CN107617442B

CN107617442B - Fischer-Tropsch synthesis precipitated iron-based catalyst, preparation method and application thereof, and method for preparing hydrocarbon compound by Fischer-Tropsch synthesis of synthesis gas through slurry bed

Info

Publication number: CN107617442B
Application number: CN201610560019.0A
Authority: CN
Inventors: 常海; 王鹏; 张魁; 吕毅军; 郭秀盈; 程萌; 王涛; 罗熙
Original assignee: Shenhua Group Corp Ltd; National Institute of Clean and Low Carbon Energy
Current assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Priority date: 2016-07-15
Filing date: 2016-07-15
Publication date: 2020-07-14
Anticipated expiration: 2036-07-15
Also published as: CN107617442A

Abstract

The invention relates to the field of Fischer-Tropsch synthesis precipitated iron-based catalysts, and discloses a Fischer-Tropsch synthesis precipitated iron-based catalyst, a preparation method and application thereof, and a method for preparing hydrocarbon compounds by Fischer-Tropsch synthesis of synthesis gas through a slurry bed. The catalyst comprises the following components in percentage by weight of Fe, Cu, K, Co, Mn and SiO₂100 (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27); the catalyst is subjected to low temperature N₂The pore structure determined by physical adsorption has the following characteristics: in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of small pores with the pore diameter less than 12nm is less than 35 percent; the proportion of mesopores with the pore diameter of 12-80 nm is more than 65%. The catalyst has good physical and chemical wear resistance, can be continuously operated for about 2000 hours without inactivation by adopting a stirred tank evaluation device for simulation experiment, and has a Fischer-Tropsch synthesis reaction result C₅ ⁺The selectivity of the product is improved.

Description

Fischer-Tropsch synthesis precipitated iron-based catalyst, preparation method and application thereof, and method for preparing hydrocarbon compound by Fischer-Tropsch synthesis of synthesis gas through slurry bed

Technical Field

The invention relates to the field of Fischer-Tropsch synthesis precipitated iron-based catalysts, in particular to a Fischer-Tropsch synthesis precipitated iron-based catalyst, a preparation method and application thereof, and a method for preparing hydrocarbon compounds by Fischer-Tropsch synthesis of synthesis gas through a slurry bed.

Background

Under the action of Fischer-Tropsch synthesis catalyst of precipitated iron or supported cobalt, etc., synthesis gas (CO and H)₂) The slurry bubble column reactor and the matched synthetic oil process for catalytic reaction and synthesis of liquid hydrocarbon/wax hydrocarbon products are more and more paid attention and favored by researchers and developers.

Unlike gas-solid reaction systems carried out using fixed bed reactors, in slurry bubble column reactors, the entire reaction system is carried out in the presence of liquid paraffin. From the catalyst perspective, whether reactants (CO and H)₂) The permeation, diffusion and adsorption, as well as the desorption and internal and external diffusion of the reaction product, will be affected by the reaction medium.

How to improve the abrasion resistance of the catalyst and ensure good catalytic performance in the production process of the slurry bed Fischer-Tropsch synthetic oil process is a key link of the synthetic oil process and is a problem which is not solved so far. The catalyst has the defects of low strength, easy abrasion or breakage and the like, and can cause a large amount of fine powder (the particle size is less than about 20 mu m), further cause the blockage of a filter, increase the load of process operation, pollute subsequent products, and even force the shutdown for treating the filter.

The operation stability of the catalytic reaction of the catalyst also directly influences the long-period operation life of the catalyst and is an important index for measuring the production efficiency of the catalytic reaction. In the slurry bed reaction process operation, if the stability of the catalyst is poor, the catalyst needs to be continuously replaced and fresh catalyst needs to be supplemented, so that stable operation is maintained and the qualified rate of products is kept.

CN1270822C discloses a ferro-manganeseThe preparation method of the synthetic catalyst comprises the steps of adding silica sol (acidic or alkaline) into a mixed solution of iron, manganese and calcium with the total metal ion concentration of 0.05-10.0 mol/L, and then mixing with an ammonia water solution with the total metal ion concentration of 0.1-5.0 mol/L; or adding silica sol into 0.1-5.0 mol/L ammonia water solution, and mixing with mixed solution of iron, manganese and calcium with total metal ion concentration of 0.05-10.0 mol/L; precipitating at 30-98 ℃ and under the condition that the pH value is 7.0-11.5, washing and filtering after precipitation to obtain a filter cake with the solid content of 10-50 wt%, adding water and potassium salt (potassium carbonate, methyl acetate and potassium bicarbonate) into the filter cake for pulping to obtain catalyst slurry with the solid content of 5-45 wt%, spray-drying the catalyst slurry to form microspheres, and roasting at 300-750 ℃ for 2-12h to obtain the iron-manganese catalyst for slurry bed Fischer-Tropsch synthesis, wherein the iron-manganese catalyst comprises the following components: fe, Mn, Ca, K, SiO₂100 (4-100): (1-40): 0.5-10): 3-50. The invention emphasizes that the calcium silicate with good strength can be formed because the silica sol is directly introduced in the precipitation step, thereby improving the mechanical strength of the catalyst. The patent does not mention any information on the pore structure of the catalyst. It has also been found that the introduction of too much silica (any silicon source that may be introduced) during the precipitation step results in a shift of the pore structure of the resulting catalyst towards small pores. Furthermore, the Rong ZHao et al (RongZHao, James G. Goodwin, Jr., K. Jothimuugesan, Santosh K. Gangwal, and James J. spivy, Ind. Eng. chem. Res.2001,40, 1065-.

CN1203920C discloses an Fe/Mn catalyst for Fischer-Tropsch synthesis, in which Fe, Mn, Ca, K and SiO are contained₂100 (4-100): (2-50): 0.2-10), wherein SiO₂The weight percentage in the catalyst is 1-45 wt%; active components Fe, Mn, Ca and K in the catalyst exist in oxide forms respectively. The preparation method specifically disclosed comprises the following steps: (1) preparing a mixed salt solution of ferric nitrate, calcium nitrate, manganese nitrate or manganese acetate with the concentration of 0.05-2.0 mol/L according to the composition of the catalyst; (2) mixing the mixed salt solution with 0.1-5.0 mol/L ammonia water solution, stirring at 30-90 deg.C and pH of 7.0-11.5, precipitating, and precipitatingStanding for 5-48 hours, and filtering to obtain a filter cake; (3) preparing potassium carbonate into a potassium carbonate solution with the concentration of 0.1-1.5 mol/L; (4) adding silica sol water solution (containing SiO) into the filter cake according to the silicon content in the catalyst₂25 wt%), and potassium carbonate solution, and adding deionized water to mix and pulp, water: the weight ratio of the formed catalyst is 5-9: 1; (5) drying the slurry in water bath at 40-95 deg.C for 5-60 hr, drying at 80-150 deg.C for 6-42 hr, calcining at 650 deg.C for 1-12 hr, cooling, and tabletting. The patent emphasizes the high specific surface area and the high mechanical strength of the obtained catalyst, but does not give any specific index data. The preparation method is conventional tabletting and molding. For Fischer-Tropsch synthesis reactions, of CO₂% selectivity 27.12-43.25%, CH₄Selectivity% of 5.69-12.11%, C₅ ⁺The% selectivity was 55.77-76.43%.

Yi Zhang et al (A new and direct prediction method of ion-based biomodulalisation and its application in Fischer-Tropsch synthesis, Applied catalysis A: General 352(2009) 277-. Carrying out an isovolumetric impregnation method on a carrier by using a mixed solution of ferric nitrate, cupric nitrate and potassium nitrate, drying the carrier in air at 120 ℃ for 12 hours, roasting the carrier at 400 ℃ for 2 hours, and loading an active component to prepare the supported iron-based catalyst, wherein the iron loading is 20 weight percent, and the Fe: cu: k is 200: 30: 5. the carrier is commercially available silica gel (Q-50) with macropores with a pore diameter of 50-60nm, and pores with a diameter of 5-7nm are formed between the impregnated active components. But the pinholes disappeared after heat treatment at only 700 c. The catalyst with double pore distribution disclosed in this article has a CO conversion activity of 89.5% by establishing on a carrier with large pores, but is a supported iron-based catalyst (iron oxide loading of 30 wt%), and the chain growth probability a is very low and is only 0.60, and it can be seen that C is C₅₊The hydrocarbon product selectivity is very low. Also the attrition resistance of the catalyst is not investigated herein.

