The fluid properties of interfacial tension and viscosity, and the fluid-solid interactions embodied in the contact angle, are important in a wide range of phenomena that affect the processing of the vacuum residue fractions of petroleum and oilsand bitumens. Direct measurements of these fluid properties at representative processing conditions can give important insight into a variety of design and operating challenges, from gas holdup in hydroconversion to fouling of furnace tubes. This review summarizes the efforts to measure fluid properties of vacuum residue materials at high temperature and pressure. Significant progress has been made in measuring surface tension and viscosity of vacuum residues at temperatures to 530°C at low pressures. Further work is needed to develop methods for measurement of contact angle, and for measurements at high pressure.
A high Si/Al ratio USY zeolite with high mesoporosity was used as the starting material for hydrocracking catalysts for residual oil to improve the catalytic selectivity for middle distillate fractions. Realumination of high Si/Al USY zeolite without destruction of the zeolitic framework and mesoporous structure was achieved by treating the USY zeolite in an aqueous solution of NaAlO2 after immersion in ethyl alcohol. Subsequently, titanium modification of the realuminated zeolite was carried out using an ethyl alcohol solution of titanium isopropoxide, followed by loading of molybdenum by equilibrium adsorption using an aqueous solution of ammonium paramolybdate. The resultant USY zeolite-based catalysts (MTAZ) showed higher selectivity for middle distillate fractions than previously reported titanium-modified USY zeolite-based catalysts in the hydrocracking of Arabian heavy atmospheric residue. Considering the characteristics of the catalysts, the acid sites on the MTAZ catalysts were mainly located on the mesopore surfaces and the production of gaseous and naphtha fractions was minimized because of the low number of acid sites inside the micropores.
A hybrid catalyst consisting of a methanol synthesis catalyst and a methanol dehydration catalyst was used for the direct synthesis of dimethyl ether (DME) from CO2 and H2. Particle-shaped hybrid catalyst (MD-12) and pellet-shaped hybrid catalyst (MD-13) gave similar results for the DME synthesis. In the MD-13 hybrid catalyst, the activity of the methanol synthesis catalyst slightly decreased whereas the activity of the methanol dehydration catalyst did not decrease during the durability test for 2000 h at 563 K. One-path and recycling experiments for MD-13 were carried out using the bench plant. The methanol synthesis reaction was retarded due to the equilibrium restriction at elevated temperatures. In contrast, the methanol dehydration reaction was promoted with increase in temperature at 543-563 K. The combined yield of methanol and DME was slightly decreased whereas the DME selectivity was remarkably increased. The methanol synthesis reaction was promoted with increase in pressure at 4-8 MPa. However, the methanol dehydration reaction was less promoted. As a result, the combined yield of methanol and DME increased, and the DME selectivity decreased. This observation was consistent with the simulation of reaction rate. Higher reaction temperature and higher recycling rate as well as lower reaction pressure favored higher CO2 conversion, combined yield of methanol and DME, and DME selectivity.
Ultra deep hydrodesulfurization (HDS) of several types of gas oil were performed over NiMo catalyst under various conditions and the carbonaceous deposits on the spent catalysts were characterized by temperature programmed oxidation (TPO). CH3CN was formed in addition to H2O, CO, CO2 and SO2 by TPO, indicating that the carbonaceous compounds deposited on the spent catalysts contain nitrogen atoms. Curve fitting analyses showed that both COx and CH3CN profiles could be deconvolved into two or three Gauss-Lorentz type peaks. Two peaks always appeared below 680 K whereas another peak was observed in the range from 680-690 K if ultra deep HDS was performed above 580 K. These results indicated that at least two or three types of carbonaceous compounds with different combustion properties are deposited on the spent catalysts depending on the reaction conditions. No clear correlation was found between the amounts of carbon and nitrogen atoms contained in the carbonaceous compounds combusted below 680 K and the reaction conditions or the feed compositions such as a total nitrogen content and 90% distillation temperature, T90. On the other hand, the amounts of carbon and nitrogen atoms included in the refractory carbonaceous compounds increased with both higher T90 and reaction temperature. Therefore, the carbon and nitrogen atoms included in the refractory carbonaceous compounds originate from the adsorption of heavy molecule(s) containing nitrogen atom(s) in the feed. At higher reaction temperatures, polymerization of the adsorbed species was facilitated, resulting in larger amounts of the refractory carbonaceous compounds. Larger amounts of refractory carbonaceous compounds were associated with lower residual HDS activity, suggesting that the deposition of such compounds is one of the reasons for the catalyst deactivation.
