Development of Mesoporous Materials and Noble Metal Based Hydrodesulfurization Catalysts
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Development of Mesoporous Materials and Noble Metal Based Hydrodesulfurization Catalysts

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Research paper presented on Catalyst Society Conference 2007

Research paper presented on Catalyst Society Conference 2007

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    Development of Mesoporous Materials and Noble Metal Based Hydrodesulfurization Catalysts Development of Mesoporous Materials and Noble Metal Based Hydrodesulfurization Catalysts Document Transcript

    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183DEVELOPMENT OF MESOPOROUS MATERIALS AND NOBLE METAL BASED HYDRODESULFURIZATION CATALYSTS Lebong Andalaluna Deputy for Information, Energy and Material Technology, Agency for the Assesment and Application of Technology (BPPT), Jl. M. H. Thamrin 8, Building II. Fl. 4, Jakarta 10340, Indonesia. E-mail: andalaluna@yahoo.com Yasuharu Kanda and Masatoshi Sugioka Department of Applied Chemistry, Muroran Institute of Technology, 27 - 1 Mizumoto-cho, Muroran-shi, 050-8585, Japan. E-mail: msugioka@mmm.muroran-it.ac.jp Abstract The paper describing progress on a series studies conducted by the authors in developing new type of highly active hydrodesulfurization catalysts by employing mesoporous materials and noble metal. It was found that Pt supported on acidic mesoporous materials MCM-41 (as-syntheses SiAlMCM-41, post-syntheses modified (Al)SiMCM-41) catalysts showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 350ºC and the activities were observed higher than that of commercial catalyst CoMo/Al2O3. Pt supported on moderately acidic MCM-41, Pt/SiAlMCM-41 (Si/Al=15) and Pt/Al(1)SiMCM-41 (1 wt% Al loading) were observed showing particular high activities for the hydrodesulfurization of thiophene. It was concluded that the acidic property of support material MCM-41 and the spillover hydrogen formed on Pt particle in Pt/MCM-41 catalysts play important role for the hydrodesulfurization of thiophene. Keywords:Noble metal, mesoporous material MCM-41, acidity, thiophene hydrodesulfurizationIntroduction Enormous growth of fossil fuel consumption in the past decades has brought detrimental consequences toboth of environmental and human life quality. In order to cope with these serious matters, various countries hasapplied new regulation which is considered much more environmentally benign and provide significant impact toimprove our living environment quality. Various organic sulfur compounds present invariably in petroleumfeedstocks and the combustion of relevant fuels, such as diesel oil, would result in sulfur dioxide (SOx) emission tothe atmosphere. The SOx emission to the atmosphere then would lead to the acid rain, ozone depletion or smog. It isstated by various countries that sulfur content for diesel oil would be lessen to 10 ppm level by 2008 as a goal. Thisgoal would limit the emission of SOx and subsequently, reduce significantly resulted pollution effects. Furthermore,low-sulfur fuels would also enable the automobile manufacturers to implement their advanced low-sulfur sensitivetechnology that can reduce further the emission of oxide and nitrogen particulate generated in fuel combustion. Hydrodesulfurization process is an important process in the petroleum refining processes which aim atexcluding sulfur component in the petroleum feedstocks and producing clean fuel products. The development ofhighly active hydrodesulfurization catalysts is a crucial issue in the petroleum industries by which petroleumfeedstocks with much lower sulfur