Patent Application
20240390851
The present invention relates to a method for the photocatalytic aerobic oxidation of yperite or an analog thereof into the corresponding sulfoxide, which is a non-toxic substance.
Yperite (also called mustard gas, sulfur mustard or 1-chloro-2-[(2-chloroethyl)sulfanyl]ethane) is a chemical warfare agent which was mostly used during world war conflicts in the form of dispersed aerosols. Nowadays, its production and storage are prohibited by international treaties, but its revival by ill-intentioned individuals cannot be excluded, considering the simplicity of its synthesis. There is thus continued interest in the development of suitable protective equipment, air-filtering devices, and degradation methods.
The chemical neutralization of yperite (A) (i.e. the degradation or conversion of yperite into non-toxic substance(s)) can proceed via either hydrolysis, β-elimination, or sulfur oxidation (references [1]-[4]). The latter option is particularly appealing but requires the process to be selective toward the harmless sulfoxide derivative (B), rather than the toxic sulfone (C) (reference [5]).
Besides selectivity issues, an “ideal” transformation should also involve non-polluting reagents and generate no side-products, making dioxygen particularly attractive as the oxidant source in case of chemical neutralization by sulfur oxidation.
Recently, a selective photocatalytic aerobic oxidation of yperite or a simulant thereof into sulfoxide has been developed. This reaction needs to be performed in the presence of an appropriate photocatalyst (a porphyrin complex), in a solvent medium, i.e. in a liquid phase, and under dioxygen (see references [6]-[9]). This reaction is generally completed within a few minutes under pure oxygen atmosphere, but require extended reaction times under air. Moreover, since the main risk of exposure to yperite is from airborne aerosols, it is important to be able to degrade yperite in an aerosol or gas phase.
Only a few studies report the decomposition of sulfur mustard in a gas phase (reference [10]-[13]). This decomposition is performed by photochemical processes involving the mineralization of gaseous yperite or a simulant thereof on a semi-conductor material (TiO2), and under UV irradiation, either in a flow circulating reactor (reference [11]-[12]) or a quartz cell (reference [13]). However, in addition to the fact that these processes are rather complex to implement, they usually involve over-stoichiometric amounts of the photocatalyst, display low selectivity and lead to a mixture of degradation products, the toxicity of which is not known, and often result in the rapid surface deactivation of the catalyst.
There is thus still a need for a method allowing the degradation of yperite or an analog thereof into non-toxic substance(s) in an aerosol or gas phase, such as by oxidation of yperite or an analog thereof into sulfoxide.
The present invention allows overcoming the problems of the prior art by providing a method for the degradation of yperite or an analog thereof by photocatalytic aerobic oxidation that:
The present invention thus relates to a method for converting a sulfide of the following formula (I) (i.e. yperite or an analog thereof):
R1—S—R2 (I)
R1—SO—R2 (II)
The present also relates to an air-filtering device comprising a catalyst of formula (I) as defined above.
The term “(C1-C3) alkyl”, as used in the present invention, refers to a straight or branched monovalent saturated hydrocarbon chain containing from 1 to 3 carbon atoms including, methyl, ethyl, n-propyl, or iso-propyl.
The term “(C2-C3) alkenyl”, as used in the present invention, refers to a straight or branched monovalent unsaturated hydrocarbon chain containing from 2 to 3 carbon atoms and comprising at least one double bond including ethenyl, and propenyl.
The term “aryl”, as used in the present invention, refers to an aromatic hydrocarbon group comprising preferably 6 to 10 carbon atoms and comprising one or more fused rings, such as, for example, a phenyl or naphthyl group. Advantageously, it will be a phenyl group.
The term “aryl-(C1-C3)alkyl”, as used in the present invention, refers to a (C1-C3)alkyl group as defined above substituted with an aryl group as defined above. In particular, it can be a benzyl group.
The term “aryl-(C2-C3)alkenyl”, as used in the present invention, refers to a (C2-C3)alkenyl group as defined above substituted with an aryl group as defined above. In particular, it can be a phenylethenyl group.
