CN107185599A - Synthesis gas fluidization methanation catalyst preparation technology by carrier of spent FCC catalyst - Google Patents

Abstract

The invention provides a synthesis gas fluidized methanation catalyst preparation process using the waste FCC catalyst as a carrier. The waste FCC catalyst of the catalytic cracking unit is pretreated by dilute acid extraction, and the residual solid is washed to neutrality and then dried as a methanation catalyst carrier. ; After removing fine particles less than 10 μm from the methanation catalyst carrier, use the methanation active component and modified component solution to impregnate and calcinate and decompose to obtain a catalyst suitable for syngas fluidized bed methanation.

Description

Preparation of Catalyst for Syngas Fluidization Methanation Using Spent FCC Catalyst as Carrier craft

1. Technical field

The invention provides a synthesis gas fluidized methanation catalyst preparation process using waste FCC catalyst as a carrier, and belongs to the fields of coal chemical industry and environmental protection solid waste treatment.

2. Background technology

Coal is gasified to obtain synthesis gas, and synthesis gas methanation to produce natural gas is an important way to cleanly convert coal, an important means to optimize the energy structure and ensure energy security in my country, and an effective means to alleviate local air pollution , and the coal-to-natural gas has certain competitiveness, which has promoted the vigorous development of the coal-to-natural gas industry.

The feed gas for syngas methanation mainly includes H ₂ , CO, CO ₂ , CH ₄ , H ₂ O, N ₂ and Ar. There are 11 chemical reactions that may occur during the methanation process, among which the main reaction For CO methanation reaction, _CO2 methanation reaction and CO shift reaction, etc.

The CO methanation reaction is CO+3H ₂ =CH ₄ +H ₂ O, the CO ₂ methanation reaction is CO ₂ +4H ₂ =CH ₄ +2H ₂ O, and the CO conversion reaction is CO+H ₂ O=H ₂ +CO _2. CO methanation reaction and CO ₂ methanation reaction are positive reactions that promote the formation of methane. The CO conversion reaction position CO+H ₂ O=H ₂ +CO ₂ is a negative reaction that inhibits methane formation. During the methanation reaction of syngas The removal of generated water is beneficial to improve the conversion rate and selectivity of methanation. In addition, the CO methanation reaction and _CO2 methanation reaction are strong exothermic reactions. Normally, every 1% of CO converted can produce a temperature rise of 74°C, and every 1% of _CO2 converted can produce a temperature rise of 60°C , and the higher the reaction temperature, the lower the CO conversion rate, and the higher the requirement for the methanation catalyst.

Since the discovery of the CO methanation reaction, the methanation reaction has been widely used in the ammonia synthesis industry, trace CO removal, fuel cells, partial coal gas methanation, and synthetic natural gas production. Since the 1940s, people have developed a variety of methanation processes, which can be divided into adiabatic fixed bed, isothermal fixed bed, fluidized bed and liquid phase methanation processes according to the type of reactor.

In the process of adiabatic fixed bed methanation, the adiabatic temperature rise of the direct methanation reaction of syngas, and the outlet temperature of the reactor exceeds 900°C, which has great influence on the selection of materials for reactors, waste heat boilers, steam superheaters, pipelines and high temperature resistance of catalysts. The performance puts forward very high requirements, and at high temperature, methane is prone to cracking reaction and carbon deposition, which increases the pressure drop of the bed and reduces the life of the catalyst. In order to effectively control the temperature rise of the reactor, it is generally realized by diluting the raw material gas. The options include high-proportion circulation of part of the process gas, part of the process gas cycle and a small amount of steam, adding part of steam, etc., to achieve methanation at decreasing temperature The reaction is balanced, and finally synthetic natural gas is obtained through multi-stage methanation. The high proportion circulation of process gas increases compression energy consumption and investment.

Fixed-bed indirect heat exchange isothermal methanation reactor, heat transfer cold pipe is embedded in the catalyst bed, and based on this isothermal methanation reactor, an isothermal fixed-bed methanation process was developed. The isothermal fixed-bed methanation reactor can by-produce steam with the help of the heat released by the methanation reaction. However, due to structural limitations, the size of the equipment is limited.

Compared with fixed-bed reactors, fluidized-bed reactors have greater advantages in mass transfer and heat transfer, and are more suitable for large-scale strong exothermic processes, especially fluidized-bed catalysts are easy to remove, add and recycle, and have the advantages of reaction With the advantages of good effect, simple operation and low operating cost, it is the best reactor for complete methanation of syngas. However, there are still some problems, especially the problems of engineering scale-up, such as serious catalyst entrainment and loss, difficult control of reaction temperature, low device operating pressure, relatively low reaction conversion rate, and large amount of catalyst replacement leading to the need for cheap catalysts, etc.

The slurry bed methanation process is that the mixed gas generated in the slurry bed reactor entrains the catalyst and the liquid phase components are separated by a gas-liquid separator, and the gas phase product is condensed and separated to produce synthetic natural gas, and the liquid phase product and the storage tank The fresh catalyst is mixed and added to the slurry bed methanation reactor to preheat the fresh catalyst. The slurry bed methanation process has good heat transfer performance, easy to realize low temperature operation, high _CH4 selectivity and good flexibility, but due to process liquid isolation, CO conversion rate is low, and catalyst loss is high big.

