Catalytic process for oxidative degradation of aqueous effluents

Details Catalytic process for oxidative degradation of aqueous effluents Catalytic process for oxidative degradation of aqueous effluents

1991-09-20

1992-10-20

Langel, Wayne

Liquid purification or separation

Processes

Chemical treatment

210763, 210909, G02F 168, G02F 172

Patent

active

051567482

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1) Field of the Invention
The invention relates to a catalytic process for oxidative degradation of aqueous effluents containing cyclic hydrocarbon compounds known to be toxic.
Aromatic residues, chlorinated ones in particular, are notoriously difficult to oxidise and resistant to biodegradation.
Methods of treating effluents containing such residues rely either on catalysts based on manganese oxide or copper oxide CuO involving drastic operating conditions (temperature, pressure) or on sophisticated processes, for example photocatalysis.
The objective of the invention is to propose a process for treating such effluents which is easy to implement and which makes it possible to achieve rapidly high efficiencies of conversion of cyclic hydrocarbon compounds.


SUMMARY OF THE INVENTION

The subject of the present invention is a process for treatment by oxidative degradation of effluents containing saturated, unsaturated or aromatic mono- or polycyclic hydrocarbon compounds known to be toxic, characterised in that it is carried out in the presence of a catalyst consisting of a water-soluble metalated meso-tetraphenylporphyrin in combination with a water-soluble peroxide as oxygen-donor.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

The effluents being treated may contain all kinds of cyclic hydrocarbon compounds known to be toxic such as, for example, polycondensed aromatics, chlorinated aromatics, chlorinated polycyclic aromatics, chlorinated cyclic aliphatic hydrocarbons and hydroxylated or alkoxylated aromatic hydrocarbons.
These compounds may be, for example:
The porphyrin which can be employed in the process of the invention will be preferably metalated with iron or manganese.
This porphyrin is meso-tetraphenyl-substituted and its water-soluble nature will be preferably conferred by at least one substituent exhibiting this nature, for example a sulphonate functional group placed in position 3, 4 or 5 of these phenyl nuclei.
The phenyl nuclei of these meso-substituted porphyrins will preferably carry in positions 2 and 6 substituents such as halogens or alkyl hydrocarbon radicals containing from 1 to 6 carbon atoms or aryl radicals, which will avoid the formation of .mu.-oxo units in the oxidising reaction medium, since these can entail a deactivation of the catalyst or even its destruction.
Processes for the synthesis of such porphyrins have been described by R. W. Wagner, J. S. Lindsey et al. Tetrahedron Lett., 28, 3069-3070; 1987 and by the Applicant Company in a pending French patent application filed on Oct.8, 1989 under No. 89/10,762.
The process of the invention can be carried out either with homogeneous catalysis, especially when the catalyst consists of an iron porphyrin, or with heterogeneous catalysis. Assuming the latter, the porphyrin is then attached to an insoluble support of resin type. The latter may, for example, be a polymer carrying pyridine or imidazole functional groups, which will be particularly well-suited to a process employing a manganese porphyrin.
The oxidation mechanism of the process involves the presence of a water-soluble peroxide as oxygen-donor. This peroxide will be inorganic or organic.
By way of example of peroxides suited to the process of the invention there may be mentioned: inorganic peroxides, such as H.sub.2 O.sub.2 or KHSO.sub.5, organic peroxides: MMPP (magnesium salt of monoperphthalic acid) for example, and alkyl hydroperoxides: for example t-Bu-OOH.
The process of the invention is carried out in an aqueous medium at an acidic pH which is generally lower than or equal to 6 and preferably lower than 4.
Furthermore, it will be advantageous to employ a reaction medium consisting of a mixture of water and acetonitrile which has an acetonitrile content of between 5 and 70% by volume and preferably between 20 and 50%.
The process of the invention will be understood better on reading the examples below by way of illustration without any limitation being implied.
The porphyrins employed in the examples below: (support 2) to support 2 89/401

REFERENCES:
patent: 2951797 (1960-09-01), Sharp
patent: 2966453 (1960-12-01), Gleim et al.
patent: 3252892 (1966-05-01), Gleim
patent: 4804480 (1989-02-01), Jayawant
patent: 5004551 (1991-04-01), Sublette

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