二甲基二硫醚对Pt/Al_2O_3催化丙烷脱氢反应性能的影响
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摘要
制备了Pt/θ-Al_2O_3催化剂,在该催化剂上进行丙烷脱氢反应过程中引入不同用量的二甲基二硫醚(DMDS),考察了DMDS对Pt/θ-Al_2O_3催化剂性能的影响。实验结果表明,在一定浓度范围内,在丙烷脱氢反应中引入DMDS可大幅提高Pt/θ-Al_2O_3催化剂的丙烯选择性及稳定性,同时降低结焦速率和结焦的石墨化程度,但催化剂活性有所降低。采用HRTEM、XPS、TG和拉曼光谱等方法对催化剂结构和结焦性质进行了分析。表征结果显示,丙烯选择性以及稳定性的提高主要是由于DMDS在Pt表面解离生成的含硫物种吸附于Pt表面,使Pt处于富电子状态,促进了丙烯的脱附并抑制了深度脱氢反应;但同时也提高了C—H键断裂难度,导致催化剂活性有所降低。
Pt/θ-Al_2 O_3 catalyst was prepared,and the effects of dimethyl disulfide(DMDS) on the Pt/θ-Al_2 O_3 catalyst were evaluated in propane dehydrogenation with different concentrations of DMDS in the feed. The results reveal that the addition of DMDS with a desired concentration can significantly improve the propylene selectivity and catalyst stability. Meanwhile,the coking rate and the degree of graphitization are reduced at the expense of a slight activity loss. The HRTEM,XPS,TG and Raman spectroscopy were used to analyze the structure of the catalyst and coking properties.The characterization results indicate that the improvement of propylene selectivity and catalyst stability is mainly due to the fact that sulfur-containing species generated by dissociation of DMDS on the surface of Pt are adsorbed on the surface of Pt,so that Pt is in an electron-rich state,desorption of propylene is promoted,and deep dehydrogenation reaction is inhibited. However,the difficulty of C—H bond breaking is also increased,resulting in inhibition of catalyst activity.
Pt/θ-Al_2 O_3 catalyst was prepared,and the effects of dimethyl disulfide(DMDS) on the Pt/θ-Al_2 O_3 catalyst were evaluated in propane dehydrogenation with different concentrations of DMDS in the feed. The results reveal that the addition of DMDS with a desired concentration can significantly improve the propylene selectivity and catalyst stability. Meanwhile,the coking rate and the degree of graphitization are reduced at the expense of a slight activity loss. The HRTEM,XPS,TG and Raman spectroscopy were used to analyze the structure of the catalyst and coking properties.The characterization results indicate that the improvement of propylene selectivity and catalyst stability is mainly due to the fact that sulfur-containing species generated by dissociation of DMDS on the surface of Pt are adsorbed on the surface of Pt,so that Pt is in an electron-rich state,desorption of propylene is promoted,and deep dehydrogenation reaction is inhibited. However,the difficulty of C—H bond breaking is also increased,resulting in inhibition of catalyst activity.
引文
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[3]Vu B K,Song M B,Ahn I Y,et al.Location and structure of coke generated over Pt-Sn/Al2O3 in propane dehydrogenation[J].J Ind Eng Chem,2011,17(1):71-76.
[4]Wang Guowei,Sun Nannan,Gao Chuancheng,et al.Promoting mechanism of sulfur addition in catalytic dehydrogenation of isobutane over Mo/Mg Al2O4 catalysts[J].Appl Catal,A,2014,478:71-80.
[5]张永军,万书宝,郭英爽,等.乙烯裂解炉的结焦及其抑制措施[J].化学工业,2011,29(12):46-51.
[6]Jazayeri S M,Karimzadeh R.Experimental investigation of initial coke formation over stainless steel,chromium,and iron in thermal cracking of ethane with hydrogen sulfide as an additive[J].Energy Fuels,2011,25(10):4235-4247.
[7]Apesteguía C R,Barbier J.The role of catalyst presulfurization in some reactions of catalytic reforming and hydrogenolysis[J].J Catal,1982,78(2):352-359.
[8]Jackson S D,Leeming P,Grenfell J.The effect of sulfur on the nonsteady state reaction of propane over a platinum/alumina catalyst at 873 K[J].J Catal,1994,150(1):170-176.
[9]Wang Haizhi,Zhang Wei,Jiang Jiawei,et al.The role of H2S addition on Pt/Al2O3 catalyzed propane dehydrogenation:Amechanistic study[J].Catal Sci Technol,2019,9(3):867-876.
[10]Shan Yuling,Zhu Yian,Sui Zhijun,et al.Insights into the effects of steam on propane dehydrogenation over a Pt/Al2O3catalyst[J].Catal Sci Technol,2015,5(8):3991-4000.
[11]Han Zhiping,Li Shuirong,Jiang Feng,et al.Propane dehydrogenation over Pt-Cu bimetallic catalysts:The nature of coke deposition and the role of copper[J].Nanoscale,2014,6(17):10000-10008.
[12]Gillan C,Fowles M,French S,et al.Ethane steam reforming over a platinum/alumina catalyst:Effect of sulfur poisoning[J].Ind Eng Chem Res,2013,52(37):13350-13356.
[13]Shan Yuling,Sui Zhijun,Zhu Yian,et al.Effect of steam addition on the structure and activity of Pt-Sn catalysts in propane dehydrogenation[J].Chem Eng J,2015,278:240-248.
[14]Sadezky A,Muckenhuber H,Grothe H,et al.Raman microspectroscopy of soot and related carbonaceous materials:Spectral analysis and structural information[J].Carbon,2005,43(8):1731-1742.
[15]Wang Haizhi,Sun Lili,Sui Zhijun,et al.Coke formation on Pt-Sn/Al2O3 catalyst for propane dehydrogenation[J].Ind Eng Chem Res,2018,57(26):8647-8654.
[16]Sattler J J H B,Beale A M,Weckhuysen B M.Operando Raman spectroscopy study on the deactivation of Pt/Al2O3and Pt-Sn/Al2O3 propane dehydrogenation catalysts[J].Phys Chem Chem Phys,2013,15(29):12095-12103.
[17]Pastor-Perez L,Belda-Alcazar V,Marini C,et al.Effect of cold Ar plasma treatment on the catalytic performance of Pt/Ce O2 in water-gas shift reaction(WGS)[J].Appl Catal,B,2018,225:121-127.
[18]Ito Koki,Tomino Tadahiro,Ohshima Masa-aki,et al.Sulfur tolerance of Pd/Al2O3 and Pd/Ti O2 in naphthalene hydrogenation in the presence of dimethyldisulfide[J].Appl Catal,A,2003,249(1):19-26.
[19]Tang Yanan,Liu Zhiyong,Chen Weiguang,et al.Theoretical study on the removal of adsorbed sulfur on Pt anchored graphene surfaces[J].Int J Hydrogen Energy,2015,40(21):6942-6949.
[20]Yang Minglei,Zhu Yian,Zhou Xinggui,et al.First-principles calculations of propane dehydrogenation over Pt Sn catalysts[J].ACS Catal,2012,2(6):1247-1258.