460 research outputs found

    Catalytic transformation of renewables (Olefin, bio‐sourced, et al.)

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    The objective of this Special Issue is to provide new diverse contributions that can demonstrate recent applications in biomass transformation using heterogeneous catalysts. In recent decades, a wide variety of biomass-derived chemicals have emerged as key platform chemicals for the production of fine chemicals and liquid fuels using heterogeneous catalysts as the preferred option for most of the developed and proposed catalytic processes. A range of heterogeneous catalysts have been evaluated for effective biomass conversion, such as supported metal nanoparticles, mixed metal oxides and zeolites, where the control of particle size, porosity, acid-basic and redox properties is crucial for providing active, stable and selective heterogeneous catalysts. Moreover, the crucial role of the solvent, choice of reactor design and final chemical processes for controlling activity, selectivity and deactivation phenomena has been demonstrate

    Ti/Zr/O Mixed Oxides for the Catalytic Transfer Hydrogenation of Furfural to GVL in a Liquid-Phase Continuous-Flow Reactor

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    This work aims to develop an efficient catalyst for the cascade reaction from furfural to y-valerolactone in a liquid-phase continuous reactor. This process requires both Lewis and BrĂžnsted acidity; hence, a bifunctional catalyst is necessary to complete the one-pot reaction. Ti/Zr/O mixed oxide-based catalysts were chosen to this end as balancing metal oxide composition allows the acidity characteristics of the overall material to be modulated. Oxides with different compositions were then synthesized using the co-precipitation method. After characterization via porosimetry and NH3-TPD, the catalyst with equimolar quantities of the two components was demonstrated to be the best one in terms of superficial area (279 m2/g) and acid site density (0.67 mmol/g). The synthesized materials were then tested using a plug flow reactor at 180 C, with a 10 min contact time. Ti/Zr/O (1:1) was demonstrated to be the most promising catalyst during the recycling tests as it allowed obtaining the highest selectivities in the desired products (about 45% in furfuryl isopropyl ether and 20% in y-valerolactone) contemporaneously with 100% furfural conversion

    Effect of dietary antioxidant supplementation on rabbit performance, meat quality and oxidative stability of muscles

