Ionic-Liquid-Catalyzed Alkylation of Extracted Oil from a Fluid Catalytic

Oct 3, 2017 - Shandong Shengli Vocational College, Dongying 257097, People,s Republic of China. ABSTRACT: The alkylation of the oil extracted from an ...
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Ionic-Liquid-Catalyzed Alkylation of Extracted Oil from a Fluid Catalytic Cracking Slurry Yan Lin,† Guozhi Nan,† Yufen Li,‡ Hui Luo,† and Weiyu Fan*,† †

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266555, People’s Republic of China Shandong Shengli Vocational College, Dongying 257097, People’s Republic of China

‡

ABSTRACT: The alkylation of the oil extracted from an FCC slurry with 1-octadecene, as catalyzed by the ionic liquid Et3NHCl·2AlCl3, was investigated in this work. The reaction conditions (such as catalyst dosage, molar ratio of extracted oil to 1octadecene, reaction temperature, and reaction time) were optimized through measurements of the conversion ratio of reactants and the chemical structure of the alkylated product. Under the optimal reaction conditions, the conversion ratios of extracted oil and 1-octadecene reached up to 78.6% and 79.3%, respectively, simultaneously yielding good selectivity to the monoalkylated product with an average molecular mass of 470. The experimental results indicate that Et3NHCl·2AlCl3 not only has a good alkylation catalytic activity for grafting long alkyl chains onto PAHs but also exhibits excellent recyclability, retaining 95% of its initial activity after eight reuses. This study suggests a promising application of the extracted oil from FCC slurries as a raw material for producing high-quality petroleum sulfonates.

1. INTRODUCTION Extracted oil (EO) from a fluid catalytic cracking (FCC) slurry refers to an aromatics-rich fraction that is obtained by solvent extraction from the heaviest fraction of the hydrocracked oils in the bottom of the fractionator.1 In the past few decades, a significant amount of extracted oil from FCC slurries has been used directly as heat-transfer oil, rubber softener, a blending component in fuel oil, and so on.2−7 However, these applications have recently started to gradually be eliminated because of environmental problems, as most of the components of the extracted oil contain polycyclic aromatic hydrocarbons (PAHs) subunits, which have strong carcinogenicity.8−11 Therefore, increasing attention has been focused on the research and development of alternative applications of extracted oil in economical and environmentally friendly ways worldwide. As one promising approach, the use of extracted oil to develop stable raw materials for the production of petroleum sulfonate anionic surfactants has become significant. Such a chemical conversion would not only upgrade the low-cost extracted oil into a high-value surfactant but also reduce the carcinogenicity through the alkylation and sulfonation of PAHs.12 In the past few decades, chemical flooding has found to be an effective method for enhancing the efficiency of oil recovery, in which suitable surfactants are used to play a key role of reducing the interfacial tension on oil−water-rock interfaces during the oil recovery process.13 Many type of surfactants have been evaluated. Among them, petroleum sulfonate is considered to be an ideal surfactant with commercial value for oil displacement because of its favorable lipophilicity−hydrophilicity, low cost, thermal stability, and water solubility.14,15 However, the general method of producing petroleum sulfonates uses raw petroleum fractions or crude oils as raw materials for sulfonation. As a result, variations in the raw materials can result in significant changes in the quality of the resulting petroleum sulfonates. Such a changeable quality of © XXXX American Chemical Society

products can increase both business and technical risks and thus limit their large-scale application in chemical flooding.16−19 Therefore, it is of significance to develop a suitable raw material with stable quality, low cost, and high efficiency for producing high-quality petroleum sulfonates. As has been widely reported, extracted oil is a good raw material for sulfonation reactions because it contains 80% aromatic molecules substituted by short side chains (one to three carbons).10 However, the direct sulfonation of extracted oil commonly does not yield sulfonates suitable for chemical flooding because of the poor surface activity of the sulfonates due to their short side chains. In contrast, some investigations of the dynamic interfacial tension between a series of monoalkylbenzenesulfonate surfactants and a crude oil (from Daqing Oil Field, Daqing, China) revealed that appropriately long alkyl side chains (for example, octadecyl chains in octadecylbenzenesulfonate) could balance the hydrophilicity and hydrophobicity of sulfonate surfactants so that the chemical flooding system achieved an ultralow dynamic interfacial tension.16 Therefore, long alkyl side chains must be grafted onto the aromatic rings of aromatics in extracted oil through alkylation before sulfonation for the preparation of highperformance sulfonate surfactants. Traditionally, aromatic alkylation reactions are usually catalyzed by strong acid catalysts such as H2SO4, HF, or anhydrous AlCl3, which have many disadvantages, such as corrosion of equipment, difficult separation of the catalyst from the reaction mixture, and environmental pollution.21,22 To solve these problems, ionic liquids such as Et3NHCl−AlCl3 complex have been used as novel alkylation catalysts with higher catalytic activities, milder reaction conditions, easier separation processes, and better selectivities.23−27 Kumar et al. Received: July 31, 2017 Revised: October 3, 2017 Published: October 3, 2017 A

