Simple and Effective Synthesis of Methoxymethyl Benzene and Its

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Simple and Effective Synthesis of Methoxymethyl Benzene and Its Application in Gasoline Hongzhu Ma,* Fengtao Chen, Bo Wang, and Yue He Institute of Energy Chemistry, School of Chemistry and Materials Science, Shaanxi Normal UniVersity, 710062, Xi’an, People’s Republic of China ReceiVed June 9, 2007. ReVised Manuscript ReceiVed September 17, 2007

A series of SO42-/MxOy (M ) Fe, Zr, Sn, Ti, and Sb) catalysts were prepared and investigated by means of Fourier transform infrared (FTIR), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Its application in the synthesis of methoxymethyl benzene from the electrochemical reaction of toluene with methanol assisted by a pair of porous graphite plane electrodes with selectivity higher than 75% was also studied. According to the experimental results, a possible radical cation reaction mechanism confirmed by XPS and ultraviolet–visible (UV–vis) spectra was proposed. It may be concluded that a simple and feasible electrochemical catalytic oxidation reaction at room temperature and standard atmosphere may be possible. In comparison to methyl tert-butyl ether (MTBE), methoxymethyl benzene used as a booster to improve fuel combustion was also studied.

1. Introduction The term “superacid” was first proposed by Conant in 1923 to describe acid systems that are stronger than conventional mineral acid. Later, Gillespie define the superacid as “an acid system stronger than that of 100% sulfuric acid, i.e., H0 e -12”.1 The catalytic activity of superacids for many reactions of hydrocarbon transformations is surprisingly high. They can even activate methane at low temperature.2,3 Conventional acids, such as H2SO4, HF, AlCl3, BF3, SbF5, H3PO4, and HCl used in organic reactions pose significant risks in handling, containment, and disposal because of their toxic and corrosive nature. As catalysts, solid acids have some additional advantages, such as ease of separation from the reaction mixture, no corrosion for the reactor, and free from pollution, etc. Therefore, they are worthy of attention in theoretical research and in synthetic application.3,4 Owing to high reactivity, ease of handling recovery, low waste generation, and environmental friendliness, heterogeneous solid acid catalysts are emerging as very attractive alternatives to the conventional homogeneous acidic reagents. Among various solid acid catalysts, such as zeolites, clays, and heteropolyacids, the sulfated metal oxides based on iron oxide have emerged as powerful catalysts because of their superacidity, high reactivity at low temperatures, and reusability.5,6 The activity, selectivity, and stability of sulfated iron oxide catalysts were also improved by the addition of noble metals and transition-metal oxides, such as Cu and Co. Oxidation of organic compounds in the liquid phase was the basis of several industrial processes developed in the past 50 * To whom correspondence should be addressed. Telephone: +86-2985308442. Fax: +86-29-85307774. E-mail: [email protected]. (1) Gillespise, R. J.; Peel, T. E. J. Am. Chem. Soc. 1995, 95, 5173. (2) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Science 1978, 13, 206. (3) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Superacids; Wiley: New York, 1985. (4) Tanabe, K. Solid Acids and Bases, Their Catalytic Properties; Tokyo Kodansha, Academic Press: New York, 1970. (5) Arata, K. AdV. Catal. 1990, 37, 165. (6) Arata, K. Appl. Catal., A 1996, 146, 3.

