CN116669847A

CN116669847A - Method for regenerating carbon and reactivating catalyst

Info

Publication number: CN116669847A
Application number: CN202180078067.5A
Authority: CN
Inventors: 莫哈末·安巴尔·雅尔莫; ***·卡西姆; 莫哈末·拉希米·尤索; 万·诺·罗斯拉姆·万·伊萨克; 马斯利·尔万·罗斯里; ***·瓦哈布·***·希萨姆; 马拉顿·纳吉哈·阿布·塔哈里; 萨尔玛·沙米丁
Original assignee: UNIVERSITI KEBANGSAAN MALAYSIA
Current assignee: UNIVERSITI KEBANGSAAN MALAYSIA
Priority date: 2020-11-19
Filing date: 2021-11-18
Publication date: 2023-08-29
Also published as: WO2022108440A8; AU2021381240A1; WO2022108440A1

Abstract

The invention relates to a method (10) for regenerating carbon and reactivating a catalyst in a catalytic reaction, i.e. for preparing the catalyst and for distributing the prepared catalyst into at least one reactor (11); activating the catalyst with carbon monoxide; injecting additional carbon monoxide to effect a first carbon production (13) and simultaneously forming a reduction catalyst; injecting steam to decompose the reduction catalyst to regenerate carbon (14) in the second carbon production; wherein in a first carbon production the catalyst converts carbon monoxide to carbon and carbon dioxide, and in a second carbon production the reduction catalyst interacts with steam to form metal oxides, hydrogen and carbon, the hydrogen being used to regenerate the carbon and reactivate the catalyst for continuous recycling of carbon formation in the reactor (15).

Description

Method for regenerating carbon and reactivating catalyst

Technical Field

The present invention relates to a method for regenerating carbon and reactivating a catalyst in a reactor.

Background

As research materials and for large-scale industrial applications, there is a great demand for high quality carbon products. Several production methods have been developed, such as arc discharge and oven laser evaporation. Both of these techniques are advantageous for producing high quality carbon tubes, but at the same time, these methods produce relatively large amounts of impurities. Furthermore, the operating temperature is very high, about 3000 ℃; this is neither economical nor convenient. Both of these methods require a large amount of energy to produce the carbon tube. Both methods require solid graphite/carbon as a target and be hit by a pulsed laser or as an anode, which must be evaporated to obtain nanotubes. It is difficult to obtain a large amount of graphite, which is one of the limitations of mass production.

Previous studies have generally used transition metals from organic metallocenes (e.g., ferrocene, cobaltocene, nickel-dicyclopentadienyl), particularly for the growth of Carbon Nanotubes (CNT). In most studies, they utilized iron pentacarbonyl (Fe (CO) ₅ ) As catalyst, carbon monoxide (CO) is used as a carbon source. Other carbon sources include methane (CH) ₄ ) Ethylene (C) ₂ H ₄ ) Acetylene (C) ₂ H ₂ ) Plastics, biomass, hydrocarbons. There have been some studies reporting the use of hydrogen (H ₂ ) To increase the yield of carbon.

The catalyst is a substance added to the reaction to increase the reaction rate by providing an alternative reaction path with a lower activation energy (Ea). However, the trip to find the best catalyst has not yet ended, and therefore, finding the best catalyst that can effectively reduce the use of energy, cost and time is a challenge for chemists.

One of the prior art for producing carbon, US1974744, discloses the use of a catalyst produced from a combination of a metal and a metal oxide, and CO as a carbon source to produce carbon black, EP0062912A1 discloses a process for producing carbon by injecting steam into a reactor to convert carbon monoxide to carbon and hydrogen in a catalytic process. While the presence of the above-described prior art catalyst can reduce the energy involved in the reaction, it is desirable to find alternative alternatives to reduce the energy required to produce carbon while maintaining efficiency and the quality of the carbon produced in a less costly and time-efficient manner. Also, it is one of the problems to be solved to find an effective catalyst that can selectively promote carbon production without damaging the final product.

Thus, there remains a need for improved catalysts to demonstrate better carbon production processes with better quality and efficiency.

Disclosure of Invention

Accordingly, the present invention relates to a method for regenerating carbon and reactivating a catalyst in a catalytic reaction, the method comprising the steps of: preparing a catalyst and distributing the prepared catalyst into at least one reactor; activating the catalyst with carbon monoxide at 300 ℃ to 900 ℃ to produce an activated catalyst; injecting additional carbon monoxide for at least 1h to effect a first carbon production while forming a reduction catalyst; injecting steam to decompose the reduction catalyst to regenerate carbon in the second carbon production; wherein in a first carbon production the catalyst converts carbon monoxide to carbon and carbon dioxide, and in a second carbon production the reduction catalyst interacts with steam to form metal oxides, hydrogen and carbon, the hydrogen being used to regenerate the carbon and reactivate the catalyst for continuous recycling of carbon formation in the reactor.

The advantages and elements of the invention will be apparent from the description of the preferred embodiment, which illustrates the principles of the invention.

Drawings

Fig. 1 shows an outline of a method of regenerating carbon and reactivating a catalyst in a reactor.

Fig. 2 shows an outline of the preparation of the catalyst.

Fig. 3 shows a schematic diagram of a Micromeritic Autochem 2920 chemisorption analyzer.

Figure 4 shows an embodiment of the invention in which the gas will flow in from the top of the column of the reactor.

Fig. 5 shows a schematic diagram explaining the general outline of an experimental design for producing carbon using carbon monoxide as a carbon source.

FIG. 6 shows iron oxide (Fe ₂ O ₃ ) By (a) 10% CO/N ₂ 、(b)20％CO/N ₂ 、(c)40％CO/N ₂ And (d) 60% CO/N ₂ Temperature Programmed Reduction (TPR) curve.

FIG. 7 shows CO stream flow versus Fe passage ₂ O ₃ The catalyst forms the influence of carbon.

Figure 8 shows the effect of promoter loading on iron oxide on carbon production at 1h exposure.

Fig. 9 shows the screening of various promoter oxides as catalysts for carbon production.

FIG. 10 shows the reaction temperature vs. the temperature of the reaction mixture passing 10% Co/Fe ₂ O ₃ And 10% Ni/Fe ₂ O ₃ The effect of carbon formation.

FIG. 11 shows exposure times (1, 2 and 6 h) versus Fe ₂ O ₃ 、10％Ni/Fe ₂ O ₃ And 10% Co/Fe ₂ O ₃ Influence of carbon yield of the catalyst.

FIG. 12 shows Fe before and after carbonization for 1h ₂ O ₃ 、10％Co/Fe ₂ O ₃ And 10% Ni/Fe ₂ O ₃ Is a surface morphology of (a).