DOI: 10.1021/acs.energyfuels.7b02227 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels

held under the preset reaction temperature for the preset time. Third, after the reaction had completed, the reaction mixture was poured into a separating funnel to separate out the ionic liquid (in the lower volume). Then, the residual mixture in the upper volume was washed several times with 80 °C deionized water (with a volume ratio of water to reaction mixture of 2:1) to completely remove the residual ionic liquid. After the sample had been dried by adding anhydrous calcium chloride and filtering it through a Buchner funnel suction filtration system to remove calcium chloride, the raw alkylation mixture was obtained. Finally, the raw alkylation mixture was distilled under vacuum conditions to remove the light fractions including unreacted olefin and solvent and to collect the heavy fraction as the final product of alkylated oil. During the alkylation process, the expected main reaction is monoalkylation, given by the equation

studied the homogeneous catalytic alkylation of benzene with 1-hexene using different cationic chlorinated aluminate ionic liquids as catalysts and found that the addition of the ionic liquid Et3NHCl·2AlCl3 increased the selectivity of the linear alkylbenzene from 32% to 40%.28 Chen et al. studied the alkylation of benzene with 1-hexene in ionic liquid systems. Their results showed that Et3NHCl·AlCl3 ionic liquid has a high catalytic activity, giving a selectivity to monoalkylbenzene of 98.1%.29 Therefore, Et3NHCl−AlCl3 complex ionic liquid has been approved as a highly efficient catalyst for the alkylation of aromatic hydrocarbons. However, extracted oil is significantly different from such pure and simple aromatic hydrocarbons as benzene and toluene in both chemical composition and reaction activity,17−20 and in particular, the ionic-liquidcatalyzed alkylation of the extracted oil has not been reported so far. In this study, Et3NHCl−AlCl3 complex ionic liquid was used as the catalyst for the alkylation of extracted oil with 1octadecene. The alkylation reaction conditions were investigated in detail and optimized. The results indicated that the extracted oil can be alkylated under easily controlled conditions, yielding alkylated oil that is suitable for further processing to produce high-performance petroleum sulfonates.

ArHm + C18H36 → C18H37ArHm − 1

However, such side reactions as dialkylation and polyalkylation can occur,30,31 as follows C18H37ArHm − 1 + nC18H36 → (C18H37)n + 1ArHm − n − 1 (m ≥ 2, n ≥ 1, dialkylation if n = 1) where ArHm is an aromatic molecule with active aromatic hydrogens and C18H36 is 1-octadecene. 2.3. Test Methods and Date Processing Method. 2.3.1. Measurement of the Average Relative Molecular Mass of the Alkylated Product. The average relative molecular mass of the alkylated products was measured by the vapor pressure osmometry (VPO) method. The increase in the relative molecular mass from the extracted oil to the alkylated product was in line with the average mass of the carbon chain grafted onto the extracted oil molecules. Accordingly, the average number of carbons in the grafted carbon chain can be calculated, and the conversion ratio of the extracted oil can be evaluated under certain assumptions. 2.3.2. Measurement of the Bromine Value. The bromine values of the samples of extracted oil and raw alkylation mixture were measured in accordance with standard test method ASTM D1159-07(2017). The bromine value X (in grams of Br2 per 100 grams) of each sample was calculated according to the equation

2. EXPERIMENTAL SECTION 2.1. Materials. The extracted oil (boiling range of 395−455 °C) from an FCC slurry was selected as the extracted oil for the alkylation reaction. It was obtained from Shengli Petrochemical Refinery. Its basic properties are presented in Table 1. 1-Octadecene was provided

