Catalyst system

Claim 1

A method for maintaining substantially constant low ignition temperature start-up combustion characteristics in a catalytically supported thermal combustion system operating essentially adiabatically at downstream temperatures above about 815° C., comprising effecting combustion by contacting a vaporous fuel and air mixture upstream and downstream in said combustion system with a catalyst system comprising: (a) a catalyst configuration consisting of at least a downstream honeycomb catalyst portion and an upstream honeycomb catalyst portion protected therefrom, each honeycomb portion comprising as support a porous unitary solid refractory skeletal structure having upstream and downstream faces and having a plurality of unobstructed gas flow channels extending therethrough; (b) means to secure said upstream and downstream portions substantially free of continuous thermal conduction paths through solid material between the upstream face of said downstream portion and the downstream face of said upstream portion to substantially minimize thermal conduction between said portions; and (c) means positioned with respect to said upstream and downstream portions to substantially reduce radiant heat transfer from said downstream portion to said protected upstream portion; said upstream portion being adapted and allowed to operate at relatively substantially lower temperatures than is said downstream portion by said means to minimize thermal conduction therebetween and by said means to reduce radiant heat transfer therebetween; said upstream portion being formulated to have a higher catalytic activity than does said downstream portion but to be thermally less stable if heated substantially above said relatively lower temperatures.

Claim 2

A method for maintaining substantially constant low ignition temperature start-up combustion characteristics in a catalytically supported thermal combustion system operating essentially adiabatically at downstream temperatures above about 815° C., comprising effecting combustion by contacting a vaporous fuel and air mixture upstream and downstream in said combustion system with a catalyst system comprising: (a) a catalyst configuration consisting of at least a downstream honeycomb catalyst portion and an upstream honeycomb catalyst portion protected therefrom, each honeycomb portion comprising as support a porous unitary solid refractory skeletal structure having upstream and downstream faces and having a plurality of unobstructed gas flow channels extending therethrough; (b) means to secure said upstream and downstream portions substantially free of continuous thermal conduction paths through solid material between the upstream face of said downstream portion and the downstream face of said upstream portion to substantially minimize thermal conduction between said portions; and (c) means positioned with respect to said upstream and downstream portions to substantially reduce radiant heat transfer from said downstream portion to said protected upstream portion; said upstream portion being adapted and allowed to operate at relatively substantially lower temperatures than is said downstream portion by said means to minimize thermal conduction therebetween and by said means to reduce radiant heat transfer therebetween; said upstream portion being formulated to have a higher catalytic activity than does said downstream portion but to be thermally less stable if heated substantially above said relatively lower temperatures.