当前位置:首页 >> 工学 >>

Energy&Fuels (2014) article Ma Hao preprint


Article pubs.acs.org/EF

Solid Formation during Composite-Ionic-Liquid-Catalyzed Isobutane Alkylation
Hao Ma,? Rui Zhang,? Xianghai Meng,? Zhichang Liu,*,? Haiyan Liu,? Chunming Xu,? Rentan Chen,? Peter A. A. Klusener,*,? and Jan de With?
? ?

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, People’s Republic of China Shell Global Solutions International B.V., Grasweg 31, 1031 HW Amsterdam, Netherlands ABSTRACT: Composite ionic liquid (CIL) prepared from triethylamine hydrochloride, anhydrous aluminum(III) chloride, and cuprous chloride is a new catalyst for isobutane alkylation. This composite ionic liquid alkylation (CILA) technology yields an alkylate with favorable product distribution. CILA is a promising replacement for sulfuric acid and hydro?uoric acid alkylation technologies. However, some solids are formed during alkylation, and solid amount increases with time on stream. In a number of separation steps, the used CIL was divided into liquid and solid. Nuclear magnetic resonance, X-ray di?raction, X-ray photoelectron spectroscopy, and elemental analyses were applied to characterize these fractions. The content of acid-soluble oil (ASO) in solid was also investigated. The results showed that the solid was mainly cuprous chloride and contained about 1 wt % ASO. The loss of aluminum chloride and detachment of CuCl as a form of solid from CIL resulted in the decrease of CIL acidity and product selectivity.

1. INTRODUCTION
Alkylation of isobutane with butene is an important process to produce a clean gasoline blending stock with a high research octane number and motor octane number.1 The current industrial catalysts for the alkylation processes are sulfuric acid and hydro?uoric acid. Both industrial processes are not environmentally friendly because of acid sludge treatments and safety aspects.2,3 Chloroaluminate ionic liquids (ILs) have been identi?ed as a potential replacement for conventional liquid acid catalysts.4 Studies of IL-catalyzed alkylation of isobutane with 2-butene have been reported.4?11 Chloroaluminate ILs show good solubility for transition-metal salts, which opens the possibility of catalyzing lots of organic reactions in these ILs.12 China University of Petroleum13 has successfully developed a composite ionic liquid (CIL) from triethylamine hydrochloride, anhydrous aluminum chloride, and cuprous chloride, which shows good catalytic performance for isobutane alkylation.14,15 Bui et al. found that a combination of CuCl with Et3NHCl in acidic chloroaluminate ILs would raise the Br?nsted acidic site density and reduce the Lewis acidic site density. The Br?nsted acidic sites would inhibit such side reactions as cracking, polymerization, and isomerization.16 The advantage of composite ionic liquid alkylation (CILA) over the existing processes, especially HF alkylation, is that CIL has a negligible vapor pressure and is environmentally friendly. CILA ?nished the pilot test and was demonstrated in an existing sulfuric acid alkylation unit.17 CILA showed good alkylation performance, and the alkylate had comparable quality compared to the existing technologies. However, it appeared during the trial that small quantities of unknown solid material were formed.18 Moreover, CIL would deactivate after a certain amount of feedstock was handled during lab experiments. CIL deactivation may be connected with solid formation and IL
? XXXX American Chemical Society

structure change. These issues should be understood and resolved before the large-scale industrial application. A few reports were published on solid formation and IL structure change during the chloroaluminate-IL-catalyzed processes. Quarmby et al.19,20 found a phenomenon of solid formation using chloroaluminate ILs. The addition of NaCl or LiCl to an acidic IL generated an IL through the reaction of eq 1, in which M+ is a metal cation.
MCl(s) + Al 2Cl 7?(l) ? 2AlCl4 ?(l) + M+(l)
(1)

A weak Lewis base B: can react with resulting in the precipitation of MCl(s), as shown in eq 2. Thus, the presence of a Lewis base provides a driving force to pull eq 2 to the right.
B:+ AlCl4 ?(l) + M+(l) ? B:AlCl3(l or s) + MCl(s)
(2)

