SSZ-13 materials have been synthesized with varying amounts of Al to produce samples with different concentrations of Brønsted acid sites, and consequently, these SSZ-13 materials contain increasing numbers of paired Al heteroatoms with increasing Al content. These materials were then characterized and tested as catalysts for the methanol-to-olefins (MTO) reaction at 400 °C and 100% methanol conversion under atmospheric pressure. A SAPO-34 sample was also synthesized and tested for comparison. SSZ-13 materials exhibited significant differences in MTO reactivity as Si/Al ratios varied. Reduced Al content (higher Si/Al ratio) and, consequently, fewer paired Al sites led to more stable light olefin selectivities, with a reduced initial transient period, lower initial propane selectivities, and longer catalyst lifetime. To further support the importance of paired Al sites in the formation of propane during this initial transient period, a series of experiments was conducted wherein an H-SSZ-13 sample was exchanged with Cu2+, steamed, and then back-exchanged to the H form. The H-SSZ-13 sample exhibited high initial propane selectivity, while the steamed H-SSZ-13, the Cu2+-exchanged SSZ-13 sample, and the steamed Cu-SSZ-13 sample did not, as expected since steaming selectively removes paired Al sites and Cu2+ exchanges onto these sites. However, when it was back-exchanged to the proton form, the steamed Cu-SSZ-13 sample still exhibited the high initial alkane selectivity and transient period typical of the higher Al content materials. This is attributed to protection of paired Al sites during steaming via the Cu2+ cation. Post-reaction coke analyses reveal that the degree of methylation for each aromatic species increases with increasing Si/Al in SSZ-13. Further, SAPO-34 produces more polycyclic species than SSZ-13 samples. From these data, the paired Al site content appears to be correlated with both MTO reaction behavior and coke species formation in SSZ-13 samples.

A trickle fixed-bed reactor model for the Fischer-Tropsch synthesis applicable to both cobalt and iron catalysts which accounts for gas and liquid recycle is described. A selection of kinetic models for both iron and cobalt catalysts (4 each) is included in the reactor model and their effect on model predictions is compared. While the model is 1-D and reaction rates are determined for quasi-average radial bed temperatures, a correlation is used to account for radial thermal conductivity and radial convective heat transfer. Traditional pressure drop calculations for a packed column were modified with a correlation to account for trickle-flow conditions. In addition to describing the model in detail and showing validation results, this paper presents results of varying fundamental, theoretically-based parameters (i.e. effective diffusivity, Prandtl number, friction factor, etc.). For example, the model predicts that decreasing effective diffusivity from 7.1E-09 to 2.8E-09 m 2 /s results in a lower maximum temperature (518 K vs. 523 K) and a longer required bed length to achieve 60% conversion of CO (8.5 m vs. 5.7 m). Using molar averages of properties to calculate the Prandtl number for the gas phase (recommended by the authors) results in average bed temperatures up to 10 K higher and reactor lengths 17-45% shorter than assuming a Prandtl number of 0.7. Using the Tallmadge equation to estimate friction losses, as recommended by the authors, results in a pressure drop 40% smaller than using the Ergun equation. Validation of the model was accomplished by matching published full-scale plant data from the SASOL Arge reactors.

A previously developed one-dimensional reactor model was employed to understand the effects of pellet size and geometry on the performance of a wall-cooled multitubular fixed-bed Fischer−Tropsch reactor for producing hydrocarbons from synthesis gas. The effects of pellet size/shape on catalyst effectiveness, bed void fraction, and overall heat transfer coefficient were studied through a comprehensive parametric study of a reactor with cobalt catalyst. The relative impact of each of these parameters on the overall required amount of catalyst was also determined. The simulations show that the amount of catalyst required to achieve a specified conversion increases with pellet size and shape in the order: trilobes < hollow cylinders < cylinders < spheres. The pressure drop per unit length can be significantly reduced and the catalyst effectiveness increased by using advanced extrudates, i.e., trilobes or hollow cylinders.

SignificanceA unique combination of classic packed bed friction factor equations and newly refit correlation constants is proposed which produces a new friction factor correlation which significantly improves predictions in high turbulence regimes, high porosity regimes, and high wall effect regimes.

