Beneficial uses of carbon black tail gas

Abstract

A process to manufacture carbon includes (a) in a carbon black reactor, converting at least a portion of at least one hydrocarbon feedstock to carbon black in the presence of combustion gases generated by burning a fuel in an oxidation gas mixture to form a first product stream comprising the carbon black, carbon dioxide, carbon monoxide, water vapor, and hydrogen, wherein the fuel is a portion of the hydrocarbon feedstock or a separate fuel source; (b) adding water to the first product stream to at least partially halt the conversion and form a second product stream comprising carbon black, carbon dioxide, carbon monoxide, hydrogen, and water vapor; (c) removing the carbon black from the second product stream to form a tail gas; (d) removing at least a portion of the water from the tail gas to form a dewatered tail gas; and (e) contacting the dewatered tail gas with a catalyst to deposit carbon on the catalyst and form a partially decarbonized tail gas comprising carbon monoxide and hydrogen.

Description

Docket No. - 2023715P- 1 of 19-TITLEBENEFICIAL USES OF CARBON BLACK TAIL GASBACKGROUND1. Field.

[0001] This relates to the beneficial use of tail gas from a carbon black production process.2, Description of the Related Art.

[0002] Carbonaceous fuels and other organic material are combusted in a wide variety of industrial processes. Furnace reactors, combustion engines, combustion chambers, boilers, furnaces, heaters, hot gas generators, burners, waste incinerators, and the like, are used to combust carbonaceous fuels. This combustion equipment may be used to make energy, incinerate waste and byproduct materials, or both. During a typical combustion process within a furnace or boiler, for example, a hydrocarbon feedstock or fuel is combusted in the presence of oxygen or other oxidizing gas, and a flow of a combustion exhaust gas is produced. In some industries, such as in carbon black production, refinery operations, or petrochemical operations, exhaust gases generated in primary process units are conveyed to heaters or boilers for energy production or heat recovery. These operations can generate emissions, which can be subject to any applicable air quality controls or requirements.

[0003] A furnace carbon black producing process, for example, typically employs a furnace reactor having a burner or combustion chamber followed by a reactor. A combustion fuel feed stream, typically a hydrocarbon gas stream such as natural gas, or the like, is combusted in the burner portion along with an oxidant feed gas stream such as air, oxygen, or oxygen enriched air to produce hot combustion gases which pass then to the reactor portion of the furnace. In the reactor, hydrocarbon feedstock is exposed to the hot combustion gases. Part of the feedstock is burned, while the rest is decomposed to form carbon black, hydrogen, carbon monoxide, and other gaseous products. The reaction products typically are quenched with water, and the resulting product stream, a mixture of carbon black and tail gas, is cooled, conveyed to a bag collector or other filter system, whereupon the carbon black content is separated from the tail gas. The recovered carbonDocket No. - 2023715P- 2 of 19- black typically is finished to a marketable product, such as, for example, by pulverizing and wet pelletizing. Water from the pelletizing typically is driven off with a dryer, which may be gas-fired, oil-fired, process-gas fired such as with tail gas, or combinations of these. The dried pellets can then be conveyed from the dryer to bulk storage or other handling. The dryer also can generate gaseous emissions. The principal source of emissions in the carbon black furnace process typically is from the tail gas. Other than direct venting, tail gas emissions have been discharged using flares. The tail gas can contain combustible gas components. This tail gas may be advantageously combusted to generate heat for a dryer as described above or for other uses. However, the tail gas may have a higher heating value than can be used in other parts of the furnace black process. As the combustion of excess tail gas may entail flaring and / or emissions penalties in certain jurisdictions, it would be advantageous to make other beneficial uses of the tail gas in addition to combustion.SUMMARY

[0004] It is desirable to capture a portion of the carbon present in the tail gas as solid carbon while still combusting a portion of the tail gas as needed to generate heat for beneficial purposes. This reduces carbon dioxide emissions from the combustion of the tail gas in excess of the heat requirements of the system.

