Introduction
Methane (CH4) is a most promising chemical feedstock and vitality vector for its excessive reserves and comparatively cheap [1], [2]. It’s also the greenhouse gasoline whose impression on international warming is 25 occasions better than carbon dioxide (CO2) [3], [4], [5], [6], [7], [8]. Given this, changing CH4 into value-added chemical substances comparable to methanol (CH3OH) has an vital impression on international vitality utilization, environmental safety and round financial system. The CH4 molecule is an everyday tetrahedron, resulting in low polarizability and intensely excessive dissociation vitality of its C-H bond (439.30 kJ/mol). CH4 activation is often vitality and CO2 emission intensive [9]. It usually take locations at excessive temperatures (>1000 Ok) and excessive pressures (>10 bar) [10], [11]. As well as, direct oxidation of CH4 to CH3OH with out overoxidation is extraordinarily tough [12]. Therefore, the extremely selective conversion of CH4 into partial oxidation merchandise underneath gentle situations stays an enormous problem [13], [14], [15]. Photocatalytic CH4 direct conversion has attracted rising researches for it may be realized underneath gentle situation [9], [16]. Nonetheless, most of them are restricted by low effectivity, apparent overoxidation, and poor stability [17], [18], [19], [20], [21], [22]. In the meantime, expensive oxidant (comparable to H2O2) and excessive depth mild supply additionally hinder the analysis and utility on this subject.
The works in pure organic techniques specializing in CH4 conversion has discovered that a few of enzymes are the best catalysts for his or her excessive selectivity at ambient temperature and stress [23], [24]. Nonetheless, many questions are associated to the practicality of utilizing methanotrophs and/or their enzymes [25]. Are complete cell (methanotrophs) quick sufficient to attain economical volumetric productiveness? Are enzymes remoted from the cell sufficient lively and secure? Mixed with the excessive selectivity of microorganisms and excessive exercise of semiconductors, we hope to assemble an modern system for the photocatalytic oxidation of CH4 to enhance the exercise and selectivity of the method. No such work has been reported within the subject of CH4 conversion.
The methanotrophs, which exist extensively in pure wetland, paddy subject, lake, soil, groundwater and ocean, can convert 80–90% of methane within the international environment [26]. Titanium dioxide is a well-studied semiconductor photocatalyst with good biocompatibility and is appropriate for photosynthesis. Based mostly on the above, a brand new photocatalytic system composed of pure brookite mesoporous titanium dioxide (BM-TiO2, known as TiO2 hereafter) and methanotrophs (Methylosinus trichosporium OB3b) was designed on this work. The TiO2/OB3b photocatalytic system achieved excessive CH3OH exercise and selectivity at gentle situation (room temperature, atmospheric stress and underneath simulated daylight irradiation), which is of groundbreaking significance within the subject of the CH4 activation.