Automobile Catalysts Research Articles

Improving the Selectivity of NH3TPD Measurements

Pt supported on ZSM-5 catalysts are important for the catalytic oxidation of CO and volatile organic compounds (VOCs) due to their extraordinary performance at low temperatures and economic purposes. However, achieving complete oxidation at low temperatures and stability under water vapor remains challenging. Herein, we report the synthesis of several loading of Pt on a ZSM-5 catalyst via a flame synthesis technique. The Pt/ZSM-5 exhibited good activity towards complete CO and C3H6 oxidation at low temperatures due to the interaction between the Pt and ZSM-5. The combined effect of the PtOx (Pt2++Pt4+) and lattice oxygen from Pt (OPtOx) as the active centers in Pt/ZSM-5 favors the complete oxidation with high reaction rates, TOFs, and low activation energies (Ea), which is well consistent with the increasing concentration of the (Pt2++Pt4+)/Pt0. Pt/ZSM-5 presents a long-time tolerance to water vapor deactivation even at temperatures below 80 °C. The distributed Pt favor the reaction occurring through the Langmuir-Hinshelwood (L-H) route. The excellent catalytic results indicate an attractive approach for designing supported Pt on ZSM-5 catalysts for automobiles and industry exhausts.

Development of High-Accuracy ICP Mass Spectrometric Procedures for the Quantification of Pt, Pd, Rh, and Pb in Used Auto Catalysts

Inductively coupled plasma mass spectrometric procedures have been developed for the high-accuracy determination of three platinum group elements (Pt, Pd, and Rh) and Pb in two used automobile catalysts. Isotope dilution quantification was applied for the certification of Pb, Pt, and Pd. The mononuclidic Rh was quantified using an internal standard after careful assessement of potential systematic errors from incomplete dissolution and instrumental interferences. The Pb concentrations are certified at 6228 ± 49 mg/kg in SRM 2556 (Used Auto Catalyst-Pellets) and 13931 ± 97 mg/kg in SRM 2557 (Used Auto Catalyst-Monolith). The certified concentrations for the platinum group elements in SRM 2556 and SRM 2557, respectively, are, for Pt, 697.4±2.3 and 1131 ± 11 mg/kg ; for Pd, 326.0 ± 1.6 and 233.2 ± 1.9 mg/kg ; and for Rh, 51.2 ± 0.5 and 135.1 ± 1.9 mg/kg.

Resolution of discrepant analytical data in the certification of platinum in two automobile catalyst SRMs

The National Institute of Standards and Technology (NIST) recently developed two recycled automobile catalyst materials as standard reference materials (SRMs), in response to a request from the International Precious Metals Institute. Results of analyses for platinum by two different analytical techniques did not agree well, with the means differing up to 6%. The palladium results for these same two techniques in the same materials showed much better agreement. Finally, it was determined that one technique (instrumental neutron activation analysis — INAA) had a small, random interference due to a tantalum impurity in/on the acid washed polyethylene bag used to hold the finely powdered sample. This Ta was not present in any of the empty bags used to evaluate the bag blank. Once this problem was identified, the unique characteristics of the INAA technique allowed the magnitude of the interference to be accurately determined for each sample, data recalculated, and a final result obtained which agreed well with the second technique.

The determination of platinum-group elements (PGE) by nickel sulfide fire-assay: Coexisting PGE-phases in the nickel sulfide button

The chemical composition of phases in buttons obtained by nickel sulfide fire-assay during the determination of platinum-group elements (PGE) has been investigated by electron microprobe analysis. Different PGE-containing phases, due to varying flux constituents and species of added PGE, have been detected. By using sodium tetraborate as flux constituent and adding PGE as chlorides, in a cryptocrystalline Ni3S2 matrix with low PGE (mainly Rh and Ru) contents, Rh- and Ru-bearing nickel sulfides ((Ni7.68–7.80Ru0.84–0.90Rh0.35–0.43)9S8) and Ir alloys ((Ir,Pt,Os)0.56–0.62(Ru,Rh)0.25–0.28Ni0.12–0.19) are found. Treatment with lithium tetraborate leads to a Ni3S2 matrix exhibiting slightly higher Rh and Ru contents, with inclusions of nickel-rhodium sulfides (Ni8Rh4S9) and platinumnickel alloys (Pt0.45Ni0.36–0.39Ru0.11–0.14Rh0.05). Finely dispersed metallic colloidals from an automobile catalyst, with platinum and rhodium as main components, have given only platinum-nickel alloys (Pt1−xNix). Considerable losses of PGE during analytical steps following the fire assay are expected when their contents in sulfidic phases, which are more likely to be dissolved, are high.

