Engelhard

About: Engelhard is a based out in . It is known for research contribution in the topics: Catalysis & Platinum. The organization has 957 authors who have published 1112 publications receiving 31519 citations. The organization is also known as: Engelhard Corporation.

Automobile exhaust catalysts

Abstract: It has now been over 25 years since the introduction of the catalytic converter to reduce emissions from the internal combustion engine. It is considered one of the greatest environmental successes of the 20th century, however, new emission control technologies are still being developed to meet ever more stringent mobile source (gasoline and diesel) emissions. This short review will discuss the basis for improvements and highlight technology area, which will require further improvements in emissions and fuel economy. Some of the issues related to fuel cells which some believe may replace the internal combustion engines for automobile applications is also be briefly discussed.

Catalytic chemistry of supported palladium for combustion of methane

Abstract: The high-temperature catalytic chemistry of supported palladium for methane oxidation has been studied. Palladium oxide supported on alumina decomposes in two distinct steps in air at one atmosphere. The first step occurs between 750 and 800 ° C and is believed to be a decomposition of palladium-oxygen species dispersed on bulk palladium metal designated (PdOx/Pd). The second decomposition is between 800 and 850 ° C and behaves like crystalline palladium oxide designated (PdO). To reform the oxide, the temperature must be decreased well below 650 ° C. Thus, there is a significant hysteresis between decomposition to palladium and re-formation of the oxide. Above 500 ° C, methane oxidation occurs readily when the catalyst contains PdO. However, when only palladium metal is present no oxygen adsorption occurs and no methane activity exists. One may conclude that the high temperature (> 500 ° C) activity of a supported palladium containing catalyst is due to the ability of palladium oxide to chemisorb oxygen. Palladium, as a metal, does not chemisorb oxygen above 650 ° C and thus, is completely inactive toward methane oxidation.

Ultraviolet radiation and skin aging: roles of reactive oxygen species, inflammation and protease activation, and strategies for prevention of inflammation-induced matrix degradation – a review

Abstract: Inflammation and the resulting accumulation of reactive oxygen species (ROS) play an important role in the intrinsic and photoaging of human skin in vivo. Environmental insults such as ultraviolet (UV) rays from sun, cigarette smoke exposure and pollutants, and the natural process of aging contribute to the generation of free radicals and ROS that stimulate the inflammatory process in the skin. UV irradiation initiates and activates a complex cascade of biochemical reactions in human skin. In short, UV causes depletion of cellular antioxidants and antioxidant enzymes (SOD, catalase), initiates DNA damage leading to the formation of thymidine dimmers, activates the neuroendocrine system leading to immunosuppression and release of neuroendocrine mediators, and causes increased synthesis and release of pro-inflammatory mediators from a variety of skin cells. The pro-inflammatory mediators increase the permeability of capillaries leading to infiltration and activation of neutrophils and other phagocytic cells into the skin. The net result of all these effects is inflammation and free radical generation (both reactive oxygen and nitrogen species). Furthermore, elastsases and other proteases (cathepsin G) released from neutrophils cause further inflammation, and activation of matrix metalloproteases. The inflammation further activates the transcription of various matrixes degrading metalloproteases, leading to abnormal matrix degradation and accumulation of non-functional matrix components. In addition, the inflammation and ROS cause oxidative damage to cellular proteins, lipids and carbohydrates, which accumulates in the dermal and epidermal compartments, contributing to the aetiology of photoaging. Strategies to prevent photodamage caused by this cascade of reactions initiated by UV include: prevention of UV penetration into skin by physical and chemical sunscreens, prevention/reduction of inflammation using anti-inflammatory compounds (e.g. cyclooxygenase inhibitors, inhibitors of cytokine generation); scavenging and quenching of ROS by antioxidants; inhibition of neutrophil elastase activity to prevent extracellular matrix damage and activation of matrix metalloproteases (MMPs), and inhibition of MMP expression (e.g. by retinoids) and activity (e.g. by natural and synthetic inhibitors).

A titanosilicate molecular sieve with adjustable pores for size-selective adsorption of molecules

Abstract: Zeolites and related crystalline microporous oxides—tetrahedrally coordinated atoms covalently linked into a porous framework—are of interest for applications ranging from catalysis to adsorption and ion-exchange1. In some of these materials (such as zeolite rho) adsorbates2, ion-exchange, and dehydration and cation relocation3,4 can induce strong framework deformations. Similar framework flexibility has to date not been seen in mixed octahedral/tetrahedral microporous framework materials, a newer and rapidly expanding class of molecular sieves5,6,7,8,9,10,11,12,13,14,15,16. Here we show that the framework of the titanium silicate ETS-4, the first member of this class of materials8, can be systematically contracted through dehydration at elevated temperatures to ‘tune’ the effective size of the pores giving access to the interior of the crystal. We show that this so-called ‘molecular gate’ effect can be used to tailor the adsorption properties of the materials to give size-selective adsorbents17 suitable for commercially important separations of gas mixtures of molecules with similar size in the 4.0 to 3.0 A range, such as that of N2/CH4, Ar/O2 and N2/O2.