The methyl t-butyl ether (MTBE) synthesis is demonstrated, where MTBE is produced by reacting methanol and t-butanol over the microporous niobium silicate AM-11 (Aveiro Manchester, structure number 11). The effect of the methanol/t-butanol molar ratio, weight hourly space velocity (WHSV) and time on stream (TOS) on this reaction is investigated. These experiments are carried out in the gas phase at temperatures in the range 50-100 degreesC and at atmospheric pressure, yielding considerable selectivity for MTBE at low reaction temperatures. The selectivity to MTBE decreases with increasing temperature due to by-products formation. There is no catalyst deactivation during a period of more than 23 h on stream at 70 degreesC. Using the catalyst three times has no effect on the catalyst activity and selectivity for MTBE.