Chang KIM, et al. -- Perovskite-strontium catalyst

Imagine a fuel-efficient, clean-burning diesel engine that costs $1,000 to $5,000 less than those built today. That's the possibility raised by research published this week in the journal Science, from chemical engineers at GM who've found a way to substitute a cheap mineral for wedding-ring-quality metals in catalytic converters.

The GM chemists found a way to use a mineral called perovskite, doped with strontium, in place of the expensive precious metals. It's something of a holy grail in the industry, which many groups have been working on for the past 15 years. While the GM scientists were focusing on diesel engines, their technology should also work in gasoline engines.

"It's an order of magnitude cheaper," says Chang Hwan Kim, a chemical engineer at GM's technology center in Warren, Mich. and the senior author on the paper.

"It's a really significant step forward," says Charles Peden, a chemist and director of the Institute for Interfacial Catalysis at the Pacific Northwest National Laboratory in Richland, Wash. "The high cost of platinum is really causing problems for these new emissions control technologies."

Getting cars today to be both fuel efficient and low-emission is a difficult trade-off.

To make a car fuel efficient, you want to get a mix of air and fuel that burns as much of the fuel as possible. But to put out few pollutants, the current catalyst technology requires that not all the fuel is burned. "The catalytic converter doesn't work if it doesn't have enough unburnt fuel," says Peden.

The catalytic converter changes the smog-creating chemicals nitrogen oxide and nitrogen dioxide put out by the engine into harmless nitrogen.

To cut down on smog car companies began adding catalytic converters to their products in the 1970s. Those catalytic converters used precious metals such as platinum, palladium and rhodium as catalysts, to speed up the conversion of the nitrogen oxide and nitrogen dioxide into plain nitrogen. It's this technology that's decreased air pollution from cars tremendously over the past 15 years. But it's also raised their price.

Newer catalytic converters require less unburnt fuel to work, but in order to do so they require a lot more platinum or other precious metals. And with prices going up, that's been a huge headache for auto manufacturers.

"There are still a few things we have to work on to develop this as a commercial product, but we were very excited," says Kim.

The high cost and poor thermal durability of current lean nitrogen oxides (NOx) aftertreatment catalysts are two of the major barriers to widespread adoption of highly fuel-efficient diesel engines. We demonstrated the use of strontium-doped perovskite oxides as efficient platinum substitutes in diesel oxidation (DOC) and lean NOx trap (LNT) catalysts. The lanthanum-based perovskite catalysts coated on monolith substrates showed excellent activities for the NO oxidation reaction, a critical step that demands heavy usage of platinum in a current diesel aftertreatment system. Under realistic conditions, La(1-x)SrxCoO3 catalysts achieved higher NO-to-NO2 conversions than a commercial platinum-based DOC catalyst. Similarly, a La(0.9)Sr(0.1)MnO3-based LNT catalyst achieved NOx reduction performance comparable to that of a commercial platinum-based counterpart. The results show promise for a considerably lower-cost diesel exhaust treatment system.

Cellular ceramic type catalyst for catalytic combustion of perovskite as well as preparation and application thereof
CN101439290

Inventor(s): YINFEI CHEN [CN]; HANFENG LU [CN]; HAIFENG HUANG [CN]; HUAYAN LIU [CN]; FANG GUAN [CN] + (CHEN YINFEI, ; LU HANFENG, ; HUANG HAIFENG, ; LIU HUAYAN, ; GUAN FANG)
Abstract -- The invention discloses a honeycomb ceramics perovskite catalytic combustion catalyst; the honeycomb ceramics with a metal oxide coating is used as a carrier; the catalytic activity components disclosed in formula (I) are loaded; wherein, La, Sr, Co, and Mn respectively represent lanthanum, strontium, cobalt, and manganese; x is equal to 0 to 0.7 and y is equal to 0 to 0.7; the honeycomb ceramics with a metal oxide coating is to load a metal oxide coating of gamma-Al2O3, CemZr1-mO2, LaMnAl11O19, BaMnAl11O19 or Sr12Al14O21 on the surface of the honeycomb ceramics of a dichroite material; wherein, m is equal to 0.1 to 0.8; the mass ratio of the honeycomb ceramics, the metal oxide coating and the catalytic activity components is 1.0 : 0.03 to 0.2 : 0.05 to 0.15. The invention also relates to a preparation method for the catalyst and the applications of the catalytic combustion thereof to eliminate the waste gases of volatile organic compound; the dichroite honeycomb ceramics carrier and the catalytic activity components of the prepared honeycomb ceramics perovskite catalytic combustion catalyst are combined by one metal oxide coating with high adhesiveness and thermal stability, thus leading the catalyst to have the advantages of high mechanical intensity, high activity and good thermal stability. The catalyst provided by the invention is simple in preparation method, is low in the price of the used materials, and has excellent industrial application prospect. La1-xSrxCoyMn1-yO3 (I).

