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Direct separation of olefins from aromatics/sulfides: Influence of the structure and content of olefins and aromatics Yongtao Wang, Yuhao Zhang, Feng Chen, Meng Zheng, Liang Zhao, Jinsen Gao, Tianzhen Hao, and Chunming Xu Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03079 • Publication Date (Web): 09 Jan 2018 Downloaded from http://pubs.acs.org on January 15, 2018

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Energy & Fuels

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Direct separation of olefins from aromatics/sulfides: Influence of the structure and content of olefins and aromatics

Yongtao Wang1,†, Yuhao Zhang1,†, Feng Chen1, Meng Zheng1, Liang Zhao1,*, Jinsen Gao1, Tianzhen Hao2, and Chunming Xu1

1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), Beijing 102249, People’s Republic of China 2. Hebei Jingzhi Technology Co., LTD, He bei 061000, People’s Republic of China

State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), 18 Fuxue Road, Beijing, P.R. China, 102249

Email:

Liang Zhao([email protected]); Tel:

86-10-89739078

Fax:

86-10-69724721

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Abstract In order to disclose the separation of olefins from aromatics or thiophene compounds by organic solvents, vapor-liquid equilibrium (VLE) data for ternary systems of olefins + aromatics/thiophenes + sulfolane (SUL) /N-methyl-2-pyrrolidone (NMP) were investigated at atmospheric pressure in a modified Rose dual-circulating vapor-liquid distiller. This work primarily focused on studying the relationship between separation efficiency on olefins and the structure/concentration of olefins/aromatics. From the point view of structure, the results showed that more methyl existing on both olefins and aromatics could lead to stronger hydrogen bond interaction with solvents than that of olefins and aromatics， which do not include methyl in their molecular structure. So there was higher separating-olefin efficiency for the systems containing 1-hexene (HEX) /3-methylthiophene (MTHI) /1,2,4-trimethylbenzene (TMB) than those of 2,4,4-trimethylpentene (TMP) /thiophene (THI) /toluene (TOL), respectively. Besides, when it came to the concentration of olefins or aromatics in model gasoline, the effect of separating olefin appeared remarkable when the concentration of olefins was below 40% or the concentration of aromatics was above 60%. Comparison of the separation effect of solvents, the SUL outperformed the NMP due to the large relative volatility observed for the systems of “HEX + THI/MTHI/TOL/TMB”. What deserves to mention is that the two oxygen atoms on SUL locating the same orientation help form stronger hydrogen bond between compounds and SUL than that of NMP. Above findings powerfully facilitated the structure-effect relationship for separation of olefins from aromatic chemical compounds, which give a clear direction for upgrading of clean gasoline by efficient separation of olefins and removal of sulfides from FCC gasoline. Keywords: vapor-liquid equilibrium, separation of olefin, interaction, hydrogen bond, 2


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desulfurization

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1. Introduction Sulfur compounds, as the one of main contaminants from fossil fuels, have undesirable effects on environment such as acid rain, haze, and photo-chemical smog. For this reason, environmental regulations have been implemented in many countries to reduce the sulfur levels in conventional fuels. The U.S. Environmental Protection Agency lowered the sulfur content to 15 µg/g in 2006, both gasoline and diesel1,2. The European Directive 2003/17/EC issued the rules in 2009, confining the sulfur content less than 10 µg/g in both diesel and gasoline3. More than that, Chinese government announced a new sulfur standard of 10 µg/g in 2016 for clean fuels4. Except sulfur content, one common item in these newly issued regulations has drawn enormous attention. That is, the olefin content was explicitly limited at 18.0 v% and 15.0 v% in Europe5 and China4, respectively. Olefins play a prominent role in keeping the high research octane number (RON) of gasoline. Thus, how to deal with this extra olefin properly is the key issue for upgrading clean gasoline. For desulfurization, plenty of approaches for lowering the sulfur content of gasoline were reported, such as hydrodesulfurization (HDS)6-8, adsorption desulfurization9,10,

reactive

adsorption

desulfurization11-14,

oxidative

desulfurization15-19, extraction desulfurization20-26, and so on. Among these, HDS is the most widely applied technology in industries, because of not only

successfully

production of ultra-low sulfur gasoline, but also its notable advantages in practical operations. For further production of low olefin content, although part of olefins could be saturated during HDS, which could decrease the content of olefins in gasoline, this is not the right way for eliminating those extra olefins because simply hydrogenation of olefins could cause significant loss of RON in gasoline. Therefore, there is an

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urgent need to find a way to produce clean gasoline with low olefin content while no or few loss of RON. Extraction desulfurization is an option for this purpose. Because this technology not only could desulfurize with universality and low cost, but also could separate compositions of gasoline. That is, the FCC naphtha could be separated into two parts: one part is mainly composed by paraffin (P), naphtha (N), and olefins (O); the other part is concentrated by aromatics (A) and sulfides (S). Based on the separation, the PON part could be blended into the gasoline pool without other desulfurization treatment, while the AS part could be sent into the HDS process for deep desulfurization, in which there is no or few loss of RON because of low content of olefins. The key point is that olefin could be separated avoiding the hydrogenation in HDS process by this means, if necessary, the olefins can be selectively transferred into other components with high octane number by isomerization, etherification, or aromatization for improving RON of gasoline or decreasing of the content of olefins. In a word, it is a good way for decreasing the content of olefin while maintaining the high RON of gasoline. In this method, the most important step is to realize the direct separation of PON and AS. The extraction technology could be divided into liquid-liquid extraction (LLE) and extraction distillation (ED) according to their different separation principle. The LLE was often used for extracting the small amount of matters on the basis of different solubility in solvents, such as aromatics extraction27-30 and purification31. For instance, AI-Jimaz et al.32 reported that the LLE could be used for separation aromatics from paraffins with a low cost using the N-methyl-2-pyrrolidone (NMP) as the extracting agent. However, these liquid-liquid extraction technologies were only limited at the low-aromatic content gasoline33, because higher aromatic content in

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feed mixture results in greater amount and cost of solvents. So liquid-liquid extraction has little contribution to the separation of high content of aromatic in mixtures. The ED was used for separating the mixture common in solubility but different in relative volatility34, therefore it could be applied for the separations of large amount of matters in mixture. This technology significantly expands the range of feedstock to high aromatic content feedstock. For high aromatic content feedstock, comparing with liquid-liquid extraction, extractive distillation appears more economically with a fewer amount of solvents when the same separating-olefin effect is required. For example, Ismael et al.35 reported that the naphtha with a high aromatic content (90 wt. %) can be separated well by extractive distillation with a significant reduction of energy required per ton of naphtha fed to the system in comparison with the separation by liquid-liquid extraction. For extractive distillation, what really matters for this technology is the suitable solvent. Generally, both extractive distillation (ED) and VLE experiments are common experimental methods for screening solvents and studying related properties of phase equilibrium. Wherein, ED process is mainly used to verify solvents’ separating effect. VLE method prefers to study the basic properties of phase equilibrium and compare the performance of solvents. Shen et al. investigated dozens of molecular solvents like sulfolane (SUL), NMP, propylene carbonate, dimethyl sulfoxide, furfural, diethylene glycol, tetraethylene glycol, and N-formylmorpholine to screen an optimal one by the VLE experiments for extractive distillation desulfurization according to the desulfurization effect36,37. However, the separation efficiency of olefins was hardly taken into consideration in screening solvents. In spite of enough experience of screening solvents from liquid-liquid extraction, there is much work to do in screening suitable entrainers mainly for separating olefins by extractive distillation. So far, very

