润滑油资料

du hy ian ity td, M tch 0 A men ber distribution. Concentrations of monocycloalkanes and isoparaffins in importance in understanding the nature and application of petroleum products [1]. Normal paraffins cannot be tolerated in a used in several refineries. In this process, hydrocracker bottoms, hydrotreated vacuum gas oils, and gas oils from deasphalted of platinum metal and acid sites [4]. Some researchers have applied the pore mouth and key–lock mechanisms to explain the formation of monomethyl and dimethyl branching of long n- alkanes over a Pt/H-ZSM-22 bifunctional catalyst [5–7]. Fuel Processing Technology 87 ⁎ Corresponding authors. Shen is to be contacted at 130 Meilong Road, ECUST, P. O. Box 435, 200237, Shanghai, PR China. Tel.: +86 21 64252916; fax: +86 21 64252160. Ng, National Centre for Upgrading Technology, 1 Oil lube base oil due to their high pour points (being waxy) whereas branched paraffins and monocycloalkanes with alkyl side chains are acceptable as they have lower pour points and viscosities and good viscosity indexes (VIs) [2]. On this basis, Chevron developed a hydroisomerization process for dewaxing in 1992. Compared with solvent dewaxing and catalytic dewaxing, hydroisomerization dewaxing was found to give a higher oil yield with equivalent VI [3]. In China, both Sinopec and Petrochina have used Chevron's technology for producing higher-quality base oils over the past decade. Sinopec's Fushun vacuum residua (simply called deasphalted oils or DAOs in this paper) can be used as feedstocks for producing higher VI lube base oils (VIN95) or white oils (to be explained later). On hydroisomerization of long-chain normal paraffins, Girgis and Tsao determined the reaction pathway and kinetics of n-hexadecane hydroisomerization/hydrocracking in the presence of each of the following platinum-containing dual- function catalysts: a proprietary zeolite, a silica–alumina catalyst, and an MCM-41 catalyst. They used the classical bifunctional reaction scheme to explain the changes in reaction pathways based on the differences in the relative concentrations the lube base oil cut had a significant impact on its viscosity index and pour point. © 2006 Elsevier B.V. All rights reserved. Keywords: Deasphalted oil; Hydroisomerization; Carbon number distribution; Hydrocarbon type 1. Introduction Hydrocarbon types of petroleum fractions are of prime Research Institute of Petroleum and Petrochemicals (FRIPP) has also developed the FIDW (Fushun Isodewaxing) series of catalysts for its own hydroisomerization process, which has been fractions, with the rise in boiling point, each cut had a wider carbon num catalyst. Liquid products were distilled, on separate occasions, by a simple method for preliminary study and by true boiling point distillation for detailed investigation. Carbon number distributions and hydrocarbon types for various cuts were performed by high temperature GC-MS. It was found that for the light fractions, isoparaffins increased while monocycloalkanes decreased as the boiling point increased. As for the heavy Evaluation of hydroisomerization pro number distribution and Qiang Wang a,b, Hao Ling a, Ben-x a Chemical Engineering Department, East China Univers b Sinopec Maoming Petrochemical Co. L c National Centre for Upgrading Technology, 1 Oil Pa Accepted 3 Abstract A gas oil fraction of a deasphalted vacuum residue, after hydrotreat Patch Drive, Suite A202, Devon, Alberta, Canada T9G 1A8. Tel.: +1 780 987 8709; fax: +1 780 987 5349. E-mail addresses: linghao@ecust.edu.cn (H. Ling), sbx@ecust.edu.cn (B. Shen), sng@nrcan.gc.ca (S. Ng). 