[0005] In one embodiment, a process to manufacture carbon includes (a) in a carbon black reactor, converting at least a portion of at least one hydrocarbon feedstock to carbon black in the presence of combustion gases generated by burning a fuel in an oxidation gas mixture to form a first product stream comprising the carbon black, carbon dioxide, carbon monoxide, water vapor, and hydrogen, wherein the fuel is a portion of the hydrocarbon feedstock or a separate fuel source; (b) adding water to the first product stream to at least partially halt the conversion and form a second product stream comprising carbon black, carbon dioxide, carbon monoxide, hydrogen, and water vapor; (c) removing the carbon black from the second product stream to form a tail gas; (d) removing at least a portion of the water from the tail gas to form a dewatered tail gas; and (e) contacting the dewatered tail gas with a catalyst to deposit carbon on the catalyst and form a partially decarbonized tail gas comprising carbon monoxide and hydrogen. In certain embodiments, the amount of carbon monoxide in the decarbonized tail gas is from 1 to 40%, for example, from 5 toDocket No. - 2023715P- 3 of 19- amount of hydrogen in the decarbonized tail gas is from 20 to 80%, for example, from 30 to 60%, of the hydrogen in the dewatered tail gas. The dewatered tailgas may have at most 5 vol% water, for example 1 vol% to 5 vol% water

[0006] Removing at least a portion of the water may include cooling the tail gas and removing resulting condensed water. Before contacting, the method may further include compressing the tail gas and bringing the compressed tail gas to an appropriate temperature to react with the catalyst. The catalyst may include one or more transition metal and / or transition metal oxides. The catalyst may include one or more of iron, cobalt, nickel, and oxides of any of the above. The catalyst may include or be pyrolysis carbon. The catalyst may comprise iron. The catalyst may be loaded on a ceramic support comprising a metal oxide or metalloid oxide, e.g., silica, titania, zirconia, or alumina, for example, silica.

[0007] The partially decarbonized tail gas may have a heating value, measured at 0 °C, of from 1.5 to 2.5 MJ / Nm3. The partially decarbonized tail gas may include methane in an amount of 0 mol% to 20 mol%, for example, from 0 mol% to 10 mol%, of the total amount of carbon in the tail gas. The method may further include combusting at least a portion of the partially decarbonized tail gas to generate heat. At least a portion of the partially decarbonized tail case may be combusted in the combustion zone. The deposited carbon may includes at least 30% of the carbon present in the original tail gas stream, for example, from 30% to 70%, from 40 to 60%, or from 45 to 55% of the carbon present in the original tail gas stream.

[0008] Carbonaceous particulate may be produced by any combination or subcombination of the above methods.

[0009] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.BRIEF DESCRIPTION OF THE DRAWING

[0010] Figure 1 is a schematic of a carbon black reactor suitable for use with various embodiments.

[0011] Figure 2 is a schematic of a carbon deposition system according to an exemplary embodiment.Docket No. - 2023715P- 4 of 19-

[0012] Figures 3A and 3B are field emission scanning electron micrographs of carbon produced according to exemplary embodiments.

[0013] Figures 4A, 4B, and 4C are transmission election micrographs of carbon produced according to an exemplary embodiment.

[0014] Figures 5A, 5B, and 5C are transmission election micrographs of carbon produced according to an exemplary embodiment.DETAILED DESCRIPTION

[0015] In one embodiment, a process to manufacture carbon includes (a) in a carbon black reactor, converting at least a portion of at least one hydrocarbon feedstock to carbon black in the presence of combustion gases generated by burning a fuel in an oxidation gas mixture to form a first product stream comprising the carbon black, carbon dioxide, carbon monoxide, water vapor, and hydrogen, wherein the fuel is a portion of the hydrocarbon feedstock or a separate fuel source: (b) adding water to the first product stream to at least partially halt the conversion and form a second product stream comprising carbon black, carbon dioxide, carbon monoxide, hydrogen, and water vapor; (c) removing the carbon black from the second product stream to form a tail gas; (d) removing at least a portion of the water from the tail gas to form a dewatered tail gas; and (e) contacting the dewatered tail gas with a catalyst to deposit carbon on the catalyst and form a partially decarbonized tail gas comprising carbon monoxide and hydrogen. In certain embodiments, the amount of carbon monoxide is from 1 to 40%, for example, from 5 to 15%, of the carbon monoxide in the dewatered tail gas. Alternatively or in addition, the amount of hydrogen is from 20 to 80%, for example, from 30 to 60%, of the hydrogen in the dewatered tail gas.

