Article pubs.acs.org/EF
Diesel Fuel Containing Zeo-HVO Biocomponent Obtained from the ZEOFINING Process Łukasz Jęczmionek,* Wojciech Krasodomski, and Xymena Badura Oil and Gas Institute - National Research Institute, Lubicz 25A, 31-503 Kraków, Poland ABSTRACT: This paper presents the results of a study on a diesel fuel containing a biocomponent obtained by the innovative ZEOFINING process. In contrast to a typical hydrotreated vegetable oil (HVO) biocomponent, the biocomponent from the ZEOFINING process contains paraffin naphthenes and aromatics as well as n-paraffins and isoparaffins. The composition and characteristics of this compound differ essentially from those of other biocomponents, in that are typically used for diesel oil production. The biocomponent obtained in the ZEOFINING process was characterized by parameters such as cetane number, density, sulfur content, carbon residue, ash residue, flash point, and low-temperature properties that are consistent with the requirements of the EN 590 standard. The use of zeo-HVO can significantly increase the content of biocomponents in diesel fuel, as shown by the example of the ZHV70 fuel with 70 vol % content of biocomponents. The properties of this fuel comply with the requirements of the EN 590 standard.
1. INTRODUCTION Hydroconversion relying on catalytic hydrogenation and deoxidation of triglycerides to n-paraffins is the basic process for the preparation of hydrocarbon fuel from vegetable oils, as widely described in the literature.1−15 As a result of the poor low-temperature properties of n-paraffins obtained by direct hydroconversion of vegetable oils in many industrial processes, an additional processing stage of isomerization is used in the production of biofuels.1−3 Isomerization of vegetable oil as the initial stage of hydroconversion is an alternative approach for biofuel production.16 This path was used in the ZEOFINING process. The fundamentals of the ZEOFINING process are described in papers16−19 and patents.20−22 The essence of this process is the initial (prior to substantial hydroconversion) treatment of the raw material (vegetable oil) using a zeolite catalyst to modify fatty acid chains by isomerization. Hydroconversion of rapeseed oil that was initially zeoformed over the H-ZSM-5 catalyst was described in a previous report.19 Zeoformed rapeseed oil (zeoformate) in a mixture with an oil fraction was subjected to hydroconversion co-processing using the catalyst NiMo/Al2O3. The formation of isoparaffins instead of n-paraffins was confirmed as a result of zeoforming and hydroconversion of vegetable oil. It was found that the amount of cloud point (CP) hydroraffinates decreased with the increasing temperature of the rapeseed oil zeoforming process or with a “deeper” modification (isomerization) of fatty acid glyceride structures by proceeding at a constant pressure and constant liquid hourly space velocity (LHSV). Other reports18 have described the results of zeoforming of rapeseed oil and hydroconversion of obtained zeoformates (without any admixture of another faction) to the so-called zeoHVO. It was found that the modification of the porous structure of the H-ZSM-5 catalyst resulted in the formation of biocomponents containing aromatic compounds, paraffin naphthenes and isoparaffins. Hydroraffinates obtained with a catalyst characterized by the presence of meso- and macropores (7−32 nm) of 0.5 cm3/g (for a total pore volume of 0.6 cm3/g) © 2016 American Chemical Society
contained 15% aromatic compounds (including approximately 0.5% polycyclic), approximately 50−60% isoparaffins (C15− C19), and 25−35% n-paraffins. Hydroraffinates were characterized by higher density (825 kg/m3) and better lowtemperature properties [cold filter plugging point (CFPP)] at −12 °C compared to hydroraffinate oil from non-zeoformed vegetable oil (at a density of 782 kg/m3 and CFPP of 22 °C). Hydroraffinates of zeoformed rapeseed oil were characterized by a lower addition temperature of approximately 100 °C, an initial distillation temperature (174 °C) that was higher by approximately 40 °C, and a final distillation temperature of 379 °C. The effect of the type of vegetable oil (palm, rapeseed, and soybean oils) and zeoforming process parameters (variable pressure of zeoforming 1.7, 2.5, or 4.0 MPa) on the presence of aromatic hydrocarbons as biocomponents of zeo-HVO and their properties for hydroconversion with constant parameters was investigated in ref 16. The increase in the process pressure had the effect of reducing the content of aromatic hydrocarbons in hydroraffinates (zeo-HVO). The reduction of these hydrocarbon hydroraffinates obtained from the zeoformates of palm oil