METHOD FOR THE COMBINED PREPARATION OF OILS AND ACTIVATED CARBONS FROM OLEAGINOUS PLANTS
[0001] The subject of the invention is a process for the combined preparation of oils and activated carbons using oleaginous plants, in particular non-food plants, as raw material. Among these plants are, in particular, the castor plant and jatropha, which are both plants that grow on ground that is not very fertile and under conditions of low relative humidity.
[0002] The invention relates to the use of solid shells or oil cakes of oleaginous plants, in particular non¬food plants, such as, for example, the castor plant or jatropha, as precursors of activated carbon, with a double advantage of providing activated carbons with a low CO2 footprint, and of diversifying the uses of these two plants, of which the oils are used, either in the biofuel industry, or as raw materials for lubricants, for polyurethane or for polyamides, including polyamide 11.
[0003] Integrating the production of oil and the exploitation of the shell and of the oil cakes through the production of activated carbon, in the same production unit (such as a biorefinery) , constitutes an improvement in current technological knowledge.
[0004] Activated carbons are usually obtained by carbonization, followed by a physical or chemical activation of carbonaceous materials.
[0005] Among said carbonaceous materials, some result from biomass and are consequently described as renewable, such as pinewood or coconut, or some result from fossil materials, which are also described as nonrenewable, such as lignite or petroleum cokes.
[0006] Peat constitutes a case apart, with a slow renewal, probably not enabling carbons with a very low CO2 footprint to be obtained.
[0007] Very few studies or industrial attempts relate to other materials, probably owing to the fact that it is necessary to combine both ready access to and a large amount of the raw material, and a reasonable cost.
[0008] Trials using fruit stones or olive marcs make it possible to obtain carbons which are advantageous, in particular by virtue of their mechanical strength, which is not readily achieved using softer materials, such as pinewood.
[0009] The oil cakes and shells of the castor plant or of jatropha meet these requirements. By way of example, the company Arkema uses 60 000 metric tons of castor oil per year, which generates the coproduction of 60 000 metric tons of oil cakes and 80 000 metric tons of shells. A particular advantage linked to the invention lies in the fact that the exploitation of these non-food coproducts can be generated on a single industrial site, for example in an oil factory.
[0010] Although it is a non-food plant, the castor plant provides, however, a revenue for farmers who are not lucky enough to be working under the best conditions, in particular climatic conditions. In India, where the castor plant is mainly cultivated, the farmers use it to supplement other crops (intercalated crops) since the castor plant, like other non-food plants, contains toxins which make it a natural insecticide.
[0011] The castor plant contains several toxins which are proteins, including ricin, but also ' a powerful
allergen, CB-1A. The presence of these toxic substances limits the uses of the castor oil cake in food, even animal feed. It is used as natural fertilizer in agricultural biology, by spreading on soils, which unfortunately contributes to the dispersion of the allergen in the environment.
[0012] The castor plant is a plant which has been cultivated industrially for more than 50 years, in particular because of the composition of its oil, which is unique since it contains approximately 85% of ricinoleic acid. This oil has many applications, in particular in lubricants, polymers, fragrances, paints, cosmetics and, only recently, in biofuels. Hybrids have been produced in order to obtain better yields, however without eliminating the drawbacks associated with the toxicity problems. This plant, just like jatropha, requires picking, and therefore an abundant and cheap workforce. Unlike jatropha, the castor plant is an annual plant.
[0013] Cultivation of the castor plant, and generally of non-food oleaginous plants, on a larger scale will result in an increase in the production of toxic oil cake, which cannot be used in animal feed, except after a thermochemical treatment at high temperature, but which denatures the proteins. The increase in the production of oil cake which is non-food, since it is toxic, poses a public health problem.
[0014] As for the oil, the content of which is about 50% relative to the weight of the seed, it has many applications in lubricants and polyurethanes for example, but also as raw material of polyamide 11
(PA11), or Rilsan® 11. PAll is the only technical polymer resulting from biomass and available in large volumes on the market.