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little information of the olefin separation is available, furthermore, these reports focused on coarse screening solvents about separating aromatics and alkanes38-40, not the system of aromatic and olefins. Actually, there is a big difference between the systems of aromatics and alkanes and those of aromatics and olefins because of the existing of carbon-carbon double bond in olefin, which made the separation of olefins from system more difficultly. Probably because of that, the separation of olefins by the method of VLE have been rarely reported. Thus it can be seen that there is great room for improvement in the separation process of olefins and it would have hopeful prospects in upgrading clean gasoline by extractive distillation. In this paper, in order to investigate the effect of the content and structure of olefins and aromatics on separation of olefins, 1-hexene and 2,4,4-trimethylpentene were selected as the olefins and toluene and 1,2,4-trimethylbenzene were selected as the aromatic hydrocarbons. In addition, thiophene and 3-methylthiophene were chosen as the sulfur containing compounds. For disclosing the separation behavior of olefins further, the VLE experiments were performed and several parameters were defined to describe the efficiency of separation of olefins.

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2. Experimental methods 2.1. Chemicals All chemicals used in this research were purchased from Aladdin Industrial Corporation and the purities of the chemicals were verified by gas chromatography. Further information about pure components, tested densities by oscillation tube method, boiling points and refractive indices along with values published in the correlative literature is shown in Table 1. As we know, about 90 % sulfides in gasoline are thiophene and its additives, whatever aromatic ring or double bond will have strong interaction with sulfides, aromatic and olefin are both difficult to separate from thiophene and its derivatives. According to the content of these hydrocarbons and sulfides in FCC naphtha, 1-hexene (>99 wt%, abbreviated as HEX), 2,4,4-trimethylpentene (>97 wt%, abbreviated

as

TMP),

toluene

(>97

wt%,

abbreviated

as

TOL),

and

1,2,4-trimethylbenzene (>97 wt%, abbreviated as TMB) were selected as the representative components for olefins and aromatics, respectively. In addition, the sulfides included thiophene (>97 wt%, abbreviated as THI) and 3-methylthiophene (>97 wt%, abbreviated as MTHI), respectively. The model gasoline used in current research was prepared with one of olefins and one of aromatic compounds. And the content of olefins in the mixture increased from 10% to 90% with a constant step of 10%. The solvents of sulfolane (SUL, >97 wt%) and N-methyl-2-pyrrolidone (NMP, >97 wt%) were used to investigate the separating effect of olefins. 2.2. Apparatus and Experimental Procedure The experimental apparatus used for vapor-liquid equilibrium (VLE) experiment

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consists of a modified Rose dual-circulating vapor-liquid distiller (presented in Fig. 1) with an intelligent condenser. The equilibrium temperature was measured by an accurate and calibrated thermometer with a standard uncertainty of 0.01K. The equilibrium pressure is determined by a manometer with an uncertainty of 0.1 kPa and kept constant at 101.3 kPa by controlling a gas buffer. The gasoline was firstly stirred for a while to ensure it was mixed well. Then the mixture comprised of 20 ml of solvent of SUL or NMP and 20 ml of model gasoline was introduced into the vessel. The heating voltage was set to 7-8V. When the temperature of the VLE system kept stable for an hour41-42, the vapor phase and liquid phase were sampled by syringe, respectively. Afterwards both of the samples were washed by a certain volume of deionized water to remove the solvents for analysis. Each experiment was replicated at least three times, and the standard deviation of the mass percentage is 0.001. 2.3. Sample analysis Densities were tested in an Anton Paar DMA 4500 M densimeter at 298.15K and atmospheric pressure with an uncertainty of ± 10-5 g/cm3. Refractive indices were measured in an ATAGO RX-5000 refractometer with an uncertainty of ± 4×10-5. The products of compositions of vapor phase and liquid phase were analyzed by an Agilent 7890B Gas Chromatograph (GC) equipped with an automatic injector, a flame ionization detector (FID) and a data processor system. Capillary column of PONA (50m*0.2mm*0.2µm) with column efficiency of over 4500 column plate per meter was filled with cross-linked methylsilicone oil. The column temperature was programmed for initial temperature of 308 K maintained for 15 min, and a final temperature of 453 K with a heating rate 2 K/min was maintained for 10 min. Nitrogen with a purity of 99.999% was used as the carrier gas at a constant flow rate of 3×10-5 9


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Energy & Fuels

m3/min. Besides, the injection temperature was 523.15 K, and the detector temperature was 553.15 K. At last, the normalization method was adopted to analyze the composition of samples. Each mass percentage was repeatedly measured three times, and the average mass percentage experimental uncertainty was ± 0.0005. 2.4. Equations In order to describe separation performance quantitatively, several parameters were defined as followed. (1) Contents of olefins in vapor phase (y1) at different conditions were used to value the influence of composition of model gasoline on separation effect. (2) The area value (S) between vapor-liquid equilibrium line (pink line) and base line (blue line) in Fig. 2-3 was determined by the contents of olefins in vapor and liquid phase. The higher the value of S is, the easier the separation of olefins and aromatic compounds is. (3) The relative volatility (α12)34,43 was introduced to present the effect of each solvent on separation of olefins.

α 12 =

y1 x 1 y2 x 2

(1)

Where y1 and x1 are the mass percentages of olefins in the vapor and liquid phase respectively. Similarly y2 and x2 represent the contents of aromatics in vapor and liquid phase.

3. Results and discussion As we all know, there exists a complicated interaction relation in a mixture system containing olefins, aromatics, and solvents. This interaction related to the charge distribution of each component in the mixture, which is determined by 10


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different molecular structure. Therefore, with the change of the structure or concentration of the components in model gasoline, the effect of separating olefin by the same solvent must be different. In order to find out the suitable solvent for different feedstock, it’s definitely worth studying the behavior about the separation of olefins from aromatic hydrocarbons or thiophenic compounds. For this aim, the vapor-liquid equilibrium data for HEX (1) + THI (2) + SUL/NMP, HEX (1) + MTHI (2) + SUL/NMP, HEX (1) + TOL (2) + SUL/NMP, HEX (1) + TMB (2) + SUL/NMP, TMP (1) + THI (2) + SUL/NMP, TMP (1) + MTHI (2) + SUL/NMP, TMP (1) + TOL (2) + SUL/NMP and TMP (1) + TMB (2) + SUL/NMP at atmospheric pressure are listed in Table 2-9, where T presents the equilibrium temperature, xi and yi are the mass percentages of component i in the liquid and vapor phase, respectively.

