Fig. 1. An ideal device for full life cycle characterization, containing in-situ probes at specific positions to diagnose the operation level of the reactor and catalyst online. This is of great significance to adjust the real-time process conditions such as temperature, pressure, and reactant feed rate a, b, and c, respectively. Reprinted with permission from Ref. [11]. Copyright 2020 American Chemical Society.

Fig. 2. (a) Schematic of the in-situ device for monitoring the hydrocarbon pool species in the MTO reaction by UV-vis spectroscopy. Reprinted with permission from Ref. [27]. Copyright 2015 American Chemical Society. (b) Conversion and selectivity profiles as a function of methanol throughput and (c) corresponding time-resolved in-situ UV-vis spectra of the MTO reaction. The green, red, blue, and black spectra correspond to the induction period (methanol conversion < 100%), complete conversion period (methanol conversion of 100%), deactivation period (methanol conversion from 100% to 20%), and complete deactivation period (methanol conversion < 20%), respectively. Reaction conditions: WHSV 0.5 h?1, 400 °C. Reprinted with permission from Ref. [28]. Copyright 2017 American Chemical Society.

Fig. 3. (a) Schematic of a glass reactor cell with a 3 mm Co/γ-Al2O3 catalyst pellet for in-situ μ-XRD-CT/μ-PDF-CT characterization. (b) Compositional profile of the different cobalt phases obtained by combined 2D diffraction data. (c) Reconstructed 2D maps for the CoO phase composition during H2 reduction and the FT reaction on Co/γ-Al2O3. The color bar shows the weight percent of CoO, balanced by Co3O4 (150 °C) or metallic Co0 (≥ 310 °C and during the FT reaction). Reaction conditions: 450 °C, 0.1 MPa. Reprinted with permission from Ref. [37]. Copyright 2017 American Chemical Society.

Fig. 4. (a) Photograph and schematic of a 700 mL pilot-scale reactor for the in-situ characterization of PDH over CrOx/Al2O3 pellets. Two UV-vis probes and a Raman fiber probe were used for in-situ characterization of coke deposition on the catalyst bed under real reaction conditions. (b) The Raman intensity (blue) and reaction temperature (black) at the top and bottom of the catalyst bed during the first hour of the two dehydrogenation cycles. Reaction conditions: 550 °C, 0.15 MPa. Reprinted with permission from Ref. [46]. Copyright 2014 Wiley.

Fig. 5. (a) Linear relationship between the amount of coke deposition and the frequency shift of the characteristic acoustic signal peak. The legends denote the test results at four different gas flow rates in the range of 0.08 to 0.12 m/s. (b) An industrial test device for the in-situ measurement of coke deposition based on acoustic emission signals collected by wave sensor equipment. Reprinted with permission from Ref. [62]. Copyright 2011 American Chemical Society.

Fig. 6. (a) Relationship between the surface free energies of the different facets and CO partial pressure at 227 °C. The numbers beside the curve represent the surface coverage. The yellow dotted line shows the surface energy of Co(100) when carbon deposition is considered. (b) The Wulff equilibrium shape of the Co particles at 227 °C under different CO partial pressures. The equilibrium CO coverages at 1 bar are shown in the inset. Reprinted with permission from Ref. [70]. Copyright 2019 American Chemical Society.