It can be seen that there is a need to provide a technique which addresses the attrition resistance deficiencies of catalysts produced by slurry bed fischer-tropsch synthesis processes.

Disclosure of Invention

The invention aims to solve the problems of insufficient strength and abrasion or breakage of a catalyst in a slurry bed Fischer-Tropsch synthesis process, and provides a Fischer-Tropsch synthesis precipitated iron-based catalyst, a preparation method and application thereof, and a method for preparing hydrocarbon compounds by Fischer-Tropsch synthesis of synthesis gas through a slurry bed.

The inventor of the invention researches the abrasion or breakage reason of the catalyst in the reaction process, and finds that besides physical abrasion caused by mutual collision of the catalyst and other factors, chemical abrasion or breakage suffered by catalyst particles is a more main reason for reducing the strength of the catalyst and generating abrasion or breakage, and specifically comprises that the inner hole structure of the catalyst is changed and small holes are collapsed in the pre-reduction process, so that the abrasion resistance strength of the catalyst is changed or weakened; in the catalytic reaction process, the accumulation, pore blocking, carbon deposition and the like of heavy products of long-chain hydrocarbons generated by the Fischer-Tropsch synthesis reaction cause the blockage and crushing of pore channels of the catalyst, and the strength of the catalyst is influenced. The inventor realizes that the problem of abrasion or breakage of the Fischer-Tropsch catalyst in the slurry bed Fischer-Tropsch synthesis reaction process needs to be solved by improving the internal structure of the catalyst, more accurately starting from the modulation and improvement of the internal hole structure, so that the strength and abrasion of the catalyst can be effectively solved, and the prepared catalyst can provide long-term stable operation of the slurry bed Fischer-Tropsch synthesis reaction.

In order to realize the aim, the invention provides a precipitated iron-based Fischer-Tropsch synthesis catalyst which comprises the following components in percentage by weight of Fe, Cu, K, Co, Mn and SiO₂100 (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27); the catalyst is subjected to low temperature N₂The pore structure determined by physical adsorption has the following characteristics: in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of small pores with the pore diameter less than 12nm is less than 35 percent; the proportion of mesopores with the pore diameter of 12-80 nm is more than 65%.

The invention also provides a preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, which comprises the following steps: (1) dissolving iron, copper, cobalt and manganese salts in water to obtain a metal salt aqueous solutionThe conductivity is below 60 mu s/cm; mixing a precipitator, a silicon-containing compound and water to obtain a precipitator aqueous solution, wherein the precipitator is at least one of sodium carbonate, potassium bicarbonate and ammonia water, and the molar ratio of the precipitator to the silicon-containing compound is 100: (1-3); (2) adding the aqueous solution of the metal salt into the aqueous solution of the precipitator, and carrying out coprecipitation reaction at the temperature of 55-90 ℃ to obtain a coprecipitation product slurry with the pH value of 5.5-8.5; (3) cooling the coprecipitation product slurry to reduce the temperature of the coprecipitation product slurry to below 20 ℃ within 15min, and diluting the coprecipitation product slurry to obtain slurry I; (4) carrying out suction filtration and washing on the slurry I to obtain a precipitate filter cake a with the solid content of 15-70 wt%; (5) mixing silica sol or potassium silicate, potassium carbonate and water with the precipitation filter cake a, pulping, and adding acid liquor to prepare slurry II with the pH value of below 7; standing the slurry II, and performing suction filtration to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring to obtain catalyst precursor slurry III with the solid content of 10-50 wt%; (6) spray drying and calcining the catalyst precursor slurry III; wherein the addition amount of iron salt, copper salt, cobalt salt, manganese salt, precipitator, potassium carbonate, potassium silicate or silica sol satisfies the condition that Fe, Cu, K, Co, Mn and SiO are added₂The weight ratio of (100), (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27).

Preferably, the cooling is to add ice blocks into the coprecipitation product slurry, and the weight ratio of the ice blocks to the coprecipitation product slurry is 1: 1 or less.

The invention also provides a Fischer-Tropsch synthesis precipitated iron-based catalyst prepared by the method.

The invention also provides application of the Fischer-Tropsch synthesis precipitated iron-based catalyst in preparation of hydrocarbon compounds by carrying out Fischer-Tropsch synthesis reaction in a slurry bed reactor.

The invention also provides a method for preparing hydrocarbon compounds by the slurry bed Fischer-Tropsch synthesis reaction of the synthesis gas, which comprises the following steps: (a) in the presence of reducing atmosphere and diluting medium, the precipitated iron-based catalyst for Fischer-Tropsch synthesis is prepared at the temperature of 230-320 ℃ and the pressure of 0.1-E2.8MPa, H in said reducing atmosphere₂The molar ratio of the carbon dioxide to CO is (0.2-35): 1, carrying out reduction reaction for 1-48 h to obtain a reduced activated catalyst; (b) in the presence of the reduced-state activated catalyst, the catalyst will contain CO and H₂The synthesis gas is subjected to Fischer-Tropsch synthesis reaction in a slurry bed reactor under the conditions that the temperature is 210-300 ℃ and the pressure is 1.2-2.8 MPa, so as to obtain hydrocarbon compounds; wherein, H in the synthesis gas₂The molar ratio of the carbon dioxide to CO is (0.5-3.5): 1, and the space velocity of the synthesis gas is 5-16N L/g-cat h.

The Fischer-Tropsch synthesis precipitated iron-based catalyst provided by the invention has low-temperature N₂The physical adsorption is characterized by the following pore structure measured by physical adsorption: in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of small pores with the pore diameter less than 12nm is less than 35 percent; the proportion of mesopores with the pore diameter of 12-80 nm is more than 65%. The pore structure distribution plot for the catalyst prepared in example 1, shown in fig. 1, shows two relatively distinct peaks of pore diameter distribution and one sweep peak. The catalyst provided by the invention has two sections of concentrated pore distributions, wherein the proportion of mesopores (the pore diameter is 12-80 nm) is obviously large and the normal broad peak characteristic is presented. The pore structure ensures that the catalyst provided by the invention has good physical abrasion resistance, and the abrasion indexes tested by adopting an ASTM D5757-00 air injection method are below 4.0%.

In addition, the catalyst provided by the invention has improved abrasion resistance, and can be used for carrying out long-period operation in a slurry bed reactor for Fischer-Tropsch synthesis reaction. A stirred tank evaluation device is adopted for simulation experiment, the catalyst can continuously run for about 2000 hours, and the Fischer-Tropsch synthesis reaction still has high reaction activity. The catalyst provided by the invention can avoid or reduce the online replacement times of the catalyst, and reduce the overall operation cost.

In the slurry bed Fischer-Tropsch synthesis reaction using the catalyst of the invention, the CO conversion rate is high, and the methane selectivity and C are reduced₂-C₄The selectivity of light hydrocarbon products is improved₅ ⁺Selectivity of the product.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is an SEM electron micrograph of a precipitated iron-based Fischer-Tropsch catalyst prepared in example 1;

FIG. 2 is a graph showing the pore structure distribution of the precipitated iron-based Fischer-Tropsch catalyst prepared in example 1;

FIG. 3 is a pore structure distribution diagram of a Fischer-Tropsch synthesis precipitated iron-based catalyst prepared in comparative example 2;

FIG. 4 is a graph showing the trend of CO conversion change in the long-term operation of the slurry bed Fischer-Tropsch synthesis reaction in evaluation example 1.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

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.