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Energy & Fuels

3.1. Effect of aromatics structure Different structure of aromatic hydrocarbons or thiophene compounds can bring about a distinct influence on the performance of separating olefin. This structure-effect relationship has been discussed in detail below. Figs. 2-3 present y1-x1 phase diagrams for eight groups model gasoline with different components in structures and by the solvent of SUL. They are “HEX + THI/MTHI/TOL/TMB + SUL” and “TMP + THI/MTHI/TOL/TMB + SUL”, respectively. As can be seen from Fig. 2, the trend of the four curves appears similar for different aromatic compounds, reflecting thus the analogous interaction relation. Comparing Fig. 2a with Fig. 2b, it could be found that with the change of thiophene compounds from THI to MTHI, a displacement that y1 upward appears, which indicates that more HEX have been separated to the vapor phase, meanwhile more thiophenic compounds are dissolved in SUL. That qualitatively implies that the interaction between SUL and MTHI is larger than that of THI. A transparent and rigorous approach, which can more accurately shine a light on the separation effect of HEX, is the comparison of the calculated area (S) between the VLE line and the base line. The area between vapor-liquid equilibrium dotted line and solid line in Fig. 2b is 0.369, nevertheless, that is just 0.306 for the system containing THI. Besides, the content of HEX in vapor phase (y1) in Fig. 2b is slightly greater than that in Fig. 2a when the content of HEX in feed stream is the same. On the basis of these data, it can be accurately inferred that MTHI can be extracted in SUL more easily than THI because of great difference of boiling point of both thiophenic compounds. As is presented in Table 1, the boiling point of MTHI is 114.0 °C, yet that of THI is just 84.0 °C. Consequently, there exists a greater difference of boiling point between HEX and MTHI, leading to a better separation effect of HEX from MTHI than THI. Probably 12


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the relative volatility of HEX to THI or MTHI is another strong parameter to present the effect of aromatics structure on separating olefin from aromatics. So there is a gap between the two lines in Fig. 4a, which gives a visualized evidence on better effect of separating HEX from MTHI than that of THI. Such as, when the content of HEX is 10%, α12 of HEX to MTHI reaches up to 29.33, yet α12 for THI is just 17.60. The difference in these two thiophenic compounds is that MTHI has a methyl connecting to its thiophene ring, meaning more proton donators of MTHI than that of THI. SUL as the hydrogen bond acceptor, there is strong electro-negativity because of the two oxygen atoms. Stronger hydrogen bonds exist between SUL and MTHI, so HEX can be separated better when THI is replaced by MTHI. Besides, the same conclusion could be drawn from Fig. 2c, Fig. 2d and Fig. 4b. The value of y1 is obviously greater than the content of HEX in vapor phase for the system containing TOL. It’s visualized that the area of “HEX + TMB + SUL” is 0.431, however, that for TOL in Fig. 2c is only 0.321. Furthermore, α12 of HEX to TOL is even smaller than that of HEX to TMB, which implies the other two methyls help TMB transfer more charges to SUL, resulting in stronger hydrogen bond with SUL. The greater interaction between SUL and TMB is, the better separating effect for HEX is. In addition, a distinct phenomenon can be found from “HEX + aromatics + SUL” system that the content of HEX in the vapor phase reaches up to 72.3 % when its content in feedstock is only 10%, suggesting that HEX can be separated from TMB by SUL very easily. It’s easily found that the difference of boiling point of TOL and TMB is about 58.3 °C, which leads to a striking difference of separation effect of olefin from TOL and TMB. As for systems of TMP + THI/MTHI + SUL and TMP + TOL/TMB + SUL, different trend has been presented in Fig. 3, meaning that the dotted lines are almost

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parallel with solid line except for Fig. 3d. In other words, the curves in Fig. 3 appear closer to the base line than those in Fig. 2. It’s noticeable that cubic dots for “TMP + MTHI + SUL” and “TMP + TMB + SUL” appear higher than the dots for “TMP + THI + SUL” and “TMP + TOL + SUL”, respectively. It’s similar to above discussions that more methyls on MTHI and TMB lead to stronger hydrogen bond than that of THI and TOL, respectively. Further, there is still a large distinction between Fig. 3c and Fig. 3d, and area value of Fig.3d is 0.356, which is much greater than 0.177 of Fig. 3c. As can be seen, the relative volatility of TMP to aromatics presented in Fig. 4c and Fig. 4d can explain well why TMP could be separated from MTHI and TMB more easily than THI and TOL, respectively. The different value of α12 implies that SUL has greater attractive forces to MTHI or TMB than THI or TOL, respectively, pushing TMP to the vapor phase, thus enhancing the relative volatility of TMP to MTHI or TMB. These findings impel us to conclude that MTHI and TMB show better performance in separating olefins from aromatics than THI and TOL, respectively. This separation behavior suggests that aromatics with one or more methyls can be dissolved more easily relative to methyl-lacking compounds due to larger interaction force. The strong electronegativity of solvents is really likely to obtain more charges from compounds with more methyls. Besides, the difference of boiling point between olefin and aromatic compounds is undoubtedly a strong evidence to demonstrate the separation effect of olefin from aromatics. 3.2. Effect of aromatics content As is exhibited in Fig. 2-4, no matter which olefin, the structure of aromatic compounds or thiophenes brings a significant impact on the olefin separation. Furthermore, it’s believed that the content of aromatics also affects the separation 14


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performance, thus detailed data about aromatic contents will be discussed afterwards. The experimental VLE data for systems of (1) HEX + THI/MTHI/TOL/TMB + SUL and (2) TMP + THI/MTHI/TOL/TMB + SUL are plotted on three-dimensional y1-F2 diagrams in Fig. 5-6, respectively. Where F2 is the volume fraction of aromatics in the feedstock ranging from 10% to 90% and y1 is the content of olefins in vapor phase for four different systems. In the Fig. 5, as for the group of “HEX + TMB + SUL”, the slope of the star dotted curve is significantly smaller than that of “HEX + TOL + SUL” at the same F2, which agrees with the conclusion obtained in previous section, implying better separating-olefin effect than that of “HEX + TOL + SUL” system. It’s common for these four lines that a 10% addition of aromatics produces a decline of y1, and the slopes of curves go up gradually as the amount of aromatics increases. The circular dotted line, taken as an example here, presents a small slope at areas of low aromatic content. However, when the content of aromatics in model gasoline (F2) rises to 60%, there is an obvious increase of this curve’s slope, relative to that of low aromatic content, which means the increase of aromatics content in the mixture leads to more prominent separating process. For a certain solvent, it has solubility for solutes. It is easy to understand that when one kind of solutes is became more, another kind of solute will be dissolved less in solvent. So there is not enough remaining solvents for dissolving HEX as the content of aromatics reaches 60% or 70% even 90%. Hence, it can be seen from this that separating-olefin performance of SUL is substantially improved at areas of high aromatic content. The same phenomena exhibited in Fig. 6 are another forceful evidence to verify above conclusion, that the higher aromatics content is, the better separating effect is. However, for the four curves in Fig. 6, its difference from systems containing HEX in

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Fig. 5 is that its slope appears a little greater.. That might suggest the performance of separating TMP from aromatics by SUL is a little better than that of HEX. The details will be analyzed in next section. From the results we have obtained, we can conclude that greater interaction between SUL and aromatics than that of olefins can help to separate high concentration aromatics mixture efficiently. It can be explained that SUL can extract aromatics more easily with the increasing of F2 and meanwhile olefin can be separated into vapor phase more effectively. 3.3. The effect of structure and content of olefins As discussed above, the structure and content of thiophenic compounds and aromatic hydrocarbons have exerted a distinct impact on the separation of olefins. Analogous structure-effect relationship can also be found for olefins. Not only the structure of olefins can affect the separation factor, but also the olefin concentration in model gasoline has a significant effect on olefin separation from aromatic compounds or thiophenes. It’s quite visualized to find that there is a higher olefin content in vapor phase for “HEX + THI + SUL”, compared with “TMP + THI + SUL” in Fig. 7. Meanwhile, even if THI is replaced by MTHI, the system including HEX lies at a dominant position, implying that SUL has a smaller interaction with HEX than TMP. In addition, what’s quite conspicuous is that y1 of every system containing HEX is greater than that of TMP. For example, when the concentration of HEX or TMP is 10%, y1 of the system “HEX + TOL + SUL” in Fig. 8 is 51.4%, whereas that of “TMP + TOL + SUL” is merely 31.2%. Comparing with HEX, there exist three methyls in TMP molecule, providing sufficient proton transferring with SUL. As a result, the hydrogen bond between TMP and SUL is a little stronger than that of HEX. This conclusion also helps make clear why y1 of “HEX + TMB + SUL” system is greater than that of 16


