2008 Spring Symposium

 
Luis Boll­mann, Joshua L. Ratts, W. Damion Williams, Jorge Pazmino,Jeffrey T. Miller1, W. Nicholas Del­gass, Fabio H. Ribeiro
School of Chem­i­cal Engi­neer­ing
Pur­due Uni­ver­si­ty
480 Sta­di­um Mall Dri­ve
West Lafayette, IN 47907–2100

¹BP Research Cen­ter
E-1F, 150 W.Warrenville Rd.
Naperville, IL 60563

Abstract — We are attempt­ing to syn­the­size a cat­a­lyst for the WGS reac­tion that has the high­turnover rate (TOR) of the Cu-based sys­tem and the capa­bil­i­ty typ­i­cal of noble met­al­sys­tems to recov­er from oper­a­tional upsets. The kinet­ic mea­sure­ments were car­ried out­at 300 °C, 1 bar, 6.8% CO, 22% H₂O, 8.5% CO₂, 37.3% H₂, and bal­ance Argon. As aref­er­ence, the TOR for a Cu based cat­a­lyst at these con­di­tions was about 2 s^-1. Wes­t­ud­ied cat­a­lysts based on Pd and Pt. For Pt on alu­mi­na, par­ti­cle size (2–15 nm) caused­no change in the TOR, which was about 1 s^-1 for Pt on CeO₂, TiO₂, and ZrO₂ supports,implying that these sup­ports do not influ­ence the reac­tiv­i­ty.

How­ev­er, cat­a­lysts sup­port­e­don sil­i­ca and alu­mi­na showed a TOR about 10 times low­er than those on these three­sup­ports. The addi­tion of, for exam­ple, Mo, Fe, and Zn to Pd and Pt cat­a­lysts on alu­mi­nasig­nif­i­cant­ly increased the rate (up to a fac­tor of 100), but only up to the rate on the non­in­ter­act­ing­sup­ports. The rates of Pd and Pt cat­a­lysts sup­port­ed on the non-inter­act­ing­sup­ports CeO₂, TiO₂, and ZrO₂ could not be fur­ther increased by any of these additives.For a series of Pd-Zn cat­a­lysts rang­ing from 2 to 19 wt% Zn on Al₂O₃, it was observed byEX­AFS and DRIFTS of CO that Pd alloyed with Zn, and that the alloy exhib­it­ed anin­creased TOR of up to 20 times as com­pared to Pd on Al₂O₃. The pres­ence of zin­ca­lu­mi­nate was also observed. The addi­tion of 2 wt% Zn to Pd cat­a­lysts sup­port­ed onTiO₂, CeO₂ and ZrO₂ did not enhance the WGS rate, although alloy­ing was ver­i­fied byEX­AFS and DRIFTS of CO. The TORs of Pd on these three sup­ports were as high as theTOR on the best PdZn on alu­mi­na. One expla­na­tion of the results is that Zn forms ana­lu­mi­nate and pre­vents a dele­te­ri­ous inter­ac­tion between Pd and alu­mi­na. Zinc is thus­not a true pro­mot­er for WGS, although it decreased the unde­sir­able metha­na­tion reac­tion­to below detec­tion lim­its. While we have found ways to mit­i­gate the dele­te­ri­ous effect­sof alu­mi­na and sil­i­ca on the WGS rate, we have not yet found a pro­mot­er that will­increase the TOR sig­nif­i­cant­ly for Pd or Pt on non-inter­act­ing sup­ports.

Speaker’s BioBiog­ra­phy — Dr. Ribeiro is Pro­fes­sor at the School of Chem­i­cal Engi­neer­ing, Pur­due­U­ni­ver­si­ty. His research inter­est is in kinet­ics of het­ero­ge­neous cat­alyt­ic processes.Before start­ing on acad­e­mia, Dr. Ribeiro has worked in indus­try and in research using­mod­el cat­a­lysts and sur­face sci­ence tech­niques.