Palladium nanoparticles find extensive applications in catalysis in both homogeneously and heterogeneously catalyzed processes. Supporting metal nanoparticles enhances their stability as compared to ...their unsupported counterparts. The role of catalytic support is increasingly recognized as crucial in determining the behaviour of these materials. However, controlling the deposition and anchoring of palladium nanoparticles remains a significant challenge. This contribution discusses the preparation of straight lines of palladium particles on zinc oxide by wet impregnation. This phenomenon is attributed to the highly stepped morphology of the employed ZnO that created steric anchoring sites to stabilize the metal particles. Palladium-based catalysts were evaluated for the valuable Suzuki-Miyaura cross-coupling reaction. The dispersed Pd/ZnO catalyst achieved a conversion rate of 86% with 100% selectivity, remarkably superior to that of the Pd/Al
2
O
3
and Pd/TiO
2
counterparts.
Precise placement of Palladium (Pd) nanoparticles onto ZnO surfaces, resulting in improved performance in Suzuki-Miyaura cross-coupling processes due to accurate catalyst dispersion.
A planar electrochemical sensor, based on flower-like CuO nanostructures growth “in situ” on a commercial screen printed carbon electrode, was fabricated by an easy and effective technique and ...employed for the non-enzymatic determination of glucose. The prepared CuO nanostructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The carbon electrode modification with CuO was optimized by investigating the effect of the number of deposition cycles of precursor and their concentration. The electrodes modified by in situ growth of CuO were compared to an electrode prepared by simple deposition of CuO powder previously synthesized by the same technique. Cyclic voltammetric and chronoamperometric tests demonstrated that the in situ growth of CuO leads to excellent electrochemical performance toward glucose oxidation in 0.1 M KOH solution. The best sensor, if operated at an applied potential of 0.6 V, has a sensitivity of 1460 μA·mM
−1
·cm
−2
and a 2.5 μM detection limit (at an S/N ratio of 3). Tests carried out within six months revealed an excellent long-term stability. This suggests that the method applied to modify the carbon electrode represents a useful tool for fabrication of an inexpensive and reliable non-enzymatic glucose sensor.
Graphical abstract
Schematic of a glucose sensor fabricated by growing flower-like CuO nanostructures in-situ on a screen printed carbon electrode (SPCE). The sensor showed excellent sensitivity and long-term stability.
The reductive amination reaction of furfural with acetonitrile has been explored employing various catalytic systems based on supported Rh, Ru, Pt and Pd nanoparticles. The synthesis of Rh and Ru ...nanoparticles supported on titania was accomplished following an environmentally friendly two step-protocol, based on the microwave assisted preparation of TiO2 and its subsequent functionalization by an impregnation/chemical reduction method. Commercial Pd/C, Pt/C and Ru/C were additionally evaluated to get insights into the effect of the metal component into the reaction progress and the products selectivity. Interestingly, the metal component resulted to have a drastic influence into the selectivity of the reaction. In particular, catalytic materials based on rhodium supported on TiO2, led to the selective formation of the reductive amination products, namely towards the secondary and tertiary amines, derived from the hydrogenated furfural ring. In turn, ruthenium-based materials drove the reaction progress towards the hydrogenation of the carbonyl functionality and did not favor the hydrogenation of the furan ring, similar to the behavior observed for platinum system. Furthermore, palladium-based catalyst favored the hydrogenation of the aldehyde group and, moreover, led to the hydrogenation of the furan ring. Products characterization was carried out by GC-MS and NMR spectroscopies. Outstanding conversion (>99%) and selectivity (76%) values towards the N-ethyl-N-((tetrahydrofuran-2-yl)methyl)ethanamine were reached for the TiO2-Rh1% catalyst.
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•Reductive amination reaction of furfural with acetonitrile was investigated.•Catalytic systems based on supported Rh, Ru, Pt and Pd nanoparticles.•Metal nanoparticles having a significant influence into reaction selectivity.•Rhodium materials for the selective formation of reductive amination products (hydrogenated furfural ring).
