Recovery Of Bioalcohols Research Articles

A perspective on downstream processing performance for recovery of bioalcohols

A perspective on downstream processing performance for recovery of bioalcohols

Graphdiyne-based integrated membrane for enhanced alcohol-permselective pervaporation

Exploring nano-engineered polymeric membrane with a customized architecture is urgent for the advance of alcoholophilic pervaporation. Graphdiyne (GDY) is a promising candidate material for constructing alcohol-permselective membranes due to its unique alkyne-rich framework in terms of well-organized porous system and strong hydrophobicity. Herein, we report a GDY-based integrated membrane composed of a loosened hydrogen-substituted GDY (HsGDY)-polydimethylsiloxane (PDMS) mixed-matrix layer on a polysulfone ultrafiltration support and a moderate pore-filling PDMS crosslinking layer. The procedure for fabricating such an integrated bilayer membrane was implemented by a simple vacuum-assisted filtration followed a dip-coating post-treatment. The resultant HsGDY-based integrated membrane shows a separation factor of 12.8 together with a total flux of 1535.7 g m−2 h−1 in the separation of a 5.0 wt% ethanol-water solution. The overall performance is also competitive among the reported ethanol-permeselective membranes, benefiting from the synergy of alcohol adsorption-preferential permeation processes by the HsGDY-based integrated bilayers. A continuous and long-term pervaporation test indicates the robust operating stability. An enhanced separation performance for other alcohols (C1–C4) suggests the great potential of HsGDY-based integrated membranes for in situ recovery of bioalcohols.

Energy-Saving and Sustainable Separation of Bioalcohols by Adsorption on Bone Char

The separation of ethanol, propanol, and butanol from aqueous solutions was studied using adsorption on bone char. Adsorption kinetics and thermodynamic parameters of this separation method were studied at different conditions of pH and temperature. Results showed that the maximum adsorption capacities of these bioalcohols were obtained at pH 6 and 20°C. An exothermic separation was identified, which can be mainly associated to hydrophobic interactions between bone char surface and bioalcohols. Binary adsorption studies were also performed using mixtures of these bioalcohols. An antagonistic adsorption was observed for all bioalcohols where the ethanol and propanol separation was significantly affected by butanol. A model based on an artificial neural network was proposed to correlate both single and binary adsorption isotherms of these bioalcohols with bone char. It was concluded that the bone char could be an interesting adsorbent for the sustainable separation and recovery of bioalcohols from fermentation broths, which are actually considered emerging liquid biofuels and relevant industrial chemicals.

Tuned Fabrication of the Aligned and Opened CNT Membrane with Exceptionally High Permeability and Selectivity for Bioalcohol Recovery.

Synthetic membranes usually suffer from a ubiquitous trade-off between permeability and selectivity. Carbon nanotube (CNT)-based hybrid materials have shown attractive properties in high-performance membrane preparation; however, the aggregation of random CNTs in polymer remains a great challenge. Herein, the aligned and open-ended CNT/(polydimethylsiloxane) PDMS membranes are controllably fabricated to form a hamburger-like structure that possesses nanochannels (∼10 nm) in the intermediate layer as well as angstrom cavities in the embedded PDMS. These aligned CNT membranes surpass the filling content limitation of the nonaligned CNT/PDMS membrane (37.4 wt % versus ∼10 wt %), leading to excellent mechanical properties and a multiplying performance increase of mass flux and selectivity for the separation of alcohols. The membranes break the permeability-selectivity trade-off with both parameters remarkably increasing (maximum 9 times) for bioalcohol separation. The established pervaporative-ultrafiltration mechanism indicates that the penetrant molecules preferentially pass through CNT internal nanochannels with increasing membrane permeability, thereby paving a way to nanoscale design of highly efficient channeled membranes for separation application.

Applying the wave theory to fixed-bed dynamics of Metal-Organic Frameworks exhibiting stepped adsorption isotherms: Water/ethanol separation on ZIF-8

