Dual catalyst system for selective vinyl chloride production via ethene oxychlorination,Catalysis Science & Technology

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Dual catalyst system for selective vinyl chloride production via ethene oxychlorination
Catalysis Science & Technology ( IF 4.4 ) Pub Date : 2019/12/11 , DOI: 10.1039/c9cy01801h
Matthias Scharfe _{1,

2,

3,

4,

5} , Vladimir Paunović _{1,

2,

3,

4,

5} , Sharon Mitchell _{1,

2,

3,

4,

5} , Roland Hauert _{5,

6,

7,

8} , Shibo Xi _{9,

10,

11,

12} , Armando Borgna _{9,

10,

11,

12} , Javier Pérez-Ramírez _{1,

2,

3,

4,

5}

Affiliation

A dual system comprising two catalytic reactors connected in series was developed for the direct conversion of ethene to vinyl chloride monomer (VCM). The first reactor uses ZrO₂-supported ceria (CeO₂/ZrO₂) to perform ethene oxychlorination to 1,2-dichloroethene (EDC) that is dehydrochlorinated to VCM in the second reactor over calcium-promoted γ-Al₂O₃. The choice of carrier for ceria is of critical importance to maximize the EDC production by reducing combustion products. While MgO, SiO₂, SiC, TiO₂, ZSM-5, and γ-Al₂O₃ carriers induced higher overoxidation compared to bulk ceria, ZrO₂ was the only carrier that suppressed CO_x formation. Moreover, the latter carrier led to the highest oxychlorination activity. The unique performance of the CeO₂/ZrO₂ catalyst was rationalized by its ability to promote chlorine evolution and to suppress the combustion of chlorinated products, as inferred from the activity evaluation in HCl and VCM oxidation, respectively. The outstanding redox properties, enabling operation at low temperature and thus high selectivity, are associated with the formation of defective CeO₂ nanoparticles, contrasting the low activity over Ce–Zr mixed oxide. In order to subsequently form VCM, an efficient EDC dehydrochlorination catalyst was designed by moderating the acidity of γ-Al₂O₃via calcium doping and used in a reactor after CeO₂/ZrO₂. This dual catalyst system displayed 100% selectivity to VCM at 25% ethene conversion, surpassing the space time yield of the best ethene-to-VCM catalyst EuOCl by a factor of four, where the first step is operated at an elevated temperature of about 100–150 K with respect to cupric chloride benchmarks. In addition, the catalytic dehydrochlorination, operated at a lower temperature of 100 K than the current non-catalytic process, showed minimized coke formation. This developed system rendered stable after slight initial deactivation, offering promising potential to intensify VCM production.

中文翻译：

通过乙烯氧氯化法选择性生产氯乙烯的双重催化剂体系

开发了包括两个串联连接的催化反应器的双系统，用于将乙烯直接转化为氯乙烯单体（VCM）。第一反应器中使用的ZrO ₂ -支持的二氧化铈（铈₂ /的ZrO ₂），以执行乙烯氧氯化到被过度钙促进的γ-Al系脱氯化氢以VCM在第二反应器1,2-二氯乙烯（EDC）₂ ö ₃。二氧化铈载体的选择对于通过减少燃烧产物来最大化EDC产量至关重要。而氧化镁，二氧化硅₂，碳化硅，二氧化钛₂，ZSM-5，和在γ-Al _2个ö ₃载体相比本体二氧化铈，的ZrO诱导更高过氧化₂是唯一抑制CO _x形成的载体。此外，后一种载体导致最高的氧氯化活性。从分别在HCl和VCM氧化中的活性评估得出，CeO ₂ / ZrO ₂催化剂具有促进氯释放和抑制氯化产物燃烧的能力，从而使其独特的性能合理化。出色的氧化还原性能，使其能够在低温下运行，从而具有很高的选择性，与有缺陷的CeO ₂纳米颗粒的形成有关，这与Ce-Zr混合氧化物的低活性形成了鲜明的对比。以便随后形成VCM，一个高效的EDC脱氯化氢催化剂通过缓和的酸度的γ-Al设计₂O ₃通过钙掺杂并在CeO ₂ / ZrO ₂之后用于反应器中。这种双催化剂体系在25％的乙烯转化率下对VCM表现出100％的选择性，比最佳的乙烯-VCM催化剂EuOCl的时空产率高出四倍，其中第一步在约100的高温下进行对于氯化铜基准，为–150K。此外，在比当前非催化过程低100 K的温度下进行的催化脱氯化氢反应，可将焦炭的生成降至最低。经过轻微的初始停用后，该开发的系统即可保持稳定，为增强VCM生产提供了可观的潜力。

更新日期：2020-02-10

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