Identifying Catalyst Property Descriptors for CO₂ Hydrogenation to Methanol via Big-Data Analysis

Abstract

Carbon dioxide (CO 2 ) capture and valorization have great potential for mitigating emissions of this greenhouse gas and accordingly for preserving the environment for future generations. In this regard, hydrogenation of CO 2 to methanol is highly attractive because this product is a valuable energy carrier and can also be used for production of various everyday commodities. Although many research papers on this topic have been published in the past decades, there is still a lack of fundamentals relevant to control catalyst performance. Herein, we demonstrate how statistically validated Big-Data analysis of available literature data identified hidden descriptors that can be applied for purposeful catalyst development and for identification of optimal reaction conditions. In view of catalyst development, the kinds of structural promoters or supports for bulk or supported Cu-, In-, or Pd-based catalysts are the most important descriptors for methanol selectivity, with Ce and Zr being the most efficient promoters. The type and the parameters of the preparation methods as well as the kind of active component precursors are also important in this regard. To validate the conclusion about the structural promoter, a series of supported CuZn-containing catalysts were prepared. The best-performing CuZn/CeO 2 catalyst outperformed the state-of-the-art CuZn-based catalysts tested at a total pressure of up to 30 bar using a feed with the ratio of H 2 /CO 2 of 3. In addition to the catalyst composition and the preparation method, our analysis suggests that the most often used Cu-based catalysts lose their methanol selectivity due to the decomposition of this product to CO. Our control experiments with the developed CuZn-based catalysts proved that this undesired reaction can be hindered when the catalyst support contains Ce or through increasing H 2 partial pressure. This knowledge is important for further catalyst development.

CO2 Hydrogenation to CH3OH over Cu‐Based Catalysts: Primary and Side Reactions

“…Under CO 2 hydrogenation conditions, CH 3 OH decomposition reaction(s) should be considered. This conclusion is supported by the results of very recent mathematical analysis of literature data on CO 2 hydrogenation to CH 3 OH [31] . The selectivity to this product formed over various Cu‐based catalysts at a certain reaction temperature and constant total pressure was shown to decrease with rising CO 2 conversion because of consecutive CH 3 OH transformations to CO.…”

“…This conclusion is supported by the results of very recent mathematical analysis of literature data on CO 2 hydrogenation to CH 3 OH. [31] The selectivity to this product formed over various Cu-based catalysts at a certain reaction temperature and constant total pressure was shown to decrease with rising CO 2 conversion because of consecutive CH 3 OH [13] Reproduced from Ref. [13] Copyright (2020), with the permission from American Chemical Society.…”

“…The selectivity to CH 3 OH over different catalysts should be compared at close/same degrees of CO 2 conversion achieved at the same reaction temperature, feed composition and total pressure. [23,31] iii. If the catalysts were tested under different reaction conditions, their comparison should be made at close/same ratio of measured CO 2 conversion to the equilibrium one characteristic for each of these conditions.…”

“…Our recent big-data analysis and experimental results revealed that CH 3 OH decomposition in the course of CO 2 hydrogenation can be hindered by increasing the ratio of H 2 /CO 2 and/or using CeO 2 as support or promoter for Cu-based catalysts. [31] The SRM reaction in academic studies is often tested at 1 bar in the temperature range between 200 and 300 °C. In the industry, this reaction operates at higher pressures (up to 20 bar) to get higher H 2 productivity, although the equilibrium conversion becomes lower according to the Le Chatelier's principle.…”

“…They can be realized when CO 2 conversion is below 10 % of the equilibrium conversion but not simply below 10 % conversion. Since the CO 2 hydrogenation is a reversible reaction, 10 % conversion under certain reaction conditions can be the equilibrium conversion. The selectivity to CH 3 OH over different catalysts should be compared at close/same degrees of CO 2 conversion achieved at the same reaction temperature, feed composition and total pressure [23,31] If the catalysts were tested under different reaction conditions, their comparison should be made at close/same ratio of measured CO 2 conversion to the equilibrium one characteristic for each of these conditions.…”