[0016] The methods and apparatus of the various embodiments and implementations can be used to modify any furnace carbon black reactor known to those of skill in the art. For example, these methods and apparatus may be used to modify furnace carbon black reactors such as those described in US Patents Nos. 3,922,335; 4,383,973; 5,190,739; 5,877,250; 5,904,762; 6,153,684; 6,156,837; 6,403,695; 6,485,693; 7,829,057; 8,871,173; and 10,829,642, the entire contents of all of which are incorporated by reference. In an exemplary embodiment shown in Figure 1, carbon black is produced in a furnace carbon black reactor 10 comprising a combustion zone 12. a feedstock injection zone 14, a reaction zone 16 and a first quench zone 18 following first injector 20 for process water 22. ProcessDocket No. - 2023715P- 5 of 19- water 22 may be pumped through first injector 20 and any subsequent injector(s) or may be injected through one or more of the injectors via a venturi mixer. To produce the carbon black, hot combustion gases are generated in combustion zone 12 by reacting liquid or gaseous burner fuel 24 and a suitable oxidation gas mixture comprising an oxidation reagent 26 and other gases described below. At least some of the components of the oxidation gas mixture enter combustion zone 12 via first oxidation gas inlet 27, and burner fuel 24 enters combustion zone 12 via fuel inlet 25. The hot combustion gas stream flows downstream from the combustion zone 12 through feedstock injection zone 14.

[0017] Carbon black yielding feedstock may be introduced into feedstock injection zone 14 radially, axially or both. Carbon black yielding feedstock is typically heated prior to introduction. As shown in Figure 1, carbon black yielding feedstock 28 is heated in feedstock heater 70 to form heated feedstock 31. Heated feedstock 31 inj ected radially may be injected from a plurality of feedstock inlets disposed about a circumference of feedstock injection zone 14 and is injected in a transverse orientation to the hot combustion gas stream traveling from combustion zone 12 to reaction zone 16. Upon introduction, the heated feedstock 31 mixes with the hot combustion gas stream to form a product stream in which the carbon black yielding feedstock is pyrolyzed and carbon black is formed in reaction zone 16.

[0018] Optionally, and as shown in Figure 1, additional oxidation gas mixture comprising oxidation reagent 26 is supplied to reaction zone 16 as a secondary7oxidation stream via secondary7oxidation gas inlet 29. The carbon black in the product stream can be quenched in one or more quench zones, e.g., first quench zone 18, each supplied by one or more injectors, e g., first injector 20. Useful diameters and lengths of the various zones and the amount of water injected through the various injectors may be selected with reference to the above-indicated patents that are incorporated by reference. The effect of these parameters on the eventual morphology of the carbon black is well understood by those of skill in the art and does not change the operation of the various embodiments herein. Alternate carbon black reactor configurations are also possible, such as configurations employing two or more reaction zones optionally separated by a quench zone in which the reaction is partially quenched, with injection of additional carbon black generating feedstock in each subsequent reaction zone. Alternatively or in addition, additionalDocket No. - 2023715P- 6 of 19- feedstock or heated feedstock may be injected into reaction zone 16 without first quenching the reaction with process water 22.

[0019] Among the fuels suitable for use in reacting with the oxidation gas mixture in combustion zone 12 to generate the hot combustion gas stream are included any readily combustible gas, vapor, and / or liquid stream such as natural gas, coal gas, biomass gas, biomass liquid, liquid fuel generated from a chemical process byproduct stream, hydrogen, carbon monoxide, methane, acetylene, alcohols, kerosene, or any gas having a lower heating value (LHV) greater than 2 MJ / Nm3. Combinations of these may also be employed. It is generally preferred, however, to utilize fuels having a high content of carbon- containing components, and, in particular, hydrocarbons. For example, any of the carbon black-yielding feedstocks listed below may also be employed as a burner fuel 24. The burner fuel 24 may be injected into combustion zone 12 at any temperature from its ambient temperature (i. e.. without any heating or cooling) to 800 °C. To facilitate the generation of hot combustion gases, oxidation reagent 26, the oxidation gas mixture comprising oxidation reagent 26, or other components of the oxidation gas mixture may be preheated before or after mixing, for example, to a temperature from 400-950 °C.

[0020] The carbon black-yielding feedstock that can be employed with the present invention can include any hydrocarbon gas, liquid or oil feedstocks useful for carbon black production. Suitable liquid feedstocks include, for example, unsaturated hydrocarbons, saturated hydrocarbons, olefins, aromatics, and other hydrocarbons such as biomass- derived liquids, decant oil. coal tar derived liquids, asphaltene containing oils, kerosenes, naphthalenes, terpenes, ethylene tars, cracker residues, oils produced from recycled materials, or any combinations thereof. In general, any hydrocarbon-containing liquid with at least 60 wt% carbon content may be employed. Suitable gaseous feedstocks include, for example, natural gas, methane, ethylene, acetylene, and other C4-C6 hydrocarbon gases. Any of these feedstocks may be processed using techniques known to those of skill in the art to remove sulfur or other undesirable species prior to use. The carbon black-yielding feedstock 28 may be injected into feedstock injection zone 14 or subsequent injection zone(s) as discussed above at any temperature from its ambient temperature (i.e., without any heating or cooling) to 500 °C for liquid feedstocks or to 900 °C for gaseous feedstocks.