Table 1. Typical Properties of the Extracted Oil property average relative molecular mass density (20 °C) (g·cm−3) viscosity (50 °C) mm2·s−1 elemental composition (wt %) C H N S group composition (wt %) saturates aromatics resins and asphaltenes

(m ≥ 1)

value 272 1.0609 48.09

X=

88.77 8.73 0.44 1.03

15.98(V2 − V0)C1 m

(1)

where V2 is the volume of KBrO3−KBr standard solution consumed during titration, V0 is the volume of KBrO3−KBr standard solution consumed during titration in a blank test, C1 is the molar concentration of the KBrO3−KBr standard solution, 15.98 is a conversion factor, and m is the mass of the sample. 2.3.3. Calculation of the Conversion Ratio of Olefin. The conversion ratio of olefin (i.e., 1-octadecene) can be indirectly evaluated by using the bromine values of extracted oil and raw alkylation mixture. The conversion ratio of olefin (CO) is defined as m −m CO (%) = 0 × 100% m0 (2)

22.75 76.46 0.79

by the Shanghai Chess Industrial Co., Ltd. The optimized catalyst of Et3NHCl−AlCl3 complex ionic liquid was synthesized by mixing anhydrous AlCl3 with Et3NHCl in an AlCl3/Et3NHCl molar ratio of 2:1, yielding an ionic liquid material that is denoted as Et3NHCl· 2AlCl3 in this article. The most active sites in the prepared catalyst could generally be considered as Al2Cl7−, and the reaction equation and chemical structure of the ionic liquid are schematically given by

where m0 is the olefin mass before the reaction and m is the residual olefin mass after the reaction. m can then be calculated as

m=

2AlCl3 + [Et3NH]+ Cl− → [Et3NH]+ [Al 2Cl 7]− 2.2. Preparation of Alkylation Products. The alkylation reactions were carried out in an apparatus constructed from a fourneck flask with heating, stirring, a dryer-capped condenser, and nitrogen protection. The whole reaction process was maintained under strong stirring and nitrogen protection. First, a certain amount of the extracted oil was added to the flask after the whole reaction apparatus had been purged completely with pure nitrogen and heated to a preset temperature. Second, the predetermined amounts of 1-octadecene and ionic liquid catalyst were added to the flask in order and mixed sufficiently with the extracted oil by stirring. The reaction mixture was

MO(X1 − XEO)(mEO + m0) 100M Br2

(3)

where X1 is the bromine value of the raw alkylation mixture after reaction; XEO and mEO refer to the bromine value and the mass, respectively, of the extracted oil before the reaction; Mo is the relative molecular mass of 1-octadecene, and MBr2 is the relative molecular mass of Br2. 2.3.4. Estimation of the Conversion Ratio of Extracted Oil. The real conversion ratio of the extracted oil is hard to measure because extracted oil itself is a complex mixture and contains a great deal of inactive or inert molecules (possibly 15−30% by weight). Assuming B

DOI: 10.1021/acs.energyfuels.7b02227 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels that only monoalkylation occurred and that no extracted oil molecule was changed by either decomposition or condensation reactions during the alkylation reaction, the conversion ratio of extracted oil (CEO) can be roughly estimated from the average relative molecular mass of the final product of alkylated oil using the equation C EO (%) =

MP − MEO × 100% MO

(4)

where MP is the average relative molecular mass of the final product of alkylated oil, MEO is the average relative molecular mass of extracted oil, and MO is the relative molecular mass of 1-octadecene. As a sample, in one reaction experiment, 100.0 g of extracted oil (equal to 0.368 mol according to an average molecular mass of 272) and 92.8 g of 1-octadecene (0.368 mol) were fed in the extracted oil/ olefin molar ratio of 1:1. The bromine value of the extracted oil was measured according to standard method ASTM D1159-07(2017) as 3.2 g of Br2 per 100 grams, and the bromine value of the alkylated product sample was determined to be 9.5 g of Br2 per 100 grams. According to eq 3, the residual olefin mass after the reaction was calculated as 19.1 g. Accordingly, the conversion ratio of olefin was calculated as 79.3% based on eq 2. Therefore, 0.292 mol of 1octadecene was consumed in the reaction. The average molecular mass of the alkylated product was measured as 470, and accordingly, the conversion ratio of extracted oil was calculated as 78.6% based on eq 4. thus, 0.289 mol of extracted oil was consumed in the reaction. Therefore, the real consumption in terms of the molar ratio of olefin to extracted oil (i.e., olefin/EO) was 1.01. It should be noted that eq 4 does not fit the products of polyalkylation. Therefore, the value calculated according to eq 4 would be greater than the real conversion ratio of the extracted oil if polyalkylation occurred to a significant extent. 2.4. 1H NMR Measurements and NMR DOSY Analysis. The chemical structures of the extracted oil and the alkylated products prepared under optimum conditions were analyzed by both onedimensional 1H NMR spectroscopy and two-dimensional diffusionordered NMR spectroscopy (DOSY) using a Bruker AV-500 nuclear magnetic resonance spectrometer. Deuterated chloroform was used as the solvent in the NMR measurements.

