CN114804023A - Preparation method and application of metal-molten salt for hydrogen production from natural gas and carbon black - Google Patents

Abstract

The invention discloses a preparation method and application of metal-molten salt for hydrogen production from natural gas and carbon black, and belongs to the technical field of methane cracking. The catalyst provided by the invention takes solid active metal porous nickel as an active non-supported catalyst, and the melting environment provided by the fused salt sodium chloride can enable the generated carbon product to float on the surface of the fused salt and can effectively reduce impurities in the carbon product through water washing, acid washing and other modes, so as to obtain the carbon black product with the purity of up to 99 percent, solve the problems that the carbon product is difficult to separate and the carbon product has low purity, and the used fused salt can be recycled and has good catalytic performance on high-temperature methane cracking. The hydrogen conversion rate can reach more than 48% when the reaction temperature is 1000 ℃, and the obtained carbon product is carbon black with the purity as high as 99%.

Description

Preparation method and use of metal-molten salt for hydrogen production from natural gas and carbon black

technical field

The invention belongs to the technical field of hydrogen production by methane cracking and high-value carbon, in particular to a metal-molten salt preparation method and application for producing hydrogen from natural gas and carbon black.

Background technique

With the rapid development of the global economy, the massive consumption of fossil fuel resources leads to a large amount of greenhouse gas emissions and global warming. Without effective action, more serious environmental and ecological problems such as freshwater depletion, ocean acidification, sea level rise and species extinction will gradually emerge. Vigorously developing clean energy and renewable energy can alleviate the high dependence of current social development on fossil energy. As a high-quality clean and renewable energy, hydrogen has the advantages of wide sources, high energy density, high combustion calorific value, easy storage, and zero carbon emissions, and has been highly valued. At present, industrial hydrogen production mainly includes coal gasification hydrogen production, water electrolysis hydrogen production, alcohol hydrogen production and natural gas hydrogen production. Among them, although water electrolysis does not emit _CO2 , its energy consumption and cost are high; methane steam reforming in natural gas hydrogen production is currently the largest and most economical way of hydrogen production in the world, but a large amount of CO is generated in the process. , CO ₂ by-products. Therefore, methane cracking to produce hydrogen has entered people's field of vision as a low-carbon emission and low-cost advanced hydrogen production technology.

Methane cracking to produce hydrogen is a mild endothermic reaction with low energy consumption. The process not only has no CO _{x by} -products, which simplifies the reaction process, and can generate carbon products with certain application value, such as carbon black, carbon nanotubes, carbon nanometers Fiber and other materials, have a wide range of application prospects.

Hydrogen production from methane cracking is a step-by-step dehydrogenation process. CH ₄ molecule has a highly stable tetrahedral structure, and its CH bond cleavage requires a high activation energy. Therefore, in order to reduce the activation energy, it is necessary to select a suitable catalyst. The molten metal catalyst in methane cracking has an excellent catalytic effect on the direct pyrolysis of methane. The disadvantage is that the carbon generated by the pyrolysis in the molten reaction system will float on the surface of the molten metal, and the metal impurities contained are extremely high. In order to obtain high economic value The separation of molten metal impurities in the product carbon is a difficult problem, and the impurities in the product carbon are more difficult to remove. The solid active metal porous nickel is an active unsupported nickel-based catalyst, and the molten salt sodium chloride is a solid-liquid system. The modified solid porous nickel in the molten sodium chloride environment provides high catalytic activity and the generated carbon The product floats on the surface of molten salt and can effectively reduce impurities in carbon products through water washing, pickling, etc., and obtain high-purity carbon black products, which solves the problem of difficult separation of carbon products and low purity of carbon products. Recycle and reuse.

SUMMARY OF THE INVENTION

In order to solve the above problems, the purpose of the present invention is to develop an easily separable solid metal-molten salt material, which catalyzes the direct cracking of methane at a temperature of 1000 ° C, and the solid active metal porous nickel is an active non-supported nickel-based catalyst, molten salt sodium chloride. For a solid-liquid system, the modified solid porous nickel in the molten sodium chloride environment provides high catalytic activity and the generated carbon products float on the surface of the molten salt and can effectively reduce carbon by washing with water, pickling, etc. The impurities in the product can be obtained as a high-purity carbon black product, which solves the problems of difficult separation of carbon products and low purity of carbon products, and the molten salt used can be recycled and reused, further reducing production costs.

