Ind. Eng. Chem. Res. 2009, 48, 3279–3283
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Low-Pressure Packed-Bed Gas-Phase Dehydration of Glycerol to Acrolein Wei Yan and Galen J. Suppes* Department of Chemical Engineering, UniVersity of Missouri, Columbia, Missouri 65211
Glycerol has become readily available from biodiesel industry. High functionality and relatively low price make it a potential building block to produce value-added derivatives such as acrolein. In this study, lowpressure packed-bed gas-phase dehydration of glycerol was investigated in presence of various solid acid catalysts, including H3PO4/activated carbon catalyst. Dehydration mechanism over H3PO4/activated carbon catalyst was validated. In the presence of H3PO4/activated carbon catalyst, yield of acroelin (66.8%) and selectivity to acrolein (84.0%) were achieved at the temperature of 260 °C and the pressure of 0.85 bar. 1. Introduction Acrolein (i.e., acrylaldehyde) is the simplest unsaturated aldehyde. Acrolein is widely used to synthesize numerous chemicals, in particular acrylic acid and its lower alkyl ester and DL-methionine, an essential amino acid. Acrolein is a third major feedstock for 1,3-propanediol, which is the monomer of industrial polyesters. Acrolein is also directly applied as a herbicide and an algicide in irrigation canals, as a microbiocide in oil wells, liquid hydrocarbon fuels, cooling-water towers, and water treatment ponds, and as a slimicide in the manufacture of paper.1 The annual capacity of acrolein is approximately 250 million pounds in the United States.2 Acrolein is mainly produced from propylene by direct catalytic oxidation.3 The cost of acrolein greatly depends on the crude-oil price. This situation motivates the development of new technologies to produce high-price chemicals from the abundant low-cost biomass.4,5 Crude glycerol is massively produced as a byproduct from biodiesel industries. Owing to its high functionality, glycerol can be used to synthesize a wide range of chemicals, including acrolein, 3-hydroxypropionaldehyde, 1-hydroxy acetone, and propylene glycol.6-9 Production of acrolein has widely been studied with heterogeneous and homogeneous catalysts. One common route10-12 is to dehydrate glycerol at high temperatures in the presence of acidic substances. The acidic catalysts included salts of bibasic acid and tribasic acid or mixture of such salts. This process was not suitable for industrial production owing to the low yield of acrolein, the high weight ratio of dehydrating salts to glycerol, and high reaction temperatures (350 to 500 °C). An alternative process13-15 is homogeneous dehydration of glycerol in sub- and supercritical water (253-390 °C and 250 -350 bar) by using sulfuric acid as the catalyst. The process could achieve conversion of glycerol in the range of 39-55% and high selectivity to acrolein. Owing to the known technical and environmental problems, this process is also not attractive for practical application. Robichaud and Noble16 reported that acrolein was formed by biotechnological breakdown of glycerol in fermentation process. Bacterial strains are available from Oenococcus oeni, Pediococcus parVulus, Lactobacillus cellobiosus, Bacillus amacrylus, and Leuconostoc mesenteroides.17 The biochemical pathway for the formation of acrolein is initiated by one kind of enzyme (dehydratase), which converts glycerol to 3-hydroxypropionaldehyde. The aldehyde undergoes slow, spontaneous dehydration * To whom correspondence should be addressed. E-mail: suppesg@ missouri.edu. Tel: 1-573-884-4562. Fax: 1-573-884-4940.
