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The understanding of lignin softening and pyrolysis is important for developing lignocellulosic biorefinery in order to produce carbon fibers, polymers additives, green aromatics, or biofuels. Protobind lignin (produced by soda pulping of a wheat straw) was characterized by thermogravimetry, calorimetry (for glass transition temperature and heat of pyrolysis reactions), in situ 1H NMR (for the analysis of the mobility of protons upon lignin thermal conversion), and solution-state 13C and 31P NMR (determination of functional groups in lignin). In situ rheology reveals the real-time viscoelastic behavior of lignin as a function of temperature. Upon heating, lignin undergoes softening, through glass transition overlapped with depolymerization, and is followed by the solidification of the softened material by cross-linking reactions. The lignin residues were quenched within the rheometer at the midpoint temperatures of softening and solidification regions and were further analyzed by elemental analysis, GPC-UV of acetylated THF soluble fractions, FTIR, solid 13C NMR, and laser desorption ionization (LDI) combined with very high-resolution mass spectrometry (HRMS). We present the first report on lignin biochars analysis by LDI-HRMS. NMR and FTIR analyses provide the evolution of functional moieties in lignin residues. 13C NMR, GPC-UV, and LDI FTICRMS analyses depict the depolymerization mechanism combined with cross-linking and demethoxylation reactions. An overall physical and chemical mechanism for the thermal conversion of alkali lignin is proposed based on these complementary analyses.

The real-time analysis of volatiles (primary tar) produced during the fast pyrolysis of biomass in a microfluidized bed reactor (MFBR) is achieved by online single photoionization mass spectrometry (SPI-MS). The effect of biomass composition (Douglas fir, oak, and miscanthus), particle shape and size (cylinder, lamella, or powder), bed temperature, and fluidizing gas flow-rate on primary tar composition is studied. Principle component analysis is conducted on the major ions analyzed by SPI-MS to evidence the significant differences between conditions. The variance in obtained SPI-MS spectra reveals the important effect of biomass composition and temperature on volatiles composition. The effect of particle size on volatiles composition is clearly evidenced. Typical pyrolysis regimes are defined according to specific markers which are key chemical compounds to characterize biomass fast pyrolysis. SPI-MS combined with a MFBR is an interesting tool to unravel the effects of biomass composition and of heat and mass transfers on biomass fast pyrolysis processes.

Iron (Fe) is an essential nutrient, but is poorly bioavailable because of its low solubility in alkaline soils; this leads to reduced agricultural productivity. To overcome this problem, we first showed that the soil application of synthetic 2′-deoxymugineic acid, a natural phytosiderophore from the Poaceae, can recover Fe deficiency in rice grown in calcareous soil. However, the high cost and poor stability of synthetic 2′-deoxymugineic acid preclude its agricultural use. In this work, we develop a more stable and less expensive analog, proline-2′-deoxymugineic acid, and demonstrate its practical synthesis and transport of its Fe-chelated form across the plasma membrane by Fe(III)•2’-deoxymugineic acid transporters. Possibility of its use as an iron fertilizer on alkaline soils is supported by promotion of rice growth in a calcareous soil by soil application of metal free proline-2’-deoxymugineic acid.

Polyimide-based materials provide attractive chemistries for the development of gas-separation membranes. Modification of inter- and intra-chain interactions is a route to improve the separation performance. In this work, copolyimides with Tröger's base (TB) monomers are designed and synthesized. In particular, a series of copolyimides is synthesized with different contents of carboxylic acid groups (0-50 wt %) to alter the inter- and intra-chain interactions and enhance the basicity of the TB-polyimides. A detailed thermal and structural analysis is provided for the new copolyimides. Gas permeation data reveal a tunable trend in separation performance with increasing carboxylic acid group content. Importantly, this is one of the few examples of copolyimide membranes materials that show enhanced plasticization resistance to high-pressure gas feeds through physical cross-linking.