In order to solve the above-mentioned technical problems, the present invention adopts the following scheme:

A metal-molten salt preparation method and application for producing hydrogen from natural gas and carbon black, the metal-molten salt is composed of solid active catalyst porous nickel and molten sodium chloride, and the solid-liquid system makes the obtained carbon black product Floating on the surface of molten salt, it is easy to separate, and the impurity content is extremely low, and the purity is as high as 99%. The weight of each component is: porous nickel 6, sodium chloride 145;

The present invention also provides a metal-molten salt preparation method for producing hydrogen from natural gas and carbon black, comprising the following steps:

(1) Acid and thermal pretreatment are performed on porous nickel;

(2) Mixing the treated porous nickel and molten salt uniformly, heating to a certain temperature, the sodium chloride becomes molten state, and more

The empty nickel remains solid, and a solid-liquid system is formed, that is, a methane cracking catalyst is obtained.

Further, the process of processing porous nickel includes:

(1) put porous nickel into crucible, put into muffle furnace and heat, then drop the temperature in nitrogen atmosphere;

(2) Put the porous nickel into the medium sonicator filled with acetone, and then put it into the solution prepared by HCl and deionized water for sonication.

Then, rinse with deionized water and anhydrous ethanol alternately, and put it in an oven to dry before use.

Further, the porous nickel in the step (1) is 2 pieces of cylinders with a diameter of 25cm and a height of 5cm, and there are circular holes with a diameter of 7cm in the middle of the cylinders, and the parts by weight are 6.

Further, the roasting conditions in the (1) step are: 10mL/min of air and 200mL/min nitrogen gas mixture, the roasting temperature is 800°C, and the heating rate is 5°C/min, until heated to 800°C and kept for 30min

Further, in the step (2), the ratio of HCl and deionized aqueous solution is 1:3.

Further, the process in which the metal-molten salt is used to directly catalyze the reaction of methane cracking to produce hydrogen and high-purity carbon black includes:

Put the pretreated porous nickel into the corundum tube of the inner tank, insert the ventilation corundum tube into the small round hole of the porous nickel from top to bottom and keep it stable and not shake, and pour the weighed sodium chloride into the corundum of the inner tank. tube to mix well. Put the inner corundum tube filled with the catalyst into the outer corundum tube, and set up the device for reaction. Further, during the heating process of the heating device, argon gas was continuously introduced, and when the sodium chloride reached a certain temperature, the sodium chloride became a molten state, and the porous nickel remained in a solid state to form a solid-liquid system, that is, a methane cracking catalyst was obtained, and then the air content in the tube was detected, Make sure the air is exhausted before proceeding to the subsequent experimental part. The temperature was kept constant, methane and argon were introduced for reaction, and the hydrogen content in the tube was detected every one hour; the argon was turned off and pure methane was introduced, and the hydrogen content in the tube was detected every one hour. After the reaction is completed, easily separable high-purity carbon black is obtained.

Further, the ventilation conditions in the process were: methane:argon=1:1, temperature 1000°C, methane gas flow rate 36sccm, argon gas flow rate 36sccm, and the reaction was performed for 2h.

Further, the ventilation conditions in the process are: pure methane gas, the temperature is 1000° C., the flow rate of the methane gas is 36 sccm, and the reaction is 2 hours.

Further, the carbon black obtained in the process is easy to separate, the function of the corundum outer tube is to collect the carbon product generated in the inner tube, and the purity of the carbon product is as high as 99% after washing with water and pickling.

After the reaction is completed, wait for the device to cool down, the generated carbon black floats on the surface of the sodium chloride molten salt in the corundum inner bile duct during the reaction process, gradually accumulates on the molten salt surface with the increase of the reaction time, and falls through the corundum tube inner bile. In the outer tube of the corundum tube, after the reaction is completed, the carbon black product obtained after the collected carbon product is washed with water and acid washed has a purity of up to 99%.

