Fixed-bed reaction systems are normally used for ICCU-DRM. Although TGA can also be used to demonstrate the stability of DFMs. However, the feeding gas composition could be different, in addition to temperature, materials and gas analytical equipment. Gas analysis can be done using GC-TCD and on-line gas analyser. The following section provides ICCU-DRM experimental procedures reported in the literature:
“The proposed CaL methane reforming process was tested using the prepared CaO-Ni bifunctional sorbent-catalysts in a ChemBET PULSAR TPR/TPD chemisorption analyzer. Approximately 0.1 g of the sorbent-catalyst was placed in a quartz U-tube and heated to 1073 K at a rate of 25 K min−1 under a N2 flow of 8 ml min−1. Then, the temperature was held for 60 min with the introduction of H2 (2 ml min−1) to reduce the sample. After that, the temperature was decreased to 873 K, followed by the introduction of a CO2 flow of 2 ml min−1 instead of the H2 flow to carbonate the sample for 6 min (the CO2 capture step). Then, the temperature was increased to 1073 K at a rate of 40 K min−1, followed by the introduction of a CH4 flow of 2 ml min−1 instead of the CO2 flow to calcine the sample for 6 min (the CO2 conversion and CH4 reforming step). Subsequently, the temperature was decreased to 873 K, and then a new CaL CH4 reforming cycle was started by the introduction of a CO2 flow. Ten CaL CH4 reforming cycles were investigated in this study, and a blank run was performed to correct for the effects of temperature and gas flow switches. During the whole experiment, concentrations of CO2, CH4, and H2 in the outlet gas from the reaction tube were monitored every 1.2 min using a micro-gas chromatograph (GC; 490-GC, Varian), while the concentration of CO in the outlet gas was monitored every 1.2 min using another GC (7890B, Agilent). Both the Varian micro-GC and the Agilent GC were equipped with a molecular sieve 5A column and a thermal conductivity detector (TCD).”
https://doi.org/10.1016/j.jcou.2020.101201
“The isothermal alternated cyclic performance of Ni-Ba catalyst in the CO2 storage and regeneration process was evaluated, feeding CO2-He and CH4-He pulses (10,000 ppm each one and GHSV = 21,220 h−1) with an intermediate purge of He, using Ar as a tracer at 600, 650, and 700 °C as three different temperatures were used at ordinary pressure. The catalyst was previously reduced in situ at 600 °C under hydrogen atmosphere. In Fig. 3, the concentration profiles of CO2, CH4, CO, H2 and Ar at the reactor outlet at 280 min (7 cycles) are represented (Fig. 3a). The steady-state is reached after the third operation cycle and the initial disturbance of the signals at the beginning of each cycle is due to the valve-shift. During the CO2-storage step, for this feed, the saturation is reached within 3 min. In the regeneration step using methane (as a reducing and regenerating agent) both, CO2 desorbed and H2 formed are detected, although CO is also detected in less extension. In the next cycle during the CO2-storage step an increased formation of CO was also evidenced. In Fig. 3b, a magnification of the first and second cycles of operation is displayed. As can be seen, in the first cycle and during the CO2-acumulation period, CO2 signal presents a shorter breakthrough time in the saturation curve. Once the CO2 storage-step was finished the reactor was purged with He and the CO2 desorption mass-signal progressively decreased until it reaches zero. For the same cycle, the regeneration period starts by feeding 10,000 ppm of CH4 and contemporaneously, joint to CO2 desorption and with a delay time of 2.5 s, H2 and CO appeared as main products. ”
https://doi.org/10.1021/acs.iecr.9b05783
“The schematic diagram of a fixed-bed reactor facility is shown in Figure 2. A stainless steel reactor tube (i.e., 10 mm inner diameter and 700 mm length) is equipped with an N-type thermocouple and an external heating unit to measure the reaction temperature and to provide the heat supply for the reaction, respectively. The flow rates for all feeding gases were controlled and that of the outlet gas was detected by the mass flowmeter. The as-prepared samples together with quartz wool were placed on a stainless steel strut in the constant temperature zone of the reactor tube. Prior to each test, the desired amount of sample was first placed in the reactor tube and 100 mL min–1 N2 (99.999%) was then introduced and functioned as: a purge gas to blow away the residual air in the tube to avoid the occurrence of unwanted reactions, a standard gas to calibrate the CO2 sensor for reducing the instrument error, and a flowing gas to detect the reactor air tightness for ensuring the accuracy of the experiment.”
