Zeolite catalyst for alkylation of toluene with methanol, preparation process and use thereof

Abstract

The disclosure relates to a zeolite catalyst for side-chain alkylation of toluene with methanol, including a zeolite NaX and Na.sub.3PO.sub.4 or Na.sub.2HPO.sub.4 supported on the zeolite NaX. The zeolite catalyst can be effective for catalyzing the side-chain alkylation of toluene with methanol. The disclosure also relates to a process for preparing a zeolite catalyst for side-chain alkylation of toluene with methanol, which is simple, practical and cheap in cost.

Claims

1. A zeolite catalyst for side-chain alkylation of toluene with methanol, comprising a zeolite NaX and Na.sub.3PO.sub.4 or Na.sub.2HPO.sub.4 supported on the zeolite NaX, wherein the zeolite catalyst for side-chain alkylation of toluene with methanol is prepared by the process of: a. immersing the zeolite NaX in Na.sub.3PO.sub.4 aqueous solution or Na.sub.2HPO.sub.4 aqueous solution with the mixture being stirred at 60 to 90° C. for 2 h and then cooled down to room temperature; b. placing the cooled mixture into an oven at 60 to 90° C. to have all liquid evaporated, leaving a solid; and c. calcinating the solid obtained in step b in air at 400 to 600° C. for 3 h at a heating rate of 3 K/min; wherein the Na.sub.3PO.sub.4 aqueous solution or the Na.sub.2HPO.sub.4 aqueous solution in step a has a concentration of 0.05 M to 0.075 M; wherein side-chain alkylation of toluene with methanol with the zeolite catalyst under conditions of a feed molar ratio of toluene to methanol of 5:1, a mass space velocity of 1.0 h.sup.−1, a nitrogen flow rate of 10 ml/min, and a reaction temperature of 425° C., yields styrene in a range of 15.3-16.6%.

2. A zeolite catalyst according to claim 1, wherein the zeolite NaX has a Si/Al ratio of 1 to 10 and a specific surface area of 40 m.sup.2/g to 600 m.sup.2/g.

3. A zeolite catalyst according to claim 2, wherein the zeolite NaX has a Si/Al ratio of 1.24 and a specific surface area of 527 m.sup.2/g.

4. A zeolite catalyst according to claim 1, wherein the zeolite catalyst has a size between 40 mesh and 60 mesh.

5. A zeolite catalyst according to claim 1, wherein the calcination temperature in step c is 500° C.

6. A zeolite catalyst according to claim 1, wherein the process further comprises crushing, pelletizing and sieving the calcinated solid to obtain the zeolite catalyst with a size between 40 mesh and 60 mesh.

7. A zeolite catalyst according to claim 1, wherein in step a the temperature is 80° C.

8. A zeolite catalyst according to claim 1, wherein in step b the cooled mixture is kept in the oven at 60 to 90° C. for 16 to 18 h to be subjected to an evaporation.

Description

DETAILED DESCRIPTION

(1) The zeolite catalyst for the side-chain alkylation of toluene with methanol and the process for preparing the same, according to the present invention, will now be described in more detail by reference to the following examples, which are illustrative only and do not limit the scope of the invention.

Example 1

(2) 10 g of zeolite NaX (Catalyst Plant of Nankai University, Si/Al=1.24, with a specific surface area of 527 m.sup.2/g) was added into 100 mL aqueous solution of Na.sub.3PO.sub.4.12H.sub.2O (0.01 M). After stirring for 2 h at 80° C., the solution was kept for some time at room temperature to cool down. This solution cooled down was kept in an oven at 80° C. without filtration for about 17 h to evaporate all the liquid inside, leaving behind a solid. This solid obtained was then calcinated in air for 3 h at 500° C. at a heating rate of 3K/min. The resulting powder was crushed, pelletized and sieved to obtain the zeolite catalyst with a size between 40 mesh and 60 mesh.

