In situ product recovery of butanol from the acetone butanol ethanol fermentation

EngD ThesisFrom 1916 the “acetone butanol ethanol”, or “ABE”, fermentation process was the main production method for n-butanol. It was superseded in the 1950s by a more economical petrochemical process, causing the majority of plants to cease operation. In the fermentation, product inhibition led to low productivity and high energy demand in the downstream processing, making the process unable to compete with the petrochemical route. Overcoming these problems could revive the ABE industry and promote a bio-based economy. In situ product recovery (ISPR) can be applied to the fermentation process to counteract the effects of product toxicity. Productivity increases of greater than 300% are theoretically possible. Many ISPR techniques have been applied to the ABE process at laboratory scale, but a direct comparison of the different techniques has been hindered by experimental inconsistencies. Here, a techno-economic analysis was performed to compare the most developed ISPR techniques, with process simulations providing comparative data on the separation efficiency and energy demand. All the techniques were found to be economically viable, with profit increases compared to an equivalent batch plant of 110-175% and payback times of 2.2-4.5 years. In addition to generating the most profit and having the shortest payback time, perstraction was the only technique to lead to a reduction in overall plant energy demand, by ~5%, compared to a traditional ABE process. Thus perstraction warrants further investigation for application to the ABE process. Perstraction is significantly underdeveloped compared to other ISPR techniques. It was originally designed to overcome various problems associated with liquid-liquid extractions, including solvent toxicity. Here, experiments focused on the use of high-distribution toxic extractants with commercially available membranes. Results showed that high-distribution toxic extractants (1-pentanol, 1-hexanol, 1-heptanol, 1-octanol and 2-ethyl-1-hexanol) have a larger mass transfer coefficient than oleyl alcohol (the main non-toxic extractant), although chemical structure differences, such as branching, can have a greater impact on mass transfer than distribution coefficient. Unfortunately, all extractants investigated here were transferred across the membrane to some extent, which would limit perstraction to non-toxic extractants. However, differences in membrane type have a greater impact on mass transfer than the choice of extractant. Porous membranes have a mass transfer coefficient 10 times greater than non-porous membranes, which would see a factor of 10 reduction in ii membrane size and cost. Overall, this work has confirmed that perstraction is technically viable and compared options for process improvements through membrane and extractant selection.EPSRC and Green Biologic

Isobaric Vapor Liquid Equilibrium Determination for 1,3,5-Trimethylbenzene + Ethanol and 1,3,5-Trimethylbenzene + n-Butanol Binary Systems

The vapor-liquid equilibrium data are necessary for the design of the distillation columns which separate the mixture mesitylene – ABE components resulting from the liquid-liquid extraction of butanol from the ABE using 1,3,5-trimethylbenzene as solvent. In this work, the vapor - liquid equilibrium data is determined for the binary systems: ethanol + 1,3,5-trimethylbenzene and n-butanol + 1,3,5-trimethylbenzene at constant pressure of 93.325 KPa using a double phase circulation apparatus. Thus, P-T-x-y data is determined, which is further processed by regression to determine the binary interaction parameters of the NRTL and UNIQUAC models. Furthermore, the T-x-y diagrams are calculated using the completed thermodynamic models (NRTL and UNIQUAC) and the UNIFAC predictive model, and compared with the experimental diagrams

Economic recovery of biobutanol-a platform chemical for the sugarcane biorefinery.

