Heavy arenes catalytic dealkylation catalyst and preparing method thereof

[0019] The preparation method of the catalyst of the present invention includes:

[0020] (1) The sodium-type ZSM-5 zeolite, β zeolite, and hydrated alumina are mixed uniformly in a dry basis weight ratio, and then kneaded, shaped, and calcined to obtain a composite carrier.

[0021] (2) Perform ion exchange on the composite carrier with an aqueous ammonium salt solution to make the sodium ion exchange degree in the carrier at least 90%, and then wash,

[0022] (3) Prepare an impregnating solution with a compound of a group VIII metal to impregnate the carrier after the ammonium exchange, dry and calcinate.

[0023] The step (1) of the above method is the preparation of the composite carrier, which is to mix sodium-type ZSM-5 zeolite and β zeolite with hydrated alumina in a predetermined ratio, and then add 25-60%, preferably 35-45% of the weight of the mixed powder. A nitric acid aqueous solution with a concentration of 1 to 5% by weight, preferably 1.5 to 3.0% by weight, is kneaded and molded, and the molded carrier is dried, and then calcined in the air at 450 to 650°C, preferably 500 to 600°C, for a baking time of 2 to 8 hours, preferably 3 to 6 hours.

[0024] The step (2) of the method is ammonium exchange, that is, the carrier is ammonium exchanged with an aqueous ammonium salt solution to remove sodium ions, so that the sodium ion exchange degree in the carrier is at least 90%, preferably 90-95%. The temperature for ion exchange is 15~120℃, preferably 85~100℃, the ammonium salt used is ammonium chloride or ammonium nitrate, and the concentration of the prepared ammonium salt is 0.1~0.8N, preferably 0.2~0.6N, each time ion exchange The time is preferably 1 to 6 hours, and the number of exchanges is preferably one or two. After ion exchange, the carrier is washed until there is no anion, and then metal components can be introduced.

[0025]In step (3) of the method of the present invention, the metal component is introduced into the carrier by the impregnation method to prepare the catalyst. The prepared impregnation solution should contain the soluble compounds of each metal component required by the catalyst. For example, when the catalyst contains only Group VIII metals, use Group VIII metal compounds to prepare the impregnation solution; when the catalyst contains Group VIII metals and rhenium or tin, use Group VIII metal compounds and rhenium-containing or tin-containing compounds to prepare the impregnation solution; When the group VIII metal, rhenium and tin are contained, the group VIII metal compound, the rhenium-containing compound and the tin-containing compound are used to prepare the impregnating solution. The preferred Group VIII metal compound is chloroplatinic acid or palladium chloride, the preferred tin-containing compound is stannous chloride, and the preferred rhenium-containing compound is perrhenic acid.

[0026] The temperature of the impregnated carrier is preferably room temperature, the liquid-to-solid volume ratio during impregnation is 1 to 3, and the impregnation time is 8 to 60 hours, preferably 12 to 36 hours. The carrier impregnated with metal should be dried and calcined. The calcining temperature is 400-600°C, preferably 450-550°C, and the time is 1-10 hours, preferably 3-6 hours.

[0027] The hydrated alumina used for preparing the composite carrier is preferably high-purity alumina prepared by hydrolysis of aluminum alkoxide, such as the high-purity alumina prepared by hydrolysis of low-carbon aluminum alkoxide disclosed in the CN 85100218 patent. The metal component Sn can also be pre-introduced into the carrier when preparing the hydrated alumina, that is, the composite carrier is prepared by using the hydrated alumina containing 0.01 to 0.5% by weight of tin.

[0028] The catalyst provided by the invention is suitable for preparing benzene, toluene and xylene by lightening heavy aromatic hydrocarbons. The heavy aromatics contains C + 9 Aromatic hydrocarbon feedstock. The lightening reaction of heavy aromatics needs to be carried out in the presence of hydrogen, and the appropriate conditions are 350~450℃, 0.5~3.5MPa, feed weight space velocity 1~5 o'clock -1 , The hydrogen/hydrocarbon volume ratio is 500-1200. After the reaction products are recovered and separated, pure aromatic products can be obtained.

[0029] The present invention is further illustrated by examples below, but the present invention is not limited to this.

[0030] Examples 1~6

[0031] The catalyst of the present invention is prepared.

[0032] (1) Preparation of composite carrier

[0033] The appropriate amount of sodium-type ZSM-5 zeolite (produced by Shanghai No. 7 Plant, with a sodium content of 0.4-0.6% by weight), sodium-type β zeolite (with a sodium content of 0.4-0.6% by weight) and HP hydrogen prepared by the method described in CN 85100218 Alumina powder is mixed, a nitric acid aqueous solution with a powder weight of 40% and a concentration of 2% is added, kneaded, extruded, dried at 110-120°C for 2 hours, and calcined in air at 550°C for 4 hours to prepare a composite carrier.

[0034] (2) Ammonium exchange

[0035] Take 10 grams of the above composite carrier and use 0.5N NH at 90±10℃ 4 Perform ion exchange on the carrier with 20 ml of Cl solution for 2 hours, filter, and wash with deionized water until there is no Cl -.

[0036] (3) Introduce metal components

[0037] Prepare a predetermined amount of the precursors of each metal component into an impregnating solution, immerse the above-mentioned ammonium ion-exchanged carrier at room temperature and a liquid-to-solid ratio of 2 for 24 hours, filter, and dry at 110-120°C for 2 hours. The catalyst was calcined at 500°C for 4 hours, and the catalysts were denoted as catalysts A, B, C, D, E, and F respectively.

[0038] In the above method, when the catalyst contains more than two metal components, the co-immersion method is used to introduce the required metal components. The platinum-containing compound used in the preparation of the impregnation solution is chloroplatinic acid with a concentration of 2.86 mg/ml. The rhenium-containing compound is perrhenic acid with a concentration of 11.8 mg/ml. The palladium-containing compound is palladium chloride, which is dissolved in hydrochloric acid and prepared into a solution with a concentration of 1% by weight during use. The tin-containing compound is stannous chloride, which is dissolved in water and prepared into a solution with a concentration of 1% by weight during use.

[0039] Table 1 lists the metal component content of each example catalyst and the preparation of the carrier NaZSM-5 zeolite, Naβ zeolite and Al 2 O 3 The dosage.

[0042] Example 7

[0043] The catalysts A to F of the present invention and the comparative catalysts were evaluated.