不同Pt前躯体对Pt/KL催化剂芳构化性能的影响
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摘要
为考察不同Pt前躯体对Pt/KL催化剂芳构化性能的影响,分别以Pt(NH_3)_4(NO_3)_2和Pt(NH_3)_4Cl_2为Pt前躯体,KL分子筛为载体,制备了TN-Pt/KL和TC-Pt/KL芳构化催化剂,其对应的再生剂为R-TN-Pt/KL和R-TC-Pt/KL。采用XRD、XRF、TGA、BET、TEM、H_2-TPR等分析手段对上述催化剂进行了表征,并以正庚烷为原料,在500℃、0.4 MPa、MHSV=1.5 h~(-1)、n(H_2)/n(n-Heptane)=3的条件下分别对新鲜剂和再生剂的芳构化性能进行评价。结果表明:2种不同的Pt前躯体对新鲜剂上Pt的粒径、比表面积和孔体积影响不大,但TC-Pt/KL催化剂上芳构化活性中心更多,且该催化剂上的Pt~(2+)与KL分子筛载体之间的相互作用力更强,有利于提高其芳构化活性,减缓Pt颗粒聚集长大;与新鲜剂相比,2种再生剂Pt粒径均明显增大,比表面积和孔体积也明显降低,但R-TC-Pt/KL的物化性质优于R-TN-Pt/KL;以Pt(NH_3)_4Cl_2为前躯体制备的催化剂具有较优异的芳构化活性和稳定性,2种催化剂的再生性能均较差, TC-Pt/KL催化剂比TN-Pt/KL的再生性能略好。
To investigate the influences of different Pt precursors on the aromatization performance of Pt/KL catalyst, TN-Pt/KL and TC-Pt/KL catalysts were prepared with Pt(NH_3)_4(NO_3)_2 and Pt(NH_3)_4Cl_2 as the Pt precursors and KL molecular sieve as the carrier, respectively, while the corresponding regenerated catalysts are R-TN-Pt/KL and R-TC-Pt/KL. These catalysts were characterized by XRD, XRF, TGA, BET, TEM and H_2-TPR. Results show that Pt precursors have little effect on the particle size of Pt, surface area and pore volume of the fresh catalysts. However, TC-Pt/KL is of more aromatization active centers and stronger interaction force between Pt~(2+) and KL molecular sieve. Thus, it is beneficial to improve aromatization activity and restrict the aggregation and growth of Pt particles. Compared with the fresh catalysts, the Pt particle sizes of the two regenerated catalysts are increased significantly, while the surface area and pore volume obviously are decreased. Moreover, R-TC-Pt/KL shows much better physical and chemical properties than R-TN-Pt/KL. Using n-heptane as feed, under the conditions of 500 ℃, 0.4 MPa, MHSV=1.5 h~(-1), n(H_2)/n(n-Heptane)=3, the aromatization performances of fresh catalysts and regenerated catalysts were evaluated respectively. The results show that the catalysts prepared by Pt(NH_3)_4Cl_2 exhibit excellent aromatization activity and stability, but both regenerated catalysts show poor catalytic performance.
To investigate the influences of different Pt precursors on the aromatization performance of Pt/KL catalyst, TN-Pt/KL and TC-Pt/KL catalysts were prepared with Pt(NH_3)_4(NO_3)_2 and Pt(NH_3)_4Cl_2 as the Pt precursors and KL molecular sieve as the carrier, respectively, while the corresponding regenerated catalysts are R-TN-Pt/KL and R-TC-Pt/KL. These catalysts were characterized by XRD, XRF, TGA, BET, TEM and H_2-TPR. Results show that Pt precursors have little effect on the particle size of Pt, surface area and pore volume of the fresh catalysts. However, TC-Pt/KL is of more aromatization active centers and stronger interaction force between Pt~(2+) and KL molecular sieve. Thus, it is beneficial to improve aromatization activity and restrict the aggregation and growth of Pt particles. Compared with the fresh catalysts, the Pt particle sizes of the two regenerated catalysts are increased significantly, while the surface area and pore volume obviously are decreased. Moreover, R-TC-Pt/KL shows much better physical and chemical properties than R-TN-Pt/KL. Using n-heptane as feed, under the conditions of 500 ℃, 0.4 MPa, MHSV=1.5 h~(-1), n(H_2)/n(n-Heptane)=3, the aromatization performances of fresh catalysts and regenerated catalysts were evaluated respectively. The results show that the catalysts prepared by Pt(NH_3)_4Cl_2 exhibit excellent aromatization activity and stability, but both regenerated catalysts show poor catalytic performance.
