Process to obtain synthetic pitches with high softening point from medium and heavy aromatic oils

Abstract

The present invention relates to a process for producing precursors of carbon materials particularly from medium and heavy aromatic oils by thermal oxidative polymerization reactions, so the invention belongs to the field of obtaining carbon precursors from different sources improving total carbon yield.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a process for obtaining synthetic pitches from medium and heavy aromatic oils by thermal oxidative polymerization reactions. The process of the invention allows obtaining a synthetic pitch with a high softening point and improving the total carbon yield in the process.BACKGROUND OF THE INVENTION

[0002] Coal tar pitches, produced in the form of distillation residue from coal tar, are commonly used as binder in the production of carbon anodes for the electrolysis of aluminium and graphite electrodes for use in electric arc furnaces. The production and consumption of these pitches is, therefore, strongly dependent on the demand for these products, and they are produced with the characteristics that will enable them to fulfil the requirements demanded by these applications. The incoming decarbonization of the steel industry will lead to the shutdown of coke oven batteries where the coal tar subproduct is produced. Therefore, there would be an increase of the demand for coal tar pitch to produce graphite electrodes and support the increase in Electrical Arch Furnaces (EAF). Besides, the decline in coal tar supply and the introduction of rigorous environmental regulations have forced pitch producers to search for new strategies to synthetize and prepare less toxic pitches. Thus, in the latest years, new strategies have been developed in order to prepare more environmentally friendly pitches and, at the same time, provide a solution to the coal tar deficit.

[0003] Furthermore, the decarbonization trend in the carbon black industry is also present and the strategies involved are centered around the use of recovered carbon black, and the substitution of fossil-based oils (anthracene oil, decant oil or similar) with pyrolysis oils from residues such as solid urban waste and waste tires. This decarbonization trend will lead to a decrease in the demand for these oils. Therefore, the heavy oil industry, such as the carbochemical sector, is looking for diversification opportunities that will not involve combustion or any other thermal valorisation.

[0004] In addition, in Asia, coal tar pitch coke is used to manufacture synthetic graphite for the Lithium-ion Battery application. In recent years the demand for synthetic graphite has increased significantly and it will continue to grow, especially for applications such as electric vehicles. It is believed that synthetic graphite will become the predominant anodic material over natural graphite. The production of synthetic graphite depends on high quality coal tar pitches, where the primary Quinoline Insoluble (QI) has been removed. The value proposal of increasing the availability of suitable feedstocks to meet the incoming demand of synthetic graphite is aligned with the electrification and the increase of electrical storage solutions.

[0005] Document EP1739153 describes a process for producing pitches, particularly those suitable to use as carbon precursors, from coal tars and distillates thereof, through a sequential and combined operation in three steps of oxidative thermal treatment, thermal treatment under inert atmosphere and fractional distillation. In this document, other properties such as the intermediate rheology of the product until its conversion into carbon materials and the carbon yield for a given softening point are prioritised. The applications targeted by this invention require a graphitic microstructure as developed as possible.

[0006] Document Environ. Sci. Technol. 2009, 43, 8126-8132 describes a procedure for producing new pitches of low toxicity from anthracene oil. The procedure involves oxidative treatment in order to polymerize and condense the anthracene oil components followed by thermal treatment and distillation. This publication is aimed at producing Söderberg anodes of aluminum and silicium, applications that nowadays are obsolete.

[0007] Document Carbon 38 (2000) 1315-1322 reports on the results achieved by the air blowing of an industrial anthracene oil under different experimental conditions of temperature, time and air flow and the studies about the influence of these parameters in the final product.

[0008] In document Coke and Chemistry, 2020, Vol. 63, No. 12, pp. 569-575, the influence on the microstructure of the coke produced of the batch composition and the oxidation conditions of mixtures of moderate-temperature coal pitch and the anthracene fraction of coal tar were investigated.

[0009] RU2750991C1 discloses methods for producing petroleum pitch, used as a binder in the manufacture of various carbon products. However, the process of the invention is a more direct method, as the raw material is used directly without any preliminary distillation steps. Furthermore, the agitator utilized in the reaction is specifically designed to ensure complete consumption of the reagent and to enhance the reaction's efficiency. Additionally, the process of the invention achieves higher reaction yields compared to those demonstrated in the examples of this document, since the yield declared in this document is at most 39%, substantially lower than the yields obtained in the present invention.

[0010] US 2014 / 0099691 A1 discloses a continuous process for converting carbonaceous materials into a liquid hydrocarbon product and consequently is not intended to obtain synthetic pitches as in the present invention.

[0011] US 4 013 540 A discloses the preparation of petroleum pitch for carbon electrode manufactured from full-range decant oil by oxyactivated condensation.

[0012] The present invention is therefore aimed at obtaining non-standard industrial synthetic pitches for applications for advanced carbon materials (carbon fibers, carbon foams, pitches for graphite pitch coating processes for anodic material in electric vehicle lithium-ion batteries, needle coke as precursors, electrical storage of renewable energy generation plants, ...). For this kind of applications, optimally the secondary QI should be minimized, the beta resin should be maximised, and the yield of fixed carbon should also be maximised. In addition, the softening point should be high.

[0013] Besides, for the manufacture of materials where a synthetic pitch with a high softening point is required, two alternatives presently exist: obtaining it from coal tar or from petrochemical bottoms (petroleum pitch). From coal tar, the current problem is removing what is called the insoluble in primary quinoline (QI), which generates heterogeneity in the precursors and which removal is tedious and costly. Starting from both raw materials, coal tar or petrochemical bottoms, requires a distillation temperature above 400 ºC, which causes the generation of mesophase and solid semi-coke waste deposits in the equipment that causes serious mechanical maintenance problems.

[0014] The main applications of the present invention are focused on the manufacture of advanced carbon materials precursors such as synthetic carbons for anodic active materials in Li-ion (graphite, pitch coating): battery or Na-ion battery (hard carbon, soft / hard carbons...) where the final yield of the process and the microstructure become crucially important.DESCRIPTION OF THE INVENTION

[0015] Therefore, there is still a need to obtain improved processes to obtain synthetic pitches or advanced carbon materials precursors for the mentioned applications to overcome the current limitations, i.e. absence of primary QI, improve the process net yield and carbon microstructure control.

