T 2233/12 (Epoxidation catalyst/SHELL) 20-05-2015

Reasons for the Decision

Main request- Claims as allowed by the opposition division

Sufficiency of disclosure

1. The expression "highly selective epoxidation catalyst"

1.1 The appellant argued that this expression had no well-defined meaning. The claims, in contrast to the description, contained no quantitative definition of the selectivity. The "highly selective epoxidation catalyst" referred to in the claims was thus neither defined by its selectivity nor by its components (grounds of appeal, page 3, penultimate paragraph). The skilled person could not clearly distinguish embodiments falling under the scope of the claims from other embodiments, even if he took into account paragraph [0019] of the description (grounds of appeal, page 5, penultimate paragraph).

1.2 The respondent submitted that the claims contained features defining the "highly selective epoxidation catalyst" according to the invention in terms of its composition (reply of 13 May 2013, page 7, second and third paragraphs).

1.3 The board has no reason for adopting another understanding of the wording of claim 1. In its view an epoxidation catalyst with the compositional features according to claim 1, i.e. "comprising silver in a quantity of at most 0.15 g per m**(2) surface area of the support, an in addition to silver, a Group IA metal and one or more selectivity enhancing dopants selected from rhenium, molybdenum and tungsten" (emphasis added) is a "highly selective epoxidation catalyst" within the meaning of the patent at issue.

1.4 Consequently, absent any evidence to the contrary, the board is satisfied that the skilled person is able to identify highly selective epoxidation catalysts suitable to be improved in selectivity by the claimed method, to distinguish them from other epoxidation catalysts and to determine any selectivity improvement achieved.

2. The expression "catalyst temperature"

2.1 The appellant pointed out that the "catalyst temperature" referred to in the claims was defined as follows in paragraph [0026] of the patent in suit: "As used herein, the catalyst temperature or the temperature of the catalyst bed is deemed to be the weight average temperature of the catalyst particles" (emphasis added). Since no further details concerning the measuring and/or determination of the "weight average temperature of the catalyst particles" were given in the patent in suit, and since such a concept or definition was also not known from the prior art, the skilled person was not in a position to put the claimed invention into practice. The appellant however conceded that methods to determine the temperature(s) prevailing in a catalyst bed were known as such.

2.2 The respondent held that the terms "catalyst temperature", "temperature of the catalyst bed" and "weight average temperature of the catalyst particles" had to be considered as interchangeable. The "catalyst temperature" could easily be determined, e.g. by using a number of thermocouples and by calculating the average temperature based on the mass of respective volume segments of the catalyst bed.

2.3 Taken literally, and absent any further detailed indications, the definition "weight average temperature of the catalyst particles" (emphasis added) given in the description (paragraph [0026]) indeed gives rise to questions regarding the meaning of the term "catalyst temperature" comprised in the claims.

2.4 The board is, however, convinced that the person skilled in the art of industrial catalysts and catalytic processes would exclude interpretations attributing some importance to the temperature differences between, or even within, individual particles. At the oral proceedings the appellant also conceded that the determination of the temperature of (individual) particles would not make sense in the context of the claimed invention.

2.4.1 More particularly, absent any proof to the contrary, the board is convinced that the skilled person taking into account the whole content of the patent in suit would thus, instead, consider the terms "catalyst" "catalyst bed" and "catalyst particles" to relate in every case to the total amount of catalyst involved. Whenever appropriate, the skilled person can, without undue burden, calculate a weight average temperature from temperature values measured in a conventional manner (e.g. by means of thermocouples) at different locations across the entire volume of the catalyst bed, said measured temperature being, respectively, representative for a certain volume (and hence weight) fraction of the entire amount of catalyst present.

2.4.2 At the oral proceedings, the appellant emphasised that the "catalyst temperature" of 250 °C represented a borderline between the first and the second phase of the method claimed. It therefore considered it to be of utmost importance to have a precise definition of said "catalyst temperature". Otherwise, the skilled person, operating close to the temperature of 250 °C would not know whether or not he was carrying out the method according to the invention.

2.4.3 For the board, this objection is, however, rather related to the clarity of a feature that was already present in claims 1 and 8 as granted and is thus not objectionable under Article 84 EPC (see G 3/14 of 24 March 2015, Order). Moreover, besides being convinced that the skilled person is able to determine the "catalyst temperature" within the meaning of claims 1 and 8 at issue with sufficient precision, the board finds that by keeping an adequate distance from this critical temperature in both phases of the claimed method, the skilled person can be sure not to be deprived of the promise of the invention. Even accepting arguendo that there is some ambiguity implied by the feature in question, such ambiguity does not permeate the whole ambit of claims 1 and 8. Hence, for the board, the insufficiency objection based on this argument in not convincing either.

