催化剂吸附性能表征研究进展

重点介绍了傅里叶红外光谱法、程序升温技术、微量热法技术、核磁共振技术、色谱法、量子化学从头计算法等研究催化剂吸附性能常用的方法,对于阐明反应物分子与催化剂表面的相互作用、催化作用的原理以及催化反应的机理具有十分重要的意义。

Study on catalyst for pyridine synthesis

The synthesis of pyridine from aldehydes and ammonia was performed over ZSM-5 catalyst. The catalytic activity in reaction was correlated with the acidity of the zeolite catalysts. A few of ZSM-5 (m(SiO2)/m(Al2O3)=120) were prepared and modified with Co2+, Fe3+. The surface acidity was determined by Py-IR technique. It was found that CoZSM-5 and FeZSM-5 have fewer Lewis acid sites than HZSM-5. The decrease of Lewis acid sites leads to decreasing the ability of NH3 adsorption, this phenomenon insures that there are adequate acid sites discovering and reacting with aldehydes. It is advantageous to the reaction. By using a CoZSM-5 catalyst, the yields of pyridine base can reach 78%. The study provides a theoretical base for preparing high activity and high selective catalyst for pyridine synthesis.

Study on Chemisorption and Desorption of Hydrogen and Nitrogen on Ru-based Ammonia Synthesis Catalyst

The effects of promoters K, Ba, Sm on the chemisorption and desorption of hydrogen and nitrogen, dispersion of metallic Ru. and catalytic activity of active carbon (AC) supported ruthenium catalyst for ammonia synthesis have been studied by means of pulse chromatography, temperature-programmed desorption, and activity test. Promoters K, Ba and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly, and particularly, potassium exhibited the best promotion on the activity because of the strong electronic donation to metallic Ru. Much higher activity can be obtained for Ru/AC catalyst with binary or triple promoters. The activity of Ru/AC catalyst is dependent on the adsorption of hydrogen and nitrogen. The high activity of catalyst could be ascribed to strong dissociation of nitrogen on the catalyst surface. Strong adsorption of hydrogen would inhibit the adsorption of nitrogen, resulted in decrease of the catalytic activity. Ru/AC catalyst promoted by Sm2O3 shows the best dispersion of metallic Ru, since the partly reduced SmOx on the surface modifies the morphology of active sites and favors the dispersion of metallic Ru. The activity of Ru/AC catalysts is in accordance to the corresponding amount of nitrogen chemisorption and the desorption activation energy of nitrogen. The desorption activation energy for nitrogen decreases in the order of Ru>Ru-Ba>Ru-Sm>Ru-Ba-Sm>Ru-K>Ru-K-Sm>Ru-K-Ba>Ru-K-Ba-Sm, just opposite to the order of catalytic activity, suggesting that the ammonia synthesis over Ru-based catalyst is controlled by the step of dissociation of nitrogen.

Conversion of bimetallic MOF to Ru-doped Cu electrocatalysts for efficient hydrogen evolution in alkaline media

The rational design and construction of inexpensive and highly active electrocatalysts for hydrogen evolution reaction(HER)is of great importance for water splitting.Herein,we develop a facile approach for preparation of porous carbon-confined Ru-doped Cu nanoparticles(denoted as Ru-Cu@C)by direct pyrolysis of the Ru-exchanged Cu-BTC metal–organic framework.When served as the electrocatalyst for HER,strikingly,the obtained Ru-Cu@C catalyst exhibits an ultralow overpotential(only 20 mV at 10 mA cm^(-2))with a small Tafel slope of 37 m V dec^(-1)in alkaline electrolyte.The excellent performance is comparable or even superior to that of commercial Pt/C catalyst.Density functional theory(DFT)calculations confirm that introducing Ru atoms into Cu nanocrystals can significantly alter the desorption of H_(2) to achieve a close-to-zero hydrogen adsorption energy and thereby boost the HER process.This strategy gives a fresh impetus to explore low-cost and high-performance catalysts for HER in alkaline media.

Preparation of a mesoporous sorption complex catalyst and its evaluation in reactive sorption enhanced reforming

A mesoporous sorption complex catalyst was prepared by pore-forming modification and evaluated by the COz reactive sorption enhanced reforming （ReSER） process, which is used to produce hydrogen from methane. Three samples of polyethylene glycol （PEG） with molecular weights between 2000 and 20 000 were added as templates into a mixed slurry to create catalysts with different pore properties by further formation and calcination. The pore characteristics determined by Brunauer- Emmett-Teller （BET） analysis showed that one of the mesoporous catalysts, named M-NiAICa-6000, had a pore size of 9.2 nm and a surface area of 70.52 m2/g and the CO2 sorption capacity of this catalyst was 44% higher than that of the catalyst without the PEG 6000 modification. The catalyst was evaluated in the ReSER process in a fixed-bed reactor system at 0.1 MPa and 600 C with an H20/CH4 molar ratio of 4. An H2 concentration of 94.2% and a CH4 conversion of 86.0% were obtained at a carbon space velocity of 1700 h 1 while CO2 was hardly detected.