阅读说明：本技术 铁基费托合成催化剂及其制备方法 (Iron-based Fischer-Tropsch synthesis catalyst and preparation method thereof ) 是由 常海 林泉 张魁 程萌 吕毅军 门卓武 马琳鸽 于 2018-06-06 设计创作，主要内容包括：本发明涉及催化剂合成领域,公开了一种铁基费托合成催化剂及其制备方法。该方法将水溶性铁盐、水溶性铜盐与含硅源、钾源、水溶性碱源和水溶性铝源的共沉淀剂溶液进行共沉淀反应,并分离出沉淀物,将沉淀物打浆,喷雾干燥,焙烧得到催化剂。所述催化剂含有具有以下重量比的元素,Fe:Cu:K:SiO<Sub>2</Sub>:Al＝100:(0.01-5):(1-7):(5-27):(0.01-4.5),其中,所述费托合成催化剂中含有KAlSiO<Sub>4</Sub>。所述催化剂在费托合成反应过程中K组分不易流失,从而大幅改善了催化剂的活性稳定性及有效产物收率,碳原子数为5以上(C<Sub>5+</Sub>)的产物的时空收率达到1.1g/g-cat./h以上。(The invention relates to the field of catalyst synthesis, and discloses an iron-based Fischer-Tropsch synthesis catalyst and a preparation method thereof. The method comprises the steps of carrying out coprecipitation reaction on water-soluble iron salt and water-soluble copper salt and a coprecipitator solution containing a silicon source, a potassium source, a water-soluble alkali source and a water-soluble aluminum source, separating out a precipitate, pulping the precipitate, carrying out spray drying, and roasting to obtain the catalyst. The catalyst contains elements with the weight ratio of Fe, Cu, K and SiO 2 Al (100) (0.01-5) (1-7) (5-27) (0.01-4.5), wherein the Fischer-Tropsch synthesis catalyst contains KAlSiO 4 . The catalyst has the advantages that the K component is not easy to lose in the Fischer-Tropsch synthesis reaction process, so that the activity stability and the effective product yield of the catalyst are greatly improved, and the carbon number is more than 5 (C) 5+ ) The space-time yield of the product reaches more than 1.1g/g-cat.)

1. A preparation method of an iron-based Fischer-Tropsch synthesis catalyst comprises the following steps:

(1) Carrying out coprecipitation reaction on water-soluble iron salt, water-soluble copper salt and a coprecipitator solution, and separating out a precipitate from a reaction product, wherein the coprecipitator solution contains a silicon source, a potassium source, a water-soluble alkali source and a water-soluble aluminum source;

(2) Pulping the precipitate obtained in the step (1) in the presence of deionized water to obtain precipitate slurry; and

(3) And (3) carrying out spray drying on the precipitate slurry obtained in the step (2), and then roasting.

2. the process of claim 1 wherein the water soluble aluminum source is selected from one or more of sodium aluminate, sodium metaaluminate, potassium aluminate and potassium metaaluminate.

3. The process according to claim 1 or 2, wherein in step (1), the silicon source is selected from one or more of potassium silicate, sodium silicate, orthosilicic acid and silica sol.

4. The process according to claim 1 or 2, wherein in step (1) the potassium source is a water soluble potassium salt, preferably selected from one or more of potassium silicate, potassium carbonate, potassium bicarbonate, potassium aluminate and potassium metaaluminate.

5. the process according to claim 1 or 2, wherein in step (1), the water-soluble alkali source is selected from one or more of potassium carbonate, potassium bicarbonate, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, ammonium carbonate, ammonium bicarbonate and urea.

6. The method according to claim 1 or 2, wherein in step (1), the conditions of the coprecipitation reaction include: the temperature is 40-80 ℃, and the pH value of the system is regulated to 4-8.

7. The method of claim 1 or 2, wherein in step (3), the conditions of the spray drying comprise: the inlet air temperature is 200-350 ℃, and the outlet air temperature is 95-115 ℃; and/or the presence of a gas in the gas,

The roasting condition comprises roasting at 100-200 ℃ for 8-16 hours, then heating to 400-550 ℃ at the heating rate of 280-350 ℃/hour, and roasting for 3-7 hours.

