Characterization of nickel based catalysts supported by different oxides and prepared by sol gel method

Transcription

1 Characterization of nickel based catalysts supported by different oxides and prepared by sol gel method Mourad Halouane 1, Ouzna Kheffache 2, Saliha Menad 1, Djamila Halliche 2 1 Laboratoire de Recherche de Chimie Appliquée et Génie Chimique, Université M. Mammerie de Tizi-Ouzou, 15000, Tizi-Ouzou, Algérie. E mail: [email protected], 2 Laboratoire de Chimie du Gaz Naturel, Faculté de Chimie, Université des Sciences et de la technologie USTHB PB 32, 16111, El Alia Bab-Ezzouar, Alger, Algérie. Mots clés: Catalyseur, Sol-Gel, Tension actif. Abstract: A sol gel method was employed to prepare three series of catalyses: the first containing Ni/CaO, and Ni/MgO the second section is composed with modified with CaO and CeO 2 finally the third section contains support of series one adding tension actif (CTAB) (Cetyle Triméthyl Ammonium Bromide). Then catalysts were calcined in air at 700 C for4 h. 1. Experimental : 1.1. Catalyst preparation: The solution was prepared by mixing Nickel nitrate dissolved into distiller water (A) and then precursor nitrate dissolved into distilled water (B) then Nitric acid was added into the solution The mixture was continuously stirred slowly at 100 C for 5 h. The sol obtained was dried at 110 C and calcined at 700 C in a furnace for 4 h at a rate of 5C/min.In the same way,we prepared the catalysts with the tensioactif by adding the solution (A) and (B)and also add quantity of tension actif (CTAB) 1.2. Characterization techniques: 1.2.1nfrared spectroscopy: The infrared spectra were recorded between 1200 and 400 cm -1 at room temperature in a Nicolet 560 spectrometer. The samples were analyzed after being mixed with KBr (1:100 by weight) X-ray diffraction (XRD): X-ray diffraction (XRD) patterns of the calcined samples were obtained by using a PW 1710 diffract meter with Cu-Ka radiation (λ= Ǻ), over range of 2θ= 10 to Surface area measurements (BET): The specific surface areas of the catalysts (S BET ) were obtained by using the BET method, from the nitrogen adsorption desorption at 77K.

2 Transmitance (%) Transmittance (%) Transmitance (%) Transmitance (%) Scanning electron microscopy (SEM): Scanning electron microscopy (SEM) analyses were performed 2. Results and discussion: 2.1. Catalyst characterizations: FTIR analysis Ni/MgO Ni/MgO+CTAB +CTAB Nombre d'onde (Cm-1) Nombre d'onde (cm -1 ) Fig.1: FTIR analysis of Ni/MgO and 3415 Fig2: FTIR analysis of and Ni/ MgO +CTAB catalysts calcined at 700 C +CTAB catalysts calcined at 700 C Ni/Cao Ni/Cao+CTAB -CaO -CeO Nombre d'onde (cm -1 ) Nombre d'onde (cm -1 ) Fig 3: FTIR analysis of Ni/CaO and Fig 4: FTIR analysis of (a) -CeO 2 and +CTAB catalysts calcined at 700 C (b) -CaO catalysts calcined at 700 C FTIR analysis was performed for both the gel and oxide fibers in the wave number region of cm 1. The spectra are shown in Figs All specters presented the similar bands. The broad band recorded at cm 1 is associated to the presence of hydrogen bonded OH [1-4].

3 Intencité Intencité Intencité Intencité The bands situated at 1632 cm -1 and 1634 cm- 1 -, are associated to the presence of HC The absorption at 1384 cm -1 is due to presence of nitrates (NO3 - ) In addition to that, a band is observed at 610 cm 1 corresponds to Ni-O-M, M=(Al, Ca, Mg, Ce) vibration. XRD spectra NiO-MgO MgO 49,6 Ni/MgO Ni/MgO+CTAB +CTAB NiO Al 2 NiAl 32 O 49 NiAl 2 O 4 2 théta 2Théta Fig.5: XRD spectra of r Ni/MgO and Fig 6:.XRD spectra of and Ni/ MgO +CTAB catalysts calcined at 700 C +CTAB catalysts calcined at 700 C 2 9, 5 6 Ni/CaO Ni/CaO+CTAB CaO CaO 4 NiO Ca(OH)2 a 2 3, ,55 29,55 3 9, , 6 43,6 5 7, ,3 Ce 2 CeAl2 NiAl 2 Al 2 b 75,95 CaAl 2 O 4 NiO 2 Théta 2 théta Fig 7: XRD spectra of Ni/CaO and Ni/CaO+CTAB catalysts calcined at 700 C Fig 8:XRD spectra of (a) -CeO 2 and (b) -CaO catalysts calcined at 700 C. X-ray diffraction patterns of Ni/MgO and Ni/MgO +CTAB catalysts calcined at 700 C. We observed formation of solid solution NiMgO 2 (JCPDS ) at 2θ = 37,1. 42,97. 62,2.74,92.78,84 (cubic system, spatial group Fm3m, parameter α=4.209 Å) this result is according to the literature data [5-7].As for Ni/MgO +CTAB what is more sold solution we observed MgO phase at 2θ= (29,4.39,4. 74,8). XP spectra of and of +CTAB are shown in Fig 6. For catalyst, there are peaks with 2θ being 18,8. 31,41. 59,72. 65,8. 77,88. 78,84 and 83,84, which are assigned to

