Study the thermal stability of nitrogen doped reduced graphite oxide supported copper catalyst

The thermal stability of the as-synthesized Nitrogen-doped reduced graphite oxide supported copper catalyst was investigated by a thermogravimetric analyzer (TGA) at a temperature range 273–1173 K under purified N2 atmosphere using three different heating rates (15, 20 and 25 K min−1). Firstly, to obtained nitrogen-doped reduced graphite oxide (N-rGO), the functionalized graphite oxide was synthesized using Staudenmaier’s method reduced by continuously stirring in an ammonia solution subsequently. The rGO was doped with nitrogen and impregnated with Cu-precursor to obtain Cu/N-rGO. The as-synthesized GO; N-rGO and Cu/N-rGO were characterized by FESEM, EDX, TEM, XRD and XPS. All these analyses were resulted in successfully samples synthesized. The TGA kinetic data were fitted into Kissinger and Flynn–Wall–Ozawa model free expressions to obtain apparent activation energies of 83.34 and 102.59 J mol−1 and pre-exponential factors of 2.40 × 107 and 5.01 × 1011 s−1. The high R2 values of 0.9999 and 0.9666 obtained from fitting TGA kinetic data using the Kissinger and Flynn–Wall–Ozawa model free expressions show that the data were well fitted to the expressions. This implies that the thermal behavior of nitrogen doped reduced graphite oxide supported Cu catalyst can be investigated using Kissinger and Flynn–Wall–Ozawa model free expressions

Evaluation of the interaction potentials for methane adsorption on graphite and in graphitic slit pores

This paper compares the performance of the Buckingham Exponential-6 and Lennard-Jones potential models in the description of bulk phase and adsorption properties of methane on graphitic surfaces and pores. The solidfluid potential used in the choice of the LJ model is Steele 10-4-3 equation and for the Exp-6 model, the Crowell and Chang equation which has been rarely used in the literature. From an extensive computer study using Grand Canonical Monte Carlo simulation, the two potential models perform almost equally well in the bulk fluid behavior except at extremely high density, where the LJ model is better. For adsorption on surface, the Exp-6 performs better in the correct description of the experimental Henry constant. However, both potential models describe well the isotherm outside the Henry law region. Under supercritical conditions, the same behavior is seen in the Henry law region, but the opposite is observed at extremely high pressures. For adsorption in slit pores, significant difference is seen at low pressure region for all pore sizes examined. In this region, the Exp-6 always predicts a higher capacity than the LJ model. In the smallest pore size examined (0.65 nm), the LJ model predicts a higher capacity than the Exp-6 with approximately 4% difference at higher pressures. However, this behavior is not seen in the other pore sizes. The comparison shows that the Exp-6 can describe experimental adsorption data, albeit only, better than the LJ

Externally initiated event in sequential risk assessment for the onshore LNG marine loading arm unit

This paper describes the failure assessment of the unloading arm unit that is connected to a Liquified Natural Gas (LNG) terminal. In this work, an external event, i.e., lightning, was simulated as the triggering event. A Temporal Fault Tree (TFT) analysis was developed, and sequential failures that function under the Priority AND (PAND) gate were assessed. The results show that the highest contributing factor to the failure of the terminal unloading arm was the sequential failure due to the loss of sensors which can happen before or after lightning strikes. The occurrence of failures for the loading arm was estimated using a Monte Carlo Simulation (MCS). For service years of 32.7, the sequential failures occurred 131 times when preventive maintenance was not considered. This work also presents that the failure distribution of the marine loading arm follows the Weibull distribution characteristic with the scale (α) and the shape (β) parameters values of 132,817.5 h-1 and 1.556, respectively