Hideo Ohuchi

Performance of platinum-group metal catalysts for the selective reduction of nitrogen oxides by hydrocarbons

Abstract The performances of platinum-group metals, platinum, iridium, palladium, rhodium and ruthenium supported on γ-alumina, as catalysts for the selective reduction of nitrogen oxides by hydrocarbons were investigated. Platinum and rhodium had high nitric oxide conversion activities both in model mixtures and in real diesel exhaust gases, especially at relatively low temperatures between 200 and 350°C. It was confirmed that the platinum-rhodium and platinum catalysts have higher activity and durability than a catalyst composed of copper supported on ZSM-5 under real diesel exhaust conditions. The platinum-containing catalysts, however, produced more nitrous oxide than nitrogen. It is expected that platinum-group metal catalysts will be able to be used for practical purposes if once their selectivity toward nitrogen is improved.

Determination of polycyclic aromatic hydrocarbons in diesel exhaust particulate matter and diesel fuel oil

Clean-up procedures were developed for a method for determining the amount of polycyclic aromatic hydrocarbons (PAHs) in diesel exhaust particulate matter and in diesel fuel oils using reversed-phase high-performance liquid chromatography (HPLC). They were based mainly on the elimination of insoluble matter and aliphatic compounds that affect the performance of HPLC, from the dichloromethane extracts of particulate matter or from oils, with the aid of a disposable preparation column containing reversed-phase packings (Sep-Pak C18). Using these procedures, it is possible to detect 1 ng of benzo(a)pyrene in 30 mg of particulate matter with more than a 97% recovery or 0.5 ng in 50 microliters of oil with 91% recovery. Examples of analyses are given for particulate matter emitted from a diesel test engine and for diesel fuel oils, such as gas oil, residual oil and coal-liquefied oil.

Effect of addition of sulphur and phosphorus on heavy oil hydrotreatment with dispersed molybdenum-based catalysts

Abstract The influence of the addition of sulphur and phosphorus on the activity of finely divided molybdenum-based catalysts formed in situ was investigated with regard to the hydrotreatment of Morichal crude oil (Venezuela). Reactions were carried out using a batch reactor at 470°C. The catalyst precursors used were molybdenum naphthenate, cobalt octylate and di-2-ethylhexyl phosphate. An increase in elemental sulphur addition led to increased catalytic activity, especially in the presence of phosphorus. It was found that the hydrogen sulphide that was generated from elemental sulphur can accelerate the decomposition of the precursors at temperatures below 240°C during the period of heating of the reactor. It was suggested that hydrogen sulphide is essential for the catalyst species to be sufficiently sulphided and activated without suffering possible coke poisoning. Phosphorus increased the hydrodesulphurization activity in amounts up to ca. 15·10−4 mol P per 70 g of feed, but further addition decreased the activity. The optimum level was unchanged irrespective of the molybdenum concentrations employed. In addition, the vanadium removal improved remarkably with increase in the amount of phosphorus added. It is concluded that phosphorus interacted strongly with the vanadium compounds in the feed and prevented the catalyst species from being deactivated by the deposition of vanadium.

Enhancement effect of Mg2+ ion on direct nitric oxide decomposition over supported palladium catalysts

Abstract Direct decomposition of nitric oxide to nitrogen and oxygen was investigated on supported palladium catalysts at 550-750°C. It was found that nitric oxide decomposition activities of Pd/MgAl2O4, Pd/MgO, Pd/Mg2Si3,O8 and Pd/MgZrO3, all of which included Mg2+ ions as the constituent of the oxides, were higher than those of Pd/γ-Al2O3, Pt/γ-Al2O3, and Cu/ZSM-5 in this temperature range. Furthermore, Mg2+ ions doped in Pd/γ-Al2O3 enhanced the catalytic activity. These results led us to conclude that Mg2+ ions on palladium catalysts play an important role in enhancing the decomposition activity.

