Synthesis,Characterization, and Evaluation of Mesoporous MCM-41-supported Molybdenum Hydrotreating Catalysts

Abstract

Mesoporous MCM-41 material with high surface area and narrow pore size distribution was synthesized and used as a support for Mo, CoMo, and NiMo catalysts. The molybdenum loading was varied from 2–14 wt% on MCM-41. On 10 wt% Mo/MCM-41, the promoter Co or Ni concentration was varied from 1–5 wt%. All the catalyst samples were characterized by surface area, low temperature oxygen chemisorption, x-ray diffraction (XRD), and temperature programmed reduction methods. Characterization results show that Mo is well dispersed on MCM-41 up to 10 wt%. The catalytic activities were evaluated for thiophene hydrodesulphurization (HDS), cyclohexene hydrogenation (HYD), and furan hydrodeoxygenation (HDO). All three catalytic functionalities vary in a similar manner to that of oxygen chemisorption as a function of Mo loading, indicating that there is a correlation between oxygen uptake and catalytic sites. The activities of these catalysts were compared with γ-Al₂O₃- and amorphous SiO₂-supported catalysts. It was found that MCM-41-supported Mo catalysts displayed superior activities.     

High temperature operation of PEMFC: A novel approach using MEA with silica in catalyst layer

Composite membranes with inorganic substances can retain water and allow the operation of polymer electrolyte membrane fuel cells (PEMFCs) at high temperature under low humidity. In this work, the single cell was operated at high temperature using silica–Nafion composite membrane in addition with silica in catalyst layer. The cell was operated at various temperatures under different relative humidity conditions. We observed that the single cell performance decreased steeply as the cell temperature increased. The role of silica in the catalyst layer at high temperature operation was studied by varying the silica content in the catalyst layers. There was a gradual decrease in cell performance when the silica content increased in catalyst layer. The single cell performance of membrane electrode assemblies (MEAs) with composite membrane and electrode was higher than that of MEA with commercial Nafion 112 membrane for high temperature operation.     

Quasi‐Continuous Wave Near‐Infrared Excitation of Upconversion Nanoparticles for Optogenetic Manipulation of C. elegans

Optogenetics is an emerging powerful tool to investigate workings of the nervous system. However, the use of low tissue penetrating visible light limits its therapeutic potential. Employing deep penetrating near‐infrared (NIR) light for optogenetics would be beneficial but it cannot be used directly. This issue can be tackled with upconversion nanoparticles (UCNs) acting as nanotransducers emitting at shorter wavelengths extending to the UV range upon NIR light excitation. Although attractive, implementation of such NIR‐optogenetics is hindered by the low UCN emission intensity that necessitates high NIR excitation intensities, resulting in overheating issues. A novel quasi‐continuous wave (quasi‐CW) excitation approach is developed that significantly enhances multiphoton emissions from UCNs, and for the first time NIR light‐triggered optogenetic manipulations are implemented in vitro and in C. elegans. The approach developed here enables the activation of channelrhodopsin‐2 with a significantly lower excitation power and UCN concentration along with negligible phototoxicity as seen with CW excitation, paving the way for therapeutic optogenetics.     

DSP-based voice activity detection and background noise reduction

These days’ speech processing devices like voice-controlled devices, radio, and cell phones have gained more popularity in the area of military, audio forensics, speech recognition, education and health sectors. In the real world, speech signal during communication always contains background noise. The main task of speech related applications is voice activity detection (VAD) which include speech communication, speech recognition, and speech coding. Noise-reduction schemes for speech communication may increase the quality of speech and improve working efficiency in military aviation. Most of the developed algorithms can improve the quality of speech but unable to remove the background noise from the speech. This study provides researchers with a summary of the challenges in speech communication with background noise and provides research directions in the area of military personnel and workforces who work in noisy environments. Results of the study reveal that the DSP-based voice activity detection and background noise reduction algorithm reduced the spurious values of the speech signal.     

