Monomeric Compounds Research Articles

Synthesis, physicochemical, and thermal characterization of coordination compounds of Cu(II) with a pyrazole-type ligand

Four new coordination compounds of Cu(II) were synthesized with ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate (L) and different co-ligands. In the reaction of warm methanolic solutions of CuX2·nH2O (X = Cl, n = 2; X = Br, n = 0; X = NO3, n = 3) and the ligand in mole ratio 1:2, bis(ligand) complexes Cu(L)2Cl2 (1), Cu(L)2Br2 (2) and Cu(L)2(NO3)2 (3) were obtained. Unlike this, reaction of CuCl2 with the ligand in the presence of LiOAc yielded to the formation of dimeric complex of the formula [Cu(L)(OAc)2]2 (4), with four acetate ions as bridging ligands. In all these complexes, ligand L is coordinated in a monodentate manner through N2 nitrogen atom. The coordination environment in the dimeric complex is octahedral, while in the monomeric complexes the central atom is tetra-coordinated. The molar conductivity data in DMF show that the acetate ions in the dimeric complex are coordinated even in solution. In the monomeric compounds, the molar conductivity data increase in the order 1 < 2 < 3. Since the applicability of the coordination compounds depends on their thermal properties, the thermal decomposition of the complexes was followed by simultaneous TG–DSC measurements. The thermal stability of the monomeric compounds in flowing argon increases in the reverse order as the molar conductivity data. The course of the decomposition is different in the case of the nitrato-compound (3). The decomposition of 3 is followed by a strong exothermic heat effect due to the presence of nitrate ion which is a strong oxidation agent. The decomposition of the other complexes is endothermic, taking place in more or less overlapped reactions. The decomposition of the compounds is completed to 600 °C.

Chrysanthemum indicum L.: A Comprehensive Review of its Botany, Phytochemistry and Pharmacology.

Chrysanthemum indicum L. (C. indicum L.), a member of the Compositae family, is a perennial plant that has been used as a traditional medicine for more than 2000 years in China and is widely used for the treatment of Pemphigus, swelling, pain, and scrofula. To date, more than 190 chemical constituents have been isolated and identified from this plant, including flavonoids, terpenoids, phenylpropanoids, and phenolic acids. Numerous modern studies have shown that extracts or monomeric compounds from C. indicum L. have several pharmacological activities, such as anti-inflammatory anti-oxidation, antipathogenic microorganism, anticancer, immune regulation, and hepatoprotective effects. However, resource availability, the research on the mechanism, and quality control are still insufficient, which deserves further efforts. In this paper, the advances in botany, phytochemistry, and pharmacology of C. indicum L were reviewed. We hope that this review can provide important information for traditional Chinese medicine, phytochemistry, synthetic and medicinal chemistry researchers for making full use of C. indicum L. resource.

A new metalorganic chemical vapor deposition process for MoS2 with a 1,4-diazabutadienyl stabilized molybdenum precursor and elemental sulfur.

Molybdenum disulfide (MoS2) is known for its versatile properties and hence is promising for a wide range of applications. The fabrication of high quality MoS2 either as homogeneous films or as two-dimensional layers on large areas is thus the objective of intense research. Since industry requirements on MoS2 thin films can hardly be matched by established exfoliation fabrication methods, there is an enhanced need for developing new chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes where a rational precursor selection is a crucial step. In this study, a new molybdenum precursor, namely 1,4-di-tert-butyl-1,4-diazabutadienyl-bis(tert-butylimido)molybdenum(vi) [Mo(NtBu)2(tBu2DAD)], is identified as a potential candidate. The combination of imido and chelating 1,4-diazadieneyl ligand moieties around the molybdenum metal center results in a monomeric compound possessing adequate thermal characteristics relevant for vapor phase deposition applications. Hexagonal MoS2 layers are fabricated in a metalorganic CVD (MOCVD) process with elemental sulfur as the co-reactant at temperatures between 600 °C and 800 °C. The structure and composition of the films are investigated by X-ray diffraction, high resolution transmission electron microscopy, synchrotron X-ray photoelectron spectroscopy and Raman spectroscopy revealing crystalline and stoichiometric MoS2 films. The new MOCVD process developed for MoS2 is highly promising due to its moderate process conditions, scalability and controlled targeted composition.