[0016] The inventors of the present invention found that this objective can be achieved with the following process: A process to obtain synthetic pitches from at least one medium or heavy aromatic oil selected from the group consisting of anthracene oil, decaline, light anthracene oil, heavy anthracene oil, decant oil and heavy fraction of hydrothermal liquefaction from tire pyrolysis oils, or their mixes in any combination, which process comprises the steps of: providing the at least one oil in a reactor; setting an initial reactor temperature below the starting boiling point of the at least one oil, and reacting the cited at least one oil with an O 2 stream or an O 2 -enriched air stream containing at least 21% O 2 v / v in in the reactor at a temperature of between 350 and 400°C and a pressure of at least 11 bar during a residence time of between 5 min and 5h, characterised in that the supply of the O2 stream or O2-enriched air stream is between 0.075 and 0.2 kg of O2 or O2-enriched air per kg of the at least one oil.

[0017] As herein described, an O 2 stream or O 2 -enriched air or gas stream is any gas that contains at least the O 2 concentration that is naturally present in air, i.e., at least 21% v / v, preferably at least 50% v / v, more preferably approximately 95% v / v. The election of the O 2 concentration in the gas depends mainly on economics and safety considerations. Due to the combined effects of the increased oxygen supply, the increased pressure and the increased reaction times, synthetic pitches with the desired properties can be obtained.

[0018] Figure 1 shows a possible sketch of the installation.

[0019] The type of medium and heavy aromatic oils that can be used as raw materials in the process of the invention should ideally have the following desirable properties: petrochemical, carbochemical or pyrolysis oils origin or any mixed fraction having the following physical-chemical properties: The vapour pressure at the reaction temperature should be at least 5 bar below the selected reaction pressure to minimize volatiles losses and enhance liquid phase reaction, An aromatic Index - C / H atomic ratio of 0.55 to 1.20, Preferred inorganic Ash Content below 5%, but more preferably, for advanced carbon materials, not higher than 0.3% and even more preferably not higher than 0.1%, in order to minimize the impurities. Illustrative examples of this type of compounds, are: Decaline, Tetraline, Light Anthracene oil, heavy Anthracene Oil, Decant Oil, heavy aromatic oil fractions from more sustainable sources like used tire pyrolysis or hydrothermal liquefaction (HTL) or biomass and urban waste residues among others, alone or in any combination among them.

[0020] In the process of the invention, a stream of O 2 or O 2 -containing gas is bubbled into the liquid heavy aromatic oil. The unreacted oxygen accumulates at the head of the reactor and, thanks to the stirrer, is reintroduced into the liquid. This is because the stirrer has a hole in the upper part that, at the speed at which it is stirred (1000 rpm), by the Venturi effect the unreacted gas is absorbed and reintroduced into the liquid through the lower part (see Figure 2).

[0021] In preferred embodiments, the supply of O 2 or O 2 -enriched air is between 0.075 - 0.1 kg of O 2 or O 2 -enriched air / kg of the at least one oil, more preferably between 0.08 - 0.095 kg of O 2 or O 2 -enriched air / kg of the at least one oil, or even more preferably around 0.091 kg of O 2 or O 2 -enriched air / kg of the at least one oil, for the entire residence time of the reactants in the reactor.

[0022] In preferred embodiments, the reaction temperature is between 300-400ºC, more preferably around 375ºC.

[0023] In preferred embodiments, the reaction pressure is between 11 and 100 bar, more preferably between 12 and 50 bar, even more preferably between 15 and 20 bar, and most preferably around 16 bar.

[0024] In preferred embodiments, the residence time is between 5 min and 5 h, more preferably between 10 min and 2 h, even more preferably between 0,5 and 1 h, and most preferably around 0,5 h.

[0025] In preferred embodiments, the at least one oil is selected from the group consisting of anthracene oil, decaline, light anthracene oil, heavy anthracene oil, decant oil, heavy fraction from tire pyrolysis oils, and heavy fraction of HTL.

[0026] After the above-explained reaction step, the process of the invention may preferably comprise a further subsequent thermal treatment at a temperature of between 350ºC and 450ºC during a residence time of between 30 min and 6 hours, in an inert atmosphere. More preferably, the residence time in the cited subsequent thermal treatment is between 2h and 5h, even more preferably between 2 and 4h.

[0027] In a preferred embodiment, the process is carried out in a reactor including an air-blow system.Products obtained

[0028] Following the above-explained process, the obtained products show the following total mass balance: Condensable oils (40ºC): <15% Incondensable gases (40ºC): < 5% Reaction Product Yield: >80% (softening point 60ºC) ∘ Distilled Oils (<25%) ∘ Exhaust gases: <2% ∘ Precursor Yield with Softening Point 110-120ºC (Mettler) (>70%) ▪ Distilled Oils: <40% ▪ Exhaust gases: <2% ▪ Carbon Yield: 40-60% ▪ Net Carbon Yield: 40-50% (from the initial precursor)

[0029] The TGA analysis of the obtained product is conducted as follows: under a nitrogen flow of 60mL / min, a first heating ramp is carried out from 25 to 270ºC at a speed of 10K / min, then an isothermal stage begins at 270ºC for 50min. After that time, it is heated from 270 to 650ºC, at 10K / min. The TGA profile and explanation of the data obtained can be seen in the Figure 3.

[0030] The value of the residue at a temperature of 650ºC corresponds to the parameter "Net Carbon", which is also called carbon residue. On the other hand, the oils obtained from the process of the invention are separated in two during the distillation step: Light Oils: Oils distilled before the isothermal ramp at 270ºC, i.e. the TG value at that point Heavy Oils: Oils distilled from the end of the isothermal ramp at 270ºC and the end of the test at 650ºC.

