CN108722426B

CN108722426B - Catalyst, preparation method and application thereof, reduction activation method of catalyst precursor and preparation method of low-carbon olefin

Info

Publication number: CN108722426B
Application number: CN201710256584.2A
Authority: CN
Inventors: 晋超; 吴玉; 张荣俊; 夏国富; 阎振楠; 侯朝鹏; 孙霞; 李明丰
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2017-04-19
Filing date: 2017-04-19
Publication date: 2021-06-11
Anticipated expiration: 2037-04-19
Also published as: CN108722426A

Abstract

The invention discloses a catalyst, a preparation method and application thereof, a reduction activation method of a catalyst precursor and a preparation method of low-carbon olefin. The invention discloses a catalyst and a preparation method and application thereof, and also discloses a method for preparing low-carbon olefin by adopting the catalyst, wherein the catalyst comprises a carrier and a VIII group metal element loaded on the carrier, the carrier is alumina, and the valence state of at least part of the VIII group metal element is lower than the highest oxidation valence state of the metal element; CO of the catalyst₂In the TPD desorption diagram, CO is present in the temperature range of 300 ℃ and 600 DEG C₂High temperature desorption peak. According to the catalyst provided by the invention, even if the Fischer-Tropsch synthesis reaction is carried out in a high-space-velocity fluidized bed reactor under mild reaction conditions, higher CO conversion rate can be obtained, the selectivity of low-carbon olefin can be obviously improved, and higher activity stability can be obtained.

Description

Catalyst, preparation method and application thereof, reduction activation method of catalyst precursor and preparation method of low-carbon olefin

Technical Field

The invention relates to the technical field of Fischer-Tropsch synthesis, in particular to a catalyst, a catalyst precursor reduction activation method, a catalyst preparation method and a catalyst prepared by the method.

Background

Olefins are important basic chemical raw materials in chemical industry production and also are a mark for measuring the development level of the national petrochemical industry. 1995-2010 world ethylene demand increased at a rate of 4.1% per year; at the same time, the world demand for propylene is also rapidly increasing, with a rate of 6.3% from 2000 to 2010.

At present, the methods for preparing low-carbon olefins can be divided into 3 major categories according to raw materials: oil routes, natural gas routes, and coal routes. The method for preparing low-carbon olefin by adopting light oil cracking, namely a method for preparing low-carbon olefin by using a petroleum route, is adopted by most countries in the world and accounts for about 65 percent of the yield of olefin. Natural gas is used as a raw material, low-carbon olefin is prepared by an oxidative coupling method or a Bensen method, ethylene is mainly used as a product, and the yield of propylene is low. The research of preparing olefin by using coal-based synthesis gas through methanol is rapidly developed, and a plurality of sets of process devices are established in China.

In recent years, the demand of three major olefins is increasing, and the price of petroleum fluctuates, so that the cost of the olefin preparation process using petroleum and the like as raw materials is increased, the price of products is increased, and the profit margin of downstream products is reduced. Traditional petroleum routes such as naphtha cracking, alkane cracking, and the like face significant challenges. With the increasing shortage of petroleum resources and the requirement of sustainable development strategy, large-scale petrochemical companies in developed countries such as europe and america actively strive to develop a process technology for producing olefins in non-petroleum routes, and among them, a process technology for producing low-carbon olefins from coal, natural gas and biomass has been receiving increasing attention.

The energy sources in China are in the resource distribution situation of rich coal, much natural gas and oil shortage, and the indirect conversion of coal or natural gas into clean and efficient liquid fuel through Fischer-Tropsch synthesis is an important aspect of reasonably utilizing resources and also a main technical way for relieving the contradiction between supply and demand of petroleum in China. The process comprises the steps of firstly converting coal or natural gas into synthesis gas, and then preparing liquid fuel or chemical products through Fischer-Tropsch synthesis. The direct preparation of low-carbon olefin from synthesis gas refers to synthesis gas (CO and H)₂) A process for preparing olefins with a carbon number less than or equal to 4 by Fischer-Tropsch synthesis in the presence of a catalyst, by-production of water and CO₂. The Fischer-Tropsch synthesis product distribution is limited by an Anderson-Schulz-Flory rule (the chain growth is in exponentially decreasing molar distribution), and the reaction is a strong exothermic reaction, so that the generation of methane and low-carbon alkane is easy to cause, the generated olefin is promoted to have a secondary reaction, and the key point is the development of a high-performance catalyst for obtaining the low-carbon olefin with high selectivity is difficult.

Currently, iron-based catalysts are commonly used in industry to produce olefins in slurry, fixed bed or fluidized bed processes. Under the condition of low-temperature Fischer-Tropsch synthesis process, the product has high heavy hydrocarbon content and low olefin content, and is not beneficial to producing low-carbon olefins. South Africa Sasol company uses high temperature fluidized bed process to produce gasoline and by-produce low carbon olefins. This process, although allowing the production of lower olefins, has a low yield.

The common iron-based Fischer-Tropsch synthesis catalyst is prepared by a coprecipitation method: the active components are precipitated, filtered and washed, then mixed with a carrier, pulped and finally dried and formed, and the active components are applied to a slurry bed reactor, a fixed bed or a fluidized bed reactor. The precipitated iron Fischer-Tropsch synthesis catalyst has poor mechanical stability, easy breakage and serious carbon deposition in the reaction process, and active components in a bulk phase are difficult to reduce. Because the Fischer-Tropsch synthesis is a strong exothermic reaction, the precipitated iron catalyst is difficult to heat in a reactor during the reaction and is easy to fly warm, so that the catalyst is quickly inactivated. Therefore, the supported iron-based catalyst has attracted more and more attention due to its advantages of good stability, uniform distribution of active components, high activity, long service life, and the like.

CN1083415A discloses a low-carbon olefin catalyst, in which MgO and other alkaline earth metal oxides of IIA group or high-silicon zeolite molecular sieve (or phosphorus-aluminium zeolite) are used to carry iron-manganese active component, and strong alkali K or Cs ion is used as adjuvant. When the catalyst is used in a fixed bed reactor, although higher CO conversion rate can be obtained in the reaction of preparing low-carbon olefin from synthesis gas, the selectivity of the low-carbon olefin is still lower, and the reaction space velocity is lower, which is not beneficial to improving the production efficiency.

Therefore, it is of great practical interest to continue to develop new supported catalysts suitable for the production of lower olefins from synthesis gas.

Disclosure of Invention

The invention aims to provide a supported catalyst suitable for Fischer-Tropsch synthesis reaction, and the catalyst is used for the Fischer-Tropsch synthesis reaction, so that not only can a higher CO conversion rate be obtained, but also higher low-carbon olefin selectivity and higher activity stability are displayed.

According to a first aspect of the present invention, there is provided a catalyst comprising a carrier and a group VIII metal element supported on the carrier, wherein the carrier is alumina, and the valence of at least a part of the group VIII metal element is lower than the maximum oxidation valence of the metal element;

CO of the catalyst₂In the TPD desorption diagram, CO is present in the temperature range of 300 ℃ and 600 DEG C₂High temperature desorption peak.

According to a second aspect of the present invention, there is provided a method of reductive activation of a catalyst precursor, the method comprising the steps of:

(1) pre-reducing a catalyst precursor in a first gas to obtain a pre-reduced catalyst, wherein the first gas is hydrogen or a mixed gas of hydrogen and an inert gas, the catalyst precursor comprises a carrier and a VIII group metal element loaded on the carrier in the form of an oxide, the valence state of the VIII group metal element in the oxide is the highest oxidation valence state of the metal element, and the carrier is alumina;

(2) and carrying out reduction activation on the pre-reduction catalyst in a second gas to obtain a reduction activation catalyst, wherein the second gas is gaseous hydrocarbon at the reduction activation temperature or a mixed gas of the gaseous hydrocarbon and an inert gas at the reduction activation temperature, and the reduction activation is carried out at the temperature of 150-500 ℃.

According to a third aspect of the invention there is provided a catalyst prepared by the process of the second aspect of the invention.

According to a fourth aspect of the present invention, there is provided a process for the preparation of a catalyst, the process comprising the steps of:

(1) loading oxides of VIII group metal elements and/or precursors of the oxides of the VIII group metal elements on a carrier, and roasting the carrier loaded with the oxides and/or the precursors to obtain a catalyst precursor, wherein the carrier is alumina;

(2) the catalyst precursor is reductively activated using the method of the second aspect of the invention.

According to a fifth aspect of the present invention there is provided a catalyst prepared by the process of the fourth aspect of the present invention.

According to a sixth aspect of the invention there is provided the use of a catalyst according to the first, third or fifth aspects of the invention as a catalyst for a Fischer-Tropsch synthesis reaction.

According to a seventh aspect of the present invention there is provided a process for the production of lower olefins from synthesis gas, the process comprising contacting hydrogen and carbon monoxide with a catalyst under fischer-tropsch synthesis reaction conditions, wherein the catalyst is as described in the first, third and fifth aspects of the present invention.

According to an eighth aspect of the present invention, there is provided a process for producing lower olefins from synthesis gas, the process comprising:

(1) preparing a catalyst by the method of the second aspect of the invention, or the method of the fourth aspect of the invention;

(2) contacting hydrogen and carbon monoxide with the catalyst under fischer-tropsch synthesis reaction conditions.

The catalyst of the invention can obtain higher CO conversion rate even if the Fischer-Tropsch synthesis reaction is carried out in a fluidized bed reactor with high airspeed under mild reaction conditions, can obviously improve the selectivity of low-carbon olefin, and can obtain higher activity stability.

Drawings

FIG. 1 is a theta-Al alloy prepared in example 1₂O₃X-ray diffraction pattern of (a).

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 the present invention, the term "lower olefin" means an olefin having a carbon number of 4 or less.

According to a first aspect of the present invention, there is provided a catalyst comprising a carrier and a group VIII metal element supported on the carrier.

The support is alumina, and specific examples thereof may include, but are not limited to: gamma-Al₂O₃、θ-Al₂O₃、δ-Al₂O₃And alpha-Al₂O₃One or more than two of them. The parameters of the specific surface area, the average pore diameter, the particle size distribution and the like of the alumina can be optimized according to the specific type of the alumina so as to further improve the catalytic performance of the catalyst. MakingAs an example, for gamma-Al₂O₃The pore volume can be 0.6-1mL/g, preferably 0.65-0.9mL/g, more preferably 0.65-0.85 mL/g; the average pore diameter may be 8-35nm, preferably 12-30nm, more preferably 15-20 nm; the content of particles having a particle diameter in the range of 70 to 150 μm may be 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more; the specific surface area can be 100-300m²Per g, preferably 120-250m²(ii)/g, more preferably 150-²(ii) in terms of/g. As another example, for theta-Al₂O₃The pore volume can be 0.3-0.8mL/g, preferably 0.35-0.7mL/g, more preferably 0.4-0.6 mL/g; the average pore size may be 12-40nm, preferably 15-35nm, more preferably 18-25 nm; the content of particles having a particle diameter in the range of 70 to 150 μm may be 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more; the specific surface area can be 50-200m²A/g, preferably from 60 to 150m²A/g, more preferably from 65 to 100m²(ii) in terms of/g. In the present invention, the specific surface area, the pore volume and the average pore diameter are measured by a nitrogen adsorption method, specifically, N is used₂Measuring an adsorption isotherm at a constant temperature of 77K, calculating a specific surface area and a pore volume according to a BET formula, and calculating an average pore size distribution according to a BJH method; the particle size distribution was determined using a laser particle sizer.

