layer was again extracted with ethyl acetate (50 mL × 2), and ethyl acetate layer was dried and evaporated to recover unreacted furfural, which can be reused again. 2.3. Acetalization of Diols and Furfural. A mixture of furfural (4 g, 41.66 mmol), diols (42 mmol), Zr-Mont (0.4 g, 10 wt % w.r.t furfural), and cyclohexane (8 mL) was refluxed in a round-bottom flask at 65 °C under magnetic stirring (800 rpm) for 2 h. After cooling the reaction mass to room temperature, water (20 mL) was added and the product was extracted with cyclohexane (50 mL × 2). Separated organic layer was dried over anhydrous Na2SO4 and evaporated under reduced pressure. Water layer was further extracted with ethyl acetate (50 mL × 1) to recover unreacted furfural. 2.4. Hydrogenation of Acetal Products. 2.4.1. In Bladder (Small Scale). A mixture of acetal product (0.500 g) dissolved in methanol (20 mL) was added into a round-bottom flask containing catalyst (5 wt % w.r.t acetal product) and then the mixture was stirred at room temperature under hydrogen pressure (with bladder) for desired time. Then, the reaction mixture was filtered to separate the catalyst and the filtrate was evaporated under reduced pressure to obtain oil. 2.4.2. In Par Reactor (Gram Scale). Hydrogenation reaction was performed in a 300 mL Parr reactor. In a typical reaction, 5 g of acetal product was dissolved in 140 mL of methanol and added into the Parr reactor containing 5% Pd/C (5 wt % w.r.t to acetal product). The resulting mixture was stirred at 800 rpm under hydrogen pressure (50 psi pressure). After a period of 2 h, the reaction mixture was filtered and the filtrate was evaporated under reduced pressure. 2.5. Acetylation of the Free Hydroxyl Group of 3 + 4. Acetylation of the free hydroxyl group present in acetal products of glycerol and furfural was performed by a mixture of 3 + 4 (0.5 g, 0.0028 mol), acetic anhydride (0.58 g, 0.00568 mol), and K2CO3 (0.22 g, 0.00159 mol) or Nano-K2CO3 (0.22 g, 0.00159 mol) in methanol (5 mL) and refluxing for 3 h. After stirring for 3 h, the mixture was diluted with ethyl acetate and washed with saturated sodium bicarbonate, water, and brine. The ethyl acetate fraction was dried over magnesium sulfate and evaporated under reduced pressure. The obtained oil was purified through column chromatography. 2.6. Etherification of 3 + 4. Etherification of the free hydroxyl group present in acetal products (3 + 4) was performed with n-butyl bromide. In brief, a solution of acetal product (0.5 g, 0.0028 mol) in tetrahydrofuran (5 mL) was treated with NaOH (0.228 g, 0.0057 mol) at room temperature for 1 h, and n-butyl bromide (0.78 g, 0.0057 mol) was added slowly and stirred for 24 h at room temperature. The resulting mixture was diluted with ethyl acetate (20 mL) and washed with dilute HCl, water, and brine. The separated ethyl acetate layer was then dried over anhydrous Na2SO4 and concentrated under reduced pressure. 2.7. Analysis of Reaction Products. Thin-layer chromatography analysis was performed using Merck 5554 aluminum-backed silica plates, and the compounds were visualized under ultraviolet (UV) light (254 nm). Conversion of furfural was calculated by using Agilent high-performance liquid chromatography (HPLC) (column: Poroshell 120 EC-C18 2.7 μm, detector: UV and mobile phase: 0.1% acetic acid in Millipore water:acetonitrile (85:15) with 0.6 mL/min flow). Pure products were characterized and confirmed by 1H NMR and 13C NMR spectroscopy analyses using CDCl3 (0.01%, tetramethylsilane) as solvent on a 200 MHz frequency Bruker instrument. The NMR spectra are shown in the Supporting Information (Section S1). The products were also confirmed using QP-Ultra 2010 GC-MS Shimadzu
instrument, RTX-5 column, helium as carrier gas, EI mode, and ionization source temperature 200 °C. 2.8. Fuel Properties Analysis. Diesel additive samples were analyzed for miscibility, cloud point, flash point, and density. Miscibility was visualized by mixing various concentrations of hydrogenated acetal samples with commercial diesel. Cloud point was determined by gradually cooling the sample and observing the temperature at which crystallization begins. The density was obtained by recording the mass of 1 cm3 of sample. Flash point was visualized by igniting the sample with flame in an open hot cup (heated with a jacketed coiled heater); at specific temperature, the sample catches fire.
