Catalytic converter success

Operational Factors Controlling Rate and Selectivity of Carbonylation. In Figures 5 and 6 are shown the effects of reaction temperature and of CO/MeOH feed gas ratio on catalytic performances. Methanol conversion increased monotonically with an increase in the temperature and was 99% at 300 C. The yield of methyl acetate reached a maximum level at 250 C and then decreased. Acetic acid yield increased with increasing temperature and was 95% at 300 C. It should be noted that the yield of DME was 2.7% or less and that its yield was almost zero at 300 C. As already pointed out by the present authors, DME and methyl acetate are converted successively to methyl acetate and acetic acid, respectively (6,2) ... 

In fact, most of us benefit from the use of catalysis. Automotive catalytic converters have represented the most massive application of environmental catalysis and one of the most challenging and successful cases in catalysis, generally. Automobile catalysts deseive a few more comments. The engine exhaust emission is a complex mixture, whose composition and flow rate change continuously depending on a variety of factors such as driving conditions, acceleration, and speed. Despite the variability of the conditions, three-way catalysts have achieved the reduction of exhaust carbon monoxide, hydrocarbons, and... 

Converters for cars are usually ceramic monoliths and occasionally metal based. Without much exaggeration, they can be claimed to be one of the major successes of recent decades in the area of chemical engineering and catalysis. In the beginning, the catalytic converter was placed underbody, where sufficient space was available and where the temperature was expected to be mild. There was no need... 

Initially, packed beds were also used. They, however, were no success, and at present monoliths are applied exclusively. This should not be misunderstood. Monolith means literally a single stone. However, metal-based analogues are also included in the definition of monolith. In fact, for catalytic converters in cars, in addition to ceramics, metal-based monoliths have been and still are used. A major advantage of metal was the thin wall thickness that could be achieved. Later, industry succeeded in manufacturing ceramic structures of comparable wall thickness. In view of their higher resistance against corrosion, ceramic monoliths are now more generally applied than metal ones. 

A billion cars and coimting, himdreds of millions of them with catalytic converters—this application is a landmark success of catalytic science and technology. Automobile catalytic converters are mostly monoliths— like ceramic honeycombs with porous catalyst layers on their inner wall surfaces. These monoliths are the most widely used structured reactors, the topic addressed by Moulijn, Kreutzer, Nijhuis, and Kapteijn. In contrast to the classical reactors containing discrete particles of catalyst and characterized by random and chaotic behavior, structured reactors are characterized by regular structures and predictable laminar flow. Structured reactors can be designed in full detail up to the local surroimdings of the... 

Oxygen storage capacity (OSC) was measured at 400°C under atmospheric pressure. A 20 mg sample was continuously purged with helium (30 cm. min ). Successive or alternate pulses (0.265 cm ) of O2 (Air Liquide, < 5 ppm total impurities) and CO (Air Liquide, N20) were injected every minutes in order to simulate lean and rich operating conditions as those encountered in an Otto engine coupled with a three-way catalytic converter. The Oxygen Storage Capacity (OSC) was calculated from the CO consumption after stabilization of the sample in alternate pulses condition. 

In spite of the commercial successes of these two millisecond reactors, few processes other than NH3 oxidation (a superoxidation) and HCN synthesis (oxidative dehydrogenation or ammoxidation) have been carried out on a large scale. In the automotive catalytic converter, contact times over noble metals on wash coated extended ceramics are used with contact times of -0.1 sec with temperatures of 400°C. 

Deaza-ll-oxahomoAMT (IV.62) was synthesized by Nair / a/. [Ill] by a modification of their synthesis of lO-deaza-lO-oxaAMT (IV.52). 1-Bromo-4-[4-(carbomethoxy)phenoxy]-2-butanone (IV.63) was converted successively to the azide (IV.64), the ketal (IV.65), and the acid (IV.66). Mixed anhydride coupling of (IV.66) and diethyl L-glutamate, followed by catalytic hydrogenation of the azido group, yielded the amine (IV.67), which, on addition to 2,4-diamino-6-chloro-5-nitropyrimidine and hydrolysis of the ketal group with acid, gave the key intermediate, (IV.68). Dithionite reduction led... 

While in the early years the classical Pt/Rh catalyst dominated the market, Pd was successively used to replace Rh and later Pt, leading finally to the development of the Pd-only catalyst. In 2008, 136.2 tonnes of Pd was used for catalytic converters, accounting for 63.9% of the worldwide demand (Johnson Matthey 2009). 

The success of the catalytic converter is up to now mainly limited to gasoline powered engines. However, in recent years progress has also been made in the development of catalytic filters for the cleaning of exhaust gas (e.g., particulate matter) from diesel engines. 

Nevertheless, secondary measures are mostly still needed to reduce exhaust emissions of cars to meet current emission standard in most countries. These so-called end-of-pipe solutions are based on the catalytic conversion of all HCs, CO and NO (three-way catalyst). The success of the monolithic catalytic converter (which has a lower pressure drop than a fixed bed) is up to now limited to gasoline powered engines. However, in recent years progress has been made in the development of catalytic filters for the cleaning of exhaust gas (e.g., particulate matter) from diesel engines. 

Unlike steel and the metals in batteries, catalyst family metals can be expected to be recycled on the basis of their value, as opposed to the dominance of their mass in fuel cell systems. For example, platinrrm family catalyst metals are currently quite successfully recycled from today s vehicles (including both platinum and rhodium). Bhakta (1994) notes that in today s catalytic converters, the catalyst is housed in a stainless steel canister. Therefore, to recycle the catalyst, special machines have been developed to slit the canisters and remove the catalyst. Given an estimated increase in the amormt of platinrrm group metals (PGMs) in fuel cells of 15 to over 200 times that of the catalytic converter for mobile fuel cell applications, it can be expected that similar technological development wotrld follow wide-scale deployment of fuel cells based onPGMs (Cooper 2003,2004a). 

In the 1970s, catalytic converters were installed on motor vehicles to reduce the emissions of NO, CO, and unburned hydrocarbons. Catalytic converters have been extremely successful. 

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