The invention provides a precipitated iron-based catalyst for Fischer-Tropsch synthesis, which comprises the following components in percentage by weight of Fe, Cu, K, Co, Mn and SiO₂100 (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27); wherein the catalyst is subjected to low temperature N₂The pore structure determined by physical adsorption has the following characteristics: in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of small pores with the pore diameter less than 12nm is less than 35 percent; the proportion of mesopores with the pore diameter of 12-80 nm is more than 65%.

Preferably, the weight ratio of the components of the catalyst is Fe, Cu, K, Co, Mn and SiO₂＝100:(0.6～5):(2.5～5.5):(0.1～0.3)：(1.0～9.6):(17～24)。

The pore structure of the precipitated iron-based catalyst for Fischer-Tropsch synthesis provided by the invention has a diplopore type distribution, for example, in the pore structure distribution diagram of the catalyst obtained in example 1 shown in FIG. 2, two relatively obvious peaks of pore diameter distribution and one sweep peak are shown. It can be seen that the catalyst has two relatively concentrated distributions of pore diameters. The precipitated iron-based Fischer-Tropsch synthesis catalyst provided by the invention has the characteristics and can have improved abrasion resistance.

According to the present invention, in the diplopore distribution characteristic of the catalyst, the small proportion of the small pores is mainly exhibited, and the medium pores have different proportions in the total pore volume, and the medium pores have a large proportion, which can contribute to the improvement of the strength and the improvement of the attrition property of the catalyst. Preferably, the proportion of small pores with a pore diameter of < 12nm in the total pore volume with a pore diameter of < 80nm is less than 30% and greater than 0%. The proportion of the small holes is preferably 15-28%.

According to the present invention, it is preferable that the proportion of mesopores having a pore diameter of 12 to 80nm is 65% or more and less than 99% in the total pore volume having a pore diameter of 80nm or less. The preferable mesopore ratio is 72-85%.

Preferably, the total pore volume of the catalyst of the invention is 0.55-0.7 cm³Preferably 0.58 to 0.68 cm/g³/g。

In the present invention, when the structure of the pores of the catalyst is defined, both the pore diameter and the pore volume are defined by the low temperature N₂The pore diameter is the average diameter of the pores, and is a value measured by physical adsorption. Further, the pore structure distribution diagram of the catalyst prepared in example 1 of the present invention was observed, as shown in fig. 2, in which the peak appearance curve of the mesopores having a pore diameter of 12 to 80nm shows a broad peak in a normal distribution. The catalyst provided by the invention can provide enough guarantee for the adsorption and diffusion of raw materials and the desorption and diffusion of products in the Fischer-Tropsch synthesis reaction process, and can effectively reduce the abrasion and strength of the catalyst caused by chemical factorsAnd (4) descending.

In the invention, preferably, the specific surface area of the catalyst is 120-260 cm²(ii)/g; preferably 142-239 cm²/g。

According to the present invention, the catalyst provided by the present invention has better abrasion resistance, and preferably, the abrasion index of the catalyst is 4.0% or less according to astm d5757-00 air injection method. Preferably 2.5 to 4%, more preferably 2.8 to 3.9%.

The invention also provides a preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, which comprises the following steps:

(1) dissolving iron salt, copper salt, cobalt salt and manganese salt into water to obtain a metal salt water solution, wherein the conductivity of the water is below 60 mu s/cm; mixing a precipitator, a silicon-containing compound and water to obtain a precipitator aqueous solution, wherein the precipitator is at least one of sodium carbonate, potassium bicarbonate and ammonia water, and the molar ratio of the precipitator to the silicon-containing compound is 100: (1-3);

(2) adding the aqueous solution of the metal salt into the aqueous solution of the precipitator, and carrying out coprecipitation reaction at the temperature of 55-90 ℃ to obtain a coprecipitation product slurry with the pH value of 5.5-8.5;

(3) cooling the coprecipitation product slurry to reduce the temperature of the coprecipitation product slurry to below 20 ℃ within 15min, and diluting the coprecipitation product slurry to obtain slurry I;

(4) carrying out suction filtration and washing on the slurry I to obtain a precipitate filter cake a with the solid content of 15-70 wt%;

(5) mixing silica sol or potassium silicate, potassium carbonate and water with the precipitation filter cake a, pulping, and adding acid liquor to prepare slurry II with the pH of below 7, preferably the pH of the slurry II is below 6; standing the slurry II, and performing suction filtration to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring to obtain catalyst precursor slurry III with the solid content of 10-50 wt%;

(6) spray drying and calcining the catalyst precursor slurry III;

wherein, iron salt, copper salt, cobalt salt, manganeseThe addition amount of the salt, the precipitator, the potassium carbonate, the potassium silicate or the silica sol meets the requirement that Fe, Cu, K, Co, Mn and SiO are added₂The weight ratio of (100), (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27).

In the preparation method of the precipitated iron-based catalyst for Fischer-Tropsch synthesis, the aqueous solution of the metal salt and the aqueous solution of the precipitator, which are prepared in the step (1), are used as reaction raw material solutions. Wherein, in the metal salt water solution, the concentration of iron salt is 1.0-6.0 wt% calculated by Fe, the concentration of copper salt is 0.05-0.36 wt% calculated by Cu, the concentration of cobalt salt is 0.00001-0.06 wt% calculated by Co, and the concentration of manganese salt is 0.001-0.6 wt% calculated by Mn.

Preferably, the iron salt may be at least one of iron nitrate, hydrate of iron nitrate, iron sulfate, hydrate of iron sulfate, iron chloride and iron oxide, preferably iron nitrate and/or hydrate of iron nitrate.

Preferably, the copper salt may be at least one of copper nitrate, a hydrate of copper nitrate, copper sulfate and a hydrate of copper sulfate, preferably copper nitrate and/or a hydrate of copper nitrate.

Preferably, the cobalt salt may be at least one of cobalt nitrate, a hydrate of cobalt nitrate, and an organic acid cobalt such as cobalt acetate, preferably cobalt nitrate and/or a hydrate of cobalt nitrate.

Preferably, the manganese salt may be at least one of manganese nitrate, a hydrate of manganese nitrate, and an aqueous solution of manganese nitrate, preferably an aqueous solution of manganese nitrate.

Among the above-mentioned raw materials, the raw material containing no hydrate may be a corresponding compound obtained by directly dissolving a corresponding metal material with an acid, and for example, the iron nitrate may be obtained by dissolving an iron-containing metal with nitric acid.

In the invention, the content of the precipitant in the precipitant aqueous solution can meet the requirement that the pH of the precipitant aqueous solution is 10-14, and preferably 12-13.

In the present invention, the precipitant may be sodium carbonate, optionally potassium carbonate and/or potassium bicarbonate, optionally aqueous ammonia. When sodium carbonate, potassium carbonate and/or potassium bicarbonate is used, sodium or potassium may also be introduced.

According to the invention, the aqueous precipitant solution is preferably added with a silicon-containing compound, preferably the silicon-containing compound comprises at least one of solid potassium silicate, liquid potassium silicate, silica sol, potassium-containing silica sol, water-soluble silica and sodium silicate.

In the present invention, the molar ratio of the precipitating agent to the silicon-containing compound is 100: (1-3), for example, when the precipitating agent is sodium carbonate and the silicon-containing compound is potassium silicate, the ratio of sodium carbonate: the molar ratio of potassium silicate is 100: (1-3).

In the preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, the coprecipitation reaction is carried out in the step (2). In a preferred embodiment, the aqueous precipitant solution is placed in a precipitation reactor, and then the aqueous metal salt solution is added to the precipitation reactor, preferably the addition of the entire aqueous metal salt solution is completed within 15min, and the aqueous metal salt solution is mixed with the aqueous precipitant solution to complete the co-precipitation reaction. In the present invention, the coprecipitation reaction is stopped after the aqueous solution of the metal salt is added. In the present invention, controlling the coprecipitation reaction to be carried out in the above manner, completion within a limited time may be more advantageous in obtaining the pore structure of the catalyst of the present invention.