FINE PARTICLE OF PEROVSKITE OXIDE, PARTICLE HAVING DEPOSITED PEROVSKITE OXIDE, CATALYST MATERIAL, CATALYST MATERIAL FOR OXYGEN REDUCTION, CATALYST MATERIAL FOR FUEL CELL, AND ELECTRODE FOR FUEL CELL
US2009200519

Inventor: SAWAKI YUKO [JP] ; KISHIMOTO MIKIO
Abstract -- A catalyst for electrodes in solid-polymer fuel cells which comprises metal oxide particles themselves. It can be used as a substituent for the carbon particles having platinum deposited thereon and platinum metal particles which are presently in general use as, e.g., a catalyst for electrodes in fuel cells, and has a possibility that the amount of platinum to be used can be greatly reduced as compared with the conventional carbon particles having platinum deposited thereon, etc. The catalyst comprises fine transition-metal oxide particles having, in the main phase, a perovskite structure represented by the general formula ABO3 (wherein A represents one or more elements selected among lanthanum, strontium, cerium, calcium, yttrium, erbium, praseodymium, neodymium, samarium, europium, silicon, magnesium, barium, niobium, lead, bismuth, and antimony; and B represents one or more elements selected among iron, cobalt, manganese, copper, titanium, chromium, nickel, and molybdenum), the fine oxide particles having lattice constants satisfying the following relationship (1): <?in-line-formulae description="In-line Formulae" end="lead"?>1.402<2b/(a+c)<1.422 (1)<?in-line-formulae description="In-line Formulae" end="tail"?> wherein a and c represent the minor-axis lengths of the perovskite type crystal lattice and b represents the major-axis length thereof.

US7291321
PEROVSKITE-BASED CATALYST, ITS PREPARATION AND ITS USE FOR CONVERSION OF METHANE TO ETHYLENE

Inventor: BAGHERZADEH EBRAHIM
Abstract -- A method of producing a perovskite catalyst comprising: forming an aqueous slurry comprising an alkaline earth metal salt, a powdered metal salt and a powdered transition metal oxide; the aqueous slurry being formed by: dispersing a powdered alkaline earth metal salt in water, the alkaline earth metal salt being selected from the group consisting of barium, calcium and strontium salts adding the powdered metal salt to the water; and adding the powdered transition metal oxide to the water, the metal oxide being titanium oxide; and adding a polymeric binder to the slurry to form a paste; drying the paste for forming a powder; heating the powder at increasing temperatures at a predetermined profile commensurate with the polymeric binder; and calcining the heated powder to form the perovskite catalyst. The catalyst thus formed and the use thereof for oxidative coupling of methane is also disclosed.

The high cost and poor thermal durability of current lean nitrogen oxides (NOx) aftertreatment catalysts are two of the major barriers to widespread adoption of highly fuel-efficient diesel engines. We demonstrated the use of strontium-doped perovskite oxides as efficient platinum substitutes in diesel oxidation (DOC) and lean NOx trap (LNT) catalysts. The lanthanum-based perovskite catalysts coated on monolith substrates showed excellent activities for the NO oxidation reaction, a critical step that demands heavy usage of platinum in a current diesel aftertreatment system. Under realistic conditions, La1-xSrxCoO3 catalysts achieved higher NO-to-NO2 conversions than a commercial platinum-based DOC catalyst. Similarly, a La0.9Sr0.1MnO3-based LNT catalyst achieved NOx reduction performance comparable to that of a commercial platinum-based counterpart. The results show promise for a considerably lower-cost diesel exhaust treatment system.