[0015] The toxic substances of the castor plant (toxins and allergen) are in the oil cake after extraction of the oil. For a better overall product (oil) and coproducts (oil cake and shells) exploitation, but also for greater safety for the industry, solutions are sought which make it possible to simultaneously destroy the toxic substances, eliminating the health risk, while at the same time exploiting the coproducts in applications with higher added value. The term "shell" defines the casing of husk or pod type which contains the seed. The term "oil cake" defines the residue of the seeds (with or without shells) after extraction of the oil by cold or hot pressing (s) of the seeds, by extraction with solvent, or else by a reactive grinding process, or by any other method for extracting the oleaginous fraction from the seed.
[0016] The term "reactive grinding" is intended to mean a process which makes it possible to produce a methyl ester, glycerol and an oil cake directly from the seed. In this type of process, a mixture containing an alcohol and a catalyst, for example methanol and sodium hydroxide, is reacted with the seed. The excess methanol plays the role of both a solvent and a reactant.
[0017] A group of oleaginous plants of shrubby type, such as the castor plant (Ricinus communis), Pongamia pinnata, Calophyllum inophyllum and Jatropha curcas have been proposed in particular on government websites or websites of NGOs or else of companies which promote their preferred species for producing biodiesel.
[0018] Jatropha is probably the species which deserves the maximum communication. The properties of the biodiesel derived from jatropha oil are equivalent to those of the biodiesels produced in Europe and meet European and United States specifications. However, the
websites and communications which carry out the promotion of Jatropha curcas do not give the common name of this plant: purging nut, physic nut or black vomit seed, or of the oil: hell oil. The fruits contain irritant compounds which affect the pickers, when picking is done by hand. The seeds contain alkaloids such as curcin, a toxalbumin similar in structure and effect to ricin. The toxic effects of this plant have been reported in the literature. Ingestion of four seeds can be toxic to a child, with effects similar to poisoning with an organophosphorus insecticide, and no antidote being known. None of the websites describes an application of the oil cake, with the exception of the use as fertilizer by spreading on soils, which can be illegal in certain countries, owing to its toxicity.
[0019] Other shrubby plants which produce a high yield of oil per hectare are also studied, in particular in India. Pongamia pinnata has oil yields of from 200 kg/ha to 2000 kg/ha. The oil cake is toxic owing to the presence of furano-flavonoids, tannins and trypsin inhibitors, which are difficult to remove, which once again excludes the use of the oil cake in animal feed.
[0020] Calophyllum inophyllum is another shrubby plant from which a non-food oil cake is obtained. The oil cake contains several cytotoxic compounds which are advantageous from the pharmaceutical point of view, but which prohibit the use of the oil cake in animal feed.
[0021] The approach proposed by the invention is an exploitation of the oil cake resulting from oleaginous plants, in particular non-food plants, and in particular from the castor plant or from jatropha, by converting it into a product of higher added value, such as an activated carbon, but it is obvious that the same approach may be applied to other non-food plants, such as ironweed, Cuphea, rubber tree, oleaginous flax,
erucic rape, honesty, safflower, gold-of-pleasure, Calophyllum inophyllum, Pongamia pinnata and the corresponding oleaginous plants which have been genetically modified, and also the mixtures of two or more of said plants.
[0022] In the literature, a reference is found to the production of activated carbon from castor plant or Delonix regia shell: M.M. Howlader et al., "Activated carbon from krishnachura fruit (Delonix regia) and castor seed {Ricinus communis)", Indian Journal of Chemical Technology, Vol. 6, May 1999, p. 146-151.
[0023] In this document only the shells and not the oil cakes are mentioned. Furthermore, the process of activation uses zinc chloride, the toxicity of which is established for food or pharmaceutical applications of the carbons. There is therefore an industrial advantage in proposing a different process.
[0024] The castor plant and jatropha grow in difficult climates and in poor soils, but also give their best yields in well-irrigated zones.
