- Theme 1: Development of α-olefin polymerization catalyst
For the purpose of producing polymeric industrial materials from α-olefins like ethylene and propylene, we have developed heterogeneous catalysts that can be applied to gas-phase polymerization processes, which has a low environmental impact.
- Metal complex catalyst immobilized into clay layers
Late transition metal complexes are known as catalysts that enable α-olefin polymerization of various molecular weights by tuning the substituents on the catalyst backbone structure.
Recently, we developed novel heterogeneous catalyst precursors immobilizing late transition metal complexes in clay mineral interlayers, which were prepared from a cation-exchange clay mineral (host material) and ligand material (guest material). These procatalysts were readily assembled by intercalation of the guest into the host interlayers and subsequent coordination of the guest with the interlayer metal cations.
These catalysts exhibited more appropriate handling property and process suitability compared with conventional organometallic complex catalysts that are unstable in air.
- Theme 2: Development of dehydrogenation process and catalyst for saturated hydrocarbons
Shale gas is an inexpensive natural gas that has been mined in recent years, and it attracts attention as a next-generation fuel for power generation. Our group has focused on using saturated hydrocarbons contained in shale gas as raw materials for olefin production, and researched dehydrogenation process and catalysts for efficient production of olefins such as ethylene, propylene, and butene.
- Butadiene production via two-step dehydrogenation reaction
1,3-Butadiene is an essential raw materiall for chemical products such as synthetic rubber, resins, and automobile parts. It was conventionally produced from the C4 fraction, whici is a by-product of ethylene production by naphtha cracking. However, naphtha-derived ethylene production is expected to scale down because cheaper shale gas containing ethylene has been produced. It is highly required to establish a new supply process of 1,3-butadiene.
We have focused on the two-step dehydrogenation reaction starting from n-butane as a new production process for 1,3-butadiene. With the goal of industrialization, we are working on developing a high-performance dehydrogenation catalyst with excellent stability and selectivity.
- Theme 3: Catalyst development for chemical utilization of natural gas
Until now, mankind has made various chemical products using petroleum resources as raw materials to enrich their lives. However, there is a concern that oil will be depleted, so a chemical process that does not rely on oil alone is required. Natural gas, which is a fossil resource comparable to oil, is mostly used as fuel (city gas, thermal power generation, etc.), and its use in the chemical industry is limited. This is because methane (CH4), which is the main component of natural gas, is a stable molecule with a strong CH bond, so it is difficult to manufacture the basic raw materials (lower olefins and aromatics) of the chemical industry from methane.
In recent years, the shale revolution has led to a rapid increase in the amount of recoverable natural gas resources, and there is growing interest in the chemical conversion of natural gas. The key to the highly difficult chemical conversion of methane is the development of highly functional catalysts, which are being actively researched all over the world. We have been studying catalysts that activate the CH bond of methane. Based on this knowledge, we are proceeding with the design and synthesis of solid catalysts that convert methane into useful substances (ethane, ethylene, benzene, etc.).
- Development of methane coupling catalyst
We have discovered that silicon alloys act as catalysts for synthesizing C2 hydrocarbons (ethane, ethylene) and hydrogen from methane. Since this alloy catalyst has an extremely low C-C bond dissociation ability, it activates and couples only methane molecules without decomposing the generated C2 hydrocarbons.
Even under conditions where stable methane does not react at all, molecules that are more reactive than methane dissociate with thermal energy and generate radical species. We have found that when methane and a different molecule coexist, methane is activated by radicals generated from the different molecule, and methyl radicals are generated from methane. We have discovered that this methane-derived methyl radical can be converted into useful hydrocarbons.
- Theme 4: Design of electrode catalysts that enable material conversion by electric power
Most chemical industries today use the heat of combustion of fossil resources to convert materials. On the other hand, the energy that drives the chemical reaction is not limited to heat, but electric power is also a strong candidate. Large-scale supply of clean electricity is expected if the utilization of renewable energy such as solar power and wind power advances. In such a society, the rise of the chemical industry, which uses electricity as an energy source, is expected.