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“TMP + TMB + SUL”. When F1 was below 40%, it is obvious that the distance between two adjacent points appears truly long comparing with the points at high olefin content. In other words, there is a distinct rise of y1 when F1 ranges from 10% to 40%, but the slopes of curves become smaller and smaller with the further increasing of F1. In view of SUL’s certain solubility for solutes, if the concentration of aromatics becomes less, olefin will be dissolved more in SUL. However, more olefins dissolved in SUL can lead to bad separating effect, so y1 increases slowly in the later period. When it comes to the aromatic hydrocarbons in Fig. 8, this behavior can be probably supported much better. The slope of the curve y1-F1 grows even smaller at the areas of F1 ranging from 60% to 90%, especially for “HEX/TMP + TMB + SUL”. In the following work we have studied the separation of all systems containing NMP. It’s revealed that NMP has greater interaction with TMP, MTHI and TMB than HEX, THI and TOL, respectively. Meanwhile, the content of olefin or aromatics has extremely similar influence on the separating effect with containing-SUL systems. 3.4. Effect of solvents Though effect of SUL on olefin separation has been illuminated fully above, the performance of separating olefins by other organic solvents might be different. To explore this concept further, NMP has been used as another solvent for a thorough research. The systems containing HEX have been further studied in this paper, considering the better separating effect than TMP. As the separation ability of solvents can be expressed by the relative volatility, the relative volatilities of HEX to aromatics for the ternary systems containing SUL or NMP were calculated and drawn in Fig. 9. Generally, relative volatility is an indicator of separation effect, and the relative volatility was 17


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Energy & Fuels

significantly enhanced with the substitution of SUL for NMP. At areas of high aromatic content, SUL shows the larger relative volatility than NMP due to the stronger interaction between SUL and aromatics. For instance, the α12 of HEX respect to TOL for SUL is 19.31 and α12 for NMP is just 12.01 when HEX concentration is10%. At areas of high HEX content, the aromatic compounds are almost surrounded by HEX. The interaction force between solvents and aromatics is weakened by the interaction between HEX and solvents, resulting in a falling curve. However, when F1 rises to 70%, α12 for NMP is 8.46 and that for SUL becomes 6.01, implying that NMP can be used as the better solvent for high HEX content feedstock. Further, a reverse performance is presented in the regions of F1 from 70% to 90%, that the points of relative volatility for NMP are over SUL by the reason of stronger solubility of NMP with HEX. What is quite amazing is that this rule appears common for the four systems presented in Fig. 9. On the other hand, it’s worth noting that y1 produced by SUL is nearly overtaken by that of NMP at areas of higher HEX content. This can be explained that SUL with the higher polarity has the greater difference of solubility and interaction with HEX and aromatics. Meanwhile, the lower the polarity of NMP is, the less difference there is. The conclusion that SUL shows a better separating effect for the model gasoline of low and middle olefin content, whereas NMP has a better separating effect for the model gasoline of high olefin content can be drawn. Comparison of the performance of organic solvents as extractants for the separation of olefins in this study, it shows the SUL is an optimal extractant for the considered process. Some explanations and analyses are discussed to characterize molecular interaction operating between solvents and individual components in this work. For the systems investigated in this research, the intermolecular interactions mainly consist of hydrogen bonds, electrostatic interaction, and van der Waals forces44.

18


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Some relevant study has reported the interaction behavior between components and ionic liquid is in the form of hydrogen bonds45. THI/MTHI, TOL/TMB and HEX/TMP can be regarded as hydrogen bonding donators due to hydrogen atoms, especially for the MTHI, TMB and TMP owning excessive methyl. For SUL and NMP, the difference presented in the influence on VLE behavior of systems all lies in the location of non-carbons. Both oxygen atoms and the sulfur atom all locate the same orientation on SUL, however, there is only one oxygen atom and the nitrogen atom is also at a different orientation from the former. There is no doubt that the oxygen atoms group on SUL has stronger electro-negativity than the oxygen atom or nitrogen atom on NMP, which forms stronger hydrogen bond between SUL and above components, resulting in greater relative volatility and olefin content in vapor phase. From the above, SUL shows a better separation effect. Meanwhile, comparing with THI, the interaction between MTHI and solvents is larger. What’s more, the interaction between solvents and TMB is also greater than that of TOL. For TMP, the proton donating capability is undoubtedly enhanced by the three methyls, leading to stronger hydrogen bond with solvents than HEX.

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Energy & Fuels

4. Conclusion To study the influence of the structure and concentration of olefins and aromatic compounds on the separation of olefins from aromatics, the isobaric VLE data for HEX + THI/MTHI/TOL/TMB + SUL/NMP and TMP + THI/MTHI/TOL/TMB + SUL/NMP were measured in a modified Rose dual-circulating distiller at atmospheric pressure. As expected, the structure of thiophene and aromatic compounds has a remarkable impact on the separation of olefins. Due to the difference of boiling point between these four aromatic compounds, the systems containing TMB or MTHI can be separated more easily than TOL or THI, respectively. It implies that SUL has a greater interaction with TMB and MTHI than TOL and THI, respectively. This conclusion can be illuminated well by stronger hydrogen bond between SUL and TMB or MTHI owing to more methyl on them. There is also a striking difference between the structure of HEX and TMP. Because of the lack of substituents, HEX has fewer proton donators than TMP. So comparing with HEX, the hydrogen bond between SUL and TMP is rather stronger. When the aromatic compound in model gasoline is certain, HEX can be separated from aromatics more easily than TMP. Furthermore, the concentration of olefins or aromatics in model gasoline is also crucial to the separation effect of olefins. The higher y1 is, the larger the relative volatility, consequently the easier the separation of olefins. No matter which olefin, when the content of aromatics is over 60%, olefins can be separated more effectively due to the greater interaction between SUL and aromatics or thiophenes than that of olefins. As separating effect changes with the aromatic content, likewise, there appears a slow growth of y1 when F1 is greater than 40%. This can be clearly demonstrated that 20


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

SUL will dissolve more olefins when there exists fewer aromatics in model gasoline because of certain dissolving capability of the solvent. Then relative volatility is used to compare both of solvents to select an optimal one. It’s explicitly confirmed that NMP prefers to separate the mixture of much higher olefin content, yet SUL is more efficient for the model gasoline of low olefin content or middle olefin content. The separation behavior for HEX and TMP from aromatics hydrocarbons or thiophenes is clearly revealed through different compounds and solvents above, which well prepares for extractive distillation. In order to quicken the upgrading of clean gasoline, more types of olefins will be considered in future study.

