CN1125681C - Catalyst for preparing C2 hydrocarbon from transition metal and methane through oxidization and coupling by cocatalysis with S and W elements and its preparing process - Google Patents

Abstract

The invention discloses a transition metal methane oxidative coupling catalyst for preparing _C2 hydrocarbons catalyzed by sulfur and tungsten elements and a preparation method thereof. As a cocatalyst, it is modified with alkali metal ions and loaded on _SiO2 carrier. The catalyst is used for methane oxidative coupling reaction. Under the conditions of lower temperature and no diluent gas, higher methane conversion rate and _C2 hydrocarbon (mainly including ethylene and ethane) selectivity are obtained, and the yield of _C2 hydrocarbon is Reaching more than 25%, up to 26.83%, is conducive to the direct utilization of natural gas in industry and the development of natural gas chemical industry.

Description

A kind of transition metal methane oxidative coupling preparation C2 hydrocarbon catalyst and preparation method thereof catalyzed by sulfur and tungsten

Technical field

The invention relates to a catalyst for directly converting methane to produce _C2 hydrocarbons (mainly including ethylene and ethane) and a preparation method thereof, in particular to a transition metal methane oxidative coupling catalyst for producing _C2 hydrocarbons catalyzed by sulfur and tungsten elements and its preparation method.

Background technique

With the increasing depletion of oil resources, the search for new alternative energy and chemical raw materials has become a topic that governments of all countries attach importance to. The existing proven oil reserves can only last for 30 years, while natural gas, which is also the basic raw material of the chemical industry, has not been well utilized; it has not been transformed into higher value chemical products.

In the past two decades, more than 2,000 methane oxidative coupling catalysts have been studied, involving almost all elements in the periodic table except group zero. If the yield of _C2 hydrocarbons is simply used as an evaluation index, none of these catalysts get better results. In recent years, some researchers have tried to improve the reaction process of methane oxidative coupling reaction from the perspective of reactor and reaction process, and directly use the dilute ethylene obtained from the reaction to synthesize ethylene oxide, propionaldehyde, ethylbenzene and oil And other downstream products, but from a technical and economic point of view, due to problems such as separation difficulties, the economy still cannot be compared with petrochemicals. Therefore, improving catalysts is still an important direction in the research of methane oxidative coupling reaction.

The key to industrialization of methane oxidative coupling reaction is to increase the yield of C ₂ hydrocarbons, and the core is to develop efficient methane oxidative coupling catalysts. At present, most of the C ₂ hydrocarbon single-pass yields of the developed methane oxidative coupling catalysts are below 25%. The analysis of the methane oxidative coupling reaction process shows that on the basis of ensuring that the selectivity of C ₂ hydrocarbons is basically unchanged, the improved The conversion of methane helps to increase the yield of _C2 hydrocarbons. The high conversion rate of methane can reduce the power consumption of the reaction process, increase the utilization rate of methane, and help to improve the economy of the reaction process.

Most of the methane oxidative coupling catalysts are alkali and alkaline earth metal catalysts. The selectivity of _C2 hydrocarbons of these catalysts is generally high, usually reaching 70-80%, but the conversion rate of methane is low, so the yield of _C2 hydrocarbons is relatively high. Not more than 23%. Some transition metal catalysts studied in recent years have shown good catalytic performance in the oxidative coupling reaction of methane, such as the Na ₄ P ₂ O ₇ -ZrOCl ₂ catalyst and Na ⁺ -ZrO ₂ -Cl ^- / _SiO2 catalyst has good catalytic performance in the reaction, among which the _C2 selectivity of the former reaches 79%, and the _CH4 conversion rate reaches 28% ( _C2 yield ≈ 22%, up to 30%). The disadvantage is that it is stable The catalyst activity is poor, and the activity of the catalyst drops significantly after 2-3 hours of reaction. The other two are the Na ⁺ -Mn-W/SiO ₂ catalyst developed by the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences and the Mn-S/SiO ₂ catalyst developed by Zhejiang University, both of which have good methane oxidative coupling reaction activity , the highest _C2 yield reaches 24.1% and 22.3% respectively, and it should be noted that the former is diluted with inert gas in the reaction process, which increases the separation difficulty of the product and is economically poor; the stability of the latter is not high, Easily deactivated.