The fluidized bed and slurry bed methanation process can control the reaction temperature within a reasonable range, make full use of the heat of methanation reaction, improve the conversion rate and selectivity of methanation, and reduce the energy consumption of the process. However, low-cost and high-efficiency synthesis of wear-resistant fluidized methanation catalysts has become the bottleneck and hotspot of fluidized bed and slurry bed methanation processes.

As the hazardous solid waste of refining and chemical enterprises, waste FCC catalyst continues to look for effective comprehensive utilization and treatment technology to solve the urgent need of catalytic cracking process. However, the spent FCC catalyst has a high specific surface area and good fluidized wear resistance, and the main heavy metals that are deactivated and discarded are nickel, iron, vanadium, calcium, magnesium, etc., but these heavy metals are synthesis gas methanation catalysts. How to effectively pretreat spent FCC catalysts as fluidized methanation catalysts, improve performance and reduce costs will be the key to improving the competitiveness of fluidized bed and slurry bed methanation processes, and it is also the key to waste FCC catalysts. An effective way for comprehensive utilization of high added value.

3. Contents of the invention

The purpose of the present invention is exactly to provide the synthetic gas fluidized methanation catalyst preparation technology that takes waste FCC catalyst as carrier in order to overcome the existing deficiencies in the preparation technology of synthetic gas fluidized methanation catalyst, by extracting and pretreating waste FCC catalyst, Reduce the acid value components that are not conducive to methanation, increase the pore size and mesopore distribution of the catalyst carrier, provide an adapted specific surface for the loading and curing of methanation catalytic active components, and make full use of the wear resistance and fluidization of FCC catalysts It provides a low-cost, high-efficiency, anti-wear suitable catalyst for fluidized bed and slurry bed methanation processes.

Technical scheme of the present invention:

The present invention is characterized in that the waste FCC catalyst of the catalytic cracking unit is pretreated by 10%-70% dilute acid extraction, the raffinate solid is washed to neutrality and then dried as a methanation catalyst carrier, and the extracted liquid is graded to recover the inorganic salt; After removing fine particles less than 10 μm from the methanation catalyst carrier, the methanation active component and modified component solution are used for impregnation and calcining decomposition to obtain a catalyst suitable for syngas fluidized bed methanation.

Dilute acid is an acid solution in sulfuric acid, hydrochloric acid, nitric acid, or a mixture of sulfuric acid and hydrochloric acid.

The technical conditions of dilute acid extraction pretreatment are solid-liquid ratio 1:0.8-5.0, temperature 30-180°C, pressure 0.0-2.0Mpa (gauge pressure), and extraction time 0-600 minutes.

The solution impregnation of the methanation active component is equal-volume spray impregnation in a fluidized bed, equal-volume saturated impregnation in a reaction kettle solution or fractional saturated impregnation in a solution.

The methanation active component is one or more mixtures of soluble salts of nickel, iron, molybdenum and tungsten, and the ratio of metal to support in the active component is 1:4-20.

The methanation modification component is one or more mixtures of soluble salts of alkaline earth metals and alkali metals, and the ratio of metal to support in the modification component is 0.1-5:100.

The methanation active component solution and the methanation modification component solution can be mixed together and impregnated on the methanation catalyst carrier, or impregnated on the methanation catalyst carrier separately.

The calcining temperature of the impregnated methanation catalyst is 300--800°C.

The present invention describes the characteristics of the present invention in detail with examples.

5. Specific implementation

Example 1, the waste FCC catalyst of the catalytic cracking unit is passed through 50% dilute sulfuric acid at a solid-to-liquid ratio of 1:2.0, a temperature of 130-135°C, a pressure of 0.001Mpa (gauge pressure), and an extraction time of 60 minutes. Treatment, the residual solid is washed with water until neutral and then dried as a methanation catalyst carrier, and the extracted liquid is graded to recover inorganic salts such as aluminum sulfate, iron sulfate, nickel sulfate, and calcium sulfate; after removing fine particles less than 10 μm from the methanation catalyst carrier, use The methanation active component nickel nitrate and the modified component calcium nitrate solution are mixed together and impregnated by equal volume spraying in a fluidized bed. The ratio of nickel to carrier is 1:10, and the ratio of calcium to carrier is 1:50; The calcination temperature of the catalyst is 500° C., and a heat-resistant, wear-resistant and high-efficiency catalyst suitable for syngas fluidized bed methanation is obtained.

The fluidized bed methanation catalyst has a CO conversion rate of 95% and a selectivity of 90% at 350°C and 2.8 MPa; the utilization rate of the spent FCC catalyst is 75%.