Author Contributions †

These authors contributed equally.

Acknowledgments The authors acknowledge the supports from the National Natural Science Foundation of China (21476260, 21336011, and 21236009) and Science Foundation of China University of Petroleum, Beijing (2462015YQ0311).

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Energy & Fuels

References: (1) Basfar, A. A.; Mohamed, K. A. Radiation-induced desulfurization of Arabian crude oil and straight-run diesel. Radiat Phys. Chem. 2011, 80, 1289-1290. (2) Sundararaman, R.; Ma, X.; Song, C. Oxidative Desulfurization of Jet and Diesel Fuels Using Hydroperoxide Generated in Situ by Catalytic Air Oxidation. Ind. Eng. Chem. Res. 2010, 49, (12), 5561-5568. (3) Alonso, L.; Arce, A.; Francisco, M. A.; Guez, O. R.; Soto, A. Gasoline Desulfurization Using Extraction with [C8mim][BF4] Ionic Liquid. AIChE J. 2007, 53, (12), 3108-3115. (4) The State Standard of the People's Republic of China, Gasoline for motor vehicles, GB 17930-2016. (5) European Commission, 2011. Commission regulation (EU) No 582/2011 of 25 May 2011 implementing and amending regulation (EC) No 595/2009 of the European Parliament and of the council with respect to emissions from heavy duty vehicles (Euro VI) and amending annexes I and III to directive 2007/46/EC of the European Parliament and of the council. Official J. Eur. Union L 167, 1-168. (6) Song, L.; Zhang, S.; Ma, Q. Synthesis of an iron phosphide catalyst based on sulfides and hydrodesulfurization property. Chem. Eng. J. 2015, 281, 281-285. (7) Xu, M.; Liu, H.; Ji, S.; Li, C. Intensification of Deep Hydrodesulfurization Through a Two-stage Combination of Monolith and Trickle Bed Reactors. Chinese J. Chem. Eng. 2014, 22, 888-897. (8) Amaya, S. L.; Alonso-Núñez, G.; Zepeda, T. A.; Fuentes, S.; Echavarría, A. Effect of the divalent metal and the activation temperature of NiMoW and CoMoW on the dibenzothiophene hydrodesulfurization reaction. Appl. Catal. B-Environ. 2014, 148-149, 221-230.

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(9) Li, H.; Dong, L.; Zhao, L.; Cao, L.; Gao, J.; Xu, C. Enhanced Adsorption Desulfurization Performance over Mesoporous ZSM-5 by Alkali Treatment. Ind. Eng. Chem. Res. 2017, 56, (14), 3813-3821. (10) Li, H.; Han, X.; Huang, H.; Wang, Y.; Zhao, L.; Cao, L.; Shen, B.; Gao, J.; Xu, C. Competitive adsorption desulfurization performance over K-Doped NiY zeolite. J. Colloid Interf. Sci. 2016, 483, 102-108. (11) Qiu, L.; Zou, K.; Xu, G. Investigation on the sulfur state and phase transformation of spent and regenerated S zorb sorbents using XPS and XRD. Appl. Surf. Sci. 2013, 266, 230-234. (12) Meng, X.; Huang, H.; Shi, L. Reactive Mechanism and Regeneration Performance of NiZnO/Al2O3-Diatomite Adsorbent by Reactive Adsorption Desulfurization. Ind. Eng. Chem. Res. 2013, 52, (18), 6092-6100. (13) Wang, L.; Zhao, L.; Xu, C.; Wang, Y.; Gao, J. Screening of active metals for reactive adsorption desulfurization adsorbent using density functional theory. Appl. Surf. Sci. 2017, 399, 440-450. (14) Ullah, R.; Bai, P.; Wu, P.; Liu, B.; Subhan, F.; Yan, Z. Cation-anion double hydrolysis derived mesoporous mixed oxides for reactive adsorption desulfurization. Micropor. Mesopor. Mat. 2017, 238, 36-45. (15) Yu, F.; Wang, Y.; Liu, C.; Xie, C.; Yu, S. Oxidative desulfurization of fuels catalyzed by ammonium oxidative-thermoregulated bifunctional ionic liquids. Chem. Eng. J. 2014, 255, 372-376. (16) Zhu, W.; Wu, P.; Yang, L.; Chang, Y.; Chao, Y.; Li, H.; Jiang, Y.; Jiang, W.; Xun, S. Pyridinium-based temperature-responsive magnetic ionic liquid for oxidative desulfurization of fuels. Chem. Eng. J. 2013, 229, 250-256. (17) Li, S.; Mominou, N.; Wang, Z.; Liu, L.; Wang, L. Ultra-deep Desulfurization of

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Energy & Fuels

Gasoline with CuW/TiO2-GO through Photocatalytic Oxidation. Energ. Fuel. 2016, 30, 962-967. (18) Rezvani, M. A.; Khandan, S.; Sabahi, N. Oxidative Desulfurization of Gas Oil Catalyzed by (TBA)4PW11Fe@PbO as an Efficient and Recoverable Heterogeneous Phase-Transfer Nanocatalyst. Energ. Fuel. 2017, 31, 5472-5481. (19) Xiao, J.; Wu, L.; Wu, Y.; Liu, B.; Dai, L.; Li, Z.; Xia, Q.; Xi, H. Effect of gasoline composition on oxidative desulfurization using a phosphotungstic acid/activated carbon catalyst with hydrogen peroxide. Appl. Energ. 2014, 113, 78-85. (20) Kȩdra-Królik, K.; Fabrice, M.; Jaubert, J. Extraction of Thiophene or Pyridine from n-Heptane Using Ionic Liquids. Gasoline and Diesel Desulfurization. Ind. Eng. Chem. Res. 2011, 50, (4), 2296-2306. (21) Hadj-Kali, M. K.; Mulyono, S.; Hizaddin, H. F.; Wazeer, I.; El-Blidi, L.; Ali, E.; Hashim, M. A.; AlNashef, I. M. Removal of Thiophene from Mixtures with n‑ Heptane by Selective Extraction Using Deep Eutectic Solvents. Ind. Eng. Chem. Res. 2016, 55, 8415-8423. (22) Nie, Y.; Li, C.; Sun, A.; Meng, H.; Wang, Z. Extractive Desulfurization of Gasoline Using Imidazolium-Based Phosphoric Ionic Liquids. Energ. Fuel. 2006, 20, 2083-2087. (23) Jiang, X.; Nie, Y.; Li, C.; Wang, Z. Imidazolium-based alkylphosphate ionic liquids–A potential solvent for extractive desulfurization of fuel. Fuel 2008, 87, 79-84. (24) Kȩdra-Krolik, K.; Mutelet, F.; Moïse, J.; Jaubert, J. Deep Fuels Desulfurization and Denitrogenation Using 1-Butyl-3-methylimidazolium Trifluoromethanesulfonate. Energ. Fuel. 2011, 25, (4), 1559-1565. (25) Królikowski, M.; Walczak, K.; Domańska, U. Solvent extraction of aromatic

