ADSORPTIVE DESULPHURISATION

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ADSORPTIVE DESULPHURISATION

• National Centre for Catalysis Research, IIT Madras

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Summary of Research Project on Adsorptive
Desulphurisation

• Activated Carbons from commercial sources , and
  Zeolites were screened for their adsorption
  characteristics of sulfur compounds in Diesel.
• Zeolites not considered for further studies for
  the following
• 1. Poor Adsorption characteristics for
  diesel
• desulfurisation.
• 2. Inorganic porous material like Zeolites
  require
• higher severity and Hydrogen for
  activation.

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Summary of Research Project on Adsorptive
Desulphurisation

• Activated Carbon requires appropriate
  modification to enhance capacity for adsorptive
  desulfurisation.
• Modification of carbon is aimed for
• 1. Textural properties improvement
• 2. Functionalisation with Oxygen
• Treatment with Nitric acid followed by Argon
  activation standardized for modifying carbon
• Effectiveness for Adsorptive Desulphurisation
  studies was studied
• The adsorbents were characterised in detail using
  XRD,FT-IR, SEM etc. to understand their
  properties

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Summary of Research Project on Adsorptive
Desulphurisation

• Adsorption studies were carried out on modified
  Carbon with CBR Diesel as feed in
• 5 10 gms Scale
• Modified Carbon could desulfurise 700 ppm feed
  sulfur to below 300 ppm
• Preliminary studies indicate treat ratio of 1 m3
  CBR Diesel to 250 kg of adsorbents .

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Summary of Research Project on Adsorptive
Desulphurisation

• Regeneration of Adsorbents
• - Gas Based Regeneration using Hydrogen
• - Solvent Based Regeneration
  (Toluene)Solvent based regeneration using
  Toluene is found to be effective
• Several cycles of Adsorption and regeneration
  was studied on modified carbon and the
  performance of fresh and solvent regenerated
  adsorbents were found similar

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Summary of Research Project on Adsorptive
Desulphurisation

• Toluene is recoverable by simple flash
  distillation of spent liquid obtained during
  regeneration of modified carbon after adsorption
  cycle.
• Recovered Toluene is free of sulfur impurities
  and diesel hydrocarbons - Suitable again for
  regeneration cycle of modified carbon

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Path Forward for ADS Studies

• Designing a bench scale unit for continuous
  studies with 200 500 ml adsorbent loading
• Validating lab scale Adsorption/ regeneration
  capacities on continuous flow mode operation
• Collecting Data for scale up to Demo unit By
  studying progression of Adsorption/Desorption
  Breakthrough point,number of cycles,
  Regenerability of adsorbents, Regeneration time
  and solvent recovery studies.

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Bench Scale unit in operation at CPCL RD for
Adsorptive Desulphurisation Studies
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Properties of CBR Diesel used in bench scale
studies
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Adsorption studies in continuous reactor using
modified carbon(Calgon Corpn.)
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Studies on ADS in Continuous mode operation

• Desulphurisation of Diesel was effective in the
  continuous flow mode operation also
• However liquid hold up in the unit is relatively
  high, which in turn affects solvent regeneration
  and subsequent cycle of adsorption.
• Liquid hold up in the bench scale reactor is the
  major constraint in studying the performance and
  cycle length of adsorbent.

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Studies on ADS in Continuous mode operation

• Adsorbent carbon selected for modification had a
  Granular Size of 0.8mm 1.2mm with Surface Area
  of 950 m2/gm and Pore Volume of 0.45cc/gm
• Modification improved the surface properties with
  enhanced SA of 1080 m2/gm and PV of 0.6 cc/gm.
  However Particle size reduced with over 20
  passing through 0.7 mm sieve.

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Studies on ADS in Continuous mode operation

• The reduction in particle size resulted in larger
  retention of liquids (feed diesel) in
  intra-particle voids
• Either retaining the granular size during
  modification or extrudating the adsorbent carbon
  are the available options for minimising the
  liquid hold up
• Liquid Hold up vitiates study on the adsorption
  progression as well as Hydrocarbon mix up during
  solvent regeneration

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Adsorbent Carbon requirement for continuous
operation

• Liquid hold up is as high as 125 ml in our
  continuous flow experiments with 250 g adsorbent
  in a fixed bed unit.
• Studies initiated to reduce liquid hold up by
  changing to extrudate form of the adsorbent
• Unit for making adsorbent carbon in extrudate
  form is procured by IIT M
• Preliminary studies for forming extrudates
  without loss of crush strength is in progress at
  IIT M . Various binders are being tried to form
  extrudates

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Plan for further work

• Extrudates of Adsorbent Carbon with optimum
  physical strength will be prepared with or
  without binders
• Continuous mode of Adsorption/Regeneration
  studies will be carried out using the extrudates.
• Based on the results obtained in the continuous
  unit at CPCL , the basis for design of
  demonstration unit will be firmed up.