In the present invention, the temperature for performing the coprecipitation reaction may be achieved by heating the precipitant aqueous solution and the metal salt aqueous solution to 55 to 90 ℃.

In the preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, the coprecipitation product slurry is processed in the step (3), so that the growth and dispersion of precipitated particles in the slurry can be controlled, and the double-pore structure distribution of the catalyst can be obtained in the subsequent steps of the preparation method. Ice is added to control the temperature reduction and dilute the co-precipitated product slurry. More preferably, the temperature of the co-precipitated product slurry is reduced to below 15 ℃. Meanwhile, the temperature of the coprecipitation product slurry is kept above 0 ℃, and no icing occurs.

In the preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, the washing in the step (4) can be repeated, and the conductivity of the final filtrate obtained by washing is below 1.2 ms/cm. At this time, the Na ion content in the precipitate cake a was negligible.

In the preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, slurry II is prepared in the step (5), silica sol or potassium silicate, potassium carbonate, water and the precipitated filter cake a are mixed and pulped, wherein the precipitated filter cake a and a certain amount of water are mixed into slurry, and then the silica sol or potassium silicate and potassium carbonate are added into the formed slurry to be mixed and pulped. Wherein, the respective feeding amounts of the silica sol or potassium silicate, potassium carbonate, water and the precipitation filter cake a can satisfy the following conditions: silica sol or potassium silicate: potassium carbonate: the precipitated filter cake a ═ 1: (0.02-0.08): (0.005-0.03): (0.2-0.5). The preferable pulping time is 20-30 min. The acid solution can be hydrochloric acid or nitric acid.

In the preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, the slurry II in the step (5) is subjected to the standing treatment, so that the growth and dispersion of particles in the slurry II can be facilitated, and the pore structure of the obtained catalyst can be formed. Preferably, when the slurry II is kept stand, the standing temperature is 20-65 ℃, and the standing time is 30-90 min.

In the preparation method of the Fischer-Tropsch synthesis precipitated iron-based catalyst, the time for carrying out high-speed shearing stirring on the filter cake b in the step (5) is 20-30 min, and the stirring speed is 80-450 rpm. Preferably in a high speed shearing machine with the stirring speed of 350-450 rpm.

According to the present invention, preferably, the spray drying is performed with an inlet air temperature of 200 to 340 ℃ and an outlet air temperature of 95 to 145 ℃. The spraying mode can be a pressure type or centrifugal spray drying method.

According to the invention, preferably, the roasting is carried out for 10-14 h at 100-120 ℃ in the air, and the temperature is raised to 500-550 ℃ at 300-340 ℃/h and is kept constant for 2-8 h.

According to the invention, water is used as a medium in the various steps of the preparation method of the precipitated iron-based catalyst for Fischer-Tropsch synthesis, and the conductivity of the water is usually below 60 mu s/cm, preferably below 35 mu s/cm. The effect of obtaining the pore structure of the catalyst can be better. The determination of the electrical conductivity can be automatically determined by a commercially available conductivity meter. The ice blocks added in the step (3) are also frozen by water meeting the conductivity.

In the invention, the weight ratio of the prepared Fischer-Tropsch synthesis precipitated iron-based catalyst is Fe, Cu, K, Co, Mn and SiO₂100 (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27); the catalyst is subjected to low temperature N₂The pore structure determined by physical adsorption has the following characteristics: in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of small pores with the pore diameter less than 12nm is less than 35 percent; the proportion of mesopores with the pore diameter of 12-80 nm is more than 65%.

Preferably, in the prepared precipitated iron-based Fischer-Tropsch synthesis catalyst, in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of small pores with the pore diameter less than 12nm is less than 30 percent and more than 0 percent. The proportion of the small holes is preferably 15-28%.

Preferably, in the prepared precipitated iron-based Fischer-Tropsch synthesis catalyst, in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of mesopores with the pore diameter of 12-80 nm is more than 65% and less than 99%. The preferable mesopore ratio is 72-85%.

The prepared Fischer-Tropsch synthesis precipitated iron-based catalyst has an attrition index of less than 4.0 percent according to an ASTM D5757-00 air injection method. Preferably 2.5 to 4%, more preferably 2.8 to 3.9%.

Preferably, the specific surface area of the catalyst is 120-260 cm²(ii)/g; preferably 142-239 cm²/g。

The invention also provides a method for preparing hydrocarbon compounds by Fischer-Tropsch synthesis of synthesis gas through a slurry bed, which comprises the following steps: (a) in the presence of a reducing atmosphere and a diluting medium, the Fischer-Tropsch synthesis precipitated iron-based catalyst is prepared at the temperature of 230-320 ℃ and the pressure of 0.1-2.8 MPa in the reducing atmosphere₂The molar ratio of the carbon dioxide to CO is (0.2-35): 1, carrying out reduction reaction for 1-48 h to obtain a reduced activated catalyst; (b) in the presence of the reduced-state activated catalyst, the catalyst will contain CO and H₂The synthesis gas is subjected to Fischer-Tropsch synthesis reaction in a slurry bed reactor under the conditions that the temperature is 210-300 ℃ and the pressure is 1.2-2.8 MPa, so as to obtain hydrocarbon compounds; wherein, H in the synthesis gas₂The molar ratio of the carbon dioxide to CO is (0.5-3.5): 1, and the space velocity of the synthesis gas is 5-16N L/g-cat h.

In the present invention, the diluting medium may be liquid paraffin, such as commercially available liquid paraffin having a trade name of KX 11. The diluting medium is preferably used in an amount such that the concentration of the precipitated iron-based Fischer-Tropsch catalyst is 5 to 30 wt%.

In the method for preparing hydrocarbon compounds by the Fischer-Tropsch synthesis reaction of the synthesis gas in the slurry bed, in the step (a), the reduction reaction can also be carried out in the slurry bed reactor for carrying out the Fischer-Tropsch synthesis reaction in the step (b). In a preferred embodiment, the reduction reaction of step (a) and the Fischer-Tropsch synthesis reaction of step (b) can be carried out in a slurry bed reactor by changing the reducing atmosphere of H in the slurry bed reactor from step (a) to step (b)₂And the molar ratio of CO, the pressure of the reaction system, the temperature and the space velocity (GHSV) are in accordance with the conditions of the step (b).

In the method for preparing hydrocarbon compounds by slurry bed Fischer-Tropsch synthesis reaction of synthesis gas, the reducing atmosphere in the step (a) can be CO and H₂In which H is₂The molar ratio to CO is 1: (3-40).

In the step (b), the concentration of CO in the synthesis gas is 15-65 vol%.

In the present invention, theThe slurry bed reactor may be any reactor conventionally used in the art suitable for conducting a Fischer-Tropsch synthesis reaction in a slurry bed manner. The invention also provides an implementation mode, and a slurry bed stirring kettle is used for carrying out long-period Fischer-Tropsch synthesis reaction, so that the Fischer-Tropsch synthesis precipitated iron-based catalyst provided by the invention is verified to have better stability. The Fischer-Tropsch synthesis precipitated iron-based catalyst provided by the invention can continuously run on a slurry bed stirring kettle for more than 2000 hours, wherein the weight ratio of the reduced catalyst to the diluent after reduction reaction of the Fischer-Tropsch synthesis precipitated iron-based catalyst is 1: (2 to 35) containing CO and H₂The Fischer-Tropsch synthesis reaction conditions of the synthesis gas are as follows: the temperature is 210-300 ℃, the pressure is 1.2-2.8 MPa, and H in the synthesis gas₂The molar ratio of the carbon dioxide to CO is 0.5-3.5, and the space velocity of the synthetic gas is 5-16N L/g-cat h.

In the present invention, the pressures are gauge pressures.

