T 0188/83 (Vinyl acetate) of 30.7.1984

Summary of Facts and Submissions

I. Patent application No. 79 105 213.7 filed on 17 December 1979 and published on 9 July 1980 (publication No. 0 012 968) claiming priority of the earlier application in the Federal Republic of Germany of 21 December 1978 was refused by a decision of the Examining Division of the European Patent Office of 24 June 1983. The decision was based on the four claims as filed on 14 January 1983, claims 1 and 3 of which read as follows:

"1. A method of producing vinyl acetate in the gaseous phase by reacting ethylene, acetic acid and molecular oxygen in the presence of supported catalysts containing a palladium compound, a cadmium compound and an alkali acetate, characterised in that the molar ratio of acetic acid to oxygen in the gas mixture used is between 2.2:1 and 3.5:1, the molar ratios 2.762:1, 2.68:1 and 2.34:1 being excepted.

3. A method of producing vinyl acetate in the gaseous phase by reacting ethylene, acetic acid and molecular oxygen in the presence of supported catalysts containing elemental palladium, elemental gold and an alkali acetate, characterised in that the molar ratio of acetic acid to oxygen in the gas mixture used is between 2:1 and 3.5:1, the molar ratios 3.30:1, 3.28:1, 3.19:1, 3.11:1, 2.98:1 and 2.762:1 being excepted."

II. The reason given for refusal was lack of inventive step. The object of the method according to the application was to design the conventional method for producing vinyl acetate so as to enable a relatively high and constant spacetime yield of vinyl acetate to be produced without the occurrence of secondary exothermal reactions leading to more rapid consumption, a decline in efficiency and damage to the catalyst. This problem must already be regarded as solved in principle and reference is made in this connection to US-A-3 759 839 (b), DE-C-2 315 037 (d), US-A-3 743 607 (e), GB-A-1 189 091 (f), US-A-3 775 342 (g) and DE-C-2 509 251 (j), the latter erroneously designated as (i). Although the processes described in these documents had been excluded from the object of the claims by disclaimers, those processes still claimed indisputably produced essentially the same results as those now excluded as conventional. The citations would have given a person skilled in the art the idea of varying the processes quoted in the examples in a range of molar ratios that was similar in the sense of lying within the range indicated and close to it. It was irrelevant that the "molar ratio of acetic acid to oxygen" was not referred to in the state of the art but could only be calculated from other process parameters. The question of whether the disclaimers guaranteed an adequate definition of novelty was left open.

III. The applicant lodged an appeal against this decision on 25 August 1983 and paid the relevant fee on 30 August 1983. The Grounds for Appeal given on 15 October 1983 were approximately as follows: The process claimed was inventive because the finding that observance of the molar ratio of acetic acid to oxygen as claimed was especially important in avoiding a decrease in efficiency was not only new but unexpected. In the processes according to the cited publications this molar ratio was said to be variable within wide limits and could be equal to, greater than or smaller than 2:1. The Examining Division had therefore failed to recognise the selective nature of the invention.

IV. The Board of Appeal considered the question of novelty of its own motion and came to the conclusion that the disclaimers of individual values contained in the claims were not sufficient to define the process claimed vis-à-vis the state of the art as resulting from (b), (d), (e), (f), (g), (j), and EPA-4 079 (k). The appellant then returned to the original claim which did not contain a disclaimer.

V. The Board drew attention in a further communication to the fact that the objection of lack of novelty continues to exist even for a claim without a disclaimer.

VI. All the same the appellant ultimately submitted such a claim, on the basis of which he asked that a patent be granted. This claim reads as follows: "A process for producing vinyl acetate in the gaseous phase by reacting ethylene, acetic acid and molecular oxygen in the presence of supported catalysts containing palladium which may, for example, contain a palladium compound such as palladium acetate, a cadmium compound such as cadmium acetate, an alkali acetate such as potassium acetate and, if appropriate, manganese acetate or elemental palladium, elemental gold and an alkali acetate such as potassium acetate, characterised in that the molar ratio of acetic acid to oxygen in the reacted gas mixture is greater than 2:1 and below 4:1, for example between 2.2:1 and 3.5:1." It was still maintained that the process so described was a selective invention. The latter was new because the lowering of catalyst activity during vinyl acetate synthesis had been described on various occasions, but it had not hitherto been possible to avoid it.