Catalyst-loaded wall-flow type honeycomb is effective for reducing the level of carbon particle emissions from diesel engines. Pt-supported oxides were investigated for the oxidation and reduction of carbon particles accumulated in the wall-flow type honeycomb. The initiation temperature of combustion of carbon particles was the same for all samples. After the initiation, Pt-supported Ce composite oxides, such as Pt/Ce0.7Zr0.3O2 and Pt/Ce0.9Pr0.1O2, combusted carbon particles at lower temperatures than Pt-supported CeO2, Pt/CeO2. In particular, combustion occurred at the lowest temperature over Pt/Ce0.9Pr0.1O2 after air aging treatment at 1073 K. Pt/Ce0.9Pr0.1O2 released the highest amount of O2 from the oxide at low temperatures and the Pt surface readily oxidized adsorbed CO by O2 in the gaseous phase. Presumably these properties improved the combustion properties of carbon particles.
Three kinds of catalysts of goethites supported on γ-Al2O3 (Fe/γ-Al2O3), SiO2-Al2O3 (Fe/SiO2-Al2O3) and SiO2 (Fe/SiO2) were investigated in terms of the catalytic activity of methane oxidation. The specific surface areas of these catalysts were larger in common than the area of goethite with no supports. The Fe/γ-Al2O3 catalyst has the highest performance in the low-temperature activity of methane oxidation which started at 623 K and completed at 923 K. When the Fe-content in Fe/γ-Al2O3 was increased, the formation of goethite was observed by the X-ray analyses and the activity of this catalyst increased up to 6 mol%. After the catalytic methane oxidation at 823 K, it was observed that goethite in Fe/γ-Al2O3 transformed to hematite which has been known as an active iron oxide in methane oxidation. The activity of Fe/γ-Al2O3 was enhanced by the addition of sodium up to the Na-content of 5 mol% although it descended above the content due to the decrease of the specific surface area of the catalyst.
Non-metallic additives are useful countermeasures to reduce smoke and particulate matter from diesel engine emissions. Non-metallic additives include nitro- and oxygenates, oxygenates and nitrogenates. Nitrites and nitrates can reduce smoke and particulate matter in the direct fuel injection engine under constant conditions of 2100 rpm and 80% load. In particular, n -hexylnitrite added to gas oil improved particulate matter and NOx reduction, and fuel consumption efficiency in the indirect fuel injection engine under Japanese 10·15 mode operation. These additives also reduced the cycle-to-cycle variation of maximum pressures in the cylinder. Smoke concentration decreased with increasing oxygenate concentration. However, oxygenates increased fuel consumption and did not stabilize cycle-to-cycle variation.
A new additive approach using polyethylene glycol (PEG) as a water soluble organic compound was proposed to improve hydrodesulfurization activity over CoO-MoO3/Al2O3 catalyst. The addition of PEG to the impregnation solution during the course of catalyst preparation significantly improved thiophene, dibenzothiophene and light gas oil hydrodesulfurization activity. XPS and TEM measurements indicated that the positive effect of PEG can be attributed to suppression of cobalt and molybdenum aggregation and increasing the number of active sites. Without PEG addition, the cobalt and molybdenum precursors tended to aggregate during the drying step due to weak interaction with the alumina support. Addition of PEG to the impregnation solution maintained high dispersion of cobalt and molybdenum precursors on the alumina support even after water removal, since PEG has higher boiling point than water. Consequently, higher dispersion of cobalt and molybdenum was maintained, because they remained dissolved in the PEG.
Pipeline safety evaluation is an important issue in the industry. Based on magnetic flux leakage (MFL) method, this paper presents an automated inspection device to inspect pipeline defects, analyzes the MFL inspection theory and some defect feature parameters, and gives a recognizing algorithm based on the dynamic wavelet basis function (WBF) neural network. The dynamic network utilizes multiscale and multiresolution orthogonal wavelet, through signals backwards propagation (BP), has more significant advantages than BP or other neural networks used in MFL inspection. It can also control the accuracy of the predicted defect profiles, possessing high-speed convergence and good approaching features. The performance applying the algorithm based on the network to predict defect profile from experimental MFL signals is also presented.