Multi-metal catalyst as well as preparation method and application thereof

Abstract

The invention provides a multi-metal catalyst as well as a preparation method and application thereof, and belongs to the technical field of metal catalysts. The preparation method of the multi-metal catalyst provided by the invention comprises the following steps: carrying out vacuum degassing on a metal raw material, and then carrying out melt alloying in an inert atmosphere to obtain the multi-metal catalyst, the metal raw materials comprise tin / bismuth and active metal. Metal raw materials are firstly subjected to vacuum degassing, and impurities brought by the raw materials are reduced; and alloying is carried out under the inert atmosphere, oxidation of air to metal can be avoided, the impurity content is reduced, and the yield is increased.

Description

Technical Field

[0001] The invention relates to the technical field of metal catalysts, in particular to a multi-metal catalyst and a preparation method and application thereof. Background Art

[0002] The metal-catalyzed hydrocarbon cracking process is widely used in the fields of hydrogen energy, carbon black, graphite and graphene preparation, mainly including solid metal catalytic cracking and molten metal catalytic cracking. Solid metal catalysts become inactivated due to carbon deposition on the surface during the catalytic cracking process, and the conversion rate and production efficiency are relatively low. They are only widely used in the fields of carbon black and graphene manufacturing. Molten metal catalytic cracking refers to the process of passing hydrocarbon gas into high-temperature molten metal liquid, decomposing it into carbon powder and hydrogen under the catalysis of liquid metal. The carbon powder adheres to the surface of hydrogen bubbles and floats above the metal liquid surface, effectively solving the problem of catalyst carbon deposition failure, while improving the conversion rate and production efficiency. It is an important process route for future research and development in the field of hydrogen and carbon production.

[0003] In order to reduce energy consumption and improve the safety performance of the catalytic process, the molten metal catalytic cracking process often selects low-melting-point metals such as bismuth or tin, but these low-melting-point metals have low catalytic efficiency and conversion rate. In order to improve the catalytic efficiency and conversion rate of molten metals, the current catalyst mainly uses low-melting-point metals such as bismuth or tin as flux, and adds nickel, copper and other materials with high catalytic activity to form binary or multi-component catalysts. At present, the melting points of metals with high catalytic activity in multi-component catalysts such as nickel, copper, cobalt, molybdenum, etc. are very high. In order to completely melt and solid-dissolve metals with high melting points and high catalytic activity into low-melting-point metals, it is necessary to heat at a higher temperature. Since low-melting-point metals such as bismuth or tin are extremely volatile, they cannot be melted in a vacuum state. Non-vacuum melting will cause a large amount of metal oxidation, resulting in low yield and high cost. The obtained catalyst has a high oxygen content and low catalytic efficiency.

[0004] Due to the difficulty in preparing multi-component catalysts, most of the current methods of use are to directly add various pure metals into the catalytic cracking device, heat them at the cracking temperature, melt them, and alloy them before use. However, due to the high melting point of active metals, such as cobalt, which has a melting point of 1495°C, it takes a long time for cobalt to completely melt and dissolve in bismuth or tin flux at a cracking temperature of 900-1100°C, which increases production preparation time and reduces production efficiency; for example, the melting point of molybdenum is 2620°C, and it is difficult for molybdenum to completely melt and dissolve in bismuth or tin flux at a cracking temperature of 900-1100°C, and the best catalytic effect cannot be achieved. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-metal catalyst and its preparation method and application. The preparation method of the multi-metal catalyst provided by the present invention has a high yield rate, and the prepared multi-metal catalyst has few impurities and high catalytic efficiency.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The invention provides a method for preparing a multi-metal catalyst, comprising: vacuum degassing metal raw materials, and then melting and alloying them in an inert atmosphere to obtain the multi-metal catalyst; the metal raw materials include tin / bismuth and active metals.

[0008] Preferably, the pressure of the vacuum degassing is less than 1 Pa, the temperature of the vacuum degassing is 150-200° C., and the insulation time of the vacuum degassing is 1-3 h.

[0009] Preferably, the pressure of the inert atmosphere is 110-130 KPa.

[0010] Preferably, the melt alloying comprises an alloying stage and a deoxidation and desulfurization stage which are performed sequentially.

[0011] Preferably, in the deoxidation and desulfurization stage, 0.005-0.015% by mass of metallic calcium is added to the metal raw material.