content or sulfur-free fuel can be produced. The authors have been investigatingthe development of highly active new generation zeolites based hydrodesulfurization catalysts [1-3]. On the otherhand, the emerging of new class of mesoporous materials recently, such as MCM-41 [4], FSM-16 [5], SBA-15 [6]with large pore diameter in recent years attracted wide attention of utilization such as materials as solid acid catalystand catalyst support. Such as materials are expected to be effective materials for treating or synthesize largemolecule chemicals. We reported that noble metals supported on mesoporous silicate FSM-16, especially Pt/FSM-16, showed highand stable activity in the hydrodesulfurization of thiophene [7]. It was proposed that weak acid sites of supportmaterial mesoporous silicates playing important role for high activity of thiophene hydrodesulfurization. Therefore, B–6–1
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183it is important to study the effect of acidity of support material to the hydrodesulfurization catalytic performance ofthe catalyst, in order to improve further the catalytic performance of the catalyst system. In present work, acidic mesoporous aluminosilicate (SiAlMCM-41, Si/Al=5, 15, 30) was synthesized and theeffect of the application of the materials as support material of noble metal catalysts for thiophenehydrodesulfurization was studied. On the other hand, the effect of application of mesoporous silicate (SiMCM-41)modified with impregnation of Al2O3, Ti(SO4)2 and ZrO2 ((MeSiMCM-41, Me=Al, Ti, Zr) as support material of Pt(Pt/MeSiMCM-41) for thiophene hydrodesulfurization, was studied. The effect of application of SiMCM-41modified with different Al modifier agent, Al2O3 and Al-sec-butoxide, as support material of Pt for thiophenehydrodesulfurization, was also compared with Pt/SiMCM-41 and Pt/SiAlMCM-41 catalytic performances, as well.Figure 1 showed an illustration of Pt/MeSiMCM-41 preparation path employed in this study. Infrared study on thepyridine adsorption was performed over SiAlMCM-41 and surface modified SiMCM-41 (MeSiMCM-41) to studythe surface character of the materials. Me (Al, Ti, Zr) NM chloride solution solution impregnation impregnation Calcination Calcination and reduction Mesoporous silica Me-modified MCM-41 Highly dispersed Pt SiMCM-41 (MeSiMCM-41) on MeSiMCM-41Figure 1 – Mesoporous silica MCM-41 supported Pt hydrodesulfurization preparation path.Experimental Mesoporous silicate MCM-41 (SiMCM-41) was synthesized using dodecyltrimethyl ammonium bromide(DTABr), tetrapropyl ammonium bromide (TPABr), hexadecyltrimethylammonium chloride (CTAC) surfactants(Aldrich) with SiO2.Na2O as silica source. Acidic SiAlMCM-41 was synthesized by adding sodium aluminate(NaAl2O4) during synthesis with Si/Al 5, 15, 30 into the gels mixture. Obtained hexagonal structure of mesoporoussilicate SiMCM-41 was further impregnated using Al, Ti and Zr aqueous solutions and Al-sec-butoxide with 1 wt%and 4 wt% metal loading to obtain surface modified mesoporous silicate MCM-41 (MeSiMCM-41). Mesoporousmaterial supported noble metal (Pt, Pd, Rh, Ru) catalysts were prepared by impregnation method using metalchloride aqueous solutions with 5 wt% metal loading. All catalysts were calcined at 500°C for 4 hours in air andreduced at 450°C for 1 hour prior to the reaction. Presulfiding treatment of the catalysts was performed using 5%H2S-H2 gas mixture at 400°C for 1 hour. Hydrodesulfurization of thiophene was carried out at 350°C under atmospheric pressure, employing 0.1 gramamount of catalyst, by use of a conventional fixed bed flow reactor. Thiophene was introduced into the reactor bypassing hydrogen (30 ml/min) through thiophene trap cooled at 0°C. The reaction products were analyzed byShimadzu gas-cromatograph equipped with SD-550 column. 