Medicinal plant of Bletilla striata: A review of its chemical constituents, pharmacological activities, and quality control

Bletilla striata belongs to the family Orchidaceae, and it is mainly distributed in East Asia. The tubers of B. striata have been utilized in Traditional Chinese Medicine for various ailments, such as hematemesis, tuberculosis, malignant ulcers, hemorrhoids, traumatic bleeding, and chapped skin. Phytochemical investigation on B. striata has resulted in the identification of 192 monomeric compounds, including bibenzyls, phenanthrene derivatives, triterpenoids and its saponins, steroids and its saponins, malic acid derivatives, and anthocyanins. Moreover, B. striata polysaccharide is another typical chemical constituent of this plant. Pharmacology studies have shown that the plant possesses wound healing, antimicrobial, anticancer, antioxidative, and antiviral activities. This review aims to provide the latest and comprehensive information on chemical constituents, pharmacological activities, and quality control of B. striata and to identify future research needs.

Becoming a Faithful Defender: Traditional Chinese Medicine against Coronavirus Disease 2019 (COVID-19).

The outbreak caused by COVID-19 is causing a major challenge to clinical management and a worldwide threat to public health. So far, there is no specific anti-coronavirus therapy approved for the treatment of COVID-19. Recently, as the efficacy and safety of traditional Chinese medicine (TCM) is widely acknowledged, it has been brought to a crucial status by the public, governments, and World Health Organization (WHO). For a better popularization of TCM, governments have made several advances in regulations and policies for treatment and measures of novel coronavirus pneumonia (NCP). Therefore, on the basis of epidemiology and virology information, we reviewed relevant meta-analysis and clinical studies of anti-coronavirus therapeutics by TCM, in the aspect of mortality, symptom improvement, duration and dosage of corticosteroid, incidence of complications and the like. In addition, we also summarized preclinical rationale for anti-coronavirus activity by TCM in terms of virion assembly and release, as well as viral entry and replication, which could be a useful contribution for figuring out effective Chinese herbal medicine (CHM) for coronavirus, including ingredients from single monomeric compounds, Chinese herbs, Chinese herb extracts and Chinese herb formulas, or potential targets for medicine. We would like to see these relevant studies, ranging from basic researches to clinical application, could provide some idea on effects of CHM to combat COVID-19 or other coronaviruses, and also offer new thinking for the exploration of therapeutic strategies under the guidance of TCM.

Adding α-pinene as a novel application for sulfur dioxide-free in red wine

ABSTRACT Sulfur dioxide (SO2) is an efficient additive that is used during winemaking to prevent microbial contamination as well as the oxidation and color changes caused by enzymatic and nonenzymatic reactions. However, this compound can cause allergic reactions to humans. In this study, α-pinene, a monomeric compound derived from fruits, was used to be an alternative for sulfur dioxide in red wine fermentation. Three concentrations of α-pinene, 0.125%, 0.25%, or 0.5%, were used. The red wine without additive or SO2 was used as controls. No significant differences were found in total soluble solids, pH values, titratable acidity, and ethanol content (n = 3, p < .05) though lower ethanol content was observed in the group at 0.5% α-pinene. The antibacterial results were the same between adding α-pinene and SO2. In the α-pinene group, significantly higher L and a values as well as transmittance were obtained than in the control and SO2 groups. Higher free radical scavenging ability was also obtained in the groups of α-pinene. However, the group with the highest concentration, 0.5%, showed negative effects to ethanol production and sensory performance. Better physicochemical and sensory characteristics were obtained in the groups at 0.125% or 0.25% of α-pinene, particularly, when 0.125% of α-pinene was added. Thus, α-pinene at 0.125% should be the optimal concentration for a potential alternative for SO2 in winemaking.

