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The selective deoxygenation of palm oil to produce green diesel has been investigated over Ni catalysts supported on ZrO2 (Ni/Zr) and CeO2–ZrO2 (Ni/CeZr) supports. The modification of the support with CeO2 acted to improve the Ni dispersion and oxygen lability of the catalyst, while reducing the overall surface acidity. The Ni/CeZr catalyst exhibited higher triglyceride (TG) conversion and yield for the desirable C15–C18 hydrocarbons, as well as improved stability compared to the unmodified Ni/Zr catalyst, with TG conversion and C15–C18 yield remaining above 85% and 80% respectively during 20 h of continuous operation at 300 oC. The high C17 yields also revealed the dominance of the deCOx (decarbonylation/decarboxylation) pathway. A fully comprehensive process simulation model has been developed to validate the experimental findings in this study, and a very good validation with the experimental data has been demonstrated. The model was then further utilised to investigate the effects of temperature, H2 partial pressure, H2/oil feed ratio and LHSV. The model predicted that maximum triglyceride conversion was attainable at reaction conditions of 300 °C temperature, 30 bar H2 partial pressure, H2/oil of 1000 cm3/cm3 feed ratio and 1.2 h−1 LHSV., MAG and NDC gratefully acknowledge that this researched was co-financed by Greece and the European Union (European Social Fund-ESF) through the Operational Programme “Human Resources Development, Education and Lifelong Learning” (MIS-5050170). KP and SA acknowledge the financial support from the Abu Dhabi Department of Education and Knowledge through the grant AARE-2019-233 and the support from Khalifa University through the grant RC2-2018-024. VS acknowledges the ICTS ELECMI-LMA for offering access to their instruments and expertise.

Ni-based catalysts supported on sol-gel prepared Pr-doped CeO2 with varied porosity and nanostructure were tested for the CO2 methanation reaction. It was found that the use of ethylene glycol in the absence of H2O during a modified Pechini synthesis led to a metal oxide support with larger pore size and volume, which was conducive toward the deposition of medium-sized Ni nanoparticles confined into the nanoporous structure. The high Ni dispersion and availability of surface defects and basic sites acted to greatly improve the catalyst’s activity. CFD simulations were used to theoretically predict the catalytic performance given the reactor geometry, whereas COMSOL and ASPEN software were employed to design the models. Both modelling approaches (CFD and process simulation) showed a good validation with the experimental results and therefore confirm their ability for applications related to the prediction of the CO2 methanation behaviour., AIT, NDC and MAG acknowledge support of this work by the project “Development of new innovative low carbon energy technologies to improve excellence in the Region of Western Macedonia” (MIS 5047197), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure” funded by the Operational Program "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014–2020) and co-financed by Greece and the European Union (European Regional Development Fund). AGSH, AAD and KP acknowledge support from Khalifa University through the grant RC2–2018-024. Additional partial support has been provided by the Abu Dhabi Award for Research Excellence (AARE) 2019 through project AARE19–233. VS acknowledges the ICTS ELECMI-LMA for offering access to their instruments and expertise.

Effective numerical weather forecasting is vital in arid regions like the United Arab Emirates (UAE) where extreme events like heat waves, flash floods, and dust storms are severe. Hence, accurate forecasting of quantities like surface temperatures and humidity is very important. To date, there have been few seasonal-to-annual scale verification studies with WRF at high spatial and temporal resolution. This study employs a convection-permitting scale (2.7 km grid scale) simulation with WRF with Noah-MP, in daily forecast mode, from 1 January to 30 November 2015. WRF was verified using measurements of 2 m air temperature (T2 m), 2 m dew point (TD2 m), and 10 m wind speed (UV10 m) from 48 UAE WMO-compliant surface weather stations. Analysis was made of seasonal and diurnal performance within the desert, marine, and mountain regions of the UAE. Results show that WRF represents temperature (T2 m) quite adequately during the daytime with biases ≤+1 ∘C. There is, however, a nocturnal cold bias (−1 to −4 ∘C), which increases during hotter months in the desert and mountain regions. The marine region has the smallest T2 m biases (≤−0.75 ∘C). WRF performs well regarding TD2 m, with mean biases mostly ≤ 1 ∘C. TD2 m over the marine region is overestimated, though (0.75–1 ∘C), and nocturnal mountain TD2 m is underestimated (∼−2 ∘C). UV10 m performance on land still needs improvement, and biases can occasionally be large (1–2 m s−1). This performance tends to worsen during the hot months, particularly inland with peak biases reaching ∼ 3 m s−1. UV10 m is better simulated in the marine region (bias ≤ 1 m s−1). There is an apparent relationship between T2 m bias and UV10 m bias, which may indicate issues in simulation of the daytime sea breeze. TD2 m biases tend to be more independent. Studies such as these are vital for accurate assessment of WRF nowcasting performance and to identify model deficiencies. By combining sensitivity tests, process, and observational studies with seasonal verification, we can further improve forecasting systems for the UAE., This material is based on work supported by the UAE Research Program for Rain Enhancement Science, under the National Center of Meteorology, Abu Dhabi, UAE. Furthermore, we are grateful to the High Performance Computing Center Stuttgart (HLRS) for providing support and computing time on the XC40 system.