was significantly lower (from 11 to 9 wt %) than that for hydroraffinates of rapeseed or soybean oils (from 14− 15 to 8−9 wt %). Reduction of the content of aromatic hydrocarbons in hydroraffinates resulted in the reduction of the final distillation temperature [final boiling point (FBP)] of approximately 10 °C. Hydroraffinates of zeoformed rapeseed and soybean oils obtained under a pressure of 4.0 MPa were characterized and compared to the zeo-HVO obtained under a pressure of 1.7 MPa and showed worse (by a few degrees) lowtemperature characteristics (the CP and CFPP). The formation of the ring structures (aromatics and paraffin naphthenes) during the zeoforming of vegetable oils was Received: September 21, 2016 Revised: November 28, 2016 Published: December 15, 2016 621
DOI: 10.1021/acs.energyfuels.6b02429 Energy Fuels 2017, 31, 621−626
Article
Energy & Fuels
and a total pore volume of 0.6 cm3/g (0.5 cm3/g meso- and macropore volume). The acidity [by temperature-programmed desorption of ammonia (NH3-TPD)] was 0.25 mmol/g. The zeolite material used had the form of circular extrusions with a diameter of 2 mm and a length of 3−5 mm. A zeoforming catalyst in an amount of 100 mL (catalyst mass of approximately 88 g) was charged to the reactor and then dried at 150 °C at atmospheric pressure in a stream of nitrogen. Then, the nitrogen pressure was changed to 1.7 MPa, followed by treatment with the raw material (refined rapeseed oil fatty acid composition as shown in Table 1) at a rate of 100 mL/h (LHSV = 1.0 h−1) based on the volume of the catalyst in the catalyst bed. Simultaneously, the temperature was raised from 150 to 300 °C with the heating rate of 10 °C/h. The supplementary flow of gas (hydrogen) through the reactor was not used. After stabilization of the temperature 300 °C, a test was carried out for 12 h and then sampling of 2 L of zeoformate was begun. Each sample was collected for 20 h. The obtained zeoformates were subjected to hydroconversion. For this purpose, a flow reactor with a capacity of 100 mL (catalyst mass of approximately 86 g) was used, analogous to the previous stage of the process (zeoforming). The NiMo/Al2O3 catalyst used in this stage of the research was sulfided by the fraction of diesel oil with 2% sulfur [in the form of the dimethyl disulfide (DMDS) compound]. Next, the naphtha fraction with a low sulfur content was used for 24 h to remove sulfur from the apparatus. The following conditions were used for the hydroconversion: temperature of 350 °C, LHSV of 0.5 h−1, pressure of 4.5 MPa, and hydrogen feed of 1500 Nm3/m3. The resulting hydroraffinates were stripped with nitrogen for 1 h to remove the dissolved gases. 2.1.3. Biocomponent HVO. The biocomponent HVO (hydrorafined vegetable oil) obtained by the direct hydroconversion of rapeseed oil and isomerization of n-paraffins was used. This fraction was obtained from Aditen, Ltd. When compared, the properties of this HVO biocomponent were similar to the other biocomponents of this type.1−3 This product was used in the study as a representative HVO biocomponent. 2.1.4. FAME. Commercially available FAMEs manufactured from rapeseed oil and supplied by Aditen, Ltd. were used. 2.1.5. Fuel Additives. Energozol43 additive was used to improve the lubricity of the fuel. This additive was produced and supplied by the Oil and Gas Institute, National Research Institute, Poland. The properties of each fraction used in the study are presented in Table 3. 2.2. Preparation of Test Samples of Fuel. All components and biocomponents (Table 3) were stored in a refrigerator at 4.5−6 °C. For the preparation of samples, biocomponents were heated to the same temperature by leaving them at 25 °C for 24 h. The components were mixed in a volume defined by a uniform temperature, as described in Table 4, and each fuel was stirred for 20 min at 25 °C using a magnetic stirrer. Prior to determination of the physicochemical properties, the resulting fuel samples were stabilized by leaving them for 24 h at 25 °C in a heat chamber. Four fuels with the following compositions (vol %) were used: fuel 1 (ZHV70), 30% base diesel oil + 50% biocomponent from the ZEOFINING process (zeo-HVO) + 20% HVO; fuel 2 (ZH30), 70% base diesel oil + 30% biocomponent from the ZEOFINING process (zeo-HVO); fuel 3 (B30), 70% base diesel oil + 30% FAME; and fuel 4 (HV30), 70% base diesel oil + 30% HVO. 2.3. Research Methods Used. For the determination of the properties of the biocomponents and fuel samples, research methods specified in the standard for diesel EN 590 were used. Furthermore, this methodology was used for determining the CP and CFPP. All research methods used in this study are listed in Table 2.