Reasons for the Decision

1. The appeal complies with the requirements of Articles 106 to 108 and Rule 64 EPC and is therefore admissible.

2. The present claim must be disallowed even on purely formal grounds because the upper limit for the required molar ratio of acetic acid to oxygen, namely less than 4:1, is not supported in the first disclosure (see page 2 of the specification and claims 1 and 2) - a point the Board of Appeal made on its own account (see communication of 4 May 1984). Article 123(2) EPC states that a patent application may not be amended in such a way that it contains subject-matter which extends beyond the content of the application as filed. In the present case such an extension is considered to have been made because the general range for the molar ratio referred to above, which was originally defined only in terms of a lower limit (above 2:1), has been arbitrarily limited by the insertion of the words "below 4:1". The limiting of a range may also be regarded as a non-allowable extension where a person skilled in the art would not have understood this from the first disclosure. The applicant answered this point by stating that a person skilled in the art would be aware that in industrial plants it was absolutely impossible to rule out 3% fluctuations in the amount of acetic acid in the reactor input gas and that having regard to this fluctuation the range now claimed was in practice equivalent to the preferred range of 2.2:1 to 3.5:1 as first disclosed. This argument is already undermined by the fact that the present claim covers not only industrial-scale production of vinyl acetate but also its production on a smaller scale where greater fluctuations in acetic acid are allowed for (see communication of 25 June 1984, 5.3(1)). In any case the insertion of an upper limit to the range, being arbitrary, is not permissible unless the size of the plant is specified at the same time. However, the Board does not consider it reasonable to reject the appeal on the grounds of failure to comply with formal requirements, because in appeal proceedings it is the question of novelty which is at the forefront.

3. The process as claimed relates to the production of vinyl acetate by reacting ethylene, acetic acid and molecular oxygen in the gaseous phase in the presence of supported catalysts containing palladium. The palladium is either in the form of a compound in combination with a cadmium compound and alkali acetate (catalyst a) or in elemental form in combination with elemental gold and alkali acetate (catalyst b). The applicant found that this kind of process did not always take its course without secondary exothermal reactions which in their turn lead to higher consumption, reduced efficiency and damage to the catalyst. The problem of the invention as claimed in the application was to obviate these disadvantages. The solution proposed was that the molar ratio of acetic acid to oxygen in the gaseous mixture used should be adjusted between a lower limit of 2:1 and an upper limit of 4:1.

4. However, processes for the production of vinyl acetate involving the same procedure and the same catalysts and using acetic acid in a molar ratio to oxygen within the range claimed are already known in the art. According to a variant of the process which utilises the "salt" catalyst a, acetic acid and oxygen are taken in the following molar ratios: 2.762:1 (see K, all examples), 2.68:1 (see B, examples 1-7) and 2.34:1 (see D, examples 1a-1i). According to the second variant with the "metal" catalyst b, the molar ratio of acetic acid to oxygen is 3.3:1 (see E, examples 4-11), 3.19:1 (see E, column 3, lines 25/26), 2.98:1 (see F, example 1), 3.11:1 (see G, examples 1-3), 3.28:1 (see G, example 5) and 2.762:1 (see J, example 5). Although the figures given for the ratios are not stated in this form in the various publications, they can be derived without difficulty from the information given concerning the quantities of the two reactants, a point which the appellant does not contest (see communication of 17 April 1984, middle of page four). All nine ratios referred to in connection with the synthesis of vinyl acetate are scattered within the range, adherence to which is stated in the application to be critical and essential to the invention. This has the effect of destroying the novelty of the range claimed and of the molar ratio to be observed between the reactants referred to. The process claimed is therefore identical in every detail with those of the state of the art described above, of which it thus forms a part, and is not patentable on grounds of lack of novelty (Article 52(1) and 54(1) EPC).