In a preferred embodiment, the support contains theta-Al₂O₃. According to this preferred embodiment, by incorporating theta-Al in the support₂O₃The catalyst can obtain higher catalytic activity and catalytic stability, shows higher CO conversion rate and lower olefin selectivity when being used as a catalyst for Fischer-Tropsch synthesis reaction, and also has more excellent activity stability. Generally, the content of the θ -alumina may be 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, further preferably 40% by weight or more, and further preferably 50% by weight or more, based on the total amount of alumina in the catalyst. In a particularly preferred embodiment of the invention, the support is theta alumina. According to this particularly preferred embodiment, with other types of alumina (e.g. alumina)γ-Al₂O₃) In contrast, with theta-Al₂O₃The catalyst shows higher catalytic activity and catalytic stability when being used as a carrier, and can further improve the CO conversion rate, the selectivity of low-carbon olefin and the activity stability when being used as a catalyst of Fischer-Tropsch synthesis reaction.

The theta-Al₂O₃Can be obtained commercially or by reacting gamma-Al₂O₃And baking to obtain the final product. Specifically, γ -Al may be added₂O₃The calcination is carried out at a temperature of 700-1050 deg.C, preferably 780-1050 deg.C. The duration of the firing may be selected based on the temperature of firing sufficient to convert the gamma-Al₂O₃Conversion to theta-Al₂O₃The standard is. In general, the duration of the calcination may be from 0.5 to 5 hours, preferably from 1 to 4 hours. The firing is performed in an air atmosphere.

The group VIII metal element as an active component of the catalyst may be a group VIII noble metal element, a group VIII non-noble metal element, or a combination of the group VIII noble metal element and the group VIII non-noble metal element. In a preferred embodiment, the group VIII metal element is a group VIII non-noble metal element, and specific examples thereof may include, but are not limited to, one or two or more of Fe, Co, and Ni. The catalyst according to this preferred embodiment is particularly suitable as a catalyst for fischer-tropsch synthesis reactions. More preferably, the group VIII metal element is Fe.

According to the catalyst of the present invention, at least a part of the metal element of group VIII has a valence lower than the maximum oxidation valence of the metal element. Generally, the content of the group VIII metal element having a valence lower than the maximum oxidation valence thereof may be 30% by weight or more, preferably 40% by weight or more, more preferably 45% by weight or more, further preferably 50% by weight or more (e.g., 55% by weight or more), further preferably 60% by weight or more, and particularly preferably 75% by weight or more, in terms of the element, based on the total amount of the group VIII metal element in the catalyst. The valence is lower than the maximum oxidation valence based on the total amount of the VIII group metal element in the catalystThe maximum content of the group VIII metal element(s) may be 100% by weight or less than 100% by weight, such as 99%, 96%, 93%, 90%, 87%. The catalyst according to the invention can be used directly for catalytic reactions without additional reductive activation, for example, can be used directly for fischer-tropsch synthesis reactions without reductive activation. In the present invention, the term "maximum oxidation state" refers to the valence of the metal element when it is completely oxidized, and in the case of Fe, the maximum oxidation state refers to iron oxide (Fe)₂O₃) The valence of the middle iron element is + 3. In the invention, the VIII group metal elements with different valence states and the content thereof are measured by an X-ray photoelectron spectroscopy.

In a particularly preferred embodiment of the catalyst according to the invention, the group VIII metal element is Fe, and the catalyst has an X-ray photoelectron spectrum in which peaks corresponding to FeO (usually at 711.9eV and 724.4 eV) and peaks corresponding to Fe are present₅C₂The spectral peak of (usually occurs at 717.9 eV). The catalyst according to this particularly preferred embodiment is particularly suitable as a catalyst for a fischer-tropsch synthesis reaction.

In this particularly preferred embodiment, the content of Fe determined from the peaks corresponding to FeO and from the peaks corresponding to Fe, calculated as element₅C₂The ratio of the Fe content determined by the spectral peaks of (a) may be 8 to 25: 1. from the viewpoint of further improving the catalytic activity and catalytic stability of the catalyst, the content of Fe determined from the peak corresponding to FeO and the content of Fe determined from the peak corresponding to Fe₅C₂The ratio of the content of Fe determined by the spectral peak of (a) is preferably 9 to 20: 1, more preferably 9.5 to 15: 1, more preferably 10 to 12: 1.

according to the catalyst of this particularly preferred embodiment, from the viewpoint of further improving the catalytic activity and catalytic stability, particularly in the Fischer-Tropsch synthesis reaction, the peaks corresponding to FeO and the peaks corresponding to Fe are calculated on an elemental basis based on the total amount of Fe determined by X-ray photoelectron spectroscopy₅C₂The content of Fe determined by the peak of the spectrum may be 30% or more (e.g., 30 to 99%), preferablyPreferably not less than 40% (e.g., 40 to 96%), more preferably not less than 45% (e.g., 45 to 93%), further preferably not less than 50% (e.g., 55% or more), further preferably not less than 60% (e.g., 60 to 90%), and particularly preferably not less than 75% (e.g., 75 to 87%).

In the present invention, the X-ray photoelectron spectroscopy was measured on an ESCALab250 type X-ray photoelectron spectrometer equipped with Thermo Avantage V5.926 software of Thermo Scientific, the excitation source was monochromatized Al Ka X-ray, the energy was 1486.6eV, the power was 150W, the transmission energy for narrow scan was 30eV, and the base vacuum during analysis and test was 6.5X 10^-10mbar, electron binding energy was corrected for the C1s peak (284.6eV) of elemental carbon, data processed on Thermo Avantage software, and quantified in the analytical module using the sensitivity factor method.

According to the catalyst of this particularly preferred embodiment, the carrier preferably contains theta-alumina. Generally, the content of the θ -alumina may be 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, further preferably 40% by weight or more, and further preferably 50% by weight or more, based on the total amount of alumina in the catalyst. Particularly preferably, the support is theta alumina.

According to the catalyst of the present invention, the content of the group VIII metal element may be conventionally selected. Generally, the group VIII metal element may be contained in an amount of 3 to 30% by weight, preferably 5 to 25% by weight, more preferably 8 to 20% by weight, and further preferably 10 to 15% by weight, in terms of the element, based on the total amount of the catalyst. In the present invention, the contents of each metal element in the catalyst and the catalyst precursor were measured by an X-ray fluorescence spectrum analysis method specified in RIPP132-92 (published in "methods of petrochemical engineering analysis (RIPP test methods)", Yangtze et al, science publishers, 1 st edition at 1990, p. 371, 379).

The catalyst according to the present invention may further contain a second metal element and/or a third metal element supported on the carrier, preferably a third metal element and optionally a second metal element supported on the carrier, in addition to the carrier and the group VIII metal element supported on the carrier. The catalyst containing the second metal element and/or the third metal element shows more excellent catalytic activity and catalytic stability, and is particularly suitable for being used as a catalyst for Fischer-Tropsch synthesis reaction. In the present invention, "optional" means either with or without.

The second metal element is one or more selected from alkali metal elements, alkaline earth metal elements and group IVB metal elements. Specific examples of the second metal element may include, but are not limited to: one or more of Li, Na, K, Mg, Ca, Zr and Ti. Preferably, the second metal element is one or two or more of Li, Zr, Mg, and K. The content of the second metal element may be 0.1 to 15% by weight, preferably 1 to 12% by weight, more preferably 2 to 11% by weight, and still more preferably 5 to 7% by weight in terms of the element, based on the total amount of the catalyst.

From the viewpoint of further improving the catalytic activity and activity stability of the catalyst, the second metal element preferably contains a group IVB metal element (preferably Zr and/or Mg) and an alkali metal element (preferably K and/or Li), and the content of the group IVB metal element (preferably Zr and/or Mg) is preferably 0.5 to 8% by weight, more preferably 1 to 4% by weight, further preferably 2 to 3% by weight, and the content of the alkali metal element (preferably K and/or Li) is preferably 1 to 8% by weight, more preferably 2 to 6% by weight, further preferably 3 to 4% by weight, in terms of the elements, based on the total amount of the catalyst.

The third metal element is one or more selected from rare earth metal elements, and specific examples thereof may include, but are not limited to, one or more of lanthanum, cerium (Ce), praseodymium, and neodymium. Preferably, the third metal element is Ce. The content of the third metal element may be 0.1 to 10% by weight, preferably 0.5 to 6% by weight, more preferably 0.8 to 3% by weight, and further preferably 1.2 to 2% by weight in terms of element based on the total amount of the catalyst.

From the viewpoint of further improving the catalytic activity and catalytic stability of the catalyst, the catalyst according to the present invention preferably contains the second metal element and the third metal element supported on the carrier. When the catalyst contains both the second metal element and the third metal element, the second metal element is more preferably one or more of Zr, Li, Mg and K, and the third metal element is more preferably Ce, so that more excellent catalytic activity and catalytic stability can be obtained.

CO₂TPD (i.e., temperature programmed desorption of CO)₂) Can be used for characterizing the desorption performance of the catalyst on hydrocarbon molecules, in CO₂In the TPD spectrogram, the higher the temperature of the desorption peak is, the catalyst is favorable for desorption of the hydrocarbon molecules, and for a plurality of catalysts with desorption peaks at the same position, the higher the peak area is, the stronger the desorption capacity of the catalyst on the hydrocarbon molecules is. The catalyst according to the invention shows a unique CO₂TPD desorption profile, with a desorption peak (herein, this desorption peak is referred to as CO) in the temperature range of 300-₂High temperature desorption peak). The CO is₂The peak area of the high-temperature desorption peak is generally 0.3 to 2.5a.u (arbitrary units), preferably 0.5 to 2a.u (arbitrary units). CO of the catalyst according to the invention₂In the desorption spectrum of TPD, another desorption peak (herein, the desorption peak is referred to as CO) exists in the temperature range of 100-200 ℃, preferably 150-190 ℃₂Low temperature desorption peak). The CO is₂The peak area of the low-temperature desorption peak is generally 0.5 to 3.5a.u (arbitrary units), preferably 1 to 3.2a.u (arbitrary units), and more preferably 2 to 3a.u (arbitrary units).

CO-TPD (i.e., temperature programmed desorption of CO) can be used to characterize the catalyst's ability to dissociate CO, with higher temperatures at which CO desorption peaks occur indicating higher activity of the catalyst. For multiple catalysts with desorption peaks at the same location, a catalyst with a larger peak area favors CO dissociation. In the CO-TPD desorption spectrum of the catalyst according to the invention, a desorption peak (herein, the desorption peak is referred to as a CO high-temperature desorption peak) exists in the temperature interval of 300-700 ℃, preferably 400-650 ℃, and more preferably 450-600 ℃. The peak area of the CO high-temperature desorption peak is generally 0.5-7a.u (arbitrary unit), preferably 1-6a.u (arbitrary unit), and more preferably 2-5.5a.u (arbitrary unit). In the desorption spectrum of CO-TPD of the catalyst according to the invention, another desorption peak (herein, the desorption peak is called CO low-temperature desorption peak) exists in the temperature interval of 100-200 ℃, preferably 150-190 ℃. The peak area of the CO low-temperature desorption peak is generally 0.5-2a.u (arbitrary unit), and preferably 0.8-1.6a.u (arbitrary unit).

