Microsoft Word - TOC_R.doc HUNGARIAN JOURNAL OF INDUSTRIAL CHEMISTRY VESZPRÉM Vol. 37(2) pp. 107-111 (2009) FUEL PURPOSE HYDROTREATING OF VEGETABLE OIL ON NiMo/γ-Al2O3 CATALYST M. KRÁR1, S. KOVÁCS1, L. BODA2, L. LEVELES2, A. THERNESZ2, I. WÁHLNÉ, HORVÁTH, J. HANCSÓK1 1University of Pannonia, Institute of Chemical and Process Engineering, Department of Hydrocarbon and Coal Processing H-8201 Veszprém, P.O.Box.: 158, HUNGARY E-mail: hancsokj@almos.uni-pannon.hu 2MOL PLC. DS Development, Százhalombatta 2443, P.O.Box 1, HUNGARY The application of biofuels has become more important in the whole world since the last decades. Intensive research has been started for the production of biofuels which can be applied in Diesel engines and has different chemical composition from the previously used ones. Among these fuels the most important one is biogasoil (normal and iso-paraffins) produced from triglycerides with catalytic hydrotreating (special hydrocracking). The aim of present study was to investigate the applicability of commercial NiMo/γ-Al2O3 catalyst for conversion of specially pretreated Hungarian sunflower oil to produce motor fuel components. The change in the hydrotreating activity of applied catalyst, the pathways of hydrodeoxigenation reactions and the effect of process parameters (T= 300–360 °C, p= 20–60 bar, LHSV= = 0.5–2.0 h-1, H2/sunflower oil volume ratio: 400 Nm 3/m3) on the yield and composition of the products were also investigated. It was concluded that on the investigated NiMo/γ-Al2O3 catalyst products with relatively high (>50%) paraffin content (T = 360–380 °C, p = 60 bar, LHSV = 0.5–1.0 h-1) could be produced. The yield of the produced target fraction was 50.7–54.5% at these advantageous process parameters. So it is necessary to separate and recirculate the heavy fraction. In case of every investigated process parameter C18-, C17-, C16- and C15 normal paraffins were formed, i.e. both the HDO and the decarboxylation/ decarbonylation reactions took place. The cetane number of the target fractions, are very high (>80, EN standard: ≥51), but the cold flow properties of this fraction are disadvantageous. To improve this disadvantageous property it is necessary to carry out selective isomerization of the target fraction. Keywords: sunflower oil hydrotreating, biogasoil, paraffinic hydrocarbons Introduction The application of biofuels has become more important in the whole world since the last decades. In Europe the production and application of diesel fuels and/or blending components derived from biomass have been emerged into the focus due to the climate, geographical conditions and the increasing demand for diesel fuel [1]. Actually the biodiesel (fatty acid methyl esters) is practically the only bio derived component used in crude oil derived diesel fuels, however it and the biodiesel technologies, which applied alkali catalyst, have numerous disadvantages [2-6]. Because of these facts and to reach better quality, intensive research has been started for the production of biofuels, which can be applied in Diesel engines and has different chemical composition from the previously used ones [6-13]. Among these fuels the most important ones are in the near and medium future the biogasoils produced from triglycerides with catalytic hydrotreating (special hydrocracking). The biogasoil is a second generation biofuel, therefore their research, production and use are strongly supported by the European Union. The biogasoil contains mainly normal and isoparaffins having similar boiling point range as the conventional gas oil [6, 10, 11]. The normal and isoparaffins are the most advantageous components of crude oil derived diesel fuels because of their chemical structure, as they have cetane number and advantageous application technology properties at low temperature, too [15, 16]. Through the reactions of special hydrocracking of triglycerides primarily normal and isoparaffins, propane, CO2, CO, water and oxygenate compounds are formed on the applied catalyst(s) and process parameters. Through this process the triglyceride molecules transform according to the following reactions [17-19]: • saturation (hydrogenation) of double bonds, • heteroatom removal, deoxygenation, - hydrodeoxygenation (HDO reaction, reduction), - (hydro)decarboxylation, - (decarbonylation), • different side reactions: hydrocracking of fatty acid chain of triglycerides, water-gas-shift, etc. • isomerization of produced normal paraffins from deoxygenation. 