“Figure 2. Schematic diagram of the fixed-bed reactor facility.”
“The decarbonation and carbonation temperatures were determined by respectively performing temperature-programmed calcination (in 50 N mL min−1 of He flow) and temperature-programmed carbonation (in 50 N mL min−1 of CO2 flow) for the as-prepared and reduced materials in the thermogravimetric analyzer (Shimadzu DTG-60). After purging with the corresponding gas at room temperature for 1 h, the sample (approximately 10–20 mg) was heated from 30 °C to 950 °C with a ramping rate of 10 °C min−1. Then, the stability of cyclic CO2 uptake of the as-prepared materials was tested by CO2 capture and release cycling experiemnts at 720 °C. Approximately 10–20 mg of the as-prepared material was loaded into the analyzer chamber, followed by purging with He for 30 min at room temperature. Afterwards, the material was precalcined at 720 °C (with a ramping rate of 10 °C min−1) for 5 min in He flow. Subsequently, the material carbonation (i.e. CO2 capture) was performed at 720 °C for 15 min in pure CO2 flow (50 N mL min−1) followed by the material regeneration (i.e. CO2 release) at same temperature for 45 min in pure He flow (50 N mL min−1). Totally 10 cycles of CO2 capture and release were performed for each material. The changes in sample weight as a function of time were monitored online, shown as the variation of TGA curve. The exothermic and endothermic properties of the reactions were respectively indicated by the positive and negative peaks in the DTA profile.”
“The activity and stability of the as-prepared materials during DRM reaction were examined by steady-state experiments conducted in a quartz tube microreactor (inner diameter: 4 mm) at 720 °C and 1 bar. The reactor was heated by a wire wound tube furnace with an inner diameter of 15 mm and a body length of 150 mm, equipped with K-type thermocouples (Carbolite, MTF 10/15/130). Typically, 50 mg of material without diluent was packed into the reactor between quartz wool plugs, positioned in the middle of the furnace within a length of 30 mm, where the heating is most uniform, with maximum temporal temperature fluctuations in the catalyst bed around 5 °C. The flow rate of feed gas was controlled by means of Brooks mass flow controllers calibrated with the corresponding gases. After passing through a water trap, the composition of the outlet gas was analyzed online using gas chromatography (GC) (Agilent, HP 6890) equipped with a TCD, while the gas flow rate was measured by an Agilent ADM digital flow meter. The concentration (vol%) of each product in the outlet gas was calculated by the corresponding conversion factor determined from the calibration curve of concentration versus GC peak area. Prior to the DRM reaction, the material was reduced at 750 °C (with a ramping rate of 10 °C min−1) under 10 vol% H2/He (50 N mL min−1) for 30 min, then the temperature was decreased to 720 °C (at a rate of 10 °C min−1) in He flow and stabilization for 20 min. Subsequently, the DRM reaction started by feeding 50 N mL min−1 of 10 vol% CH4 + 10 vol% CO2 + 80 vol% He mixture gas. After 10 min, GC online analysis started and sampling was taken every 1 h. The H2/CO ratio of syngas was determined by the ratio between H2 and CO concentrations in the outlet product. “
https://doi.org/10.1016/j.seppur.2021.119476
“Figure S1. Schematic of the experimental test system. (https://doi.org/10.1016/j.seppur.2021.119476)”