Pervaporation of organic compounds from aqueous mixtures using polydimethylsiloxane‐containing block copolymer membranes

Pervaporation of aqueous mixtures of ethanol, acetone, butanol, isobutanol, and furfural through polystyrene‐b‐polydimethylsiloxane‐b‐polystyrene (SDS) triblock copolymer membranes is reported. These mixtures are important for biofuel production from lignocellulosic feedstocks. Feedstock depolymerization results in the formation of furfural which must be removed before fermentation. Ethanol, butanol, isobutanol, and acetone are important fermentation biofuels. The membrane selectivity of SDS is about unity over a wide range of concentrations of aqueous ethanol mixtures, similar to the membrane selectivity of crosslinked polydimethylsiloxane (PDMS). The permeabilities of butanol, isobutanol, and furfural are larger than those of ethanol and acetone. The volatile organic compound permeability through SDS is similar to or higher than that through PDMS across a broad range of temperatures and feed concentrations is found. More selective and permeable membranes are needed to lower the cost of biofuel purification. The SDS membranes developed are but one step toward improved membranes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2789–2794, 2015     

Alternatives for the Purification of the Blend Butanol/Ethanol from an Acetone/Butanol/Ethanol Fermentation Effluent

Biobutanol is a biofuel with potential to substitute gasoline. It can be generated through fermentation of lignocellulosic material, by which acetone, butanol, and ethanol (ABE) are obtained and subsequently separated. Nevertheless, the blend ethanol/butanol itself is a fuel, so its separation could be not even necessary. An alternative is proposed to simplify the purification step of the ABE mixture, avoiding the separation of the ethanol/butanol blend. Intensification alternatives are suggested for the resulting structure. The proposed schemes are optimized through a stochastic approach, minimizing the total annual cost and the eco‐indicator 99. The individual risk index is computed for selected designs. The suggested designs reduce the individual risk index by around 30–66 %.     

Butanol production in a sugarcane biorefinery using ethanol as feedstock. Part II: Integration to a second generation sugarcane distillery

Production of second generation ethanol and other added value chemicals from sugarcane bagasse and straw integrated to first generation sugarcane biorefineries presents large potential for industrial implementation, since part of the infrastructure where first generation ethanol is produced may be shared between both plants. In this context, butanol from renewable resources has attracted increasing interest, mostly for its use as a drop in liquid biofuel for transportation, since its energy density is greater than that of ethanol, but also for its use as feedstock in the chemical industry. In this paper, vapor-phase catalytic production of butanol from first and second generation ethanol in a sugarcane biorefinery was assessed, using data available from the literature. The objective is to evaluate the potential of butanol either as fuel or feedstock for industry, taking into account economical/environmental issues through computer simulation. The results obtained show that, although promising, butanol sold as chemical has a limited market and as fuel presents economic constraints. In addition, investments on the butanol conversion plant could be an obstacle to its practical implementation. Nevertheless, environmental assessment pointed out advantages of its use as fuel for road transportation, if compared with gasoline in terms of global environmental impacts such as global warming.     

Butanol production in a sugarcane biorefinery using ethanol as feedstock. Part I: Integration to a first generation sugarcane distillery

Butanol production from renewable resources has been increasingly investigated over the past decade, mostly for its use as a liquid biofuel for road transportation, since its energy density is higher than that of ethanol and it may be used in gasoline driven engines with practically no changes, but also for use as a feedstock in the chemical industry. Most of the research concerning butanol production focuses on the ABE process (fermentation of sugars into a mixture of acetone, butanol and ethanol), which has several drawbacks regarding microorganism performance and product inhibition. An alternative to ABE fermentation, ethanol catalytic conversion to butanol can produce a higher quality product with less retrofitting than ABE in existing ethanol producing facilities. There are different types of catalysts for the chemical conversion of ethanol to butanol being developed in laboratory scale, but their actual use in a sugarcane processing plant has never before been assessed. Butanol production from ethanol in a sugarcane biorefinery, using data from the literature, was assessed in this study; different technological alternatives (catalytic routes) were evaluated through computer simulation in Aspen Plus (including production of electricity, sugar, ethanol and other products) and economic and environmental impacts were assessed. Results indicate that vapor-phase catalysis presents higher potential for industrial implementation, and commercialization of butanol for use as a chemical feedstock has an economic performance similar to that of current, optimized first generation sugarcane distilleries, but can potentially contribute to cost reduction that will allow commercialization of butanol as a fuel in the future.     