Contents of Invention

The purpose of the present invention is to provide a transition metal methane oxidative coupling catalyst for the production of _C2 hydrocarbons and a preparation method thereof, so as to solve the problems existing in the background technology.

The methane oxidative coupling catalyst for preparing _C2 hydrocarbons provided by the present invention is mainly composed of two transition metals, Mn and Zr, with S and W elements as promoters, modified with alkali metal ions, and loaded on a _SiO2 carrier , the catalyst of the invention contains:

1) 10-35 (mol)% of at least one alkali or alkaline earth metal salt;

2) 0.5-12 (mol)% sulfur oxo acid salt;

3) Oxygenates of 1.0-2.5 (mol)% tungsten;

4) 0.5-13 (mol)% zirconium soluble oxo acid salt;

5) 1.0～4.0(mol)% soluble salt of manganese element;

6) Balance silicon dioxide.

The alkali or alkaline earth metal salt used is one or more of Na ⁺ , K ⁺ , Li ⁺ , Mg ²⁺ and Ca ²⁺ , among which Na ⁺ has the best effect; the sulfur element oxyacid used The salt can be sodium sulfate or potassium sulfate or sodium sulfite, and sodium sulfate is the best; the tungsten element oxysalt used can be sodium tungstate or potassium tungstate, and sodium tungstate is the best; the soluble salt of manganese used can be Manganese chloride or manganese acetate; the soluble zirconium salt used is preferably zirconium oxychloride.

Methane oxidative coupling provided by the invention prepares the preparation method of _C2 hydrocarbon catalyst, comprises the following steps successively:

1) Take a silica gel solution with a concentration of 20-35% silicon dioxide, adjust its pH to 5-9, preferably 6-8, and a temperature of 10-100°C, preferably 20-50°C;

2) Add the required amount of alkali or alkaline earth metal salt and oxysalt solution containing sulfur and tungsten into the silica gel solution to prepare a gel. The pH value of the solution during the gel process is 8-12, preferably 9 ~10;

3) Dry the gel obtained in step 2) at a temperature of 60 to 180°C for 2 to 12 hours, preferably at a drying temperature of 100 to 150°C, then roast at a high temperature in the air, and finally cool to room temperature. Step method, the first step of roasting temperature is 400-650°C, the preferred roasting temperature is 500-600°C, the roasting time is 2-4 hours, the second step of roasting temperature is 800-1100°C, the preferred roasting temperature is 850-950°C , the roasting time is 5-8 hours;

4) Dissolving the required amount of soluble salts of manganese and zirconium with an appropriate amount of water, impregnating the roasted product obtained in step 3) with an equal impregnation method, the pH value of the solution during the impregnation process is 8-12, preferably 9-10 ;

5) Dry the impregnation obtained in step 4) at a temperature of 60-180°C for 2-12 hours, preferably at a drying temperature of 100-150°C, and then roast at high temperature in the air. The roasting adopts a two-step method, and the first step is roasting The temperature is 400-650°C, preferably the roasting temperature is 500-600°C, the roasting time is 2-4 hours, the second-step roasting temperature is 800-1100°C, the preferred roasting temperature is 850-950°C, and the roasting time is 5-8 Hour.

Catalyst of the present invention is implemented by following experimental scheme:

The experiment uses a fixed-bed quartz reactor at atmospheric pressure. Methane with a content of more than 99% is mixed with oxygen with a content of more than 99%, and the mol ratio of methane and oxygen is controlled at 2-4. The mixed gas of methane and oxygen is reacted through the catalyst bed prepared by the above-mentioned method. The reaction temperature is 750-850°C, and 770-800°C is the best; the reaction ^is carried out under ^normal pressure ^; Preferably, it is 0.7×10 ⁴ to 1.5×10 ⁴ hr ^-1 .

Compared with the background technology, the present invention has the beneficial effects that: the present invention can effectively improve the activation of methane through the strong oxidizing properties of Mn and Zr, promote the conversion of methane, reduce the temperature of reaction, and simultaneously add sulfur, tungsten and alkali metal salts to Ensure the selectivity of _C2 hydrocarbons and increase the yield of _C2 hydrocarbons. In addition, no inert gas needs to be added to the reaction raw material gas, which is beneficial to the industrialization of methane oxidative coupling reaction.