108 C CH2 O OCH2 CH C O OCH2 C O O CH2 CH3CH2 CH CH 76 CH2 CH2 CH3CH2 CH CH 76 CH2 CH2 CH3CH2 CH CH 76 + 15 H2 3 n-C18H38 + C3H8 + 6 H2O + 6 H2 3 n-C17H36 + C3H8 + 3 CO2 + 9 H2 3 n-C17H36 + C3H8 + 3 CO + 3H2O I. III. II. Figure 1: Possible reaction pathways for oxygen removal from trioleic triglycerides Through the deoxygenation (Fig. 1) of tryglicerides in the HDO reaction (reaction route I.) 1 mol triglyceride molecule is converted to 3 mol n-paraffins having the same chain length as the fatty acid. The carbon number of the produced normal paraffins by decarboxylation (reaction route II.) and decarbonylation (reaction route III.) reactions are lower by one compared to the fatty acid chains of triglycerides [17, 19]. The produced mixture having high n-paraffin content (cold filter pluggin point – CFPP: 18–28 °C) has to be isomerized after separation to the necessary level to improve the flow properties. The biogasoil can be also used alone in Diesel engines, but in conventional utilization it is unnecessary to apply this excellent product. Furthermore, due to the limited availability of the currently used feedstock and the amount of the produced biogasoil allows limited application. Therefore the application of biogasoil as gas oil blending components will be primarily of practical significance. For the production of biogasoil several technologies are proposed in the literature: Neste Oil NExBTL [20], UOP/Eni EcofiningTM technology [18] and the SuperCetane process [9]. In the last couple of years our widespread and systematic research and development activity has been focused on the field of conversion of natural triglycerides to diesel fuels. In this paper the most important results of triglycerides hydrotreating obtained on commercial NiMo/γ-Al2O3 catalyst are presented. Experimental work Based on the introduction the aim of our experimental work was to determine the applicability of the commercial NiMo/γ-Al2O3 catalyst in the fuel purpose (hydrocarbons with high n-paraffin content in gas oil boiling range) hydrotreating (special hydrocracking) of properly pretreated Hungarian sunflower oil. Our objective was to study the change of the hydrocracking activity (deoxygention activity) and the effect of the operating parameters (temperature, pressure, LHSV) on the yield and the composition of products. Apparatus The experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. It contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant. The experiments were carried out in continuous operation [21]. The products of the experiment were fractionated to three main fractions: gaseous-, water- and liquid organic fractions. The liquid products which were separated in the separator of the apparatus contained water, hydrocarbons (C5 and larger) and compounds with oxygen content. The organic phases were separated from the water phase and analyzed without phase separation. Feedstock and catalyst The feedstock of the hydrotreating experiments was properly pretreated Hungarian sunflower oil (Table 1). Table 1: The main properties of the feedstock of hydrotreating Properties Value Density (15°C) g/cm3 0.9252 Acid number, mgKOH/g 2.2 Iodine number, g I2/100g 136 Water content, mg/kg 244 Fatty acid composition, % C16:0 6.5 C18:0 3.8 C18:1 20.7 C18:2 68.4 C22:0 0.6 The catalyst was an expediently chosen and commercial NiMo/γ-Al2O3 catalyst. The BET surface area of the catalyst was 115 m2/g, Mo-content was 2.9% and the Ni-content was 1.5%. Before the experiments we increased the temperature of catalyst “in-situ” with 25 °C/hour to 400 °C, then we held the temperature at 400 °C for 2 hours at a gas flow-rate of 40 dm3/h. Thereafter we decreased the temperature of the catalyst to the temperature of the first experimental point. 