In the present invention, CO₂the-TPD and the CO-TPD are detected on line by using a Michmark chemical adsorption instrument and an OMistar mass spectrometer as a detector, wherein the CO is detected₂TPD recorded signals for the nuclear to cytoplasmic ratio of 44 by the mass spectrometer and CO-TPD recorded signals for the nuclear to cytoplasmic ratio of 28 by the mass spectrometer. In the present invention, the position of the desorption peak refers to the position at which the peak top of the desorption peak is located.

(1) pre-reducing a catalyst precursor in a first gas to obtain a pre-reduced catalyst;

(2) and carrying out reduction activation on the pre-reduction catalyst in a second gas to obtain a reduction activation catalyst.

According to the reduction activation method of the present invention, the catalyst precursor contains a carrier and a group VIII metal element supported on the carrier.

According to the reductive activation method of the present invention, the support is alumina, and specific examples thereof may include, but are not limited to: gamma-Al₂O₃、θ-Al₂O₃、δ-Al₂O₃And alpha-Al₂O₃One or more than two of them. The parameters of the specific surface area, the average pore diameter, the particle size distribution and the like of the alumina can be optimized according to the specific type of the alumina so as to further improve the catalytic performance of the catalyst. As an example, for γ -Al₂O₃The pore volume can be 0.6-1mL/g, preferably 0.65-0.9mL/g, more preferably 0.65-0.85 mL/g; the average pore diameter may be 8-35nm, preferably 12-30nm, more preferably 15-20 nm; the content of particles having a particle diameter in the range of 70 to 150 μm may be 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more; the specific surface area can be 100-300m²Per g, preferably 120-250m²(ii)/g, more preferably 150-²(ii) in terms of/g. As another example, for theta-Al₂O₃The pore volume can be 0.3-0.8mL/g, preferably 0.35-0.7mL/g, more preferably 0.4-0.6 mL/g; the average pore size may be 12-40nm, preferably 15-35nm, more preferably 18-25 nm; the content of particles having a particle diameter in the range of 70 to 150 μm may be 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more; the specific surface area can be 50-200m²A/g, preferably from 60 to 150m²A/g, more preferably from 65 to 100m²/g。

In a preferred embodiment, the support contains theta-Al₂O₃. According to this preferred embodiment, by incorporating theta-Al in the support₂O₃The finally obtained reduction activation catalyst can obtain higher catalytic activity and catalytic stability, and when the catalyst is used as a catalyst for Fischer-Tropsch synthesis reaction, the catalyst shows higher CO conversion rate and lower olefin selectivity, and has more excellent activity stability. From the viewpoint of further improving the catalytic activity and catalytic stability of the catalyst, based on the total amount of alumina in the catalyst, the theta-Al₂O₃The content of (b) may be 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, still more preferably 40% by weight or more, and still more preferably 50% by weight or more. In a particularly preferred embodiment of the invention, the support is theta alumina. According to this particularly preferred embodiment, with other types of alumina (e.g. gamma-Al)₂O₃) In contrast, with theta-Al₂O₃The catalyst prepared by the carrier has higher catalytic activity and catalytic stability, and particularly can obtain further improved CO conversion rate, low-carbon olefin selectivity and activity stability when being used as a catalyst for Fischer-Tropsch synthesis reaction. The theta-Al₂O₃The preparation method is described in detail above and will not be described herein again.

According to the reduction activation method of the present invention, in the catalyst precursor, the group VIII metal element is supported on the carrier in the form of an oxide, and the valence of the group VIII metal element in the oxide is the highest oxidation valence of the metal element (herein, the oxide in which the valence of the metal element in the metal oxide is the highest oxidation valence is also referred to as a complete oxide). A typical example of the catalyst precursor is a catalyst precursor which has undergone drying and calcination (i.e., heat treatment in an oxygen atmosphere) during the preparation process without being subjected to reduction treatment. The VIII group metal element in the form of complete oxide needs to be subjected to reduction activation so as to have catalytic performance meeting the use requirement.

In the catalyst precursor, the group VIII metal element may be a group VIII noble metal element, a group VIII non-noble metal element, or a combination of a group VIII noble metal element and a group VIII non-noble metal element. In a preferred embodiment, the group VIII metal element is a group VIII non-noble metal element, and specific examples thereof may include, but are not limited to, one or two or more of Fe, Co, and Ni. Preferably, the group VIII metal element is Fe. The content of the group VIII metal element in the catalyst precursor may be conventionally selected. Generally, the content of the group VIII metal element may be 3 to 30% by weight, preferably 5 to 25% by weight, more preferably 8 to 20% by weight, and further preferably 10 to 15% by weight, in terms of the element, based on the total amount of the catalyst precursor.

According to the reduction activation method of the present invention, the catalyst precursor may further contain a second metal element and/or a third metal element supported on the carrier, preferably a third metal element supported on the carrier, and optionally a second metal element. The types of the second metal element and the third metal element are the same as those described above, and are not described in detail here. The content of the second metal element may be 0.1 to 15% by weight, preferably 1 to 12% by weight, more preferably 2 to 11% by weight, and still more preferably 5 to 7% by weight in terms of element, based on the total amount of the catalyst precursor; the content of the third metal element may be 0.1 to 10% by weight, preferably 0.5 to 6% by weight, more preferably 0.8 to 3% by weight, and still more preferably 1.2 to 2% by weight.

From the viewpoint of further improving the catalytic activity and activity stability of the catalyst, the second metal element preferably contains a group IVB metal element (preferably Zr and/or Mg) and an alkali metal element (preferably K and/or Li), and the content of the group IVB metal element (preferably Zr and/or Mg) is preferably 0.5 to 8% by weight, more preferably 1 to 4% by weight, further preferably 2 to 3% by weight, and the content of the alkali metal element (preferably K and/or Li) is preferably 1 to 8% by weight, more preferably 2 to 6% by weight, further preferably 3 to 4% by weight, in terms of the elements, based on the total amount of the catalyst precursor.

From the viewpoint of further improving the catalytic activity and catalytic stability of the catalyst, the catalyst precursor preferably contains the second metal element and the third metal element supported on the carrier. When the catalyst contains the second metal element and the third metal element at the same time, the second metal element is more preferably one or more of Zr, Li, Mg and K, and the third metal element is more preferably Ce, so that the prepared catalyst can obtain more excellent catalytic activity and catalytic stability.

According to the reduction activation method of the present invention, the first gas is hydrogen gas or a mixed gas of hydrogen gas and an inert gas. The inert gas may be one or two or more selected from nitrogen and a group zero element gas, and the group zero element gas may be, for example, argon. Preferably, the inert gas is nitrogen and/or argon. When the first gas is a mixed gas of hydrogen and an inert gas, the molar ratio of the inert gas to the hydrogen may be 1 to 30: 1.

the contact temperature of the catalyst precursor with the first gas is such that the group VIII metal element in the catalyst precursor in the highest oxidation state is reduced (i.e., reduced in valence state).

Specifically, the catalyst precursor and the first gas may be contacted at a temperature of 200-. The volume space velocity of the first gas (in terms of hydrogen) can be 5000-^-1Preferably 10000-^-1. By gauge pressureThe pressure in the reactor in which the pre-reduction is carried out may be 0 to 2.5MPa, preferably 0.1 to 2 MPa. The duration of the pre-reduction may be selected depending on the temperature of the pre-reduction. Generally, the duration of the pre-reduction may be 1 to 20 hours, preferably 2 to 10 hours, more preferably 5 to 8 hours.

The second gas is a hydrocarbon that is gaseous at the reduction activation temperature, or a mixed gas of a hydrocarbon that is gaseous at the reduction activation temperature and an inert gas. The hydrocarbon which is gaseous at the reduction activation temperature may be one or two or more selected from an alkane which is gaseous at the reduction activation temperature and an alkene which is gaseous at the reduction activation temperature, and may be, for example, selected from C₁-C₄Alkane and C₂-C₄One or more kinds of olefins. Specific examples of the hydrocarbon that is gaseous at the reduction activation temperature may include, but are not limited to, one or two or more of methane, ethane, ethylene, propylene, propane, butane, and butene. From the viewpoint of further improving the catalytic activity and catalytic stability of the finally prepared reduction-activated catalyst, the hydrocarbon which is gaseous at the reduction-activation temperature is preferably one or more selected from alkanes which are gaseous at the reduction-activation temperature, and more preferably selected from C₁-C₄One or two or more kinds of alkanes, and ethane is more preferable. The inert gas may be one or two or more selected from nitrogen and a group zero element gas, and the group zero element gas may be, for example, argon. Preferably, the inert gas is nitrogen and/or argon. When the second gas is a mixed gas of a hydrocarbon that is gaseous at the reduction activation temperature and an inert gas, the molar ratio of the inert gas to the hydrocarbon that is gaseous at the reduction activation temperature may be 1 to 200: 1, preferably 1 to 100: 1, more preferably 10 to 50: 1, more preferably 15 to 30: 1.

according to the reduction activation method of the present invention, the reduction activation can be performed at a temperature of 150-. The volume space velocity of the second gas (in terms of hydrocarbon that is gaseous at the reduction activation temperature) may be 5000-^-1Preferably 10000-^-1. In the process of carrying out the reduction activation, the pressure in the reactor for carrying out the reduction activation may be 0 to 2.5MPa, preferably 0.1 to 2MPa, in terms of gauge pressure. The duration of the reductive activation may be selected according to the temperature of the reductive activation and the pressure of the second gas. Generally, the duration of the reductive activation may be 1 to 20 hours, preferably 2 to 15 hours, more preferably 4 to 12 hours.

According to a third aspect of the invention there is provided a catalyst prepared by the process of the second aspect of the invention. The catalyst has improved catalytic activity and activity stability, can obtain higher CO conversion rate and low-carbon olefin selectivity when being used as a catalyst for Fischer-Tropsch synthesis reaction, and simultaneously shows better activity stability.

Compared with the method that the pre-reduction catalyst is directly used as a reaction catalyst, such as a catalyst for Fischer-Tropsch synthesis reaction, according to the reduction activation method, the pre-reduction catalyst is further subjected to reduction activation in the second gas before the Fischer-Tropsch synthesis reaction is carried out, so that the catalytic activity and the activity stability of the catalyst (namely, the reduction activation catalyst) can be obviously improved. The catalyst obtained by reductive activation using the process of the present invention shows significantly higher catalytic performance than the catalyst obtained by pre-reduction by reduction with CO before the catalyst used for the reaction is brought into contact with the reactants, for example, the catalyst used for fischer-tropsch synthesis is brought into contact with synthesis gas.