8. An iron-based fischer-tropsch synthesis catalyst prepared by the process of any one of claims 1 to 7, wherein the fischer-tropsch synthesis catalyst comprises the elements in the following weight ratios, Fe: Cu: K: SiO₂Al (100) (0.01-5) (1-7) (5-27) (0.01-4.5), and the Fischer-Tropsch synthesis catalyst contains KAlSiO₄。

9. The catalyst of claim 8, wherein Fe is α -Fe₂O₃Exist in the form of (1).

10. The catalyst according to claim 8 or 9, wherein the catalyst further contains Na element.

Technical Field

The invention relates to the field of catalyst synthesis, in particular to an iron-based Fischer-Tropsch synthesis catalyst and a preparation method thereof.

Background

Fischer-Tropsch (F-T) synthesis is the core technology of coal indirect liquefaction, and synthesis gas (CO + H) is usually prepared by the action of F-T synthesis catalysts such as precipitated iron base or supported cobalt₂) The catalytic reaction is carried out to synthesize liquid hydrocarbon/wax hydrocarbon products. Precipitated iron-based catalysts, which are inexpensive and readily available in raw materials, are suitable for reaction operating temperatures and H of synthesis gas₂The advantages of wider/CO ratio, lower methane selectivity and the like are still the key points of research and development in the industry. However, the precipitated iron-based catalyst is inferior in reaction stability to the cobalt-based catalyst, which is one of the reasons for preventing its industrial application on a larger scale.

The method mainly comprises the steps of adding a potassium source compound into a sediment filter cake after washing and filtering, wherein no matter the precipitated iron is an ICC-I (Fe/Cu/K) series catalyst or an ICC- П (Fe/Mn/K) series catalyst, no potassium additive is needed, and the indispensability of the potassium additive to the precipitated iron-based Fischer-Tropsch synthesis catalyst is laterally proved.

CN100584454C discloses an iron based fischer-tropsch synthesis catalyst composition wherein the main iron phase is ferrihydrite and the catalyst composition comprises alumina as a structural promoter. It also discloses that the use of alumina as a structural promoter in an iron-based catalyst composition in which the main iron phase is ferrihydrite increases the activity and selectivity of the catalyst by a factor of 1.5 to 3.

CN101869840A discloses a Fischer-Tropsch synthesis catalyst and a preparation method thereof, wherein the active component of the catalyst is Fe, the catalyst also comprises a transition metal auxiliary agent M, a structure auxiliary agent S and a K auxiliary agent, the transition metal auxiliary agent M is selected from one or a combination of Mn, Cr and Zn, and the structure auxiliary agent S is SiO₂Or/and Al₂O₃(ii) a The weight ratio of the components is Fe, transition metal additive M and structural additive S, K is 100:1-50:1-50: 0.5-10. However, in the preparation method of the catalyst, the structural auxiliary agent Al₂O₃The raw materials of (a) are alumina sol, i.e. water and alumina. It also discloses that a certain amount of transition metal auxiliary agent and structure auxiliary agent (SiO) are added in the preparation process₂Or/and Al₂O₃) The active phase of the catalyst can be fully dispersed and stabilized, and the active phase and the catalyst structure can keep high stability in the reaction process.

However, in the actual application of the catalyst prepared by the above method, there is still a problem that the activity of the catalyst is lowered as the time for the catalytic reaction is prolonged.

The invention finds that the deactivation of the catalyst has a great relationship with the stability of the K component as the time of the catalytic reaction is prolonged. The activity and effective yield (i.e. number of carbon atoms greater than 5 (C)) of the catalyst with greater potassium loss from the bulk of the catalyst during the Fischer-Tropsch synthesis reaction₅₊) The yield of the product of (a) is much more reduced than in catalysts in which the potassium component is relatively stable. Therefore, how to consolidate the K component in the precipitated iron-based catalyst and effectively prevent the K component from losing from the catalyst body can be a key technical link for improving the activity and the effective yield of the precipitated iron-based Fischer-Tropsch synthesis catalyst.