A novel application of terpene compound α-pinene for alternative use of sulfur dioxide-free white wine

ABSTRACT Sulfur dioxide is widely used as a preservative in winemaking owing to its antioxidant and antimicrobial properties. However, it exerts adverse effects on health, causing dermatitis, urticaria, angioedema, diarrhea, and abdominal pain. In the present study, we used α-pinene, which is a fragrant monomeric compound derived from fruit-aroma compounds, as an alternative for SO2 in white wine fermentation. Three concentrations of α-pinene, 0.03125 g/100 mL, 0.0625 g/100 mL, and 0.125 g/100 mL were used. White wine added with SO2 at 40 ppm was also used (SO2 group). The white wine without addition of SO2 and α-pinene as used as the control. Total bacterial count and physicochemical characteristics including pectin content, degree of esterification, ethanol content, color, total phenolic acid content, and DPPH activity were analyzed. The antibacterial activities of α-pinene groups were similar to SO2 group but significantly higher than the control group. Specifically, 0.03125 g/100 mL and 0.0625 g/100 mL α-pinene groups showed significantly higher transmittance, L values, and color values than the control at the day 180, which suggested that the addition of α-pinene effectively inhibited the browning of white wine during storage. These findings indicated that α-pinene possessed an excellent antibacterial ability and could be a viable alternative for SO2 in winemaking.

ANTIMICROBIAL EFFECT OF ORGANOTIN COMPOUNDS DERIVED FROM PHENOLIC SCHIFF BASES

Several organotin(IV) derivatives of phenolic Schiff bases were prepared and investigated by spectroscopic methods. These compounds were bioassayed to evaluate their bacterial effect against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Salmonella typhimurium) microorganisms. Dimeric and monomeric compounds were characterized by infrared in solid state. Metallic centers having penta-, hexa-, and heptacoordination were identified by multinuclear NMR (1H, 13C and 119Sn) in solution. The di- and triorganotin(IV) derivatives were also investigated by conductimetric measurements in methanol, elemental analysis and melting point. The bioassay of these tin(IV) compounds showed that the best resulting activity was against S. aureus for the triphenyltin(IV) phenolic Schiff base derivatives, presenting MICs of 1.1 µM (0.6 mg mL-1) and 2.2 µM (1.3 mg mL-1).

Hydrogenation of Abies Wood and Ethanol Lignin by Hydrogen in Supercritical Ethanol in the Presence of Bifunctional Catalyst Pt/ZrO₂

The effect of bifunctional catalyst Pt/ZrO₂ on the yield and composition of products of abies wood and ethanol lignin hydrogenation in supercritical ethanol at temperature of 250 °C was established. In the process of abies wood hydrogenation, the catalyst Pt/ZrO₂ increases the degree of conversion of wood from 52.0 to 65.7 wt.%, the yield of liquid products from 31.0 to 38.1 wt.%,.%, and also increases the content of monomeric compounds in the liquid products. In the presence of catalyst, the cellulose content in the solid product of wood catalytic hydrogenation reaches to 77.1 wt.%, and the content of lignin and hemicelluloses decreases to 21.2 wt.% and 1.7 wt.%, respectively. In the process of ethanol lignin hydrogenation the catalyst Pt/ZrO₂ increases the degree of lignin conversion from 86.0 to 99.4 wt.%, the yield of liquid products from 75.0 to 90.0 wt.%, and also reduces the yield of solid residue from 14.0 to 0.6 wt.% and the yield of gases from 4.7 to 3.3 wt.%. Thus, the polysaccharides of wood biomass complicate the reductive depolymerization of native lignin in comparison with the depolymerization of isolated ethanol lignin. The use of the catalyst Pt/ZrO₂ makes it possible to fractionate the abies wood in supercritical ethanol at 250 °C on solid product with a high content of cellulose, as well as liquid and gaseous products from lignin and hemicelluloses

Genomic analysis of Burkholderia sp. ISTR5 for biofunneling of lignin-derived compounds