Separation of a Biofuel: Recovery of Biobutanol by Salting‐Out and Distillation

The second generation biofuel butanol can be produced by acetone‐butanol‐ethanol (ABE) fermentation, but the separation from the broth is still challenging. Therefore, dipotassium hydrogen phosphate was investigated as salting‐out agent. The ABE fermentation broth was enriched by a prefractionator after being preheated. The enriched ABE solution was salted out by K₂HPO₄ solutions at different temperatures. The water in the supplemented ABE solution was largely removed by the salting‐out method. The energy requirements for the prefractionator and the butanol column were significantly reduced. The total energy demand for the recovery of acetone, butanol, and ethanol by salting‐out and subsequent distillation was optimized. With the salting‐out process, the entire salting‐out and distillation method turned out to be more energy‐saving than the conventional one.     

PermSMBR—A new hybrid technology: Application on green solvent and biofuel production

A new technology, the simulated moving bed membrane reactor (PermSMBR), was presented and applied for the production of the green solvent ethyl lactate and of the biofuel 1,1‐diethoxyethane. Its conception was a result of process reintensification for oxygenates production, by integrating the simulated moving bed reactor with hydrophilic membranes to enhance the water removal, leading to high process performance. For ethyl lactate synthesis, the PermSMBR technology proved to have better performance than the reactive distillation (RD) and the simulated moving bed reactor (SMBR) processes; the RD and SMBR processes require more 152 and 165% of ethanol consumption than the new technology, respectively. For the 1,1‐diethoxyethane production, the PermSMBR also leads to a decrease in ethanol consumption of 69% and a productivity enhancement of 53%, when comparing with the SMBR. © 2010 American Institute of Chemical Engineers AIChE J, 57: 000–000, 2011     

The effects of dilution rate and glucose concentration on continuous acetone–butanol–ethanol fermentation by Clostridium acetobutylicum immobilized on bricks

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of butanol through biological routes has attracted increasing attention. However, low butanol productivity severely impedes its potential industrial production. It is known that the immobilization of whole cells can enhance productivity in the acetone‐butanol‐ethanol (ABE) continuous fermentation process. Therefore, the objective of this study was to develop a low‐cost continuous operation for butanol production. RESULTS: Bricks were chosen as cell support because of their low cost and ease of use for immobilization. The solvent productivity for the bricks with immobilized cells was 0.7 g L^?1 h^?1, 1.89 times that of free cells (0.37 g L^?1 h^?1) at a dilution rate of 0.054 h^?1. The productivity improvement can contribute to greater retention of biomass inside the reactor due to immobilization. The increase in glucose feed concentration raised total solvent production. However, it resulted in a decrease in yield (grams of solvents produced per gram of glucose introduced). Continuous operation with immobilized cells at a dilution rate of 0.107 h^?1 resulted in a solvent productivity of 1.21 g L^?1 h^?1, 2.1 times that of the operation at 0.027 h^?1. However, the yield (butanol produced per glucose consumed) was decreased to 0.19 from 0.29 under the same glucose feeding condition of 60 g L^?1. CONCLUSION: The increase in dilution rate and feed glucose concentration enhanced productivity, but decreased the utilization of substrates and the final solvent concentration. Therefore, a balance between productivity and glucose utilization is required to ensure continuous process operation. Copyright © 2011 Society of Chemical Industry     

Biochemical Conversion of Microalgae Biomass into Biofuel

Biofuel production via microalgae is a promising and sustainable alternative to replace the typical fossil fuel that is the main contributor to the global warming. However, for a cost‐effective biofuel production, further advanced research is still needed for large‐scale operation. This article is a tutorial review on conversion processes of microalgae into biofuel, with emphasis on biochemical conversion. The following topics are discussed: (i) microalgae biomass and its composition, (ii) thermochemical conversion, (iii) chemical conversion, and (iv) biochemical conversion. In addition, various aspects of anaerobic digestion, digester designs, and effects of operating conditions on the production of methane, bioethanol, and biohydrogen are discussed. The general kinetics of biomass conversion into biofuel is presented. This study suggests, if that biomass contains less than 50 % moisture, then it is recommended to use the direct combustion method; otherwise, biochemical conversion is the most suitable process to biofuel production.     