0378-3820/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2006.04.004 cts as lube base oils based on carbon drocarbon type analysis Shen a,⁎, Kun Li b, Siauw Ng c,⁎ of Science and Technology, Shanghai 200237, PR China aoming, Guangdong 525011, PR China Drive, Suite A202, Devon, Alberta, Canada T9G 1A8 pril 2006 t, was hydroisomerized in a flow fixed-bed reactor over a commercial (2006) 1063–1070 www.elsevier.com/locate/fuproc However, industrial feedstocks for hydroisomerization are always more complex than model compounds such as pure long-chain normal paraffins. For achieving the required erization process with a fixed-bed reactor. Technology 87 (2006) 1063–1070 hydroisomerization products, it is necessary to understand the nature of the base oil, as determined by hydrocarbon type analysis, which is usually expressed as SARA (saturates, aromatics, resins, and asphaltenes) [8,9]. Since feedstocks for hydroisomerization have always been hydrotreated to remove impurities, the amounts of resins and asphaltenes are much smaller than those of saturates and aromatics; the first two components, therefore, will be ignored in this paper. For saturates, branched alkanes and cycloalkanes (naphthenes) are Fig. 1. Flow scheme of the hydroisom 1064 Q. Wang et al. / Fuel Processing in greater abundance and are different in viscosity, pour point, and oxidation stability [2]. Further, cycloalkanes having different rings and structures, display different rheological properties. For these reasons, it is necessary to analyze a lube base oil for normal paraffins (NP), isoparaffins (IP), mono- cycloalkanes (MC), dicycloalkanes (DC), tricycloalkanes (TC), tetracycloalkanes (TTC), polycycloalkanes (PC), and aromatics (AR). Many studies have reported on the relationships between lube structures and viscosities or low temperature flow properties. For example, the American Petroleum Institute (API) has investigated a large number of hydrocarbons from C10 to C35 of different chemical families [2]. The relationships were interpreted based on the properties of pure hydrocarbons. In this study, we attempted to use a different approach. A hydrotreated deasphalted oil was hydroisomerized at various reaction conditions. The resulting liquid products were distilled under vacuum into different cuts where the carbon number distribu- tions and hydrocarbon types were studied to assess each cut's quality as a lube base oil. 2. Experimental 2.1. Hydroisomerization Experiments were conducted in a continuous fixed-bed stainless steel reactor, 48 mm ID and 1300 mm L with 800 mm constant-temperature zone (Fig. 1). It was loaded with 100 mL FRIPP FIDW-1 catalyst, a molecular sieve containing platinum and a new type of phosphate on silica–alumina with AEL (Aluminophosphate Eleven) structure, having strong acidity and more mesopores than the conventional hydrodewaxing catalysts [10]. The catalyst was mixed with an equal volume of pretreated quartz, which was washed with HCl, followed by heating at 800 °C. The catalyst mixture was placed at the center of the reactor. Hydrogen used in the experiment was +96 vol.% pure after combining the fresh hydrogen with the recycled hydrogen, which was pre- washed with 0.5 wt.% NaOH solution to remove H2S. The reaction temperature was controlled by a computer and the system pressure was controlled by a back- Table 1 Feedstock properties Density at 20 °C, kg m−3 863.2 ASTM D 1160 distillation, °C IBP 199 10% 353 30% 493 50% 535 70% 538 90% 547 EP 551 Residue carbon, wt.% 0.005 Solidification point, °C 52 Viscosity at 80 °C, mm2 s−1 15.24 Viscosity at 100 °C, mm2 s−1 9.712 Refractive index at 20 °C 1.4769 Average molecular weight 484 C/H weight ratio, g g−1 6.52 S, wppm 10.5 N, wppm 1.0 Hydrocarbon type analysis, wt.