to acrolein in an acid medium.17 Although biotechnological production of acrolein has a number of operational advantages over catalytic conversion (e.g., moderate temperature 30-40 °C), low concentration of acrolein in the broth and high energy consumption for product recovery make the biochemical route less economically feasible. Our research focuses on developing a technology to convert glycerol to acrolein with high selectivity under mild conditions. It is also necessary to study the mechanism of dehydration reaction. Suppes18,19 reported that 1-hydroxy acetone was the major glycerol dehydration intermediate over metallic catalysts in the process for propylene glycol production. 1-Hydroxy acetone was detected as well in the process of gas-phase dehydration for acrolein. Therefore, the question is whether acetol is an intermediate in the reaction of glycerol to acrolein? A reaction scheme that would account for the mechanism is shown in Figure 1. This reaction mechanism will be validated in this study. 2. Experimental Section 2.1. Materials. Glycerol (99.9%), acrolein (90%), 1-hydroxy acetone (90%), allyl alcohol (99.9%), phosphoric acid (85%), R-Al2O3, and BASF F24 were purchased from Sigma-Aldrich (Milwaukee, WI). High-purity nitrogen and helium were obtained from Praxair (Columbia, MO). Table 1. Steps and Conditions for H3PO4/Activated Carbon Catalysts H3PO4/activated carbon step
No 1
No 2
No 3
Acid Soaking H3PO4/corncob (wt/wt) H3PO4 (wt %) temperature (°C) time (h)
1.5-1 40 45 8-10
temperature (°C) time (h) base activation KOH/char (wt/wt) activation temperature (°C) activation time (h)
480 1.5
H3PO4 (wt %) temperature (°C) soaking time (h) drying temperature (°C) drying time (h)
40 40 1 130 12
1.5-1 40 45 8-10
1.5-1 40 45 8-10
Charring 480 1.5 2-3 790 1 Catalyst formation
10.1021/ie801200p CCC: $40.75 2009 American Chemical Society Published on Web 03/05/2009
40 40 1 130 12
480 1.5
3280 Ind. Eng. Chem. Res., Vol. 48, No. 7, 2009
Figure 1. Reaction mechanism for gas-phase dehydration of glycerol to acrolein over solid acid catalyst.
Figure 2. Experimental system for gas-phase dehydration of glycerol to acrolein. The different components are as follows: 1, feed pump; 2, evaporator; 3, trap; 4, packed-bed reactor; 5, air-cooled condenser; 6, ice-water condenser; 7, vacuum pump; 8, product collector.
2.2. Catalyst Preparation. R-Al2O3 was evaluated as a catalyst without modification. H3PO4/R-Al2O3 and H3PO4/BASF F24 were prepared by wet impregnation of commercial R-Al2O3 with the required amount of aqueous solution of phosphoric acid at room temperature. The solution was evaporated in a rotary evaporator at 60 °C; the residual solid was dried in an oven at 110 °C overnight.20 H3PO4/activated carbon (surface area ∼2000 m2 · g-1) was prepared by the patented procedures.21 The procedure consists of sequential steps such as preparing biomass, acid soaking, charring, activating the char in the presence of base, water washing, and acid activation of catalyst. Three H3PO4/activated carbon catalysts were evaluated in gasphase dehydration of glycerol for acrolein. The catalytic performance of H3PO4/activated carbon catalysts depends on the steps and conditions of preparation, which are shown in Table 1. 2.3. Experimental Setup. Low-pressure packed-bed gasphase dehydration of glycerol was performed at temperatures of 230-290 °C and pressures of 0.7-1 bar. Figure 2 is a schematic of the reaction system, including an evaporator, trap, packed-bed reactor, air-cooled condenser, and ice-water condenser. The trap was for gas-liquid separation. Two condensers were used to achieve better product condensation at low pressures. The temperatures of the evaporator, trap, and reactor
Figure 3. Gas chromatograph of gas-phase dehydration reaction product.