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

In the following examples, the diluent for carrying out the Fischer-Tropsch synthesis reaction is liquid paraffin of KX11 brand from Jiangsu Yonghua fine chemicals Co.Ltd;

the specific surface area and the pore volume of the prepared Fischer-Tropsch synthesis precipitated iron-based catalyst are measured by a low-temperature nitrogen adsorption method, and the specific surface area is BET specific surface area;

the particle size of the prepared Fischer-Tropsch synthesis precipitated iron-based catalyst is measured by a laser particle sizer (MalvernMastersizer 2000) for size distribution, and water is used as a dispersing agent;

analyzing the component content of the prepared Fischer-Tropsch synthesis precipitated iron-based catalyst by using an X-ray fluorescence component analyzer (XRF) (Shimadzu XRF-1800);

the abrasion resistance of the prepared Fischer-Tropsch synthesis precipitated iron-based catalyst is tested by adopting an air jet method (ASTM D5757-00), and specifically, the weight of each test sample is 50g of a catalyst particle sample with the particle size range of 50-150 mu m. For testing, the samples were first dried and equilibrated at 35% humidity. The 1h abrasion fines were collected and then another fines collector was replaced and the 4h abrasion test was performed. Test results are given as air jet wear index (AJI);

the conductivity of the water used in the examples was automatically measured by a conductivity meter (Shanghai Rongham automated Meter, Inc., model L RS-D23).

Example 1

This example illustrates the preparation of a precipitated iron-based Fischer-Tropsch catalyst of the invention.

The conductivity of the water used in this example was 34. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.58kg of Cu (NO)₃)₂·3H₂O and 0.045kg of Co (NO)₃)₂·6H₂O, 100L water was added and dissolved by stirring, and 1.35kg of 50 wt% Mn (NO) was added to the stirred solution₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

12.0kg of Na was weighed₂CO₃63.0L water was added and dissolved by stirring, and 0.47kg of potassium silicate (Na) was added₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 2.1) stirring and dissolving to obtain a precipitant aqueous solution, and testing the pH value to be 12.7;

(2) heating the precipitant aqueous solution to 65 ℃, and heating the metal salt aqueous solution to 63 ℃ through a coil pipe preheater; adding the metal salt aqueous solution into the precipitator aqueous solution which is stirred vigorously within 15min, and carrying out coprecipitation reaction; monitoring the temperature of the coprecipitation reaction to be 63 ℃ on line, wherein the pH value of the slurry of the coprecipitation product is 7.3;

(3) adding 90kg of ice blocks into 190kg of the obtained coprecipitation product slurry, and reducing the temperature of the coprecipitation product slurry to about 19 ℃ within 10min to obtain slurry I;

(4) and immediately transferring the slurry I to a suction filtration device for suction filtration, and washing a filter cake with water after removing the filtrate. Repeatedly washing until the conductivity of the final filtrate is below 1.2ms/cm to obtain a precipitate filter cake a with the solid content of 35 wt%;

(5) 12.8kg of precipitated cake a was added as precipitated cake a: the mass ratio of water is 3:1 mixing to form slurry, and adding 1.38kg of potassium silicate water glass(modulus 2.01, potassium content 13.67 wt.%, SiO)₂Content 27.54 wt%) and potassium carbonate (national pharmacy group) (weight ratio of potassium silicate water glass to potassium carbonate is 2.9: 1) mixing and pulping for 25 min; then 10kg of dilute nitric acid with the concentration of 13.6 weight percent is added to obtain slurry II with the pH value of 6; standing the slurry II at 55 ℃ for 45min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (360rpm, 25min) to obtain catalyst slurry III with the solid content of about 21 wt%;

(6) inputting the catalyst slurry III into a spray drying device, and carrying out spray drying under the conditions that the inlet air temperature is 280 ℃ and the outlet air temperature is about 102 ℃, wherein the spraying is finished after about 8 min; and putting the obtained catalyst particles into a muffle furnace, roasting for 12h at the temperature of 110 ℃ in the air, then heating to 520 ℃ at the heating rate of 320 ℃/h, and roasting for 4h at the temperature to obtain about 4.1kg of the final catalyst.

The resulting catalyst was observed by SEM electron microscope, and SEM electron micrograph thereof is shown in fig. 1, showing that the sphericity and surface gloss of the particles of the catalyst were good.

The catalyst is subjected to component analysis, and Fe, Cu, K, Co, Mn and SiO₂The weight ratio of (1) to (5.0: 2.5:0.3:6.5: 19.0).

The pore structure distribution of the catalyst measured by low-temperature nitrogen adsorption method is shown in figure 2.

Specific surface area, total pore volume and wear index data are shown in table 1.

Example 2

The conductivity of the water used in this example was 32. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.46kg of Cu (NO)₃)₂·3H₂O and 0.075kg of Co (NO)₃)₂·6H₂O, 100L water was added and dissolved by stirring, and 1.45kg of 50 wt% Mn (NO) was added to the stirred solution₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

14.0kg of Na was weighed₂CO₃63.0L water was added and dissolved by stirring, and 0.51kg of potassium silicate (Na) was added₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 2.5) stirring and dissolving to obtain a precipitant aqueous solution, and testing the pH value to be 12.8;

(2) heating the precipitant aqueous solution to 85 ℃; the aqueous metal salt solution was also heated to 87 ℃ via a coil preheater; adding the metal salt aqueous solution into the precipitator aqueous solution which is stirred vigorously within 15min, and carrying out coprecipitation reaction; monitoring the temperature of the coprecipitation reaction to be 83 ℃ on line, wherein the pH value of the slurry of the coprecipitation product is 7.8;

(3) adding 130kg of ice blocks into 195kg of the obtained coprecipitation product slurry, and reducing the temperature of the coprecipitation product slurry to about 17 ℃ within 9min to obtain slurry I;

(4) and immediately transferring the slurry I to a suction filtration device for suction filtration, and washing a filter cake with water after removing the filtrate. Repeatedly washing until the conductivity of the final filtrate is below 1.2ms/cm to obtain a precipitate filter cake a with the solid content of 33 wt%;

(5) 13.4kg of precipitated cake a was added as precipitated cake a: the mass ratio of water is 3.5: 1 to slurry and 2.15kg of a potassium-containing silica sol (modulus 0.7, potassium content 35.28 wt%, SiO) were added₂25.24 wt%) and potassium carbonate (fine chemicals in the modern oriental of beijing) (the weight ratio of silica sol to potassium carbonate is 15: 1) mixing and pulping for 20 min; then 12kg of dilute nitric acid with the concentration of 15.0 weight percent is added to obtain slurry II with the pH value of 5; standing the slurry II at 65 ℃ for 80min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (380rpm, 30min) to obtain catalyst slurry III with the solid content of about 22 wt%;

(6) inputting the catalyst slurry III into a spray drying device, and carrying out spray drying under the conditions that the inlet air temperature is 290 ℃ and the outlet air temperature is about 105 ℃, wherein the spraying is finished after about 8 min; and putting the obtained catalyst particles into a muffle furnace, roasting for 12h at the temperature of 110 ℃ in the air, then heating to 520 ℃ at the heating rate of 320 ℃/h, and roasting for 5h at the temperature to obtain about 4.1kg of the final catalyst.

The resultant catalyst was observed by an SEM electron microscope, and similarly to fig. 1, the sphericity and the surface gloss of the particles of the catalyst were good.

The catalyst is subjected to component analysis, and Fe, Cu, K, Co, Mn and SiO₂The weight ratio of (1) to (4.0: 5.1:0.5:7.0: 24.0).

