Effects of zeolite type and acidic properties on the catalytic cracking performance of dodecane

The phase composition of the sample was analyzed using the D8 Advance X-ray diffractometer from Bruker, Germany. Cu K α rays were used as the radiation source (wavelength of 0.1542 nm), with a working current of 40 mA, a working voltage of 40 kV, and a scanning range of 5-45 °. The surface morphology and particle size of the sample were observed using a JSM-7900F thermal field emission scanning electron microscope from Japan Electronics Corporation. The pore structure of the sample was characterized using the ASAP 2460 fully automatic surface area and porosity analyzer from Micromeritics in the United States. After vacuum degassing at 300 ℃ for 4 hours, the sample was subjected to adsorption desorption isotherms at 77 K using nitrogen as the adsorbate. The total specific surface area was calculated using the BET method, and the micropore specific surface area and micropore volume were obtained using the t-plot method. The TP-5080-D fully automatic multi-purpose adsorption instrument (equipped with TCD detector) from Tianjin Xianquan Industry and Trade Development Co., Ltd. was used to measure the acidity and acid strength of the sample. 0.1 g of the sample was placed in the middle of a quartz tube, and first pretreated at 300 ℃ for 2 hours in a helium flow. Then, the temperature was lowered to 110 ℃ and a 10% ammonia helium mixture was introduced for adsorption for 40 minutes. Finally, the gas was switched back to helium blowing, and the ammonia gas was desorbed at a programmed temperature (110-700 ℃). The NH3-TPD curve of the sample was recorded. Use the VERTEX70V infrared spectrometer from Bruker, Germany to analyze the acid type of the sample. Use a special mold to press 10-15 mg of the test sample into a self-supporting sheet and place it in the middle constant temperature zone of a vacuum infrared in-situ cell. Pre treat at 500 ℃ for 1 hour under vacuum, then cool to 150 ℃ to collect the background spectrum. After collection, continue to cool to room temperature for 40 minutes of adsorption pyridine treatment. Finally, heat up to 150 ℃ to desorb pyridine molecules and record the spectrum. Use the SHIMADZU DTG-60H differential thermal gravimetric analyzer from Shimadzu Corporation in Japan to measure the thermogravimetric and differential thermogravimetric curves of the catalyst after the reaction. Use Renishaw's inVia Qontor in-situ laser confocal Raman spectrometer (equipped with a 325 nm ultraviolet laser) from China to characterize the degree of order of carbon deposition on the catalyst after the reaction. Evaluate the catalytic cracking performance of catalysts for dodecane on a fixed bed reactor. 3.6 g of catalyst particles (20-40 mesh) were loaded into the constant temperature section of the reactor, and the reaction was carried out under the conditions of a pressure of 101.325 kPa, a temperature of 600 ℃, and a weight hour space velocity (WHSV) of 14 h-1. The generated oil and gas are separated into gas phase and liquid phase products after two-stage condensation cooling. The gas-phase products were analyzed using a SCION 8500 GC gas chromatograph, while the distillation range and chemical composition of the liquid-phase products were characterized using a SCION 436 GC simulated distillation apparatus and a SCION 8500GC-8700SQ gas chromatography-mass spectrometry instrument, respectively. The carbon deposition content of the catalyst after the reaction was accurately measured using the HX-HW8 high-frequency infrared carbon sulfur analyzer from Nanjing Huaxin Analytical Instrument Company.