Fig. 4: Surface species and the key formaldehyde intermediates derived from the reactions.
From: CO2 hydrogenation toward toluene methylation for selective para-xylene synthesis
a In situ DRIFTS spectra over the ZZO & 4Si/M-22 catalyst exposed to the stream of C7H8 + CO2 + H2 and subsequently switched to C7H8 + 13CO2 + H2. b In situ DRIFTS of CO2 + H2 over ZZO and ZZO & 4Si/M-22. c Quasi in situ13C CP MAS NMR experiment for 13CO2 + H2 on ZZO and 13CO2 + H2 + C7H8 on ZZO & 4Si/M-22. d Quasi in situ 2D 13C-1H HETCOR MAS NMR experiment for 13CO2 + H2 on ZZO. e Quasi in situ 2D 13C-1H HETCOR MAS NMR experiment for 13CO2 + H2 + C7H8 on ZZO & 4Si/M-22. Reaction conditions: 320 °C, 3 MPa, 30 min tube-sealing test. f The GC-MS chromatograms of the others aromatics in the products from alkylation of toluene with different alkylation reagents (CO2 + H2, formaldehyde and methanol) over the ZZO & M-22 and M-22 catalyst. g The GC-MS chromatograms of the others aromatics in the products from alkylation of toluene with CO2 + H2 over the ZZO & M-22 and ZZO catalyst. h In situ SVUV-PIMS detection of gas-phase products and i photoionization efficiency spectra of the signals at m/z = 30 and 32 over ZZO catalyst during CO2 + H2. (300 °C, 0.8 MPa, 9,000 mL gcat−1 h−1 and H2/CO2 = 3/1). j The reaction pathway over the ZZO & M-22 catalyst.
