In industrial production, methanol (CH3OH), carbon atoms are usually derived from methane (CH4) and are mainly derived from oil, natural gas, and shale deposits. A new strategy for preparing methanol from formic acid (HCOOH), which in turn is derived from CO2, was proposed by the team at NIMBE/LCMCE. The process uses disproportionation* of silylated formate (HCOO-Si-R). -3) is a methoxysilane (CH3-O-Si-R type 3), a reaction catalyzed by a ruthenium complex. Methanol is then obtained by simple hydrolysis. Therefore, a methanol aqueous solution (> 1 ml) is obtained with high efficiency (>70%). In addition, it has been shown that the siliconization by-products of the reaction can be recovered with inexpensive and readily available reagents. This makes the process sustainable and environmentally friendly.
The demands of the world's population growth, the depletion of carbon-based fossil fuels and their contribution to global warming require a paradigm shift in the energy and chemical sectors: the goal is to close the cycle of basic raw materials (carbon, silicon, etc.) by using renewable materials as a source and reserve of raw materials. Due to its highly oxidizing nature, the conversion of carbon emissions (CO2 or biomass waste) into chemicals or fuels requires the development of efficient reduction methods to form energy-rich C-H bonds, such as those found in fossil hydrocarbons.
The NIMBE/LCMCE team has just demonstrated a process for producing methanol, an important precursor to industrial chemicals (formaldehyde, acetic acid, or light olefins) and a promising molecule for energy storage applications, with materials that help recycle CO2 as well as waste from the silicon industry. In the spirit of sustainable development, the research work aims to obtain a process in which the undesirable by-products of the reaction are also easily recycled.
The LCMCE team at UMR NIMBE proposed the first process to efficiently catalyze the disproportionation* of formic acid to methanol[1]; Formic acid can be produced by electroreduction of CO2 or from biomass. A highly efficient catalyst, the Ruthenium(II) complex, contains 50% methanol solution in THF, achieving high yields. However, this disproportionation reaction competes with a dehydrogenation reaction with a thermodynamic equilibrium close to 33 and 36 KJmol, respectively-1 formic acid per mole).
Different methanol production routes:
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It is carried out by electroreduction and hydrogenation at high temperature (~850°C) and pressure (1 to 2MPa).
Industrial processes.
- Formic acid disproportionation [1]
- Formate silane disproportionation [2]
To overcome this inherent limitation, the team proposed a new alternative method using silanized formate, i.e., waste produced using siloxanes. The process includes a high yield of HCOO-SiR silylated formate disproportionation3 in methoxysilane CH3-O-SiR3 and CO2, followed by the release of CH3 hydrolysis without OH. Formate silane disproportionation of various ruthenium-based catalysts has been tested, with yields of more than 75% for this step. By a separate reaction, it was also shown that the resulting silica-containing by-products were recovered by reaction with formic acid (Figure 2), thereby closing the Si cycle and thus regaining the silylated formate.
Closure and reaction efficiency of carbon and silicon rings:
a) HMDSO (or Hexamethyldisiloxane:O[Si(CH3)3]2) silylated 2b formate: HCOOSi(CH3)3. (In the diagram, HMDSO is represented in an extended way: I3SiOSiMe (Theosimi Hotel)3, call me methylCH part 3)
(b) Evaluation of the entire methanol production process by formatic acid silanization, disproportionation and hydrolysis. The yield in parentheses refers to the situation where the product is not separated. [a] Total yield of products separated by disproportionation and hydrolysis.
These results suggest that the substitution of protons on formic acid by formyl groups shorts the dehydrogenation of formic acid and provides an alternative disproportionation pathway for the production of high-yielding, globally redox-neutral, and easy-to-manipulate methanol. As a result, this chemical reaction with silicon-based gearboxes helps open up a new renewable avenue for the recovery of silanized formate to produce methanol. Compiled by Chen Jiaoyun