Copper Chromite Catalyst Research Articles

Copper chromite catalyst activity correlation for the hydrogenation of 2-ethyl-3-propylacrolein

We describe and evaluate a Thiele-type pore diffusion model for correlating the catalyst activity of various formed copper chromite catalysts with key physicochemical catalyst properties. Catalyst activity was determined during the batch hydrogenation of 2-ethyl-3-propylacrolein (EPA) to 2-ethylhexanol (2-EH) and expressed in terms of an EPA rate constant without regard to product selectivities

Flammability limits and ballistic properties of fuel‐rich propellants

AbstractThe flammability limits and ballistic properties of composite fuel‐rich propellants were studied experimentally, using PBAN/AP propellant formulations. Higher pressure and AP contents as well as smaller AP particle size were found to promote sustained combustion and to increase burning rate. The addition of potassium perchlorate (KP) in place of AP increased the burning rate pressure exponent from about 0.3 to over 0.7 at optimum conditions. Ferric oxide and copper chromite catalysts caused an increase of the burning rate by a factor of 2, while the addition of aluminum powder at the expense of the fuel binder was found to have a remarkable effect on the burning rate with a maximum increase of as high as 5‐fold.

Changes in alumina-supported copper and copper—chromite catalysts by the introduction of water during carbon monoxide oxidation

The effect of water on carbon monoxide oxidation over alumina-supported CuO and CuCr 2O 4 catalysts has been examined. The results suggest a relation between catalyst deactivation effected by the introduction of water to the reaction mixture and sintering of copper. The copper-chromite phase apparently protects the catalyst against this detrimental effect.

Determination of the longer chain n-alkyl content of coals

Yields of longer chain n-alkanes, consistently higher than those resulting from hydrous pyrolysis, are obtained when coals are hydrogenated using a sulphided nickel-molybdenum catalyst rather than a copper chromite catalyst. The lower yields of n-alkanes are attributed to: the incomplete conversion of carboxylic acids together with thermal chain splitting reactions under hydrous pyrolysis conditions; and deterioration in the activity of the copper chromite catalyst used in hydrogenation. A sequential hydrous pyrolysis/hydrogenation procedure failed to demonstrate that the physical release of n-alkanes from coal is significantly favoured by hydrous pyrolysis. Therefore, hydrogenation in the presence of a sulphided catalyst is superior to hydrous pyrolysis in the determination of n-alkyl content of coals.

Surface copper enrichment by reduction of copper chromite catalyst employed for carbon monoxide oxidation

The effect of prereduction on CO oxidation activity of unsupported copper-chromite oxide catalysts was examined. Results were found to be in good agreement with two mechanisms for a surface copper enrichment due to CO prereduction which produced an activity increase in the copper-chromite catalyst.

Stability of 1,4‐dioxane, tetrahydrofuran and ethanol under hydrogenation conditions over various catalysts

AbstractThe stability of 1,4‐dioxane, tetrahydrofuran and ethanol under hydrogenation conditions was investigated over six different catalysts. The reactions occurring in a fixed‐bed reactor in the temperature range between 150 and 350°C were characterized by chemical analysis of the reactor effluent stream and by measurement of the temperature—time profiles within the catalyst bed. On nickel catalysts, dioxane showed a runaway reaction with ignition at about 190°C (Mozingo, Org. Synth., 21 (1941)). (Ignition is referred to as the temperature where the initiation of the runaway reaction is observed.) Similar reactions were observed with tetrahydrofuran and ethanol over nickel, and with dioxane and ethanol over rhodium and cobalt. The predominant reaction was hydrogenolysis and the main products formed were methane and water. Under some conditions small amounts of ethane, propane, carbon monoxide and carbon dioxide were also observed. Dioxane did not show methane formation on platinum, palladium and copper chromite catalysts.