2-propanol dehydration and cumene cracking ofsupport materials was carried out by use of pulse reactor system at 200°C and 400°C. Characterization of SiAlMCM-41 and surface modified SiMCM-41 was performed by employing infraredspectroscopic measurement of pyridine adsorption using Jasco FT-IR spectrometer. Pyridine adsorption wasperformed by introducing 10 Torr of pyridine vapour into the cell at 100°C for 0.5 hour followed with 0.5 hourevacuation at the same temperature.Results and DiscussionsCatalytic activities of MCM-41 supported noble metal catalysts in thiophene hydrodesulfurization The hydrodesulfurization of thiophene over various noble metals (NM=Pt, Pd, Rh, Ru) supported onmesoporous silicate MCM-41 (SiMCM-41) and aluminosilicate MCM-41 (SiAlMCM-41, Si/Al=15) catalysts at350°C is shown in Figure 2. The catalytic activities of NM/SiMCM-41 were observed vary remarkably for differendkind of noble metal supported on SiMCM-41 and the catalytic activities after 2 hours reaction were revealed in theorder as follow; Pt/SiMCM-41 > Pd/SiMCM-41 > Rh/SiMCM-41 >> Ru/SiMCM-41. Pt/SiMCM-41 andPd/SiMCM-41 catalysts were observed showing higher activities than that of commercial catalyst CoMo/Al2O3. Thehigh activities for both catalysts were maintained after 5 hours reaction. The effect of application of acidic support to the catalytic activities of noble metals/MCM-41 were observedvary remarkably for differend kind of noble metals and the catalytic activities after 2 hours reaction were revealed in B–6–2
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183the order as follow; Pt/SiAlMCM-41 > Pd/SiAlMCM-41 > Rh/SiAlMCM-41 >> Ru/SiAlMCM-41. Moreover,Pt/SiAlMCM-41 catalyst was revealed showing much higher activity than that of commercial catalyst CoMo/Al2O3at steady after 5 hours reaction. It was revealed that the application of acidic mesoporous material MCM-41 assupport material was very effective to improve the hydrodesulfurization performance of Pt based catalyst system. Ru SiAlMCM-41 SiMCM-41 Rh Pd Pt CoMo/ALO 0 10 20 30 40 50 60 70 80 Conversion (% )Figure 2 - Thiophene hydrosulfurization over noble metals (NM=Pt, Pd, Rh, Ru) supported on mesoporous silicateMCM-41 (SiMCM-41) and aluminosilicate MCM-41 (SiAlMCM-41).W/F = 37.9 g.h/mol, reaction temperature 350°C.Catalytic activities of Pt supported on acidic SiAlMCM-41 in thiophene hydrodesulfurization In order to study further the effect of support acidity to Pt/MCM-41 catalysts system we employing severalSiAlMCM-41 (Si/Al = 30, 15, 5) with different acidic properties in order to examine the effect of support acidityproperties toward the hydrodesulfurization performance of Pt/SiAlMCM-41 catalysts. It is assumed that the acidicproperties of support material is in the order of Si/Al as follow: Si/Al=30<15<5 as studied using 2-propanoldehydration and cumene cracking and infrared spectroscopic measurement of pyridine adsorption as well.Table 1 – Thiophene hydrodesulfurization over Pt supported on acidic SiAlMCM-41. Composition (%) Catalysts Conversion (%) C1-C3 n-C4 C4= CoMo/ALO 46.4 0.6 17.5 81.9 5 wt% Pt/SiMCM-41 51.5 1.9 71.5 26.2 5 wt% Pt/SiAlMCM-41 (Si/Al=30) 62.8 0.5 78.8 20.7 5 wt% Pt/SiAlMCM-41 (Si/Al=15) 74.1 1.4 90.6 7.9 5 wt% Pt/SiAlMCM-41 (Si/Al = 5) 36.0 0.6 71.8 27.6 Catalytic activities of Pt supported on various mesoporous aluminosilicate MCM-41 in thehydrodesulfurization of thiophene is shown in Table 1. As shown in the table, Pt/SiAlMCM-41 with Si/Al=15showed the most optimum thiophene hydrodesulfurization activity which lead to the conclusion that moderateacidity (Si/Al=15) of support material would be most suitable for synthesizing highly active Pt/SiAlMCM-41catalyst system for thiophene hydrodesulfurization. Less (Si/Al=30) or more (Si/Al=5) acidic support materialwould lead to the decrease of catalytic performance. It is assumed that proper acidic properties of support materialwould improve the hydrogenation capability of the catalyst system that lead to higher thiophenehydrodesulfurization catalytic performance, as higher saturated product of n-C4 observed as shown in Table 1. B–6–3