引文
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[14]HAN W J,KOOH A B,HICKS R F.Infrared spectroscopy of carbon monoxide adsorbed on Pt/Lzeolite[J].Catalysis Letters,1993,18(3):193-208.
[15]ROLDN R,BEALE A M,SNCHEZ-SNCHEZ M,et al.Effect of the impregnation order on the nature of metal particles of bi-functional Pt/Pd-supported zeolite Beta materials and on their catalytic activity for the hydroisomerization of alkanes[J].Journal of Catalysis,2008,254(1):12-26.
[16]郑坚,董家禄,须沁华.Pt/L及Pt/β沸石中Pt的自还原研究[J].科学通报,1997,(5):498-500.(ZHENGJian,DONG Jialu,XU Qinhua.Study on Pt selfreduction in Pt/L and Pt/beta zeolite[J].China Science Bulletin,1997,(5):498-500.)
[17]卢维奇,李凤仪,万惠霖.Pt-Gd/KL和Pt/GdKL分子筛的重整催化活性中心研究[J].中国稀土学报,1998,16(4):319-324.(LU Weiqi,LI Fengyi,WAN Huilin.Study on reforming catalytic activity center of Pt-Gd/KLand Pt/GdKL molecular sieves[J].Journal of the Chinese Rare Earth Society,1998,16(4):319-324.)
[18]GRAU J M,DAZA L,SEOANE X L,et al.Effect of Ba and rare earths cations on the properties and dehydrocyclization activity of Pt/K-LTL catalysts[J].Catalysis Letters,1998,53(3/4):161-166.
[19]PRIMET M,BASSET J M,MATHIEU M V,et al.Infrared study of CO adsorbed on Pt/Al2O3.A method for determining metal-adsorbate interactions[J].Journal of Catalysis,1973,29(2):213-223.
[20]KUMAR M,SAXENA A K,NEGI B S,et al.Role of pore size analysis in development of zeolite reforming catalyst[J].Catalysis Today,2008,130(2):501-508.
[21]BOURNONVILLE J P,MARTINO G.Sintering of alumina supported platinum[J].Studies in Surface Science&Catalysis,1980,6:159-166.
[2]TAMM P W,MOHR D H,WILSON C R.Octane enhancement by selective reforming of light paraffins[J].Studies in Surface Science&Catalysis,1988,38:335-353.
[3]TROWBRIDGE T D.Extruded zeolite catalysts:EP,0251564[P].1991.
[4]MOHR D H.A process for regenerating a monofunctional large-pore zeolite catalyst having high selectivity for paraffin dehydrocyclization:EP,0294448B1[P].1991.
[5]HONG S B,MIELCZARSKI E,DAVIS M E.Aromatization of n-hexane by platinum-containing molecular sieves I Catalyst preparation by the vapor phase impregnation method[J].Journal of Catalysis,2010,23(22):359-369.
[6]FANG X,LI F,QIANG Z,et al.Effects of heavy rare earth addition on properties of KL zeolite-supported platinum reforming catalyst[J].Applied Catalysis AGeneral,1997,161(1/2):227-234.
