7.18 A certain spherical porous catalyst with a pellet diameter of 1/8 in. has a Thiele modulus of 0.5 for a first-order reaction and gives 90% conversion in a packed bed reactor. It is proposed to replace this catalyst by the exact same catalyst but with pellets of 1/4 or 1/2 in. to reduce the pressure drop. How will the conversion change with these catalysts?