Example 3

The conductivity of the water used in this example was 33. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.174kg of Cu (NO)₃)₂·3H₂O and 0.06kg of Co (NO)₃)₂·6H₂O, 100L water was added and dissolved by stirring, and 1.0kg of 50 wt% Mn (NO) was added to the stirred solution₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

15.0kg of Na was weighed₂CO₃63.0L water was added and dissolved by stirring, and 0.47kg of potassium silicate (Na) was added₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 2.5) stirring and dissolving to obtain a precipitant aqueous solution, and testing the pH value to be 12.9;

(2) heating the precipitant aqueous solution to 57 ℃, and heating the metal salt aqueous solution to 58 ℃ through a coil preheater; adding the metal salt aqueous solution into the precipitator aqueous solution which is stirred vigorously within 15min, and carrying out coprecipitation reaction; the temperature of the coprecipitation reaction is monitored to be 55 ℃ on line, and the pH value of the slurry of the coprecipitation product is 8.5;

(3) adding 133kg of ice blocks into 197kg of the obtained coprecipitation product slurry, and reducing the temperature of the coprecipitation product slurry to about 17 ℃ within 10min to obtain slurry I;

(4) and immediately transferring the slurry I to a suction filtration device for suction filtration, and washing a filter cake with water after removing the filtrate. Repeatedly washing until the conductivity of the final filtrate is below 1.2ms/cm to obtain a precipitate filter cake a with the solid content of 36 wt%;

(5) 11.7kg of precipitated cake a was added as precipitated cake a: the mass ratio of water is 5:1 into a slurry, and 1.41kg of potassium silicate (potassium content 47.1% by weight, SiO) was added₂30.0 weight percent) and water with the weight of 20 weight percent of the weight of the precipitated filter cake a are mixed and beaten for 25 min; then 10kg of dilute nitric acid with the concentration of 12.0 weight percent is added to obtain slurry II with the pH value of 5.7; standing the slurry II at 20 ℃ for 60min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (420rpm, 25min) to obtain catalyst slurry III with the solid content of about 24 wt%;

(6) inputting the catalyst slurry III into a spray drying device, and carrying out spray drying under the conditions that the inlet air temperature is 310 ℃ and the outlet air temperature is about 108 ℃, wherein the spraying is finished after about 8 min; and (3) putting the obtained catalyst particles into a muffle furnace, roasting for 12h at the temperature of 110 ℃ in the air, then heating to 450 ℃ at the heating rate of 320 ℃/h, and roasting for 7h at the temperature to obtain about 4.1kg of the final catalyst.

The catalyst is subjected to component analysis, and Fe, Cu, K, Co, Mn and SiO₂The weight ratio of (1: 100:1.5:5.5:0.4:5.0: 20.0).

Example 4

The conductivity of the water used in this example was 35. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.69kg of Cu (NO)₃)₂·3H₂O and 0.105kg of Co (NO)₃)₂·6H₂O, 100L, and 0.53kg of Mn (NO) with a concentration of 50 wt% was added to the stirred solution₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

13.0kg of Na was weighed₂CO₃63.0L water was added and dissolved by stirring, and 0.47kg of potassium silicate (Na) was added₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 2.5) stirring and dissolving to obtain a precipitant aqueous solution, and testing the pH value to be 12.7;

(2) heating the precipitant aqueous solution to 70 ℃, and heating the metal salt aqueous solution to 70 ℃ through a coil preheater; adding the metal salt aqueous solution into the precipitator aqueous solution which is stirred vigorously within 15min, and carrying out coprecipitation reaction; monitoring the temperature of the coprecipitation reaction to be 68 ℃ on line, wherein the pH value of the slurry of the coprecipitation product is 7.5;

(3) adding 125kg of ice blocks into 193kg of the obtained coprecipitation product slurry, and reducing the temperature of the coprecipitation product slurry to about 15 ℃ within 5min to obtain slurry I;

(5) 12.7kg of precipitated cake a was added as precipitated cake a: the mass ratio of water is 3:1 to slurry and 1.38kg of potassium silicate waterglass (modulus 2.01, potassium content 13.67% by weight, SiO)₂Content 27.54 wt%) and potassium carbonate (national pharmacy group) (weight ratio of potassium silicate water glass to potassium carbonate is 2.9: 1) mixing and pulping for 25 min; then 10kg of dilute nitric acid with the concentration of 13.6 weight percent is added to obtain slurry II with the pH value of 6; standing the slurry II at 45 ℃ for 45min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (360rpm, 25min) to obtain catalyst slurry III with the solid content of about 21 wt%;

The resulting catalyst was observed by SEM electron microscope, and similarly to fig. 1, it was shown that the sphericity and the surface gloss of the particles of the catalyst were both good.

Example 5

The conductivity of the water used in this example was 33.6. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.069kg of Cu (NO)₃)₂·3H₂O and 0.035kg of Co (NO)₃)₂·6H₂O85L, and adding 50 wt% Mn (NO) 1.92kg₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

12.0kg of Na was weighed₂CO₃Adding 63.0L water, stirring to dissolve, adding 0.3kg potassium silicate (Na)₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 1.7) stirring and dissolving to obtain a precipitant aqueous solution, and testing the pH value to be 12.6;

(2) heating the precipitant aqueous solution to 60 ℃, and heating the metal salt aqueous solution to 63 ℃ through a coil pipe preheater; adding the metal salt aqueous solution into the precipitator aqueous solution which is stirred vigorously within 15min, and carrying out coprecipitation reaction; monitoring the temperature of the coprecipitation reaction to be 60 ℃ on line, wherein the pH value of the slurry of the coprecipitation product is 7.0;

(3) adding 108kg of ice blocks into 192kg of the obtained coprecipitation product slurry, and reducing the temperature of the coprecipitation product slurry to about 18 ℃ within 12min to obtain slurry I;

(5) 13.0kg of precipitated cake a was added as precipitated cake a: the mass ratio of water is 3.5: 1 Water was added and mixed to form a slurry, and 1.42kg of potassium silicate waterglass (modulus 2.01, potassium content 13.67% by weight, SiO)₂Content 27.54 wt%) and potassium carbonate (fine chemicals in the modern oriental of beijing) (weight ratio of potassium silicate waterglass to potassium carbonate is 2: 1) mixing and pulping for 25 min; then 12kg of dilute nitric acid with the concentration of 10.0 weight percent is added to obtain slurry II with the pH value of 6.3; standing the slurry II at 45 ℃ for 40min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (350rpm, 25min) to obtain catalyst slurry III with the solid content of about 20 wt%;

The catalyst is subjected to component analysis, and Fe, Cu, K, Co, Mn and SiO₂The weight ratio of (1) to (0.6: 4.8:0.1:9.6: 17.0).

Example 6

The conductivity of the water used in this example was 34. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.50kg of Cu (NO)₃)₂·3H₂O and 0.135kg of Co (NO)₃)₂·6H₂Adding 90L water, stirring to dissolve, and adding into the solution0.2kg of Mn (NO) with a concentration of 50% by weight₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

13.0kg of Na was weighed₂CO₃Adding 63.0L water, stirring to dissolve, adding 0.55kg potassium silicate (Na)₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 2.9), stirring and dissolving to obtain a precipitant aqueous solution, and testing the pH value to be 12.8;

(2) heating the precipitant aqueous solution to 77 deg.C; heating the metal salt water solution to 79 ℃ through a coil pipe preheater; adding the metal salt aqueous solution into the precipitator aqueous solution which is stirred vigorously within 15min, and carrying out coprecipitation reaction; monitoring the temperature of the coprecipitation reaction at 77 ℃ on line, wherein the pH value of the slurry of the coprecipitation product is 7.5;

(3) adding 115kg of ice blocks into 196kg of the obtained coprecipitation product slurry, and reducing the temperature of the coprecipitation product slurry to about 20 ℃ within 13min to obtain slurry I;

(4) and immediately transferring the slurry I to a suction filtration device for suction filtration, and washing a filter cake by using deionized water after removing the filtrate. Repeatedly washing until the conductivity of the final filtrate is below 1.2ms/cm to obtain a precipitate filter cake a with the solid content of 35 wt%;

(5) 12.3kg of precipitated cake a was added as precipitated cake a: the mass ratio of water is 3:1 Water was added and mixed to form a slurry, and 1.7kg of potassium silicate waterglass (modulus 2.01, potassium content 13.67% by weight, SiO)₂Content 27.54 wt%) and potassium carbonate (national pharmacy group) (weight ratio of potassium silicate water glass to potassium carbonate is 1.8: 1) mixing and pulping for 25 min; then 10kg of dilute nitric acid with the concentration of 8.5 weight percent is added to obtain slurry II with the pH value of 6; standing the slurry II at 45 ℃ for 45min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (380rpm, 25min) to obtain catalyst slurry III with the solid content of about 21 wt%;

The catalyst is subjected to component analysis, and Fe, Cu, K, Co, Mn and SiO₂The weight ratio of (1) to (5.0: 2.5:0.3:1.0: 19.0).