Fig. 13 shows the effect of carbonization temperature on carbon yield.

Figure 14 shows the XRD patterns of the catalyst after carbon production reactions at four different temperatures.

Figure 15 shows the effect of water vapor dose on catalyst weight gain.

Figure 16 shows the XRD pattern of the catalyst after the carbon production process at five different water vapor doses.

FIG. 17 shows Fe after carbonization with 5 and 40 water vapor doses ₂ O ₃ Surface morphology of the catalyst.

FIG. 18 shows Fe after carbonization with 40 water vapor dose ₂ O ₃ HRTEM diagram of catalyst.

FIG. 19 shows the use of different catalysts NiO, cr ₂ O ₃ And various Cr (5% -35%) doped NiO catalysts.

Fig. 20 shows the carbon weight gain percentage (w/w%) for different doped NiO catalysts: (a) A low percentage metal salt loading and (b) a high percentage metal salt loading.

Figure 21 shows the effect of reaction temperature on carbon production.

Fig. 22 shows the effect of Cr-doped NiO with different metal loadings on carbon production, (a) no soak time (b) soak for 1h.

Figure 23 shows the effect of flow on carbon production.

FIG. 24 shows the reaction time dependence of carbon yield at constant reaction temperature 500℃and 40% CO:20 mL/min.

Figure 25 shows XRD results of the thus prepared product synthesized with constant precursor 40% co, flow 20mL/min, reaction temperature 400-900 ℃ (a) no incubation time, (b) incubation for 60 minutes.

FIG. 26 shows an FESEM image of the morphology of carbon deposits resulting from CO decomposition on a 25% Cr-NiO catalyst at 500℃and a flow rate of 20 mL/min.

Fig. 27 shows a TEM image of carbon prepared by decomposing CO over a 25% cr—nio catalyst, (a) unreduced catalyst, (b) a graph of carbon growth over the catalyst.

FIG. 28 shows NiO-based and 10% CO/N ₂ Carbon yield of (2).

FIG. 29 shows NiO-based and 40% CO/N ₂ Carbon yield of (2).

FIG. 30 shows NiO-based and 60% CO/N ₂ Carbon yield of (2).

Fig. 31 (a) shows XRD patterns of NiO catalysts after reaction at 10%, 40% and 60% co.

Fig. 32 shows a TEM image of NiO catalyst after treatment in 10% co at 700 ℃.

Fig. 32 shows a TEM image of the NiO catalyst.

Detailed Description

The invention will now be described in connection with figures 1 to 32 of the accompanying drawings, alone or in any combination thereof.

The present invention relates generally to a method for regenerating carbon and reactivating a catalyst in a catalytic reaction, the method comprising the steps of: preparing a catalyst and distributing the prepared catalyst into at least one reactor; activating the catalyst with carbon monoxide at 300 ℃ to 900 ℃ to produce an activated catalyst; injecting additional carbon monoxide for at least 1h to effect a first carbon production while forming a reduction catalyst; injecting steam to decompose the reduction catalyst to regenerate carbon in the second carbon production; wherein in a first carbon production the catalyst converts carbon monoxide to carbon and carbon dioxide, and in a second carbon production the reduction catalyst interacts with steam to form metal oxides, hydrogen and carbon, the hydrogen being used to regenerate the carbon and reactivate the catalyst for continuous recycling of carbon formation in the reactor.

Specifically, the catalyst is a metal oxide-based catalyst or an impregnated catalyst, wherein the impregnated catalyst is a combination of a metal oxide and a promoter.

Thus, the metal oxide based catalyst is iron oxide or nickel oxide.

In addition to the above, the promoter in the impregnated catalyst is in the form of a nitrate of a metal selected from the group consisting of: cobalt, chromium, zinc, molybdenum, zirconium, manganese, cerium, magnesium, nickel, iron, calcium, and barium.

In a preferred embodiment, the carbon collected is in the form of amorphous carbon or Carbon Nanotubes (CNT) or a combination of both.

In a preferred embodiment, the optimum temperature for producing the reduction catalyst is 500 ℃.

In view of the preferred embodiments described above, the reduction catalyst is a metal carbide.

In another preferred embodiment, the flow of carbon monoxide in steps (12) and (13) is from 5mL/min to 50mL/min.

In a preferred embodiment, the flow of carbon monoxide is optimized to 10mL/min and 20mL/min for the iron oxide based catalyst and the nickel oxide based catalyst, respectively.

In one embodiment, pulsed Chemisorbed Water Vapor (PCWV) is used to inject the vapor at doses of 5 to 40 and each dose is made of at least 0.23cm ³ Is composed of water vapor.

Advantageously, the carbon produced using the above method can selectively produce pure carbon. For example, the physical properties of the produced CNTs can be obtained in a variety of forms, including powders, thin or thick films, aligned or entangled, straight or coiled, or even the desired nanotube structure (Mukul & Yoshinori 2010).

Advantageously, the above method utilizes a carbonization process, the design of the reaction is simple, and the carbon growth parameters can be easily controlled, compared to other synthetic methods (Mukul & Yoshinori 2010& krzystonf et al 2010).

Advantageously, carbon growth occurs at much lower temperatures of about 550-1000 ℃ (Dresselhaus et al, 2001 and Ci et al, 2005), so the process does not require large amounts of energy to produce carbon, and can be considered a cheaper option.

Advantageously, the CO is reacted by thermocatalytic reaction ₂ Conversion to CO can readily produce CO.

The present invention uses steam containing water vapor instead of adding pure hydrogen (H ₂ ) (separately prepared) to reactivate the impregnated catalyst. Adding water vapor to the systemThe aim of (a) is to regenerate the catalyst mainly by decomposing the metal carbide into metal oxide and carbon. H ₂ Is generated in situ after the decomposition of the metal carbide and is used to reduce the catalyst during in situ regeneration and reactivation. Thus, an activated catalyst is formed and ready for the next carbon formation cycle, and activity is sustained to produce a large amount of carbon in a single reactor.

In the present invention, carbon is produced by Chemical Vapor Deposition (CVD) and a chemical reaction method in which carbon monoxide (CO) is thermally decomposed in the presence of a catalyst. This process involves catalyst activation and subsequent carbon production. H ₂ Gases are commonly used for catalyst activation.

In the present invention, CO is selected as the reducing agent to activate the catalyst, also as the carbon source. Typically, once the catalyst is activated, it is further exposed to carbon monoxide gas to initiate the formation of Carbon Nanotubes (CNT) and/or amorphous carbon, depending on the presence of the catalyst in the reaction system.