[0025] The current average yields of the castor plant are about 2 t of seeds per hectare, and up to 4 t per hectare according to certain sources, for the best results. In the poorest zones, the yields can go down to less than 0.7 t per hectare.
[0026] The castor seed is particularly rich in oil, with a content close to 50%, which classifies this plant second in the scale of oil production per hectare, behind the palm (plants cultivated on a large scale) . The advantage of castor oil is especially its high ricinoleic acid content (85%).
[0027] Castor oil is conventionally extracted by pressing, and by extraction with hexane. An oil cake is thus coproduced, but it still contains ricin and especially CB-1A allergen.
[0028] The castor seeds are in a shell or husk (of chestnut husk type). In order to avoid natural opening of the husks and dropping of the seeds (dehiscence) , varieties were selected and the current hybrids retain the seeds in the husks at the time of harvesting. These husks are therefore naturally hard and rich in polysaccharides and therefore potentially lend themselves well to the production of activated carbon.
[0029] Another way to exploit castor or jatropha oil cakes consists in carbonizing them in order to develop a little porosity, and then in using the resulting product as a fuel or as a raw material in a gasification process. This method can be applied to products that are purely of vegetable origin, but also for producing a carbonaceous product that can be used as a mixture with solid fuels of fossil origin.
[0030] Since the development of the porosity of the vegetable material facilitates initiation of the combustion of the mixture, a more effective combustion and a better energy yield will be obtained.
[0031] There is an advantage in using a vegetable carbon as raw material for a gasification process rather than using the biomass itself. This is because, during the carbonization process, the vegetable material is partially degraded and is gradually distilled. In carbonization processes, the degradation products are recovered and burnt in order to provide energy. These processes thus avoid the formation of tars (heavy products in general), which are, on the other hand, produced when the "fresh" biomass is
directly gasified. This tar formation causes numerous dysfunctions in units of this type. When vegetable or mineral carbons are used in gasification units, the processes can be carried out without difficulty.
[0032] Thus, the present invention relates first of all to a process for exploiting the residues, in particular the toxic residues, obtained as by-products during processes for extracting oils from oleaginous plants, preferably from non-food oleaginous plants, said process comprising, and preferably consisting of, the process of the combined production of oils of oleaginous plants, preferably non-food oleaginous plants, and production of activated carbon from the oil cakes, optionally in combination with the shells, of said oleaginous plants.
[0033] Said exploitation process (or process for the combined production of activated carbon and of oil) can be advantageously carried out on a single industrial site, for example an oil factory, but can also be carried out on different industrial sites. In the latter case, the two industrial sites will advantageously be as close as possible with the aim of preserving as much as possible the environmentally friendly character, and increasing as little as possible the carbon footprint that would be generated by transporting the by-products from the oil factory to the activated carbon production site.
[0034] In the exploitation process of the invention, the production of oil from oleaginous plants, preferably non-food oleaginous plants, can be carried out according to any process known to those skilled in the art, and for example by pressing, optionally after heating, it being possible for the extraction of oil to be carried out once (first pressing), twice (first and second pressing) or several times, it being possible
for said extraction to be optionally carried out by solvent extraction, or else by a combination of one or more of the methods indicated above, heating, pressing(s), solvent extraction.
[0035] According to another aspect, the present invention relates to the use of oil cakes, optionally with the shells, of oleaginous plants, preferably non¬food oleaginous plants, for the preparation of activated carbon.
[0036] The present invention also relates to the process for preparing activated carbon from said oil cakes, and optionally from shells, of oleaginous plants, preferably non-food oleaginous plants, said process comprising at least the following steps:
a) carbonization of oil cakes, and optionally of shells, at a temperature of between 200°C and 700°C, for example around 550°C;
b) activation at a temperature of between 500°C and 1200°C, advantageously around 900°C;
c) optionally, washing with an acid, preferably a strong acid; and
d) recovering of the activated carbon.
