Narrow Results

Density functional theory method is used to explore the mechanism of dissociative adsorption of methane (CH₄) on S_A type stepped Si(100) surface. Two reaction paths are described that produce CH₃ and hydrogen atom fragments adsorbed on the dimer bonds present on each terraces. It has been found that, in the initial stage of the carbonization of stepped Si(100) surface, the CH₃ and H fragments bound to the Si dimer atoms by following the first reaction path.

According to new research, methane emissions contribute 25 percent more to global warming than previously assumed. Methane is a crucial precursor gas of tropospheric ozone, a dangerous air pollutant. Methane emissions are responsible for almost half of the reported growth in tropospheric ozone levels on a global scale. But it plays a vital role as an energy source, therefore, the study of methane cut reservoirs is essential. The injection of air can extract additional energy in high methane-cut reservoirs. The analysis is made to compute the theoretical potential of low air flooding in high methane-cut reservoirs. Computational Fluid Dynamics (CFD) is used to study the impact of injecting air on methane. The presence of carbon dioxide and oxygen when injected into the methane cut reservoir produces high-pressure air injection that may cause significant safety damage such as the potential for corrosion or explosion. Past field studies and reported solutions indicate that there are no insurmountable problems in the execution of high-pressure air injection. The results are harmful and need to take useful safety precautions for the engineers who are interested in experiments. The users of CFD use mathematical laws and models that exactly represent the phenomenon they are dealing with. The pressure induced by the air injection is simulated with the help of the Finite Volume Method (FVM). The velocity field near the outlet arises as higher pressure of air from the inlet is observed, whereas, the pressure near the outlet declines. The findings of this study can help for better understanding of outflow of methane from methane reservoirs.

Carbon nanotubes (CNTs) were synthesized by a low-cost floating catalyst (FC) chemical vapor deposition (CVD) method in a horizontal reactor. It was found that iron (III) chloride (FeCl₃) is a high efficient FC precursor for methane CVD to grow CNTs. In this study, the effects of reaction temperature and flow ratio of methane to nitrogen (CH₄:N₂) on the morphology of the CNTs were investigated. The morphological analysis by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that increasing the reaction temperature and flow ratio of CH₄:N₂ grew CNTs of larger diameters. Energy dispersive X-ray (EDX) and thermogravimetric analysis (TGA) were employed to study the purity of the produced CNTs. As shown by the TGA, the highest yield of 74.19% was recorded for the CNTs grown at 1000°C and flow ratio CH₄:N₂ of 300:200.

Multi-walled carbon nanotubes (MWCNTs) were prepared by floating catalyst (FC) method, using methane as a carbon source and iron (III) chloride (FeCl₃) as a catalyst precursor, followed by purification with air oxidation and acid treatment. The as-grown and purified MWCNTs were characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry analysis and Raman spectroscopy. The average inner and outer diameters of the MWCNTs were 25 and 39 nm, respectively. The purity and yield of the purified MWCNTs were more than 92% and 71% weight fraction, respectively.

Conversion of methane into high value added chemicals and clean fuels such as methanol under mild conditions is of great importance to the chemical industry. However, traditional thermal catalytic of methane always suffer from harsh reaction conditions and poor product selectivity. Here, we reported photoelectrocatalytic oxidation of methane over BiVO₄/Au/FeCo–LDH under simulated sunlight illumination with ambient‘ conditions. The results demonstrate that BiVO₄/Au/FeCo–LDH exhibits excellent photoelectrochemical properties and catalytic activity. The double-layer capacitance ($C_{dl}$) value of BiVO₄/Au/FeCo–LDH is estimated to be 3.00mF$\cdot$cm${}^{-2}$, indicating its considerable electrochemical active areas. The photocurrent density of BiVO₄/Au/FeCo–LDH reaches up to 1.46mA$\cdot$cm${}^{-2}$ in methane atmosphere. The methanol yield for photoelectrocatalytic oxidation of methane is 8.46 times that of pure BiVO₄, and the corresponding Faraday efficiency is 56.09%. Finally, the reaction mechanism of photoelectrocatalytic conversion of methane to methanol based on hydroxyl radical and methyl radical as intermediate products is proposed. Our finding is expected to provide new insight for the design of active and selective catalysts toward photoelectrocatalytic conversion of methane.