The beneficial effects of the present invention are: the molten metal catalyst in the current methane cracking has an excellent catalytic effect on the direct pyrolysis of methane, the disadvantage is that the carbon generated by the pyrolysis in the molten reaction system will float on the surface of the molten metal, and the contained metal impurities are extremely In order to obtain carbon products with high economic value, the separation of molten metal impurities in the product carbon is a difficult problem, and the impurities in the product carbon are more difficult to remove. The catalyst of the invention uses solid active metal porous nickel as an active unsupported nickel-based catalyst, and its porous structure can increase the contact surface area of the introduced methane gas with it, thereby improving the methane conversion rate; the molten environment provided by molten salt sodium chloride can make porous The nickel catalyst will not deactivate the catalyst due to carbon deposition and affect the catalytic activity, and the carbon black generated in the reaction process gradually accumulates on the surface of the molten salt with the increase of the reaction time, and falls into the outer tube of the corundum tube through the inner liner of the corundum tube. After the reaction is completed, the carbon black product obtained after the collected carbon product is washed with water and acid washed has a purity of up to 99%, which solves the problems of difficult separation of the carbon product and low purity of the carbon product, and the used molten salt can be recycled and reused. The method achieves a methane conversion rate of 48% and obtains carbon black products with a purity of up to 99%. Carbon black is one of the indispensable important chemical raw materials in my country's modern economy. It is used in rubber, ink, paint, plastic, synthetic leather, etc. In other fields, carbon black can also be used in dry batteries, electrical appliances, electronic components, high-purity graphite, printing and dyeing, gunpowder, electrostatic toner, etc. In these fields, carbon black also plays a great role. Carbon black is of great significance to the development of the national transportation industry, the realization of agricultural mechanization, and the strengthening of national defense construction. The catalyst in the present invention can obtain high methane conversion rate and high-value carbon, and does not emit CO ₂ . Based on the above, the present invention has a good application prospect.

Description of drawings

Fig. 1 is the Raman spectrogram of the metal-molten salt catalyzed methane cracking of the present invention to generate carbon black material;

2 and 3 are scanning transmission electron microscope images of the metal-molten salt catalyzed methane cracking of the present invention to generate carbon black material;

Fig. 4 is the X-ray powder diffraction spectrogram of the metal-molten salt catalyzed methane cracking of the present invention to generate carbon black material;

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solutions of the present invention are now described in detail below, but should not be construed as limiting the scope of implementation of the present invention

The present embodiment provides a metal-molten salt preparation method for hydrogen production and carbon black from natural gas.

Example 1:

Firstly, 2 pieces of porous nickel with a diameter of 25cm and a height of 5cm and a circular hole of 7cm in the middle, with a weight portion of 6, were put into a crucible, heated in a muffle furnace, and fed with 10mL/min of air and 200mL/min nitrogen mixed gas, heating rate 5°C/min until heated to 800°C, maintained at this temperature for 30min, then cooled under nitrogen atmosphere. Then put the pretreated porous nickel into the corundum liner, make two pieces of porous nickel overlap, insert the ventilated corundum tube into the small round hole of the porous nickel from top to bottom and keep it stable and not shake; weigh 145g of chloride Sodium is added to the corundum liner with the porous nickel placed, and the corundum tube of the inner liner is slightly shaken to fully mix the porous nickel and sodium chloride; the inner liner corundum tube with the catalyst is put into the outer liner corundum tube, and then each part is assembled. The structure is put into the heating equipment for ventilation and heating until the sodium chloride becomes a molten state, forming a solid-liquid system, and the carbon product carbon black floats on the surface of the sodium chloride molten salt in the corundum inner bile duct. The increase of the reaction time gradually accumulates on the surface of the molten salt, and drops to the outer tube of the corundum tube through the inner liner of the corundum tube, and the carbon black is collected, and the purity of the carbon black product obtained after washing with water and pickling is up to 99%;

Example 2:

