Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2000-10-19
2002-07-02
Hoey, Betsey Morrison (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S757000, C210S915000, C423S24000R, C502S020000, C502S035000, C502S300000, C502S340000, C502S344000
Reexamination Certificate
active
06413434
ABSTRACT:
The present invention relates to a process for eliminating, reducing and/or suppressing halogenated compounds, in particular chlorinated compounds, contained in a gas or a liquid. In some industrial applications, it is necessary to eliminate halogenated compounds, in particular chlorinated compounds, which contaminate the stream, whether it is gaseous or a liquid.
By way of illustration, halogenated compounds, in particular chlorinated compounds contained in the gas or liquid from catalytic reforming, are eliminated in the petroleum industry.
One aim of catalytic reforming is to obtain hydrocarbons with an increased octane number. Hydrocarbon cyclisation and aromatisation reactions are thus desirable since the octane number of a hydrocarbon is higher when it is branched, cyclic or even aromatic. Catalytic reforming produces hydrogen in parallel.
Normally, these hydrocarbon cyclisation and aromatisation reactions take place in the presence of heterogeneous bimetallic chlorinated catalysts. Such chlorinated catalysts are based on alumina and usually comprise platinum and another metal such as tin, rhenium or iridium. The presence of chlorine in said catalysts is important as when added to alumina, it provides the system with an overall acidity and participates in re-dispersing the platinum over time and thus stabilises the catalytic activity of the catalyst.
However, adding chlorine is not a solution without disadvantages. It has been shown that over time, the chlorine partially elutes, in particular in the form of HCl. Such elution means that the catalyst must constantly be recharged with chlorine. It also leads to the presence of HCl and other chlorinated compounds in the gaseous and liquid effluents from catalytic reforming, which can lead to a problem with corrosion of the facility and to the formation of other products which are undesirable and a nuisance to the operation of the facility.
A catalytic reforming process is conventionally operated at high pressure, usually about 20 bars or even higher.
Regenerative processes or new generation processes have recently been developed and are being further developed in the field. Such processes are characterized by being operated at substantially lower pressures, around 3 to 15 bars, or even lower.
The effluents leaving a traditional reforming process contain mainly hydrogen, light saturated hydrocarbons such as methane, ethane. . . , traces of chlorinated compounds, in particular HCl, and water.
The Applicant has surprisingly and unexpectedly discovered that in regenerative processes, traditional adsorbents used up to now in catalytic reforming at higher pressure, based in a high specific surface area alumina, optionally comprising an alkali or alkaline-earth compound, have substantial disadvantages.
Downstream of regenerative processes, and probably because of the lower pressure operation, in addition to hydrogen, light saturated hydrocarbons, traces of chlorinated compounds in particular HCl, and water, the presence of traces of unsaturated hydrocarbons such as ethylene, propylene, butadiene, . . . , has also been observed.
The traces of unsaturated hydrocarbons present in the streams downstream of regenerative processes are at least partially transformed into organo-chlorinated compounds in the presence of chlorinated compounds when in contact with the alumina. Such organo-chlorinated compounds, after multiple reactions with each other and/or with other unsaturated compounds also present in the stream and at the surface of prior art adsorbants, lead to the production of chlorinated oligomers which are aromatic to a greater or lesser extent and have high molecular weights, known as green oils.
After their formation, green oils can no longer be eliminated by traditional adsorbents and migrate in the direction downstream of the adsorber. They can then cause blockages in the facility. Further, a significant drop in the service life of the adsorbent is noted: in some cases, a fall of 4 to 5 times has been observed.
The aim of the present invention is to provide a process which can use a composition which substantially reduces or even suppresses the formation of halogenated oligomers, and in particular chlorinated oligomers known as green oils.
The present invention also aims to provide a process which uses a composition which can more efficiently eliminate halogenated compounds, in particular chlorinated compounds, contained in a gas or a liquid.
These aims are achieved by the present invention which provides a process for eliminating halogenated compounds and for reducing or suppressing the formation of halogenated oligomers contained in a gas or a liquid.
The expression “process for eliminating, reducing and/or suppressing halogenated compounds” as used below designates a “process for eliminating, reducing and/or suppressing both organic and inorganic halogenated compounds and high molecular weight halogenated oligomers”. This expression also designates the process aimed at preventing the formation of the halogenated oligomers cited above.
In a first variation, the invention concerns a process for eliminating, reducing and/or suppressing halogenated compounds contained in a gas or a liquid, characterized in that the gas or liquid is brought into contact with a composition obtained by depositing on alumina at least one compound comprising at least one element selected from alkalis on an alumina, followed after deposition by calcining the alumina at a temperature of at least 600° C.
In a second variation, the invention concerns a process for eliminating, reducing and/or suppressing halogenated compounds contained in a gas or a liquid, characterized in that the gas or liquid is brought into contact with a composition obtained by depositing at least one compound comprising at least one element selected from alkaline-earths and rare earths on an alumina, followed after deposition by calcining the alumina at a temperature of at least 500° C., more particularly at least 600° C.
In a third variation, the invention concerns a process for eliminating, reducing and/or suppressing halogenated compounds contained in a gas or a liquid, characterized in that the gas or liquid is brought into contact with a composition obtained by depositing at least one compound comprising at least one element selected from alkalis on an alumina, followed after deposition by calcining the alumina at a temperature of at least 600° C., said composition having a specific surface area of at most 110 m
2
/g.
In a fourth variation, the invention concerns a process for eliminating, reducing and/or suppressing halogenated compounds contained in a gas or a liquid, characterized in that the gas or liquid is brought into contact with a composition obtained by depositing at least one compound comprising at least one element selected from alkalis on an alumina, followed after deposition by calcining the alumina at a temperature of at least 500° C., more particularly at least 600° C., said composition having a specific surface area of at most 140 m
2
/g.
Finally, in a fifth variation, the invention concerns a process for eliminating, reducing and/or suppressing halogenated compounds contained in a gas or a liquid, characterized in that the gas or liquid is brought into contact with a composition obtained by depositing at least one compound comprising at least one element selected from the rare earths on an alumina, followed after deposition by calcining the alumina at a temperature of at least 500° C., more particularly at least 600° C., said composition having a specific surface area of at most 250 m
2
/g.
The upper temperature for the calcinations of alumina preferably does not 1200° C.
The composition used in the process of the present invention can be in a variety of forms. As an example, it can be in the form of powders, beads, extrudates, compresses, or monoliths.
The first essential constituent of the composition is alumina.
The specific surface area of the starting alumina is generally at least 30 m
2
/g, preferably at least 100 m
2
/g, more preferably at least 200
Hoey Betsey Morrison
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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