Format And Type Fonts CHEMICAL ENGINEERING TRANSACTIONS VOL. 45, 2015 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Petar Sabev Varbanov, Jiří Jaromír Klemeš, Sharifah Rafidah Wan Alwi, Jun Yow Yong, Xia Liu Copyright © 2015, AIDIC Servizi S.r.l., ISBN 978-88-95608-36-5; ISSN 2283-9216 DOI: 10.3303/CET1545213 Please cite this article as: Choopun W., Jitkarnka S., 2015, Enhancing bio-kerosene and bio-gas oil production from bio- ethanol dehydration using the hierarchical mesoporous msu-szsm-5, Chemical Engineering Transactions, 45, 1273-1278 DOI:10.3303/CET1545213 1273 Enhancing Bio-Kerosene and Bio-Gas Oil Production from Bio-ethanol Dehydration Using The Hierarchical Mesoporous MSU-SZSM-5 Waranpong Choopun a,b , Sirirat Jitkarnka* ,a,b a The Petroleum and Petrochemical College, Chulalongkorn University, 254 Soi Chulalongkorn 12, Phayathai Rd. Pathumwan, Bangkok 10330, Thailand b Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University Research Building, Soi Chulalongkorn 12, Phayathai Rd., Bangkok 10330, Thailand sirirat.j@chula.ac.th HZSM-5 zeolite has been noticed for its potential to convert bio-ethanol to monoaromatics hydrocarbons such as C6-C8s due to its suitable pore size and shape selectivity. In case of producing heavier hydrocarbons, a catalyst with larger pore sizes is necessary. In this work, the hierarchical mesoporous MSU-S embeded with ZSM-5 seed (MSU-SZSM5) was employed, aiming to produce heavier hydrocarbon compounds from bio- ethanol dehydration. MSU-SZSM5 was synthesized using TPAOH as a structure directing agent and CTAB as a surfactant. The characterization of catalysts was performed by using XRD with both small- and wide-angle modes, SAA, and XRF. Bio-ethanol dehydration was conducted in a U-tube fixed bed reactor at 450 °C for 8 h at 0.5 -1 h LHSV of bio-ethanol. Then, the gaseous products were analyzed by using GC-TCD, and ethanol conversion was examined by using GC-FID. The oil products were analyzed by using SIMDIST GC for petroleum fractions and GCxGC-TOF/MS for oil compositions. As a result, the hierarchical mesoporous MSU- SZSM5, found to have hexagonal structure, can produce more bio-kerosene and gas oil than conventional HZSM-5. For the oil compositions, C9 and C10 + aromatics hydrocarbons were the majority. 1. Introduction Nowadays, the world is facing the depletion of petroleum sources. Demand of the oil is still rising which is the opposite way with the amount of resources. Therefore, some alternative fuels such as bio-ethanol had been studied. Bio-ethanol can be produced by fermentation process of agricultural feedstocks such as corn, sugarcane, and cassava. It has many advantages such as renewable source, reduce greenhouse gases. Purified bio-ethanol can be blended with gasoline to be gasohol E10, E20, and E85 for use in the vehicles. Moreover, bio-ethanol can be used as a feedstock to produce valuable hydrocarbons via dehydration process. The previous research studied on HZSM-5 zeolite catalyst to produce ethylene (Takahara et al., 2005) and propylene (Takahashi et al., 2012). In addition, HZSM-5 also has potential to convert ethanol into liquid hydrocarbons. Talukda et al. (1997) studied effect of temperature on product distributions. They found that when temperature increased, the liquid yield was decreased via cracking activity. However, aromatic hydrocarbons such as benzene, toluene, xylenes exhibited an increasing trend when increasing temperature. Rownaghi et al. (2011) studied the yield of gasoline range hydrocarbons via methanol dehydration ZSM-5 with uniform crystal size. The results showed that light olefins (ethylene and propylene), and paraffins (C1-C4) selectivities were increased when the crystal size of ZSM-5 decreased. Furthermore, nano-size ZSM-5 also gave better catalytic stability than conventional ZSM-5. Not only can methanol dehydration be catalyzed by HZSM-5, but also ethanol dehydration