Prospects of CO2 capture via 13X for low-carbon hydrogen production using a Pd-based metallic membrane reactor

In this work steam methane reforming (SMR) was carried in a palladium-based membrane reactor and its performance was evaluated in terms of methane conversion, hydrogen recovery, hydrogen purity, and CO and CO2 selectivity. The membrane reactor was found to produce ultrahigh purity hydrogen with methane conversions as high as 40% at moderate operating conditions and in the absence of sweep gas. Permeation tests using pure hydrogen and inert gases indicate that the membrane reactor is highly selective toward hydrogen. The SMR reactions were performed at 673 K and operating pressures ranging from 100 to 400 kPa. A gas hourly space velocity of 2,600 hr(-1) and a steam-to-carbon ratio of 3.5 were used. Methane conversion increased from approximately 23% at 100 kPa to 42% at 400 kPa while a maximum hydrogen recovery value of 43% was achieved at 400 kPa. Furthermore, the purity of the recovered hydrogen was >99.999%. The carbon capture experiments performed in this work consist of dehydrating the retentate stream and redirecting it to a zeolite 13X packed bed before analyzing the stream via mass spectrometry. The carbon capture studies reveal that approximately 5.96 mmol CO2 (262.25 mg of CO2) can be captured per gram of 13X. This value indicates that approximately 80% of the produced CO2 via the SMR, can be captured before the sorbent bed is completely saturated. SEM-EDS, XRD, and XPS techniques were used to characterize the crystal structure and morphology of the membrane surface. These studies reveal that the surface of the membrane underwent significant oxidation during the SMR reaction. This oxidation is only limited to a few nanometers within the top surface of the palladium.

Automated summary

In this work, steam methane reforming was conducted in a palladium-based membrane reactor to produce ultrahigh purity hydrogen with methane conversions as high as 40%, even in the absence of sweep gas. The membrane reactor showed high selectivity towards hydrogen, with a maximum hydrogen recovery value of 43% achieved at an operating pressure of 400 kPa.