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183Catalytic activities of Pt supported on surface modified SiMCM-41 (MeSiMCM-41, Me=Al, Ti, Zr) inthiophene hydrodesulfurization It was revealed in the previous section that moderate acidic property of support mesoporous material play animportant role in developing highly active Pt based hydrodesulfurization catalyst. Therefore, it is important to studymethodology in controlling surface acidity of support mesoporous material that would possibly improve further thecatalytic performance of the catalyst system. In this section, we studied the effect of the application of mesoporoussilicate SiMCM-41 modified with impregnation of Al2O3, Ti(SO4)2 and ZrO2 ((MeSiMCM-41, Me=Al, Ti, Zr) assupport material of Pt (Pt/MeSiMCM-41) for thiophene hydrodesulfurization, in order to develop highly active Ptbased hydrodesulfurization catalyst. The catalytic activities of Pt supported on SiMCM-41 modified with Al, Ti and Zr in the hydrodesulfurizationof thiophene are shown in Figure 3, Figure 4 and Figure 5, respectively. It was revealed that Pt supported on surfacemodified SiMCM-41 (Pt/MeSiMCM-41) with Me=Al, Zr showed better catalytic performance for thehydrodesulfurization of thiophene than Pt/SiMCM-41 catalyst. Moreover, It was observed that Pt/AlSiMCM-41showed better catalytic performance than Pt/ZrSiMCM-41 for thiophene hydrodesulfurization. On the other hand,the application of TiSiMCM-41 as support material resulted in decreasing of catalytic activity of thiophenehydrodesulfurization.As shown in Figure 3, Pt/AlSiMCM-41 showed higher catalytic performance of thiophene hydrodesulfuri- zationthan that of Pt/SiMCM-41 for both of 1 wt% and 4 wt% Al loading. The catalytic performance was improved betterfor lower Al loading (1 wt%) and decreased at higher Al loading (4 wt%). 5 wt% Pt/Al(4)SiMCM-41 5 wt% Pt/Al(1)SiMCM-41 5 wt% Pt/SiMCM-41 CoMo/ALO 0 10 20 30 40 50 60 70 Conversion (%)Figure 3 - Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with Al. 5 wt% Pt/Ti(4)SiMCM-41 5 wt% Pt/Ti(1)SiMCM-41 5 wt% Pt/SiMCM-41 CoMo/ALO 0 10 20 30 40 50 60 70 Conversion (%)Figure 4 - Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with Ti. In the case of Pt/TiSiMCM-41, the catalytic activity was oberved almost the same with that of Pt/SiMCM-41for lower Ti loading (1 wt%) while the activity was decreased, lower than that of Pt/SiMCM-41, for higher Tiloading (4 wt%), as shown in Figure 4. Furthermore, Pt/ZrSiMCM-41 showed better catalytic performance forthiophene hydrodesulfurization than that of Pt/SiMCM-41 for 4, 8 and 16 wt% Zr loading, as shown in Figure 5. B–6–4
