Study of the Combined Deactivation Due to Sulfur Poisoning and Carbon Deposition during Biogas Dry Reforming on Supported Ni Catalyst

Abstract

This paper presents a detailed study of catalyst deactivation as a result of simultaneous sulfur poisoning and coke deposition during biogas dry reforming. Experiments are performed at 700 and 800 °C with 5 and 10 ppm of H2S in model biogas with CH4/CO2 = 1.5 and 2.0. To assess the relative effect of chemisorbed sulfur in deactivating the supported Ni catalyst as compared to that of coke deposition, the experiments are performed with and without H2S in the feed. The catalyst deactivation is found to be faster in the presence of H2S. The deactivation due to sulfur chemisorption is not reversible at 700 °C, while at 800 °C the catalytic activity of Ni starts to recover on removing H2S from the feed stream. The results show that the exit CO mole fraction goes up for the sulfur poisoned catalyst which suggests that the reverse water gas shift and coke gasification reactions are not suppressed to the same degree as the reforming reaction. The fresh and the spent catalysts are characterized using XRD, BET, EDS, and TEM. The characterization of the spent catalyst shows that dry reforming of model biogas, with and without the presence of H2S, leads to the formation of multiwalled carbon nanotubes for the chosen operating conditions.

Experimental studies of catalyst deactivation due to carbon and sulphur during CO2 reforming of CH4 over Ni washcoated monolith in the presence of H2S

“…The promotional effect of sulphur coverage for the RWGS reaction has been reported in the case of Ni/γ-Al 2 O 3 pellets. [10] The higher H 2 mole fraction compared to CO in the absence of H 2 S is consistent with thermodynamic equilibrium calculations. If dry reforming can be carried out without the formation of surface carbon, then product stream will contain equimolar composition of CO and H 2 .…”

“…[9] The dry reforming of biogas over Ni catalysts leads to the formation of carbon nanotubes (CNTs), which block the pores and active sites and thus reduce the turnover frequency. [6,10] CNT formation is favoured when the size of a catalyst particle is more than 2 nm; however, due to the requirement of high operating temperature, it is very difficult to limit the particle sizes to less than 2 nm as a result of agglomeration. [7] Other than the reactor configuration and operating conditions, the activity of a catalyst towards carbon formation depends on factors such as the catalyst formulation, metal support interaction, and activation conditions.…”

“…[ 9 ] The dry reforming of biogas over Ni catalysts leads to the formation of carbon nanotubes (CNTs), which block the pores and active sites and thus reduce the turnover frequency. [ 6,10 ] CNT formation is favoured when the size of a catalyst particle is more than 2 nm; however, due to the requirement of high operating temperature, it is very difficult to limit the particle sizes to less than 2 nm as a result of agglomeration. [ 7 ]…”

RuO2 Nanoparticle-Embedded Graphitic Carbon Nitride for Efficient Photocatalytic H2 Evolution

“…The initial H 2 evolution rates were observed in the order of NMe 2 > NHMe ∼ SMe > OMe ∼ H. This result also supported the correlation between the effective H 2 evolution rates and the HOMO levels of the substrates (Figure S11). Although sulfur-containing organic compounds have been often reported to poison catalysts, − MeS-C 2 H 4 OH (2-methylthioethanol) was applicable as an electron donor for modest H 2 evolution in this study. Thus, we can conclude that substrates with an OH group are promising candidates for catalytic application in photocatalytic H 2 evolution and selective oxidation over RuO 2 /g-CN simultaneously.…”

A Brief Summary of Research Progress on the Application of Rare Earth Materials in Heterogeneous Catalysis

“…同时, 还可以将稳定性优良 的稀土元素引入反应体系充当结构助剂 [77] , 对载体的 结 构 和 形 貌 进 行 调 控 , 起 到 增 加 体 系 稳 定 性 的 作 用 [22][23][24] . 例如, Cunha 等 [76] [74] Figure 5 The linear correlation between the yields of ethanol condensation and the concentration of oxygen vacancies based on various CeO 2 catalysts (■) [74] 另外, 从表 图 6 La2O3 修饰的不同 Fe/Al 合金催化剂(50Fe(☆), 50FeLa(5)(○), 50FeLa(10)(□), 50FeLa(20)(△), 50FeLa(50)(◇))催化甲烷分解反应活 性随时间变化曲线 [76] Figure 6 Methane conversion comparison on La2O3 modified Fe/Al alloy catalysts (50Fe(☆), 50FeLa(5)(○), 50FeLa(10)(□), 50FeLa(20)(△) and 50FeLa(50)(◇)) [76] Lercher 团队 [25] The conversion (red •) and product selectivities (H 2 (olive ■), CO 2 (black ◆), CO(wine ◇), (CH 3 ) 2 CO (olive □), CH 4 (dark cyan •)) as a function of time (T＝650 ℃, S/C＝3, gas hourly space velocity (GHSV)＝28000 h -1 ) [25] 有下降, 这是因为 [26][27][28][29] (CH 4 ＋ CO 2 →2CO＋2H 2 ), 但由于镍表面容易积碳, 导致其很 容易失活, 因此需要找到合适的助催化剂来抑制表面积 碳的产生 [30] . 大多数稀土金属和氧化物都可以用作镍 基催化剂的助剂, 钆、铈和镧等稀土元素被广泛用于修 饰镍基催化剂 [31][32][33] , 其中借助镧氧化物来修饰镍基催化 剂最为常见 [32][33][34] .…”