|Title of Invention||
PROCESS FOR THE PRODUCTION OF RUTHENIUM (III) ACETATE SOLUTION
|Abstract||The present invention relates to a solution of ruthenium acetate comprising concentration of ruthenium from 4 to 8 wt% and acetic acid concentration from 40 to 80 wt % wherein said solution is characterized in having low levels of impurities.|
|Full Text||The present invention relates to a solution of ruthenium acetate.
The present invention concerns improvements in precious metal compounds. More especially, it concerns improvements in ruthenium compounds and methods for their production!
Ruthenium (III) acetate is the term that will be used herein to describe [Ru30(OAc)6(H20)n(AcOH)3-n]OAc where n has a value from 0 to 3, and the product of its desolvation, that is [Ru30(OAc)6]OAc, and products consisting substantially of ruthenium (III) acetate, possibly in admixture with minor amounts of other ruthenium acetates, oxides and/or hydroxides. Ruthenium (III) acetate is a compound known per se and is available commercially, although it is not a bulk or commodity chemical. It may be used as a starting"material for other ruthenium compounds, and its use has been suggested as a catalyst or catalyst precursor. The generally, accepted processes for the production of ruthenium (III) acetate involve reacting RUCI3.XH2O with either acetic acid/acetic anhydride or sodium acetate in ethanol, but these routes suffer from rather poor yields and contamination of the product with other ruthenium species such as [Ru2(OAc)4Cl] and with chloride and/or sodium ions. An alternative would be to react ruthenium (VIII) oxide with a mixture of acetic acid and a reductant such as acetaldehyde or ethanol. This latter reaction is hazardous owing to the explosive nature of ruthenium (VIII) oxide, although it could be expected.to yield a high purity product. It is desirable to have alternative processes suited to the large scale, high yield preparation of ruthenium (III) acetate of high purity. The known processes tend to produce material contamination with impurities such as halide, which can contribute to plant and/or vessel corrosion, and undesired metallic impurities, which may contribute to a loss of selectivity in catalytic processes. Another undesirable impurity is sulfur, which is a well-known catalyst poison.
The present invention provides a process for the production of ruthenium
(III) acetate solution in high yield and which comprises reacting ruthenium (IV)
oxide with the stoichiometric amount of hydrazine reductant in the presence of
The process is desirably carried out in two steps, the first being reduction
of ruthenium (IV) to ruthenium (III) by the hydrazine reductant in the presence of
acetic acid, followed by heating, preferably at reflux, for an extended period, eg for
8-24 hours. The acetic acid reagent may be glacial acetic acid, but is preferably
aqueous acetic acid, prepared by diluting glacial acetic acid with a small proportion
of water, which readily permits the production of ruthenium (III) acetate solution
of the preferred acetic acid composition.
Recommended hydrazine proportions are from 95 to 115% of the
stoichiometric requirement. The stoichiometry of the reaction requires 1 mole of
hydrazine to 4 moles of ruthenium, since hydrazine acts as a 4 electron reductant.
The amount of hydrazine used should preferably be as close as possible to
stoichiometric, to avoid significant over- or under-reduction of the ruthenium (IV)
species. During the process, the hydrazine is converted to nitrogen gas, which
escapes. The hydrazine is preferably used as an aqueous solution, but may be used
as a neat liquid, or as a hydrazine salt in solid or solution form. The hydrazine
reductant may be a substituted hydrazine, for example methylhydrazine, in which
case the stoichiometry is altered. However, it is likely that this would generate
unwanted by products from the substituted hydrazine, for example methylamine,
which would contaminate the final product. For certain uses, such contamination
may be unimportant.
It is believed that the reduction reaction may be described by the following
The product may be desirably recovered as a solution by cooling the
reaction mixture and removing any unreacted ruthenium (IV) oxide by filtration or
centrifugation. It may be isolated as a solid by a variety of means obvious to those
skilled in the art such as solution concentration, spray drying, or precipitation of
the compound by treatment at low temperature or by addition of a suitable solvent.
The invention further provides ruthenium (III) acetate dissolved in aqueous
acetic acid and containing low levels of impurities such as nitrogen (no greater than
200 ppm), halide (no greater than 50 ppm). Preferably, the solution contains no
greater than 50 ppm-of sulfiir and no greater than 100 ppm of metallic impurities.
Most desirably, the acetic acid concentration is between 40 and 80 wt% and the
ruthenium concentration between 4 and 8 wt%.
The starting material, hydrated ruthenium (IV) oxide is itself a known
compound, but for the present invention is desirably prepared by the reduction of
sodium ruthenate (VI) using an alcohol. The sodium ruthenate (VI) is a material
known per se.
The present invention further extends to other ruthenium carboxylates
which may be prepared in analogous manner to the acetate.
The invention is further described by way of example only in the following
Hydrated ruthenium (IV) oxide (43.88 g) as prepared above was
transferred to a 250'ml beaker and mixed well with glacial acetic acid (42.3 g), and
transferred into a 250 ml round-bottomed flask equipped with a Teflon coated
stirrer bar. The suspension was washed in with a further portion of glacial acetic
acid (42.3 g) followed by water (9.0 g). The suspension was vigorously stirred
then hydrazine (4.37 g of a 15.26 wt% solution in water) added slowly through a
pipette over 10 minutes. The amount of hydrazine solution used was 110% of the
stoichiometric proportion based on the estimated ruthenium content of the reaction
mixture. There was a vigorous effervescence and a gradual temperature rise of
about 15°C. The flask was fitted for reflux with a Liebig condenser and gently
heated to reflux, which was continued for 21 hours, by which time the reaction
mixture had become a dark green solution. Stirring was stopped and the flask
allowed to cool and stand for 24 hours. The product was filtered through a 7 cm
diameter glass fibre paper, yielding a clear, dark green product solution (141.0 g)
containing 5.59 wt% of ruthenium as ruthenium (III). This corresponds to an
overall yield of 98.5%. The product solution contained less than 50 ppm of halide
and less than 100 ppm of nitrogen.
1. A solution of ruthenium acetate comprising concentration of ruthenium from 4 to 8 wt% and acetic acid concentration from 40 to 80 wt % wherein said solution is characterized in having low levels of impurities.
2. A solution as claimed in claim 1, wherein the said solution comprises no greater than 200 ppm nitrogen.
3. A solution as claimed in claim 1, wherein the said solution comprises no greater than 50ppm halide.
4. A solution as claimed in claim 1, wherein the said solution comprises no greater than 50 ppm sulphur and no greater than 100 ppm of metallic impurities.
|Indian Patent Application Number||1316/DEL/2005|
|PG Journal Number||40/2009|
|Date of Filing||24-May-2005|
|Name of Patentee||BP CHEMICALS LIMITED|
|Applicant Address||BRITANNIC HOUSE, 1 FINSBURY CIRCUS, LONDON EC2M 7BA, ENGLAND,|
|PCT International Classification Number||c07c51/41|
|PCT International Application Number||N/A|
|PCT International Filing date|