5. This statement applies not only to the individual ratio values which may usually be calculated from examples, since examples are in general only specific embodiments of a broader teaching and must therefore be considered in conjunction therewith and in the light of the general knowledge of the art. Although the citations referred to above do not define in numerical terms any general acetic acid: oxygen ratios to be preferred, it is part of the basic knowledge of a person skilled in the art that chemical processes such as the production of vinyl acetate by synthesis involving the reaction of ignitable gas mixtures must in practice be effected outside the known explosion limits (see also (k), page 9, lines 20-23, (e) column 3, lines 23/24 and (j) column 5, lines 12-15). According to the two citations (k) and (j), therefore, the concentration of oxygen in the gaseous mixture is kept low, for example below 8% by volume, relative to the gaseous mixture containing no acetic acid. It is also general knowledge in the art that the ignition limit of the gaseous mixture shifts in the direction of lower oxygen concentrations as pressure increases (see (d) column 1, lines 64-66). Since the conventional process is carried out at 1-20 atm (1 atm = 1.01325 bar), especially between 1 and 10 atm (see (e) column 3, line 29), and in particular 5-10 atm (see (d) page 2, lines 1-2) any individual values taken from the examples must also be viewed in this light. Consequently, the ratio of acetic acid to oxygen calculated in each case from the state of the art and given only by way of example extends, if read as intended, to those values which - having regard to the pressure range or at least the preferred pressure range - meet the above requirements for non-ignitable mixtures. Thus, the applicant's computation for (d) (see communication of 14 January 1983, page 2) shows that according to examples 1a to i and with a pressure of 9 atm the ratio of acetic acid to oxygen of 2.34:1 at low pressure, i.e. 5-8 atm, which would make the choice of a higher oxygen content of 8% appear advisable, shifts to the ratio 1.88:1. In other words the individual value 2.34:1 does not conform to the teaching of this citation with regard to the above ratio as reflected in the examples because it includes the range claimed at least from 2.34 down to the lower limit. Conversely, if in the context of the conventional teaching the pressure is increased from 9 to 10 atm, the ratio referred to rises beyond 2.34:1. The same applies of course to the other ratio values previously excluded from the application by the disclaimer, which are accordingly extended into ratio ranges. Moreover, the applicant himself provides another example of how a person skilled in the art understands the acetic acid to oxygen ratios contained in the examples in the above-mentioned citations not as individual values but in the sense of a narrower or wider range. According to the applicant, the person skilled in the art knows from experience that, when vinyl acetate is produced on an industrial scale using the conventional process, fluctuations of 3% in the acetic acid content of the initial gas mixture cannot be ruled out, and that in smaller plants these fluctuations are of an even higher order. If a fluctuation of 3% is taken into account, and on the basis of the applicant's computation from the example of a molar ratio of acetic acid to oxygen of 2.67:1, there results a ratio range of 2.59:1 to 2.75:1 (see communication of 25 June 1984, page 3, para. 1). In the light of this empirical knowledge, each of the specific individual values given for the ratio of acetic acid to oxygen contained in the citations will be understood by a person skilled in the art as being a range.

6. A chemical production process previously described with all its technical features is not rendered novel by the fact that attention is drawn to an advantage associated with the process but not hitherto acknowledged by the art and which occurs when the process is carried out without any change. From the point of view of patent law a chemical production process is clearly defined by a statement of the initial substances, the process parameters and the end products, and can be subsequently modified. The additional information contained in the application to the effect that when the conventional processes are used without any technical modification the catalyst activity is maintained may be of great value in practical terms; but at the same time, because of the lack of any suggestion as to additional technical means that might be employed, this information incorporates no new technical teaching. Nothing, in other words, is added to what is already known because the alleged invention consists solely in following the procedure already described.

7. For the same reason the appellant's argument that the process claimed involves a selection because it cannot with its advantages be derived directly from the state of the art (see communication of 14 April 1984, page 4, end of paragraph 2) must be discounted. Even in the case of inventions involving selection, the same prerequisites apply for patenting as for other inventions, namely first of all that they must be new and thus differ from the conventional art by virtue of specific technical features. This, as has been explained, was not true in the present case. The lack of novelty therefore means that no European patent can be granted for the subject-matter of the application.

ORDER

For these reasons, it is decided that:

The appeal is rejected.