[0021] Also, any of the feedstocks for the described process schemes and methods can contain additional materials or compositions which are commonly used to makeDocket No. - 2023715P- 7 of 19- conventional carbon black. The method of the present invention can further include introducing at least one substance that is or that contains at least one Group IA and / or Group II A element (or ion thereof) of the Periodic Table. The substance containing at least one Group IA and / or Group IIA element (or ion thereof) contains at least one alkali metal or alkaline earth metal. Examples include lithium, sodium, potassium, rubidium, cesium, francium, calcium, barium, strontium, or radium, or combinations thereof. Any mixtures of one or more of these components can be present in the substance. The substance can be a solid, solution, dispersion, gas, or any combinations thereof. More than one substance having the same or different Group IA and / or Group IIA metal (or ion thereof) can be used. If multiple substances are used, the substances can be added together, separately, sequentially, or in different reaction locations. For purposes of the present invention, the substance can be the metal (or metal ion) itself, a compound containing one or more of these elements, including a salt containing one or more of these elements, and the like. The substance can be capable of introducing a metal or metal ion into the reaction that is ongoing to form the carbon black product. For purposes of the present invention, the substance containing at least one Group I A and / or IIA metal (or ion thereof), if used, can be introduced at any point in the reactor, for example, prior to the complete quenching. The amount of the Group I A and / or Group IIA metal (or ion thereof) containing substance, if used, can be any amount as long as a carbon black product can be formed. The substance can be added in the same manner that a carbon black yielding feedstock is introduced. The substance can be added as a gas, liquid, or solid, or any combination thereof. The substance can be added at one point or several points and can be added as a single stream or a plurality of streams. The substance can be mixed in with the feedstock, fuel, and / or oxidant prior to or during their introduction.

[0022] In addition to carbon black, the product stream contains carbon dioxide, carbon monoxide, hydrogen, and water vapor. Water vapor is present before quenching and the product stream becomes more humid as a result of the quench. In addition, the product stream may include some nitrogen, acetylene, SOx, NOX, and other species that are typically generated during furnace carbon black production processes. Following quenching, the product stream containing hot carbon black can be passed through one or more heat exchangers, for example, through heat exchanger 30. The use of the heat extracted thereby is discussed in more detail below. As shown in Figure 1, heat exchanger 30 transfers heatDocket No. - 2023715P- 8 of 19- from the product stream to a gas, but heat exchanger 30 and any subsequent heat exchanger(s) may also be a boiler or other heat exchanger that transfers heat from the hot product stream to a liquid. After the product stream passes through the heat exchanger(s), a cooling zone 32 supplied with process water 22 by cooling zone injector 34 may provide an additional opportunity to control the temperature of the product stream prior to any separating and cooling steps described below. Alternatively or in addition, similar cooling zones may precede a particular heat exchanger to control the temperature of the product stream entering the heat exchanger.

[0023] After the product stream is quenched, it passes downstream into any conventional separating and cooling steps whereby the carbon black is recovered, denoted in Figure 1 as separator 36. Separator 36 may include devices such as a bag filter, ceramic filter, cyclone separator, other devices known to those of skill in the art for separating particulates from a gas stream, or a combination of two or more of these. Separation of the quenched product stream results in two product streams, carbon black 37 and tail gas 38. One of skill in the art will recognize that small amounts of tail gas may be present in the stream of carbon black 37 and vice versa.

[0024] Carbon black 37 may be any conventional carbon black. For example, carbon black 37 may be any of the N-series carbon blacks in accordance with ASTM D-1765. for example, an N100, N200, N300, N500, N600, N700, N800, or N900 series carbon black. More particular examples of ASTM N-series carbon blacks include N110, N121, N134, N 220, N231. N234, N299, N326, N330, N339, N347, N351, N358, N375, N550. N660, N683, N762. N765, N774, or N990 carbon blacks. Alternatively or in addition, carbon blacks produced according to the embodiments provided herein may have a structure, as given by the oil adsorption number for the carbon black, (OAN, ASTM D-6556) from 30 to 450 mL / lOOg, for example, 30 to 100 mL / lOOg, from 100 mL / lOOg to 200 mL / lOOg, from 200 mL / lOOg to 300 mL / lOOg, or from 300 mL / lOOg to 450 mL / lOOg. Alternatively or in addition, and in combination with any of the structure values provided above, the carbon black may have a surface area (BET surface area, ASTM D-2414) from 5 to 1800 m2 / g, for example, from 8 m2 / g to 150 m2 / g, from 150 m2 / g to 350 m2 / g, from 350 m2 / g to 600 m2 / g, from 600 m2 / g to 900 m2 / g, from 900 m2 / g to 1300, or from 1300 m2 / g to 1800 m2 / g. The carbon black may be used in any end-use application in which carbon black is exploited, for example, as a pigment, reinforcing agent, filler, and / or thermal and / orDocket No. - 2023715P- 9 of 19- electrical conductor and be useful in elastomers, plastics, polymers, toners, inks, batteries, adhesives, coatings, and the like.

