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Dinaphthobenzo[1,2:4,5]dicyclobutadiene: Antiaromatic and Orthogonally Tunable Electronics and Packing
No full textPolycyclic conjugated hydrocarbons containing antiaromatic four-membered cyclobutadienoids (CDB) are of great fundamental and technical interest. However, their challenging synthesis has hampered the exploration and understanding of such systems. Reported herein is a modular and efficient synthesis of novel CBD-containing acene analogues, dinaphthobenzo[1,2:4,5]dicyclobutadiene (DNBDCs), with orthogonally tunable electronic properties and molecular packing. The design also features strong antiaromaticity of the CBD units, as revealed by nucleus-independent chemical shift and anisotropy of the induced current density calculations, as well as X-ray crystallography. Tuning the size of silyl substituents resulted in the most favorable brick-layer packing for triisobutylsilyl-DNBDC and a charge mobility of up to 0.52cm(2)V(-1)s(-1) in field-effect transistors
Mapping the dynamics of methanol and xenon co- adsorption in SWNTs by in situ continuous- flow hyperpolarized 129Xe NMR+
No full textA comparative study of the adsorption and desorption processes of methanol in two kinds of nanochannels (i.e. MCM-41 and SWNTs) is performed by in situ continuous-flow laser-hyperpolarized Xe-129 NMR. The high sensitivity and short acquisition time of hyperpolarized Xe-129 allow for probing the molecular dynamics in a confined geometry under real working conditions. Hyperpolarized Xe-129 NMR spectra indicate that the methanol adsorption behavior in nanochannels is determined by the characters of adsorption sites and that the methanol adsorption rate in the nanochannels of SWNTs is faster than in MCM-41. The experimental data shown in this work also indicate that there is a change in gas phase Xe-129 NMR signal intensity during the adsorption and desorption of methanol in SWNTs. This may be because there is a strong depolarization of hyperpolarized Xe-129 in SWNTs
Construction of consolidated bio-saccharification biocatalyst and process optimization for highly efficient lignocellulose solubilization
No full textBackgroundThe industrial conversion of biomass to high-value biofuels and biochemical is mainly restricted by lignocellulose solubilization. Consolidated bio-saccharification (CBS) is considered a promising process for lignocellulose solubilization depending on whole-cell biocatalysts that simultaneously perform effective cellulase production and hydrolysis. However, it usually takes a long time to reach a high saccharification level using the current CBS biocatalyst and process.ResultsTo promote the saccharification efficiency and reduce the cost, a Clostridium thermocellum recombinant strain pyrF::KBm was constructed as a new CBS biocatalyst in this study. The key CBS factors, including the medium, inoculum size and cultivation, and substrate load, were investigated and optimized. The saccharification process was also stimulated by adding free hemicellulases, suggesting the need to further enhance hemicellulase activity of the whole-cell catalyst. Under the optimal conditions, the CBS process was shortened by 50% with pretreated wheat straw as the substrate. The sugar yield reached 0.795g/g and the saccharification level was 89.3%.ConclusionsThis work provided a new biocatalyst and an optimized process of CBS and confirmed that CBS is a feasible strategy for cost-efficient solubilization of lignocellulose, which will greatly promote the industrial utilization of lignocellulosic biomass
Effect of Na Promoter on Fe-Based Catalyst for CO2 Hydrogenation to Alkenes
No full textA series of Fe-based catalysts with accurately controlled amounts of Na are synthesized to investigate the relationship between the promoter and the catalytic performance for CO2 hydrogenation to alkenes. With the increasing amount of Na, both CO2 conversion and alkenes selectivity increase at low and moderate amounts and then plateau (with the highest to be 36.8% and 64.3%, respectively), while the corresponding methane production decreases to 7.2%. It is found that the addition of Na enhances the adsorption of CO2, facilitates the formation and stability of active species Fe5C2, and inhibits the secondary hydrogenation of alkenes. All these effects lead to the desirable catalytic performance. Besides, it is observed that the content of Fe5C2 is related to the amount of Na. This study can provide scientific guidance to the design and the synthesis of high-efficiency catalysts for CO2 hydrogenation to high-value chemicals