Currently, there are two FT operating modes: [11][12][13] highand low-temperature FT processes (Figure 1). In the hightemperature FT (573-623 K, HTFT) process 14 syngas reacts in a fluidized bed reactor in the presence of iron-based catalyst to yield hydrocarbons in the C1-C15 hydrocarbon range. This process is primarily used to produce liquid fuels, although a number of valuable chemicals, e.g., R-olefins, can be extracted from the crude synthetic oil. Oxygenates in the aqueous stream are separated and purified to produce alcohols, acetic acid, and ketones including acetone, methyl ethyl ketone, and methyl isobutyl ketone.Both iron and cobalt (Fe, Co) catalysts can be used in the low-temperature FT (473-513 K, LTFT) process 8,10 (Figure 1) for synthesis of linear long-chain hydrocarbon waxes and paraffins. High-quality sulfur-free diesel fuels are produced in this process. Most of the FT technologies developed in last two decades are based on the LTFT process. These new LTFT processes have involved syngas with a high H 2 /CO ratio, which is generated by vaporeforming, autothermal reforming, or partial oxidation using natural gas as a feedstock.Because of their stability, higher per pass conversion, 8 and high hydrocarbon productivity, cobalt catalysts represent the optimal choice for synthesis of long-chain hydrocarbons in the LTFT process.

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Spectroscopic techniques (X-ray absorption, Raman, and UV-visible) were utilized to monitor the effect of adsorbed water, calcination temperature, and reduction in H 2 on the structure of dispersed VO x for vanadia supported on SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , and HfO 2 prepared with VO x surface densities ranging from 0.46 VO x /nm 2 to 11.1 VO x /nm 2 . Supported vanadia was found to exist as monovanadate, polyvanadate, or V 2 O 5 species, the distribution among these species depending on the support for a given VO x surface density. Dehydration resulted in the appearance of monovanadate species on all supports, with the extent of these species decreasing in the order HfO 2 > Al 2 O 3 > ZrO 2 > TiO 2 > SiO 2 . Hydration of the samples caused a decrease in the monovanadate species and a slight increase in polyvanadate species. Oxidation at elevated temperature resulted in an increase in the crystallinity of V 2 O 5 present on SiO 2 , a conversion of V 2 O 5 into polyvanadate species on Al 2 O 3 , and the appearance of mixed-metal oxide phases on TiO 2 , ZrO 2 (ZrV 2 O 7 ), and HfO 2 (HfV 2 O 7 ). The appearance of an interaction between vanadia and titania coincides with the transformation from anatase to rutile TiO 2 . ZrV 2 O 7 and HfV 2 O 7 are postulated to form via the interaction of surface VO x species with the support as the support begins to undergo a phase transition from tetragonal to monoclinic. H 2 reduction produced limited changes in the structure of dispersed vanadia except on Al 2 O 3 , where V 2 O 5 was transformed into polyvanadate species.

Carbon dioxide is an iconic greenhouse gas and a major factor for current global climate changes, making essential its capture and recycling into valuable products and fuels.Methanol is a key compound that could be obtained from the 6-electrons, 6-protons CO2 reduction and that can be used both as a fuel and as a platform-molecule. The goal of this review is to present a comparative analysis of the CO2 reduction routes to methanol via heterogeneous and homogeneous catalytic hydrogenation, as well as enzymatic, photo-and electro-catalysis.After identifying catalytic materials and reaction conditions, we provide a comparative assessment of their respective advantages and drawbacks in terms of selectivity, productivity, stability, operating conditions, cost and technical readiness level. Currently, heterogeneous hydrogenation catalysis and electrocatalysis have the highest potential for the CO2 reduction to methanol at larger scale. Availability and price of sustainable electricity appear as essential prerequisites for efficient methanol synthesis from CO2.

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