The hydrotreatment of n‐C16 over Pt/HPMo/SBA‐15 and the investigation of diffusion effect using a novel W‐P criterion

Abstract

A series of Pt/HPMo/SBA‐15 catalysts with the pore size as a single variable were prepared to elucidate the internal diffusion effect on the hydrotreatment of n‐C16. A novel model was developed to calculate the Weisz‐Prater number (NW‐P) because the traditional model relies on excessive empirical reference values and affects the accuracy remarkably. The utilization of the internal effectiveness factor, Thiele modulus, and the apparent activities over catalysts with different diffusion capacity gave rise to NW‐P with improved accuracy, which can also be extended to other heterogeneous catalytic systems with macromolecules as reactants. Combining the novel model with the diffusion–reaction kinetic method, a conclusion has been drawn that the formation of m‐i‐C16 is more susceptible to internal diffusion than the consumption of n‐C16. Besides, the pore size should be not less than 10 nm to avoid the step‐limitation of internal diffusion, in the premise of adequate acid sites.

Testing conditions for CoMo HDS catalyst in the kinetic region: integrated approach using the math calculations and catalytic experiments

“…When the liquid feedstock contacts with a solid catalyst during hydrotreating, the following processes occur in the reactor: mass transferring of reagents from the liquid volume to the external surface of a catalyst granule (external diffusion), and diffusion of reagents from external catalyst surface into pores and then to active sites that carry out the reaction (internal diffusion). Internal diffusion has the greatest influence on hydrotreating reactions, since these reactions proceed over solid catalysts via contact of feedstock molecules and active sites in pores of a catalyst [10,11]. It is obvious that the influence of diffusion limitations greatly depends on textural properties of a catalyst, size of granules, reaction conditions and feedstock.…”

“…There is a good theoretical background [10][11][12][13] a flow tube reactor to determine the influence of diffusion limitations on catalyst activity. Catalytic experiments, including proportional changes of a linear feedstock velocity and volume of a catalyst at constant liquid hour space velocity (LHSV), are usually carried out.…”

Effects of Intimacy between Acid and Metal Sites on the Isomerization of n-C16 at the Large/Minor Nanoscale and Atomic Scale

“…Compared to Pt/HY@0.4AMS, Pt/Al-MCM-41 also possesses more weak acid sites with few strong acid sites (Figure S12), which is favorable for the isomerization reaction because the strong acid sites will exacerbate the overcracking of the intermediate . Besides, the abundant mesopores in Pt/Al-MCM-41 can promote the mass transfer and production of isomers with large dynamic diameters . Compared to Pt/HY@0.4AMS, the acid and textural properties of Pt/Al-MCM-41 are conducive to the isomerization in theory.…”

“…The components of the liquid products were analyzed using an offline GC (SP-2100GC, PC-PONA). Following our previous work, , the products were divided into cracking products and isomers of C16.…”

“…18 Besides, the abundant mesopores in Pt/Al-MCM-41 can promote the mass transfer and production of isomers with large dynamic diameters. 17 Compared to Pt/HY@0.4AMS, the acid and textural properties of Pt/Al-MCM-41 are conducive to the isomerization in theory. However, as is clearly shown in Figure 15, in practice, Pt/Al-MCM-41 exhibits lower selectivity of isomers than Pt/HY@0.4AMS, which can be attributed to the difference in the intimacy.…”