Zeolitic Imidazolate Framework-8 (ZIF-8) is a promising material for the energy-efficient recovery of bio-alcohols from aqueous mixtures. Its adsorption isotherms have inflection points and breakthrough curves obtained in dynamic column separation experiments exhibit stepped profiles. With the aim to optimize this adsorptive alcohol recovery process using ZIF-8, the correlation between the shape of the adsorption isotherms and the breakthrough curves was further explored in this work by means of liquid phase batch measurements and breakthrough experiments, with diluted ethanol/water mixtures. The shape of the concentration profiles, in adsorption mode as well in desorption mode, have been carefully analyzed making use of simple theoretical tools, including an axial dispersion model and a wave theory based approach. It was shown that, as a direct expression of the adsorption isotherm and the feed concentration, the concentration profiles were composed of different “shock waves” and “dispersive waves” propagating at different velocities along the column length. The description of the breakthrough and desorption curves in terms of propagation velocities enabled to gain insights into the fundamental role of the adsorption isotherm into the characteristics and the formation of the concentration profiles. The concept of “fractional used bed capacity” (FUBC) was introduced to illustrate the effect of the adsorption isotherm shape on the dynamic capacity at breakthrough point. According to the shape of the adsorption isotherm, efficient desorption could be achieved with the ZIF-8 material. This work provides, with limited computational effort, new perspectives for the further development and optimization of adsorptive separation processes with MOF materials, such as the recovery of bio-alcohols from aqueous mixtures with the ZIF-8 adsorbent.

Vapor-phase membrane concentration of bioethanol and biobutanol using hydrophobic membranes based on glassy polymers

Pervaporation and vapor-phase membrane separation methods for the recovery of bioalcohols from dilute aqueous solutions have been critically compared. The importance of taking into account the liquid–vapor equilibrium diagram in studies on the separation of binary aqueous–alcoholic liquid media by these methods has been shown. Previously published experimental data on the transport of water, ethanol, and n-butanol vapors in hydrophobic membranes based on the glassy polymers poly(vinyltrimethylsilane) (PVTMS), poly(1-trimethylsilyl-1-propyne) (PTMSP), and poly(4-methyl-1-pentyne) (PMP) have been analyzed. Schemes of butanol and ethanol recovery by the vapor-phase membrane separation process from fermentation broths for the cases of application of water-selective and alcohol-selective membranes have been presented, as well as the results of mathematical simulation of the process and assessment of energy consumption.

Preparation of MFI zeolite membranes on coarse macropore stainless steel hollow fibers for the recovery of bioalcohols

Hydrophobic MFI zeolite membranes are considered suitable for the recovery of bioalcohols (bioethanol and biobutanol) from fermentation broths.

A superhydrophobic zeolitic imidazolate framework (ZIF-90) with high steam stability for efficient recovery of bioalcohols.

A superhydrophobic zeolitic imidazolate framework (ZIF-90) with high steam stability is prepared through post-functionalization via an amine condensation reaction. The developed superhydrophobic ZIF-90 is highly promising as an effective and reusable adsorbent for bio-alcohol recovery.

ZIF-71 as a potential filler to prepare pervaporation membranes for bio-alcohol recovery

Metal–organic frameworks (MOFs) are an emerging class of materials for potential use in separation. ZIF-71 has super-hydrophobic pore channels and a very flexible pore architecture, which make ZIF-71 a potential candidate for recovering bio-alcohols from fermentation broths. In the present study, mixed matrix membranes (MMMs) based on PDMS and ZIF-71 were prepared for separation of alcohols (methanol, ethanol, isopropanol (IPA) or sec-butanol) from aqueous solutions. Experimental results reveal that the pervaporation performance of the PDMS membrane was improved in both flux and separation factors upon embedment of ZIF-71. The pervaporation separation factors for alcohols of ZIF-71 filled the PDMS membrane (PDMS : ZIF-71 = 10 : 2) nearly double compared to those of unfilled PDMS membranes, suggesting that ZIF-71 is an excellent filler to prepare organophilic pervaporation membranes for bio-alcohol recovery.

Simultaneous Spray Self‐Assembly of Highly Loaded ZIF‐8–PDMS Nanohybrid Membranes Exhibiting Exceptionally High Biobutanol‐Permselective Pervaporation

The ability to obtain a maximum loading of inorganic nanoparticles while maintaining uniform dispersion in the polymer is the key to the fabrication of mixed-matrix membranes with high pervaporation performance in bioalcohol recovery from aqueous solution. Herein, we report the simultaneous spray self-assembly of a zeolitic imidazolate framework (ZIF)-polymer suspension and a cross-linker/catalyst solution as a method for the fabrication of a well-dispersed ZIF-8-PDMS nanohybrid membrane with an extremely high loading. The ZIF-8-PDMS membrane showed excellent biobutanol-permselective pervaporation performance. When the ZIF-8 loading was increased to 40 wt%, the total flux and separation factor could reach 4846.2 g m(-2) h(-1) and 81.6, respectively, in the recovery of n-butanol from 1.0 wt% aqueous solution (80 °C). This new method is expected to have serious implications for the preparation of defect-free mixed-matrix membranes for many applications.