% n-Paraffins (NP) 3.9 i-Paraffins (IP) 30.2 Monocycloalkanes (MC) 27.5 Dicycloalkanes (DC) 17.4 Tricycloalkanes (TC) 10.0 Tetracycloalkanes (TTC) 3.8 Aromatics (AR) 7.2 pressure regulator. As a prerequisite for hydroisomerization, the sulfur and nitrogen levels in the feed (a deasphalted oil) were reduced to ∼10 wppm or lower through hydrotreating (Table 1). The hydrotreated deasphalted oil (HT- 2.3. True boiling point distillation The true boiling point distillation, for the detailed investigation only, was carried out in a packed column unit, designed to distill samples up to 540 °CAET maximum, to obtain various fractions of the hydroisomerization liquid product. The distillation column, complying fully with ASTM D 2892, has 14–18 theoretical plates. The distillation for b350 °C fractions was conducted with a reflux ratio of 5 and at atmospheric pressure for the IBP–107 °C fraction, and 1.33 kPa for the 170–350 °C cut (temperatures were all in AET). Then, the remaining residue was transferred to another pot, which was equipped with a low-pressure separator to remove fog and foam in the bottom liquid. The distillation continued with a reflux ratio of 5 and at 0.13 and 0.026 kPa for 350– 460 and 460–540 °C fractions, respectively. 2.4. Carbon number distribution Carbon number distribution analyses of various cuts were performed on a gas chromatograph (HP5890II GC), equipped with a UA1 30 m×0.25 mm high temperature nonpolar column, in combination with a mass spectrograph (HP5989A MS). The GC conditions were chosen as follows: 10.0 mL/min Table 2 Reaction conditions and properties of lube base oils Reaction temperature, °C 360 370 380 Pressure, MPa 9.0 9.0 9.0 Space velocity, h−1 0.8 0.8 0.8 H2/oil, v/v 800 800 800 Total liquid product yield (relative to HT-DAO), wt.% 84.85 82.76 79.34 Base oil yield (relative to HT-DAO), wt.% 63.85 62.52 59.03 Viscosity at 40 °C, mm2s–1 92.32 88.51 86.56 Viscosity at 100 °C, mm2s–1 11.51 11.40 10.83 VI 110 110 110 Pour point, °C −24 −23.5 −23.1 Average molecular weight 465 467 461 1065Q. Wang et al. / Fuel Processing Technology 87 (2006) 1063–1070 DAO) was delivered from the feed tank to the reactor by a constant-flux pump. Hydrogen flow rate was kept constant by a mass flow controller. Experiments were performed in two parts— for a preliminary study and for a detailed investigation. For the former, the reaction temperature was varied from 360 to 380 °C in 10 °C interval to study its effect on hydroisomerization. The space velocity, pressure, and hydrogen/oil volumetric ratio were kept constant at 0.8 h−1, 9.0 MPa, and 800 v/v (4492 SCF/bbl), respectively. For the second part, the reaction temperature was chosen at 380 °C with the rest of the parameters unchanged. Prior to the first hydroisomerization experiment, the catalyst was reduced in hydrogen with H2/catalyst ratio of 1200:1 v/v at 300 °C for 8 h. Reaction products in the first 1 h were discarded. Liquid products, condensed either in the high-pressure separator or the gas/liquid separator, were sent to the total liquid product receiver indirectly (through the low-pressure separator) or directly. The gaseous product leaving the gas/liquid separator was also collected for analysis. 2.2. Simple vacuum distillation According to the Chinese Petroleum Industry Standard SH/T 0165-92, which is equivalent to ASTM D 1160, a simple vacuum distillation was performed, for the preliminary study only, to obtain b350 °C and N350 °C cuts. The equipment used featured an automatic fractionation with cuts directed to individual receivers. It required 60 min to distill the 100 mL sample at 6.6 kPa and 220 °C — i.e., 350 °C atmospheric equivalent temperature (AET). The N350 °C cut was the lube base oil. The yield of lube base oil was calculated from the distillation feed. Fig. 2. Carbon number distributions at various reaction temperatures; content is relative to each of the lube base oil or feed. helium carrier gas; splitless injection mode; 340 °C injector temperature and 330 °C GC–MS interface temperature; temperature program―100 °C for 1 min, 5 °C/min to 340 °C, then held for 20 min. The MS conditions were: EI at 70 eV; 40–550 m/e+ scanning range; 320 °C ion source temperature; and 130 °C detector temperature. Retention times of normal paraffins of different carbon numbers were established based on the standard mass database and standard samples from the US National Bureau of Standards (NBS). Then, the chromatogram of a sample could be divided into groups based on the retention times, and the total area of each group was measured by the integration method. Compounds with peaks between those of the two neighboring normal paraffins were designated to the higher carbon number group. For instance, areas between normal C27 and C28 were grouped into C28 compounds. Hydroisomerization products consisted mainly of paraffins and cycloalkanes. Their respond factors, varying to some degree but difficult to determine individually, were assumed in this study to be a constant. Under this assumption, the area normalization method based on the total area (=100 wt.