Pérez, Alan
E-Mail-Adresse
Geburtsdatum
Suchergebnisse
Influence of pulping conditions on the pulp yield and fiber properties for pulping of spruce chips by deep eutectic solvent
The chemical pulping of wood chips using deep eutectic solvents (DES-pulping) has emerged as an alternative technology to conventional pulping in the paper industry, allowing the production of pulp in combination with the recovery of lignin and sugars for valorization. A challenge in the development of this technology is the understanding of how the operating conditions influence the crucial pulp manufacturing parameters such as delignification percentage, pulp yield, and fiber quality. This work is focused on investigating the effect of operating conditions such as cooking temperature, cooking time, liquor-to-wood ratio, initial water content on DES, type of mixing, the addition of a pre-treatment step (pre-impregnation of DES into the wood chips) to cooking process, and DES composition (lactic acid:choline chloride, lactic acid:sodium chloride, and lactic acid:sodium bromide) on the cooking of wood chips by DES. A shortcut quality evaluation parameter (Q), defined as the product of the fiber length and the degree of delignification quantified the quality of the pulping process in a single value, shows values similar to a reference unbleached kraft pulp for cooking at 130 °C in a range of cooking times from 3 to 4.5 h at a L/W of 10:1 by using lactic acid:choline chloride DES. More elaborate property analysis on the fibers showed that several of the the quality-indicating properties of the fibers (coarseness, shape factor, fibril area, and crill index) are comparable with typical sulfite pulping fibers.
Continuous in situ lactic acid extraction from sweet whey fermentation broth using a tubular membrane contactor
Background Whey, as the major dairy by-product, has become a severe problem for the dairy industry because its demand has decreased, while its production has increased in the past years. Since the high demand for dairy products tends to further increase, suitable routes for whey valorization are required. Whey contains valuables like lactate, but due its composition matrix, processing is challenging. The high sugar content in whey makes it a potential feedstock to produce lactic acid (LA) via microbial fermentation. Still, the known drawbacks of biotechnological LA production, such as growth inhibition by the product, the use of neutralizers, low productivity, and high overall costs of the process must be overcome. In situ LA recovering using a suitable separation technology is a potential strategy to overcome the mentioned drawbacks. In this work, the in situ LA extraction from a whey fermentation broth was evaluated. Sweet whey was used as feedstock for lactic acid production via microbial fermentation, while LA was recovered by reactive liquid-liquid extraction using a tubular membrane contactor. Method The feed material used in this work is a fermentation broth from sweet whey, which was filtered prior to extraction experiments using microfiltration. In a first series of experiments, two-phase extraction experiments were conducted in temperature controlled separation funnels, to investigate different solvent phase combinations for the lactic acid extraction. Special attention was paid to replace commonly applied fossil-based solvents with green alternatives, such as deep eutectic solvents (DES). After extraction, the extract was treated in a back-extraction step to recover LA from the solvent phase. Here, an anti-solvent, e.g. heptane or p-cymene, was used to transfer LA to the receiving phase, which was water. Afterwards the performance of reactive liquid-liquid extraction of LA using a PTFE membrane contactor was evaluated by using two potential solvent phases, namely tri-n-octyl amine (TOA) with n-decanol and a DES formed from thymol and menthol. From the experimental results the overall mass transfer coefficient was calculated based on a rigorous mass transfer model to predict the LA concentration in both phases. Finally, performance of the in situ LA recovery from sweet whey by using membrane contactor was investigated from both, experimentally and theoretically points of view. Results & Conclusion In the two-phase extraction experiments, the reactive extractants Aliquat336, TOA, trioctylphosphinoxid (TOPO), and the mixture Aliquat336/TOA were found to be most efficient with the diluents 1-decanol, limonene, and a deep eutectic solvent consisting of thymol and menthol. Especially, the DES and limonene are promising as they can be produced from renewable resources. With respect to back-extraction, heptane and p-cymene showed the highest efficiencies for transferring lactic acid into the receiving phase water. In the next step, the selected solvents were used to perform LA recovery in the tubular membrane contactor from a model aqueous solution of LA and a fermentation broth of sweet whey. The proposed technology for valorizing dairy waste through LA biotechnological production shows the feasibility to scaling it up.
Modeling of a liquid membrane in Taylor flow integrated with lactic acid fermentation
The application of a liquid membrane in Taylor flow (LMTF) is a promising method that can be integrated with other separation or reactive processes in view of process intensification. In this work, a model for a hybrid LMTF – fermentation system was developed for lactic acid production using batch fermentation and LMTF experimental data. The hybrid model is compared to experimental data of the hybrid system. Through a sensitivity analysis of the main variables of the LMTF an optimum value of the overall volumetric mass transfer coefficient (0.0122 1/s) was achieved for lactic acid removal. This was further used for modeling the hybrid system. The fermentation time of the hybrid system is reduced by 7 h, the productivity and biomass concentration is increased by 2.578 g/(L·h) and 2.7016 g/L, respectively, as compared with a batch fermentation. In addition, the effect of the number of channels of the LMTF is modeled and its impact on productivity, fermentation time, and final biomass concentration is analyzed. It was concluded that lactic acid removal through the LMTF from the fermentation broth is an alternative to control the pH within fermenter.