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sulfur

compounds

from

n-heptane

using

Page 26 of 46

the

1-ethyl-3-methylimidazolium

tricyanomethanide ionic liquid. J Chem. Thermodyn. 2013, 65, 168-173. (26) Shen, H.; Mei, Z.; Shen, B.; Ling, H. The Desulfurization of Fluid Catalytic Cracking Gasoline by Extractive Distillation. Energ. Source. Part. A. 2012, 34, 187-196. (27) Revelli, A.; Mutelet, F.; Jaubert, J. Extraction of Benzene or Thiophene from n-Heptane Using Ionic Liquids. NMR and Thermodynamic Study. J. Phys. Chem. B. 2010, 114, (13), 4600-4608. (28) Larriba, M.; Navarro, P.; Delgado-Mellado, N.; Stanisci, V.; García, J.; Rodríguez, F. Extraction of aromatic hydrocarbons from pyrolysis gasoline using tetrathiocyanatocobaltate-based ionic liquids: Experimental study and simulation. Fuel Process. Technol. 2017, 159, 96-110. (29) Lee, F.; Gentry, J. C.; Wytcherley, R. W.; Cretoiu, L.; Shyamkumar, C. Process of Removing Sulfur Compounds from Gasoline. GTC Technology Corporation. U.S. Patent 6,551,502, B1, Apr 22, 2003. (30) Aromatics separation Process and Method of Retrofitting Existing Equipment for Same. GTC Technology Inc. U.S. Patent 6565742 B1, May 20, 2003.. (31) Banda, R.; Sohn, S. H.; Lee, M. S. Process development for the separation and recovery of Mo and Co from chloride leach liquors of petroleum refining catalyst by solvent extraction. J. Hazard. Mater. 2012, 213-214, 1-6. (32) Al-Jimaz, A. S.; Fandary, M. S.; Alkhaldi, K. H. A. E.; Al-Kandary, J. A.; Fahim, M. A. Extraction of Aromatics from Middle Distillate Using N-Methyl-2-pyrrolidone: Experiment, Modeling, and Optimization. Ind. Eng. Chem. Res. 2007, 46, (17), 5686-5696. (33) Navarro, P.; Larriba, M.; Delgado-Mellado, N.; Sánchez-Migallón, P.; García, J.;

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Energy & Fuels

Rodríguez, F. Extraction and recovery process to selectively separate aromatics from naphtha feed to ethylene crackers using 1-ethyl-3-methylimidazolium thiocyanate ionic liquid. Chem. Eng. Res. Des. 2017, 120, 102-112. (34) Li, Q.; Liu, P.; Cao, L.; Wen, F.; Zhang, S.; Wang, B. Vapor-liquid equilibrium for tetrahydrofuran+methanol+tetrafluoroborate-based ionic liquids at 101.3kPa. Fluid Phase Equilibr. 2013, 360, 439-444. (35) Díaz, I.; Palomar, J.; Rodríguez, M.; de Riva, J.; Ferro, V.; González, E. J. Ionic liquids as entrainers for the separation of aromatic - aliphatic hydrocarbon mixtures by extractive distillation. Chem. Eng. Res. Des. 2016, 115, 382-393. (36) Schucker, R. C. Extractive distillation process for the reduction of sulfur species in hydrocarbons streams. U.S. Patent 6,358,402, B1, Mar 19, 2002. (37) Shen, H.; Shen, B.; Ling, H. Desulfurization of Fluid Catalytic Cracking Gasoline by Extractive Distillation Coupled with Hydrodesulfurization of Heavy Fraction. Energ. Fuel. 2013, 27, 5153-5160. (38) Calvar, N.; Domínguez, I.; Gómez, E.; Domínguez, Á. Separation of binary mixtures aromatic+aliphatic using ionic liquids: Influence of the structure of the ionic liquid, aromatic and aliphatic. Chem. Eng. J. 2011, 175, 213-221. (39) Larriba, M.; Navarro, P.; Delgado-Mellado, N.; Stanisci, V.; García, J.; Rodríguez, F. Separation of aromatics from n-alkanes using tricyanomethanide-based ionic liquids: Liquid-liquid extraction, vapor-liquid separation, and thermophysical characterization. J. Mol. Liq. 2016, 223, 880-889. (40) García, S.; Larriba, M.; García, J.; Torrecilla, J. S.; Rodríguez, F. Liquid-liquid extraction of toluene from n-heptane using binary mixtures of N-butylpyridinium tetrafluoroborate and N-butylpyridinium bis (trifluoromethylsulfonyl) imide ionic liquids. Chem. Eng. J. 2012, 180, 210-215.

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Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(41) Sapei, E.; Zaytseva, A.; Uusi-Kyyny, P.; Keskinen, K. I.; Aittamaa, J. Vapor−Liquid Equilibrium for Binary System of Thiophene + n-Hexane at (338.15 and 323.15) K and Thiophene + 1-Hexene at (333.15 and 323.15) K. J. Chem. Eng. Data. 2006, 51, (6), 2203-2208. (42) Sapei, E.; Uusi-Kyyny, P.; Keskinen, K. I.; Aittamaa, J. Phase equilibria on four binary systems containing 3-methylthiophene. Fluid Phase Equilibr. 2009, 279, (2), 81-86. (43) Li, W.; Sun, D.; Zhang, T.; Dai, S.; Pan, F.; Zhang, Z. Separation of acetone and methanol azeotropic system using ionic liquid as entrainer. Fluid Phase Equilibr. 2014, 383, 182-187. (44) Li, J.; Yang, X.; Chen, K.; Zheng, Y.; Peng, C.; Liu, H. Sifting Ionic Liquids as Additives for Separation of Acetonitrile and Water Azeotropic Mixture Using the COSMO-RS Method. Ind. Eng. Chem. Res. 2012, 51, (27), 9376-9385. (45) Ruiz, E.; Ferro, V. R.; Palomar, J.; Ortega, J.; Rodriguez, J. J. Interactions of Ionic Liquids and Acetone: Thermodynamic Properties, Quantum-Chemical Calculations, and NMR Analysis. J. Phys. Chem. B. 2013, 117, 7388-7398.

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Energy & Fuels

Table 1. The detailed properties of chemicals at 298.15K and atmospheric pressure GC

Soluble

Boiling

purity

in

points

(%)

water

(℃)

98.22

Yes

97.84

1-hexene

Component

Structural formula

nD20

ρ (g/cm3)

Exp.

Lit.

Exp.

Lit.

287.3

1.263230

1.26130

1.4899

1.481

Yes

203.0

1.0286

1.028

1.4703

1.4684

99.41

No

63.0

0.6736

0.673

1.3985

1.3837

2,4,4-trimethyl pentene

97.05

No

101.4

0.7135

0.715

1.4113

1.411

toluene

99.54

No

110.6

0.8622

0.866

1.4968

1.494122

1,2,4-trimethyl benzene

98.35

No

168.9

0.8812

0.880

1.5049

1.50

99.28

No

84.0

1.0590

1.051

1.5296

1.525723

98.37

No

114.0

1.0000

1.014

1.5205

1.518

O

O S

sulfolane Solvents N-methyl-2pyrrolidone

O N CH3

Olefins

Aromatic

S

compounds thiophene

S

3-methyl thiophene

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Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 46