Selective separation of n‐butanol from aqueous solutions by pervaporation using silicone rubber‐coated silicalite membranes

BACKGROUND: To use butanol as a liquid fuel and feedstock, it is necessary to establish processes for refining low‐concentration butanol solutions. Pervaporation (PV) employing hydrophobic silicalite membranes for selective recovery of butanol is a promising approach. In this study, the adsorption behavior of components present in clostridia fermentation broths on membrane material (silicalite powder) was investigated. The potential of PV using silicone rubber‐coated silicalite membranes for the selective separation of butanol from model acetone–butanol–ethanol (ABE) solutions was investigated. RESULTS: The equilibrium adsorbed amounts of ABE per gram of silicalite from aqueous solutions of binary mixtures at 30 °C increased as follows: ethanol (95 mg) < acetone (100 mg) < n‐butanol (120 mg). The amount of butanol adsorbed is decreased by the adsorption of acetone and butyric acid. In the separation of ternary butanol/water/acetone mixtures, the enrichment factor for acetone decreased, compared with that in binary acetone/water mixtures. In the separation of a model acetone–butanol–ethanol (ABE) fermentation broth containing butyric acid by PV using a silicone rubber‐coated silicalite membrane, the permeate butanol concentration was comparable with that obtained in the separation of a model ABE broth without butyric acid. The total flux decreased with decreasing feed solution pH. CONCLUSION: A silicone rubber‐coated silicalite membrane exhibited highly selective PV performance in the separation of a model ABE solution. It is very important to demonstrate the effectiveness of PV in the separation of actual clostridia fermentation broths, and to identify the factors affecting PV performance. Copyright © 2011 Society of Chemical Industry     

ClostridiumsaccharobutylicumDSM13864细胞表面理化特性及固定化细胞产丁醇的性能

糖丁基梭菌Clostridium saccharobutylicum DSM 13864能利用多种糖类为底物发酵产丁醇。本文研究了该菌体细胞表面的理化特性,并以砖块作为细胞固定化材料进行丁醇发酵。采用细菌吸附有机溶剂(MATS)法证明糖丁基梭菌细胞表面有强烈的亲水性,并且等电点在pH值为3左右,这些特性有利于菌体与表面亲水多孔的砖块吸附。在60g/L葡萄糖发酵培养基中,以5～8目砖块作为固定化材料,流速为1.1L/min,发酵48h后,丁醇的浓度、得率和生产率分别达到11.02g/L、0.18g/g和0.23g/(L·h),相比悬浮细胞发酵分别提高了10.53%、5.88%和9.52%。结果表明:砖块作为一种固定化材料可有效提高糖丁基梭菌的发酵产丁醇水平。     

小麦秸秆催化液化工艺研究

常温常压下小麦秸秆催化液化制绿色化学品。分别研究了小麦秸秆在甲醇、乙醇、丙三醇和丁醇中的液化效果,考察了甲醇和苯酚的混合体系下液化时间与不同催化剂对液化产率的影响。结果表明,常温常压下,4种醇对小麦秸秆的液化产率的高低顺序:甲醇>乙醇>丙三醇>丁醇,甲醇的液化产率最高,达到17.23%,可以作为木质素液化的有效试剂。甲醇和苯酚混合液化体系的液化产率可达到24.52%,以对甲苯磺酸作为催化剂液化产率可达到28.40%。     

The addition of ethanol as defoamer in fermentation of rhamnolipids

BACKGROUND: Rhamnolipids biosurfactants mainly produced by Pseudomonas aeruginosa have a wide range of potential applications. However, production of rhamnolipids on a large scale is constrained by severe foaming in fermentation. This study addressed the applicability of organic solvents as both defoamer and carbon substrate in rhamnolipids fermentation. RESULTS: In this work, although isopropanol and n‐butanol performed better defoaming activities against rhamnolipid‐induced foams, ethanol was focused on as a potential defoamer due to its high bioavailability and low toxicity in a shaking culture of P. aeruginosa ZJU. The most appropriate dose of ethanol addition was determined to be 1% (v/v) and the best time for addition was after 48 h of culture in shaking flasks. The capability of ethanol to control foaming was further illustrated during rhamnolipids fermentation in 2 L and 50 L bioreactors. In both fermentations, the addition of ethanol not only suppressed severe foaming but also supported cell growth. CONCLUSIONS: The use of ethanol as a defoamer is a potential strategy to avoid undesirable foam in fermentation of biosurfactant. Copyright © 2012 Society of Chemical Industry     

