CN1106219C - Supported heteropolyacid catalyst for preparing dimethyl ether by methanol dehydration and production method thereof - Google Patents

Abstract

The present invention belongs to a supported heteropoly acid composite catalyst. The invention is mainly characterized by containing a novel catalytic material, namely Heteropoly acid (HPA). The catalyst composition is HPA (1-50% (m)), and gamma-Al₂O₃：25-98.2%(m)，TiO₂：0.1-20%(m)，La₂O₃: 0.1-5% (m). Prepared by an impregnation method, and the preparation conditions are as follows: the impregnation time of the active component (HPA) is 12h, the drying temperature is 120 ℃, and the roasting temperature is 350 ℃. The catalyst is used for catalyzing methanol dehydration to generate dimethyl ether. The reaction temperature is 240 ℃ and 320 ℃, the pressure is 0-1.0MPa (table), and the weight space velocity is 1.0-3.5h^-1Under the reaction condition, the conversion rate of the methanol reaches 85 percent, and the selectivity of the dimethyl ether is 99.99 percent.

Description

Supported heteropolyacid catalyst for methanol dehydration to dimethyl ether and production method thereof

The invention belongs to a loaded heteropolyacid composite catalyst, which catalyzes the dehydration of methanol to generate dimethyl ether.

Dimethyl ether has a wide range of uses and has increasingly attracted the attention of developed countries. It is mainly used in aerosols, civil raw materials, automotive fuels, refrigerants, and chemical raw materials. The current method of producing dimethyl ether is mainly to use methanol as a raw material, which is obtained after dehydration under the action of a catalyst. The catalyst used is generally aluminum phosphate [EP 169953, 1986], HZSM-5 [Wu Deming et al., Petrochemical Industry, 1988, 17(9): 557], γ-Al ₂ O ₃ [JP 63056433, 1988]. The surface of aluminum phosphate is prone to carbon deposition and deactivation, the cost of HZSM-5 is high, and the reaction temperature of γ-Al ₂ O ₃ is high. Because the above catalysts have their own shortcomings, the preparation of dimethyl ether requires large investment and high cost, resulting in restrictions on the production and use of dimethyl ether.

The purpose of the present invention is to utilize the excellent characteristics of heteropolyacids: strong acidity (protonic acid and Lewis acid), pseudo-liquid phase properties, no corrosion and no pollution, etc., to make a loaded composite catalyst for methanol dehydration to prepare dimethylformamide Ether, providing an excellent and efficient catalyst for the preparation of dimethyl ether.

The composition of the catalyst:

(1) Carrier: γ-Al ₂ O ₃ , with a mass content of 25-98.8%, expressed as 25-98.8% (m), the same below.

(2) Active ingredients:

Heteropoly acid (Hetropoly acid is abbreviated as HPA), content: 1-50% (m)

Chemical formula: HaXbMcOd nH ₂ O

Among them: a: 3-6 b: 1-2 c: 6-18 d: 24-62 n: 5-40; X: P, As, Sb, B, Si, Ge, Ga, In, Fe, Co, etc. , M: Mo, W, V, Nb, etc.

(3) Anti-coking components: TiO ₂ , content: 0.1-20% (m); La ₂ O ₃ , content: 0.1-5% (m)

The preparation method of the catalyst adopts impregnation method.

Add the γ-Al ₂ O ₃ powder into the TiCl ₄ solution, let it stand for 12-24 hours, adjust the pH to 7.5-8.5 with NH ₃ ·H ₂ O, stir and heat at 50-70°C for 0.5 hours, and filter, The precipitate was dried at 110-130°C for 2 hours, and pressed into tablets. Calcined at 450-550°C for 2h to obtain Al ₂ O ₃ -TiO ₂ . Dissolve HPA in water, add La(NO ₃ ) ₃ , after dissolving, add Al ₂ O ₃ -TiO ₂ , impregnate for 2-24 hours, then dry at 110-130°C for 2 hours, and bake at 300-400°C for 4 hours to obtain Supported heteropolyacid composite catalyst. The addition amount of each of the above components is added in the amount calculated according to the ratio described in the catalyst composition.