The present study provides, for the first time in the literature, a comparative assessment of the catalytic performance of Ni catalysts supported on γ-Al2O3 and γ-Al2O3 modified with La2O3, in a continuous flow trickle bed reactor, for the selective deoxygenation of palm oil. The catalysts were prepared via the wet impregnation method and were characterized, after calcination and/or reduction, by N2 adsorption/desorption, XRD, NH3-TPD, CO2-TPD, H2-TPR, H2-TPD, XPS and TEM, and after the time-on-stream tests, by TGA, TPO, Raman and TEM. Catalytic experiments were performed between 300–400 °C, at a constant pressure (30 bar) and different LHSV (1.2–3.6 h−1). The results show that the incorporation of La2O3 in the Al2O3 support increased the Ni surface atomic concentration (XPS), affected the nature and abundance of surface basicity (CO2-TPD), and despite leading to a drop in surface acidity (NH3-TPD), the Ni/LaAl catalyst presented a larger population of medium-strength acid sites. These characteristics helped promote the SDO process and prevented extended cracking and the formation of coke. Thus, higher triglyceride conversions and n-C15 to n-C18 hydrocarbon yields were achieved with the Ni/LaAl at lower reaction temperatures. Moreover, the Ni/LaAl catalyst was considerably more stable during 20 h of time-on-stream. Examination of the spent catalysts revealed that both carbon deposition and degree of graphitization of the surface coke, as well as, the extent of sintering were lower on the Ni/LaAl catalyst, explaining its excellent performance during time-on-stream., MAG, NDC and KNP gratefully acknowledge that this researched was co-financed by Greece and the European Union (European Social Fund-ESF) through the Operational Programme “Human Resources Development, Education and Lifelong Learning” (MIS-5050170). SD is thankful for financial assistance provided by the Research Committee of the University of Western Macedonia (grant number 70277). KP acknowledges the financial support from the Abu Dhabi Department of Education and Knowledge (ADEK) under the AARE 2019-233 grant and the support from Khalifa University under the RCII-2018-024.

In the study presented herein, nickel catalysts supported on CeO2 and, for the first time in the literature, on La2O3-Sm2O3-CeO2, La2O3-Pr2O3-CeO2 and La2O3-MgO-CeO2 were prepared and evaluated for the reaction of CO2 methanation. The carriers were prepared through a sol-gel microwave assisted method and the catalysts were obtained following wet impregnation. The physicochemical properties of the catalysts prior to reaction were determined through H2-TPR, H2-TPD, Raman spectroscopy, XRD, CO2-TPD, N2 physisorption-desorption, XPS and TEM. The spent catalysts, after the time-on-stream experiments were further characterised using TEM and TGA. It was shown that the simultaneous incorporation of La3+, Pr3+ and La3+, Sm3+ into the crystal structure of cerium oxide created higher population of oxygen vacant sites. Moreover, the co-presence of La3+, Mg2+ and La3+, Pr3+ into the CeO2 increased the plethos of moderate basic sites. These physicochemical properties increased the rate of CO2 methanation reaction at relatively low temperatures. Furthermore, it is argued that the addition of La3+ stabilized the Ni active sites via the probable formation of a new compound (La-O-Ni) on the catalyst surface or synergetic catalytic centers at the interfacial area improving the catalytic properties (activity and stability). Finally, the catalytic performance tests revealed that the addition of La3+ mainly improved the conversion of CO2 and yield of CH4 for the Ni/La-Mg-Ce and Ni/La-Sm-Ce samples. The rCO2 and XCO2 values at 300 °C followed the order Ni/La-Sm-Ce >> Ni/La-Mg-Ce > Ni/La-Pr-Ce > Ni/Ce., GIS is grateful for financial support by Greece and ESF through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Strengthening Human Resources Research Potential via Doctorate Research” (MIS-5000432), implemented by the State Scholarships Foundation (IKY). MAG is grateful to the Regional Excellence program (MIS 5047197), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund). IVY and NDC are grateful for financial support from the European Union and Greek national funds through the operational program Competitiveness, Entrepreneurship and Innovation, under the call Research-Create-Innovate (Project code: T1EDK-00782). SAK and KP acknowledge the financial support from the Abu Dhabi Department of Education and Knowledge (ADEK) under the AARE 2019-233 grant and support by the Khalifa University of Science and Technology under Award No. RC2-2018-024.

14 pags., 10 figs., 3 tabs. -- This article belongs to the Special Issue Advances in Elastic Micro-Structured Systems and Metamaterials, A numerical simulation study on elastic wave propagation of a phononic composite structure consisting of epoxy and tungsten carbide is presented for low-frequency elastic wave attenuation applications. The calculated dispersion curves of the epoxy/tungsten carbide composite show that the propagation of elastic waves is prohibited inside the periodic structure over a frequency range. To achieve a wide bandgap, the elastic composite structure can be optimized by changing its dimensions and arrangement, including size, number, and rotation angle of square inclusions. The simulation results show that increasing the number of inclusions and the filling fraction of the unit cell significantly broaden the phononic bandgap compared to other geometric tunings. Additionally, a nonmonotonic relationship between the bandwidth and filling fraction of the composite was found, and this relationship results from spacing among inclusions and inclusion sizes causing different effects on Bragg scatterings and localized resonances of elastic waves. Moreover, the calculated transmission spectra of the epoxy/tungsten carbide composite structure verify its low-frequency bandgap behavior., The authors thank the support from other members in the Advanced Materials Research Centre at Technology Innovation Institute and also thank Abu Dhabi Government’s Advanced Technology Research Council (ATRC), which oversees technology research in the emirate.