Comparative example 1

The conductivity of the water used in comparative example 1 was 112. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.59kg of Cu (NO)₃)₂·3H₂O and 0.03kg of Co (NO)₃)₂·6H₂O, 100L water was added and dissolved by stirring, and 1.2kg of Mn (NO) with a concentration of 50% by weight was added to the stirred solution₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

13.0kg of Na was weighed₂CO₃63.0L water was added and dissolved by stirring, and 0.47kg of potassium silicate (Na) was added₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 2.5) stirring and dissolving to obtain a precipitant aqueous solution, and testing the pH value to be 12.6;

(2) heating the metal salt water solution and the precipitant water solution to 75 ℃ through a coil preheater respectively, adding the metal salt water solution into the precipitant water solution which is stirred vigorously within 15min, and carrying out coprecipitation reaction; monitoring the temperature of the coprecipitation reaction to be 73 ℃ on line, wherein the pH value of the slurry of the coprecipitation product is 7.3;

(3) adding 118kg of ice blocks into 190kg of the obtained coprecipitation product slurry, and reducing the temperature of the coprecipitation product slurry to about 18 ℃ within 5min to obtain slurry I;

(4) and transferring the coprecipitation product slurry I to a suction filtration device for suction filtration, and washing a filter cake with water after filtrate is discarded. Repeatedly washing until the conductivity of the final filtrate is below 1.2ms/cm to obtain a precipitate filter cake a with the solid content of 36 wt%;

(5) 12.8kg of precipitated cake a was added as precipitated cake a: the mass ratio of water is 4: 1 Water was added to mix to form a slurry, and 1.41kg of potassium silicate (potassium content 47.1% by weight, SiO) was added₂Content of 30.0 wt%) and 20 wt% of water based on the weight of the precipitate cake a, and mixing and pulping for 25 min; then 10kg of dilute nitric acid with the concentration of 12.0 weight percent is added to obtain slurry II with the pH value of 6.7; standing the slurry II at 45 ℃ for 30min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (380rpm, 25min) to obtain catalyst slurry III with the solid content of about 22 wt%;

The catalyst is subjected to component analysis, and Fe, Cu, K, Co, Mn and SiO₂The weight ratio of (1) to (5.1: 2.7:0.2:6.0: 18.0).

Comparative example 2

The conductivity of the water used in comparative example 2 was 38. mu.s/cm.

(1) 22.0kg of Fe (NO) are weighed out₃)₃·9H₂O, 0.50kg of Cu (NO)₃)₂·3H₂O and 0.06kg of Co (NO)₃)₂·6H₂O, 100L, and 1.36kg of Mn (NO) with a concentration of 50 wt% was added to the stirred solution₃)₂Fully stirring the aqueous solution to obtain a metal salt aqueous solution;

(2) 15.0kg of Na was weighed₂CO₃63.0L water was added and dissolved by stirring, and 0.51kg of potassium silicate (Na) was added₂CO₃The molar ratio of the potassium silicate to the potassium silicate is 100: 2.5) stirring to dissolve to obtain a precipitant aqueous solution, and testingThe pH value is 12.8;

(3) heating the precipitant aqueous solution to 85 ℃, heating the metal salt aqueous solution to 87 ℃ through a coil pipe preheater, and adding the metal salt aqueous solution into the precipitant aqueous solution which is stirred violently within 15min to carry out and complete the coprecipitation reaction; monitoring the temperature of the coprecipitation reaction to be 83 ℃ on line, wherein the pH value of the slurry of the coprecipitation product is 7.8;

(4) and standing the coprecipitation product slurry at 45 ℃ for 5min, transferring the coprecipitation product slurry to a suction filtration device for suction filtration, and washing a filter cake with water after filtrate is discarded. Repeatedly washing until the conductivity of the final filtrate is below 1.2ms/cm to obtain a precipitate filter cake a with the solid content of 35 wt%;

(5) the precipitated cake a was filtered as precipitated cake a: the mass ratio of water is 3.5: 1 Water was added and mixed to give a slurry, and 2.15kg of a potassium-containing silica sol (modulus 0.7, potassium content 35.28% by weight, SiO) was added₂25.24 wt%) and potassium carbonate (fine chemicals in the modern oriental of beijing) (the weight ratio of silica sol to potassium carbonate is 15: 1) mixing and pulping for 25 min; then 12kg of dilute nitric acid with the concentration of 15.0 weight percent is added to obtain slurry II with the pH value of 7; standing the slurry II at 45 ℃ for 80min, and then performing suction filtration again to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring (385rpm, 25min) to obtain catalyst slurry III with the solid content of about 24 wt%;

The catalyst is subjected to component analysis, and Fe, Cu, K, Co, Mn and SiO₂The weight ratio of (1) to (4.3: 5.0:0.4:6.8: 25.0).

The pore structure distribution of the catalyst measured by low-temperature nitrogen adsorption method is shown in figure 3.

TABLE 1

Note: and (3) small holes: the diameter of the hole is less than 12 nm; mesopore: the diameter of the pores is 12-80 nm.

The attrition index was determined using fresh catalyst as a sample, and the test samples selected for each example and comparative example were prepared using particles of similar size, as shown in table 2.

From the above examples and comparative examples, and the data in table 1, it can be seen that the precipitated iron-based fischer-tropsch catalyst provided by the present invention has a specific pore structure, for example, the pore structure distribution of the catalyst obtained in example 1 shown in fig. 2 shows two distinct peaks corresponding to regions of different pore diameters. The data in table 1 shows the respective ratios of pore volumes for the two pore diameter regions, and it can be seen that the ratio of small pores is low and the ratio of medium pores is high. Meanwhile, the morphology sphericity and the surface gloss of the catalyst shown in FIG. 1 are good. The catalyst provided by the invention has improved attrition properties, and an attrition index of less than 4.0% as determined by ASTM D5757-00 air sparging.

In the method for preparing the precipitated iron-based catalyst for fischer-tropsch synthesis according to the present invention, the conductivity of water used in comparative example 1 was higher than 60 μ s/cm, and the obtained catalyst had a pore structure in which the small pore ratio was higher than 35% and the medium pore ratio was less than 65%, and thus had a high attrition index and a poor attrition resistance. In comparative example 2 in which the coprecipitation product slurry was not cooled and diluted by adding ice, the pore structure of the resulting catalyst was as shown in fig. 3, and the total pore volume was significantly smaller in combination with the data shown in table 1, and the small pore ratio was 51.1% and the medium pore ratio was 48.9%, which were different from examples 1 to 6, and the abrasion resistance was poor.

Evaluation example 1

This evaluation example illustrates the use of the catalyst of example 1 according to the invention for a slurry bed Fischer-Tropsch synthesis reaction.

The evaluation apparatus was a laboratory 2L slurry bed stirred tank.

The loading of the catalyst is as follows: about 700g of liquid paraffin was used to dilute the precipitated iron-based catalyst for Fischer-Tropsch synthesis prepared in example 1 at a concentration of 20% by weight, and then charged into a slurry-bed stirred tank.

