METHOD FOR PRODUCING ALKYL SUBSTITUTED BENZENE

Abstract

A method for producing alkyl substituted benzene includes (a) providing a starting material selecting from the group consisting of furan, an alkyl substituted furan, 2-methylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, 2,5-hexanedione, and combinations thereof, and (b) subjecting the starting material to a cycloaddition reaction with a monoene in the absence of solvent and in the presence of the metal triflate catalyst to produce an alkyl substituted benzene.

Claims

1. A method for producing alkyl substituted benzene, comprising the steps of: (a) providing a starting material selecting from the group consisting of furan, an alkyl substituted furan, 2-methylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, 2,5-hexanedione, and combinations thereof; and (b) subjecting the starting material to a cycloaddition reaction with a monoene in the absence of solvent and in the presence of the metal triflate catalyst to produce an alkyl substituted benzene.

2. The method according to claim 1, wherein the metal trilflate catalyst is selected from the group consisting of copper (II) trifluoromethanesulfonate, zinc trifluoromethanesulfonate, scandium trifluoromethanesulfonate, yttrium trifluoromethanesulfonate, yttrium trifluoromethanesulfonate hydrate, indium(III) trifluoromethanesulfonate, and combinations thereof.

3. The method according to claim 2, wherein, instep (d), a molar ratio of the metal triflate catalylst to the starting material ranging from 1:50 to 1:100000.

4. The method according to claim 3, wherein, instep (d), a molar ratio of the metal triflate catalylst to the starting material ranging from 1:5000 to 1:30000.

5. The method according to claim 1, wherein the monoene is selected from the group consisting of ethylene, propene, 1-hexene, cyclohexene, and combinations thereof.

6. The method according to claim 1, wherein the starting material is 2,5-dimethylfuran or 2,5-hexanedione, and the monoene is ethylene.

7. The method according to claim 1, wherein the starting material in step (b) is in a liquid state.

8. The method according to claim 6, wherein the cycloaddition reaction is conducted under a pressure ranging from 1000 psi to 2000 psi at a temperature ranging from 200 C. to 300 C.

9. The method according to claim 8, wherein step (b) is implemented in two stages: in an initial stage, the temperature is controlled above 200 C. and less than 270 C. for a time period ranging from 30 minutes to 60 minutes; and in a subsequent final stage, the temperature is controlled at a range from 270 C. to 300 C. for a time period ranging from 4 hours to 10 hours.

Description

DETAILED DESCRIPTION

[0013] A method for producing alkyl substituted benzene according an embodiment of the disclosure includes steps (a) and (b).

[0014] In step (a), a starting material is provided. The starting material is selected from the group consisting of furan, an alkyl substituted furan, 2,5-hexanedione (HD), and combinations thereof.

[0015] The alkyl substituted furan may include one or more C1 to C8 linear alkyl substituted furan. Preferably, the alkyl substituted furan is selected from 2 -methylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran (DMF), and combinations thereof.

[0016] Preferably, the starting material is 2,5-dimethylfuran (DMF) or 2,5-hexanedione (HD).

[0017] In step (b), the starting material is subjected to a cycloaddition reaction with a monoene in the absence of solvent and in the presence of the metal triflate catalyst to produce an alkyl substituted benzene.

[0018] For producing the alkyl substituted benzene at lower cost, a molar ratio of the metal triflate catalylst to the starting material ranging from 1:50 to 1: 100000. For producing the alkyl substituted benzene at higher yield, a molar ratio of the metal triflate catalylst to the starting material ranging from 1:5000 to 1: 30000. For allowing the starting material to contact and mix with the monoene in more effective manner, the starting material in step (b) is in a liquid state.

[0019] The monoene may include one or more C1 to C8 monoene. Preferably, the monoene is selected from the group consisting of ethylene, propene, 1-hexene, cyclohexene, and combinations thereof. More preferably, the monoene is ethylene.

[0020] The metal trilflate catalyst is selected from the group consisting of copper (II) trifluoromethanesulfonate (Cu(OTf).sub.2), zinc trifluoromethanesulfonate (Zn(OTf).sub.2), scandium trifluoromethanesulfonate (Sc(OTf).sub.2), yttrium trifluoromethanesulfonate (Y(OTf).sub.2), yttrium trifluoromethanesulfonate hydrate (Y(OTf).sub.2 hydrate), indium(III) trifluoromethanesulfonate (In(OTf).sub.2), and combinations thereof.

[0021] For allowing the starting material to contact and mix with the monoene in more effective manner, the cycloaddition reaction is conducted under a pressure ranging from 1000 psi to 2000 psi at a temperature ranging from 200 C. to 300 C.

