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.

采用德国布鲁克（Bruker）公司的D8 Advance型X射线衍射仪对样品的物相组成进行分析。以Cu Kα射线为辐射源（波长0.1542nm），工作电流40mA，工作电压40kV，扫描范围5~45°。采用日本电子株式会社（Japan Electronics Corporation）的JSM-7900F型热场发射扫描电子显微镜观察样品的表面形貌与粒径尺寸。采用美国麦克默瑞提克（Micromeritics）公司的ASAP 2460型全自动比表面积与孔隙度分析仪对样品的孔结构进行表征：先在300℃下真空脱气4h，随后以氮气为吸附质，在77K下测定吸附-脱附等温线；采用Brunauer-Emmett-Teller（BET）法计算总比表面积，采用t-plot法得到微孔比表面积与微孔孔容。采用天津先权工贸发展有限公司（Tianjin Xianquan Industry and Trade Development Co., Ltd.）的TP-5080-D型全自动多功能吸附仪（配备热导检测器（TCD））测定样品的酸性与酸强度：称取0.1g样品置于石英管中部，先在氦气流中于300℃预处理2h；随后降温至110℃，通入10%氨氦混合气吸附40min；最后切换为氦气吹扫，以程序升温（110~700℃）脱附氨气，记录样品的NH₃程序升温脱附（NH₃-TPD）曲线。采用德国布鲁克公司的VERTEX70V型红外光谱仪分析样品的酸类型：使用专用模具将10~15mg待测样品压制成自支撑薄片，置于真空红外原位池的恒温中部区域；先在真空条件下于500℃预处理1h，随后降温至150℃采集本底光谱；采集完成后继续降温至室温，进行40min的吡啶吸附处理；最后升温至150℃脱附吡啶分子并记录光谱。采用日本岛津（Shimadzu）公司的DTG-60H型差热-热重分析仪测定反应后催化剂的热重与差热重曲线。采用产自中国的雷尼绍（Renishaw）公司的inVia Qontor型原位激光共聚焦拉曼光谱仪（配备325nm紫外激光器）表征反应后催化剂上积碳的有序程度。在固定床反应器上评价催化剂对十二烷的催化裂解性能：称取3.6g粒径为20~40目的催化剂颗粒装填至反应器的恒温段，在压力101.325kPa、温度600℃、重时空速（WHSV）14h⁻¹的条件下进行反应；反应生成的油气经两级冷凝冷却后分离为气相产物与液相产物，采用SCION 8500型气相色谱仪分析气相产物，分别采用SCION 436型气相色谱模拟蒸馏仪与SCION 8500GC-8700SQ型气相色谱-质谱联用仪表征液相产物的馏程与化学组成。采用南京华欣分析仪器公司（Nanjing Huaxin Analytical Instrument Company）的HX-HW8型高频红外碳硫分析仪准确测定反应后催化剂的积碳含量。