Peipei Ai

Active and regioselective rhodium catalyst supported on reduced graphene oxide for 1-hexene hydroformylation

Alkene hydroformylation with syngas (CO + H2) to produce aldehydes is one of the most important chemical reactions. However, designing heterogeneous catalysts to realize comparable performance with mature homogeneous catalysts is challenging. In this report, a reduced graphene oxide (RGO) supported rhodium nanoparticle (Rh/RGO) catalyst was successfully prepared via a one-pot liquid-phase reduction method and first applied in 1-hexene hydroformylation. 1-Hexene hydroformylation reaction under different reaction conditions with this Rh/RGO catalyst was investigated in detail. Low reaction temperature and short reaction time effectively enhanced the n/i (normal to iso) ratio of heptanal in the products. The catalytic performance of the Rh/RGO catalyst was also compared with those of Rh supported on other carbon materials, including activated carbon and carbon nanotubes (Rh/AC and Rh/CNTs). The results showed that the Rh/RGO catalyst exhibited the highest 1-hexene conversion and the largest n/i ratio of 4.0 among the tested catalysts. The special 2D nanosheet structure of the Rh/RGO catalyst, rather than the 3D porous and 1D nanotube structures of Rh/AC and Rh/CNTs, respectively, principally contributed to its excellent catalytic performance. These findings disclosed that reduced graphene oxide could be a promising catalyst support for designing heterogeneous hydroformylation catalysts.

Building premium secondary reaction field with a miniaturized capsule catalyst to realize efficient synthesis of a liquid fuel directly from syngas

Herein, we report a new miniaturized capsule catalyst, Co/SiO2-M-Z6ET, which is different from routine capsule catalysts, has a smaller core size and has stronger Bronsted acidity. The premium secondary reaction field and the significant capsule size effect on Co/SiO2-M-Z6ET were demonstrated using a model compound of n-hexadecane (n-C16). Furthermore, a striking gasoline selectivity of 72% was facilely obtained from FT synthesis.

Designing auto-reduced Cu@CNTs catalysts to realize the precisely selective hydrogenation of dimethyl oxalate

An autoreduced catalyst that comprised Cu nanoparticles encapsulated inside the nanochannels of carbon nanotubes (Cu@CNTs) was designed and prepared. As a result of the interaction of Cu species with the electron‐deficient interior surface of the CNTs, calcination could realize the autoreduction of copper oxide directly with CNTs as the reductant. In the hydrogenation of dimethyl oxalate (DMO), the autoreduced Cu@CNTs catalyst, which did not need to be prereduced, exhibited an excellent catalytic activity, high target product selectivity, and high catalytic efficiency. Furthermore, the effect of the calcination temperature on the autoreduction degree of Cu@CNTs and the product selectivity in DMO hydrogenation were investigated in detail. The results showed that the autoreduction degree could be tuned easily by changing the calcination temperature, and the highest selectivity of ethanol could be obtained over the catalyst calcined at 500 °C. The findings obtained will inspire the development of other autoreduced catalysts, the reduction degree and catalytic performance of which can be tuned as desired.

Synergistic Effect of a Boron-Doped Carbon-Nanotube-Supported Cu Catalyst for Selective Hydrogenation of Dimethyl Oxalate to Ethanol

Heteroatom doping is a promising approach to improve the properties of carbon materials for customized applications. Herein, a series of Cu catalysts supported on boron-doped carbon nanotubes (Cu/xB-CNTs) were prepared for the hydrogenation of dimethyl oxalate (DMO) to ethanol. The structure and chemical properties of boron-doped catalysts were characterized by XRD, TEM, N2 O pulse adsorption, CO chemisorption, H2 temperature-programmed reduction, and NH3 temperature-programmed desorption, which revealed that doping boron into CNT supports improved the Cu dispersion, strengthened the interaction of Cu species with the CNT support, introduced more surface acid sites, and increased the surface area of Cu0 and especially Cu+ sites. Consequently, the catalytic activity and stability of the catalysts were greatly enhanced by boron doping. 100 % DMO conversion and 78.1 % ethanol selectivity could be achieved over the Cu/1B-CNTs catalyst, the ethanol selectivity of which was almost 1.7 times higher than that of the catalyst without boron doping. These results suggest that doping CNTs with boron is an efficient approach to improve the catalytic performance of CNT-based catalysts for hydrogenation of DMO. The boron-doped CNT-based catalyst with improved ethanol selectivity and catalytic stability will be helpful in the development of efficient Cu catalysts supported on non-silica materials for selective hydrogenation of DMO to ethanol.

Direct fabrication of catalytically active FexC sites by sol–gel autocombustion for preparing Fischer–Tropsch synthesis catalysts without reduction

Fe-based Fischer–Tropsch synthesis (FTS) catalysts, promoted by copper and potassium, were directly prepared through a novel modified sol–gel autocombustion without further reduction. It was disclosed that the citric acid contents controlled the reduction/carburization of the catalyst, and the performance of FTS reaction was investigated. The molar ratio of citric acid to nitrates (denoted as CA/N) played a noteworthy role in the phase change of the Fe active sites and catalytic performances of the catalysts. Adding CA not only considerably improved the Fe reduction/carburization during the preparation but also the FTS catalytic performance even without a reduction process. Enhancement of the CA/N molar ratio resulted in the increase of the reducibility of catalysts. However, the FTS performance increased first and then decreased because an unnecessary reductant could lead to accumulation of the carbonic residual on the catalyst surface and decreases the catalyst performance for FTS. The FeCuK catalysts prepared using the sol–gel autocombustion method with CA as a reductant could achieve a high FTS performance without further reduction; therefore, this method could be widely applied in designing other metallic nanoparticle catalysts.