267 research outputs found
Highly Active and Easily Accessible Catalysts for Vinyl Polymerization of Norbornene Obtained by Oxidative Addition of Salicylaldimine Ligands to Bis(1,5-cyclooctadiene)nickel(0) and Methylaluminoxane
No full textHighly active, cheap, and easy to synthesize catalytic
systems, obtained in situ by the oxidative addition of salicylaldimine
ligands to bis(1,5-cyclooctadiene)nickel(0) and
activated by methylaluminoxane (MAO), are now reported for
the vinyl polymerization of norbornene. Their activity resulted
mainly influenced by the nature of the substituents present
both on the phenolate moiety and on the N-aryl ring as well as
the content of free trimethylaluminum (TMA) present in the
commercial MAO. In particular, the maximum activity, up
to about 78,000 kg polynorbornene/mol Ni h, was ascertained
when 3,5-dinitro-N-(2,6-diisopropylphenyl)salicylaldimine
ligand was adopted in conjunction with Ni(cod)2 and
TMA-depleted MAO. This remarkable performance, to the best
of our knowledge, the highest never reported working in toluene
instead of chlorinated aromatics, was reached adopting
this more sustainable reaction medium. The influence of the
main reaction parameters such as reaction time, temperature,
monomer/Ni, and Al/Ni molar ratios on the catalytic performances
and polymer characteristics was studied as well
Green valorisation of defatted waste of Cynara cardunculus L. to single cell oil and high-quality lignin
No full textIn recent years a growing interest has been directed to 3rd-generation biomass, such as the infesting plant species Cynara cardunculus (cardoon). It is a very common variety in the center of Italy and in the Mediterranean region. Cardoon offers a wide spectrum of potential applications, being a rich source of fibers, oil and bioactive compounds. The cultivation of this perennial herbaceous biomass shows significant advantages, such as good adaptability to climate change and growth on marginal or uncultivated lands with modest inputs, including moderate irrigation and minimal need of nutrients. The seeds of the flower are exploited for oil production for food and bio-diesel supply chains. The nonedible lignocellulosic residues can undergo pretreatments that favour further exploitation of this biomass [1,2]. In this study, the steam exploded defatted cardoon was used as feedstock for the production of sugars-rich hydrolysates by enzymatic hydrolysis. Two different commercial enzymatic mixture Cellic® CTec2 and Cellic® CTec3 were tested at different dosages (15, 30, 45 FPU/g glucan) and in the presence of different biomass loadings (2, 5, 10 wt%). The hydrolysates obtained under optimised reaction conditions (Cellic® CTec3, 30 FPU/g glucan, 2 or 5 wt% biomass loading, 72 h) were then fermented to new generation oil by the two oleaginous yeasts Lipomyces starkeyi DSM 70296 and Cryptococcus curvatus DSM 70022. The lipid contents of 45 and 60 wt% and the lipids yields of 20 and 24 wt% were reached, respectively. The single cell oils profile was similar to that of food oils usually employed for the production of biodiesel. Finally, in order to valorise all the fractions of cardoon, a green extraction protocol was optimised in order to recover high quality organosolv lignin from exploded cardoon suitable for material applications such as dielectric for organic thin film devices and bio-based component for functional coatings (Fig. 1). Different green solvents were tested, such as EtOH, EtOH:NH3 1:1, EtOH:H2O 1:1, MeTHF, MeTHF:EtOH:NH3 1.6:0.2:0.2, in an orbital shaker at 55 °C, 90 min, 50 g/L biomass loading, agitation speed 250 rpm. The lignin yield extracted by EtOH, EtOH:NH3 and MeTHF was around 10 wt% respect to the exploded cardoon and around 30% respect to the lignin content.
Figure 1 – Schematic representation of the implemented biorefinery scheme.
1. Raspolli Galletti, A. M., Licursi, D., Ciorba, S., Di Fidio, N., Coccia, V., Cotana, F., Antonetti, C. Catalysts, 2021, 11, 1082-1100.