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183 The main reaction products in the hydrodesulfurization over Pt/SiMCM-41 were C4 hydrocarbons (butane71%, butenes 27%) with trace amount of C1-C3 hydrocarbons. These results indicate that Pt/SiMCM-41 catalyst hashigh hydrogenation ability for unsaturated C4 hydrocarbons and low hydrocracking activity for hydrocarbons in thepresence of hydrogen sulfide. It was observed for Pt/MeSiMCM-41 that butane composition in the reaction productswas higher than that of Pt/SiMCM-41 while the composition of cracking products was almost unchanged. Therefore,it can be assumed that Pt/MeSiMCM-41 has higher hydrogenation ability than Pt/SiMCM-41. 5 wt% Pt/Zr(16)SiMCM-41 5 wt% Pt/Zr(8)SiMCM-41 5 wt% Pt/Zr(4)SiMCM-41 5 wt% Pt/SiMCM-41 CoMo/ALO 0 10 20 30 40 50 60 70 Conversion (%)Figure 5 - Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with Zr.Catalytic activities of Pt supported on SiAlMCM-41 modified with different Al modifier agent in thiophenehydrodesulfurization It was revealed that the application of SiMCM-41 modified with aqueous solution Al2O3 as support materialfor Pt improved the catalytic performance of Pt/mesoporous silicate in the hydrodesulfurization of thiophene. Theimprovement is concluded having related with the increase of surface acidity of support material in the catalystsystem. In this section, we examine further the modification of siliceous SiMCM-41 in order to improve thecatalytic activity in thiophene hydrodesulfurization. In the study, siliceous SiMCM-41 was modified with aqueoussolution Al2O3 and organic Al-sec-butoxide with Al metal loading 1 wt% and 4 wt% and the hydrodesulfurizationperformance with Pt as supported metal was evaluated.Table 2 – Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with different modifier agent. Composition (%) Catalysts Conversion (%) C1-C3 n-C4 C4= CoMo/ALO 46.4 0.6 17.5 81.9 5 wt% Pt/SiMCM-41 51.5 1.9 71.5 26.2 5 wt% Pt/Al(1)SiMCM-41 64.4 0.6 86.9 12.4 5 wt% Pt/Al(4)SiMCM-41 62.8 1.0 82.9 16.2 5 wt% Pt/Al-OR(1)SiMCM-41 60.7 0.4 90.7 8.8 5 wt% Pt/Al-OR(4)SiMCM-41 65.0 0.8 84.4 14.8 Catalytic activities of Pt supported on surface modified mesoporous silicate SiMCM-41 ((Al)SiMCM-41,(Al-OR)SiMCM-41) in the hydrodesulfurization of thiophene is shown in Table 2. The activities were based onconversion after 2 hours reaction. As shown in the table, the application of SiMCM-41 modified with both of Al2O3and Al-sec-butoxide improved the catalytic performance in thiophene hydrodesulfurization. It is assumed that acidicproperties of modified support material plays an important role for the catalytic activity improvement. It was observed that for modification with aqueous solution Al2O3, the performance improvement is better forlower Al metal loading. It was also observed, that higher saturated product n-C4 obtained at lower Al metal loading,indicating better hydrogenation capability have some contribution for high catalytic activity of Pt/ Al(1)SiMCM-41. B–6–5
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183On the other hand, in the modification with organic Al-sec-butoxide the catalytic activity improvement wasobserved better for higher metal loading. It is interesting to note that lower saturated product n-C4 obtained forhigher Al metal loading.Catalytic activities of MCM-41 in 2-propanol dehydration and cumene cracking Dehydration of 2-propanol and cumene cracking were employed as model reactions in this study, in order toevaluate surface character and property of aluminosilicate MCM-41 and mesoporous silica MCM-41 modified withmetal impregnation (MeSiMCM-41, Me=Al, Ti, Zr). Dehydration of 2-propanol produces acetone as product overbasic and metallic catalyst. On the other hand, it produces propylene over acidic (Lewis and Broensted) catalyst.Cumene cracking is known required relatively strong Broensted acid sites to proceed and producing benzene andpropylene as products. Figure 6 shows the catalytic activities of SiAlMCM-41 with various Si/Al ratio in the dehydration of 2-propanol and cumene cracking. It was observed that the surface acidity of SiAlMCM-41 increased for smaller Si/Alratio. The trend is attributed to the increase of surface acid sites along with the increase of Al numbers. 