[0037] Carbonization is a technique well known to those skilled in the art.
[0038] The oil cakes, optionally with the shells, can be ground before carbonization or simply coarsely crushed. According to one advantageous embodiment, the finest materials are removed from the oil cakes, optionally with the shells according to any method known in the field, for example by sieving or elutriation.
[0039] Optionally, it may be sought to give the oil cake a particular shape by extrusion, pelletizing or
granulation, optionally using a binder such as starch, cellulose or even glycerol and any material well known in the food-processing industry for conferring a texture on products. This operation is advantageously carried out upstream of the carbonization step.
[0040] The carbonization temperature and time are chosen so as to obtain a carbonized product of which the weight loss is stabilized, and preferably when grains of millimetric size are obtained.
[0041] The carbonization is generally carried out under a neutral or low-oxygen atmosphere, for example under nitrogen or under argon, or, according to one preferred embodiment, in an atmosphere consisting of the combustion gases of a hydrocarbon-based fuel (such as, for example, methane, ethane, propane, butane, and the like) or else distillation gases. In the latter case, use is advantageously made of the gases produced by the distillation of products, for example such as those obtained during the carbonization of biomass, in order to supply an incinerator of which the purpose is to completely burn them with air or oxygen. This operation causes a large increase in the temperature of the gases burnt, and which are partly re-injected into the carbonization unit in order to raise the temperature of the biomass during treatment. This method is particularly suitable for processes carried out continuously.
[0042] The residue obtained after carbonization is activated according to methods known to those skilled in the art, under partial water vapor pressure and/or under partial C02 pressure, the rest at atmospheric pressure possibly being provided by any gas that is inert with respect to the activation, for example, nitrogen, combustion gas, and the like. The activation time depends on the final characteristics desired for
the activated carbon, as illustrated in the examples which follow.
[0043] According to the applications intended, it may be desirable to reduce the ash content of the activated carbon obtained according to the process of the invention.
[0044] This can be carried out by any means known to those skilled in the art, and for example by an acid treatment of the activated carbon, preferably a strong organic or inorganic acid. Examples of acids that are suitable for the needs of the invention are chosen from nitric acid, hydrochloric acid, sulfuric acid, acetic acid, citric acid, methanesulfonic acid and the like, and also mixtures thereof.
[0045] The activated carbons obtained according to the process of the present invention are characterized by a microporosity (pore volume occupied by pores of less than 2 nanometers) which is entirely advantageous, and in particular a micropore (< 2 nm) volume of greater than 0.37 ml/g, most commonly greater than 0.375 ml/g.
[0046] The activated carbons obtained according to the process of the present invention can thus be used in many fields.
[0047] Thus, according to another subject, the present invention relates to the use of the activated carbons obtained according to the process of the invention, as an agent for purifying solids, liquids or gases, in particular in the food industry, for example as an agent for purifying water, wine, beer, synthesis intermediates or final products, in particular pharmaceutical ingredients, but also in all the fields where activated carbons are normally used, for example as a constituent of supercapacitor electrodes, as a
catalyst support, or else as an adsorbent of volatile organic compounds (VOCs), in particular in the gas phase.
[0048] The carbons obtained according to the process of the invention can also be used as fertilizer by spreading on fields. This is because the activated carbons have lost, any residual toxicity originating from the oil cakes owing to their preparation process. The carbons, in particular by virtue of their porous structure, allow aeration of the soil, thus promoting microorganism proliferation and therefore soil enrichment. It so happens, as indicated above, that the soils where non-food oleaginous plants grow are precisely soils that are not very fertile and not very favorable to the cultivation of food plants. The combined process according to the invention therefore also allows an enrichment of poor soils by spreading the activated carbons obtained as by-products of non¬food oil production.