Figure 1. Effects of the molar ratio of AlCl3 to Et3NHCl on the conversion ratios of extracted oil (red circles and line) and olefin (black diamonds and line) and the average relative molecular mass of the product (blue squares and line).

the AlCl3/Et3NHCl molar ratio was selected as 2:1, and the catalyst is referred to as Et3NHCl·2AlCl3. In addition to the chemical structure of the catalyst, its dosage also has a significant influence on the alkylation reaction. Therefore, the effects of the catalyst dosage on the alkylation reaction of extracted oil with 1-octadecene were investigated. Using the ionic liquid Et3NHCl·2AlCl3 as the catalyst and nitrobenzene as the solvent (the solvent effect is discussed later in relation to Figure 4), the alkylation reaction was conducted under the following conditions: reaction time of 2 h, solvent/EO volume ratio of 3:1, reaction temperature of 80 °C, and EO/olefins molar ratio of 1:1. The experimental results are shown in Figure 2.

3. RESULTS AND DISCUSSION The catalyst plays a key role in alkylation reactions. Because the chemical structure (and, therefore, the acidity and active species of the acidic centers) of the Et3NHCl−AlCl3 complex is mainly determined by the molar ratio of AlCl3 to Et3NHCl, its catalytic performance could be adjusted by varying the AlCl3/Et3NHCl molar ratio during the syntheses of the ionic liquids. The catalytic effects on the alkylation reaction of extracted oil with 1-octadecene of catalysts with different AlCl3/Et3NHCl molar ratios were first investigated under the following reaction conditions: catalyst dosage of 6.0 wt % (mass of anhydrous AlCl3 accounts for the total mass of extracted oil and 1octadecene), EO/olefins molar ratio of 1.0, no solvent, reaction time of 2 h, and reaction temperature of 80 °C. The resulting changes in the relative molecular mass of the alkylated products and the conversion ratios of both the extracted oil and the olefin are shown in Figure 1. Figure 1 indicates the AlCl3/Et3NHCl molar ratio can significantly affect the reaction activity and the conversion ratio of the alkylation reaction. In this case, the alkylation reaction could be significantly catalyzed to proceed after the AlCl3/ Et3NHCl molar ratio had been increased to just 2:1, achieving a high conversion ratio of both extracted oil and olefin of about 79%. More importantly, the reaction conversion ratio was maintained near 80% when the AlCl3/Et3NHCl molar ratio was further increased from 2:1 to 3:1, yielding products with an average relative molecular mass of 474. An appropriate value of

Figure 2. Effects of catalyst dosage on the conversion ratios of extracted oil (red circles and line) and olefin (black diamonds and line) and the average relative molecular mass of the product (blue squares and line).

As shown in Figure 2, when the catalyst was used at a low dosage of less than 6.0 wt %, the conversion ratios of both extracted oil and olefin could initially be markedly increased by increasing the catalyst dosage from 4.0 to 6.0 wt %, and they could then be slightly changed to their top values for catalyst dosages of 6.0−9.0 wt %, yielding products with average relative molecular masses in the range of 380−390. Considering the C

DOI: 10.1021/acs.energyfuels.7b02227 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels overall catalyst cost and efficiency, an appropriate catalyst dosage was selected as 6.0 wt %. The effects of the reaction time on the alkylation of the extracted oil with 1-octadecene were evaluated as shown in Figure 3. Using the ionic liquid Et3NHCl·2AlCl3 as the catalyst

Figure 4. Effects of the solvent/extracted oil volume ratio on the conversion ratios of extracted oil (red circles and line) and olefin (black diamonds and line) and the average relative molecular mass of the product (blue squares and line).

alkylation reaction of extracted oil with 1-octadecene be performed without additional solvents under the proposed conditions. In addition, the alkylation is markedly affected by the reaction temperature. Using the ionic liquid Et3NHCl·2AlCl3 as the catalyst, the reaction was investigated under following conditions: catalyst dosage of 6.0 wt %, EO/olefins molar ratio of 1:1, reaction time of 2 h, and no solvent. The effects of reaction temperature are presented in Figure 5.

