Catalysts pore volume

Another coke formed in a FCC unit is occluded or residual coke. In a commercial unit this coke corresponds to coke formed on catalyst porosity and its content depends on textural properties of the catalyst (pore volume and pore size distribution) and the stripping system capacity in the reaction section. Finally on the FCC catalyst rests some high-molecular weight of nonvaporized hydrocarbons. These molecules do not vaporize or react at the reactor conditions and accumulate in the catalyst pores like a soft carbonaceous residue with high hydrogen content. 

Occluded coke is a function of the operating conditions of the FCCU stripper, of catalyst pore volume and pore size distribution. This coke that has the higher content of hydrogen is the lowest refractory between the different kinds of coke produced in the FCC process. Althongh in this study it was not directly evalnated, it may be associated with the peak A at the lowest temperature ( 500°C-550°C). So once the... 

Fig. 12. The porosity of the catalyst determines not only its activity but also the chain length. Here melt index (MI) varies with catalyst pore volume in a series in which a common hydrogel was dried by extraction with different organic solvents to achieve variations in porosity.

Experimental variables which alter the shape of the metal profiles are a manifestation of the intrinsic reactivity and transport characteristics of the metal-bearing species. The extent to which the catalyst pore volume is utilized to accommodate metal deposits in response to these changes is... 

In this project, the feasibility of catalyst regeneration by supercritical fluid extraction was studied. A spent catalyst from an industrial naphtha hydrotreater was extracted with tetrahydrofuran, pyridine, carbon dioxide, and sulfur dioxide under subcritical and supercritical conditions. The coke reduction and changes in the catalyst pore characteristics were measured and to a limited extent the catalyst activity was evaluated. It is shown that by supercritical extraction, the coke content of spent hydrotreating catalysts can be reduced and the catalyst pore volume and surface area can be increased. 

Catalyst Pore Volume (ml/g) Meso-Pore Distribution(%) Macro-Pore Distribution(%) ... 

Figure 6 Relation between Catalyst Pore Volume and Parameters...

The expected catalyst pore volume in the sample, V , Is given by... 

Subsequent deposition of vanadium, nickel and coke is shown to be considerably in excess of that needed to fill the catalyst pore volume. Migration of molybdenum to the used catalyst surface is established and is suggested to result in reasonable catalytic activity via the formation of sulphides containing nickel, vanadium and molybdenum. Subsequent deactivation would result from infilling pores in the deposit, with final catastrophic deactivation resulting from the wave of heavy deposits of metal sulphides approaching the end of the catalyst bed. 

Some 5 gm of supported catalyst were used, which exposed some 10 metal atoms to the gas phase (measured by in situ chemisorption), on which an amount of C as varying between 1 and 8 x 10 atoms was deposited. The catalyst was contacted with a batch of some 2 x 10 ° COand6 x 10 ° H2 molecules, and the synthesis reaction was allowed lo proceed until some 1 X 10 hydrocarbon molecules had been formed. With mass spectrometry it was then verified whether these hydrocarbon molecules has been formed from the C j or from the CO,3 5, reservoir. A reactor with a minimized holdup of some 10 ml was used, 4 ml of it being catalyst pore volume. The reactant pressure initially exceeded 1 bar, while the number of reactant molecules was of the same order as the number of predeposited C as atoms. 

However, if LCB is tied to structural reinforcement of the silica matrix, as proposed above, then for a constant degree of coalescence, low pore volume might be expected to raise LCB levels, because more points of contact between primary particles are generated, as illustrated in Scheme 21. Therefore, it was of interest to compare samples having the same degree of coalescence but differing widely in pore volume, to determine the independent effect of catalyst pore volume on LCB levels in the polymer. 

Figure 88A shows a plot of the JC analyses for LCB level as a function of the catalyst pore volume. The LCB levels indicate a single relationship with pore volume, although high and low surface areas are well distributed over the whole graph. In Figure 88B, the LCB level is shown as a function of the average coordination number of the silica, as defined in Scheme 21. Plotting the data in this way produces a straight line, making it even clearer that LCB levels respond to the strength of the silica matrix. MW (not shown) was also entirely a function of pore volume in this series [500].

High temperatures, which can sinter or reduce catalyst pore volume. 

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