Effect of the Purification Treatment on the Valorization of Natural Cellulosic Residues as Fillers in PHB-Based Composites for Short Shelf Life Applications

This is a pre-print of an article published in Waste and Biomass Valorization. The final authenticated version is available online at: https://doi.org/10.1007/s12649-020-01192-1In this work the effect of a combined NaOH + peracetic acid (PAA) purification treatment on the valorization of almond shell (AS) and rice husk (RH) lignocellulosic residues as fillers in PHB-based composites for short shelf life applications has been studied. The efficiency of the treatment at removing the non-cellulosic components of the fibers has been evaluated by SEM, FTIR, WAXS and TGA taking a commercial cellulose as reference. The influence of the untreated and treated fibers on the morphology, thermal, crystallization, tensile properties, fracture toughness and dynamo mechanical behavior of the PHB/fiber composites has been studied. The treatment has demonstrated its ability at removing the lignin, hemicelluloses and waxes allowing the obtention of fibers with relative crystallinity, thermal stability and composition similar to the commercial cellulose. The different agro-food based lignocellulosic residues used resulted in two suitable reinforcing fillers for a PHB matrix. Hence, composites prepared with the treated fibers presented better thermal and mechanical performance than those prepared with the untreated ones. Therefore, the so-obtained purified residue fibers are comparable to a pure cellulose as a filler for PHB composites

Study of the Compatibilization Effect of Different Reactive Agents in PHB/Natural Fiber-Based Composites

Fiber–matrix interfacial adhesion is one of the key factors governing the final properties of natural fiber-based polymer composites. In this work, four extrusion reactive agents were tested as potential compatibilizers in polyhydroxylbutyrate (PHB)/cellulose composites: dicumyl peroxide (DCP), hexamethylene diisocyanate (HMDI), resorcinol diglycidyl ether (RDGE), and triglycidyl isocyanurate (TGIC). The influence of the fibers and the different reactive agents on the mechanical properties, physical aging, and crystallization behavior were assessed. To evaluate the compatibilization effectiveness of each reactive agent, highly purified commercial cellulose fibers (TC90) were used as reference filler. Then, the influence of fiber purity on the compatibilization effect of the reactive agent HMDI was evaluated using untreated (U_RH) and chemically purified (T_RH) rice husk fibers, comparing the results with the ones using TC90 fibers. The results show that reactive agents interact with the polymer matrix at different levels, but all compositions showed a drastic embrittlement due to the aging of PHB. No clear compatibilization effect was found using DCP, RDGE, or TGIC reactive agents. On the other hand, the fiber–polymer interfacial adhesion was enhanced with HMDI. The purity of the fiber played an important role in the effectiveness of HMDI as a compatibilizer, since composites with highly purified fibers showed the greatest improvements in tensile strength and the most favorable morphology. None of the reactive agents negatively affected the compostability of PHB. Finally, thermoformed trays with good mold reproducibility were successfully obtained for PHB/T_RH/HMDI composition

Biocomposites of different lignocellulosic wastes for sustainable food packaging applications

The suitability of three local lignocellulosic wastes i.e. almond shell (AS), rice husk (RH) and seagrass (SG) as fillers in PHB/Fiber composites applications has been studied. PHB/Fiber composites with 10 phr and 20 phr fiber content were prepared by melt blending. The influence of the fiber type (size, morphology and origin) and content on the morphological, mechanical and thermal properties of the as obtained composites has been assessed. To evaluate the potential use in food packaging applications, the barrier performance to water, thermoforming ability and disintegration in controlled composting conditions of the composites were also studied. All the fibers have demonstrated to be apt for their use as fillers in PHB/Fiber composites, showing a reinforcing effect without affecting the crystallinity and the disintegration rate of PHB. The thermal stability and the water barrier performance of the composites were reduced by the presence of the fibers. Nevertheless, the addition of AS resulted in the best balance of properties, in terms of permeability and mechanical properties, finding an enhancement of the thermoforming ability of PHB when 10 phr of AS was added

