Research progress of catalysts for hydrogenation of carbon dioxide to methanol
The extensive use of fossil fuels not only promotes the development of modern society, but also brings serious environmental problems. In particular, the issue of carbon dioxide emissions has become a global concern. In this context, scientists are exploring a way to reduce greenhouse gas emissions and solve the energy crisis, that is, the technology of synthesizing methanol by hydrogenation of carbon dioxide. This technology can not only effectively utilize carbon dioxide and reduce its negative impact on the environment, but also produce methanol with high added value, which provides a new source for chemical raw materials and clean energy.
As a stable molecule, carbon dioxide (CO2) needs high energy in its transformation process. Hydrogen, as a kind of high-energy substance produced by renewable clean energy, has become the key to realize this transformation. The process of producing methanol by hydrogenation of carbon dioxide not only reduces the emission of greenhouse gases, but also can be widely used in human production and life, showing great research significance and application prospects.
In this process, the performance of the catalyst is very important. It directly affects the conversion rate of carbon dioxide and the yield and selectivity of methanol. Cu-based catalysts, precious metal catalysts and other types of catalysts, including some new catalysts, are the most typical catalytic systems in the hydrogenation of CO2 to methanol. The results show that the activity of the catalyst is not only related to the properties of the metal, but also related to the cocatalyst, carrier type and dispersion.
Cu-based catalysts are widely used in various catalytic reactions because of their high catalytic activity and selectivity, low price and good selectivity. As for the existence of active sites, especially copper in catalytic reaction, there is still great controversy at present, and the problem will become more complicated due to the oxidation of CO2 gas itself. There are several opinions about the active sites of Cu-based catalysts: Cu0, Cu+,Cu δ+and Cu/ZnO interface. The Cu-based catalyst for hydrogenation of CO2 to methanol can not only activate CO2 molecules to transfer their electrons, but also dissociate H2 molecules into H atoms with adsorption.
Precious metals such as platinum, palladium, rhodium, silver and ruthenium are considered as good catalyst materials because of their good low-temperature reducibility and high dispersibility, among which palladium-based catalysts have the most outstanding catalytic performance. The loading forms of noble metal catalysts can be divided into two types: one is to directly load the noble metal active components on the carriers such as SiO2, ZrO2, La2O3, ThO2 and carbon nanotubes (CNF), and the other is to load the noble metal active components on Cu-based catalysts. In addition to these common catalysts, there are some special catalysts such as ZnZrO2 solid solution catalyst prepared by reflux ammonia method.
In addition, the carrier and promoter of the catalyst also have significant influence on its performance. The carrier can not only increase the dispersion, mechanical strength and stability of the catalyst, but also its physical and chemical properties, especially its acidity and alkalinity, are more critical to the catalytic performance. The function of additives also needs systematic research, so as to provide scientific guidance for the selection and modification of additives.
Although the research on hydrogenation of carbon dioxide to methanol is still in the basic stage, with the development of in-situ characterization technology, scientists are expected to deeply understand the structure-activity relationship and catalytic reaction mechanism of catalysts at the molecular and atomic level. This will not only help to optimize the catalyst design, but also promote the technological breakthrough of direct conversion of carbon dioxide hydrogenation into high value-added chemicals such as methanol.
In a word, the technology of hydrogenation of carbon dioxide to methanol shows great potential to solve the dual problems of energy and environment. With the deepening of related research and the gradual maturity of technology, it is expected to achieve more breakthroughs in this field in the future and make important contributions to the sustainable development of human society.
Source:
1. Hu Bo, Wang Jianjie, Xiao Xia, et al. Research progress of catalysts for hydrogenation of carbon dioxide to methanol [J]. Chemical Bulletin, 2024, 87 (06): 685-692.
2. https://mp.weixin.qq.com/s/YYjGlVx_AdKovBFRjcxykA