Is the presence of C2+, CO2 and N2 in natural gas bad for its reforming to give syngas?

How much C2+ (propane and higher hydrocarbons),CO2 and N2 contents in natural gas are acceptable for syngas production by the autothermal reforming of natural gas? The produced syngas is to be fed to a furnace for reduction of iron ore. Does the syngas also need to have as low as possible contents of CO2 and N2 before sending it to the furnace?