Examples 2-5

(3) Examples 2-5 were identical to Example 1, but with the difference that the concentration of the aqueous solution of Na.sub.3PO.sub.4.12H.sub.2O as used in Examples 2-5 was 0.025 M, 0.05 M, 0.075 M and 0.1 M, respectively.

Example 6

(4) The catalysts prepared in Examples 1-5 above were tested for their catalytic performance for side-chain alkylation of toluene with methanol in a fixed bed reactor at atmospheric pressure.

(5) 1.2 g of the catalyst was placed in the middle of a stainless-steel tube having an inner diameter of 7 mm, and the catalyst was supported by quartz sands at an outlet of the reaction tube, and separated by quartz cotton in the middle. Nitrogen was used as a carrier gas, a flow rate was 10.0 ml/min, a molar ratio of toluene to methanol was 5:1, and a mass space velocity was 1.0 h.sup.−1. The catalyst was activated at 450° C. for 2 h under atmospheric nitrogen atmosphere and then lowered to 425° C. for evaluation. To prevent the reaction gases from being condensed, a heating belt was wrapped around from the reactor to a six-way valve to keep a temperature of about 200° C., and a auxiliary furnace was also equipped to keep the temperature from the six-way valve to a chromatographic injector at 200° C.

(6) Reaction products were quantitatively analyzed online by Haixin GC950 gas chromatograph equipped with HP-FFAP column (0.53 mm×50 m) and the products were detected by a hydrogen flame ionization detector (FID). Measurement conditions of the gas chromatograph were as follows: column furnace temperature: 70° C., detector temperature: 220° C., gasification chamber temperature: 200° C., air partial pressure: 0.05 MPa, hydrogen partial pressure: 0.12 MPa, carrier gas flow rate: 35 ml/min, and gas injection volume: 0.1 ml/h. The products were quantified by the area correction normalization method. Since an excess of toluene in the reaction system was used, product selectivity and yield were calculated based on methanol.

(7) Table 1 below presents the results of the catalyst evaluation in Example 6, comparing methanol conversion and a selectivity and yield for each of ethylbenzene and styrene as well as a yield for both of them, provided by the five catalysts prepared in Example 1-5 using a feed composition of toluene and methanol in a molar ratio of 5:1 at a mass space velocity of 1.0 h.sup.−1, a nitrogen flow rate of 10 ml/min and at a reaction temperature of 425° C.

(8) TABLE-US-00001 TABLE 1 Performance of Catalyst Selectivity (%) Yield (%) Example MET Conv. % S.sub.EB S.sub.STY Y.sub.EB Y.sub.STY Y.sub.(EB + .sub.STY) 1 100 41.2 1.3 41.2 1.3 42.5 2 99.8 29.4 4.2 29.3 4.2 33.5 3 100 48.4 16.6 48.3 16.6 64.9 4 99.9 45.6 15.3 45.5 15.3 60.9 5 100 22.1 3.6 22.1 3.6 25.7

(9) As apparent from the results of Table 1, the Na.sub.3PO.sub.4/NaX catalyst according to the embodiments of the invention can be effective for catalyzing the side-chain alkylation of toluene with methanol. Surprisingly, the Na.sub.3PO.sub.4/NaX catalyst prepared by using a Na.sub.3PO.sub.4 solution at a concentration of about 0.05 M to about 0.075 M, enables a selectivity and yield for both ethylbenzene and styrene to be each up to over 60%, and the yield of styrene to be much higher, in particular at least 91% higher, than that provided by the K.sub.3PO.sub.4/NaX catalyst described in CN 103935767 A.

(10) In addition it was found that results similar to those achieved by the Na.sub.3PO.sub.4/NaX catalysts mentioned above were obtained with Na.sub.2HPO.sub.4/NaX catalysts prepared by using Na.sub.2HPO.sub.4 solution at a concentration of 0.01 M to 0.1 M when used in the side-chain alkylation of toluene with methanol to produce styrene.

(11) The present invention has been described in detail by reference to the specific embodiments. It will be apparent that modifications and variations are possible without departing from the scope of the invention which is defined in the appended claims.