A life cycle assessment of advanced biofuel production from a hectare of corn

Conventional agricultural life cycle assessments (LCAs) measure greenhouse gas (GHG) emissions for biofuel pathways as the amount of carbon dioxide equivalent emitted per unit of energy provided by the pathway (i.e. gCO₂e/MJ). This measure of GHG emissions, as computed by the Environmental Protection Agency (EPA) is then used to determine the extent to which the corresponding biofuel pathway complies with the GHG emission standards set forth by the Energy Independence and Security Act (EISA) of 2007. Under current legislation, ethanol produced from corn grain is prohibited from qualifying as an advanced biofuel, even if it were to meet the GHG emission standards. This paper proposes a measure of GHG emissions based on a unit of land rather than the energy provided by a biofuel pathway utilizing only one feedstock. A hectare of corn thus provides two feedstocks for the biofuel pathway considered here; corn grain is used for production of ethanol while corn stover is subjected to fast pyrolysis for production of biochar and bio-oil. The bio-oil is then subsequently upgraded to a fuel suitable for use as a drop in fuel in internal combustion engines. A LCA of this pathway is conducted and it is found that such a pathway generates a 52.1% reduction in GHG emissions. This is a reduction that is sufficient to qualify the combined output of a hectare of corn as an advanced biofuel if the current restriction in EISA were removed.     

Polycyclic aromatic hydrocarbons (PAHs) adsorption on solid surfaces applied to waste lubricant oils recovery process

Lubricant oils undergo degradation increasing polycyclic aromatic hydrocarbons (PAHs) concentration. In this work, PAHs adsorption onto activated carbon, powder silica, and powder chitosan surfaces was estimated, with their concentrations in organic solvents (ethanol, 2‐propanol, 1‐butanol, and terc‐butanol) monitored by UV‐visible absorption. Equilibrium concentration was attained after 72 h and the isotherms presented characteristic of multilayer formation. The greater surface density was determined for the chitosan, but the system containing activated carbon and 1‐butanol presented better efficiency for PAHs removal. Results indicated that the adsorption evaluated in this work can be a potential stage in the waste lubricant oils global recovery process.     

Pervaporative enrichment of 2,3‐butanediol from its mixture with 1‐butanol using a polydimethylsiloxane and ZSM‐5 mixed matrix membrane: Effects of ethanol as a by‐product

A ZSM‐5 filled polydimethylsiloxane membrane with 44.4 wt.% zeolite loading was used in the pervaporative removal of 1‐butanol from its mixtures with 1‐butanol. A small quantity of ethanol was added to the feed as a by‐product to test the response of the membrane. It was found that the permeation behaviour of other feed components was changed and membrane selectivity decreased. This change was attributed to the frequently‐observed inter‐component coupled transport in multi‐component feed systems. The impact of ethanol on recovery of 2,3‐butanediol was evaluated using a simulated continuous operation, which enriched 2,3‐butanediol to 99.5 wt.% from a feed containing 5 wt.% 2,3‐butanediol and less than 1.0 wt.% ethanol. It was observed that membrane selectivity improves as ethanol concentration decreases in the stream due to its preferential removal. The final recovery of 2,3‐butanediol was not significantly reduced as the concentration of ethanol was below 1.0 wt.%. © 2011 Canadian Society for Chemical Engineering     