[0022] In addition, a time period for the cycloaddition reaction is greater than 4 hours and not greater than 11 hours. Preferably, step (b) is implemented in two stages, i.e., an initial stage and a subsequent final stage. In the initial stage, the temperature is controlled above 200 C. and less than 270 C. for a time period ranging from 30 minutes to 60 minutes. In the subsequent final stage, the temperature is controlled at a range from 270 C. to 300 C. for a time period ranging from 4 hours to 10 hours.

[0023] The embodiments of the disclosure will now be explained in more detail below by way of the following examples and comparative examples.

EXAMPLE 1 (EX 1)

[0024] A starting material (2,5-dimethylfuran, 90 g, about 100 ml) was placed in a high pressure reactor. Then, a metal triflate catalyst (copper (II) trifluoromethanesulfonate, 0.051 g) was added to the reactor, and nitrogen gas was introduced into the reactor to replace air for 3 times. Next, ethylene was introduced into the reactor at the room temperature to permit the pressure inside the reactor to reach to 520 psi. Thereafter, the temperature inside the reactor was raised to and kept at 250 C. for reaction for 0.5 hour, and then raised to and kept at 270 C. for reaction for 4.5 hours. During the above reactions, the pressure inside the reactor was gradually decreased from 1600 psi to 1200 psi. Finally, the temperature inside the reactor was cooled to room temperature, the pressure inside the reactor was relieved, and a yellowish-brown product including para-xylene was poured out of the reactor.

EXAMPLES 2 to 11 (EX 2 to EX 11)

[0025] Products of Examples 2 to 11 were prepared according to the process employed for preparing the product of Example 1, except that the starting materials and/or the catalysts are different, as listed in the following Table 1.

COMPARATIVE EXAMPLE 1 (CE 1)

[0026] A starting material (2,5-dimethylfuran, 8 g) and a solvent (tetrahydrofuran (THF), 221 ml) were placed in a high pressure reactor to have a total volume of about 230 ml. Then, copper (II) trifluoromethanesulfonate, (0.045 g) was added to the reactor, and nitrogen gas was introduced into the reactor to replace air for 3 times. Next, ethylene was introduced into the reactor at the room temperature to permit the pressure inside the reactor to reach to 520 psi. Thereafter, the temperature inside the reactor was raised to and kept at 270 C. for reaction for 5 hour. During the above reactions, the pressure inside the reactor was gradtially decreased from 1600 psi to 1200 psi. Finally, the temperature inside the reactor was cooled to room temperature, the pressure inside the reactor was relieved, and a yellowish-brown product including para-xylene was poured out of the reactor.

COMPARATIVE EXAMPLES 2 to 13 (CE 2 to CE 13)

[0027] Products of Comparative Examples 2 to 13 were prepared according to the process employed for preparing the product of Comparative Example 1, except that the ratios of the starting material, the solvent, and/or the copper (II) trifluoromethanesulfonate are different, as listed in the following Table 2.

COMPARATIVE EXAMPLE 14 (CE 14)

[0028] A starting material (2,5-dimethylfuran, 57.6 g) and a solvent (tetrahydrofuran (THF), 35 ml) were placed in a high pressure reactor to have a total volume of about 100 ml. Then, copper (II) trifluoromethanesulfonate, (0.007 g) was added to the reactor, and nitrogen gas was introduced into the reactor to replace air for 3 times. Next, ethylene was introduced into the reactor at the room temperature to permit the pressure inside the reactor to reach to 520 psi. Thereafter, the temperature inside the reactor was raised to and kept at 250 C. for reaction for 0.5 hour, and then raised to and kept at 270 C. for reaction for 4.5 hours. During the above reactions, the pressure inside the reactor was gradually decreased from 1600 psi to 1200 psi. Finally, the temperature inside the reactor was cooled to room temperature, the pressure inside the reactor was relieved, and a yellowish-brown product including para-xylene was poured out of the reactor.

[0029] Evaluations

[0030] Amounts of para-xylene obtained in the products of Examples 1 to 11 and Comparative Examples 1 to 14 were analyzed using a high performance liquid chromatography (HPLC) equipped with a diode array detector and a C18 column. A mobile phase for the HPLC was 0.05wt % phosphoric acid aqueous solution/acetonitrile, and a flow rate of the mobile phase was of 0.1 ml/min. Initially, the C18 column was eluated with 0.05wt % phosphoric acid aqueous solution. Then, the C18 column was further eluated with a mixture of 0.05wt % phosphoric acid aqueous solution and acetonitrile for a 30-minute period. During the 30-minute period, the percentage of acetonitrile in the mobile phase was gradually increased to 100%, and the percentage of 0.05wt % phosphoric acid aqueous solution was gradually decreased to 0%. Based on the obtained amounts of the para-xylene, yield, conversion, and selectivity for each of Examples 1 to 11 and Comparative Examples 1 to 14 were calculated based on the following equations (I) to (III), and are listed in Tables 1 and 2.

