Jinghu Zhu,Hui Liu,Xueyan Zhou,Zhijun Wang,Liancheng Bing,Dezhi Han,Guangjian Wang,Fang Wang
Cu-based catalysts, modified by gallium addition via the stepwise co-precipitation method, were studied for the liquid phase hydrogenation of hydroxypivalaldehyde (HPA) to neopentyl glycol (NPG). Through physico-chemical techniques, the effects of gallium introduction on the Cu trimetallic catalyst performance and the reaction mechanism of HPA hydrogenation were discussed. The characterization results showed that gallium introduction can influence the dispersion, reduction, and distribution of active Cu species, as well as their reactivity. Herein, the catalyst with 2 wt% gallium addition exhibited excellent catalytic performance with HPA conversion rate and NPG selectivity of 93.5% and 95.5%, at a reaction pressure of 3 MPa, temperature of 110 °C, hydrogen-aldehyde ratio (molar ratio) 10:1, and liquid space-time at a speed of 8.4 h−1. The good performance could be attributed to gallium doping tending to dynamically tune the interaction between the components, increasing Cu dispersion and the distributions of Cu+and Cu0species on the catalyst surfaces.Keywords:HPA hydrogenation;NPG synthesis;Cu-based catalyst;gallium modification;Cu+/Cu0
Xingling Zhao,Jun Xu,Yueying Chu,Guodong Qi,Qiang Wang,Wei Gao,Shenhui Li,Ningdong Feng,Feng Deng
Graphical Methane activation : Different types of Ga-CH 3 species were observed in methane activation on Ga-modified ZSM-5 zeolite, evidencing different pathways for heterolytic cleavage of C−H bond of methane. Two-dimensional solid-state NMR experiments provided detailed information on the location and local environment of the Ga-CH 3 species. Methane activation on Ga-modified ZSM-5 zeolites (Ga/ZSM-5) was studied by solid-state NMR spectroscopy. Two types of Ga species, namely highly dispersed oxides and cationic Ga species, were determined by 71 Ga QCPMG NMR. The activation of methane on Ga/ZSM-5 was explored by using 13 C and 1 H MAS NMR. Four types of Ga-CH 3 species along with Ga-OH groups were observed on Ga/ZSM-5, evidencing different pathways for heterolytic cleavage of C−H bond of methane. Two-dimensional (2D) 1 H- 1 H correlation NMR experiments provide detailed information on the location and local environment of the Ga-CH 3 species by correlating the protons in Ga-CH 3 with those in Ga-OH and other hydroxyls on zeolite. The structures of different Ga-CH 3 species were further determined by 2D 1 H- 13 C heteronuclear correlation NMR experiments, which were supported by theoretical calculations. The activation routes of C−H bond in methane were proposed on Ga/ZSM-5 zeolite.
Yumeng Xia,Zehua Li,Ying Li,Kai Cai,Yunduo Liu,Jing Lv,Shouying Huang,Xinbin Ma
Dimethyl ether (DME) carbonylation is an important reaction for methyl acetate (MA) and ethanol production from syngas. Mordenite (MOR) has been used as an industrial catalyst due to the competitive catalytic properties, especially with extremely high selectivity of MA (>99%). Given the Brønsted acid sites (BAS) in 8-MR are proved the active centers, the properties of BAS are crucial factors that influence the reaction. Until now, most of the researches focus on increasing the number of BAS rather than tuning the acid strength. Here we modified H-MOR by Ga introduction using incipient wetness impregnation. Catalyst evaluation results suggest that Ga species can enhance DME conversion with a maintained MA selectivity. Combining with characterizations and DFT calculation, the textural and acidic properties along with the existing form of Ga species are determined. Further in-situ IR, theoretical and kinetics investigations demonstrated that the enhanced acid strength accelerates the reaction on Ga-modified MOR catalysts. This work inspires us that improving the acid strength is an efficient strategy for Brønsted acid-catalyzed reaction, such as DME carbonylation .
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