using HZSM-5 had been studied. Viswanadham et al. (2012) studied ethanol to gasoline using nano-crystalline HZSM-5. The results showed that nano-crystalline HZSM-5 gave higher gasoline yield than that of micro-crystalline. The nano-crystalline HZSM-5 exhibited the additional mesoporosity by stacking of nano-crystal, which can enhance gasoline production. The obtained gasoline contained a low concentration of benzene, but high concentrations of xylenes, toluene, and isodecane, which was suitable for fuel applications. Bio-ethanol dehydration using HZSM-5 was also studied by 1274 Kittikarnchanaporn et al. (2014). The results showed that HZSM-5 had a great potential to convert bio-ethanol into hydrocarbons. Propane was the main component in the gas due to H-transfer to propylene. Moreover, HZSM-5 gave the highest oil yield compared to HY and HBeta, and C9 and C10 + aromatic hydrocarbons were the main composition in oil. Although, microporous catalysts had potentials to convert bio-ethanol into hydrocarbons, but their small pore size limits the production of heavy hydrocarbons. Liu et al. (2001) synthesized MSU-S aluminosilicate mesostructure assembled from ZSM-5 and Beta seeds. MSU-S with hexagonal mesostructure was assembled by cetyltrimetylammonium bromide (CTAB) as a surfactant. Both of MSU-S with ZSM-5 and Beta seeds had higher hydrothermal stability and higher cumene cracking activity than those of Al-MCM-41. Moreover, MSU-S with ZSM-5 seed (MSU-SZSM-5) was studied for methanol dehydration by Rashidi et al. (2013). In their work, MSU-SZSM5 was used to convert methanol into dimethyl ether (DME). They found that MSU-SZSM5 gave DME selectivity up to 100 % at 320 °C, and the coking rate on MSU-SZSM5 was also slower than the conventional zeolite catalysts because of its larger pore size. Furthermore, bio-ethanol dehydration using MSU-S with Beta seeds as a catalyst was also investigated by Sujeerakulkai and Jitkarnka (2014), aiming to produce more kerosene- and gas oil-range products. The results exhibited that ethylene was the main component in the gas stream, and the oils contained a high amount of C9 and C10 + aromatics due to its large pore size. Mesoporous zeolites can be divided into three categories that are hierarchical zeolites, nano-crystal sized zeolites, and supported zeolites. The hierarchical zeolites are the ones that have additional meso-porosity in each crystal, and also have intercrystalline pore, normally defined as macropore. The nano-crystal sized zeolites typically have crystal sizes below 100 nm. Either intracrystalline or intercrystalline systems can be found in the nano-crystal sized zeolites, defined as the micropore and mesopore system. The last one is supported zeolites, defined as those of which are supported or dispersed in the pore of another material. The mesopore systems therefore depend on the nature of the support material (Egeblad et al., 2008) Normally, the stability of a hierarchical mesoporoucatalyst is higher than a microporous catalyst due to their larger pore size that allows large hydrocarbon molecules to pass throughout. Moreover, Ramasamy et al. (2014) synthesized nano-size hierarchical HZSM-5 with mesoporore created from stacked nano-crystals, and compared its stability with that of a conventional HZSM-5 at the same Si/Al ratio on ethanol dehydration to hydrocarbons. It was found that the nano-sized hierarchical HZSM-5 gave higher actual/theoretical oil yield and higher olefinic compound than the conventional HZSM-5. Moreover, it exhibited the higher catalytic stability than the conventional one at all Si/Al ratios. Thus, a hierarchical mesoporous HZSM-5 has great potential and high stability to convert bio-ethanol into fuel range products contaning toluene, and xylenes due to its large mesopore size. In this work, the hierarchical mesoporous MSU-SZSM5, which is the composite of ZSM-5 and MCM-41 with a large mesopore size, was