The catalytic activities and properties of noble metals (Pt, Pd, Rh, Ru) supported on silica gel (SiO2) and alumina-modified silica gel (Al2O3-SiO2) were investigated for the hydrodesulfurization of thiophene. Al2O3-SiO2 was prepared by an impregnation method using aluminum nitrate (Al(NO3)3·9H2O) aqueous solution. Pt/8 wt%Al2O3-SiO2 catalyst showed the highest activity for hydrodesulfurization of thiophene among various supported noble metal catalysts and this activity was higher than that of commercial CoMo/Al2O3 hydrodesulfurization catalyst. The sulfur tolerance of noble metal/SiO2 was enhanced by Al2O3 modification of SiO2 and Pt/8 wt%Al2O3-SiO2 catalyst showed the highest sulfur tolerance among the supported noble metal catalysts. Pt/8 wt%Al2O3-SiO2 catalyst had high hydrogenating ability for unsaturated C4 hydrocarbons formed in the hydrodesulfurization of thiophene. The catalysts were characterized by 2-propanol dehydration, cumene cracking, XRD, H2 adsorption and FT-IR. Dispersion of Pt on 8 wt%Al2O3-SiO2 was remarkably higher than that on SiO2 and the particle size of Pt on 8 wt%Al2O3-SiO2 was the lowest among the supported noble metal catalysts. The acidity of 8 wt%Al2O3-SiO2 was higher than that of SiO2. Furthermore, Brönsted acid sites were present on 8 wt%Al2O3-SiO2. FT-IR spectroscopy of thiophene adsorbed on 8 wt%Al2O3-SiO2 support indicated that the thiophene molecule interacts with the Brönsted acid site on 8 wt%Al2O3-SiO2. The activity of the double-layer (Pt/SiO2 + 8 wt%Al2O3-SiO2) catalyst obtained experimentally was higher than that calculated. This suggests that spillover hydrogen was present on Pt/Al2O3-SiO2 in the hydrodesulfurization of thiophene. Both the Brönsted acid sites of Al2O3-SiO2 and the Pt particles in the Pt/Al2O3-SiO2 catalyst act as active sites for the hydrodesulfurization of thiophene.
The blistering phenomenon is one of the major damages in bituminous pavement during a hot summer. The phenomenon was believed to be caused by water permeating from outside via channels of connected pores in bituminous mixtures. However, the surface course in bituminous pavement is not permeable to water, particularly near the blistering area. Therefore, permeation of liquid water is unlikely to be responsible for the water accumulation that causes the blistering phenomenon. Moisture vapor in the air is important in water intrusion into bituminous mixtures. This study examined moisture transfer mechanisms in bituminous pavements, focusing on the coefficient of permeability of pavement mixtures of both liquid water and humid air (i.e. air containing water vapor).
Filtrate volume and permeability of filtercake are two main properties of drilling fluids. During this decade, various ways for estimating of them are proposed. In this study, a new approach based on artificial neural networks (ANNs) has been designed to estimate filtrate volume and permeability of filtercake using the static filtration data. In this speeding up approach 75% of experimental data have been used to train the neural network and the remaining data have been applied to test the performance of the network. Finally, the estimated results of filtrate volume and permeability of filtercake obtained from the network have been compared against the values obtained by empirical correlations used for calculation of these parameters.
Ethane oxidation was examined over silica supported silicomolybdic acid (SMA) catalysts under conditions described as excellent for partial oxidation to investigate the catalytic activities in the presence of non-catalytic ethane oxidation. When water vapor was absent or limited, SMA was transformed to the α-MoO3 phase, C2H6 conversion was enhanced, and the major products were C2H4 and CO, whereas little HCHO was formed. However, the selectivity for HCHO was improved by the addition of excess water vapor. The acidity of SMA, which was stabilized by water vapor as β-MoO3, might catalyze the scission of the C-C bond, so partial oxidation to HCHO could be promoted in preference to oxidation to CH3CHO. In addition, the formation of the MoO2 phase, which was observed in the co-presence of C2H6 and water vapor, suggested that the lattice oxygen participated in the activation and oxidation of C2H6.
This study proposes and examines a practical technique for monitoring underground fluid migration using tidal deformation of the Earth. The gravitational attraction of the bodies in the solar system causes deformation of the Earth, and the pore pressure of the geological reservoirs changes in response to such tidal phenomena. These pore pressure changes are related to the poroelastic parameter χ, which is a function of fluid saturations in the pore space, and χ can be an indicator for monitoring the underground fluid migration. To retrieve the pressure changes caused by the Earth tide from field-measured pressure data including long-term pressure trends and noises, a pressure-analysis algorithm based on the cubic spline interpolation and the least squares method was employed. A set of numerical experiments were performed and the results showed that a proper selection of the time-node span for the interpolation enabled retrieval of diurnal and/or semi-diurnal pressure fluctuations. The developed algorithm was applied to actual field data, which confirmed that the diurnal and semi-diurnal features of the pressure fluctuations can be explained by the Earth tide. The estimated χ values indicated the arrival of the displacing fluid at the monitoring well, showing that fluid migration can be monitored by analyzing the χ profiles.
Hydroconversion of n-heptane was investigated over Pd-supported H-zeolite and hybrid catalyst consisting of Pd/SiO2 and USY. Highly selective hydrocracking occurred over Pd/ZSM-5 whereas hydroisomerization dominated over Pd/USY and Pd/β. Skeletal isomerization occurred before the cracking reactions. The zeolite used and hydrogen spillover onto the zeolite were important in determining the isomerization selectivity. Experiments over hybrid catalysts suggested that close contact and the balance of metal and acidic sites are crucial in determining the activity and selectivity of isomerization and cracking. A reaction scheme based on the concept of hydrogen spillover was proposed.
Of interest in this study are the effects of well arrangement on the characterization of distributed multiple fractures through tracer tests. Numerical experiments with 1000 fracture-system realizations were conducted to simulate tracer tests for three different well arrangements: parallel, diagonal, and perpendicular with respect to the fracture orientation. Based on the numerical experiment outcomes, correlations between the representative fracture parameters (the total fracture length and the geometric mean of fracture lengths) and the characteristic parameters of the effluent tracer concentration curve were developed by using a non-parametric regression technique. The quality of the fracture parameter estimations is acceptable for the parallel and perpendicular well arrangements. However, the individual fracture-system realizations cannot be distinguished for the diagonal arrangement using representative fracture parameters; thus, the estimation quality is poor. The diagonal well arrangement should be avoided when designing tracer tests for characterizing fracture systems.
LPG is a promising candidate for use in residential fuel cell systems, because the infrastructure to supply LPG is already established. However, no suitable sulfur removal technology is available for LPG. Sulfur concentration in LPG varies widely from a few wtppm to 100 wtppm dependent on the quantity consumed, and so sulfur removers are usually designed with high capacity to include a safety margin. A sulfur remover with capacity matched to the standard LPG cylinder was developed, which would enable easy maintenance by the exchange of both sulfur remover and LPG cylinder at the same time, and is smaller in size than the conventional sulfur remover attached to the fuel cell unit. Investigation of suitable materials found that Cu-loaded activated carbon provided adequate removal of sulfur from LPG. The combination of this new sulfur remover with the standard LPG cylinder is expected to promote the use of residential fuel cell systems.