Abstract: Systems for hydrocarbon pyrolysis are provided, which may comprise a reactor configured to contain a liquid metal; a heater operably coupled to the reactor to form a heating zone; a cooler operably coupled to the reactor to form a cooling zone; a gas delivery assembly comprising an inlet and configured to deliver a feed gas comprising a hydrocarbon as a plurality of bubbles through the liquid metal; an outlet configured to deliver a product gas to a separation assembly, the product gas formed from pyrolysis of the hydrocarbon in the liquid metal, the product gas comprising H2 and carbon; and the separation assembly configured to separate the carbon from other components of the product gas. The reactor is configured to entrain the carbon from pyrolysis of the hydrocarbon in the liquid metal into the product gas without accumulating the carbon in the interior chamber during pyrolysis.