Embodiment 2, the waste FCC catalyst of the catalytic cracking unit is passed through 25% dilute nitric acid at a solid-to-liquid ratio of 1:3.0, a temperature of 60°C, a pressure of 0.03Mpa (gauge pressure), and an extraction time of 10 minutes for extraction pretreatment, The remaining solid is washed with water until neutral and then dried as a methanation catalyst carrier. The extracted liquid is graded to recover inorganic salts such as aluminum nitrate, iron nitrate, nickel nitrate, and calcium nitrate; The active components nickel nitrate and cobalt nitrate and the modified component magnesium nitrate solution are mixed together and impregnated through the equal volume of the reaction kettle solution. The ratio of nickel to carrier is 0.8; 10, the ratio of cobalt to carrier is 0.2:10, and the ratio of magnesium to carrier The ratio is 1:60; the calcination temperature of the methanation catalyst after impregnation is 350°C, and a heat-resistant and wear-resistant high-efficiency catalyst suitable for syngas fluidized bed methanation is obtained.

The fluidized bed methanation catalyst has a CO conversion rate of 85% and a selectivity of 95% at 350°C and 0.1 MPa; the utilization rate of the spent FCC catalyst is 85%.

Example 3, after the waste FCC catalyst of the catalytic cracking unit is removed from the fine particles less than 10 μm, the methanation active components nickel nitrate and cobalt nitrate and the modified component magnesium nitrate solution are mixed together and impregnated with equal volume of the reactor solution , the ratio of nickel to support is 0.8; 10, the ratio of cobalt to support is 0.2:10, and the ratio of magnesium to support is 1:60; the calcination temperature of the impregnated methanation catalyst is 350°C, and the catalyst suitable for syngas fluidized bed methanation is obtained Heat-resistant and wear-resistant high-efficiency catalyst.

The fluidized bed methanation catalyst has a CO conversion rate of 80% and a selectivity of 90% at 350°C and 0.1 MPa; the utilization rate of the spent FCC catalyst is 98%.

The synthesis gas fluidized methanation catalyst preparation process using waste FCC catalyst as a carrier provided by the present invention reduces the acid value components that are not conducive to methanation by extracting and pretreating the waste FCC catalyst, and improves the pore size and methanation of the catalyst carrier. The pore distribution provides a suitable specific surface for the loading and solidification of methanation catalytic active components, and at the same time makes full use of the wear resistance and fluidization performance of FCC catalysts to provide low-cost and high-efficiency resistance to fluidized bed and slurry bed methanation processes. Suitable catalyst for wear, the catalyst wear resistance index is less than 0.3%, and the temperature resistance can reach up to 850°C.

Claims (8)

1. the synthesis gas fluidization methanation catalyst preparation technology by carrier of spent FCC catalyst, its technical characteristic is to urge The discarded FCC catalyst for changing cracking unit extracts pretreatment by 10%-70% diluted acid, and raffinate solid is washed to after neutrality and done It is dry to be used as methanation catalyst carrier, Extract classification recovery inorganic salts；Methanation catalyst carrier removing is less than 10 μm thin After particle, impregnated and calcining and decomposing using methanation activity component and modified component solution, obtain being adapted to synthesis gas fluidisation The catalyst of bed methanation.

2. the synthesis gas fluidization methanation catalyst according to claim 1 using spent FCC catalyst as carrier prepares work Skill, it is characterised in that diluted acid is a kind of acid solution in the mixture of sulfuric acid, hydrochloric acid, nitric acid or sulfuric acid and hydrochloric acid.

3. the synthesis gas fluidization methanation catalyst according to claim 1 using spent FCC catalyst as carrier prepares work Skill, it is characterised in that the process conditions of diluted acid extracting pretreatment are solid-to-liquid ratios 1:0.8-5.0,30-180 DEG C of temperature, pressure 0.0- 2.0Mpa (gauge pressure), extraction times are 0-600 minutes.

4. the synthesis gas fluidization methanation catalyst according to claim 1 using spent FCC catalyst as carrier prepares work Skill, it is characterised in that methanation activity component solution dipping sprays dipping, reactor solution for fluid bed and satisfied in equal volume in equal volume With dipping or solution gradation saturation dipping.

5. the synthesis gas fluidization methanation catalyst according to claim 1 using spent FCC catalyst as carrier prepares work Skill, it is characterised in that methanation activity component is one or more mixtures in nickel, iron, molybdenum, tungsten soluble salt, in active component The ratio of metal and carrier is 1:4-20.

6. the synthesis gas fluidization methanation catalyst according to claim 1 using spent FCC catalyst as carrier prepares work Skill, it is characterised in that methanation modified component is one or more mixtures in the soluble salt of alkaline-earth metal and alkali metal, is changed Property component in metal and carrier ratio be 0.1-5:100.

7. the synthesis gas fluidization methanation catalyst according to claim 1 using spent FCC catalyst as carrier prepares work Skill, it is characterised in that methanation activity component solution and methanation modified component solution may be mixed together and is immersed in methanation In catalyst carrier, it can also be immersed in respectively on methanation catalyst carrier.

8. the synthesis gas fluidization methanation catalyst according to claim 1 using spent FCC catalyst as carrier prepares work Skill, it is characterised in that the calcining heat of methanation catalyst is 300--800 DEG C after dipping.