The catalyst obtained by the reductive activation process of the present invention exhibits unique CO₂-TPD spectrum. In particular, CO of the catalyst according to the third aspect of the invention₂In the desorption spectrum of TPD, a desorption peak (i.e. CO) exists in a temperature interval of 300-600 ℃, preferably 320-500 ℃ and more preferably 350-480 ℃₂High temperature desorption peak). The CO is₂The peak area of the high-temperature desorption peak is generally 0.3 to 2.5a.u (arbitrary units), preferably 0.5 to 2a.u (arbitrary units). CO of the catalyst according to the third aspect of the invention₂In the TPD desorption spectrum, another desorption peak (i.e. CO) exists in the temperature interval of 100-200 ℃, preferably 150-190 ℃₂Low temperature desorption peak). The CO is₂The peak area of the low-temperature desorption peak is generally 0.5 to 3.5a.u (arbitrary units), preferably 1 to 3.2a.u (arbitrary units), and more preferably 2 to 3a.u (arbitrary units). In the CO-TPD desorption spectrum of the catalyst according to the third aspect of the invention, a desorption peak (i.e. a CO high-temperature desorption peak) exists in a temperature interval of 300-700 ℃, preferably 400-650 ℃, and more preferably 450-600 ℃. The peak area of the CO high-temperature desorption peak is generally 0.5-7a.u (arbitrary unit), preferably 1-6a.u (arbitrary unit), and more preferably 2-5.5a.u (arbitrary unit). In the CO-TPD desorption spectrum of the catalyst according to the third aspect of the invention, another desorption peak (namely a CO low-temperature desorption peak) exists in a temperature interval of 100-200 ℃ and preferably 150-190 ℃. The peak area of the CO low-temperature desorption peak is generally 0.5-2a.u (arbitrary unit), and preferably 0.8-1.6a.u (arbitrary unit).

(1) loading oxides of VIII group metal elements and/or precursors of the oxides of the VIII group metal elements on a carrier, and roasting the carrier loaded with the oxides and/or the precursors to obtain a catalyst precursor;

The method of reduction activation is described in detail above, and is not described in detail here, and only step (1) is described in detail here. In the present invention, the term "precursor of an oxide of a group VIII metal element" means a substance capable of forming a complete oxide of the group VIII metal element under the firing conditions.

According to the method of the fourth aspect of the present invention, the carrier is alumina, and specific examples thereof may include, but are not limited to: gamma-Al₂O₃、θ-Al₂O₃、δ-Al₂O₃And alpha-Al₂O₃One or more than two of them. The specific surface area, the average pore diameter, the particle size distribution and other parameters of the alumina can be optimized according to the specific type of the alumina so as to further improve the catalytic performance of the catalyst. As an example, for γ -Al₂O₃The pore volume can be 0.6-1mL/g, preferably 0.65-0.9mL/g, more preferably 0.65-0.85 mL/g; the average pore diameter may be 8-35nm, preferably 12-30nm, more preferably 15-20 nm; the content of particles having a particle diameter in the range of 70 to 150 μm may be 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more; the specific surface area can be 100-300m²Per g, preferably 120-250m²(ii)/g, more preferably 150-²(ii) in terms of/g. As another example, for theta-Al₂O₃The pore volume can be 0.3-0.8mL/g, preferably 0.35-0.7mL/g, more preferably 0.4-0.6 mL/g; the average pore size may be 12-40nm, preferably 15-35nm, more preferably 18-25 nm; the content of particles having a particle diameter in the range of 70 to 150 μm may be 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more; the specific surface area can be 50-200m²A/g, preferably from 60 to 150m²A/g, more preferably from 65 to 100m²/g。

In a preferred embodiment, the support contains theta-Al₂O₃. According to this preferred embodiment, by incorporating theta-Al in the support₂O₃The finally prepared catalyst can obtain higher catalytic activity and catalytic stability, and particularly shows higher catalytic activity and catalytic stability when being used as a catalyst for Fischer-Tropsch synthesis reaction. From the viewpoint of further improving the catalytic activity and catalytic stability of the finally prepared catalyst, the theta-Al is based on the total amount of the carrier₂O₃The content of (b) may be 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, still more preferably 40% by weight or more, and still more preferably 50% by weight or more. In a particularly preferred embodiment of the invention, the support is theta alumina. According to this particularly preferred embodiment, with other types of alumina (e.g. gamma-Al)₂O₃) In contrast, with theta-Al₂O₃The catalyst has higher catalytic activity and catalytic stability as a carrier, and can obtain obviously improved CO conversion rate and low carbon particularly when being used as a catalyst for Fischer-Tropsch synthesis reactionOlefin selectivity and activity stability.

According to this preferred embodiment, theta-Al₂O₃Can be obtained commercially or by reacting gamma-Al₂O₃And baking to obtain the final product. Preferably by reacting gamma-Al₂O₃Baking to obtain theta-Al₂O₃。

The method according to the fourth aspect of the present invention preferably further comprises a step of providing alumina, and in the step of providing alumina, γ -Al is added₂O₃And (4) roasting. The calcination may be carried out at a temperature of 700-1050 deg.C, preferably 780-1050 deg.C. The duration of the firing may be selected based on the temperature of firing sufficient to convert the gamma-Al₂O₃Conversion to theta-Al₂O₃The standard is. In general, the duration of the calcination may be from 0.5 to 5 hours, preferably from 1 to 4 hours. The firing is performed in an air atmosphere.

According to the method of the fourth aspect of the present invention, the alumina may be used as a support without loading an additional modifying element (i.e., pure alumina may be used as a support), or may be used as a support after modification.

In a preferred embodiment, at least a part of the support is alumina containing a modifying element, which is one or two or more selected from the group consisting of alkali metal elements, alkaline earth metal elements, and group IVB metal elements. Specific examples of the modifying element may include, but are not limited to, one or two or more of Li, Na, K, Mg, Ca, Zr, and Ti. More preferably, the modifying element is one or two or more of K, Mg and Zr. In general, the content of the alumina containing the modifying element may be 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, further preferably 70% by weight or more, and further preferably 90% by weight or more, based on the total amount of the carrier. Particularly preferably, the support is alumina containing a modifying element.

From the viewpoint of further improving the catalytic activity and activity stability of the finally prepared catalyst, the content of the modifying element may be 0.1 to 15% by weight, preferably 0.5 to 12% by weight, more preferably 1 to 10% by weight, and still more preferably 1.5 to 8% by weight, in terms of the element, based on the total amount of the carrier.

According to this preferred embodiment, the alumina containing the modifying element can be obtained by a conventional method. For example, the modifying element may be supported on the alumina during the preparation of the alumina, such as by coprecipitation, while the alumina is being prepared.

In a preferred example, alumina loaded with a compound containing a modifying element is calcined to obtain a modifying element-containing alumina. The calcination may be carried out under conventional conditions, and generally, the calcination may be carried out at a temperature of 300-900 deg.C, preferably 400-800 deg.C, and the duration of the calcination may be selected depending on the calcination temperature, and may be generally 0.5 to 8 hours, preferably 1 to 6 hours. The firing is performed in an air atmosphere.

The compound containing the modifying element may be supported on the alumina by means of impregnation. Specifically, alumina may be impregnated with an impregnation solution containing a compound containing a modifying element, and the alumina having the impregnation solution adsorbed thereon may be sequentially dried and calcined to obtain alumina containing a modifying element.

In this example, the modifying element-containing compound may be a modifying element-containing water-soluble salt and/or a water-soluble base, and specific examples thereof may include, but are not limited to: one or more of nitrate, oxalate, acetate, chloride, hydroxide, carbonate, bicarbonate and phosphate.

In this example, the impregnation may be by conventional impregnation methods, such as saturation impregnation or excess impregnation. The impregnation may be carried out at ambient temperature.

In this example, the drying may be carried out under conditions sufficient to remove volatile species (primarily solvent in the impregnating solution) from the alumina on which the impregnating solution is adsorbed. Specifically, the drying may be performed at a temperature of 50 to 300 ℃, preferably 80 to 300 ℃, more preferably 120 ℃ to 300 ℃, and the drying may be performed under normal pressure (i.e., 1 atm, the same applies) or under reduced pressure. The duration of the drying may be selected depending on the temperature of the drying and the pressure of the drying, and may be generally 1 to 12 hours, preferably 2 to 6 hours. The drying may be performed in an air atmosphere.

According to the method of the fourth aspect of the present invention, the group VIII metal element may be a group VIII noble metal element, a group VIII non-noble metal element, or a combination of a group VIII noble metal element and a group VIII non-noble metal element. In a preferred embodiment, the group VIII metal element is a group VIII non-noble metal element, and specific examples thereof may include, but are not limited to, one or two or more of Fe, Co, and Ni. More preferably, the group VIII metal element is Fe.

The amount of the group VIII metal element supported on the carrier is generally such that the content of the group VIII metal element may be from 3 to 30% by weight, preferably from 5 to 25% by weight, more preferably from 8 to 20% by weight, further preferably from 10 to 15% by weight, in terms of the element, based on the total amount of the catalyst precursor.

The oxide of the group VIII metal element and/or the precursor of the oxide of the group VIII metal element may be supported on the carrier by a conventional method. For example, the co-precipitation method may be used to support the oxide of the group VIII metal element on the carrier during the preparation of the alumina (or the alumina containing the modifying element).

In a more preferred embodiment, a carrier is impregnated with an impregnation solution containing an oxide of a group VIII metal element and/or a precursor of an oxide of a group VIII metal element, and the carrier having the impregnation solution adsorbed thereon is dried to obtain a carrier having the oxide and/or the precursor supported thereon.

The type of the precursor of the group VIII metal element oxide may be selected depending on the solvent of the immersion liquid so that the precursor of the group VIII metal element oxide is soluble in the solvent, and may be one or more selected from the group consisting of an oxalate of the group VIII metal element, a nitrate of the group VIII metal element, a sulfate of the group VIII metal element, an acetate of the group VIII metal element, a chloride of the group VIII metal element, a carbonate of the group VIII metal element, a basic carbonate of the group VIII metal element, a hydroxide of the group VIII metal element, a phosphate of the group VIII metal element, a molybdate of the group VIII metal element, a tungstate of the group VIII metal element, and a water-soluble complex of the group VIII metal element. Specific examples of the precursor of the oxide of the group VIII metal element may include, but are not limited to: one or more of ferric nitrate, ferric sulfate, ferric acetate, nickel nitrate, nickel sulfate, nickel acetate, basic nickel carbonate, cobalt nitrate, cobalt sulfate, cobalt acetate, basic cobalt carbonate, cobalt chloride, nickel chloride and ferric ammonium citrate.

The alumina adsorbed with the impregnation liquid may be dried under conventional conditions to remove the solvent from the impregnation liquid, thereby obtaining the support loaded with the oxide and/or precursor. Generally, the drying may be carried out at a temperature of 50 to 300 ℃, preferably 80 to 280 ℃, more preferably 120 to 280 ℃, and the drying may be carried out under normal pressure or under reduced pressure. The duration of the drying may be selected depending on the temperature of the drying and the pressure of the drying, and may be generally 1 to 12 hours, preferably 2 to 6 hours. The drying may be performed in an air atmosphere.

The support carrying the oxide and/or the precursor may be calcined under conventional conditions to obtain a catalyst precursor. The group VIII metal element in the catalyst precursor is substantially in its highest oxidation state. Generally, the calcination may be performed at a temperature of 300-900 deg.C, preferably 350-800 deg.C, more preferably 400-600 deg.C, and the duration of the calcination may be selected according to the calcination temperature, and may be generally 1-10 hours, preferably 2-6 hours. The firing is performed in an air atmosphere.