3. RESULTS AND DISCUSSION Initially, the catalytic performance of several solid and liquid acids was investigated for acetalization of glycerol with furfural and the results are presented in Table 1. Acetalization of Table 1. Acetalization of Furfural with Glycerola
entry
catalyst
FUR conversion (%)
1 2 3 4 5 6 7 8 9 10
conc. H2SO4 amberlite-IR 120 montmorillonite Fe-Mont Al-Mont Sn-Mont Zr-Mont Al-pillared clay KP-10 KP-30
100 91 11 67 70 85 84 71 77 76
yield of mixture 1 and 2 (%)b
ratio of product 1:2
00 56 00 51 54 74 78 56 59 58
polymer 34:66 00:00 50:50 66.66:33.33 71:29 33.19:66.81 50:50 60:40 50:50
a
Reaction conditions: furfural (2 g, 0.021 mol), glycerol (1.91 g, 0.021 mol), catalyst (0.2 g), room temperature, 4 h. bIsolated yield.
glycerol with furfural generally forms two types of cyclic acetals, (2-(furan-2-yl)-1,3-dioxolan-4-yl) methanol (five-member) and 2-(furan-2-yl)-1,3-dioxan-5-ol (six-member). The catalytic experiments were carried out at room temperature under solvent-free conditions with a 1:1 molar ratio of furfural to glycerol. It was found that conc. H2SO4 even at room temperature imparts black color to the reaction mixture, which indicates the loss of furfural through resin formation (Table 1, entry 1). Hence, we evaluated several solid acids, e.g., sulfonic acid-functionalized solid acidic resin (amberlite-IR 120) provided 56% isolated yield of acetal products (Table 1, entry 2). However, use of amberlite-IR 120 promoted the formation of polymeric product but to a lesser extent than that was formed using conc. H2SO4. To control the polymer formation, moderate acidic catalysts like montmorillonite catalyst were tested. However, in this case, the lowest conversion of furfural was obtained without any product formation (Table 1, entry 3). It is well known that acidity of montmorillonite clay can be enhanced by structural modification by treatment with metal chloride salt.11 With Fe-exchanged montmorillonite (Fe-Mont), conversion of furfural significantly increased to 67% along with 51% isolated yield of acetals (Table 1, entry 4). On the other hand, Al-Mont showed slightly higher conversion (70%) and higher yield of C
DOI: 10.1021/acs.energyfuels.9b01640 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels mixture of 1 and 2 (Table 1, entry 5), while Sn-Mont catalyst gave the highest conversion of 85% with 74% yield of mixture of 1 and 2, with 71:29 ratio achieved due to higher acidity than Fe and Al-Mont (Table 1, entry 6). Interestingly, with ZrMont, the highest isolated yield (78%) of mixture of 1 and 2 was achieved in 33.19:66.81 ratio (Table 1, entry 7). The highest selectivity of Zr-Mont catalyst could be attributed to its controlled acidity. Other modified montmorillonite clays such as Al-pillared, Mont KP-10, and Mont KP-30 showed 71, 77, and 76% conversions of furfural and 56, 59, and 58% yields, respectively (Table 1, entries 8−10). In general, isolation of acetal products (mixture of 1 and 2) would be effective by combining extraction with organic solvent and column chromatography. Interestingly, use of cyclohexane as an extractant enables easy isolation of pure acetal products in high yield that avoided critical extraction and purification steps (Figure 2). The same process was employed in all catalyst screening experiments except for H2SO4 and montmorillonite because, in these cases, no product formation was noted (Figure 1).