Therefore, we are advancing the development of the substance conversion process by electrochemical reaction. Although CO2 is always generated by burning fossil resources, electricity derived from renewable energy is a clean and environmentally friendly chemical process.
- Synthesis of methyl formate by electrolytic oxidation of methanol
Methyl formate is useful as a raw material for formamide. Methyl formate is produced by gas phase carbonylation of methanol, but deactivation of the catalyst is a problem. We have developed a process that allows the constant synthesis of methyl formate by the electrochemical oxidation of methanol. By devising the catalyst and electrolysis conditions, methyl formate is generated at high selectivity and at high speed even under mild reaction conditions at room temperature and pressure.
- Theme 5: Synthesis and development of nano-oxide material by precursor integration method
We are developing a new method for synthesizing oxide nanostructures, which we named the “precursor integration method”. The precursor integration method is a simple liquid phase method that does not require special equipment or harsh synthesis conditions. The precursor can be uniformly accumulated on the surface of the nanocarbon simply by dropping a solution of the oxide precursor onto the nanocarbon powder and drying it. When nanocarbon is burned and removed by heat treatment, oxide nanolayers are formed. There are various kinds of oxides that can be synthesized by the precursor integration method (SiO2, Al2O3, ZrO2, TiO2, Co2O3, NiO, Fe2O3, perovskite, ferrite, etc.). We aim to deepen the precursor integration method and make it one of the options for oxide nanomaterial synthesis method.
- Synthesis of Perovskite Nanoparticles by Precursor Assembly Method and Catalytic Utilization
Perovskite oxide (ABO3) is an attractive material that can induce various physical property changes by controlling structural strain. However, perovskite-type oxides contain multiple metal cations in their structure, so their synthesis methods are limited. “Mixing and baking (solid phase method)” is a simple and classic synthetic method, but it requires high temperature and the surface area is extremely low, so it is not suitable for catalyst use. Therefore, some soft chemical low-temperature synthesis methods have been proposed there. In low temperature soft chemical synthesis, it is important to "mix different metal cations at the molecular level in advance". We have found that high-surface-area perovskite nanomaterials can be synthesized at low temperature by performing "molecular level mixing of precursors" using the carbon surface as a synthesis site by the precursor integration method. Furthermore, it was revealed that LaCoO3 nanoparticles are extremely active in the anodic reaction of water electrolysis.
- Effect of carbon surface functional groups on silica nanolayer synthesis
Until now, silicon tetrachloride (SiCl4) has been used as a precursor when synthesizing silica nanolayers by the precursor integration method. This is because SiCl4 is easily hydrolyzed and has the property of rapidly forming a silica layer by the progress of hydrolysis at the same time as precursor accumulation. However, SiCl4 is a substance that requires careful handling, such as generating hydrochloric acid during decomposition. Therefore, we tried to form a silica nanolayer using tetraethyl orthosilicate (TEOS), which is the most representative silicon precursor. It was clarified that the introduction of a functional group on the carbon surface promotes the hydrolysis of TEOS on the carbon surface and that a silica nanolayer can be synthesized.
- Theme 6: Development of oxidative desulfurization process of diesel fuel (Joint research theme with Al-Farabi Kazakh National University)
In recent years, air pollution caused by sulfur compounds (SOx) contained in the exhaust gas of diesel engine vehicles has been attracting attention as one of the serious environmental problems in Asian countries. In collaboration with the Kazakh National University, we are studying the desulfurization process and desulfurization catalyst for the sulfur component, which is a source of harmful substances, mainly SOx.
The mainstream desulfurization process for diesel fuel is the hydrodesulfurization process. The hydrodesulfurization reaction is carried out in the presence of hydrogen using a catalyst to carry out hydrodesulfurization and desulfurization, and removes sulfur in the form of hydrogen sulfide from the sulfur compound, leaving the carbon skeleton as it is. In this laboratory, we are conducting research on desulfurization catalysts, focusing on oxidative desulfurization reaction, with the aim of developing a desulfurization process that can be performed easily under milder conditions.