Yield of para-xylene=(moles of the obtained para-xylene/moles of the starting material before the reaction)100% (I)

Conversion of the starting material=[1(moles of the starting material after the reaction/moles of the staring material before the reaction)]100% (II)

Selectivity for para-xylene=(yield of para-xylene/conversion of the starting material)100% (III)

TABLE-US-00001 TABLE 1 (Examples, no solvent, total volume of the starting material of 0.1 L) Starting material Metal triflate catalyst Weight Weight mole Yield Conv. Sele. Amount EX Comp. (g) Comp. (g) % (%) (%) (%) (g) 1 DMF 90 Cu(OTf).sub.2 0.051 0.015 73 97 75 72.5 2 0.034 0.01 78 97 80 77.5 3 0.020 0.006 80 96 83 79.5 4 0.010 0.003 80 95 84 79.5 5 0.005 0.0015 74 91 81 73.5 6 DMF 90 Zn(OTf).sub.2 0.010 0.003 81 94 86 80.5 7 90 Sc(OTf).sub.2 0.014 77 94 82 76.5 8 90 Y(OTf).sub.2 0.015 77 94 82 76.5 9 90 Y(OTf).sub.2 hydrate 0.016 75 94 80 74.5 10 90 In(OTf).sub.2 0.016 80 96 83 79.5 11 HD 96 Cu(OTf).sub.2 0.009 0.003 44 74 59 46.6 Note: Comp. = component; DMF = 2,5-dimethylfuran; HD = 2,5-hexanedione; mole % of catalyst = (moles of the catalyst/moles of the starting material) 100% Yield = Yield of para-xylene; Conv. = Conversion of the starting material; Sele. = Selectivity for para-xylene. Amount = the obtained amount of para-xylene

TABLE-US-00002 TABLE 2 (Comparative Examples, with solvent) DMF starting material THF Total Cu(OTf).sub.2 catalyst Weight Conc. solvent vol. Weight mole Yield Conv. Sele. Amount CE (g) (M) (mL) (L) (g) % (%) (%) (%) (g) 1 8 0.4 221 0.23 0.045 0.15 90 96 94 7.9 2 0.024 0.08 89 95 94 7.8 3 0.018 0.06 85 91 93 7.5 4 0.012 0.04 78 84 93 6.9 5 22 1 205 0.23 0.050 0.06 91 96 95 22.1 6 44 2 181 0.066 0.04 87 94 93 42.3 7 66 3 156 0.025 0.01 87 93 93 63.4 8 3.8 0.4 96 0.1 0.021 0.15 90 96 94 3.8 9 28.8 3 68 0.022 0.02 90 95 95 28.6 10 38.4 4 57 0.217 0.15 70 99 71 29.7 11 38.4 4 57 0.022 0.015 90 96 94 38.2 12 48 5 46 0.027 0.015 87 96 91 46.1 13 57.6 6 35 0.022 0.01 83 94 88 52.8 14 57.6 6 35 0.007 0.003 68 81 84 43.2 Note: DMF = 2,5-dimethylfuran; THF = tetrahydrofuran; Total vol. = total volume of DMF and THF; Conc. = molar concentration of DMF = moles of DMF/total vol.; mole % is of catalyst = (moles of the catalyst/moles of the DMF starting material) 100% Yield = Yield of para-xylene; Conv. = Conversion of the starting material; Sele. = Selectivity for para-xylene. Amount = the obtained amount of para-xylene

[0031] Please refer to entries 2 to 5 of Table 2 disclosed in U.S. Pat. No. 9,260,359 B2, the conversion of DMF and the selectivity for para-xylene are relatively low when para-xylene was obtained from the cycloaddition reaction between DMF and ethylene in the absence of solvent and in the presence of a Lewis acid of acetic anhydride, acetic acid, chloroacetic anhydride, or chloroacetic acid. The inventors of this application had found that when the Lewis acid used in the prior art was replaced by metal triflate catalyst, as shown in Table 1, the yield of para-xylene, the conversion of the starting material, and the selectivity for para-xylene can be greatly improved.

[0032] Furthermore, as shown in Tables 1 and 2, compared to Comparative Examples 1 to 14, the obtained amount of para-xylene in each of Examples 1 to 10 was relatively high (72.5 g-80.5 g). In other words, in the reactor with the same volume, alkyl substituted benzene (para-xylene) can be produced in greater amount by using the method of this application. In addition, the cycloaddition reaction between the starting material and monoene without solvent is environmental-friendly and cost-saving.

[0033] While the disclosure has been described in connection with what is (are) considered the exemplary embodiment(s), it is understood that this disclosure is not limited to the disclosed embodiment(s) but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.