[0031] Apart from these values and given that the evolution profiles of weight loss with temperature are different in each sample, the different carbon yields of the product obtained can be simulated if a previous distillation at a certain temperature is carried out. In this way we can obtain the Fixed Carbons FC #XXX values, where the "#XXX" value refers to the temperature in the TGA graph (see Figure 3). Table 1: Comparison of the composition in weight percentage of selected samples measured by Thermogravimetric analysis (TGA) for Standard Coal Tar (STD Coal Tar) and Anthracene Oil (AOil).Light Oils wt% Heavy Oils wt% Net Carbon wt% FC #270 wt% FC #350 wt% FC #400 wt% STD Coal Tar 53.928.717.437.741.350.0AOil 93.95.70.45.823.372.3

[0032] Distillation was carried out at temperatures between 270ºC and 400ºC; distillation at temperatures above 400ºC is not convenient due to the progressive thermal decomposition of the pitch that become coke.

[0033] From the data of the table, we can conclude that, although the fixed carbon values of AOil at 400ºC are very interesting, it does not make economic sense given that its overall yield is very low (Net Carbon=0.4%).

[0034] To enhance its performance, the obtained reaction product can be subjected to a subsequent thermal treatment step to stabilize its structure and gain in fixed carbon and net carbon yield.

[0035] According to the specification of the final product and the total conversion rate, the reaction may require and additional distillation stage to the desired final softening point.BRIEF DESCRIPTION OF FIGURES

[0036] Figure 1: Scheme of reactor. Figure 2: Scheme of a typical jet stirrer. Figure 3. Thermogravimetric analysis (TGA) of an unreacted oil (grey line) and standard coal tar (black). Figure 4. Optical Texture Microscopy of the synthetic pitches obtained in Example 1A. The photograph shows the typical optical structure obtained in these synthetic pitches obtained by the process of the invention after a carbonization step (temperature 650ºC). The photo shows absence of primary QI (several defects during polishing can also be observed). Figure 5. Optical Texture Microscopy of the synthetic pitches obtained in Example 1B. The photograph shows a mosaic structure which is significantly different to the structure shown in the Example 1A. This shows that the process of this invention is capable to modulate the crystalline structure. EXPERIMENTAL EXAMPLES

[0037] In the experimental examples, the following conditions reactions were used. A comparison with the condition reactions used in prior art EP1739153 is also provided: Table 2: Comparison between the synthetic pitch properties from the present invention and the pitches obtained in EP1739153Pitches obtained in EP1739153Synthetic pitches obtained in the process of the inventionConditions during reactionConditions during post-reaction thermal treatmentConditions during reactionConditions during post-reaction thermal treatmentT (°C)350-400340-400375375P (bar)5-100-101616Residence Time2-10 s3-10 h30 min2 hSingle-step conversion (%)<40-90-Oxygen supply (kg O2 / kg anthracene oil)0.021-0.053-0.091- Example 1

[0038] In the previously described set up, an anthracene oil (AOil) sample was processed under the following conditions: Example #1A: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 30 min. AOil Flow: 1 kg / h Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1B: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 45 min. Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1C Raw material: Decant Oil Temperature: 300ºC Residence time: 1.82 hours. Oxygen supply: 0.083 kg pure O 2 / kg oil Pressure: 16 bar

[0039] TGA results of the Examples #1A, 1B and 1C compared to a standard coal tar and two heavy aromatic oils, Anthracene oil (AOil) and Decant oil (DOil). Table 3. Properties comparison of Example 1.Light Oils wt% Heavy Oils wt% Net Carbon wt% FC #270 wt% FC #350 wt% FC #400 wt% STD Coal Tar 53.928.717.437.741.350.0AOil 93.95.70.45.823.372.3DOil 39.051.49.615.819.433.1Example #1A 54.718.926.458.361.368.1Example #1B 53.819.726.657.461.067.3Example #1C 33.330.436.354.457.864.3

[0040] The values provided for the AOil refer to the raw material used in Examples #1A and #1B, whereas the DOil refers to the raw material used in Example #1C. The values provided for the Standard Coal Tar are given for comparative purposes.

[0041] In the table above, the advantages of the process of the invention can be clearly observed: Previous Patent EP1739153 B1 was focused on the optimization of the process to obtain an intermediate product, a pitch, with specific rheological characteristics (a softening point around 110ºC Mettler) for the specific requirements of the applications to which it was directed, i.e. electrodes for alumina electrolysis and standard graphite electrodes. In this sense, patent EP1739153 B1 placed special emphasis on limiting the conversion of the process to around 30-35%. In the present invention, these rheological requirements do not exist, and a high softening point pitch can or even should be used, the process can be taken to a greater extent, thereby obtaining a greater carbon yield as shown in the FC#350 and FC#400 values.

[0042] The values presented in data FCXXX represents the fixed carbon of the product obtained after distilling @XXX ºC by TGA simulation. Considering the amount of volatile matter when distilling at a certain temperature, using the process of the invention, it is possible to obtain a higher softening point precursors at certain temperature and gain in fixed carbon. It is enhanced by the increase of distillation temperature.

[0043] Additionally, another advantage can be achieved in the process when obtaining a high softening point pitch. Since the oxidative heat treatment process generates heavy structures, the oils that need to be distilled to obtain them are mainly light oils. Obtaining a high softening point pitch (>250ºC Mettler) can be considered a technologically complex process if it starts directly from a carbochemical tar where it is required to reach distillation temperatures above 400ºC (even if working with high vacuum). These process temperatures generate mesophase and high levels of solid deposits in the product and equipment by generating semi-coke solids. From examples #1A and #1B, pitches with a softening point of 300ºC can be obtained without the need to reach such high temperatures (<400ºC).

