Process for the manufacture of an aldehyde

Details Process for the manufacture of an aldehyde Process for the manufacture of an aldehyde

1984-08-15

1986-04-15

Niebling, John F.

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

204 59R, 204 78, C07C 47542

Patent

active

045829420

DESCRIPTION:

BRIEF SUMMARY
The invention is concerned with a process for the manufacture of p-tert.butylbenzaldehyde (TBB). This aldehyde is a known substance, especially as an intermediate.
The process comprises oxidizing p-tert.butyltoluene (TBT) with a Mn.sup.3+ salt, which salt is generated by electrochemical oxidation of a Mn.sup.2+ salt, and whereby the chemical oxidation and the electrochemical oxidation are carried out in separate reaction vessels.
The sulphate is preferably used as the manganese salt. However, the phosphate can also be used. This salt gives no problems at all with respect to electrochemical stability (i.e. cathodic as well as anodic), with respect to interference with organic materials and with respect to corrosion.
The electrochemical oxidation is conveniently carried out in moderately concentrated sulphuric acid, namely in 40% (5.3 molar) to 90% (16.6 molar), especially in 50% (7.1 molar) to 65% (10.3 molar), sulphuric acid.
The electrochemical oxidation is conveniently carried out at an elevated temperature, preferably in a temperature range of about 60.degree. C. to 110.degree. C., especially at 80.degree. C. to 100.degree. C. and particularly at about 85.degree. C.
The concentration of the manganese salt in the inorganic phase conveniently amounts of 1 to 5 mol/l, especially 3.0 to 4.0 mol/l and particularly about 3 mol/l.
The anode material used can be in principle any electrode material which is stable under the process conditions, namely for example:
Vitreous graphite, lead, lead alloys, noble metals such as platinum or metals which are passive towards anodic corrosion (e.g. zirconium and tantalum) and which are coated with a noble metal (e.g. with palladium or ruthenium).
Lead alloys, for example those with a content of silver (e.g. Chromin from Blasberg, GFR) are especially preferred. In the electrolytes there are found in this manner Ag ions which act as the catalyst, namely the lower valued metal ions of a transition metal-redox pair with an oxidation potential greater than Mn.sup.2+ /Mn.sup.3+. It has been found that the use of such lead alloys is especially economical, since the life of the electrodes is long (e.g. it can amount to 1 to 11/2 years).
As the cathode material there is likewise used vitreous graphite, lead, lead alloys, noble metals such as platinum, but especially also lead or lead alloys (e.g. Chromin).
The reaction can be carried out in an undivided cell or in a cell which is divided by a porous diaphragm consisting of usual inert materials. The reaction is preferably carried out in a cell without a diaphragm. Although in the latter case it is convenient to carry out the reaction in a protective gas atmosphere (e.g. under nitrogen) in order to protect against explosive gas formation (from anodically-formed oxygen and cathodically-produced hydrogen), the gases which result in the reaction during the electrolysis can also simply be rarefied by the addition of a protective gas (e.g. nitrogen); however, rarefaction with air also leads to the prevention of the danger of explosion.
For the electrochemical oxidation there can be used essentially any conventional, especially commercially available, type of cell. Thus, for example, there can be used
channel cells [flow cells] (in which the electrodes are arranged as a comb or as a package (stack) (in the form of plates, cylinders etc), these cells being preferred;
filter press cells (consisting of frames and plates);
trough (tank) cells (the stirring action required being realized by electrolyte circulation, by means of an inert gas or by means of rotating electrodes, etc.). described by D. Pletcher in Industrial Electrochemistry, Chapman & Hall (London, New York), (1982), 162.
As the cell material there can be used any inert material, but especially a synthetic polymeric material (e.g. polypropylene).
The current densities in the reaction in accordance with the invention conveniently lie at 100 to 600 mA/cm.sup.2, especially at 300 to 500 mA/cm.sup.2 (i.e. 3 to 5 kA/m.sup.2).
The cell potential adjusts itself as a function of the compo

REFERENCES:
patent: 4148696 (1979-04-01), Halter
patent: 4212710 (1980-07-01), Halter
patent: 4212711 (1980-07-01), Halter et al.
patent: 4277318 (1981-07-01), Matlock
patent: 4298438 (1981-11-01), Degner et al.
patent: 4387007 (1983-06-01), Seiler
patent: 4411746 (1983-10-01), Degner
Ramaswamy et al., J. Electrochem. Soc., Mar. 1963, pp. 202-204.
D. Pletcher, "Industrial Electrochemistry", p. 162, Chapman & Hall Ltd., London (1982).
Ch. Comninellis, et al., J. Electrochem. Soc. 129, No. 4, 749 (1982).

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