Methane steam reforming is the most common industrial process used for almost the 50% of the world’s hydrogen production. Commonly, this reaction is performed in fixed bed reactors and several stages are needed for separating hydrogen with the desired purity. The membrane reactors represent a valid alternative to the fixed bed reactors, by combining the reforming reaction for producing hydrogen and its separation in only one stage. This article deals with the recent progress on methane steam reforming reaction, giving a short overview on catalysts utilization as well as on the fundamentals of membrane reactors, also summarizing the relevant advancements in this field.

This work explores the possibility of using CO 2 captured directly from the atmosphere for several applications that require low to moderate purities. Comparisons of the minimum and real work for separating CO 2 from air, natural gas combined cycle flue gas and pulverized coal combustion flue gas are proposed and discussed. Although it is widely accepted that the separation of CO 2 from air to high purity is more energy-intensive than separating CO 2 from more concentrated sources, this study presents select cases where the separation of CO 2 from air to low and moderate purities is energetically equivalent with the work required for flue gas CO 2 separation. These energetically-competitive cases are shown to be dependent on the percent capture and final CO 2 purity desired. In particular, several technologies can be considered as CO 2 utilization opportunities in which dilute CO 2 may be an adequate feedstock. Specifically, this study is focused on enhanced oil recovery and microalgae cultivation technologies, which appear to be the most beneficial near-term applications for utilization of CO 2 from direct air capture.