Pervaporative separation of butanol using a composite PDMS/PEI hollow fiber membrane

In the study, the separation and purification of butanol was carried out using the composite hollow fiber membrane having the active layer of polydimethylsiloxane (PDMS) on the macroporous support of polyetherimide (PEI). The pervaporation results with the initial butanol concentration showed a trade-off between flux and separation factor. However, both the flux and the separation factor increased as the operating temperature increased. The pervaporation results showed the butanol flux and the separation factor were higher than those of the reported results. In this study, butanol was concentrated by the pervaporation as a feasibility study for the biofuel applications.     

Advances of macroalgae biomass for the third generation of bioethanol production

In recent years, utilization of renewable sources for biofuel production is gaining popularity due to growing greenhouse gas (GHG) emissions which causes global warming. There has been a great effort in exploring alternative feedstock for bioethanol production. In this context, the production of third-generation bioethanol from macroalgae has emerged as an alternative feedstock to food crop-based starch and lignocellulosic biomass. This is mainly due to the fast growth rate of macroalgae, no competition with agricultural land, high carbohydrate content and relatively simple processing steps compared to lignocellulosic biomass. This review paper provides an insight of recent innovative approaches for macroalgae bioethanol production, including conventional and advanced hydrolysis process to produce fermentable sugar, various fermentation technologies, economic analysis and life cycle assessment. With the current technology maturity, efficient utilization of macroalgae as sustainable source for bioethanol and other value-added chemicals production could be achieved in the near future.     

Selective removal of acetone and butan-1-ol from water with supported ionic liquid–polydimethylsiloxane membrane by pervaporation

The use of ionic liquid–polymer in supported ultrafiltration membrane in vacuum pervaporation has been verified. The ultrafiltration membranes were impregnated by two ionic liquids (1-ethenyl-3-ethyl-imidazolium hexafluorophosphate and tetrapropylammonium tetracyano-borate) and polydimethylsiloxane. These new and very stable supported ionic liquid–polymer membranes were used for separation of ternary mixtures butan-1-ol–acetone–water by vacuum pervaporation. In comparison with polydimethylsiloxane membranes, the average enrichment factor of butan-1-ol increased in both cases. This higher selectivity shows a good potential for improving pervaporation separation process.     

有机混合物的渗透蒸发分离

有机混合物渗透蒸发分离技术在技术发展很快,膜的种类繁多,和化学性质差别很大,本文首先总结了分离有机混合物渗透蒸发膜的详细分类 及膜对应的分离物系,不同膜的物理性能和分离效果比较,在后对膜的多种改性方法作了较合面的论述。     

Evaluation of sediments of the waste from beer fermentation broth for bioethanol production

As our previous studies showed, the waste from beer fermentation broth (WBFB) is a potential resource for bio-ethanol production. The original WBFB was superior to the supernatant in this regard. The current study investigates the potential of the WBFB sediment alone for bio-ethanol production after it has been diluted with distilled water or a chemically-defined medium. The effect of stock time on WBFB sediments for ethanol production was also studied. The fermentations were carried out using 50 ml vials placed in a bioreactor in static conditions. There was relatively little increase in ethanol production with fermentation time (up to 2 h) and stock time (up to 7 days) using 20% (v/v) sediment in distilled water which did not contain any nutrients or enzymes. A 2.09% increase in ethanol production was recorded after 2 h fermentation with 20% (v/v) WBFB sediments (1 day old) in a chemically-defined medium. The increase was 3.25% for WBFB sediments with a stock time of three days in a chemically-defined medium. The results also showed some residual activity of starch hydrolyzing enzymes in the sediments, especially at 60 °C. The overall results of this study revealed that the sediments alone were capable of bio-ethanol production even though they were five-fold diluted with distilled water or the chemically-defined medium.     

Process operation performance of PDMS membrane pervaporation coupled with fermentation for efficient bioethanol production

There would be strong product inhibition on ethanol fermentation process if ethanol is not removed in situ from broth. PDMS membrane pervaporation coupled with fermentation is a promising process for efficient bioethanol production since ethanol inhibition is relieved or eliminated. From the perspective of process operation, membrane separation performance, ethanol fermentation performance and the subsequent processing on membrane downstream are the three key issues. This review aims at contributing a comprehensive overview on the operation performance of the integrated process. The state-of-the-art of the three key issues related to the operation performance is focused. Finally, the tentative perspective on the possible future prospects of the integrated process is briefly presented.     

