2023, Pérez, Alan, Roy, Yagnaseni, Rip, Constantijn, Kersten, Sascha R. A., Schuur, Boelo

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.

2019-05, Pérez, Alan, Fontalvo, Javier

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.

2022, Demmelmayer, Paul, Pérez, Alan, Riedl, Wolfgang, Kienberger, Marlene

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.

2021-06-09, Pérez, Alan, Fiskari, Juha, Schuur, Boelo

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.