| WO2009117753A1 | 2009-10-01 | |||
| WO2002083591A1 | 2002-10-24 |
| CN113278995A | 2021-08-20 | |||
| CN109516912A | 2019-03-26 | |||
| FR2669918A1 | 1992-06-05 | |||
| JP2003095711A | 2003-04-03 | |||
| EP2257362A1 | 2010-12-08 |
CHAN, W.L, ACS CATAL, vol. 8, no. 2, 2018, pages 931 - 937
ALISSANDRATOS, A: "in Bioresour Technol", vol. 164, 2014, pages: 7 - 1
ENZYMES FOR SOLVING HUMANKIND'S PROBLEMS
| CLAIMS 1 . A method of producing calcium oxalate from calcium carbonate the method comprising the steps of: (a) producing CO2 by heating calcium carbonate; (b) contacting the CO2 from step (a) with hydrogen to produce at least one formate; and (c) thermal treatment of the formate of step (b) to produce calcium oxalate and hydrogen wherein the thermal treatment of the formate in step (c) to produce the oxalate involves heating the formate at a temperature of about 360 to 390°C. 2. The method according to claim 1 , wherein the calcium oxalate in step (c) is a calcium oxalate hydrate. 3. The method according to either claim 1 or 2, wherein the formate in step (b) is produced by a catalytic or biotechnological means using hydrogen as a reducing agent. 4. The method according to any one of the preceding claims, wherein the hydrogen released in step (c) is recycled to step (b) for the production of formate. 5. The method according to any one of the preceding claims, wherein the formate in step (b) is produced by a catalytic means where the CO2 is brought into contact with at least one alkali in the presence of hydrogen. 6. The method according to any one of the preceding claims, wherein the formate produced in step (b) is an alkali formate. 7. The method according to any one of the preceding claims, wherein the formate produced in step (b) is sodium or potassium formate. 8. The method according to any one of the preceding claims, wherein none or no measurable amount of CO is present in any of steps (a), (b) and (c). 9. A method of storing CO2, the method comprising the steps of: (a) contacting isolated CO2 with hydrogen to produce at least one formate; and (b) thermal treatment of the formate of step (a) to produce calcium oxalate and hydrogen wherein the CO2 is produced from calcium carbonate; and wherein the thermal treatment of the formate in step (c) to produce the oxalate involves heating the formate at a temperature of about 360 to 390°C. 10. The method according to claim 9, wherein the oxalate in step (b) is a calcium oxalate hydrate. The method according to either claim 9 or 10, wherein the CO2 is produced during the production of burnt lime and/or cement. The method according to any one of claims 9 to 11 , wherein the CO2 is stored in close proximity to the source of CO2 and/or calcium carbonate. The method according to any one of claims 9 to 12, wherein none or no measurable amount of CO is present in step (a). |
FIELD OF THE INVENTION
The present invention relates to a method of converting carbon dioxide (CO2) released from limestone during cement production to calcium oxalate. In particular, the calcium oxalate produced, provides a means of storage of CO2 and prevents the C02from being released into the environment.
BACKGROUND OF THE INVENTION
Carbon dioxide (CO2) is a greenhouse gas that is collecting in the atmosphere and causing global warming problems and unwanted climate changes. Most industrial processes that are being carried out internationally release inadvertently significant amounts of CO2 in their exhaust fumes. This CO2 is being accumulated in the environment and causing an increase in temperature that is leading to uncontrollable climate changes such as melting of the polar ice caps, increase in sea-level globally, floods and the like.
Manufacturing cement from raw materials such as lime (calcium carbonate) and calcium hydroxide, is an example of a process where at least 200 or 300 kg of carbon dioxide is emitted per 1000kg of cement produced. This amount of carbon dioxide is not only detrimental for the environment, but it is also a waste of raw materials that be used for another purpose.
One way to resolve this issue, is to reduce emissions by increasing the efficiency of cement production or reducing the amount of cement produced. However, this is an arduous task taking into the account the increase in construction in the world and consequently the increase in carbon dioxide emissions. Further, collecting the CO2 released during cement production and transporting it away from the production site is also very cost intensive since transport of CO2 is not only generally expensive but also a logistical nightmare.
There are some methods disclosed in the art that attempt to solve this problem. For example, CN109516912A discloses a method for utilizing and sequestering carbon dioxide produced during any method known in the art. In particular, in CN109516912A, sodium carbonate is used as a chemical absorbent of CO2, to produce bicarbonate. This method has the disadvantage that a large amount of sodium carbonate has to be present close to the cement plant. FR-A-2 669 918 and JP 200309571 1 A attempt to use other starting materials of non-carbonate origin for making of cement. However, in addition to the considerable costs of these processes, the question of final disposal of the carbon dioxide produced is still unacceptable.