In activating the impregnated catalyst, the chemical reaction that occurs is shown in equation 1 below:

M _a O _b +CO→M ⁰ +M _x O _y +CO ₂ (equation 1)

In the presence of an activated impregnated catalyst (M ⁰ /M _x O _y ) For the first carbon production, the thermal decomposition of CO is shown in equation 2, followed by reduction of the impregnated catalyst to metal carbide in equation 3. These reactions are shown below:

2CO→C+CO ₂ (equation 2)

M ⁰ +M _x O _y +CO→M _x C _z +CO ₂ (equation 3)

During carbon regeneration and impregnated catalyst reactivation, the reaction that occurs is shown in equation 4:

M _x C _z +H ₂ O→M _x O _y +H ₂ +C (equation 4)

M _x O _y +H ₂ →M ⁰ +H ₂ O (equation 5)

Hereinafter, embodiments of the present invention will be provided for more detailed explanation. From these embodiments, the advantages of the present invention may be more readily understood and put into practice. It should be understood, however, that the following examples are not intended to limit the scope of the present invention in any way.

Example 1

Method

Catalyst preparation

The composition of the catalyst for carbon production used in the present invention comprises 100% of metal oxide and 5 to 35% by weight of promoter-metal oxide. The metal oxide is selected from the group consisting of d-block elements, i.e., iron oxide and nickel oxide. The selected promoter is any one of cobalt, chromium, copper, zinc, molybdenum, zirconium, manganese, cerium, magnesium, nickel, iron, calcium and barium. These promoters are in the form of nitrates. The selected metal oxide (i.e., iron oxide or nickel oxide) was heat treated at 400 c for 4 hours before being used as a catalyst for the carbon production reaction. The promoter-metal oxide is synthesized by wet impregnation by mixing the metal oxide with the promoter nitrate. The chemicals used to prepare the metal catalysts were supplied by FLUKA in analytical grade and used without further purification. Dissolving a calculated amount of nitrate and metal oxide corresponding to the metal cation in H ₂ O to form an aqueous solution, and stirring the mixture at 40 ℃ to 50 ℃ to form a homogeneously impregnated catalyst. After 4h, the aqueous solution was dried in an oven at 110℃for 24h. The fully dried catalyst was ground and sieved to give a particle size of 60 microns. After grinding, the catalyst was calcined at 400-600 ℃ for 4 hours and stored in a vacuum sealed glass jar. Iron oxide and nickel oxide containing various percentages of promoters are labeled as x% M/Fe ₂ O ₃ And x% M/NiO. Fig. 2 shows an outline of the catalyst preparation.

Catalyst activation

The metal oxide and promoter-metal oxide are exposed to 10% -60% carbon monoxide to activate the catalyst at a temperature of 300 ℃ -900 ℃. The living bodyThe step of converting is also referred to as reduction, wherein the metal oxide is reduced to a lower oxidation number. As shown in fig. 3, temperature Programmed Reduction (TPR) has been used to activate the catalyst and was measured by a micromeritics autochem 2920 chemisorption analyzer under atmospheric pressure and non-isothermal conditions. 50mg of catalyst was distributed on quartz wool in a quartz u-tube and connected to the reactor. First, at 20mL/min pure N ₂ The catalyst was heated to 150℃for 10 minutes to remove any moisture and then activated with 20mL/min of carbon monoxide gas. The temperature was increased from 150 ℃ to 900 ℃ at a ramp rate of 10 ℃/min to obtain a complete TPR curve. The TPR curve was recorded using a Thermal Conductivity Detector (TCD).

Carbon production

The synthesis of carbon is carried out at atmospheric pressure by catalytic decomposition of carbon monoxide in a small reactor (micro-instrument (micromeritics instrument)). As shown in FIG. 4, the thermal catalytic CVD process is performed in a fixed bed reactor, in which gas is to be flowed in from the top of the column. 50mg of the sample was distributed on quartz wool in a quartz u-tube connected to the reactor. After catalyst activation, the activated catalyst is exposed to 10-20 mL/min of carbon monoxide for 1-6 hours at a temperature similar to the activation step for the carbon production process.

Steam is added to the reaction to regenerate the catalyst for the next carbon formation. Water was added by Pulse Chemisorption of Water Vapor (PCWV). During carbon production, 10mL/min of carbon monoxide is continuously flowing while 10mL/min of nitrogen will carry water vapor and be injected into the system. The amount of steam injected per test varies from 5 to 40 doses. Specifically, at N ₂ Using 0.98cm in the flow ³ Sample loop, about 0.23cm ³ Or 10.4. Mu. Mol of water vapor is metered into the reduced metal oxide in each pulse to effect the water splitting reaction in equation 4 to produce carbon, metal oxide and hydrogen as a by-product. The hydrogen is further used to regenerate and reactivate the catalyst for the next carbon formation cycle.

Analysis of carbon yield

The total amount of carbon deposited during production is determined by the percentage of weight gain. After cooling the product to ambient temperature (about 30 ℃), weight gain was calculated by gravimetric analysis. The carbon produced is defined by the weight of carbon formed per weight of activated catalyst, using the following formula:

example 2

Iron oxide catalyst

Many applications of iron-based elements have been developed including catalysis, pigments, coagulants, gas sensors, ion exchange and lubricants (mohaptra & Anand, 2010). Iron oxide is widely used as a catalyst due to its stability during catalysis of high temperature reactions. Iron oxide is also widely available in nature and can be considered an inexpensive catalyst.

Investigation of reduction Properties of catalysts Using CO-TPR technology

Based on thermodynamic studies, the carbon production process requires the addition of Fe ₂ O ₃ Reduction to FeO and/or Fe _x And C active phase. Thus, TPR analysis is important for studying the reduction potential of activated catalysts. FIG. 6 shows Fe under non-isothermal conditions ₂ O ₃ Analysis of reduction.

From the graph in fig. 6, there are 4 peaks, which clearly indicate that the reduction process is followed by a four-step reduction. In this case, reducing agents CO were used at concentrations of 10%, 20%, 40% and 60%, and the TPR curves for each reducing agent were significantly different.

The first reduction peak indicates Fe ₂ O ₃ Is reduced to Fe ₃ O ₄ This is also consistent with the view of (Kuo et al, 2013). There is a very sharp separation peak around 415 to 570 ℃, which is attributable to Fe ₃ O ₄ Reduction to FeO and Fe _x And C, a step of a mixture of C. Especially at high concentrations of CO (40% and 60%) can formFeO and Fe _x And C. By further reduction of Fe at higher temperatures ₂ O ₃ This promotes FeO to Fe _x C, and will eventually form metallic iron (Fe).

