A ternary-mixed oxide catalyst, H3PO4-WO3-Nb2O5, was prepared with the evacuation of a mixed solution of phosphoric acid, niobic oxalate, and (NH4)10W12O41, followed by calcination in air. We found that the oxide catalyst (Cat-A) exhibited excellent activity in the Friedel-Crafts alkylation. The recycle use of the catalyst was possible through separation of the oxide by filtration. Interestingly, the catalytic performance was remarkably sensitive to the calcination temperature, and the temperature of 773 K was found to be the optimum condition. On the basis of 31P NMR studies, formation of the Nb-containing heteropoly acid, H4PNbW11O40, was observed at the preparation procedure. The active species was derived from the heteropoly acid as a result of the partial decomposition at 773 K. The evolution of novel acidity with relatively strong character was observed in the temperature programmed desorption of ammonia. The amount of the novel acidity was in good correlation with the catalytic performance. The catalytic activity was much improved by using H4PNbW11O40 as the precursor for the preparation of the catalyst (Cat-B). The catalyst exhibited high activity in the Friedel-Crafts acylations using carboxylic acids as well, in which a flow-type reaction was also possible over a period of 7 days. Further improvement in the catalytic activity and thermal stability was achieved by using a Nb-containing Dawson-type HPA (H9P2Nb3W15O62) as the precursor for preparation of the SiO2-loaded catalyst. In particular, the catalyst became insoluble even in hot water when it was calcined at 743 K. Based on the IR, EXAFS and 31P NMR studies, the active species was obtained through the removal of Nb atoms from the Dawson-type structure on the SiO2 support.
This paper presents a specialized finite element procedure to analyze the elastoplastic response of rock surrounding an inclined wellbore. The procedure enables this special three-dimensional problem to be solved using a 2-D finite element mesh. The only assumption made in this model is that the properties of the rock and the far-field stress do not vary significantly along the wellbore axis over the region of interest. The resulting procedure allows for a significant reduction in numerical computation over three dimensional elements without suffering any loss of generality for analyzing inclined wellbores. The Drucker-Prager yield criterion for perfectly plastic material is then incorporated into the finite element code in order to simulate the evolution of the plastic zone around a pressurized wellbore. The spread of the yielding region around vertical, inclined, and horizontal wellbores subjected to various levels of pressures of drilling mud can then be examined to study the progressing and extent of failure in the rock surrounding the borehole.
The effects of Ni addition on the catalytic activity of MFI zeolite catalysts were examined with the ethanol conversion reaction under high space velocity conditions, using pure ethanol, ethanol diluted with water, and bioethanol produced from corn, and the effects of impurities on deactivation were evaluated. Addition of Ni to MFI zeolite strongly suppressed the formation of aromatic compounds, and greatly improved the selectivities for C3 and C4 olefins from pure ethanol, but decreased the selectivities for C3 and C4 olefins, and slightly reduced the suppression effect of the Ni site for aromatic formation from bioethanol. The yields of C3 and C4 olefins decreased with time-on-stream despite the presence of the Ni sites. XPS analysis of the catalysts after reaction at 673 K showed presence of oxidized carbon species, indicating the deposit of the impurity from the bioethanol. In addition, the electronic state of Ni after the reaction of bioethanol was also different to that after the reaction of reagent ethanol. XPS analysis showed the formation of Ni2O3 species or nickel sulfate during the reaction of bioethanol, which caused catalyst deactivation. In the reaction at 773 K, a large amount of filament carbon was deposited on the catalyst surface. These factors caused significant decreases in the formation of C3 and C4 olefins in the conversion of bioethanol.
The application of the ensemble Kalman filter (EnKF) using function transformation to the estimation of relative permeability is presented. Inconsistent values may be calculated in the filtering process of the EnKF for model variables consisting of parameters which have physical constraints. In this study, the relative permeabilities of water/oil, which have physical ranges from 0 to 1, were given to model variables. Estimations of these parameters with the EnKF were attempted using the simulated results of one-dimensional displacement experiments. Negative values were calculated by the conventional application method for relative permeabilities after several filterings. As an effective solution for this problem, application of the EnKF using function transformation is proposed in this study. The developed scheme definitely prevented inconsistent valuations, and accurate estimations could be achieved. The numerical tests showed that the uncertainties of the estimated parameters were different for each water saturation in improvement behavior. However, the same tendencies of accelerating the improvement in the vicinity of the breakthrough time were shown for all water saturations. Comparison of the resulting estimates for various observation frequencies proved that the variance of the model variables was inversely proportional to the observation frequency, whereas the average relative permeabilities of ensembles were almost in agreement. Also, comparison of the resulting estimates for various dimensions of model-variable vector confirmed that both ensemble averages exhibited minor differences through analogous behaviors of uncertainty improvement.
Numerical simulation technology for two-phase flow in porous media was developed using the Constrained Interpolation Profile (CIP) method. Both the finite difference method and streamline method combined with discrete gridblocks used the hyperbolic-type governing equations of saturation by transforming the flow equations so that the CIP method could be applied to the Implicit-Pressure/Explicit-Saturation (IMPES) method. Application of the CIP method included both the value of the saturation and the spatial derivatives of saturation as model variables. The equations of the derivatives were also required and obtained by differentiating the saturation equations. Both the governing equations of saturation and its spatial derivatives were solved simultaneously by the time-split method, which divided these equations into advection and non-advection phases. The advection phase was calculated first by the CIP scheme, and then the non-advection phase by the finite difference scheme. The results of numerical tests confirmed that this method mitigated the numerical difficulties around the discontinuous shock front and was more accurate than the conventional method.
