Morphological Study of Supported Copper Particles

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Apr 24, 2009 - for the obtaining copper phthalocyanine from phthalonitrile as ... over an alumina surface is 142 ± 30 ˚A. The synthesis method for the.
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LSRT #391968, VOL 39, ISS 5

Morphological Study of Supported Copper Particles on the Alumina Surface Javier Rivera de la Rosa, Boris I. Kharisov, Oxana V. Kharissova, and Ubaldo Ortiz M´endez QUERY SHEET This page lists questions we have about your paper. The numbers displayed at left can be found in the text of the paper for reference. In addition, please review your paper as a whole for correctness. Q1: Au: Fill in dates.

TABLE OF CONTENTS LISTING The table of contents for the journal will list your paper exactly as it appears below: Morphological Study of Supported Copper Particles on the Alumina Surface Javier Rivera de la Rosa, Boris I. Kharisov, Oxana V. Kharissova, and Ubaldo Ortiz M´endez

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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:1–4, 2009 Copyright © Taylor & Francis Group, LLC ISSN: 1553-3174 print / 1553-3182 online DOI: 10.1080/15533170902917967

Morphological Study of Supported Copper Particles on the Alumina Surface Javier Rivera de la Rosa, Boris I. Kharisov, Oxana V. Kharissova, and Ubaldo Ortiz M´endez 5

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CIIDIT-Universidad Aut´onoma de Nuevo Le´on, Monterrey, M´exico

external conditions (such as temperature and solution chemistry) in which copper crystals are formed, determine resulting external morphology of copper crystals. Space group [9]: Fm-3m (space group number: 225), structure: ccp (cubic close-packed), cell parameters: a = 361.49 pm, b = 361.49 pm, c = 361.49 pm, α = 90.00◦ β = 90.00◦ γ = 90.00◦ .

The composite on the basis of copper-supported alumina, used for the obtaining copper phthalocyanine from phthalonitrile as a precursor at temperatures close to r.t. (0–50◦ C), was prepared from a mixture of a copper salt with alumina and characterized by atomic force microscopy (AFM), X-ray diffraction, measurement of surface area and adsorption-desorption isotherms. It is shown that the height average of cubic-shape copper particles deposited ˚ The synthesis method for the over an alumina surface is 142 ± 30 A. alumina-supported copper affects drastically the available area of alumina that diminishes the surface catalytic properties. However, the supported copper particles act as a driving force for obtaining metal phthalocyanines at relatively low temperature. Keywords

Previous Microscopy Studies Pang et al.[10] used non-contact atomic force microscopy (AFM) to image the room-temperature √ √growth of copper and palladium on the (1 × 1) and ( 31 × 31) R ± 9◦ terminations of α-Al2 O3 (0001). In a 3D representation of an non-contact ˚ × 413 A) ˚ of 0.3 ML atomic force microscopy image (492 A of copper on Al2 O3 (0001) found a line profile across two cop˚ in height and per clusters; islands between the sizes of 3–8 A ˚ 20–30 A in diameter were distributed randomly on the surface. Tatschl[11] et al. developed an experimental procedure to investigate systematically the local deformation behavior of polycrystalline copper at the micrometer scale. The procedure consists of a combination of the measurement of the local in-plane strains and the local crystal orientation during an in-situ deformation test in the scanning electron microscope (SEM). Different grain regions were designated the initial lattice orientations, given in the Euler angles (ϕ 1 , , ϕ 2 ), were collected. The cubic symmetry, there exist 24 physically equivalent solutions to give the orientation of each crystal. In the micrograph presented of conducted experiments on oxygen free high conductivity copper in this work, prism solid-body multigrains were founded with edges of 100 µm in average. In the present work, we carried out the characterization of copper-containing alumina by X-ray diffraction, microscopy and surface-measurement methods.

copper particles, AFM, alumina, deposited particles

INTRODUCTION The growth and properties of elemental metals on oxide surfaces are of considerable importance in applications ranging from catalysis to the electronics industry.[1−5] Alumina is a particularly important supporting substrate in this context, pos25 sessing catalytic applications[6,7] due to its cheapness, availability and inertness. Among other its numerous uses, the metalcontaining alumina was successfully applied in the synthesis of copper and nickel phthalocyanines from phthalonitrile at low temperatures (0–40◦ C); the mechanism of phthalonitrile 30 tetramerization on these supported metals was proposed.[8] 20

Basic Literature Data on the Study of Copper Particles The crystal structure of copper is face-centered cubic (fcc) structure. It is based on one of the 14 Bravais lattices. Each copper atom has 12 nearest neighbors. Both crystal structure and