years.7 As a clean and convenient method for the generation on a preparative scale of many reactive intermediates (radical ions, radicals, carbanions, carbocations, and quinodimethanes), electrochemistry became one of the highlights in organic synthesis and industrial chemistry.8–10 Electrochemical synthesis in microreactors provides an attractive approach to organic synthesis and electrochemical technology, avoiding toxic and expensive organic solvents and often providing unique pathways to control the reactant and product distribution.11,12 It has received considerable attention in recent years, because of its potential applications in the synthesis of pharmaceutical drugs, amino acids, dyestuffs, pesticides, spicery, and organic reagents.8,13 Several methods to use the higher selectivity of anodic toluene oxidation are reported, and some mechanisms were supposed for the direct oxidation of toluene in an alcoholic electrolyte (Scheme 1). A mechanism14 supposed that the toluene oxidation is initiated by an anodic electron transfer and the formation of the radical cation (step 1), which is stabilized in alcoholic solvents by the formation of benzyl radical (step 2). Because of its lower oxidation potential of benzyl radical, the formation of benzylcation occurs quickly at the anode (step 3). Then, benzylmethylether, the first stable oxidation intermediate, was produced by the reaction of benzylcation with methanolic solvent (step 4). Dimethylacetal may be formed by repeated electron transfers, stabilization, and the addition of the alcoholic solvent (step 5). (7) Raghavendrachar, P.; Ramachandran, S. Ind. Eng. Chem. Res. 1992, 31, 453. (8) Nishiguchi, I.; Hirashima, T. J. Org. Chem. 1985, 50, 539. (9) Ma, H. Zh.; Wang, B.; Liang, Y. Q. Catal. Commun. 2004, 5, 617. (10) Chang, C. J.; Deng, Y.; Shi, C.; Chang, C. K.; Anson, F. C.; Nocera, D. G. Chem. Commun. 2000, 5, 1355. (11) Ehrfeld, W.; Hessel, V.; Low ¨ e, H. Wiley-VCH: Weinheim, Germany, 2000. (12) Micro Total Analysis Systems 2000. Proceedings of the lTAS 2000 Symposium, Enschede: The Netherlands, May 14–18, 2000; van den Berg, A., Olthuis, W., Bergveld, P., Eds.; Kluwer Academic: Boston, MA. (13) Utley, J. Chem. Soc. ReV. 1997, 26, 157. (14) Wendt, H.; Schneider, H. J. Appl. Electrochem. 1986, 16.

10.1021/ef7003283 CCC: $37.00  2007 American Chemical Society Published on Web 10/31/2007

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Scheme 1. Reaction Sequence of Anodic Toluene Oxidation in Methanol

Other studies15–20 have allowed for the following reaction scheme for the aldehyde formation to be determined. Oxidation proceeds via a free-radical chain mechanism, which was initiated by a change in the oxidation state of the metal. The benzyl radical reacted rapidly with triplet dioxygen. In the presence of a catalyst, the process was ended by acid formation.21,22 ArCH3 + CoIII f ArCH2· + H+ + CoII

(1)

ArCH2· + O2 f ArCH2O2·

(2)

ArCH2O2· + CoII f ArCH2O2CoIII f ArCHO + CoIIIOH CoIIIOH + H+ f CoIII + H2O

with methanol on a pair of porous graphite plane electrodes assisted by clean catalytic oxidants of SO42-/MxOy (M ) Fe, Zr, Sn, Ti, and Sb), simply and effectively, at room temperature and atmospheric pressure. The catalysts were prepared and detected by Fourier transform infrared (FTIR), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the products were checked by ultraviolet–visible (UV–vis) spectra and gas chromatography/mass spectrometry (GC/MS). The effect of the different medium and its addition in gasoline was also discussed.

(3)

2. Experimental Section

(4)

2.1. Materials and General Methods. All chemical reagents used in the experiment were analytical-grade and used without any further purification. The effect of the medium was inspected by a UV–vis 7504 spectrum apparatus, which was made by the Shanghai Xinmao Co. The component and its distribution of product distillation were analyzed by GC/MS (QP2010, Japan). The application of the products were checked by the research octane number (RON) (SYP2102-I, China). The catalyst was detected by FTIR (Eouinx55, Germany), XRD (Rigaluc, Japan), and XPS (Perkin-Elmer PHI5400). 2.2. Preparation of SO42-/ MxOy Catalysts. SO42-/MxOy (M ) Fe, Zr, Sn, Ti, and Sb) catalysts were prepared by adopting a two-step route. In the first stage, M(OH)2y/x was obtained by adding aqueous ammonia slowly into an aqueous solution of MCl2y/x · zH2O and the final pH of the solution was adjusted to 9. The precipitates were filtered, washed, and then dried at 373 K for 12 h. Second, sulfation of the obtained fixed oxide powder was done by percolating 1.0 mol/L H2SO4 solution through it for 24 h, filtered by suction, dried at 383 K for 2 h, and finally, calcined in air at 823 K for 3 h to obtain SO42-/MxOy.26 2.3. Experimental Setup. Figure 1 showed the schematic diagram of the experimental setup for electrochemical catalytic oxidation. The experiments were conducted in a single cell of 0.25 L capacity at 30.0 V voltage and 2.2 A current intensity. The reaction cell was cooled by cooling water in a trough to form the room-temperature condition. The reaction cell was air-proofed to prevent the volatilization of the methanol. The anode and cathode were positioned vertically and paralleled to each other with a constant inter gap of 1.0 cm. The anode and cathode were both the porous graphite plate (supplied by Spring Chemical Industrial Company Limited, Shaanxi, China; 50 × 50 × 6 mm). A total of 3.0 g of catalyst of the solid superacid and 3.0 g of assisted catalyst of KF were packed around the working electrode, forming a multiphase electrochemical oxidation packed bed. The solution was constantly stirred at 300 rpm using a magnetic stirrer to maintain a uniform concentration of the electrolyte solution. The electric power was supplied with a regulated DC power supply, WYK302b, China. The current and voltage were adjustable in the range of 0–2.5 A and 0–35 V, respectively. 2.4. Electrolysis Procedures. The electrolysis was carried out in cells without compartments. The anode and cathode (graphite plate) were activated by methanol solution before use. The solvent-