Liquid–liquid equilibria of lactic acid/water solutions in tri-iso-octylamine/dodecane/1-dodecanol at 306.1, 310.1, and 316.1 K. Experimental data and prediction
The liquid–liquid equilibria of systems that involves lactic acid in the aqueous phase and tri-iso-octylamine with diluents as dodecane and 1-dodecanol (active or/and inert) were measured experimentally at three temperatures (306.15, 310.15, and 316.15 K). A previous liquid–liquid equilibrium model that is based on Nernst’s distribution law and mass action law equilibrium equations was extended and generalized for stoichiometric ratios (amine/acid) 1:n. The effect of the diluents and the tertiary amine on the liquid–liquid equilibrium is shown and quantified in terms of the predicted values of the distribution coefficient, chemical equilibrium constants, and temperature. The lactic acid concentration in equilibrium for the organic phase decreases as follows: water/LA/TiOA/1-dodecanol system > water/LA/TiOA/dodecane/1-dodecanol > system water/LA/TiOA/dodecane system.
Liquid extraction with immobilized liquids for product recovery from fermentation broths
Nowadays, many fermentation chemicals are produced at an industrial scale. Numerous technological improvements have been developed and implemented to achieve high quality and quantity of fermentation products. However, several drawbacks in fermentation processes still limit their application at an industrial level. In situ product removal (ISPR) is a potential alternative to overcome the conventional drawbacks of the fermentative processes, increasing the fermentation's productivity and reducing the separation steps for recovery and purification. Currently, liquid extraction has emerged as a promising separation technology for ISPR, with immobilized liquids such as membrane-assisted extraction and microchannel liquid membrane, due to the high mass transfer rates, scalability, easy integration, and efficiency. This chapter will discuss these technologies regarding their integration into fermentative processes.
Delignification of low-energy mechanical pulp (asplund fibers) in a deep eutectic solvent system of choline chloride and lactic acid
Deep eutectic solvents (DESs) are considered as a green and environmentally benign solvent class for various applications, including delignification of biomass. One of the major challenges in the delignification of biomass by DES is attributed to the limitations in mass transfer. By subjecting wood chips to a low-energy mechanical refining, i.e., the Asplund process, the accessible surface area increases greatly, which in turn improves the mass transfer and increases the reaction rate. In this research, the DES delignification of Asplund fibers made of Norway spruce was studied as a strategy to produce papermaking fibers under mild conditions. A DES consisting of lactic acid and choline chloride was used due to its proven performance in delignification. Various operational conditions, such as temperature, time, DES-to-wood ratio, and the type of stirring were studied. A novel parameter, Q, allowed to evaluate the impact of the operational conditions on the quality of the pulp in terms of delignification degree and fiber length. The results showed that cooking temperature had the most significant effect on the pulp quality. Additionally, it was observed that cooking times between 30 and 45 min result in a pulp yield of about 50%, while fibers have a lignin content of about 14% and a fiber length of 0.6 mm. These results demonstrate that it is possible to obtain fibers of relatively good quality from DES delignification using Asplund fibers as the starting material.
Integration of a liquid membrane in Taylor flow regime with a fermentation by Lactobacillus casei ATCC 393 for in-situ lactic acid removal
A new type of liquid membranes called liquid membrane in Taylor flow was integrated to a lactic acid fermentation, using Lactobacillus casei ATCC 393, for lactic acid removal during fermentation. The performance in terms of lactic acid production of the hybrid batch system is compared to a conventional batch fermentation. Lactic acid removal rate increases proportionally with the LA concentration within the fermenter. The lactic acid, the biomass production and the LA productivity in the hybrid system increased by 41.8, 12 and 26.6%, respectively, as compared to the conventional batch fermentation. However, toxicity effects reduce LA to glucose yield in 15.9% as compared to conventional fermentation. Liquid membranes in Taylor flow results promising for enhancing batch and continuous fermentation processes by a hybrid system.
Liquid–liquid equilibria for trioctylamine/1-dodecanol/citric acid/water system at 303.1 and 308.1 K: Experimental data and prediction
The present work experimentally tests the liquid–liquid equilibria (LLE) of aqueous citric acid (CA) solutions with trioctylamine (TOA) in 1-dodecanol at 303.2 and 308.2 K. A predictive model has been developed based on the experimental data. This model considers the physical dissolution of CA and complexation with TOA. At low CA concentrations, the stoichiometric ratio of acid/amine is (1:1). However, the acid/amine ratios of (1:1), (1:2), and (2:1) are present at high CA concentrations. The equilibrium constants for the different complexes were determined and compared to previous studies, which employed other organic solvents. The equilibrium constants obtained in this study are comparatively higher, making 1-dodecanol an attractive solvation medium. Also, the literature presents LLE experiments with contact times from minutes to hours. Because of this lack of consensus, this work displays experimental evidence to suggest contact and settling times required for experimental evaluation of the equilibria in liquid–liquid systems based on the standard deviation.
A new concept of liquid membranes in Taylor flow. Performance for lactic acid removal
A liquid membrane in Taylor flow regime is a novel alternative kind of contact in three-phase flow for liquid membranes that preserves the advantages of conventional emulsion liquid membranes while overcomes the stability problems of emulsion systems. As a proof of concept, this work presents experimental results of a liquid membrane in Taylor flow for lactic acid removal. Several operating conditions, such as injection times, delay times and flow of the membrane phase were tested for a channel length and inner diameter of 348.8 cm and 2.5 mm, respectively. The lactic acid removal is mainly affected by the driving force of lactic acid concentrations between donor droplets and the membrane interface, and the space-time. Thus, the lactic acid removal process through the liquid membrane in Taylor flow is enhanced at low injection times and high droplet velocity considering that enough space-time is provided. This technology results promising as an alternative to conventional liquid membranes and the intensification of chemical and fermentative processes.