Deriving high value products from depolymerized lignin oil, aided by (bio)catalytic funneling strategies

Lignin holds tremendous and versatile possibilities to produce value-added chemicals and high performing polymeric materials. Over the years, different cutting-edge lignin depolymerization methodologies have been developed, mainly focusing on achieving excellent yields of mono-phenolic products, some even approaching the theoretical maximum. However, due to lignin's inherent heterogeneity and recalcitrance, its depolymerization leads to relatively complex product streams, also containing dimers, and higher molecular weight fragments in substantial quantities. The subsequent chemo-catalytic valorization of these higher molecular weight streams, containing difficult-to-break, mainly C-C covalent bonds, is tremendously challenging, and has consequently received much less attention. In this minireview, we present an overview of recent advances on the development of sustainable biorefinery strategies aimed at the production of well-defined chemicals and polymeric materials, the prime focus being on depolymerized lignin oils, containing high molecular weight fractions. The key central unit operation to achieve this is (bio)catalytic funneling, which holds great potential to overcome separation and purification challenges.</p

Primary amines from lignocellulose by direct amination of alcohol intermediates, catalyzed by RANEY® Ni

Primary amines are crucially important building blocks for the synthesis of a wide range of industrially relevant products. Our comprehensive catalytic strategy presented here allows diverse primary amines from lignocellulosic biomass to be sourced in a straightforward manner and with minimal purification effort. The core of the methodology is the efficient RANEY® Ni-catalyzed hydrogen-borrowing amination (with ammonia) of the alcohol intermediates, namely alkyl-phenol derivatives as well as aliphatic alcohols, obtained through the two-stage LignoFlex process. Hereby the first stage entails the copper-doped porous metal oxide (Cu20PMO) catalyzed reductive catalytic fractionation (RCF) of pine lignocellulose into a crude bio-oil, rich in dihydroconiferyl alcohol (1G), which could be converted into dihydroconiferyl amine (1G amine) in high selectivity using ammonia gas, by applying our selective amination protocol. Notably also, the crude RCF-oil directly afforded 1G amine in a high 4.6 wt% isolated yield (based on lignin content). Finally it was also shown that the here developed Ni-catalysed heterogeneous catalytic procedure was equally capable of transforming a range of aliphatic linear/cyclic primary/secondary alcohols – available from the second stage of the LignoFlex procedure – into their respective primary amines

A Diamine-Oriented Biorefinery Concept Using Ammonia and Raney Ni as a Multifaceted Catalyst

Diamines are important industrial chemicals. In this paper we outline the feasibility of lignocellulose as a source of diol‐containing molecules. We also illustrate the possibility of turning these diols into their diamines in good to excellent yields. Central to these transformations is the use of commercially available Raney Ni. For diol formation, the Raney Ni engages in hydrogenation and often also demethoxylation, that way funneling multiple components to one single molecule. For diamine formation, Raney Ni catalyzes hydrogen‐borrowing mediated diamination in the presence of NH(3)

One-Pot Catalytic Conversion of Lignin-Derivable Guaiacols and Syringols to Cyclohexylamines

Cyclic primary amines are elementary building blocks to many fine chemicals, pharmaceuticals, and polymers. Here, a powerful one-pot Raney Ni-based catalytic strategy was developed to transform guaiacol into cyclohexylamine using NH3 (7 bar) and H2 (10 bar) in up to 94 % yield. The methodology was extendable to the conversion of a wider range of guaiacols and syringols into their corresponding cyclohexylamines. Notably, a crude bio-oil originating from the reductive catalytic fractionation of birch lignocellulose was transformed into a product mixture rich in 4-propylcyclohexylamine, constituting an interesting case of catalytic funneling. The isolated yield of the desired 4-propylcyclohexylamine reached as high as 7 wt % (on lignin basis). Preliminary mechanistic studies pointed at the consecutive occurrence of three key catalytic transformations, namely, demethoxylation, hydrogenation, and amination

Optimization of quantitative polymerase chain reactions for detection and quantification of eight periodontal bacterial pathogens