therefore investigated in the dehydration of bio-ethanol, aiming to produce heavy petroleum fractions such as kerosene and gas oil. 2. Experimental 2.1 Synthesis of the hierarchical mesoporous MSU-SZSM5 To prepare the ZSM5-seed solution, 10.2 g of tetrapropylammonium hydroxide (TPAOH, 40 %wt) was added into 79.26 g of deionized water. After that, 0.34 g of sodium aluminate and 6.0 g of fumed silica as an aluminum and silicon sources were sequentially added into the solution of TPAOH and deionized water. The solution was kept stirred at 50 °C for 18 h to form the ZSM5-seed solution. Then, 100 g of deionized water and 9.44 g of CTAB were mixed with the ZSM5-seed solution. The final gel was hydrothermally treated in a Teflon- line autoclave at 150 °C for 2 d to form the mesoporestructure. After the solution was filtered, washed, and dried, the white powder was ion-exchanged with 0.1M NH4NO3 in 96 % ethanol at 80 °C reflux temperature for 2 h. The final catalyst was dried and calcined at 1 °C/min to 550 °C kept for 10 h to obtain the MSU-SZSM5 (Rashidi et al., 2013). Then, the calcined sample powder was pelletized by pelletizer, crushed, and sieved into 20 - 40 mesh particles before use in the reactor. 2.2 Catalyst characterization The surface area (BET), pore volume (Horvath Kawazoe method), and pore size (Barrett-Joyner-Halenda method) were determined based on N2 physisorption using the Thermo Finnigan/Sorptomatic 1990. Both of small- and wide-angle modes of XRD patterns of the zeolites were determined by Rigaku SmartLab®. For the small-angle mode, the machine collected the data from 1 o – 7 o at 1 o /min. For the wide-angle mode, the machine collected the data from 5° – 50° at 5°/min. The Si/Al ratio of the synthesized MSU-SZSM5 was determined by X-ray Fluorescence Analyzer (XRF). 1275 2.3 Catalytic dehydration of bio-ethanol 99.5% purity bio-ethanol was obtained from Sapthip Co., Ltd. The catalytic dehydration of bio-ethanol was performed in a U-tube fixed bed reactor under atmospheric pressure at 450 °C for 8 h with 3 g of catalyst using helium as a carrier gas as shown in Figure 1. Bio-ethanol was fed at 2 mL/h mixed with helium at 13.725 mL/min. The gaseous products were analyzed by using a GC-TCD (Agilent 6890N) for compositions, and a GC-FID (Agilent 6890N) was used to determine the ethanol conversion. The liquid product was condensed in the collector in an ice bath. Then, CS2 was used to extract the oil from the liquid products. After that, a SIMDIST GC was used to determine the true boiling point curve of oils. The range of boiling point indicates the type of petroleum products; < 149 °C for gasoline, 149 – 232 °C for kerosene, 232 – 343 °C for gas oil, 343 – 371 °C for light vacuum gas oil, and > 371 °C for high vacuum gas oil (Dũng et al., 2009). The oil composition was determined by using Gas Chromatograph equipped with a Mass Spectrometry of “Time of Flight” type (GC×GC- TOF/MS) (installed with Rxi-5SilMS and RXi-17 consecutive columns). The conditions were set as follows: the initial temperature was set at 50 °C held for 30 min, the heating temperature was set at 2 °C/min in range 50 – 120 °C/min, and 10 °C/min in range 120 – 310 °C with split ratio of 5. Figure 1: Experimental set-up of bio-ethanol dehydration 3. Results and discussions 3.1 Catalyst characterization X-ray Diffraction (XRD) pattern in both small-angle (1 – 7°) and wide-angle (5 – 50°) modes were dertermined by Rigaku Smartlab®. Surface area, pore volume and pore size of the MSU-SZSM5 was determined by using Thermo Finnigan/Sorptomatics 1990. The crystallographic spectra of the hierarchical mesoporous MSU-SZSM5 was determined by using XRD in the small-angle mode (SAX) and wide-angle mode are shown in Figures 2 (a) and (b), which indicate that MSU-SZSM5 semi-crystalline structure was successfully synthesized. Figure 2: (a) SAX pattern of MSU-SZSM5, and (b) XRD pattern of HZSM-5 and