This indicates that the existence of the metal in the electrochemical system will contribute effectively to the reaction mechanism. Methyl tert-butyl ether (MTBE) is a common fuel oxygenate added to petrol to improve fuel combustion. It was introduced in the U.S.A. in 1979 and has been used in the U.K. since the late 1980s.23,24 While there is ample evidence to show that the use of MTBE in gasoline has led to considerable improvement in air quality throughout the U.S.A., MTBE appears to have imposed significant adverse impacts on groundwater resources. The presence and frequent detection of MTBE in groundwater and drinking water led to a ban on its further use in gasoline in California, while other states are seeking ways to reduce or eliminate it.25 It should be noted that concentrations of MTBE added to gasoline in the U.S.A. and U.K. vary widely; typically, U.S.A. fuels contain 10–15% by weight, while U.K. fuels contain 0–5% by weight.24 1-(Methoxymethyl)benzene is very similar to MTBE in structure. Its solubility in water is lower than that of MTBE, while it can dissolve in gasoline easily, which can prevent its adverse impacts on groundwater resources; therefore, 1-(methoxymethyl)benzene can be used as an good substitute of MTBE. Here, we report the synthesis of a series of solid superacid catalysts and its application in the synthesis of methoxymethyl benzene, derived from the highly selective oxidation of toluene (15) Sheldon, R. A.; Kochi, J. K. Metal-Catalyzed Oxidations of Aromatic Compounds; Academic Press: New York, 1981. (16) Morimoto, T.; Ogata, Y. J. Chem. Soc. B 1967, 1353–1357. (17) Heiba, E. I.; Dessau, R. M.; Koehl, W. J. J. Am. Chem. Soc. 1969, 91, 6830–6837. (18) Scott, E. J.; Chester, A. W. J. Phys. Chem. 1972, 76, 1520–1524. (19) Kamiya, Y.; Kashima, M. Bull. Chem. Soc. Jpn. 1973, 46, 905– 908. (20) Hendricks, C. F.; van Beek, H. C. A.; Heertjes, P. M. Ind. Eng. Chem. Prod. Res. DeV. 1978, 17, 256–260. (21) Vinek, H. Appl. Catal. 1991, 68, 277. (22) Zhao, J.; Wang, B.; Ma, H. Zh.; Zhang, J. T. Ind. Eng. Chem. Res. 2006, 45, 4530. (23) Fiorenza, S.; Rifai, H. S. Biorem. J. 2003, 7, 1. (24) Environment Agency (EA). A review of the current MTBE usage and occurrence in U.K. groundwaters. R&D Project Report. EA, U.K., 2000; pp 2-176. (25) Pamela, R. D.; Williams, P. EnViron. Forensics 2001, 2, 75.

(26) Arata, K.; Nakamura, H.; Shouji, M. Appl. Catal., A 2000, 197, 213.

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Ma et al.

Figure 1. Experimental setup for the electrochemical catalytic oxidation.

supporting electrolyte system was formed as follows: 3.0 g of KF and 50 mL of toluene were added in 50 mL of anhydrous methanol with 3.0 g of SO42-/MxOy (M ) Fe, Zr, Sn, Ti, and Sb, respectively). The resulting solutions were placed in the cells and electrolyzed at a current intensity of 2.2 A (with the time prolonged and the current intensity decreased to 1.0 A gradually) with stirring at room temperature. The conversion of the starting material was investigated by UV–vis spectrometry. The electronic spectra of the reaction system were detected during each electrolysis, and the conversion of starting material was investigated by a UV–vis spectrum every 30 min as follows: transferring 0.01 mL of solution by transfer pipet accurately and diluting it to 20 mL in a volumetric flask, and then the electronic spectra were observed in the range of 200–400 nm using methanol as a blank. The methanol used for the research of the UV–vis spectrum was reclaimed for the next experiment without pollutions and waste. 2.5. Characterization of the Products and the Catalyst. After the reaction finished, the solution was distilled under the air pressure. The distillates were analyzed by a GC/MS system using a capillary column (0.25 cm × 30 m). The catalyst was washed with water for several times, dried in vacuo, and then detected by XPS.