Table 2. Isobaric VLE data for ternary system of HEX (1) + THI (2) + SUL/NMP at atmospheric pressure HEX (1) + THI (2) + SUL content of olefins 0.1 0.2

vapor phase

HEX (1) + THI (2) + NMP

liquid phase

vapor phase α12

T(K) y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

347.2 0.456 0.544 0.045 0.955 17.60 366.1 0.325 0.675 0.056 0.944 8.06 345

0.617 0.383 0.090 0.910 16.26 363.2 0.521 0.476 0.127 0.854 7.36

0.3

343.2 0.731 0.265 0.158 0.842 14.76 360.6 0.644 0.352 0.215 0.784 6.67

0.4

342.5 0.799 0.197 0.252 0.746 12.04 358.4 0.667 0.333 0.246 0.754 6.16

0.5

341.1 0.844 0.152 0.329 0.669 11.31 357.1 0.699 0.297 0.293 0.707 5.66

0.6

340.6 0.870 0.126 0.580 0.420

5.01

0.7

339.8 0.899 0.096 0.709 0.286

3.80

0.8

0.9

338

0.928 0.067 0.857 0.138

2.25

337.1 0.950 0.050 0.916 0.084

1.75

356

0.773 0.222 0.409 0.588 5.00

353.9 0.832 0.163 0.513 0.487 4.85 353

0.914 0.080 0.704 0.292 4.73

351.1 0.928 0.072 0.812 0.188 2.99

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Energy & Fuels

Table 3. Isobaric VLE data for ternary system of HEX (1) + MTHI (2) + SUL/NMP at atmospheric pressure HEX (1) + MTHI (2) + SUL content of olefins

vapor phase

HEX (1) + MTHI (2) + NMP vapor phase

liquid phase

T(K)

α12 y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

0.1

351.4 0.496

0.504

0.032 0.968 29.33 383.1 0.393 0.607 0.044 0.956 14.06

0.2

349.2 0.686

0.310

0.074 0.926 27.74 379.2 0.565 0.431 0.094 0.899 12.59

0.3

347.6 0.774

0.221

0.120 0.880 25.62 376.4 0.692 0.304 0.159 0.841 12.04

0.4

346.9 0.863

0.132

0.218 0.781 23.39 366.7 0.790 0.205 0.247 0.752 11.73

0.5

345.5 0.897

0.098

0.305 0.693 20.82 358.3 0.872 0.123 0.380 0.618 11.53

0.6

344.4 0.933 0.0618 0.443 0.554 18.88 349.3 0.894 0.101 0.438 0.559 11.31

0.7

343.2 0.941

0.053

0.632 0.513 14.31 347.1 0.946 0.049 0.658 0.352 10.32

0.8

342.1 0.954

0.040

0.852 0.142

3.95

0.9

340.6 0.970

0.032

0.916 0.084

2.96

343

0.952 0.042 0.717 0.279

8.77

340.3 0.963 0.037 0.896 0.104

3.06

30


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 46

Table 4. Isobaric VLE data for ternary system of HEX (1) + TOL (2) + SUL/NMP at atmospheric pressure HEX (1) + TOL (2) + SUL content of olefins

vapor phase

HEX (1) + TOL (2) + NMP

liquid phase

vapor phase α12

T(K) y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

0.1

370.2 0.514 0.486 0.052 0.948 19.31 374.5 0.499 0.501 0.077 0.923 12.01

0.2

362.1 0.598 0.409 0.080 0.920 16.88 369.1 0.568 0.440 0.104 0.896 11.14

0.3

352.8 0.673 0.323 0.118 0.881 15.54 363.4 0.627 0.372 0.145 0.855

9.94

0.4

348.2 0.787 0.209 0.209 0.789 14.18 360.6 0.715 0.281 0.211 0.789

9.50

0.5

346.2 0.838 0.158 0.283 0.716 13.47 358.3 0.798 0.198 0.306 0.693

9.15

0.6

344.1 0.872 0.123 0.383 0.615 11.37 348.1 0.873 0.127 0.443 0.554

8.61

0.7

342.3 0.916 0.079 0.655 0.341

6.01

8.46

0.8

341.2 0.938 0.057 0.763 0.233

5.05

0.9

339.8 0.968 0.318 0.886 0.114

3.92

345.3 0.903 0.092 0.536 0.460 343

0.945 0.049 0.695 0.300

8.25

340.8 0.962 0.038 0.815 0.185

5.78

31


Page 33 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 5. Isobaric VLE data for ternary system of HEX (1) + TMB (2) + SUL/NMP at atmospheric pressure HEX (1) + TMB (2) + SUL content of olefins

vapor phase

HEX (1) + TMB (2) + NMP

liquid phase

vapor phase α12

T(K) y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

0.1

360.2 0.723 0.277 0.032 0.968 78.47 394.6 0.688 0.312 0.035 0.965 60.63

0.2

354.1 0.843 0.157 0.066 0.936 76.38 388.1 0.787 0.213 0.059 0.941 58.90

0.3

348.2 0.890 0.110 0.104 0.896 70.18 381.5 0.867 0.139 0.096 0.904 58.55

0.4

347

0.935 0.065 0.176 0.824 67.20 374.4 0.908 0.092 0.152 0.848 55.23

0.5

346.1 0.946 0.054 0.216 0.784 64.08 365.7 0.927 0.073 0.192 0.808 53.77

0.6

343.9 0.969 0.031 0.347 0.653 59.42 359.8 0.944 0.056 0.249 0.751 50.85

0.7

342.6 0.979 0.021 0.510 0.490 45.53 355.3 0.975 0.025 0.444 0.556 47.94

0.8

339.2 0.990 0.010 0.710 0.290 40.58 354.1 0.987 0.013 0.633 0.367 44.73

0.9

336.6 0.998 0.002 0.933 0.067 32.14 351.9 0.991 0.009 0.772 0.228 34.10

32


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 46

Table 6. Isobaric VLE data for ternary system of TMP (1) + THI (2) + SUL/NMP at atmospheric pressure TMP (1) + THI (2) + SUL content of olefins

vapor phase

TMP (1) + THI (2) + NMP

liquid phase

vapor phase α12

T(K) y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

0.1

357.8 0.305 0.695 0.093 0.907 4.27 366.6 0.223 0.777 0.111 0.889 2.29

0.2

360.1 0.436 0.564 0.165 0.835 3.92 368.1 0.349 0.651 0.199 0.801 2.15

0.3

362

0.577 0.423 0.280 0.720 3.51 369.2 0.464 0.536 0.293 0.707 2.09

0.4

364.2 0.645 0.355 0.364 0.636 3.17 371.4 0.554 0.439 0.400 0.560 1.89

0.5

365.4 0.725 0.274 0.471 0.529 2.96 372.6 0.654 0.346 0.507 0.493 1.84

0.6

366.6 0.791 0.209 0.653 0.347 2.01 375.1 0.733 0.267 0.605 0.395 1.80

0.7

367.8 0.825 0.175 0.753 0.248 1.55

0.8

372.1 0.875 0.125 0.828 0.172 1.45 381.2 0.884 0.116 0.829 0.171 1.58

0.9

376.6 0.923 0.077 0.903 0.097 1.30 383.1 0.934 0.066 0.906 0.094 1.46

380

0.817 0.183 0.724 0.276 1.70

33


Page 35 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 7. Isobaric VLE data for ternary system of TMP (1) + MTHI (2) + SUL/NMP at atmospheric pressure TMP (1) + MTHI (2) + SUL content of olefins