MSU-SZSM-5 From Figure 2 (a), the SAX pattern of MSU-SZSM5 exhibited a strongly peak at d100 which confirms that the mesostructure of MSU-SZSM5. However, two peaks at d110 and d200 were unclearly separated from one another 1276 which indicate that the success synthesizing MSU-SZSM5 with a non-uniform hexagonal structure (Schwanke et al., 2013). Figure 2 (b) exhibits the characteristic peaks of HZSM-5 zeolite located at 7.94°, 8.89°, 14.77°, and 23.96°. Although MSU-SZSM5 has a broad reflection at about 23°, but it corresponds to the diffraction peak of HZSM-5 (Park et al., 2011). The result from XRF shows that MSU-SZSM5 has the Si/Al2 ratio of 39.6. Next, Figure 3 (a) exhibits the N2 adsorption-desorption isotherm of MSU-SZSM5, which illustrates the same sudden step as Al-MCM-41 at P/P0 nearby 0.35 (Triantafyllidis et al., 2007). Furthermore, Figure 3 (b) shows the pore size distribution of the hierarchical mesoporous MSU-SZSM5. The micropore and mesopore diameters of MSU-SZSM5 determined by using H.K. and B.J.H methods are at 8.97 and 28.66 Å. Moreover, the synthesized MSU-SZSM5 also has three times higher surface area than the conventional HZSM-5 as shown in Table 1. Figure 3: (a) N2 adsorption-desorption isotherm, and (b) Pore size distribution of MSU-SZSM5 using B.J.H method Table 1: Physical properties of HZSM-5 and MSU-SZSM5 a Determined by BET method, b Determined by H.K. method, and c Determined by B.J.H. method Figure 4: (a) Petroleum fractions, and (b) True boiling point curves of HZSM-5 and MSU-SZSM5 3.2 The activity of MSU-SZSM5 on bio-ethanol dehydration For the dehydration of bio-ethanol, MSU-SZSM5 exhibited high ethanol conversion about 99.7 %. The large pore size of MSU-SZSM5 tends to produce a high gaseous yield (84.6 %) with a low oil yield (3.7 %). The main component in the gas products from using MSU-SZSM5 was ethylene (98.7 %), followed by propane and Catalyst Surface area (m 2 /g) a Pore volume (cm 3 /g) b Micropore Diameter (Å) b Mesopore Diameter (Å) c HZSM-5 361.2 0.159 8.97 - MSU-SZSM5 1,028.3 1.02 5.97 28.66 (a) 1277 ethane, accordingly. Due to its larger pore size, the hierarchical mesoporous MSU-SZSM5 gives greater quantities of kerosene- and gas oil-range products than the conventional HZSM-5 that yield mostly gasoline, as shown in Figure 4 (a). Moreover, the true boiling point curves of HZSM-5 and MSU-Szsm5 are compared in Figure 4 (b), which indicates that MSU-SZSM5 gives significantly heavier oil. Furthermore, from GCxGC-TOF/MS results, the large pore size of MSU-SZSM5 favours C10 + and C9 aromatics production in contrast with the medium pore size of HZSM-5 that is proper to produce toluene and xylenes (Vu et al., 2006) because the large pore size of MSU-SZSM5 can also improve the diffusion of large hydrocarbon molecules. However, the result from using MSU-SZSM5 is different from nano-sized hierarchical HZSM-5 (Ramasamy et al., 2014). The mesoporous-stacked nano-sized hierarchical HZSM-5 gave higher olefinic but lower aromatic yield than conventional HZSM-5 whereas the hierarchical mesoporous composite of MSU- SZSM5 provides higher aromatic yield instead. Figure 5 illustrates that C10 + aromatics are the majority in oil (41.2 %wt), followed by based on C9 aromatics (22.4 %wt), and xylenes (12.6 %wt). In addition, the boiling points, C9 and C10 + aromatics are in kerosene and gas oil fractions. Figure 5: Oil composition from using HZSM-5 and MSU-SZSM5 4. Conclusions The hierarchical mesoporous MSU-SZSM5 employed in the dehydration of bio-ethanol was synthesized by using TPAOH as a structure directing agent and CTAB as a surfactant. The hexagonal mesostructure of MSU- SZSM5 was confirmed by using small-angled XRD whereas the wide-angle pattern of XRD assured the semi- crystalline structure. The synthesized MSU-SZSM5 also had 3 times higher surface area than the conventional HZSM-5. 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