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    [EN] The aim of this study was to cast light on the effects of EconomasEℱ (EcoE), a patented pre-mixture of nutritional additives consisting mainly of organic selenium (0.15 or 0.30 mg/kg feed; Se) combined with vitamin C (5 and 10 mg/kg feed; VC), compared to DL-α-tocopherol acetate (100 or 200 mg/kg feed; VE) dietary supplementation on rabbit performance and meat quality. In fact, the role of Se supplementation in the rabbit diet has not yet been elucidated in the literature and, more specifically, there are no studies on the possible synergistic action between organic Se compared with VE on lipids, fatty acids (FA) and the oxidative stability of two glycolytic muscles, longissimus lumborum (LL) and biceps femoris (BF). Two hundred and seventy New Zealand White rabbits were divided into five dietary groups of 54 rabbits each: 1) control (basal diet = BD; CTRL); 2) VE100 (BD + VE100 mg/kg); 3) VE200 (BD + VE200 mg/kg); 4) EcoE100 (BD + EcoE100 mg/kg); and 5) EcoE200 (BD + EcoE200 mg/kg). Neither of the antioxidant treatments affected growth performance, carcass traits or meat characteristics. Lipid and fatty acid contents were similar in LL and BF and not influenced by the dietary treatment. Meat oxidative stability was strongly improved by both antioxidants. These findings indicate that both EcoE and VE greatly improved the oxidative stability of LL and BF muscles at the dosage rates which, from an economic point of view, would normally be included in the formulation of feeds for rabbits.This study is part of a multidisciplinary research project funded by the Department of Veterinary Medical Science (University of Bologna, Italy). The authors thank Martini Group Spa (Budrio di Longiano, FC, Italy) who provided animals and feeds, and Alltech (Casalecchio di Reno, BO, Italy) who supplied the EcoE.Minardi, P.; Mordenti, A.; Badiani, A.; Pirini, M.; Trombetti, F.; Albonetti, S. (2020). Effect of dietary antioxidant supplementation on rabbit performance, meat quality and oxidative stability of muscles. World Rabbit Science. 28(3):145-159. https://doi.org/10.4995/wrs.2020.12273OJS145159283Abdel-Khalek A.M. 2013. Supplemental antioxidants in rabbit nutrition: A review. Livest. Sci., 158: 95-105. https://doi.org/10.1016/j.livsci.2013.10.019Alasnier C., Gandemer G. 1998. Fatty acid and aldehyde composition of individual phospholipid classes of rabbit skeletal muscles is related to the metabolic type of the fiber. Meat Sci., 48: 225-235. https://doi.org/10.1016/S0309-1740(97)00096-XAlbonetti S., Minardi P., Trombetti F., Savigni F., Mordenti A.L., Baranzoni G.M., Trivisano C., Greco F.P., Badiani A. 2017. 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Rabbit meat production and consumption: State of knowledge and future perspectives. Meat Sci., 143: 137-146. https://doi.org/10.1016/j.meatsci.2018.04.029Dalle Zotte A., Cullere M., RĂ©mignon H., Alberghini L., Paci G. 2016. Meat physical quality and muscle fiber properties of rabbit meat as affected by the sire breed, season, parity order and gender in an organic production system. World Rabbit Sci., 24: 145-154. https://doi.org/10.4995/wrs.2016.4300Dalle Zotte A., RĂ©mignon H., Ouhayoun J. 2005. Effect of feed rationing during post-weaning growth on meat quality, muscle energy metabolism and fiber properties of Biceps femoris muscle in the rabbit. Meat Sci., 70: 301-306. https://doi.org/10.1016/j.meatsci.2005.01.016Dalle Zotte A., SzendrƑ Z. 2011. The role of rabbit meat as functional food. Meat Sci., 88: 319-331. https://doi.org/10.1016/j.meatsci.2011.02.017DokoupilovĂĄ A., Marounek M., Skrivanova V., Brezina P. 2007. 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Sci., 139: 196-205. https://doi.org/10.1016/j.livsci.2011.01.010ErdĂšlyi M., VirĂĄg G., MĂ©zes M. 2000. Effect of supranutritional additive selenium supply on the tissue selenium concentration and the activity of glutathione peroxidase enzyme in rabbit. World Rabbit Sci., 8: 183-191.Erickson M.C. 1992. Variation of lipid and tocopherol composition in three strains of channel catfish (Ictalurus punctatus). J. Sci. Food Agric., 59: 529-536. https://doi.org/10.1002/jsfa.2740590416European Communities: Council Regulation (EC) 2011. 1169/2011 on the Provision of Food Information to Consumers. Available at: http://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32011R1169&from=EN. Accessed April 2017.Giaretta E., Mordenti A., Palmonari A., Brogna N., Canestrari G., Belloni P., Cavallini D., Mammi L., Cabbri R., Formigoni A. 2019. NIRs calibration models for chemical composition and fatty acid families of raw and freeze-dried beef: A comparison. J. Food Compost. 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CABI Publishing, New York: USA, 119-150. https://doi.org/10.1079/9781845936693.0222Matics Z., Cullere M., SzĂ­n M., GerencsĂ©r Zs., SzabĂł A., FĂ©bel H., Odermatt M., Radnai I., Dalle Zotte A., SzendrƑ Zs. 2017. Effect of a dietary supplementation with linseed oil and selenium to growing rabbits on their productive performances, carcass traits and fresh and cooked meat quality. J. Anim. Physiol. Anim. Nutr., 101: 685-693. https://doi.org/10.1111/jpn.12589Mattioli S., Cardinali R., Balzano M., Pacetti D., Castellini C., Dal Bosco A., Frega N.G. 2017. Influence of dietary supplementation with prebiotic, oregano extract, and vitamin E on fatty acid profile and oxidative status of rabbit meat. J. Food Qual., Article ID 3015120, 1-9. https://doi.org/10.1155/2017/3015120McLellan M.R., Lind L.R., Kime R.W. 1995. Hue angle determinations and statistical analysis for multiquadrant hunter L,a,b data. J. 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    AquivionÂź PFSA-based spray-freeze dried composite materials with SiO2 and TiO2 as hybrid catalysts for the gas phase dehydration of ethanol to ethylene in mild conditions

