Vulcan Series Chloride Removal Technology VGP CRT 2000 and ...

HCl Transformation occurs when HCl inlet a chloride removal bed is transformed to
organic chlorides or into chloride salts which are not retained by the bed and flow out with
the carrier stream. This occurs over acidic alumina sites and the process is accelerated
in the presence of adsorbed HCl, adsorbed water and unsaturates (please see section D
on by-product formation overleaf). There is evidence to suggest the organic chloride
formation occurs in the top layers (down flow mode) of alumina beds. The entire organic
chloride reaction front has been observed to be contained in as little as 0.5 meters depth.
Adsorbed HCl on the alumina surface appears to initiate organic chloride formation and
this involves all of the HCl entering the reactor. Organic chlorides are difficult to detect
and frequently lead to the false assumption that HCl is being removed and retained by
the alumina bed on line.
4.4 BY-PRODUCT FORMATION
The Vulcan Series - VGP CRT 2000/3000 are not adsorbents but are true catalyst.
They have been specifically manufactured to a low surface area and its constituent
materials (a proprietary doubly promoted and highly porous ceramic support) do not have
adsorption properties. HCl therefore does not exist freely or in an adsorbed or in a
partially dissociated state inside the catalyst or on its surface. VGP CRT 2000/3000 is
not acidic and greatly minimizes organic chloride synthesis or
condensation/polymerization reactions.
Alumina Side Reactions
Alumina itself is slightly acidic in nature because of its ability to donate protons its surface
hydroxyl groups. Once it has adsorbed hydrogen chloride its surface acidity is increased
dramatically and this acidity can cause undesirable side reactions to occur in the process
stream:
a) In normal operation there will be small traces of unsaturates in the reformer
reactor product, which will go into both the offgas and reformate streams. For
example in hydrogen gas ex catalytic reformers the concentration of unsaturates
varies from 400 ppmv to 1000 ppmv. These unsaturates will react with hydrogen
chloride when promoted by an acid catalyst. Thus organic chlorides can be
formed across the alumina bed. These organic chlorides are not removed by the
alumina and will slip from the bed into the product stream. If the offgas stream
goes to hydrotreating or hydrocracking units these organic chlorides will be
hydrogenated to HCl and will then cause corrosion problems and may also
deactivate the hydroprocessing catalyst.
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