The term “halogen atom”, as used in the present invention, refers to a fluorine, bromine, chlorine or iodine atom.
The terms “catalyst” and “photocatalyst” are used interchangeably.
The method according to the invention allows converting a sulfide of formula (I), i.e. yperite or an analog thereof that can be used notably as a simulant of yperite, into a sulfoxide that is a non-toxic substance. Such a method allows the neutralization of yperite, i.e. its degradation into non-toxic substance(s).
The sulfide is a sulfide of formula (I), wherein R1 and R2, identical or different, are a (C1-C3)alkyl, (C2-C3)alkenyl, aryl, aryl-(C1-C3)alkyl, or aryl-(C2-C3)alkenyl group said group being optionally substituted by one or several groups selected from a halogen atom (e.g. Cl), OR3 (e.g. OH), and NR4R5; in particular optionally substituted by one or several groups selected from a halogen atom (e.g. Cl), OH, and NH2; more particularly optionally substituted by one group selected from a halogen atom (e.g. Cl), OH, and NH2, preferably selected from halogen atom (e.g. Cl), and OH, especially from Cl and OH. According to a particular embodiment, at least one of R1 and R2 is a group substituted by one or several groups selected from a halogen atom (e.g. Cl), OR3 (e.g. OH), and NR4R5; in particular substituted by one or several groups selected from a halogen atom (e.g. Cl), OH, and NH2; more particularly substituted by one group selected from a halogen atom (e.g. Cl), OH, and NH2, preferably selected from halogen atom (e.g. Cl), and OH, especially from Cl and OH.
The sulfide can be in particular a sulfide of formula (I), wherein R1 and R2, identical or different, are a (C1-C3)alkyl, (C2-C3)alkenyl, or aryl group, said group being optionally substituted by one or several groups selected from a halogen atom (e.g. Cl), OR3 (e.g. OH), and NR4R5; in particular optionally substituted by one or several groups selected from a halogen atom (e.g. Cl), OH, and NH2; more particularly optionally substituted by one group selected from a halogen atom (e.g. Cl), OH, and NH2, preferably selected from halogen atom (e.g. Cl), and OH, especially from Cl and OH. According to a particular embodiment, at least one of R1 and R2 is a group substituted by one or several groups selected from a halogen atom (e.g. Cl), OR3 (e.g. OH), and NR4R5; in particular substituted by one or several groups selected from a halogen atom (e.g. Cl), OH, and NH2; more particularly substituted by one group selected from a halogen atom (e.g. Cl), OH, and NH2, preferably selected from halogen atom (e.g. Cl), and OH, especially from Cl and OH.
The sulfide can be more particularly a sulfide of formula (I), wherein R1 and R2, identical or different, are a (C1-C3)alkyl group, said group being optionally substituted by one or several groups selected from a halogen atom (e.g. Cl), OR3 (e.g. OH), and NR4R5; in particular optionally substituted by one or several groups selected from a halogen atom (e.g. Cl), OH, and NH2; more particularly optionally substituted by one group selected from a halogen atom (e.g. Cl), OH, and NH2, preferably selected from halogen atom (e.g. Cl), and OH, especially from Cl and OH. According to a particular embodiment, at least one of R1 and R2 is a group substituted by one or several groups selected from a halogen atom (e.g. Cl), OR3 (e.g. OH), and NR4R5; in particular substituted by one or several groups selected from a halogen atom (e.g. Cl), OH, and NH2; more particularly substituted by one group selected from a halogen atom (e.g. Cl), OH, and NH2, preferably selected from halogen atom (e.g. Cl), and OH, especially from Cl and OH.
According to a particular embodiment, the sulfide is yperite.
The atmosphere comprising dioxygen is preferably air.
The white light irradiation can be a sunlight irradiation. The white or blue light irradiation, in particular the white light irradiation, can be also an irradiation from a white or blue LED (light-emitting diode).