4 NiAl 2 (cubic system, parameter α=8,048a )and coexistence of NiAl 2 and NiO peaks with 2θ being 37,17.and 45,09 the +CTAB catalyst. We observed at 2θ = 29,6. 36,2. 37,2. 39,6. 43,4. 48,8. 57,4. 60,8. 62, attributed of NiAl 32 O 49 [JCPDS ] at 2θ =23,4.29,6, 32,2. 39,6. 47,6. 48,8. 57,4. 57,6. 65 attributed Al 2 finally we notice presence of NiO at 2θ = 37, ,8 In Fig 7 XP spectra of Ni/CaO and Ni/CaO+CTAB catalysts calcined at 700 C we notice peaks with 2θ being at 2θ= 32,4. 37,5. 54,2. 64,8. 67, (JCPDS ) which are assigned to CaO at 2θ = ,1. 46,6. 50,12. 53,9. 61, ,8). (JCPDS ) A weak peak with 2θ being 37,8. 43,6. 62,8. 76,2. 80,2 can be ascribed to NiO phase. However, Ca(OH) 2 phase can be obtained du to hydration of CaO according to this reaction Fig 8 shows the XRD patterns for Ni /Al 2 doped with CaO and CeO 2 calcined at 700 C.The Ni /Al 2 - CaO XRD analysis showed the formation NiO and CaAl 2 O 4 phases concerning the -CeO 2 we observed CeAl, Al 2 and Ce 2 phases. Specific surface areas Table 1: Specific surface areas and diameters of catalysts prepared by a sol gel calcined at 700 C Catalysts BET (m 2 /g) d (A ) Ni/CaO+CTAB 16,3 104,1 Ni/CaO 2,2 281,9 Ni /Al 2 +CTAB 15,3 104,5 Ni /Al 2 56,1 73,0 Ni /Al 2 - CeO 2 36,8 550,1 Ni /Al 2 - CaO 10,5 327,8 As listed in Table 1, the 11% Ni/ Al 2 - CeO 2 catalyst exhibited high specific surface area (36,8m 2 /g) compared to 11% Ni/ Al 2 - CaO CaO, and the specific surface area of 11% Ni/CaO+CTAB was 16,3 m 2 /g, significantly higher than that Ni/CaO (2,2 m 2 /g). Wbe observed higher specific surface area of Ni /Al 2 (56,1 m 2 /g).

5 Scanning electron microscopy (SEM). Fig 9: SEM Images of the (a) Ni /Al 2 _CeO 2 (b) Ni /Al 2 _CaO, Fig 10: SEM Images of the (c) Ni/CaO, (d) Ni /Al 2, (e) Ni/MgO. (f) Ni/CaO+CTAB, (g) Ni /Al 2 +CTAB and and (h) Ni/MgO+CTAB. The similar images for catalysts modified with CaO and CeO 2 are observed Fig 9 the scanning electron microscopy (SEM). of the catalyst Ni /Al 2 _CeO 2 and Ni /Al 2 _CaO. The catalysts prepared without CTAB can be seen as small particulars with irregular shapes, in different way with a visible porosity unlike the catalysts with CTAB which do not have a visible porosity.

6 References [1] A.C. Roger, C. Petit, A. Kiennemann, J. Catal.,167 (1997) 447. [2] R.I.Bickley, H.G.M.Edwards, R.Gustar,S.J.Rose. J.Mol.Struct.,237 (1991) 248. [3] H. Provendier. Thèse U.L.P Strasbourg, France [4] G.Sinquin. Thèse U.L.P Stasbourg, France [5] Jiahe Liu, Haoquan Hu, Lijun Jin, Pengfei Wang, Shengwei Zhu ; Fuel Processing Technology., 91 (2010) 419. [6] E. Ruckenstein, Y.H. Hu, Appl Cat A: Gen., 183 (1999) 85. [7] J. Barbero, M.A. Peña, J.M. Campos-Martin, J.L.G. Fierro, P.L. Arias, CatalLett., 87 (2003) 211.