•Supported nickel complexes as heterogeneous catalysts for ethylene oligomerization.•New one-pot preparation method for supported organometallic catalysts.•Quinoline-imine nickel complexes immobilized into clay mineral interlayers.•High catalytic activity for ethylene oligomerization to produce α-olefins.Quinoline-imine nickel (II) complexes were immobilized in fluorotetrasilicic mica interlayers by a one-pot synthesis through the reaction of a nickel ion-exchanged fluorotetrasilicic mica (Ni2+-mica) with the corresponding quinoline and aniline derivatives. After activation of the prepared precatalyst by a co-catalyst (Et3Al, iBu3Al, or Et2AlCl), it showed a high catalytic activity for the oligomerization of ethylene with the formation of oligomers having carbon numbers 4–20. The maximum activity (168 g-product g-cat−1 h−1) was obtained by the oligomerization at 40 °C and 1.0 MPa in the presence of Et3Al using the precatalyst prepared from Ni2+-mica, 2-acetylquinoline, and 2, 6-dimethylaniline. In all the oligomerization runs, a long induction period was observed, and the induction time significantly depended on the co-catalyst. This induction period might be caused by the characteristic structure of the precatalysts. The FT-IR and XRD spectra of the precatalysts indicated the formation of the intended nickel complexes in the mica interlayer.

The cyclodimerization of crotonaldehyde was performed over acid or base catalysts in the gas phase. We first attempted the reaction over various acid and base catalysts using a pulse reactor. The typical bases, CaO and MgO, effectively promoted the reaction to form methylcyclohexadienecarbaldehydes (MCHC) and tolaldehydes. In contrast, no significant formation of the dimers was observed over the acid catalysts, such as SiO2–Al2O3 and H-mordenite. Aluminum oxide also promoted the dimerization, indicating that the dimerization proceeds on the weaker base sites. The main products in the formed dimers were 6-methylcyclohexa-1,3-dienecarbaldehyde and o-tolualdehyde. In addition, small amounts of 4-methylcyclohexa-1,5-dienecarbaldehyde and p-tolaldehyde were produced as dimers. When the dimerization was performed over CaO, MgO, and Al2O3 using a fixed-bed flow reactor, the catalytic activities of all the catalysts significantly decreased during the initial stage of the reaction. The TG–DTA analysis of the used catalysts clearly indicated that a large amount of the condensation products had adsorbed on the catalyst surface. The maximum selectivity to the dimers (MCHC and tolaldehydes) was 38% for an approximate 30% conversion, which was obtained during the initial stage of the reaction over the Al2O3 and CaO catalysts.

Aluminium triisopropoxide (AIP) promoted the methanolysis of polyethylene terephthalate (PET) to form monomers, dimethyl terephthalate (DMT) and ethylene glycol (EG), in an equimolar ratio. The methanolysis at 200 °C in methanol with an AIP catalyst gave DMT and EG in 64% and 63% yields, respectively. The yields were increased by using a toluene/methanol mixed solvent containing 20–50 vol.% toluene; maximum yields, 88% for DMT and 87% for EG, were obtained at 20 vol.% toluene. These results indicate that the rate of methanolysis strongly depends on the solubility of PET. The results of GPC analysis suggest that the methanolysis of PET in the absence of the catalyst includes three steps. In the first step, the depolymerisation occurred at a tie molecule connecting PET crystals and the chain length was shortened to about 1/3. The shortened chain was depolymerized to oligomers in the second step. The GPC curve of the oligomers tailed to low molecular weight, clearly indicating that the depolymerization took place at random positions on the polymer chain. The third step, the depolymerisation from the oligomers to the monomers, was promoted only in the presence of the AIP catalyst.