Intensification of cellulose hydrolysis process by supercritical water: Obtaining of added value products

En la Presente tesis doctoral se ha estudiado el proceso de hidrólisis de celulosa V Uiomása vegetal en agua supercritica. Se ha estudiado la cinética de hidrólisis de celulosa y sus productos derivados, Un intensivo estudio sobre la dependencia de las cineticas con la presion y temperatura fue desarrollado. La produccion de compuestos de alto valor añadido como ácido láctico o glicolaldehido fue analizado utilizando agua supercritica como medio de reaccion e hidróxido de sodio como medio de reaccion. El reactor diseñado y construido para el estudio de la hidrólisis en agua supecritica fue probado con salvado le trigo, como ejemplo de biomasa natural. Además, se ha estudiado teoricamnete la integracion energetica del proceso de hidrólisis de celulosa en agua supercrita con los procesos comerciales de produccion combinada de calor y potencia.Departamento de Ingeniería Química y Tecnología del Medio Ambient

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

Governing Chemistry of Cellulose Hydrolysis in Supercritical Water

Producción CientíficaAt extremely low reaction times (0.02 s), cellulose was hydrolyzed in supercritical water (T=400 °C and P=25 MPa) to obtain a sugar yield higher than 95 wt %, whereas the 5-hydroxymethylfurfural (5-HMF) yield was lower than 0.01 wt %. If the reaction time was increased to 1 s, the main product was glycolaldehyde (60 wt %). Independently of the reaction time, the yield of 5-HMF was always lower than 0.01 wt %. To evaluate the reaction mechanism of biomass hydrolysis in pressurized water, several parameters (temperature, pressure, reaction time, and reaction medium) were studied for different biomasses (cellulose, glucose, fructose, and wheat bran). It was found that the H+ and OH− ion concentration in the reaction medium as a result of water dissociation is the determining factor in the selectivity. The reaction of glucose isomerization to fructose and the further dehydration to 5-HMF are highly dependent on the ion concentration. By an increase in the pOH/pH value, these reactions were minimized to allow control of 5-HMF production. Under these conditions, the retroaldol condensation pathway was enhanced, instead of the isomerization/dehydration pathway.Ministerio de Economía, Industria y Competitividad - FEDER (Proyect CTQ2013-44143-R

Scaling up the production of sugars from agricultural biomass by ultrafast hydrolysis in supercritical water

Producción CientíficaThe FASTSUGARS process for sugars’ recovery from agricultural biomass was scaled up from laboratory to pilot plant scale. System performance was evaluated by comparing the results obtained from sugar beet pulp and wheat bran in laboratory and pilot plants. Similar trends were found for each biomass in both plant: as reaction time increased, selectivity to sugars decreased and conversion and degradation rate increased. Then, to bring the FASTSUGARS process closer to industrial applications, the particle size of the biomass was increased in the pilot plant. It was found that the particle size acted as a mass transfer resistance, slowing down the hydrolysis of biomass, providing lower conversion and therefore reducing sugars’ degradation (degradation yield was lower than 15 % in the pilot plant). In that way, higher selectivity to sugars was obtained, reaching values around 90 % for both sugar beet pulp and wheat bran in the pilot plant.Ministerio de Economía, Industria y Competitividad (Project CTQ2013-44143-R, CTQ2016-79777-R)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA040U16

PMMA stability under hydrothermal conditions

Producción CientíficaPMMA is a synthetic polymer of methyl methacrylate. PMMA is used widely in many applications and the interest in their physicochemical properties is growing. In this work, a hydrothermal study was carried out to evaluate the PMMA stability under hydrothermal conditions (up to 200˚C), pH (2 to 10) and reaction time (up to 360 min). The water-PMMA system is affected by different mechanisms when dosed with bases or acids suggesting predominantly an interaction of ester groups with the medium. The results prove that the polymer is highly stable at the tested conditions. It is observed that water molecules are encapsulated in the polymer due to the softening and hardening during the process. This phenomenon was seen in the thermogravimetric analysis. The glass transition temperature of PMMA was slightly reduced after the treatment. This suggests that the hydrothermal process promotes the degradation of the shortest polymeric chains.Agencia Estatal de Investigación (PID2020-119249RA-I00)Junta de Castilla y León - EU-FEDER (CLU-2019-04)Ministerio de Ciencia, Innovación y Universidades - grant “Beatriz Galindo” (BEAGAL18/00247

Hydrolysis of cellulose in supercritical water: reagent concentration as a selectivity factor

Producción CientíficaIn this work, the influence of reagent concentration on hydrolysis reactions of cellulose in supercritical water was analyzed. The hydrolysis was carried out at 400 °C and 25 MPa with reaction times between 0.07 and 1.57 s and feeding cellulose concentrations between 5 and 20 % w/w (1.5–6 % w/w at reactor inlet). Also, a flash separator was used to separate vapor in the product stream in order to increase the final concentration. The best result for sugar production (79 % w/w) was obtained working with a cellulose concentration of 5 % w/w and 0.07-s reaction time. For glycolaldehyde production, the best result (42 % w/w) was obtained with a concentration of 20 % w/w and 1.57 s. The employment of a flash separator allowed reducing the water content by 50 %. It was also observed that by increasing the cellulose concentration in the reactor up to 4 % w/w, the hydrolysis took place with a similar kinetic as that in the heterogeneous media, thus reducing the conversion rate of cellulose in supercritical water.Ministerio de Economía, Industria y Competitividad - FEDER (Proyect CTQ2013-44143-R