In this work, the efficiency of 20 kHz frequency ultrasounds versus the classical stirring procedure was investigated on the solvent extraction of Jordanian El-Lajjun oil shale by employing a horn type sonicator. The influence of sonication parameters (sonication time and ultrasonic power) and extraction parameters (extraction solvent and oil shale particle size) on the solubilization of organic matter (bitumen) from oil shale are reported here. The influence of seven individual solvents, namely: tetrahydrofuran, benzene, carbon tetrachloride, chloroform, kerosene, toluene, acetone and a mixture of methanol-acetone-chloroform on the fraction extracted was investigated and it was found that the fraction extracted was 90% after only ten minutes of sonication at 33 W when tetrahydrofuran was used as extraction solvent. It was found that the fraction extracted percentage is strongly influenced by the solvent extraction, ultrasonic power and exposure time and less influenced by the particle size. Under the current experimental conditions and using the tetrahydrofuran as extraction solvent, the extraction time was decreased by four folds while the fraction extracted percentage (E%) was increased by three times.
Water is associated with natural gas from the reservoir, through production and processing and is a concern in transmission. Also the water content of sour natural gases is an important parameter in the design of facilities for the natural gas production, transmission, and processing. The aim of this study is to develop an easy-to-use method which is simpler than current available models involving a large number of parameters and requiring more complicated and longer computations, for an appropriate estimation of water content of sour natural gas mixtures containing up to 40% acid gas components (CO2 and H2S). The new developed method works for pressures ranging from 1000 to 15,000 kPa and temperatures from 15 to 120°C. Simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on the water content of sour natural gases at various temperatures and pressures without performing any experimental measurements. In particular, gas process engineers would find the proposed approach to be user friendly involving no complex expressions with transparent calculations. Results have been compared with the reported data and excellent agreement has been obtained between the predicted results and observed values. The average absolute deviations from the reported data were found to be 3.5%.
Application of the ensemble Kalman filter (EnKF) to reservoir characterization has the limitation that the observed watercut data cannot be reflected for tuning model variables in some time intervals. The present study assumed a homogeneous isotropic porous medium including a single fracture with adequate width, so that tracer tests could be simulated by the complex variable boundary element method. The resulting tracer effluent behavior was used as observed data, and the EnKF was applied for identifying fracture location to match the data. Using the conventional method, the effluent tracer concentration was measured as the observed variable. Depending on the initial ensemble, the data was not reflected for tuning the fracture location in some time intervals, resulting in a mismatch between the fracture location obtained by EnKF and the referenced location. Furthermore, the poor correspondence of observation data resulted in inaccurate identification even for initial ensembles not including the problematic time interval. Therefore, the observed variable was transformed from the effluent tracer concentration into the time corresponding to the amount of tracer recovery. Consequently, the observed data were adequately assimilated, and the correspondence of the observation data was improved. Accurate localization of the fracture was possible regardless of the initial ensembles.
The nature of aggregation kinetics of colloidal asphaltene particles in mixture of toluene and heptane was investigated by utilizing a polarizing microscope with appropriate magnification. The concentration of asphaltene in toluene-heptane mixture varied from 1 g/l to 8 g/l. There are two main mechanisms associated with the aggregation process. These mechanisms are diffusion limited aggregation (DLA) and reaction limited aggregation (RLA). Each mechanism has its own characteristics and acts on limited values of asphaltene concentration. At the asphaltene concentrations below the critical micelle concentration (CMC), the DLA mechanism is dominant, while at concentrations above the CMC, at the initial stage of aggregation process, the RLA mechanism is observed and then the mechanism tends toward DLA (crossover behavior). It should be noted that the CMC for asphaltene in the solution is around 3 g/l.
The applicability of the tubular reactor (TR) to the manufacturing of soap was investigated by saponification of mixtures of two types of oils and fats using the batch-type reactor (BR) and TR under similar conditions to those used in the manufacturing of soaps (starting materials and ratios). Effect(s) of replacement of animal fat (tallow) with vegetable oils (palm oil and rice bran oil) on the properties of the soaps produced were also investigated. For all combinations of oils and fats (tallow-coconut oil, palm oil-coconut oil, rice bran oil-coconut oil), the rates of saponification in the TR were much larger than the rates of saponification in the BR, resulting in shortening of reaction times to about one-fourth for complete saponification of oils and fats. The seven most important properties of the soaps produced using the TR were evaluated and compared with those of commercial soaps, indicating that the soaps produced using the TR satisfied all standards for these properties, and that these properties were identical to those of commercial soaps. Therefore, the TR can be applied to the manufacture of soaps from mixtures of two types of oils and fats in industrial grades in the presence of ethanol.
The catalytic characteristics of various rare-earth oxide supports for Ni catalysts were investigated for the initiation of the oxidative reforming (OR) of C4H10 at ambient temperature. Ni/PrO1.83, reduced at 873 K, successfully initiated the OR of C4H10 as previously reported for Ni/CeO2. PrO1.83 undergoes reduction by H2 at 873 K and subsequent oxidation at ambient temperature, so the catalyst is heated to initiate the auto-ignition temperature (633 K) of C4H10 OR over the catalyst.