CIS-2-Butene: Properties, Role in Isobutene Dimerization, and Sensing Applications

CIS-2-Butene is a colorless liquefied petroleum gas with a boiling point of 3.7°C and a flammability limit of 1.8-9.7% by volume. Strong oxidizers may react vigorously with them. Reducing agents can react exothermically to release gaseous hydrogen. In the presence of various catalysts (such as acids) or initiators, compounds in this class can undergo very exothermic addition polymerization reactions. Aluminum borohydride reacts with alkenes and in the presence of oxygen, combustion is initiated even in the absence of moisture.cis-2-Butene is an unsaturated olefinic hydrocarbon used as a precursor in the polymerization of gasoline. It is also used to synthesize butadiene and other aliphatic C4/C5 organic molecules. It is also employed as a cross-linking agent.

Influence of Linear Butenes in the Dimerization of Isobutene

Isobutene (iB) dimerization as part of the isooctane production process is being successfully applied industrially in Edmonton, Canada.  Isooctane is produced for the Californian market because groundwater contamination has led to a ban there on methyl tert-butyl ether (MTBE) in gasoline. Dimerization of isobutene and further hydrogenation of the produced diisobutenes are carried out to obtain MTBE-free isooctane with good gasoline blending properties. Although linear butenes have been fed together with isobutene to the isobutene dimerization system,11,4 no study has been made of their effect in a system where TBA is used as the selectivity-enhancing component. The purpose of the present work was to study the effect of linear butenes on the yield and kinetics of the isobutene dimerization in the presence of TBA. Experiments were carried out with pure 1-butene and cis-2-butene (c-2B) feeds and with an isobutene and cis-2-butene mixture. Alkene conversions and dimer selectivities were calculated from the results. To supplement our previous kinetic model for isobutene dimerization,  we constructed a kinetic rate equation for the codimerization reaction.Experiments were carried out with pure 1-butene and cis-2-butene feeds and with a mixture of isobutene and cis-2-butene. The experiments showed that the reactivity of linear alkenes under the isobutene dimerization conditions was low. Mainly, isomerization to other linear alkenes was observed with the pure feeds, although conversion of 2-butenes to 1-butene was low.[1]

Experiments were carried out with pure cis-2-butene with 2-butanol as the additive to compare the effects of TBA and 2-butanol. The feed and product compositions with cis-2-butene and with 0.4 wt % TBA or 2-butanol as the additive are presented in Table 1. At 353 K, slightly higher trans-2-butene contents were obtained with 2-butanol than with TBA (6 wt % vs 3 wt %). The alcohol and dimer contents in the steady state are about the same independent of the type of alcohol in the feed. There is virtually no isomerization or dimerization of linear butenes at 353 K. Isomerization of cis-2-butene to trans-2-butene is more significant at higher temperatures. In experiments with the mixture, cis-2-butene isomerization to trans-2-butene was observed under all conditions, especially at low TBA contents and high temperatures. 2-Butene conversion was also high under these conditions, and codimers with isobutene were formed. Feeding 2-butene as part of the solvent had little effect on the isobutene conversion, and the selectivity for C8 dimers remained the same. Some 2-butanol was formed from the water from TBA dehydration.

Molecular adsorption on hydrogenated fullerite C24 nanosheets

Cis-2-butene and trans-2-butene are highly flammable and hazardous vapours that are commonly evolved in the production of various chemicals, such as plastics, rubbers, and resins. In this research work, we used hydrogenated fullerite C24 nanosheets as a sensing material to detect cis-2-butene and trans-2-butene. Firstly, the structural firmness of hydrogenated fullerite C24 is studied through the cohesive formation energy. Furthermore, the PDOS maps and energy band structures are utilised to comprehend the electronic properties of the base material. The band gap of hydrogenated fullerite C24 nanosheets has been calculated to be 2.785 eV. By analysing the adsorption energy, Mulliken charge transfer, and relative band gap variations, we can understand the adsorption properties of cis-2-butene and trans-2-butene isomers on the base material. Altogether, the results conclude that hydrogenated fullerite C24 could detect hazardous cis-2-butene and trans-2-butene vapours in the vicinity.[2]

References

[1]Honkela, M. L., & Krause, A. O. I. (2005). Influence of Linear Butenes in the Dimerization of Isobutene. Industrial & Engineering Chemistry Research, 44(14), 5291-5297.

[2]Nagarajan, V., Tejaswini, R., & Chandiramouli, R. (2025). Molecular adsorption of butene isomers on hydrogenated fullerite C24 nanosheets based on first - principles study. Molecular Physics, Article e2449181.