BACKGROUND: The aim of this study was to optimize quantitative (real-time) polymerase chain reaction (qPCR) assays for 8 major periodontal pathogens, i.e. Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Parvimonas micros, Porphyromonas gingivalis, Prevotella intermedia, Tanerella forsythia and Treponema denticola, and of the caries pathogen Streptococcus mutans. RESULTS: Eighteen different primer pairs were analyzed in silico regarding specificity (using BLAST analysis) and the presence of secondary structures at primer binding sites (using mFOLD). The most specific and efficiently binding primer pairs, according to these analyses, were selected for qPCR-analysis to determine amplification efficiency, limit of quantification and intra-run reproducibility. For the selected primer pairs, one for each species, the specificity was confirmed by assessing amplification of DNA extracts from isolates of closely related species. For these primer pairs, the intercycler portability was evaluated on 3 different thermal cyclers (the Applied Biosystems 7300, the Bio-Rad iQ5 and the Roche Light Cycler 480). For all assays on the different cyclers, a good correlation of the standard series was obtained (i.e. r2 >= 0.98), but quantification limits varied among cyclers. The overall best quantification limit was obtained by using a 2 mul sample in a final volume of 10 mul on the Light Cycler 480. CONCLUSIONS: In conclusion, the proposed assays allow to quantify the bacterial loads of S. mutans, 6 periodontal pathogenic species and the genus Fusobacterium.This can be of use in assessing periodontal risk, determination of the optimal periodontal therapy and evaluation of this treatment

High yield production of 1,4-cyclohexanediol and 1,4-cyclohexanediamine from high molecular-weight lignin oil

The complete utilization of all lignin depolymerization streams obtained from the reductive catalytic fractionation (RCF) of woody biomass into high-value-added compounds is a timely and challenging objective. Here, we present a catalytic methodology to transform beech lignin-derived dimers and oligomers (DO) into well-defined 1,4-cyclohexanediol and 1,4-cyclohexanediamine. The latter two compounds have vast industrial relevance as monomers for polymer synthesis as well as pharmaceutical building blocks. The proposed two-step catalytic sequence involves the use of the commercially available RANEY® Ni catalyst. Therefore, the first step involves the efficient defunctionalization of lignin-derived 2,6-dimethoxybenzoquinone (DMBQ) into 1,4-cyclohexanediol (14CHDO) in 86.5% molar yield, representing a 10.7 wt% yield calculated on a DO weight basis. The second step concerns the highly selective amination of 1,4-cyclohexanediol with ammonia to give 1,4-cyclohexanediamine (14CHDA) in near quantitative yield. The ability to use RANEY® Ni and ammonia in this process holds great potential for future industrial synthesis of 1,4-cyclohexanediamine from renewable resources

Subtle Microwave-Induced Overheating Effects in an Industrial Demethylation Reaction and Their Direct Use in the Development of an Innovative Microwave Reactor

A systematic study of the conventional and microwave (MW) kinetics of an industrially relevant demethylation reaction is presented. In using industrially relevant reaction conditions the dominant influence of the solvent on the MW energy dissipation is avoided. Below the boiling point, the effect of MWs on the activation energy Ea and k0 is found nonexistent. Interestingly, under reflux conditions, the microwave-heated (MWH) reaction displays very pronounced zero-order kinetics, displaying a much higher reaction rate than observed for the conventionally thermal-heated (CTH) reaction. This is related to a different gas product (methyl bromide, MeBr) removal mechanism, changing from classic nucleation into gaseous bubbles to a facilitated removal through escaping gases/vapors. Additionally, the use of MWs compensates better for the strong heat losses in this reaction, associated with the boiling of HBr/water and the loss of MeBr, than under CTH. Through modeling, MWH was shown to occur inhomogeneously around gas/liquid interfaces, resulting in localized overheating in the very near vicinity of the bubbles, overall increasing the average heating rate in the bubble vicinity vis-à-vis the bulk of the liquid. Based on these observations and findings, a novel continuous reactor concept is proposed in which the escaping MeBr and the generated HBr/water vapors are the main driving forces for circulation. This reactor concept is generic in that it offers a viable and low cost option for the use of very strong acids and the managed removal/quenching of gaseous byproducts

Dehydration of Alginic Acid Cryogel by TiCl4 vapor : Direct Access to Mesoporous TiO2@C Nanocomposites and Their Performance in Lithium-Ion Batteries