PDMS/ceramic composite membrane for pervaporation separation of acetone–butanol–ethanol (ABE) aqueous solutions and its application in intensification of ABE fermentation process

Pervaporation (PV) has attracted increasing attention because of its potential application in bio-butanol recovery from fermentation process. In this work, PDMS/ceramic composite membrane was employed for PV separation of acetone–butanol–ethanol (ABE) aqueous solutions. The influence of coupling effect on the molecular transport during the PV process was systematically investigated. The separation performance and transport phenomena of ABE molecules were discussed based on the analysis and calculation of physicochemical properties such as solubility parameter, polarity parameter, interaction parameter, activity coefficient. The results suggested that the ABE separation factor was mainly determined by the intrinsic solubility parameter and driving force. Coupling effect in the ABE multicomponent system was closely related to the interaction parameters between components themselves and between component and membrane. Also, the PDMS membrane was integrated with ABE fermentation to construct an efficient intensification process. It was found that the rate matching of fermentation and in situ removal could improve the ABE productivity by 2 times.     

Ceramic membrane synthesis based on alkali activated blast furnace slag for separation of water from ethanol

The main purpose of this research is synthesis of zeolite ceramic membranes based on alkali activated blast furnace slag for pervaporation separation of ethanol/water mixture (90 wt%). A new and simple method was applied to fabricate these ceramic membranes. In addition, gross waste of steel industry (blast furnace slag) was firstly used as the main starting material for making the membranes. In this study, for making the zeolite ceramic membranes, some experiments were conducted with water levels of 38, 40, 42 and 44 wt% of the blast furnace slag and NaOH levels of 4, 4.2, 4.4 and 4.6 wt% of the blast furnace slag. At first, for making the membranes, a primary geopolymer gel was prepared. Afterward the membranes were cast at 25 °C for 24 h. In order to form the zeolite layer, the membranes after geopolymerization process were kept at 90 °C for 24 h. The maximum value of selectivity (2579.48) was obtained for separation of water from ethanol using the synthesized membrane with 42 wt% water and 4 wt% NaOH.     

Fabrication of Aromatic Polyimide Membrane to Study the Pervaporative Separation of Phenanthrene/n-tetradecane Mixtures (Model Diesel) and Process Optimization Using Response Surface Methodology

To meet stringent fuel specifications, separation of aromatics from aliphatics is an everyday challenge for a refiner. In the present investigation, an aromatic polyimide membrane is fabricated and explored for the separation of a polyaromatic hydrocarbon (phenanthrene) from a model diesel composition (n-tetradecane) via pervaporation. The pervaporative membrane is prepared by casting a solution of polyamic acid, N,N-dimethylacetamide (DMAc), and phenanthrene using a simple and low-cost procedure. Scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), and swelling in feed solution of the synthesized membrane have been conducted for its characterization. The membrane allows preferential permeation of phenanthrene. The influence of different physico-chemical parameters, on permeation flux and enrichment factor for n-tetradecane/phenanthrene mixtures, has been studied. Statistical software Design Expert 7.1.4 is used to derive the regression equation, which describes the effect of time, downstream pressure, feed solute concentration, and operating temperature on the Pervaporation Separation Index (PSI). These factors are optimized using response surface methodology (RSM). The highest value of the PSI obtained is 0.623 kg m^?2 h^?1 and the corresponding optimized condition is: operating time is 11.58 h, the feed solute concentration is 162.96 ppm with a downstream pressure of 0.58 mm of Hg and an operating temperature of 449.03 K.     

An investigation of the catalytic abatement of emissions from the combustion of diesel/bioethanol blends

In this study, we investigated the activity of pre-sulfated 1%Pt–2%Sn/γ–Al₂O₃ on the catalytic abatement of the combustion emissions of three fuels: pure diesel E(0), pure bioethanol E(100) and bioethanol blended diesel containing 10% bioethanol E(10). The emissions generated, by each blend combustion, were conducted continuously to the catalyst sample. The catalytic activity was determined by following the evolution of the outflow emissions concentrations by FTIR gas spectroscopy as a function of the catalyst temperature. Results showed that the addition of bioethanol to diesel may be necessary to enhance the catalytic oxidation of diesel unburned hydrocarbons and particulate matter on pre-sulfated 1%Pt–2%Sn/γ–Al₂O₃.     