[0025] Following the removal of the carbon black, the tail gas includes carbon dioxide, carbon monoxide, hydrogen, water vapor, and optionally other gases such as nitrogen and methane. The water vapor may adversely affect the equilibria of various reactions leading to deposition of carbon on the catalyst and is preferably removed. For example, the tail gas may be cooled according to any method known to those of skill in the art to condense the water vapor, which is then removed from the tail gas to produce a dewatered tail gas having no more than 5 vol% water, for example, 0.5 to 5 vol % water. Furthermore, the resulting condensate can be used in other unit operations in the carbon black production process.

[0026] In some embodiments, sulfur-containing species in the tail gas are removed before the tail gas is contacted with the catalyst. The sulfur-containing species may be removed before or after dewatering using any method known to those of skill in the art. For example, an amine-Claus process may be used to remove H2S. A Shell Claus Off-gas Treatment process may be used to remove non-FFS species.

[0027] The dewatered tail gas is then preferably compressed and heated to an appropriate temperature to react in the presence of a catalyst. The compression and heating may be accomplished using any method known to those of skill in the art. In some embodiments, the dewatered tailgas is brought to a temperature of 350 °C to 650 °C, for example, from 450 °C to 500 °C and a pressure from 0 barg to 100 barg, for example, atmospheric or ambient pressure, or pressurized sufficiently to overcome any pressure drop during the reaction. The dewatered and heated tail gas is contacted with the catalyst in a fluidized bed or other reactor known to those of skill in the art. As the reactions described below may generate heat, the reactor may be cooled or maintained at a desired temperature using any method known to those of skill in the art.

[0028] The catalyst promotes one or more of the following reactions that result in the formation of carbon:Reverse Boudouard reaction: 2 CO C + CO2Methane decomposition: CFU C + 2 H2Direct CO hydrogenation: CO + H2 = C + H2ODocket No. - 2023715P- 10 of 19-Optionally, the catalyst may also promote the reverse water-gas shift reaction (CO2 + H2CO + H2O) that further increases the yield of carbon formed according to the reactions above.

[0029] Any suitable catalyst used by those of skill in the art for such reactions may be employed. Exemplary catalysts include, but are not limited to, transition metals especially iron, cobalt, and / or nickel, and their alloys and / or oxides, optionally supported on ceramics comprising metal or metalloid oxides such as silica, alumina, titania and / or zirconia. The choice of catalyst and reaction conditions will influence the morphology’ of the resulting carbon. The solid carbon is deposited on the catalyst particles, with a partially decarbonized tail gas proceeding downstream. The carbon may be separated from the catalyst particles by mechanical force or other methods known to those of skill in the art. The catalyst may be reused. Alternatively or in addition, the resulting carbon-catalyst composite particles may be removed from the reactor and used with or without further purification or other treatment. The solid carbon generated in the process may include at least 30% of the carbon present in the original tail gas stream, for example, from 30% to 70%, from 40 to 60%, or from 45 to 55% of the carbon present in the original tail gas stream.

[0030] Alternatively or in addition, pyrolysis carbon may be employed as the catalyst or in combination with one or more of the catalysts described above. The pyrolysis carbon may be or comprise one or more of char, raw reclaimed carbon, and processed reclaimed carbon. Char is solid material resulting from pyrolysis of rubber goods. Raw' reclaimed carbon is solid material resulting from pyrolysis of rubber goods that contain carbonaceous particulate fillers, including but not limited to carbon black, in any amount. Processed reclaimed carbon means raw- reclaimed carbon that has been processed to remove at least one macroscopic contaminant such as fabric or wire. Pyrolysis carbon in any form may be milled or classified by any method known in the art to control or change the particle size distribution.

