Direct Methane Conversion under Mild Condition by Thermo-, Electro-, or Photocatalysis

Abstract

Direct conversion of earth-abundant methane into value-added chemicals under mild conditions is an attractive technology in response to the increasing industrial demand of feedstocks and worldwide appeal of energy conservation. Exploring advanced low-temperature C-H activation catalysts and reaction systems is the key to converting methane in a direct and mild manner. The recently developed reaction processes operated at low-temperature thermocatalysis systems or driven in electro-and photocatalysis systems shine light on the way to achieve efficient methane conversion with much economical energy input. In this review, we summarize the typical catalytic processes employed in these reaction systems and in particular highlight the potential heterogeneous catalysts with noteworthy C-H activation performance. We also present the progress along with our perspectives on catalyst design, theoretical simulations, the choice of reaction condition, and the method of reaction product analysis to encourage more viable technology for low-temperature methane conversion in the future.

Progress in Computational and Machine‐Learning Methods for Heterogeneous Small‐Molecule Activation

“…Kim et al formulated for the first time a general method to systematically consider acidity level (pH) through firstprinciples. [49] In analogy to the first-principles defect theory for semiconductors, they treated solutes (i.e., H + , OH − , NH 3 , NH 4 + , HCOOH, and HCOO − ) as defects in homogeneous liquids (i.e., water) and used molecular dynamics (MD) to calculate the formation energy of solutes under proton chemical potential, pH. .…”

“…In this section, we discuss the applications of fundamental theory and methodology for the conversion of H 2 , O 2 , H 2 O, N 2 , CO 2 , and CH 4 activation. We refer to other refs for in-depth reviews (H 2 , [149][150][151] O 2 , [152,153] H 2 O, [154][155][156] N 2 , [157][158][159][160] CO 2 , [161][162][163] and CH 4 [4,5] ). Here, we focus on the demonstrations of the catalyst design methods such as the Sabatier principle, d-band theory, high-throughput screening, and machine learning for the activation of small molecules discussed above.…”

“…[2,3] Conversion of CH 4 to methanol and C 2+ compounds have been receiving large attention as it is abundant in shale gas and natural gas. [4,5] As the demand decomposition of substances on metals and oxides at high temperature and discovered that the products vary depending on the catalyst. [13] Back then, the understanding of the catalysis phenomenon was limited to qualitative observations, and molecular level understanding did not exist.…”

“…However, the conversion of these molecules is difficult due to their high chemical stability caused by their symmetricity and nonpolar nature. The activation of N 2 and CH 4 requires high temperature (>400 °C), [2][3][4][5][6][7] and the deployment of fuel cell and electrolysis has been limited by the lack of economic catalysts. To convert these small molecules more efficiently, discovering superior catalysts is essential.…”

Selective Photo‐Oxygenation of Light Alkanes Using Iodine Oxides and Chloride

“…The ethane and propane components of natural gas are cracked at high temperatures (>900 °C) to generate ethylene and propylene, respectively, which serve as precursors for a variety of higher value chemicals . The demand for efficient use of energy and the need for on‐site conversion of natural gas to liquids have provided motivation to develop new methods for direct and selective low‐temperature (<200 °C) light alkane oxy‐functionalization . But, a key goal and major challenge is to develop processes that selectively produce mono‐functionalized products…”