[0012] Preferably, based on 100% by mass of the metal raw material, the active metals include: Ni 7-9%, Co 1.5-2.5%, Cu 14-17% and Mo 0.5-1.5%.

[0013] Preferably, the temperature of the melt alloying is 1200-1300°C.

[0014] The present invention also provides a multi-metal catalyst prepared by the preparation method described in the above technical solution. In terms of mass percentage, O≤0.005% and S≤0.001% in the multi-metal catalyst.

[0015] Preferably, the multi-metal catalyst comprises, by mass percentage, 7-9% Ni, 1.5-2.5% Co, 14-17% Cu, 0.5-1.5% Mo, ≤0.005% O, ≤0.001% S and the balance Bi / Sn.

[0016] The present invention also provides the use of the multi-metal catalyst described in the above technical solution in catalytic cracking of hydrocarbons.

[0017] The present invention provides a method for preparing a multi-metal catalyst, comprising: vacuum degassing a metal raw material, and then melting and alloying it in an inert atmosphere to obtain a multi-metal catalyst; the metal raw material comprises tin / bismuth and an active metal. The present invention first vacuum degasses the metal raw material to reduce impurities brought by the raw material; alloying is performed in an inert atmosphere to avoid oxidation of the metal by air, reduce the impurity content, and improve the yield rate. The results of the embodiment show that the yield rate of the multi-metal catalyst prepared according to the preparation method provided by the present invention reaches 97.3-97.6%; the oxygen content of the prepared multi-metal catalyst is 0.0021-0.0023%, the sulfur content is 0.0003-0.0005%, and the catalytic hydrocarbon cracking rate reaches 95.80-96.73%. DETAILED DESCRIPTION

[0018] All raw materials of the present invention have no particular limitation on their sources and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0019] The invention provides a method for preparing a multi-metal catalyst, comprising: vacuum degassing metal raw materials, and then melting and alloying them in an inert atmosphere to obtain the multi-metal catalyst; the metal raw materials include tin / bismuth and active metals.

[0020] In the present invention, the preparation of the multi-metal catalyst is preferably carried out in a sealable pressure vessel, preferably a vacuum melting furnace.

[0021] In the present invention, the tin / bismuth is preferably a high-purity tin block or a high-purity bismuth block.

[0022] In the present invention, based on the mass of the metal raw material being 100%, the active metal preferably includes Ni7-9%; the Ni is preferably an electrolytic nickel plate. The active metal preferably includes Co 1.5-2.5%; the Co is preferably an electrolytic cobalt plate. The active metal preferably includes Cu 14-17%; the Cu is preferably an electrolytic copper plate. The active metal preferably includes Mo 0.5-1.5%; the Mo is preferably a high-purity molybdenum block.

[0023] In the present invention, the metal raw material is preferably first shot blasted or polished to remove oxidation and slag inclusions on the metal surface. The present invention has no special requirements for the shot blasting and polishing methods, as long as the oxidation and slag inclusions on the metal surface can be removed.

[0024] In the present invention, the pressure of the vacuum degassing is preferably less than 1 Pa, the temperature of the vacuum degassing is preferably 150-200°C, the heating rate is preferably 40-60°C / h; the holding time of the vacuum degassing is preferably 1-3h. The present invention removes the gas adsorbed on the metal surface through vacuum degassing to improve the purity of the metal.

[0025] In the present invention, the inert atmosphere is preferably an argon atmosphere; the pressure of the inert atmosphere is preferably 110-130 KPa. The present invention performs melting alloying in a slightly positive pressure argon atmosphere, which can avoid the volatilization of low melting point metal tin or bismuth during vacuum melting, and can also avoid metal oxidation caused by non-vacuum melting; at the same time, the slightly positive pressure has little effect on the melting point of the metal, and the slightly positive pressure is also convenient for operation.

[0026] In the present invention, the temperature of the melt alloying is preferably 1200-1300° C. The higher the temperature of the melt alloying, the shorter the melt alloying time and the higher the energy consumption. The present invention limits the temperature of the melt alloying to the above range, which can take into account both production efficiency and energy consumption.

[0027] In the present invention, the melt alloying is preferably carried out under stirring conditions, and the stirring rate is preferably 10 to 30 r / min.

