Welcome to 3.091 Lecture 23

November 5, 2004

diffusion in molten

ferrous alloys

helium ingress into various oxide glasses

helium ingress into various oxide glasses

same glass different gases

catalytic converters for automobiles

x

º H2O, CO2

º CO2

* NOx º N2, O2, CO2

* Rh for NOx

why unleaded gasoline?

* (C2H5)4

function: 3-way catalyst promoting conversion of HCs, CO, and NO

* hydrocarbons * CO

GM tried over 1500 catalyst formulations before settling on the present combination:

* Pt-Pd for hydrocarbons and CO

Pb (tetraethyl lead) burns to produce PbO * PbO is volatile and on the catalyst will decompose to Pb * Pb alloys with precious metals poisoning them