AlCl4?,

Patent applications by Chevron21,22 describe that acid-soluble oil (ASO) is formed during isobutane alkylation catalyzed by chloroaluminate ILs, and ASO contains polycyclic ole?n structures. The ASO deactivates the ionic liquid catalyst by weakening the acid strength through the formation of complexes with chloroaluminate species. Therefore, ASO changes the structure of chloroaluminate ILs and, accordingly, their reactivity. It was observed in our lab experiments that CIL reacting with water, e.g., moisture in air, forms solid, most likely hydroxyl chloroaluminates. The formation of solid and ASO during CILA may change the structure of CIL, and the ionic structure change will a?ect the catalytic performance of CIL. The study of solid and ASO formation during CILA can deepen the understanding of the catalytic mechanism, and it is also helpful to improve the CILA
Received: March 27, 2014 Revised: July 14, 2014

A

dx.doi.org/10.1021/ef500684r | Energy Fuels XXXX, XXX, XXX?XXX

Energy & Fuels

Article

Figure 1. Apparatus used for IL-catalyzed isobutane alkylation: (1) high-pressure nitrogen cylinder, (2) C4 feed tank, (3) electronic balance, (4) ?lter, (5) double plunger pump, (6) drying tube, (7) autoclave, and (8) gathering tank.

technology and its industrial application. In addition, it is important to establish a systematic and e?ective isolation and analysis methodology for ILs, which is useful for the study of IL-catalyzed processes. This work describes our study on the analysis of used IL, hereafter called spent IL, and solids formed during CILA. An e?ective method to handle and characterize solids is reported herein. From the analysis result, the composition of solid and the relation between the solid, product selectivity, and catalyst deactivation with the CIL structure can be obtained.

2. EXPERIMENTAL SECTION
2.1. General. Analytical-grade triethylamine hydrochloride, analytical-grade dichloromethane (DCM), anhydrous AlCl3, and CuCl were obtained from Aladdin Industrial Corporation. DCM was dried with a molecular sieve.23 2.2. Preparation of ILs, IL Deactivation Experiment, and Analysis Methods of Samples. CIL was synthesized from triethylamine hydrochloride, anhydrous AlCl3, and CuCl according to the reported method.13?15 The industrial CIL is the same as the industrial CIL reported.17 The analysis of fast-atom bombardment mass spectrometry, 27Al nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy15,17 showed that CIL contained a multi-center ligand of AlCl4CuCl?, which played important roles in improving alkylate quality.15 A semi-continuous isobutane alkylation experiment was conducted to obtain spent IL in the apparatus, as shown in Figure 1. The feed composition is listed in Table 1. The concentrations of possible

remaining C4 hydrocarbons were released, about 188 g of the spent IL was separated from the alkylate. Industrial spent IL (100 g) was obtained from the industrial trial of isobutane alkylation catalyzed by CIL in a re?nery of China National Petroleum Corporation.17 The volume percentage of components in the gas sample was measured by a re?nery gas analyzer, which is an Agilent 6890 gas chromatograph that was equipped with a hydrogen ?ame ionization detector, thermal conductivity detector, and ChemStation software. The liquid sample was analyzed by a SP3420 gas chromatograph that was equipped with a ?ame ionization detector. The chromatographic column is a PONA capillary column (50 m × 0.25 mm × 0.25 μm). The temperatures of the injector and detector were 250 and 300 °C, respectively. The temperature program was as follows: holding at 35 °C for 10 min, increasing to 60 °C at a speed of 0.5 °C/min, increasing to 180 °C at a speed of 2 °C/min, and ?nally holding at 180 °C for 10 min. The qualitative analysis was conducted on the basis of the holding time of the peak, whereas the quantitative analysis was conducted through the area normalization method. The research octane number (RON) of the alkylate was calculated according to the method applied in ref 10. 2.3. Separation of Spent IL into Isolated IL, Extracted IL and Solid, and Separation of ASO from Isolated IL and Solid. The separation steps shown in Figure 2 are described here below in detail for spent IL from the industrial trial. The relative sizes of the di?erent fractions are given in Table 2.