Detailed ways

Below by embodiment the present invention is described in further detail:

Example 1

The catalyst contained 16.45 mol% Na, 5.73 mol% S, 1.45 mol% W, 6.75 mol% Zr and 2.27 mol% Mn. Select a silica gel solution containing 8 grams of silicon dioxide, adjust the pH value to 9, and the temperature is 30 ° C, add 0.06 grams of sodium carbonate, 1.10 grams of sodium sulfate, and 0.65 grams of sodium tungstate under stirring; dry the resulting gel at 130 ° C 3 hours, 550°C roasting for 3 hours, 875°C roasting for 5 hours; use a mixed solution containing 2.90 grams of zirconium oxychloride and 0.56 grams of manganese acetate to impregnate the calcined gel in an equal amount under the condition of pH 10, and then heat it at 130°C Dry for 3 hours, bake at 550°C for 3 hours, and bake at 875°C for 5 hours.

The prepared catalyst was applied to the oxidative coupling reaction of methane. Put the 20-40 mesh 0.5ml catalyst obtained by sieving into a quartz reactor with an inner diameter of 6mm, ^and continuously pass the mixed gas of methane and oxygen with a molar ratio of 3 through the catalyst bed, and the reaction gas space velocity (STP) is 8000 hours- ^1. The reaction is carried out at a temperature of 770°C and normal pressure. The reaction products were detected online by two 102G gas chromatographs. The results are shown in Table 1.

Table 1 temperature reflex Reagent gas space velocity Alkoxy ratio methane conversion rate _C2 selectivity C ₂ yield Enane ratio ℃ hour ^-1 mol.mol ^-1 % % % Mol.mol ^-1 770 8000 3:1 36.54 73.07 26.70 4.0

Example 2

The preparation steps and method are the same as in Example 1. The catalyst contained 14.54 mol% K, 3.33 mol% S, 1.99 mol% W, 6.50 mol% Zr and 2.68 mol% Mn. S uses sodium sulfite, W uses sodium tungstate, Zr uses zirconium oxychloride, and Mn uses manganese acetate. Take 0.5ml of catalyst with a particle size of 20-40 mesh to carry out methane oxidative coupling reaction. The reaction conditions and results are shown in Table 2.

Table 2 temperature reflex Reagent gas space velocity Alkoxy ratio methane conversion rate _C2 selectivity C ₂ yield Enane ratio ℃ hour ^-1 mol.mol ^-1 % % % Mol.mol ^-1 800 7000 3:1 30.67 83.26 25.54 3.4

Example 3

The preparation steps and method are the same as in Example 1. The catalyst contained 18.91 mol% K, 2.65 mol% S, 1.99 mol% W, 5.05 mol% Zr and 3.67 mol% Mn. Potassium sulfate is used for S, potassium tungstate is used for W, zirconium oxychloride is used for Zr, and manganese acetate is used for Mn. Take 0.5ml of catalyst with a particle size of 20-40 mesh for methane oxidative coupling reaction. The reaction conditions and results are shown in Table 3.

table 3 temperature reflex Reagent gas space velocity Alkoxy ratio methane conversion rate _C2 selectivity C ₂ yield Enane ratio ℃ hour ^-1 mol.mol ^-1 % % % Mol.mol ^-1 770 7000 3:1 36.91 73.36 27.08 4.0 800 9000 3:1 35.67 70.26 25.06 3.7 830 11000 3:1 33.44 66.24 22.15 2.3

Example 4

The preparation steps and method are the same as in Example 1. The catalyst contained 22.88 mol% Na, 8.13 mol% S, 1.93 mol% W, 11.85 mol% Zr and 3.44 mol% Mn. Sodium sulfate is used for S, sodium tungstate is used for W, zirconium oxychloride is used for Zr, and manganese acetate is used for Mn. Take 0.5ml of the catalyst with a particle size of 20-40 mesh to carry out the methane oxidative coupling reaction. The reaction conditions and results are shown in Table 4.

