Influence of Sinusoidal Drive Speed Modulation on Rotor with Continuous Stator Contact

Torsional vibrations experienced by drill strings can be detrimental to drilling operations. With a goal of understanding torsional vibrations experienced by drill strings and determining means to attenuate undesired vibrations, the authors have studied the effect of adding a sinusoidal modulation to a constant rotation speed of a drill string. A combination of modeling, analysis, and experiments is used to explore the influence of this rotation input modulation on the system response. The drill string is modeled as a modified Jeffcott rotor, which is described by a system with three degrees of freedom. Considering the case of forward whirling of a rotor in continuous contact with a stator, the equations of motion are reduced to a single degree-of-freedom nonlinear oscillator describing the torsional motions. In order to understand the fast time scale and slow time scale components of the motion, the method of direct partitions of motions is used to determine an approximate response to the nonlinear oscillator. The obtained results of the analysis illustrate that with the sinusoidal modulation of the rotor drive speed, the equivalent torsion stiffness can be enhanced and the character of the friction force at the contact can be made smooth. The analyses helps bring forth the stabilizing influence of the added sinusoidal input to the rotor drive speed. Over the considered parameter ranges, the numerical results obtained with the full three degree-of-freedom model and the reduced single degree-of-freedom model are found to be in agreement with each other. Furthermore, the results from these models are found to compare well with those obtained by using the method of direct partition of motions. Experiments with a laboratory scale drill-string arrangement are to be carried out to validate the analytical and numerical findings and further explore the effectiveness of the drive speed modulation on the rotor dynamics.qscienc

Microwave-Assisted Solvothermal Synthesis of Mo-Doped TiO2 with Exceptional Textural Properties and Superior Adsorption Kinetics

Assigned to their outstanding physicochemical properties, TiO2-based materials have been studied in various applications. Herein, TiO2 doped with different Mo contents (Mo-TiO2) was synthesized via a microwave-assisted solvothermal approach. This was achieved using titanium (IV) butoxide and molybdenum (III) chloride as a precursor and dodecylamine as a surface directing agent. The uniform effective heating delivered by microwave heating reduced the reaction time to less than 30 min, representing several orders of magnitude lower than conventional heating methods. The average particle size ranged between 9.7 and 27.5 nm and it decreased with increasing the Mo content. Furthermore, Mo-TiO2 revealed mesoporous architectures with a high surface area ranging between 170 and 260 m2 g−1, which is superior compared to previously reported Mo-doped TiO2. The performance of Mo-TiO2 was evaluated towards the adsorption of Rhodamine B (RhB). In contrast to TiO2, which revealed negligible adsorption for RhB, Mo-doped samples depicted rapid adsorption for RhB, with a rate that increased with the increase in Mo content. Additionally, Mo-TiO2 expressed enhanced adsorption kinetics for RhB compared to state-of-the-art adsorbents. The introduced synthesis procedure holds a grand promise for the versatile synthesis of metal-doped TiO2 nanostructures with outstanding physicochemical properties.NPRP Grant no. NPRP 12S-0304-190218 from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors

Solution combustion synthesis of Ni/La2O3for dry reforming of methane: Tuning the basicity via alkali and alkaline earth metal oxide promoters

The production of syngas via dry reforming of methane (DRM) has drawn tremendous research interest, ascribed to its remarkable economic and environmental impacts. Herein, we report the synthesis of K, Na, Cs, Li, and Mg-promoted Ni/La2O3 using solution combustion synthesis (SCS). The properties of the catalysts were determined by N2 physisorption experiments, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), and H2-TPR (temperature programmed reduction). In addition, their catalytic performance towards DRM was evaluated at 700 °C. The results demonstrated that all catalysts exhibited porous structures with high specific surface area, in particular, Mg-promoted Ni/La2O3 (Mg–Ni–La2O3) which depicted the highest surface area and highest pore volume (54.2 m2 g−1, 0.36 cm3 g−1). Furthermore, Mg–Ni–La2O3 exhibited outstanding catalytic performance in terms of activity and chemical stability compared to its counterparts. For instance, at a gas hourly space velocity (GHSV) of 30 000 mL g−1 h−1, it afforded 83.2% methane conversion and 90.8% CO2 conversion at 700 °C with no detectable carbon deposition over an operating period of 100 h. The superb DRM catalytic performance of Mg–Ni–La2O3 was attributed to the high specific surface area/porosity, strong metal-support interaction (MSI), and enhanced basicity, in particular the strong basic sites compared to other promoted catalysts. These factors remarkably enhance the catalytic performance and foster resistance to coke deposition.This publication was supported by Qatar University, internal grant number QUCG-CENG-19/20-7. The ?ndings achieved herein are solely the responsibility of the authors. The authors also acknowledge the technical support of Central Laboratories Unit (CLU), Center for Advanced Materials (CAM), and Gas Processing Center (GPC), Qatar University, Doha, Qatar.Scopu

