Conversion of methane to acetonitrile over GaN catalysts derived from gallium nitrate hydrate co-pyrolyzed with melamine, melem, or g-C3N4: the influence of nitrogen precursors

Co-pyrolyzing gallium nitrate hydrate and melamine, melem, or g-C3N4 generates gallium nitride (GaN) for the conversion of methane to acetonitrile (AcCN). The solid-state-pyrolysis-made GaN catalysts exhibited better activity than commercial GaN. Among the as-prepared catalysts, GaN made by using g-C3N4 with a N/Ga ratio of 2 (i.e., GaN-(C3N4)-(2)) was the most attractive: a high initial methane conversion (28.2%), a high initial AcCN productivity (151 mu mol gcat(-1) min(-1)), and a 6 h accumulated AcCN yield (5816 mu mol gcat(-1)) were obtained at 700 degrees C with a space time of 3000 mLCH(4) gcat(-1) h(-1). GaN-(C3N4)-(2) had finely dispersed GaN crystals and enriched amorphous CN species (e.g., sp(2) N and C N groups), and both are important in promoting the methane conversion rate. GaN agglomeration, coke deposition, and depleted CN species contributed to the deactivation of the catalyst, and a nitridation-activation process could rejuvenate the activity partially. The analysis of the structure-activity correlation revealed that the accumulated AcCN yield had an inverse trend with respect to the crystallite size of GaN and the sp(3)/sp(2) ratio of the N environment.

Automated summary

Co-pyrolyzing gallium nitrate hydrate and melamine, melem, or g-C3N4 generates gallium nitride (GaN) for the conversion of methane to acetonitrile (AcCN). The solid-state-pyrolysis-made GaN catalysts exhibited better activity than commercial GaN. Among the as-prepared catalysts, GaN made by using g-C3N4 with a N/Ga ratio of 2 (i.e., GaN-(C3N4)-(2)) showed the highest initial methane conversion and AcCN productivity.