Reaction Path Analysis of CO2 Reduction to Methanol through Multisite Microkinetic Modelling over Cu/ZnO/Al2O3 Catalysts

Abstract

The changing hierarchical structure of the applied heterogeneous Cu/ZnO/Al 2 O 3 material during methanol synthesis reactions hinders an efficient engineered process condition optimization, causing sub-optimal functional performance. A robust literature comparison is conducted to determine that activity is tightly coupled with Cu-Zn interactions. In order to investigate this physical behaviour further, characteristic experimental data is acquired through the catalytic reactor tests with an activated commercial catalyst, aged at different input measurements, monitored and characterized by the Brunauer-Emmett-Teller (BET), Xray diffraction (XRD), scanning transmission electron microscopy (STEM) with energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), H 2 transient adsorption (TA) and N 2 O pulsed surface oxidation (PSO) methodologies. It is shown that apparent rate law, exponents and activation energies do not vary significantly by increasing the ZnO X coverage from 7% to 23%, while not all of ZnO X over-layer is catalytically active.For Cu/ZnO/Al 2 O 3 with ZnO X over 7%, a highly-dispersed Al 2 O 3 decreases the measured intrinsic kinetics of the Cu-Zn site, implying a steric hindrance effect. Finally, building on unveiled chemical relations, a thorough multisite system micro-kinetic model, based on systematic contribution analysis, mechanisms and quantitative density functional theory (DFT) constants is developed. Values were optimized using the sequential screening results for an industrially relevant application (the temperatures of 160-260 °C, 50 bar pressure, 12,000-200,000 h -1 gas hourly space velocity (GHSV) flow and relative feed compositions).Designed mathematical relationships can therefore be utilised to accurately predict the turnover, selectivity and stability/deactivation in correspondence to ZnO X over Cu.

Century of Technology Trends in Methanol Synthesis: Any Need for Kinetics Refitting?

“…Many kinetic studies have been conducted to find the best kinetic rates for the model, but research is still ongoing for a definitive solution. Microkinetic models, which also include adsorption interactions, can use as many as 50 reactions to describe the process, as shown in several recent works. ,, The kinetic models industrially used for optimization and design of chemical reactors consider only the three reactions mentioned in reactions – or, in some cases, only two of them. In the literature, different models have been proposed; a comprehensive summary of them is reported and has been listed in the review by Bozzano and Manenti .…”

Sulphur poisoning, water vapour and nitrogen dilution effects on copper-based catalyst dynamics, stability and deactivation during CO2 reduction reactions to methanol

“…The effectiveness factor (ratio of the average rate of reaction in particle to the rate on the surface of the particle) is below 1 21 and can range from 0.4 to 1 for 4.2 mm particles. 22 In our previous work, 23 we did not observe any activity change by varying the particle size between 0.1 mm and 0.55 mm. Therefore, deactivation in H 2 S was described using simple linear (0 th 3 Results and discussion…”

“…21) and can range from 0.4 to 1 for 4.2 mm particles. 22 In our previous work, 23 we did not observe any activity change by varying the particle size between 0.1 mm and 0.55 mm. Therefore, deactivation in H 2 S was described using a simple linear (0th order) model based on the active site deactivation by surface sulphide formation.…”

“…An increase of specific activity was observed by long-term H 2 O-promoted Al 2 O 3 phase removal from the copper surface in the case of CuZnAl catalyst . 26 During the operation at 50 bar, the mass flow controller of H 2 /CO 2 /N 2 mixture temporarily malfunctioned (for 20 h) resulting in an increased H 2 /CO 2 ratio during that period. To elucidate the effect of operating pressure on the catalyst activity, we developed a model based on Equation 1, which takes into account isothermal ageing as well as hightemperature jumps.…”

CO2 Hydrogenation to Olefin-Rich Hydrocarbons Over Fe-Cu Bimetallic Catalysts: An Investigation of Fe-Cu Interaction and Surface Species

“…However, such an energy demand could be much reduced and CO 2 conversion would become thermodynamically easier when one or more molecules with high Gibbs free energy such as hydrogen (ΔG ° 0 kJ/mol) could co-react with CO 2 (Song, 2006). The synthesis of oxygenates (Jiang et al, 2015;Sun et al, 2015;Prašnikar et al, 2019;Prašnikar et al, 2021) [such as methanol over Cu-based catalysts (Huš et al, 2017;Prašnikar et al, 2019;Prašnikar et al, 2021)] and hydrocarbons (Willauer et al, 2013;Satthawong et al, 2015;Zhang et al, 2015) from CO 2 and H 2 , where CO 2 is captured from flue gas and H 2 is produced using renewable energy sources (e.g., such as solar or wind) (Pontzen et al, 2011), is one promising approach for sustainable production of chemicals and fuels. Among them, C 2 -C 4 light olefins are primary building blocks for various chemicals and polymers.…”