Hydrocarbon catalysts, performance testing

Benefits depend upon location. There is reason to beheve that the ratio of hydrocarbon emissions to NO has an influence on the degree of benefit from methanol substitution in reducing the formation of photochemical smog (69). Additionally, continued testing on methanol vehicles, particularly on vehicles which have accumulated a considerable number of miles, may show that some of the assumptions made in the Carnegie Mellon assessment are not vahd. Air quaUty benefits of methanol also depend on good catalyst performance, especially in controlling formaldehyde, over the entire useful life of the vehicle. 

The final authority on the durability of catalysts is performance in road vehicles. Such data have been rapidly accumulated by the various automobile manufacturers in recent months. This data takes into consideration all the accidents of everyday usage, serving to test how much abuse the catalyst can withstand and still perform its duty. Experience has shown that fresh oxidation and reduction catalysts by a large variety of formulations from many manufacturers would indeed perform their duty. Many oxidation catalysts perform well enough at 25,000 accumulated miles to satisfy the requirement of 0.41 g hydrocarbon/mile and 3.4 g CO/mile, but few would perform well enough at 50,000 miles without maintenance and adjustment of the engine. Many such vehicle endurance tests have to be terminated because of malfunction of the engine or the auxiliary equipment. 

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an additive in many commercial unleaded gasolines, and thus its potential effect on catalyst performance is an important consideration. It was reported by Faggan et al. 8) that MMT at a recommended level of 0.125 g Mn/gal shows no adverse effect on emissions, when compared to unleaded gasoline, in tests on cars operated on the 50,000-mile EPA certification schedule. These findings have been confirmed by a number of unpublished test reports from several industrial laboratories. In fact, it is indicated that some of the manganese deposits can aid catalytically in the removal of CO, and possibly to some extent also of hydrocarbons. The consequence of such a catalytic effect of Mn has still to be explored. 

The effect has been studied in a small-scale pilot plant (see detail of the plant in reference [1]). This unit has a 60 cm down-flow fixed bed reactor that operates isothermally. The hydrogen and the hydrocarbon feed were preheated before entering the reactor. After reaction, the liquid product (C5+) was fractionated and analyzed using conventional ASTM method. In addition, a Mass Spectrometry coupled with gas chromatograph (GC MS) was used to measure aromatics, paraffins and naphthenics compounds distribution in the feed and in the products. In addition, a special NMR analysis was performed to determine the PNA. The VGO was desulfurized using commercial catalyst (not described here) and the product characteristics are shown in Table 4 as well as the feed. The MHCK catalysts were tested at 380 and 400 °C, LHSV=0.75 and 100 bar of total pressure, using 800 mVm of H/HC ratio at the inlet of the reactor. The... 

This paper reports first results of research and development work to achieve nitrogen oxide reduction under lean diesel exhaust gas conditions. Much attention is paid to the influence of operation conditions on catalyst performance. A major part of the paper deals with the influence of the hydrocarbon component, the hydrocarbon concentration and the HC/NO ratio on the activity of a special developed platinum based catalyst. Other aspects discussed are a spectroscopic characterization and a selectivity study. A hypothesis of a "dual-site" reaction mechanism for NOx-reduction in lean diesel exhaust gas precious metal based catalyst is established. Finally, first promising results on the performance of the catalyst system in a vehicle dynamometer test are given. 

Zeolite catalyst performances were also checked in a direct manner in the methane oxidation reaction, a model reaction which tested the spinel oxide type catalysts prepared by us for hydrocarbons oxidation to the purpose of purifying engines exhaust gases. The results are presented in Table 2. From among the... 

Catalyst performance may be influenced by oxidative pretreatment of carbon supports. The AC samples shown in Table 12 were used for the preparation of the Mo/AC and NiMo/AC catalysts. The activity of the catalysts was tested in the flow reactor at 3 MPa and 623 K using the 7% solution of pyridine in cyclohexane. Figure 39 shows that for the catalyst consisting of the pretreated supports, the overall conversion (to C5 hydrocarbons and piperidine) decreased, indicating an enhanced deactivation of catalyst. However, in the presence of H2S, the activity difference was much less evident. For pretreated... 

