High pressure reactor for supercritical ammonia

A cylindrical high-pressure reactor for a process using supercritical ammonia comprising

• (a) a main body having an annular cross-section and made of precipitation hardenable Ni—Cr based superalloy, having its longest dimension along the vertical direction, its inner diameter larger than 2 inches, its minimum outer diameter larger than 4 inches, and its minimum wall thickness larger than 1 inch;
• (b) at least one lid on an end of the main body;
• (c) a gasket to seal the lid to the main body, wherein the gasket has an annular cross-section with an inner radius and an outer radius, and the gasket comprises a Ni-based metal with a Ni content greater than a Ni content of the body's precipitation hardenable Ni—Cr based superalloy;
• (d) the gasket's Ni-based metal has an ultimate tensile strength between 50 and 100 ksi at room temperature;
• and
• (e) a first major surface of the gasket tapers so that the gasket has a thicker portion at the inner radius and a thinner portion toward the outer radius, and wherein the gasket when positioned horizontally has a first taper forming an angle to a horizontal plane of about 10 to about 23 degrees.