Effect of Different Chelating Agents on the Physicochemical Properties of Cu/ZnO Catalysts for Low-temperature Methanol Synthesis from Syngas Containing CO₂

Abstract

Nanostructured Cu/ZnO catalysts were prepared by a simple solid-state method, using cheap metal nitrates as raw materials. Special attention was paid to the influence of different chelating agents such as citric acid, formic acid and oxalic acid on the physicochemical properties of Cu/ZnO catalysts, which were characterized by detailed investigations. CuO crystallite size, oxygen vacancies and surface compositions were clearly affected by chelating agent types, leading to different CuO _ ZnO interactions in the calcined catalysts as well as distinct reducibility. Different chelating agents also had significant effects on specific surface area, metallic Cu 0 surface area, and Cu crystallite size, as well as ZnO (002) plane to ZnO (100) plane ratio (I(002)/I(100)) calculated based on the peak intensity of XRD patterns of the reduced samples, so influencing the catalytic activity for low-temperature methanol synthesis from syngas containing CO2. The structure-activity correlations, particularly the relationships between space time yield (STY) of methanol with Cu 0 surface area and I(002)/I(100) ratio, were evaluated. Cu/ZnO catalyst prepared with oxalic acid showed the highest STY value, which was 2.3 and 5.3 times higher that of the catalysts obtained with citric acid and formic acid, respectively. The excellent catalytic performance was due to its greater Cu 0 surface area, higher specific surface area and smaller Cu crystallite size. Stronger interactions between Cu and ZnO in the reduced samples were also favorable for enhancing catalytic activity for low-temperature methanol synthesis.

Tuning Lattice Strain of Copper Particles in Cu/ZnO/Al2O3 Catalysts for Methanol Steam Reforming

“…The smallest crystallite size is acquired on CuZnAl-OA, and it is plausible that the crystallite size increased with the carbon number of the organic acids. A possible interpretation is that the organic acid of more carbon number will release more heat during the calcination, leading to partial sintering of CuO and ZnO particles . The tendency of the crystallite size is exactly opposite to that of the specific surface area.…”

“…A possible interpretation is that the organic acid of more carbon number will release more heat during the calcination, leading to partial sintering of CuO and ZnO particles. 37 The tendency of the crystallite size is exactly opposite to that of the specific surface area. As displayed in SEM images, the catalyst is composed of numerous aggregations of nanoparticles, and the surface area is derived from the slits among the nanoparticles; accordingly, the smaller crystallite size will generate a larger specific surface area.…”

Alcohol Solvent Assisted Synthesis of Metallic and Metal Oxide Catalysts: As-Prepared Cu/ZnO/Al2O3 Catalysts for Low-Temperature Methanol Synthesis with an Ultrahigh Yield

“…Compared to a conventional BNL homogeneous catalyst, the very weak basicity of Cu-based catalysts is less affected by CO 2 and H 2 O, which would show excellent catalyst stability. In our recent work, low-temperature methanol synthesis is further developed and methanol can be directly obtained without additional separation engineering because methanol itself is used as the catalytic promoter. − …”