BackgroundLignin is the second most abundant natural polymer on earth. Industries using lignocellulosic biomass as feedstock generate a considerable amount of lignin as a byproduct with minimal usage. For a sustainable biorefinery, the lignin must be utilized in improved ways. Lignin is recalcitrant to degradation due to the complex and heterogeneous structure. The depolymerization of lignin and its conversion into specific product stream are the major challenges associated with lignin valorization. The blend of oligomeric, dimeric and monomeric lignin-derived compounds (LDCs) generated during depolymerization can be utilized by microbes for production of bioproducts.ResultsIn the present study, a novel bacterium Burkholderia sp. strain ISTR5 (R5), a proteobacteria belonging to class betaproteobacteria, order Burkholderiales and family Burkholderiaceae, was isolated and characterized for the degradation of LDCs. R5 strain was cultured on 12 LDCs in mineral salt medium (MSM) supplemented with individual compounds such as syringic acid, p-coumaric acid, ferulic acid, vanillin, vanillic acid, guaiacol, 4-hydroxybenzoic acid, gallic acid, benzoic acid, syringaldehyde, veratryl alcohol and catechol. R5 was able to grow and utilize all the selected LDCs. The degradation of selected LDCs was monitored by bacterial growth, total organic carbon (TOC) removal and UV–Vis absorption spectra in scan mode. TOC reduction shown in the sample contains syringic acid 80.7%, ferulic acid 84.1%, p-coumaric acid 85.9% and benzoic acid 83.2%. In UV–Vis absorption spectral scan, most of the lignin-associated peaks were found at or near 280 nm wavelength in the obtained absorption spectra. Enzyme assay for the ligninolytic enzymes was also performed, and it was observed that lignin peroxidase and laccase were predominantly expressed. Furthermore, the GC–MS analysis of LDCs was performed to identify the degradation intermediates from these compounds. The genomic analysis showed the robustness of this strain and identified various candidate genes responsible for the degradation of aromatic or lignin derivatives, detoxification mechanism, oxidative stress response and fatty acid synthesis. The presence of peroxidases (13%), laccases (4%), monooxygenases (23%), dioxygenase (44%), NADPH: quinone oxidoreductases (16%) and many other related enzymes supported the degradation of LDCs.ConclusionNumerous pathway intermediates were observed during experiment. Vanillin was found during growth on syringic acid, ferulic acid and p-coumaric acid. Some other intermediates like catechol, acetovanillone, syringaldehyde and 3,4-dihydroxybenzaldehyde from the recognized bacterial metabolic pathways existed during growth on the LDCs. The ortho- and meta cleavage pathway enzymes, such as the catechol-1,2-dioxygenase, protocatechuate 3,4-dioxygenase, catechol-2,3-dioxygenase and toluene-2,3-dioxygenase, were observed in the genome. In addition to the common aromatic degradation pathways, presence of the epoxyqueuosine reductase, 1,2-epoxyphenylacetyl-CoA isomerase in the genome advocates that this strain may follow the epoxy Coenzyme A thioester pathway for degradation.

Effect of catalysts on liquefaction of alkali lignin for production of aromatic phenolic monomer

Hydrothermal liquefaction (HTL) has emerged as a promising technology for producing fuels/chemicals. Lignin liquefaction was carried out with different temperature 250, 270, 290 and 310 °C in the presence of 50% ethanol-50% water (v/v) and a reaction time 30 min. The catalyst reaction with 10 wt% each catalyst of Pd/C, Fe/C, Co/C and Ni/C at 270 °C for 30 min reaction time was carried out. For non-catalytic reaction maximum bio-oil (68.2 wt%) was obtained at 270 °C while catalytic reaction with Co/C catalyst gave highest bio-oil (73.2 wt%). The obtained bio-oil has been analyzed with the help of GC-MS, FT-IR, NMR, GPC and CHNS. On the basis of GC-MS analysis, the main monomeric phenolic compounds produced were phenol, 2-methoxy-phenol, 4-ethyl-phenol, 2-methoxy-4-ethyl-phenol and 2,6-dimethoxy-phenol, due to their high concentrations it was feasible to select these five monomeric phenols as target compounds. It was seen that compared to the non-catalytic liquefaction reaction, the catalytic (Pd/C, Co/C, Ni/C and Fe/C) liquefaction reaction promotes the hydrogenation and hydrogeoxygenation of bio-oils. The possible reaction pathways have been explored in this studied.