Fault Detection and Diagnosis of Cyber-Physical System Using the Computer Vision and Image Processing

Wireless Personal Communications - This paper investigates the performance of an energy-harvesting (EH) relay network, where multiple sources communicate with a destination via multiple EH...     

Performance analysis of spiral and serpentine tube solar collector with carbon nanotube nanofluids under natural flow method

This study communicates the performance analysis of spiral and serpentine tube solar collector with carbon nanotube nanofluids under natural flow method. Experiments were carried out at three different mass flow rates namely 3, 5, and 7 kg/hour while the concentration of nanoparticles was varied from 0.05% and 0.1%, respectively. Experiments were carried out under the same condition of ambient parameters for validation. Results show that the maximum exit water temperature was found to be about 75°C with a maximum concentration of 0.1% under a minimum flow rate of 3 kg/hour during the peak intensity. Similarly, the improvement in temperature of the water is found to be 6% under peak intensity and decreased to about 4.3% and 4.2% for the flow rates of 5 and 7 kg/hour, respectively     

Synthesis, Characterization, and Evaluation of Mesoporous MCM-41-supported Molybdenum Hydrotreating Catalysts

Mesoporous MCM-41 material with high surface area and narrow pore size distribution was synthesized and used as a support for Mo, CoMo, and NiMo catalysts. The molybdenum loading was varied from 2-14 wt% on MCM-41. On 10 wt% Mo/MCM-41, the promoter Co or Ni concentration was varied from 1-5 wt%. All the catalyst samples were characterized by surface area, low temperature oxygen chemisorption, x-ray diffraction (XRD), and temperature programmed reduction methods. Characterization results show that Mo is well dispersed on MCM-41 up to 10 wt%. The catalytic activities were evaluated for thiophene hydrodesulphurization (HDS), cyclohexene hydrogenation (HYD), and furan hydrodeoxygenation (HDO). All three catalytic functionalities vary in a similar manner to that of oxygen chemisorption as a function of Mo loading, indicating that there is a correlation between oxygen uptake and catalytic sites. The activities of these catalysts were compared with γ-Al₂O₃- and amorphous SiO₂-supported catalysts. It was found that MCM-41-supported Mo catalysts displayed superior activities.     

Raman Spectroscopy of the Charge Transfer Complex (TTF)x C60 Br8

We report Raman studies on powder samples of the charge transfer complex (TTF)_x C₆₀Br₈ at room temperature. The phonons show considerable softening with respect to the frequencies observed in the Raman spectrum of solid C₆₀ Brg. The strongest mode at 1464 cm^-1 in C₆₀Br₈ is red shifted to a doublet with peaks at 1414 and 1421 cm^-1, implying an average phonon softening Δω of -47 cm^-1. A comparison with the phonon softening of the corresponding A_g(2) mode in alkali-doped C₆₀ (Δω ~ - 36 cm^-1 for A₆C₆₀, A = K, Rb or Cs) suggests that 8 electrons are transferred per C₆₀Br₈ molecule in the charge transfer complex. The mode at 503 cm_--1 in C₆₀Br₈ is shifted upwards, similar to that in A₆ C₆₀ compounds.     

Thermal properties of silicate esters

Fourteen dimethyldialkoxysilanes are prepared by reacting dimethyldichlorosilane with corresponding alcohols in the liquid phase. Their physicochemical properties are determined by standard methods and their tentative empirical formulae are elucidated. The thermal conductivity values of dimethyldialkoxysilanes are determined using a two slab guarded hot plate apparatus over a temperature range of 30–190°C. The thermal conductivity values of dimethyldialkoxysilanes calculated from empirical equations are found to vary from -14% to +19%. Because thermal conductivity is an important parameter in heat transfer calculations, and to minimise the deviation of the values, new equations involving easily measurable ultrasonic parameters have been formulated. The proposed equations have been tested for the series of dimethyldialkoxysilanes, tetraalkoxysilanes and polydimethylsiloxanes. The thermal conductivity values computed from the proposed equations are comparable with experimental thermal conductivity values. Further, an equation involving the calculation of thermal conductivity values at varying temperatures is also proposed.