Ni-Cu/Al2O3 from Layered Double Hydroxides Hydrogenates Furfural to Alcohols

The hydrogenation of furfural is an important process in the synthesis of bio-based chemicals. Copper-based catalysts favor the hydrogenation of furfural to alcohols. Catalytic activity and stability were higher at a Ni-to-Cu atomic ratio of 1:1 and 1.5:0.5 compared to 0.5:1.5. Here, we prepared Ni-Cu/Al2O3 hydrogenation catalysts derived from layered double hydroxides (LDHs). Catalysts calcined at 673 K and reduced at 773 K with nominal Ni/Cu atomic ratios y/x = 1.5/0.5, 1/1 and 0.5/1.5 were characterized by XRD, FESEM-EDX, H2-TPR, XPS, FAA and BET. Their activity was tested at 463 K and in a 0.05 g g−1 furfural solution in ethanol, and the space velocity in a packed-bed reactor (PBR) was 2.85 gFF gcat−1 h−1. In a slurry reactor (SSR) at 5 MPa H2 and a contact time of 4 h, conversion was complete, while it varied from 91 to 99% in the PBR. Tetrahydrofurfuryl alcohol (TFA) was the main product in the SSR, with a selectivity of 32%, 63% and 56% for Ni0.5Cu1.5Al1, Ni1Cu1Al1 and Ni1.5Cu0.5Al1, respectively. The main product in the atmospheric PBR was furfuryl alcohol (FA), with a selectivity of 57% (Ni0.5Cu1.5Al1), 61% (Ni1Cu1Al1) and 58% (Ni1.5Cu0.5Al1). Other products included furan, methylfuran, 1-butanol and 1,2-pentanediol. Ethyl tetrahydrofurfuryl ether and difurfuryl ether were also formed via the nucleophilic addition of furfural with ethanol and furfuryl alcohol

Catalytic Hydrogenation/Hydrogenolysis of Biomass-Derived Platform Chemicals

A causa de l'actual escenari polític mundial i a la mancança de fonts d'energia, la biomassa s'ha proposat com a una de les matèries primeres alternatives i sostenibles per a fer front a la urgent necessitat de recursos energètics renovables. Aquesta tesi es centra en el furfural, considerat un dels productes químics de major valor afegit derivats de la biomassa. Hem sintetitzat diferents catalitzadors per a utilitzar-los en la hidrogenació del furfural i posterior conversió a productes químics importants com el 1,2-pentanediol, 1,5-pentanediol, alcohol furfurílic i tetrahidrofurfurílic. Aquests compostos derivats del furfural poden utilitzar-se en la producció de biocombustibles, la producció de polímers, com a additius per a combustibles, dissolvents, etc. Tots els catalitzadors utilitzats es van preparar a base de metalls no nobles (Ni, Co, Cu, Mg, Al), i derivats d'hidròxids dobles laminars (HDL). A continuació, es van calcinar en aire atmosfèric a 673 K durant 4 hores i es van reduir en H2 pur a 773 K durant 1 hora. Finalment es van caracteritzar per XRD, FESEM-*EDX, H2-TPR, TPD-NH3, ICP i BET.En la actual crisis energética y contexto político, la biomasa ha emergido con fuerza como una de las materias primas alternativas y sostenibles para hacer frente a la urgente necesidad de recursos energéticos renovables. Esta tesis se centra en el estudio del furfural, considerado uno de los productos químicos de mayor valor añadido derivados de la biomasa. Para ello, se sintetizaron diferentes catalizadores diferentes para evaluarlos en la reacción de hidrogenación del furfural y transformarlo en productos químicos de interés industrial como 1,2-pentanodiol, 1,5-pentanodiol, alcohol furfurílico y alcohol tetrahidrofurfurílico. Estos compuestos derivados del furfural pueden ser utilizados en la producción de biocombustibles, la producción de polímeros, como aditivos para combustibles, disolventes, etc. Todos los catalizadores estudiados se sintetizaron con base de metales no nobles (Ni, Co, Cu, Mg, Al), y derivados de hidróxidos doble laminares (HDL). A continuación, se calcinaron en atmósfera de aire a 673 K durante 4 horas, se redujeron en hidrógeno gas puro a 773K durante 1 hora y se caracterizaron por XRD, FESEM-EDX, H2-TPR, TPD-NH3, ICP y BET.Due to the current worldwide political scenario and lack of energy sources, biomass has been proposed as one of the alternative and sustainable raw materials to address the urgent need for renewable energy resources. This thesis focuses on furfural which is considered one of the most value-added chemicals derived from biomass. We synthesized different catalysts to be used for the hydrogenation of furfural, converting it into commodity chemicals such as 1,2-pentanediol, 1,5-pentanediol, furfuryl alcohol and tetrahydrofurfuryl alcohol. These furfural´s derivatives may utilize in the production of biofuels, the production of polymers, as fuel additives, solvents, etc. All used catalysts were prepared based on non-noble metals (Ni, Co, Cu, Mg, Al), and derived from layered double hydroxides (LDHs). Next, they were calcined under air at 673 K for 4 hours, reduced under pure H2 at 773 K for 1 hour and characterized by XRD, FESEM-EDX, H2-TPR, TPD-NH3, ICP and BET. The catalyst performance was tested in two different types of reactors, the continuous packed-bed reactor (PBR) and the high-pressure slurry reactor (SSR)