Application of thin-layer chromatography with flame ionization detection to the characterization of organic extracts from diesel exhaust particulates

Thin-layer chromatography with flame ionization detection has been applied to the analysis of organic extracts of diesel exhaust particulates. Non-volatile organics whose boiling points are higher than ca. 300 degrees C can be analyzed, with a detection limit of ca. 0.03 micrograms and a relative standard deviation of ca. 10%. The organic extracts are separated into aliphatics , aromatics and polars by the development procedure with n-hexane, and the polars can be separated further by using toluene as the solvent. Some examples of application are presented.

Properties of PdAu and PtCu alloy surfaces for the adsorption and catalytic reduction of O2 and NO by H2

Abstract The adsorption and catalytic properties of PdAu and PtC alloy surfaces were investigated under low pressure conditions, with the real surface composition being monitored using Auger electron spectroscopy. Flash desorption experiments on O2 and NO, and steady state kinetic experiments involving the reduction of these substances by H2 were performed on polycrystalline alloy surfaces. For the PdAu system, O2 desorption was promoted by gold, as shown by the shift of O2 desorption toward lower temperature and a linear decrease in the saturated amount of O2 adsorption with increase in gold content. For the PtCu system, O2 desorption was retarded by copper i.e. the O2 desorption temperature shifted upward with increase in copper content. In both the alloy systems, catalytic activities for the above reactions were significantly suppressed by the addition of gold or copper to the platinum group metals. The drop was more pronounced for NO reduction, suggesting that a larger ensemble of active platinum group metal atoms are necessary for NO dissociation.

Evaluation of gaseous and particulate emission characteristics of a single cylinder diesel engine

Abstract Emission characteristics of a single cylinder diesel engine with a swirl chamber were investigated. Specific fuel consumption, exhaust gas temperature, specific mass emissions of CO, total hydrocarbon (THC), nitrogen oxides (NO x ), and particulates were measured. In addition, contents of carbon, hydrogen, CH 2 Cl 2 soluble fraction (SOF), aliphatic hydrocarbons, polar organics, benzo(a)pyrene (B(a)P), and low temperature combustion fraction in the particulates, and the burnout temperature of the particulates were analyzed. All these results were represented as contour maps on a speed-torque plane. The emission of CO and the particulates increased steeply near the maximum speed and torque investigated, whereas the NO x emission was almost independent of speed, increasing as the torque decreased. Content of hydrogen, SOF, aliphatic hydrocarbons, and low temperature combustion fraction showed similar patterns, having the maximum value at 1500 rpm at 1 4 load and decreasing toward 2500 rpm at full load. Burnout temperature of the particulate matter ranged from 673 to 707°C and correlated with the carbon content.

Hysteresis and self-oscillation in a selective catalytic reduction of nitric oxide by hydrocarbons on alumina

Abstract Hysteresis and periodical self-oscillating behaviors in the reaction rate were observed during the selective catalytic reduction of NO on an alumina catalyst when 1-butene (C 4 H 8 ) or propene (C 3 H 6 ) was used as the reducing agent. Carbonaceous deposits produced on the catalyst were involved in the appearance of these phenomena.

Mechanism of selective catalytic reduction of nitrogen monoxide by organic compounds

Carbonaceous radicals have been identified in a γ-alumina catalyst in the selective reduction of NO by organic compounds; these are probably produced from carbon deposits that accumulate on the catalyst and are proposed to be active spacies which preferentially react with NO.

A Study of an Optical Temperature Monitoring Device Sensitive in the Extended Region to Controlled Regeneration of a Diesel Particulate Filter

A device for monitoring the maximum temperature in an extended region was applied to the control of combustion for regeneration of a diesel particulate filter. The devices main objective is to monitor internal thermal radiation of an optically transparent rod probe at its end. In both the experiments using carbon black and real diesel exhaust particulates, a stable regeneration process was realized by controlling the flow rate of air needed for combustion according to the light intensity from the probe.