Production of BTX through Catalytic Depolymerization of Lignin

Lignin is the only nature renewable resource which can provide large quantities of aromatic compounds. In the work, transformation of lignin into benzene, toluene, and xylenes （BTX） was investigated over the HZSM-5, HY, and MCM-22 catalysts, and the HZSM-5 catalyst showed the highest carbon yield of BTX. The reaction condition, including temperature, the gas flow rate, and the catalyst/lignin ratio, was also investigated. The carbon yield of BTX reached about 25.3 C-mol% over HZSM-5 catalyst under T=550℃, f（N2）=300 cm^3/min, and catalyst/lignin ratio of 2.

Lignin depolymerization for phenolic monomers production by sustainable processes

Biomass wastes(almond shell and olive tree pruning) were used in this work as raw materials for the extraction of high purity lignin by different delignification methods. A pretreatment stage was carried out to remove the major hemicelluloses content in the solid feedstocks. Afterward, two sulfur-free pulping processes(soda and organosolv) were applied to extract the largest fraction of lignin. The extracted lignin contained in the liquors was isolated using selective precipitation methods to design a tailor-made technique for obtaining high-purity lignin(in all cases more 90% of purity was reached). Soda process allowed the extraction of more lignin(around 40%–47%) than organosolv process(lower than 20%) regardless of the lignocellulosic source employed.Once the different lignin samples were isolated and characterized, they were depolymerized for the obtaining of small phenolic compounds. Three main streams were produced after the reaction: phenolic enriched oil, residual lignin and coke. After the purification of these fractions, their quantifications and characterization were conducted.The most abundant product of the reaction was residual lignin generated by the undesirable repolymerization of the initial lignin with yields around 30%–45%. The yield of the stream enriched in phenolic oil was higher than 20%. Coke, the lowest added-value product, presented a yield lower than 12% in all the cases. Lignin from organosolv presented higher phenolic oil yields, mainly due to their lower molecular size. This parameter was, thus, considered a key factor to obtain higher yields.

Catalytic depolymerization of calcium lignosulfonate by NiMgFeO_x derived from sub-micron sized NiMgFe hydrotalcite prepared by introducing hydroxyl compounds

A new method for regulating the synthesis of Ni Mg Fe hydrotalcites(NMF LDHs) with the addition of hydroxyl compounds was proposed. A series of NMF LDHs were prepared by the above method, and then were calcined to obtain the Ni Mg FeOx(NMFOx) samples. The NMFOxsamples were characterized by XRD,SEM, TG-DTG, XPS and CO2-TPD, respectively. The catalytic performance of NMFOxfor depolymerizing calcium lignosulfonate(CLS) was evaluated by hydrothermal reaction. The results showed that the addition of hydroxyl compounds favored reducing the particle sizes of NMF LDHs. For the depolymerization of CSL, the yield of liquid product increased from 45% to 75.8% with the addition of NMFOx-ethanol(NMFOxET). The liquid products were mainly phenolics, aromatics, ketones and esters. The total selectivity of oxy-containing compounds was over 90.6%, among them, the phenolics were approximately 35.2%. The valence of Ni and Fe, crystalline phase and basicity almost remained unchanged. The NMFOx-ET samples were recycled for the depolymerization of CLS, moreover, the NMFOx-ET samples had high activity and stability after 4 cycles.

Depolymerization of Poly(bisphenol A carbonate) in Subcritical and Supercritical Toluene

The depolymerization of poly（bisphenol A carbonate）（PC） in subcritical and supercritical toluene was studied. The experimental parameters, which influence the depolymerization reaction such as temperature （570-633 K）, pressure （4.0-7.0 MPa）, reaction time （5-60 min）, and toluene to PC weight ratio （3.0-11.0）, were investigated, and the reaction products were determined by CrC, GC/MS and FT-IR spectrometer. It was found that the main product of the depolymerization reaction was bisphenol A（BPA）. BPA accounted for over 55.7% of the depolymerization products at reaction temperature 613 K, pressure 5.0-6.0 MPa, reaction time 15 min and toluene/PC weight ratio of around 7.0.

