Kinetic and Thermodynamic Study on Adsorption by Starchy Materials in the Ethanol-Water System

Carmo, María Auxiliadora Vieira do; Gubulin, J.C.

doi:10.1590/s0104-66321997000300005

Cited by 4 publications

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“…5 The economic viability of the ethanol production process is strongly affected by the low ethanol concentration obtained in the fermenter, as well as the need to break the azeotrope between ethanol and water, which occurs at an ethanol concentration of 95.57 wt %. A lot of research has been directed toward using adsorption to break the azeotrope at high ethanol concentrations, including the use of zeolites [6][7][8] and cellulosic adsorbents. [9][10][11][12][13] One alternative to decrease the cost of production of ethanol is to increase the productivity by reducing ethanol inhibition within the fermentation broth.…”

Section: Introductionmentioning

confidence: 99%

Ethanol Recovery from Fermentation Broth via Carbon Dioxide Stripping and Adsorption

2010

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With the depletion of fossil fuels, research in alternative energy sources that can provide the world's energy demand has increased significantly during the past decade. One alternative energy source in particular that has gained worldwide recognition as a potential replacement to oil is bioethanol. It is renewable and environmentally friendlier than fossil fuels. In this study, adsorption is used to increase the efficiency of ethanol production by decreasing the effect of product inhibition using carbon dioxide stripping technology. The reduction in product inhibition is particularly important when ethanol is produced from lignocellulosic biomass because microorganisms that are able to use all fermentable sugars are less tolerant to ethanol. Carbon dioxide removes ethanol from the fermentation broth and reduces the level of ethanol toxicity, while adsorption is used to recover the entrained ethanol from the vapor phase. The literature review showed that activated carbon and hydrophobic zeolites would be the most appropriate adsorbents for ethanol recovery in the vapor phase. A series of adsorption screening experiments were performed to compare four activated carbon adsorbents (Filtrasorb 200, Nuchar RGC 40, Sorbonorit B4, and WV-B 1500) and two hydrophobic ZSM-5-type zeolites (HiSiv 3000 and CBV 8014). The vapor composition used was controlled to resemble the fermenter outlet vapor concentration after stripping with carbon dioxide. Activated WV-B 1500 exhibited the highest ethanol capacity among activated carbons, having higher ethanol adsorption capacities than the two zeolites. Adsorption isotherms for ethanol and water in the presence of carbon dioxide at different temperatures were determined using WV-B 1500 as the adsorbent with the temperature-dependent Toth isotherm model providing satisfactory fits for these isotherms. Ethanol adsorption experiments with and without the presence of water were conducted and showed similar ethanol adsorption capacities, indicating that the presence of water has a negligible effect on ethanol adsorption.

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Section: Introductionmentioning

confidence: 99%

Ethanol Recovery from Fermentation Broth via Carbon Dioxide Stripping and Adsorption

2010

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“…[1][2][3] The adsorption properties have been studied for corn starch, corn grits, and particles synthesized from a mixture of corn starch and either corn cobs or hemicellulose. [3][4][5][6][7][8][9][10][11] Other materials less referenced as adsorbents for water-ethanol separation are cornmeal, wheat flour, and wheat straw. 12 Starch is a mixture of amylose, a linear polymer of D-glucose units joined by R-1,4 bonds, and amylopectin, a polymer of linear, 1,4 D-glucose chains linked at branches points by R-1,6bonds.…”

Section: Introductionmentioning

confidence: 99%

“…The removal of water from ethanol using a fixed-bed adsorber is a well-known process using mainly molecular sieves as adsorbents. Starch, starch-based materials, cellulose and hemicellulose have an affinity for water. − The adsorption properties have been studied for corn starch, corn grits, and particles synthesized from a mixture of corn starch and either corn cobs or hemicellulose. − Other materials less referenced as adsorbents for water−ethanol separation are cornmeal, wheat flour, and wheat straw …”

Section: Introductionmentioning

confidence: 99%

Ethanol Dehydration by Adsorption with Starchy and Cellulosic Materials

Quintero

2009

Ind. Eng. Chem. Res.