3. The expression "surface area of the support"

3.1 At the oral proceedings, the appellant did not pursue the objection raised in writing (letter of 30 December 2014, point 2) against this feature comprised in claims 1 and 8.

3.2 As was pointed out by the respondent it its reply to said letter, it is indicated in paragraph [0013] of the patent in suit that the surface area of the carrier is deemed to be measured by the B.E.T. method. It was not disputed that this method is well-known.

3.3 The board is thus convinced that the skilled person is in a position to identify, without undue burden, catalysts meeting the criterion "comprising silver in a quantity of at most 0.15 g per m**(2) surface area of the support" (emphasis added).

4. Based on the above considerations the board concludes that the patent discloses the invention in a manner sufficiently clear and complete to be carried out by the person skilled in the art without undue burden (Articles 100(b)/83 EPC).

Clarity objection

5. In the course of the opposition procedure, the wording of claims 1 and 8 was, respectively, amended as follows: "... contacting a catalyst,[deleted: or a precursor of the catalyst comprising the silver in cationic form] ... ".

5.1 The appellant argued that due to deletion of the alternative directed to the "precursor", the resulting amended claims at issue lacked clarity. Since the claims did not contain indications regarding the amount of silver that had to be present in reduced form, it would not be clear what should be considered as a "catalyst", rather than as a precursor.

5.2 For the board, the skilled person understands that in the context of the patent in suit, a given material qualifies as silver "catalyst" for epoxidation when it contains a significant and catalytically effective amount of reduced, i.e. metallic silver, whereas a "precursor" will comprise silver essentially in ionic, unreduced form. This understanding is in line with the description of the patent (see e.g. paragraph [0025]): "By precursor of the catalyst is meant the supported composition which comprises the silver in unreduced, i.e. cationic form, and which further comprises the components necessary for obtaining after reduction the intended highly selective catalyst." (emphasis added).

5.3 In the board's judgement, the term "catalyst" as appearing in claims 1 and 8 is sufficiently clear. Thus, the claims as amended are not objectionable under Article 84 EPC for lack of clarity.

Novelty

6. Document P10

6.1 P10 discloses epoxidation catalysts (page 1, paragraph 1) containing silver and an alkali metal as promoter.

6.1.1 Optionally, it may contain other promoters selected from, inter alia, rhenium and rhenium with Mo or W as co-promoters (page 12, lines 12 to 20). The catalysts generally comprise silver in a concentration of 1 to 40 % by weight of the total catalyst (page 12, lines 22 to 28), on a carrier with a surface area between 0.15 to 3.0 m**(2)/g (page 11, lines 19 to 23). According to the appellant, the calculated silver loading may thus range between 0,0034 and 2,86 g/m**(2) support.

6.1.2 As regards the preparation of the catalysts, P10 describes heating the impregnated carriers "to a temperature between about 50 and 600 °C ... to evaporate the liquid an produce metallic silver" (page 16, lines 5 to 9) within "0.5 to 8 hours" (page 16, line 32).

6.1.3 The catalysts are put to use in an epoxidation process comprising feeding ethylene and oxygen to a catalyst at a temperature ranging from 180 to 325 °C (page 19, table I).

6.2 The appellant also pointed to another passage of P10 (on page 20, last paragraph), describing an optional heat treatment of the catalyst at about 350 °C in an oxygen-containing atmosphere for about 4 hours.

6.3 Finally, the appellant invoked the combination of catalyst A of P10 with the passage on page 20 of P10.

6.4 For the board, even when read in combination, the various elements of information contained in P10 invoked by the appellant do not amount to a direct and unambiguous disclosure of a method with all the features of claim 1 at issue for the following reasons.

6.4.1 In the list of components on page 12, lines 13 to 28 for preparing the catalyst, rhenium is only an optional component. Moreover, the range calculated by the appellant as regards the silver loading only overlaps with the one specified in claim 1.

6.4.2 Even considering, arguendo, that the final phase of the curing step described on page 16, carried out at a temperature above 250 °C, already is a catalyst treatment (and no longer a treatment of the precursor), a duration of such phase of at least 0.5 hours is not expressly disclosed.

6.4.3 Catalyst A of P10 (page 26, last paragraph; page 29, first paragraph; page 30, table 2, first data row), comprises silver, lithium and rhenium. It has a calculated silver loading of 0,154 g Ag/m**(2) support (to be compared to the value of "0.15" in claim 1 at issue). The board observes that the preparation of catalyst A comprises curing the impregnated carrier in an air stream "at 240-270°C for 3-6 minutes", but that after that "the cured catalyst" was "ready for testing" (page 29, lines 11 to 15).