First, 2 pieces of porous nickel with a diameter of 25cm and a height of 5cm and a circular hole with a diameter of 7cm in the middle, with a weight portion of 6, were put into the medium of acetone and ultrasonicated for 10min, and then put into 10mL of HCl and 30mL of deionization. The solution prepared with water was sonicated for 10 min, then rinsed alternately with deionized water and absolute ethanol, and dried in an oven at 60 °C for 4 h before use. Then put the pretreated porous nickel into the corundum liner, place 2 pieces of porous nickel on top of each other, and insert the ventilation corundum tube into the bottom of the liner corundum tube from top to bottom to keep it stable and not shake; weigh 145g of sodium chloride and add Place the corundum liner with porous nickel, shake the corundum tube of the inner liner slightly to fully mix the porous nickel and sodium chloride; put the corundum tube of the inner liner with the catalyst into the corundum tube of the outer liner, and then assemble the parts. Enter the heating equipment to ventilate and heat up until the sodium chloride becomes a molten state, forming a solid-liquid system, the carbon product carbon black floats on the surface of the sodium chloride molten salt in the corundum inner bile duct, and the carbon black obtained in the reaction process increases with the reaction time. The increase of carbon black gradually accumulates on the surface of the molten salt, drops to the outer tube of the corundum tube through the inner liner of the corundum tube, and collects the carbon black, and then the purity of the carbon black product obtained after washing and pickling is as high as 99%;

Comparative Example 3:

First, two pieces of porous nickel with a diameter of 25cm and a height of 5cm and having a circular hole with a diameter of 7cm in the middle, with a weight part of 6, were subjected to the heat treatment and acid treatment in the above-mentioned Example 1 and Example 2, respectively. Put it into the corundum liner, make two pieces of porous nickel overlap, insert the ventilation corundum tube into the bottom of the inner liner corundum tube from top to bottom to keep it stable and not shake, put the catalyst-filled inner liner corundum tube into the outer liner corundum In the tube, each part is assembled and built into the heating equipment for ventilation and heating. During the catalytic cracking process, the surface of the porous nickel is gradually covered by the generated carbon products, and the catalyst is deactivated due to carbon deposition. When the catalyst is taken out, the generated carbon product is difficult to separate from the catalyst, and the obtained carbon product has a high metal impurity content, which is difficult to remove through water washing, pickling, etc. The obtained carbon product has a purity of only 56% and a methane conversion rate of 38%. ;

Comparative Example 4:

First weigh 145g of sodium chloride and add it to the inner liner of the corundum tube, put the inner liner corundum tube with the catalyst into the outer liner corundum tube, and then assemble and build each part into the heating equipment for ventilation and heating to sodium chloride It becomes a molten state and is a single liquid phase system, and the generated carbon product floats on the surface of the molten salt. After the reaction is completed, the carbon product is taken out and washed with water, pickling, etc. The obtained carbon product has a high purity, but its methane conversion rate is only 25%.

Argon gas was introduced into the equipment during the heating process, and the air in the tube was continuously evacuated to ensure the normal operation of subsequent experiments;

Introduce 1:1 methane and argon to react, react for two hours, and detect the hydrogen content in the tube every one hour;

Pure methane was introduced for the reaction, and the reaction time was two hours, and the hydrogen content in the tube was detected every one hour;

After the reaction, wait for the device to cool down, and take out the obtained carbon product.

Through the Raman spectrum, the graphitization degree of the obtained carbon product can be judged by the ratio of D peak to G peak in Figure 1;

Scanning electron microscope was used to analyze the morphology of carbon black generated by the above catalyst after methane cracking reaction at 1000 °C. As shown in Figures 2 and 3, the carbon particles have a microcrystalline layered structure and a large specific surface area. The particles are fine, there are many carbon particles per unit mass, the carbon particles are aggregated and connected in a spherical shape, there are many faults, and there are many grain boundaries, which is a short-range ordered amorphous carbon, that is, carbon black.

The above sample is analyzed by X-ray powder diffraction, as shown in Figure 4, it is located at 2θ=25°, and the diffraction peak corresponds to the peak position of carbon black;

The catalyst evaluation results show that: under the condition of 1000 ℃, the reaction time is four hours, the methane conversion rate of the catalyst after heat treatment is 48%, and the obtained carbon product is carbon black with a purity of up to 99%.

