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Abstract: Using flux variability analysis of a genome scale metabolic network of Streptomyces coelicolor, a series of reactions were identified, from disparate pathways that could be combined into an actinorhodin-generating mini-network. Candidate process feed nutrients that might be expected to influence this network were used in process simulations and in silico predictions compared to experimental findings. Ranking potential process feeds by flux balance analysis optimisation, using either growth or antibiotic production as objective function, did not correlate with experimental actinorhodin yields in fed processes. However, the effect of the feeds on glucose assimilation rate (using glucose uptake as objective function) ranked them in the same order as in vivo antibiotic production efficiency, consistent with results of a robustness analysis of the effect of glucose assimilation on actinorhodin production. [Copyright &y& Elsevier]

[Display omitted] • Great differences in coordination structures of Mg were found in Mg- and Mg/ZSM-5. • Mg well modulate the location of the framework Al in Mg-ZSM-5 zeolites. • Mg-ZSM-5 has more single Al and framework Al in straight and sinusoidal channels. • Propylene yields were improved markedly by inhibiting hydride transfer process. Al distribution engineering is an effective way to tune the catalytic performance of ZSM-5 zeolite. In the present work, a series of [Al, Mg]-ZSM-5 with different Mg contents were obtained by hydrothermal synthesis method. For comparison, Mg/ZSM-5 with a comparable Mg content were also prepared using the conventional impregnation method. Characterizations of XPS-sputtering, H 2 -TPR and Py-IR indicated the distribution and coordination structures of Mg in the samples obtained by the two preparation methods were quite different. Besides, the introduction of magnesium by hydrothermal synthesis well regulates the location of framework Al, which is not possible by the impregnation method. 27Al MAS NMR and UV–vis-DRS of Co2+-exchanged zeolites demonstrated [Al,1.0 Mg]-ZSM-5 has less aluminum in the channel intersections compared to conventional HZSM-5. Finally, the significantly lower content of "Al pairs" in [Al,1.0 Mg]-ZSM-5 inhibits the hydride transfer process, resulting in higher yields of propylene in n -octane and crude oil catalytic cracking reactions. [ABSTRACT FROM AUTHOR]

Connectivity of mesopores in zeolites, which is a key factor for the high efficiency catalyst design, is still a challenge to be generated without using organic template. Herein, a hierarchical porous Y zeolite (USY B ) was synthesized by introducing catalytic amounts of boron into the framework of NaY, followed by steaming. The introduction of framework boron promoted the hydrolysis of the surrounding Si O Al and Si O B bonds in steaming treatment. When the boron was dislocated from framework, it could further create more mesopores by steaming. It was deemed that boron played catalytic like role for leading to generate well interconnected mesoporosity. As a result, the mesopore volume of the zeolite increased by 46% relatively. The influence of the generated interconnected mesoporosity on the higher activity was evidenced in both iso -octane (i.e. 2,2,4-trimethylpentane) and 1,3,5-triisopropylbenzene (TIPB) cracking over USY B zeolite. Compared with conventional USY zeolite, there would be 2.1% increase in the yield of gasoline for the cracking of heavy oil over USY B catalyst. [ABSTRACT FROM AUTHOR]

To elucidate the migration process of cerium-cations and the resulting chemical diversification in cerium-NaY (Ce-NaY) ion-exchange processes, three calcination atmospheres (N 2 -atmosphere, O 2 -oxidation, N 2 -atmosphere followed by O 2 -oxidation) were adopted to study the influence of variable valence (III to IV) on ion migration, thermal stability, and catalytic activity. The results indicated that under N 2 -protection, significant amounts of Ce-(III) ions moved into the sodalite cage and increased the thermal stability of Ce-NaY. Under O 2 -oxidation, most Ce-(III) were converted to Ce-(IV) and remained inside the supercage. Ce-(IV) promoted water polarization and exhibited a unique hydroxyl group at 3582 cm −1 in the infrared spectra. Ce ion-exchanged ultrastable Y zeolite (CeUSY O2 ) exhibited the highest amount of Brønsted acid due to the location of the Ce ions. Compared to CeUSY N2 , CeUSY O2 increased light oil selectivity in vacuum gas oil catalytic cracking due to its higher Brønsted acidity. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous ultra-stable Y zeolite with outstanding performance for heavy oil cracking was prepared through the combination of desilication and dealumination. Atomic removal of silicon atoms from the starting NaY zeolite framework during desilication was reported. Nucleation and propagation of mesopores in the following dealumination process was studied. Si(0Al) and Si(1Al) atoms are selectively removed from zeolite framework by desilication. Consequently, silanol nests and unique hydroxyl nests with framework associated Al-OH were created in the framework of the desilicated zeolite. The artificial defects effect the initiation of mesopores in crystal parts where used to be rich in framework silicon and unfavorable for mesopore formation and promote the propagation and coalescence of mesopores. Catalytic studies revealed improved activity and lifetime in the crack of 1,3,5-triisopropylbenzene and showed increased gasoline and light cycle oil selectivity when the conversion of a heavy oil was compared. [Copyright &y& Elsevier]