Oxidative depolymerization of lignin improved by enzymolysis pretreatment with laccase

A new lignin depolymerization approach for improving the yield of aromatic monomers（YAM） by enzymolysis pretreatment was investigated, in which lignin was pretreated with laccase followed by oxidative depolymerization. It was found that lignin depolymeirzation was enhanced significantly by enzymolysis. The oxidative depolymerization contributed to 21.37% of YAM after the enzymolysis pretreatment,whereas the conventional oxidative depolymerization only gave 14.10% of YAM. The addition of ethanol in enzymatic pretreatment process improved the efficiency of enzymolysis, which effectively improved the solubility of pretreated lignin and depolymerization degree（DD） of lignin. The enzymolysis pretreatment increased the content of syringyl（S） style aromatic monomers, which hindered the recondensation among polymerized products. As lignin has low solubility in acidic aqueous solution, ethanol was added into enzymolysis system to improve the efficiency. However, the enzymolysis of lignin should be carried out for a limited period of time to prevent the inactivation of laccase.

Hydroxyl radicals-mediated oxidative cleavage of the glycosidic bond in cellobiose by copper catalysts and its application to low-temperature depolymerization of cellulose

As the most abundant source of biomass in nature for sustainable production of fuels and chemicals,efficient depolymerization of cellulose under mild conditions,due to the difficulty in selective cleavage of itsβ-1,4-glycosidic bonds,still remains challenging.Here,we report a novel method for oxidative cleavage of the glycosidic bonds by free radicals.Probed by the cellobiose reaction,it was found that·OH radicals,generated from the decomposition of H2O2 catalyzed by CuSO4 or CuO/SiO2,were efficient for selective conversion of cellobiose to glucose and gluconic acid at a low temperature of 333 K,and their selectivities reached 30.0%and 34.6%,respectively,at 23.4%cellobiose conversion.Other radicals,such as·SO4?,also exhibited high efficacy in the cellobiose reaction.Mechanistic studies suggest that the oxidative cleavage of theβ-1,4-glycosidic bond by the free radicals involve formation of the carbon radical intermediate via abstraction of the H atom dominantly at the C1 position.Following this oxidative mechanism,treatment of microcrystalline cellulose with·OH by impregnation with H2O2 and CuSO4 catalyst at 343 K led to significant enhancement in its hydrolysis efficiency.These results demonstrate the effectiveness of this new method in the oxidative cleavage of glycosidic bonds,and its viability for the efficient depolymerization of cellulose at low temperatures,which can be further improved,for example,by exploring new free radicals and optimizing their reactivity and selectivity.

Radical and(photo)electron transfer induced mechanisms for lignin photo-and electro-catalytic depolymerization

As one of the three major components of woody biomass,lignin is a kind of natural organic polymer and the only abundant natural renewable resource with aromatic nucleus.Chemical catalysis induced depolymerization is an important and effective approach for lignin utilization.In particular,photocatalysis and electrocatalysis show great potential in accurately activating C-O/C-C bonds,which is a critical point of selective cleavage of lignin.In this contribution,we focus on radical and(photo)electron transfer induced reaction mechanisms of the photo(electro)catalytic depolymerization of lignin.Primarily,the general situation of Carbon-centered radicals and active oxygen species mediated lignin conversion has been discussed.Then the mechanisms for(photo)electron transfer mediated lignin depolymerization have been summarized.At the end of this review,the challenges and opportunities of photo(electro)catalysis in the applications of lignin valorization have been forecasted.

Co@CoO:An efficient catalyst for the depolymerization and upgrading of lignocellulose to alkylcyclohexanols with cellulose intact

The depolymerization and upgrading of lignin from raw biomass,while keeping cellulose intact is important in biorefinery and various metal-based catalysts have been used in reductive catalytic fractionation,a key method in"lignin-first"strategy,Recently,we found that a core-shell structured Co@CoO catalyst with CoO shell as the real active site had excellent performance in the hydrogenolysis of 5-hydromethylfurfural to 2,5-dimethylfuran due to its unique ability to dissociate H_(2)and yield active H^(δ-)species(Xiang et al.,2022).In this work,we report a one-pot depolymerization and upgrading of lignocellulose to alkylcyclohexanols,a flavour precursor,with intact cellulose over this unique core-shell structured catalyst,Co@CoO.Lignin model compounds(β-O-4,4-O-5,α-O-4)were first used to clarify the activity of Co@CoO catalyst.Then,the one-pot conversion of various organosolv lignin(birch,pine and poplar)to alkylcyclohexanols was realized with the mass yield of alkylcyclohexanols up to25.8 wt%from birch lignin under the reaction condition of 210℃,1 MPa H_(2),16 h.Finally,the corresponding woody sawdusts were used as feedstocks and found that the Co@CoO catalyst indeed preferentially depolymerized and upgraded the lignin part and obtained the same alkylcyclohexanols products with the retention of cellulose-rich pulp.The collected alkylcyclohexanols were further esterified to obtain valueadded esters,which can be used as flavors.This work will inspire the design of new efficient metal oxide catalysts in lignin fractionation and depolymerization to high-value-added chemicals with intact cellulose.

