载体表面性质对活性相形貌结构及植物油加氢脱氧选择性的影响

Effects of Surface Characteristics of Support on Morphology of Active Phase and Selectivity of Hydrodeoxygenation Reaction

分别以未改性氧化铝（A）、K改性氧化铝（A-K）和Si改性氧化铝（A-Si）为载体,采用饱和浸渍法制备了RZ、RZ-K和RZ-Si 3个NiMo催化剂,并采用Py-IR、XRD、BET、XRF、HRTEM、XPS等技术对其进行了表征。在中型固定床反应器中,以棕榈油为原料,考察了载体表面性质对硫化态催化剂活性及加氢直接脱氧、加氢脱羧基和加氢脱羰基路径选择性的影响。结果表明,A-Si、A、A-K载体表面总酸量和强酸量依次降低;载体表面性质对硫化态（Ni）MoS2活性相形貌结构有较大影响,虽然3个催化剂Mo硫化度相当,但RZ-K的片晶长度较短,层数较低,而RZ-Si片晶长度较长,层数较高,且NiMoS活性相中Ni占总Ni的比（n（NiNiMoS）/n（Nitotal））按RZ-Si、RZ、RZ-K顺序依次降低。3个催化剂加氢脱羰基活性相当（320~380℃）,但加氢直接脱氧和加氢脱羧基活性不同。适当提高催化剂酸性,增加反应温度和压力对提高加氢脱羧基路径选择性有利;适当降低催化剂酸性和减小活性相晶片,降低反应温度和提高压力对提高加氢直接脱氧路径选择性有利。Si改性导致载体酸性的增强以及相应催化剂Ni-Mo-S活性位的增多,促进了加氢脱羧基反应,与RZ和RZ-K催化剂相比,催化剂RZ-Si的整体脱氧活性提升。

The Ni-Mo catalysts RZ-K, RZ and RZ-Si supported, respectively, on K modified Al2O3 （A-K）, A1203 （A） and Si modified Al2O3 （A-Si） were prepared by incipient-wetness impregnation, and characterized by Py-IR, XRD, BET, XRF, HRTEM and XPS techniques. The catalytic hydrodeoxygenation reaction （HDO） of palm oil was carried out in a fixed-bed reactor to investigate the properties of support surface on the catalytic activity of these catalysts and on the selectivities of direct hydrodeoxygenation, hydrodecarboxylation and hydrodecarbonylation paths. The results showed that the amount of total acid sites and strong acid sites of A-Si, A, A-K decreased in turn. Surface properties of the supports had great influence on the mophology of sulfided active phase （Ni）MoS2, although the degrees of Mo sulfidation of three catalysts were equivalent. In comparison with RZ catalyst, RZ-K catalyst was of shorter average slab length and lower stacking number, RZ-Si catalyst was of longer average slab length and higher stacking number. Morover, n （NiN2MoS）/n （Nitotal） values of RZ-Si, RZ, RZ-K decreased in turn. Besides, the hydrodecarbonylation path selectivities at 320-- 380℃ were similar over the three catalysts, but direct hydrodeoxygenation and hydrodecarboxylation path selectivities were different. Increasing the acidity of catalyst and increasing reaction temperature and pressure will favor hydrodecarboxylation reaction, while decreasing the acidity and n （NiNiMoS）/n（Nitotal） of catalyst and lowering reaction temperature and increasing reaction pressure will favor direct hydrodeoxygenation reaction. RZ-Si catalyst was of more total acid sites and strong acid sites and n（NiNiMoS）/n（Nitotal） ratio, which is the reason why RZ-Si catalyst has the highest HDO activity among the three catalysts of RZ, RZ-K and RZ-Si.