Master of Science in Chemical Engineering. University of KwaZulu-Natal. Durban, 2017.In recent years, the South African sugar industry has faced challenges, such as drought, low prices and labour issues that have impacted negatively on the perceived sustainability. The adoption of the sugarcane biorefinery concept by the sugar industry is a possible solution to improving the sustainability of the industry amid these challenges. In this envisioned biorefinery, multiple products are created within an integrated system that maximises sustainability, as opposed to relying on producing one or very few products. In this study, the potential economic viability of the recovery of biobutanol was explored with the ultimate intention of using this biobutanol as a platform chemical for the production of higher value products to include in the biorefinery’s product portfolio. Biobutanol is produced from biomass via the ABE (acetone, butanol, and ethanol) fermentation process. Biobutanol production is characterised by very low butanol concentrations in the fermentation broth (around 2 wt. %) due to high inhibition, resulting in a very high cost of recovery (distillation) and the need for several downstream purification steps. Following a literature search on technologies that have been proposed and previously implemented for biobutanol production, processes integrating gas stripping and extraction were simulated on Aspen Plus® and techno economic analyses performed to determine the profitability based on cash flows over a 25 year period. Gas stripping and liquid-liquid extraction experiments were first carried out in order to have a way of validating simulation results. Gas stripping experiments created scenario-based results of the expected butanol concentration in the gas phase once a steady state butanol concentration can be maintained in the fermenter. The extraction experiments were conducted to establish a quick way of evaluating the extractive properties of a solvent based on the distribution coefficients and selectivities with respect to butanol. Five solvents were evaluated including hexyl acetate and diethyl carbonate, which have not been reported on but have been previously applied in biomass processing. Distribution coefficients of 3.57 and 6.15 and selectivities of 367.09 and 396.00, with respect to butanol, were obtained for hexyl acetate and diethyl carbonate, respectively. Four processes were then simulated on Aspen Plus® and they all assumed a fermentation process that make use of 281.67 t/h clear juice from a South African generic sugar mill iv model. A study estimate type economic evaluation, accurate within ±30% error, was performed with profitability being assessed in terms of the Net Present Value (NPV) and the Internal Rate of Return (IRR) over the 25 year period. Process Scheme 1 was the benchmarking case and consists of the conventional series of five distillation columns. For this process a Total Capital Investment (TCI) of US$124.85 million was obtained and based on the sales and production costs a negative NPV of US$3.80 million was obtained. This indicates a non-viable process under the current economic conditions. Process Scheme 2 included in situ recovery by gas stripping and final purification using distillation. Five distillation columns were still required to purify the condensate from the stripper due to a large amount of water that is carried in. The increased productivity in the fermenter and the reduction the downstream column sizes in this process, compared to the benchmarking case, resulted in a reduced capital cost of US$67.43 million. This recovery process also yielded a potential to be profitable with a positive NPV of US$505.88 million and an IRR of 31%. This was attributed to the reduced TCI as well as the ability of the process to yield all the three ABE solvents to sellable purities. Process Scheme 3 that included gas stripping and liquid-liquid extraction had almost the same TCI as Process Scheme 2 (US$68.94 million) but could only yield butanol to sellable quality due to the selective property of the solvent used (2-ethyl-hexanol). This reduction in sales led to an IRR of 6NPV of US$82.38 million resulted. Process Scheme 4, making use of a two-stage gas stripping and distillation, was the most profitable process and it was concluded it would be the process to attach to the sugar mill model and also to be considered for the higher value chemical production. An NPV of US$524.09 and an IRR of 32% were realised for this process. Sensitivity analyses on these four processes showed that the cost of the substrate (clear juice) and the butanol selling price have the major effects on the profitability. It was, therefore, recommended that other streams from the sugar mill be considered as substrates for higher value chemical products which can attract higher prices than butanol which is regulated by the petro based butanol. Finally, a structure of a functionalised ionic liquid was suggested based on group contribution methods to be a potential reactive extraction reactant for converting butanol to a higher value ester product

The Production of Biobutanol from Biomass Via a Hybrid Biological/Chemical Process

Biobutanol use as a fuel began in the late 19th century. Problems remain in economic viability. A review of the state of the art and need for technical advances is presented. The technical potential of producing biofuel from a naturally occurring macroalgae was studied. The algae grow in Jamaica Bay, New York City, in contaminated water. The process consisted of mechanical harvesting, drying, grinding, and acid hydrolysis to form an algal sugar solution. Clostridium beijerinckii and C. saccharoperbutylacetonicum were used in an acetone butanol ethanol (ABE) fermentation to make butanol. Fermentation was followed by distillation Butanol concentrations during fermentation reached 4 g/L. The recovery of reducing sugars in the media was 0.29 g butanol/g sugar. Feedstock with greater than 7 g/L butyric acid caused death of the butanol-producing bacteria. The kinetics of the production of 1-octadecanol from octadecanoic acid was investigated in a liquid-phase trickle-bed reactor by hydrogenation. The primary reactions occurring in the reactor were the desired conversion of octadecanoic acid to 1-octadecanol and the subsequent undesired conversion of 1-octadecanol to octadecane. A series-parallel kinetics model first order in acid and zero order in hydrogen was developed to predict these two reactions. The activation energies of the reactions were 63.7.8 and 45.6 kJ/mole, respectively. The conversion of octadecanoic acid and the selectivity to the desired product as functions of temperature, space velocity, and inlet octadecanoic acid concentration were then estimated. The model predicts maximum productivity of 1-octadecanol at higher temperatures and short residence times. Parametric plots show productivity to be ≥0.48 g 1-octadecanol/g octadecanoic acid at 566 oF and a 0.1 h residence time. The model from the 1-octadecanoic acid study was fitted to several sets of data for the hydrogenation of butyric acid to butanol in the temperature regime of 300-400 oF and pressures of 700-1000 psig. The model failed to accurately predict the final concentrations of 1-butanol and butane. Reasons for this are suggested and future work to fix this problem is presented and discussed