Mathematical Modeling and Inverse Analysis for Microbial Depolymerization Processes of Xenobiotic Polymers

Microbial depolymerization processes of xenobiotic polymers are discussed. A mathematical model is formulated and inverse problems for a time factor and a molecular factor of a degradation rate are described. Experimental outcomes are introduced in inverse analyses. Once the time factor and the molecular factor are obtained, the microbial depolymerization process is simu-lated. Numerical techniques are illustrated and numerical results are presented.

Effect of pH conditions on the depolymerization of Wucaiwan coal by mixed acids/ultrasound method and the product structures and performance

The cleavage of the aliphatic chain or ether bond connecting the polycyclic aromatic hydrocarbons in coal can be achieved by not only hydrogenation reduction but also oxidative acid treatment. In this paper, coal samples from Wucaiwan in Xinjiang were pretreated with HNO3 followed by mixed acids/ultrasound treatment. The depolymerized coal samples obtained under different pH conditions were then separated by fractional washing. The structures and properties of the resulting coal samples were studied by elemental analysis, FT-IR, XRD, TG-DTA, TEM, UV-Vis, and PL. The results showed that when pH = 0.012, the obtained coal samples were fragments stripped off from the raw coal samples by ultrasound in strong acid conditions, aliphatic hydrocarbons linked with oxygen-containing groups such as nitro group, a small amount of small aromatic molecules and mineral salts; when pH -- 1.99-4.09, the obtained coal samples were polycyclic aromatic hydrocarbons linked with oxygen-containing groups such as nitro group,possessing the annulus wall of multilayer graphene fragment structures built up by sp2 carbons, and they are typical fluorescent substances of carbon nanoparticle structure. The former has no solubility in organic solvents, while the latter can be well dissolved in polar solvents such as acetone. All the depolymerized coal samples obtained under different pH conditions exhibited good absorption and ability of fluorescence emission.

A Bifunctional Brønsted Acidic Deep Eutectic Solvent to Dissolve and Catalyze the Depolymerization of Alkali Lignin

Lignin is an abundant renewable macromolecular material in nature,and degradation of lignin to improve its hydroxyl content is the key to its efficient use.Alkali lignin(AL)was treated with Brønsted acidic deep eutectic solvent(DES)based on choline chloride and p-toluenesulfonic acid at mild reaction temperature,the structure of the lignin before and after degradation,as well as the composition of small molecules of lignin were analyzed in order to investigate the chemical structure changes of lignin with DES treatment,and the degradation mechanism of lignin in this acidic DES was elucidated in this work.FTIR and NMR analyses demonstrated the selective cleavage of the lignin ether linkages in the degradation process,which was in line with the increased content of phenolic hydroxyl species.XPS revealed that the O/C atomic ratio of the regenerated lignin was lower than that of the AL sample,revealing that the lignin underwent decarbonylation during the DES treatment.Regenerated lignin with low molecular weight and narrow polydispersity index was obtained,and the average molecular weight(Mw)decreased from 17680 g/mol to 2792 g/mol(130°C,3 h)according to GPC analysis.The lignin-degraded products were mainly G-type phenolics and ketones,and small number of aldehydes were also generated,the possible degradation pathway of lignin in this acidic DES was proposed.