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Adsorption with starchy and cellulosic materials was evaluated as an energy efficient technology for ethanol dehydration. Corn (Zea mays), upright elephant ear (Alocasia macrorrhiza), cassava (Manihot esculenta), and sugar cane bagasse (Saccharum), were used as sources of starch and cellulosic fibers and further used as adsorbents for water removal. Enzymes (α-amylase and cellulase for starch and cellulose, respectively) were evaluated as modifying agents with the aim of increasing water adsorption capacity. Native and enzyme-treated materials were examined with SEM, XRD, and BET analysis to determine the hydrolysis influence on structure and superficial area. Partial hydrolysis was obtained under operation conditions evaluated, as was shown by the SEM micrographs. Crystallinity increased with the enzymatic hydrolysis for all materials. For all materials, superficial area was not increased with enzymatic hydrolysis but water adsorption capacity was improved reaching an anhydrous product with enzyme-treated materials. Water adsorption capacity ranges from 4 to 19 g/ 100 g adsorbent were found for evaluated materials. Corn starch had the highest water adsorption capacity (19 g/ 100 g ads) while upright elephant ear starch presented the lowest (4.2 g/ 100 g ads). Tested materials showed affinity with water for both native and enzyme-treated cases. This allowed water to adsorb from the feed for obtaining anhydrous ethanol. It was suggested that water adsorption capacity was increased because of the more exposed hydroxyl groups from the polymeric structures evaluated (starch and cellulose). Applicability of these materials was oriented to small scale ethanol production plants in developing countries where rural areas are the objective and small productions are expected.

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“…These materials are highly effective due to both their hydrophilic nature and small aperture (<0.4 nm) capable of rejecting organic molecules larger than water. 1 Recently, however, the need for hydrophobic adsorbents capable of concentrating dilute organics (i.e., ethanol, propanol, butanol) from aqueous solutions has increased due to the rapid growth in algae-based biofuel research and development. 2,3 Among hydrophobic materials, zeolites with the MFI-type structure are among the most widely studied for this purpose due to their large pore size (∼0.54 nm) and thermal/structural stability.…”

Section: ■ Introductionmentioning

confidence: 99%

Effect of Crystal Size on Framework Defects and Water Uptake in Fluoride Mediated Silicalite-1

Dose¹,

Zhang

Thompson

et al. 2014

Chem. Mater.

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The relationship between framework defects and crystal size in fluoride mediated silicalite-1 was investigated through nitrogen physisorption, X-ray diffraction, and vapor adsorption of ethanol and water on samples with crystal sizes ranging from 0.4 to 30 μm in the b direction of the silicalite-1 crystals. X-ray diffraction reveals a shift in the lattice system from a predominantly monoclinic phase in smaller crystals to an orthorhombic phase in the larger crystals. 29 Si MAS studies reveal minimal differences in framework silanol defect concentration. An H-4 type hysteresis in 77 K N 2 adsorption isotherm and BdB-FHH pore size analysis reveal the presence of slit-like pores and a larger average pore size as well as a larger volume fraction of "microfissures" in the larger crystals. Pure vapor adsorption measurements show more than a 2-fold increase in water uptake from 0.21 mmol/g to 0.51 mmol/g from the smallest to largest samples at 308 K near unit activity, while ethanol uptake remains on the order of 2.4 mmol/g for all samples. An increase in desorption hysteresis with crystal size and negligible differences in isosteric heats of adsorption of water lend support to the presence of microfissure defects in the larger samples. IAST predications for binary adsorption of ethanol and water in the silicalite-1 samples reveal a 2-fold ethanol/water selectivity enhancement for dilute (<5 wt % EtOH) solutions when crystal size is reduced. This systematic study of N 2 physisorption, framework composition, and ethanol/water adsorption highlights the critical role that crystal size plays in the adsorption process, which can have significant implications for biofuel processes that produce dilute aqueous ethanol as a raw product.

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Kinetic and Thermodynamic Study on Adsorption by Starchy Materials in the Ethanol-Water System

Cited by 4 publications

References 0 publications

Ethanol Recovery from Fermentation Broth via Carbon Dioxide Stripping and Adsorption

Ethanol Recovery from Fermentation Broth via Carbon Dioxide Stripping and Adsorption

Ethanol Dehydration by Adsorption with Starchy and Cellulosic Materials

Effect of Crystal Size on Framework Defects and Water Uptake in Fluoride Mediated Silicalite-1

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