Search results for "Propene"
showing 10 items of 67 documents
Gas phase heterogeneous partial oxidation reactions
2018
Abstract Mixed metal oxides are used as catalysts in the gas phase partial oxidation of hydrocarbons. This paper will present the principles of catalyst choice for selective oxidation reactions as well as the structural features of metal oxide catalysts. The nature of active sites in selective oxidation reactions will also be briefly discussed. We will pay special attention to several representative reactions: (1) ODH of short chain alkanes (from C1 to C4), (2) propene partial oxidation/ammoxidation on bismuth molybdate based catalysts, (3) n-butane direct oxidation to maleic anhydride on VPO type catalysts, and (4) propane direct oxidation/ammoxidation on mixed MoVTe(Sb)Nb–O catalysts. Fin…
Extending the Shelf Life of White Peach Fruit with 1-Methylcyclopropene and Aloe arborescens Edible Coating
2020
The maintenance of high-quality standards for prolonging the shelf life of fruit and preserving sensory and nutritional quality is a priority for horticultural products. The aim of this work is to test the effectiveness of a single treatment of edible coating based on Aloe arborescens (EC) and a combined treatment of 1-methylcycyclopropene (1-MCP) and edible coating to prolong the shelf life of &ldquo
Effects of 1-Methylcyclopropene on postharvest quality traits, antioxidant activity and ascorbic acid content of mature-ripe mango fruits
2017
Introduction - Mango (Mangifera indica L.) is a climacteric fruit, very sensitive to prolonged storage with a relatively short postharvest life. The aim of this study was to investigate the effects of 1-MCP treatment on the pomological and sensory traits, antioxidant capacity and ascorbic acid content in late ripening mature-ripe mango fruits submitted to a simulated shelf life at 20 degrees C. Materials and methods - Mango late ripening fruits (cv. Keitt) were harvested from a commercial orchard, located at Furiano, province of Messina (Sicily, Italy; 38 degrees 3'N, 14 degrees 33'E; 5 m a.s.l.). Fruits were treated with 1-MCP (0.005 kg m(-3)) for 20 h in 1 m(3) closed containers and then …
Keggin heteropolyacid supported on BN and C3N4: Comparison between catalytic and photocatalytic alcohol dehydration
2020
The Keggin heteropolyacid (HPA), H3PW12O40 (PW12) has been supported on commercial boron nitride (BN) and two types of home prepared carbon nitride (C3N4). The supported PW12 was used in the gas-solid (photo)catalytic 2-propanol dehydration reaction to give propene at atmospheric pressure and temperatures in the range 70–120 °C and resulted more active than the pristine PW12. Reaction rate increased by increasing the temperature. Noticeably, the propene formation rate was higher by irradiating the catalytic system. The PW12/BN material resulted more active than PW12/C3N4. The acidity of the HPA cluster accounts for the catalytic role, whereas both the acidity and the redox properties of the…
Selective Introduction of Acid Sites in Different Confined Positions in ZSM-5 and Its Catalytic Implications
2018
Controlling the location of acid sites in zeolites can have a great effect on catalysis. In this work we face the objective of directing the location of Al into the 10R channels of ZSM-5 by taking advantage of the structural preference of B to occupy certain positions at the channel intersections, as suggested by theoretical calculations. The synthesis of B-Al-ZSM-5 zeolites with variable Si/Al and Si/B ratios, followed by B removal in a postsynthesis treatment, produces ZSM-5 samples enriched in Al occupying positions at 10R channels. The location of the acid sites is determined on the basis of the product distribution of 1-hexene cracking as a test reaction. The higher selectivity to prop…
Improved (photo)catalytic propene hydration in a gas/solid system by using heteropolyacid/oxide composites: Electron paramagnetic resonance, acidity,…
2017
Binary materials composed of the oxides SiO2, TiO2 and N-doped TiO2 and the Keggin heteropolyacid (PW12) were prepared and physicochemically characterized. They were used as catalysts and photocatalysts for the hydration of propene to 2-propanol. The characterization of the samples, particularly the electron paramagnetic resonance (EPR) spectroscopy results and the acidity properties, were useful to explain the key role played by the PW12 in the composite materials in the thermal and photoassisted catalytic processes. The simultaneous pres-ence of heat and UV light improved the activity of PW12 in the thermal process, and the binary materials showed better (photo)catalytic activities than t…
Cyclopentadienylmolybdenum(II) and -(III) complexes containing diene and allyl ligands. Part 4. Reactivity studies of the bisallyl complex CpMo(supin…
1998
Abstract Compound CpMo( η 3 -C 3 H 5 ) 2 , 3, has been synthesized from CpMoCl 4 and four equivalents of allylmagnesium bromide. While the compound is stable in donor solvents at room temperature, warming in refluxing MeCN induces the formation of 1,5-hexadiene by a metal-mediated allyl-allyl coupling process. Treatment of 3 with Bu t NC at room temperature affords CpMo( η 3 -C 3 H 5 )(Bu t NC) 2 , 4. A similar reduction with presumed allyl radical loss occurs for [CpMo( η 3 -C 3 H 5 )( η 4 -C 4 H 6 )] + , [1c] + , to afford [CpMo( η 4 -C 4 H 6 )(Bu t NC) 2 ] + , 5. Treatment of [1c] + with methyllithium affords two products, the major one (1c) corresponding to the one-electron reduction pa…
Photoactivity of shape-controlled TiO2 in gas-solid regime under solar irradiation
2019
Abstract Differently shape-controlled anatase TiO2 materials were tested as photocatalysts under both simulated and natural solar irradiation. Their photocatalytic activity in 2-propanol and propene partial oxidation and in the complete mineralization of acetaldehyde appears to increase with decreasing the shape control of the TiO2 material. This insight seems to be related to the residual presence of the templating species (fluoride anions) employed during the preparation of the shape-controlled TiO2 materials. In fact, the calcination of the powders, leading to levelling of the fluoride ions content, but also to a remarkable surface area decrease, gave rise to an increase of photocatalyti…
Selective oxidation of propane over alkali-doped Mo-V-Sb-O catalysts
2009
[EN] Alkali metal-doped MoVSbO catalysts have been prepared by impregnation of a MoVSbO-mixed oxide (prepared previously by a hydrothermal synthesis) and finally activated at 500 or 600 degrees C in N-2. The catalysts have been characterized and tested for the selective oxidation of propane and propylene. Alkali-doped catalysts improved in general the catalytic performance of MoVSbO, resulting more selective to acrylic acid and less selective to acetic acid than the corresponding alkali-free MoVSbO catalysts. However, the specific behaviour strongly depends on both the alkali metal added and/or the final activation temperature. At isoconversion conditions, catalysts activated at 600 degrees…
Comparison between catalytic and catalytic photo-assisted propene hydration by using supported heteropolyacid
2012
Abstract Hybrid materials have been prepared by impregnation of the heteropolyacid H 3 PW 12 O 40 on commercial TiO 2 . The polyoxometalates (POM) amount deposited was 15, 30, 50 and 70% with respect to the weight of the TiO 2 support. Moreover two samples containing a POM amount of 15, and 50% with respect to the weight of SiO 2 were also prepared for the sake of comparison. All prepared samples were efficient catalysts for the hydration of propene to 2-propanol in gas–solid regime at atmospheric pressure and at temperatures ranging between 50 and 85 °C. The study carried out on the hybrid TiO 2 based materials evidenced that, as far as the catalytic activity is concerned, exists an optimu…