Disclosure of Invention

The invention aims to solve the problems of catalyst activity stability and effective product yield reduction caused by the loss of a potassium component from a catalyst body in the prior art, and provides an iron-based Fischer-Tropsch synthesis catalyst and a preparation method thereof.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing an iron-based fischer-tropsch synthesis catalyst, the method comprising the steps of:

(1) Carrying out coprecipitation reaction on water-soluble iron salt, water-soluble copper salt and a coprecipitator solution, and separating out a precipitate from a reaction product, wherein the coprecipitator solution contains a silicon source, a potassium source, a water-soluble alkali source and a water-soluble aluminum source;

(2) Pulping the precipitate obtained in the step (1) in the presence of deionized water to obtain precipitate slurry; and

(3) and (3) carrying out spray drying on the precipitate slurry obtained in the step (2), and then roasting.

In a second aspect, the invention provides the iron-based Fischer-Tropsch synthesis catalyst prepared by the method in the first aspect, wherein the Fischer-Tropsch synthesis catalyst contains the following elements in weight ratio of Fe to Cu to K to SiO_2:al 100 (0.01-5): 1-7): 5-27): 0.01-4.5), wherein the aluminum, part of silicon and part of potassium are KAlSiO₄Exist in the form of (1).

The precipitated iron-based catalyst prepared by the method has the advantages that the stability of the metal component K is greatly improved, so that the loss of the metal component K from an iron catalyst body in the Fischer-Tropsch synthesis reaction process is effectively prevented, and the stability of the component Fe is improved. Compared with the conventional catalyst, the activity stability of the catalyst is greatly improved, the long-period catalytic life of the precipitated iron-based catalyst is effectively prolonged, and the number of carbon atoms is more than 5 (C)₅₊) The yield of the target product (C) is 5 or more carbon atoms₅₊) The space-time yield of the product reaches more than 1.1g/g-cat. In addition, compared with the traditional preparation method of the precipitated iron-based catalyst, the method provided by the invention has the advantages that the preparation process is greatly shortened, the discharge capacity is greatly reduced, and the equipment investment and the production operation cost can be greatly reduced.

Drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of the catalyst of example 1 of the present invention.

Detailed Description

the endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the invention provides a process for the preparation of an iron-based fischer-tropsch synthesis catalyst, the process comprising the steps of:

(1) Carrying out coprecipitation reaction on water-soluble iron salt, water-soluble copper salt and a coprecipitator solution, and separating out a precipitate from a reaction product, wherein the coprecipitator solution contains a silicon source, a potassium source, a water-soluble alkali source and a water-soluble aluminum source;

(2) Pulping the precipitate obtained in the step (1) in the presence of deionized water to obtain precipitate slurry; and

(3) And (3) carrying out spray drying on the precipitate slurry obtained in the step (2), and then roasting.

In the invention, in the step (1), the water-soluble iron salt is selected from one or more of ferric nitrate and ferric chloride; the water-soluble copper salt is selected from one or more of copper nitrate, copper chloride, cuprous chloride and copper acetate.

In the present invention, in the step (1), the coprecipitator solution contains a water-soluble aluminum source selected from one or more of sodium aluminate, sodium metaaluminate, potassium aluminate and potassium metaaluminate. The coprecipitate solution contains a silicon source, which may be a soluble silicon compound and/or a silica sol, for example, one or more selected from the group consisting of potassium silicate, sodium silicate, orthosilicic acid, and silica sol. The coprecipitate solution contains a water-soluble alkali source, wherein the water-soluble alkali source is selected from one or more of potassium carbonate, potassium bicarbonate, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, ammonium carbonate, ammonium bicarbonate and urea, and is preferably the combination of potassium carbonate and potassium bicarbonate. The coprecipitate solution also contains a potassium source, wherein the potassium source is a potassium-containing compound and can be water-soluble potassium salt, such as one or more of potassium silicate, potassium carbonate, potassium bicarbonate, potassium aluminate and potassium metaaluminate. In one embodiment, the potassium source is the same as the water-soluble aluminum source, the silicon source, or the water-soluble alkali source.

In a preferred embodiment, the potassium source, the water-soluble aluminum source and the silicon source are mixed uniformly during the formation of the coprecipitate solution in step (1), which has the advantage that during the coprecipitation process, the two elements K and Al can be adsorbed on the metal micelles and silica micelles in-line and then further interact under the coprecipitation reaction conditions. During subsequent high-temperature treatment (drying and roasting), the interaction is further strengthened and even chemical interaction occurs, so that the effect of firmly binding the potassium element on the surface of the final catalyst crystal grain is achieved.