[0049] Yet another advantaged linked to the combined exploitation process according to the invention is that the oil cake of non-food oleaginous plants normally produced in oil factories is a biomass which is unstable over time, which degrades and which therefore cannot be stored or is difficult to store. It so happens that this oil cake is toxic and oil producers are confronted with the delicate management of this toxic biomass. The process of the invention thus provides an effective and more environmentally friendly solution in that the oil cakes are converted into activated carbon, products that are economically more advantageous with numerous applications, such as, for example, those described above.
[0050] The activated carbons prepared according to the process of the present invention can also be used for
the production of energy, either as a pure compound, or as a mixture with at least one other fuel of renewable or fossil origin.
[0051] Indeed, the production of activated carbon is accompanied by a very large amount of heat, which can be partially or totally recovered for the needs of oil production, for example for heating the seeds before pressing, in order to soften them, for facilitating the oil extraction, or else for purifying the crude oil. It is also possible to adjust and regulate the temperature of production of activated carbon in order to adjust and provide the amount of energy necessary for the production, extraction and/or purification of the oil obtained from said oleaginous plants.
[0052] In addition, the vegetable carbon obtained has a specific surface area which makes it reactive. Certain mineral (fossil) carbons of low quality produce a lot of ash because of incomplete combustion. In a mixture with poor-quality mineral carbon, a synergistic effect is obtained since the greater reactivity of the vegetable carbon allows a large increase in temperature of the mixture and therefore better combustion and thus a better energy yield, resulting in a lower greenhouse-effect gas emission.
[0053] The following illustrative examples will make it possible to understand more clearly the scope of the invention, without however limiting the scope thereof.
Example 1:
[0054] A castor oil cake supplied by the company
Jayant-Agro Organics Ltd (India) has the
characteristics summarized in Table 1 below. This oil
cake was produced after extraction of the oil with
hexane.
Table 1: characteristics of the crude castor oil cake
(Table Removed)
[0055] The first operation consists in carbonizing at
550°C for 1 hour under a propane combustion gas
atmosphere, after having removed the finest parts
< 1 mm.
[0056] The yield is 37%, expressed as the weight ratio between the material leaving the oven and the initial material. An ash content of 14% and a bulk density of 0.37 are noted.
[0057] After activation at 900°C under water vapor (192 g/h) and nitrogen (200 1/h) for 25 minutes or
50 minutes, the final products have the properties
presented in the following Table 2.
[0058] It is rapidly recalled here that the pore volume is the total volume of nitrogen adsorbed at saturation at the temperature of 77 K (-196°C, temperature of liquid nitrogen at atmospheric pressure), measured according to French standard NF X 11-621 and expressed in cm3 per gram of carbon.
[0059] The BET specific surface area is the total surface area accessible to the nitrogen at 77 K, in m2
per gram of carbon; it is measured, like the preceding amount, by volumetric adsorption of nitrogen at low temperature (French standard NF X 11-621).
[0060] The iodine number is measured according to standard ASTM D4607 and the methylene blue number is measured by the number of milliliters of standard methylene blue solution discolored with 0.1 g of activated carbon (counted dry), according to the CEFIC
(Conseil Europeen des Federations de 1'Industrie Chimique) [European Chemical Industry Council] method . as described in Deutsches Arzneibuch, 6th edition.
[0061] The ash content is determined using an activated carbon dried at 100°C, and then subjected to heat treatment at 650°C ± 25°C in an oxidizing atmosphere until disappearance of the gray or black carbon particles. The ash content is defined by the amount of residual materials relative to the initial weight of dry activated carbon.
[0062] The determination of the average particle size is carried out by sieving on sieves having various mesh sizes. The particle size distribution results from weighing the various batches of carbon particles retained on or passing through sieves of defined mesh sizes.
Table 2
(Table Removed)
[0063] The yields over the two operations therefore amount to 23% and 16%, respectively, which is higher than what is obtained on other vegetable materials.
[0064] The relatively high ash contents do not represent a real handicap since, industrially, washing treatments are carried out. The extractions with acid show the presence of potassium, phosphorus, magnesium and calcium. No heavy metals (Hg, Cd, Pb, etc.) are detected.