were controlled by using Single Display Proportional-IntegralDerivative Controller (Winona, MN). The pressure of the reactor was indicated and controlled by a vacuum pump (Benton Harbor, MI). Solid acid catalysts including H3PO4/R-Al2O3, H3PO4/BASF F24, and H3PO4/activated carbon were evaluated. For each run, a known amount of catalyst (2 g) was loaded into packed-bed reactor (i.d. ) 1 in.). When the reaction system reached the desired temperature and pressure, the aqueousglycerol feed (mass ratio of glycerol to water ) 0.2) was pumped into the evaporator by a micropump at 300 g · h-1. The product samples were condensed and collected at desired intervals. The reaction was performed continuously for 5 h. After 5 h, the reaction system was washed with distilled water for 1 h and dried for 0.5 h. The carbon deposit (coke) for each run was determined by weighing the reactor before and after the reaction. It was assumed that the carbon deposit was calculated from different weight of packed-bed reactor. Gas-chromatography analysis of the dehydration products indicated that 1-hydroxy acetone was formed as one major dehydration product. The reactant used to determine whether it is the likely intermediate to acrolein was 5% (mass fraction) 1-hydroxy acetone. The reaction conditions were maintained the same as 5% (mass fraction) glycerol dehydration. 2.4. Gas Chromatography. The samples were analyzed with a Hewlett-Packard 6890 gas chromatograph equipped with a flame ionization detector and mass specter detector (Wilmington, DE). A gas-chromatography column (J&W Scientific DB-WAX 123-7033, 30 m × 320 µm × 0.5 µm) was used for separation. The detector and injector temperatures were 250 and 230 °C, respectively. The oven temperature increase was programmed at 10 °C · min-1 from 45 to 200 °C and at 15 °C · min-1 to 225 °C. The final temperature was held for 10 min. Helium was used as carrier gas at 1.0 mL · min-1. The split ratio was 1:120. Figure 3 shows a typical gas chromatogram of the dehydration reaction samples. By using the calibration curves prepared for all components, the integrated peak areas were transformed to
Ind. Eng. Chem. Res., Vol. 48, No. 7, 2009 3281 Table 2. Summary of Conversion of Glycerol and Yield and Selectivity of Acrolein from Glycerol with Various Catalystsa catalyst
support
C (%)
Y (%)
S (%)
R-Al2O3 H3PO4 H3PO4 H3PO4 H3PO4 H3PO4
R-Al2O3 BASF F24 AC (No 1) AC (No 2) AC (No 3)
65.3 ( 0.7 98.0 ( 1.6 73.1 ( 0.9 79.5 ( 1.1 79.2 ( 1.2 87.4 ( 1.5
5.5 ( 0.1 6.5 ( 0.1 6.2 ( 0.1 66.8 ( 0.7 36.2 ( 0.4 21.9 ( 0.3
8.4 ( 0.2 6.6 ( 0.1 8.5 ( 0.2 84.0 ( 1.3 45.7 ( 0.4 25.1 ( 0.3
a
AC (No 1, 2, 3): activated carbon from biomass with three preparation methods. Reactions were carried out by using 16.7% mass fraction glycerol solution at 260 °C and 0.85 bar for 5 h. C represents conversion of glycerol. Y represents yield of acrolein. S represents selectivity of acrolein. Table 3. Effect of Reaction Conditions on Conversion of Glycerol and Yield and Selectivity of Acrolein from Glycerol over Various Catalystsa t (°C)
P (bar)
C (%)
1 1 1 0.7
R-Al2O3 62.9 ( 0.6 68.6 ( 0.7 72.1 ( 0.9 70.8 ( 0.5
230 260 290 260
1 1 1 0.7
H3PO4/R-Al2O3 82.3 ( 1.1 91.6 ( 1.5 96.0 ( 1.7 93.8 ( 0.7
230 260 290 260
1 1 1 0.7
230 260 290 260
Y (%) 4.4 ( 0.2 5.4 ( 0.2 5.0 ( 0.2 5.5 ( 0.3
Table 4. Summary of Carbon Deposit in the Reactor and Selectivity of Acroleina S (%) t (°C) P (bar) G/W CD (g) 230 260 290 230 260 290 230 260 290
1.0 1.0 1.0 0.85 0.85 0.85 0.70 0.70 0.70
0.2 0.6 0.4 0.4 0.2 0.6 0.6 0.4 0.2
2.63 2.42 2.44 1.21 0.96 0.57 0.8 0.43 1.19
4.3 ( 0.2 5.1 ( 0.3 4.5 ( 0.2 3.9 ( 0.1
5.2 ( 0.3 5.6 ( 0.3 4.7 ( 0.1 4.1 ( 0.1
H3PO4/BASF F24 143.1 ( 0.4 2.9 ( 0.1 163.9 ( 0.5 5.1 ( 0.3 175.4 ( 0.8 5.3 ( 0.3 68.7 ( 0.5 4.3 ( 0.2
6.7 ( 0.2 7.9 ( 0.4 7.1 ( 0.4 6.2 ( 0.2
a t represents temperature. P represents pressure. C represents conversion of glycerol. Y represents yield of acrolein. S represents selectivity of acrolein.