109 Process parameters The range of the chosen process parameters – based on our pre-experimental results – were the following: temperature 300–360 °C, total pressure 20–60 bar, liquid hourly space velocity (LHSV): 0.5–2.0 h-1 and H2/sunflower oil volume ratio: 400 Nm 3/m3. Analytical methods The properties of the feedstock and the products were measured according to standard methods (Table 2). The compounds of the products were determined with high temperature gas chromatograph on special column (6m x 0,53mm x 0,1 μm, DB5-HT AluClad column). Table 2: The applied analytical methods Properties Method Density EN ISO 12185:1996 Iodine number EN ISO 3961:2000 Acid number EN 14104:2003 Water content EN ISO 12937:2001 Hydrocarbon composition EN 15199-2:2007 Fatty acid composition EN ISO 5509:2000 EN 14103:2003 Results and discussion The main aim of the fuel purpose hydrotreating experiments of sunflower oil was – besides the saturation of double bonds – the removal of the oxygen atom from the sunflower oil and the production of the target fraction (primary C15-C18 n- and i-paraffins) in gas oil boiling range with the highest yield. Based on our results it can be concluded that the yield of the liquid organic fraction was higher than 88% in every case related to the weight of the feedstock (depending on the process parameters). The cause of this is the conversion of the oxygen content of the sunflower oil to water and CO2 (and CO) in different amounts, the elimination of propane and the lower carbon number (≤4) gas products formed by cracking reactions. The conversion of triglycerides increased with increasing temperature. The amount of the not conversed triglyceride was below 10% at 380 °C temperature, at 60 bar pressure and at every LHSV (Fig. 2). The conversion of triglycerides significantly increased with increasing pressure (if the other process parameters were constant) (Fig. 3). But at 300 °C the hydrocrack reactions took place only to produce carboxylic acids. Accordingly the organic fraction contained primarily carboxylic acids (methyl esters) and other esters, diglycerides and triglycerides and the amount of the target fraction was below 5%. The conversion of triglycerides decreased with increasing the LHSV (and decreasing the time on stream) so the content of triglyceride was higher in the product mixture (Fig. 4). But at 300 °C and 60 bar the deoxygenation reactions took place only in a little extent because the target fraction was formed in a small amount. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 280 300 320 340 360 380 400 Temperature, °C Y ie ld , % Paraffins up to C16 C17 paraffins C18 paraffins Carboxylic acids + FAMEs Other esters Diglycerides Triglycerides LHSV: 1.0h-1, p = 60 bar Figure 2: The yield of important compounds in organic phase as a function of the temperature (LHSV: 1.0 h-1; p = 60 bar) 0 5 10 15 20 25 30 35 40 45 50 10 20 30 40 50 60 70 Pressure, bar Y ie ld , % Paraffins up to C16 C17 paraffins C18 paraffins Carboxylic acids + FAMEs Other esters Diglycerides Triglycerides T=300°C, LHSV: 0.5h-1 Figure 3: A The yield of important compounds in organic phase as a function of the pressure (LHSV: 0.5 h-1; T = 300 °C) 0 10 20 30 40 50 60 70 0.0 0.5 1.0 1.5 2.0 2.5 LHSV, h-1 Y ie ld , % Paraffins up to C16 C17 paraffins C18 paraffins Carboxylic acids + FAMEs Other esters Diglycerides Triglycerides T=300°C, p=60 bar Figure 4: The yield of important compounds in organic phase as a function of the LHSV (p = 60 bar; T = 300 °C) 110 The yield of the target fraction (50.7–54.5%) was significantly lower at advantageous process parameters (370–380 °C, 60 bar, 0.5 h-1) than the theoretical values (82–86%). So it is necessary to separate the target fraction from the not converted triglyceides and from the produced intermediates. The heavy fraction has to be recirculated to the reactor after the separation. One of the intermediates, which were formed by the special hydrocracking reactions, is the different carboxylic acids. The yield of this intermediate at the applied pressure and LHSVs changed according to maximum curve as a function of temperature. The maxiumal yield of carboxylic acids were between 320–340 °C (LHSV: 0.5 h-1), about 340 °C (LHSV: 1.0 h-1), and about 360 °C (LHSV: 1.5 h-1 and 2.0 h-1) (Fig. 5). Consequently it is necessary to apply properly high temperature in order to convert the intermediates to valuable components (target fraction) in further reactions. 