[0044] These results are even enhanced when using a petrochemical oil like Decant Oil.Example 2

[0045] Example 2 pitch was produced using the following conditions: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 30 min. Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar

[0046] Distillation: adjustment to softening point 110ºC Mettler

[0047] The product distilled at 110ºC is compared in the table below to the product obtained in EP1739153B1 and to a standard pitch. The pitches obtained in this example show a clear advantage in the Net Carbon Yield value. Table 4. Comparison between Example #2, Standard Pitch and patent EP 1739153.Parameter Softening Point (ASTM D3104) Fixed Carbon (ALCAN) Pitch Yield Net Carbon Yield Quinoline Insoluble (QI) Units ºC, Mettler wt% wt% wt% wt% Example #2 11044.668.330.50.65Standard Pitch 110574827.42-12EP1739153 B111056.835.020.01.3

[0048] In the case of a standard Pitch obtained from coal tar, the value of QI corresponds to primary QI which is an infusible material obtained during the production of the coal tar raw material, whereas for the case of the synthetic pitches obtained in the invention and in the patent EP1739153 B1 it corresponds to secondary QI, which is a fusible heavily condensed material. In other words, the table above shows that the standard pitches have a significant amount of QI (which corresponds to primary QI), while the significant pitches have a significant lower amount of QI (which is not primary QI, but secondary QI).Example 3

[0049] The product obtained from Example 2 was subjected to a subsequent thermal treatment in inert atmosphere after the polymerization reaction to modify the final properties of the pitch and it was conducted under the following conditions: Raw material: The product obtained in Example 2. Thermal treatment: 2h, 375ºC, 16 bar, nitrogen atmosphere. Distillation: adjustment to softening point 110ºC Mettler Table 5. Comparison of Example 3, Standard Pitch and patent EP1739153 Parameter Softening Point (ASTM D3104) Fixed Carbon (ALCAN) Pitch Yield Net Carbon Yield Quinoline Insoluble (QI) Units ºC, Mettler wt% wt% wt% wt% Example 3 11052.181.442.40.44Standard Pitch 110574827.42-12EP1739153B111056.835.020.01.3

[0050] In this experiment, the advantages obtained in previous examples are enhanced in that the fixed carbon, the pitch yield and the net carbon yield are improved.

[0051] Therefore, when a heat treatment is carried out after the oxidative reaction, the benefits of the product are enhanced.

[0052] In summary, with the process of the invention it is possible to obtain, at a temperature similar to other prior art processes, a higher softening point precursor showing also a higher fixed carbon value. Or, alternatively, it is also possible to obtain a similar softening point precursor at a lower temperature than in the prior art processes, and this effect is enhanced by the increase of the distillation temperature or softening point required. This technical effect is very advantageous and completely unexpected from the reading of the prior art. The products obtained with the process of the invention can be advantageously used in advanced applications like carbon fibers, carbon foams, pitches for graphite pitch coating processes for anodic material in electric vehicle lithium-ion batteries, needle coke as precursors, electrical storage of renewable energy generation plants, etc.

[0053] As it was shown in the previous example, the QI value is significantly lower than the QI values obtained in a standard pitch. Therefore, due to the change on the process conditions, the process of this invention results in a reduction of the QI value vs the patent EP1739153B1. This is an improvement of the quality of the final pitch, since the pitch presents a more fluid state, and less probability to find carbonaceous structures manufactured during the undesired partial combustion of Anthracene oil with O2. This particular combustion creates a local increase of the temperature (hot spots), and the creation of soot.

[0054] In conclusion, with the process of the invention, the following advantages are obtained: It is easier to obtain high softening point pitches vs those obtained in prior art patent EP1739153B1 and the conventional tar route (distillation to 110ºC pitch --> distillation to high point pitch). A higher overall yield from the starting materials for carbon generation vs prior art patent EP1739153B1 and tar is obtained. The process is of particular interest if the synergy of having this process together with the process of obtaining carbonaceous materials to recycle and convert distillates into carbonaceous materials is exploited.

[0055] It is especially recommended to combine both processes, i.e. thermal oxidation of the raw material with or without thermal treatment with or without distillation to obtain a certain softening point, and the process to produce carbons. The oils generated to obtain the carbonaceous material can be reintroduced into the process, obtaining the maximum conversion of initial raw material into carbon.

[0056] In a net process, the oils that evolve during the precursor formation, and those released during carbonization, can be recirculated to the process, and therefore do not need to be burned for carbon black application or as fuel, thereby increasing the overall yield and contributing to the decarbonization.

Examples

example # 1a

Example #1A: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 30 min. AOil Flow: 1 kg / h Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1B: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 45 min. Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1C Raw material: Decant Oil Temperature: 300ºC Residence time: 1.82 hours. Oxygen supply: 0.083 kg pure O 2 / kg oil Pressure: 16 bar

[0039]TGA results of the Examples #1A, 1B and 1C compared to a standard coal tar and two heavy aromatic oils, Anthracene oil (AOil) and Decant oil (DOil).

Table 3. Properties comparison of Example 1.

Light Oils wt% Heavy Oils wt% Net Carbon wt% FC #270 wt% FC #350 wt% FC #400 wt%

STD Coal Tar 53.928.717.437.741.350.0

AOil 93.95.70.45.823.372.3

DOil 39.051.49.615.819.433.1

Example #1A 54.718.926.458.361.368.1

Example #1B 53.819.726.657.461.067.3

Example #1C 33.330.436.354.457.864.3

[0040]The values provided for the AOil refer to the raw m...

FIELD OF THE INVENTION

[0001] The present invention relates to a process for obtaining synthetic pitches from medium and heavy aromatic oils by thermal oxidative polymerization reactions. The process of the invention allows obtaining a synthetic pitch with a high softening point and improving the total carbon yield in the process.BACKGROUND OF THE INVENTION

[0002] Coal tar pitches, produced in the form of distillation residue from coal tar, are commonly used as binder in the production of carbon anodes for the electrolysis of aluminium and graphite electrodes for use in electric arc furnaces. The production and consumption of these pitches is, therefore, strongly dependent on the demand for these products, and they are produced with the characteristics that will enable them to fulfil the requirements demanded by these applications. The incoming decarbonization of the steel industry will lead to the shutdown of coke oven batteries where the coal tar subproduct is produced. Therefore, there would be an increase of the demand for coal tar pitch to produce graphite electrodes and support the increase in Electrical Arch Furnaces (EAF). Besides, the decline in coal tar supply and the introduction of rigorous environmental regulations have forced pitch producers to search for new strategies to synthetize and prepare less toxic pitches. Thus, in the latest years, new strategies have been developed in order to prepare more environmentally friendly pitches and, at the same time, provide a solution to the coal tar deficit.