2. Di Fidio, N., Antonetti, C., Raspolli Galletti, A. M. Proceeding 29th EUBCE, 2021
Optimized synthesis of highly microporous activated carbon from residual biomass lignin for efficient CO2 capture
No full textA versatile innovative biorefinery model for the complete valorization of lignocellulosic giant reed (Arundo donax L.) to give valuable bio-based products was implemented and optimized. The hemicellulose fraction was selectively fractionated and depolymerized by microwave-assisted FeCl3-catalyzed hydrolysis to give xylose-rich hydrolysates, which were then converted to new generation bio-oil (triglycerides) and biodiesel (fatty acids methyl esters) by fermentation with the oleaginous yeast Lipomyces starkeyi.1 The cellulose fraction of the pretreated solid was then exploited by MW-assisted FeCl3-catalyzed hydrolysis to give levulinic and formic acid.2 Finally, the lignin-rich solid residue obtained at the end of the proposed cascade process was chemically activated to produce activated carbon with a microporous structure suitable for CO2 adsorption. The activation protocol was optimized by a chemometric approach based on the Response Surface Methodology (RSM). Activation temperature and KOH/lignin weight ratio were selected as independent variables. The reaction time was fixed at 60 min. The selected responses were: i) activated carbon yield (wt%); ii) carbon yield (wt%); iii) CO2 uptake (mg/g). Under the optimized process conditions (633 °C, KOH/lignin 3.0 wt/wt, 60 min) the AC yield was 34.4 wt% and the CO2 uptake was 72.3 mg/g confirming the promising application of the residual lignin. Moreover, the obtained material (Fig. 1) showed similar CO2 uptake values over 10 cycles of adsorption and desorption tests, demonstrating the regeneration of the bio-based material obtained without losing its gas uptake capacity. The complete conversion of each main fraction of the starting raw material represents a crucial strategy for favoring the economic and environmental sustainability of integrated biorefinery processes in the perspective of the Green Chemistry principles.
Figure 1. SEM images of the activated carbon under the optimised process conditions.
References
1. Di Fidio, N., Ragaglini, G., Dragoni, F., Antonetti, C., Raspolli Galletti, A. M. Bioresour. Technol. 2021, 325, 124635-124644.
2. Di Fidio, N., Antonetti, C., Raspolli Galletti, A. M. Bioresour. Technol. 2019, 293, 122050-122058.
Acknowledgements: This work was funded by PRA 2020/2021 project “New horizons in CO2 chemistry: from capture to fine chemicals and metal based drugs” (code PRA_2020_39) of the University of Pisa
Thermal and structural investigation of random ethylene/1-hexene copolymers with high 1-hexene content
No full textRandom ethylene/1-hexene copolymers with the 1-hexene content in the range from 2 to 28 mol% were produced with a novel post-metallocene catalyst and analyzed by three techniques, FTIR, 13C NMR, and DSC. The 1-hexene content and the sequence distribution in the copolymers were determined by means of FTIR-M and 13C NMR. The crystallization behavior of the copolymers was studied by DSC under dynamic and isothermal conditions; the Avrami model was used to analyze the crystallization kinetics. It was found that both the 1-hexene content and the crystallization temperature affect the relative crystallinity. The bulk crystallization rate decreases with the 1-hexene content and reduces exponentially with an increase of T c. The melting behavior of isothermally crystallized samples was also investigated and it was found that the melting temperatures of the copolymers under equilibrium conditions were related to the compositio
Componente solido di catalizzatore, catalizzatore comprendente detto componente solido, e procedimento di (co)polimerizzazione delle alfa olefine
No full text
A NOVEL SYNTHESIS OF RE2(CO)10 BY H2/CO REDUCTION OF RE2O7
No full textRe2(CO)10 has been obtained in yields as high as 80% by the reaction of Re2O7 or NH4ReO4 with hydrogen-rich CO/H-2 mixtures at 15 MPa and 150-degrees-C in an organic solvent, being the capability to generate in situ well-dispersed rhenium metal the key to obtain Re2(CO)10
Solid catalyst component, catalyst comprising said solid component, and process for the (co)polymerization of alpha-olefins
No full textA solid catalyst component for the (co) polymn. of α-olefins having general formula (I): ZrnMA1xC1Mgp (I) wherein : M represents titanium (Ti), vanadium (V), or mixts. thereof; n is a no. ranging from 0.01 to 2; x is a no. ranging from 0.1 to 4; y is a no. ranging from 5 to 53; p is a no. ranging from 0 to 15; obtained by means of a process comprising putting at least one zirconium arene in contact with at least one metal compd. and, optionally, with at least one com not pound of magnesium. Said solid catalyst component can be advantageously used as a solid component in a catalyst for the (co) polymn. of α-olefins. Said catalyst can be advantageously used in a process for the (co) polymn. of α-olefins
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