mass concentrations for each component in the sample. Glycerol conversion, product selectivity, and product yield were calculated according to the following equations: glycerol conversion (%) ) moles of glycerol reacted × 100 moles of glycerol in the feed
acrolein
acetol
allyl alcohol
60.0 ( 0.6 42.7 ( 0.4 42.3 ( 0.4 21.9 ( 0.3 84.0 ( 1.1 49.6 ( 0.4 32.1 ( 0.3 26.7 ( 0.2 73.7 ( 0.8
6.1 ( 0.1 9.9 ( 0.2 14.0 ( 0.2 23.6 ( 0.3 10.8 ( 0.2 1.4 ( 0.1 14.3 ( 0.2 3.3 ( 0.1 16.6 ( 0.2
1.3 ( 0.1 2.3 ( 0.1 6.4 ( 0.1 9.4 ( 0.2 2.6 ( 0.1 0.9 ( 0.1 1.1 ( 0.1 0.7 ( 0.1 2.2 ( 0.1
a t represents temperature. P represents pressure. G/W represents the mass ratio of glycerol and water in the feed. CD represents carbon deposit in the reactor. C represents conversion of glycerol. S represents selectivity of each product.
Table 5. Statistical Analysis (F-Test) of Fractional Factorial Design
S (%) 7.0 ( 0.3 7.9 ( 0.4 6.9 ( 0.3 7.8 ( 0.4
C (%) 85.5 ( 3.4 52.9 ( 4.2 97.8 ( 4.9 51.6 ( 2.7 79.5 ( 3.8 86.4 ( 4.5 055.2 ( 2.5 62.3 ( 2.8 80.0 ( 2.6
carbon deposit
temperature pressure glycerol/water
selectivity
R
F
p-value
R
F
p-value
0.05 0.05 0.05
0.48 22.7 0.72
0.678 0.042 0.583
0.05 0.05 0.05
4.75 0.85 28.5
0.174 0.541 0.034
catalyst22 and showed a poor steady selectivity for the acrolein production. The supported phosphoric acids are typical Brønsted acids.22 Other than the type of acid sites, the surface area of supports (distribution of acidic catalytic sites) and the acid-base strength of catalyst are key factors to affect the catalyst performance.23 3.2. Reaction Mechanism. Because 1-hydroxy acetone is also produced as a main product in this reaction, the question arises whether 1-hydroxy acetone is the intermediate to produce acrolein. Reactions were performed with 5% (mass fraction) 1-hydroxy acetone aqueous feed in the presence of H3PO4/ activated carbon catalyst. The gas-chromatography analysis indicated that no acrolein was formed, and 95% of 1-hydroxy acetone could be recovered from reaction samples. It is concluded that 1-hydroxy acetone is stable under these conditions and could not be consumed to produce acrolein. The actual intermediate to acrolein in dehydration reaction could be 3-hydroxypropionaldehyde. H3PO4/activated carbon
product selectivity (%) ) moles of carbon in a product defined × 100 moles of carbon in glycerol product product yield (%) ) moles of carbon in a product defined × 100 moles of carbon in glycerol reacted 3. Results and Discussion 3.1. Catalyst Selection. Acid catalysts in this study were indicated in Table 2. The results of the dehydration reaction over R-Al2O3, H3PO4/R-Al2O3, and H3PO4/BASF F24 are summarized in Table 3. R-Al2O3, H3PO4/R-Al2O3, and H3PO4/ BASF F24 showed low selectivity to acrolein (e10%) and produced a wide range of byproduct (lower alcohols and aldehydes). Under the same conditions, H3PO4/activated carbon achieved higher selectivity for acrolein and produced lower amounts of 1-hydroxy acetone, ally alcohol, and other degradation byproduct. Hence, catalysts (H3PO4/activated carbon) were selected for further studies. The nature of acid sites (Brønsted or Lewis type) would play a key role in determining catalytic performance for solid acid catalysts. R-Al2O3 can be considered as a typical Lewis acid
Figure 4. A time case study of conversion, selectivity, and yield at high flow rate (300 g · h-1). Reactions were performed by using 16.7% mass fraction glycerol solution at 290 °C and 1 bar for 5 h. 9 represents conversion of glycerol. b represents yield of acrolein. 2 represents selectivity of acrolein. Solid lines represent the trends of conversion of glycerol and yield and selectivity of acrolein.