3. Results and Discussion 3.1. Characterization of the Catalysts. 3.1.1. Infrared Spectroscopy. The different catalyst samples, which were dried in vacuo at 373 K for 1 h first, were diluted in KBr. They showed the infrared absorption spectra, at room temperature, displayed in Figure 2. In all cases, a wide band appeared at 1631 cm-1, corresponding to the flexion vibration band of the H2O molecule, which was ascribed to the physisorbed water in the catalyst. The peaks between 800 and 1400 cm-1 assigned to the SdO or S-O bond were the characteristic peaks, and the structure of the solid catalysts remained stable even when many other components existed.27–29 As Figure 2 showed, the peak at 1629.32 cm-1 can be assigned to the Brønsted acidity characteristic absorption, peaks between 847.54 and 1396.35 cm-1 can be assigned to the mixture absorption of Brønsted and Lewis acidity, the strong absorption peak at 3432.47 cm-1 and mild peak at 1633.27 cm-1 may be assigned to the dissociative hydroxyl of H2O absorbed on the solid superacid. (27) Schulz, G. D. J. Org. Chem. 1972, 37, 25. (28) Partenheimer, W. Catal. Today 1995, 23, 69. (29) Salas, P.; Heranadez, J. G.; Montoya, J. A.; Navarrete, J.; Salmones, J.; Schifter, I.; Morales, J. J. Mol. Catal. 1997, 123, 149.

Figure 2. Representative infrared spectrum of solid superacid.

It was noted that a chelate bidentate SO42- coordinated to metal oxides, such as Ti4+, because the highest stretching vibration band of the SO42- in the samples occurred above 1217 cm-1. It should be pointed out that the acidity of the catalyst strengthens with the band of 847.54-1396.35 cm-1 extend in height, as follow: SO42-/TiO2 catalyst > SO42-/Sb2O3 catalyst > SO42-/SnO2 catalyst. According to Figure 2, the SdO of the solid catalysts was a covalent double bond; therefore, it could induce the acid and improve the catalysis, and the SO42-/MxOy catalyst has been formed. 3.1.2. XRD. The solid superacid catalyst detected by XRD before and after the reaction had been shown in Figure 3. It could be seen that the iron in the catalyst presented itself as the formation of Fe2O3 (2θ ) 23.90°, 33.12°, 49.54°, 53.87°, 63.06°, and 64.76°) before the reaction and as the mixture of Fe2O3 and FeO (2θ ) 42.05°, 36.23°, 60.90°, 72.84°, and 76.61°) after the reaction, indicating that iron in the solid superacid were related to the electrochemical reaction system. 3.1.3. XPS. After the coupling reaction, the solid superacid catalyst was dried in vacuo and tested by XPS. The binding energy and its composition of the catalyst were shown in Figure 4. XPS Fe 2p3/2 peak of the SO42-/Fe2O3 catalyst after the reaction was shown in Figure 5. Because a mass of the organic compounds and the electrolyte were adsorbed on the surface of the catalyst, the carbon element, oxygen element, and fluorine element were detected by XPS. The XPS Fe 2p3/2 peak has been deconvoluted to two different valent components (FeO and Fe2O3) and the ratio of

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Figure 5. Fe 2p3/2 binding energy of the SO42-/Fe2O3 catalyst after the reaction.

Figure 3. XRD patterns of the solid superacid catalyst before and after the reaction.

Figure 4. XPS of the SO42-/Fe2O3 catalyst after the reaction.

two atoms is 21.73:78.63 (molar ratio), inferring that the iron was the mixture of FeO and Fe2O3 in the catalyst after the reaction. In comparison to Fe3+ that occupied 100% of the total iron element before the coupling reaction, it can illuminated that Fe3+ was reduced to Fe2+ during the coupling reaction process. XPS of the other solid superacid catalysts were also studied. The results indicated that most metal ions were concerned with the coupling reaction and were reduced to a lower valent, respectively, maybe inferring that the mechanism of the oxidation reaction of toluene catalyzed by these catalysts were almost the same.

Figure 6. Effect of time on the coupling reaction with SO42-/ZrO2 as the catalyst.

