Hydrodesulfurisation hydrogen

Hydrodesulfurisation of thiophene must be accompanied by hydrogenation of double bonds otherwise there may exist thermodynamic constraints [46],... 

Hydrotreating and Hydrogenation. - Nitride and oxynitride catalysts have been extensively investigated as catalysts for hydrotreating (in particular hydronitrogenation and hydrodesulfurisation) and hydrogenation (for CO, aromatics, crotonaldehyde and alkenes ° the reduction of NO with H2 has been covered in the previous section). 

Leglise, J. Van Gestel, J. Duchet, J.C. Promotion and inhibition by hydrogen sulfide of thiophene hydrodesulfurisation over a sulfide catalyst. 

The soft (chloroform-extractable) and hard coke fractions fi om a suite of deactivated Co/Mo hydrodesulfurisation (HDS) catalysts with carbon contents ranging from 5 to 18% have been characterised. The hard coke accounted for between 50 and 70% of the total carbon, but was responsible for much less of a reduction in BET surface area as the carbon content increased. Indeed, significant variations in hard coke structure were revealed by solid state C NMR with the aromaticity ranging from 0.6 to over 0.9 with increasing carbon content and time on stream. The relatively high aliphatic contents and atomic H/C ratios for the hard cokes obtained at low levels of carbon deposition (5-7%) suggested that much of the carbon should be removed under reductive conditions. Indeed, hydropyrolysis, in which the deactivated catalysts were heated from ambient to 500°C under a hydrogen pressure of 15 MPa, removed over 90% of the carbon and recovered 70% of the BET surface that had been lost. 

In this type of reactors, the gas and the liquid phase flow over a fixed bed of catalysts. The fixed bed reactors can be mainly classified into three types, (i) co-current down-flow of both gas and liquid phases (ii) downward flow of liquid with gas in the countercurrent upward direction and (iii) co-current up-flow of both gas and liquid. Reactors with co-current down-flow of gas and liquid is called as trickle bed reactors (TBR) and the co-current up-flow reactors are also referred to as packed bubble column reactors. Trickle bed reactors, wherein, the liquid reactant trickles down concurrently along with the gaseous reactant, over a fixed bed of catalyst pellets finds its application in wide variety of chemical, petrochemical and biochemical processes along with its application in waste water treatment. The examples of application of trickle bed reactors are given in detail in several monographs. (Satterfield (1975), Shah (1979), Al-Dahhan (1997) and Saroha (1996)). These include oxidation, hydrogenation, isomerisation, hydrodesulfurisation, hydroprocessing. These types of reactors are also applicable for esterification reactions (Hanika (2003)). 

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