Simultaneous Spray Self‐Assembly of Highly Loaded ZIF‐8–PDMS Nanohybrid Membranes Exhibiting Exceptionally High Biobutanol‐Permselective Pervaporation

AbstractThe ability to obtain a maximum loading of inorganic nanoparticles while maintaining uniform dispersion in the polymer is the key to the fabrication of mixed‐matrix membranes with high pervaporation performance in bioalcohol recovery from aqueous solution. Herein, we report the simultaneous spray self‐assembly of a zeolitic imidazolate framework (ZIF)–polymer suspension and a cross‐linker/catalyst solution as a method for the fabrication of a well‐dispersed ZIF‐8–PDMS nanohybrid membrane with an extremely high loading. The ZIF‐8–PDMS membrane showed excellent biobutanol‐permselective pervaporation performance. When the ZIF‐8 loading was increased to 40 wt %, the total flux and separation factor could reach 4846.2 g m−2 h−1 and 81.6, respectively, in the recovery of n‐butanol from 1.0 wt % aqueous solution (80 °C). This new method is expected to have serious implications for the preparation of defect‐free mixed‐matrix membranes for many applications.

Polydopamine-based superhydrophobic membranes for biofuel recovery

The development of renewable energy sources like biofuels has emerged as a promising road to resolve future energy supplies. Fermentation is a common process for producing biofuels from biomass, and the biofuels have to be extracted and concentrated from the fermentation broth before they can be used. In comparison with conventional separation methods such as distillation and adsorption, membrane-based separation has been considered to be the most promising alternative because of its low energy consumption, ease of operation, and cost effectiveness. Hydrophobic polymeric membranes and inorganic membranes have been developed for recovery of bioalcohols from diluted fermentation broths via pervaporation. However, the separation performances of the previously reported hydrophobic membranes are usually unsatisfactory for the recovery of bioalcohols. It is desired to develop a novel hydrophobic membrane for efficient recovery of bioalcohols. Inspired by the adhesive ability of dopamine and the hierarchical structure of a lotus leaf, superhydrophobic membranes are developed to concentrate bioalcohols. The superhydrophobic membranes with a water contact angle of about 172.0° show a promising application for the recovery of bioalcohols from dilute aqueous solutions due to the superhydrophobicity and 0.2 μm thickness of the membrane, which offers a high potential application for in situ recovery of bioalcohols.

Alcohol and water adsorption in zeolitic imidazolate frameworks

Alcohol (methanol, ethanol, 1-propanol, 2-propanol and 1-butanol) and water vapor adsorption in zeolitic imidazolate frameworks (ZIF-8, ZIF-71 and ZIF-90) with similar crystal sizes was systematically studied. The feasibility of applying these ZIF materials to the recovery of bio-alcohols is evaluated by estimating the vapor-phase alcohol-water sorption selectivity.

An Organophilic Pervaporation Membrane Derived from Metal–Organic Framework Nanoparticles for Efficient Recovery of Bio‐Alcohols

On the road to recovery: The dynamic apertures and superhydrophobic surfaces of the metal–organic framework ZIF-8 result in its extraordinary ability to selectively adsorb alcohols. When incorporated into a polymer matrix, the ZIF-8 nanoparticles provide preferential pathways for the permeation of organic compounds and allow the efficient pervaporative recovery of bio-alcohols from fermentation broths (see picture).

Rapid thermal processing and separation performance of columnar MFI membranes on porous stainless steel tubes

Continuous MFI-type zeolite membranes were fabricated on porous stainless steel tube supports by secondary (seeded) growth. The physical attachment of zeolite seed particles was initiated through sonication assistance on unmodified supports. Despite a sparse seed layer, a single hydrothermal growth step reliably led to c-/h0h-out-of-plane-oriented pure-silica MFI membranes. Rapid thermal processing was applied to as-synthesized membranes, extending the findings of a previous report on controlling the density of grain boundary defects. The RTP-treated membranes showed an improved separation factor of 29 for p-/o-xylene with a maximum p-xylene permeance of 6.6 × 10−8 mol m−2 s−1Pa−1, while conventionally (slowly) calcined counterparts had a maximum separation factor and p-xylene permeance of 3–4 and 2.7–4.5 × 10−8 mol m−2 s−1Pa−1, respectively. The membranes also showed insensitivity to temperature for n-/i-butane separation performance (separation factor ca. 15 and n-butane permeance ca. 1.3 × 10−7 mol m−2 s−1Pa−1), while conventionally calcined ones exhibited a significant decrease in the separation factor with temperature. Pervaporation measurements from a dilute aqueous feed that exploited the hydrophobicity of RTP-treated membranes revealed their potential use in bioalcohol recovery processes from fermentation broths, specifically for ethanol (total flux and separation factor of 1.2 kg m−2 h−1 and 43, respectively) and n-butanol (total flux and separation factor of 0.11 kg m−2 h−1 and 21, respectively) extraction from the aqueous phase.