Pure Metal Chelate Solutions by Ion Exchange

A new method for modification AlPO4 molecular sieves has been presented. Lack of ion-exchange properties makes the modification of aluminium phosphates for catalytic applications difficult. We have developed a method that involves the crystallization of AlPO4 molecular sieves around metal complexes. This results in encapsulation of the complexes within the intracrystalline pore system. Several metallophthalocyanines have been successfully encapsulated into AlPO4-5 and subsequently tested as catalysts for cyclohexene oxidation. Significant differences in activity result from the presence of different metallophthalocyanines.

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Peculiarities of palladium-containing MFI-type zeolites as catalysts of isomerization of linear alkanes

Voprosy Khimii i Khimicheskoi Tekhnologii ◽

10.32434/0321-4095-2020-133-6-26-32 ◽

2020 ◽

pp. 26-32

Keyword(s):

Ion Exchange ◽

Average Pore Size ◽

Pure Metal ◽

Platinum Group Metals ◽

Zeolite Catalysts ◽

Palladium Chloride ◽

Metal Component ◽

Average Pore ◽

Exchange Method ◽

Linear Alkanes

Platinum group metals are widely used as a hydrogenating-dehydrogenating component of a number of petroleum refining and petrochemical catalysts, in particular for isomerization of linear alkanes. The main direction in improving the preparation of these catalysts is to reduce their cost by optimizing the metal component amount. However, insufficient attention was paid to the method of introduction of an active metal into the carrier; at the same time, this issue is especially important in case of zeolite catalysts, for which ion exchange can be used in addition to traditional impregnation. Therefore, the purpose of this work was to compare the catalytic efficiencies of Pd-containing MFI zeolites in which metal was introduced by two methods: impregnation from a solution of palladium chloride and ion exchange from tetraamminepalladium(II) chloride in the amount of 0.5 wt.% in terms of pure metal. Study of texture characteristics by nitrogen low-temperature adsorption/desorption technique showed that the specific surface area of samples and the total sorption volume remained practically unchanged, regardless of the procedure of metal component introduction. A significant decrease in average pore size was observed only in case of ion-exchange metal introduction; this indicated the localization of palladium mainly in zeolite pores, which was confirmed by transmission electron microscopy. The stage of transformation from ammonium form to hydrogen one strongly affects the activity of samples, this stage should precede the final stage of metal recovery. The highest yield of hexane isomers of about 46.5 wt.% with the selectivity of 88.7% was observed over a catalyst with Pd introduced by ion-exchange method with the smallest palladium particles (3–7 nm).

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Characterization of a metalloprotease from ovine chromaffin granules which cleaves a proenkephalin fragment (BAM12P) at a single arginine residue

Biochemical Journal ◽

10.1042/bj3010607 ◽

1994 ◽

Vol 301 (2) ◽

pp. 607-614 ◽

Cited By ~ 6

Author(s):

N Tezapsidis ◽

D C Parish

Keyword(s):

Ion Exchange ◽

Metal Chelate ◽

Ion Exchange Chromatography ◽

Exchange Chromatography ◽

Arginine Residue ◽

Affinity Column ◽

Intermediate Step ◽

Chromaffin Granules ◽

Reverse Phase ◽

Ph Optimum

A metalloprotease has been identified in ovine chromaffin granules which cleaves the proenkephalin fragment BAM12P to produce adrenorphin-Gly. This cleavage occurs at a single arginine residue and is an intermediate step in the production of the opiate adrenorphin in vivo. The identity of the product was confirmed by reverse-phase and ion-exchange chromatography. The adrenorphin-Gly-generating enzyme (AGE) was determined by chromatofocusing to have a pI value of 5.2 and bound strongly to a metal-chelate affinity column. After purification by gel-filtration and ion-exchange chromatography AGE was free of contaminating activities, as cleavage of radiolabelled BAM12P generated a single product as judged by reverse-phase and ion-exchange chromatography. The enzyme has a molecular mass of approx. 45 kDa and a pH optimum of 8.6 in Mops, Taps and Hepes buffers, but was inhibited by phosphate buffers. It was inhibited by micromolar concentrations of copper and zinc ions, but not by millimolar concentrations of calcium or manganese ions. The addition of BAM22P, dynorphin 1-13 or dynorphin 1-8 to the incubation mixture inhibited the cleavage of radiolabelled BAM12P. The cleavage was also inhibited by the presence of catecholamines at concentrations similar to those found within the chromaffin granule. This may explain the known effect of reserpine on chromaffin cells of reducing catecholamine levels and simultaneously increasing adrenorphin levels. It may also indicate a function for AGE and adrenorphin as reporters of intragranular conditions.

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Embedding Procedure for Water Swollen Samples

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010006951x ◽

1970 ◽

Vol 28 ◽

pp. 504-505

Author(s):

Ann M. Thomas ◽

Virginia Shemeley

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Ion Exchange ◽

Structural Changes ◽

Cross Linking ◽

Ion Exchange Resins ◽

Transmission Electron ◽

First Pass ◽

Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

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Microstructure of sputter deposited Ni-Sb ohmic contacts on GaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154226 ◽

1989 ◽

Vol 47 ◽

pp. 450-451

Author(s):

S. Yegnasubramanian ◽

V.C. Kannan ◽

R. Dutto ◽

P.J. Sakach

Keyword(s):

High Performance ◽

Ohmic Contacts ◽

Surface Defects ◽

Pure Metal ◽

Device Fabrication ◽

Native Oxide ◽

Metal Thin Films ◽

Recent Developments ◽

Different Temperatures ◽

Sputter Deposited

Recent developments in the fabrication of high performance GaAs devices impose crucial requirements of low resistance ohmic contacts with excellent contact properties such as, thermal stability, contact resistivity, contact depth, Schottky barrier height etc. The nature of the interface plays an important role in the stability of the contacts due to problems associated with interdiffusion and compound formation at the interface during device fabrication. Contacts of pure metal thin films on GaAs are not desirable due to the presence of the native oxide and surface defects at the interface. Nickel has been used as a contact metal on GaAs and has been found to be reactive at low temperatures. Formation Of Ni2 GaAs at 200 - 350C is reported and is found to grow epitaxially on (001) and on (111) GaAs, but is shown to be unstable at 450C. This paper reports the investigations carried out to understand the microstructure, nature of the interface and composition of sputter deposited and annealed (at different temperatures) Ni-Sb ohmic contacts on GaAs by TEM. Attempts were made to correlate the electrical properties of the films such as the sheet resistance and contact resistance, with the microstructure. The observations are corroborated by Scanning Auger Microprobe (SAM) investigations.

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