3282 Ind. Eng. Chem. Res., Vol. 48, No. 7, 2009
Figure 5. A time case study of conversion, selectivity, and yield at low flow rate (40 g · h-1). Reactions were performed by using 16.7% mass fraction glycerol solution at 290 °C and 1bar for 5 h.
catalysts were not effective to produce 1-hydroxy acetone from glycerol because the catalysts′ high-acidic sites favor the dehydration of glycerol to acrolein. In the temperature range 230-290 °C in this study, 3-hydroxypropionaldehyde is very unstable and can quickly dehydrate to acrolein in the presence of acid catalysts. Hall,24 Pressman,25 and Clacens26 confirmed that acrolein is hydrated into 3-hydroxypropionaldehyde at lower temperatures and 3-hydroxypropionaldehyde is dehydrated into acrolein when temperature increased. 3.3. Study of Fractional Factorial Design. The fractional factorial experiment of L9(34) was designed to study the effect of three factors: temperature, pressure, and initial glycerol content. Three levels of each factor were investigated. Temperatures of 230, 260, and 290 °C were selected, because the aqueous glycerol feed forms a gas phase with reduced tendencies to polymerize in this temperature range. Pressures of 0.7, 0.85, and 1.0 bar were selected. The mild-vacuum environment helps evaporation of glycerol and removes the reaction mixture from dew-point conditions. It is important to avoid dew-point conditions, because the formation of liquids on the catalyst surface creates more-favorable conditions for oligomer and carbon-deposit (coke) formation. In this study, the aqueous-glycerol feed was used instead of pure glycerol, because pure glycerol is viscous and apt to polymerize in the evaporator at selected temperatures. The initial glycerol content (mass ratio of glycerol to water) was evaluated at three levels of 0.2, 0.4, and 0.6. Besides temperature, pressure, and initial glycerol content, other conditions were maintained the same in each run. For instance, the flow rate of aqueous glycerol solution was 300 g · h-1, and the catalyst loading was 2 g of catalyst. The results of the fractional factorial experiment summarized in Table 4. Statistical analysis (F-test) showed how temperature, pressure, and initial glycerol content affect the amount of coke deposited and the selectivity to acrolein (see Table 5). Pressure had a significant influence on the carbon deposit (coke), because the p-value of pressure is lower than R (0.05). The coke may consist of heavier products including higher aldehydes, olefins, and heterocyclic and/or aromatic compounds by a complex side
reactions. Lower carbon deposit at lower pressures is consistent with a mechanism where lower pressures are effective for rapidly removing the more-volatile products from the catalyst sites. Hence, a long catalyst service life could be achieved at lower pressures, which correspond to conditions with greater potential for practical application. Statistical analysis also indicated that initial glycerol content significantly affected the selectivity of glycerol to acrolein. The catalyst could maintain high selectivity of glycerol to acrolein with low glycerol concentration in the feed. As previous illustration shows, high initial glycerol content lead to glycerol polymerization which occurred on the catalytic sites. The consequence was high carbon deposit and low selectivity to acrolein. On the other hand, dilution of glycerol with water lowers the partial pressure of glycerol in a manner similar to the way that lower static