Table 1. Composition of Feedstock
component isobutane n-butane trans-2-butene cis-2-butene content (wt %) 89.62 1.88 4.92 3.58

contaminants, such as diole?ns, organic sulfur, and oxygen-containing compounds, were below the detection limit of our gas chromatography (GC) analysis. Water was removed from the feed by a molecular sieve. The 500 mL autoclave was ?lled with 208 g of CIL and, subsequently, isobutane. The pressure was maintained at 0.5 MPa to ensure the liquefaction of C4 hydrocarbons. A 10.5:1 molar mixture of isobutane and 2-butene was fed at a rate of 850 mL/h. The reaction temperature was 20 °C. The stirring rate was 900 rpm, at which the CIL remained predominantly in the middle and lower parts of the autoclave, while in the upper part, the hydrocarbon was leaving the autoclave and sampled for GC analysis. The CIL was considered to be deactivated totally when the conversion of 2-butene dropped to nearly zero, which was when 17 kg of the C4 mixture was fed into the autoclave. After the
B

Figure 2. Spent IL separation steps to isolated IL, extracted IL, and solid. Spent IL (100 g) from the industrial trial was centrifuged by a centrifuge (2-16PK, Sigma Labor Zentrifugen) at 4000 rpm for 5 h and split into 87.25 g of liquid phase (isolated IL) and 12.75 g of precipitate (paste). A mixture of paste (12.75 g) and DCM (50 mL) was centrifuged at 4000 rpm for 30 min. The sediment was separated o?, mixed with DCM (50 mL), and centrifuged again. This process was repeated 8
dx.doi.org/10.1021/ef500684r | Energy Fuels XXXX, XXX, XXX?XXX

Energy & Fuels Table 2. Spent IL Separated in Fractions
fractions (wt %) lab experiment industrial trial
a

Article

isolated IL 70.28 87.25

extracted IL 22.09a 8.74

solid 7.63 4.01

ASO as a weight percentage of solid 0.64 1.06

Extracted IL from the lab spent IL lost its ?uidity at room temperature.

deionized water to a volume of 8 L and then ?ltrated. The ?ltered solution was analyzed with ICP?OES to obtain the copper content. X-ray di?raction (XRD) pro?les were recorded with a Bruker D8 Advance X-ray powder di?ractometer at a scan rate of 1.2°/min for 1.3?5° and 5°/min for 5?90°. X-ray photoelectron spectroscopy (XPS) measurement was performed with a Thermo Fisher K-Alpha electron spectrometer. The base pressure was about 5 × 10?9 mbar. ASO in solid was dissolved in CDCl3 and analyzed by 1H NMR at 600 MHz on a JEOL JNM-ECA600. Traces of CHCl3 in the solvent were used as an internal standard for calibrating the chemical shift [δ CHCl3 = 7.24 ppm from tetramethylsilane (TMS)].