Dependence of Catalyst Deterioration on the Noble Metals in Three Way Catalyst for Natural Gas-fueled Engines.

The deterioration of three way catalysts for the reduction of NOx from the exhaust of natural gasfueled engine cogeneration systems was studied using the analyses of used catalysts and accelerated tests of trial catalysts which contain a variety of species and amounts of noble metals. The results show that the catalysts for gasoline-fueled automobiles do not have sufficient activity of methane oxidation after a couple of thousands hours operation, the window in which NOx and CO are simultaneously converted shifts to a rich air/fuel (A/F) ratio, though the window still exists. This means that NOx is not removed at the controlled A/F ratio. The results of the tests using artificially deteriorated catalysts clarified that the deterioration is caused by the sintering of noble metals. Further, from the experiments varying species and amounts of noble metals, it was also proven that Pt plays an essential role in methane oxidation and that the shift of the window can be suppressed by maintaining the surface area of Pt with increases in Pt amounts and in the Pt/Rh ratio. Besides, the increase in Pt amount contributed to an increase in the oxygen storage capacity of the catalyst due to CeO2 and enabled operation under dynamic A/F control for a long time.

Development status of a sealed bipolar lead/acid battery for high-power battery applications

A sealed bipolar lead/acid (SBLA) battery is being developed by Arias Research Associates (ARA) which will offer a number of important advantages in applications requiring high power densities. These applications include electric vehicles (EVs) and hybrid electric vehicles, uninterruptable power supplies (UPS), electrically-heated catalysts (EHCs) for automobiles, utility-power peak-shaving, and others. The advantages of the SBLA over other types of batteries will by significantly higher power density, together with good energy density, high cycle life, high voltage density, low production cost and zero maintenance. In addition, the lead/acid battery represents a technology which is familiar and accepted by Society, is recyclable within the existing infrastructure, and does not raise the safety concerns of many other new batteries (e.g., fire, explosion and toxic gases). This paper briefly reviews the basic design concepts and issues of the SBLA battery technology, various quasi-bipolar approaches and the results of ARA's development work during the past four years. Performance data are given based on both in-house and independent testing of ARA laboratory test batteries. In addition, performance projections and other characteristics are given for three ARA SBLA battery designs, which are compared with other batteries in three example applications: UPS, EHCs, and EVs. The most notable advantages of the SBLA battery are substantial reductions in product size and weight for the UPS, smaller packaging and longer life for the EHC, and higher vehicle performance and lower cost for the EV, compared to both existing and advanced EV batteries.

The Effect of Fuel and Oil Additives on Automobile Catalyst Performance

Stringent standards controlling the emission of exhaust pollutants from gasoline-fuelled spark ignition engines have necessitated studies of many factors that influence the efficiency of the catalysts used for the destruction of carbon monoxide, unburnt hydrocarbons and nitrogen oxides. This review of the literature considers the effects on the catalyst of lead, manganese and phosphorus, which may be present as additives in fuel or lubricating oils. The first two elements can be detrimental to catalytic activity, and also to the environment, so must be minimised. The deactivation caused by phosphorus can be avoided by the use of catalysts designed to be compatable with the specified lubricants. Catalysts containing platinum group metals remain the preferred means of controlling the three designated exhaust gases.

Enhancement Errors in the Determination of Platinum Group Metals in Alumina-Based Matrices by Direct-Current Plasma Emission Spectrometry

Direct-current plasma emission spectrometric analysis of platinum group metals in solutions from automobile catalyst shows significant enhancement of analyte values Addition of a lithium buffer does not remove the interference The only matrix constituents in these solutions were aluminum and magnesium, both of which were found to cause enhancement in the determination of platinum, palladium, and rhodium A buffer consisting of 3500 mg/L lithium and 2500 mg/L lanthanum removed the enhancement effect of both magnesium and aluminum on these metals 8-hydroxyquinoline also reduced the degree of interference due to aluminum, although not as efficiently as lanthanum, indicating that formation of compounds in the dc plasma is a possible source for the observed interference

Study on the Reduction Catalysts for Automobiles Produced by Using Ultra Fine Metal Powders