(a) Reduction reaction: with a gas containing CO and H₂Reducing atmosphere (CO and H)₂In a molar ratio of 0.1: 1) carrying out reduction reaction for 24 hours at 270 ℃ and under the pressure of 0.1 MPa;

(b) Fischer-Tropsch synthesis: introduction of synthesis gas (H)₂The mol ratio of the catalyst to CO is 1.9: 1), the space velocity of the synthetic gas is 5.0N L/g-cat h at 260 ℃ and 2.2MPa, and the Fischer-Tropsch synthesis reaction is carried out.

The results of the reaction performance of the catalyst for carrying out the continuous reaction are shown in Table 2.

By observing the obtained catalyst through an SEM electron microscope, the catalyst is less abraded after 1803h of reaction, and the catalyst particles still have good sphericity and surface gloss.

The catalyst is subjected to on-line determination of CO conversion rate and CO in the long-period operation process₂Selective, CH₄The selectivity plot, as shown in FIG. 4, shows that the catalyst has CO conversion and CO conversion in a long reaction period₂Selective, CH₄The selectivity curve is smooth, and the high CO conversion rate and the low CO are still remained after 1803h₂Selectivity and CH₄And (4) selectivity, showing that the catalyst has stable catalytic conversion activity.

Evaluation example 2

The catalyst of example 2 was subjected to a slurry Fischer-Tropsch synthesis reaction in accordance with the procedure of evaluation example 1, except that "the space velocity of synthesis gas" was 8N L/g-cat h "instead of" the space velocity of synthesis gas "being 5.0N L/g-cat h".

Evaluation example 3

This evaluation example illustrates the use of the catalyst of example 3 according to the invention for a slurry bed Fischer-Tropsch synthesis reaction.

The evaluation apparatus was a laboratory 2L slurry bed stirred tank.

The loading of the catalyst is as follows: about 700g of liquid paraffin was used to dilute the precipitated iron-based catalyst for Fischer-Tropsch synthesis prepared in example 3 at a concentration of 10% by weight, and then charged into a slurry-bed stirred tank.

(b) Fischer-Tropsch synthesis: introduction of synthesis gas (H)₂The mol ratio of the catalyst to CO is 1.9: 1), the space velocity of the synthetic gas is 7N L/g-cat h at 260 ℃ and 2.2MPa, and the Fischer-Tropsch synthesis reaction is carried out.

Evaluation examples 4 to 6

The catalysts of examples 4 to 6 were subjected to a slurry bed Fischer-Tropsch synthesis reaction in place of the catalyst of example 3 according to the method of evaluation example 3.

Evaluation examples 7 to 8

The catalyst of comparative examples 1-2 was subjected to a slurry bed Fischer-Tropsch synthesis reaction in place of the catalyst of example 3, in accordance with the method of evaluation example 3.

TABLE 2

Note: d (0.5) is the corresponding particle size when the cumulative percentage of particle size distribution of the fresh catalyst reaches 50%, and is measured by a laser particle sizer.

As can be seen from the above evaluation examples and the results in Table 2, the catalyst of the present invention can be operated for a long period of time while performing a slurry Fischer-Tropsch synthesis reaction, and the reaction performance of the catalyst remains stable. And in the Fischer-Tropsch synthesis reaction result, C₅ ⁺The selectivity is improved to be more than 89.4 percent; whereas comparative examples 1 and 2 only gave a maximum of 85.77%.

In the preparation process of the catalyst of comparative example 1, the metal salt aqueous solution and the precipitant aqueous solution used high conductivity dissolved water, so the pore ratio of the obtained catalyst was significantly increased and the abrasion resistance was poor. The long-term running effect of carrying out the Fischer-Tropsch synthesis reaction is poor.

In the preparation process of the catalyst of the comparative example 2, after the coprecipitation reaction is finished, the slurry of the coprecipitation product is not rapidly cooled and diluted, so that the pore proportion of the obtained catalyst is further increased, and the abrasion resistance is poor. The long-term running effect of carrying out the Fischer-Tropsch synthesis reaction is poor.

Claims

1. The Fischer-Tropsch synthesis precipitated iron-based catalyst comprises the following components in percentage by weight of Fe, Cu, K, Co, Mn and SiO₂100 (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27); the catalyst is subjected to low temperature N₂The pore structure determined by physical adsorption has the following characteristics: in the total pore volume with the pore diameter less than or equal to 80nm, the proportion of small pores with the pore diameter less than 12nm is less than 35 percent; the proportion of mesopores with the pore diameter of 12-80 nm is more than 65%.

2. The catalyst according to claim 1, wherein the proportion of small pores having a pore diameter < 12nm is less than 30% and more than 0% in the total pore volume having a pore diameter of 80nm or less.

3. The catalyst according to claim 1 or 2, wherein a mesopore having a pore diameter of 12 to 80nm accounts for 65% or more and less than 99% of the total pore volume having a pore diameter of 80nm or less.

4. The catalyst of claim 1 or 2, wherein the catalyst has an attrition index of 4.0% or less as measured by ASTM D5757-00 air sparging.

5. The catalyst of claim 3, wherein the catalyst has an attrition index of 4.0% or less as measured by ASTM D5757-00 air sparging.

6. A preparation method of a precipitated iron-based Fischer-Tropsch synthesis catalyst comprises the following steps:

(5) mixing silica sol or potassium silicate, potassium carbonate and water with the precipitation filter cake a, pulping, and adding acid liquor to prepare slurry II with the pH value of below 7; standing the slurry II, and performing suction filtration to obtain a filter cake b; adding water into the filter cake b, and carrying out high-speed shearing stirring to obtain catalyst precursor slurry III with the solid content of 10-50 wt%;

(6) spray drying and calcining the catalyst precursor slurry III;

wherein the addition amount of iron salt, copper salt, cobalt salt, manganese salt, precipitator, potassium carbonate, potassium silicate or silica sol satisfies the condition that Fe, Cu, K, Co, Mn and SiO are added₂The weight ratio of (100), (0.1-6), (0.6-6), (0.01-0.6): (0.01-10) and (5-27).

7. The process of claim 6, wherein the cooling is by adding ice to the co-precipitated product slurry, the weight ratio of ice to co-precipitated product slurry being 1: 1 or less.

8. The method of claim 6, wherein the silicon-containing compound comprises at least one of solid potassium silicate, liquid potassium silicate, silica sol, potassium-containing silica sol, water-soluble silica, and sodium silicate.

9. The method according to claim 6, wherein, in step (2), the aqueous metal salt solution is added to the aqueous precipitant solution within 15 min.

10. The method according to claim 6, wherein in the step (5), the slurry II is allowed to stand at a temperature of 20 to 65 ℃ for 30 to 90 min.

11. The method according to any one of claims 6-10, wherein the electrical conductivity of the water is 35 μ s/cm or less.

12. A precipitated iron-based fischer-tropsch catalyst prepared by the process of any one of claims 6 to 11.

13. Use of a precipitated iron-based fischer-tropsch catalyst of any one of claims 1 to 5 and 12 in a slurry bed reactor for the fischer-tropsch reaction to produce hydrocarbon compounds.

14. A method for preparing hydrocarbon compounds from synthesis gas through a slurry bed Fischer-Tropsch synthesis reaction comprises the following steps:

(a) a precipitated iron-based Fischer-Tropsch catalyst of any one of claims 1 to 5 and 12 in a reducing atmosphere at a temperature of 230 to 320 ℃ and a pressure of 0.1 to 2.8MPa in the presence of a diluting medium₂The molar ratio of the carbon dioxide to CO is (0.2-35): 1, carrying out reduction reaction for 1-48 h to obtain a reduced activated catalyst;

(b) in the presence of the reduced-state activated catalyst, the catalyst will contain CO and H₂The synthesis gas is subjected to Fischer-Tropsch synthesis reaction in a slurry bed reactor under the conditions that the temperature is 210-300 ℃ and the pressure is 1.2-2.8 MPa, so as to obtain hydrocarbon compounds; wherein, H in the synthesis gas₂The molar ratio of the carbon dioxide to CO is (0.5-3.5): 1, and the space velocity of the synthesis gas is 5-16N L/g-cat h.