Coking: Difference between revisions
eq |
section taken in part from catalyst poisoning |
||
| Line 3: | Line 3: | ||
A simplified equation for coking is shown in the case of [[ethylene]]: |
A simplified equation for coking is shown in the case of [[ethylene]]: |
||
: 3 C<sub>2</sub>H<sub>4</sub> → 2 C ("coke") + 2 C<sub>2</sub>H<sub>6</sub> |
: 3 C<sub>2</sub>H<sub>4</sub> → 2 C ("coke") + 2 C<sub>2</sub>H<sub>6</sub> |
||
A more realistic but complex view involves the [[alkylation]] of an aromatic ring of a coke nucleus. [[solid acid|Acidic]] catalysts are thus especially prone to coking because they are effective at generating [[carbocation]]s (i.e., alkylating agents). |
|||
Coking is one of several mechanisms for the deactivation of a [[catalyst]]. Other mechanisms include [[sintering]], [[catalyst poisoning|poisoning]], and [[phase change|solid-state transformation]] of the catalyst.<ref>{{cite journal|title=Catalyst Deactivation|authors=Forzatti, P.; Lietti, L.|journal=Catalysis Today|year=1999|volume=52|pages=165-181|doi=10.1016/S0920-5861(99)00074-7}}</ref><ref>{{cite journal|last1=Bartholomew|first1=Calvin H|title=Mechanisms of Catalyst Deactivation|journal=Applied Catalysis A: General|volume=212|issue=1–2|pages=17–60|doi=10.1016/S0926-860X(00)00843-7|year=2001}}</ref> |
|||
==References== |
==References== |
||
Revision as of 22:32, 22 April 2018
Coking is the deposition of carbon-rich solids. In heterogeneous catalysis, the process is undesirable because the coke blocks the catalytic sites. Coking is characteristic of high temperature reactions involving hydrocarbons feedstocks. Typically coking is reversed by combustion, provided that the catalyst will tolerate such.[1]2
A simplified equation for coking is shown in the case of ethylene:
- 3 C2H4 → 2 C ("coke") + 2 C2H6
A more realistic but complex view involves the alkylation of an aromatic ring of a coke nucleus. Acidic catalysts are thus especially prone to coking because they are effective at generating carbocations (i.e., alkylating agents).
Coking is one of several mechanisms for the deactivation of a catalyst. Other mechanisms include sintering, poisoning, and solid-state transformation of the catalyst.[2][3]
References
- ^ H. Schultz. ""Coking" of zeolites during methanol conversion: Basic reactions of the MTO-, MTP- and MTG processes". Catalysis Today. 154: 183–194. doi:10.1016/j.cattod.2010.05.012.
- ^ "Catalyst Deactivation". Catalysis Today. 52: 165–181. 1999. doi:10.1016/S0920-5861(99)00074-7.
{{cite journal}}: Unknown parameter|authors=ignored (help) - ^ Bartholomew, Calvin H (2001). "Mechanisms of Catalyst Deactivation". Applied Catalysis A: General. 212 (1–2): 17–60. doi:10.1016/S0926-860X(00)00843-7.