[0003] Furthermore, the decarbonization trend in the carbon black industry is also present and the strategies involved are centered around the use of recovered carbon black, and the substitution of fossil-based oils (anthracene oil, decant oil or similar) with pyrolysis oils from residues such as solid urban waste and waste tires. This decarbonization trend will lead to a decrease in the demand for these oils. Therefore, the heavy oil industry, such as the carbochemical sector, is looking for diversification opportunities that will not involve combustion or any other thermal valorisation.

[0004] In addition, in Asia, coal tar pitch coke is used to manufacture synthetic graphite for the Lithium-ion Battery application. In recent years the demand for synthetic graphite has increased significantly and it will continue to grow, especially for applications such as electric vehicles. It is believed that synthetic graphite will become the predominant anodic material over natural graphite. The production of synthetic graphite depends on high quality coal tar pitches, where the primary Quinoline Insoluble (QI) has been removed. The value proposal of increasing the availability of suitable feedstocks to meet the incoming demand of synthetic graphite is aligned with the electrification and the increase of electrical storage solutions.

[0005] Document EP1739153 describes a process for producing pitches, particularly those suitable to use as carbon precursors, from coal tars and distillates thereof, through a sequential and combined operation in three steps of oxidative thermal treatment, thermal treatment under inert atmosphere and fractional distillation. In this document, other properties such as the intermediate rheology of the product until its conversion into carbon materials and the carbon yield for a given softening point are prioritised. The applications targeted by this invention require a graphitic microstructure as developed as possible.

[0006] Document Environ. Sci. Technol. 2009, 43, 8126-8132 describes a procedure for producing new pitches of low toxicity from anthracene oil. The procedure involves oxidative treatment in order to polymerize and condense the anthracene oil components followed by thermal treatment and distillation. This publication is aimed at producing Söderberg anodes of aluminum and silicium, applications that nowadays are obsolete.

[0007] Document Carbon 38 (2000) 1315-1322 reports on the results achieved by the air blowing of an industrial anthracene oil under different experimental conditions of temperature, time and air flow and the studies about the influence of these parameters in the final product.

[0008] In document Coke and Chemistry, 2020, Vol. 63, No. 12, pp. 569-575, the influence on the microstructure of the coke produced of the batch composition and the oxidation conditions of mixtures of moderate-temperature coal pitch and the anthracene fraction of coal tar were investigated.

[0009] RU2750991C1 discloses methods for producing petroleum pitch, used as a binder in the manufacture of various carbon products. However, the process of the invention is a more direct method, as the raw material is used directly without any preliminary distillation steps. Furthermore, the agitator utilized in the reaction is specifically designed to ensure complete consumption of the reagent and to enhance the reaction's efficiency. Additionally, the process of the invention achieves higher reaction yields compared to those demonstrated in the examples of this document, since the yield declared in this document is at most 39%, substantially lower than the yields obtained in the present invention.

[0010] US 2014 / 0099691 A1 discloses a continuous process for converting carbonaceous materials into a liquid hydrocarbon product and consequently is not intended to obtain synthetic pitches as in the present invention.

[0011] US 4 013 540 A discloses the preparation of petroleum pitch for carbon electrode manufactured from full-range decant oil by oxyactivated condensation.

[0012] The present invention is therefore aimed at obtaining non-standard industrial synthetic pitches for applications for advanced carbon materials (carbon fibers, carbon foams, pitches for graphite pitch coating processes for anodic material in electric vehicle lithium-ion batteries, needle coke as precursors, electrical storage of renewable energy generation plants, ...). For this kind of applications, optimally the secondary QI should be minimized, the beta resin should be maximised, and the yield of fixed carbon should also be maximised. In addition, the softening point should be high.

[0013] Besides, for the manufacture of materials where a synthetic pitch with a high softening point is required, two alternatives presently exist: obtaining it from coal tar or from petrochemical bottoms (petroleum pitch). From coal tar, the current problem is removing what is called the insoluble in primary quinoline (QI), which generates heterogeneity in the precursors and which removal is tedious and costly. Starting from both raw materials, coal tar or petrochemical bottoms, requires a distillation temperature above 400 ºC, which causes the generation of mesophase and solid semi-coke waste deposits in the equipment that causes serious mechanical maintenance problems.

[0014] The main applications of the present invention are focused on the manufacture of advanced carbon materials precursors such as synthetic carbons for anodic active materials in Li-ion (graphite, pitch coating): battery or Na-ion battery (hard carbon, soft / hard carbons...) where the final yield of the process and the microstructure become crucially important.DESCRIPTION OF THE INVENTION

[0015] Therefore, there is still a need to obtain improved processes to obtain synthetic pitches or advanced carbon materials precursors for the mentioned applications to overcome the current limitations, i.e. absence of primary QI, improve the process net yield and carbon microstructure control.

[0016] The inventors of the present invention found that this objective can be achieved with the following process: A process to obtain synthetic pitches from at least one medium or heavy aromatic oil selected from the group consisting of anthracene oil, decaline, light anthracene oil, heavy anthracene oil, decant oil and heavy fraction of hydrothermal liquefaction from tire pyrolysis oils, or their mixes in any combination, which process comprises the steps of: providing the at least one oil in a reactor; setting an initial reactor temperature below the starting boiling point of the at least one oil, and reacting the cited at least one oil with an O 2 stream or an O 2 -enriched air stream containing at least 21% O 2 v / v in in the reactor at a temperature of between 350 and 400°C and a pressure of at least 11 bar during a residence time of between 5 min and 5h, characterised in that the supply of the O2 stream or O2-enriched air stream is between 0.075 and 0.2 kg of O2 or O2-enriched air per kg of the at least one oil.

[0017] As herein described, an O 2 stream or O 2 -enriched air or gas stream is any gas that contains at least the O 2 concentration that is naturally present in air, i.e., at least 21% v / v, preferably at least 50% v / v, more preferably approximately 95% v / v. The election of the O 2 concentration in the gas depends mainly on economics and safety considerations. Due to the combined effects of the increased oxygen supply, the increased pressure and the increased reaction times, synthetic pitches with the desired properties can be obtained.