pressures lower partial pressure. However, the higher water concentration definitely causes the high energy consumption for evaporation of water and product recovery from low-acroleinconcentration solution. Therefore, the water concentration in the feed should be optimized according to technical and economic consideration. Reaction temperature (lower than that of the previous research)20 was not a significant factor to selectivity of acrolein. The results showed that high selectivity of acrolein (84.0%) can be achieved at low temperature in the presence of H3PO4/ activated carbon catalyst. Catalyst life can be affected by the feed flow rate. From experimental observation, the pH value of samples at the beginning stage of the reaction was about 3.0-4.0 when feed flow rate was high (300 g · h-1). Figure 4 shows that the conversion of glycerol and the selectivity and yield of acrolein decreased dramatically at a feed flow rate of 300 g · h-1. However, long catalyst life can be achieved at low feed flow rate (40 g · h-1). Figure 5 proves that the conversion of glycerol and the yield and selectivity of acrolein maintained at the same level for 5 h. Addition of a low-concentration of phosphoric acid solution, mixed with glycerol vapor at the entrance of the reactor, was also investigated as a way to increase catalyst life. Although it
Ind. Eng. Chem. Res., Vol. 48, No. 7, 2009 3283
Figure 6. Effect of phosphoric acid concentration in feed on carbon deposit in the reactor. Reactions were performed with 16.7% mass fraction glycerol solution at 290 °C and 1 bar for 5 h.
did improve the catalyst life, a higher amount of coke was obtained correspondingly (see Figure 6). The way to continuously replenish the catalyst seemed not successful. Careful selection of reaction conditions (e.g., the feed flow rate) can be a much more effective way to achieve the highest yield of acrolein. There was not much effort made in this study to understand how strong phosphoric acid was on the activated carbon. This work is important to avoid the acid leaching during the reaction, which will be a part of future work. Moreover, to convert of crude glycerol to valuable chemicals, the future study of crude glycerol in acrolein production will be performed, because other compounds including sodium salts and heavy metals in crude glycerol might affect the catalyst performance and reaction conditions. 4. Conclusion H3PO4/activated carbon catalysts were prepared from sustainable biomass by using a patented technology. Reaction mechanism showed that 3-hydroxypropanaldehyde other than 1-hydroxy acetone is the hydration intermediate to acrolein. H3PO4/ activated carbon catalysts proved to be more effective than catalysts such as R-Al2O3, H3PO4/R-Al2O3 and H3PO4/BASF F24. High selectivity to acrolein and low carbon deposit were achieved under mild conditions (low temperatures and pressures). This dehydration process provides a great potential for production of acrolein from low-value abundant crude glycerol from biodiesel industry. Literature Cited (1) Monograph on the EValuation of the Carcinogenic Risk of Chemicals to Humans: Allyl Compounds, Aldehydes, Epoxides and Peroxides; International Agency for Research on Cancer, IARC: Lyon, 1985; p 133. (2) Etzkorn, W. G.; Neilsen, W. D. Acrolein Derivatives. Kirk-Othmer Encyclopedia of Chemical Technology; Wiley: New York, 2001. (3) Contractor, R. M.; Andersen, M. W.; Campos, D. Vapor phase oxidation of propylene to acrolein. U.S. Patent 6,437,193, 1997.