Versatile Synthesis of Pd and Cu Co-Doped Porous Carbon Nitride Nanowires for Catalytic CO Oxidation Reaction

Developing efficient catalyst for CO oxidation at low-temperature is crucial in various industrial and environmental remediation applications. Herein, we present a versatile approach for controlled synthesis of carbon nitride nanowires (CN NWs) doped with palladium and copper (Pd/Cu/CN NWs) for CO oxidation reactions. This is based on the polymerization of melamine by nitric acid in the presence of metal-precursors followed by annealing under nitrogen. This intriguingly drove the formation of well-defined, one-dimensional nanowires architecture with a high surface area (120 m2 g−1) and doped atomically with Pd and Cu. The newly-designed Pd/Cu/CN NWs fully converted CO to CO2 at 149 °C, that was substantially more active than that of Pd/CN NWs (283 °C) and Cu/CN NWs (329 °C). Moreover, Pd/Cu/CN NWs fully reserved their initial CO oxidation activity after 20 h. This is mainly attributed to the combination between the unique catalytic properties of Pd/Cu and outstanding physicochemical properties of CN NWs, which tune the adsorption energies of CO reactant and reaction product during the CO oxidation reaction. The as-developed method may open new frontiers on using CN NWs supported various noble metals for CO oxidation reaction

Design of Ni/La2O3 catalysts for dry reforming of methane: Understanding the impact of synthesis methods

Fine-tuning of materials properties, particularly the catalytic properties, through innovative synthesis procedures has gained an increased research interest in the last decades. It is well known that synthesis procedures have considerable impact on the physio-chemical properties of the synthesized materials even if the chemical composition is maintained. Herein, we investigated the impact of selected synthesis methods on the catalytic performance of Ni/La2O3 for the dry reforming of methane (DRM), a challenging reaction known for severe coking. Although this catalyst has been frequently studied for DRM, however, tuning the structure-activity relationship by varying the synthesis routes has not been reported. Herein, the chosen synthesis techniques; for example the solution combustion synthesis (Ni/La-SC), sol-gel (Ni/La-SG), homogeneous precipitation (Ni/La-HP), solvothermal (Ni/La-ST), and modified oleylamine-assisted synthesis (Ni/La-ME); considerably affected the morphology, metal support interaction (MSI), and surface area of Ni/La2O3 catalysts leading to variation in their performance for DRM. The investigated catalysts were thoroughly characterized by using SEM-EDX, TEM, N2-physisorption, XRD, XPS, and H2-TPR to understand the structural properties. Their catalytic performance towards the DRM was evaluated by varying the temperature between 550 and 800 °C. DRM experiments demonstrated that among the studied catalysts, Ni/La-SC showed the best performance for DRM with a high catalytic activity and coking resistance. For instance, Ni/La-SC revealed the highest CO2 and CH4 conversions i.e. 97.9 ± 1.5% and 96.6 ± 1.8%, respectively at 800 °C. The same sample revealed the highest hydrogen yield i.e. 71.9% and the highest H2/CO ratio i.e. 1.03 ± 0.013 at the same temperature. The results revealed that Ni/La-SC demonstrated the lowest increment (20.9%) in the Ni crystallite size after DRM reaction, highest durability, and the lowest rate of coke formation (42 ± 5.2 mg C/gcatalyst) over an operating period of 100 h at 800 °C. The outstanding performance of Ni/La-SC catalyst was credited to the small crystallite size of Ni, high Ni0/Ni2+ ratio, high BET area, and a good dispersion of nickel sites over the La2O3 support. The obtained results may open new frontiers for size and shape-controlled synthesis of nanostructured metals/metal oxides catalysts with controllable morphologies and dispersion that can lead to desirable catalytic properties.This publication was supported by Qatar University , internal grant number QUCG-CENG-19/20-7 . The findings reported herein are solely the responsibility of the authors.Scopu

