Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing organic compound
Reexamination Certificate
1999-04-08
2001-02-13
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing organic compound
C205S560000, C205S565000, C205S573000, C205S574000, C205S587000, C205S602000, C562S030000, C562S041000, C562S118000, C562S124000
Reexamination Certificate
active
06187169
ABSTRACT:
FIELD OF THE INVENTION
This invention is an efficient and economical method for the generation of substantially pure forms of alkanesulfonic or aromatic sulfonic acids (hereinafter sometimes referred to as organosulfonic acid or sulfonic acid) from solutions of corresponding organosulfonate compounds of VIB, VIIB, VIIIB, IB, IIB and/or VA metals. The method involves either the electrowinning of a solution of the metal salt and/or the hydrolytic generation of acid through oxidation of the metal cation. A combination of electrowinning and hydrolysis can also be used.
BACKGROUND OF THE INVENTION
Electrowinning systems for the recovery of metals from salt solutions are well known. In most systems of this type, the intent is to dispose of spent electrolyte solutions as waste and/or to recover metal value for reuse. In some cases, a limited incidental amount of recovery of acid value is obtained in conjunction with related processes. A procedure is disclosed in U.S. Pat. No. 4,944,851 for the regeneration of a spent tin/lead stripping composition comprising an aqueous solution of an alkanesulfonic acid, metal alkanesulfonate salts and metal nitrate salts by electrolyzing the solution and thus removing certain metal salts at the cathode while regenerating other metal salts along with some acid at the anode. In this system, inorganic nitrate is an essential component of the solution since it is required to act upon the tin-lead layer to effect its removal from the substrate. The procedure described pertains only to the regeneration of stripping capacity in solutions which contain at a minimum both metal alkanesulfonate salts and metal nitrate salts. The objective of the process, as stated by the inventors, is specifically to restore the stripping effectiveness of two-component compositions. The process of the aforementioned U.S. Pat. No. 4,944,851 is not designed to generate sulfonic acid which may have general application in electrolytic and/or other processes as well as in the process from which the sulfonic acid was originally obtained.
U.S. Pat. No. 5,520,794 by Gernon discloses the use of an undivided cell electrowinning process for the recovery of methanesulfonic acid value from a solution of plumbous methanesulfonate. However, when an electrowinning process is carried out, as described by Gernon, in an undivided cell, then the resulting acid product has poor purity owing mostly to contamination by some residue of the metal(s) originally present.
The applications in which such poor purity MSA can be used are usually somewhat restricted.
Vork (Tijdschr. Oppervlaktetech. Corrosiebestrijd. 1995, 39(6), 242-4) discloses the use of an anion-exchange membrane divided electrowinning cell for the recovery of pure methanesulfonic acid from methanesulfonic acid based tin/lead plating solutions. The methanesulfonic acid recovered by Vork was sufficiently pure to be of value for general use, for instance, as an acid catalyst in a number of esterification reactions.
It would be useful to have a general process for obtaining alkanesulfonic acid value and/or pure alkanesulfonic acid from an aqueous solution containing one or more VIB, VIIB, VIII, IB, IIB and/or VA metal alkanesulfonates. Neither such a process nor the possibility for general acid recovery from metal alkanesulfonates are disclosed in the prior art, except for the distinct IVA metal salts tin and lead methanesulfonate.
An element's physical and chemical properties are related to the element's position in the periodic table and since tin and lead are in the same family of the Periodic Table (i.e., the IVA metals) they have certain similarities in physical and chemical properties which are not common to metals outside of group IVA.
Also, in electrowinning processes for the recovery of alkanesulfonic acid value or pure alkanesulfonic acid from aqueous solutions containing metal alkanesulfonates, the specific metal alkanesulfonate involved strongly influences the many operational parameters present (e.g., electrode material selection, membrane selection, membrane fouling prevention schemes, metal hydrolysis accommodation, etc.). Thus, a process designed for tin methanesulfonate and/or lead methanesulfonate does not simply extrapolate to the whole of the periodic table.
Therefore, though it has previously been shown that methanesulfonic acid can be recovered from tin methanesulfonate and lead methanesulfonate under certain conditions, it is not known generally that alkanesulfonic acid can be recovered from other electrodepositable metals (namely metals in groups VIB, VIIB, VIII, IB, IIB and VA).
SUMMARY OF THE INVENTION
This invention is a process for the generation of alkanesulfonic or aromatic sulfonic acids from their soluble salts of metals of Group VIB, VIIB, VIIIB, IB, IIB or VA of the periodic table comprising subjecting an inorganic nitrate-free solution of said salt to:
a) electrowinning in a cell employing a reactive cathode and an anode, electrogenerating, within an effective current density range, an alkanesulfonic or aromatic sulfonic acid from said salt at said anode and electrolytically producing a metal or metal compound from said salt adjacent to or on said cathode, and substantially removing any metal containing precipitate from said solution, wherein the cell is undivided when the soluble salts are of metals of Group VA of the periodic table; or
b) electrolysis in a cell employing a reactive cathode and an anode, electrogenerating an oxidized species at said anode with said oxidized species reacting further to produce a sulfonic acid and a metal containing precipitate, and substantially removing said metal precipitate from the solution, or
c) a chemical oxidizing agent in an amount sufficient to create an oxidized species which reacts further to produce a sulfonic acid along with a metal containing precipitate, and substantially removing said metal containing precipitate from said solution, or
d) any combination of a), b) and c).
In a preferred embodiment the present invention is directed to (a) the recovery of alkanesulfonic acid value from VIB, VIIB, VIII, IB, IIB and VA (i.e., Cr, Mo, W, Mn, Tc, Re, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag, Au, Zn, Cd, Hg, As, Sb, Bi) metal alkanesulfonates by electrowinning in an undivided cell, and (b) the recovery of pure alkanesulfonic acid from metal alkanesulfonates, defined as described above for a, by electrowinning in an anion-exchange membrane separated cell. The present invention describes how, in general, to obtain either alkanesulfonic acid value or pure alkanesulfonic acid from select metal alkanesulfonates, as defined above, which can be electrodeposited from an aqueous solution. The present invention also describes when a divided cell process versus an undivided cell process is truly necessary.
In the electrowinning reaction referred to above, the sulfonic acid is regenerated at the anode by electrochemical reaction while the metal cation of the salt is taken up at the cathode by electrodeposition of the metal and/or by the formation of some other type of metal containing precipitate (e.g., sludge) adjacent to the cathode. In the electrolysis reaction referred to above in b), sulfonic acid and metal oxide/hydroxide type compounds are formed at or near the anode by hydrolytic reactions of anodically produced higher oxidation states of the metal cation of the salt.
While the term “electrowinning” is normally intended to cover electrolytic processing of an electrolyte to form a pure metal on or near the reactive cathode of the system, as used herein, “electrowinning” also includes processes wherein the formation of insoluble metal oxide type species, a process sometimes referred to as “sludging”, occurs at or near the cathode. To efficiently run an electrowinning system which operates with a significant amount of sludging, a divided cell must be employed so as to prevent the intermixing of anodically generated acid with cathodically generated base.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides a method for the generation of one or more o
Gernon Michael D.
Martyak Nicholas M.
Nosowitz Martin
Smith Gary S.
ATOFINA Chemicals, Inc.
Marcus Stanley A.
Rudman Gilbert W.
Wong Edna
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