[7]PAULMR,CLAUDENACCACHE.Dehydrocyclization of alkanes over zeolite-supported metal catalysts:Monofunctional or bifunctional route[J].Catalysis Reviews,1997,39(1/2):5-48.
[8]郑坚,傅乐峰,董家禄,等.镧改性Pt/KL沸石芳构化催化剂的研究[C]//北京:第九届全国催化学术会议论文集,1998:887-888.
[9]FUKUNAGA T,KATSUNO H.Halogen-promoted Pt/KL zeolite catalyst for the production of aromatic hydrocarbons from light naphtha[J].Catalysis Surveys from Asia,2010,14(3/4):96-102.
[10]KATSUNO H,FUKUNAGA T,SUGIMOTO M.New modification method of Pt/L zeolite catalyst for hexanes aromatization[J].Studies in Surface Science&Catalysis,1993,75(10):2419-2422.
[11]VERDUIJN J P,JANSSEN M,de GRUIJTER C B,et al.Zeolite L preparation:US,5064630[P].1991.
[12]宋婕,马怀军,阎立军,等.KL分子筛的碱性对Pt/KL催化剂上正己烷芳构化的影响[J].石油化工,2015,44(6):683-688.(SONG Jie,MA Huaijun,YANLijun,et al.Effect of basicity of KL molecular sieves on n-hexane aromatization over Pt/KL catalysts[J].Petrochemical Technology,2015,44(6):683-688.)
[13]薛炼,张玉红,马爱增.Pt/KL催化剂的正己烷芳构化反应性能研究[J].石油炼制与化工,2007,38(7):18-21.(XUE Lian,ZHANG Yuhong,MA Aizeng,et al.Study on the aromatization of Pt/KL catalyst with n-hexane[J].Petroleum Processing and Petrochemicals,2007,38(7):18-21.)
[14]HAN W J,KOOH A B,HICKS R F.Infrared spectroscopy of carbon monoxide adsorbed on Pt/Lzeolite[J].Catalysis Letters,1993,18(3):193-208.
[15]ROLDN R,BEALE A M,SNCHEZ-SNCHEZ M,et al.Effect of the impregnation order on the nature of metal particles of bi-functional Pt/Pd-supported zeolite Beta materials and on their catalytic activity for the hydroisomerization of alkanes[J].Journal of Catalysis,2008,254(1):12-26.
[16]郑坚,董家禄,须沁华.Pt/L及Pt/β沸石中Pt的自还原研究[J].科学通报,1997,(5):498-500.(ZHENGJian,DONG Jialu,XU Qinhua.Study on Pt selfreduction in Pt/L and Pt/beta zeolite[J].China Science Bulletin,1997,(5):498-500.)
[17]卢维奇,李凤仪,万惠霖.Pt-Gd/KL和Pt/GdKL分子筛的重整催化活性中心研究[J].中国稀土学报,1998,16(4):319-324.(LU Weiqi,LI Fengyi,WAN Huilin.Study on reforming catalytic activity center of Pt-Gd/KLand Pt/GdKL molecular sieves[J].Journal of the Chinese Rare Earth Society,1998,16(4):319-324.)
[18]GRAU J M,DAZA L,SEOANE X L,et al.Effect of Ba and rare earths cations on the properties and dehydrocyclization activity of Pt/K-LTL catalysts[J].Catalysis Letters,1998,53(3/4):161-166.
[19]PRIMET M,BASSET J M,MATHIEU M V,et al.Infrared study of CO adsorbed on Pt/Al2O3.A method for determining metal-adsorbate interactions[J].Journal of Catalysis,1973,29(2):213-223.
[20]KUMAR M,SAXENA A K,NEGI B S,et al.Role of pore size analysis in development of zeolite reforming catalyst[J].Catalysis Today,2008,130(2):501-508.
[21]BOURNONVILLE J P,MARTINO G.Sintering of alumina supported platinum[J].Studies in Surface Science&Catalysis,1980,6:159-166.