times in total until the DCM layer became colorless. The remaining sediment was dried in vacuum, yielding 4.01 g of solid. The DCM layers were combined, and DCM was removed in vacuo, yielding a residue of 8.74 g (extracted IL). A mixture of solid (1.94 g) and DCM (50 mL) was slowly poured into 50 g of an aqueous NaOH solution (10 wt %) in a ?ask placed in a water bath at 5 °C. After the hydrolysis, the mixture was stirred at room temperature for 8 h. The lower DCM layer was separated o?. The upper aqueous layer was extracted with 50 mL of DCM. The combined DCM layers were washed 3 times with 150 mL of NaOH solution (10 wt %) and then twice with 150 mL of deionized water. The DCM layer was dried over anhydrous solid MgSO4 and subsequently ?ltrated through a polytetra?uoroethylene (PTFE) ?lter. DCM was removed in vacuo, and the residue was considered as ASO (0.0206 g, 1.06% of the solid). A further study showed that the above obtained ASO was about 50 times the ASO remaining in the upper aqueous layer after DCM extraction (0.39 mg, 0.02% of the solid), and both ASOs had similar 1H NMR spectra. To simplify research, the ASO remaining in the upper aqueous layer after DCM extraction was not considered in the following study. Isolated IL from the lab experiment (20 g) was slowly poured into a 20 wt % aqueous NaOH solution (300 g) in a ?ask placed in a water bath at 5 °C. After the hydrolysis, the mixture was stirred at room temperature for 8 h. The aqueous solution was extracted by 50 mL of normal hexane. The upper hydrocarbon phase was separated o?. The lower aqueous layer was extracted with 50 mL of normal hexane. The combined normal hexane layers were washed 3 times with 150 mL of NaOH solution (10 wt %) and then twice with 150 mL of deionized water. The normal hexane layer was dried over anhydrous solid MgSO4 and, subsequently, ?ltrated through a PTFE ?lter. Normal hexane and triethylamine were removed in vacuo at 38 °C, and the residue was considered as ASO (0.914 g, 4.57% of the isolated IL). 2.4. Characterization of Isolated IL, Extracted IL, Solid, and ASO in Solid. Inductively coupled plasma?optical emission spectrometry (ICP?OES, OPTIMA7000DV, PerkinElmer, Inc., Waltham, MA) was used to investigate the metal contents in the samples. Cuprous, Cu(I), in samples was ?rst oxidized to cupric, Cu(II), by nitric acid, and then its metal composition was measured with ICP?OES. The inorganic chloride content of the solid was determined by potentiometric titration with a potentiometer (PHS-2F, Shanghai Leici Instrument Factory, China). The contents of C, H, N, and O were measured with an elemental analyzer (vario MICRO cube, Elementar). Isolated IL or extracted IL (150 mg) was hydrolyzed with 20 wt % nitric acid (10 g). The mixture was stirred for 5 h. The mixture was diluted with deionized water to a volume of 2.5 L and then ?ltrated. The ?ltered solution was analyzed by ICP?OES to determine the aluminum and copper contents. Fresh IL, isolated IL, and extracted IL were dissolved in CD2Cl2 and analyzed by 1H and 27Al NMR at 600 MHz on a JEOL AM 360 spectrometer. Solid (150 mg) was mixed with 20 wt % nitric acid (30 g). The mixture was stirred for 5 h and then diluted with deionized water to a volume of 250 mL. Part of the mixture (25 mL) was sampled, and its pH value was adjusted to 2 by the addition of NaOH solution. Potentiometric titration was used to measure the inorganic chlorine content. Part of the mixture (25 mL) was ?ltrated, and the ?ltered solution was analyzed with ICP?OES to obtain aluminum content. The remaining part of the mixture (200 mL) was diluted with
C

3. RESULTS AND DISCUSSION 3.1. Product of Catalytic Reaction. Table 3 lists the alkylate composition as a function of time on stream (TOS).
Table 3. Butene Conversion and Alkylate Composition as a Function of TOSa
TOS (h) 12.35 butene conversion (%) 100 alkylate composition (wt %) C5 2.11 C6 1.97 C7 3.54 C8 84.98 C9+ 7.39 T/D 6.21 RON 93.38
a

22.35 100 1.98 2.39 4.10 83.38 8.15 9.33 94.73

28.95 100 3.31 2.86 4.63 78.91 10.28 9.06 93.92

33.75 100 6.89 5.95 6.81 67.29 13.06 8.52 92.02

35.45 49.35 5.00 5.22 6.03 58.67 25.08 8.83 86.8

CIL, 208 g; I/O ratio, 10.5:1; and feed rate, 850 mL/h.

Butene conversion reached 100% at TOS below 33.75 h and decreased to 49.25% at TOS of 35.65 h. This shows that CIL maintained good catalytic activity at a long period. Alkylate showed good quality with high selectivity of C8 and high RON when TOS was below 28.75 h. Alkylate quality decreased gradually when TOS was above 28.75 h because both the selectivity of C8 and RON decreased. The selectivity to C9+ in the product increased during whole TOS. It results from gradual lower acid strength of catalyst. Gradual precipitation of solid from CIL is one reason for the deactivation of the catalyst, and the acidity reduction of CIL is another reason, which was also con?rmed by the NMR result in section 3.2. 3.2. Separation and Characterization of Spent IL in Fractions. Spent ILs from both the industrial trial and the lab experiment were separated into fractions (Table 2). Less paste was obtained from the industrial spent IL centrifugation than from the lab experiment. The paste was extracted with DCM and separated into IL and solid. The contents of Al and Cu in the fresh IL and the isolated fractions of spent IL are compared in Table 4. The copper contents in fresh IL and the isolated fractions of spent IL from the industrial trial were signi?cantly higher than those from the lab experiment, whereas the copper content in the solid fractions were almost the same. The loss of copper content in the IL fraction is thus related to the solid formation. The solids were therefore analyzed in more detail to understand these phenomena. The 1H NMR spectra of fresh IL, isolated IL, and extracted IL from the lab are illustrated in Figure 3. The chemical shift signals of fresh IL, isolated IL, and extracted IL were similar. For cation signals, the weak signals of isolated IL and extracted IL at 0.83, 2.15, and 2.85 ppm belong to the small amount of
dx.doi.org/10.1021/ef500684r | Energy Fuels XXXX, XXX, XXX?XXX

