Solution Of Cerium Ammonium Nitrate Research Articles

Stereo‐ and Chemoselective Character of Supported CeO2 Catalysts for Continuous‐Flow Three‐Phase Alkyne Hydrogenation

AbstractTiO2‐, Al2O3‐, and ZrO2‐supported CeO2 catalysts with different Ce loadings were prepared by wet impregnation of the carriers with an acidified solution of cerium ammonium nitrate. The calcined catalysts were characterized by bulk and surface‐sensitive techniques, which included microcalorimetry, and evaluated in the three‐phase hydrogenation of alkynes under continuous‐flow conditions at variable temperature (293–413 K) and pressure (1–90 bar). A number of acetylenic compounds, which contain terminal or internal triple bonds, conjugated unsaturations, and additional functionalities, were systematically assessed. The results revealed the full stereo‐ and chemoselective character of the ceria catalysts, which outperform the well‐known Lindlar catalyst, and open promising perspectives for the revolutionary use of a cost‐effective oxide for the production of olefinic compounds in the vitamin and fine chemical industries.

Effect of Synthesis Routes on Microstructure of Nanocrystalline Cerium Oxide Powder

The effect of different processing routes on the microstructure of nanocrystalline ceria powder has been investigated. The nanocrystalline ceria is produced by solid state high energy ball milling (HEBM) and liquid state solution combustion synthesis (SCS) method. The liquid state route consists of a high temperature combustion reaction to form ceria from an aqueous solution of cerium ammonium nitrate (CAN) as an oxidizer and citric acid (CA) plus glycine (G) as mixed fuels. The powders have been characterized using techniques of X-ray diffraction (XRD), particle size analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The microstructural characterizations show that the particle size distribution of the ball milled ceria powder is much wider than that of ceria produced by the SCS. The scanning electron micrographs show that the ball milled ceria powders are compact and dense structure while SCS ceria powders are scattered and porous.

Synthesis and Characterization of Stable and Crystalline Ce1-xZrxO2 Nanoparticle Sols

Ce1-xZrxO2 nanoparticle sols (x = 0−1) are synthesized by hydroxide coprecipitation of a mixed precursor solution of cerium ammonium nitrate and zirconyl chloride followed by redispersion in an aqueous medium by sonication using nitric acid as the peptizing agent. The obtained sols are highly concentrated and stable for weeks. Analytical ultracentrifugation measurements show a particularly narrow particle distribution with an average particle size of about 3.5 nm for pure CeO2 and 2.5 nm for pure ZrO2 nanoparticles. Wide-angle X-ray scattering (XRD) as well as high-resolution transmission electron microscopy give evidence that all of the as-synthesized nanoparticle sols with a ceria content larger than 20 mol % are well crystalline. The formation of a solid solution with an increasing amount of Zr was monitored by XRD and Raman spectroscopy.

The Two-phase Oxidation of Some Aromatic Compounds with Cerium Ammonium Nitrate in the Presence of Surfactants

Abstract The two-phase oxidations of 3,6-dimethoxydurene and xylenes in cyclohexane solutions with the aqueous solution of cerium ammonium nitrate were carried out in the presence of cationic, nonionic, and anionic surfactants. Both cationic (ammonium salt) and nonionic (Dipodand) surfactants inhibited the reaction. The anionic surfactant (sodium dodecyl sulfate, SDS) catalyzed these oxidations. From the product distribution it was concluded that the catalytic action of SDS is due to the binding of aromatic compounds and the Ce(IV) ions to the surface of the SDS micelles. The micellar oxidant has the high oxidation potential which should allow to oxidize the comparatively nonreactive substrates.

VAPOUR PHASE GRAFTING OF VINYL MONOMERS ONTO RAYON BY CERIUM INITIATOR

Based on our experience of the vapour phase acetylation of cellulose, the vapour phase grafting of methyl acrylate, ethyl acrylate, methyl methacrylate and acrylonitrile onto viscose rayon pretreated by cerium ammonium nitrate solution were studied and the influence of the initiator and nitric acid concentration in the pretreating solution, atmospheric pressure in the reaction vessel, and reaction temperature upon the grafting were investigated. Some mechanical properties of the grafted rayon were measured. The results obtained are as follows:(1) For e. g. AN grafting, about 150% retention of the pretreating solution by the rayon is most favourable.(2) MA or EA grafting is the first order reaction, MMA the sigmoid, and AN the fibrous reaction controlled by diffusion.(3) Ultimate graft amount of each monomer shows the maximum in relation to the initiator and nitric acid concentration in the pretreating solution.(4) Ultimate graft efficiency of AN or MMA is about 90%, but that of MA or EA decreases linearly with the initiator concentration.(5) Ultimate graft amount of each monomer decreases with the increase of carbonyl content of the rayon when the initiator concentration is increased.(6) DP of MMA graft polymer increases nearly parallel to the increase in the amount of graft with reaction time. The minimum of DP curve of ultimate graft polymer with respect to the initiator or nitric acid concentration, corresponds nearly to the maximum of the related graft amount curve.(7) The apparent activation energies obtained are MA6.7, EA8.5, MMA8.2, and AN 10.1 kcal/mol.(8) Atmosphere in the reaction vessel controlls the monomer vapour diffusion by the pressure variation and retards the grafting by oxygen in air. If air is replaced by nitrogen, graft amount of MA or EA increases several folds, but that of MMA or AN does not.(9) The breaking load of the grafted rayon is almost constant, the extension increases slightly, the initial modulus of MA or EA grafted decreases slightly, that of MMA or AN grafted increases slightly with graft amount.