3.2. Liquid Products. 3.2.1. UV Spectroscopy Analysis. Figure 6 shows that the effect of time on the coupling reaction catalyzed by the solid superacid catalyst was detected by UV–vis adsorption spectroscopy. With the time prolonged, the K adsorption band of the benzene ring shifted but changed unconspicuously and the B adsorption band of the benzene ring hypsochromic shifted from 263 to 255 nm (arrowhead area), owing to the interaction between the methyl of the toluene and hydroxyl group enlarged in the energy band of π f π* contrast to that of the benzene ring; while the hydrogen atom in the methyl of toluene was substituted by a methoxyl or hydroxyl group, the conjugation between the methyl group in the toluene and the benzene ring was weakened and the energy needed by the π f π* transition increased. The increased absorption band indicated that the reaction extent was directly proportioned to the reaction time and the content of the oxygenous aromatic products. The electronic spectra of the reaction system in the different mediums under the same reaction time (180 min) and the identical current intensity of 1.0 A were shown in Figure 7. It can be found that the K adsorption band shifted unconspicuously, the B adsorption band hypsochromic shifted, and the adsorbed peak height was decreased as follows: SO42-/ ZrO2 catalyst > SO42-/TiO2 catalyst > SO42-/Sb2O3 catalyst > SO42-/SnO2 catalyst > SO42-/Fe2O3 catalyst. This suggested that the electrochemical catalytic oxidation degree enhanced with the enhancing of the catalytic activity by the different solid superacid catalysts.

3128 Energy & Fuels, Vol. 21, No. 6, 2007

Ma et al. Scheme 2. Possible Mechanism for the Main Reactions with SO42-/Fe2O3 as the Catalysta

Figure 7. Effect of the medium on the reaction system (180 min).

a

The asterisk indicates the reaction mechanisms that are unknown thus

far.

Figure 8. GC of the products (SO42-/ZrO2 as the catalyst). Table 1. Electrolysis of Toluene in Methanol Solvent by the Different Catalystsa product selectivity (mass %)b catalyst

a

b

c

d

e

f

SO42-/Fe2O3 SO42-/SnO2 SO42-/Sb2O3 SO42-/TiO2 SO42-/ZrO2

46.107 55.728 57.503 60.434 75.883

29.722 25.618 33.431 7.037 9.230

10.307 18.654 9.066 26.348 9.254

little little little little 5.633

little little little 6.182 little

6.375 little little little little

a Reaction conditions: current intensity, 1.0 A; reaction temperature, 298 K; reaction time, 180 min. b GC/MS spectrum, 70 eV, m/z (relative intensity): (a) 1-(methoxymethyl)benzene, 122 M (70), 105 (8), 91 (100), 77 (25), 65 (18), 51 (10), 39 (9), 27 (2), 15 (2); (b) 4-methylbenzenesulfinic acid, 155 M+ (8), 126 (10), 123 (82), 107 (22), 91 (100), 79 (28), 65 (30), 45 (22), 39 (18); (c) methyl-4-methoxybenzoate, 166 M (31), 135 (100), 123 (2), 107 (13), 92 (20), 77 (28), 64 (15), 50 (8), 38 (7), 31 (1); (d) 1-(dimethoxymethyl)benzene, 152 M (4), 121 (100), 105 (19), 91 (19), 77 (30), 59 (4), 51 (10), 39 (5), 27 (2), 15 (2); (e) 1-benzyl-4-methylbenzene, 182 M (78), 168 (13), 167 (100), 152 (25), 128 (9), 115 (10), 104 (32), 91 (15), 77 (13), 65 (14), 51 (11), 39 (13), 27 (5); and (f) 3,3,6,6,9,9,12,12-octamethoxy-pentacyclo[9.1.0.0.(2,4).0(5,7).0(8,10)]dodecane, 385 M+ (2), 237 (2), 211 (2), 200 (1), 187 (5), 172 (2), 159 (3), 141 (2), 131 (12), 115 (2), 105 (100), 85 (2), 75 (9), 59 (9), 41 (2), 28 (2).

