Methylacetylene, removal

C4 raw cuts of stream crackers typically contain butanes (4-6%), butenes (40-65%) and 1,3-butadiene (30-50%), as well as some vinylacetylene, 1-butyne, propadiene and methylacetylene. First, acetylenes are selectively hydrogenated and the 1,3-butadiene is extracted resulting in butene cut (or raffinate I). Isobutylene is next removed to produce raffinate II which contains linear butenes and some residual 1,3-butadiene. The latter needs to be removed to achieve maximum butene yields. The methods and catalysts for this process are chosen according to the final use of butenes. The demand for polymer-grade... 

C3 material from the deethanizer bottom (10) is depropanized (15), hydrotreated (16) to remove methylacetylene and propadiene and fractionated to recover polymer-grade propylene. C4 components are separated from heavier components in the debutanizer (18) to recover raw C4 product and a C5 stream that forms a gasoline product when combined with hydrocarbon condensates from the hot section. 

Use of beta zeolite catalyst does not require the benzene feed to be clay treated prior to use in alkylation service. Some of the unsaturated material in the benzene can lead to the formation in the alkylation reactors of polycyclic-aromatic material which will get preferentially trapped in some zeolites having relatively small-sized pores. This can lead to increased deactivation rates in such small-pore zeolites. Beta zeolite s large pore structure makes it possible to more easily handle this polycyclic-aromatic material and as a result does not require further treatment of the benzene feed to remove unsaturated material. In addition, alpha-methylstyrene (AMS) is produced by alkylation of benzene with methylacetylene or propadiene. Some of the AMS alkylates with benzene, forming diphenyl-propane, a heavy aromatic that leaves the unit with the DIPB column bottoms. 

The phosphine-catalyzed umpolung y-addition of diphenylphosphine oxide to diphenylphosphinoyl-methylacetylene was accomplished best under MW conditions in isopropanol. The bis(phosphine oxide) was obtained in 72% yield The reaction was extended also to other model compounds, but in these cases another isomer was also formed. The unsaturation of the primary products was removed by catalytic hydrogenation (Scheme 21) ... 

Hydrogenation of methylacetylene and propadiene, its isomer (MAPD) in the separated C3 stream is very similar to tail-end acetylene removal. The possible reactions are ... 

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