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EXPERIMENTAL PART

Received xxx; accepted xxx. The authors are very grateful to UANL (project PAICyT-2007) for financial support. Address correspondence to Boris Kharisov, Universidad Autonoma de Nuevo Le´on, A.P. 18-F, C.P. 66450, Ciudad Universitaria UANL, San Nicolas de los Graza, N.L., M´exico. E-mail: [email protected]

Materials and Equipment Alumina and CuSO4 ·5H2 O were purchased with Aldrich and used as supplied. The crystal phases of all samples were characterized by X-ray diffraction using a Siemens D-5000 instrument with Cu-Kα radiation at a scan rate of 0.05◦ at 2θ /min and 1

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Preparation and Characterization of Alumina-Supported Copper The copper-containing alumina was prepared according to the technique described earlier.[8] The alumina powder (50 g) was put into 200 mL of aqueous 20% solution of CuSO4 ·5H2 O and stirred for 10 min. Some mL of NH3 (10% aqueous solution) was added to pass this salt to the corresponding insoluble hydroxide and the formed mixture was stirred for 10 min. Then the precipitate was filtered, heated in an oven to convert Cu(OH)2 to CuO at 250–300◦ C for 5 h and collocated into the tube, through which the flow of dry hydrogen was passed for 4 h at 350◦ C. The formed product was kept in sealed tubes.

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FIG. 1. X-Ray pattern of Al2 O3 -Cu.

40 kV/30 mA. The surface areas of the powders were measured using a Quantachrom, Autosorb-1 surface area analyser. Nitrogen adsorption isotherms were obtained at 77 K, after the 75 samples were degassed below 10−3 Torr and 200◦ C for 8 h. The BET adsorption model was applied for the interpretation of the N2 isotherms to evaluate the surface area. Microscopy studies were carried out in the AFM equipment Veeco CP.

RESULTS AND DISCUSSION For copper-aluminium oxide system, the copper metal phase was identified as a main phase and aluminium oxide phase was also identified, as is shown in Figure 1. AFM analysis images were obtained in order to obtain more information about the crystals deposited over alumina surfaces. Figure 2 shows the analysis of AFM, made over a single copper particle over a large alumina surface, as is showed in SEM

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FIG. 2. An 0.8 µm AFM image as well as the section analysis showing a single copper crystal over alumina surface.

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STUDY OF SUPPORTED COPPER PARTICLES

FIG. 3. Liquid nitrogen sorption isotherms for alumina (a) and particles of copper deposited over the same alumina (b).

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micrographs in the previously reported work.[8] From the analysis section, it can be seen the distance is 0.215 µm for the line profile A, 0.176 µm for line profile B and 0.211 µm for line profile C. The height average of this particle deposited over an ˚ The particle is very near a cubic alumina surface is 142 ± 30 A. shape. Figure 3 compares isotherms of adsorption-desorption of N2 at 77 K for both pure alumina and copper particles deposited over same type of alumina. Filled symbols indicate values of adsorption, open symbols indicate the desorption curve. The shapes of isotherms for both samples, according to IUPAC classification, correspond to type V.[12] Isotherms indicate mesoporous material (2–50 nm of porous diameter) and showed flat adsorption and desorption branch under 0.35 of relative pressure (P/Po ) that demonstrates weak adsorbate-adsorbent interactions. The hysteresis loop is type H3 for both samples; this type is usually given by aggregates of plately particles or adsorbents containing slit pores.[12,13] Both samples present very closed hysteresis loops and hysteresis loops approach P/Po = 1, suggesting the presence of macropores (>50 nm). Alumina adsorption curve changes dramatically its slope at P/Po = 0.9 and reaches values of adsorbed liquid N2 of 700 cc and the adsorption curve

FIG. 4. Pore volume distribution of alumina(a) and particles of copper deposited over the same alumina (b).

of copper alumina sample maintain its slope and reaches lower 120 values of liquid N2 , only until 70 cc. The number of macropores diminished in the alumina with the application of particles of copper. Figure 4 presents the pore volume distribution (PVD) by BJH method for both samples that confirms how the number of macropores was diminished. Table 1 resumes the microstructure 125 characteristics for both samples. TABLE 1 Characteristics of alumina (A) and alumina with copper particle deposited (ACu) Average pore size (Nm) Sample A ACu

ABET (m2 g−1 )

BJH

DFT & MONTE-CARLO

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ABET is the BET surface area.

