Supercritical water processes: future prospects

Producción CientíficaThis contribution examines the challenges faced by supercritical water processes for industrial development. As an alternative, the intensification of the supercritical water processes is presented in order to reduce the size of the equipment needed and to facilitate the scaling up of the process. The perspective of developing micro combustors using hydrothermal flames as the internal heat source could open up an alternative for the in-situ energy generation in biorefineries, for example. The fundamental studies about supercritical water hydrolysis using ultrafast reactors has enabled extremely high selectivity in the biomass fractionation processes, and in the production of C2 and C3 building blocks from key components. The high-energy consumption of this process is another issue that limit its commercialization. In the examples proposed, the energy, work recovery and energy integration allows the reduction of the total energy consumption and, in some processes, the availability of extra energy as heat and work.2018-12-30Ministerio de Economía, Industria y Competitividad - FEDER (Proyect CTQ2013-44143-R)Ministerio de Economía, Industria y Competitividad - FEDER (Proyect CTQ2016-79777-R)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA040U16

CFD-Aspen Plus interconnection method. Improving thermodynamic modelling in computational fluid dynamic simulations

Producción CientíficaThermodynamic modelling in CFD is basically limited to the models available in the simulators. The method presented in this paper connects CFD simulators with Aspen Plus which instantaneously calculates and returns the value of any physical property required. Therefore, all the thermodynamic models and compounds available in Aspen Plus can be implemented in CFD simulations. The connection, created via Matlab and Excel-VBA, has been validated solving two identical CFD simulations first selecting a thermodynamic model available in the simulator and then connecting the simulator with Aspen Plus and selecting the same model. The maximum absolute average deviation between the density and viscosity values obtained in both simulations, for the two case studies analyzed, is lower than 0.7% which demonstrates the proper interconnection. The accuracy of the results obtained modeling multicomponent mixtures and supercritical fluids proves the applicability of the method to any scenarios2018-12-31Ministerio de Economía, Industria y Competitividad - FEDER (Proyects CTQ2013-44143-R and CTQ2016-79777-R

Ultrafast heating by high efficient biomass direct mixing with supercritical water

Producción CientíficaThis work analyzes the influence of the mixer configuration on the mixing efficiency in the process of biomass ultrafast hydrolysis by supercritical water. The results of the CFD simulations of a horizontal tee, a vertical tee and a mixing cross, selected as the optimum mixing configurations, together with the experimental results obtained in our hydrolysis plant, are the base to determine the configuration which provides the best mixing performance. Although slightly higher conversions are obtained in those experiments performed with a horizontal tee, the small differences between the results demand a theoretical analysis. Therefore, according to the CFD simulation results, since the mixing cross provides the best flow distribution and temperature homogenization at the outlet of the mixers and because of the great similarity between the residence time distribution curves of the mixers, the mixing cross is selected as the optimum geometry to perform the mixing.Ministerio de Economía, Industria y Competitividad - FEDER (Projects CTQ2013-44143-R and CTQ2016-79777-R

Heterogeneous catalysis for the extraction of arabinoxylans from wheat bran

Introduction The conversion of biomass within biorefineries into chemicals and energy is seen as a real possibility for the substitution of fossil resources. Raw materials of high lignocellulosic content are an interesting option. Besides wood and non-food crops, agricultural residues like straw and corn stover as well as other by-products of various origins are of high interest as feedstocks. Wheat bran represents such a by-product, which accrues in enormous quantities during the production of white wheat flour. It is estimated that 150 million tons are produced per year worldwide [1]. Currently wheat bran is mainly used as a low value ingredient in animal feed. Arabinoxylans are the most abundant structural polysaccharides in wheat bran, and they can be suitable compounds for the production of sugar alcohols. In general terms, the conversion of these hemicellulosic components from biomass into sugar alcohols is a two‑step reaction: 1) extraction and hydrolysis of arabinoxylans and 2) hydrogenation of these hemicelluloses into polyols (Figure 1). Please click Additional Files below to see the full abstract

Barley and yeast β-glucans as new emulsifier agents for the development of aqueous natural antifungal formulations

Producción CientíficaBarley and yeast β-glucans were selected, together with lecithin, to encapsulate resveratrol by emulsification-evaporation method to develop new and safer antifungal formulations. Different emulsification techniques were used: high-shear, high pressure and high pressure and temperature emulsification. Morphology, crystallinity, encapsulation efficiency and in vitro antifungal activity against Botrytis cinerea of the different formulations were evaluated. No significant differences between each emulsification procedure in particle size (below 90 nm) and in encapsulation efficiency (70–100%) were observed; only barley β-glucan emulsions showed lower efficiency due to the formation of a gel that retained most of the active compound. A great influence of the emulsification method and the encapsulating material on the crystallinity of the particles was observed. The highest antifungal activity (up to 53% growth inhibition) was obtained by the formulations with yeast β-glucans, indicating an enhanced absorption of encapsulated resveratrol through the cell wall of the fungus at the presence of (1–3, 1–6)-β-glucans.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA040U16

Aromatics from Lignin through Ultrafast Reactions in Water

Producción CientíficaNowadays, the valorization of lignin, the major natural source of aromatics in earth, is being a challenge for the scientific community. In this study, kraft lignin is effectively converted into aromatic monomers by ultrafast depolymerization in hot and pressurized water. At reaction times below 500 ms, it is possible to avoid char formation originated from undesirable condensation reactions by controlling accurately the reaction time. Under alkaline medium, the reaction reaches an optimum point at 386ºC and 300 ms with a light oil yield of 60% with a concentration in key compounds such as guaiacol, creosol, vanillin and acetovanillone of around 20 %w/w. The char formation in this point was surprisingly low (4 %w/w). Analysis and quantification of the products allows to identify the evolution of the different reaction steps and propose plausible mechanism for the depolymerization and repolymerization stages. Furthermore, it is proven that the proposed technology is equally effective to treat directly industrial black liquors with a yield higher than 50% to light oil, containing as main monomers guaiacol (2.7%), syringol (3.0%) and syringaldehyde (7.3%).2020-02-152020-02-15Ministerio de Economía, Industria y Competitividad (Project CTQ2016-79777-R)Ministerio de Educación, Cultura y Deporte (Proyect FPU15/00409