W002083591A describes a carbon dioxide emission-free operation of a cement plant. The resulting carbon dioxide is bound to calcium chloride (or other metal oxides/chlorides from sea salt or waste) to form calcium carbonate. The newly formed calcium carbonate is then processed again. Calcium oxide is produced from calcium chloride and the carbon dioxide produced is not emitted and remains in the circuit. However, this method is not only costly but also has the disadvantage that the carbonate produced usually cannot be processed further. EP2257362 provides an alternative where the carbon monoxide and/or carbon dioxide produced during the process of cement production may be used to produce at least one oxalate. However, in the method disclosed carbon monoxide had to be always present in a larger concentration compared to carbon dioxide which is not always the case in cement production.
Accordingly, there is a need in the art to not only capture CO2 emitted during the production of cement but also to store the CO2 in a form where it may be used not only for another purpose but also be easy to transport.
DESCRIPTION OF THE INVENTION
The present invention attempts to solve the problems above by providing a method of converting CO2, released from limestone during cement production, to at least one oxalate. In particular, the oxalate produced is calcium oxalate. This method is especially advantageous as then, CO2 is not released to the environment and instead of transporting the isolated CO2 from the exhaust gases elsewhere, the CO2 is converted into a solid, an oxalate salt, which is much easier and cheaper to transport than CO2. In particular, oxalate salts contain a high amount of CC>2and can be easily stored or transported. Further, this is the least energy consuming conversion of CO2, as only one molecule of H2 is consumed for every two molecules of CO2. In particular, calcium oxalate is known to bind two moles of carbon per mole of calcium in an extremely stable form. This makes the method according to any aspect of the present invention efficient and reliable for removing CO2 released from the exhaust gases during cement production and converting the CO2 to stable calcium oxalate. The extremely stable compound, calcium oxalate with a lower water solubility compared to at least calcium carbonate, is then suitable for use in production of sand and/or stones. Calcium oxalate can also be used as a binder or as an additive to hydraulic binders.
According to one aspect of the present invention, there is provided a method of producing calcium oxalate from calcium carbonate the method comprising the steps of:
(a) producing CO2 from calcium carbonate;
(b) contacting the CO2 from step (a) with hydrogen to produce at least one formate; and
(c) thermal treatment of the formate of step (b) to produce calcium oxalate and hydrogen.
Calcium carbonate also known as limestone or lime. Because of the abundance of lime and its relative cheapness, it would be desirable to be able to treat high-calcium lime with a minimum amount of an additive in order to be able to dead burn it to make it usable as a high-temperature refractory which would not be subject to hydration or delayed slaking. It would also, of course, be desirable to be able to use an additive which itself would not add materially to the cost of the final refractory. Accordingly, limestone is used in cement and/or burnt lime production. More precisely, calcium oxide, CaO, is known as quick lime or burnt lime and calcium hydroxide, Ca(OH)2, is known as hydrated lime. The lime applicable to the method according to any aspect of the present invention, relates to calcium carbonate (limestone) which is the starting material in the production of cement and/or burnt lime. The method according to any aspect of the present invention provides a means to turn lime into burnt lime and calcium oxalate, using hydrogen. The method according to any aspect of the present invention, provides a CO2 sink that not only prevents CO2 produced during cement production to be emitted into the environment but also allows the CO2 produced to be used in the cement production itself. The captured CO2 as calcium oxalate is also in close proximity to the site of production so that costs will be reduced for transportation.
In step (a) according to any aspect of the present invention, calcium carbonate is heated to produce CO2. In particular, clinker is produced by pyro-processing. Calcium carbonate is burned at high temperatures, first calcinating the materials, followed by clinkerization to produce clinker. More in particular, calcination of the limestone takes place at a relatively moderate temperature, typically around 900°C to 1 100°C. Calcination of limestone refers to the thermal decomposition of limestone to produce quicklime/ unslaked lime (calcium oxide) and CO2. The reaction for the thermal decomposition of calcium carbonate may be expressed as:
CaCOs + Heat <=» CaO + CO2
In another example, CO2 may be produced from CaCOs by bringing CaCOs in contact with at least one acid. In particular, the acid may be selected from the group consisting of HCI, HNO3, and H2SO4, acetic acid, formic acid, succinic acid and oxalic acid.