Production of bioethanol under high pressure of CO2: The effect of process conditions

The aim of this work is to investigate the possibility of producing ethanol by glucose fermentation under high pressure of carbon dioxide up to 48 bar, in order to exploit both ethanol and denser CO₂ as a by-product of the process. The fermentation is carried out using Ethanol Red™-Lesaffre Saccharomyces cerevisiae yeast strain, which is commonly applied in industrial bioethanol production.The experiments were performed in six small reactors (2 mL of volume each) connected in parallel, to investigate the effect of the process variables at the same conditions of temperature and pressure, and in one pilot reactor (1 L of volume) to confirm the results obtained at the lower scale.The influence of operative variables, such as carbon dioxide pressure (0–48 bar), temperature (32 and 36 °C), glucose (150–250 g/L), inositol (0–400 mg/L) and biomass concentration (OD 2 and 3.5), was measured in terms of ethanol concentration (by gas chromatography) and ethanol productivity (expressed as grams of ethanol per CFU of yeast). Both of these parameters were found to be strongly dependent on glucose concentration and CO₂ pressure, which negatively affects the fermentation. Nevertheless, also at 50 bar it is possible to produce appreciable amounts of ethanol.     

Recovery of 1-butanol from a model pharmaceutical aqueous waste by pervaporation

Pervaporation experiments were conducted to recover 1-butanol from model pharmaceutical aqueous waste using a surface modified poly(vinylidene difluoride) membrane. The surface modification of the membrane was made using silicone grease as an ultra-thin layer on the surface to improve the pervaporation performance of the membrane. The effect of operating variables such as feed composition, feed temperature and feed flow rate on permeation fluxes, separation factor and pervaporative separation index were studied in order to optimize the operating variables. The experimental results showed that surface modified poly(vinylidene difluoride) membrane was 1-butanol permselective, especially for low feed compositions. 1-Butanol separation factor of 6.4 and a total flux of have been obtained at a feed composition of 7.5 wt%, feed temperature of , feed flow rate of and permeate pressure of 50 mmHg. The total flux of the surface modified membrane increased with increasing the feed composition, feed temperature, feed flow rate of the mixture whereas the separation factor follows a reversed order except for flow rate. The influence of operating variables such as feed composition and temperature on partial flux and permeate composition was modelled based on Fick's first law to understand the process behaviour and it will be very useful for design purpose. These models will be used to predict the required membrane surface area for recovery of 1-butanol for the range of experimental feed compositions.     

Development of a Mixed-Matrix Membrane for Pervaporation

Abstract

In the production of pure alcohol, pervaporation is developing into an important technology. In this study, in order to improve the performance of the pervaporation process, a mixed-matrix polymer-zeolite membrane is developed. In the preparation of these membranes, cellulose acetate as base polymer, acetone or DMF as solvent, and 13X or 4A zeolites as fillers were used. To test the performance of homogeneous and mixed-matrix membranes, a laboratory-scale pervaporation setup was constructed. The effect of the following experimental parameters on the selectivity and flux were experimentally studied to determine the optimum values of operating conditions and to understand the separation mechanism in the indicated ranges: feed concentration, 70–90 wt%; feed temperature, 30–70°C; feed flow rate, 32–76 L/h. It was observed that the addition of zeolite to the membrane matrix improves the flux value twofold with respect to its homogeneous membranes with some loss in their selectivity. For example, for a feed concentration of 74 wt% EtOH at 50°C and 1 mmHg, the flux value for the unfilled membrane is 0.6 L/m²·h, and for a 30% zeolite-filled membrane, the flux is increased to 1.33. For these cases, the selectivities are 7.76 and 5.0 for the unfilled and filled membranes, respectively. TEM micrographs of the mixed-matrix membranes show a homogeneous distribution of zeolite particles which produce a cavelike porous structure in the matrix. The combined effect of this modified morphology and zeolite selectivity is the possible reason for the observed pervaporation performances of mixed-matrix membranes.     

用膜分离技术生产乙醇的探讨

发酵法制备燃料乙醇是一种相当传统的工艺,但由于原材料的问题,迟迟不能大范围的推广。由于世界能源危机的加剧,针对这个问题引发了诸多先进的生物技术,其中,膜分离技术的诸多优点,得到了及大的关注,而渗透汽化膜分离法具有节能的重要特点,使其成为了研究的重要方向。     

A characterization of pdms pervaporation membranes for the removal of trace organic from water

A new silicone pervaporation membrane for the removal of one of trace organies, 1,2-dichloroethane from water has been developed using polydimethylsiloxane (PDMS) and oligomeric silylstyrene as a crosslinking agent of PDMS. Optimal conditions for fabricating the best membrane were determined from swelling measurements ard pervaporation experiments and then the membrane was characterized at different membrane thickness and operating conditions. In the pervaporation separation of 55–70 ppm of l,2-dichlorocthanc aqueous mixtures, the developed membrane has flux of 2.5–330 g/(m².h) and selectivity of 230–1750 depending on membrane thickness, permeate pressure and operating Temperature. Water permeation through thin membrane was found to be subjected to significant desorption resistance, while the desorption resistance and thermodynamic factors as well as the concentration polarization of the organic at the boundary layer in feed can affect the organic permeation, depending on membrane thickness. Selectivity change with permcaic pressure depends on membrane thickness: at small membrane thickness range, selectivity increases with permeate pressure and at large thickness region it decreases. From the Arrhenius plots of each component fluxes, the permeation activation energies were determined. Through an analysis of the permeation activation energies of each components, the desorption resistance as well as the effects of the thermodynamic factors on permeation was qualitatively characterized.     

