Comparative Technical, Economic, and Environmental Analysis of Different Cyanamide Production Processes Optimized through Heat Integration Design

CO2 conversion to aromatics with high selectivity has great significance for improving the environment and realizing the resource utilization of CO2. However, the chemical inertness of CO2 and the high energy barrier to generate aromatics result in difficulties in catalysts design. Here, we report a tandem catalyst combining indium-promoted composite metal oxides In2O3-ZnZrOx with hierarchical nanosized ZSM-5 modified by controllable alkali desilication (NZ5-DS) for efficient conversion of CO2 to aromatics. Indium species were highly dispersed on the surface of ZnZrOx. DFT calculation results demonstrated that the adsorption and activation ability of CO2 on more abundant oxygen vacancy of indium-modified ZnZrOx was enhanced, as well as the diffusion properties of products in the hierarchical zeolite channels were significantly improved, which promoted conversion of CO2 to aromatics on the yIn(2)O(3)-ZnZrOx/NZ5-DS tandem catalysts. An excellent catalytic performance was obtained over 10In(2)O(3)-ZnZrOx/NZ5-DS with the closest proximity of metal sites and acid sites. A high aromatics selectivity of 92.1% was reached at a CO2 conversion of 22.4%, and the selectivity for tetramethylbenzenes was as high as 66.3%. The selectivity of undesirable CO was reduced to 11.0% due to inhibition of reverse water gas shift (RWGS) reaction. This catalyst system has potential applications in the conversion of CO2 to produce tetramethylbenzenes.