China News Service, Beijing, October 21 (Reporter Sun Zifa) The carbonylation reaction, known as the "basic skill" of the modern chemical industry, has been developed for more than a hundred years. However, the mainstream methods in industry still rely on modifications with precious metals such as rhodium and iridium and organic ligands. There are challenges such as complex systems, cumbersome processes, high costs, and difficulty in separating catalysts and products. How to solve these problems has attracted widespread attention in academia and industry.
News from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences (Dalian Institute of Chemical Physics) said that after successfully applying molecular sieves to catalyze the carbonylation reaction of dimethyl ether and realizing large-scale industrial production of anhydrous ethanol in 2017, the team of Academician Liu Zhongmin of the Institute of Chemical Physics, Chinese Academy of Sciences (Dalian Institute of Chemical Physics), has recently found a new approach with collaborators and made innovative breakthroughs in the field of molecular sieve catalysis, promoting the carbonylation reaction to "grow new branches from a century-old tree."
This research and development result does not require metals or ligands, allowing the molecular sieve to complete the catalysis "alone", thus realizing two new reactions of the molecular sieve catalytic carbonylation of propylene to isobutyric acid and the carbonylation of ethylene to propionic acid with the participation of water. At the same time, the research team also discovered basic rules - where the "gate" of the molecular sieve channel is and how big the "gate" is will affect the catalytic reaction.
This important catalytic research and development paper in the chemical industry was published online in the international academic journal Nature on the night of October 21st, Beijing time.
This study provides a solid underlying logical support for the subsequent construction of a universal framework for molecular sieve catalytic carbonylation that can reverse predict and rationally design new processes.
"This research itself is also a vivid practice of organized basic research. The questions come from practice and the answers go to industry." Academician Liu Zhongmin said that along this chain, the research team will push the reactions in the laboratory to process amplification, so that molecular sieve carbonylation can truly enter the factory, opening up a broader space for the efficient and green preparation of various high-end chemicals and new materials such as oxygenated compounds in the future.
According to the research team, from acetic acid, plasticizer alcohol, to spices and pharmaceutical intermediates, every industrial chain is built on the carbonylation reaction. Simply put, the carbonylation reaction is the process of "grafting" carbon monoxide onto olefin molecules to produce acids, esters, and alcohols.
Molecular sieve is a porous, ordered crystal material with pore size accurate to the molecular level. It has precise pore screening capabilities and can "block" molecules of inappropriate shape and size. Therefore, it plays an irreplaceable role in petroleum refining, gas separation and green chemical industry.
The significance of the research team's successful application of molecular sieves in catalyzing the carbonylation reaction of dimethyl ether 9 years ago not only provides a green route for ethanol production, but also shows that molecular sieves not only play the role of "sieve elements" in chemical equipment, but can also be an excellent catalyst in themselves.
Inspired by this industrialization path, the research team began to think about whether molecular sieves could be used to catalyze more carbonylation reactions, and whether a general theoretical framework could be refined from specific reactions.
After nearly three years of research, the research team cleverly used the confinement effect of molecular sieves to successfully realize two new reactions catalyzed by molecular sieves: the carbonylation of propylene with the participation of water to generate isobutyric acid and the carbonylation of ethylene to generate propionic acid. The reaction process does not require metals or organic ligands.
The research team found that the confinement of molecular sieves brings multiple "benefits": while it promotes the smooth progress of olefin carbonylation, it also perfectly suppresses side reactions of olefin polymerization; as a solid catalyst, molecular sieves and products are naturally separated into two phases, and separation and recovery are much simpler than liquid phase systems, which just makes up for the shortcomings of traditional route products that are difficult to separate.
What is more noteworthy is that the research team discovered basic rules from two new reactions: choosing different pore-limited sites can catalyze completely different reaction processes: the active sites near the pore of the ten-membered ring can catalyze propylene, while the active sites of the eight-membered ring can catalyze ethylene.
The research team stated that this precise active site matching mechanism not only achieves specific recognition of substrate molecules like a "precision switch", breaking the inherent thinking of traditional catalysts relying on metal or ligand regulation, but also proves that the pore microenvironment itself can be used as the "core code" to control the reaction path. The selective catalysis of the reaction can no longer only be "touched" by repeated preparations, but can be "customized" in advance by the geometric structure of the pore.