Vapor-Phase Transport Synthesis of MnSAPO-34 and Its Catalytic Properties

MnSAPO-34 molecular sieves were synthesized by vapor-phase transport （VPT） method using triethylamine （Et3N） as a structure directing agent （SDA）, and were characterized by XRD, BET, SEM, UV-Vis, FT-IR, and TG analy- ses. The influence of the zeolite crystallization conditions and the dry-gel composition were investigated. The results showed that the synthesis conditions had an effect on the crystalline phase. Pure MnSAPO-34 had been obtained when it was crystallized at 140 C for 18 hours. The ratio of MnO/A1203 in the starting gel ranging from 0.1 to 0.2 resulted in pure MnSAPO-34 with a CHA topology. Beyond this scope, MnSAPO-5 with an AFI topology structure was obtained as an impurity substance. UV-Vis spectroscopy and FT-IR spectroscopy study indicated that manganese was incorporated into the framework of the molecular sieve. The catalytic performance of MnSAPO-34 molecular sieve was tested by ketalization reaction of l, 2-propanediol with cyclohexanone. High yield of cyclohexanone-1, 2-propanediol ketal was obtained.

Synthesis of 4-Phenylphthalonitrile by Vapor-Phase Catalytic Ammoxidation of Intermediate 4-Phenyl-<i>o</i>-Tolunitrile: Reaction Kinetics

Kinetic regularities of 4-phenyl-o-tolunitrile ammoxidation on V-Sb-Bi-Zr/γ-Al2O3 oxide catalyst in the temperature interval 633 - 673 K have been studied. It has been established that rates of conversion of 4-phenyl-o-tolu- nitrile into the aimed 4-phenylphthalonitrile and CO2 are described by half-order equation on concentration of substratum and to be independent of the oxygen and ammonia partial pressures. It has been revealed that formation of 4-phenylphthalimide from byproducts is due to hydrolysis of 4-phenylphthalonitrile;carbon dioxide is produced by oxidation of 4-phenyl-o-tolunitrile and decarboxylation of 4-phenylphthalimide, and 4-phenylben- zonitrile is produced from 4-phenyl-o-tolunitrile and 4-phenylphthalimide.

Numerical Simulation of Microwaveassisted Depolymerization of Kraft Lignin

Kraft lignin has the potential to replace traditional fossil resources for the preparation of high-value chemicals because it is rich in aromatic rings and active functional groups.An effective method for the pyrolysis of kraft lignin into chemicals/fuels is microwave-assisted depolymerization.A simulation model is urgently needed to illustrate the coupling effect and mechanism of lignin conversion during the depolymerization process.In this study,COMSOL Multiphysics was used to simulate the microwave-assisted depolymerization process.The results showed that microwave power had a significant effect on the electric field and temperature distribution in the microwave cavity,while the reaction time had little effect on the electric field.The effect of the nitrogen flow rate on the electric field and temperature was negligible.The intensity of the electric field,heating rate of lignin,and final temperature of lignin depolymerization increased with increasing microwave power.

DEPOLYMERIZATION AND KINETICS OF DEPOLYMERIZATION OF POLYETHYLENE TEREPHTHALATE USING DIBUTYLTIN OXIDE CATALYST

Depolymerization of poly（ethylene terephthalate） （PET） was performed in the tubular bomb microreactor which contained the solution of PET in methanol and dibutyltin oxide at the temperature ranging from 433 K to 473 K, the reaction time from 5 to 45 min and the catalyst-to-PET ratio of 0.3%-2% by weight. The optimal condition for PET depolymerization catalyzed by dibutyltin oxide is the temperature of 443-453 K, the reaction time of 20-25 min and 0.8% by weight of catalyst. By using differential methods, the activation energy for the depolymerization process was found to be 154.05 kJ/mol in the temperature range from 433-463 K.

Depolymerization of <i>α</i>- &<i>β</i>-Chitosan by <i>e</i>-Beam Irradiation

α- and β-chitosan with molecular weight of 190,000 and 800,000 respectively, were depolymerized by e-beam irradiation with various doses. The radiation yield of scission (Gs) and degradation rate of the chitosans were identified. The synergistic chemical degradation in the presence of hydrogen peroxide is more effective at lower doses. Mw of β-chitosan was dramatically decreased from 800,000 to 21,030 at the irradiation dose 5 kGy, on the other hand, that of α-chitosan was decreased much more gradually from 190,000 to 36,000. The values of Gs at 10 kGy in the solution without H2O2 and with H2O2 were respectively 6.09 × 10-5 mol/cal and 30.6 × 10-5 mol/cal for α-Chitosan, and 8.18 × 10-5 mol/cal and 43.8 × 10-5 mol/cal for β-chitosan. It was obviously effective on depolymerization by using the combination of e-beam and H2O2. α-Chitosan molecules are likely to adopt a diffuse conformation in the solution and make the different morphologies depending on the concentration.