Figure 4 shows the CO conversion curves (calculated from a mass balance on the amount of carbon in CO and of all the hydrocarbons, revealed by the detector of the gas-chromatograph) vs time for two RU/AI2O3 samples (1% Ru w/w). The runs were performed at 275 C, 5 bar in a tubular continuously fed reactor, with a molar ratio H2/CO = 2. Pd/C catalysts were tested in the hydrogenation of acetophenone in ethanol at 25°C and atmospheric pressure with flowing H2 as reactant in a slurry laboratory-scale plant. The activity values were measured by the consumed hydrogen in mL-min i. 

However, it is questionable whether the water-gas shift catalysts can withstand the presence of higher hydrocarbons in the feed in the longer term. The group working with the author of this book has performed tests over a precious metal based water-gas shift catalyst, which had already passed a 1000-h stability test in the presence of 5 vol.% methane without apparent deactivation. It degraded significantly within less than 200 h when exposed to 5 vol.% propane in the feed. 

The primary contaminants of a PEFC are carbon monoxide (CO) and sulfur (S). Carbon dioxide (CO2) and unreacted hydrocarbon fuel act as diluents. Reformed hydrocarbon fuels typically contain at least 1 percent CO. Even small amounts of CO in the gas stream, however, will preferentially adsorb on the platinum catalyst and block hydrogen from the catalyst sites. Tests indicate that as little as 10 ppm of CO in the gas stream impacts cell performance (35, 36). Fuel processing can reduce CO content to several ppm, but there are system costs associated with increased fuel purification. Platinum/ruthenium catalysts with intrinsic tolerance to CO have been developed. These electrodes have been shown to tolerate CO up to 200 ppm (37). 

Alkanes and Alkenes. For this study, C150-1-01 and C150-1-03 were tested under primary wet gas conditions with ethylene, ethane, propylene, and propane being added to the feed gas. This study was made in order to determine whether these hydrocarbons would deposit carbon on the catalyst, would reform, or would pass through without reaction. The test was conducted using the dual-reactor heat sink unit with a water pump and vaporizer as the source of steam. All gas analyses were performed by gas chromatography. The test was stopped with the poisons still in the feed gas in order to preserve any carbon buildup which may have occurred on the catalysts. 

These tests were performed to establish the limits in flexibility and operability of a methanation scheme. The two demonstration plants have been operated in order to determine the optimum design parameters as well as the possible variation range which can be tolerated without an effect on catalyst life and SNG specification. Using a recycle methanation system, the requirements for the synthesis gas concerning H2/CO ratio, C02 content, and higher hydrocarbon content are not fixed to a small range only the content of poisons should be kept to a minimum. The catalyst has proved thermostability and resistance to high steam content with a resultant expected life of more than 16,000 hrs. 

The photocatalytic experiments were performed in a horizontal quartz tube which it have TiOi. Illumination was provided by 500 W mercury lamps, located above the horizontal quartz tube. The reactant was 0.1% (v/v) ethylene in air. In case of Photo-Catalyst test, reactor effluent samples were taken at 30 min intervals and analyzed by GC. The composition of hydrocarbons in the feed and product stream was analyzed by a Shimadzu GC14B (VZIO) gas chromatograph equipped with a flame ionization detector. In all case, steady state was reached within 3 h. 

Catalytic testings have been performed using the same rig and a conventional fixed-bed placed in the inner volume of the tubular membrane. The catalyst for isobutane dehydrogenation [9] was a Pt-based solid and sweep gas was used as indicated in Fig. 2. For propane oxidative dehydrogenation a V-Mg-0 mixed oxide [10] was used and the membrane separates oxygen and propane (the hydrocarbon being introduced in the inner part of the reactor). 

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