Catalyst A was thus not subjected to the merely optional treatment described on page 20 before being used in an epoxidation process under the general conditions indicated in Table I on page 19 of P10, e.g. at a catalyst temperature under 250 °C.

Furthermore, the board observes that subsequently to the optional calcining step at 350 °C for about 4 hours, the temperature is not reduced to less than 250 °C, but the catalyst is subjected to an "activation treatment" at 300 to 350 °C in a hydrogen containing atmosphere for more than 1 hour before being "ready for use".

6.4.4 In the board's judgement, the skilled person cannot, without the benefit of hindsight, derive from these passages the combination of features according to claim 1. Such a combination would result only from several non-suggested choices to be made within the more general disclosure of P10.

7. Document P13

7.1 Example 2 of P13 describes the preparation and use, in an epoxidation reaction, of a catalyst comprising Ag, potassium and rhenium as promotors, and calcium carbonate as carrier. Example 2 does not mention a specific silver loading value, let alone a value falling within the range specified in claim 1 at issue. Indeed, the specific surface area (in g/m**(2)) of the calcium carbonate carrier use is not indicated.

7.1.1 The appellant pointed to general indications in P13 (paragraph bridging columns 3 and 4; paragraph bridging columns 5 and 6) concerning the surface area of the support (0.6 to 100 m**(2)/g) and the silver concentration of the finished catalyst (2 to 70% by weight), deriving therefrom silver load ranges from 0,0034 to 2.86 g Ag/m**(2) support, preferably 0.07 to 1 g Ag/m**(2) support.

7.1.2 However, the fact that these ranges overlap with the range of "at most 0.15 g per m**(2)" does not establish that a support meeting this latter criterion was actually used according to example 2 of P13.

7.2 Moreover, the preparation of said catalyst includes a calcination step which is briefly described in example 1 of P13 (to which example 2 refers back in this respect) as follows: "...then calcine at 300°C for three hours to yield the calcium carbonate-supported catalyst".

In a more general passage of P13 (column 4, lines 44 to 51) invoked by the appellant it is merely stated: "the slurry is then dried and calcined by placing the mixture in an oven or furnace at about 100 to about 120 °C for 0.5 to 6 hours and then heating the mixture at a temperature of from about 250 °C to about 600 °C for another 1 to 6 hours. This procedure accomplishes drying of the alkaline earth metal compound/silver mixture, removes volatile components and reduces the silver present to its elemental form."

7.2.1 No further details are given as regards the gas in contact with the material being treated during said calcination step. However, the use of an inert gas atmosphere during the reducing calcination step is not unusual in the field of silver epoxidation catalysts as can be gathered from the cited prior art (see for instance P7 (WO 96/16734 A1), page 2, line 21 to page 3, line 2; P3, paragraph bridging columns 11 and 12).

7.2.2 Hence, for the board, any views on the presence or absence of oxygen during the heating step are mere assumptions finding no clear and unambiguous basis in D13.

7.3 Thus, based on the above considerations, the board concludes that P13 does not directly and unambiguously disclose a method comprising treating a catalyst as defined in claim 1 at issue, i.e. with a silver loading of "at most 0.15 g/m**(2)" by "contacting the catalyst with a feed comprising oxygen".

8. The subject-matter of claim 1 is thus novel (Article 52(1) and 54 EPC) over the prior art invoked by the appellant.

The epoxidation process of independent claim 8, and the production process of independent claim 11 both include the novel selectivity improving method of claim 1. Consequently, their subject-matters, as well as the subject-matter of the dependent claims 2 to 7, 9 and 10, are also novel.

Inventive step

9. The invention

The invention relates to a method for improving the selectivity of a "supported highly selective epoxidation catalyst comprising silver ... a Group IA metal, and one or more selectivity enhancing dopants selected from rhenium, molybdenum, and tungsten" and to processes for the epoxidation of an olefin and for producing a 1,2-diol, 1,2-diol-ether or an alkanolamine (claims 1, 8 and 11; paragraphs [0001], [0006] and [0007]) which include said method.

10. Closest prior art

The board accepts that P13 can be considered as the most appropriate starting point for the assessment of inventive step according to the problem-solution approach as submitted by the appellant.

More particularly, this document relates also to supported highly selective catalysts containing alia silver, potassium and rhenium, to be used in the epoxidation of propylene (e.g. see example 2; points 7 et seq., supra).

11. Technical problem

In the light of the closest prior art disclosed in P13, the technical problem is, for the board, to be seen in providing a method for improving the selectivity of supported highly selective epoxidation catalysts of the Ag/alkali metal/Rh or Mo or W - type.

