Aggregation state effects in shape-selective hydroconversion

A unified model for the description of vapor- and liquid-phase hydroconversion has been developed. The high isomer yield, which is typical for the shape selectivity exhibited by Pt/H-ZSM-22 at vapor-phase conditions, is still observed at liquid-phase conditions. However, the molar cracking yield is enhanced by at least 10 mol % when operating at liquid-phase conditions. The latter effect is mainly due to an increased physisorption competitiveness of lighter alkanes, which also results in enhanced cracking of lighter alkanes. The effect amounts to approximately 3 orders of magnitude for a difference of 2 in carbon number. These aggregation state effects are accounted for in the model through (i) liquid phase thermodynamic nonideality, (ii) destabilization of the physisorbed state by compression of the adsorbate by the bulk fluid, and (iii) carbenium ion stabilization by sorbent solvation by the bulk fluid. F-values of the order of 103 indicate the model's adequacy in describing the observed phenomena

Skeletal isomerizaton of octadecane on 10-membered ring zeolites

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Rapid Induction of Astaxanthin in <i>Haematococcus lacustris</i> by Mild Electric Stimulation

Efficient induction of astaxanthin (AXT) biosynthesis remains a considerable challenge for the industrialization of the biorefinement of the microalga Haematococcus lacustris. In this study, we evaluated the technical feasibility of photosynthetic electrotreatment to enhance AXT accumulation in H. lacustris. The AXT content of H. lacustris electrotreated at an optimal current intensity (10 mA for 4 h) was 21.8% to 34.9% higher than that of the untreated control group, depending on the physiological state of the initial palmella cells. The contents of other carotenoids (i.e., canthaxanthin, zeaxanthin, and β-carotene) were also increased by this electrotreatment. However, when H. lacustris cells were exposed to more intense electric treatments, particularly at 20 and 30 mA, cell viability significantly decreased to 84.2% and 65.6%, respectively, with a concurrent reduction in the contents of both AXT and the three other carotenoids compared to those of the control group. The cumulative effect of electric stimulation is likely related to two opposing functions of reactive oxygen species, which facilitate AXT biosynthesis as signaling molecules while also causing cellular damage as oxidizing radicals. Collectively, our findings indicate that when adequately controlled, electric stimulation can be an effective and eco-friendly strategy for inducing targeted carotenoid pigments in photosynthetic microalgae