(4) Yan, W.; Suppes, G. J. Vapor Pressure and Evaporation Studies of Sugar and Sugar Alcohol. J. Chem. Eng. Data 2008, 53, 2033. (5) Yan, W.; Li, S. F.; Tian, S. J. Ultrasound-Assisted Extraction Technology. Chem. Ind. Eng. Prog. 2002, 21, 27. (6) Suppes, G. J.; Dasari, M. A.; Doskocil, E. J.; Mankidy, P. J.; Goff, M. J. Transesterification of Soybean Oil with Zeolite and Metal Catalysts. Appl. Catal., A 2004, 257, 213. (7) Canakci, M.; Gerpen, J. V. Biodiesel Production from Oils and Fats with High Free Fatty Acids. Trans. ASAE 2001, 44, 1429. (8) Chiu, C. W.; Schumacher, L. G.; Suppes, G. J. Impact of Cold Flow Improvers on Soybean Biodiesel Blend. Biomass Bioen. 2004, 27, 485. (9) Dasari, M. A.; Goff, M. J.; Suppes, G. J. Noncatalytic Alcoholysis Kinetics of Soybean Oil. J. Am. Oil Chem. Soc. 2003, 80, 189. (10) Brachttal, A. N.; Haas, T.; Arntz, D.; Klenk, H.; Girke, W. Process for the production of acroleinU.S. Patent 5,387,720, 1995. (11) Adkins, H.; Hartung, W. H. Chemical Reactions to Synthesize Acrolein. Org. Synth., Coll. 1941, 1, 15. (12) Schwenk, E.; Gehrke M.; Aichner, F. Production of acroleinU.S. Patent 1,916,743, 1933. (13) Ramayya, S.; Brittain, A.; DeAlmeida, C.; Mok, W. M. AcidCatalyzed Dehydration of Alcohols in Supercritical Water. Fuel 1987, 66, 1364. (14) Antal, M. J.; Mok, W. S. L.; Richards, G. N. Four-Carbon Model Compounds for the Reactions of Sugars in Water at High Temperature. Carbohydr. Res. 1990, 199, 111. (15) Ott, L.; Bicker, M.; Vogel, H. Catalytic Dehydration of Glycerol in Sub- and Supercritical Water: A New Chemical Process for Acrolein Production. Green Chem. 2006, 8, 214. (16) Robichaud, J. L.; Noble, A. C. Astringency and Bitterness of Selected Phenolics in Wine. J. Sci. Food Agric. 1990, 53, 343. (17) Sponholz, W. R. Wine Spoilage by Microorganisms. Wine Microbiology and Biotechnology; Howard Academic: Switzerland, 1993; p 395. (18) Dasari, M. A.; Kiatsimkul, P.; Sutterlin, W. R.; Suppes, G. J. LowPressure Hydrogenolysis of Glycerol to Propylene Glycol. Appl. Catal., A 2005, 281, 225. (19) Chiu, C. W.; Dasari, M. A.; Suppes, G. J. Dehydraotion of Glycerol to Acetol via Catalytic Reactive Distillation. AIChE J. 2006, 52, 3543. (20) Bratchttal, A. N.; Frankfurt, T. H.; Oberursel, D. A.; Klenk, H.; Girke, W. Process for the production of acroleinU.S. Patent 5,387,720, 1995. (21) Pfeifer, P.; Suppes, J. G.; Shah, P.; Burress, W. J. High surface area carbon and process for its productionWorld Patent WO/2008/058231, 2008. (22) Tanabe, K.; Misono, M.; Ono, Y.; Hattori, H. New Solid Acids and Bases: Their Catalytic Properties; Elsevier: Amsterdam 1989; pp 247260. (23) Chai, S. H.; Wang, H. P.; Liang, Y.; Xu, B. Q. Sustainable Production of Acrolein: Investigation of Solid-Base Catalysts for Gas-Phase Dehydration of Glycerol. Green Chem. 2007, 9, 1130. (24) Hall, R. H.; Stern, E. S. Acid-Catalysed Hydration of Acraldeyde: Kinetics of the Reaction and Isolation of 3-Hydrooxypropaldehyde. J. Chem. Soc. 1950, 490. (25) Pressman, D.; Lucas, H. J. Hydration of Unsaturated Compounds. XI. Acrolein and Acrylic Acid. J. Am. Chem. Soc. 1942, 64, 1953. (26) Clacens, J. M.; Pouilloux, Y.; Barrault, J. Selective Etherification of Glycerol to Polyglycerols over Impregnated Basic MCM-41 Type Mesoporous Catalyst. Appl. Catal., A 2002, 227, 181–190.
ReceiVed for reView August 4, 2008 ReVised manuscript receiVed December 4, 2008 Accepted January 29, 2009 IE801200P
