Difference between revisions of "Heterogeneous catalysis"

<onlyinclude>Heterogeneous catalysis is a catalysis in which the catalyst and the feedstock are different phases. In practice, this often means that the feedstock is a liquid or gas and the catalyst is a solid, also known as ''solid catalysis.'' Heterogeneous catalysis is the most widely used form of catalysis in the current chemical industry.<ref>{{Cite journal|title=The critical role of heterogeneous catalysis in lignocellulosic biomass conversion|year=2009|author=Yu-Chuan Lin, George W. Huber|journal=Energy Environ. Sci.|volume=2|issue=1|page=68–80|doi=10.1039/B814955K}}</ref> There is a wide variety of catalytic systems and many reactions can be catalysed with a solid catalyst. Examples are [[pyrolysis]], hydro-processing, [[oxidation]], amination, dehydration, [[hydrolysis]], (trans)esterification, and isomerisation.<ref name=":1">{{Cite journal|title=Functionalised heterogeneous catalysts for sustainable biomass valorisation|year=2018|author=Putla Sudarsanam, Ruyi Zhong, Sander Van den Bosch, Simona M. Coman, Vasile I. Parvulescu, Bert F. Sels|journal=Chemical Society Reviews|volume=47|issue=22|page=8349–8402|doi=10.1039/C8CS00410B}}</ref> Common heterogeneous catalysts are heterogeneous solid base catalysts and heterogeneous solid acid catalysts.<ref name=":0">{{Cite journal|title=A review of sustainable biodiesel production using biomass derived heterogeneous catalysts|year=2021-10-22|author=Semakula Maroa, Freddie Inambao|journal=Engineering in Life Sciences|page=elsc.202100025|doi=10.1002/elsc.202100025}}</ref></onlyinclude>

The pre-treatment of the feedstock for a heterogeneous catalysis is depending on the specific process and feedstock used. In principal the feedstock normally is a liquid or gas so for solid feedstocks a conversion process like a pyrolysis or gasification or a solution is needed.

A wide range of processes and technologies can make use of heterogeneous catalysts. Examples are [[pyrolysis]], hydro-processing, [[oxidation]], amination, dehydration, [[hydrolysis]], (trans)esterification, and isomerisation.<ref name=":1" /> The most common heterogeneous catalysts are heterogeneous solid base catalysts and heterogeneous solid acid catalysts. Base catalysts have a high concentration of basic sites that ensures the catalytic activity, often from Ba, Ca, Mg, and Sr and can be mixed or doped. Soap formation is a recurring drawback of these systems. Acid catalysts get their activity either from Brønsted or Lewis acidity and are commonly zirconia, silica, zeolites or zeotype materials. Major advantages of heterogeneous catalysis is the ease of separation, recyclability and high selectivity.<ref name=":0" /> Current development for future heterogeneous catalytic systems are in metal-organic frameworks (MOFs), magnetic catalysts, and solid phase ionic liquids.<ref name=":1" />