Influence of carbon monoxide flow on carbon production

From thermodynamic considerations, carbon formation from CO is optimal at a temperature of 500 ℃. In this case, an optimum CO concentration of 40% is chosen to be the same as Fe ₂ O ₃ The catalyst interacts to produce carbon black and/or Carbon Nanotubes (CNT) because this is the lowest concentration that initiates the iron carbide phase.

As shown in FIG. 7, 3 different CO flows, i.e., 5, 10 and 20mL/min, were studied in order to obtain the optimal amount of carbon source during carbonization.

In the first 1h of carbonization, 20mL/min of CO produced the greatest weight gain, 12w/w%, compared to 5mL/min and 10mL/min of CO, indicating the highest percentage of carbon produced. Referring to fig. 7, it is apparent that the carbon yield gradually increases after 2-4 hours, and it can be inferred that the carbon yield is proportional to the exposure time and the weight gain.

However, when comparing the flow rate of the carbon source with the reaction time, 10mL/min showed the highest carbon growth. Carbon formation from 20mL/min CO was also considered quite high, but the percentage increase was not as high as 10 mL/min. Thus, 10mL/min of CO was chosen as the optimal flow rate for carbonization, and this value was used throughout the study.

Effect of promoter-oxide loading on iron oxide on carbon production

Impregnated catalysts comprising iron oxide and promoter-oxide are capable of producing carbon and operate at a reduction and carbonization temperature of 500 ℃. The iron oxide without any promoter is capable of producing 6w/w% carbon. For impregnated catalysts, the presence of nickel oxide increases the carbon yield by 39-55 w/w%. For example, cobalt oxide on iron also gives good results with a percentage of carbon production of 35-49w/w%.

Referring to FIG. 8, other promoters are combined with the iron oxide, such as Cr/Fe, as compared to the iron monoxide catalyst ₂ O ₃ 、Cu/Fe ₂ O ₃ 、Zn/Fe ₂ O ₃ 、Zr/Fe ₂ O ₃ 、Mn/Fe ₂ O ₃ And Ce/Fe ₂ O ₃ Further improvement of carbon growth was also shown. However, only Mo/Fe ₂ O ₃ The catalyst produces a negative weight gain. This is probably because exposure to CO for 1h only serves to reduce the catalyst, no carbon is produced, and thus the weight of the catalyst is reduced.

Meanwhile, nickel, cobalt, zirconium and cerium show similar trends in their carbon growth as iron oxide, with weight gain being proportional to promoter loading. However, in this case, 10% promoters are considered the best metal loadings, as they are not significantly different from 20% promoters.

The oxides of the promoters were also screened by carbonization, as shown in fig. 9. All promoter oxides were first reduced and then exposed to CO for 1h at a temperature of 500 ℃. The results show that only molybdenum can increase the weight by 4w/w%, while the weight gain of the other promoter oxides is negative. This demonstrates that the single metal oxide powder is not active for catalyzing the conversion of CO to C.

Influence of the reaction temperature on the carbon yield

10％Ni/Fe ₂ O ₃ And 10% Co/Fe ₂ O ₃ The impregnated catalyst of (2) has the best effect on carbon production. For the reduction and carbonization processes, the reaction was carried out at a temperature of 500℃with carbon percentages of 50w/w% and 45w/w%, respectively.

Further studies were carried out on both catalysts to obtain their optimal reaction temperatures, as shown in fig. 10. The reduction and carbonization were carried out at similar temperatures of 450, 500, 550 and 600 ℃. The weight of the catalyst increased significantly over all temperature ranges. However, carbonization at 500 ℃ showed the highest carbon growth compared to other temperatures. This is because at 500 c the catalyst comprises iron carbide, which promotes carbon formation when in contact with CO for too long. The carbon gain is not proportional to the temperature because the reaction entropy becomes more negative as the reaction temperature increases. Therefore, the optimum temperature was 500 ℃, and the same parameters were used in the following experiments.

When exposed toThe interpair adopts Fe ₂ O ₃ 、Ni/Fe ₂ O ₃ And Co/Fe ₂ O ₃ Influence of carbon production of the catalyst

By further increasing the exposure time to CO, the best promoter-iron oxide catalyst is combined with a single metal Fe ₂ O ₃ The catalysts were compared. The exposure time varies from 1, 2 to 6 hours for each catalyst and carbon growth is measured gravimetrically.

As shown in fig. 11, the presence of the promoter significantly increased carbon growth during the first hour of carbonization. Using 10% Co/Fe ₂ O ₃ And 10% Ni/Fe ₂ O ₃ The carbon yield was further increased by 40-45w/w%, respectively. The carbon continues to grow and is consistent with an extended exposure time.

In this case, the promoter enhances the active site of the catalyst, thus allowing more catalyst-CO interactions to occur; meanwhile, during carbonization for 1-2 hours, the C-O bond is weakened, and more carbon is generated. After 6h of reaction with CO, the conversion of CO becomes slower than the single metal catalyst, probably due to the slower diffusion rate of CO to the promoted catalyst.

On the other hand, fe ₂ O ₃ The catalyst was able to produce the highest percentage of carbon, i.e. 134w/w% after 6h exposure to CO, in contrast to Ni/Fe ₂ O ₃ And Co/Fe ₂ O ₃ 127w/w% and 117w/w%, respectively. Although carbon formation is lower at the initial reaction, the conversion of CO increases significantly with prolonged exposure time.

Catalyst and carbon characterization

FESEM of produced carbon

The morphology of the catalyst before and after carbonization was analyzed using FESEM magnification of 50K. The promoter alters the morphology of the iron catalyst by forming small pores in the catalyst particles. With the presence of small and irregularly shaped Co and Ni particles, the iron particles in the promoted catalyst become smaller as well. As shown in FIG. 12, after carbonization for 1h, 10% Co/Fe ₂ O ₃ A mixture of short carbon tubes and coated carbon was produced, as shown in FIG. 13, 10% Ni/Fe ₂ O ₃ Initial growth of large and short carbon tubes is established. However, in Fe ₂ O ₃ No carbon tubes were formed on the catalyst because the amount of carbon formation was very low, i.e. 6w/w%, compared to other catalysts. Thus, in Fe ₂ O ₃ The carbon produced on the catalyst is formed in the form of amorphous carbon rather than carbon nanotubes.

Example 3

Production of carbon using CO as a carbon source and steam addition

In view of the above, fe is selected ₂ O ₃ The catalyst was used for further investigation, carbon regeneration was performed using another carbonization and water splitting method, and the catalyst was reactivated for the next carbon formation. This allows for continuous production of carbon while saving costs and time.

Generally, in this study, the catalyst was reduced for catalyst activation followed by carbonization, which involves exposure to CO and addition of water vapor.