[0031] The decarbonized tail gas still has significant heating value by virtue of at least the remaining hydrogen from the original tail gas and, in some embodiments, also carbon monoxide and methane. In certain embodiments, the decarbonized tail gas has a heating value, measured at 0 °C, of from 1.5 to 2.5 MJ / Nm3. In certain embodiments, the decarbonized tail gas is partially depleted in H2 and CO. The overall CO conversion.Docket No. - 2023715P- 11 of 19- defined as the amount of CO reacted divided by the total amount of CO in the inlet gas, may be from 60% to 99%, for example, from 85% to 95%. The overall H2 conversion, defined as the amount of H2 reacted divided by the total amount of H2 in the inlet gas, may be from 20% to 80%, for example, from 40% to 70%. Alternatively or in addition, the decarbonized tail gas may also be enriched in methane owing to the partial gasification of solid carbon. The overall yield of methane may be from 0 mol% to 20 mol%, for example, from 0 mol% to 10 mol%, of the total amount of carbon in the original tail gas. As a result, the decarbonized tail gas may still be combusted to produce heal for the oxidation gas mixture and / or feedstock and / or to dry the carbon black and / or accomplish other processes during production of the carbon black that require heat. Alternatively or in addition, at least a portion of the decarbonized tail gas may be recycled to the combustion zone 12.EXAMPLESExample 1

[0032] To quantitatively demonstrate the process of the present invention, a simulation was performed using Aspen Plus vl2. The inlet gas composition into the simulation is based on aggregated tail gas data from a carbon black production facility. The simulation is as illustrated in the schematic of Fig. 2.

[0033] In Fig. 2, the abbreviations / symbols are as follows:Fl: Gas dewatering system (e.g.. cooling tower or fin fan-based system)Rl: Carbon deposition reaction system (e.g., fluidized bed reactor comprising heating and cooling apparatus)F2: Solids separation system (e.g., cyclone)

[0034] This simulation is set up as follows. The NRTL equation of state was used to model the entire system consisting of the following species: N2. CO, CO2, H2, CH4, C2H2, H2O, H2S, COS, CS2, SO2, and C (solid; graphite). The gas dewatering system (unit Fl) was modeled as a flash column. The carbon deposition reaction system (unit Rl) was modeled as an isothermal Gibbs reactor in which all species except CH4 were allowed to equilibrate. As methane formation is much slower than the other reactions that might occur inside the reactor, the outlet CFU flow rate was set to 30 kmol / h to reflect a lower-than-equihbriumDocket No. - 2023715P- 12 of 19- extent of methanation. Finally, the solids separation system was modeled as another flash column.

[0035] In this simulation, Table 1 below sets forth the results for the gas stream as it progresses through the units shown in Fig. 2. The stream number depicted in the table corresponds to the stream labels shown in Fig. 2.Table 1

[0036] In this model process, 68000 Nm3 / h of a hypothetical tail gas representative of a commonly used carbon black production process and containing 36 vol% N2, 41 vol% H2O, 12 vol% H2, 8 vol% CO, and 2.5 vol% CO2 in addition to other components listed in Table 1, was processed to generate 37400 Nm3 / h of a partially decarbonized tail gas containing 66 vol% N2, 13 vol% H2O, 12 vol% H2, 1 vol% CO, 7 vol% CO2, and 2 vol% CH4in addition to other components listed in Table 1. With a lower heating value of 2.1 MJ / Nm3at 0 °C, this stream may be combusted to provide energy7to satisfy needs elsewhere in theDocket No. - 2023715P- 13 of 19- carbon black process. A stream comprising 2000 kg / h of solid carbon or about 50 wt% of the carbon originally present in the tail gas stream, which may be further processed for sale or for use in other beneficial processes, was also generated.Example 2

[0037] Fe / SiCh (iron supported on silica): Iron(III) nitrate nonahydrate (1.80 g, Fisher Chemical, reagent grade) was dissolved in deionized water (0.8 g). The solution was added dropwise to fumed silica (1.0 g, CAB-O-SIL® M-5) under constant mixing in a mortar and pestle. The gel was dried in an oven (100 °C, 16 h), then crushed and calcined in a muffle furnace under static air (400 °C, 1 h, 1 °C / min ramp rate) to yield an orange powder.

[0038] FeCo / SiCh (iron-cobalt supported on silica): Iron(III) nitrate nonahydrate (0.55 g, Fisher Chemical, reagent grade) and cobalt(II) nitrate hexahydrate (0.80 g, Fisher Chemical, reagent grade) were dissolved in deionized water (1 .0 g). The solution was added dropwise to fumed silica (1.0 g, CAB-O-SIL® M-5) under constant mixing in a mortar and pestle. The gel was dried in an oven (100 °C, 16 h), then crushed and calcined in a muffle furnace under static air (400 °C, 1 h, 1 °C / min ramp rate) to yield a black powder.

[0039] For each experiment, 200 mg catalyst powder was spread in a thin layer over a small ceramic boat (3 mL capacity ) placed in the middle of a quartz tube (1 inch inner diameter). For samples 1, 2, 4, and 5, the catalyst was pre-reduced by first heating to 500 °C (5 °C / min ramp rate) under house N2 (100 mL / min), followed by switching the inlet gas to 50 vol% H2 / N2 (100 mL / min, Airgas, certified standard) for 1 hour. To deposit carbon, the catalyst was then brought to the reaction temperature (450 °C for samples 1-4, 550 °C for sample 5) under house N2 and the inlet gas switched to the feed gas mixture (H2 / CO / CO2 / Ar = 20 / 15 / 5 / 60 vol%, Airgas, certified standard). Argon was substituted for the nitrogen that would be present in a manufacturing environment to facilitate characterization by mass spectrometry (N2 would interfere with the molecular ion peak of CO at m / z = 28). For Sample 2, the feed gas was saturated with water at 25-30 °C via a bubbler. After the desired reaction time (one hour), the system was purged with house N2 and cooled to ambient temperature. The spent catalyst was then weighed and transferred to a glass vial for storage. Effluent gases from Samples 1 and 4 were dehydrated throughDocket No. - 2023715P- 14 of 19- a knockout pot followed by a desiccant tube prior to collection in sampling bags (Restek Corporation, Catalog No. 22049) at regular intervals for offline analysis by mass spectrometry, which confirmed the presence of carbon monoxide in effluent gases from both experiments. The resulting weight gain is listed in Table 2.Table 2

[0040] The carbon products from samples 2 and 5 were characterized as-is (without removal of residual catalyst) as follows:

[0041] Thermogravimetric analysis (TGA): TGA measurements were performed using a TA Instruments Q600 STD Horizontal thermogravimetric analyzer. Around 15-20 mg of powder was sampled and pressed into a fractionated, compressed pellet. The pellet was loaded into an alumina crucible that was heated under flowing air (300 mL / min) to 800 °C (10 °C / min ramp rate with a 30 min isothermal hold) with continuous monitoring of the weight loss. Both samples exhibited weight loss beginning at a temperature below 400 °C, suggesting the presence of amorphous carbon, with an overall weight loss of 24% for Sample 2 and 21% for Sample 5, consistent with the weight gain listed in Table 2.

[0042] Field-emission scanning electron microscopy (FE-SEM): The FE-SEM images were collected using a ZEISS Ultra Plus field emission scanning electron microscope at an acceleration voltage of 3 KeV. The samples were prepared by attaching a thin layer of powder to a standard SEM mount using double sided carbon tape. Figure 3A (Sample 2) and Figure 3B (Sample 5) both show networks of filamentous structures interspersed with the original fumed silica catalyst support, suggesting that carbon nanotubes or nanofibers were formed.

[0043] Transmission electron microscopy (TEM): TEM images were collected on a JEOL JEM 2100 electron microscope operating at 200 kV. 60 mg of powder was sampled and dispersed in 30 mL chloroform. The dispersion was further diluted to 100 ppm using aDocket No. - 2023715P- 15 of 19-Misonix XL2020 probe sonicator with 1 ” Ti tip under continuous sonication for 10 min. One drop of the dispersion was then deposited on a 200-mesh carbon-coated copper TEM grid and air-dried prior to imaging. Figure 4 (Sample 2) and Figure 5 (Sample 5) demonstrate the presence of tubular nanostructures in both samples, while also revealing additional plate-like nanostructures in Sample 5 (Figures 5A and 5B) that are not readily apparent from the FE-SEM images. Analysis of interlayer spacings (Figures 4C and 5C) confirmed the presence of graphitic carbon. The distances annotated in Figures 4C and 5C represent the spacings between five graphitic layers, indicating an interlayer spacing of 0.34-0.35 nm vs. 0.335 nm for perfectly crystallized graphite. Due to breakage induced by the sonication used in sample preparation, the dimensions of the carbon nanostructures could not be estimated from the TEM images.