According to the method of the fourth aspect of the present invention, from the viewpoint of further improving the catalytic activity and activity stability of the finally prepared catalyst, it is preferable that the method further comprises loading an auxiliary element, which is one or two or more selected from alkali metal elements and rare earth metal elements (one or two or more of lanthanum, cerium, praseodymium and neodymium), on the carrier. Specific examples of the auxiliary element may include, but are not limited to: one or more than two of Li, Na, K and Ce. Preferably, the auxiliary element is one or more than two of Li, K and Ce. More preferably, the promoter element is K and/or Ce. Further preferably, the additive element is Ce. It should be noted that, although the kind of the auxiliary element and the modifying element used for modifying the alumina may be the same, when the auxiliary element and the modifying element are the same, even if the carrier is a carrier containing the modifying element, it is still necessary to additionally load the auxiliary element on the carrier containing the modifying element, and vice versa.

The supporting amount of the promoter element on the carrier is such that the content of the promoter element may be 0.1 to 10% by weight, preferably 1 to 8% by weight, more preferably 2 to 6% by weight, in terms of the element, based on the total amount of the catalyst precursor.

The auxiliary elements may be supported on the support by conventional methods, such as impregnation. The auxiliary element and the group VIII metal element may be simultaneously supported on the carrier, or the auxiliary element and the group VIII metal element may not be simultaneously supported on the carrier. Preferably, the promoter element and the group VIII metal element are simultaneously supported on the carrier, and in this case, the carrier may be impregnated with an impregnation solution containing an oxide of the group VIII metal element and/or a precursor of the oxide of the group VIII metal element and a compound containing the promoter element, and the carrier on which the impregnation solution is adsorbed may be successively dried and calcined to obtain the catalyst precursor.

The compound containing an auxiliary element may be a conventional compound capable of dissolving and dispersing in the impregnation solution, and may be one or two or more of nitrate, chloride, sulfate, acetate, oxalate, carbonate, bicarbonate, and hydroxide, for example. Specific examples of the compound containing an auxiliary element may include, but are not limited to: one or more of sodium nitrate, sodium chloride, sodium sulfate, sodium acetate, sodium oxalate, sodium carbonate, sodium hydrogen carbonate, lithium nitrate, lithium chloride, lithium carbonate, potassium nitrate, potassium chloride, potassium sulfate, potassium acetate, potassium oxalate, potassium carbonate, potassium hydrogen carbonate, cerium nitrate, and cerium chloride.

When the group VIII metal element and the optional auxiliary element are supported on the carrier by impregnation, the number of times of impregnation may be one or two or more. From the viewpoint of further improving the catalytic activity and activity stability of the finally prepared catalyst, it is preferable to perform impregnation twice or more. In the case where the impregnation is performed twice or more, it is preferable that the carrier having the impregnation liquid adsorbed thereon is dried and calcined once after each impregnation.

The catalyst according to the fifth aspect of the invention exhibits unique CO₂-TPD spectrum. Specifically, CO of the catalyst according to the fifth aspect of the present invention₂In the desorption spectrum of TPD, a desorption peak (i.e. CO) exists in a temperature interval of 300-600 ℃, preferably 320-500 ℃ and more preferably 350-480 ℃₂High temperature desorption peak). The CO is₂The peak area of the high-temperature desorption peak is generally 0.3 to 2.5a.u (arbitrary units), preferably 0.5 to 2a.u (arbitrary units). CO of the catalyst according to the fifth aspect of the present invention₂In the TPD desorption spectrum, another desorption peak (i.e. CO) exists in the temperature interval of 100-200 ℃, preferably 150-190 ℃₂Low temperature desorption peak). The CO is₂The peak area of the low-temperature desorption peak is generally 0.5 to 3.5a.u (arbitrary units), preferably 1 to 3.2a.u (arbitrary units), and more preferably 2 to 3a.u (arbitrary units). In the CO-TPD desorption spectrum of the catalyst according to the fifth aspect of the invention, a desorption peak (i.e. a CO high-temperature desorption peak) exists in a temperature interval of 300-700 ℃, preferably 400-650 ℃, and more preferably 450-600 ℃. The peak area of the CO high-temperature desorption peak is generally 0.5-7a.u (arbitrary unit), preferably 1-6a.u (arbitrary unit), and more preferably 2-5.5a.u (arbitrary unit). In the CO-TPD desorption spectrum of the catalyst according to the fifth aspect of the invention, another desorption peak (i.e. low CO) exists in the temperature interval of 100-200 ℃, preferably 150-190 ℃Warm desorption peak). The peak area of the CO low-temperature desorption peak is generally 0.5-2a.u (arbitrary unit), and preferably 0.8-1.6a.u (arbitrary unit).

According to a sixth aspect of the present invention there is provided the use of a catalyst according to the first aspect of the present invention, a catalyst according to the third aspect of the present invention and a catalyst according to the fifth aspect of the present invention as a catalyst for a fischer-tropsch synthesis reaction.

The catalyst according to the invention shows improved catalytic activity and prolonged activity stability in fischer-tropsch synthesis reactions, and in particular can significantly improve the selectivity to lower olefins.

According to a seventh aspect of the present invention, there is provided a process for the production of lower olefins, the process comprising contacting hydrogen and carbon monoxide with a catalyst under fischer-tropsch synthesis reaction conditions, wherein the catalyst is as described in the first, third or fifth aspect of the present invention.

According to an eighth aspect of the present invention, there is provided a method for producing lower olefins, comprising:

The methods according to the seventh and eighth aspects of the present invention, the catalyst and the method for preparing the same, which have been described in detail above, are not described in detail herein, and the fischer-tropsch synthesis reaction involved in the methods according to the seventh and eighth aspects of the present invention will be described in detail below.

According to the method for producing lower olefins of the present invention, the ratio between hydrogen and carbon monoxide may be a conventional ratio for producing lower olefins. Specifically, the molar ratio of hydrogen to carbon monoxide may be from 0.4 to 2.5: 1, preferably 0.6 to 2.5: 1, more preferably 0.8 to 2.2: 1, more preferably 1 to 1.5: 1.

the hydrogen and carbon monoxide as reaction raw materials may be subjected to the fischer-tropsch synthesis reaction by feeding pure hydrogen and pure carbon monoxide into the reactor, respectively, to contact the catalyst. Preferably, the hydrogen and carbon monoxide used as reaction raw materials are derived from synthesis gas, i.e. the synthesis gas is sent into a reactor to contact with a catalyst to carry out Fischer-Tropsch synthesis reaction. The source of the synthesis gas is not particularly limited, and may be synthesis gas mainly composed of hydrogen and carbon monoxide generated by various processes, for example: syngas resulting from the conversion of carbonaceous materials, specific examples of which may include, but are not limited to: one or more of coal, petroleum, natural gas, coke oven gas, refinery gas and biomass.

The fischer-tropsch synthesis reaction can be carried out by contacting hydrogen and carbon monoxide with a catalyst under conventional conditions. Generally, the hydrogen and carbon monoxide may be contacted with the catalyst at a temperature of 320-550 deg.C, preferably 330-400 deg.C, more preferably 340-360 deg.C. The pressure in the reactor in which the Fischer-Tropsch synthesis reaction is carried out may be in the range 0.5 to 8MPa, preferably 1 to 5MPa, the pressure being expressed as gauge pressure. The catalyst adopted by the invention has good catalytic activity, and even if hydrogen and carbon monoxide are contacted with the catalyst at a higher space velocity, a good catalytic reaction effect can be obtained. In particular, the volumetric space velocity of the gas feed may be 20000-50000 hours^-1Preferably 25000-^-1. Wherein, the gas feed means hydrogen and carbon monoxide which are fed to the reactor as reaction raw materials.

According to the process for producing lower olefins of the present invention, hydrogen and carbon monoxide may be contacted with a catalyst in a conventional reactor, for example: the contacting may be carried out in a fixed bed reactor, a fluidized bed reactor, or a combination of a fixed bed reactor and a fluidized bed reactor. Preferably, the hydrogen and carbon monoxide are contacted with the catalyst in a fluidized bed reactor.

According to the preparation method of the low-carbon olefin, the pre-reduction and the reduction activation can be carried out outside a Fischer-Tropsch synthesis reactor or in the Fischer-Tropsch synthesis reactor. Preferably, the pre-reduction and the reductive activation are carried out in a fischer-tropsch synthesis reactor.

The present invention will be described in detail with reference to examples, but the scope of the present invention is not limited thereto.

In the following examples and comparative examples, the specific surface area, pore volume and average pore diameter were measured by nitrogen adsorption method, specifically, N was used₂Measuring an adsorption isotherm at a constant temperature of 77K, calculating a specific surface area and a pore volume according to a BET formula, and calculating an average pore size distribution according to a BJH method; the particle size distribution was determined using a laser particle sizer.

In the following examples and comparative examples, the contents of each metal element in the catalyst and the catalyst precursor were measured by the X-ray fluorescence spectrum analysis method specified in RIPP132-92 (compiled in methods for petrochemical engineering analysis (RIPP test method), Yangshui et al, science publishers, 1 st edition at 1990/9, p 371) -379). When the catalyst was tested, a sample of the catalyst was stored under an argon atmosphere.

In the following examples and comparative examples, CO₂the-TPD and the CO-TPD are detected on line by using a Michmark chemical adsorption instrument and an OMistar mass spectrometer as a detector, wherein the CO is detected₂TPD recorded signals for the nuclear to cytoplasmic ratio of 44 by the mass spectrometer and CO-TPD recorded signals for the nuclear to cytoplasmic ratio of 28 by the mass spectrometer.

In the following examples and comparative examples, the X-ray photoelectron spectroscopy was carried out on an ESCALB 250 type X-ray photoelectron spectrometer equipped with Thermo Avantage V5.926 software, manufactured by Thermo Scientific, with an excitation source of monochromated Al K.alpha.X rays, an energy of 1486.6eV, a power of 150W, a transmission energy for narrow scanning of 30eV, and a base vacuum of 6.5X 10 during analytical testing^-10mbar, electron binding energy was corrected by the C1s peak (284.6eV) of elemental carbon, data were processed on Thermo Avantage software, and quantitative analysis was performed in the analysis module using the sensitivity factor method.

In the following examples and comparative examples, the CO conversion (X)_CO)、CH₄Selectivity is

And C₂-C₄The selectivity of the hydrocarbon (among them,

is represented by C₂-C₄The selectivity of the olefin is high,

is represented by C₂-C₄Alkane selectivity) was calculated by the following formula:

wherein, V₁、V₂Respectively representing the volume of feed gas entering the reaction system and the volume of tail gas flowing out of the reaction system in a certain time period under a standard condition;

C_1,CO、C_2,COrespectively representing the molar contents of CO in raw gas entering a reaction system and tail gas flowing out of the reaction system;

n_conis the mole number of CO participating in the reaction;

to generate CH₄The number of moles of (a);

to generate C₂-C₄Moles of hydrocarbons.

In the following examples and comparative examples, the pressures are gauge pressures.

Examples 1-16 are intended to illustrate the invention.

Example 1

(1) Preparation of the support

Taking gamma-Al₂O₃(Sasol product, its specific surface area, pore volume, average pore diameter and particle size distribution are shown in Table 1) 200g, calcining in air atmosphere at 980 ℃ for 2 hours, subjecting the calcined product to X-ray diffraction analysis (shown in FIG. 1), and determining that theta-Al is obtained₂O₃The specific surface area, pore volume, average pore diameter and particle size distribution are shown in Table 1.

