A Highly Active Molybdenum Phosphide Catalyst for Methanol Synthesis from CO and CO₂

Abstract

Methanol is a major fuel and chemical feedstock currently produced from syngas, a CO/CO /H mixture. Herein we identify formate binding strength as a key parameter limiting the activity and stability of known catalysts for methanol synthesis in the presence of CO . We present a molybdenum phosphide catalyst for CO and CO reduction to methanol, which through a weaker interaction with formate, can improve the activity and stability of methanol synthesis catalysts in a wide range of CO/CO /H feeds.

Development of Molybdenum Phosphide Catalysts for Higher Alcohol Synthesis from Syngas by Exploiting Support and Promoter Effects

“…Therefore, the excess phosphorus forms oxide species. A previous study using XPS showed that oxidized Mo species form on the surface of a silica‐supported MoP catalyst upon exposure to air, and can be reduced using a pre‐reduction treatment prior to catalytic testing . The present study used the same pre‐reduction treatment, which is expected to reduce the surface phosphate or the oxide of molybdenum prior to catalytic testing.…”

“…Before investigating promoter effects for HAS on MoP‐based catalysts, a systematic study was first performed to understand the effect of synthesis parameters on the structure and activity of the KMoP on amorphous SiO 2 catalyst system developed previously for MS from CO and CO 2 . The key parameters for synthesis are identified in the following sections as the P/Mo ratio, K/Mo ratio, and MoP loading.…”

“…Moreover, sulfur is incorporated in the products, which is in conflict with environmental legislation . Recently, it was shown that silica‐supported molybdenum phosphide (MoP) catalysts exhibit a high selectivity toward MS from both CO and CO 2 , and C 2+ oxygenate formation from syngas has been reported over K‐promoted MoP/SiO 2 catalysts . However, investigations on the MoP system for HAS have only just begun, and it will be worthwhile to conduct wider screenings of promoters and supports and to better understand the structure and function of the catalytic centers …”

“…Because the active phosphide phase is formed inside the support pores, the support morphology and nature play important roles in the synthesis of MoP catalysts. MoP catalysts reported previously for syngas conversion were synthesized using the temperature‐programmed reduction (TPR) method ending at 600–700 °C and oxidic precursors of Mo and P . This synthesis creates highly sintering conditions due to both the high‐temperature requirement and the generation of a large quantity of water during the reduction of precursors .…”

“…A systematic approach is used involving both commercial amorphous silica and a model silica support with an ordered pore structure and well‐known nature. The role of the previously reported K promoter is elucidated; Co, Ni, and Pd are screened as potential promoters; and carbon is explored as a promising support for HAS. In‐depth knowledge is developed about the role of the MoP‐support interactions and promoter effects, and a rational design strategy is used to tune the product selectivity toward the desired C 2+ products .…”