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    Aquivion PFSA resin, a perfluorinated ion-exchange polymer, has been used as a heterogeneous strong acid catalyst for a range of reactions; however, the activity of this material is limited due to the extremely low surface area of the polymer. In this paper we described the one-step synthesis of AquivionÂź PFSA-based hybrid materials using heterocoagulation and spray-freeze-drying of sols containing the precursor of the active phases. The intimated encapsulation of different nano-oxides, such as TiO2 and SiO2 in the superacid resin matrix was easily obtained using this technique and compared with similar catalysts prepared by the impregnation conventional route. The approach led to the preparation of porous micro-granules characterised by a high homogeneity in the phase distribution and high surface area. The prepared materials were active and selective for the gas phase dehydration of ethanol to ethylene in mild conditions. The increase of the porosity improved the activity of the composites, compared to the pure AquivionÂź PFSA, and allowed to reduce the amount of the superacid resin. Moreover, the type of encapsulated oxide, TiO2 or SiO2, modified the improved performance of the catalysts, having TiO2 the higher efficiency for ethanol conversion and selectivity in ethylene at very low temperature

    A fixed-time second order sliding mode observer for a class of nonlinear systems

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    This paper presents a second order fixed time sliding mode observer based on an extension of the super-twisting algorithm. This observer can be applied to a class of nonlinear system with a block-wise representation. The block structure provides a straightforward form to the application of the proposed second order sliding mode algorithm, yielding to finite-time convergence with a settling time independent to the system initial conditions. Finally, as numerical simulation example, the case of a linear induction motor is studied, exposing the efficiency and feasibility of the proposal

    Morphology and mechanics of star copolymer ultrathin films probed by atomic force microscopy in the air and in liquid

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    Star copolymer films were produced by using spin-coating, drop-casting, and casting deposition techniques, thus obtaining ultrathin and thick films, respectively. The morphology is generally flat, but it becomes substrate-dependent for ultrathin films where the planarization effect of films is not efficient. The indentation hardness of films was investigated by Force Volume Maps in both the air and liquid. In the air, ultrathin films are in the substrate-dominated zone and, thus, the elastic modulus E is overestimated, while E reaches its bulk value for drop-casted ultrathin and thick films. In liquid (water), E follows an exponential decay for all films with a minimum soaked time t0 of 0.37 and 2.65 h for ultrathin and drop-casted ultrathin and thick films, respectively. After this time, E saturates to a value on average 92% smaller than that measured in the air due to film swelling. Such results support the role of film morphology in the antimicrobial activity envisaged in the literature, suggesting also an additional role of film hardness

    Superacid resin-based heterogeneous catalysts for the selective acylation of 1,2-methylenedioxybenzene

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    In this work, we firstly report on the use of highly active and selective Aquivion superacid resins as heterogeneous catalysts for the acylation of 1,2-methylenedioxybenzene (MDB) with propionic anhydride (AP). The reaction was investigated and optimized using solvent-free conditions to selectively produce 3,4-methylenedioxypropiophenone (MDP1P), a key intermediate for the manufacture of active ingredients used in insecticide formulations with a volume of production of roughly 3000 t/y. Interestingly, Aquivion-based catalysts allows to work in mild reaction conditions (i. e. 80 °C), obtaining MDP1P yields as high as 44 % after only 1 h of reaction (selectivity 83 %). A detailed study of the AP reactivity demonstrated its tendency to promote oligomerization reactions that, as confirmed by ex-situ and in-situ FT-ATR analyses, caused the deactivation of the catalyst forming surficial carbonaceous residues. In this context, a fast oxidation of the resin surface organic residues using a diluted HNO3 (or H2O2) solution was proven to be an efficient method to regenerate the catalyst, which can be reused for several reaction cycles. The results obtained in preliminary scale-up tests were basically unaffected by the reaction volume (up to 800 mL), paving the way for possible future applications of the process