Natural clay-supported palladium catalysts for methane oxidation reaction: Effect of alloying

The catalytic combustion of methane (CCM) has been extensively studied owing to the wide use of methane in motor vehicles and power generation turbines. However, the absence of polarizability and the high C-H bond strength are considered to be the main drawbacks that limit its oxidation by traditional catalytic converters. Palladium-based catalysts are recognized as the benchmark catalysts for methane oxidation, especially under oxidizing conditions, and their activity is dependent on different parameters such as size, dispersion, and the nature of the support. Additionally, metal oxides are the most common supports used for CCM; however, they can become saturated with water, especially during steady-state operation at low temperatures, owing to their hydrophilic nature. This causes saturation of the active sites with OH species, which poisons the active centers of the catalyst, prevents activation of methane molecules, and induces catalyst sintering. Herein, we reported the synthesis of a binary palladium nanoalloy on a halloysite nanotube support (PdM@Hal). This one-pot synthesis procedure was performed via ultrasound-enhanced reduction of metal precursors in aqueous solution containing dispersed halloysite nanotubes, using NaBH4 as reducing agent. Transmission electron microscopy revealed that the synthesized PdM@Hal catalysts preserved the morphology of the pristine support after synthesis and calcination, with good dispersion of the catalyst on the surface of the support. Promoted metal-support interactions revealed enhanced catalytic performance, following the order PdNi > PdCo > Pd > PdCu, with activation energies of 68-94 kJ mol-1. This journal is - The Royal Society of Chemistry.Scopu

Rational synthesis of ternary PtIrNi nanocrystals with enhanced poisoning tolerance for electrochemical ethanol oxidation

The development of highly efficient and durable anode materials for ethanol electro-oxidation remains a challenge. Herein, we report the synthesis of Pt1−x−yIrxNiy nanocrystals via one-step procedure by ultrasonic-assisted co-reduction of the metal precursors using ascorbic acid as a mild reducing agent and pluronic F127 as a structure directing agent. The catalytic performance of this ternary catalyst towards electrochemical oxidation of ethanol was examined and compared to its mono and binary Pt counterparts (Pt, Pt1−xIrx, and Pt1−yNiy) that are synthesized by the same method. TEM analysis showed a porous nanodendritic structure for the synthesized ternary electrocatalyst with an average size of 20 ± 1 nm. The electrochemical measurements revealed an electrochemically active surface area, ECSA, of 73 m2 g−1. The as-synthesized ternary electrocatalyst showed an improved catalytic activity towards ethanol oxidation in 1 M KOH with a measured mass activity of 3.8 A mg−1 which is 1.7, 2.0, and 3.2 times higher than that of Pt1−xIrx, Pt1−yNiy, and Pt, respectively. Additionally, the Pt1−x−yIrxNiy nanocrystals expressed high poisoning tolerance (jf/jb = 4.5) and high durability compared to its mono and binary counterparts. Keywords: Platinum alloy, Iridium, Nickel, Porous nanodendrites, Electro-oxidation, Ethano

Transition metal nanoparticles doped carbon paper as a cost-effective anode in a microbial fuel cell powered by pure and mixed biocatalyst cultures

The poor wettability and high cost of the carbonaceous electrodes materials prohibited the practical applications of microbial fuel cells (MFCs) on large scale. Here, a novel nanoparticles of metal sheathed with metal oxide is electrodeposited on carbon paper (CP) to introduce as high-performance anodes of microbial fuel cell (MFC). This thin layer of metal/metal oxide significantly enhance the microbial adhesion, the wettability of the anode surface and decrease the electron transfer resistance. The investigation of the modified CP anodes in an air-cathode MFCs fed by various biocatalyst cultures shows a significant improving in the MFC performance. Where, the generated power and current density was 140% and 210% higher as compared to the pristine CP. Mixed culture of exoelectrogenic microorganism in wastewater exhibited good performance and generated higher power and current density compared to yeast as pure culture. The excellent capacitance with a distinctive nanostructure morphology of the modified-CP open an avenues for practical applications of MFCs.This work was supported by the National Research Foundation of Korea (NRF) via a grant funded by the government of Korea ( MSIP ) (Grant No. 2015R1C1A1A01054039 ) and in part by Open Laboratory Operational Business Developing and Diffusing the Regional Specialization Technology funded by the Busan Institute of S&T Evaluation and Planning (BISTEP) . Appendix AScopu