100 2-PA Dehydration Cumene cracking 80 Conversion (%) 60 40 20 0 SiMCM SiAlMCM SiAlMCM SiAlMCM (Si/Al=30) (Si/Al=15) (Si/Al=5)Figure 6 – Catalytic activities of SiAlMCM-41 with various Si/Al ratio in 2-PA dehydration and cumene cracking. The catalytic activities of SiMCM-41 and surface modified SiMCM-41 in the dehydration of 2-propanol andcumene cracking is shown in Figure 7. Mesoporous silicate SiMCM-41 showed some catatlytic activity for thedehydration of 2-propanol and the product was mainly propylene. However, SiMCM-41 was observed inactive forcumene cracking in employed condition which indicated the absence of Broensted acid sites. Based on these results,it can be assumed that SiMCM-41 has low surface acidity and mainly is Lewis acid. The activity of SiMCM-41 wasimproved after modification with Al and Ti impregnation. TiSiMCM-41 showed higher activity of 2-propanoldehydration than that of original SiMCM-41. However, no activity of cumene cracking was observed overTiSiMCM-41. On the other hand, AlSiMCM-41 showed remarkable high activity of 2-propanol and some activityof cumene cracking. These results showed that modification of SiMCM-41 with Al improved the surface acidity ofSiMCM-41 and generated both of Broensted and Lewis acid sites. Therefore, it can be concluded that Al is effectiveas modifier metal in order to enhance surface acidity of SiMCM-41. 100 2-PA Dehydration Cumene cracking 80 Conversion (%) 60 40 20 0 SiMCM-41 Al(4) Ti(4) Zr(4) SiMCM-41 SiMCM-41 SiMCM-41Figure 7 – Catalytic activities of surface modified SiMCM-41 in 2-PA and cumene cracking. B–6–6
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183Infrared study of support materials mesoporous MCM-41 We proposed in previous study that surface acidity of support material plays an important role for highactivity of Pt/mesoporous material catalyst system for thiophene hydrodesulfurization [1,2,7]. In order to clarify theacidic properties of synthesized mesoporous aluminosilicate MCM-41 and the effect of modification of mesoporoussilicate MCM-41 with Al2O3, we observed the infrared spectras of SiMCM-41, SiAlMCM-41, surface modifiedSiMCM-41 in the pyridine adsorption. Figure 8 shows infrared spectras of pyridine adsorbed on SiAlMCM-41(Si/Al=30, 15, 5). Pyridine was adsorbed at 100°C followed with subsequent evacuation at the same temperature. Itwas observed that SiMCM-41 showed weak absorption band of coordinated pyridine on Lewis acid site indicatingthe present of small amount of Lewis acid sites. In the case of SiAlMCM-41, absorption bands of coordinatedpyridine on Lewis acid site was observed along with small absorption bands based on Bronsted acid sites around1550 cm-1. It was observed that surface acidity of SiAlMCM-41 is in good relationship with Si/Al ratio, whichacidic property of SiAlMCM-41 is greater for lower Si/Al ratio. Figure 9 shows infrared spectras of MeSiMCM-41 in the hydroxyl group region. The spectras were recordedafter evacuation at 500°C for 2 hours. For SiMCM-41 the silanol group (Si-OH) was observed at 3743 cm-1. Afterimpregnation with Al the SiOH absorption band was almost unchanged, indicating weak interaction of surface SiOHwith Al2O3 particle. The SiOH absorption band was decreased for modification of SiMCM-41 with Ti and Zr andshoulder absorption band was also observed. The appearance of this shoulder might indicate that surface Ti(SO4)2and ZrO2 particle interact strongly with surface SiOH. L Pyr 0 .1 B Pyr d) Abs c) b) a) 1570 1500 1400 W a v e N u m b e r [c m -1 ]Figure 8 – Infrared spectras of SiMCM-41 and SiAlMCM-41 (Si/Al = 30, 15, 5) in the pyridine adsorption region.a) SiMCM-41, b) SiAlMCM-41 (Si/Al=30), c) SiAlMCM-41 (Si/Al=15), d) SiAlMCM-41 (Si/Al=5). 