Structural characterization of the bagasse lignin pretreated using solid alkali

Abstract The pretreatment using solid alkali had a high delignification rate and could improve the followed conversion efficiency of the biomass. In the present work, the bagasse lignin was separated and pretreated using a solid alkali to discuss their structural changes. The results showed that the main basic structures S/S′/S′′, G/G′, and H had different reactivity, where only the H unit was a stable structure in the pretreatment. The phenolic structure of the lignin was easily degraded in the pretreatment, and the lignin without phenolic structure was difficult to be degraded. The P structure was a novel structure that generated in the pretreatment. Some monomeric aromatic compounds simulated lignin monomer were also pretreated by solid alkali, the result showed that the phenol structure with side chain on para-position, as well as the carboxyl group, eater linkage, and double bond on the side chain are easily reacted in the pretreatment.

Aromatic vs. Aliphatic Hyperbranched Polyphosphoesters as Flame Retardants in Epoxy Resins.

The current trend for future flame retardants (FRs) goes to novel efficient halogen-free materials, due to the ban of several halogenated FRs. Among the most promising alternatives are phosphorus-based FRs, and of those, polymeric materials with complex shape have been recently reported. Herein, we present novel halogen-free aromatic and aliphatic hyperbranched polyphosphoesters (hbPPEs), which were synthesized by olefin metathesis polymerization and investigated them as a FR in epoxy resins. We compare their efficiency (aliphatic vs. aromatic) and further assess the differences between the monomeric compounds and the hbPPEs. The decomposition and vaporizing behavior of a compound is an important factor in its flame-retardant behavior, but also the interaction with the pyrolyzing matrix has a significant influence on the performance. Therefore, the challenge in designing a FR is to optimize the chemical structure and its decomposition pathway to the matrix, with regards to time and temperature. This behavior becomes obvious in this study, and explains the superior gas phase activity of the aliphatic FRs.

A Near-Complete Series of Four Atropisomeric Jozimine A2-Type Naphthylisoquinoline Dimers with Antiplasmodial and Cytotoxic Activities and Related Alkaloids from Ancistrocladus abbreviatus.

Three new naphthylisoquinoline dimers, jozibrevines A-C (1a-c), were isolated from the West African shrub Ancistrocladus abbreviatus, along with the known dimer jozimine A2 (1d). The two molecular moieties of 1a-d are coupled via the sterically constrained 3',3″-positions of their two naphthalene units, so that the central biaryl linkage is rotationally hindered. With the two outer axes also being chiral, 1a-d possess three consecutive stereogenic axes. The four isolated dimers all have the same constitutions and identical absolute configurations at the four stereogenic centers, but differ by their axial chirality. They belong to the extremely small class of Dioncophyllaceae-type naphthylisoquinoline dimers, i.e., being devoid of oxygen functions at C-6 and bearing the R-configuration at C-3 in their isoquinoline portions. Besides these dimers, the plant produces predominantly typical Ancistrocladaceae-type monomeric compounds, i.e., with the S-configuration at C-3 and an oxygen function at C-6, such as the new ancistrobrevines K (5) and L (6). Furthermore, a new hybrid-type (i.e., mixed Ancistrocladaceae/Dioncophyllaceae-type) alkaloid was identified, named ancistrobrevine M (7), which is 3R-configured and 6-oxygenated. Remarkable was the discovery of its "inverse hybrid-type" counterpart, dioncoline A (8). It is the as yet only known 3S-configured naphthylisoquinoline lacking an O-functionality at C-6. The new jozibrevines A-C (1a-c) exhibited pronounced antiplasmodial activities in the submicromolar range, with 1a being the most potent compound (IC50, 0.012 μM). Furthermore, jozimine A2 (1d) showed cytotoxicity against human colon carcinoma (HT-29), fibrosarcoma (HT1080), and multiple myeloma (MM.1S) cancer cells, displaying IC50 values of 12.0, 9.0, and 5.0 μM, respectively, whereas jozibrevines A (1a) and B (1b) were nontoxic in this concentration range.