Figure 2. Effect of catalyst amount on acetalization of glycerol with furfural. Reaction conditions: furfural (2 g), glycerol (2.24 g), catalyst (0.1−0.4 g), room temperature, 4 h.
catalyst amount beyond 0.2 g does not improve either conversion of furfural or yield of acetal products. 3.3. Recycle Study for Zr-Mont. In our earlier studies on etherification and Friedel−Crafts alkylation,13 we have successfully recycled Zr-Mont catalyst.12 Here, the first run of acetalization of furfural and glycerol was carried out with the fresh Zr-Mont catalyst at room temperature for 4 h. After the reaction was complete, the reaction crude was diluted with cyclohexane and water and the resultant mixture was filtered. The recovered catalyst was washed with water and acetone and then dried in an oven for 2 h at 110 °C, which was then used for the next run with fresh furfural and glycerol. The same procedure was followed for the repeated use of the catalyst for a series of five reactions. No significant loss in the catalytic activity was noted (Figure 3).
Figure 1. Product isolation strategy for acetal product 1 + 2.
3.1. Influence of Solvents on Acetalization. To understand the role of the solvent in acetalization of furfural with glycerol, several solvents were tested (Table 2). In case of all tested solvents, very low conversion of furfural was observed; however, it was noted that the neat reaction conditions (solventless) gave promising results. Table 2. Influence of Solvent on Acetalization of Furfural with Glycerola entry
solvent
FUR conversion (%)
1 2 3 4 5 6
N,N-dimethylformamide dichloromethane methanol 1,4-dioxane acetonitrile toluene
46 23 30 29 16 51
yield of mixture 1 + 2 (%)
ratio of product 1:2
29 15 16 17 11 42
64.02:35.97 51:49 53.91:46.91 47.36:52.63 50:50 54.05:45.94
Figure 3. Recycle study of Zr-Mont. Reaction conditions: furfural (2 g, 0.021 mol), glycerol (2.24 g, 0.024 mol), catalyst (0.2 g), room temperature, 4 h.
After successful acetalization of furfural with glycerol, the resultant mixture of acetal products 1 and 2 was hydrogenated under ambient conditions, and unlike reported studies,9 a high pressure of 26.7 bar of hydrogen was used. Initially, several different supported noble-metal catalysts were screened for furan ring hydrogenation under very low pressure of H2 to provide a complex mixture of tetrahydrofuryl-1,3-dioxacyclanes. The non-noble-metal 5% Ni/C catalyst showed no conversion of furfural (Table 2, entry 1). However, the introduction of palladium in a bimetallic Pd−Ni/C catalyst gave 68.97% yield of furan ring-hydrogenated product. In the subsequent runs, palladium loading was varied, and with 2% Pd/C, 92% yield of hydrogenation product was obtained, but a longer reaction time of 14 h was required (Table 2, entry 3). Increasing the Pd loading led to significant reduction in reaction time; however, the yield of hydrogenation product
a
Reaction condition: furfural (2 g), glycerol (2.24 g), catalyst (0.2 g), solvent, room temperature, 4 h.