Simulation and heat integration of downstream processing of aqueous Acetone-Butanol-Ethanol solutions

Acetone-Butanol-Ethanol (ABE) fermentation is a process which converts carbohydrates to acetone, butanol and ethanol in anaerobic conditions. In the industry, this process started to become popular in the early 20th century but with the start of the petrochemical industry it almost disappeared, since this new route provided larger quantities of butanol for less cost and also less consumption of energy. Nowadays, the increase in the price of petroleum and its future extinction, as well as the damage to the environment due to fossil fuels, is putting in the main spot of interest this route and a lot of research is being done to get it economically viable. Literature provides relevant information about the most common sequences, based on boiling point and ending with an azeotropic distillation. This one consists of two columns connected through a decanter and it is useful because of the heterogeneous azeotrope that can be found in the vapour-liquid equilibria of n-butanol and water. Moreover, some other efforts are put in improving different sequences. Last reports are investigating and providing the first results about the use of some alternative methods for removing directly the prOutgoin

Lignocellulosic Biomass – A Sustainable Feedstock for Acetone-Butanol-Ethanol Fermentation

Biobutanol has been identified as a promising future biofuel. However, generally the extraction and separation of biobutanol from the fermentation mixture is a costly process. Therefore, the idea of using acetone-butanol-ethanol (ABE) mixture directly as biofuel were proposed to eliminate the recovery process. ABE has been identified as a promising future biofuel. The feedstocks play an important role in the feasibility of ABE as a fuel. Lignocellulosic biomass is seen as a promising feedstock for the production of biofuels. Thus, in this review, ABE biofuel is been summarized from three aspects namely (i) selection of feedstocks, (ii) microbial selection and (iii) hydrolysis, fermentation, and purification techniques. Anaerobic fermentation together with commonly employed recovery processes are discussed in the second part of this review. This review concludes with different challenges and future research in ABE fermentation that can pave the way for future commercialization of this promising biofuel

Co-substrate Fermentation of Jerusalem Artichoke Tubers and Crude Glycerol to Butanol with Integrated Product Recovery

Butanol has long been considered a potential advanced liquid biofuel, in addition to its current application as an industrial solvent. It can be produced biologically; however, the conventional ABE fermentation suffers from many limitations, including low butanol titer, high cost of traditional raw materials, end-product inhibition and high butanol recovery costs. Possible solutions are the use of renewable low-cost feedstocks, genetic manipulations of Clostridia spp. to improve the strains’ butanol titer and tolerance, advanced fermentation techniques, and in-situ product recovery technologies. In order to overcome some of these limitations, the overall goal of this thesis was to develop a process to produce butanol via fermentation using low-cost feedstocks and integrated product recovery. Jerusalem artichoke tubers and biodiesel-derived glycerol were investigated as potential feedstocks for fermentative butanol production. Pervaporation was evaluated as an online butanol recovery technique and was integrated into the butanol fermentation process. In the first phase of this research the suitability of Jerusalem artichoke tubers as a renewable feedstock for butanol production was studied and statistical experimental design was used to optimize enzymatic and acid hydrolysis of the feedstock. Both enzymatic and sulfuric acid hydrolysate of Jerusalem artichoke tubers were fermented via solventogenic Clostridia to acetone- butanol- ethanol (ABE). An overall ABE productivity of 0.25 g L-1 hr-1 was obtained from both hydrolysates, indicating the suitability of this feedstock for fermentative butanol production. In the second phase, the feasibility of butanol production from biodiesel-derived glycerol was investigated. The initial fermentation conditions for butanol production from glycerol were optimized via a central composite design. In the next phase, Jerusalem artichoke hydrolysate and crude glycerol were used as co-substrate for enhanced butanol production. A co-substrate system was characterized and optimized. The optimized conditions were then used for an integrated fed-batch fermentation including pervaporation for in situ butanol recovery. The integrated process achieved a butanol productivity of 0.6 gL-1 hr-1

Solvent-based approaches to evaluate the ABE extractive fermentation

The reindustrialization of ABE fermentation is hampered by significant production costs, linked to high product inhibition and limited intrinsic yield. The reduction of these costs depends on the effective application of integrated toxic product removal techniques. The evaluation of ABE extractive fermentation with solvents of different nature in terms of extraction capacity or biocompatibility is the main objective of this thesis. Attention is focused on the assessment of the solvent influence, not only on the physical effects but also on the metabolism and microbial population dynamics evolution. A mathematical model based on the evolution of the heterogeneous culture inside the bioreactor was proposed and validated ABE extractive fermentation is techno and economically evaluated on a solvent-based comparative basis. The integration of this process within a LCB biorefinery using a 2G type substrate is also considered