Statistical Analysis of Past Catalytic Data on Oxidative Methane Coupling for New Insights into the Composition of High‐Performance Catalysts

Abstract

A database consisting of 1870 data sets on catalyst compositions and their performances in the oxidative coupling of methane was compiled. For this goal, about 1000 full-text references from the last 30 years have been analyzed and about 420 of them, which contained all the necessary information, were selected for the data extraction. The accumulated data were subject to statistical analysis: analysis of variance, correlation analysis, and decision tree. On the basis of the results, 18 catalytic key elements were selected from originally 68 elements. All oxides of the selected elements, which positively affect the selectivity to C2 products, show strong basicity. Analysis of binary and ternary interactions between the selected key elements shows that high-performance catalysts are mainly based on Mg and La oxides. Alkali (Cs, Na) and alkalineearth (Sr, Ba) metals used as dopants increase the selectivity of the host oxides, whereas dopants such as Mn, W, and the Cl anion have positive effects on the catalyst activity. The maximal C2 selectivities for the proposed catalyst compositions range from 72 to 82%, and the respective C2 yields range from 16 to 26%

Methane Activation by Heterogeneous Catalysis

“…Zavyalova and Baerns [57] reviewed the vast OCM literature in 2011 and reported more than 2,700 research articles and about 140 patents at that time. Already in 1993 Maitra reviewed global performance data of OCM catalysts and identified those for which the sum of methane conversion and C 2þ selectivitiy was higher than 80 % at more than 5 % CH 4 conversion [58].…”

“…Figure 8 shows X; S-data of the best OCM catalysts reported in literature that were scrutinized by Zavyalova and Baerns [57] for being measured in kinetically sound experiments. These data indicate that C 2 selectivity (C 2 H 4 þ C 2 H 6 ) decreases with increasing CH 4 conversion resulting in a virtual one pass yield limit between 25 and 30 %.…”

Structure sensitivity of the oxidative activation of methane over MgO model catalysts: I. Kinetic study

“…[6] In return it was shown that lithium, which completely desorbs by formation of volatile compounds during the oxidative pretreatment of the catalyst (which involves the loss of all [Li-O] -centers), acts as a structural promoter that favors the formation of terminating higher index planes like {111} or {110}. [2,7] The highest selectivity to C 2+ products was found for pure MgO catalysts, which expose a greater fraction of {111} planes. [8] Inconsistent findings have also been reported with respect to activity.…”

“…All synthesis techniques result in Mg(OH) 2 or MgO-Mg(OH) 2 phase mixtures which were transformed into the oxide by calcination in a O 2 /Ar (20/80) atmosphere applying a flow of 150 mL/min. The precursor (3 g) was placed into a ceramic crucible, which was positioned into a quartz tube.…”

“…In addition, the diversity of known active catalyst masses complicates the identification of a general functional model. [2] The not yet fully resolved relationship between surface and gas phase chemistry of CH 4 at the high reaction temperatures inspired us to deal with fundamental questions of methane activation on the surface of heterogeneous catalysts in a systematic approach addressing in particular the function of surface defects using magnesium oxide as a model.…”