This invention relates to the use of a supplemental promoter in conjunction with a noble-metal-containing catalyst comprising a carbon support in catalyzing liquid phase oxidation reactions. In a particularly preferred embodiment, a supplemental promoter (most preferably bismuth or tellurium) is used in conjunction with a noble-metal-containing catalyst comprising a carbon support in a liquid phase oxidation process wherein N-(phosphonomethyl) iminodiacetic acid (i.e., "PMIDA") or a salt thereof is oxidized to form N-(phosphonomethyl)glycine (i.e., "glyphosate") or a salt thereof. The benefits of such a process include oxidation of the formaldehyde and formic acid by-products, and, consequently, decreased final concentrations of those by-products as well as other undesirable by-products, most notably N-methyl-N-(phosphonomethyl)glycine (i.e., "NMG").