In vitro anticomplementary activity and quality evaluation of dried blossoms of Inula nervosa Wall. from different geographical origins.

Blossoms of Inula nervosa Wall. (BINW) are traditionally used as an analgesic and antitussive in China. In this study, in vitro anticomplementary activities of crude extract from BINW in 21 batches and of extracts of four monomeric compounds were evaluated by the classical pathway. The effect of the region of origin on the quality of BINW was evaluated by fingerprint analysis for the first time. Furthermore, chemometric methods including similarity analysis and principal component analysis were employed to evaluate the quality of BINW. The nine major monomeric compounds were quantitated by ultra-high-performance liquid chromatography. All nine analytes demonstrated excellent linearity with recoveries ranging from 97.25% to 102.76%. The limits of detection and quantification were 0.07-12.20 μg/mL and 0.22-40.27 μg/mL, respectively. Results indicate that different regions of origin have a significant effect on the quality of BINW. Fingerprint analysis in combination with chemometrics and multi-ingredient determination is an efficient and reliable approach for quality evaluation. The BINW samples from Yunnan had the highest ratio of 1,5-dicaffeoylquinic acid and thymol; they also exhibited significantly higher anticomplementary activity than those from three other areas. This study successfully established a rapid and efficient method to evaluate the quality and biological activity of BINW.

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes (sodium, manganese, copper, nickel, cobalt and zinc) with pyrimidine-5-carboxylic and pyrimidine-2-carboxylic acids

The new 3d metal complexes of pyrimidine-2-carboxylic (2PCA) and pyrimidine-5-carboxylic (5PCA) acids were synthesized and characterized using thermal analysis (TG–DSC, TG–FTIR), X-ray, spectroscopic (IR, Raman) methods and theoretical (DFT) studies. In the complexes of pyrimidine-2-carboxylic acid of the general formula M(2PCA)2·xH2O (where 2PCA-pyrimidine-2-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 0 for Mn and Cu; x = 2 for Co, Ni and Zn) coordination of metal ions occurs through nitrogen atom from pyrimidine ring and carboxylate oxygen atom. The complexes of pyrimidine-5-carboxylic acid of the general formula M(5PCA)2·xH2O (where 5PCA—pyrimidine-5-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 6 for Cu and 4 for remaining complexes) were obtained as monomeric isostructural compounds. Coordination of metal centers occurs through two nitrogen atom from different pyrimidine-5-carboxylate ligand and four oxygen atoms from water molecules. The IR and Raman spectra of free acids as well as obtained metal(II) complexes were described in detail. Aromaticity (HOMA, EN, GEO and I6) of complexes was determined and discussed. The investigated compounds decompose in air in two main stages connected with dehydration and decomposition/burning of anhydrous compounds to the suitable metal oxides. Thermal decomposition in nitrogen leads to the evolution of water, carbon oxides, ammonia and pyrimidine molecules.

Synthesis of new triazolyl-oxazoline chiral ligands and study of their coordination to Pd(II) metal centers

We report an improved protocol for the synthesis of TryOx, a family of N,N chiral ligands in which a 1,2,3-triazol-4-yl moiety bears a chiral 2-oxazoline as the substituent in 4 position. TryOxs were successfully employed for the preparation of cationic Pd(II)-allyl complexes of formulation [Pd(allyl)(TryOx)]+ in which they behave as bidentate N,N chelating ligands. On the other hand, reaction of TryOxs with an equimolecular amount of [PdCl2(CH3CN)2] leads to the formation of neutral complexes which according to NMR, ESI-MS and molar mass determination (VPO) appear to be dimeric species of formulation [PdCl(µCl)(TryOx)]2 in which monodentate TryOxs link to palladium with the N atom of the oxazoline ring. X-rays diffraction studies show that upon crystallization these dimers transform into monomeric compounds of formulation [PdCl2(TryOx)], where the ligands behave as N,N chelating.Treatment of the [PdCl(µCl)(TryOx)]2 dimers with an equivalent of TryOx affords mononuclear neutral dichloro species of formulation [PdCl2(TryOx)2]. X-ray diffraction studies show that the two TryOx units are equivalent behaving as monodentate ligands coordinated to the metal through the oxazoline N atom.