[0018] Figure 1 shows a possible sketch of the installation.

[0019] The type of medium and heavy aromatic oils that can be used as raw materials in the process of the invention should ideally have the following desirable properties: petrochemical, carbochemical or pyrolysis oils origin or any mixed fraction having the following physical-chemical properties: The vapour pressure at the reaction temperature should be at least 5 bar below the selected reaction pressure to minimize volatiles losses and enhance liquid phase reaction, An aromatic Index - C / H atomic ratio of 0.55 to 1.20, Preferred inorganic Ash Content below 5%, but more preferably, for advanced carbon materials, not higher than 0.3% and even more preferably not higher than 0.1%, in order to minimize the impurities. Illustrative examples of this type of compounds, are: Decaline, Tetraline, Light Anthracene oil, heavy Anthracene Oil, Decant Oil, heavy aromatic oil fractions from more sustainable sources like used tire pyrolysis or hydrothermal liquefaction (HTL) or biomass and urban waste residues among others, alone or in any combination among them.

[0020] In the process of the invention, a stream of O 2 or O 2 -containing gas is bubbled into the liquid heavy aromatic oil. The unreacted oxygen accumulates at the head of the reactor and, thanks to the stirrer, is reintroduced into the liquid. This is because the stirrer has a hole in the upper part that, at the speed at which it is stirred (1000 rpm), by the Venturi effect the unreacted gas is absorbed and reintroduced into the liquid through the lower part (see Figure 2).

[0021] In preferred embodiments, the supply of O 2 or O 2 -enriched air is between 0.075 - 0.1 kg of O 2 or O 2 -enriched air / kg of the at least one oil, more preferably between 0.08 - 0.095 kg of O 2 or O 2 -enriched air / kg of the at least one oil, or even more preferably around 0.091 kg of O 2 or O 2 -enriched air / kg of the at least one oil, for the entire residence time of the reactants in the reactor.

[0022] In preferred embodiments, the reaction temperature is between 300-400ºC, more preferably around 375ºC.

[0023] In preferred embodiments, the reaction pressure is between 11 and 100 bar, more preferably between 12 and 50 bar, even more preferably between 15 and 20 bar, and most preferably around 16 bar.

[0024] In preferred embodiments, the residence time is between 5 min and 5 h, more preferably between 10 min and 2 h, even more preferably between 0,5 and 1 h, and most preferably around 0,5 h.

[0025] In preferred embodiments, the at least one oil is selected from the group consisting of anthracene oil, decaline, light anthracene oil, heavy anthracene oil, decant oil, heavy fraction from tire pyrolysis oils, and heavy fraction of HTL.

[0026] After the above-explained reaction step, the process of the invention may preferably comprise a further subsequent thermal treatment at a temperature of between 350ºC and 450ºC during a residence time of between 30 min and 6 hours, in an inert atmosphere. More preferably, the residence time in the cited subsequent thermal treatment is between 2h and 5h, even more preferably between 2 and 4h.

[0027] In a preferred embodiment, the process is carried out in a reactor including an air-blow system.Products obtained

[0028] Following the above-explained process, the obtained products show the following total mass balance: Condensable oils (40ºC): <15% Incondensable gases (40ºC): < 5% Reaction Product Yield: >80% (softening point 60ºC) ∘ Distilled Oils (<25%) ∘ Exhaust gases: <2% ∘ Precursor Yield with Softening Point 110-120ºC (Mettler) (>70%) ▪ Distilled Oils: <40% ▪ Exhaust gases: <2% ▪ Carbon Yield: 40-60% ▪ Net Carbon Yield: 40-50% (from the initial precursor)

[0029] The TGA analysis of the obtained product is conducted as follows: under a nitrogen flow of 60mL / min, a first heating ramp is carried out from 25 to 270ºC at a speed of 10K / min, then an isothermal stage begins at 270ºC for 50min. After that time, it is heated from 270 to 650ºC, at 10K / min. The TGA profile and explanation of the data obtained can be seen in the Figure 3.

[0030] The value of the residue at a temperature of 650ºC corresponds to the parameter "Net Carbon", which is also called carbon residue. On the other hand, the oils obtained from the process of the invention are separated in two during the distillation step: Light Oils: Oils distilled before the isothermal ramp at 270ºC, i.e. the TG value at that point Heavy Oils: Oils distilled from the end of the isothermal ramp at 270ºC and the end of the test at 650ºC.

[0031] Apart from these values and given that the evolution profiles of weight loss with temperature are different in each sample, the different carbon yields of the product obtained can be simulated if a previous distillation at a certain temperature is carried out. In this way we can obtain the Fixed Carbons FC #XXX values, where the "#XXX" value refers to the temperature in the TGA graph (see Figure 3). Table 1: Comparison of the composition in weight percentage of selected samples measured by Thermogravimetric analysis (TGA) for Standard Coal Tar (STD Coal Tar) and Anthracene Oil (AOil).Light Oils wt% Heavy Oils wt% Net Carbon wt% FC #270 wt% FC #350 wt% FC #400 wt% STD Coal Tar 53.928.717.437.741.350.0AOil 93.95.70.45.823.372.3

[0032] Distillation was carried out at temperatures between 270ºC and 400ºC; distillation at temperatures above 400ºC is not convenient due to the progressive thermal decomposition of the pitch that become coke.

[0033] From the data of the table, we can conclude that, although the fixed carbon values of AOil at 400ºC are very interesting, it does not make economic sense given that its overall yield is very low (Net Carbon=0.4%).

[0034] To enhance its performance, the obtained reaction product can be subjected to a subsequent thermal treatment step to stabilize its structure and gain in fixed carbon and net carbon yield.

