Effect of Composition on Electrical and Optical Properties of Thin Films of Amorphous GaxSe100−x Nanorods

We report the electrical and optical studies of thin films of a-GaxSe100−x nanorods (x = 3, 6, 9 and 12). Thin films of a-GaxSe100−x nanorods have been synthesized thermal evaporation technique. DC electrical conductivity of deposited thin films of a-GaxSe100−x nanorods is measured as a function of temperature range from 298 to 383 K. An exponential increase in the dc conductivity is observed with the increase in temperature, suggesting thereby a semiconducting behavior. The estimated value of activation energy decreases on incorporation of dopant (Ga) content in the Se system. The calculated value of pre-exponential factor (σ0) is of the order of 101 Ω−1 cm−1, which suggests that the conduction takes place in the band tails of localized states. It is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. On the basis of the optical absorption measurements, an indirect optical band gap is observed in this system, and the value of optical band gap decreases on increasing Ga concentration

Hydrocarbon hydrogen carriers for catalytic transfer hydrogenation of guaiacol

Polycyclic hydrocarbons are known to be efficient hydrogen carriers capable of yielding high purity H2 upon dehydrogenation. Due to their high hydrogen density, high boiling point, and stability, these compounds demonstrate the potential to be used as hydrogen donors under catalytic transfer hydrogenation (CTH) conditions. In this work, the potential of a suite of hydrogen carriers to donate hydrogen, as well as the mechanisms affecting their hydrogen transfer, are assessed through the CTH of guaiacol, on Pd/Al2O3, as a model system. The results indicated the following descending order of transfer hydrogenation rate: bicyclohexyl > tetralin » hydrogenated terphenyl (HTP) > cyclohexylbenzene. Among the products, cyclohexanone and phenol are the most abundant, directly resulting from CTH. Detailed analysis of the hydrogen carrier conversion and selectivity clearly shows that the potential for CTH is highly linked to the molecular structure of the donor, rather than the amount of hydrogen available for transfer. A density functional theory (DFT) study, supported by experimental data, reveals that when unsaturated hydrocarbons are utilized, such as tetralin, cyclohexylbenzene, and HTP, the effective CTH rate to guaiacol is limited, despite dehydrogenation being more favorable for those molecules than from fully saturated donors, such as bicyclohexyl

Zeolite shape selectivity impact on LDPE and PP catalytic pyrolysis products and coke nature

Catalytic pyrolysis of plastic waste can offer an economical process for plastic waste conversion due to the capability to produce high-quality products with high yields. A simple stirred tank reactor was used for two significant types of polyolefin (low-density polyethylene and polypropylene) under thermal and catalytic conditions, i.e., promoted by HZSM-5, HBEA, and HY. Complete conversion of the polymers into light gases, aromatic coke, and liquid products (mainly in the gasoline range) was achieved in the presence of all catalysts. The detailed analysis of the gas, liquid, and coke deposited inside the zeolite framework was used to unravel the mechanism responsible for converting LDPE and PP over the different zeolites. LDPE and PP particular polymer structures significantly impacted the reaction pathway, with PP yielding more reactive and stereochemically cumbersome intermediates. Furthermore, secondary reactions, particularly hydrogen transfer, secondary cracking, cyclization, and oligomerization, significantly impacted the product distribution. The higher acidity and particular framework shape of HZSM-5 benefited secondary cracking and hydrogen transfer reaction leading to higher selectivity towards gas and aromatic compounds. Further, HBEA and HY, respectively, favored isomerization and cyclization instead. Additionally, the spent catalysts' physicochemical properties combined with the information obtained from the analysis of coke composition were used to differentiate the processes responsible for the deactivation of the different zeolites. The presence of polyaromatic coke promoted the deactivation of the catalysts, with HZSM-5 retaining more than 50% of its acidity after the reaction. In contrast, more than 80% of HY and HBEA acid sites were lost under the same conditions

Conversion of agricultural waste into stable biocrude using spinel oxide catalysts

Biomass, the feedstock for biocrude and ultimately renewable diesel is a low energy density feedstock. The transport of this feedstock over long distance has been proven to be a major burden on the commercialisation of biorefining. Therefore, it has been generally accepted that biomass should be upgraded to biocrude (a relatively high energy density liquid) in close proximity to the biomass sources. The biocrude liquid would then be transported to a biorefinery. Biocrude contains large amounts of oxygen (generally up to 38 wt%) that is removed from the crude in the refining process. In this study, we have synthesised a range of spinel oxide based catalysts to remove oxygen from the biocrude during the catalytic fast pyrolysis. The activity of spinel oxide (MgB2O4 where B = Fe, Al, Cr, Ga, La, Y, In) catalysts were screened for the pyrolysis reaction. While all the tested spinel oxides deoxygenated the pyrolysis vapour, MgCr2O4 was found to be effective in terms of oxygen removal efficiency relative to the quantity of bio oil produced

Code and selected model outputs for <i>"Interpreting gas sorption isotherms in glassy polymers using a Bayesian framework: A view on parameter uncertainty propagation into mixture sorption predictions"</i>

All of the code and selected model output files associated with the paper "Interpreting gas sorption isotherms in glassy polymers using a Bayesian framework: A view on parameter uncertainty propagation into mixture sorption predictions".The Bayesian Inference code and sorption model output files contained in this repository are sufficient to generate the results shown in the paper (including all of the results shown in the Supporting Information).Authors: Gloria M. Monsalve Bravo, Ravi C. Dutta, Christian C. Zuluaga-Bedoya, Matthew P. Adams, Simon Smart, Muxina Konarova, and Suresh K. Bhatia</p

Improved Hydrogen Storage Performance of MgH 2

The catalytic effects of MnFe2O4 nanoparticles on the hydrogen storage properties of MgH2–LiAlH4, prepared by ball milling, are studied for the first time. The hydrogen storage properties and reaction mechanism are investigated by pressure–composition–temperature (PCT), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The nonisothermal desorption results show that MgH2–LiAlH4 + 5 mol % MnFe2O4 has a lower onset dehydrogenation temperature, 85, 50, and 40 °C lower than these of ball-milled MgH2–LiAlH4 sample for each stage in the dehydrogenation process. The isothermal dehydriding kinetics and isothermal rehydrogenation kinetics results indicate that adding MnFe2O4 to MgH2–LiAlH4 could significantly enhance the absorption/desorption kinetics of MgH2–LiAlH4. From the differential scanning calorimetry and Kissinger analysis, the apparent activation energy of the 5 mol % MnFe2O4-doped sample for the three decomposition stage is 55.8, 70.8, and 96.5 kJ/mol, resulting in a 45.7, 85.5, and 99.6 kJ/mol decrease, respectively, compared with the MgH2–LiAlH4 sample. These improvements are mainly attributed to in situ formed Fe0.872O phase and the amorphous Mn-containing phase during the dehydrogenation process, which act as the real catalyst in the MgH2–LiAlH4 + 5 mol % MnFe2O4 composite