通过掺入碱金属改性的SBA-15：其结构变化对费托合成中Fe / SBA-15体系催化性能的影响,Energy Technology

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通过掺入碱金属改性的SBA-15：其结构变化对费托合成中Fe / SBA-15体系催化性能的影响
Energy Technology ( IF 3.6 ) Pub Date : 2020-05-14 , DOI: 10.1002/ente.202000150
Leonardo A. Cano ₁ , María V. Cagnoli ₂ , José F. Bengoa ₂ , Sergio G. Marchetti ₂

Affiliation

介孔SBA-15固体掺杂有Li，K或Cs。这些系统用作铁纳米粒子的载体，每种复合物均用作费托合成中的催化剂。活化处理后，在所有固体中检测到相同的Fe物种：SBA-15壁内的Fe ₃ O ₄，α-Fe和Fe ²⁺。然而，根据所存在的掺杂剂，物种百分比及其分布是不同的。在所有的“工作”的催化剂，碳化物的ε'-的Fe的混合物_2.2 C和χ -铁₂ Ç ₅，铁₃ Ò ₄，和离子铁⁺²在SBA-15墙内。碱性阳离子产生不同数量和强度的碱性部位。在1个大气压和T = 703 K时，催化活性顺序为：Li> K>无掺杂> Cs，并且碱金属有利于烯烃的生产。在20 atm时，即使在低至543 K的温度下，活性也要高得多，这归因于载体的结构特性和扩散效应。所有催化剂都显示出在汽油范围内有希望的烃产量。从静电效应的角度讨论了碱金属的影响，而有限的烃链增长归因于对活性铁物种尺寸的控制。

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SBA‐15 Modified by Incorporation of Alkali Metals: Effect of Its Structural Changes on the Catalytic Properties of Fe/SBA‐15 System in the Fischer–Tropsch Synthesis

A mesoporous SBA‐15 solid is doped with Li, K, or Cs. These systems are used as support of iron nanoparticles, and each composite is utilized as a catalyst in the Fischer–Tropsch synthesis. After the activation treatment, the same Fe species are detected in all solids: Fe₃O₄, α‐Fe, and Fe²⁺ inside SBA‐15 walls. However, the species percentages and their distribution are different according to the dopant present. In all “working” catalysts, a mixture of carbides ε'‐Fe_2.2C and χ‐Fe₂C₅, Fe₃O₄, and ions Fe⁺² inside the SBA‐15 walls are found. Alkali cations produce different amounts and strengths of basic sites. At 1 atm and T = 703 K, the catalytic activity order is: Li > K > no doped > Cs, and the alkali metals favor the production of olefins. At 20 atm, the activity is considerably higher, even at a temperature as low as 543 K, which is attributed to structural properties of the support and to diffusional effects. All catalysts show a promising hydrocarbon production in the gasoline range. The influence of alkali metals is discussed in terms of electrostatic effects, and the limited hydrocarbon chain growth is attributed to the control over size of active iron species.

更新日期：2020-07-02

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