The invention relates to a permeable catalytic device for converting urea to ammonia. It is characterized in that the permeable catalytic device comprises a separate first portion (210) and a separate second portion (212), and the first portion (210) comprises a pyrolysis catalyst (210) and the second portion (212) comprises a hydrolysis catalyst (212), wherein the first portion (210) and the second portion (212) are positioned adjacent to each other to form the catalytic device and the catalytic device is parallelogram-shaped in cross-section or trapezoid-shaped in cross-section.