3744 a) Abs b) 3680 c) d) 4000 3200 Wave number [cm-1]Figure 9 - Infrared spectras of MeSiMCM-41 in the –OH region. a) SiMCM-41, b) Al(4)SiMCM-41, c)Ti(4)SiMCM-41, d) Zr(4)SiMCM-41. Figure 10 shows the spectra of adsorbed pyridine on SiMCM-41 and MeSiMCM-41 support materials afterpyridine adsorption at 100°C. It was observed that SiMCM-41 show weak absorption band of coordinated pyridineon Lewis acid site indicating the presence of small amount of Lewis acid site. The modification of SiMCM-41 byimpregnation of Al2O3, Ti(SO4)2 and ZrO2 increased the intencity of absorption band of coordinated pyridine. In B–6–7
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183the case of Al as modifier, small absorption band based on Bronsted acid site was also observed around 1550 cm-1.The absorption band of Bronsted acid site was not observed for other MeSiMCM-41 at this measurement condition.Based on these results, it is concluded that modification of SiMCM-41 with Al is more effective for generation ofBronsted acid site over SiMCM-41 than using Ti or Zr. L Pyr 1492 d) B Pyr A bs c) 1456 b) 1547 a) 1447 1580 1400 Wave number [cm-1]Figure 10 - Infrared spectras of MeSiMCM-41 in the pyridine absorption region. a) SiMCM-41, b) Al(4)SiMCM-41,c) Ti(4)SiMCM-41, d) Zr(4)SiMCM-41.Conclussions It was revealed in current study that the application of moderate acidic mesoporous materials as supportmaterial for Pt catalysts (Pt/SiAlMCM-41) improved significantly the catalytic performance of thiophenehydrodesulfurization. Some methods of siliceous MCM-41 modification, such as using Al2O3 or Al-sec-butoxidewas demonstrated as effective ways to control surface acidity of support material MCM-41 in order to synthesizehighly active hydrodesulfurization catalysts. Based on the results, we propose a possible mechanism for thiophenehydrodesulfurization over Pt/mesoporous materials as shown in scheme-1. In the proposed mechanism, thiophene isactivated on the acid site of mesoporous silicates and hydrogen is activated on Pt to form spillover hydrogen. Thespillover hydrogen formed on Pt particle attacks the activated thiophene formed on the acid site of mesoporoussilicates.Scheme-1. Model of hydrodesulfurization mechanism over Pt/Mesoporous catalysts.References[1] Sugioka M., (1995), "Highly active zeolite-based hydrodesulfurization catalysts", Erdol and Kohle, ErdgasPetrochemie, Vol. 48, p. 128-132[2] Sugioka M., Tochiyama C., Matsumoto Y., Sado F, (1995), "Hydrodesulfurization of Thiophene over NobleMetals Supported on ZSM-5 Zeolites", Studies in Surface Science and Catalysis, Vol 94, p. 544-549.[3] Sugioka M., Andalaluna L., Morishita S, (1997), Proc. 47th Canadian Chem. Eng. Conf., 765.[4] Beck J.S., Vartulli J.C., Roth W.J., Leonowicz M.E., Kresge C.T., Smith K.D., Chu T.W., Olson D.H.,Sheppard E.W., McCulleni S.B., Higgins J.B., Schlenker J.L., (1992), “A New Family of Mesoporous MolecularSieves Prepared with Liquid Crystal Templates”, J. Am. Chem. Soc., 114, p. 10834-10843.[5] Inagaki S., Fukushima Y., Kuroda K., (1993), “Synthesis of Highly Ordered Mesoporous Materials from aLayered Polysilicate”, J. Chem. Soc. Chem. Commun., p. 680-682. B–6–8
    • PROSIDING KONGGRES DAN SIMPOSIUM NASIONAL KEDUA MKICS 2007 ISSN : 0216 - 4183[6] Zhao D., Feng J., Huo Q., Melosh N., Fredrickson G., Chmelka B.F., Stucky G.D., (1998), “Triblock CopolymerSynthesis of Mesoporous Silica with Periodic 50 to 300 Angstrom Pores” , Science, 279, p. 548.[7] Andalaluna L., Sugioka M., Morishita S. and Kurosaka T., (2001), “Development of Mesoporous ZeolitesSupported Noble Metals as New Generation Hydrodesulfurization Catalysts”, Proc. RSCE 2001, p. CR15-1-6. B–6–9