Taking the catalyst system for the slurry-bed hydrogenation reactor in refining technology as an example, as if handling heavy loads were easy

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It is generally understood that the catalyst system in a slurry-bed hydrogenation reactor includes the amount of precursor for replenishing the fresh feed and the MOS2 circulation volume of the recycled oil; however, the author believes this understanding is rather one-sided and contrary to the fundamental theory of the synergistic action in slurry-bed hydrogenation catalyst systems. The catalyst system within a slurry bed reactor is highly complex. The flow pattern inside the reactor is non-ideal plug flow; it involves a highly mixed discontinuous phase, namely the dispersed phase. This constitutes a composite \"bed\" that combines a fixed \"bed\" rich in highly dispersed catalysts, determined by the reactor volume and slurry density, with a downward boiling \"bed\" characterized by intense mixing and multiple flow patterns, as well as a moving \"bed\" resulting from external circulation and reflux variations, plus fresh feed to compensate for losses. These four types of beds work together to form the catalyst system within the reactor, enabling momentum transfer related to fluid dynamics of the catalysts and mass transfer related to reaction kinetics, thereby facilitating the activation of hydrogen at the catalyst core and the interaction between radical reactants on a second-by-second basis. Therefore, the catalyst system in a slurry-bed hydrogenation reactor consists of a fixed amount that is added once at startup and remains in the \"bed\" after equilibrium is reached, a circulation amount at a certain rate both inside and outside the reactor, and an amount of fresh feed precursor added. This can be understood in a similar manner to the fixed loading amount and circulation amount between reaction and regeneration stages in a reforming unit. The slurry-bed hydrogenation reaction possesses a metal-removal function; nickel, iron, and vanadium in the feedstock are removed and accumulate in the slurry system, including the reactor, as different types of adsorption groups. Similar to molybdenum, nickel and iron exist in sulfur-containing forms that possess hydrogenation activity, thereby having both hydrogen-activation and hydrogenation functions. The saturation overflow rate of nickel sulfide is higher than that of molybdenum sulfide, giving it a stronger ability to prevent reaction coking ； Vanadium is more oxygen-loving and exists as oxides or oxysulfides, and the advantages and disadvantages of its role remain to be studied. Therefore, the catalyst system for slurry-bed residue hydrogenation involves both the functional interactions among multiple metals such as molybdenum, nickel, and iron, as well as the synergistic effects between different bed flow regimes. It falls within the scope of reaction kinetics and fluid dynamics in gas-liquid-solid three-phase tubular reactors, and the reaction CFD model requires repeated verification using production data and iterative data correction.