Summary. An extended field test at the Grubb Lease, San Miguelito field, Ventura, CA, has shown that the catalytic deoxygenation (Cadeox TM) process is an effective new oxygen-scavenging method for oilfield injection waters. The process can reduce oxygen concentration from the saturation level in seawater (about 8 ppm) to substantially below the corrosive level (less than or equal to 0.01 ppm) with less than 60 seconds of contact time. The process is effective at temperatures as low as 5 deg. C [41 deg. F] and at process is effective at temperatures as low as 5 deg. C [41 deg. F] and at a water pH range of 4 to 10. The Cadeox process uses a simple hydrogen and oxygen reaction to remove corrosive oxygen from injection waters. Palladium-impregnated anion-exchange resin beads in a packed column are used as reaction sites for H2 and O2 to form water. Introduction Dissolved oxygen in water can cause destructive corrosion to metal pipes and process equipment. The corrosion byproducts, in turn, cause formation damage by plugging. Thus, oxygen needs to be removed from oilfield waters. In the past, chemical and/or mechanical methods have been used to remove oxygen. However, the chemical scavenging systems--e.g., sodium sulfite (Na2SO3)--introduce unnecessary dissolved solids (sulfates) to treating waters, and the commonly used vacuum deaerators are bulky and costly. The Cadeox method presented is a new process in oilfield oxygen scavenging. (This procedure was originally used for scavenging oxygen in boiler feedwaters in Europe.) Cadeox uses palladium-covered anion-exchange resin beads as the catalyst. palladium-covered anion-exchange resin beads as the catalyst. Oxygen dissolved in water is catalytically reduced by its reaction with hydrogen to form water. To test the applicability of this scavenging process for injection waters (seawater), an extended field test was conducted at the oceanwater treatment plant (OWTP) of the Grubb Lease, San Miguelito field. The test results indicated that Cadeox is a viable process for scavenging oxygen from seawater. Background Catalytic Reduction of Oxygen. Oxygen can be removed from water by its reaction with hydrogen under appropriate conditions to form water:(1) The reaction is exothermic; however, a catalyst is necessary to accelerate the process. Otherwise, the rate is too slow to be effective, particularly at low temperatures (less than 20 deg. C [less than 68 deg. F]). Catalysts that can be used in the reaction are palladium (Pd) or other metals from the eighth group of the periodic table. In our application, Pd was chosen because Pd-covered resins were commercially available. Polystyrene-based anion-exchange resins are used as the catalyst-carrier material because anion-exchange resins have very high chemical and mechanical stability. Finely dispersed metallic palladium is impregnated in the matrix of the resin. (The resin itself does not enter into the scavenging action.) The concentration of palladium in a resin matrix decreases from near the surface to the center of the bead. The catalyzed reaction between dissolved oxygen and hydrogen occurs stoichiometrically--8 g of 02 reacts with 1 g of H2. The final product is water. Therefore, this scavenging method does not add unwanted dissolved solids (to water) as do chemical scavenging methods. Theoretically, the catalyst should last indefinitely. The hydrogen gas is readily available. Thus, the catalytic reduction of oxygen can be an economical way to remove oxygen in water. Dissolved Oxygen in Water. The amount of dissolved oxygen in water depends on the solubility of oxygen in water. Solubility of oxygen is primarily a function of pressure, temperature, and salinity. When the partial pressure of oxygen vs. concentration is plotted, there is a linear relationship between the two. For example, plotted, there is a linear relationship between the two. For example, if at a partial pressure of 101 kPa [1 atm], 02 saturation is 41.3 mg/L, then at 21.2 kPa [0.21 atm], the saturation is 8.6 mg/L.4 Therefore, with the slope of the line known, the saturated oxygen concentration can be estimated at any partial pressure (at a given temperature). An increase in temperature generally causes a decrease in the solubility of a gas in a liquid. This inverse relationship is shown in Fig. 1. If the temperature of a gaseous solution is allowed to increase continuously (at atmospheric pressure), then complete degassing will ultimately occur (near the boiling point of water). When a strong electrolyte is present in a solution, the activity coefficient of the solution is increased. The concentration of dissolved oxygen decreases as the activity coefficient increases. Therefore, the solubility of oxygen in water decreases as total salt concentration increases. As a result, the hydrogen concentration necessary to achieve stoichiometric reaction also varies with temperature, pressure, and salinity. Experimental Procedures and Equipment Setup OWTP. At the Grubb Lease OWTP, the ocean water is pumped through a rotary screen to remove the large debris. The water is then treated with chlorine and alum as it enters a clarifier. Effluent from the clarifier goes into a downflow sand filter and into a clear well. A booster pump then lifts the water to a vacuum tower for deaeration. From the vacuum tower, the water is rechlorinated and transferred to the separate, lease-water-injection plants. The Cadeox feedwater is taken from the discharge of the clear-well booster pump (see Fig. 2). Cadeox Flow System. As shown in Fig. 3, the oxygen-saturated (6- to 8-ppm) feedwater enters the test system at 207 to 276 kPa [30 to 40 psig]. It is filtered through a 3-mu m cartridge filter. The seawater flow rate is controlled at 1.89 X 10–3 m3/min [0.5 gal/min] by a flow-control valve and measured with a rotometer. The water then enters a cell and is saturated with hydrogen entering at 20 to 25 mL/min, which is 5 to 10% above the stoichiometric amount of necessary H2. SPEPE P. 619