A new strategy for the synthesis of mesoporous TiO2@C nanocomposites through the direct mineralization of seaweed-derived alginic acid cryogel by TiCl4 through a solid/vapor reaction pathway is presented. In this synthesis, alginic acid cryogel can have multiple roles; i) mesoporous template, ii) carbon source, and iii) oxygen source for the TiO2 precursor, TiCl4. The resulting TiO2@alginic acid composite was transformed either into pure mesoporous TiO2 by calcination or into mesoporous TiO2@C nanocomposites by pyrolysis. By comparing with a nonporous TiO2@C composite, the importance of the mesopores on the performance of electrodes for lithium-ion batteries based on mesoporous TiO2@C composite was clearly evidenced. In addition, the carbon matrix in the mesoporous TiO2@C nanocomposite also showed electrochemical activity versus lithium ions, providing twice the capacity of pure mesoporous TiO2 or alginic acid-derived mesoporous carbon (A600). Given the simplicity and environmental friendliness of the process, the mesoporous TiO2@C nanocomposite could satisfy the main prerequisites of green and sustainable chemistry while showing improved electrochemical performance as a negative electrode for lithium-ion batteries

Serum albumin concentration of donor cows as an indicator of developmental competence of oocytes

Adequate nutrition is required for maintenance of normal reproduction in cattle. Albumin, the best marker and fundamental part of nutrition, most abundant plasma protein and major component of fetal bovine serum, is the best predictor of malnourishment in South African cattle. The aim of this study was to determine if serum albumin concentrations of donor cows predict the developmental competence of oocytes, and if additional protein supplementation of the in vitro culture media improves embryo outcomes in oocytes from cows with inadequate serum albumin concentrations. Oocytes (n = 1024) were recovered from donors with inadequate (≤35.9 g/L), or adequate serum albumin concentrations (≥36.0 g/L). Four hundred and sixty oocytes originated from cows with inadequate serum albumin and 564 from cows with adequate serum albumin. Oocytes of these cohorts were randomly allocated to a control and supplemented fetal bovine serum in vitro embryo culture protocol. Multiple linear, logistic and Poisson regression analyses were performed to estimate the effects of different covariates on linear, binary and count data respectively. Mixed effects Poisson regression was performed for the number of oocytes that developed into blastocysts by the seventh day of culture. Adequate serum albumin concentration of donor cows independently resulted in 46% increased blastocyst formation in the control protocol (P = 0.02). Although fetal bovine serum supplementation of the culture protocol did not affect blastocyst formation in oocytes originating from cows with inadequate serum albumin, it independently reduced blastocyst formation by 30% in oocytes originating from cows with adequate serum albumin (P = 0.02). Other independent predictors of blastocyst outcome included higher serum urea nitrogen, lower beta (β)-hydroxybutyric acid concentrations and lower fat classification of donor cows. It is concluded that adequate serum albumin of donor cows is a significant predictor of developmental competence of oocytes, and that in vitro supplementation of fetal bovine serum does not improve developmental competence of oocytes and can lead to negative blastocyst outcomes. Further research is required to determine optimal protein supplementation for oocytes originating from inadequately nourished cows.The Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria.http://www.theriojournal.com2020-02-01hj2018Production Animal Studie

Polysaccharide-derived mesoporous materials (Starbon®) for sustainable separation of complex mixtures

The recovery and separation of high value and low volume extractives are a considerable challenge for the commercial realisation of zero-waste biorefineries. Using solid-phase extractions (SPE) based on sustainable sorbents is a promising method to enable efficient, green and selective separation of these complex extractive mixtures. Mesoporous carbonaceous solids derived from renewable polysaccharides are ideal stationary phases due to their tuneable functionality and surface structure. In this study, the structure-separation relationships of thirteen polysaccharide-derived mesoporous materials and two modified types as sorbents for ten naturally-occurring bioactive phenolic compounds were investigated. For the first time, a comprehensive statistical analysis of the key molecular and surface properties influencing the recovery of these species was carried out. The obtained results show the possibility of developing tailored materials for purification, separation or extraction, depending on the molecular composition of the analyte. The wide versatility and application span of these polysaccharide-derived mesoporous materials offer new sustainable and inexpensive alternatives to traditional silica-based stationary phases