Figure 3. Effects of reaction time on the conversion ratios of extracted oil (red circles and line) and olefin (black diamonds and line) and the average relative molecular mass of the product (blue squares and line).

and nitrobenzene as the solvent, the reaction was performed under the following conditions: catalytic dosage of 6.0 wt %, solvent/EO volume ratio of 3:1, reaction temperature of 80 °C, and EO/olefins molar ratio of 1:1. Figure 3 indicates that the reaction time is another important factor affecting the reaction conversion ratio. When the reaction time was shorter than 1.5 h, both the olefin conversion ratio and the relative molecular mass of the product increased rapidly with increasing reaction time. Furthermore, when the reaction time was prolonged beyond 1.5 h, the conversion ratio and the average relative molecular mass of the product varied slowly with time. Considering the overall time efficiency and reaction conversion ratio, an appropriate reaction time was selected as 2 h, properly longer than 1.5 h. During alkylation, the appropriate addition of solvent to dissolve reactants can reduce the viscosity of the reaction mixture, accelerate mixing, and facilitate mass and heat transfer in the reaction system. To reveal whether the use of a solvent can be beneficial to the alkylation of extracted oil with 1octadecene, the effects of different solvent/EO volume ratios on the alkylation reaction were investigated (see Figure 4). Using the ionic liquid Et3NHCl·2AlCl3 as the catalyst and nitrobenzene as the solvent, the extracted oil was alkylated under the following conditions: catalyst dosage of 6.0 wt %, reaction temperature of 80 °C, reaction time of 2 h, and EO/ olefins molar ratio of 1:1. Figure 4 shows that increasing the solvent/EO volume ratio can result in an approximately linear decrease in the reaction conversion ratio, from 83% without solvent to 45% at a 3:1 solvent/EO ratio and further to 26% at a 4:1 solvent/EO ratio. These results can be reasonably attributed to the dilution effect of solvent that would reduce not only the concentrations of reactants but also the effective concentration and efficiency of the catalyst.30 Furthermore, the absence of additional solvent did not bring out undesirable phenomena (such as high viscosity to retard mixing or heat transfer) during the overall reaction process. As a conclusion, it is suggested that the

Figure 5. Effects of reaction temperature on the conversion ratios of extracted oil (red circles and line) and olefin (black diamonds and line) and the average relative molecular mass of the product (blue squares and line).

As shown in Figure 5, when the reaction temperature was below 80 °C, both the olefin conversion ratio and the average relative molecular mass of the product increased rapidly with increasing temperature. Moreover, when the reaction temperature was higher than 80 °C, the reaction conversion ratio could reach 78.6% and started to vary slowly with temperature, yielding products with an average relative molecular mass of 470. In practice, an adequate temperature is necessary increase the reaction rate. However, excessive temperature can result in undesired side reactions, additional energy consumption, and D

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Energy & Fuels additional equipment investments. Thus, 80 °C was selected as an appropriate reaction temperature. Figure 6 demonstrates that the molar ratio of extracted oil to olefin in the alkylation reaction can affect not only the reactant

suggest that an appropriate EO/olefins feeding molar ratio for producing monoalkylated oil is 1:1. According to the above results, the optimized conditions for the ionic-liquid-catalyzed alkylation of extracted oil with 1octadecene can be concluded to be the following: AlCl3/ Et3NHCl molar ratio of 2:1 (i.e., ionic liquid Et3NHCl·2AlCl3 as the catalyst), catalyst dosage of 6.0 wt %, extracted oil/olefins molar ratio of 1:1, reaction time of 2 h, reaction temperature of 80 °C, and no solvent. Furthermore, the recyclability of the ionic liquid Et3NHCl· 2AlCl3 was investigated under the optimized conditions. Based on the large density difference between ionic liquid and alkylation products as two immiscible liquids, the ionic liquid was separated from the alkylation reaction mixture using a separating funnel and was collected under dry conditions. The collected ionic liquid was then dried in a vacuum oven at 80 °C for 24 h before each reuse. The results of the reuse experiments are shown in Figure 7.

