Inhibiting CO emissions during catalyst regeneration
Some examples herein provide a method of removing deposits from a catalyst. The method may include flowing oxygen-containing gas over a catalyst coated with deposits at oxygen deficient conditions. The method may include, while flowing the oxygen-containing gas at oxygen deficient conditions over the catalyst, heating the catalyst to a first temperature to begin combusting the deposits and generating effluent gas including carbon dioxide and substantially no carbon monoxide. The method may include, while continuing to flow the oxygen-containing gas over the catalyst, gradually increasing a temperature of the catalyst from the first temperature to a second temperature at a rate selected to continue combusting the deposits and generating effluent gas including carbon dioxide and substantially no carbon monoxide.
1 . A method of removing deposits from a catalyst, the method comprising:
flowing, over a catalyst coated with deposits, oxygen-containing gas at oxygen deficient conditions;
while flowing the oxygen-containing gas at oxygen deficient conditions over the catalyst, heating the catalyst to a first temperature to begin combusting the deposits and generating effluent gas comprising carbon dioxide and substantially no carbon monoxide; and
while continuing to flow the oxygen-containing gas over the catalyst, gradually increasing a temperature of the catalyst from the first temperature to a second temperature at a rate selected to continue combusting the deposits and generating effluent gas comprising carbon dioxide and substantially no carbon monoxide, wherein the deposits comprise organic byproducts of converting a renewable feedstock to an intermediate composition.
2 . The method of claim 1 , wherein the catalyst comprises a metal oxide on an oxide support.
3 . The method of claim 1 , wherein the first temperature is approximately an ignition temperature of the deposits.
4 . The method of claim 1 , wherein:
the deposits comprise at least one organic deposit and coke; and
the first temperature is selected based on an ignition temperature of the at least one organic deposit, the ignition temperature of the at least one organic deposit being lower than an ignition temperature of the coke.
5 . The method of claim 1 , wherein the first temperature is about 450-650° F. and the second temperature is about 800-1500° F.
6 . The method of claim 1 , wherein a temperature profile between the first temperature and the second temperature monotonically increases.
7 . The method of claim 1 , wherein a temperature profile between the first temperature and the second temperature is continuous.
8 . The method of claim 1 , wherein a temperature profile between the first temperature and the second temperature is stepped.
9 . The method of claim 1 , wherein the rate is about 10-100° F./hr.
10 . The method of claim 1 , further comprising using the catalyst to convert the renewable feedstock to the intermediate composition before heating the catalyst to the first temperature to begin combusting the deposits.
11 . The method of claim 10 , wherein converting the renewable feedstock to the intermediate composition and heating the catalyst to the first temperature to begin combusting the deposits are performed in the same reaction vessel.
12 . The method of claim 11 , wherein the reaction vessel is a fixed-bed reactor.
13 . The method of claim 1 , wherein the oxygen-containing gas comprises about 0.1-5 vol % oxygen in an inert gas.
14 . The method of claim 1 , wherein an oxygen content of the oxygen-containing gas is increased while combusting the deposits.
15 . The method of claim 14 , wherein the oxygen content of the oxygen-containing gas is about 0.1-1 vol % at a beginning of combusting the deposits, and is increased to about 2-5 vol % after the beginning of combusting the deposits.
16 . The method of claim 1 , wherein carbon monoxide forms less than about 2 mol % of the total CO x formed while combusting the deposits.
17 . A system for removing deposits from a catalyst, the system comprising:
a reaction vessel containing a catalyst coated with deposits;
an inlet to flow an oxygen-containing gas over the catalyst in the reaction vessel;
one or more processors; and
memory storing machine-readable instructions that, when executed by the one or more processors, cause the system to:
while the oxygen-containing gas flows over the catalyst, heat the catalyst to a first temperature to begin combusting the deposits and generating effluent gas comprising carbon dioxide and substantially no carbon monoxide; and
while the oxygen-containing gas continues to flow over the catalyst, gradually increase a temperature of the catalyst from the first temperature to a second temperature at a rate selected to continue combusting the deposits and generating effluent gas comprising carbon dioxide and substantially no carbon monoxide.
18 . The system of claim 17 , further comprising a heater configured to heat the catalyst to the first temperature and the second temperature.
19 . The system of claim 17 , wherein gradually increasing the temperature of the catalyst from the first temperature to the second temperature at the rate comprises adjusting an oxygen content of the oxygen-containing gas.