Dissolving zirconium nitrate pentahydrate in 43g of deionized water to prepare a modified zirconium solution, and adding 100.0g of prepared theta-Al into the modified zirconium solution₂O₃The resulting mixture was saturated and immersed at 25 ℃ for 2 hours. Then, the impregnated mixture was placed in an oven and dried at 120 ℃ under atmospheric pressure (1 atm, the same applies hereinafter) for 5 hours in an air atmosphere. And roasting the dried substance in an air atmosphere at 400 ℃ for 3 hours to obtain the carrier. The prepared carrier was subjected to X-ray fluorescence spectroscopic analysis to determine that the content of Zr was 3% by weight in terms of element based on the total amount of the carrier.

(2) Preparation of the catalyst precursor

Adding ammonium ferric citrate, potassium carbonate and cerous nitrate hexahydrate into 12mL of deionized water, heating in a water bath at 50 ℃, stirring and mixing uniformly to obtain an impregnation liquid.

A50 vol% of the impregnation solution was taken, 15g of the carrier was added to the impregnation solution, and the mixture was saturated and impregnated at ambient temperature (25 ℃ C.) for 1 hour. Then, the impregnated mixture was placed in an oven and dried at 120 ℃ under atmospheric pressure for 5 hours in an air atmosphere. And roasting the dried substance in an air atmosphere at 400 ℃ for 3 hours to obtain the catalyst after primary leaching.

The catalyst after the first impregnation was added to the remaining impregnation solution, and saturated impregnation was carried out at ambient temperature (25 ℃ C.) for 1 hour. Then, the impregnated mixture was placed in an oven and dried at 120 ℃ under atmospheric pressure for 5 hours in an air atmosphere. The dried substance was calcined at 400 ℃ for 3 hours in an air atmosphere to obtain a catalyst precursor.

(3) Reductive activation of catalyst precursor

The catalyst precursor is charged into a fluidized bed reactor, and H is introduced into the reactor₂The pressure of the reactor is adjusted to be 0.1MPa, and the volume space velocity of the hydrogen is 20000 hours^-1The temperature of the reactor was raised from 25 ℃ to 400 ℃ and maintained at this temperature for 8 hours. The reactor was then cooled to 200 ℃, hydrogen switched to ethane, and the volumetric space velocity of ethane was 15000 hours^-1After 12 hours of maintenance, a catalyst according to the invention is obtained, the composition of which is shown in tables 2 and 4, CO₂The results of the-TPD and CO-TPD tests are listed in Table 3.

(4) Preparation of low-carbon olefin

After the reduction activation is finished, introducing synthesis gas into the reactor, raising the temperature of the reactor to 340 ℃, and carrying out Fischer-Tropsch synthesis reaction, wherein the volume space velocity of the synthesis gas is 30000 hours^-1At a pressure of 1.5MPa (in terms of gauge pressure), the synthesis gas is a mixture of hydrogen and carbon monoxide, the composition of which is H₂: 50 of CO: 50 (molar ratio). During the reaction, the composition of the reaction mixture gas outputted from the reactor was analyzed by an on-line gas chromatograph, and the results measured at 50 hours and 200 hours of the reaction were shown in tables 5 and 6, respectively.

Example 2

A catalyst was prepared and a low-carbon olefin was produced by the same method as in example 1, except that in the step (1), γ -Al₂O₃The carrier was prepared without calcination and was directly impregnated with a modified zirconium solution, wherein the Zr content was 3 wt% in terms of the element based on the total amount of the carrier.

Example 3

A catalyst was prepared and a low-carbon olefin was produced by the same method as in example 1, except that in the step (1), theta-Al₂O₃Is not contacted with the modified zirconium solution but is directly used in step (2) to prepare the catalyst precursor.

Example 4

A catalyst was prepared and a low carbon olefin was prepared in the same manner as in example 1, except that potassium carbonate and cerous nitrate hexahydrate were not used in preparing the impregnation liquid in step (2).

Example 5

A catalyst was prepared and a lower olefin was prepared in the same manner as in example 1, except that in the step (2), impregnation was carried out once and the conditions of impregnation, drying and calcination were the same as in example 1, that is, the carrier was impregnated with 6mL of the impregnation solution, and the impregnated mixture was sequentially dried and calcined, thereby obtaining a catalyst precursor.

Example 6

A catalyst was prepared and lower olefins were prepared in the same manner as in example 1, except that in step (3), ethane was replaced with an equal volume of ethylene.

Example 7

A catalyst was prepared and a low-carbon olefin was produced in the same manner as in example 1, except that in the step (1), gamma-Al was brought into contact with the modified zirconium solution₂O₃And theta-Al₂O₃According to the weight ratio of 1: 1 mixing the resulting mixture.

Example 8

A catalyst was prepared and a low carbon olefin was prepared in the same manner as in example 1, except that in the step (1), the amount of zirconium nitrate pentahydrate was changed to prepare a carrier in which the Zr content was 1.5% by weight in terms of element based on the total amount of the carrier.

Example 9

A catalyst was prepared and a low carbon olefin was prepared in the same manner as in example 1, except that in the step (1), the amount of zirconium nitrate pentahydrate was changed to prepare a carrier in which the Zr content was 8% by weight in terms of element based on the total amount of the carrier.

Comparative example 1

The catalyst was prepared and the lower olefins were prepared in the same manner as in example 1, except that in step (3), after the introduction of hydrogen, the introduction of ethane was not continued, but step (4) was directly performed, i.e., only hydrogen was used for the reductive activation, instead of ethane.

Comparative example 2

A catalyst was prepared and lower olefins were prepared in the same manner as in example 1, except that in step (3), ethane was replaced with an equal volume of CO.

Comparative example 3

A catalyst was prepared and lower olefins were produced in the same manner as in example 1, except that in step (3), the operation of passing hydrogen was not performed, but ethane was directly passed through the reactor, that is, only ethane was used for reductive activation, and hydrogen was not used.

Comparative example 4

The catalyst was prepared and the lower olefins were prepared in the same manner as in example 2, except that in step (3), after the introduction of hydrogen, the introduction of ethane was not continued, but step (4) was directly performed, i.e., only hydrogen was used for the reductive activation, and no ethane was used.

Comparative example 5

A catalyst was prepared and a lower olefin was produced in the same manner as in example 2, except that in the step (3), ethane was replaced with an equal volume of CO.

Comparative example 6

The catalyst was prepared and the lower olefins were prepared in the same manner as in example 3, except that in step (3), after the introduction of hydrogen, the introduction of ethane was not continued, but step (4) was directly performed, i.e., only hydrogen was used for the reductive activation, and no ethane was used.

Comparative example 7

A catalyst was prepared and a lower olefin was produced in the same manner as in example 3, except that in the step (3), ethane was replaced with an equal volume of CO.

Example 10

(1) Preparation of the support

Taking gamma-Al₂O₃(Sasol product, its specific surface area, pore volume, average pore diameter and particle size distribution are shown in Table 1) 200g, calcining at 1050 deg.C for 1 hr in air atmosphere, subjecting the calcined product to X-ray diffraction analysis to determine that the product is theta-Al₂O₃The specific surface area, pore volume, average pore diameter and particle size distribution are shown in Table 1.

Dissolving magnesium nitrate in 41g deionized water to obtain modified magnesium solution, and adding 100.0g of prepared theta-Al into the modified magnesium solution₂O₃At 25 deg.CAnd dipping for 2 hours. Then, the impregnated mixture was placed in an oven and dried at 200 ℃ under atmospheric pressure for 3 hours in an air atmosphere. And roasting the dried substance at 800 ℃ in an air atmosphere for 1 hour to obtain the carrier. The prepared carrier was subjected to X-ray fluorescence spectroscopic analysis to determine that the content of Mg was 6% by weight in terms of element based on the total amount of the carrier.

(2) Preparation of the catalyst precursor

Adding ferric nitrate, lithium carbonate and cerous nitrate hexahydrate into 12mL of deionized water, heating in a water bath at 50 ℃, stirring and mixing uniformly to obtain an impregnation liquid.

A50 vol% of the impregnation solution was taken, 15g of the carrier was added to the impregnation solution, and the mixture was saturated and impregnated at ambient temperature (25 ℃ C.) for 1 hour. Then, the impregnated mixture was placed in an oven and dried at 200 ℃ under atmospheric pressure for 3 hours in an air atmosphere. And roasting the dried substance in an air atmosphere at 600 ℃ for 2 hours to obtain the catalyst after primary leaching.

The catalyst after the first impregnation was added to the remaining impregnation solution, and saturated impregnation was carried out at ambient temperature (25 ℃ C.) for 1 hour. Then, the impregnated mixture was placed in an oven and dried at 200 ℃ under atmospheric pressure for 3 hours in an air atmosphere. The dried substance was calcined at 600 ℃ for 2 hours in an air atmosphere to obtain a catalyst precursor.

(3) Reductive activation of catalyst precursor

The catalyst precursor is charged into a fluidized bed reactor, and H is introduced into the reactor₂And argon (wherein the molar ratio of argon to hydrogen is 10: 1), adjusting the pressure of the reactor to be 0.1MPa, and the volume space velocity of hydrogen to be 15000 hours^-1The temperature of the reactor was raised from 25 ℃ to 350 ℃ and maintained at this temperature for 8 hours. The reactor was then cooled to 250 ℃, hydrogen switched to ethane, and the volumetric space velocity of ethane was 10000 hours^-1After 4 hours of maintenance, a catalyst according to the invention is obtained, the composition of which is shown in tables 2 and 4, CO₂The results of the-TPD and CO-TPD tests are listed in Table 3.

(4) Preparation of low-carbon olefin

Reduction activation junctionAnd (3) after the reaction, introducing the synthesis gas into the reactor, heating the temperature of the reactor to 340 ℃, and carrying out the Fischer-Tropsch synthesis reaction, wherein the volume space velocity of the synthesis gas is 30000 hours^-1At a pressure of 5MPa (gauge pressure), the synthesis gas is a mixture of hydrogen and carbon monoxide and has a composition of H₂: 50 of CO: 50 (molar ratio). During the reaction, the composition of the reaction mixture gas outputted from the reactor was analyzed by an on-line gas chromatograph, and the results measured at 50 hours and 200 hours of the reaction were shown in tables 5 and 6, respectively.

Example 11

A catalyst was prepared and a low-carbon olefin was produced by the same method as in example 10, except that in the step (1), γ -Al₂O₃The carrier was prepared without calcination by direct impregnation with a modified magnesium solution, in which the Mg content was 6 wt% in terms of the element, based on the total amount of the carrier.

Example 12

(1) Preparation of the support

Taking gamma-Al₂O₃(Sasol product, its specific surface area, pore volume, average pore diameter and particle size distribution are shown in Table 1) 200g, roasting at 780 deg.C for 4 hr in air atmosphere, subjecting the roasted product to X-ray diffraction analysis to determine that the product is theta-Al₂O₃The specific surface area, pore volume, average pore diameter and particle size distribution are shown in Table 1.

Potassium nitrate was dissolved in 53g of deionized water to prepare a modified potassium solution, and 100.0g of the prepared theta-Al was added to the modified potassium solution₂O₃The resulting mixture was saturated and immersed at 25 ℃ for 2 hours. Then, the impregnated mixture was placed in an oven and dried at 300 ℃ under atmospheric pressure (1 atm, the same applies hereinafter) for 2 hours in an air atmosphere. The dried material was calcined at 500 ℃ for 6 hours in an air atmosphere to obtain a carrier. The prepared carrier was subjected to X-ray fluorescence spectroscopic analysis to determine that the content of potassium was 2.5% by weight in terms of element based on the total amount of the carrier.

