CoMo型耐硫变换催化剂不同硫化剂的器外预硫化研究

Study on ex-situ presulfurization technologies with different presulfiding agents for CoMo-based sulfur-tolerant shift catalysts

从多种硫化剂中筛选出(NH_4)_2S和Na_2S,分别采用不同的预硫化技术对工业级CoMo型耐硫变换催化剂进行器外预硫化,采用XRD、XPS和HRTEM等表征手段对催化剂的晶相结构、表面特性和微观形貌进行表征。(NH_4)_2S和Na2S作为预硫化剂对催化剂的晶相结构没有明显影响;用(NH_4)_2S进行预硫化时活性组分发生部分O-S交换,而用Na_2S进行预硫化时活性组分仍保持为氧化态,两种预硫化型催化剂在反应器内随着反应温度升高,硫化深度为S-Na_2S>S-(NH_4)_2S>常规器内预硫化;器内预硫化和(NH_4)_2S作为预硫化剂MoS_2片层结构堆叠层数集中在2-3层,而用Na_2S进行预硫化时MoS_2片层堆叠层数明显变多,集中在3-5层。采用微型固定床评价装置,选择285、350、450℃三个反应温度,催化剂的活性顺序为SNa_2S>S-(NH_4)_2S>常规器内预硫化。

(NH_4)_2S and Na_2 S were selected from several presulfiding agents. Industrial Co-Mo based sulfurtolerant shift catalysts were ex-situ presulfided with different presulfurization technologies. The crystal structures,surface characteristics and micro appearance were characterized by X-ray diffraction( XRD), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(HRTEM).( NH_4)_2S and Na_2S as presulfiding agents did not show obvious effects on the crystal structures of the catalysts. Partial O-S exchange of the active components was observed when(NH_4)_2S was used for presulfirization. And when presulfided with Na2 S,the active components still remained oxidation state. As the ex-situ presulfurization temperature increased,the extent of vulcanization was: S-Na_2S >S-(NH_4)_2S >the general in situ pre-vulcanization. When presulfided with(NH_4)_2S or the general in situ pre-vulcanization,the stacking number of MoS2 layers was mainly two to three. And when presulfided with Na_2S,the stacking number of MoS_2 layers increased obviously,mostly three to five. The activity sequence of the catalysts was S-Na_2S>S-(NH_4)_2S>the general in situ pre-vulcanization when the catalysts were tested in a micro-fixed reactor at temperatures of 285,350 and 450 ℃ respectively.