The catalyst has the formula (I) as defined above with Ar1, Ar2, Ar3, and Ar4 being, independently of one another, an aryl group, preferably a phenyl, optionally substituted by one or several, in particular 1, 2, or 3 groups selected from halogen, a (C1-C3)alkyl, OR6, and NR7R8, and
R6, R7, and R8 being, independently of one another, H or a (C1-C3)alkyl.
In particular, Ar1, Ar2, Ar3, and Ar4 are, independently of one another, an aryl group optionally substituted by one or several, in particular one (C1-C3)alkyl, such as a phenyl or a tolyl (i.e. a methylphenyl such as o-, m-or p-methylphenyl).
Preferably, Ar1, Ar2, Ar3, and Ar4 are identical, and most preferably, they are a phenyl or a tolyl.
Preferably, the catalyst is meso-tetraphenylporphyrin (TPP).
The catalyst can be used in an amount from 0.01 to 10 mol %, preferably from 0.1 to 1mol %, relatively to the molar amount of the sulfide.
According to a particular embodiment, the oxidizing step is performed in an aerosol or gas phase. In such an embodiment, the sulfide is in a gas state or in the form of an aerosol (i.e. a suspension of liquid droplets in air) when it is contacted with the catalyst. In consequence, the temperature and the pressure, preferably the temperature, may be adapted so that the sulfide is at least partially in a gas state or in the form of an aerosol. Typically, the reaction can be carried out at a temperature from 20° C. to 100° C., especially from 40° C. to 100° C.
Depending on its boiling point and its vapor pressure, the sulfide may be at least partially in a vapor state, i.e. it may be both in a vapor phase and a liquid phase which are in equilibrium. As the oxidation reaction progresses at the contact of the sulfide with the catalyst, the sulfide in the vapor phase is oxidized so that additional sulfide is vaporized to maintain the equilibrium between the gas phase and the liquid phase of the sulfide.
In such an embodiment, the catalyst is advantageously deposited on a substrate, especially a porous substrate, such as a filter paper, a filter of an air-filtering device, a piece of cloth, a cartridge of silica or alumina, etc.
According to a particular embodiment, the oxidizing step is performed in a liquid phase. In such an embodiment, the sulfide and the catalyst are present and contacted in a liquid phase. For that, the sulfide and the catalyst may by dissolved in a solvent.
The catalyst (or the substrate on which the catalyst is deposited) may be recovered at the end of the oxidizing step, and re-used in another oxidizing step. In these conditions, the catalyst may be recycled.
According to an embodiment, the method is performed in a continuous manner, preferably in an aerosol or gas phase. Such a method can be performed for example in an air-filtering device, where the air, that may contain a sulfide such as yperite, may be continuously treated/filtered.
According to another embodiment, the method is performed batchwise.
The present invention also relates to an air-filtering device comprising a catalyst of formula (I) as defined above, such as meso-tetraphenylporphyrin (TPP).
Said catalyst is preferably deposited on the filter of the air-filtering device.
In particular, the air-filtering device further comprises:
In particular, the air-filtering device comprises a filter on which the catalyst is deposited and a ventilating means that draws the air through the filter.
The air-filtering device may further comprise a source of white or blue light irradiation, in particular white light irradiation. However, such a source of white or blue light irradiation is not necessary since the sunlight may be used as source of white light irradiation.
Such an air-filtering device may be used in order to perform the method according to the present invention.
The present invention is illustrated by the following non-limitative examples.
CEES was chosen as a model sulfide, i.e. as a simulant of sulfur mustard. A typical procedure is given below, the experimental setup being presented on
Experiments under N2 and O2 atmosphere were run by pre-purging the round-bottom flask with the suitable gas for 5 min.
The results obtained are presented in Table 1 below.
(a)7 h of reaction time under a mid-winter sun on a partly cloudy day
Under the conditions of the above-mentioned protocol (Entry 1), the starting CEES material was fully converted in 1 h for the most part into CEESO (expected first oxidation product, 90%), together with some minor CEESO2 (over-oxidation product, 8%), and vinyl derivatives (B-elimination products, <2%).