Study on the Reduction Catalysts for Automobiles Produced by Using Ultra Fine Metal Powders

Mass spectrometry of nickel carbonyl for modeling of automobile catalysts

The charge exchange mass spectrum of nickel carbonyl has been reported using a typical gasoline engine exhaust gas as the reactant gas. Various positive ions which can be attributed to nickel carbonyl and its fragments were observed in this mass spectrum. The effect of pressure on the intensity of both the reactant gas ions and the nickel carbonyl was studied in an attempt to find the optimum condition for the quantification of nickel carbonyl. Using these data, the minimum detectable limit was found to be 10 ppb for nickel carbonyl. This methodology was used to monitor nickel carbonyl in the effluent from a model reactor for a catalytic controlled automobile. Based on these studies, no measureable quantities of nickel carbonyl can be expected from catalytic controlled automobiles. 4 figures, 1 table.

Deactivation of a composite automobile catalyst pellet: II. Bimolecular Langmuir reaction

In this work, the deactivation of a composite catalyst pellet is analyzed for reaction and deactivation conditions similar to those found in automobile catalytic converters. The composite catalyst is made of two layers; the inner layer supports the active metal in a high-area support, whereas the outer layer consists of an inert support that protects the active metal from poisons that deactivate the catalyst. The reaction kinetics used is a bimolecular Langmuir kinetics characteristic of CO oxidation on Pt Al 2O 3 catalysts, and it is assumed that the catalyst operates under diffusion-controlled conditions. It is also assumed that the catalyst deactivates following a pore mouth-poisoning mechanism which is characteristic of Pb or P poisoning of automobile catalysts. The results obtained show that using a composite catalyst one obtains an enhancement of the activity when operating in the region of high reactant concentration. However, at low reactant concentration, the kinetics becomes first order and only the catalyst lifetime can be improved. The results presented here further support previous findings for the first-order reaction indicating that both long-term activity and catalyst lifetime can be improved by using a composite catalyst.

Activity and lifetime of a composite automobile catalyst pellet

This work analyzes the performance of a composite catalyst pellet under deactivation conditions characteristic of those found in automobile catalysis. The composite pellet is made of two layers, the inner layer supports the active metal in a high area support, whereas the outer layer is made of a different inert support. Analytical solutions relating activity and lifetime are obtained for a first order reaction and pore mouth poisoning. The results indicate that when the effective diffusivity of the outer layer is higher than in the inner support, the activity relative to initial activity can be maintained at a higher level for a longer period of time than when using a single supported catalyst. The results presented in this work indicate a significant potential to develop such catalyst for application in automobile catalysis.

Car catalysts pose health problems

This brief article is concerned with the health problems that arise from the use of catalysts to reduce car exhaust emissions. The author first refers to the environmental protection agency's decision to give automobile manufacturers at least another year to make reductions in car exhaust exissions in America. It is pointed out that although the catalytic converters that are being adopted by American car manufacturers do a good job in oxidising hydrocarbons and carbon monoxide, they also oxidize sulphur dioxide to sulphuric acid; and that EPA have found that cars equipped with catalysts produce 35 times more than cars without catalysts and if an air pump is used to meet stricter pollution control standards, the production would be 70 times more. The dangers of sulphuric acid emission from cars are discussed together with the possible health problems which might arise when concentrated along motorways and in cities. The author also discusses this particular problem in relation to the problems of rapidly introducing legislation to deal with environmental problems, the absence of an immediate solution to the sulphuric acid problem and the probable need for a completely different car engine design such as the stratified charge engine. /TRRL/

A Multiple Regression Procedure for Elemental Analysis at Low Concentrations

AbstractUsing a multiple regression procedure, X-ray fluorescence analysis has been applied to a 15-element system associated with ceramic supported automobile emissions catalysts. An equation taking inter-element effects into account was used to relate the concentrations and X-ray intensities of the active elements and contaminants deposited on the ceramic substrate. The major elements present in the substrate were intentionally excluded from the regression. The regression coefficients were determined from a set of 240 calibration standards using a multiple linear least-square regression. Elemental concentrations in the standards ranged from 0.05 to ten weight percent. The ceramic matrix was the same in both the standards and the unknowns to be analyzed and constituted at least 85 percent of the total weight of each sample. The regression coefficients were then used to solve for the contents of the elements in unknown samples. Limits of accuracy were determined by using the set of available standards. The performance of the regression was improved in certain cases by imposing constraints on the regression.