Cutting Methane Emissions with New Catalysts

Since global warming became a hot topic, methane (CH₄) gas emissions have been a point of concern on the backburners of carbon dioxide. Considering that methane's global warming potential is 72 times that of carbon dioxide over 20 years and 25 times over 100 years, it shouldn't be ignored. Two primary contributors to methane gas production in the atmosphere are cows and automobiles, raising the infamous question 'does a cow pollute more than a car?' For those concerned about that debate, here is some insightful reading on cow backpacks.

One of the ways methane emissions are curbed in cars (and gas turbines, another big methane producer) is through the use of catalysts to encourage combustion. In cars, these are found in catalytic converters, which facilitate the oxidation (burning) of methane along with many other nasties produced by the engine. The combustion reaction for methane is:

CH₄ + 2O₂ --> CO₂ + 2H₂O

(<-- The catalytic converter - an asset to the environment and a target for car thieves... Credit: Wired)

In traditional catalytic converters, though, it's hard to find catalysts that fit the bill for encouraging this reaction. Catalysts are designed to assist chemical reactions by making them happen more efficiently and effectively. Currently available catalysts for methane combustion are not 100% efficient however, allowing a lot of unburned fumes to leave with the exhaust. The difficulty is, methane combustion catalysts need to be both active enough to do their job effectively, and stable enough to withstand the harsh conditions surrounding the process - particularly in regards to temperature.

A new catalyst for methane, developed by a collaboration of catalysis and energy specialists, could potentially fix these problems. It achieves complete methane combustion at 400°C, the approximate exhaust temperature for normal cars. This is crucial, considering most other catalysts can only achieve 100% efficiency at temperatures above 600°C. The catalyst also resists breakdown from hotter temperatures up to 850°C, which can occur when more load is put on the engine (climbing hills and driving fast).

(Representation of the catalyst's core-shell structure on an aluminum oxide surface. Credit: University of Pennsylvania -->)

The new catalyst has yet to be tested under real-world conditions, which could be drastically different than the performance recorded in lab. Vehicle exhaust in particular, which contains catalyst-disabling components (like sulfurous compounds, oil-additives, and steam), could deter the effectiveness of the substance. However, this development is a big first step towards a real solution, and opens the doors for creating similar structures which may perform better.

References

Catalyst Could Zap Methane Emissions - CR4

Cheaper and Cleaner Catalyst for Burning Methane - Science Daily