General Motors Global Research and Development, Chemical Sciences and Materials Systems Lab, 30500 Mound Road, Warren, MI 48090, USA.

* To whom correspondence should be addressed. E-mail: wei.1.li@gm.com

Researchers from the General Motors Global Research and Development, Chemical Sciences and Materials Systems Lab have developed and demonstrated the use of strontium-doped perovskite oxides as efficient platinum substitutes in diesel oxidation (DOC) and lean NOx trap (LNT) catalysts. Their work may help to lower the cost of NOx treatments and thus ultimately make diesel a more cost-effective automotive fuel. A paper on the work was published in the 26 March issue of the journal Science.

One of the obstacles to the more widespread adoption of diesel engines—especially in the face of increasingly stringent emissions requirements—is the requirement for a lean NOx aftertreatment system. The aftertreatment system is a key contributor to the cost premium for diesel vehicles.

A typical diesel aftertreatment system will include a diesel oxidation catalyst to oxidizes hydrocarbons, CO, and NO, followed by NOx reduction. The two leading technologies for NOx reduction in the oxygen-rich environment are ammonia selective catalytic reduction (SCR) and a lean NOx trap (LNT).

    Many reports have suggested that NO oxidation to NO2 is an important step in lean NOx reduction, because NO2 enhances the activities of ammonia SCR and LNT. For SCR catalysts, a NO:NO2 ratio of 1:1 is most effective for NOx reduction at lower temperatures (<250 °C). For LNT catalysts, NO must be oxidized to NO2 before adsorption on the storage components. Because NO2 constitutes less than 10% of NOx in the diesel engine-out exhaust, an oxidation catalyst is required to increase the NO2 fraction. Platinum has been found to be especially active for NO oxidation; thus, Pt-based diesel oxidation (DOC) and LNT catalysts have been widely used for diesel exhaust aftertreatment. However, they suffer from issues such as high cost and poor thermal durability. Consequently, there is substantial interest in the development of better-performing, low-cost, and more durable NO oxidation catalysts.

    —Kim et al.

The catalysts developed by the GM team are based on perovskite oxides, La1–xSrxCoO3 and La1–xSrxMnO3. Under realistic conditions, La1-xSrxCoO3 catalysts achieved higher NO-to-NO2 conversions than a commercial platinum-based DOC catalyst. Similarly, a La0.9Sr0.1MnO3-based LNT catalyst achieved NOx reduction performance comparable to that of a commercial platinum-based counterpart.

These perovskite catalysts are prone to deactivation by sulfur, a contaminant present in fuel. However, the oxidation activity of the catalyst can be improved in the presence of sulfur by adding palladium.

    The potential use of perovskites for automotive applications is hindered by the fact that the perovskites alone are susceptible to deactivation by S. However, the NOx-treating performance of Pd/perovskite-based DOC and LNT catalysts in simulated diesel exhaust demonstrated the potential of Pd/perovskite catalysts as a viable substitute for Pt in diesel aftertreatment catalysts. This substitution could drastically reduce the cost of diesel aftertreatment systems for mobile applications. Lean-burn gasoline engines will also benefit from this technology.

    —Kim et al.

In an accompanying Perspective in Science, James E. Parks, II from Oak Ridge National Laboratory noted that:

    The catalyst developed by Kim et al. greatly reduces the amount of PGM in LNTs while still maintaining their effectiveness for NOx reduction from lean engines. This alternative technology will allow engineers greater flexibility as they work to develop better catalysts in a market where volatile PGM prices have made commercial introduction of fuel-efficient lean vehicles challenging. It is possible that these catalysts may allow lean-burn technology to be used with minimal added cost compared to conventional engines.

Resources

Chang Hwan Kim, Gongshin Qi, Kevin Dahlberg, Wei Li (2010) Strontium-Doped Perovskites Rival Platinum Catalysts for Treating NOx in Simulated Diesel Exhaust. Science Vol. 327. no. 5973, pp. 1624 - 1627 doi: 10.1126/science.1184087
James E. Parks, II (2010) Less Costly Catalysts for Controlling Engine Emissions. Science Vol. 327. no. 5973, pp. 1584 - 1585 doi: 10.1126/science.1187154