SYNTHESIS AND CHARACTERIZATION OF MODIFIED MESOPOROUS SILICA-IMOBILIZED Cu(II)-ACETONITRILE COMPLEX AND ITS APPLICATION IN TRANSESTERIFICATION OF FRYING OIL Syukri *, Rycce Sylviana Pratikha, and Novesar Jamarun

Mesoporous silica has attracted rapidly growing attention in catalysis. In this work, mesoporous silica was synthesized by using CTAB surfactant and then modified by AlCl3. Such material was used as support for Cu(II)--acetonitile complex and applied in transesterification of frying oil. The XRD pattern of the obtained silica confirms the availability of chracteristic peak on silica surface while its TEM exhibits the uniformity of nanochannel of the mesoporous silica. The particle size of silica support has become smaller after grafting process showed by SEM images. FT-IR spectra of the materials indicated that the Cu(II) grafted on the mesoporous silica was in the form of its acetonitrile complex. Supprisingly, the Cu loading the grafted catalyst was found to be very high. That was 21%, when the catalyst applied on transesterification of the examined frying oil the amount of total methyl ester yielded were of 65%.


INTRODUCTION
Highly ordered mesoporous silica in 1992 attracts rapidly growing attention in its application. MCM-41 as one member of M41s family from Mobile Corporation has been synthesized using CTAB as structure directing agent and confirm the uniform pore size (2-50 nm), tunable pore size, large surface area, high pore volume, and high thermal stability [1] . Their advantages have great interesting and promising field and potential to apply in catalysis, support [2] , and adsorbent [3] .
The important limitation of mesoporous silica is the lack of active site in it framework. Many researches have been reported to increase the potential application by incorporated other metals such as Al [4] , B [5][6][7] , Ti [8] , Pd-Au [9] to it framework and modification of silica surface with weakly coordinated anion BF 4 -[10] , B(C 6  . These ways attributed to improve thermal stability and active site in mesoporous silica. Cu(II)-acetonitrile complex has employed in catalytic process. Syukri et al reported Cu(II)-acetonitrile complex potential to enhance in cyclopropanation reaction [2,14] . It's complex confirm poor efficiency for economic and environmental due to recyclability, reuse, and regeneration of homogeneous catalysts isn't applicable. And the great attempt have been done a immobilization of homogeneous catalyst in support material t. In our previous work, modified silica was synthesized with AlCl 3 in surface silica via electronic interaction and potential to applied in transesterification reaction [13] . In this work, mesoporous silica as supported material was modified by AlCl 3 and then was immobilized by complex of Cu(II)-acetonitrile. Mesoporous silica and the grafted catalyst was characterized by FT-IR, XRD, SEM, TEM, and AAS. This catalyst obtained was then applied in transterification of frying oil. Frying oil confirm the pure oil that contains low free fatty acid.

Instrumentation
Mesoporous silica and the obtained catalyst were characterized by XRD, FTIR, SEM, TEM, and BET. Copper contain in grafted catalyst was analysed by AAS and methyl ester formation as a product of reaction was followed by GC-MS.

Synthesis of mesoporous silica
We have prepared mesoporous silica with follow the molar ratio 1 SiO 2 : 0.27 CTAB : 60 H 2 O [14]. In a typical synthesis, 49.20075 g CTAB was dissolved in 270 mL H 2 O. 45.2088 mL Na 2 SiO 3 in H 2 O was added dropwise under stirring, pH adjusted at 11 by adding CH 3 COOH, stirred for 24 hs and aged for 16 hs. The resulting gel is transferred into polyethylene bottle and followed hydrothermal treatment at 373 K for 3 days. The obtained solid was washed with aquadest and dried at 373 K for 24 hs. The powder was extracted with acidified methanol for 3 hs to remove surfactant in mesoporous silica. The obtained solid product was washed by aquadest/methanol and dried at 373 K for 24 hs and white powder formed.

Synthesis of modified mesoporous silica
Mesoporous silica was mixed with aniline (toluene) and stirred for 24 hs. Anhydrous aluminium trichloride was added into the mixture. The resulting suspension was filtered, washed with toluene, and dried at room temperature. Solid obtained was grayish colours.

Synthesis of grafted catalysts
Modified silica, anhydrous CuCl 2 , and acetonitrile were starting materials for synthesis of the catalyst. Starting materials were mixed and stirred for 24 hs and washed with acetonitrile, and dried at room temperature. The catalyst obtained were characterized by FTIR, XRD, SEM, BET, and TEM.

Catalytic activity test of grafted catalyst on frying oil transesterification
The amount of 1 weight % of catalyst was respectively added to methanol and stirred (300 rpm, 60 o C) for 15 minutes. Afterward, frying oil was put into catalysts-methanol solution and stirred for 3 hs. The solution was analyzed by GC-MS. Yield of methyl ester product was accounted as in equation 1. (1)

FT-IR Analysis of The Grafted Catalyst
The IR technique was employed to identify the formation of grafted catalyst on the bands characterisitic.
FTIR spectra in Figure 2 showed bands at 1085 cm -1 and 794 cm -1 observed stretching vibrations of Si-O-Si framework. The stretching band at 3434 cm -1 characteristic -OH groups from adsorbed water and silanol groups in mesoporous silica and additional bands at 461 cm -1 due to their deformation of Si-O bonding from SiO 4 . Band at 797 cm-1 revealed that -O-H bending from Si-OH. Present band at 2927 cm -1 prove that the methyl groups from surfactant. Modification of surface mesoporous silica with AlCl 3 attributed stretching vibrations of Si-O-Si at 960 cm -1 [15] .

Morphology Surface Analysis
The morphology for mesoporous silica are detected by scanning electron microscopy. Images of mesoporous silica and grafted sample are shown in Figure 3.
Mesoporous silica samples exhibit smooth surface silica and the TEM images in Figure  4 showed the uniform morpholgy of mesoporous silica and found the nanometer scale of particle. While grafted catalyst showed the irreguler shape particle. Irreguler particle revealed with XRD in figure 1 that lower crystallinity and disorder of particle will be occur after grafting complex.

BET
Mesoporous silica exhibits isotherm type IV (IUPAC) that it confirm the hysteresis loop of mesoporous silica in figure 5. Monolayer adsorption in pore wall was followed capillar condensation at P/P o 0,7-0,85. Pore diameter of mesoporous silica obtained was 7.05 nm. Its confirm the mesoporous silica was obtained using CTAB as molecular templating agent.

AAS Analysis
Copper metal loading in grafted catalyst was analyzed by AAS and found 21,32% Cu content in catalyst. In our previous work, using modified silica gel as support which have micrometer size only found 6.19% Cu in catalyst [13]. Higher content of metal loading was influenced by the amount of silanol groups in surface. Mesoporous silica has larger surface area than silica amorphous and surely, the amount of silanol groups can be increased.

Catalytic Activity of Grafted Catalyst
Yield of methyl ester in grafted catalyst found 65,24% of product that it contain hexadecanoic acid methyl ester (31.16%), octadecanoic acid methyl ester (3.18%), 9octadecenoic acid methyl ester (32.40%), and 9,12-octadecadienoic acid methyl ester (3.62%) in Figure 6. The increasing of metal loading can increase the yield of product due to the active site of catalyst and larger surface area.

CONCLUSION
The mesoporous silica is the one of candidate a support material in catalyst. Mesoporous silica obtained has the pore diameter about 7 nm. Using mesoporous silica as support can increase the metal loading cotent and catalytic activity. The catalyst obtained exhibit good catalytic activity which 21% Cu contain was found 65% of product.