'Shift-less' fuel processing unit to produce hydrogen from gasolinefor fuel cell systems

摘要

The rapid development of the proton–exchange membrane (PEM) fuel cell technology inrecent years has stimulated research in all areas of fuel processing catalysis for hydrogengeneration. A new precious metal catalyst with an improved precious metal utilisation, whichallows the low temperature reforming (550-650℃) of hydrocarbons, was developed. The lowtemperature reforming results in low carbon monoxide concentrations, in the range of 2-4vol-% making it possible to skip the shift units before entering the preferential oxidation unit(PROX). For the PROX unit a selective catalyst was developed to oxidize the carbon monoxidedown to a level acceptable for PEM fuel cells.To demonstrate the "shift-less" fuel processing concept, a test unit was built containing agasoline reformer and a PROX unit. At GHSV 5'000 – 19'000 h -1 and T = 515 - 630 ℃complete conversion of C2+ was achieved. First, a dual fixed-bed reactor configuration withstaged air supply was tested for the PROX. With these configurations hot spots over 100℃occurred, which made a 100% conversion of carbon monoxide impossible. The hot-spotproblem was drastically reduced to 40℃ by using an annulus reactor achieving > 99.93%carbon monoxide conversion due to the better heat dissipation. The hydrogen conversion in thePROX unit was around 27%. Reformate gas with hydrogen concentrations of 32-51% could beproduced from sulphur-free gasoline (RON = 95). Reformate gas with < 36 ppmv CO was fedto a PEM fuel cell, producing a constant cell voltage [1] for several hours.