Acid-base properties of Cu1-xCoxFe2O4ferrospinels: FTIR investigations

Systematic IR spectroscopic studies were undertaken to investigate the acid–base properties of Cu–Co ferrospinels Cu1−xCoxFe2O4 (x = 0 to 1) employed in phenol methylation to produce 2,6-xylenol. The IR spectra of the ferrospinels reveal that Fe3+ and Co2+ ions are mainly responsible for the various hydroxy groups on the surface. Temperature dependent IR studies of pyridine adsorbed on spinels and on the spinel phase with deliberately added metal oxide exemplify the contribution of the metal ions and their coordination state towards Lewis acidity. IR studies of the spinel surface with adsorbed CO2 and adsorption studies of electron acceptors such as 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro-1-4-benzoquinone and p-dinitrobenzene were carried out to evaluate the nature of the basic sites and the strength and distribution of the electron donor sites present on the spinel surface. It was found that the acidity (basicity) of the Cu1−xCoxFe2O4 spinel system increases (decreases) from x = 0 to 1. A correlation between acidity, basicity and catalytic performance reveals that an intermediate acid–base character enhances the phenol methylation activity.

[1]  L. Guczi,et al.  Cu1−xCoxFe2O4 ferrospinels in alkylation: Structural changes upon reaction , 2002 .

[2]  S. Sugunan,et al.  Surface properties and catalytic activity of ferrospinels of nickel, cobalt and copper, prepared by soft chemical methods , 2001 .

[3]  R. Pullar,et al.  Magnetic properties of nanocrystalline CoFe2O4 powders prepared at room temperature: variation with crystallite size , 2001 .

[4]  K. Sreekumar,et al.  Vapor-phase methylation of pyridine with methanol to 3-picoline over Zn1−xCoxFe2O4 (x=0, 0.2, 0.5, 0.8 and 1.0)-type ternary spinels prepared via a low temperature method , 2001 .

[5]  K. Sreekumar,et al.  A comparative study on aniline alkylation activity using methanol and dimethyl carbonate as the alkylating agents over Zn-Co-Fe ternary spinel systems , 2000 .

[6]  K. Sreekumar,et al.  Selective synthesis of 3-picoline via the vapor-phase methylation of pyridine with methanol over Ni1-xCoxFe2O4 (x = 0, 0.2, 0.5, 0.8 and 1.0) type ferrites , 2000 .

[7]  E. Iglesia,et al.  Structure and Surface and Catalytic Properties of Mg-Al Basic Oxides , 1998 .

[8]  G. Busca.  Spectroscopic characterization of the acid properties of metal oxide catalysts , 1998 .

[9]  S. G. Dixit,et al.  Liquid-phase Friedel-Crafts alkylation using CuCr2−xFexO4 spinel catalysts , 1998 .

[10]  S. Date,et al.  Low temperature synthesis of Ni0.8Zn0.2Fe2O4 powder and its characterization , 1996 .

[11]  Guido Busca,et al.  The use of vibrational spectroscopies in studies of heterogeneous catalysis by metal oxides: an introduction , 1996 .

[12]  Jean-Claude Lavalley,et al.  Infrared spectrometric studies of the surface basicity of metal oxides and zeolites using adsorbed probe molecules , 1996 .

[13]  J. Dřímal,et al.  The Surface of Catalytically Active Spinels , 1994 .

[14]  G. Busca,et al.  Surface sites on spinel-type and corundum-type metal oxide powders , 1993 .

[15]  S. Sugunan,et al.  Acid-base, electron-donating and magnetic properties of Nd2O3 and its mixed oxides with alumina catalysts , 1993, Journal of Materials Science.

[16]  Kaoru Fujimoto,et al.  FTIR spectroscopic study of carbon dioxide adsorption/desorption on magnesia/calcium oxide catalysts , 1992 .

[17]  F. Trifiró,et al.  Cobalt-modified CuZnCr catalysts in the synthesis of methanol , 1992 .

