Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts

The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298 K and 40 bar over modified supported iridium catalysts has been studied. Cinchonidine has been used as chiral inducer. The catalysts were obtained by impregnation of Ir(acac)3 on three different supports: SiO2, TiO2 and MoO3, followed by calcination in air and reduction under hydrogen at 773 K. All the solids were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption, XRD, TEM, TPR and XPS. It was found that Ir/SiO2 and Ir/TiO2 catalysts reduced at high temperatures, 773 K, possess similar metal particle size, close to 2.0 nm, eventhough the H/Ir ratio obtained from H2 chemisorption showed larger differences, with the H/Ir ratio being lower for titania- and molybdenum-supported iridium catalysts. In these samples, migration of the partially reduced supports, TiOx and MoOx moieties, on the metal crystals induce the creation of Ird+ species. TPR and XPS results confirmed that the metal component was not completely reduced. The activity was influenced by the nature of the support, being more active those in the SMSI state such as Ir/TiO2 and Ir/MoO3 being more active. This has been attributed to the presence of electron deficient metal species, Ird+, which are responsible for the polarization of the carbonyl bond of the substrates, thus favoring the activity and enantioselectivity of the reaction. The effect of different solvents on the activity and the enantioselectivity of the reaction was also studied. The highest enantiomeric excess (ee) of (R)-1-phenyl-1-hydroxy-2-propanone (20%) was obtained with the Ir/TiO2 catalyst using acetic acid as solvent.The authors thank the support of Núcleo Científico Milenio ICM P99-92, and FONDECYT Grant 1030670.Peer reviewe

Root Zone Sensors for Irrigation Management in Intensive Agriculture

Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower’s experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS’ (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy

Thermal weed control in Photinia x Fraseri “Red Robin” container nurseries

A near-zero tolerance policy on weeds by markets for nursery crops calls for weed-free container-grown plants, and forces growers to frequently remove weeds. Thermal weed control could represent a novel method to control weeds in shrubs from container nurseries, thus avoiding the use of herbicides and mulches. The aims of this study were to develop custom-built machinery for thermal weed control in container nurseries and to test the weed control efficiency of flame weeding and steaming in Photinia x fraseri "Red Robin" containers. A liquefied petroleum gas (LPG) fed flamer and a steamer with a dedicated diffuser were built. Four treatments were applied for a total period of 24 months: steaming once every four months, steaming once every two months, flame weeding once every two months or once a month. Temperature values measured at different depths in the substrate after thermal applications were recorded and analyzed. Photinia x fraseri features (height, diameter, and dry biomass) and aesthetic parameters as affected by thermal treatments were also evaluated. The trend in temperature values of the substrate over time followed a two-phase exponential decay. All the thermal treatments lead to a continuous near-100% weed control level, which is the level required by growers for aesthetic reasons. No damages caused by heat on Photinia x fraseri were observed. Container nursery producers could thus adopt thermal methods as a substitute for chemical solutions for weed control management

Reduction of nutrient run-off by the use of coated slow-release fertilizers on two container-grown nursery crops

The agricultural district of Pistoia (Tuscany, Italy) is one of the most important sites in Europe for the production of Hardy Ornamental Nursery Stock (HONS). One of the main problems of this sector is the environmental impact of the pot cultivation, mainly due to an incorrect irrigation scheduling that leads to high nitrogen and phosphorus losses. The aim of this research has been to compare the effects of the traditional fertigation versus new fertilization strategies, based on the use of controlled slow-release fertilizers (CRFs), on plant growth and on nitrogen and phosphorus run-off in two container HONS species (Photinia × fraseri and Prunus laurocerasus). Every week, plant height, cumulate irrigation and drainage volume were measured on four replicates for each treatment and species. Every four weeks two average samples of drainage water and irrigation water for each treatment and species were analysed, determining total nitrogen and phosphorus content, in order to draft a water and nutrient balance. The three different fertilization strategies did not produce any relevant effect on the final plant height and all plants were ranked in the top quality market category. The data confirmed that the use of CRFs could contribute to a huge reduction of nitrogen and phosphorus run-off in the environment and could be a winning strategy for the fertilization of HONS in nitrate vulnerable zones

A primary offshore wind farm site assessment using reanalysis data: a case study for Samothraki island

The correct strategy for monitoring and assessing marine Renewable Energy Sources (RESs) is of great importance for local/national sustainable development. To achieve this goal, it is necessary to measure in the most precise possible manner the local/regional RESs potential. This is especially true for Offshore Wind (OW) energy potential, since the most precise techniques are long and expensive, and are not able to assess the RESs potential of large areas. Today, Remote Sensing (RS) satellites can be considered the most important land and marine observation tools. The RS tools can be used to identify the interested areas for future OW energy converters installations in large and small-scale areas. In this study, the OW energy potential has been analysed by means of a 40 years wind speed data from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset of the Samothraki island surrounding area in the Mediterranean Sea. The OW speed potential has been analysed by means of monthly data from ECMWF Interim reanalysis (ERA-Interim) datasets using the Network Common Data Form (NetCDF) format. Automatically, analyses have been carried out using the Region Of Interest (ROI) tool and Geographical Information System (GIS) software in order to extract information about the OW speed assessment of the Samothraki island area. The primary results of this study show that the southwest area of Samothraki island has good potential for future OW farms installation (bottom fixed and floating version) in near and offshore areas. This study shows the OW energy potential per location, as well as the trend of OW speed, which has changed over the past 40 years in the Mediterranean Sea

Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts

The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298 K and 40 bar over modified supported iridium catalysts has been studied. Cinchonidine has been used as chiral inducer. The catalysts were obtained by impregnation of Ir(acac)3 on three different supports: SiO2, TiO2 and MoO3, followed by calcination in air and reduction under hydrogen at 773 K. All the solids were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption, XRD, TEM, TPR and XPS. It was found that Ir/SiO2 and Ir/TiO2 catalysts reduced at high temperatures, 773 K, possess similar metal particle size, close to 2.0 nm, eventhough the H/Ir ratio obtained from H2 chemisorption showed larger differences, with the H/Ir ratio being lower for titania- and molybdenum-supported iridium catalysts. In these samples, migration of the partially reduced supports, TiOx and MoOx moieties, on the metal crystals induce the creation of Ird+ species. TPR and XPS results confirmed that the metal component was not completely reduced. The activity was influenced by the nature of the support, being more active those in the SMSI state such as Ir/TiO2 and Ir/MoO3 being more active. This has been attributed to the presence of electron deficient metal species, Ird+, which are responsible for the polarization of the carbonyl bond of the substrates, thus favoring the activity and enantioselectivity of the reaction. The effect of different solvents on the activity and the enantioselectivity of the reaction was also studied. The highest enantiomeric excess (ee) of (R)-1-phenyl-1-hydroxy-2-propanone (20%) was obtained with the Ir/TiO2 catalyst using acetic acid as solvent.The authors thank the support of Núcleo Científico Milenio ICM P99-92, and FONDECYT Grant 1030670.Peer reviewe