Kinetics of two-step methanol synthesis in the slurry phase

The carbonylation of methanol using potassium methoxide catalyst and hydrogenolysis of methyl formate using a copper-chromite catalyst (39% Cu; 37% Cr and 3% Mn) were studied in the temperature ranges of 60–110°C and 100–140°C and pressure ranges of 25–65 and 30–60 bar respectively in a mechanically agitated reactor. Kinetic rate expressions are presented for both reactions. The carbonylation reaction was found to be rapid and limited by equilibrium at the conditions studied. The apparent activation energy for the carbonylation was found to be 67.7 ± 1.5 kJ/mol. CO 2 reacts with the potassium methoxide catalyst and stops the reaction. The hydrogenolysis reaction was found to be slow at the studied conditions with an apparent activation energy of 69.8 ± 2.0 kJ/mol. CO inhibited the hydrogenolysis reaction over the copper-chromite catalyst used. CO 2 poisoned the copper-chromite catalyst. A Langmuir-Hinshelwood type rate model was used to fit the experimental data. A brief discussion of the feasibility of the two-step methanol synthesis in a single stage reactor is given. The data would be useful for evaluating the possibility of synthesizing methanol from H 2 and CO using these reactions either in two separate reactors or concurrently in one reactor.

Regiospecific hydrogenation of quinolines and indoles in the heterocyclic ring

AbstractQuinolines, indoles, acridine, and carbazole were hydrogenated using a large variety of heterogeneous catalysts in hydrocarbon solvents in an effort to achieve selective hydrogenation of the heterocyclic ring. When quinolines were hydrogenated using supported platinum, palladium, rhodium, ruthenium, or nickel metal catalysts in the presence of hydrogen sulfide, carbon disulfide, or carbon monoxide, there was exclusive hydrogenation of the heterocyclic ring to give only 1,2,3,4‐tetrahydroquinolines. Use of iridium, rhenium, molybdenum(VI) oxide, tungsten(VI) oxide, chromium(III) oxide, iron(III) oxide, cobalt(II) oxide‐molybdenum(VI) oxide, or copper chromite catalysts also caused exclusive hydrogenation of the heterocyclic ring even without addition of sulfur Compounds or carbon monoxide. Hydrogenation of indoles using platinum, rhenium, or, in some cases, nickel catalysts (with or without sulfur Compounds) occurred exclusively in the heterocyclic ring to give indolines, but conversions were affected by indole‐indoline equilibria.

Study of copper chromite catalysts, III. Structure and catalytic activity of copper chromite catalyst in reductive alkylation reaction

The catalytic activity of copper chromite catalysts prepared by thermal decomposition reaction of basic copper(II) ammonium chromate, CuCrO4[Cu(OH)2]0.17−(NH4OH)0.78, and copper(II) chromate CuCrO4, has been studied. The catalysts with highly disordered structure, prepared from basic copper(II) ammonium chromate at 270–320 °C, show the highest catalytic activity in reductive alkylation reaction. The activity of recrystallized catalysts, prepared from basic copper(II) ammonium chromate or CuCrO4 at higher decomposition temperature, is significantly lower.

ChemInform Abstract: Selective Hydrogenation on Copper Chromite Catalysts. Part 5. Reactions of Allylic Alcohols.

Chemischer InformationsdienstVolume 17, Issue 33 Preparative Organic Chemistry ChemInform Abstract: Selective Hydrogenation on Copper Chromite Catalysts. Part 5. Reactions of Allylic Alcohols. R. HUBAUT, R. HUBAUTSearch for more papers by this authorM. DAAGE, M. DAAGESearch for more papers by this authorJ. P. BONNELLE, J. P. BONNELLESearch for more papers by this author R. HUBAUT, R. HUBAUTSearch for more papers by this authorM. DAAGE, M. DAAGESearch for more papers by this authorJ. P. BONNELLE, J. P. BONNELLESearch for more papers by this author First published: August 19, 1986 https://doi.org/10.1002/chin.198633111AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume17, Issue33August 19, 1986 RelatedInformation

ChemInform Abstract: Selective Hydrogenation on Copper Chromite Catalysts. Part. 4.