[0028] In the present invention, the melt alloying includes an alloying stage and a deoxidation and desulfurization stage performed in sequence. In the present invention, the holding time of the alloying stage is preferably 20 to 40 minutes. When the alloying holding time is within the above range, each metal raw material can be completely melted and the solid solution can be uniform.

[0029] In the present invention, the metal calcium with a mass fraction of 0.005-0.015% of the metal raw material is preferably added in the deoxidation and desulfurization stage. Calcium can react with oxygen in the molten metal to form calcium oxide, and react with sulfur to form calcium sulfide. Calcium oxide and calcium sulfide aggregate and float up to achieve deoxidation and desulfurization, further reduce the impurity content, and improve the yield rate and catalytic efficiency. In the present invention, the insulation time of the deoxidation and desulfurization stage is preferably 20-40 minutes. The insulation time of deoxidation and desulfurization is within the above range, which can effectively remove oxygen and sulfur in the molten metal.

[0030] After the melt alloying is completed, the present invention preferably casts the obtained molten metal to obtain the multi-metal catalyst. In the present invention, the casting is preferably performed under an argon atmosphere.

[0031] The present invention firstly performs vacuum degassing on the metal raw material to reduce impurities brought by the raw material; and performs alloying in an inert atmosphere to avoid oxidation of the metal by air, reduce the impurity content and improve the yield rate.

[0032] The present invention also provides a multi-metal catalyst prepared by the preparation method described in the above technical solution. In the invention, in terms of mass percentage, O≤0.005% and S≤0.001% in the multi-metal catalyst.

[0033] In the present invention, the Ni content in the multi-metal catalyst is preferably 7-9% by mass. In embodiments of the present invention, the Ni content may be 7%, 7.5%, 8%, 8.5%, or 9%; the Co content in the multi-metal catalyst is preferably 1.5-2.5%. In embodiments of the present invention, the Co content may be 1.5%, 1.8%, 2%, 2.2%, or 2.5%; the Cu content in the multi-metal catalyst is preferably 14-17%. In embodiments of the present invention, the Cu content may be 14%, 15%, 16%, or 17%; the Mo content in the multi-metal catalyst is preferably 0.5-1.5%. In embodiments of the present invention, the Mo content may be 0.5%, 0.7%, 0.8%, 1%, 1.2%, or 1.5%; the multi-metal catalyst preferably also includes a balance of Bi or Sn. The present invention limits the composition and dosage of the multi-metal catalyst within the above range, uses low-melting-point Bi or Sn as a flux, and cooperates with high-melting-point Ni, Co, Cu, and Mo metals to make the melting point of the multi-metal catalyst between 750 and 950°C, and can be completely melted at the temperature for cracking hydrocarbons; in addition, Ni, Co, Cu, and Mo metals have relatively high catalytic activity, and the present invention limits their dosage within the above range to improve the catalytic activity of the multi-metal catalyst.

[0034] The present invention also provides the use of the multi-metal catalyst described in the above technical solution in catalytic cracking of hydrocarbons.

[0035] In the present invention, the application method is preferably to place the multi-metal catalyst in a hydrocarbon catalytic cracking reactor, heat it to the catalytic cracking temperature, and introduce hydrocarbons after the multi-metal catalyst is completely melted to start the catalytic cracking reaction.

[0036] In an embodiment of the present invention, the hydrocarbon is preferably methane or ethane; and the temperature of the catalytic cracking is preferably 1050°C.

[0037] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] A bismuth-based multi-metal catalyst, the alloy composition is 8% Ni, 2% Co, 15% Cu, 1% Mo, 0.0023% O, 0.0003% S and the balance Bi, the preparation method is as follows:

[0040] 1) Raw material preparation: grinding to remove the oxidation and slag inclusions on the surface of the raw material bismuth block, electrolytic nickel plate, electrolytic cobalt plate, electrolytic copper plate, metal molybdenum, and metal calcium, weighing each metal raw material according to mass percentage, weighing a total mass of 100 kg, and the amount of metal calcium added is 10 g;

[0041] 2) Raw material charging: the raw materials bismuth block, electrolytic nickel plate, electrolytic cobalt plate, electrolytic copper plate and metal molybdenum are loaded into the crucible of the vacuum melting furnace, wherein the electrolytic nickel plate, electrolytic cobalt plate and metal molybdenum are loaded in the middle and upper part of the crucible;

