Catalytic reforming deactivation

C, 0.356—1.069 m H2/L (2000—6000 fU/bbl) of Hquid feed, and a space velocity (wt feed per wt catalyst) of 1—5 h. Operation of reformers at low pressure, high temperature, and low hydrogen recycle rates favors the kinetics and the thermodynamics for aromatics production and reduces operating costs. However, all three of these factors, which tend to increase coking, increase the deactivation rate of the catalyst therefore, operating conditions are a compromise. More detailed treatment of the catalysis and chemistry of catalytic reforming is available (33—35). Typical reformate compositions are shown in Table 6. 

Hydrofining is applied to virgin naphthas mainly in the form of a pretreatment step for the feed to catalytic reformers (Powerforming). Sulfur levels of 5 parts per million (ppm) or less are required to avoid deactivation of the platinum reforming catalyst. 

The elements of range in value from 0 to 1 and are the ratio of the reformer kinetic constants at time on stream t to the values at start of cycle. At any time on stream t, the deactivation rate constant matrix K(a) is determined by modifying the start-of-cycle K with a. From the catalytic chemistry, it is known that each reaction class—dehydrogenation, isomerization, ring closure, and cracking—takes place on a different combination of metal and acid sites (see Section II). As the catalyst ages, the catalytic sites deactivate at... 

Regeneration is a critical step in catalytic reformer operation to regain activity, selectivity and stability of deactivated catalyst. Regeneration procedures and capabilities are dependent on the causes of deactivation. The procedures are proprietary in nature and supplied by catalyst vendors or process licensors The catalyst deactivated by coke can be easily regenerated to restore it s activity, Modified methods are adopted when catalyst had suffered from sulfur or water upset. It is important to emphasize that on line catalyst samplers are good tools to know the state of catalyst, causes of deactivation and help in improving operational and regeneration effkiency[ll]. There are no samplers installed in the reformer under discussion... 

It is rewarding that both fundamental and applied aspects are dealt with. The deactivation of catalysts in important industrial processes like fluid bed catalytic cracking, hydrotreatment, hydrodesul furization, catalytic reforming, hydrodenitrogenation, steam reforming,... 

The Likun Process (China) uses a two-stage cracking process under normal pressures where the waste plastics are first pyrolyzed at 350-400°C in the pyrolysis reactor and then the hot pyrolytic gases flow to a catalyst tower where they undergo catalytic reforming over zeolite at 300-380°C. By having the catalyst in the second stage this overcomes the problems of rapid catalyst deactivation from coke deposits on the surface of the catalyst. 

One of the most critical issues in developing catalytic reformers, especially for the reforming of hydrocarbon fuels, is the risk of carbon deposition on the catalyst surface and consequent catalyst deactivation. Carbon formation can occur in several regions of the steam reformer where hot fuel gas is present. Natural gas for example will decompose when heated in the absence of air or steam at temperatures above 650 °C via pyrolysis reaction as shown in Equation 2.4. 

A reactor system similar to the fixed-bed reactor is the moving-bed reactor, in which the deactivation rate is relatively low, but too high for pure fixed-bed operation. An example of its application is the catalytic reforming processes. 

A Model for Catalyst Deactivation in Industrial Catalytic Reforming... 

The deactivation of catalytic reforming catalysts was studied in Platforming units. The deactivation was measured by the increase in the operation temperature necessary to obtain a specified performance in processes using Pt-Re and Pt-Sn catalysts. The statistical analysis produced an equation capable to predict the deactivation degree in terms of the operation parameters and properties of the feed. 

Most poisons are type (1), i.e., independent compounds present tn the feed, perhaps in minute quantities, that deactivate the site with a mechanism different from the main reaction. Examples are also found of types (2) and (3), where either parallel or series reactions generate side products that poison the sites. These mechanisms may also be classified as examples of kinetic inhibition but are considered poisoning if adsorption on the site is irreversible. In situations where multiple sites are involved (for example, dual-functional catalytic reforming), poisoning patterns become more complex. 

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