Chemischer InformationsdienstVolume 17, Issue 33 Preparative Organic Chemistry ChemInform Abstract: Selective Hydrogenation on Copper Chromite Catalysts. Part. 4. R. HUBAUT, R. HUBAUTSearch for more papers by this authorM. DAAGE, M. DAAGESearch for more papers by this authorJ. P. BONNELLE, J. P. BONNELLESearch for more papers by this author R. HUBAUT, R. HUBAUTSearch for more papers by this authorM. DAAGE, M. DAAGESearch for more papers by this authorJ. P. BONNELLE, J. P. BONNELLESearch for more papers by this author First published: August 19, 1986 https://doi.org/10.1002/chin.198633110AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume17, Issue33August 19, 1986 RelatedInformation

Particle radiative feedback in ammonium perchlorate deflagration

The deflagration behavior of ammonium perchlorate (AP) with carbon black and copper chromite catalyst additives was studied over a pressure range of 4.3-171 MPa (50-2500 psig) using light transmission and emission measurements in a window bomb and burn rate measurements in a conventional strand burner. It was found that a maximum value of the lower pressure limit PDL exists at intermediate values of carbon black concentration similar to that already reported for copper chromite catalyst. It was also found that sufficiently high concentrations of carbon black augment the steady deflagration rate of AP. Since carbon black is not a catalyst of AP decomposition , it is postulated that particle radiative feedback is more likely to be the cause of the observed behavior than previously suggested catalyst effects. To quantify the amount of radiative heat feedback, flame temperature and emissivity values were calculated from light emission/transmission measurements. These calculations yielded flame temperatures between 1406 and 1449 K and a value for the effective particle absorption efficiency over diameter Qa/d of 4.1 jun1 in good agreement with expected values. A simple analysis shows that the observed trends (increasing PDL at low particle concentrations and decreasing PDL at higher concentrations) can be predicted from simple radiative transfer considerations together with particle and matrix continuity equations.

Selective hydrogenation on copper chromite catalysts

Reactions of various allylic alcohols were studied on a copper chromite catalyst. Three different reactions were observed: hydrogenation, isomerization and deoxygenation. By comparison with some other model compounds such as butanol, butanone and butadiene, analysis of the mechanism of the deoxygenation process suggests that, in fact, this reaction corresponds to a hydrodehydroxylation. Moreover, it is suggested that, in view of Siegel's model, the allylic alcohols constitute a good test model for characterizing the specificity and the nature of the catalytic sites on transition metal oxides.

Selective hydrogenation on copper chromite catalysts IV. Hydrogenation selectivity for α, β-unsaturated aldehydes and ketones

Hydrogenation reactions of crotonaldehyde, methyl vinyl ketone and methacrolein were studied on a copper chromite catalyst at 40°C under atmospheric hydrogen pressure. The high polarization of these molecules led mostly to a 1,4-addition process, whereas 1,2-hydrogenation reactions were observed with dienes. The functional group selectivity was found to be controlled by steric hindrance and electronic effects induced by the methyl substituent. These results were consistent with the copper hydride-like chemistry previously reported for the copper chromite catalyst. Moreover, the formation of allylic alcohols was found to be responsible for the low mono-dihydrogenation selectivity. The decrease in activity is believed to be related to the formation of stable anions (e.g. car☐ylates or alcoholates).

Liquid phase hydrogenolysis of methyl formate in a semi batch reactor

The liquid phase hydrogenolysis of methyl formate has been studied in a three phase slurry reactor using a Girdler G-89 copper chromite catalyst. Measurements at 446 K show a very high selectivity to methanol. The reaction is first order in methyl formate, first order in hydrogen for pressures of 1.7 to 4.5 MPa and has an apparent activation energy of 62 kJ mol −1. Unlike the corresponding vapour phase process at atmospheric pressure, the liquid phase reaction shows no evidence of catalyst deactivation at 450 K and to conversions beyond 70%. However, inhibition, which is at least partially reversible, becomes apparent at 473 K when carbon monoxide is detectable as a by-product. Inhibition can be observed at lower temperatures if carbon monoxide is deliberately introduced at pressures above 0.1 MPa. The apparent reaction order in carbon monoxide is then −0.32.

