Countercurrent process with froth control for treating heavy hydrocarbons

A countercurrent continuous process for treating a viscous liquid hydrocarbon with a gaseous reactant comprising the steps of:

• containing a fixed porous bed of solid catalyst in an enclosed reactor shell;
• introducing a stream of liquid hydrocarbon at an upper liquid inlet substantially above the catalyst bed for downward gravity flow through the bed;
• withdrawing treated liquid from a lower liquid outlet of the reactor shell;
• introducing a gaseous reactant stream under pressure at a gas inlet disposed below the catalyst bed for countercurrently contacting downwardly flowing liquid in a mixed phase reaction zone, whereby gaseous reactant is dispersed through the liquid phase in intimate contact with the solid catalyst;
• withdrawing gas from the reactor shell through an upper gas outlet means above the catalyst bed;
• detecting level of a mixed gas-liquid froth in a froth zone above the catalyst bed and generating a signal representative of froth level;
• and
• regulating froth level above the catalyst bed by fluid handling control means operatively connected to the level detector and responsive to said level signal to control flow rate for withdrawing treated liquid at increased rate with increased froth level, thereby permitting disengagement of dispersed gas from the liquid phase of the froth and preventing excessive liquid entrainment in the gas outlet.

In the process for catalytic treating waxy heavy petroleum feedstock in a multi-phase catalytic reaction zone containing a fixed porous bed of solid medium pore zeolite catalyst particles;

• the improvement which comprises:
• introducing the heavy feedstock predominately in liquid phase under superatmospheric process conditions at elevated temperature and distributing the feedstock uniformly over the catalyst bed for downward flow in contact with the catalyst;
• introducing a pressurized reacting gas rich in hydrogen below the catalyst bed at a rate to establish countercurrent contact dispersed in downcoming liquid;
• disengaging upwardly flowing dispersed gas from feedstock above the catalyst bed;
• controlling mixed gas-liquid froth level to prevent substantial entrainment of liquid in disengaged gas by measuring differential pressure between vertically spaced points in the froth zone, generating a control signal in response to said differential pressure measurement and regulating the outflow of a treated petroleum stream, the inflow of the liquid phase heavy feedstock, and/or the inflow of the pressurized reactant gas in response to the froth level control signal;
• and
• recovering treated petroleum and offgas.