3.2. Influence of Catalyst Amount. To achieve maximum conversion of furfural and yield of acetal products, investigation of the influence of catalyst amount on reaction is primarily important (Figure 2). Here, we observed that under optimized reaction conditions, optimum loading of Zr-Mont was 0.2 g. Lowering of catalyst loading affects the conversion of furfural as well as the yield of acetal products. Increasing D
DOI: 10.1021/acs.energyfuels.9b01640 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels
diol, and 1,2-propanediol to react with furfural over Zr-Mont, and the product was hydrogenated over palladium catalyst (Table 4) and further fuel properties of the obtained hydrogenated products were investigated (Tables 5 and 6). Condensation of various diols with furfural was conducted in cyclohexane solvent at 65 °C. Acetylation of 1,2-propanediol and furfural gave 77% yield, and its hydrogenation product gave 89% yield (Table 4, entry 1). Use of 1,2-propanediol can be promising as it is derived from renewable glycerol by hydrogenolysis over metal catalysts.17 Ethylene glycol when reacted with furfural also furnished its acetal derivative in 89% yield. Further, the produced acetal was hydrogenated to ring saturated product in 85% yield (Table 4, entry 2). Choice of ethylene glycol as a diol would be fascinating as it can be produced from cellulose.18 1,3-Propanediol is another diol that can be selectively produced from renewable glycerol using microbial consortium.19 Acetal product of furfural and 1,3propanediol was obtained in 82% yield, and further hydrogenation product was obtained in 87% yield (Table 4, entry 3). Similarly, 1,4-pentanediol can be produced from the biomassderived γ-valerolactone;20 with furfural, the corresponding acetal was produced in 80% yield; and in the next step (hydrogenation), the ring hydrogenation product was obtained in 85% yield (Table 4, entry 4). 1,2-Pentanediol was also tested for acetalization with furfural to afford acetalization product in 88% yield and further hydrogenation product in 86% yield (Table 4, entry 5). 1,4-Butanediol with furfural also gave an acetal product in 80% yield, and its hydrogenation product was obtained in 83% yield (Table 4, entry 6). 1,4-Butanediol can be produced from 1,4-anhydroerythritol and a physical mixture of ReOx−Au/CeO2 and carbon-supported rhenium catalysts with H2 as a reductant.21 3.4. Evaluation of Modified Acetal Products of Furfural and Diols as Diesel Additives. Fuel properties of synthesized hydrogenated acetal products were also evaluated and are presented in Tables 5 and 6. Miscibility of modified (hydrogenated) acetal products in commercial diesel is an important parameter, which was visualized at room temperature. Compounds 10, 12, 18, and 20 were found to be miscible with the commercial diesel sample at room temperature. Surprisingly, compounds 12 and 18 were found to be miscible up to 80 vol % in diesel sample, which indicates that these compounds have excellent application as fuel blenders. The cloud point measurement is another important test for the suitability of diesel fuel. The cloud point of modified (hydrogenated) acetal products and blended samples was measured by gradually lowering the temperature and observing the point at which crystals begin to form. From our test results, it was found that compounds 12 and 18 can be blended with diesel at high levels and showed improvement in the cloud point of the commercial diesel sample. Flash point is also an important parameter of suitability of fuel additives. The low
was almost the same. With the highest loading of 5% Pd/C, the maximum yield of ∼95% of the hydrogenated product was achieved within 6.5 h (Table 2, entry 6). The hydrogenation activities of other noble-metal catalysts were compared with 5% Pd/C catalyst under optimized reaction conditions. After 6.5 h, 5% Pt/C, 5% Ru/C, 5% Rh/C, and 5% Pd/Al2O3 catalysts gave 48, 66, 59, and 90% yields of hydrogenation products, respectively (Table 3, entries 7−10). This was in Table 3. Hydrogenation of Mixture of 1 and 2a
entry
catalyst
time (h)
yield of 3 and 4 mixture (%)b
1 2 3 4 5 6 7 8 9 10
5% Ni/C 0.9% Pd-0.1% Ni/C 2% Pd/C 3% Pd/C 4% Pd/C 5% Pd/C 5% Pt/C 5% Ru/C 5% Rh/C 5% Pd/Al2O3
10 10 14 11 9.5 6.5 6.5 6.5 6.5 6.5
69 92 94 94 95 48 66 59 90
a
Reaction conditions: 1 and 2 mixtures (0.5 g), catalyst (0.05 g; 10 wt % with respect to mixture of 1 and 2), methanol (20 mL), H2 (balloon). bIsolated yield.
