Federal Circuit Confirms Propriety of Functional Limitations in Exhaust Catalyst Patent

BASF sued Johnson Matthey for patent infringement of its SCR catalyst for treating NOx emissions. The invention relates to a special layering of a full length SCR catalyst layer with an undercoat layer at the end of the catalyst. Ammonia, which can be injected upstream of the catalyst reacts with and converts NOx via the SCR catalyst, and the undercoat converts unreacted ammonia and thus reduces ammonia slip. Claim 1 requires:

A catalyst system for treating an exhaust gas stream containing NOx, the system comprising:
at least one monolithic catalyst substrate having an inlet end and an outlet end; an undercoat washcoat layer coated on one the outlet end of the monolithic substrate and which covers less than 100% of the total length of the monolithic substrate, and containing a material composition A effective for catalyzing NH3 oxidation; an overcoat washcoat layer coated over a total length of the monolithic substrate from the inlet end to the outlet end sufficient to overlay the undercoat washcoat layer, and containing a material composition B effective to catalyze selective catalytic reduction (SCR) of NOx; and wherein material composition A and material composition B are maintained as physically separate catalytic compositions.

Johnson Matthey argued that the claims were indefinite because of the functional limitations relating to including a material composition "effective for catalyzing NH3 oxidation" and "effective to catalyst selective catalyst reduction (SCR) of NOx." Specifically, Johnson Matthey argued that one skilled in the art does not know how to determine whether a material is "effective" without knowing how much reduction (e.g., percent conversion) is required to be effective.

The Federal Circuit shut down this argument straight away. The court first confirmed that the Supreme Court's Nautilus decision requires only reasonable certainty, not mathematical precision and thus there is no exclusion of functional language under Nautilus. Rather, what is needed, according to this decision, is a context-specific inquiry into whether particular functional language actually provides the required reasonable certainty.

Next the court addressed the supposed unanswered questions left open the claim. Specifically, the district court had questioned what minimum level of function qualified as effective. However, because the claims did not recite any minimum level this question was not relevant because an inventor does not have to claim every detail and the relevant question is merely whether a person skilled in the art would need to be given a the minimum level to understand, with reasonable certainty, whether a composition is "effective to catalyze" the SCR of NOx or ammonia. 

This district court's reasoning is similar to many examiner rejections at present from the USPTO regarding indefiniteness of functional limitations. Examiner often ask questions regarding features not specified by the claims in an attempt to support an indefiniteness rejection. Such question often miss the point as the purpose of the functional claim element is that there could be various structures that achieve the desired function and the claim is not intended to be limited to any particular one. As the Federal Circuit explains in this case:

The intrinsic evidence in this case makes clear that the asserted advance over the prior art is in the partly dual-layer arrangement to create a two-phase operation for performing the identified conversion processes, not in the choices of materials to perform each of the required catalytic processes. It is in this context that the question of the certainty or uncertainty experienced by a relevant skilled artisan in understanding the claims, read in light of the specification, is presented. And it is in this context that the relevant skilled artisan would be informed by the specification’s numerous examples of qualifying compositions A and B, disclosure of the stoichiometric reactions, and equating of the “composition . . . effective to catalyze” phrases with familiar terms such as “SCR catalyst” and “AMOx catalyst.”

Here, the patent specification made clear that the structural layering of the catalyst that was an important aspect of the invention, and thus confirmed that any known SCR and ammonia catalyst can be used as long as they play their claimed role as laid out in claim 1. The specification gave example material compositions, defined the relevant chemical reactions, and give figures and tables that explained how the novel arrangement resulted in improved percent conversion. 

So, the next time an Examiner rejects functional claim limitations by asking questions about features not specified in the claims, consider pointing out the Federal Circuit's reasoning in this case as well as support in the specification that would allow one skilled in the art to be reasonably certain as to the scope of coverage.