12. Solution

As a solution to the above problem, the patent as amended proposes the method according to claim 1 at issue, which is characterised in particular in that the highly selective catalyst comprises

"silver in an amount of at most 0.15 g/m**(2) surface area of the support"

and is subjected to a heat treatment comprising

"contacting the catalyst with a feed comprising oxygen at a catalyst temperature above 250 °C for a duration of at least 0.5 hours and up to 150 hours, and subsequently decreasing the catalyst temperature to a value of at most 250 °C".

13. Success of the solution

13.1 As convincingly demonstrated by the examples of the patent in suit (see Table I), a more pronounced selectivity is indeed obtained when subjecting a highly selective epoxidation catalyst as defined in claim 1 to such a heat treatment: Whereas under nitrogen gas (comparative example 1) the selectivity achieved at a given reaction temperature of 222/224°C was only increased from 82.0 to 84.4 %-mole after of 24h at 260°C, it was increased from 82.0/82.1/83.0 to 88.6/89.3/89.4 %-mole in a gas mixture comprising, besides nitrogen as the main component, 9.4/9.4/7.0 %v oxygen (examples 2 to 4).

13.2 This was not disputed by the appellant. Hence, the board accepts that the technical problem posed is effectively solved by the claimed process and, in the absence of evidence to the contrary, that even small concentrations of oxygen will, to some degree, result in a selectivity increase.

14. Non-obviousness of the solution

14.1 It remains to be decided whether the claimed subject-matter was obvious to a skilled person having regard to the state of the art.

14.2 The appellant argued that starting from the method described in example 2 of P13, implementing those two features which were not disclosed by this example, i.e. a silver loading of "at most 0.15 g per m**(2) surface area of the support" and "contacting the catalyst with a feed comprising oxygen" was an obvious thing to do for the skilled person.

14.2.1 It was common ground that the use of high surface supports described in P13 (see column 3, last paragraph) may, in combination with low relative amounts of silver per weight of the support (column 5, last line: "2 to 70 % by weight") lead to silver loadings (in g Ag/m**(2) support) falling within the range claimed according to claim 1.

For the board said high surface area supports are presented as one alternative which is not presented as preferred compared to supports having lower surface areas. The authors of P13 merely considered the fact that they were "also effective" as "surprising"

(P13: sentence bridging columns 3 and 4).

14.2.2 However, contacting a catalyst as defined in claim 1, i.e. having a relatively low silver loading, with a feed comprising oxygen, in order solve the technical problem posed, i.e. to provide a catalyst with a particularly pronounced selectivity, is not, in the board's judgement, suggested by P13, when read without the benefit of hindsight.

14.2.3 In the board's judgement, it was thus not obvious to the skilled person unaware of the present invention, to modify the process described in example 2 of P13 such as to arrive at a method falling within the ambit of claim 1 at issue.

15. Further inventive step objections

15.1 At the oral proceedings, the parties also debated the issue of inventive step in the light of a combination of documents P3, taken as the closest prior art, with P1.

For the board, such combination does not lead the skilled person to a method as claimed in an obvious manner for the following reasons.

15.1.1 As pointed out by the respondent, P1, although disclosing (column 6, lines 48 to 59) the "activation" of freshly prepared "catalyst intermediates" comprising a final step of heating them in the presence of oxygen to a temperature of up to 300°C (but preferably only up to 240 °C), is not concerned with silver/alkali metal/rhenium catalysts, and proposes to improve the selectivity of silver catalysts comprising alkali and/or earth alkali metal promoters by including nitrate ions in a lactic acid impregnation solution (column 2, lines 21 to 26, lines 61 to 67).

15.2 Hence, the skilled person seeking to improve the selectivity of Ag/alkali metal/Rh catalyst as disclosed in P3 is not, in the board's judgement, induced by P1 to apply certain measures (activation step) disclosed in P1 to a catalyst according to P3 which must, moreover, have a relatively low a silver loading of at most 0.15 g/m**(2) according to claim 1 at issue, although this is not a preferred option according to P3.

15.3 As regards the further inventive step objections that the appellant raised in writing but did not pursue at the oral proceedings, the board is satisfied that they do not establish that a method with all the features was obvious to the skilled person.

16. In the board's judgement, the subject-matter of claim 1 at issue thus involves an inventive step (Articles 52(1) and 56 EPC).

The epoxidation process of independent claim 8 and the the production process of independent claim 11 both include the inventive selectivity improving method of claim 1. Consequently, their subject-matters, as well as the subject-matter of the dependent claims 2 to 7, 9 and 10, also involve an inventive step.