Production of saccharides from sugar beet pulp by ultrafast hydrolysis in supercritical water

Producción CientíficaSugar beet pulp (SBP) is the major by-product in sugar industry. To make profit out of this undervalued residue, the FASTSUGARS process was proposed as a solution, combining the advantages of supercritical water as hydrolysis medium with very short reaction times in the so-called ultrafast reactors. Operating at 390 °C, 25 MPa and reaction times between 0.11 and 1.15 s it was possible to convert SBP into sugars and to obtain a lignin-like solid fraction. The highest yields of C-6 and C-5 sugars (61 and 71% w/w, respectively) were obtained at 0.11 s with the lowest yield of degradation products. The solid product obtained at 0.14 s was thoroughly analyzed by acid hydrolysis, TGA and FTIR analysis to prove its enhanced thermal properties and aromaticity. The FASTSUGARS process demonstrated being a versatile and promising technology to be integrated in the future biorefineries.Ministerio de Economía, Industria y Competitividad (Project CTQ2013-44143-R and CTQ2016-79777-R

Titanium dioxide nanoparticle coating in fluidized bed via supercritical anti-solvent process (SAS)

A process to coat nanoparticle agglomerates has been developed and its critical operation parameters have been studied in this work. It consists on a fluidized bed where a supercritical anti-solvent process (SAS) takes place. Titanium dioxide (TiO2), used as model nanoparticle, has been coated with a polymer, Pluronic F-127, from an ethanolic solution. As main factors that can affect the coating process, the following process parameters were studied: the ratio between the velocity of carbon dioxide through the bed and the minimum fluidization velocity (umf), with values from 1.5 to 2.5 times the umf; the density of carbon dioxide, varying from 640 kg/m3 to 735 kg/m3 approximately; the flow rate of solution, within an interval between 0.5-2 mL/min; the concentration of the solution, from 0.030 mg/mL to 0.090 mg/mL and the mass ratio polymer-particle, 0.45-1.8 g/g. The process parameters were selected taking into account the values that increased the yield, defined as gram of coating material per gram of introduced polymer amount, and maintained a unimodal particle size distribution (PSD), with low increment in the mean particle size with respect to raw TiO2. All the samples were analyzed by four different methods, which showed the successful results of the experiments. The yield was analyzed gravimetrically, and the PSD was determined by laser diffraction. The presence of polymer on the surface of the nanoparticle agglomerates was verified by FT-IR spectrum and fluorescence microscopy, which also showed the quality and uniformity of the coating. Furthermore, the bulk density of the samples was measured showing a lineal variation with the mass ratio polymer-particle.2017-09-01This work is partially supported by the project Shyman FP7-NMP-2011-LARGE-280983 and the project CTQ2013-44143-R of the Spanish Ministerio de Economía y Competitividad. Víctor Martín thanks the University of Valladolid for his doctoral grant. Rut Romero-Díez would like to thanks her agreement with the University of Valladolid. Soraya Rodríguez-Rojo thanks the Spanish Ministerio de Ciencia e Innovación and the University of Valladolid for her Juan de la Cierva fellowship (JCI-2012-14992)

Characterization of rosemary essential oil for biodegradable emulsions

The characterization of rosemary essential oil (EO) for its formulation in biodegradable emulsions has been carried out. Firstly, the required HLB (hydrophile–lipophile balance) value of the oil was determined to be 15 based on droplet size analysis and the stability of emulsions with synthetic surfactants. Moreover the emulsion resulted to be stable after 50 days of storage in ambient conditions. Secondly, four biodegradable and non-toxic surfactants derived from starch were tested. The effect of these surfactants was analyzed by measuring interfacial tension between the oil and the aqueous phase.The authors thank the financial support of Junta de Castilla y Leon (Spain) through the project GR11/2008. National Starch Group is acknowledged for supplying the OSAmodified starches and giving permission to publish the results obtained with them. S.Rodríguez-Rojo thanks the Spanish Ministry of Education for her postdoctoral grant. S. Varona thanks the University of Valladolid through the FPI-UVa research program

Understanding sulfonated kraft lignin re-polymerization by ultrafast reactions in supercritical water

Producción CientíficaRe-polymerization reactions are a commonly reported issue on the way to the higher recovery of monomers from lignin. The reactivity of monomers obtained from lignin depolymerization and their contribution to the re-polymerization in supercritical water (SCW) was investigated. Sulfonated Kraft lignin (SKL) was used along with four monomers: vanillin, vanillic acid, vanillyl alcohol and acetovanillone. Indulin Kraft lignin was also employed as the reference to understand the re-polymerization of SKL in SCW. The formation of diarylmethane structures was detected in HSQC spectra of solid residue after the SCW process. Lignin released fragments with free phenolic β-O-4 structures, as well as the monomeric product vanillyl alcohol are involved with the formation of o-o´ and o-p´ diarylmethane structures. Chemical structure of Kraft lignin and its polymeric product after the SCW process was remarkably similar, as shown by HSQC, indicating that re-polymerization reactions occur through cross-linking polymerization, mainly in their fractions of low molecular weight products.Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (projects CTQ2016-79777-R and PID2019-105975GB-I00)Junta de Castilla y León (project CLU-2019-04 T