Influence of different reduction temperatures on carbon production

In the present study, fe was changed ₂ O ₃ To determine the active phase of carbon production thereof. Various concentrations of CO were used, 10, 20, 30, 40, 50 and 60%, the parameters of reduction and carbonization flow rates were as follows:

1. reduced CO flow rate: 20mL/min

2. CO flow for carbon production: 10mL/min

3. Water vapor dose: 1 hour 10 times

The following are the results obtained based on the above parameters:

TABLE 110% CO/N ₂

Reduction temperature (. Degree. C.)	Reduced phase	Carbon production temperature (. Degree. C.)	Weight gain (%)
				510	Fe ₂ O ₃ 、Fe ₃ O ₄	500	-26.73
570	Fe ₃ O ₄ 、FeO	500	-22.55
				610	Fe ₃ O ₄ 、FeO、Fe	500	-25.44
885	FeO、Fe	500	-10.12

TABLE 2.20% CO/N ₂

Reduction temperature (. Degree. C.)	Reduced phase	Carbon production temperature (. Degree. C.)	Weight gain (%)
				440	Fe ₃ O ₄	500	-20.43
560	FeO、Fe ₃ C、Fe	500	-15.61
				630	FeO、Fe	500	-10.78
850	FeO、Fe	500	-6.21

TABLE 3 30% CO/N ₂

Reduction temperature (. Degree. C.)	Reduced phase	Carbon production temperature (. Degree. C.)	Weight gain (%)
				420	Fe ₃ O ₄	500	-10.23
540	FeO、Fe ₃ C	500	-5.34
				620	FeO、Fe ₃ C、Fe	500	-0.5
840	Fe	500	+1.65

TABLE 4.40% CO/N ₂

Reduction temperature (. Degree. C.)	Reduced phase	Carbon production temperature (. Degree. C.)	Weight gain (%)
				400	Fe ₃ O ₄	500	+23.74
500	FeO、Fe ₃ C	500	+26.40
				610	FeO、Fe ₃ C、Fe	500	+25.10
820	Fe	500	+11.49

TABLE 5.50% CO/N ₂

Reduction temperature (. Degree. C.)	Reduced phase	Carbon production temperature (. Degree. C.)	Weight gain (%)
				350	Fe ₃ O ₄	500	+42.54
460	FeO、Fe ₃ C	500	+47.12
				550	FeO、Fe ₃ C、Fe	500	+44.34
835	Fe	500	+36.55

TABLE 6.60% CO/N ₂

Reduction temperature (. Degree. C.)	Phase (C)	Carbon production temperature (. Degree. C.)	Weight gain (%)
				325	Fe ₃ O ₄	500	+68.05
415	FeO、Fe ₃ C	500	+72.98
				500	FeO、Fe ₃ C、Fe	500	+71.15
850	Fe	500	+70.54

According to tables 1-6, 40% CO/N is recorded ₂ At various reduction temperatures, the lowest concentration that produces positive weight gain is then 50% and 60% CO/N ₂ . For 60% CO/N ₂ The highest weight gain recorded at 415℃of reduction temperature was 72.98% (g/g). After reduction at this temperature, the catalyst is FeO and Fe ₃ And C phase.

Other concentrations, i.e., 10%, 20% and 30%, do not contribute to any weight gain because the amount of CO gas is insufficient to initiate the formation of iron carbide. In other words, excess CO is required to form iron carbide and promote carbon formation.

Although 50% and 60% CO/N ₂ The best concentration is shown in carbon production with the greatest positive gain, but due to current instrument limitations, CO concentrations of 50% to 60% will be too rich, toxic, and damage the filaments of the detectors in the instrument. Furthermore, further reactions involving the addition of water vapor doses lead to an increase in pressure in the reactor. Thus, to investigate the effect of other parameters on carbon production, 40% CO was used.

Influence of different carbon production temperatures on weight gain

Since the recorded optimal reduction temperature is 500 ℃, carbonization was tested at 40% co at various temperatures (i.e., 400, 500, 600, and 700 ℃) as listed in table 7.

The reaction parameters were as follows:

1. reduced 40% co flow: 20mL/min

2. 40% CO flow for carbon production: 10mL/min

3. Water vapor dose: 1 hour 10 times

In view of the above, as shown in FIG. 13, 500℃is the optimum carbonization temperature, and the carbon formation amount is 26.40w/w%. By increasing the temperature to 600-700 ℃, the value of the weight gain becomes negative because of FeO and Fe ₃ The C phase is reduced to metallic Fe as shown in fig. 14. The metallic iron is in an inactive phase during carbonization. Thus, the reduction and carbonization temperatures of 500 ℃ are recorded as the optimal temperature, since it gives the best weight gain compared to other temperatures.

TABLE 7 influence of carbonization temperature on carbon yield

Reduction temperature (. Degree. C.)	Reduced phase	Carbon production temperature (. Degree. C.)	Weight gain (%)
				500	FeO、Fe ₃ C	400	-10.12
500	FeO、Fe ₃ C	500	26.40
				500	FeO、Fe ₃ C	600	1.19
500	FeO、Fe ₃ C	700	-22.00

Effect of different flow rates of 40% co and water vapor carrier on carbon production during carbonization

As shown in Table 8, 5mL/min of 40% CO/N compared to 10mL/min ₂ And a water vapor carrier (N) ₂ ) Resulting in a higher weight gain. Lower flow rates will increase the contact time between the catalyst and the CO gas, so that efficient collisions between catalyst and CO molecules occur and promote carbon formation.

TABLE 8 influence of CO flux on carbon yield during carbonization

Influence of different amounts of aqueous agent on carbon production

The purpose of adding steam during carbonization is to increase the carbon yield while regenerating and reactivating the catalyst for the next carbon formation.

In this study, the reaction parameters were set as follows:

1. reduction temperature: 500 DEG C

2. Reduced 40% co flow: 20mL/min

3. 40% CO flow for carbon production: 10mL/min

4. Water vapor dose: 10-40 times

5. Carbonization temperature: 500 DEG C

Referring to fig. 15, in the absence of added water, the catalyst is prepared by Fe ₂ O ₃ Carbonization for 1h produced only 6w/w% carbon. However, carbonization for 30 minutes with 5 doses of water vapor showed a further increase in carbon formation, i.e. 11w/w%. Thus, by increasing the dose of water vapor, the carbon yield is also increased.

