Appeal No. 1998-2624
Application No. 08/696,578
[I]t would have been obvious to one of ordinary skill
in the art to employ the solvent disclosed by Dunlop
to separate paraffins (including methane) from the
gaseous mixture of olefins and paraffins and hydrogen
in the Mehra et al demethanization absorber. This is
because (1) the Dunlop et al absorbent solution is not
expensive (2) it can separate paraffins (including
methane) from the mixture of olefins and paraffins and
especially, (3) since the Dunlop et al absorbent
solution can separate olefins from paraffins including
methane, the additional conventional downstream
separation steps *** required/needed in the Mehra et
al process such as separating ethylene (an olefin)
from ethane (a paraffin) and separating propylene
(olefin) from propane (a paraffin) can be eliminated
or reduced to a smaller scale. [Id. at p. 9.]
Initially, we note that the examiner has combined Mehra’s
discussion of the prior art with Mehra’s disclosure of the
hydrogen and ethylene recovery process. However, the basis for
mixing the two disclosures as if they related to exactly the
same process is not entirely clear to us. Nevertheless, we are
in substantial agreement with the appellant’s arguments that the
examiner’s basic position is not well founded. (Appeal brief,
pages 7 through 14; reply brief, pages 1-7.)
Mehra’s abstract describes a process for contacting an
olefins-containing feed gas stream, which has been freed of CO2
and sulfur compounds, compressed, cooled, and dried, with a
solvent in an intercooled and reboiled demethanizing absorber to
produce a rich solvent bottom stream containing ethylene and
heavier hydrocarbons and an absorber overhead stream. According
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