    Strategies to improve hydrogen activation on gold catalysts

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    Catalytic reactions involving molecular hydrogen are at the heart of many transformations in the chemical industry. Classically, hydrogenations are carried out on Pd, Pt, Ru or Ni catalysts. However, the use of supported Au catalysts has garnered attention in recent years owing to their exceptional selectivity in hydrogenation reactions. This is despite the limited understanding of the physicochemical aspects of hydrogen activation and reaction on Au surfaces. A rational design of new improved catalysts relies on making better use of the hydrogenating properties of Au. This Review analyses the strategies utilized to improve hydrogen–Au interactions, from addressing the importance of the Au particle size to exploring alternative mechanisms for H2 dissociation on Au cations and Au–ligand interfaces. These insights hold the potential to drive future applications of Au catalysis. (Figure presented.)

    Design of TiO2-Surfactin Hybrid Systems with Multifunctional Properties

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    In recent years, multifunctional inorganic-organic hybrid materials have been widely investigated in order to determine their potential synergetic, antagonist, or independent effects in terms of reactivity. The aim of this study was to design and characterize a new hybrid material by coupling well-known photocatalytic TiO2 nanoparticles with sodium surfactin (SS), a biosurfactant showing high binding affinity for metal cations as well as the ability to interact with and disrupt microorganisms' cell membranes. We used both chemical and colloidal synthesis methodologies and investigated how different TiO2:SS weight ratios affected colloidal, physicochemical, and functional properties. We discovered a clear breaking point between TiO2 and SS single-component trends and identified different ranges of applicability by considering different functional properties such as photocatalytic, heavy metal sorption capacity, and antibacterial properties. At low SS contents, the photocatalytic properties of TiO2 are preserved (conversion of organic dye = 99% after 40 min), and the hybrid system can be used in advanced oxidation processes, taking advantage of the additional antimicrobial SS properties. At high SS contents, the TiO2 photoactivity is inhibited, and the hybrid can be usefully exploited as a UV blocker in cosmetics, avoiding undesired oxidative effects (UV adsorption in the range between 300-400 nm). Around the breaking point (TiO2:SS 1:1), the hybrid material preserves the high surface area of TiO2 (specific surface area around 180 m(2)/g) and demonstrates NOx depletion of up to 100% in 80 min, together with improved adhesion of hybrid antibacterial coating. The last design demonstrated the best results for the concurrent removal of inorganic, organic, and biological pollutants in water/soil remediation applications

    Transition metal b-site substitutions in laalo3 perovskites reorient bio-ethanol conversion reactions

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    LaAlO3 perovskites, as such and with 25% molar Al substitution by Cu, Co, or Ga, have been prepared by sol-gel methods and tested as heterogeneous catalysts in the gas-phase conversion of ethanol. LaAlO3 presented a significant acidic character, with high formation of ethylene by ethanol dehydration. B-site substitutions increased the basicity of the catalysts, favoring the dehydrogenation of ethanol to acetaldehyde. The most reducible Cu-and Co-substituted materials, characterized by easier formation of surface oxygen vacancies, promoted the self-condensation of acetaldehyde by the Tishchenko mechanism, with formation of acetone and odd-carbon number products. Aldol coupling of acetaldehyde, favored on pure and Ga-substituted LaAlO3, led to the formation of butadiene and hexadiene. The role of Ga insertion, favoring both dehydrogenation of ethylene and dehydration of higher alcohols, corresponds to an amphoteric character. The formation of olefins and diolefins on all catalysts suggests that LaAl-based materials present the most acidic character among La-perovskites
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