Continuous pyrolysis of organosolv lignin and application of biochar on gasification of high density polyethylene

In the pyrolysis of lignin, lignin tends to agglomerate during the feeding stage, and the char produced can expand easily to form foam that prevents continuous operation. To solve this problem, a new bench-scale rotary kiln reactor with alumina balls was used for the pyrolysis of organosolv lignin. Also, a bench-scale fixed-bed reactor was used as a reference reactor to gain an insight on the pyrolysis phenomena from rotary kiln reactor. Compared to the fixed bed reactor, the rotary kiln reactor resulted in a higher yield of organic phase oil with high selectivity to monomeric phenolic compounds. Moreover, a larger amount of CO2 was obtained from the rotary kiln reactor, which strongly suggests that decarboxylation is main deoxygenation path. Furthermore, a char without agglomeration and foaming inside the reactor was generated from the rotary kiln reactor. The catalytic properties of the chars produced from both reactors with nickel impregnation were tested for the gasification of high-density polyethylene to produce H2. Among the four different catalysts (Ni/Rotary Kiln char, Ni/Fixed Bed char, Ni/Al2O3, Ni/Activated carbon) tested, the Ni/Fixed Bed char exhibited the highest yield of H2 (~two times higher H2 generation) from the gasification process of high-density polyethylene. X-ray photoelectron spectroscopy and scanning electron microscopy offers that the high dispersion/distribution of Ni occurred when the fixed bed char was used as a support. All experimental findings from this study significantly suggest that Ni supported on char could be an economically viable catalyst for producing H2 from gasification of high-density polyethylene.

Catalytic hydrothermal liquefaction of rice straw for production of monomers phenol over metal supported mesoporous catalyst

The catalytic (SBA-15, Ni/SBA-15, Al/SBA-15 and Ni-Al/SBA-15) hydrothermal liquefaction (HTL) of rice straw biomass was examined at different temperature with different amount of catalyst in the presence of different solvents. In comparison with water solvent liquefaction, the bio-oil yield significantly increased under alcoholic solvent (ethanol and methanol). The highest bio-oil yield was observed for water (44.3 wt%) with Ni-Al/SBA-15, while for ethanol (56.2 wt%), and for methanol (48.1 wt%) with, Ni/SBA-15 catalyst. The loading of Ni and Al on SBA-15, the acid strength of the catalyst enhanced. Bio-oils yield were analyzed with the help of GC–MS, FT-IR, NMR, GPC and CHNS. From the GC–MS analysis, the main monomeric phenolic compounds were produced, phenol, 4-ethyl-phenol, 2-methoxy-phenol, 2-methoxy-4-ethyl-phenol and Vanillin. It was observed by CHNS and GPC analysis of the bio-oil, compared to the non-catalytic liquefaction reaction, the catalytic liquefaction reaction promotes the hydrogenation/hydrodeoxygenation and produced lower molecular weight bio-oils.

Direct lignin depolymerization process from sulfur-free black liquors

Agricultural residues (olive tree pruning and almond shell) were subjected to different delignification treatments (organosolv and soda) and the obtained liquors were treated in a high-pressure reactor at 300 °C for 80 min to depolymerize the dissolved lignin. In this way, the step of precipitating lignin from the liquor was avoided. The phenolic oil obtained after liquors treatment was around 20% of the organic matter contained in previous liquors in all cases. However, phenolic monomeric compounds varied in function of the liquor source. Soda black liquors produced higher quantity of catechols, phenol and cresols whereas using organosolv black liquors, more guaiacol and syringol were obtained, highlighting the higher potential enabled by base catalyst for demethoxylation, demethylation and dealkylation reactions. Furthermore, the NaOH present in soda black liquors prevented undesirable repolymerization reactions by inhibiting the char formation and noticeably dropping the molecular weight of residual lignin. However, organosolv liquors presented a significant higher yield of phenolic monomers, about three times higher than the one obtained in the soda process. Residual lignin, which was not only unconverted lignin, was proved to be different from the initial lignin, pointing out the totally conversion of the initial lignin samples.