Energy & Fuels Table 4. Contents of Al and Cu in IL and Solid Fractions
fresh IL element (wt %) lab experiment industrial trial Al 12.7 12.5 Cu 4.64 7.27 Al 12.9 13.5 isolated IL Cu 0.21 5.70 Al 10.5 12.8 extracted IL Cu 0.09 4.60 Al 1.97 0.98 solid

Article

Cu 59.28 59.21

Figure 3. 1H NMR spectra of fresh IL, isolated IL, and extracted IL from the lab experiment.

ASO. It indicates that the cation structure of isolated IL and extracted IL is likely still the same as that of fresh CIL. The 27Al NMR spectra of fresh IL, isolated IL, and extracted IL from the lab experiment are shown in Figure 4. The largest

Figure 4. 27Al NMR spectra of fresh IL, isolated IL, and extracted IL from the lab experiment.

signal at 102 ppm belonged to AlCl4? and Al2Cl7?.24 The largest signal of fresh IL, isolated IL, and extracted IL nearby 97 ppm belonged to AlCl4CuCl?.15 The signal of fresh IL about Table 5. Elemental Contents of Solid Isolated from Spent ILs
element content (wt %) lab experiment industrial trial Cl 34.40 35.46 Cu 59.28 59.21 Al 1.97 0.98
D

AlCl4CuCl? was higher than those of isolated IL and extracted IL. It was likely caused by the decomposition of AlCl4CuCl?. In the alkylation process, AlCl4CuCl? could be decomposed into AlCl4? and CuCl, which is detached from the catalyst as a form of solid. The element analysis proves this viewpoint because the copper content in the isolated IL and extracted IL was nearly zero. Moreover, the copper content in isolated IL was higher than that in extracted IL. It can explain that isolated IL has a more obvious signal about AlCl4CuCl? than that of extracted IL. Moreover, AlCl4? at 102 ppm is found in Figure 4. It proves that the CIL has lost its acidity,25 resulting in the catalyst deactivation. The aluminum chloride is partly ?ushed away by feedstock and product. The IL mass change (9.6 wt %) and aluminum mass change (17.9 wt %) between fresh IL and used IL can prove it. Aluminum is an essential component of the CIL anion. The NMR result also indicates that the anion structures of isolated IL and extracted IL are similar. 3.3. Characterization of Solid. Elemental analysis of the solids isolated from spent ILs is shown in Table 5. The main elements in the solid were Cu and Cl, together being about 94 wt %. The Cu/Cl molar ratio was nearly 1, indicating that CuCl is the main component in the solid. The Al and N contents in the solid could indicate the presence of some remaining ionic liquid (although not expected after eight extractions), while the O content suggest that some hydrolysis of chloroaluminate has occurred. A further study showed that only about 12% of Al in the solid can dissolve in water. The H/N weight ratio is higher than 1.15, being the H/N ratio of Et3NH, indicating the presence of ASO. The XRD patterns of the solids are compared in Figure 5. The XRD patterns of the solid from the industrial trial and the lab experiment were identical and match the reference XRD pattern of CuCl (JCPDS PDF card 06-0344). It con?rms that the main content of solids is CuCl. XPS was applied to further characterize the solids (Figure 6). The binding energy of carbon was 284.18 eV (Figure 6b), and it can be associated with C?C or C?H (aliphatic C), being either from triethylamine and/or ASO. The shoulder at 286 eV can be assigned to C?N.26 The amount of remaining ionic liquid (containing a C?N bond) in solid was con?rmed to be very low, and thus, there were some hydrocarbons, e.g., ASO, remaining in the solid. Apparently, ASO was not thoroughly removed by the extraction of DCM. The binding energy of C 1s was slightly lower than that of aliphatic C in the literature,26 possibly because C of ASO interacts with the metal in solid. The binding energy of Cu 2p3/2 of 933.0 eV (Figure 6c) can be associated with CuCl, whereby the shoulder in the lab sample is most likely some oxidized product: CuCl2 or CuO.26 The binding energy of Cu 2p3/2 was slightly lower than that in