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It is well-known that heterogeneous reactions are favored by increasing permeability. Percolation and permeability are found only in open pores, then, the value of permeability is larger in the case of macropores, just for geometrical reasons. For porous materials, reactions can be carried out on the surface of the particle and also significant amount of reactant can diffuse well into the particle interior with further reaction. But another important characteristic is the active phase; in this case the copper particles that are a precursor in the synthesis of metal phthalocyaninates. As it was mentioned above, the studied composite was applied[8] for decreasing synthesis temperature for phthalonitrile cyclization in appropriate solvents (generally low-weight alcohols) from 120–150◦ C up to 0–30◦ C. This process is considerably accelerated at simultaneous application of ultrasound. Cun /Al2 O3 , as a metallic aggregate inside the alumina structure, possesses a high number of defects. This copper aggregate, under applied strong ultrasonic treatment, forms preferential sites of reaction and further undergoes to separation from the alumina support and destruction forming smaller metallic particles (probably, having the size of cavitation bubbles), serving as centers for phthalonitrile cyclization. CONCLUSIONS AND RECOMMENDATIONS The method utilized to deposit copper particles over powder alumina allowed obtaining particles very near to a cubic shape. The number of macropores of alumina diminished after deposition of copper particles. The method of synthesis of copper-alumina composite affects drastically the available area of alumina; this affects its surface catalytic properties, as well as the adsorption and desorption mechanisms which are not favored by low specific areas; the pore structural characteristics promote percolation and permeability phenomena. The main catalytic contribution is the homogenous and well-formed copper particles on the alumina. Due to both low solubility non-substituted phthalocyanine in non-aqueous solvents and insolubility of alumina, it is still difficult to develop an industrial method for phthalocyanine production, based on the use of alumina-supported copper. How-

ever, it, probably, will be possible for the case of substituted phthalocyanines bearing polar or non-polar groups, soluble in 165 corresponding organic solvents; this fact would allow successful separation of reaction product (metal phthalocyanine) and alumina. REFERENCES 1. Furstner, A. Supported metals. In: Active Metals. Preparation, Characterization, Applications. F¨urstner A. (Ed.), Weinheim: VCH, 1996, 381–426. 2. Anderson, J.A. Supported Metals In Catalysis. Fernandez Garcia, M. (Eds.). Catalytic Science Series, Series Editor Hutchings, G.J. Imperial College Press. 2005, 5, 380 pp. 3. McGuire, N.R. An overview of supported metal catalysts. Platinum Met. Rev., 2006, 50(1), 20–21. 4. Wallace, W.T., Min, B.K., and Goodman, D.W. The nucleation, growth, and stability of oxide-supported metal clusters. Topics in Catalysis, 2005, 34(1–4), 17–30. 5. Kharissova, O.V., and Kharisov, B.I. Synthetic techniques and applications of activated nanostructurized metals: highlights up to 2008. Recent Patents on Nanotechnology, 2008, 2(2), 103–119. 6. Devic, M. Supported metal catalyst, preparation and applications for directly making hydrogen peroxide. US6958138 (2005). http://www. freepatentsonline.com/6958138.html. 7. Chunnian, H., Zhao, N., Shi, C., Du, X., and Jiajun, L. Synthesis of binary and triple carbon nanotubes over Ni/Cu/Al2 O3 catalyst by chemical vapor deposition. Mat. Lett., 2007, 61(27), 4940–4943. 8. Kharisov, B.I., Rivera de la Rosa, J., Kharissova, O.V., Almaraz Garza, J.L., Almaguer Rodr´ıguez, J.R., Puente, L.I., Ortiz, U., and Ibarra Arvizu, A.K. Use of elemental copper and nickel, supported in alumina, for preparation of non-substituted metal phthalocyaninates at low temperature. J. Coord. Chem., 2007, 60(3), 355–364. 9. Straumanis, M.E., and Yu, L.S. Lattice parameters, densities, expansion coefficients and perfection of structure of Cu and of Cu-In phase. Acta Crystallogr., 1969, 25A, 676–682. 10. Pang, C.L., Raza, H., Haycock, S.A., and Thornton, G. Growth of copper and palladium on α -Al2 O3 (0001). Surface Science, 2000, 460, L510–L514. 11. Tatschl, A., and Kolednik, O. On the experimental characterization of crystal plasticity in polycrystals. Mat. Sci. Engin. A, 2004, 364(1–2), 384–399. 12. Sing, K.S.W., Everett D.H., Haul, R.A.W., Moscou, L., Pierotti, R.A., Rouqu´erol, J., and Siemieniewska, T. Reporting physisorption data gas/solid systems with special reference to the determination of surface area and porosity. Pure Appl. Chem., 1985, 57, 603. 13. Yu, H., Yu, J., Cheng, B., and Zhou, M. Effects of hydrothermal posttreatment on microstructures and morphology of titanate nanoribbons. J. Solid State Chem., 2006, 179, 349.

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