Mathematical analysis of physicochemical phenomena in the catalyst during hydrogenating depolymerization of coal extract benzene insoluble fraction

Efficiency and selectivity of hydrogenating depolymerization of the coal extract benzene-insoluble part over the heterogeneous Co–Mo/Al2O3 catalyst were assessed using a mathematical model. The analytical equations of the mathematical model were generated based on material balance incorporating the physico-chemical phenomena(reaction and diffusion) both in the autoclave and the catalyst grain. The equations offer the possibility for predicting changes of the reactants in the autoclave during the process and for determining the distribution of reactant concentrations in the grain as a function of its radius. The analytical equations of the model serve as the basis of the algorithm for assessing the influence of restrictive diffusion on the effectiveness and selectivity of the catalyst, and also for defining the optimal radii of the catalyst's pores to enable free transport of reactants in the grain interior.

Vapor-phase Nitration of Benzene to Nitrobenzene over Supported Sulfuric Acid Catalyst

Vapor-phase nitration of benzene over solid acid catalyst is expected to be a clean process with no sulfuric acid waste. We investigated this process over solid acidic catalysts utilizing diluted nitric acid (60-70%) as nitrating agent, and found that supported sulfuric acid catalyst exhibited a very high catalytic activity. Under the conditions of reaction temperature 160-170℃, space velocity (SV) 1200 h-1, the yield and the space-time yield (STY) of nitrobenzene (NB) based on HNO3 were more than 98% and 0.75 kg穔gcat-1穐-1 over 10% H2SO4/SiO2 (by weight) catalyst respectively.

Increase of Lignin Reactivity by Means of Depolymerization and Hydroxymethylation for Its Use in Synthetic Wood Elaboration

Lignin was extracted from peat by Sosa Method. In order to increase its chemical activity, it is necessary to make a structural modification by hydroxymethylation so it can be used in preparation of synthetic wood. Depolymerization was made by two methods： （1） reaction oflignin with NaOH 2%; （2） exposition oflignin to UV beam for 6, 12, 24, 36, 48 and 60 hours. The best depolimerization result was with exposition of lignin to UV by 12 hours since phenylpropanoic structure with higher number of free positions （unoccupied carbons） in C3 and C5 of its aromatic ring was obtained. It is known by Mannich Reaction and determination of phenolic OH by UV analysis. Later, its reactivity was increased by hydroxymethylation process by means of reaction of depolymerizated product with formaldehyde and later with glyoxal since it is less toxic. The modified product was mixed with six different kinds of resins （phenol-formaldehyde, urea-formaldehyde, melamine-formaldehyde, Glyoxal-formaldehyde, urea-formaldehyde and melamine-formaldehyde） to obtain a better mechanical characteristic as a synthetic wood. The best result was the one with melamine-formaldehyde. Finally, this product was mixed with testa rice so final product showed a great hardness and a shinny and smooth appearance.

Inhibition effects of using sequential microtubule depolymerization drug and polymerization drug on tumor cells

Objective: To investigate the different inhibition effects of different sequential usages of microtubule depolymerization drug and polymerization drug on tumor cells. Methods: Three tumor cell lines including MCF-7, SK-OV3, A549 were incubated with paclitaxel (PTX) and/or vinorelbine (NVB) of different concentrations. The cyto-toxicity was exam- ined by MTT test after incubating 72 h. According to different drugs and different sequences added to 96-well tissue culture plates, 5 groups were divided: PTX group (Group 1), NVB group (Group 2), PTX plus NVB group (Group 3), PTX first and NVB 4-h-later group (Group 4), and NVB first and PTX 4-h-later group (Group 5). Drug concentrations were 100% peak plasma concentration (PPC), 50% PPC, 25% PPC, 12.5% PPC, and 6. 25% PPC. Results: The inhibition effects on the three tumor cell lines in Group 5 were stronger than those in the other four groups (P < 0.01). And the inhibition effects in Group 4 were not stronger than those in Groups 1, 2 or 3 (P > 0.1). Conclusion: Using microtubule depolymerization drug first and then using microtubule polymerization drug has synergic inhibition effect on tumor cells.