ADSORPTIVE DESULPHURISATION National Centre for Catalysis Research, IIT Madras

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.

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

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 m 3 CBR Diesel to 250 kg of adsorbents.

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

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

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.

Bench Scale unit in operation at CPCL R&D for Adsorptive Desulphurisation Studies

PropertyValue Flash point, º C 93 Aniline point, º C 81 Viscosity at 40 º C, Cst 4.04 Pour point, º C +6 Total Sulfur, ppm737 Density, g/cc Diesel index60 Cetane Index53 Properties of CBR Diesel used in bench scale studies

Adsorption studies in continuous reactor using modified carbon(Calgon Corpn.) Sample #Adsorption cycle – I Adsorption cycle – II

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.

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 m 2 /gm and Pore Volume of 0.45cc/gm Modification improved the surface properties with enhanced SA of 1080 m 2 /gm and PV of 0.6 cc/gm. However Particle size reduced with over 20% passing through 0.7 mm sieve.

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

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

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.