vapor phase

TMP (1) + MTHI (2) + NMP

liquid phase

vapor phase α12

T(K) y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

0.1

384.5 0.387 0.613 0.082 0.918 7.05 401.2 0.349 0.651 0.098 0.902 4.90

0.2

382.1 0.495 0.499 0.135 0.865 6.37 397.6 0.436 0.564 0.155 0.845 4.19

0.3

380

0.613 0.387 0.206 0.791 6.08 394.4 0.589 0.411 0.262 0.738 4.03

0.4

379.1 0.727 0.273 0.313 0.678 5.79 393.1 0.666 0.334 0.339 0.661 3.88

0.5

377.9 0.791 0.209 0.404 0.596 5.58 391.7 0.737 0.263 0.443 0.557 3.52

0.6

376.8 0.854 0.146 0.537 0.455 4.95

0.7

375.6 0.872 0.128 0.682 0.318 3.17 384.1 0.854 0.146 0.647 0.353 3.19

0.8

374.2 0.910 0.090 0.838 0.162 1.94 383.3 0.915 0.085 0.773 0.227 3.16

0.9

372.4 0.914 0.086 0.857 0.143 1.78 381.5 0.933 0.067 0.826 0.174 2.91

386

0.802 0.198 0.545 0.455 3.37

34


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 46

Table 8. Isobaric VLE data for ternary system of TMP (1) + TOL (2) + SUL/NMP at atmospheric pressure TMP (1) + TOL (2) + SUL content of olefins

vapor phase

TMP (1) + TOL (2) + NMP

liquid phase

vapor phase α12

T(K) y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

0.1

381.5 0.312 0.688 0.084 0.916 4.97 398.1 0.259 0.741 0.102 0.898 3.08

0.2

379.4 0.398 0.602 0.126 0.874 4.59 395.3 0.306 0.694 0.131 0.869 2.94

0.3

378.1 0.475 0.525 0.186 0.814 3.95 393.5 0.429 0.571 0.216 0.784 2.72

0.4

376.9 0.605 0.395 0.279 0.714 3.92 391.6 0.517 0.476 0.291 0.703 2.62

0.5

375

0.674 0.326 0.375 0.625 3.45 383.3 0.631 0.369 0.398 0.602 2.59

0.6

373.7 0.755 0.245 0.496 0.504 3.13 381.4 0.718 0.282 0.488 0.512 2.67

0.7

372.2 0.827 0.173 0.695 0.305 2.10

0.8

370.6 0.895 0.105 0.810 0.190 2.01 377.1 0.868 0.132 0.725 0.275 2.49

0.9

368.7 0.933 0.067 0.921 0.079 1.19 375.5 0.952 0.048 0.914 0.086 1.88

379

0.794 0.206 0.601 0.399 2.57

35


Page 37 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 9. Isobaric VLE data for ternary system of TMP (1) + TMB (2) + SUL/NMP at atmospheric pressure TMP (1) + TMB (2) + SUL content of olefins

vapor phase

TMP (1) + TMB (2) + NMP

liquid phase

vapor phase α12

T(K) y1

y2

x1

liquid phase α12

T(K)

x2

y1

y2

x1

x2

0.1

409.4 0.440 0.560 0.038 0.962 19.79 434.2 0.368 0.632 0.047 0.953 11.76

0.2

401.2 0.670 0.330 0.095 0.906 19.42 423.2 0.563 0.437 0.101 0.899 11.43

0.3

394.6 0.757 0.243 0.141 0.859 18.94 413.6 0.684 0.316 0.167 0.833 10.74

0.4

388.3 0.847 0.153 0.235 0.765 18.06 405.4 0.793 0.207 0.267 0.733 10.50

0.5

383.2 0.890 0.110 0.313 0.687 17.76 400.8 0.845 0.455 0.342 0.658 10.48

0.6

382

0.914 0.086 0.427 0.573 14.35 396.4 0.894 0.106 0.452 0.548 10.24

0.7

380.5 0.950 0.061 0.616 0.384

9.78

390.9 0.929 0.071 0.570 0.430

9.86

0.8

378.7 0.963 0.037 0.756 0.244

8.46

388.7 0.953 0.047 0.697 0.303

8.79

0.9

376.4 0.977 0.023 0.896 0.104

4.96

384.4 0.968 0.032 0.855 0.145

5.22

36


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 1. Modified Rose dual-circulating vapor-liquid distiller. 1, heating rod; 2, liquid sample port; 3, thermometer; 4, vapor sample port; 5, cold water; 6, port to atmosphere; 7, condenser 152x296mm (300 x 300 DPI)


Page 38 of 46

Page 39 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Fig. 2. Isobaric VLE y1-x1 phase diagram for HEX (1) + aromatics (2) + SUL systems at atmospheric pressure: a, HEX + THI + SUL; b, HEX + MTHI + SUL; c, HEX + TOL + SUL; d, HEX + TMB + SUL. 279x215mm (300 x 300 DPI)


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 3. Isobaric VLE y1-x1 phase diagram for TMP (1) + aromatics (2) + SUL systems at atmospheric pressure: a, TMP + THI + SUL; b, TMP + MTHI + SUL; c, TMP + TOL + SUL; d, TMP + TMB + SUL. 279x215mm (300 x 300 DPI)


Page 40 of 46

Page 41 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Fig. 4. Relative volatility of olefin (1) to aromatics (2) with the HEX volume fraction for SUL at atmospheric pressure: a, HEX + THI/MTHI + SUL; b, HEX + TOL/TMB + SUL; c, TMP + THI/MTHI + SUL; d, TMP + TOL/TMB + SUL. F1, volume fraction of olefin in model gasoline. 279x215mm (300 x 300 DPI)


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 5. Isobaric VLE y1-F2 distribution diagram for the systems of HEX (1) + THI (2) + SUL, HEX (1) + MTHI (2) + SUL, HEX (1) + TOL (2) + SUL and HEX (1) + TMB (2) + SUL at atmospheric pressure. F2, volume fraction of aromatics in model gasoline. 288x200mm (300 x 300 DPI)


Page 42 of 46

Page 43 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Fig. 6. Isobaric VLE y1-F2 distribution diagram for the systems of TMP (1) + THI (2) + SUL, TMP (1) + MTHI (2) + SUL, TMP (1) + TOL (2) + SUL and TMP (1) + TMB (2) + SUL at atmospheric pressure. F2, volume fraction of aromatics in model gasoline. 288x200mm (300 x 300 DPI)


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 7. Isobaric VLE y1-F1 distribution diagram for the systems of HEX (1) + THI (2) + SUL, TMP (1) + THI (2) + SUL, HEX (1) + MTHI (2) + SUL and TMP (1) + MTHI (2) + SUL at atmospheric pressure. F1, volume fraction of olefin in model gasoline. 288x200mm (300 x 300 DPI)


Page 44 of 46

Page 45 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Fig. 8. Isobaric VLE y1-F1 distribution diagram for the systems of HEX (1) + TOL (2) + SUL, TMP (1) + TOL (2) + SUL, HEX (1) + TMB (2) + SUL and TMP (1) + TMB (2) + SUL at atmospheric pressure. F1, volume fraction of olefin in model gasoline. 288x200mm (300 x 300 DPI)


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 9. Relative volatility of HEX (1) to aromatics (2) and content of HEX in vapor phase with the HEX volume fraction for SUL and NMP at atmospheric pressure: △, SUL; □, NMP; —, y1;–––, α12. F1, volume fraction of olefin in model gasoline. 279x215mm (300 x 300 DPI)


Page 46 of 46

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