(2) Preparation of the catalyst precursor

Adding ferric nitrate, potassium carbonate and cerous nitrate hexahydrate into 15mL of deionized water, heating in a water bath at 50 ℃, stirring and mixing uniformly to obtain an impregnation liquid.

A50 vol% of the impregnation solution was taken, 15g of the carrier was added to the impregnation solution, and the mixture was saturated and impregnated at ambient temperature (25 ℃ C.) for 1 hour. Then, the impregnated mixture was placed in an oven and dried at 280 ℃ for 2 hours under atmospheric pressure in an air atmosphere. And roasting the dried substance for 6 hours at 500 ℃ in an air atmosphere to obtain the catalyst after primary leaching.

The catalyst after the first impregnation was added to the remaining impregnation solution, and saturated impregnation was carried out at ambient temperature (25 ℃ C.) for 1 hour. Then, the impregnated mixture was placed in an oven and dried at 280 ℃ for 2 hours under atmospheric pressure in an air atmosphere. The dried substance was calcined at 500 ℃ for 6 hours in an air atmosphere to obtain a catalyst precursor.

(3) Reductive activation of catalyst precursor

The catalyst precursor is charged into a fluidized bed reactor, and H is introduced into the reactor₂The pressure of the reactor is adjusted to be 0.15MPa, and the volume space velocity of hydrogen is 10000 hours^-1The temperature of the reactor was raised from 25 ℃ to 500 ℃ and kept constant at this temperature for 6 hours. Then, the reactor was cooled to 350 ℃, hydrogen was switched to a mixed gas of ethane and argon (in which the molar ratio of ethane to argon was 1: 20), and the volume space velocity of ethane was 20000 hours^-1After 4 hours of maintenance, a catalyst according to the invention is obtained, the composition of which is shown in tables 2 and 4, CO₂The results of the-TPD and CO-TPD tests are listed in Table 3.

(4) Preparation of low-carbon olefin

After the reduction activation is finished, introducing synthesis gas into the reactor, raising the temperature of the reactor to 340 ℃, and carrying out Fischer-Tropsch synthesis reaction, wherein the volume space velocity of the synthesis gas is 30000 hours^-1The pressure is 1MPa (measured by gauge pressure), and the synthesis gas is a mixed gas of hydrogen and carbon monoxide, and the composition of the mixed gas is H₂: CO 60: 40 (molar ratio). During the reaction, the composition of the reaction mixture gas outputted from the reactor was analyzed by an on-line gas chromatograph, and the results measured at 50 hours and 200 hours of the reaction were shown in tables 5 and 6, respectively.

Example 13

A catalyst was prepared and lower olefins were produced in the same manner as in example 12, except that in step (2), the iron nitrate was replaced with cobalt nitrate.

Example 14

A catalyst was prepared and lower olefins were produced in the same manner as in example 12, except that in step (2), the iron nitrate was replaced with nickel nitrate.

Comparative example 8

A catalyst was prepared and a low carbon olefin was prepared in the same manner as in example 12 except that in step (3), ethane was replaced with a mixed gas of CO and argon in an equal volume (wherein the molar ratio of CO to argon was 1: 20), that is, after the prereduction of hydrogen was completed, the reactor was cooled to 200 ℃ and hydrogen was switched to a mixed gas of CO and argon, and the volume space velocity of CO was 10000 hours^-1And maintained for 4 hours.

Example 15

A catalyst was prepared and a low-carbon olefin was prepared in the same manner as in example 12, except that in the step (2), potassium carbonate was not used in preparing the impregnation solution, and the amount of cerium nitrate hexahydrate was increased accordingly.

Example 16

A catalyst was prepared and a low-carbon olefin was prepared in the same manner as in example 12, except that in the step (2), cerium nitrate as a running water was not used in preparing the impregnation liquid, and the amount of potassium carbonate was increased accordingly.

TABLE 1

TABLE 2 (based on the total amount of catalyst)

TABLE 3

TABLE 4

¹: no Fe detected₅C₂ ²: FeO and Fe were not detected₅C₂

TABLE 5

*: O/P is C₂-C₄Olefin selectivity (S) of_C2 ^＝ _-C4 ^＝) And C₂-C₄Alkane selectivity (S)_C2 ^o _-C4 ^o) The ratio of (a) to (b).

TABLE 6

*: based on the corresponding data for 50 hours

The results of examples 1 to 16 confirm that the catalyst according to the present invention can achieve a higher co conversion rate even when the reaction is carried out in a fluidized bed reactor at a high space velocity when used in a fischer-tropsch synthesis reaction for preparing lower olefins from synthesis gas, and can significantly improve the selectivity of lower olefins and stabilize the activity of the catalyst.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A catalyst for Fischer-Tropsch synthesis reaction of synthesis gas to prepare low-carbon olefin comprises a carrier and a VIII group metal element loaded on the carrier, wherein the carrier is alumina, the alumina contains theta-alumina, the theta-alumina content is more than 50 wt% based on the total amount of the alumina in the catalyst, the valence state of at least part of the VIII group metal element is lower than the highest oxidation valence state of the metal element, the VIII group metal element content is 3-30 wt% based on the total amount of the catalyst, the catalyst also comprises a second metal element and/or a third metal element loaded on the carrier, the second metal element is one or more selected from alkali metal elements, alkaline earth metal elements and IVB group metal elements, and the third metal element is one or more selected from rare earth metal elements, on the basis of the total amount of the catalyst, the content of the second metal element is 0-15 wt%, the content of the third metal element is 0-10 wt%, and the content of the second metal element and the content of the third metal element are not 0 at the same time;

CO of the catalyst₂In the TPD desorption diagram, CO is present in the temperature range of 369-₂High temperature desorption peak.

2. The catalyst according to claim 1, wherein the group VIII metal element is one or two or more of Fe, Co and Ni.

3. The catalyst according to claim 1, wherein the group VIII metal element is Fe, and the catalyst has an X-ray photoelectron spectrum in which a peak corresponding to FeO is present and a spectrum corresponding to Fe is present₅C₂Spectrum peak of (2).

4. The catalyst according to claim 3, wherein the content of Fe determined by the peak corresponding to FeO is related to the content of Fe determined by the peak corresponding to Fe on an elemental basis₅C₂The ratio of the determined Fe content of the peaks of (a) is 8-25: 1.

5. the catalyst according to claim 4, wherein the content of Fe determined by the peak corresponding to FeO is related to the content of Fe determined by the peak corresponding to Fe on an elemental basis₅C₂The ratio of the determined Fe content of the peaks of (a) is 10-12: 1.

6. the catalyst according to any one of claims 3 to 5, wherein the peaks corresponding to FeO and the peaks corresponding to Fe are calculated on an elemental basis based on the total amount of Fe determined by X-ray photoelectron spectroscopy₅C₂The content of Fe determined by the peak of the spectrum is 30-99%.

7. The catalyst according to claim 6, wherein the total amount of Fe determined by X-ray photoelectron spectroscopy is represented by a peak corresponding to FeO and a peak corresponding to Fe on an elemental basis₅C₂The content of Fe determined by the peak of the spectrum is 50-99%.

8. The catalyst according to claim 7, wherein the total amount of Fe determined by X-ray photoelectron spectroscopy is represented by a peak corresponding to FeO and a peak corresponding to Fe on an elemental basis₅C₂The content of Fe determined by the peak of (1) is 75-99%.

9. The catalyst according to any one of claims 1 to 5, wherein the content of the group VIII metal element having a valence lower than its maximum oxidation valence is 30% by weight or more in terms of the element based on the total amount of the group VIII metal element in the catalyst.

10. The catalyst according to claim 9, wherein the content of the group VIII metal element having a valence lower than its maximum oxidation valence is 50% by weight or more in terms of the element based on the total amount of the group VIII metal element in the catalyst.

11. The catalyst according to claim 10, wherein the content of the group VIII metal element having a valence lower than its maximum oxidation valence is 55% by weight or more in terms of the element based on the total amount of the group VIII metal element in the catalyst.

12. The catalyst according to claim 11, wherein the content of the group VIII metal element having a valence lower than its maximum oxidation valence is 60% by weight or more in terms of the element based on the total amount of the group VIII metal element in the catalyst.

13. The catalyst according to any one of claims 1 to 5, wherein the group VIII metal element is contained in an amount of 8 to 20% by weight in terms of element based on the total amount of the catalyst.

14. The catalyst according to claim 13, wherein the group VIII metal element is contained in an amount of 10 to 15% by weight in terms of element based on the total amount of the catalyst.

15. The catalyst according to claim 1, wherein the second metal element is one or two or more of Li, K, Mg, and Zr, and the third metal element is Ce.

16. The catalyst according to any one of claims 1 to 5 and 15, wherein the content of the second metal element is 2 to 11% by weight and the content of the third metal element is 0.5 to 6% by weight in terms of element based on the total amount of the catalyst.

17. The catalyst according to claim 16, wherein the content of the second metal element is 5 to 7% by weight and the content of the third metal element is 0.8 to 3% by weight in terms of element based on the total amount of the catalyst.

18. The catalyst according to claim 1, wherein the catalyst contains a second metal element and a third metal element supported on the carrier.

19. The catalyst according to claim 1 or 18, wherein the second metal element is one or two or more of Zr, Li, Mg and K, and the third metal element is Ce.

20. The catalyst of any one of claims 1-5, 15, and 18, wherein the alumina is theta alumina.

21. The catalyst of any one of claims 1-5, 15, and 18, wherein the CO₂The high-temperature desorption peak is positioned in a temperature range of 380-500 ℃.

22. The catalyst of claim 21, wherein the CO₂The high-temperature desorption peak is positioned in the temperature interval of 385-480 ℃.

23. The catalyst of any one of claims 1-5, 15, and 18, wherein the CO of the catalyst₂In the TPD desorption diagram, CO is also present in the temperature range of 100-₂Low temperature desorption peak.

24. The catalyst of claim 23, wherein the catalyst has CO₂In the TPD desorption diagram, CO is also present in the temperature range of 150 ℃ and 190 DEG C₂Low temperature desorption peak.

25. The catalyst according to any one of claims 1 to 5, 15 and 18, wherein the catalyst has a CO-TPD desorption profile in which a CO high temperature desorption peak is present in a temperature range of 300 ℃ to 700 ℃.

26. The catalyst of claim 25, wherein in the desorption spectrum of CO-TPD of the catalyst, a CO low-temperature desorption peak exists in the temperature interval of 100-200 ℃.