C 1.14 1.10

H 0.61 0.46

N 0.38 0.38

O 2.21 2.42

Cu/Cl molar ratio 0.96 0.93

dx.doi.org/10.1021/ef500684r | Energy Fuels XXXX, XXX, XXX?XXX

Energy & Fuels

Article

Figure 5. XRD patterns of solids from the industrial trial and the lab experiment.

the literature,27 possibly because the unoccupied orbital of Cu interacts with electrons of the ASO in the solid. The Cl 2p3/2 peaks at 198.28 eV and Cl 2p1/2 peaks at 199.78 eV (Figure 6b) can be related to CuCl according to the literature.27 The Al 2p binding energy (Figure 6e) was observed at 74.48 eV, which according to the literature can be associated with aluminum halide.26 The shoulder at 76.28 eV (Figure 6e) was associated with Cu 3p.27 Only one peak was observed for O 1s, namely, at 531.88 eV (Figure 6f), which matches with the O 1s binding energy of Al?O and not with Cu?O, which was

expected near 530 eV.26,28 Therefore, it can be concluded that the amount of CuO was very small. Finally, it should be noted that XPS is a surface technique, and the XPS results might not be representative for the bulk composition. Nevertheless, it can be concluded that the XPS results match the elemental analysis to a large extent. 3.4. Isolation and Characterization of ASO in Solid. ASO has been reported to be formed during isobutane alkylation.21,22,29,30 The ASO in the solid was isolated by hydrolysis of the solid and subsequent extraction with DCM. ASO in solid fractions of 1.06 and 0.64 wt % was isolated from the industrial trail and the lab experiment, respectively (Table 2). The small amounts of ASO in solid can partly explain the carbon and hydrogen contents in solid element analysis, and it also agrees with the XPS result. The 1H NMR spectra (Figure 7) of ASO isolated from the solids from the industrial trial and the lab experiment appeared to be similar. The signals with chemical shifts at 4?5.5 and 8.2 ppm indicate that ASO contained some ole?nic and aromatic structural units, respectively. The ASO from CILA solid shows similar ole?nic character as reported in the literature.21,22 3.5. Discussion of the Mechanism. The main solid formed is CuCl. Therefore, the formation of hydroxyl chloroaluminates by hydrolysis of CIL with wet feed plays only a minor role because only low levels of Al?O were found in the solid. The presence of ASO in the solid might be relevant to understand the solid formation mechanism despite its low content. Patent applications21,22 describe that ole?ns could deactivate chloroaluminate ILs by weakening the acid strength through the formation of complexes with Al2Cl7?, possibly by

Figure 6. XPS spectra of solids.
E
dx.doi.org/10.1021/ef500684r | Energy Fuels XXXX, XXX, XXX?XXX

Energy & Fuels

■ ■

Article

AUTHOR INFORMATION

Corresponding Authors

*Telephone: 8610-8973-1252. Fax: 8610-6972-4721. E-mail: lzch@cup.edu.cn. *Telephone: +31-0-20-630-2743. Fax: +31-0-20-630-2052. Email: peter.klusener@shell.com.
Notes

The authors declare no competing ?nancial interest.