[0035] According to the specification of the final product and the total conversion rate, the reaction may require and additional distillation stage to the desired final softening point.BRIEF DESCRIPTION OF FIGURES

[0036] Figure 1: Scheme of reactor. Figure 2: Scheme of a typical jet stirrer. Figure 3. Thermogravimetric analysis (TGA) of an unreacted oil (grey line) and standard coal tar (black). Figure 4. Optical Texture Microscopy of the synthetic pitches obtained in Example 1A. The photograph shows the typical optical structure obtained in these synthetic pitches obtained by the process of the invention after a carbonization step (temperature 650ºC). The photo shows absence of primary QI (several defects during polishing can also be observed). Figure 5. Optical Texture Microscopy of the synthetic pitches obtained in Example 1B. The photograph shows a mosaic structure which is significantly different to the structure shown in the Example 1A. This shows that the process of this invention is capable to modulate the crystalline structure. EXPERIMENTAL EXAMPLES

[0037] In the experimental examples, the following conditions reactions were used. A comparison with the condition reactions used in prior art EP1739153 is also provided: Table 2: Comparison between the synthetic pitch properties from the present invention and the pitches obtained in EP1739153Pitches obtained in EP1739153Synthetic pitches obtained in the process of the inventionConditions during reactionConditions during post-reaction thermal treatmentConditions during reactionConditions during post-reaction thermal treatmentT (°C)350-400340-400375375P (bar)5-100-101616Residence Time2-10 s3-10 h30 min2 hSingle-step conversion (%)<40-90-Oxygen supply (kg O2 / kg anthracene oil)0.021-0.053-0.091- Example 1

[0038] In the previously described set up, an anthracene oil (AOil) sample was processed under the following conditions: Example #1A: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 30 min. AOil Flow: 1 kg / h Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1B: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 45 min. Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1C Raw material: Decant Oil Temperature: 300ºC Residence time: 1.82 hours. Oxygen supply: 0.083 kg pure O 2 / kg oil Pressure: 16 bar

[0039] TGA results of the Examples #1A, 1B and 1C compared to a standard coal tar and two heavy aromatic oils, Anthracene oil (AOil) and Decant oil (DOil). Table 3. Properties comparison of Example 1.Light Oils wt% Heavy Oils wt% Net Carbon wt% FC #270 wt% FC #350 wt% FC #400 wt% STD Coal Tar 53.928.717.437.741.350.0AOil 93.95.70.45.823.372.3DOil 39.051.49.615.819.433.1Example #1A 54.718.926.458.361.368.1Example #1B 53.819.726.657.461.067.3Example #1C 33.330.436.354.457.864.3

[0040] The values provided for the AOil refer to the raw material used in Examples #1A and #1B, whereas the DOil refers to the raw material used in Example #1C. The values provided for the Standard Coal Tar are given for comparative purposes.

[0041] In the table above, the advantages of the process of the invention can be clearly observed: Previous Patent EP1739153 B1 was focused on the optimization of the process to obtain an intermediate product, a pitch, with specific rheological characteristics (a softening point around 110ºC Mettler) for the specific requirements of the applications to which it was directed, i.e. electrodes for alumina electrolysis and standard graphite electrodes. In this sense, patent EP1739153 B1 placed special emphasis on limiting the conversion of the process to around 30-35%. In the present invention, these rheological requirements do not exist, and a high softening point pitch can or even should be used, the process can be taken to a greater extent, thereby obtaining a greater carbon yield as shown in the FC#350 and FC#400 values.

[0042] The values presented in data FCXXX represents the fixed carbon of the product obtained after distilling @XXX ºC by TGA simulation. Considering the amount of volatile matter when distilling at a certain temperature, using the process of the invention, it is possible to obtain a higher softening point precursors at certain temperature and gain in fixed carbon. It is enhanced by the increase of distillation temperature.

[0043] Additionally, another advantage can be achieved in the process when obtaining a high softening point pitch. Since the oxidative heat treatment process generates heavy structures, the oils that need to be distilled to obtain them are mainly light oils. Obtaining a high softening point pitch (>250ºC Mettler) can be considered a technologically complex process if it starts directly from a carbochemical tar where it is required to reach distillation temperatures above 400ºC (even if working with high vacuum). These process temperatures generate mesophase and high levels of solid deposits in the product and equipment by generating semi-coke solids. From examples #1A and #1B, pitches with a softening point of 300ºC can be obtained without the need to reach such high temperatures (<400ºC).

[0044] These results are even enhanced when using a petrochemical oil like Decant Oil.Example 2

[0045] Example 2 pitch was produced using the following conditions: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 30 min. Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar

[0046] Distillation: adjustment to softening point 110ºC Mettler

[0047] The product distilled at 110ºC is compared in the table below to the product obtained in EP1739153B1 and to a standard pitch. The pitches obtained in this example show a clear advantage in the Net Carbon Yield value. Table 4. Comparison between Example #2, Standard Pitch and patent EP 1739153.Parameter Softening Point (ASTM D3104) Fixed Carbon (ALCAN) Pitch Yield Net Carbon Yield Quinoline Insoluble (QI) Units ºC, Mettler wt% wt% wt% wt% Example #2 11044.668.330.50.65Standard Pitch 110574827.42-12EP1739153 B111056.835.020.01.3

[0048] In the case of a standard Pitch obtained from coal tar, the value of QI corresponds to primary QI which is an infusible material obtained during the production of the coal tar raw material, whereas for the case of the synthetic pitches obtained in the invention and in the patent EP1739153 B1 it corresponds to secondary QI, which is a fusible heavily condensed material. In other words, the table above shows that the standard pitches have a significant amount of QI (which corresponds to primary QI), while the significant pitches have a significant lower amount of QI (which is not primary QI, but secondary QI).Example 3

[0049] The product obtained from Example 2 was subjected to a subsequent thermal treatment in inert atmosphere after the polymerization reaction to modify the final properties of the pitch and it was conducted under the following conditions: Raw material: The product obtained in Example 2. Thermal treatment: 2h, 375ºC, 16 bar, nitrogen atmosphere. Distillation: adjustment to softening point 110ºC Mettler Table 5. Comparison of Example 3, Standard Pitch and patent EP1739153 Parameter Softening Point (ASTM D3104) Fixed Carbon (ALCAN) Pitch Yield Net Carbon Yield Quinoline Insoluble (QI) Units ºC, Mettler wt% wt% wt% wt% Example 3 11052.181.442.40.44Standard Pitch 110574827.42-12EP1739153B111056.835.020.01.3

[0050] In this experiment, the advantages obtained in previous examples are enhanced in that the fixed carbon, the pitch yield and the net carbon yield are improved.

