4 replies to this topic

[azhar_uk]

Hi for all

I would like to get detail information for my issue,while my inquiry is what is effect of high and low level of H2O in recycle gas and water content in feedstock (naphtha) of catalytic reforming parameter pressure ,temperature,H2/HC ratio,catalyst activity and stability and selectivity ,C5+ yield , hydrogen production , LPG production,methane and ethane production ,reaction rate on main reactions (Dehydrogenation ,isomerazatin , deheydrocyclization and hydrocracking ?
what is your recommendation to reduce these effects?

Edited by azhar_uk, 04 March 2012 - 05:50 AM.

[Himanshu Sharma]

You need to get hold of D. M. Little, Catalytic Reforming, Pennwell Publishing

[azhar_uk]

how can i get this book

[S.AHMAD]

1. The textbook proposed is a good book but not sure whwther it is still available in the market.
2. Normally, process licencor provides technology manual. It contains the information that you are looking for.
3. Simply put, the H2O affects the acidic function of the catalyst. Too much water, the chloride will be leached away. Too little, the catalyst will be too acidic and result in more cracking of naphtha (this comment comes from my old memory - forgive and correct me if I am wrong)

[Himanshu Sharma]

@ S.Ahmad ,sir indeed a very good memory you have ,your four lines are crux of the details i am going to add in this post.However you may add a quick note to your memory that chlorine/water balance also dictates a very important factor i.e Coke formation/Catalyst deactivation rate and in a way limit throughput of a continuous regenerating reformer.

@Azhar_Uk

As you might be aware that Naphtha reforming reactions occur on the bifunctional catalyst. but the Acidity provided by alumina is not enough and must be adjusted by adding chloride compounds.

Therefore, chlorine content remains an important environmental factor and will influence catalyst coking behavior in the reforming process.Historically people have reported the presence of chlorine produces more uniform deposition of Pt over alumina in the Pt/Al2O3 catalyst and thus improves the dispersion of the metallic phase. Metal redispersion by chlorine under an oxidizing condition after coke
burnoff in the regenerator has been industrially used to refresh activity of the catalyst . Highly dispersed reforming catalysts are more resistant to deactivation by coke deposition because small platinum crystallites present an electron deficiency due to metal–support interaction that in turn result in a lower stability of the intermediate adsorbed unsaturated hydrocarbons.

coking is connected with catalyst acidic properties that are related to chloride content that promotes polymerization of coke precursors.Therefore, it can be concluded that there is an optimal chloride content on the Pt/Al2O3 that allows a reduction of the coke deposit through a mechanism involving the hydrogen spillover from metal to the support. principally the acid function, but to some extent they can alter the metallic properties of the platinum.

Residual water must be maintained in the hydrotreated naphtha feed. An
alumina-supported reforming catalyst requires moisture to activate the acid function and provide homogeneous chloride content over the whole catalyst bed. When the environmental atmosphere is too wet, however, chloride in the catalyst may be leached off and thus deteriorate its acidic behavior. Therefore, water control must be performed along with chloride control to maintain a proper chloride–water balance in the environmental atmosphere.As per what my memory recalls , the chloride content on the catalyst should be kept in the range of 0.9– 1.2 wt% for most bimetallic catalysts. To meet this requirement you should maiantain an environment of 1–5 ppm of hydrogen chloride and 10–20 ppm of
water should be provided in the circulating gas over the bimetallic reforming catalysts.At lower Cl level, WAIT will need to be raised to maintain octane number level and hence increase coke deposition. When chloride content is higher than 1.2%, catalyst acidity would be too strong and thus drastically increase the coking rate and shorten the cycle life of a reforming catalyst.

I hope this answers your queries .Wish i had the patience to make you go through Pt-Re interaction and ir2o7 formation for a deeper undertsanding but then its too much chemistry and not required for discussion at hand.

Edited by Himanshu Sharma, 11 March 2012 - 09:59 AM.