Active coke

The activity, coke, and gas factors are the tests that reflect the relative catalytic behavior of the catalyst. 

See also Activated charcoal Activated coke Carbon entries adsorption isotherm for hydrocarbons on coconut-shell, 2 635t chemical properties of, 4 741-743 economic aspects, 4 748 environmental concerns, 4 750 forms of, 4 747... 

U.S. producers of, 4 748t Activated carbon adsorption, as advanced wastewater treatment, 25 909 Activated catalyst layer, 70 40-42 Activated charcoal, 73 461 Activated coke, for SO and NO removal, 77 720... 

FCC catalyst testing prior to use in commercial reactors is essential for assuring acceptable performance. Purely correlative relations for ranking catalysts based on laboratory tests, however, can be erroneous because of the complex interaction of the hydrodynamics in the test equipment with the cracking kinetics. This paper shows how the catalyst activity, coke-conversion selectivity and other product selectivities can be translated from transient laboratory tests to steady state risers. Mathematical models are described which allow this translation from FFB and MAT tests. The model predictions are in good agreement with experimental data on identical catalysts run in the FFB, MAT and a laboratory riser. 

An industrially spent hydrotreating catalyst from naphtha service was extracted with tetrahydrofuran, carbon dioxide, pyridine and sulfur dioxide under subcritical and supercritical conditions. After extraction, the catalyst activity, coke content, and pore characteristics were measured. Tetrahydrofuran was not effective in the removal of coke from catalyst, but the other three solvents could remove from 18% to 54% of the coke from catalyst. 

Mitsui-BF [Bergbau-Forschung] A process for removing sulfur dioxide from flue gas by adsorption on a moving bed of activated coke. A complex process leads to the production of sulfuric acid. 

Although more information is needed to determine details concerning factors that favor inactive coke formation, relatively high levels of surface sulfides probably promote formation of such coke. On the other hand, metal oxides on the surface likely favor production of active coke. Sulfiding the reactor tube immediately upon completion of the decoking step would form metal sulfides. An aluminized surface, such as provided by the alonized Incoloy 800 reactor, also has been found to be an effective way to prevent the production of active coke. Quite possibly, the initial type of coke formed on the just-cleaned tube would have an important effect on the length of time a reactor tube could be used in a commercial plant before decoking would be required. 

The two-stage process was licensed by Mitsui Mining Company (MMC) in Japan in 1982, and by 1993 a modified form of the process was installed in four commercial plants in Japan and Germany [58]. The granular carbon or activated coke used in this process has a surface area of initially 150 to 250 mVg, which is much lower than that of commercial activated carbons. It is produced from a bituminous coal and a pitch binder. Low surface area carbons have been found to be the most effective in this process they are cheaper than high surface area activated carbons, they retain their SO2 adsorption capacity more efficiently on repeated cycling, and their relatively low porosity contributes to strength and abrasion resistance. 

In the MMC combined process for SOi adsorption, NO, removal, and air toxics adsorption, the granular activated coke flows downwards through the two adsorbers, countercurrent to the flow of flue gas. A booster fan is required in the flue gas stream to overcome the pressure drop across the beds. Oxides of nitrogen are... 

This process has not gained widespread use due to the large capital investment required and its high operating costs. Power is consumed in overcoming the pressure drop across the adsorbers, and fresh activated coke must be constantly added to make up for the losses of carbon on regeneration and attrition in the moving... 

For industrial catalytic processes, It is iBiportant to understand cataly.<%t deactivation and the role that coke plays. Most models assume an activity-coke relationship which is probably true when coke is deposited only on active sites and when the window of conditions Is kept small or constant. However, in practice significant differences occur in many of the variables including the nature and type of catalyst and feed. The present study was undertaken to elucidate some of these problems for the teformlng process by providing a better understanding of the kinetics of coking. 

The temperature does not influence the total amount of PNAs or nitrogen compounds adsorbed, although the rate of adsorption is seen to increase with temperature. Nitrogen is found in the adsorbed species (coke) hut on the active catalyst the m or part of the nitrogen may be located on the NiMoS phase. The N-containing compounds are probably not active coke precursors. 

Therefore, the coke in the MTO and DTO should be divided in two categories Inactive coke formed from olefins having a deactivating effect and active coke formed from oxygenates having a promoting effect. The activity at different coke contents depends on the ratio of active to inactive coke. 

The coke, which was recorded as the total mass increase in the TEOM reactor, can be divided into active coke formed from oxygenates and inactive coke formed from olefins. The active coke promotes the conversion to olefins and could in fact represent the true surface intermediate of the reaction. 

For the simultaneous removal of SO and NO from waste gas at low temperatures (383-443 K) activated coke is a promising option [101]. SO2 reacts with water and oxygen to form sulfuric acid which is trapped on a column with coke. The coke catalyst accumulates the acid and is regenerated regularly. The desulfurized gas is then passed to a reactor which contains a coke eatalyst aetivated with sulfuric acid and NO is removed with ammonia in the presence or absence of oxygen [101]. 

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