Semiconductor Photocatalysts for Non-oxidative Coupling, Dry Reforming and Steam Reforming of Methane

Abstract

Methane is one of the promising alternatives of petroleum, which should be used for not only a fuel but also a resource for hydrogen and more useful chemicals as with the petroleum. However, the selective methane conversion to them is still difficult in contrast to the combustion. Three types of photocatalytic reactions for methane conversion, i.e., the photocatalytic non-oxidative coupling of methane (PNOCM: 2CH4 → C2H6 + H2), the photocatalytic dry reforming of methane (PDRM: CH4 + CO2 → 2CO + 2H2) and the photocatalytic steam reforming of methane (PSRM: CH4 + 2H2O → 4H2 + CO2), can take place around room temperature or at a mild condition (ca. 473 K) using photoenergy and semiconductor photocatalyst. In the present short review, the details of each photocatalytic reaction and the design concept of the semiconductor photocatalysts for each photocatalytic methane conversion were summarized and discussed.

A review on coke management during dry reforming of methane

“…They are mostly generated when inappropriate ratio of CH 4 :CO 2 is employed at elevated temperatures exceeding 800°C [32,33]. Linearly, the total amount of deposited coke has shown consistency with the overall decay in catalyst activity [34,35]. Surface deposits are difficult to be removed from the metallic catalyst surfaces (especially because of the formation of carbides in some instances) during regeneration [35,36].…”

“…Linearly, the total amount of deposited coke has shown consistency with the overall decay in catalyst activity [34,35]. Surface deposits are difficult to be removed from the metallic catalyst surfaces (especially because of the formation of carbides in some instances) during regeneration [35,36]. They exhibited slow burning rates and therefore render catalyst regeneration tedious.…”

Platinum Cocatalyst Loaded on Calcium Titanate Photocatalyst for Water Splitting in a Flow of Water Vapor

“…Thus, heterogeneous photocatalysts for water splitting, especially for water vapor splitting, require ac ocatalyst that is catalytically inactive for the reverser eaction. Pt is ar epresentative andh ighly active cocatalyst for many photocatalytic reactions, including hydrogen production from methane and water [8][9][10][11][12] and various organic reactions involving hydrogen formation, [13][14][15][16][17][18][19] and the properties of the Pt cocatalyst can vary with the loading method andt he resulting chemical state. [7,20] Thus, if it becomes inactive for the reverser eaction, Pt may be an excellent cocatalyst.…”

Advances in catalytic conversion of methane and carbon dioxide to highly valuable products

“…Therefore, photocatalysis was exploited to break this thermodynamic limitation and to solve the issue of large energy requirement . Shimura and Yoshida explored Ga 2 O 3 as a photocatalyst for CH 4 and CO 2 at lower temperature . They found that, under UV irradiation, DRM could not occur at temperature below 200°C.…”

“…,[286][287][288][289][290][291][292] Shimura and Yoshida explored Ga 2 O 3 as a photocatalyst for CH4 and CO 2 at lower temperature 289. They found that, under UV irradiation, DRM could not occur at temperature below 200°C.…”