A process for the synthesis of methanol, comprising the steps of reforming a hydrocarbon source obtaining a make-up gas feed (101 ), feeding said make up gas to a synthesis loop (L), converting said make up gas to methanol (108) in a substantially isothermal catalytic environment, wherein said catalytic environment comprises a plurality of isothermal catalytic beds (1 1, 12, 21 ) preferably arranged in series, and at least a portion of make-up gas (101 ) is mixed with recycle gas (1 12) from the loop (L), obtaining a gaseous mixture of fresh gas and recycle gas, and at least a portion of said gaseous mixture is directed between two consecutive catalytic beds acting as a quench gas. A related plant is also disclosed.