Activation energy hydrocracking

The kinetics of hydrocracking reactions has been studied with real feedstocks and apparent kinetic equations have been proposed. First-order kinetics with activation energy close to 50 kcal/gmol was derived for VGO. The reactions declines as metal removal > olefin saturation > sulfur removal > nitrogen removal > saturation of rings > cracking of naphthenes > cracking of paraffins [102],... 

Kinetics studies of the hydrotreatment (and hydrocracking) of VR has led to the conclusion that most of the metals, sulfur and nitrogen removal takes place during the first 50% of the whole VR conversion [119-123], More than one reactor was needed for HDM and HDS of a Maya VR, when HDT is used as feed pretreatment [119,120], Although vanadium removal appears easier and faster than nickel removal, their kinetics results showed very similar values of the activation energy for the demetallization reactions [122],... 

The experimental data obtained in the hydrocracking of coal, coal oil and phenanthrene were tested with equations (iii) and (iv) as shown in Figures 8 and 9 and the data were found compatible with the model. This compatibility confirmed that the rates of hydrocracking were controlled by surface chemical reactions as were also indicated by arrhenius activation energies (Table VIII). 

The activation energy for adsorption of hydrocarbons on nickel is about 40 kJ/mole (76) and the activation energy for hydrocracking is in the range 160-200 kJ/mole (77). This means that below the temperature, Tp, at which Ta > rn, i.e. rp > 0, gum formation takes place. To ensure trouble free operation the prereformer must operate within the temperature window of T < T < Tc. 

The kinetic parameters (apparent activation energies, orders versus hydrogen and hydrocarbon) have been determined for all the isomerization and hydrocracking reactions of n-pentane and 2-methylbutane on a Pt/AljOj catalyst of low dispersion (10% Pt d = 90 A) 40). n-Pentane-2- C and 2-methylbutane-2- C were used to estimate the contributions of cyclic type and bond shift isomerization, respectively. As shown in Table II, the reactions... 

FIGURE 10.14 ZSM-5 catalytic dewaxing of waxy hydrocrackates activation energies versus percent non-normals. 

The observed behavior in the yield of middle distillates and vacuum gas oil may explain why there is an increase in the total liquid recovery of the product with boiling temperatures above 300°C. It also implies that vacuum gas oil is more feasible to hydrocrack than the middle distillates fraction. The yield of gases does not change substantially at the operating conditions studied and remains almost in the same low limits. This is probably due to the fact that the activation energy to hydrocrack the light fractions such as naphtha has not been reached. 

For the hydrocracking of both vacuum residue and VGO, the lower activation energies dictate that middle distillates are preferentially obtained over naphtha and gases. The hydrocracking of middle distillates toward naphtha and gases happens more quickly than the other reactions, while the reaction of naphtha toward gases is the least favored. 

D(kjjos) Species-type distribution function for hydrodesulfurization reaction. EfjDc Activation energy of hydrocracking reaction. 

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