associated with the oligomerization reactions of fatty acids, as reported in a previous paper.17 On the basis of 1H and 13C nuclear magnetic resonance (NMR) analyses, it was found that reactions occurring during the process include polyaddition reactions, leading to the formation of aromatic structures (ring) that may undergo hydrogenation to paraffin naphthenes during hydroconversion, and the Diels−Alder reaction, leading to the synthesis of aliphatic oligomers. A comparative study of fresh or waste rapeseed oil zeoforming on a porous H-ZSM-5 followed by the hydroconversion of obtained zeoformates in coprocessing embodiment was described in ref 23. It was found that the effect of zeoforming for improving the low-temperature properties of the final hydroraffinate waste oil was weaker than that of the fresh oil under the same process conditions. This paper presents the results of testing of the properties of conventional diesel fuel containing up to 30 vol % biocomponents obtained from rapeseed oil in the ZEOFINING process as well as the experimental HV70 fuel containing 70 vol % bio-hydrocarbons [hydrotreated vegetable oil (HVO) + zeoHVO)], including 50 vol % biocomponent zeo-HVO. The properties of the resulting fuel were related to those of other biocomponents and fuels, including fatty acid methyl ester (FAME) and HVO.
2. MATERIALS AND METHODS 2.1. Components and Biocomponents of Fuels Used in These Studies. To prepare the samples for diesel fuel testing, the following components and biocomponents were used. 2.1.1. Base Diesel Oil “Summer”. To prepare samples of diesel fuel with the content of biocomponent vegetable oils, the fuel base “summer” oil having characteristics typical of the fuels sold on the Polish fuel market was used. The base fuel consisted entirely of hydrotreated middle fractions from conservative crude oil, was supplied by Addition, Ltd., and was produced by a domestic petroleum refinery. 2.1.2. Biocomponent from the ZEOFINING Process (Biocomponent Called Zeo-HVO). In the study, we used a biocomponent from the ZEOFINING process. It was obtained by the zeoforming and hydroconversion of rapeseed oil (ZEOFINING process). The fatty acid content in triglycerides is shown in Table 1. The details of obtaining the biocomponent were consistent with the description given in the previous reports16−19 and can be summarized as follows: In the ZEOFINING process, two catalysts were used: the H-ZSM-5 zeoforming catalyst and the NiMo/Al2O3 hydrotreating catalyst. The H-ZSM-5 zeoforming catalyst was characterized by a silicon module of approximately 80−90, an external surface area of 150 m2/g,
Table 1. Fatty Acid Content in Triglycerides fatty acid
content in rapeseed oil (wt %)
miristic C14:0 palmitic C16:0 palmitoleic C16:1 stearic C18:0 oleic C18:1 linoleic C18:2 linolenic C18:3 arachidic C20:0 eikozenoic C20:1 behenic C22:0 erucic C22:1 lignoceric C24:0 nervonic C24:1 unidentified
0.1 4.3 0.2 1.9 63.2 18.5 7.4 0.6 1.6 0.4 1.4 0.2 0.1 0.1
3. RESULTS AND DISCUSSION 3.1. Cetane Number. The cetane number for the base diesel and FAME was approximately 51.3 and was therefore equal to the minimum value required by the standard EN 590.24 Cetane numbers of other biocomponents (zeo-HVO and HVO) were significantly higher (∼70 and ∼90, respectively). 622
DOI: 10.1021/acs.energyfuels.6b02429 Energy Fuels 2017, 31, 621−626
Article
Energy & Fuels
less restrictive,3 allowing for the use of HVO biocomponents in a wider range than for the EN 590 standard. However, it should be noted that lowering the density of a diesel fuel results in an increase in its combustion, limiting the positive impact of the reduction of harmful exhaust gas emissions.25,26 3.3. Viscosity. The values of this parameter for the base oil and biocomponents were in the range indicated by the EN 590 standard.24 In the case of bioadditives to the base oil of 30 vol %, there was no deterioration in this parameter. 3.4. Distillation Characteristics. In comparison of the characteristics of the distillation used in this work to base diesel oil, it was found that the zeo-HVO component had the broadest range of boiling (174.0−379.3 °C), while the FAME biocomponent FAME had the narrowest range (295.3−356.3 °C) (Table 3). However, we noted that the FAME distillation decomposed under normal conditions.26 The zeo-HVO biocomponent was characterized by a relatively high FBP of the distillation that was tens of degrees higher than that for the HVO biocomponent.27 This phenomenon was probably due to the formation of fatty acid oligomers (increased FBP) during zeoforming, which then underwent oligomerization during the hydroconversion of paraffin hydrogenated to naphthenes or branched aliphatic hydrocarbons.17 The zeo-HVO biocomponent parameters did not meet the EN 590 standard, “up to 350 °C recovered of >85 vol %” requirement (Table 3). The impact of individual biocomponents of the diesel fuel distillation characteristics using mixtures containing 30 vol % biocomponents is shown in Figure 1. The distillation curves for the different fuels with biocomponents are shown in Figure 2. The addition of biocomponent zeo-HVO generally caused an increase in the boiling temperature of fuel, almost to the full extent with respect to the fuel containing FAME and HVO. This effect was particularly pronounced for the ZHV70 fuel containing 50 vol % zeo-HVO and 20 vol % HVO. However, the fuel with the composition characterized by the distillation parameters conformed to EN 590.24
Table 2. Research Methods Used parameter cetane number density at 15 °C distillation characteristic sulfur content carbon residue (on 10% distillation residue) ash content flash point cloud point (CP) cold filter plugging point (CFPP) lubricity aromatic hydrocarbon content
method EN EN EN EN EN EN EN EN EN EN EN
ISO 5165 ISO 12185 ISO 3405 ISO 20884 ISO 10370 ISO 6245 ISO 2719 ISO 3015 ISO 3016 ISO 12156-1 12916
The addition of these biofuels increased the cetane number of the fuel, while the addition of 30% FAME did not have any effect on this parameter (Table 4). In the case of a 30 vol % admixture of zeo-HVO or HVO, the cetane number of the fuel was increased by more than 10 units. The results were consistent with the previous reports by other authors.25 3.2. Density. Comparison of the diesel oil to biocomponents (Table 3) showed that the HVO and FAME had the lowest and highest densities, respectively, and that the value of this parameter is not within the range required by the EN 590 standard.24 In contrast, the component obtained from the ZEOFINING was characterized by a density that is within the range indicated by the EN 590 standard. Therefore, the addition of zeo-HVO base oil in an amount of 30 vol % did not lead to the deterioration of this parameter, but the order of the addition of FAME or HVO led to a change in the density to a level inconsistent with the requirements of the standard. According to some authors,3 up to 30 vol % HVO can be added to the conventional diesel without exceeding the EN 590 requirements but the high content of biocomponents requires a base oil with special density characteristics.3 For the U.S. ASTM D975 standard, the requirements for the densities are
Table 3. Properties of Biocomponents in Comparison to EN 590 Requirements property cetane number density at 15 °C viscosity at 40 °C distillation initial boiling point (IBP) final boiling point (FBP) up to 250 °C recovered up to 350 °C recovered sulfur content carbon residue (on 10% distillation residue) ash content flash point cloud point (CP) cold filter plugging point (CFPP) lubricity aromatic hydrocarbon content, monocyclic aromatic hydrocarbon content, dicyclic aromatic hydrocarbon content, polycyclic
unit
ON
zeo-HVO
FAMEa
HVO
kg/m3 mm2/s
51.3 834 3.5
∼70 825 3.2
51 883 4.5
∼90 775 2.8
°C °C vol % vol % mg/kg wt % wt % °C °C °C μm wt % wt % wt %
173.2 363.4 35.3 93.5 6 0.06