Table 1 embodiment and comparative example performance comparison

Table 2 embodiment and comparative example performance comparison

From Table 1 is the methane conversion rate measured in Example 1-2 under the same reaction conditions and different reaction times. It can be seen from Table 1 that the use of heat-treated porous nickel and molten salt as catalysts has a higher methane conversion rate, the reason is that the surface morphology, surface nickel grain size and pore structure of porous nickel after heat treatment Change, its surface can be derived from relatively small nickel particles, so the activity has a significant improvement. It can be seen from Table 2 that the obtained carbon products can obtain carbon black products with a purity of up to 99% through different treatment methods.

Claims (9)

1. a metal-molten salt preparation method for hydrogen production from natural gas and carbon black, is characterized in that: (1) Acid and thermal pretreatment are performed on porous nickel; (2) Mixing the treated porous nickel and molten salt uniformly, heating to a certain temperature, the sodium chloride becomes molten state, and the porous nickel remains solid at any time to form a solid-liquid system, that is, a methane cracking catalyst is obtained. 2. the preparation method of a kind of catalyst for methane cracking hydrogen production and high-purity carbon black according to claim 1, is characterized in that, the process of porous nickel pretreatment in described (1) step comprises: (1) put porous nickel into crucible, put into muffle furnace and heat, then drop the temperature in nitrogen atmosphere; (2) Put the porous nickel into the medium sonicated in acetone, then put it into the solution prepared by HCl and deionized water for ultrasonic, then rinse with deionized water and anhydrous ethanol alternately, put it in an oven to dry before use. 3. preparation method according to claim 1, is characterized in that: in described (1) step, porous nickel is 2 pieces of cylinders with diameter 25cm and height 5cm, and there is a circular hole with diameter of 7cm in the middle of the cylinder, and parts by weight are 6 . 4. catalyst pretreatment preparation method according to claim 2, is characterized in that: the roasting condition in described (1) step is: the air of 10mL/min and 200mL/min nitrogen mixed gas, roasting temperature 800 ℃, temperature rises The rate was 5°C/min until heating to 800°C and hold for 30 min. 5 . The preparation method of catalyst pretreatment according to claim 2 , wherein in the step (2), the ratio of HCl and deionized aqueous solution is 1:3. 6 . 6. The metal-molten salt use for hydrogen production from natural gas and carbon black according to claims 1 to 5, wherein the metal-molten salt is used for the reaction of direct catalytic methane cracking for hydrogen production and high-purity carbon black The process includes: putting the pretreated porous nickel into the corundum tube of the inner tank, inserting the ventilating corundum tube into the small round hole of the porous nickel from top to bottom and keeping it stable and not shaking, pouring the weighed sodium chloride Put it into the corundum tube of the inner gallbladder to make it evenly mixed; put the corundum tube of the inner gallbladder filled with the catalyst into the corundum tube of the outer gallbladder, and set up a device for reaction; At a certain temperature, sodium chloride becomes molten, and the long and empty nickel remains solid to form a solid-liquid system, that is, a methane cracking catalyst is obtained, and then the air content in the tube is detected to ensure that the air is exhausted and the subsequent experimental part is carried out; the temperature remains constant. , pass methane and argon to react, and detect the hydrogen content in the tube every one hour; turn off the argon and pass pure methane, and conduct the hydrogen content detection in the tube every one hour; the carbon product carbon black floats in the corundum inner tube of chlorine The surface of sodium molten salt, the carbon black generated in the reaction process gradually accumulates on the surface of the molten salt with the increase of the reaction time, and falls into the outer tube of corundum through the inner tube of corundum. After the reaction is completed, the collected carbon products are washed with water, High-purity carbon black obtained after pickling. 7. purposes according to claim 6, is characterized in that: the ventilation condition in described process is: methane: argon gas=1:1, temperature 1000 ℃, methane gas flow rate 36sccm, argon gas flow rate 36sccm, reaction 2h. 8 . The use according to claim 6 , wherein the ventilation conditions in the process are: pure methane gas, temperature 1000° C., methane gas flow rate 36 sccm, and reaction for 2 h. 9 . 9. purposes according to claim 6 is characterized in that: the carbon black obtained in the described process is easy to separate, the function of the corundum outer tube is to collect the carbon products generated in the inner tube, and the carbon products are washed with water and pickled. Purity up to 99%.

Images