Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Organic
Reexamination Certificate
2000-03-22
2001-10-02
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Organic
C210S198200
Reexamination Certificate
active
06297191
ABSTRACT:
FIELD OF INVENTION
This invention pertains to metal removal from liquids.
DESCRIPTION OF PRIOR ART
Trace quantities of metals can promote unwanted oxidative processes in organic systems. While iron, zinc and lead can lead to oxidative degradation of hydrocarbon fuels, copper is believed to comprise the most prevalent and active instability promoters. Freshly refined hydrocarbon fuels generally do not contain any copper although trace amounts of copper can be introduced into the fuels during the copper sweetening process or from the contact of refinery streams with copper lines, brass fittings, admiralty metal, and other copper-bearing alloys. Copper concentrations as low as about 50 ppb are believed to exert a marked effect on fuel stability. In gas-drive fuel coker tests, as little as 15-25 ppb of added copper or iron and 100-250 ppb of added zinc or lead appear to have deleterious effects on fuel thermal stability.
Metal-deactivator additives have been employed as one approach to reduce the catalytic activity of the dissolved metals. These additives are intended to reduce activity of the dissolved metals through formation of chelate complexes which are not intended to be deleterious to fuel stability. The problem with such an approach is that since the chelate complexes are soluble in the fuel, they are introduced into engines where they undergo thermal degradation at high temperature. Thermal degradation of the chelate complexes can lead to the release of catalytically active metals which can result in undesirable deposition on engine surfaces and other undesirable consequences.
SUMMARY OF INVENTION
An object of this invention is the removal of metals, particularly heavy metals such as copper, from a medium, particularly a liquid hydrocarbon fuel.
Another object of this invention is removal of copper from a hydrocarbon fuel to a level below 20 ppb.
Another object of this invention is removal of a metal from a medium with an immobilized chelant material in a quick and facile fashion.
These and other objects of this invention can be accomplished by contacting a medium containing a metal with an immobilized chelant material which has a chelant attached to a linker and the linker attached to a solid substrate.
DETAILED DESCRIPTION OF INVENTION
Immobilized chelant material and a process for removing at least one metal from a liquid medium using the immobilized chelant material. The immobilized chelant material includes a chelant, a linker and a solid substrate. The linker attaches the chelant to this substrate. Purpose of the substrate is to act as a support to which the linker is attached. Purpose of the linker is to facilitate contact of the chelant with a hydrocarbon medium and as a point of attachment for the chelant. Purpose of the chelant is to chelate soluble metal in the medium.
The substrate is in a solid state and can take the form of a support of any shape or form, including beads. The substrate can be a polymer or a metal oxide such as a ceramic. Examples of polymers include polystyrene, polyethylene, polyvinyl chloride, and polymethylmethacrylate. Examples of ceramics include zirconia, silica and alumina.
The substrate surface can have functional groups thereon to attach linker thereto or it can be devoid of functional groups. Some substrates have functional groups thereon, in which case, the substrate need not be functionalized to provide the functional groups. Examples of substrate materials which have functional groups include silica, polyvinyl chlorides, polystyrene, and polymethylmethacrylate. If the substrate has functional groups thereon, then attachment to the linker is straightforward. For instance, if silica is used as a substrate, then the pendant silanol groups (—Si—OH—) on the silica substrate are used to directly link the silanol groups of the silica substrate to a linker in a known way.
In another example where substrate is functionalized and, therefore, is provided with functional groups is where the substrate is polymethylmethacryate. In this instance, the hydrogen on the carboxylic group of the methylmethacrylate group is used to directly link to the linker in a known way.
In a situation where a substrate is devoid of a group to which a linker can be attached, a linker with functional groups at two locations thereon must be used or the substrate is functionalized to provide a functional group to which a linker can be attached.
The linker is non-polar and is characterized by a saturated hydrocarbon group that contains a minimum of 1 carbon atom and up to a large number of carbon atoms. In a preferred embodiment, the linker contains 1-40 carbon atoms. The linker can be a straight or a branched chain hydrocarbon and the more carbon atoms in the linker, the more likely that it will be a waxy solid. In a preferred embodiment, the linker is a straight chain hydrocarbon.
The longer the hydrocarbon chain on the linker the less soluble it will be in an aqueous medium and the more soluble it will be in a hydrocarbon medium. For extraction of a metal ion from an aqueous medium, the linker chain can be shorter, as short as 1-4 carbon atoms, whereas in a hydrocarbon medium, the linker can have a larger number of carbon atoms.
The linker can have functional groups between ends thereof as long as the groups do not interfere with the function of the immobilized chelant material, particularly the metal chelating property of the chelant itself, and do not adversely affect stability of the medium. Typically, the linker is an unsubstituted straight chain hydrocarbon.
Functional groups can appear on the linker to facilitate attachment of the linker to the substrate. If the substrate is devoid of a functional group, then the linker should contain at least two function groups—one functional group for chemical attachment to the substrate and the second functional group for chemical attachment to the chelant, assuming that the chelant is devoid of a functional group, which is typically the case. If the substrate is devoid of a functional group and the linker has only one functional group, then after attaching itself to the substrate through its sole functional group, the linker will not be able to attach itself to the chelant unless the chelant carries at least one functional group.
Typical functional groups which can be present on the substrate, the linker or the chelant include epoxides, halides, acid chlorides, anhydrides, acetates, nosylates, brosylates and tosylates. Of the halide functional groups, chlorides and bromides are preferred. If there is more than one functional group on the substrate, the linker or the chelant, the functional groups can be same or different, although, typically, they are same.
The substrate and the linker attached thereto are typically commercially available and can be purchased with a functional group attached to the linker. An example of such is agarose epoxide which can be schematically represented as follows:
A-L-F
where:
A represents agarose, i.e., a galoctose polymer responsible for gel strength of agarose;
L represents a linker, i.e, a straight chain hydrocarbon
F represents the epoxide functional group.
Any metal chelant can be used to attach to a linker. Metal chelants are typically polar and, therefore, insoluble in a hydrocarbon medium but soluble in an aqueous medium. The linker can be attached to a substrate or it can be free. The chelant used dictates specificity for chelation for a particular metal or metals. Nitrogen-containing chelants, whether cyclic or acyclic, are preferred for metals, particularly copper. Especially preferred chelants for metals, particularly copper, include the following:
Of the especially preferred chelants, multi-N containing chelants, such as cyclam, appear to be most preferred for copper, although it can chelate other metals at a reduced degree.
Although the chelators as such are used, it is possible to use modified chelants, particularly derivatives or precursors thereof, to achieve same or similar result.
Spent immobilized chelant material can be regenerated by washing it in an acid bath or by
Chang Eddie L.
Morris Robert E.
Puranik Dhananjay
Bell Mark L.
Kap George A.
Karasek John J.
Pasterczyk J.
The United States of America as represented by the Secretary of
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