蒸汽渗透技术在燃料乙醇生产中的应用研究进展

蒸汽渗透作为一种新型膜分离技术,可有效解决生物燃料乙醇生产中发酵产物浓度低、能源消耗量大、污染环境等诸多瓶颈问题。与渗透蒸发相比,蒸汽渗透技术具有分离性能好、进料清洁、能量损耗低、操作弹性大等优点,在燃料乙醇生产领域具备更广阔的应用前景。本文在比较渗透蒸发和气体分离技术的基础上,简述了蒸汽渗透过程的机理和特点。介绍了优先透水膜和优先透醇膜两类应用于燃料乙醇生产不同阶段的蒸汽渗透膜和这两类膜材料当前的研究进展,重点阐述了有机/无机杂化膜在成膜方法、杂化材料选择等方面的最新成果。回顾了蒸汽渗透在乙醇脱水方面的工业应用成果,指出该技术在发酵原位分离乙醇和替代精馏工艺方面所具有的优势,探讨了与固态发酵技术相结合进行一次相变生产燃料乙醇工艺实现的可能性,并提出未来亟待研究和解决的问题,为蒸汽渗透技术在燃料乙醇生产领域大规模发展提供参考。     

Experimental determination of laminar burning velocity for butanol and ethanol iso-octane blends

The potential of butanol as an additive in iso-octane used as gasoline fuel was characterized with respect to laminar combustion, and compared with ethanol. New sets of data of laminar burning velocity are provided by using the spherical expanding flame methodology, in a constant volume vessel. This paper presents the first results obtained for pure fuels (iso-octane, ethanol and butanol) at an initial pressure of 0.1 MPa and a temperature of 400 K, and for an equivalence range from 0.8 to 1.4. New data of laminar burning velocity for three fuel blends containing up to 75% alcohol by liquid volume are also provided. From these new experimental data, a correlation to estimate the laminar burning velocity of any butanol or ethanol blend iso-octane-air mixture is proposed.     

Pervaporation and Vapor Permeation Tutorial: Membrane Processes for the Selective Separation of Liquid and Vapor Mixtures

Pervaporation and vapor permeation are membrane-based processes proposed as alternatives to conventional separation technologies. Applications range from organic solvent removal from water, ethanol, or butanol recovery from fermentation broths, solvent/biofuel dehydration to meet dryness specifications, and organic-organic separations such as the removal of sulfur compounds from gasoline. Unlike membrane filtration processes, which rely on an applied liquid pressure gradient and size sieving to accomplish a separation, pervaporation and vapor permeation separate compounds based on a chemical activity driving force and the sorption and diffusion of the compounds through the membrane. These properties enable the separation of even miscible liquid mixtures.     

Controllability Analysis of Process Alternatives for Biobutanol Purification

Biobutanol has characteristics similar to petroleum fuel and is considered as a superior biofuel compared to ethanol. The development of technologies for biobutanol production by fermentation has resulted in higher final biobutanol concentrations together with less energy‐intensive separation and purification techniques. These new technological developments have the potential to provide a production process for biobutanol that is economically viable in comparison to the petrochemical pathway for its production. The control properties of four different possible process designs for biobutanol purification are analyzed. The results, using the singular value decomposition technique, indicated that the scheme where only biobutanol flow is purified, and both ethanol and acetone leaving the purification process mixed with water and biobutanol traces, showed the best control properties.     

Liquid–Liquid Extraction of Butanol from Dilute Aqueous Solutions Using Soybean-Derived Biodiesel

Liquid–liquid extraction (LLE) of mixtures of butanol, 1,3-propanediol (PDO), and ethanol was performed using soybean-derived biodiesel as the extractant. The composition of the mixtures simulated the product of the anaerobic fermentation of biodiesel-derived crude glycerol, which has recently been reported for the first time by the authors. Using a biodiesel: with an aqueous phase volume ratio of 1:1, butanol recovery ranged from 45 to 51% at initial butanol concentrations of 150 and 225 mM, respectively. Less than 10% of the ethanol was extracted, and essentially no PDO was extracted. The partition coefficient for butanol in biodiesel was determined to be 0.91 ± 0.097. This partition coefficient is less than that of oleyl alcohol, which is considered the standard for LLE. However, butanol is suitable for blending with biodiesel, which would eliminate the need for separating the butanol after extraction. Additionally, biodiesel is much less costly than oleyl alcohol. If biodiesel-derived glycerol is used as the feedstock for butanol production, and biodiesel is used as the extractant to recover butanol from the fermentation broth, production of a biodiesel/butanol fuel blend could be a fully integrated process within a biodiesel facility. This process could ultimately help reduce the cost of butanol separation and ultimately help improve the overall economics of butanol fermentation using renewable feedstocks.