Preferably, in step (1), the silicon source and the potassium source are added together during the formation of the coprecipitate solution, or the silicon source and the potassium source are the same substance. A water soluble aluminum source is mixed as a water soluble salt with the silicon source and the potassium source.

in the present invention, preferably, the pH of the coprecipitant solution is adjusted to greater than 8, preferably greater than 9.0, at ambient temperature.

In the invention, the amount of each component in the coprecipitator can be adjusted according to other requirements on the premise of completely precipitating the Fe element and the Cu element.

In the present invention, in step (1), the conditions of the coprecipitation reaction include: the temperature is 40-80 ℃, preferably 45-75 ℃, and more preferably 45-60 ℃; the pH value of the regulation system is 4-8, preferably 4-7; the time is 20-35 min.

In the present invention, the adjustment of the temperature during the coprecipitation reaction can be selected according to the prior art, such as jacket heating, electric heating, etc., and the adjustment of the pH during the coprecipitation reaction can be selected according to the prior art, such as adjusting the pH of the reaction system by adjusting the flow rates of the precipitant solution and the water-soluble iron salt and the water-soluble copper salt. After the coprecipitation reaction is completed, the system is aged for a certain period of time, and the precipitate (i.e., filter cake) is separated by suction filtration or the like, and the obtained filter cake is preferably washed once with deionized water, and more preferably the obtained filter cake is not washed.

in the invention, the step (1) is used for realizing the precipitation of the iron element and the copper element, gelling the silicon monomer in the silicon source and simultaneously realizing the loading of the elements K and Al.

In the present invention, in step (2), the cake obtained in step (1) is beaten by mixing and stirring an appropriate amount of deionized water, for example, by beating under high shear conditions.

In the invention, the conditions of the spray drying in the step (3) comprise that the inlet air temperature is 200-350 ℃, and the outlet air temperature is 95-135 ℃; the roasting condition comprises roasting at 100-200 ℃ for 8-16 hours, then heating to 400-550 ℃ at the heating rate of 280-350 ℃/hour, and roasting at the temperature for 3-7 hours.

In a second aspect, the invention provides an iron-based fischer-tropsch catalyst prepared by the method of the first aspect, wherein the fischer-tropsch catalyst comprises the following elements in the weight ratio of Fe: Cu: K: SiO₂:Al＝100:(0.01-5):(1-7):(5-27):(0.01-4.5)。

In the present invention, the aluminum, part of the silicon and part of the potassium are KAlSiO₄In the form of alpha-Fe₂O₃Exist in the form of (1). This can be determined by X-ray diffraction (XRD) testing.

Preferably, in the catalyst, Cu may be present in the form of copper oxide.

In the invention, the catalyst can also contain Na elements, wherein Fe, Cu, K, Na and SiO₂The weight ratio of Al is 100 (0.01-5): (1-7): 0.01-1): 5-27): 0.01-4.5, preferably 100 (0.01-4.9): 1-7): 0.01-0.4): 5-27): 0.01-4.5.

The BET specific surface area of the catalyst is 80-180m²Per g, preferably 120-165m²Per g, pore volume of 0.35-0.65cm³a/g, preferably from 0.4 to 0.60m²/g。

The catalyst of the invention has the following advantages:

(1) In the catalyst, the stability of the metal component (particularly K) is greatly improved, so that the metal component (particularly K) is prevented from losing from an iron-based catalyst body in the Fischer-Tropsch synthesis reaction process;

(2) The catalyst of the method can maintain long-period stable operation, namely the conversion rate and the effective product yield are stable. And target product (C)₅₊) The yield is high, and the space-time yield reaches more than 1.1g/g-cat.

(3) Compared with the traditional method, the method for preparing the catalyst has the advantages of simple process, greatly shortened production flow, especially obviously reduced washing times, reduced water consumption, reduced discharge capacity, and greatly reduced equipment investment and operation cost.

The present invention will be described in detail below by way of examples.