The CO2 produced from step (a) is first isolated and then brought into contact with hydrogen to produce formate. Any method known in the art may be used to produce formate from CO2. In particular, a catalytic means may be used to produce at least one formate from CO2. The formate may be an alkali formate where an alkali is brought in in contact with at least one alkali to produce an alkali formate. In particular, CO2 is hydrogenated to produce formic acid. The formic acid will be neutralized by sodium or potassium hydroxide to produce the alkali formate. The alkali may be selected from the group consisting of barium, sodium, ammonium, calcium, lithium, and potassium hydroxides. More in particular, the alkali brought in contact with CO2 may at least be sodium or potassium hydroxide and the resulting formate produced may be sodium or potassium formate. Even more in particular, the alkali may be sodium hydroxide and a saturated solution of sodium formate may be produced at around 210°C under high pressure. The reaction equation is:
NaOH + CO 2 + H 2 ^ HCOONa + H 2 O
Different formates may be formed depending on the alkali used. For example, when KOH is used potassium formate is produced, when barium hydroxide is used, then barium formate is produced and the like. In one example, calcium hydroxide may be used as the alkali and the following reaction takes place:
Ca(OH) 2 + 2CO 2 + 2H 2 -> (HCOO) 2 Ca + 2H 2 O
In the catalytic production of formate from CO2, any method known in the art may be used. Also, any catalyst known to function in such a method may be used in the art. Example of catalysts that may be function in step (b) are at least disclosed in Al-Tamreh S.A. Chem Electro Chem (2021) ,8: 3207- 3220. Also, Bismuth-Based Catalysts which can also be used in formate production from CO2 are provided at least Chan, W.L in ACS Catal. 2018, 8 (2): 931-937. Alternatively, formate may be produced from CO2 using a biotechnological method. This method is disclosed at least by Alissandratos, A., in Bioresour Technol. 2014,164: 7-1 and Maia, L.B. in J. J. G. Moura et al. (eds.), Enzymes for Solving Humankind's Problems.
In the method according to any aspect of the present invention, hydrogen is used in step (b) as a reducing agent. In particular, hydrogen is used in both the catalytic and biotechnological means of producing formate from CO2 as a reducing agent.
The calcium oxalate produced according to any aspect of the present invention, particularly in step (c) may be a calcium oxalate hydrate.
The hydrogen released in step (c) is recycled to step (b) for the production of formate. Accordingly, very little hydrogen is needed to carry out the method according to any aspect of the present invention. In particular, since the amount of hydrogen needed to carry out the method according to any aspect of the present invention is not that high, the hydrogen be produced onsite. The production of hydrogen may be carried out by a windmill and/or solar panel in combination with an electrolyzer. In another example, the hydrogen may be produced using litter incineration, which also converts through partial oxidation limestone into CaO.
Thermal treatment of the formate in step (c) to produce the oxalate involves heating the formate at a temperature of about 360 to 420°C. In one example, the heating is done rapidly so that the reaction takes place efficiently. More in particular, the formate according to any aspect of the present invention is heated at a temperature of about 360 to 390°C, 360 to 385, 360 to 380, 360 to 375, 360 to 365, 365 to 390, 365 to 385, 365 to 380, 365 to 375, 365 to 370, 370 to 390, 370 to 385, 370 to 380, 370 to 375, 375 to 390, 375 to 385, 375 to 380, 380 to 390, or 385 to 390. In one example, the thermal treatment of format in step (c) is carried out at least or at about 360, 365, 370, 375, 380, 385 or 390°C. These lower temperatures compared to those carried out in the past are better to achieve higher selectivity of the desired product.
In particular, the following reaction takes place from sodium formate to produce sodium oxalate:
The sodium oxalate obtained after the above step may then be converted into calcium oxalate by reacting it with calcium hydroxide to form calcium oxalate:
Na 2 C 2 O4 + Ca(OH) 2 - CaC 2 O4 + 2NaOH
In this example, the sodium or potassium oxalate is converted to calcium oxalate, which is precipitated, releasing sodium- or potassium hydroxide. In particular, calcium oxalate is precipitated, because the solubility is much lower than the solubility of sodium or potassium oxalate.
In another example, the following reaction takes place from calcium formate to produce calcium oxalate:
(HCOO) 2 Ca CaC 2 O4+ H 2 The hydrogen produced according to this method may then be recycled in step (a) and the calcium oxalate may be isolated used a method known in the art.
In particular, none or no measurable amount of CO is present in any of steps (a), (b) and (c).
According to another aspect of the present invention, there is provided a method of storing CO2, the method comprising the steps of:
(a) contacting isolated CO2 with hydrogen to produce at least one formate; and
(b) thermal treatment of the formate of step (a) to produce calcium oxalate and hydrogen wherein the CO2 is produced from calcium carbonate.
The oxalate in step (b) may be a calcium oxalate hydrate. In particular, the CO2 is produced according to any aspect of the present invention is during the production of burnt lime and/or cement. In particular, the CO2 is stored in close proximity to the source of CO2 and/or calcium carbonate.
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