Selective hydrogenation of dienes on copper-chromite catalysts III reaction mechanism and nature of the occluded hydrogen species

We reported previously that the selective hydrogenation of dienes on copper chromite involves the association of a cuprous ion in an octahedral environment and an occluded hydrogen species as the catalytic sites. In this work, the reaction mechanism of isoprene hydrogenation is studied using deuterium as a tracer atom. The deuterium location, as well as the selectivities observed in the hydrogenation of 1,3-pentadienes are consistent with the formation of allylic carbanions. Moreover, these results suggest that a hydridic nature of at least a part of the occluded hydrogen is required. According to Siegel's model, a general reaction scheme is proposed and similarities between the properties of the copper chromite and the cuprous ion in homogeneous catalysts are reported.

Selective hydrogenation of dienes on copper chromite catalysts I. Catalytic role of occluded hydrogen species

Mixed copper chromium oxides are excellent catalysts for selective hydrogenation of unsaturated compounds. We reported recently that the cubic spinel phase of copper chromite catalysts contained some occluded hydrogen species able to hydrogenate dienes in absence of gaseous hydrogen. In this work, the hydrogen content of the solid has been varied and controlled by usinq the preceding reaction, and a kinetic model is proposed for the hydrogen extraction. Moreover, the catalytic role of these occluded species is shown by studying the 1,3-pentadiene cis-trans isomerization activity and isoprene deuterogenation.

Selective hydrogenation of dienes on copper chromite catalysts II. Structure-activity relationships and catalytic sites

In a previous paper, we reported that the catalytic role of the hydrogen species (H*), occluded in copper chromite catalysts, was of great importance in the hydrogenation and isomerization processes which they induce. In this work, we establish some quantitative relationships between the structural characteristics of these catalysts and their activities. The hydrogenation site was found to be identified as the association of a Cu + ion in an octahedral environment with a H* species. The Cr 3+ ions are responsible for the isomerization process. There is evidence for a dynamic interaction of the surface with the gas phase as a result of the existence of two different hydroxyl groups on this surface.

Electrical transport in copper chromite catalyst

The electrical conductivity, σ, and thermoelectric power, S, of copper chromite (CuCr2O4) are reported in the temperature range 295 to 815 K. A break (TB) in the slope of the plot of log σ against T−1 was observed around 556 K. Apart from this break, the curves are linear, and their slopes correspond to activation energies of 0.60 eV (TB 556 K). A break (T′B) in the slope of the -S against T−1 plot was also observed round 556 K. Apart from the break at this temperature, the S against T−1 curves are linear. At T′B>556, S can be expressed by the relation $$S = - \left[ {\left( {\frac{{0.65 eV}}{{{\text{2}}eT}}} \right) + (0.42) mV K^{ - {\text{1}}} } \right]$$ The mechanism involved in the electrical transport is the hopping of holes from Cr4+ centres to neighbouring Cr3+ ions. The typical hopping mobility of the holes is of the order of 106 m2 V−1 sec−1. The mobility activation energy of the holes in CuCr2O4 decreases with temperature due to the smoothing of the potential barriers between Cr4+ and Cr3+ sites.

Characterization of copper chromite catalysts for methanol dehydrogenation

Copper chromite catalysts have been characterised by total and metal surface areas. X-ray powder diffraction, thermal gravimetric analysis and selective extraction of copper oxide in order to investigate the nature of the active catalyst for methanol dehydrogenation. After reduction in hydrogen at atmospheric pressure, the catalyst surface has been shown to consist essentially of copper metal crystallites supported on cuprous chromite. The mechanism of catalyst reduction has been identified.