Mechanistic Insight into Heteroatom Removal from Vacuum Gas Oil Blended with PMMA or PET Waste.

This work analyzes vacuum gas oil (VGO) and hydrocracking products of this feed blended with polymethylmethacrylate (PMMA) or polyethylene terephthalate (PET) to clarify the oxygen, nitrogen, and sulfur removal pathways in these complex mixtures. Hydrocracking reactions are conducted in a semi-batch reactor with a Pt-Pd/HY bifunctional catalyst at 400 °C and 80 bar for 300 min with 10 wt % waste plastic using 0.1 catalyst/feed weight ratio. The samples are analyzed using various techniques, including high-resolution mass spectrometry, providing an improved, more detailed analytical representation. The results demonstrate the synergistic effect of cofeeding oxygenated plastics to the VGO, altering the preferential reaction pathways of heteroatom-containing species in the following order: nitrogen, oxygen, and sulfur. We assess the nature of the species from the gathered data, establish plausible reaction mechanisms, and evaluate the catalyst's role.

Designing a Multifunctional Catalyst for the Direct Production of Gasoline-Range Isoparaffins from CO2.

The production of carbon-neutral fuels from CO2 presents an avenue for causing an appreciable effect in terms of volume toward the mitigation of global carbon emissions. To that end, the production of isoparaffin-rich fuels is highly desirable. Here, we demonstrate the potential of a multifunctional catalyst combination, consisting of a methanol producer (InCo) and a Zn-modified zeolite beta, which produces a mostly isoparaffinic hydrocarbon mixture from CO2 (up to ∼85% isoparaffin selectivity among hydrocarbons) at a CO2 conversion of >15%. The catalyst combination was thoroughly characterized via an extensive complement of techniques. Specifically, operando X-ray absorption spectroscopy (XAS) reveals that Zn (which plays a crucial role of providing a hydrogenating function, improving the stability of the overall catalyst combination and isomerization performance) is likely present in the form of Zn6O6 clusters within the zeolite component, in contrast to previously reported estimations.

Insight into structure-reactivity relationships for the iron-catalyzed hydrotreatment of technical lignins.

The viability of several technical lignins as a source for biobased platform chemicals was investigated via hydrotreatment using a cheap Fe-based limonite catalyst and without using a solvent. In general, high-quality oils (up to 29 wt% total monomers) with an average relative composition of 55% alkylphenolics and 27% aromatics were obtained. Detailed structural investigations showed that the S-G aromatic unit content of the lignins was the most important factor positively affecting overall oil yields. A second parameter was the lignocellulose processing method. Even though alkaline lignin isolation provides more recalcitrant lignins, their lower aliphaticity and methoxy group content partially limit char and gas formation. Finally, enhanced monomer yields could be obtained irrespective of the ether linkage content, and a high amount of ß-O-4 linkages actually showed a slightly negative effect on monomer yields. Overall, the results demonstrate that this route is particularly suitable for processing residual lignin streams.

Experimental Studies on the Hydrotreatment of Kraft Lignin to Aromatics and Alkylphenolics Using Economically Viable Fe-Based Catalysts.

Limonite, a low-cost iron ore, was investigated as a potential hydrotreatment catalyst for kraft lignin without the use of an external solvent (batch reactor, initial H2 pressure of 100 bar, 4 h). The best results were obtained at 450 °C resulting in 34 wt % of liquefied kraft lignin (lignin oil) on lignin intake. The composition of the lignin oil was determined in detail (elemental composition, GC-MS, GC×GC-FID, and GPC). The total GC-detectable monomeric species amounts up to 31 wt % on lignin intake, indicating that 92 wt % of the products in the lignin oil are volatile and thus of low molecular weight. The lignin oil was rich in low-molecular-weight alkylphenolics (17 wt % on lignin) and aromatics (8 wt % on lignin). Performance of the limonite catalyst was compared to other Fe-based catalysts (goethite and iron disulfide) and limonite was shown to give the highest yields of alkylphenolics and aromatics. The limonite catalyst before and after reaction was characterized using XRD, TEM, and nitrogen physisorption to determine changes in structure during reaction. Catalyst recycling tests were performed and show that the catalyst is active after reuse, despite the fact that the morphology changed and that the surface area of the catalyst particles was decreased. Our results clearly reveal that cheap limonite catalysts have the potential to be used for the depolymerization/hydrodeoxygenation of kraft lignin for the production of valuable biobased phenolics and aromatics.