Figure 7. 1H NMR of ASO in solids.

means of electron donor/acceptor interactions. Moreover, CuCl is also a Lewis acid, and it could form complexes with ole?ns,31?33 such as present in ASO. Thus, CuCl could react with ASO, forming a complex that does not dissolve in spent ILs. This may be a possible reason for solid formation and CuCl precipitation from CIL. However, ASO in solid represents only a small part of solid isolated. To test the in?uence of ASO on the IL structure, the ASO from the isolated IL was added to fresh CIL with the same mass of the isolated IL. However, the CIL with ASO still kept clear, and no solid was formed. Moreover, the ASO in extracted IL was also added to fresh IL in this way; nevertheless, it showed the same result with the ASO in isolated IL. This indicates that ASO is not the main reason for the detachment of CuCl and the loss of AlCl3 from CIL. Meanwhile, no obvious signal of the complex of ASO and Al2Cl7? or AlCl3 was found in Figure 4. It means that Al2Cl7? or AlCl3 does not combine with the obtained ASO on a large scale. The detachment of AlCl3 from Al2Cl7? is considered as the initial step of n-alkane cracking catalyzed by Lewis acidic chloroaluminate ILs, and AlCl3 will dissolve back to the ILs after the reaction.34 Because of the unstable status of AlCl3 in IL during Lewis acid catalysis, AlCl3 is likely separated out from CIL and then taken away by feedstock and product gradually. This will lead to the decrease of CIL acidity and the ?nal deactivation of the catalyst. The gradual loss of AlCl3 in CIL will result in the structural damage of the anion of AlCl4CuCl?, which will lead to the detachment of CuCl.

ACKNOWLEDGMENTS The authors thank Chunqi Xie and Xuan Zhang for assisting with alkylation experiments and Changchun Yu and Yun Liang for XPS analyses. The authors gratefully acknowledge the ?nancial support provided by Shell Global Solutions International B.V., Netherlands, the Natural Science Foundation of China (21036008, 21276275, 21206193, 20976194, and 20806091), the Program for New Century Excellent Talents in the University of China (NCET-12-0970), and the Science Foundation of China University of Petroleum, Beijing (KYJJ2012-03-23 and KYJJ2012-03-25).

4. CONCLUSION Some solids are formed in CIL-catalyzed isobutane alkylation. A suitable method has been developed to isolate the solid from the used IL. XRD and XPS analyses showed that the solid was mainly composed of CuCl. Extraction of the hydrolyzed solid showed the presence of about 1 wt % ASO. The ASO in the solid contains ole ? nic and aromatic hydrocarbons, as demonstrated by 1H NMR analysis. The solid from the lab experiment showed similar characteristics to those from the industrial trial, respectively. The isolated IL and extracted IL from used IL have a similar structure, which was proven by NMR. The loss of AlCl3 and detachment of CuCl from CIL result in the decrease of CIL acidity and alkylate quality.
F