%) could be used to calculate the content or relative yield at a given carbon number. 2.5. Hydrocarbon type analysis Hydrocarbon type analysis, conducted in the same GC-MS system as for the carbon number distribution, was determined according to ASTM D 2786-91 in Fig. 3. Hydrocarbon type analyses of products at various reaction conditions; content is relative to each of the lube base oil or feed; NP in the feed not shown. average molecular weight of a base oil was obtained using a vapor pressure osmometer. After the reaction, liquid products were collected and distilled by simple vacuum distillation. At each condition, the liquid yield could reach 79 wt.% or higher while the yield of lube base oil (N350 °C fraction), in the neighborhood of 60 wt.%, decreased slightly with the increase in reaction temperature. VI values, which reflect the temperature effect on oil viscosities, were found to be 110, meeting the API II requirement of 80–119 for lube base oil. The carbon number distributions of lube base oils are illustrated in Fig. 2. It should be noted that some Cb20 compounds, ranging from 4 to 7.5 wt.%, existed in the heavy Table 3 Composition of gaseous product Compound group Compound or I/N ratio wt.% Cb4 CH4 0.13 C2H6 4.66 C3H8 32.39 Cb4 total 37.19 C4 i-C4H10 13.09 n-C4H10 26.56 C4 total 39.65 I/N ratio 0.49 C5 i-C5H11 13.11 n-C5H12 5.41 C6 total 3.96 I/N ratio 6.28 1066 Q. Wang et al. / Fuel Processing Technology 87 (2006) 1063–1070 C7 2-Methylhexane 0.19 3-Methylhexane 0.11 Methylcyclohexane 0.02 2,4-Dimethylcyclopentane 0.08 1,2-Dimethylcyclopentane 0.04 Cyclopentane 0.23 C5 total 18.75 I/N ratio 2.46 C6 2,2-Dimethylbutane 0.04 2-Methylpentane 2.05 3-Methylpentane 1.29 n-C6H14 0.54 Methylcyclopentane 0.03 Cyclohexane 0.01 combination with a Chinese Petroleum Industry Standard SH/T 0659-1998. The system was equipped with a 30 m×0.25 mm empty quartz column. The GC and MS conditions were the same as before except for 20 mL/min helium carrier gas and a 60–550 m/e+ scanning range. 3. Results and discussion 3.1. Preliminary study—effects of reaction temperature Results of hydroisomerization of HT-DAO at different operating conditions are presented in Table 2. VI values of oil samples were determined according to ASTM D2270-75. The 2,2-Dimethylpentane 0.01 C7 total 0.45 C1–7 total 100.00 Table 4 Properties of low OBP cuts Boiling range, °C b164 164–190 190–210 Yields (relative to total liquid product), wt.% 3.96 1.30 1.38 Viscosity at 40 °C, mm2s–1 0.522 1.183 1.489 S, wppm 140 13.7 34.1 AR, wt.% 0.44 1.78 2.80 Products based on Sinopec's classification Gasoline SNO #200 Punching o SNO #200: mineral solvent for paints. Punching oil #5: base oil for metals working fluids. Light distillate #1: smell-free light distillate for making aerosol insect killer. SNO #260: special solvent for minerals extraction. Mineral solvent #310: solvent for producing high-quality printing ink. White oil #7: ingredient of textile lubricant and finishing agent, and plastics modifi base oil fractions as a result of the one-plate vacuum distillation. These light compounds are not shown in Fig. 2. The carbon number distribution plot shows that the contents of compounds with Cb33 from runs at various conditions were obviously higher than that of the feed. This was in agreement with the observation reported by V. Calemma et al. [11] that in hydroisomerization, the selectivity of long-chain paraffins increased with the decrease in carbon number. Another contributing factor for the higher contents of Cb33 products was the associated hydrocracking of CN33 compounds in the feed to lighter products. As a result, the yields of lube base oil fractions at various conditions were comparatively low (less than 64 wt.