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Journal ArticleDOI

Decomposition mechanism of copper ammonium chromate: A basic material for copper chromite catalyst

15 Sep 1983-Thermochimica Acta (Elsevier)-Vol. 68, Iss: 1, pp 17-25

Abstract: The mechanism of thermal decomposition of basic copper ammonium chromate has been investigated using TG/DTG/DSC and X-ray studies The decomposition is a three-step process Calcination at lower temperatures can be achieved by taking advantage of the exothermicity of the decomposition process
Topics: Thermal decomposition (66%), Copper chromite (64%), Ammonium chromate (62%), Chemical process of decomposition (58%), Calcination (57%)
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Journal ArticleDOI
Sanoop Paulose1, Deepthi Thomas1, T. Jayalatha1, R. Rajeev1  +1 moreInstitutions (1)
Abstract: Copper chromite is a well-known burn rate modifier for the combustion of composite solid propellants. In this study, basic copper ethylamine chromate (CEC), a new precursor for copper chromite catalyst, was synthesized by precipitation method. The thermal decomposition of the precursor was followed by thermogravimetry–mass spectroscopy (TG–MS) and X-ray diffraction techniques and compared with that of copper ammonium chromate, a conventional precursor for copper chromite catalyst. TG–MS analysis for the decomposition of CEC revealed that the decomposition starts with the liberation of ethylamine. The change in enthalpy for the decomposition reaction of copper ethylamine chromate was higher than that of copper ammonium chromate due to the oxidation of ethyl group. The reducing atmosphere created by the presence of carbon during the decomposition of CEC produced a mixture of Cu, CuCr2O4, CuCrO2 and CuO, while the oxidizing atmosphere of copper ammonium chromate produced a mixture of CuCr2O4 and CuO. Mechanistic study based on Criado and Coats–Redfern methods showed that CEC follows random nucleation (F1) mechanism as the rate-determining step for the thermal decomposition process.

3 citations

Journal ArticleDOI
A.P. Sanoop1, R. Rajeev1, Benny K. George1Institutions (1)
Abstract: A novel copper chromite based burning rate catalyst for composite solid propellants was synthesized by the thermal decomposition of basic copper ethylamine chromate. Thermal decomposition of the precursor to copper chromite was followed by TG–DSC techniques and the volatile products formed were characterized by TG–MS analysis. Copper content, surface area and Lewis acid sites of the new catalyst are higher than that in the standard copper chromite. XRD analysis showed the presence of CuCrO 2 phases along with CuO and CuCr 2 O 4 . SEM analysis revealed the presence of rod shaped nanoparticles of copper chromite having diameter of 20–30 nm and length of 200–300 nm. The improved surface properties as well as the synergetic action of three phases of oxides, viz., CuO, CuCr 2 O 4 and CuCrO 2 in the system increase the catalytic activity of new catalyst resulting in a reduction of 60 °C in the decomposition temperature of ammonium perchlorate.

40 citations

Journal ArticleDOI
Rajniti Prasad1, Pratichi Singh1Institutions (1)
18 Apr 2012
Abstract: CO is a toxic and detrimental air pollutant. It not only affects human beings but also vegetation and indirectly increases global warming. An estimate has shown that vehicular exhaust contributes about 64% of the CO pollution in developed countries. Due to the exponentially increasing number of automobiles on roads, CO concentrations have reached an alarming level in urban areas and regulatory measures had been adopted to curb the menace of vehicular pollution. To control vehicular exhaust pollution, end-of-pipe-technology using noble metals catalytic converters are recommended. The increasing prices of noble metals with the increasing number of vehicles motivates the investigation of material concepts to reduce the precious metal content in automotive catalysts or to find a substitute for noble metals. Among non-noble metals, copper chromite is found to be most promising and exhibits comparable activity for CO oxidation to that of precious metals. Further, low cost, easy availability and advance synthesi...

116 citations

Cites background from "Decomposition mechanism of copper a..."

  • ...The effect of pretreatment on catalytic activity of a catalyst was studied by several workers ( 28 , 182–184 )....


Journal ArticleDOI
Abstract: The nature of the chemical transformations occurring during the thermal activation of chromium(III) and copper(II) doubly promoted tin(IV) oxide catalysts of three stoichiometries (Sn:Cr:Cu atom ratios 1:0.30:0.34, 1:0.30:0.13, and 1:0.13:0.27) have been investigated by a combination of FT-IR, powder X-ray diffraction, transmission electron microscopy, extended X-ray absorption fine structure and near edge structure, and X-ray photoelectron spectroscopy. The freshly prepared gel catalyst materials comprise small (ca. 1−2 nm) particles. Calcination results in a progressive increase in the size of the tin(IV) oxide particles, only slowly initially (ca. ×2 by 673 K, ca. ×10 by 873 K), but sintering to very large particles occurs at higher temperatures. No incorporation of chromium or copper into the tin(IV) oxide lattice occurs even at high temperature. Interaction of the two promoter metals at calcination temperatures of 573 K leads to the formation of copper(II) chromate(VI), CuCrO4. At temperatures ≥873 K...

17 citations

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Journal ArticleDOI
Abstract: In the hydrogenation of soybean and rapeseed oils with fresh copper chromite catalyst, the rate of reaction −d(IV)/dt varies extensively with time. These variations are ascribable to changes in phase composition of the catalyst during its reduction. This reduction is not restricted to an initial period but proceeds in two steps during the major part of a normal hydrogenation for the reduction of the linolenate content of the oil. Variations of the catalyst activity followed by experimental measurements have been related to the changes of the catalyst composition.

44 citations

01 Jan 1970

279 citations

Journal ArticleDOI
TL;DR: To ensure maximum activity of some of these catalysts, soybean oil should be more thoroughly bleached than is customarily done for nickel hydrogenation.
Abstract: Copper-chromium catalysts promote selective reduction of linolenyl groups in soybean oil. Since commercially available catalysts possess only moderate activity, more active catalysts were sought. Copper was dispersed on high-surface-area supports, such as silica, alumina, and molecular sieves. These catalysts had varying activities. Precipitation of copper on Cab-O-Sil, a pure form of silica with a large external surface area, gave the most active catalyst. Selectivity ratios (KLe/KLo) for the hydrogenation of soybean oil with these catalysts varied from 4 to 16; a copper-on-Cab-O-Sil catalyst exhibited the greatest selectivity. Improved selectivity and activity were observed when some supports were treated with hydrochloric acid. For example, with a copper-on-Celite catalyst, soybean oil was hydrogenated in 165 min and gave a selectivity ratio of 5.9. Hydrochloric acid treatment of Celite improved the selectivity to 9.9 and reduced hydrogenation time to 54 min. To ensure maximum activity of some of these catalysts, soybean oil should be more thoroughly bleached than is customarily done for nickel hydrogenation. A commercially refined and bleached soybean oil was hydrogenated with a copper-on-Cab-O-Sil catalyst in 18 min. The same oil, re-refined in the laboratory, was reduced in 11.5 min and had the same selectivity ratio of 15.

25 citations

04 Apr 1958

312 citations

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