Ni-Cu/Al2O3 from Layered Double Hydroxides Hydrogenates Furfural to Alcohols

The hydrogenation of furfural is an important process in the synthesis of bio-based chemicals. Copper-based catalysts favor the hydrogenation of furfural to alcohols. Catalytic activity and stability were higher at a Ni-to-Cu atomic ratio of 1:1 and 1.5:0.5 compared to 0.5:1.5. Here, we prepared Ni-Cu/Al2O3 hydrogenation catalysts derived from layered double hydroxides (LDHs). Catalysts calcined at 673 K and reduced at 773 K with nominal Ni/Cu atomic ratios y/x = 1.5/0.5, 1/1 and 0.5/1.5 were characterized by XRD, FESEM-EDX, H2-TPR, XPS, FAA and BET. Their activity was tested at 463 K and in a 0.05 g g−1 furfural solution in ethanol, and the space velocity in a packed-bed reactor (PBR) was 2.85 gFF gcat−1 h−1. In a slurry reactor (SSR) at 5 MPa H2 and a contact time of 4 h, conversion was complete, while it varied from 91 to 99% in the PBR. Tetrahydrofurfuryl alcohol (TFA) was the main product in the SSR, with a selectivity of 32%, 63% and 56% for Ni0.5Cu1.5Al1, Ni1Cu1Al1 and Ni1.5Cu0.5Al1, respectively. The main product in the atmospheric PBR was furfuryl alcohol (FA), with a selectivity of 57% (Ni0.5Cu1.5Al1), 61% (Ni1Cu1Al1) and 58% (Ni1.5Cu0.5Al1). Other products included furan, methylfuran, 1-butanol and 1,2-pentanediol. Ethyl tetrahydrofurfuryl ether and difurfuryl ether were also formed via the nucleophilic addition of furfural with ethanol and furfuryl alcohol

Reactive melt mixing of poly(3-hydroxybutyrate)/rice husk flour composites with purified biosustainably produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Novel green composites based on commercial poly(3-hydroxybutyrate) (PHB) filled with 10 wt % rice husk flour (RHF) were melt-compounded in a mini-mixer unit using triglycidyl isocyanurate (TGIC) as compatibilizer and dicumyl peroxide (DCP) as initiator. Purified poly(3- hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) produced by mixed bacterial cultures derived from fruit pulp waste was then incorporated into the green composite in contents in the 5-50 wt % range. Films for testing were obtained thereafter by thermo-compression and characterized. Results showed that the incorporation of up to 20 wt % of biowaste derived PHBV yielded green composite films with a high contact transparency, relatively low crystallinity, high thermal stability, improved mechanical ductility, and medium barrier performance to water vapor and aroma. This study puts forth the potential use of purified biosustainably produced PHBV as a cost-effective additive to develop more affordable and waste valorized food packaging articles.This research was supported by the Spanish Ministry of Science, Innovation, and Universities (MICIU) program number AGL2015-63855-C2-1-R and by the EU H2020 projects YPACK (reference number 773872) and ResUrbis (reference number 730349). B.M.-R. and S.T.-G. acknowledge MICIU for her FPI grant (BES-2016-077972) and his Juan de la Cierva-Incorporación contract (IJCI-2016-29675), respectively. The authors also thank the Joint Unit in Polymers Technology between IATA–CSIC and PIMA-Universitat Jaume I.Peer Reviewe