[18]  G. Busca,et al.  Preparation, bulk characterization and surface chemistry of high-surface-area cobalt aluminate , 1992 .

[19]  G. Busca,et al.  FT-113 study of the surface properties of the spinels NiAl2O4 and CoAl2O4 in relation to those of transitional aluminas , 1991 .

[20]  G. Busca,et al.  Low-temperature CO2 adsorption on metal oxides: spectroscopic characterization of some weakly adsorbed species , 1991 .

[21]  A. Auroux,et al.  Microcalorimetric study of the acidity and basicity of metal oxide surfaces , 1990 .

[22]  H. Knözinger,et al.  Infrared spectroscopic study of the adsorption and reactions of CO2 on K-modified Rh/SiO2 , 1990 .

[23]  G. Busca,et al.  Fourier-transform infrared study of the surface properties of cobalt oxides , 1990 .

[24]  B. Delmon,et al.  Modified Aluminas : Relationship between activity in 1-butanol dehydration and acidity measured by NH3 TPD , 1989 .

[25]  Guido Busca,et al.  FT-IR study of the surface of copper oxide , 1987 .

[26]  K. Esumi,et al.  Adsorption of Tetrachloro-p-benzoquinone from Various Solvents on Metal Oxides , 1986 .

[27]  Harold H. Kung,et al.  IR Studies of NH3, Pyridine, CO, and NO Adsorbed on Transition Metal Oxides , 1985 .

[28]  G. Busca,et al.  Infrared spectroscopic identification of species arising from reactive adsorption of carbon oxides on metal oxide surfaces , 1982 .

[29]  G. Busca,et al.  Infrared study of chemisorption and reactivity of pyridine on haematite , 1981 .

[30]  G. Keresztury,et al.  CO2 inclusion bands in i.r. spectra of KBr pellets , 1980 .

[31]  G. Ghiotti,et al.  Surface acidity of η-alumina. Part 1.—Pyridine chemisorption at room temperature , 1979 .

[32]  C. Bennett,et al.  Infrared study of CO2 adsorption on SiO2 , 1978 .

[33]  G. Ghiotti,et al.  An infrared spectroscopic investigation of the surface properties of magnesium aluminate spinel , 1978 .

[34]  K. Nakamoto.  Infrared and Raman Spectra of Inorganic and Coordination Compounds , 1978 .

[35]  K. Esumi,et al.  OH− as a Possible Cause of the Electron-donor Property of the ZrO2–TiO2 System , 1977 .

[36]  G. Ghiotti,et al.  An IR Spectroscopic Characterization of Alpha Alumina Surface Properties. Carbon Dioxide Adsorption , 1977 .

[37]  C. H. Rochester,et al.  Infrared study of the adsorption of [2H4]acetic acid on to rutile , 1977 .

[38]  P. Harrison,et al.  Tin oxide surfaces. Part 2.—Infra-red study of the adsorption of pyridine and ammonia on tin(IV) oxide , 1975 .

[39]  G. Gatta,et al.  Surface rehydration of variously dehydrated eta-alumina , 1974 .

[40]  P. Tarte,et al.  Infrared studies of spinels—I: A critical discussion of the actual interpretations , 1971 .

[41]  W. White,et al.  Interpretation of the vibrational spectra of spinels , 1967 .

[42]  J. V. Evans,et al.  Infra-red study of adsorption of carbon dioxide and water on magnesium oxide , 1967 .

[43]  P. Tarte.  Etude infra-rouge des orthosilicates et des orthogermanates—III: Structures du type spinelle , 1963 .

[44]  G. H. Jonker.  Analysis of the semiconducting properties of cobalt ferrite , 1959 .

[45]  R. G. Treuting,et al.  The structure of tetragonal copper ferrite , 1956 .

[46]  R. Waldron.  Infrared Spectra of Ferrites , 1955 .

[47]  C. H. Kline,et al.  The Vibrational Spectrum of Pyridine and the Thermodynamic Properties of Pyridine Vapors , 1944 .