The total annual production of agricultural biomass such as wood, corn cobs, leaves, and citrus peels, is estimated at 956 million tons (Mt). Since crop residues are by-products of agricultural ...production, crop residue collection does not compete with food crops for acreage and therefore, it does not negatively impact food prices. Moreover, it has the advantage of reducing the amount of waste, the disposal of which often becomes a serious problem despite natural sources. Biomass conversion becomes a very valid alternative to diversify energy sources and reduce global warming. Thermochemical treatment of biomass is a promising way to convert biomass into bio-oil, biochar, and gas. In recent years, interest in the conversion of plant biomass into biochar has increased because this carbonaceous material has interesting properties that guarantee applications in wastewater treatment, soil improvement, solid fuels, and energy. The processes performed to convert biomass into biochar are different and the most used are thermochemical processes: pyrolysis, torrefaction, hydrothermal treatment, and gasification. The studies of the thermokinetic parameters that control these processes are carried out using different methods that provide the necessary information for the applicability of the processes on an industrial scale. One of the objectives of the present review is to compare kinetic models in order to clarify the role of the conversion process and the effects of the process parameters on the final product. A comprehensive investigation of the thermokinetic parameters controlling the conversion of crop residues to biochar was conducted. The mathematical description of kinetic processes is usually performed using the Arrhenius equation and its derivatives to obtain the activation energies (
E
a
), the pre-exponential parameter, and the process mechanisms. While isothermal processes can be described using the model fitting method, isoconversional processes can be studied using both the model fitting method and model-free methods. The high complexity and diversity of the reactions involved could lead to the use of approximations. In this paper, an overview of the kinetic parameters determined for biochar production processes and the model used to determine them is given.
Thermokinetics of Biochar production.
We report in this paper the effects of Ethyl Ester L-Lysine Triisocyanate (LTI) on the physical-mechanical properties of Poly(lactide)/Poly(ε-caprolactone) (PLA/PCL) polyesters blends. The PLA/PCL ...ratios considered were 20/80, 50/50 and 80/20 (wt/wt %) and LTI was added in amounts of 0.0–0.5-1.0 phr. PLA and PCL reacted with LTI during processing in a Brabender twin screw internal mixer to produce block copolymers in-situ. The resulting blends have been characterized by torque measurements, uniaxial tensile tests, Differential Scanning Calorimeter, contact angle measurements with a Phosphate Buffered Saline (PBS) solution, ATR analysis and morphological SEM observations. Experimental results highlighted how LTI enhanced interaction and dispersion of the two components, resulting into a synergic effect in mechanical properties. Mechanical and physical properties can be tailored by changing the blend composition. The most noticeable trend was an increase in ductility of the mixed polymers. Besides, LTI decreased blend's wet ability in PBS and lowered the starting of crystalline phase formation for both polymers, confirming an interaction among them. These reactive blends could find use as biomedical materials, e.g. absorbable suture threads or scaffolds for cellular growth.
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•The blends were based on PLA, PCL and L-Lysine Triisocyanate ( LTI).•Reactive mixing reaction occurred during the materials processing.•Mechanical torque, tensile test and physical analyses were performed in the blends.•LTI compatibilizes PLA and PCL, improving the mechanical features of blends.•Mechanical -physical properties can be tailored by changing the blend composition.
In the last decades, inedible lignocellulosic biomasses have attracted significant attention for being abundant resources that are not in competition with agricultural land or food production and, ...therefore, can be used as starting renewable material for the production of a wide variety of platform chemicals. The three main components of lignocellulosic biomasses are cellulose, hemicellulose and lignin, complex biopolymers that can be converted into a pool of platform molecules including sugars, polyols, alchols, ketons, ethers, acids and aromatics. Various technologies have been explored for their one-pot conversion into chemicals, fuels and materials. However, in order to develop new catalytic processes for the selective production of desired products, a complete understanding of the molecular aspects of the basic chemistry and reactivity of biomass derived molecules is still crucial. This Special Issue reports on recent progress and advances in the catalytic valorization of cellulose, hemicellulose and lignin model molecules promoted by novel heterogeneous systems for the production of energy, fuels and chemicals.
•Carbon dots from waste via an hydrothermal and electrochemical bottom-up synthesis.•Carbon dots by electrochemical bottom-up synthesis from 5-hydroxymethylfurfural.•Biomass-derived carbon dots for ...promoting Knoevenagel condensation.•Very significant integrated method in terms of recycling and circular chemistry.
