Mutual Tailored Bimetallic Rh–Co Supported on La Modified SiO₂ for Direct Ethanol Synthesis from Syngas

Abstract

In this work, Rh–Co/La2O3–SiO2 showed excellent selectivity to ethanol for direct ethanol synthesis from syngas. The best catalyst exhibited 42.8% selectivity to ethanol with CO conversion of 12.3% and in 145 h’ running maintained stable at 553 K, 3 MPa and GHSV of 3900 mL (gcat h)−1. The investigate results indicated that the interaction of cobalt denoting electron to rhodium adjusted the amounts of carbon monoxide adsorbed associatively and dissociatively, and maybe created a new active site pair of Rh0/Coδ+ for generating ethanol. Moreover, the mutually doping effect could dilute Co and Rh atoms in Rh–Co nanoparticles (NPs), which effectively suppressed the formation of C2+H and C3+OH, and thus led to the high ethanol selectivity and good anticoking property assisting with the carbon eliminating effect of La2O3. Owing to the high dispersion of Rh–Co NPs, the catalyst showed good activity and high resistance to sintering.

Co–Ni Alloy Nanoparticles on La-Doped SiO2 for Direct Ethanol Synthesis from Syngas

“…37,39,40 The CO adsorbed associatively on the sites of cobalt or nickel would be hydrogenated to generate methanol, while the CO adsorbed dissociatively would be hydrogenated to generate CH 4 or other hydrocarbons, and the cooperation of the associative adsorption sites with dissociative adsorption sites would produce ethanol. 11,16,37,39,40 As shown in Figure 6a, for the monometallic Ni catalyst, Peak II′ was too small to be detected, and Peak II was attributed to the desorption of CO adsorbed associatively on nickel. For the monometallic Co catalyst, the peak located around 530 °C, considering the high desorption temperature, which should be attributed to the desorption of CO adsorbed dissociatively on metallic Co. With regard to the three bimetallic catalysts, the CO desorption profiles were similar, and both exhibited two desorption peaks corresponding to chemisorbed CO, where Peak II was attributed to the desorption of CO adsorbed associatively on Co δ+ /Co 2 C and Peak II′ was attributed to the desorption of CO adsorbed dissociatively on Ni.…”

“…The BEs of La 3d 5/2 for all the catalysts after reaction showed two peaks at 835.5 to 835.8 and 838.9 to 839.1 eV, which are close to that in La 2 O 2 CO 3 . 28,57 It is known that La 2 O 3 could react with CO 2 to form La 2 O 2 CO 3 during the reaction process, 16,27,58 which has a higher La 3d 5/2 BEs than pure La 2 O 3 . 59 The XPS results indicated that La 2 O 2 CO 3 was the main phase for La species in the used catalysts.…”

“…As stated above, for DES from syngas, the associatively adsorbed CO on positively charged Co or Ni and the dissociatively adsorbed CO on metallic or negatively charged Co or Ni would synergistically catalyze the formation of ethanol. 11,12,16,37 According to the results XPS and CO-TPD, for the Co−Ni alloy catalyst obtained from reducing LaCo 1−x Ni x O 3 /SiO 2 , CO was adsorbed associatively on the sites of Co δ+ /Co 2 C and was adsorbed dissociatively on the sites of metallic Ni; thus, the two forms of adsorbed CO combined to generate ethanol. Meanwhile, the formation of the alloy can reduce the size of the metal NPs and facilitate the mutual dilution between Ni and Co, which is equivalent to reducing the size of each single metal.…”

“…39,40 Three types of active site pairs for ethanol generation were observed in LaRh 1−x Co x O 3 /SiO 2 catalyst researched by Zhong et al, and they were Rh 0 −Rh + , Co 0 −Co δ+ , and Rh 0 −Co δ+ , where CO was dissociatively adsorbed on the sites of metallic Co and Rh, and CO was associatively adsorbed on the sites of positively charged Co and Rh. 16 A series of Co−Ga-based catalysts supported on Al 2 O 3 derived from hydrotalcite were prepared by Ning and An et al, which were superiorly selective for higher alcohol synthesis. They found that in the well-defined Co−Ga particles, electrons of Ga would transfer to its nearby Co sites, resulting in the negatively charged cobalt, which is in charge of CO dissociative adsorption.…”

In‐Situ Electrodeposition of Rhodium nanoparticles Anchored on Reduced Graphene Oxide nanosheets as an Efficient Oxygen Reduction Electrocatalyst

“…To overcome this challenge, considerable efforts have been exerted to stabilize Rh nanostructures against agglomeration by providing suitable support materials with large surface area. Traditional oxides, such as SiO 2 , Al 2 O 3 , and zeolite, or carbon materials such as graphene have been explored as supporting materials for Rh nanostructures.…”