Single Step Bi-reforming and Oxidative Bi-reforming of Methane (Natural Gas) with Steam and Carbon Dioxide to Metgas (CO-2H₂) for Methanol Synthesis: Self-Sufficient Effective and Exclusive Oxygenation of Methane to Methanol with Oxygen

Abstract

Catalysts based on suitable metal oxide supports, such as NiO/MgO and CoO/MgO, were shown to be active for single step bi-reforming, the combined steam and dry reforming of methane or natural gas with H2O and CO2 exclusively to metgas (CO-2H2) for efficient methanol synthesis. Reactions were carried out in a tubular flow reactor under pressures up to 42 bar at 830-910 °C. Using a CH4 to steam to CO2 ratio of ∼3:2:1 in the gas feed, the H2/CO ratio of 2:1 was achieved, which is desired for subsequent methanol synthesis. The needed 2/1 steam/CO2 feed ratio together with the reaction heat for the endothermic bi-reforming can be conveniently obtained by the complete combustion of a quarter part of the overall used methane (natural gas) with oxygen of the air (oxidative bi-reforming). Complete combustion of a part of methane followed by bi-reforming leads to the production of metgas (H2/CO in 2:1 mol ratio) for self-sufficient exclusive methanol synthesis. The long sought after but elusive efficient and selective oxygenation of methane to methanol is thus achieved in an effective and economic way without any oxidation byproduct formation according to CH4 + 1/2O2 → CH3OH.

Ordered mesoporous “one-pot” synthesized Ni-Mg(Ca)-Al2O3 as effective and remarkably stable catalysts for combined steam and dry reforming of methane (CSDRM)

“…Amongst such technologies, great attention is focused on the production of synthesis gas (syngas, gaseous mixture of CO and H 2 ) that constitutes a versatile building block for subsequent production of synthetic fuels or chemical intermediates in petrochemical industries [2]. Particularly, combined steam and dry reforming of methane (CSDRM, 3CH 4 + 1CO 2 + 2H 2 O → 8H 2 + 4CO), also known as bireforming [3][4][5][6], appears as a very promising CO 2 valorization route yielding a syngas with H 2 /CO molar ratio close to 2, called metgas [3][4][5][6]. The latter can be directly used in methanol [4][5][6][7][8][9][10] or dimethylether production [5][6][7][8][9][10] as well as in some Fisher-Tropsch operations aiming the preparation of long hydrocarbons chains [11,12].…”

“…Particularly, combined steam and dry reforming of methane (CSDRM, 3CH 4 + 1CO 2 + 2H 2 O → 8H 2 + 4CO), also known as bireforming [3][4][5][6], appears as a very promising CO 2 valorization route yielding a syngas with H 2 /CO molar ratio close to 2, called metgas [3][4][5][6]. The latter can be directly used in methanol [4][5][6][7][8][9][10] or dimethylether production [5][6][7][8][9][10] as well as in some Fisher-Tropsch operations aiming the preparation of long hydrocarbons chains [11,12]. By comparison, conventional dry reforming of methane (DRM, CH 4 + CO 2 → 2H 2 + 2CO) and steam reforming of methane (SRM, CH 4 + H 2 O → 3H 2 + CO) yield a H 2 /CO ratio of either 1 (too low) or around 3 (too high), respectively, which imposes supplementary stages (often expensive) if adjustment of the product ratio near 2 is required for the next steps of the process [3][4][5][6]13,14].…”

“…The latter can be directly used in methanol [4][5][6][7][8][9][10] or dimethylether production [5][6][7][8][9][10] as well as in some Fisher-Tropsch operations aiming the preparation of long hydrocarbons chains [11,12]. By comparison, conventional dry reforming of methane (DRM, CH 4 + CO 2 → 2H 2 + 2CO) and steam reforming of methane (SRM, CH 4 + H 2 O → 3H 2 + CO) yield a H 2 /CO ratio of either 1 (too low) or around 3 (too high), respectively, which imposes supplementary stages (often expensive) if adjustment of the product ratio near 2 is required for the next steps of the process [3][4][5][6]13,14]. Moreover, from a sustainable point of view, the CSDRM reaction presents as additional benefit to consume CH 4 , CO 2 and water as main reactants, these gases being also those present in biogas, a non-fossil fuel resource [3][4][5][6].…”

“…By comparison, conventional dry reforming of methane (DRM, CH 4 + CO 2 → 2H 2 + 2CO) and steam reforming of methane (SRM, CH 4 + H 2 O → 3H 2 + CO) yield a H 2 /CO ratio of either 1 (too low) or around 3 (too high), respectively, which imposes supplementary stages (often expensive) if adjustment of the product ratio near 2 is required for the next steps of the process [3][4][5][6]13,14]. Moreover, from a sustainable point of view, the CSDRM reaction presents as additional benefit to consume CH 4 , CO 2 and water as main reactants, these gases being also those present in biogas, a non-fossil fuel resource [3][4][5][6]. Thus, CSDRM offers a way to produce metgas from renewable energy sources without the need of auxiliary separation and purification procedures.…”

“…The main direction for catalyst development in this field is focused on the use of nickel as active phase, this transition metal being the most attractive candidate for largescale industrial applications due to its high reactivity in DRM and SRM [3][4][5] together with low cost and wide availability compared to noble metals (Ru, Rh, Ir) [16][17][18][19]. However, the stability of supported Ni-based catalysts under the harsh reaction conditions of CSDRM [20][21][22][23] is still an important concern.…”