Catalyst unit and gas distributor

Claim 1

A CATALYST UNIT COMPRISING MEANS FORMING A LOWER HORIZONTAL CHAMBER, A PLURALITY OF GAS INLETS FOR SAID CHAMBER, AN UPPER HORIZONTAL CHAMBER, A CATALYST BED IN THE BOTTOM OF SAID UPPER CHAMBER, AND A GAS-DIFFUSING LAYER OF REFRACTORY BRICKWORK BETWEEN SAID CHAMBERS CHARACTERIZED BY SUBSTANTIALLY VENTURI-SHAPED PASSAGES THERETHROUGH, SAID VENTURI-SHAPED PASSAGES BEING FORMED BY A LAYER OF ALTERNATE ROWS OF RECTANGULAR UNITS AND INVERTED ISOSCELES TRAPEZOID UNITS AND A SUPERPOSED LAYER OF WEDGE UNITS WHOSE BASES COVER THE WIDEST END OF SAID TRAPEZOID UNITS, THE PRESSURE DROP OF GAS PASSING THROUGH SAID UNIT BEING GREATEST IN SAID PASSAGES, WHEREBY VARIATIONS OF PRESSURE ACROSS SAID LOWER CHAMBER ARE PREVENTED FROM REACHING SAID UPPER CHAMBER AND SAID CATALYST BED.