accordance with the reported studies that the palladium showed significantly higher activity for complete ring hydrogenation of 2,5-dimethylfuran to 2,5-dimethyltetrahydrofuran than other noble metals.14,15 Due to free hydroxyl groups present in the mixture of 1 + 2, it showed poor fuel properties. The postmodification of acetal products of glycerol and furfural via acetylation of free hydroxyl groups can make it better suited as a fuel component.8 However, when the same strategy was followed, the yield of acetylated product obtained was as low as 13%. In addition, use of acetic anhydride for acetylation is restricted in the United States and in many other countries.16 Alternatively, we could successfully achieve the etherification of free hydroxyl groups, which provided a better (34%) yield of etherified products (Scheme 2). To make it more suitable as a fuel component, use of glycerol, which is a triol, for acetalization with furfural requires one extra step to protect its free hydroxyl group. However, use of diols would ultimately avoid this additional step. In this direction, we screened several diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-pentanediol, 1,2-pentane-
Scheme 2. Etherification and Esterification of Free Hydroxides of Hydrogenated Acetal Products of Glycerol and Furfural
E
DOI: 10.1021/acs.energyfuels.9b01640 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels Table 4. Synthesis of Diesel Fuel Additives from Furfural and Diols
4. CONCLUSIONS A variety of diesel fuel additives were synthesized by acidcatalyzed condensation of furfural and different diols followed by furan ring hydrogenation. Furfural and glycerol with 1:1 molar ratio were chosen as model substrates optimizing the catalyst and reaction conditions. For this reaction, Zr-Mont was found to be the best suitable catalyst due to its controlled acidity and provided very high yield of acetal products under neat reaction conditions at room temperature. Interestingly, acetal products of furfural and glycerol can be selectively extracted from reaction mixture in pure form using cyclohexane as extractant; this will avoid purification process. Unreacted starting materials can be reused for the acidcatalyzed condensation reaction. Hydrogenation of acetal product was performed with several catalysts under very low hydrogen pressure (balloon) at room temperature. With 5% Pd/C catalyst, a very high yield of hydrogenation product was achieved without formation of side products. Free hydroxyl group present in the hydrogenated product was acetylated and etherified. Higher yield of etherified product was achieved compared to acetylated product. To find suitability of other substrates than glycerol, other diols were also tested with furfural. Surprisingly, hydrogenation products formed from condensation of furfural with ethylene glycol and 1,2pentanediol are found to be excellent diesel additives. When these compounds were blended in commercial diesel, flash
Table 5. Fuel Properties of Commercial Diesel and Hydrogenated Acetal Products entry
compound
miscibility in diesel at RT (wt %)
1 2 3 4 5 6 7 8 9 11 12
diesel 1+2 3+4 5+6 7+8 10 12 14 16 18 20
immiscible immiscible up to 5% up to 15% up to 15% up to 80% immiscible immiscible up to 80% up to 25%
density 0.821 1.132 1.093 1.070 1.073 1.018 1.150 1.050 0.972 1.003 1.102
cloud point (°C) 5
−4 −7 ≥66 ≥66
≥66 ≥66
flash point (°C) 36 141−150 144−151 142−150 143−151 134−140 131−137 146−154 137−144 149−156 148−156
flash point affects the handling and storage of a fuel and is also an indication of fire hazard. Importantly, flash point of commercial diesel was significantly enhanced after blending it with compounds 12 and 18. Density of commercial diesel was found to increase after blending with the compounds synthesized in this work. F
DOI: 10.1021/acs.energyfuels.9b01640 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels Table 6. Properties of Blended Compounds 10, 12, 18, and 20 in Commercial Diesel compounds flash point (°C)