(1) Das, D.; Chakrabarty, D. K. Energy Fuels 1998, 12 (1), 109?114. (2) Albright, L. F. Ind. Eng. Chem. Res. 2009, 48 (3), 1409?1413. (3) Corma, A.; Martínez, A. Catal. Rev.: Sci. Eng. 1993, 35 (4), 483? 570. (4) Zhang, J.; Huang, C. P.; Chen, B. H.; Ren, P. J.; Pu, M. J. Catal. 2007, 249 (2), 261?268. (5) Chauvin, Y.; Hirschauer, A.; Olivier, H. J. Mol. Catal. 1994, 92 (2), 155?165. (6) Yoo, K.; Namboodiri, V. V.; Varma, R. S.; Smirniotis, P. G. J. Catal. 2004, 222 (2), 511?519. (7) Olah, G. A.; Mathew, T.; Goeppert, A.; To?ro?k, B.; Bucsi, I.; Li, X. Y.; Wang, Q.; Marinez, E. R.; Batamack, P.; Aniszfeld, R.; Prakash, G. K. S. J. Am. Chem. Soc. 2005, 127 (16), 5964?5969. (8) Bui, T. L. T.; Korth, W.; Aschauer, S.; Jess, A. Green Chem. 2009, 11 (12), 1961?1967. (9) Zhang, J.; Huang, C. P.; Chen, B. H.; Li, J. W.; Li, Y. X. Korean J. Chem. Eng. 2008, 25 (5), 982?986. (10) Liu, Z. C.; Meng, X. H.; Zhang, R.; Xu, C. M.; Dong, H.; Hu, Y. F. AIChE J. 2014, 60 (6), 2244?2253. (11) Po?hlmann, F.; Schilder, L.; Korth, W.; Jess, A. ChemPlusChem 2013, 78 (6), 570?577. (12) Wasserscheid, P.; Keim, W. Angew. Chem., Int. Ed. 2000, 39 (21), 3772?3789. (13) Liu, Z. C.; Xu, C. M.; Huang, C. P. Method for manufacturing alkylate oil with composite ionic liquid used as catalyst. U.S. Patent 7,285,698 B2, Oct 23, 2007. (14) Huang, C. P.; Liu, Z. C.; Xu, C. M.; Chen, B. H.; Liu, Y. F. Appl. Catal., A 2004, 277 (1?2), 41?43. (15) Liu, Y.; Hu, R. S.; Xu, C. M.; Su, H. Q. Appl. Catal., A 2008, 346 (1?2), 189?193. (16) Bui, T. L. T.; Korth, W.; Jess, A. Catal. Commun. 2012, 25, 118? 124. (17) Liu, Z. C.; Zhang, R.; Xu, C. M.; Xia, R. Oil Gas J. 2006, 104 (40), 52?56. (18) Liu, Z. C.; Xu, C. M.; Zhang, R.; Meng, X. H.; Patroni, A. C.; Klusener, P. A. A.; Van den Bosch, A. V. P. Method for revamping an HF or sulphuric acid alkylation unit. WO Patent 2011015640 A2, Feb 10, 2011. (19) Quarmby, I. C.; Mantz, R. A.; Goldenberg, L. M.; Osteryoung, R. A. Anal. Chem. 1994, 66 (21), 3558?3561. (20) Quarmby, I. C.; Osteryoung, R. A. J. Am. Chem. Soc. 1994, 116 (6), 2649?2650.
dx.doi.org/10.1021/ef500684r | Energy Fuels XXXX, XXX, XXX?XXX



REFERENCES

Energy & Fuels
(21) Elomari, S. A.; Timken, H. C. Recovery and use of conjunct polymers from ionic liquid catalysts. U.S. Patent 20100147740 A1, June 17, 2010. (22) Elomari, S.; Harris, T. V. Regeneration of acidic catalysts. U.S. Patent 20100248940 A1, Sep. 30, 2010. (23) Williams, D. B. G.; Lawton, M. J. Org. Chem. 2010, 75 (24), 8351?8354. (24) Gray, J. L.; Maciel, G. E. J. Am. Chem. Soc. 1981, 103 (24), 7147?7151. (25) Smith, G. P.; Dworkin, A. S.; Pagni, R. M.; Zingg, S. P. J. Am. Chem. Soc. 1989, 111 (2), 525?530. (26) Wagner, C. D.; Riggs, W. M.; Davis, L. E.; Moulder, J. F.; Muilenberg, G. E. Handbook of X-ray Photoelectron Spectroscopy; Perkin-Elmer Corporation: Eden Prairie, MN, 1979. (27) Vasquez, R. P. Surf. Sci. Spectra 1993, 2 (2), 138?143. (28) Vasquez, R. P. Surf. Sci. Spectra 1998, 5 (4), 262?266. (29) Miron, S.; Lee, R. J. J. Chem. Eng. Data 1963, 8 (1), 150?160. (30) Albright, L. F.; Spalding, M. A.; Kopser, C. G.; Eckert, R. E. Ind. Eng. Chem. Res. 1988, 27 (3), 386?391. (31) Stern, E. W. Ind. Eng. Chem. Process Des. Dev. 1962, 1 (4), 281? 284. (32) Safarik, D. J.; Eldridge, R. B. Ind. Eng. Chem. Res. 1998, 37 (7), 2571?2581. (33) Boudreau, L. C.; Driver, M. S.; Munson, C. L.; Schinski, W. L. Separation of dienes from ole?ns using ionic liquids. U.S. Patent 20030125599 A1, July 3, 2003. (34) Li, Q.; Hunter, K. C.; East, A. L. L. J. Phys. Chem. A 2005, 109 (28), 6223?6231.

Article

G

dx.doi.org/10.1021/ef500684r | Energy Fuels XXXX, XXX, XXX?XXX


相关文章:
更多相关标签: