Patent Application
20210387158
Embodiments of the present disclosure generally relate to a process for the conversion of carbon black into highly microporous carbon without the need for strong alkaline activators.
For the time being, fossil fuels remain dominant source of supply for global energy demand and CO2 emission as a consequence of burning fossil fuels remain the major global problem (Brockway et al., 2019). Among CO2 mitigation strategies, CO2 capture and storage (CCS) has become increasingly popular over the past decades as it can effectively remove CO2 from the source point of emission to great extent. From 1930 to the present, the most used technology to remove CO2 has been based on sorption and stripping with aqueous amines as a feasible method which suffers from a series of inherent problems including the corrosive nature of the liquid phase amine-based absorption, unpleasant poisonous smell, fouling of the process equipment, decomposition at high temperature, and high regeneration energy (Dutcher et al., 2015). To overcome these critical problems solid sorbents such as porous carbons (PCs) (Zhang, et al, 2019), metal-organic frameworks (MOFs) (Ding et al., 2019), and zeolite (Murge et al., 2019) etc. have emerged as promising capture materials because they usually require lower capital cost, lower pressure for gas recovery, and less regenerated energy (Wang et al., 2014). In spite of having general advantages over liquid amines, the solid capture materials also have some drawbacks. For example, most of the MOFs and zeolites are unstable in moisture or at high-temperature, expensive, or require sacrificial templates (Hu et al., 2019) Therefore, inexpensive and widely available materials are needed, which include PCs. In this way, carbon black (CB) and porous carbon (PC) appear as excellent alternatives because these materials are widely used in industry or generated as combustion by products. The use of PCs as gas adsorbent has grown over the past years because of their inherent strength, low preparation cost, high stability against humidity and high operating temperature, easy regeneration, and sustainability (Zhang et al., 2019).
Most current methods for production of activated carbon (AC) or porous carbon (PC) is through activation of a carbon precursor by treatment with a base, such as potassium hydroxide (KOH), sodium hydroxide (NaOH) or lithium hydroxide (LiOH) (Ghosh, et al., U.S. Pat. No. 10,232,342). Unfortunately, these hydroxides and their solutions are severe irritants to skin and other tissue. Furthermore, the vapor formed during activation is corrosive and etch typical reaction chambers such as glass. The resulting PC needs additional purification step using acids which makes the process harsh and tedious, and they are also corrosive which is a hindering its use in terms of industrial production of amorphous carbon (AC). This makes scale-up problematical and impractical. Other activation processes involve the use of strong acids.
In addition, activated carbons are usually produced by pyrolysis with a low heating rate of 1-10° C./min which make the process long and energy intensive.
There are a few methods for CB conversion into PC, including method for producing activated carbon from carbon black using waste tires (Teng & Wang, U.S. Pat. No. 6,337,302) and production of molded activated carbon from carbon black and petroleum pitch by alkaline activation (Kugatov et al, 2016).
The fabrication of AC for CO2 capture has been accomplished in a variety of different ways mostly using alkali activating agents and various precursors such as polysaccharide (Li et al., 2017), heterocyclic aromatic organic compounds (El-Kaderi et al., US Application 2019/0119120), a hyper-cross-linked porous aromatic polymer (Marchese, et al., EP3328537A1), lignocellulose (Baker, U.S. Pat. No. 5,710,092), or a carbon precursor solution prepared by reacting phenol with formaldehyde (Meisner et al., US Application 2011/0177940).
The incorporation of mesopores into microporous carbon (preferably activated coconut carbon) has been demonstrated using and alkaline earth metal salt or an alkali metal salt such as calcium nitrate (Branton et al., US Application 2012/0174936A1). As an alternative method involves modification of the microporous structure of a carbon material by a post-carbonization process (Putyera et al., U.S. Pat. No. 6,225,257).
It is desirable to have a synthesis of highly porous carbon materials that does not require activation with strong bases. The present invention provides the method for reaching this goal.
In one embodiment, a new alkali-free approach to the conversion of commercial carbon black (CB) into carbon nanoribbons and different grades of heteroatom-doped microporous carbons with high CO2 capture performance is provided. Considering the high tendency of industries to clean and cost-effective production, the most adventitious feature is the use of an alkali metal-free process where porous carbons (PCs) with different textural properties are synthesized from different grade of carbon black (CB), namely commercial carbon soot (CS).
In another embodiment, all synthesized PCs were evaluated for CO2 capture and showed high performance particularly at low pressure because of abundance of ultramicropores. Most of materials for CO2 capture also suffer from some disadvantages, including low CO2 sorption capacity and selectivity at low pressure and room temperature, high regeneration cost, corrosiveness, and instability.
In yet another embodiment, a method of preparing oxygenated nanoribbons and various mPC with different morphology from CB containing different level of oxygen is provided. In a variation of the present invention, a wide range of CB grades are employed. The method for oxygenated nanoribbons and microporous nanocubes applies to CB grade Pearl 2000 and the method for mPC production in general applies to all CB grades (acetylene black, channel black, furnace black, lamp black and thermal black). Using nitric acid for CB oxidation offers a desired level of oxygen content by controlling the reaction time. Both high and low heating rate for pyrolysis process are applied and there is no appreciable difference in final product making fast pyrolysis more reasonable in terms of energy saving.
Different type of commercial soots or carbon blacks (CBs) have been used as a precursor for synthesis of new types of nanomaterials with different morphology and porosity. Among all CB used, Pearl 2000 as one of the most porous CB in the market proved to be an interesting precursor to produce new homogenous graphitic-like ribbons with high oxygen content of ˜50 w % and diameter of 20 nm while other CB grades lead to different randomly shaped nanoparticles and carbon quantum dots. The representative nanomaterials then were used to produce microporous carbons by slow and fast carbonization in a self-templated method without using activating agent yielding unshaped particles and highly ordered nanocubes (˜250 nm), respectively. Although the best microporous carbons synthesized have lower surface area and pore volume than pristine CB model, they showed more capacity for the CO2 uptake at low and atmospheric pressures and ambient temperature. Although porous carbon can be obtained from biomass but always needs KOH/HCL which makes the process costly and hazardous and we should burn a green source. It can be also produced from chemicals which need complicated chemistry and comes with much price and low yield as the result of burn-off. On the other hand, herein, we present an efficient approach for alkali activation-free conversion of almost all CB grades to different O/N-doped mPCs with high CO2 capture performance at room temperature and atmospheric pressure while most pristine CBs even with high surface area fail to respond.
In some embodiments, the mPCs of the present invention include a porous carbon material with a carbon content of between 75% and 92% as measured by elemental analysis. In some embodiments, the porous materials of the present disclosure include a porous carbon material with a surface area of 250-850 m2/g, a total pore volume of at least 1.35 cm3/g, and a carbon content of between 80% and 95% as measured by X-ray photoelectron spectroscopy.
In a further embodiment, the oxidized carbon black (OCB) of the present disclosure are prepared in different times and four fractions are separated by centrifugation. In some embodiments, the temperature of pyrolysis is between 700° C. and 900° C. Oxygen functionalities can be introduced during the acid treatment step and oxygen content can be manipulated by time control.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had reference to embodiments, some of which are illustrated in the appended drawings. It is also noted, however, that the appended drawings illustrate only exemplary embodiments. And are therefore not to be considered limiting in scope, may be admit to other equally effective embodiments.
Various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components and/or features.
The present disclosure relates to the application of wet oxidation of CB to make oxidized carbon black (OCB) as precursor for production of our new porous carbon materials (PCs). The aim supporting the use of this strategy to make CB-containing oxygen group is to take advantage of its unique ability in self-activation rather than using auxiliary activating agent during pyrolysis. In fact, we supposed that oxygen functionalities can play a similar role to that of auxiliary activating agents like alkali metals, but they can eliminate the cumbersome and hazardous purification steps after carbonization.
Followed by more examining and in order to maximize the performance of PC-P, in another variation, we also set a series of experiments where three different fractions could have been separated from OCB-P for subsequent pyrolysis.
Scanning electron microscopy (SEM) images of all oxidized carbon blacks (OCBs) and their pyrolyzed products are collected in
As representative,
The elemental analyses of the pristine CB-P, oxidized, and pyrolyzed products are summarized in Table 1. It is clear that the level of oxygen content increases remarkably after oxidation. CB-P was found to be fully oxidized in 5 days giving OCBs and NRs with oxygen content up to roughly 52 w %. However, some nitrogen can be also detected as a result of reaction of CB active sites with NOx. After carbonization, most of the oxygen functionalities were removed from carbon framework while most of nitrogen remains within the structure. This is worth mentioning that heating rate also can influence the mechanism of carbonization as PC-C contain much more oxygen content than PC-C′ meaning less oxygen is released during fast pyrolysis.
The textural properties of the spheres such as surface area and pore volume, and pore size distribution for all samples (Except PC-Ac) were measured and the textural parameters obtained from the N2 (77 K) and CO2 (273 K) adsorption data are shown in Table 2. BET surface areas were estimated using N2 at 77 K, while pore size distributions were calculated using non-localized density functional theory (NL-DFT) with data collected with CO2 at 273 K. In accordance with the IUPAC classification, all samples showed type I isotherms, suggesting microporous structures (Robens, 1999)
The CO2 uptake performance of the first group of synthesized microporous carbons (
From carbon capture, utilization and storage (CCUS) economical point of view, one of the major criteria in adsorption-based CO2 capture unit is high selectivity of CO2 over N2. Considering that a typical flue gas stream emitted from coal-fired power plants contains about 15% of CO2, 75% of N2, and 10% of other volatile components, we applied CO2 and N2 estimated partial pressures (0.15 and 0.85 bar, respectively) to calculate the selectivity. Accordingly, the adsorption selectivity of CO2 over N2 for all samples at 25° C. are also seen in
High performance of PC-P encouraged us to expand the scope of synthesis and scrutinize the potential of Pearl 2000 as a model precursor for production of more PCs. As mentioned earlier, CB-P could be efficiently converted into three different OCB fractions as OCB-A, OCB-B, and highly oxygenated NRs. After thermal treatment under inert gas, each fraction led to microporous carbons with different surface area, pore volume, and oxygen content.
Scanning tunneling electron microscopy (STEM) and high-resolution transmission electron microscopy (HRTEM) images of the spheres were performed using a JEOL 2100F Transmission Electron Microscope. Energy dispersive X-ray spectroscopy (EDS) was conducted on a carbon grid. Scanning electron microscopy (SEM) images of the spheres were obtained with a JEOL 7800F FEG SEM (JEOL, Akishima, Tokyo, Japan). The Raman data of the carbon spheres were recorded at room temperature using a Renishaw inVia Raman Microscope (Renishaw plc, Miskin, Pontyclun, UK) with excitation wavelength of 457, 514, and 633 nm. The elemental analyzer (vario EL cubewas, Germany) was used to determine the amount of carbon, hydrogen and oxygen. The samples were characterized using a Thermo Scientific Nicolet iS10 FT-IR Spectrometer. Thermogravimetric analysis (TGA) was carried out using 10-mg samples with a TA Instruments SDT Q600 at a heating rate of 5° C.·min−1 from room temperature to 900° C. in air. N2 adsorption/desorption isotherms were obtained using a Quadrosorb SI (Quantachrome Instruments, Boynton Beach, Fla., USA). Specific surface areas were calculated based on the Brunauer-Emmett-Teller (BET) method, and pore size distribution was determined using the non-localized density functional theory (NL-DFT) method. X-ray photoelectron spectroscopy (XPS) was performed using a Kratos Axis Supra (Kratos Analytical, Japan) utilizing a monochromatic Al-Kα X-ray source (Kα 1486.58 eV), 15 mA emission current, magnetic hybrid lens, and slot aperture. Region scans were performed using a pass energy of 40 eV and step size of 0.1 eV. Peak fitting of the narrow region spectra was performed using a Shirley type background, and the synthetic peaks were of a mixed Gaussian-Lorentzian type. Carbon sp2 was used for charge reference assumed to have a binding energy of 284 eV. The thermal synthesis reactions were carried out in a two-zone furnace (SSP-354 Reactor, Nanotech Innovations, 132 Artino St., Oberlin, Ohio, USA). All the adsorbents were degassed at 160° C. under vacuum for 2 h prior to adsorption study. CO2 adsorption performance of carbon spheres were measured volumetrically in an Isorb apparatus (Germany) at four different temperatures (0, 25, 35 and 45° C.) and pressures from 0.1 to 10 bar. Degasification temperature was internally controlled by covering the cell, containing the sample, with a thermojacket, while the adsorption temperature was adjusted by a jacketed beaker connected to a circulating bath containing water and ethylene glycol. For each experiment, about 200 mg of carbon spheres was used for the adsorption studies. Ultra-pure CO2 (99.9%) and N2 (99.9%) as gas sources were used throughout the experiments. N2 adsorption experiments at 25° C. and different pressures were also recorded through the same procedure for CO2. NOVA 2000e volumetric adsorption analyzer (Quantochrome) was carried out to assess the surface area, pore volume, and pore size distribution using N2 (−196° C., 99.9% purity) and CO2 (0° C.). For each adsorption-desorption analysis, the cell was filled with a specific amount of sample, it was then weighted and loaded into the degas port. After this, the heating pockets were attached, and then degassed under a vacuum pump for 8 h at 150° C. Once degassing time was completed, each carbon sphere sample was backfilled with helium to avoid the sample being dosed with CO2 before analysis. It is noted that, carbon-based materials are mostly non-microporous and highly sensitive. The specific surface area (SBET) measurement was taken from N2 adsorption and analyzed using the Brunauer-Emmett-Teller (BET) model within relative pressure (p/p0) of 0.05-0.99. Incremental pore size distribution and pore volume were taken from CO2 measurements and calculated using the DFT method.
Example 1. 5 g of CB (acetylene black) was placed in a round bottom flask containing 100 mL nitric acid (HNO3) and stirred at 90° C. for 120 h. Then, the nitric acid was removed by evaporation under vacuumed yielding oxidized carbon black (OCB) as dark brown powder. Obtained OCB were used for the next step without any further process and purification.
Example 2. 5 g of CB (Pearl 2000) was placed in a round bottom flask containing 100 mL nitric acid (HNO3) and stirred at 90° C. for 48 h. Then, the nitric acid was removed by evaporation under vacuumed yielding oxidized carbon black (OCB) as dark brown powder. Obtained OCB were used for the next step without any further process and purification.
Example 3. 5 g of CB (Pearl 2000) was placed in a round bottom flask containing 100 mL nitric acid (HNO3) and stirred at 90° C. for 120 h. Then, the nitric acid was removed by evaporation under vacuumed yielding oxidized carbon black (OCB) as dark brown powder. Obtained OCB were used for the next step without any further process and purification.
Example 4. 5 g of CB (Monarch 1000) was placed in a round bottom flask containing 100 mL nitric acid (HNO3) and stirred at 90° C. for 120 h. Then, the nitric acid was removed by evaporation under vacuumed yielding oxidized carbon black (OCB) as dark brown powder. Obtained OCB were used for the next step without any further process and purification.
Example 5. 5 g of CB (Vulcan R-X72) was placed in a round bottom flask containing 100 mL nitric acid (HNO3) and stirred at 90° C. for 120 h. Then, the nitric acid was removed by evaporation under vacuumed yielding oxidized carbon black (OCB) as dark brown powder. Obtained OCB were used for the next step without any further process and purification.
Example 6. 5 g of CB (Vulcan 3) was placed in a round bottom flask containing 100 mL nitric acid (HNO3) and stirred at 90° C. for 120 h. Then, the nitric acid was removed by evaporation under vacuumed yielding oxidized carbon black (OCB) as dark brown powder. Obtained OCB were used for the next step without any further process and purification.
Example 7. 1 g of OCB (obtained from Example 1) was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and used directly for CO2 uptake experiment without any purification.
Example 8. 1 g of OCB (obtained from Example 2) was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and used directly for CO2 uptake experiment without any purification.
Example 9. 1 g of OCB (obtained from Example 3) was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and used directly for CO2 uptake experiment without any purification.
Example 10. 1 g of OCB (obtained from Example 4) was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and used directly for CO2 uptake experiment without any purification.
Example 11. 1 g of OCB (obtained from Example 5) was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and used directly for CO2 uptake experiment without any purification.
Example 12. 1 g of OCB (obtained from Example 6) was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and used directly for CO2 uptake experiment without any purification.
Example 13. 5 g of CB (Pearl 2000) was placed in a round bottom flask containing 100 mL HNO3 and stirred at 90° C. for 120 h. The mixture was cooled down and centrifuged (5000 rpm, 20 min) to separate supernatant from sediment. The HNO3 was removed from supernatant and the resulting brown powder was further dried at 80° C. overnight to give carbon nanoribbons (OCB small fragments, 3.3 g) and used for the pyrolysis.
Example 14. 5 g of CB (Pearl 2000) was placed in a round bottom flask containing 100 mL HNO3 and stirred at 90° C. for 120 h. The mixture was cooled down and centrifuged (5000 rpm, 20 min) to separate supernatant from sediment. The sediment was centrifuged from H2O (5000 rpm, 20 min) twice to remove yellowish transparent solution. The third centrifugation resulted in a black sediment (OCB-A, 1.3 g) and black supernatant containing OCB-B (0.9 g). H2O was removed from the mixture of OCB-B and both OCB-A and OCB-B were further dried separately at 80° C. overnight and used for pyrolysis.
Example 15. 1 g of OCB-A was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and labelled PC-A used directly for CO2 uptake experiment.
Example 16. 1 g of OCB-B was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and labelled PC-B used directly for CO2 uptake experiment.
Example 17. 1 g of nanoribbons was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and labelled PC-C used directly for CO2 uptake experiment.
Example 18. 1 g of nanoribbons was placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 3° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and labelled PC-C′ used directly for CO2 uptake experiment.
Example 19. 1 g of nanoribbons was mixed with 1 g of urea and placed in a ceramic boat in a horizontal cylindrical furnace with an inner diameter of 35 mm and then heated at a rate of 60° C. min−1 up to 800° C. under argon. Heating was kept for 1 h, then, the furnace was cooled down to room temperature under argon. The resulting black powder was collected from the boat and labelled PC-C′ used directly for CO2 uptake experiment.
While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims benefit of U.S. provisional patent application Ser. No. 63/038,138, filed Jun. 12, 2020, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63038138 | Jun 2020 | US |