[0044] Raman spectroscopy: Samples were collected from the dispersion used for TEM imaging (see above). Approximately 500 pL of sediment was applied to a glass microscope slide using a transfer pipet. The chloroform was allowed to evaporate, leaving the carbonaceous material behind on the slide surface. A lab spatula was used to transfer the carbonaceous material to a piece of double-sided adhesive tape affixed to a microscope slide surface. Each carbon sample was pressed firmly into the respective tape surfaces using the lab spatula. The loaded tapes were then analyzed under a Horiba XploRA Raman micro-spectrometer equipped with a 100 mW 532 nm laser, 1000 gr / mm grating, and MPlan 100X / 0.90 objective. Ten locations were examined for each sample at 1% total energy and 5 acquisitions at 5 s residence time for each location. The resulting spectra showed the expected G band at about 1580 cm’1, corresponding to graphitic carbon, and D and D’ bands at 1330 and 1605 cm’1, respectively, corresponding to disordered carbon. The ratios of the integrated D and G peak areas (ID / IG) were 2.1 for Sample 2 and 2.4 for Sample 5, indicating a relatively high degree of disorder in the carbon product.

[0045] The foregoing description of certain embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the claimed invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings, or may be acquired from practice of the claimed invention. The embodiments were chosen and described in order to explain the principles of the claimed invention and its practical application to enable one skilled in the art to utilize theDocket No. - 2023715P- 16 of 19- claimed invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.

[0046] What is claimed is:

Claims

Docket No. - 2023715P- 17 of 19-CLAIMS1. A process to manufacture carbon, said process comprising(a) in a carbon black reactor, converting at least a portion of at least one hydrocarbon feedstock to carbon black in the presence of combustion gases generated by burning a fuel in an oxidation gas mixture to form a first product stream comprising the carbon black, carbon dioxide, carbon monoxide, water vapor, and hydrogen, wherein the fuel is a portion of the hydrocarbon feedstock or a separate fuel source;(b) adding water to the first product stream to at least partially halt the conversion and form a second product stream comprising carbon black, carbon dioxide, carbon monoxide, hydrogen, and water vapor;(c) removing the carbon black from the second product stream to form a tail gas;(d) removing at least a portion of the water from the tail gas to form a dewatered tail gas; and(e) contacting the dewatered tail gas with a catalyst to deposit carbon on the catalyst and form a partially decarbonized tail gas comprising carbon monoxide and hy drogen.

2. The method of claim 1 Error! Reference source not found., wherein the dewatered tailgas has at most 5 vol% water, for example 1 vol% to 5 vol%.

3. The method of claim 1, wherein the amount of carbon monoxide in the decarbonized tail gas is from 1 to 40%, for example, from 5 to 15%, of the carbon monoxide in the dewatered tail gas.

4. The method of claim 1. the amount of hydrogen in the decarbonized tail gas is from 20 to 80%, for example, from 30 to 60%, of the hydrogen in the dewatered tail gas.

5. The method of claim 1, wherein removing at least a portion of the water comprises cooling the tail gas and removing resulting condensed water.Docket No. - 2023715P- 18 of 19-6. The method of claim 1, wherein the method further comprises, before contacting, compressing the tail gas and bringing the compressed tail gas to an appropriate temperature to react with the catalyst.

7. The method of claim 1, wherein the catalyst comprises one or more transition metal and / or transition metal oxides.

8. The method of claim 1, wherein the catalyst comprises one or more of iron, cobalt, nickel, oxides of any of the above, and pyrolysis carbon.

9. The method of claim 1. wherein the catalyst comprises iron.

10. The method of claim 1, wherein the catalyst is loaded on a ceramic support comprising a metal oxide or metalloid oxide.

11. The method of claim 8. wherein the ceramic support comprises silica, titania, zirconia, or alumina.

12. The method of claim 8, wherein the ceramic support comprises silica.

13. The method of claim 1. wherein the partially decarbonized tail gas has a heating value, measured at 0 °C, of from 1.5 to 2.5 MJ / Nm3.

14. The method of claim 1. wherein the partially decarbonized tail gas comprises methane in an amount of 0 mol% to 20 mol%. for example, from 0 mol% to 10 mol%, of the total amount of carbon in the tail gas.

15. The method of claim 1, further comprising combusting at least a portion of the partially decarbonized tail gas to generate heat.

16. The method of claim 1 , wherein at least a portion of the partially decarbonized tail case is combusted in the combustion zone.

17. The method of claim 1, wherein the deposited carbon includes at least 30% of the carbon present in the original tail gas stream, for example, from 30% to 70%, from 40 to 60%, or from 45 to 55% of the carbon present in the original tail gas stream.

18. Carbonaceous particulate produced by the method of any of claims 1-17.

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