[0065] The surface area and porosity measurements show that these carbons resulting from oil cakes are especially microporous, compared with pinewood-based carbons. Table 3 below summarizes the data.
Table 3
(Table Removed)
[0066] All these characteristics show that it is possible to obtain a carbon which has properties close to certain commercial products.
[0067] Applications of such carbons in the form of grains for the treatment of VOCs are possible with characteristics of this type.
Example 2:
[0068] An acid washing of the carbon corresponding to the second activation of Example 1 is carried out.
[0069] To do this, by treating 10 g of carbon in 100 ml of 1M nitric acid for 2 hours at 25°C, the following characteristics will be obtained after filtration:
ash content: 0.5%;
iodine number (ASTM D4607): .1190 mg/g;
methylene blue index (CEFIC): 14;
BET surface area: 1300 m2/g.
[0070] These characteristics show that the carbon obtained, from which this ash has been removed, is advantageous in applications such as the purification of pharmaceutical ingredients, the forming of supercapacitor electrodes or as a catalyst support.

CLAIMS
1. A process for exploiting the residues, in particular the toxic residues, obtained as by-products during processes for extracting oils from oleaginous plants, preferably non-food oleaginous plants, said process comprising the process of the combined production of oils of oleaginous plants, preferably non-food oleaginous plants, and production of activated carbon from oil cakes, optionally in combination with the shells, of said oleaginous plants.
2. The process as claimed in claim 1, in which the oil production and the activated carbon production are carried out on the same industrial site.
3. The process as claimed in claim 1 or claim 2, in which the process for preparing activated carbon from oil cakes, and optionally from shells, of oleaginous plants, preferably non-food oleaginous plants, comprises at least the following steps:

a) carbonization of oil cakes, and optionally of shells, at a temperature of between 200°C and 700°C, for example around 550°C;
b) activation at a temperature of between 500°C and 1200°C, advantageously around 900°C;
c) optionally, washing with an acid, preferably a strong acid; and
d) recovery of the activated carbon.
4. The process as claimed in claim 3, in which the
carbonization step is carried out under a neutral or
low-oxygen atmosphere, for example under nitrogen or
under argon, or, according to one preferred embodiment,
in an atmosphere consisting of the combustion gases of
a hydrocarbon-based fuel, such as, for example,
methane, ethane, propane, butane, and the like, or else
distillation gases.
5. The process as claimed in claim 3, in which the activation step is carried out under partial vapor pressure and/or under partial CO2 pressure, the rest at atmospheric pressure possibly being provided by any gas that is inert with respect to the activation, for example, nitrogen, combustion gas, and the like.
6. The process as claimed in claim 3, in which the optional acid washing is carried out with at least one acid chosen from nitric acid, hydrochloric acid, sulfuric acid, acetic acid, citric acid, methanesulfonic acid and the like, and also mixtures thereof.
7. The use of oil cakes, optionally with the shells, of oleaginous plants, preferably non-food oleaginous plants, for the preparation of activated carbon.
8. The use as claimed in claim 7, in which the plant is chosen from the castor plant, jatropha, ironweed, Cuphea, rubber tree, oleaginous flax, erucic rape, honesty, safflower, gold-of-pleasure, Calophyllum inophyllum, Pongamia pinnata and the corresponding oleaginous plants which have been genetically modified, and also the mixtures of two or more of said plants.
9. The use of activated carbon obtained according to the process of claim 1, as an agent for purifying solids, liquids or gases, in particular in the food industry, for example as an agent for purifying water, wine, beer, synthesis intermediates or final products, in particular pharmaceutical ingredients, but also in all the fields where activated carbons are normally used, for example as a constituent of supercapacitor electrodes, as a catalyst support, or else as an adsorbent of volatile organic compounds (VOCs), in particular in the gas phase.
10. The use of activated carbon obtained according to the process of claim 1, for the production of energy, either as a pure compound, or as a mixture with at least one other fuel of renewable or fossil origin.