cloud point (°C)
density
blending in diesel (wt %)
10
12
18
20
10
12
18
20
10
12
18
20
10 20 30 40 50 60 70 80
−6 −2
−6 −6 −8 −10 −10 −12 −11 −10
−6 −6 −11 −10 −10 −12 −11 −10
−6 −2
38 41
36 39 41 44 48 51 55 59
37 40 41 44 49 53 56 59
39 43
0.901 0.931 0.950 0.970 0.979 0.992 0.999 1.007
0.919 0.959 0.967 0.979 0.988 1.007 1.031 1.067
0.909 0.917 0.929 0.939 0.953 0.971 0.989 0.997
0.914 0.954 0.961 0.974 0.987 1.003 1.022 1.045
(8) Wegenhart, B. L.; Liu, S.; Thom, M.; Stanley, D.; Abu-Omar, M. M. Solvent free method for making acetals Derived from Glycerol and Furfural and their use as a Biodiesel fuel component. ACS Catal. 2012, 2, 2524−2530. (9) Mallesham, B.; Sudarsanam, P.; Reddy, B. M. Eco-friendly synthesis of bio-additives fuel from renewable glycerol using nanocrystalline SnO2-based solid acids. Catal. Sci. Technol. 2014, 4, 803−813. (10) Mallesham, B.; Sudarsanam, P.; Raju, G.; Reddy, B. M. Design of highly efficient Mo and W-promoted SnO2 solid acid for heterogeneous catalysts acetalization of bio-glycerol. Green Chem. 2013, 15, 478−489. (11) Shinde, S. Rode, Selective self-etherification of 5-(hydroxymethyl) furfural over Sn-Mont catalyst. Catal. Commun. 2017, 88, 77−80. (12) Shinde, S.; Rode, C. Cascade Reductive Etherification of Bioderived Aldehydes over Zr-Based catalysts. ChemSusChem 2017, 10, 4090−4101. (13) Shinde, S.; Rode, C. Friedel−Crafts Alkylation over Zr-Mont Catalyst for the Production of Diesel Fuel Precursors. ACS Omega 2018, 03, 5491−5501. (14) Chatterjee, M.; Ishizaka, T.; Kawanami, H. Hydrogenation of 5HMF in supercritical carbon dioxide water: a tunable approach to dimethylfuran selectivity. Green Chem. 2014, 16, 1543−1551. (15) Thananatthanachon, T.; Rauchfuss, T. B. Efficient production of the liquid fuel 2,5-dimethylfuran from fructose using formic acids as reagent. Angew. Chem., Int. Ed. 2010, 122, 6766−6768. (16) UN Intercepts Taliban’s Heroin Chemical in Rare Afghan Victory; Bloomberg, 2008; p 10. (17) Mane, R. B.; Hengne, A. M.; Ghalwadkar, A. A.; Vijayanand, S.; Mohite, P. H.; Potdar, H. S.; Rode, C. V. Cu:Al Nano catalyst for selective Hydrogenolysis of Glycerol to 1,2-propanediol. Catal. Lett. 2010, 135, 141−147. (18) Xu, G.; Wang, A.; Pang, J.; Zhao, X.; Xu, J.; Lie, N.; Wang, J.; Zheng, M.; et al. Chemo catalytic Conversion of Cellulosic Biomass to Methyl Glycolate, Ethylene Glycol, and Ethanol. ChemSusChem 2017, 10, 1390−1394. (19) Jiang, L.; Liu, H.; Mu, Y.; Sun, Y.; Xiu, Z. High tolerance to glycerol and high production of 1,3-propanediol in batch fermentation by microbial consortium from marine sludge. Eng. Life Sci. 2017, 17, 635−644. (20) Wang, T.; Liu, S.; Tamura, M.; Nakagawa, Y.; Hiyoshi, N.; Tomishige, K. One-pot catalytic selective synthesis of 1,4 anhydroerythrito and Hydrogen. Green Chem. 2018, 20, 2547−2557. (21) Yuwen, J.; Chakraborty, S.; Brennessel, W. W.; Jones, W. D. Additive-Free Cobalt-Catalyzed Hydrogenation of Esters to Alcohols. ACS Catal. 2017, 7, 3735−3740.
point of commercial diesel was significantly enhanced, which makes its safer for storage and transport.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.energyfuels.9b01640. 1 H NMR and 13C NMR analyses of synthesized product (Section S1); leaching test (Section S2); and catalyst preparation method (Section S3) (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Tel.: +9120 2590 2349. Fax: (+91)20 2590 2621. ORCID
Chandrashekhar V. Rode: 0000-0002-2093-2708 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS AMP acknowledges the Council of Scientific and Industrial Research (CSIR)-National Chemical Laboratory, Pune, for providing research facility.
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REFERENCES
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DOI: 10.1021/acs.energyfuels.9b01640 Energy Fuels XXXX, XXX, XXX−XXX