Comparison of bioethanol production of simultaneous saccharification & fermentation and separation hydrolysis & fermentation from cellulose-rich barley straw

Cellulose rich barley straw, which has a glucan content of 62.5%, followed by dilute acid pretreatment, was converted to bioethanol by simultaneous saccharification and fermentation (SSF). The optimum fractionation conditions for barley straw were an acid concentration of 1% (w/v), a reaction temperature of 158 °C and a reaction time of 15 min. The maximum saccharification of glucan in the fractionated barley straw was 70.8% in 72 h at 60 FPU/gglucan, while the maximum digestibility of the untreated straw was only 18.9%. With 6% content WIS (water insoluble solid) for the fractionated barley straw, 70.5 and 83.2% of the saccharification yield were in SHF and SSF (representing with glucose equivalent), respectively, and a final ethanol concentration of 18.46 g/L was obtained under the optimized SSF conditions: 34 °C with 15 FPU/g-glucan enzyme loading and 1 g dry yeast cells/L. The results demonstrate that the SSF process is more effective than SHF for bioethanol production by around 18%.     

Development of polybenzoxazine membranes for ethanol–water separation via pervaporation

Polybenzoxazine membranes have been successfully synthesized from bisphenol-A, formaldehyde, and three different types of diamines: hexa-methylenediamine (hda), tetraethylenepentamine (tepa), and tetraethylenetriamine (teta) via a facile “quasi-solventless” method. To study the possibility of using polybenzoxazine membranes in a pervaporation system for ethanol–water separation, the sorption and swelling behaviors of these membranes were investigated. When hda was used as a reactant, the resulting polybenzoxazine membranes showed the best service time and interestingly only water permeated the membranes under the studied operation conditions. The total permeation flux was found to be 1.52 kg/m²h and the separation factor was higher than 10,000. Additionally, an increased permeation flux was achieved by raising the temperature of the feed solution and decreasing the membrane thickness. The optimum conditions for this study were 70 °C for the feed mixtures when a 200 μm thick was used.     

Preparation of zeolite-coated pervaporation membranes for the integration of reaction and separation

Pervaporation is a promising option to enhance conversion of reversible condensation reactions, generating water as a by-product. In this work, composite catalytic membranes for pervaporation-assisted esterification processes are prepared. Catalytic zeolite H-USY layers have been deposited on silica membranes by dip-coating using TEOS and Ludox AS-40 as binder material. Membrane pre-treatment and the addition of binder to the dip-coat suspension appear to be crucial in the process. Tuning of catalytic layer thickness is possible by varying the number of dip-coat steps. This procedure avoids failure of the coating due to the high stresses, which can occur in thicker coatings during firing. In the pervaporation-assisted esterification reaction the H-USY coated catalytic pervaporation membrane was able to couple catalytic activity and water removal. The catalytic activity is comparable to the activity of the bulk zeolite catalyst. The collected permeate consists mainly of water and the loss of acid, alcohol and ester through the membrane is negligible. The performance of the membrane reactor is mainly limited by reaction kinetics and can be improved by using a more active catalyst.     

膜分离技术在长链二元酸发酵液分离中的应用

采用膜分离工艺代替传统的过滤工艺分离长链二元酸发酵液。发酵液经过陶瓷微滤膜、卷式超滤膜过滤后,除去菌丝体、蛋白质、色素及杂质,澄清透明的透析液直接进行酸化结晶,即可得到合格产品。使用膜分离工艺不仅可以简化操作、降低劳动强度,还可以提高产品质量和收率,降低生产成本。     

膜分离技术用于气体脱湿的研究现状

随着膜科学的发展,气体膜分离技术由于具有选择性高、能耗低、费用低、耐用性等优点,优于吸附等传统分离方法,广泛应用于石油、化工、电力、能源和环保等行业,该方法在气体除湿领域表现尤为突出,受到广泛关注。作者详细论述了气体膜分离技术的研究和发展现状,并介绍了分子模拟方法应用于该领域的研究。最后指出,随着膜材料及其制备工艺的发展和新型研究技术的应用与开发等,膜法脱湿将得到更大的发展。