Catalyst and carbon characterization

XRD results

Referring to fig. 16, XRD patterns of the catalyst carbonized with five different water vapor doses show that the carbon signal becomes strong and increases in proportion to the water vapor dose. Due to Fe ₂ O ₃ Conversion to Fe ₃ C, excessive CO exposure results in Fe ₂ O ₃ The phase signal decreases. The presence of water vapor is also achieved by oxidation of Fe ₃ C forms Fe ₃ O ₄ And carbon to promote carbon formation. Then Fe ₃ O ₄ Is reduced again to form Fe again ₃ C. These processes are repeated simultaneously during carbonization and the catalyst will be continuously activated by water vapor.

FESEM of produced carbon

FIG. 17 shows Fe after carbonization at 5 and 40 doses of water vapor ₂ O ₃ Morphology comparison of the catalysts. During the 5 doses of water, a smooth surface of the catalyst can be seen, indicating that the carbon has coated the catalyst particles (fig. 17 (a-b)). Meanwhile, when Fe ₂ O ₃ The formation of carbon tubes was clearly detected when exposed to CO and water vapor for a long period of time (fig. 17 (c-d)).

HRTEM diagram of produced carbon

On the other hand, FIG. 18 shows Fe after carbonization with 40 doses of water vapor ₂ O ₃ HRTEM diagram of catalyst. The catalyst comprises short carbon tubes and carbon coated around the catalyst particles.

Example 4

Nickel oxide catalyst

Nickel oxide is commonly used as a catalyst due to its high surface oxidation properties during catalysis, which makes it a suitable candidate for carbon production in this study. Doping is a widely used method for altering the electronic structure of nanoparticles to achieve new or improved catalytic, optoelectronic, magnetic, chemical and physical properties (Liao et al, 2008). Like other transition metal catalysts, niO catalysts require reduction to provide the active phase (i.e., metallic Ni) prior to use. For industrial applications, catalyst reduction is usually carried out with hydrogen-containing gases or natural gas-steam mixtures. The reducing conditions are important because they have an influence on the subsequent catalytic activity. For example, high temperature and rapid reduction may result in lower nickel dispersion and lower 10 activity, and the introduction of carbon or sulfur may accelerate catalyst deactivation (Sehested, 2006 and Valle et al, 2014). Therefore, in the present study, nickel was selected as a catalyst for carbon production, and its chemical properties after regeneration were studied.

CO-TPR technology activated catalyst

FIG. 19 shows the use of different catalysts NiO, cr during TPR analysis ₂ O ₃ And various Cr (5% -35%) doped NiO catalysts. Peak i (a) shows the first reduction stage of NiO, and the high intensity at peak i (a) of fig. 19 (a) indicates a strong interaction between nickel oxide and carbon monoxide. This interaction is also known as the Boudouard reaction. NiO then converts CO to C and CO ₂ 。

In addition, the peak in i (a) shows a very high intensity peak due to the gas reduction process occurring on the pores of the catalyst surface. In this case, carbon monoxide is adsorbed and dissociated on the oxide surface of the catalyst. The carbon atoms then react with the oxygen portion of the nickel oxide to form carbon dioxide and metallic nickel.

Peak ii (a) of the TPR curve shows a low intensity peak due to the reaction occurring at the inner surface of the catalyst. Peak ii (a) is also due to Ni ²⁺ And Ni ⁰ Is a partially reduced phase of (a). Although the peak isiii (a) shows a very low intensity peak, but this is probably due to the reaction taking place on the catalyst surface. High temperatures are required for chemical reactions to occur at the surface of the catalyst body due to particle diffusion that may trigger the reaction rate.

The peaks shown in FIG. 19 also indicate that chemical reduction and CO to CO occurred during the chemical process ₂ Is transformed by the above method. The chemical reaction that occurs is shown in the following formula:

NiO(s)+CO(g)→CO ₂ (g)+Ni ⁰ (s) equation 6

Thus, it can be concluded that Ni ²⁺ →Ni ⁰ Is in the complete reduction of>At 700℃with CO.

As shown in FIG. 19 (b), cr ₂ O ₃ The reduction curve of (c) may not be apparent because the reduction peak has a very low intensity and no color change is observed after the sample is treated at 900 ℃.

Fig. 19 (c) to 19 (i) show doped catalysts in which chromium is doped to nickel oxide, 5% to 35% of the chromium being doped to NiO. Fig. 19 (c) and 19 (d), the TPR curves show only a single peak of CO consumption, with maximum temperatures of 526 ℃ and 429 ℃, respectively.

For fig. 19 (e) to 19 (i), the TPR curve shows two peaks of the first peak in the range of 271 ℃ to 279 ℃ and the highest broad peak in the range of 427 ℃ to 455 ℃.

The addition of Cr as a promoter to the NiO catalyst enhanced the reducibility of NiO, supported by the data obtained from XRD. When Cr is doped, niO is converted to Ni at 500 DEG C ⁰ Is reduced by (a).

Effect of promoter loading on nickel oxide on carbon production

For carbon production, the effect of promoters on NiO catalysts was investigated using a variety of metal salt loadings with low and high percentages of metal salts (i.e., 5% and 25% relative to NiO). Promoters added to the NiO catalyst are expressed as Cr-NiO, co-NiO, cu-NiO Ce-NiO, mo-NiO, ba-NiO, zr-NiO, fe-NiO, ca-NiO and Mg-NiO, the percentages are 5% and 25%.

The addition of promoters to the catalyst NiO initiates carbon growth and increases catalyst activity. All catalysts were subjected to a reduction process using TPR chemisorption at 500℃with a CO flow of 20mL/min and continued exposure at 10℃per minute for 1h before cooling to room temperature.

Figure 20 shows the weight gain (w/w%) of carbon production. Chromium doped into NiO has the highest value at either 5% or 25% catalyst loading compared to other metal salts. Meanwhile, for Fe-NiO, carbon formation will be induced by increasing the percentage of promoter, and the results obtained confirm that carbon formation increases proportionally with increasing percentage of promoter loading.

Influence of the reaction temperature on the carbon yield

Since different temperatures during carbon production will form different phases, thereby affecting the value of the resulting product, the effect of reduction temperature on carbon production was investigated.

In this case, 25% cr—nio was chosen as the best catalyst in the process, as it showed the highest yield compared to other metal salt doping. The highest potential determination of carbon production activity was selected from five different temperatures of 400 ℃, 500 ℃, 600 ℃, 700 ℃ and 800 ℃. The reaction was then run in two ways, namely until the selected temperature ended (no incubation time) and another hour above the selected temperature (incubation for 1 h).