27. A process for the reductive activation of a catalyst precursor for use in a fischer-tropsch synthesis reaction for the production of lower olefins from synthesis gas, the process comprising the steps of:

(1) pre-reducing a catalyst precursor in a first gas to obtain a pre-reduced catalyst, wherein the first gas is hydrogen or a mixed gas of hydrogen and an inert gas, the catalyst precursor comprises a carrier and a VIII group metal element loaded on the carrier in the form of an oxide, the valence state of the VIII group metal element in the oxide is the highest oxidation valence state of the metal element, the carrier is alumina, the alumina contains theta-alumina, the content of the theta-alumina is more than 50 wt% based on the total amount of the alumina in the catalyst, the content of the VIII group metal element is 3-30 wt% based on the total amount of the catalyst precursor, and the catalyst precursor further contains a second metal element and/or a third metal element loaded on the carrier, the second metal element is one or more than two selected from alkali metal elements, alkaline earth metal elements and IVB group metal elements, the third metal element is one or more than two selected from rare earth metal elements, the content of the second metal element is 0-15 wt%, the content of the third metal element is 0-10 wt%, and the content of the second metal element and the content of the third metal element are not 0 at the same time based on the total amount of the catalyst precursor;

(2) reducing and activating the pre-reduction catalyst in a second gas to obtain a reduction-activated catalystCO₂In the TPD desorption diagram, CO is present in the temperature range of 369-₂And a high-temperature desorption peak, wherein the second gas is hydrocarbon which is gaseous at the reduction activation temperature or the mixed gas of the hydrocarbon which is gaseous at the reduction activation temperature and inert gas, and the reduction activation is carried out at the temperature of 150-500 ℃.

28. The method as claimed in claim 27, wherein the pre-reduction is carried out at a temperature of 200-600 ℃ and the duration of the pre-reduction is 1-20 hours.

29. The method of claim 28, wherein the pre-reduction is performed at a temperature of 300-550 ℃.

30. The process as claimed in any one of claims 27 to 29, wherein the pressure in the reactor in which the pre-reduction is carried out is from 0 to 3MPa, measured as gauge pressure.

31. The process of claim 30, wherein the pressure in the reactor at which the pre-reduction is carried out is from 0.1 to 1MPa, gauge.

32. The method as claimed in any one of claims 27 to 29, wherein the first gas has a volumetric space velocity, measured as hydrogen, of 5000-^-1。

33. The method as claimed in claim 32, wherein the volume space velocity of the first gas is 10000-^-1。

34. The method of any one of claims 27-29, wherein the duration of the pre-reduction is 2-10 hours.

35. The method of claim 27, wherein the second gas is a mixture of a hydrocarbon and an inert gas that is gaseous at a reduction activation temperature.

36. The method of claim 35, wherein the molar ratio of the inert gas to the hydrocarbon that is gaseous at the reductive activation temperature is from 1 to 200: 1.

37. the method of claim 36, wherein the molar ratio of the inert gas to the hydrocarbon that is gaseous at the reductive activation temperature is from 15 to 30: 1.

38. the method of any one of claims 27 and 35-37, wherein the hydrocarbon that is gaseous at the reduction activation temperature is one or more than two selected from the group consisting of an alkane that is gaseous at the reduction activation temperature, and an alkene that is gaseous at the reduction activation temperature.

39. The method of claim 38, wherein the hydrocarbon that is gaseous at the reductive activation temperature is selected from C₁-C₄Alkane and C₂-C₄One or more than two kinds of olefins.

40. The method according to claim 39, wherein the hydrocarbon that is gaseous at the reduction activation temperature is one or two or more selected from methane, ethane, ethylene, propylene, propane, butane, and butene.

41. The method as claimed in any one of claims 27 and 35 to 37, wherein the reductive activation is carried out at a temperature of 180 ℃ and 450 ℃.

42. The method of claim 41, wherein the reductive activation is carried out at a temperature of 200-400 ℃.

43. The process as set forth in any one of claims 27 and 35 to 37 wherein the pressure in the reactor in which the reductive activation is carried out is from 0 to 2.5MPa, gauge.

44. The process as set forth in claim 43, wherein the pressure in the reactor in which the reductive activation is carried out is from 0.1 to 2MPa by gauge.

45. The method as claimed in any one of claims 27 and 35 to 37, wherein the volume space velocity of the second gas is 5000-^-1。

46. The method as claimed in claim 45, wherein the volume space velocity of the second gas is 10000-20000 hours based on the hydrocarbon being gaseous at the reductive activation temperature^-1。

47. The method of any one of claims 27 and 35-37, wherein the duration of reductive activation is 1-20 hours.

48. The method of claim 47, wherein the duration of the reductive activation is 2-15 hours.

49. The method of claim 48, wherein the duration of said reductive activation is from 4 to 12 hours.

50. The method according to any one of claims 27 to 29 and 35 to 37, wherein the inert gas in the first gas and the second gas is the same or different and each is one or two or more selected from nitrogen and a group zero element gas.

51. The method of claim 50, wherein the inert gas in the first gas and the second gas is each nitrogen and/or argon.

52. The process of any one of claims 27-29 and 35-37, wherein the group VIII metal element is present in an amount of 8-20 wt.% on an elemental basis, based on the total amount of catalyst precursor.

53. A process as claimed in claim 52, in which the group VIII metal element is present in an amount of from 10 to 15% by weight, calculated as element, based on the total amount of catalyst precursor.

54. The method according to claim 27, wherein the second metal element is one or two or more of Li, K, Mg, and Zr, and the third metal element is Ce.

55. The method as claimed in claim 27 or 54, wherein the content of the second metal element is 2 to 11% by weight and the content of the third metal element is 0.5 to 6% by weight in terms of element based on the total amount of the catalyst precursor.

56. The process as claimed in claim 55, wherein the content of the second metal element is 5 to 7% by weight and the content of the third metal element is 0.8 to 3% by weight in terms of element, based on the total amount of the catalyst precursor.

57. The method according to claim 27, wherein the catalyst precursor contains a second metal element and a third metal element supported on the carrier.

58. The method of claim 57, wherein the second metal element is one or more of Zr, Li, Mg, and K, and the third metal element is Ce.

59. The method of any one of claims 27-29, 35-37, and 54, wherein the alumina is theta alumina.

60. A catalyst prepared by the method of any one of claims 27-59.

61. A preparation method of a catalyst for Fischer-Tropsch synthesis reaction for preparing low-carbon olefin from synthesis gas comprises the following steps:

(1) loading an oxide of a group VIII metal element and/or a precursor of an oxide of a group VIII metal element on a carrier, and calcining the carrier loaded with the oxide and/or the precursor to obtain a catalyst precursor, wherein the carrier is alumina, at least a part of the carrier is alumina containing a modifying element, the modifying element is one or more selected from alkali metal elements, alkaline earth metal elements and group IVB metal elements, the content of the modifying element is 0.1 to 15 wt% in terms of the element based on the total amount of the carrier, the alumina contains theta-alumina, the content of the theta-alumina is 50 wt% or more in terms of the total amount of alumina in the catalyst, the content of the group VIII metal element is 3 to 30 wt% in terms of the element based on the total amount of the catalyst precursor, the method also comprises loading an auxiliary element on the carrier, wherein the auxiliary element is one or more than two of alkali metal elements and rare earth metal elements, and the loading amount of the auxiliary element on the carrier is such that the content of the auxiliary element is 0.1-10 wt% calculated by the element based on the total amount of the catalyst precursor;

(2) reductive activation of the catalyst precursor by a process according to any of claims 27 to 51 to yield a catalyst with CO₂In the TPD desorption diagram, CO is present in the temperature range of 369-₂High temperature desorption peak.

62. A process as claimed in claim 61, in which the loading of the group VIII metal element on the support is such that the content of group VIII metal element is from 8 to 20% by weight, calculated as element, based on the total amount of the catalyst precursor.

63. A process as claimed in claim 62, in which the loading of the group VIII metal element on the support is such that the content of group VIII metal element is from 10 to 15% by weight, calculated as element, based on the total amount of the catalyst precursor.

64. The method of claim 61, wherein the promoter element is one or more of Li, K and Ce.

65. The method of claim 64, wherein the promoter element is K and/or Ce.

66. A process as claimed in any one of claims 61 to 65, in which the promoter element is supported on the support in an amount such that the promoter element is present in an amount of from 2 to 6% by weight, calculated as element, based on the total amount of catalyst precursor.

67. The method of any one of claims 61-65, wherein the promoter element is supported on the support simultaneously with the group VIII metal element.

68. The method as claimed in claim 61, wherein the calcination is carried out at a temperature of 300-900 ℃.

69. The method as claimed in claim 68, wherein the calcination is carried out at a temperature of 400-600 ℃.

70. The method of any one of claims 61, 68, and 69, wherein the duration of said roasting is 1-10 hours.

71. The method of any one of claims 61-65, 68, and 69, wherein the alumina is theta alumina.

72. The method of any one of claims 61-65, 68, and 69, wherein the method further comprises the step of providing alumina, and in the step of providing alumina, gamma-Al is added₂O₃The calcination is carried out in an air atmosphere at a temperature of 700-1050 ℃.

73. The method of claim 72, wherein, in the step of providing alumina, the duration of calcination is from 0.5 to 5 hours.

74. The method of any one of claims 61-65, 68, and 69, wherein the modifying element is one or more of K, Mg and Zr.

75. The method of claim 74, wherein said modifying element is Mg and/or Zr.

76. The method of any one of claims 61-65, 68, and 69, wherein the modifying element is present in an amount of 1.5-8% by weight on an elemental basis, based on the total amount of the support.

77. The method of any one of claims 61-65, 68, and 69, wherein the modifying element-containing alumina is prepared by a method comprising: and (2) impregnating alumina with an impregnating solution containing a compound containing a modifying element, and drying and roasting the alumina adsorbed with the impregnating solution in sequence to obtain the carrier containing the modifying element.

78. The method of claim 77, wherein the alumina containing a modifying element is prepared by a process wherein the drying is carried out at a temperature of 50-300 ℃ for a duration of 1-12 hours; the calcination is carried out at a temperature of 300-900 ℃ for a duration of 0.5-8 hours.

79. A catalyst prepared by the method of any one of claims 61-78.

80. Use of a catalyst as claimed in any one of claims 1 to 26, 60 and 79 as a catalyst for a fischer-tropsch synthesis reaction.

81. A process for the production of lower olefins comprising contacting hydrogen and carbon monoxide with a catalyst under Fischer-Tropsch reaction conditions, wherein the catalyst is as claimed in any one of claims 1 to 26, 60 and 79.

82. The process of claim 81, wherein the molar ratio of hydrogen to carbon monoxide is from 0.4 to 2.5: 1.

83. the process of claim 82, wherein the molar ratio of hydrogen to carbon monoxide is from 0.6 to 2.5: 1.

84. the process of claim 83, wherein the molar ratio of hydrogen to carbon monoxide is from 0.8 to 2.2: 1.

85. the method of claim 81, wherein the contacting is performed in a fluidized bed reactor.

86. The process as claimed in claim 85, wherein the contacting temperature is 320-550 ℃, the pressure in the reactor is 0.5-8MPa in gauge pressure, and the gas hourly space velocity is 20000-50000 h^-1。

87. A method for preparing low-carbon olefin comprises the following steps:

(1) preparing a catalyst by the method of any one of claims 27 to 59, or the method of any one of claims 61 to 78;

88. The process of claim 87, wherein the molar ratio of hydrogen to carbon monoxide is from 0.4 to 2.5: 1.

89. the process of claim 88, wherein the molar ratio of hydrogen to carbon monoxide is from 0.6 to 2.5: 1.

90. the process of claim 89, wherein the molar ratio of hydrogen to carbon monoxide is from 0.8 to 2.2: 1.

91. the method of claim 87, wherein the contacting is performed in a fluidized bed reactor.

92. The process as claimed in claim 91, wherein the contacting temperature is 320-550 ℃, the pressure in the reactor is 0.5-8MPa in gauge pressure, and the gas hourly space velocity is 20000-50000 h^-1。