Hydrothermal fractionation of woody biomass: lignin effect over sugars recovery

Producción CientíficaSubcritical water was employed to fractionate woody biomass into carbohydrates and lignin. Nine urban trees species (hardwood and softwood) from Spain were studied. The experiments were carried out in a semi-continuous reactor at 250 °C for 64 min. The hemicellulose and cellulose recovery yields were between 30% wt. and 80% wt. while the lignin content in the solid product ranged between 32% wt. and 92% wt. It was observed that an increment of solubilized lignin disfavored the hydrolysis of hemicelluloses. It was determined that the maximum extraction of hemicellulose was achieved at 20 min of solid reaction time while the extraction of celluloses not exhibited a maximum value. The hydrolysis of hemicellulose and cellulose would be governed by the hydrolysis kinetic and the polymers accessibility. In addition, the extraction of hemicellulose was negatively affected by the lignin content in the raw material while cellulose hydrolysis was not affected by this parameter.FEDER and Spanish Economy and Competitiveness Ministry (former Science and Innovation Ministry) Project Reference: CTQ2011-27347, ENE2012-33613 (FracBioFuel), CTQ2013-44143-R and Junta de Castilla y León Project Reference: VA254B11-2 for fundin

Pretreatment Processes of Biomass for Biorefineries: Current Status and Prospects

Producción CientíficaThis article seeks to be a handy document for the academy and the industry to get quickly up to speed on the current status and prospects of biomass pretreatment for biorefineries. It is divided into two biomass sources: vegetal and animal. Vegetal biomass is the material produced by plants on land or in water (algae), consuming sunlight, CO2, water, and soil nutrients. This includes residues or main products from, for example, intensive grass crops, forestry, and industrial and agricultural activities. Animal biomass is the residual biomass generated from the production of food from animals (e.g., manure and whey). This review does not mean to include every technology in the area, but it does evaluate physical pretreatments, microwave-assisted extraction, and water treatments for vegetal biomass. A general review is given for animal biomass based in physical, chemical, and biological pretreatments

Online integrated fractionation-hydrolysis of lignocellulosic biomass using sub- and supercritical water

Producción CientíficaA novel process coupling the fractionation and hydrolysis reactors is presented. Holm oak was used as real lignocellulosic biomass to be treated. In the fractionation reactor, hemicellulose and cellulose were solubilized and partially hydrolyzed in different stages with the aim of feeding the hydrolysis reactor with high C5 or C6 concentrations respectively. The fractionation was performed in two stages: at 180 °C optimizing the hemicellulose extraction and at 260 °C extracting cellulose and hard hemicellulose remaining in the biomass structure. Three water flows were tested: 11, 17 and 26 cm3/min. Sugar yields from 71 to 75% were reached, mainly composed of xylose and glucose oligomers and lower amounts of other chemicals, like retro-aldol products, acetic acid or 5-HMF. The outlet stream from the fractionation reactor was directly mixed with sub or supercritical water at the inlet mixer of a supercritical hydrolysis reactor where the reaction time was precisely controlled. The temperature, pressure and reaction time were modified to get an insight of their effect on the yield of retro-aldol condensation products. Yields of 24% for glycolaldehyde, and pyruvaldehyde were found at 8.3 s, 350 °C and 162 bar (hydrolysis reactor conditions). On other hand, 25% of lactic acid was found at 0.23 s, 396 °C and 245 bar. A discussion based on a known reaction pathway is proposed. Moreover, a kinetic model for the hydrolysis reactor was put forward, being able to reproduce the experimental data with deviations below 10% for sugars and other products extracted. This combined process performs a selective valorization of real lignocellulosic biomass, avoiding the costly process of extreme grinding needed for the fluidization in a continuous hydrothermal process.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA330U13

Ultrafast hydrolysis of inulin in supercritical water: Fructooligosaccharides reaction pathway and Jerusalem artichoke valorization

Producción CientíficaIn a biorefinery approach, inulin and inulin-rich biomass as Jerusalem artichoke (JA) could be transformed into platform chemicals such as fructose and/or pyruvaldehyde. To do so, the FASTSUGARS pilot plant proved to be a promising alternative for the selective conversion of biomass. In this work, inulin and JA were hydrolyzed in supercritical water (SCW) for the first time. Commercial inulin was selected as a model for fructooligosaccharides (FOS) and its reaction pathway in SCW was elucidated. It was found that fructose was the primary product from FOS hydrolysis in SCW, which was then selectively transformed into pyruvaldehyde as reaction time increased. Operating with extremely low reaction times (0.12 s) the sugars selectivity of JA was as high as 76% w/w. In both cases, the production of degradation products such as 5-HMF and acids was very low. Finally, comparing JA results to those from lignocellulosic biomass it was found that higher conversion was achieved in the case of JA due to its inulin-based composition.Ministerio de Economía, Industria y Competitividad (project CTQ2016-79777-R)Junta de Castilla y León (project VA040U16