Processes and systems for upgrading a hydrocarbon feed. The process can include feeding a hydrocarbon feed, catalyst particles, and molecular hydrogen (H2) into a separation zone. The hydrocarbon feed and H2 can be contacted in the presence of the catalyst particles under hydrotreating conditions in the separation zone that can include contacting under a total pressure of less than 3,500 kilopascals-gauge. The H2 can be fed into the separation zone at a rate of no greater than 270 cubic meters of H2 per cubic meter of the hydrocarbon feed, where the volume of H2 and hydrocarbon feed are based on a temperature of 25 C and a pressure of 101 kilopascals-absolute. A vapor phase hydrocarbon stream and a liquid phase hydrocarbon stream can be obtained from the separation zone. At least a portion of the vapor phase hydrocarbon stream can be fed into a pyrolysis reaction zone to produce a pyrolysis effluent.