The supported heteropolyacid composite catalyst is used in the reaction of methanol dehydration to dimethyl ether. The reaction equation is as follows:

ΔH ₂₉₈ =-22.52KJ/mol

The catalytic reaction takes place in a tubular reactor. Under the reaction conditions of pressure of 0-1.0MPa (table), temperature of 240-320°C, and weight space velocity of 1.0-3.5h ^-1 , the conversion rate of methanol reaches 85%, and the selectivity of dimethyl ether is 99.99%.

Compared with the catalyst CM-3-1 [Lin Jing et al., Chemical Production and Technology, 1996, 2:9] that has been put into use in industry, the supported heteropolyacid composite catalyst has high activity, low reaction temperature and good selectivity. . For example, under the same conditions (particle size, pressure, space velocity and conversion rate), the reaction temperature is low; for fine particle catalysts, under normal pressure, 260°C, and space velocity of 1.0h ^-1 , the methanol conversion rate increases by 10%.

The supported heteropolyacid composite catalyst was prepared by impregnation method. The catalyst composition is HPA: 1-30% (m), γ-Al ₂ O ₃ 55-98.2% (m), TiO ₂ : 0.1-10% (m), La ₂ O ₃ : 0.1-5% (m) . The preparation conditions are as follows: the immersion time of the active component (HPA) is 12 hours, the drying temperature is 120°C, and the calcination temperature is 350°C. Put 5g of catalyst (20-40 mesh) into the reaction tube, and activate it at 400°C for 2h under the protection of _N2 . At normal pressure, the weight space velocity is 1.0h ^-1 , under the reaction conditions of 260°C, the conversion rate of methanol is 77%, and the selectivity of dimethyl ether is 99.99%; The conversion rate was 84%, and the selectivity to dimethyl ether was 99.99%. Put 15g of catalyst (8-16 mesh) into the reaction tube, the catalyst bed is 8.5cm high, and activate at 400°C for 2h under the protection of _N2 . Reaction temperature: 290°C, pressure: 1.0MPa (table), weight space velocity: 2.0h ^-1 , methanol preheating temperature 320°C, through the reaction tube from top to bottom, the conversion rate of methanol is 83%, the selectivity of dimethyl ether 99.99%

Claims (2)

1, a kind of production method that is used for the carried heteropoly acid composite catalyst of methanol dehydration dimethyl ether-preparing, it is characterized in that: the composition of this catalyst mainly contains carrier: γ-Al ₂O ₃, 25-98.2% (m); Active component: heteropoly acid (HPA), 1-50% (m); Anti-carbon deposit component: titanium dioxide (TiO ₂), 0.1-20% (m), lanthanum sesquioxide (La ₂O ₃), 0.1-5% (m) uses immersion process for preparing, with γ-Al ₂O ₃Powder joins TiCl ₄In the solution, behind the placement 12-24h, use NH ₃H ₂O transfers pH=7.5-8.5, and agitating heating 0.5h under 50-70 ℃ of temperature after the filtration, will be deposited in 110-130 ℃ of dry 2h, and compression molding at 450-550 ℃ of roasting 2h, makes Al ₂O ₃-TiO ₂, HPA is water-soluble, add La (NO ₃) ₃, after the dissolving, add Al again ₂O ₃-TiO ₂, dipping 2-24h, then at 110-130 ℃ of dry 2h, 300-400 ℃ of roasting 4h.

2, a kind of carried heteropoly acid composite catalyst that is used for methanol dehydration dimethyl ether-preparing, it is characterized in that: the composition of this catalyst mainly contains carrier: γ-Al ₂O ₃, 25-98.2% (m); Active component: heteropoly acid (HPA), 1-50% (m); Anti-carbon deposit component: titanium dioxide (TiO ₂), 0.1-20% (m), lanthanum sesquioxide (La ₂O ₃), 0.1-5% (m).