Natural raw materials such as biomass and plant wastes are the most interesting feedstocks for the synthesis of carbonaceous nanomaterials due to their high availability, environmental compatibility, and affinity with Green Chemistry principles. Carbon dots (CDs), a new type of carbon nanomaterials, perform an important role in this matter by serving in the development of environmentally friendly catalysts. In this study, CDs were synthesized in good yields by using the electrochemical bottom-up synthesis starting from the liquid phase that is separated during the hydrothermal carbonization (HTC) process involving orange peel waste (OPW). The electrochemical setup was also optimized to synthesize CDs based on 5-hydroxymethylfurfural, which represents one of the main components of the liquid phase obtained by HTC. The comprehensive optical and chemo-physical characterization of CDs samples carried out by several techniques such as SEM, TEM, XRD, PL, TGA, and FTIR, highlighted their distinctive morphological and microstructural features. The obtained CDs were successfully employed to catalyse the Knoevenagel condensation, showing excellent results in terms of yield and reproducibility. In addition, the sustainable nature of the CDs was demonstrated by recycling the catalysts up to five cycles without significant activity loss.
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•The hydrogenolysis of C6-C3 polyols can be effectively promoted by the heterogeneous Pd/Fe3O4, catalyst at low H2 pressure.•At 240 °C, sorbitol (C6 polyol) is fully converted into ...lower alcohols with ethanol being the main reaction product in liquid phase.•The gas phase analysis reveals the excellent performance of the Pd/Fe3O4 catalyst in promoting the water-gas-shift reaction.•The high activity shown by the Pd/Fe3O4 catalyst has to be attributed to the strong interaction between palladium and Fe3O4 support.
The hydrogenolysis of sorbitol and various C5-C3 polyols (xylitol; erythritol; 1,2- 1,4- and 2,3-butandiol; 1,2-propandiol; glycerol) have been investigated at low molecular hydrogen pressure (5 bar) by using Pd/Fe3O4, as heterogeneous catalyst and water as the reaction medium. Catalytic experiments show that the carbon chain of polyols is initially shortened through dehydrogenation/decarbonylation and dehydrogenation/retro-aldol mechanisms followed by a series of cascade reactions that include dehydrogenation/decarbonylation and dehydration/hydrogenation processes. At 240 °C, sorbitol is fully converted into lower alcohols with ethanol being the main reaction product in liquid phase.
A simple and efficient synthesis of carbon nanodots (CNDs) was proposed by using hydrochar obtained through hydrothermal carbonization of beer bagasse (BB), a by-product of the beer industry that ...possesses several appealing advantages as a lignocellulosic source for carbon material synthesis. Raw materials and produced CNDs were characterized by several techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR, CHNS elemental analysis, diffusion light scattering (DLS), and zeta potential, and the optical properties were studied by spectrofluorophotometry (PL) and UV-vis absorption spectroscopy. The synthesized CNDs exhibited small dimensions, interesting fluorescence behaviour, high stability and remarkable water solubility due to the presence of hydroxyl and carboxyl functional groups. Exploiting these properties, CNDs were employed in the development of highly sensitive fluorimetric and electrochemical probes for heavy metal ions, which are of great concern for human health, aquatic life, and environmental sustainability. Hg
2+
and Pb
2+
were detected by the fluorimetric probe with a limit of detection of 11.3 nM and 78.8 nM, respectively, while the electrochemical platform allowed the selective and simultaneous detection of heavy metal ions, reaching a detection limit of 124 ng L
−1
and 551 ng L
−1
, respectively for mercury and lead ions with high sensitivity, in the range between 11.4 and 34.1 μA nM
−1
cm
−2
.
Sustainable synthesis of carbon nanodots (CNDs) through a green route - converting beer bagasse, a by-product of the beer industry, into hydrochar
via
eco-friendly hydrothermal carbonization, and their application for the selective detection of harmful heavy metal ions.
The hydrogenolysis and the aqueous phase reforming of glycerol have been investigated under mild reaction conditions, using water as the reaction medium and Pd/Fe as the catalyst. The experiments, in ...the presence of added H 2 or under inert atmosphere, clearly show that the dehydration/hydrogenation route is the key step in the case of C–O bond cleavage (hydrogenolysis) while dehydrogenation is a prerequisite for C–C bond breaking (APR), with the latter favoured at higher reaction temperatures. The temperature dependence of the C–C and C–O bond rupture is discussed by taking into account the bond energies involved in the competitive hydrogenolysis and APR reactions. Finally, the Pd/Fe catalyst was also tested in the hydrogenolysis and APR of ethylene glycol in the same temperature range, with the aim of clarifying the selective cleavage of C–O and C–C bonds in biomass derived C 2 –C 3 polyols.
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