[0051] Therefore, when a heat treatment is carried out after the oxidative reaction, the benefits of the product are enhanced.

[0052] In summary, with the process of the invention it is possible to obtain, at a temperature similar to other prior art processes, a higher softening point precursor showing also a higher fixed carbon value. Or, alternatively, it is also possible to obtain a similar softening point precursor at a lower temperature than in the prior art processes, and this effect is enhanced by the increase of the distillation temperature or softening point required. This technical effect is very advantageous and completely unexpected from the reading of the prior art. The products obtained with the process of the invention can be advantageously used in advanced applications like carbon fibers, carbon foams, pitches for graphite pitch coating processes for anodic material in electric vehicle lithium-ion batteries, needle coke as precursors, electrical storage of renewable energy generation plants, etc.

[0053] As it was shown in the previous example, the QI value is significantly lower than the QI values obtained in a standard pitch. Therefore, due to the change on the process conditions, the process of this invention results in a reduction of the QI value vs the patent EP1739153B1. This is an improvement of the quality of the final pitch, since the pitch presents a more fluid state, and less probability to find carbonaceous structures manufactured during the undesired partial combustion of Anthracene oil with O2. This particular combustion creates a local increase of the temperature (hot spots), and the creation of soot.

[0054] In conclusion, with the process of the invention, the following advantages are obtained: It is easier to obtain high softening point pitches vs those obtained in prior art patent EP1739153B1 and the conventional tar route (distillation to 110ºC pitch --> distillation to high point pitch). A higher overall yield from the starting materials for carbon generation vs prior art patent EP1739153B1 and tar is obtained. The process is of particular interest if the synergy of having this process together with the process of obtaining carbonaceous materials to recycle and convert distillates into carbonaceous materials is exploited.

[0055] It is especially recommended to combine both processes, i.e. thermal oxidation of the raw material with or without thermal treatment with or without distillation to obtain a certain softening point, and the process to produce carbons. The oils generated to obtain the carbonaceous material can be reintroduced into the process, obtaining the maximum conversion of initial raw material into carbon.

[0056] In a net process, the oils that evolve during the precursor formation, and those released during carbonization, can be recirculated to the process, and therefore do not need to be burned for carbon black application or as fuel, thereby increasing the overall yield and contributing to the decarbonization.

Examples

example # 1a

Example #1A: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 30 min. AOil Flow: 1 kg / h Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1B: Raw material: Anthracene Oil Temperature: 375ºC Residence time: 45 min. Oxygen supply: 0.091 kg pure O 2 / kg oil Pressure: 16 bar Example #1C Raw material: Decant Oil Temperature: 300ºC Residence time: 1.82 hours. Oxygen supply: 0.083 kg pure O 2 / kg oil Pressure: 16 bar

[0039]TGA results of the Examples #1A, 1B and 1C compared to a standard coal tar and two heavy aromatic oils, Anthracene oil (AOil) and Decant oil (DOil).

Table 3. Properties comparison of Example 1.

Light Oils wt% Heavy Oils wt% Net Carbon wt% FC #270 wt% FC #350 wt% FC #400 wt%

STD Coal Tar 53.928.717.437.741.350.0

AOil 93.95.70.45.823.372.3

DOil 39.051.49.615.819.433.1

Example #1A 54.718.926.458.361.368.1

Example #1B 53.819.726.657.461.067.3

Example #1C 33.330.436.354.457.864.3

[0040]The values provided for the AOil refer to the raw m...

Claims

1. A process to obtain synthetic pitches from at least one medium or heavy liquid oil selected from the group consisting of anthracene oil, decaline, light anthracene oil, heavy anthracene oil, decant oil and heavy fraction of hydrothermal liquefaction (HTL) from tire pyrolysis oils, or their mixes in any combination, which process comprises the steps of: - setting an initial reactor temperature below the starting boiling point of the at least one oil, and - reacting the cited at least one oil with O2 or an O2-enriched air stream containing at least 21% O2 v / v in the reactor at a temperature of between 350 and 400ºC and a pressure of at least 11 bar during a residence time of between 5 min and 5h, characterised in that the supply of O2 or O2-enriched air is between 0.075 and 0.2 kg of O2 or O2-enriched air per kg of the at least one oil.

2. The process of claim 1 wherein the supply of O2 or O2-enriched air stream is between 0.08 - 0.095 kg of O2 or O2-enriched air / kg of the at least one oil.

3. The process of claim 1 wherein the supply of O2 or O2-enriched air stream is around 0.091 kg of O2 or O2-enriched air / kg of the at least one oil.

4. The process of claim 1 wherein the temperature is 375ºC.

5. The process of any one of previous claims 1-4 wherein the pressure is between 11 and 100 bar.

6. The process of claim 5, where the pressure is between 12 and 50 bar.

7. The process of claim 5, wherein the pressure is approximately 16 bar.

8. The process of any one of previous claims 1-7, wherein the residence time is between 10 minutes and 2 hours.

9. The process of any one of previous claims 1 to 8, wherein the concentration of O2 in the O2-enriched air is at least 50% v / v.

10. The process of claim 9, wherein the concentration of O2 in the O2-enriched air is approximately 95% v / v.

11. The process of any one of previous claims 1 to 10 wherein the O2 or O2-enriched air stream is bubbled into the liquid medium or heavy aromatic oil.

12. The process of any one of previous claims 1 to 11, further comprising a subsequent thermal treatment at a temperature of between 350ºC and 450ºC during a residence time of between 30 minutes and 6 hours in an inert atmosphere.

13. The process of claim 12, wherein the residence time is between 2 and 4 hours.

14. The process of claims 12 or 13, where in temperature in the subsequent thermal treatment is the same as the temperature in the reaction step of the oil with the O2 or O2-enriched air stream.

Images