Figure 6. Effects of the extracted oil/olefins molar ratio on the conversion ratios of extracted oil (red circles and line) and olefin (black diamonds and line) and the average relative molecular mass of the product (blue squares and line).

conversion ratio but also the product selectivity. Under stoichiometric conditions for monoalkylation, performing the reaction by feeding a 1:1 molar ratio of EO to olefins yielded a product with an average molecular mass of 470, and accordingly, the conversion ratio of extracted oil was calculated as 78.6%. Meanwhile, the conversion ratio of olefin was measured as 79.5%. Therefore, the real consumption in terms of molar ratio was calculated as olefin/EO = 1.01. This ratio value is equal to the stoichiometric value for monoalkylation, which suggests that the product was almost entirely composed of monoalkylated components. The fact that the measured molecular mass of product was smaller than the predicted molecular mass of monoalkylated product, that is, 470 versus 524, was because of the presence of a lot of inactive or inert components in the extracted oil. For comparison, increasing the EO/olefins feeding molar ratio to 1.4:1 resulted in conversion ratios of olefin and extracted oil of 83.2% and 75.0%, respectively, leading to a real consumption in terms of molar ratio of olefin/EO = 0.79. In theory, the use of an excess amount of extracted oil compared to olefins can benefit the reaction selectivity for monoalkylated product,32,33 but meanwhile, the relatively inadequate amount of olefin can cause a much greater amount of unreacted extracted oil to be left in product, which is difficult to separate from the alkylated oil. On the contrary, the use of excess amounts of olefin over extracted oil tends to lead to more side reactions such as dialkylation. It was found that the real consumptions in terms of olefin/EO molar ratio became larger than 1 and increased with as the EO/olefins feeding molar ratio was decreased from 0.8 to 0.4. The dominance of the dialkylated product was also confirmed by the average molecular mass of 552 for the product from the EO/olefins feeding molar ratio of 0.4, significantly greater than either the measured value of 470 or the theoretically predicted value of 524 for the monoalkylationdominated product. To summarize, the results from Figure 6

Figure 7. Recyclability test of ionic liquid catalyst: conversion ratios of extracted oil (red circles and line) and olefin (black diamonds and line) and average relative molecular mass of the product (blue squares and line).

Repetitively recycled ionic liquid was reused to catalyze the alkylation of extracted oil with 1-octadecene in eight runs. As shown in Figure 7, the reactant conversion ratios decreased from an initial value of 77.4% to a final value of 74.5% for 1octadecene and from an initial value of 77.9% to a final value of 74.1% for extracted oil. These results indicate that the ionic liquid Et3NHCl·2AlCl3 has excellent recyclability in terms of catalytic performance, maintaining its catalytic activity at over 95% of the original performance after eight reuses. The changes in chemical structure from the extracted oil to the alkylated product were identified by nuclear magnetic resonance (NMR) spectroscopies. The sample of the alkylated product was produced according to the optimized reaction, with an average molecular mass of 470. The 1H NMR spectra of both extracted oil and alkylated product are presented in Figure 8. Four typical hydrogen signals can be assigned as (1) aromatic hydrogen (HA) in the chemical shift range of 6.7−8.9 ppm, which is bonded with aromatic carbon in aromatic ring; (2) alkyl alpha hydrogen (Hα) in the chemical shift range of 2.0−3.5 ppm, which is in the first methylene (or methyl) bonded with aromatic carbon; (3) alkyl beta hydrogen (Hβ) in the chemical shift range of 1.1−2.0 ppm, which is in the middle methylene (not bonded with E

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Figure 8. 1H NMR spectra of (a) extracted oil and (b) alkylated oil product. Figure 9. NMR DOSY spectra of (a) extracted oil and (b) alkylated oil product.

