Cyclopentadiene Dimerization Kinetics in the Presence of C₅ Alkenes and Alkadienes

Abstract

This work describes an experimental kinetic study and the development of a kinetic model for the dimerization of cyclopentadiene (CPD) to dicyclopentadiene (DCPD) in multicomponent reaction mixtures at temperatures ranging from 80 to 160 °C. The reaction mixtures consist of CPD and other reactive C 5 compounds, including isoprene, trans-1,3-pentadiene, 1-pentene, cis-2-pentene, and trans-2-pentene, which are normally present in the CPD stream derived from steam cracking of naphtha. Reaction rate constants for (a) dimerization of CPD to form exo-and endo-DCPD, (b) the codimerization of CPD with the other reactive components, and the homodimerization of each of the reactive components are presented along with the corresponding activation energies and pre-exponential factors. By including the retro Diels−Alder reaction of endo-DCPD and the formation of CPD trimers, our kinetic model accurately predicts concentrations of CPD, endo-DCPD, exo-DCPD, and codimers with respect to time. The model identifies CPD self-dimerization as the dominant reaction occurring in the multicomponent mixture, followed by the codimerization between cyclopentadiene and isoprene. At 120 °C, codimerization reactivity with CPD was found in the following order: 1-pentene > cis-2-pentene > 2-methyl-1-butene > cyclopentene > 2methyl-2-butene > trans-2-pentene, with reaction rate constants 1 to 2 orders of magnitude lower than that of exo-DCPD formation. Overall, the model established herein allows an accurate prediction of the DCPD purity that can be obtained from a petroleum pyrolysis stream no matter what the impurity concentrations may be.

Isomer-dependent catalytic pyrolysis mechanism of the lignin model compounds catechol, resorcinol and hydroquinone

“…The appearance of cyclopentadiene proves that the dimer undergoes a retro-Diels–Alder reaction on the catalyst surface, which is an endothermic process. 46 The product distribution of dicyclopentadiene is similar to that of cyclopentadiene (Fig. S11 † left), and naphthalene ( m / z 128) appeared at elevated temperatures, too.…”

Trends in the Diels–Alder reaction in polymer chemistry

“…Scheme 22 : Dimerization of cyclopentadiene[173] Since the beginning of the 20 th century, many DA reactions involving CPD have been reported with a lot of dienophiles[175], such as quinones [176], unsaturated trihalosilanes [177], acrylate derivatives [178], vinyl ketones [179] or fullerenes [180]. DA reaction with CPD is well-documented and many articles focus on the ab initio calculations with plenty of dienophiles and solvents for a better understanding of the reactivity of CPD and to anticipate some possible reactions [181-183].…”

Role of Surface Acidity in Formation and Performance of Active Ni Single Sites in Supported Catalysts for Butene Dimerization: A View inside by Operando EPR and In Situ FTIR Spectroscopy

“…When a Ni­(Cp) 2 precursor is used, this proceeds in two steps: (1) reaction of a Brønsted proton with one of the two Cp – ligands and the release of a neutral cyclopentadiene molecule, as detected by electrospray ionization mass spectrometry (ESI-MS, Figure S3). The remaining [CpNi] + fragment (in which Ni is still divalent) is attached to the support surface, compensating the negative charge on the bridging oxygen, which is also known from other supports possessing Brønsted acid sites. ,, (2) Reduction to Ni + occurs upon the release of the second cyclopentadienyl (Cp) ligand, supposed to form initially a radical that reacts further to dicyclopentadiene and/or even higher oligomers. − This is also supported by higher m / z fragments in the ESI-MS spectrum (Figure S3) as well as by a narrow signal at g = 2.004 in the EPR spectrum of the thus prepared fresh supported Ni catalyst, which will be discussed below. As confirmed by DFT calculations, the most stable position of Ni + is between two neighboring surface oxide ions …”