Referring to FIG. 21, the carbon yield at low temperature, i.e., 400 ℃, is negative (-4%). This means that only the catalyst is reduced, but no conversion of CO has yet occurred. After raising the temperature to 500 ℃ and 600 ℃, the carbon yields were 18% and 35%, which correspond to obtaining 22% and 17% carbon, respectively. However, at high temperatures (i.e., 700 ℃ and 800 ℃) the increase in carbon weight is only 6% and 5%, indicating that these values are not suitable for carbon production. This may be due to deep reduction to form metal, aggregation and formation of metallic metal (metal) at temperatures above 700 c, inhibiting CNT or carbon formation. In our example, niO is fully reduced to metal at 700 ℃.

In view of the above, when the temperature was maintained for 1h, the reduction of the catalyst occurred at 400 ℃. Based onThe TPR curve of fig. 19, at 400 ℃, the reduction of NiO had started and as the exposure time increased to 1h, more reduction occurred, probably due to the active sites of the catalyst (Ni ⁰ ) The number of (3) increases. This promotes carbon growth due to the presence of the active phase in the bourduouard reaction.

Interestingly, at a temperature of 500 ℃, the carbon yield without elongation was +18% and increased to +173% after exposure to CO 1 h. This is due to the formation of active sites (Ni ⁰ ) The number increases, inducing more carbon growth over an extended period of time.

At T <500 ℃, the carbon yield increases with increasing reaction temperature, and at T: maximum yield was reached at 500 ℃. However, at T >500 ℃, the carbon yield begins to decrease due to the negative impact on the reaction caused by the exothermic reaction. This is because at higher temperatures, for example at 700 ℃, more metallic nickel particles are produced, where they tend to agglomerate, forming larger metal clusters. Most likely, these clusters lead to CO decomposition to form surface-coated carbon, which in turn deactivates the catalyst.

Effect of varying loadings of chromium doped nickel oxide (CrNiO) on carbon production

To investigate the effect of catalyst concentration on carbon production yield, synthesis was completed at 500 ℃ using different concentrations (cr=5%, 10%, 15%, 20%, 25%, 30% and 35%) of Cr/NiO catalyst, extending reaction times 60 and 0 minutes, CO/N ₂ The flow rate was 20mL/min. Fig. 22 shows the effect of Cr-doped NiO of different metal loadings on carbon production (a) no soak time (b) soak for 1h.

Influence of CO flow on carbon production

The contact time is reported to have an important role in catalytic activity, and therefore the effect of residence time was studied by varying the volumetric feed rate (ml/min).

As can be seen from the bar graph of fig. 23, the carbon yield increases with the precursor flow rate. At low flows of 5mL/min, only small carbon yield values (37%) were formed. This reflects that the CO flux is insufficient to initiate rapid growth of CNTs on the thermally activated catalyst. The reaction of the catalyst with the carbon precursor is insufficient due to the minimal diffusion of carbon atoms into the metal catalyst.

Furthermore, since the carbon diffusion rate in the bulk of the metal particles is relatively low at this temperature, part of the carbon cannot be transferred in time, thus blocking the surface of the activated catalyst, resulting in reduced reactivity.

At a flow rate of 10mL/min, the carbon yield increased slightly, but the increase was only +48%. This may be due to the precursor flow rate still being insufficient to fully fluidize the catalytic particles and generate enough carbon atoms to diffuse and grow into a continuous CNT structure.

However, when the flow rate of CO was further increased to 20mL/min, the carbon yield increased to 173% (carbon gain approximately +88%). This flow provides sufficient impetus for the catalyst particles to suspend in the bed and to make good contact with the gas molecules. As the CO flow rate was further increased from 20mL/min, the weight gain was increased by only +5%, +40% and +36% for flows of 30mL/min, 40mL/min and 50 mL/min. With a further increase in CO flux >20mL/min, it was shown that only a smaller number of reactive carbon atoms can grow fewer nanotubes with higher structural defects.

In addition, when the temperature is kept constant (i.e., 500 ℃) and the flow rate of CO is increased to 30mL to 50mL, the conversion of CO decreases probably due to the increased rate of carbon formation.

The data obtained show that at this flow rate (20 mL/min), the rates of carbon atom formation and removal from the catalyst surface are perfectly matched and a balance is created between the supply of activated carbon and nucleation of CNT structures. During the optimization, an equilibrium state occurs between the decomposition rate of CO and the rate of carbon diffusion into the catalyst particles.

Influence of exposure time on carbon production

FIG. 24 shows the effect of reaction time on carbon yield and the difference in increasing reaction time at a constant reaction temperature of 500℃and a CO flow ratio of 20mL/min, indicating that carbon yield increases with increasing reaction time.

The trend in average growth rate indicated a decrease in productivity after 60 minutes, apparently due to the loss of catalyst activity in the reaction.

At a reaction time of 60 minutes, the growth rate showed the highest rate (1.5 mg/min) compared to the other reaction times.

Catalyst and carbon characterization

CHNS results

Table 14 demonstrates carbon formation with NiO and 20% Cr-NiO catalyst at soak time and no soak time (or untreated). About 63.14% (w/w) of carbon was detected by CHNS instrument analysis, which corresponds to a weight gain of 118% (w/w).

Table 14 shows the carbon content of the different types of catalysts

XRD results

Figure 25 shows XRD patterns of carbon produced by using 25% cr-NiO catalyst at 40% carbon monoxide at different temperatures (400 ℃ -700 ℃).

The experiment was performed under two conditions:

(a) No heat-insulating time, and

(b) The heat preservation time is 1h.

As shown in fig. 25, the peak 2θ: the presence of 22.23 confirms the formation of carbon. The addition of Cr as a promoter for the NiO catalyst initiates carbon growth and increases carbon yield by increasing the exposure time of the precursor.

FESEM of produced carbon

From the morphological analysis using FESEM (fig. 26), it is clearly shown that carbon nanotube type Carbon (CNT) is produced after different reaction times.

While maintaining the reaction temperature under a CO gas stream, CNTs grow on the surface of the activated metal catalyst.

TEM image of produced carbon

Fig. 27 shows a TEM image of carbon produced after decomposition of CO over a 25% cr—nio catalyst, where (a) shows a graph of carbon using unreduced catalyst, and (b) a graph of carbon grown over activated catalyst. The graph demonstrates that carbon nanotubes are grown at a constant reaction temperature of 500 ℃ and a reaction time of 60min at a CO flow rate of 20 mL/min.

Production of carbon using CO as a carbon source and steam addition

In this process, the catalyst is subjected to a reduction step to activate the catalyst, followed by carbonization, which involves exposure to CO and addition of water vapor. Here, 10%, 40% and 60% CO were chosen as precursors, as it can summarize the effect of low, medium and high concentrations of CO on carbon formation on NiO catalysts.