aromatic carbon) in the alkyl side chains; and (4) alkyl gama hydrogen (Hγ) in the chemical shift range of 0.5−1.0 ppm, which is in the terminal methyl group at the end of the long alkyl side chains. By comparing the 1H NMR spectrum of the alkylated oil with that of extracted oil, the most significant change can be verified by the NMR peak in the chemical shift range of 1.5−1.7 ppm. Its integrated area in the 1H NMR spectrum of the alkylated oil was normalized as 46.34% of the total, much greater than the normalized value in the extracted oil (normalized as 30.26% of the total). The increased NMR peak area was attributed to the addition of Hβ in the grafted octadecyl side chains . The introduce of the octadecyl side chains also resulted in the decrease of the percentage contents of both HA and Hα as a result not only of the substitution of HA but also of the octadecyl Hβ-induced increase in total hydrogens, in line with the decrease in the normalized areas of the HA and Hα bands in the 1H NMR spectrum of the alkylated oil. Diffusion-ordered NMR spectroscopy (NMR DOSY) is a two-dimensional NMR measuring technique used to distinguish different chemicals by both the chemical shift of hydrogen (in the first dimension of the 1H NMR spectrum) and the molecular diffusion coefficient (in the second dimension of the diffusion-ordered spectrum). Different molecules with markedly different molecular diffusion coefficients can be separately presented as different groups of hydrogen signals in the diffusion-ordered spectrum. Figure 9a reveals that only one group of hydrogen signals from one sample of extracted oil appeared in the diffusion-ordered spectrum, indicating that the sample had a characteristic molecular diffusion coefficient of 10−8.00 m2·s−1. In addition, Figure 9b shows one group of hydrogen signals appearing in the diffusion-ordered spectrum: These signals resulted from the alkylated oil with a characteristic molecular diffusion coefficient of 10−8.05 m2·s−1. The greater diffusion coefficient of the alkylated oil compared to the

extracted oil can be attributed to the increased molecular mass and molecular volume of the alkylated oil as a result of the grafting of octadecyl side chains. Both the 1H NMR and NMR DOSY spectra indicate that 1octadecene was well grafted onto the extracted oil molecules.

4. CONCLUSIONS Both the increased molecular mass and the changed molecular structure of the alkylated product indicate that extracted oil can be well alkylated by our approach. In this work, the low-cost and readily available ionic liquid Et3NHCl·2AlCl3 was employed to catalyze the alkylation of 1-octadecene with extracted oil from an FCC slurry, which could be used as raw materials to produce high-quality petroleum sulfonates. The reaction conditions were optimized as follows: ionic liquid Et3NHCl·2AlCl3 as the catalyst with a dosage of 6.0 wt %, extracted oil/olefins molar ratio of 1:1, reaction temperature of 80 °C, and reaction time of 2 h. Under these conditions, the average relative molecular mass of the alkylated product was 470, and the conversion ratios of extracted oil and 1-octadecene reached 78.6% and 79.3%, respectively. The experimental results indicate that the ionic liquid Et3NHCl·2AlCl3 not only has a good alkylation catalytic activity for grafting long alkyl chains onto PAHs but also exhibits excellent recyclability, as it retained 95% of its initial activity after eight runs. This study suggests a very promising application of the extracted oil from FCC slurries .

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. F

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(26) Zhang, J.; Huang, C.; Chen, B.; Ren, P.; Pu, M. J. Catal. 2007, 249, 261−268. (27) Elomari, S.; Trumbull, S.; Timken, H. K. C. International Patent WO 2006068983A3, 2006. (28) Kumar, R.; Kumar, A.; Khanna, A. Catal. Ind. 2015, 7, 188−197. (29) Chen, H.; Dai, L.; Shan, Y. Hua Hsueh Shih Chieh 2003, 4, 171− 173. (30) Zhang, H. Master Degree Dissertation, Dalian Maritime University, Dalian, China, 2016. (31) Corma, C. A.; Rey, G. F.; Li, G.-X.; Diaz, C. M. J. European Patent EP2017005, 2009. (32) Robert, M. S. U.S. Patent 2,927,087. 1960. (33) Tang, P. Textbook of Fine Organic Synthesis Chemistry and Technology; Tianjin University Press: Tianjin, China, 2003; pp 120− 122.

Weiyu Fan: 0000-0001-7553-4347 Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support by the Postgraduate Innovation Project of China University of Petroleum (15CX06046A).

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ABBREVIATIONS EO = extracted oil FCC = fluid catalytic cracking REFERENCES

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DOI: 10.1021/acs.energyfuels.7b02227 Energy Fuels XXXX, XXX, XXX−XXX