3.2.2. GC/MS Spectrum. The GC of the products is shown in Figure 8 (the peak of the solvent was taken off). Alternatively, gas chromatography in conjunction with mass spectrometry (GC/ MS) has been known for its superior separation of complex organic compounds, greater sensitivity, and shorter measuring time and, hence, is better suited for the detection and identification of volatile organic compounds.30 Table 1 compared the product selectivity in different mediums at the same reaction time of 180 min and the identical current intensity of 1.0 A. It (30) Giumanini, A. G.; Verardo, G. Ind. Eng. Chem. Res. 2001, 40, 1449.

can be found that the selectivity of the oxygenous aromatic product [1-(methoxymethyl)benzene] was higher with SO42-/ ZrO2 as the catalyst than that of others; moreover, the highest selectivity was obtained with SO42-/ZrO2 as the catalyst in the same reaction system (Figure 8), indicating a novel method that methoxymethyl benzene with high selectivity (75.883%) was obtained simply and effectively, maybe inferring that it can be simply synthesized one pot by electrochemical coupling of toluene assisted by SO42-/MxOy solid superacid containing methanol at room temperature and atmospheric pressure, which simplified the synthetic technology of aromatic ether and used methanol in an economic way. 3.3. Possible Mechanism.15–22,31,32 A possible mechanism of the reaction catalyzed by SO42-/Fe2O3 was proposed. Oxidation proceeds via a radical radicals cation mechanism, which was initiated by a change in the oxidation state of the metal, which was confirmed by XPS spectra. A free-radical cation formed in the oxidation of the side chain of toluene assisted by SO42-/Fe2O3 catalysts. Fe2O3 + 2ArCH3 f 2[ArCH3]+· + 2FeO

(5)

This radical cation is stabilized in alcoholic solvents by the formation of the benzyl radical +

[ArCH3]+· f ArCH2· + H

(6)

Because of its lower oxidation potential of the benzyl radical, the formation of benzylcation occurs fast at the anode, which was assisted by a change in the oxidation state of the metal Fe2O3 + 2ArCH2· f 2ArCH2+ + 2FeO

(7)

Meanwhile, the benzyl radical may react with triplet dioxygen in the presence of molecular oxygen. (31) Partenheimer, W. Catal. Today 1995, 23, 69. (32) Guo, C. C.; Liu, Q.; Wang, X. T.; Hu, H. Y. Appl. Catal. 2005, 282, 55.

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Table 2. Comparison of MTBE and Methoxymethyl Benzene in Gasoline RON RONa

a

additive

MTBE

methoxymethyl benzene

10% 20% 30%

91.3 95.7 98.6

92.9 95.3 99.3

RON of sample oil ) 88.2.

ArCH2 + O2· f ArCH2O2·

(8)

ArCH2O2· + FeO f Fe2O3 + ArCHO + OH-

(9)

Thus, the reaction between the benzyl radical and Fe2O3 is competitive with the formation of the radical peroxide ArCH2O2 · (eq 8). However, no aldehyde was detected, which indicates that Fe2O3 is much more reactive than dioxygen toward the benzyl radical. Then, 1-(methoxymethyl)benzene was produced by the reaction of benzylcation with methanolic solvent, 1-(dimethoxymethyl)benzene, which can also be formed by repeated electron transfers, stabilization, and the addition of the alcoholic solvent. All products were obtained by the reaction of the free radical with toluene or methanol. The catalyst can be successively recylcled by the anodic oxidation of FeO to Fe2O3, which was confirmed by XPS spectra. It can be assumed that all of the useful reactions were accomplished at the surface of the catalyst and the anode. The possible mechanism was proposed and listed

in Scheme 2. The formation of toluene free-radical cation was the rate-determining step in the coupling reaction. Thereby, the spectra of the different media and reaction times were various. 3.4. Comparison of the Addition of MTBE and Methoxymethyl Benzene in the Gasoline RON. When the concentrations of MTBE and methoxymethyl benzene added to gasoline were the same, the octane number of the sample oil was tested and the results were listed in Table 2. From the results, it can be found that the addition of methoxymethyl benzene into the gasoline can improve the fuel combustion properties obviously, indicating that the substitution of MTBE may be possible. 4. Conclusion A novel synthesis method for 1-(methoxymethyl)benzene simply and effectively with high yield (75.883%) from electrochemical oxidation of toluene in methanol solvent catalyzed by SO42-/MxOy (M ) Fe, Zr, Sn, Ti, and Sb) catalysts at room temperature and atmospheric pressure was studied. The results indicated that SO42-/ZrO2 act as a good catalyst for the electrochemical reaction of toluene. The application of the product as a gasoline booster has also been investigated and can be used as an good substitute of MTBE. However, 4-methylbenzenesulfinic acid produced in the reaction system shows a negative impact on the catalytic activity of the catalyst, which should be further improved. EF7003283