With water vapour at 10% CO/N ₂ Down-screening NiO catalyst

The reduction temperatures of NiO were varied to determine their activation phase towards carbon formation. Different concentrations of CO were used, 10%, 40% and 60%, constant flow rate 20mL/min, water vapor dose: 10 doses. As shown in fig. 28, the weight gain of the carbon production was negative, indicating that no carbon was formed at 10% co. At a temperature of 500 to 800 ℃, even if H is added ₂ O, the catalyst is also inactive to carbon formation. Thus, this study demonstrates that low concentrations of CO are insufficient to catalyze the formation of carbon.

Using steam at 40% CO/N ₂ Down-screening NiO catalyst

Further investigation of carbon screening by NiO was continued by increasing the concentration of precursor to 40% (v/v). Based on fig. 29, it shows that the yield is negative. Even if the temperature of the water vapor for carbon production is increased to 500 ℃, the value of the carbon yield is still negative. Thus, it can be concluded that at such a flow rate, the flow rate of the carbon raw material has not been completely effective for forming carbon nanotubes. In addition, ni ²⁺ Deep reduction to Ni ⁰ And Ni is generated ⁰ Metal nickel is formed on the surface to inhibit CNT growth on the catalyst.

With water vapour at 60% CO/N ₂ Down-screening NiO catalyst

FIG. 30 shows the concentration of CO/N at 60% ₂ Data for carbon production for the lower treatment and temperature increase to 600 ℃ to 700 ℃ and an additional 10 doses of water vapor were used. When T is<At 600 deg.C, the reduction temperatures are 410 deg.C, 450 deg.C and 500 deg.C respectivelyAt temperatures of 550 c and 600 c, no carbon is formed. However, when the temperature of the water vapor was increased to 700 ℃, the weight of the catalyst increased, thus confirming the formation of carbon on the catalyst.

Catalyst and carbon characterization

XRD results

FIG. 31 (A) shows XRD diffraction patterns of NiO catalysts after the course of the reaction, including at 10% CO/N ₂ 、40％CO/N ₂ 、60％CO/N ₂ Diffractograms of NiO reacted at 700 ℃ reduction temperature under atmosphere, carbon was produced with steam at 700 ℃.

At 10% CO and 40% CO, the catalyst was fully reduced to Ni ⁰ At the same time, at 60% CO, a peak (002) was formed, which indicated a graphite peak.

FESEM of produced carbon

The graph in fig. 31 (B) shows a graph of crude NiO at a reduction temperature of 700 ℃. Carbonization on NiO and additional water demonstrated the presence of amorphous carbon deposition on the catalyst and was further demonstrated by XRD diffraction forming carbon graphite at peak (002).

TEM image of produced carbon

Fig. 32 shows a TEM image of NiO at 700 ℃, 40% CO concentration, CO flow of 20mL/min and exposure time of 1 h. A Transmission Electron Microscope (TEM) was performed to confirm the formation of carbon nanotubes. As shown in fig. 32, no carbon was formed on the catalyst and the exposure time did not initiate carbon growth on the nickel oxide catalyst.

Summary

Of the Ni/Fe and Co/Fe catalysts, iron oxide based catalysts can produce the highest carbon yields (134 w/w%) by extending CO exposure times at 500 ℃. The presence of 10% promoter significantly increases the carbon yield at the initial reaction time, especially at the first hour (45 and 50 w/w%). In the case of 40% CO, 10 doses of steam were used to react for 1h, the addition of steam further increased the carbon yield by 20w/w%. The carbon yield was proportional to the carbon concentration, exposure time and water vapor dose (5 doses: 11w/w%,10 doses: 26w/w%,15 doses: 55w/w%,20 doses: 79w/w%, and 40 doses: 107 w/w%). In a systemThe presence of water vapor induces H ₂ In situ generation of (c), wherein H ₂ Is essential for in situ carbon regeneration and catalyst reactivation. Thus, an activated catalyst is formed and ready for the next carbon formation cycle and continues to be active to produce a large amount of carbon. Cr-NiO is selected as the optimal catalyst in the carbonization reaction, and the yield of the carbon nano tube is highest when the catalyst loading on the nickel oxide is 25% Cr. When high concentrations of CO (60%) are used, niO catalysts exhibit positive carbon weight percent values, which are quite high in routine experimentation. However, the gain obtained was lower than 25% crnio (173%, w/w%). The best conditions proposed are: the gas reaction is carried out for 40% CO for 60min at 500 ℃ with a flow rate of 20mL/min. The yield of the product exceeds 173%, and the growth rate is 1.5mg/min.

Claims

1. A method (10) of regenerating carbon and reactivating a catalyst in a catalytic reaction, the method comprising the steps of:

preparing the catalyst and distributing the prepared catalyst into at least one reactor (11);

activating the catalyst with carbon monoxide at 300 ℃ to 900 ℃ to produce an activated catalyst (12);

injecting additional carbon monoxide for at least 1h to effect a first carbon production (13) while forming a reduction catalyst;

injecting steam to decompose the reduction catalyst to regenerate carbon (14) in the second carbon production;

wherein in the first carbon production, the catalyst converts carbon monoxide to carbon and carbon dioxide, an

In the second carbon production, the reduction catalyst interacts with steam to form metal oxides, hydrogen and carbon, the hydrogen being used to regenerate the carbon and reactivate the catalyst for continuous recycling of carbon formation in the reactor (15).

2. The method of claim 1, wherein the catalyst is a metal oxide-based catalyst or an impregnated catalyst, wherein the impregnated catalyst is a combination of a metal oxide and a promoter.

3. The method of claim 2, wherein the metal oxide-based catalyst is iron oxide or nickel oxide.

4. The method of claim 2, wherein the promoter is in the form of a nitrate of a metal selected from the group consisting of: cobalt, chromium, zinc, molybdenum, zirconium, manganese, cerium, magnesium, nickel, iron, calcium, and barium.

5. The method of claim 1, wherein the carbon collected is in the form of amorphous carbon or Carbon Nanotubes (CNTs) or a combination of both.

6. The method of claim 1, wherein the optimum temperature for producing the reduction catalyst is 500 ℃.

7. A process according to any one of claims 1 to 3, wherein the reduction catalyst is a metal carbide.

8. The process of claim 1, wherein the flow rate of carbon monoxide in step (12) and step (13) is from 5mL/min to 50mL/min.

9. The method of 8, wherein the flow rate of carbon monoxide is optimized to 10mL/min and 20mL/min for the iron oxide based catalyst and the nickel oxide based catalyst, respectively.

10. The method of claim 1, wherein the steam is injected at 5 to 40 doses using Pulsed Chemisorbed Water Vapor (PCWV) and at least 0.23cm per dose ³ Is composed of water vapor.