T 0363/19 (PURIFICATION OF PHENOL / BOREALIS) 14-06-2022

Main request (patent as granted) -

1. Claim 13 - novelty

1.1 Document (3)

According to the appellant, the subject-matter of claim 13 lacks novelty over the distillation apparatus disclosed in figure 19.9 on page 596 of document (3).

This distillation apparatus comprises a distillation column, a condenser connected to the distillation column and to a condensate drum. A second condenser is connected to the drum and comprises a line to recycle the condensate from this second condenser to the drum.

This second condenser does not comprise a second line to take off the condensate from the distillation apparatus.

However, claim 13 of the patent as granted requires that the second condenser (9) is provided with a line (14) arranged to recycle material from second condenser (9) to drum (10),

and a line (15) arranged to remove condensate from condenser (9).

This feature is not disclosed in document (3). Thus the subject-matter of claim 13 is novel over document (3).

According to the appellant, claim 13 defines the line (15) as a line for removing condensate from the condenser, but does not specify that said line (15) is to be arranged to remove condensate from the system. Accordingly, the line which removes condensate from the second condenser of the distillation apparatus disclosed in document (3) and recycles it to the drum fulfils both the requirement of lines (14) and (15) required by claim 13.

The board cannot concur with the appellant's interpretation of claim 13.

Claim 13 requires that the second condenser (9) is provided with a line (14) arranged to recycle material from second condenser (9) to drum (10). Therefore, the line (14) removes condensate from the condenser to recycle it to the drum.

Claim 13, however, also requires another line (15) to remove condensate from the condenser. Thus, claim 13 requires two lines (14) and (15). These lines do not have the same function. They cannot therefore form a single line. It is clear from the context of the patent in suit (see, for example, paragraph [0031]), that line (15) required by claim 13 is a line which takes the condensate out of the distillation apparatus.

Accordingly, the appellant's claim interpretation must be rejected, with the consequence that the subject-matter of claim 13 is novel over document (3), since the apparatus disclosed in figure 19.9 does not comprise a second line which removes condensate from the second condenser out of the distillation apparatus.

1.2 Document (4)

According to the appellant, the subject-matter of claim 13 lacks novelty over the distillation apparatus disclosed in the figure of document (4).

The distillation apparatus disclosed in document (4) comprises a distillation column and a condenser 27 connected to the distillation column via a scrubber 22. The condenser 27 is connected to a condensate drum 29 via line 28. Drum 29 is connected to a second condenser 43 via line 33. This second condenser is connected to a separation drum 35 via line 34.

The second condenser 43, however, is not provided with a line to recycle material from said condenser to drum 29, as required by claim 13.

According to the appellant, this line to recycle material from condenser 43 to drum 29 is provided by the route condenser 43 to drum 35 via line 34; drum 35 to scrubber 22 via lines 36, 31 and 23, 24 or 25; scrubber 22 to condenser 27 via line 26 and condenser 27 to drum 29 via line 28.

However, a line is simply a pipe or tube that allows a material to be transferred. It is a conduit that may possibly be fitted with means to control the material transfer, such as pumps, valves, etc. A line therefore does not include a device that changes the composition of the material, such as a scrubber or a condenser.

The condenser 43 of the distillation apparatus disclosed in document (4) is not provided with a line arranged to recycle material from the second condenser 43 to the drum 29, with the consequence that the subject-matter of claim 13 is novel over document (4).

2. Inventive step

2.1 Closest prior art

It is agreed that document (1) represents the closest prior art to the invention.

This document discloses a process for purifying crude phenol, which process comprises introducing crude phenol as a feed to a fractional distillation column (see figure 2, inlet 2) and separating the crude phenol into a base fraction (see figure 2, outlet 4), an intermediate fraction (outlet 3) and overhead vapours (outlet 5). The overhead vapours are fed to a first condenser (6) whereby the major portion of the vapours are condensed. The condensate is returned to the distillation column as reflux (inlet 8).

A portion of the overhead vapours withdrawn from the condenser (6) is fed via line (7) to the lower part of a distillation/stripping column (13), wherein water is injected via line 18. The overhead vapours are removed from the column and fed to a second condenser (15) via line (14). A portion of the second condensate is returned to the distillation/stripping column as reflux via line 16.