[0042] 3) Vacuum degassing: After the pressure in the vacuum melting furnace is pumped down to below 1Pa, power is supplied to raise the temperature to 200℃ at a heating rate of 50℃ / h and keep warm for 2h. During the degassing stage, the pressure in the furnace is always kept below 1Pa;

[0043] 4) Alloying, deoxidation and desulfurization: After degassing, close all vacuum gauge valves, open the pressure reducing valve, set the pressure reducing valve to 1.1 standard atmospheres, fill the furnace with argon to 1.1 standard atmospheres, heat to 1300°C to melt the metals in the crucible and start stirring at a stirring rate of 20r / min. After alloying at 1300°C for 0.5 hour, add metallic calcium. After the metallic calcium is completely melted, cast it after alloying at 1300°C for 0.5 hour to obtain a multi-metal catalyst ingot.

[0044] 5) Weighing: The weight of the ingot is 97.3 kg, and the calculated yield is 97.3%.

[0045] Sampling and testing: an oxygen-nitrogen combined tester was used to test the oxygen content of the multi-metal catalyst, and the result was 0.0023%. A carbon-sulfur tester was used to test the sulfur content of the multi-metal catalyst, and the result was 0.0003%.

[0046] Application test: 15 kg of multi-metal catalyst was added into the reactor of the cracking device, and heated to 1050°C at a heating rate of 250°C / h. The multi-metal catalyst was completely melted and dissolved evenly. At this temperature, methane was introduced at a rate of 3.6 L / h to start catalytic cracking of methane. After 72 hours of reaction, 44.5 g of hydrogen and 133.5 g of carbon powder were obtained, with a cracking rate of 95.80%.

[0047] Cracking rate = (hydrogen production + carbon powder production) / hydrocarbon addition amount = (44.5 + 133.5) / (3.6L / h*72h*0.717g / L) = 178 / 185.8 = 95.80%.

[0048] Example 2

[0049] A tin-based multi-metal catalyst, the alloy composition is 8% Ni, 2% Co, 15% Cu, 1% Mo, 0.0021% O, 0.0005% S and the balance Sn, the preparation method is as follows:

[0050] 1) Raw material preparation: polish and remove the oxidation and slag on the surface of raw material tin block, electrolytic nickel plate, electrolytic cobalt plate, electrolytic copper plate, metal molybdenum, and metal calcium, weigh each metal raw material according to mass percentage, weigh the total mass of 100kg, and the amount of metal calcium added is 10g;

[0051] 2) Raw material charging: the raw materials tin block, electrolytic nickel plate, electrolytic cobalt plate, electrolytic copper plate and metal molybdenum are loaded into the crucible of the vacuum melting furnace, wherein the electrolytic nickel plate, electrolytic cobalt plate and metal molybdenum are loaded in the middle and upper part of the crucible;

[0052] 3) Vacuum degassing: After the pressure in the vacuum melting furnace is pumped down to below 1Pa, power is supplied to raise the temperature to 200℃ at a heating rate of 50℃ / h and keep warm for 2h. During the degassing stage, the pressure in the furnace is always kept below 1Pa;

[0053] 4) Alloying, deoxidation and desulfurization: After degassing, close all vacuum gauge valves, open the pressure reducing valve, set the pressure reducing valve to 1.1 standard atmospheres, fill the furnace with argon to 1.1 standard atmospheres, heat to 1200°C to melt the metals in the crucible and start stirring at a stirring rate of 20r / min. After alloying at 1200°C for 0.5 hour, add metallic calcium. After the metallic calcium is completely melted, cast it after alloying at 1200°C for 0.5 hour to obtain a multi-metal catalyst ingot.

[0054] 5) Weighing: The weight of the ingot is 97.6 kg, and the calculated yield is 97.6%.

[0055] Sampling and testing: The oxygen content of the multi-metal catalyst was tested using an oxygen-nitrogen combined tester, and the result was 0.0021%. The sulfur content of the multi-metal catalyst was tested using a carbon-sulfur tester, and the result was 0.0005%.

