T 1394/19 (Hydrogen peroxide solution/SOLVAY) 28-06-2022

Main request

The claims of the main request are those of the patent as granted.

1. Novelty

1.1 It has not been disputed that Example 2 of D1 discloses all the features of claims 1 and 2 other than an apparent pH in the claimed range.

Indeed, this example discloses the manufacture of propylene oxide by reaction between propylene and hydrogen peroxide using an aqueous hydrogen peroxide solution.

It has also not been contested that this example discloses pH values decreasing from about 6 to about 3.4 (see Figure 2).

What has been contested, however, is the nature of these pH values.

1.2 In the respondent's view, the pH values of Example 2 of D1 were conventional ones, i.e. pH values that (only) reflected the H**(+) activity (see entry for pH in F1 or curve 2 in Figure 2 of F5).

Conversion of these conventional pH values resulted in apparent pH values that overlapped with the range of claim 1 of the main request. The subject-matter of claim 1 was therefore not novel.

1.3 By contrast, the appellant considers that the pH values of Example 2 of D1 are apparent pH values as determined from the potential measured by a glass electrode. This potential, however, not only depended on the H**(+) activity but also on the nature of the solvent (see for example D3, paragraph [0015], or curve 1 of Figure 2 of F5), which in D1 was an aqueous 50% H2O2 solution instead of pure water. For this reason, the pH values of Example 2 of D1 were above the range of claim 1.

1.4 The board notes that it is a prerequisite for the acceptance of lack of novelty that the claimed subject-matter is "directly and unambiguously derivable from the prior art". In other words, it has to be "beyond doubt - not merely probable - that the claimed subject-matter was directly and unambiguously disclosed in a patent document" (Case Law of the Boards of Appeal, 2019, 9th edition ["Case Law"], I.C.4.1).

Another principle is that terms used in patent documents should usually be given their normal meaning in the relevant art, unless they have been given a special meaning in the case at issue (also Case Law, I.C.4.1).

1.5 While at first glance the terminology in D1 seems to refer to the conventional pH value (following the IUPAC recommendation as mentioned in F1 for example), doubts remain that the pH values of Example 2 of D1 may rather be apparent ones (which are then outside the range of claim 1 of the patent in suit).

- Documents do not always employ precise terminology in this regard. Thus paragraph [0027] of D3 states that a pH of 2.8 is measured with a glass electrode ("pH-Wert von 2.8 gemessen"). The absence of the qualifying term "apparent" would suggest that the conventional pH is meant. However, the last sentence in this paragraph makes it clear that the measured pH is, rather, the apparent pH. Indeed, a correction is necessary to obtain the conventional pH ("tatsächlicher pH-Wert von 4.6"). Likewise, claim 1 of D3 refers to a pH between 4 and 9.5, again without the qualifying term "apparent", but the fact that Examples 1 and 7 are comparative ones and have pH values outside the claimed range makes it clear that claim 1 of D3 specifies the apparent pH.

- A glass electrode is used in D1 (column 14, line 30). This seems to confirm that the potential measured also accounts for the nature of the solvent and not only for the H**(+) activity (D3, paragraph [0015]). Yet D1 is entirely silent on how the measured potential is converted into a pH value. In particular, D1 neither mentions any calibration nor does it indicate any correction to account for the fact that the aqueous solution of Example 2 of D1 is not pure water but contains 50% H2O2.

- According to column 14, lines 23 to 24, the original 50% H2O2 solution in Example 2 of D1 has a pH value of 2; according to lines 24 to 29, the other 50% H2O2 solution having a pH value of 6 was generated from this commercial pH 2 solution by means of an additional treatment with a basic exchange resin ("durch Behandlung der kommerziellen Ware mit einem basischen Ionentauscher").

Yet several documents on file, namely D3, D5 or F5, indicate that a pH value of 2 is closer to the apparent pH value of a 50% H2O2 solution than to the conventional pH value:

| |wt.% H2O2|pH conventional|pHapparent |

D3|[0027] |50.7|4.6 |2.8 |

D5|column 5, lines 8 to 12|50 | |2.7 |

F5|Fig. 2 |49.6|between 4 and 5|between 2 and 3|

The respondent argued that the solution with a pH of 2 could be the result of an acid treatment. While such a treatment cannot be entirely excluded, it is not mentioned in D1 (in contrast to the treatment with a basic ion exchange resin to obtain the solution with a pH of 6, column 14, lines 24 to 29).

Consequently, it seems at least possible that the pH values given in Example 2 of D1 are apparent ones. If this were the case the pH values would be outside the range of claim 1: while claim 1 requires an apparent pH between 1.57 and 1.87 for a 50% H2O2 solution, the pH in Example 2 of D1 is between about 6 and about 3.4 (Figure 2).

Hence D1 does not disclose the subject-matter of claims 1 and 2 in a direct and unambiguous manner. The subject-matter of these claims is thus novel over D1 (Article 54(1) and (2) EPC).

2. Inventive step

For the reasons set out below, the subject-matter of the claims of the main request involves an inventive step within the meaning of Article 56 EPC.

2.1 The invention relates to the use of an aqueous hydrogen peroxide solution for producing propylene oxide or epichlorohydrine and to a process for the manufacture of propylene oxide or epichlorohydrine.

2.2 The parties concur that Example 2 of D1 is the closest prior art.

Since this example also relates to the manufacture of propylene oxide from propylene and hydrogen peroxide using an aqueous hydrogen peroxide solution, it is indeed an appropriate starting point for assessing inventive step.

2.3 According to the patent in suit, the problem to be solved is to provide a use of an aqueous H2O2 solution and a process for the manufacture of propylene oxide or epichlorohydrine yielding improved selectivity towards oxiranes such as propylene oxide without impairing the hydrogen peroxide conversion rate (paragraph [0005]).

2.4 It is proposed to solve this problem by means of the use of claim 1 and by the process for manufacture of claim 2, characterised in that the apparent pH of the aqueous H2O2 solution is in the claimed range.

2.5 Experiments D6, provided by the appellant with its reply to the notice of opposition, confirm that the use of an aqueous H2O2 solution having an apparent pH in the claimed range yields a higher selectivity and a higher conversion rate:

Experiment "No. 1" (Table 1) has an apparent pH of 2, which is within the claimed range of between 1.9 and 2.2 in the case of a 41.2 wt.% H2O2 solution, and this experiment does indeed have the highest selectivity towards propylene oxide and also the highest conversion when compared to solutions with:

- a lower apparent pH ("No. 2"), and

- a higher apparent pH ("No. 3").

The respondent argued that the presence of the Na2HPO4·2H2O buffer in the experiments of D6 masked the influence of the apparent pH.

This argument is however not convincing, since identical amounts of buffer are used in examples Nos. 1 to 3 of D6. More importantly, the respondent has provided only arguments and no experimental evidence for its allegations.

There is hence no evidence on file showing that the problem was not successfully solved.

2.6 The respondent argued that the skilled person would use an aqueous H2O2 solution with a conventional pH of between about 6 and about 3.4 when starting from Example 2 of D1, and this would thus fall within the scope of claim 1.

However, this line of argument is an ex post facto analysis since there is no indication in the available prior art that an apparent pH of the H2O2 solution in the claimed range solves the technical problem posed.

The subject-matter of claims 1 and 2 therefore involves an inventive step within the meaning of Article 56 EPC.

2.7 For the same reasons, the subject-matter of the dependent claims also involves an inventive step within the meaning of Article 56 EPC.