Biofuels Production projects
Nanostructured Polymer Membranes for Alcohol Separation and Hydrolysate Detoxification
This project takes a systematic approach to designing membranes for selective separation of alcohols such as ethanol and butanol from aqueous mixtures. The membrane morphology is controlled by the well-established principles of block copolymer self-assembly. Examples of morphologies include alternating lamellae of A and B or cylinders of A in a B matrix. The size and geometry of the transporting channels are controlled by varying the molecular weight and composition of the copolymer. The project will enable the quantification of the effect of channel structure on selectivity and throughput.
Our goal has been to create a new class of pervaporation membranes for biofuel production by utilizing the ability of block copolymers to self-assemble into predictable morphologies. Pervaporation is used to detoxify hydrolysate, separate alcohol from fermentation broth, and separate furfural from acid-catalyzed sugar dehydration products. Surface modification is used to address the issue of biofouling. We developed a method for separation and recovery of acetic acid from water in production. Our ultimate goal is to enable continuous biofuel production. The project entails block copolymer synthesis and characterization, membrane fabrication, construction of separation modules, and integrating these modules with reactors for biofuel production.
Our goal is to create a new class of pervaporation membranes for biofuel production by utilizing the ability of block copolymers to self-assemble into predictable morphologies. Pervaporation will be used to detoxify hydrolysate, separate alcohol from fermentation broth, and separate furfural from acid-catalyzed sugar dehydration products. Surface modification will be used to address the issue of biofouling. Our ultimate goal is to enable continuous biofuel production. The project entails block copolymer synthesis and characterization, membrane fabrication, construction of separation modules, and integrating these modules with reactors for biofuel production. Our main accomplishments are: publication of our first peer-reviewed paper on pervaporation through poly(styrene-b-dimethylsiloxane-b-styrene) (SDS) membranes; synthesis of a new class of poly(ethylene-b-dimethylsiloxane-b-ethylene) (ED) membranes that show superior pervaporation characteristics relative to SDS membranes; and initiating experiments showing the efficacy of SDS membranes for hydrolysate purification and fermentation.
Pervaporation is a membrane separation process that is utilized to separate liquid mixtures through a membrane via a solution-diffusion mechanism. We utilized pervaporation as a method for the efficient isolation of biofuels. In our approach, block copolymer (BCP) membranes that were synthesized by a combination of anionic polymerization and silane coupling chemistries were studied. The resulting materials have polydimethylsiloxane (PDMS) volume fractions ranging from 0.59 to 0.83 and molecular weights 47.8 to 179.0 kg/mol according to NMR and GPC analysis. The ethanol concentration in the permeate reached ≈48 and ≈78% (wt/wt) for 8 and 45% aqueous ethanol feed. Likewise, the isobutanol concentration in the permeate reached ≈34 and ≈50 (wt/wt) for 1 and 2% aqueous isobutanol feed. The permeate flux was increased with increasing PDMS volume fraction up to 0.73 and then leveled off for all the aqueous alcohol mixtures studied in this work. Furthermore, biofuel production via the catalytic dehydration of sugars and the In-situ pervaporation and fermentation for continuous product removal were investigated with the PDMS-based membranes.
Balsara’s group synthesized a new set of block copolymers, polystyreneb- polydimethylsiloxane-b-polystyrene (SDS). They tested the separation performance of the SDS copolymers using aqueous solutions of ethanol, n-butanol, isobutanol, acetone and furfural. High separation factors and flux values were obtained for all the feed solutions. A mixture of organics did not diminish the efficient removal of organics from aqueous solvent mixture. Balsara’s group also demonstrated effective removal of toxins, especially furfural, from pre-treated biomass using SDS membranes. The SDS membranes did not deteriorate after ~40 days of continuous operation using a variety of feed solutions including hydrolysate at different temperatures (up to 96°C).
Balsara’s group synthesized and characterized nanostructured membranes comprising soft domains that selectively transport alcohol and rigid domains that provide the membrane with the mechanical properties necessary for withstanding stresses during operation. Membranes with larger domains were more efficient at separating alcohol and possessed better mechanical properties than those with smaller domains. Membranes with thicknesses of 50 mm were able to convert an 8-weight % aqueous ethanol feed stream into a 40-weight % ethanol stream. The ethanol flux after separation was 75 g/(m2h). When fermentation broth is used as the feed similar separation characteristics are obtained.
Balsara’s group has carried out a systematic approach to designing membranes for selectively separating alcohols from aqueous mixtures. Polystyrene domains in the membrane improve the mechanical properties necessary to withstand the stresses that occur during operation. Preliminary results show that membranes with cylindrical morphology with continuous structures as transport domains perform better than the membranes with transport domains of lamellar morphology in terms of alcohol permeation selectivity. This interplay between membrane transport and underlying membrane morphology provides a basis for creating optimal pervaporation membranes.
Published in 2014
Synthesis of Well-Defined Polyethylene-Polydimethylsiloxane-Polyethyelene Triblock Copolymers by Diimide-based Hydrogenation of Polybutadiene Blocks, N. Petzetakis, G. M. Stone, N. P. Balsara, Macromolecules, V. 47, pp. 4151, June 19, 2014.
Fermentation of hydrolysate detoxified by pervaporation through block copolymer membranes, Greer DR, Basso TP, Ibanez AB, Green Chem, 16(9):4206, doi:10.1039/C4GC00756E. 2014.
Published in 2013
Relationship Between Segregation Strength and Permeability of Ethanol/Water Mixtures Through Block Copolymer Membranes, A. E. Ozcam, N. Petzetakis, S. Silverman, A. Jha, N. P. Balsara, Macromolecules 46(24), pp. 9652-9658, doi: 10.1021/ma401957s, Dec. 2, 2013.
Published in 2012
Master Curve Captures the Effect of Domain Morphology on Ethanol Pervaporation Through Block Copolymer Membranes, Ashish Jha, So Ling Tsang, Ali Evren Ozcam, Richard Offeman, Nitash Balsara, Journal of Membrane Science, http://dx.doi.org/10.1016/j.memsci.2012.01.037, February 6, 2012.
Published in 2011
Effect of Nanoscale Morphology on Selective Ethanol Transport Through Block Copolymer Membranes, Ashish Jha, Liang Chen, Richard Offeman, Nitash Balsara, Journal of Membrane Science, doi:10.1016/j.memsci.2011.02.043, March 4, 2011.