[0056] Application test: 20 kg of multi-metal catalyst was added into the reactor of the cracking device, and heated to 1050°C at a heating rate of 250°C / h, and the multi-metal catalyst was completely melted and dissolved evenly; ethane was catalytically cracked at this temperature, and the catalytic cracking parameters were the same as those in Example 1. After the reaction, 68 g of hydrogen and 272 g of carbon powder were obtained, and the cracking rate was 96.73%.

[0057] Comparative Example 1

[0058] According to the metal content of the multi-metal catalyst in Example 1, weigh bismuth block, electrolytic nickel plate, electrolytic cobalt plate, electrolytic copper plate, and metal molybdenum, a total of 15 kg, and directly add the raw materials into the reaction kettle of the cracking device for use. When heated to 1050°C at a heating rate of 250°C / h, the bismuth block has completely melted, and the nickel plate, cobalt plate and copper plate can be completely melted and dissolved uniformly after one hour of heat preservation, but the metal molybdenum has not melted; after bismuth, nickel, cobalt and copper are completely melted and dissolved uniformly, but molybdenum has not melted, methane catalytic cracking (the same as Example 1) is carried out, and 42.25g of hydrogen and 126.75g of carbon powder are obtained after the reaction is completed, and the cracking rate is 90.96%. After the reaction is completed, the molybdenum in the multi-metal catalyst is still not completely melted.

[0059] Comparative Example 2

[0060] According to the metal content of the multi-metal catalyst in Example 2, weigh the tin block, electrolytic nickel plate, electrolytic cobalt plate, electrolytic copper plate, and metal molybdenum, the total weight of the raw materials is 100kg, add them into a non-vacuum melting furnace, directly heat to 1200℃, alloy at this temperature for 1 hour and then cast, weigh the ingot weight is 85.3kg. The yield rate of this preparation method is only 85.3%; the multi-metal catalyst prepared by this preparation method is tested by oxygen-nitrogen joint tester and carbon-sulfur tester, the oxygen content is 0.0236%, and the sulfur content is 0.0013%. The multi-metal catalyst obtained by this preparation method is completely melted and solid-dissolved uniformly at a catalytic temperature of 1050℃, but catalytically cracks ethane (the same as Example 2), and obtains 59.6g of hydrogen and 238.4g of carbon powder after cracking, and the cracking rate is only 84.78%.

[0061] It can be seen from the above embodiments and comparative examples that the preparation method provided by the present invention is used to prepare a multi-metal catalyst with few impurities and a high yield, and the obtained multi-metal catalyst has a low melting point and can be completely melted at the catalytic cracking temperature of hydrocarbons, with a high catalytic efficiency, which is conducive to the application of the multi-metal catalyst in the catalytic cracking of hydrocarbons.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a multi-metal catalyst, characterized in that: include: The metal raw materials are vacuum degassed and then melted and alloyed in an inert atmosphere to obtain a multi-metal catalyst; the metal raw materials include tin / bismuth and an active metal.

2. The preparation method according to claim 1, characterized in that: The pressure of the vacuum degassing is less than 1 Pa, the temperature of the vacuum degassing is 150-200° C., and the insulation time of the vacuum degassing is 1-3 hours.

3. The preparation method according to claim 1, characterized in that: The pressure of the inert atmosphere is 110-130 KPa.

4. The preparation method according to claim 1, characterized in that: The melt alloying includes an alloying stage and a deoxidation and desulfurization stage which are performed sequentially.

5. The preparation method according to claim 4, characterized in that: In the deoxidation and desulfurization stage, 0.005-0.015% of metallic calcium is added into the metal raw material by mass.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Based on 100% of the mass of the metal raw material, the active metals include: Ni 7-9%, Co 1.5-2.5%, Cu 14-17% and Mo 0.5-1.5%.

7. The preparation method according to claim 6, characterized in that: The temperature of the melt alloying is 1200-1300°C.

8. The multi-metal catalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that: In terms of mass percentage, in the multi-metal catalyst, O≤0.005%, S≤0.001%.

9. The multi-metal catalyst according to claim 8, characterized in that Calculated by mass percentage, the components of the multi-metal catalyst are: Ni 7-9%, Co 1.5-2.5%, Cu 14-17%, Mo 0.5-1.5%, O≤0.005%, S≤0.001% and the balance Bi / Sn.

10. Use of the multi-metal catalyst according to claim 8 or 9 in catalytic cracking of hydrocarbons.