Table 4 temperature reflex Reagent gas space velocity Alkoxy ratio methane conversion rate _C2 selectivity C ₂ yield Enane ratio ℃ hour ^-1 mol.mol ^-1 % % % mol.mol ^-1 830 8000 3:1 34.24 74.90 25.65 3.4

Claims (8)

1. one kind is helped the transition metal and methane oxidative coupling system C2 hydrocarbon catalyst of catalysis with sulphur, W elements, it is characterized in that this catalyst contains;

1) at least a alkaline or alkaline-earth salts of 10～35 (mol) %;

2) oxysalt of 0.5～12 (mol) % element sulphur;

3) oxysalt of 1.0～2.5 (mol) % W elements;

4) the solubility oxysalt of 0.5～13 (mol) % zr element;

5) soluble-salt of 1.0～4.0 (mol) % manganese element;

6) surplus silica.

2. by the described transition metal and methane oxidative coupling system C that helps catalysis with sulphur, W elements of claim 1 ₂Hydrocarbon catalyst is characterized in that said alkaline or alkaline-earth salts is Na ⁺, K ⁺, Li ⁺, Mg ²⁺, Ca ²⁺In one or more, the element sulphur oxysalt is sodium sulphate or potassium sulfate or sodium sulfite; The W elements oxysalt is sodium tungstate or potassium tungstate; The soluble-salt of manganese is manganese chloride or manganese acetate; The soluble-salt of used zirconium is a zirconium oxychloride.

3. one kind is used for the described transition metal and methane oxidative coupling system C that helps catalysis with sulphur, W elements of claim 1 ₂The preparation method of hydrocarbon catalyst is characterized in that it in turn includes the following steps:

1) get the silica gel solution that concentration is 20～35% silica, regulating its pH value is 5～9, and temperature is 10～100 ℃;

2) the oxysalt aqueous solution that will contain the alkaline or alkaline-earth salts of requirement and sulfur-bearing, tungsten adds in the silica gel solution, prepares gel, and the pH value of solution value of gel process is 8～12;

3) with step 2) gel of gained is under 60～180 ℃ of temperature, dry 2～12 hours, high-temperature roasting in air then, last cool to room temperature, wherein two-step method is adopted in high-temperature roasting, and first step sintering temperature is 400～650 ℃, and roasting time is 2～4 hours, the second one-step baking temperature is 800～1100 ℃, and roasting time is 5～8 hours;

4) manganese of aequum and the soluble-salt of zirconium are dissolved with suitable quantity of water, with equivalent impregnation method impregnation steps 3) calcining matter that obtains, the pH value of solution value of dipping process is 8～12;

5) macerate that step 4) is obtained is under 60～180 ℃ of temperature, dry 2～12 hours, high-temperature roasting in air then, two-step method is adopted in roasting, first step sintering temperature is 400～650 ℃, roasting time is 2～4 hours, and the second one-step baking temperature is 800～1100 ℃, and roasting time is 5～8 hours.

4. by the described methane oxidation coupling system C of claim 3 ₂The preparation method of hydrocarbon catalyst, the pH value that it is characterized in that said step 1) silica sol solution is 6～8, temperature is 20～50 ℃.

5. by the described methane oxidation coupling system C of claim 3 ₂The preparation method of hydrocarbon catalyst is characterized in that said step 2) the pH value of solution value of gel process is 9～10.

6. by the described methane oxidation coupling system C of claim 3 ₂The preparation method of hydrocarbon catalyst, the temperature that it is characterized in that said step 3) desiccant gel is 100～150 ℃, and first step sintering temperature is 500～600 ℃, and the second one-step baking temperature is 850～950 ℃.

7. by the described methane oxidation coupling system C of claim 3 ₂The preparation method of hydrocarbon catalyst, the pH value of solution value that it is characterized in that said step 4) dipping process is 9～10.

8. by the described methane oxidation coupling system C of claim 3 ₂The preparation method of hydrocarbon catalyst is characterized in that the temperature of the dry macerate of said step 5) is 100～150 ℃, and first step sintering temperature is 500～600 ℃, and the second one-step baking temperature is 850～950 ℃.