Search

We investigated the roles of nickel and vanadium in the properties of ZSM-5 additives and in the fluid catalytic cracking (FCC) products, yielding 4000 and 12 000 ppm loadings of Ni + V. The ZSM-5 additive was deactivated in a cyclic deactivation unit (CDU), where cracking–regeneration reactions were carried out with vacuum gas oil (VGO) spiked with Ni and V naphthenates. Characterization of the deactivated ZSM-5 additives with N2physisorption, SEM, and pyridine FTIR techniques showed a uniform Ni distribution across a particle, little variation in the Brønsted acidity, and an increase in Lewis acidity, when Ni and V were added. Tests were carried out in a short contact time microactivity test (SCT-MAT) unit with ZSM-5 and n-hexane and blends of equilibrium catalyst (ECAT) and ZSM-5 with VGO. With hexane Ni and V, the dehydrogenation, aromatization, and coking reactions are enhanced. With VGO, the metals were found to decrease the propylene selectivity whereas that of butylene increased.

This short critical review gives an insight on the potential that lignin and its bio-oils present towards the production of thermosetting epoxy polymers and composites. Green and sustainable ways of producing monomers and polymers from renewable sources are critical and lignin, as an underutilized bio-based waste material, presents a high exploitation potential. Due to its versatile and highly functional phenolic structure, the utilization of lignin or its depolymerized fractions (bio-oils) has been investigated in the last years as alternative for fossil-based epoxy resin pre-polymers and crosslinkers. Lignin can in fact be considered as a crosslinker for epoxy resins, especially after appropriate functionalization with amine groups or with additional hydroxyl groups, or it can be modified with epoxide groups towards the replacement of toxic BPA-based epoxy prepolymers. Furthermore, lignin derived pyrolysis or hydrogenolysis bio-oils may offer highly reactive soluble oligomers that after appropriate functionalization could be utilized as bio-based epoxy prepolymers. The lignin-based epoxy resins and composites exhibit similar or even better and novel properties, compared to those of pristine epoxy polymers, thus rendering lignin a highly valuable feedstock for further utilization in the thermoset polymer industry.

The scope of this work is the experimental and modeling study of adsorptive deep desulfurization of model fuels utilizing activated carbons. Emphasis is given on how oxidative chemical treatment affects the textural and surface chemistry properties and hence the desulfurization kinetics and performance, while the effect of the copresence of aromatics is also investigated. The derivation of the kinetic model and the understanding of adsorption mechanism(s) are also among the main focuses of the work. Two model solutions, one to mimic gasoline/petrol (DBT in hexane) and another for diesel (4,6-DMDBT in hexadecane), with low initial sulfur concentration (20 ppmwS), as well as a model fuel consisting of 4,6-DMDBT, benzene, and naphthalene in hexadecane mimicking the real diesel fuel, were prepared. Adsorption equilibrium and kinetic experiments were conducted, while the results were fitted by simple empirical models and phenomenological models. Chemical treatment through oxidation enhanced the performance of the carbon, reaching a final concentration of less than 2 ppmwS in the case of DBT in hexane and 7.2 ppmwS for 4,6-DMDBT in hexadecane, thus achieving deep desulfurization. In contrast, the copresence of aromatic compounds in high concentrations decreased the efficiency of the carbons, revealing their competitive character in adsorptive desulfurization. Surface diffusion is considered the main mechanism governing the adsorption kinetics. A strong inhibition in diffusion is observed due to the competitive adsorption/interactions, as well as of the already adsorbed compounds. Interestingly, as regards the DBT/hexane system, the hindrance is so strong that the model has to be replaced by a system of two steps in series having kinetics of quite disparate time scales.