Effect of propylene in feedstock on the coking behavior of PtSnK/Al2O3 catalyst of propane dehydrogenation
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摘要: 以含有不同比例丙烯的丙烷为原料进行丙烷脱氢反应,重点考察富丙烯条件下Pt基催化剂上的碳沉积行为。研究结果表明,原料中丙烯的存在加快了催化剂的积炭速率,缩短了积炭在载体上达到积炭平衡的时间,促进了活性相表面积炭的形成及积炭石墨化;同时原料中富含丙烯,使不饱和脂肪族化合物的生成量增加,从而促进了芳香性的碳、石墨化的碳的生成,但催化剂结构未遭到破坏。在丙烷脱氢过程中,当丙烯含量增加到1.5%时,出现活性相表面上的积炭“峰I”,而“峰II”向高温区移动。当烯烃含量增加3.0%时,峰I和峰II融合在一起,整个峰的面积明显增加,积炭量超过10.26%时,催化剂积炭石墨化程度越来越高。丙烯含量增加,加速了载体的容碳能力迅速饱和过程,同样的反应时间下,积炭量增加。
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关键词:
- PtSnK/Al2O3催化剂 /
- 丙烷 /
- 丙烯 /
- 积炭 /
- 脱氢
Abstract: The dehydrogenation of propane was carried out with propane containing different proportions of propylene, and the carbon deposition behavior of Pt-based catalyst under propene-rich condition was investigated. The results show that the presence of propylene in the raw material accelerates the rate of carbon deposition, shortening the time of dynamic equilibrium of carbon deposition on the support, and promoting the formation of carbon on the surface area of the active phase and the graphitization of carbon deposition. At the same time, the rich propylene in the raw material increases the amount of unsaturated aliphatic compounds, thus promoting the generation of aromatic carbon and graphitized carbon, but the catalyst structure is not destroyed. In the process of propane dehydrogenation, when the propylene content increases to 1.5%, the carbon “peak I” appears on the surface of the active phase, and the "peak II" moves to the high temperature region. When the alkene content increases by 3.0%, peak I and peak II merge together, and the area of the entire peak increases significantly. When the carbon deposition exceeds 10.26%, the degree of carbon deposition and graphitization of the catalyst becomes higher and higher. The increase of the propylene content accelerates the saturation process of the carbon holding capacity of the carrier. Under the same reaction time, the amount of carbon deposit increases.-
Key words:
- PtSnK/Al2O3 catalyst /
- propane /
- propylene /
- carbon deposition /
- dehydrogenation
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表 1 丙烷脱氢入口原料与出口产物组成
Table 1 Composition of feedstock in inlet and products in outlet
Product Inlet
composition/%Outlet
composition/%Methane 0 2.04 Ethane 0 1.76 Ethylene 0 0.35 Propane 54.91 36.51 Propylene 0 11.63 Hydrogen 45.08 47.70 表 2 原料中含有丙烯对催化剂积炭速率的影响
Table 2 Effect of propylene in feedstock on the rate of coke decomposition of catalyst
Propylene content/% Reaction time/h Coke amount/% Rate of coke
decomposition of catalyst/g(C)∙(g(cat)∙h)−10 48 2.58 0.0005 0.8 48 3.15 0.0006 1.5 48 5.50 0.0011 3.0 48 10.26 0.0021 表 3 原料中不同烯烃含量下积炭催化剂酸量及酸分布
Table 3 Acid amount and acid distribution of different catalysts of coke decomposition under different content of propylene in feedstock conditions
Propylene content/% Total acid amount/
(mmol∙g−1)Acid distribution/% 150−250 ℃ 250−400 ℃ 400−500 ℃ 0 0.248 51.21 28.63 20.16 0.8 0.219 53.88 27.40 18.72 1.5 0.117 60.68 22.22 17.09 3.0 0.035 65.71 25.71 8.57 表 4 D峰和G峰积分数据
Table 4 Integral data of the D Peak and the G Peak
Sample D Peak G Peak ID/IG D0 41423 18023 2.3 D0.8 245212 119508 2.05 D1.5 197065 99606 1.89 D3.0 167072 100787 1.67 表 5 原料中不同烯烃含量下催化剂积炭的元素分析
Table 5 Analysis of C and H of coke catalyst under different content of propylene in feedstock conditions
C3H6/% 0 0.8 1.5 3 C 2.58 3.15 5.5 10.26 H 0.23 0.27 0.24 0.36 H/C 1.07 1.02 0.52 0.42 -
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