0 5 10 15 20 25 30 35 40 280 300 320 340 360 380 400 Temperature, °C Y ie ld o f ca rb ox yl ic a ci ds , % . p=60 bar, LHSV=2.0h-1 p=60 bar, LHSV=1.5h-1 p=60 bar, LHSV=1.0h-1 p=60 bar, LHSV=0.5h-1 Figure 5: The yield of the produced carboxylic acids as a function of the temperature (p = 60 bar) Based on the hydrocarbon composition (determined by gas chromatograph) it can be concluded that these intermediates are converted primarily to C16 and C18 paraffins in HDO reaction and to C15 and C17 paraffins in the decarboxilation/decarbonylation reaction and in a lower amount to C14 and shorter hydrocarbons (with cracking of C–C bonds) The yield of the C18 paraffins which were formed in HDO reaction – similarly to the yield of carboxylic acids – changed according to maximum curve as a function of temperature (Fig. 6) so the amount of C18 paraffins significantly decreased with further strictening of the process parameters due to the chain crakcing reactions. The yield of C17 paraffins which were obtained by decarboxylation/decarbonylation reactions changed similarly to the yield of C18 paraffins for example at the lowest LHSV (0.5 h-1) (Fig. 7). The yield of C17 paraffins increased with increasing the temperature at higher LHSVs. The further increase of the temperature will probably increase the rate of chain cracking reactions and the yield of C17 paraffins will be lower, too. 0.0 5.0 10.0 15.0 20.0 25.0 30.0 280 300 320 340 360 380 400 Temperature, °C Y ie ld o f C 18 p ar af fs , % . p=60 bar, LHSV=2.0h-1 p=60 bar, LHSV=1.5h-1 p=60 bar, LHSV=1.0h-1 p=60 bar, LHSV=0.5h-1 Figure 6: The yield of the C18 paraffins as a function of the temperature (p = 60 bar) 0 2 4 6 8 10 12 14 16 280 300 320 340 360 380 400 Temperature, °C Y ile d of C 17 p ar af fin s, % . p=60 bar, LHSV=2.0h-1 p=60 bar, LHSV=1.5h-1 p=60 bar, LHSV=1.0h-1 p=60 bar, LHSV=0.5h-1 Figure 7: The yield of the C17 paraffins as a function of the temperature (p = 60 bar) To summarize the results we concluded that in case of every investigated process parameter the C18-, C17-, C16- and C15 paraffins were formed, i.e. on the applied catalyst both the HDO and the decarboxylation/decarbonylation reactions took place. We obtained the target fraction (gas oil boiling range fraction) with destillation of organic fractions. These target fractions, which were produced under optimal process parameters (360–380 °C, 60 bar, 0.5 h-1, 400 Nm3/m3), contained more than 95% normal paraffins (from this 5.3–6.9% n-C15, 19.2–29.1% n-C16, 16.5–18.0% n-C17, 20.3–34.0% n-C18) and <5% isoparaffins. The use of the target fraction as engine fuels (diesel) is limited, because its cetane number is high (>80) but its CFPP value is also high (>20 °C). So to improve this disadvantageous property it is necessary to carry out selective isomerization of the target fraction. Summary To summarize the results, it can be concluded that with the hydrotreating (special hydrocracking) of sunflower oil high paraffin containing (>50%) product mixtures 111 (target fraction) with high yield can be produced on the applied NiMo/γ-Al2O3 catalyst. But it is necessary to apply high pressure (p = 60 bar), high temperature (T = 360–380 °C) and low LHSV (LHSV = 0.5–1.0 h-1); for example 370–380 °C, 60 bar, 0.5 h-1. The yield of the produced target fraction (gas oil boiling range fraction) was significantly lower (50.7– 54.5%) at advantageous process parameters (370–380 °C, 60 bar, 0.5 h-1) than the theoretical values (82–86%). That is why it is necessary to separate and recirculate the heavy fraction. The conversion of triglycerides significantly increased with increasing pressure, but at lower temperature (300 °C) the hydrocracking reactions took place only until the formation of carboxylic acids. The yield of produced intermediates (esters, carboxylic acids) and the target fraction changed according to maximum curve as a function of temperature in every LHSV. In case of every investigated process parameter the C18-, C17-, C16- and C15 paraffins were formed, i.e. on the applied catalyst both the HDO and the decarboxylation/decarbonylation reactions took place. The cetane number of the target fractions which were obtained from organic fraction with distillation are very high (>80, EN standard: ≥51), but the cold flow properties of this fraction are disadvantageous. So to improve this disadvantageous property it is necessery to carry out selective isomerization of the target fraction [8, 11]. REFERENCES 1. LARIVÉ J. F.: Concawe Review, 15 (2) (2006) 2. DEMIRBAS A.: Progress and recent trends in biodiesel fuels, Energy Conversion and Management, (2009) 50, 14–34 3. MEHER L. C., VIDYA S. D., NAIK S. N.: Technical aspects of biodiesel production by transesterification - A review, Renew. and Sust. Energy Reviews, (2006) 10, 248–268 4. KNOTHE G., VAN GERPEN J., KRAHL J.: The Biodiesel Handbook. The American Oil Chemists' Society, Champaign, IL USA, (2005) 303 pp 5. HANCSÓK J., KRÁR M., HOLLÓ A., THERNESZ A.: Újgenerációs bio-motorhajtóanyagok I., Magyar Kémikusok Lapja, (2006) 61(8), 260–264 6. HANCSÓK J., KRÁR M., MAGYAR SZ., BODA L., HOLLÓ A., KALLÓ D.: Investigation of the production of high cetane number biogasoil from pre- hydrogenated vegetable oils over Pt/HZSM-22/Al2O3, Microporous and Mesoporous Materials, (2007) 101, 148–152 7. TWAIQ F. A., ZABIDI N. A. M., MOHAMED A. R., BHATIA S.: Catalytic conversion of palm oil over mesoporous aluminosilicate MCM-41 for the production of liquid hydrocarbon fuels, Fuel Processing Technology, (2003) 84, 105–120 8. KLOPROGGE J. T., DUONG L. V., FROST R. L., A Review of the synthesis and characterisation of pillared clays and related porous materials for cracking of vegetable oils to produce biofuels, Environmental Geology, (2005) 47, 967–981 9. STUMBORG M., WONG A., HOGAN E.: Hydroprocessed Vegetable Oils for Diesel Fuel Improvement, Bioresource Technology, (1996) 56, 13–18 10. KRÁR M., MAGYAR SZ., THERNESZ A., HOLLÓ A. BODA L., HANCSÓK J.: Study of the hydrodeoxygenation of vegetable oils, 15th European Biomass Conference Proceedings, (2007), 1988– 1992 11. HANCSÓK J., KRÁR M., MAGYAR SZ., BODA L., HOLLÓ A., KALLÓ D.: Investigation of the production of high quality biogasoil from pre-hydrogenated vegetable oils over Pt/SAPO-11/Al2O3, Studies in Surface Science and Catalysis, (2007) 170, 1605– 1610 12. VAN VLIET O. P. R., FAAIJ A. P. C.: Fischer-Tropsch diesel production in a well-to-wheel perspective: A carbon, energy flow and cost analysis, Energy Conversion and Management, (2009) 50, 855–876 13. CHEW T. L., BHATIA S.: Catalytic processes towards the production of biofuels in a palm oil and oil palm biomass-based biorefinery, Bioresource Technology, (2008) 99, 7911–7922 14. Commission of the European Communities, An EU Strategy for Biofuels, COM(2006) 34 final, (2006) 15. CORMA A.: Zeolites in Oil Refining and Petrochemistry, Zeolite Microporous Solids: Synthesis, Structure, and Reactivity, (1992), 373–436 16. MURPHY M. J., TAYLOR J. D., MCCORMIK R. L.: NREL/SR-540-36805, (2004) 17. HUBER G. W., O’CONNOR P., CORMA A.: Processing biomass in conventional oil refineries: Production of high quality diesel by hydrotreating vegetable oils in heavy vacuum oil mixtures, Applied Catalysis A: General, (2007) 329, 120–129 18. KALNES T., MARKER T., SHONNARD D. R.: Green Diesel: A Second Generation Biofuel, International Journal of Chemical Reactor Engineering, (2007) 5, Article A48, 19. KRÁR M., HANCSΌK J.: Investigation of the Transformability of Vegetable Oil Containing Gas Oils with Heterogenous Catalyst, 7th International Colloquium Fuels Proceedings, (2009), 507–514 20. TURPEINEN H.: Renewable NExBTL diesel, Biofuel 2G Conference, Pamplona, Navarra, 24.01.2008. 21. NAGY G., HANCSÓK J., VARGA Z., PÖLCZMANN GY., KALLÓ D.: Investigation of hydrodearomatization of prehydrogenated gas oil fractions on Pt-Pd/H-USY catalysts, Topics in Catalysis, (2007) 45, 195–201