Although mixed matrix membranes (MMM) possess remarkably improved gas separation performance compared to traditional polymeric membranes, membrane stability including CO2 plasticization and aging is still a serious issue due to the existence of interfacial defects. In this work, we report an efficient and less destructive route to cross-link the MOFs/polyimide (PI) MMM, where amine group-functionalized MOF (NH2-UiO-66) nanoparticles are thermally cross-linked with a carboxylic acid-functionalized PI (COOH-PI) matrix to form an amide bond at the interface at 150 °C under vacuum condition. Such a chemical cross-linking strategy conducted at a relatively mild condition improves membrane stability greatly while ensuring that the membrane structure is not destroyed. The resulting cross-linked MMM achieves enhanced mechanical strength with higher Young’s modulus than a pristine polymer membrane. The CO2 antiplasticization pressure of the MMM after cross-linking is enhanced by 200% from ∼10 to >30 bar and the CO2 permeability of MMM only drops slightly from 995 to 735 Barrer after 450 days. At the same time, the separation performance of H2/CH4 gas pair surpasses the 2008 upper bound and that of CO2/CH4 gas pair nearly approaches the 2008 upper bound. The cross-linking strategy used herein provides a feasible and effective route for improving membrane stability and membrane performance in the MMM system for gas separation.

The correlation between the bowl-inversion energy and the bowl depth for sumanenes monosubstituted with an iodo, formyl, or nitro group was investigated experimentally and by theoretical calculations. The bowl-inversion energies of the substituted sumanenes were determined experimentally by two-dimensional NMR exchange spectroscopy measurements. Various density functional theory methods were examined for the calculation of the structure and the bowl-inversion energy of sumanene, and it was found that PBE0, ωB97XD, and M06-2X gave better fits of the experimental value than did B3LYP. The experimental value was well reproduced at these levels of theory. The bowl structures and bowl-inversion energies of monosubstituted sumanenes were therefore calculated at the ωB97XD/6-311+G(d,p) level of theory. In both the experiments and the calculations, the correlation followed the equation ΔE = acos 4 θ, where a is a coefficient, ΔE is the bowl-inversion energy, and cos θ is the normalized bowl depth, indicating that the bowl inversion follows a double-well potential energy diagram.

Electrophilic substitution reactions of sumanene were studied. Mono-, di-, and trisubstituted sumanenes were selectively prepared with the separation of all regioisomers. The regioselectivity was predicted well by the HOMO density values determined by DFT calculations.The regioselective synthesis of aromatic compounds, including sumanene derivatives, is very important in order to explore their physical properties.1 For example, two sumanene derivatives trisubstituted at the benzene rings, C 3 symmetric and unsymmetrical, are possible if ortho-substituted derivatives are excluded. Previously, we developed the functionalization of C 3 symmetric derivatives from precursor A (Scheme 1).2 However, direct preparation of both isomers from sumanene (1) 3 is also beneficial if these isomers can be easily separated or one isomer can be selectively obtained. A more complicated situation is encountered in the case of disubstituted sumanene synthesis; three possible isomers may be produced (Table 1).Electrophilic aromatic substitution (S E Ar) is one of the most reliable methods for the direct functionalization of aromatic compounds. However, due to the lack of regioselectivity and the difficulty in separation of the regioisomers, the S E Ar route has rarely been applied to sumanene derivatization. 4 The purpose of this study involves the development of regioselective electrophilic substitution reactions of sumanene, and prediction of their regioselectivity by DFT calculations.Selective syntheses of monosubstituted sumanenes were first investigated as summarized in Scheme 2.5 Iodosumanene (2) was selectively prepared in 75% yield by AuCl 3 -catalyzed iodination 6 with N-iodosuccinimide (NIS) with recovery of 1. Nitrosumanene (3) was obtained in 65% yield by nitration using trifluoroacetyl nitrate, generated in situ from trifluoroacetic anhydride and concd nitric acid.7 1 was completely consumed and dinitrosumanenes were not formed. However, some amount of degradation was observed due to the harsh conditions. Formylation was achieved using triflic anhydride and DMF 8 under microwave-assisted heating conditions to afford formylsumanene (4) in 60% yield. Because of the low reactivity of the reagent, high temperature (130°C) was required to complete the reaction. Although diformylsumanenes were also formed in 20% yield with 4, these compounds were easily separated from 4 by preparative thin layer chromatography (PTLC). Acetylation was achieved by adopting similar conditions as the formylation in the presence of DMA to afford acetylsumanene (5) in 64% yield and diacetylsumanenes in 10% yield. Benzoylsumanene (6) was also prepared in 68% yield using triflic acid and PhCOCl with complete consumption of 1.9 They were easily purified by PTLC as well.The thus-employed reaction conditions were further applied to the syntheses of disubstituted sumanenes (Table 1).10 Preparation of diiodosumanenes 7, dinitrosumanenes 8, diformylsumanenes 9, diacetylsumanenes 10, and dibenzoylsumanenes 11 were achieved by increasing the amount of reagent...