%). Fig. 3 depicts the variation of hydrocarbon types as a function of reaction temperature. It shows that at higher temperatures, IP compounds in base oil fractions tended to increase due to hydroisomerization and/or hydrocracking of NP in the feed, whereas MC, DC and TC slightly decreased. TTC varied very little due to its small amount present but AR exhibited some increases. It was possible that hydrocracking of benzene ring, through hydrogenation first, did not take place at rather mild conditions of 9 MPa (1306 psig) and 360–380 °C. Instead, a thermodynamic equilibrium might be reached leading to the reverse reaction of hydrogenation, i.e., dehydrogenation of naphthenes to aromatics—the higher the temperature, the higher the aromatics yield. This could explain the small increases in AR at higher temperatures at the expense of MC, DC, and TC. Another contributing factor for aromatics increase was the enrichment effect due to the decrease in lube base oil yield at a higher temperature. Note that AR in the feed was slightly higher 210–243 225–255 235–270 270–350 2.65 2.53 3.04 8.28 2.011 2.425 2.861 6.684 8.7 5.1 3.3 b1.0 3.82 3.86 3.74 6.1 il #5 Light distillate #1 SNO #260 Mineral solvent #310 White oil #7 er. g Te Table 5 Hydrocarbon types of low OBP cuts as a function of carbon number Content a, wt.% b164 °C NP IP MC DC TC C4 0.99 0.33 C5 2.27 2.17 C6 2.89 7.33 C7 1.92 9.37 3.44 C8 0.57 6.62 14.12 C9 5.06 13.84 1.36 C10 4.65 14.1 0.98 C11 0.91 2.54 0.96 Q. Wang et al. / Fuel Processin than that in the product at 360 °C. This was probably due to the cracking of the side chains of aromatics in the feed. 3.2. Detailed investigation In a typical lubricant base oil manufacturing plant, intermediate products are distilled to remove light ends for obtaining heavy fractions of the desired viscosity. A detailed study was conducted to separate the hydroisomerization product into low and high overall boiling point (OBP) cuts, defined as b350 and N350 °C (for lube base oils) fractions, respectively, by means of true boiling point distillation. For this, reaction conditions at 380 °C and 0.8 h−1 were selected for producing a larger quantity of the hydroisomerization liquid product. The C12 0.58 1.06 0.68 0.18 C13 0.1 0.07 0.06 0.02 Total 8.63 37.11 49.16 4.03 0.2 Contenta, wt.% 190–210 °C IP MC DC TC A C9 0.01 C10 0.17 1.05 0.36 0. C11 1.88 16.8 4.2 0. C12 11.66 31.16 11.11 0.5 0. C13 6.21 9.32 2.91 0.33 0. C14 0.18 0.14 0.12 0.1 0. C15 C16 Total 20.1 58.48 18.7 0.93 1. Contenta, wt.% 225–255 °C 230–270 °C IP MC DC TC AR IP MC C11 0.02 0.1 0.12 0.01 0.03 C12 0.24 1.72 0.97 0.19 0.1 0.1 0.4 C13 2.93 11.04 4.19 0.48 0.4 0.94 5.11 C14 9.48 19.34 7.34 4.01 0.37 5.65 14.75 C15 9.57 13.96 4.61 3.16 0.29 10 17.53 C16 2 2.17 0.63 0.36 0.08 7.35 9.79 C17 0.03 0.04 0.03 0.02 1.09 0.96 C18 0.03 0.03 C19 C20 C21 C22 C23 C24 Total 24.27 48.37 17.9 8.22 1.25 25.16 48.6 a Content is relative to each cut. 164–190 °C AR IP MC DC TC AR 0.01 0.03 0.37 0.34 1.33 0.44 0.07 0.32 3.3 17.92 0.76 0.34 0.1 9.68 39.85 6.34 0.74 1067chnology 87 (2006) 1063–1070 associated hydrocracking entailed ∼20 wt.% gaseous by- product of which the composition is shown in Table 3. The following are the key observations: (1) no olefins were produced in an environment in the presence of hydrogen at medium pressure, and (2) the ratio of isoparaffins to n-paraffins (I/N ratio) increased with higher carbon number indicating that the catalyst used was not efficient in isomerizing the small straight-chain paraffins. Note that in Table 3 no n-paraffins were found in C7 as most of the C6 and C7 hyd