Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-IV-10EFFECT OF SULPHUR ON THE CATALYTIC PARTIAL OXIDATIONOF METHANE OVER RHODIUM BASED CATALYSTSR. Torbati 1 , L. Lisi 2 , S. Cimino 2 , G. Russo 1,21 Dipartimento di Ingegneria Chimica – Università degli Studi di Napoli Federico II,;2 Istituto di Ricerche sulla Combustione - C.N.R., P.le Tecchio 80, 80125, Napoli – Italy;Phone: +39 081 7682220 Fax: +39 081 5936936 e-mail: reza.torbati@irc.cnr.itIntroductionThe presence of sulphur containing compounds, naturally occurring in natural gas oradded as odorants, can adversely affect the performance of noble metals based catalysts forthe partial oxidation of methane to syngas. Until now, studies on the effect of S compoundson the catalytic partial oxidation of hydrocarbons over Rh based catalysts remain scarce andonly recently few papers have been published highlighting its detrimental effect, even at verylow concentrations [1, 2]. It is therefore of significant importance to investigate themechanism by which sulphur affects the catalytic performance of catalytic partial oxidation(CPO) and how to increase the tolerance of the catalyst to sulphur poisoning. In this work theeffect of SO 2 addition on the CPO of methane was investigated on Rh (1wt.%) catalystsprepared by IW impregnation method on to two different high temperature commercialγ-alumina supports, stabilized either with 10% SiO 2 or 3% La 2 O 3 (Sasol).ExperimentalCatalysts were mainly characterized by BET, H 2 -TPR and FT-IR spectroscopy. FTIRexperiments were performed on powders pressed into self-supporting disk and placed in theIR cell, where temperatures of up to 800 °C can be achieved under reaction mixture. TPD-MSexperiments (up to 1000 °C) were also carried out to measure the extent of sulphation afterstandard treatment with 100 ppm SO 2 in air at 300 °C for 2 h. Catalytic tests on powders werecarried out in order to compare the intrinsic activity of samples: a fixed bed flow reactor wasrun pseudo-isothermally with a very diluted feed mixture CH 4 /O 2 /N 2 = 1/0.6/98.4, at GHSV =8 × 10 4 h –1 and externally heated from 300 °C to 800 °C at 10 °C/min. To examine thepoisoning effects of sulphur, 20/100 ppm SO 2 were added under reaction at 500 °C for 1 hrfollowing transient response; thereafter the light-off was repeated in order to determine theextent of catalyst deactivation and recovery from poisoning. CPO experiments were alsoperformed under autothermal conditions at high temperatures and short contact times in orderto reproduce conditions of practical interest, using 600 cpsi monoliths in the shape of disks(L=11 mm, D=17mm). Reactor temperatures were measured by means of thermocouples inthe centre of each monolith and in the exit gas. In these experiments the undiluted inlet414