Reactions run with either no TPP-catalyst (Entry 2) or in the dark (Entry 3) led to no conversion confirming that the oxidation reaction is photocatalyzed by TPP. The aerobic nature of the transformation was evidenced by running the photocatalytic reaction under an inert nitrogen atmosphere (Entry 6), which failed to provide the expected compound in satisfactory yield (<5%), while the reaction run under pure oxygen (Entry 7) mostly afforded the over-oxidized sulfone product.
Moreover, the process can be performed with higher or lower amounts of TPP (Entries 4-5) and with sunlight as irradiation source (Entry 8).
Other photocatalysts were tested under similar conditions (200 μmol CEES, 0.1 mol % photocatalyst) as reported above, except for the phthalocyanine photocatalyst which was deposited as a 1 mM suspension in CHCl3 (due to solubility issues). No conversion was detected for phthalocyanin and (meso-tetraphenylporphyrin) iron(III), whereas a low 4% yield was obtained with (meso-tetraphenylporphyrin) zinc(II).
Other sulfides were also tested under similar conditions (200 μmol sulfide, 0.1 mol % TPP) as reported above. Reaction times were adjusted to get optimal conversion and selectivity.
The results obtained are presented in Table 2 below.
(a)Sulfide deposited directly on the paper support.
The oxidation of HEES is complete after 8 h, which is consistent with the hydrogen bonding effect of the alcoholic group, imparting lower vapor pressure to the sulfide. Alkyl-substituted sulfides are in general more prone to over-oxidation due to the electron-donating effect of the alkyl substituents that increases the electron density of the central sulfur atom (Entries 3-4). Less electron-rich sulfides such as EES (Entry 5) and VES (Entry 6) were converted to their sulfoxide counterparts with better selectivities than those observed for butyl-substituted compounds BBS and TBTBS. Concerning aromatic sulfides, the high boiling point of CEPS (245° C.) is responsible for the mediocre reactivity/selectivity observed (Entry 7) as confirmed by the fact that the deposition of CEPS directly on the paper support affords 98% conversion with 87% selectivity (Entry 8). Besides, MPS, which has a lower boiling point (188° C.), was efficiently oxidized into the corresponding sulfoxide with a selectivity of 72% and 92% conversion (Entry 9). These results confirm that aromatic sulfides can also react satisfactorily.
Successive CEES oxidation experiments have been performed in the aerosol/gas phase according to the above-mentioned procedure by recovering and re-using the same piece of filter paper embedded with the TPP photocatalyst (0.1 mol %) with a fresh batch of CEES. The experiments were performed in triplicate.
The results obtained in terms of percentage of conversion of CEES and percentage of selectivity to CEESO are presented in
A typical procedure is given below for the oxidation of CEES.
TPP (100 μL of a 2 mM solution in CDCl3, 0.2 μmol) is added to a 25 mL round-bottom flask containing 900 μL CD3OD and filled with air. CEES (23.5 μL, 200 μmol) is then added and the flask is closed with a rubber septum. The flask is positioned in a beaker and illuminated with white LEDs for 1 h as done for the experimentation in an aerosol/gas phase. The product distributions are analyzed directly by 1H-NMR. For absolute quantification, a solution of dioxane (20 μL, 1 M) was added to the NMR tube to serve as an internal standard.
Such a procedure allows the complete conversion of CEES with a selectivity to sulfoxide of 97%.
A filtration device simulator has been used to perform a photocatalytic oxidation. A photograph of the experimental setup is presented on
The device has been exposed to blue light irradiation.
The only product identified in the collecting compartment corresponds to the oxidized form of the sulfide comprised in the “source” compartment, i.e. the sulfoxide Et-S(O)—(CH2)2—Cl.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21306560.0 | Nov 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/080872 | 11/4/2022 | WO |