Document (1) does not disclose the presence of a condensate drum between the condenser 6 and the distillation column 1. It is not contested that the process of claim 1 differs from document (1) in that the separation of the overhead vapours into a portion of the vapours and a first condensate is effected by means of a condenser coupled to a condensate drum, and not only in a condenser.

Furthermore, the process of granted claim 1 requires that the first uncondensed fraction is conducted to a second condenser wherein a second condensed fraction is formed and that at least a portion of this second condensed fraction is recycled to the condensate drum.

In the process of document (1), a vapour portion (first uncondensed fraction) is conducted to a distillation/stripping column 13, where water is added. The overhead of the column 13 is sent to a second condenser 15, where a second condensed fraction is recycled to the distillation unit via the distillation/stripping column.

The appellant submitted that the distillation/striping column 13 of document (1) is a condenser for the purposes of the claimed process.

For the person skilled in the art, the meaning of a condenser is clear, it is an apparatus designed to transform a material from the gaseous state to the liquid state. A distillation column is a device for separating liquids using the differences in their boiling points. These two devices do not require the same equipment, in particular a condenser requires heat removal means, whereas a distillation column requires heating means. Even if a distillation column consists of a multitude of trays where vapour and liquid are in equilibrium, thus condensation effects take place, the person skilled in the art will not consider a distillation column as a condenser. The appellant's argument that the distillation column (13) disclosed in document (1) is a condenser must therefore be rejected. The process of claim 1 thus differs from that disclosed in document (1) also in that the first uncondensed fraction is conducted to a second condenser.

2.2 Technical problem

The respondent has pointed out several improvements achieved by the claimed process. However, the technical problem is at least that of the provision of an alternative process for purifying a phenolic mixture. As the board has come to the conclusion that the solution to the problem of providing an alternative process for purifying phenol is not obvious in the light of the state of the art, it is not necessary to examine whether the improvements put forward by the respondent are indeed achieved by the claimed process.

2.3 Solution

The proposed solution is the process of claim 1 characterised by the use of a drum which receives the overhead stream from the distillation column after it has passed through a first condenser and into which at least part of the second condensed fraction is recycled and by conducting the first uncondensed fraction formed in the drum to a second condenser.

2.4 Obviousness

It remains to be decided whether or not the proposed solution to the problem of providing an alternative process of purifying phenol is obvious in view of the cited prior art.

According to the appellant, the proposed solution is obvious, since it is common in the art to couple a drum to a condenser for many reasons. This is highlighted in document (2) which discloses a distillation where the overhead of the distillation column is condensed in a condenser coupled to a drum.

Document 2 discloses the distillation of a pyrolysate in which phenol and alpha-methylstyrene are recovered by condensing the overhead stream (see paragraph [0005]). The condensation of the overhead fraction is achieved by coupling a condenser (6) with a drum (7) (see figure).

First, it appears questionable whether the person skilled in the art would turn to document (2) in order to provide an alternative process for purifying phenol. In the process of document (1), phenol is recovered from the purification distillation column as an intermediate fraction (line 3). Document (2) does not disclose a process for purifying phenol, but a process for recovering a phenolic mixture comprising alpha-methylstyrene from a pyrolysate. The phenolic mixture is recovered from the overhead fraction. In the process of document (2), part of the condensed phenolic mixture is returned to the distillation column while the other part of the phenolic fraction is collected by line 12.

This equivalent line 12 in the purification process of document (1) is used to take away phenolic by-products, not to recover phenol. Therefore, the skilled person would not combine the teaching of document (1) with that of document (2).

Further, even if the person skilled in the art were to combine document (2) with document (1), they would still not arrive at the claimed solution, since in the process of document (2), as in document (1), the non-condensed fraction coming from the drum 7 is fed to a second distillation column 9 via line 8, and not to a second condenser.

The Board therefore comes to the conclusion that the subject-matter of claim 1 of the main request is not obvious in the light of the cited prior art.

For the same reason, the apparatus of claim 13 which is characterized by a second partial condenser (9) arranged in series with condenser (2) and a line (14) arranged to recycle material from the second condenser (9) to drum 10 is also not rendered obvious by the combination of document (1) with document (2).

2.5 Accordingly, the subject-matter of independent claims 1 and 13, and by the same token that of dependent claims 2 to 12, 14 and 15 involves an inventive step.