Yield Of Aromatic Hydrocarbons Research Articles

An efficient way to synthesize biomass-based molybdenum carbide catalyst via pyrolysis carbonization and its application for lignin catalytic pyrolysis

In this study, a simple and rapid method was proposed to synthesize orthorhombic α-Mo2C as catalyst for lignin catalytic pyrolysis. Biomass in-situ pyrolysis products were used as the carbon source and supporter, the carbonization of Mo precursor was realized under rapid heating. Experimental results show that Pine-Mo2C catalyst can achieve lignin pyrolysis vapor bond breaking and deoxidation under normal pressure, and the yield of monocyclic aromatic hydrocarbons is 13.26 wt%, of which aromatic hydrocarbons with side chain account for 74%. The side chain aliphatic hydrocarbons of lignin are effectively retained, and hydrogen consumption is minimized. The characterization of catalyst and experiments of guaiacol, 2-phenoxy-1-phenylethanol and 4,4′-biphenol shows that efficient deoxidation is due to targeted attack of catalyst on C-O. Therefore, Pine-Mo2C shows excellent activity in promoting direct bond breaking deoxidation of lignin.

Efficient and selective catalytic pyrolysis of cellulose to monocyclic aromatic hydrocarbons over Zn-containing HZSM-5

A series of Zn-containing HZSM-5 (HZ5) with hierarchical pores (xZn(DS)) were obtained by adding different amounts of Zn(NO3)2 solution in a hydrothermal synthesis process. The performances of xZn(DS) in catalytic reforming of cellulose pyrolysis volatiles were investigated at 500 °C. The results showed that the addition of Zn during synthesis increased in the total pore volume of xZn(DS) and reduced the content of strong acid sites, and introduced new weak acid sites. The Zn species were highly dispersed inside the zeolite, and enhanced the accessibility of acid sites, so that the yields of light aromatic hydrocarbons and monocyclic aromatic hydrocarbons (MAHs) over 0.7Zn(DS) (The molar ratio of ZnO/Al2O3 in the synthesis process of xZn(DS) was 0.7) were higher than those over S-HZ5 (Zn was not added in the synthesis process) and commercial HZ5. Compared with S-HZ5, the yield of MAHs over 0.7Zn(DS) increased from 92.8 to 114.1 mg/g and the coke yield decreased by 2.9%. The selectivity of MAHs over 0.7Zn(DS) was 87.7%, which was 5.3% higher than that over S-HZ5. Simultaneously, the increase in mesopores of xZn(DS) accelerated the mass transfer process, shortened the diffusion path and improved the anti-coking performance of the catalysts. In addition, this study also proposed a possible mechanism for the catalyst to adjust the distribution of aromatic products and provided a new idea for promoting the selective production of MAHs for the pyrolysis of cellulose.

Aromatic and aliphatic production of catalytic pyrolysis of lignin using ZSM-5/Al-SBA-15 catalyst derived from high-calcium fly ash

In this work, lignin was utilized as biomass feedstocks to study the feasibility of fuels and chemical production, while fly ash was used for synthesizing ZSM-5 (FA-ZSM-5) and SBA-15 (FA-SBA-15) catalysts for upgrading pyrolysis products. The use of fly ash offers several benefits such as reducing the fly ash disposal cost, solving environmental problems, and significantly increasing high valued products. Catalytic fast pyrolysis of kraft lignin using ZSM-5/ SBA-15 catalyst prepared from fly ash was studied using a pyrolysis-GC/MS system. The influence of temperature (400–600°C) during thermal pyrolysis, the FA-ZSM-5 and FA-SBA-15 ratios (1:0 ,2:1, 1:1, 1:2, 0:1), and lignin-to-catalyst ratios (1:5 and 1:10) on the hydrocarbon selectivity was investigated. Non-catalytic pyrolysis volatiles consisted of a high proportion of guaiacol compounds (G-type, 66.7%) and p-hydroxyl phenols (H-type, 18.0%). The presence of zeolite catalysts contributed to enhance both aliphatic and aromatic production, while a proportion of guaiacyl decreased significantly. The highest selectivity of aliphatic and aromatic HCs was achieved at feed to catalyst ratios of 1:10. Coupling HZSM-5 and Al-SBA-15 catalysts were more reactive in converting the alkoxy-phenol (G-type) and p-hydroxyphenyl compounds (P-type) toward both aliphatic HCs and monocyclic-aromatic HCs (MAHs), particularly benzene, toluene and xylene (BTX). Among all catalysts, FA-ZSM-5/ FA-SBA-15 ratio of 1:2 showed the optimum dual catalyst ratio to enhance the highest yield of aliphatic and aromatic hydrocarbons of 15.1 and 21.4 % with the acceptable yield of phenolic compounds (34%). ZSM-5/ SBA-15 catalyst prepared from fly ash showed high efficiency to convert solid lignin to MAHs (BTX). The decrease in the PAHs selectivity seemed to be good performing of this dual catalyst because it expected to decrease the coke formation on the catalyst surface.

Unraveling the role of reaction environment and catalysts for pyrolysis of technical lignin into different functional bio-oil yield

Catalytic pyrolysis of Kraft Lignin (KL) experiments were carried out at different temperatures (350–500 °C) over base MgO, acidic ZSM-5 and mixture of MgO-ZSM-5 catalysts under different environments (N2 and CO2). Non-catalytic reaction produced maximum bio-oil (35.3 wt%) under CO2 at 450 °C. Upgrading of pyrolysis vapor under different environment with catalysts produced lower bio-oil as it is enhanced cracking and coke formation. Higher intensity peak at 1695–1720 cm-1 was found in up-gradation pyrolysis KL vapor under CO2, which showed that the higher aldehyde/acidic or ketone functionality in bio-oil. The content of monocyclic aromatic hydrocarbons increased whereas phenolic compound decreased with using the catalysts under N2 while acidic functionality increased under CO2 environment. Our results suggest that mixture of catalysts showed synergistic effects which increased the bio-oil quality. Overall, mixture of MgO-ZSM-5 showed the highest yield of aromatic hydrocarbons (ca. 49.2%) under N2. Significant amount oxygen content reduced with the mixture of catalyst (MgO-ZSM-5, 1:1 ratio) under N2 with the increasing of aromatic hydrocarbon. Higher heating value bio-oil was obtained with catalytic up-gradation.

In-situ catalytic upgrading of bio-oil from rapid pyrolysis of biomass over hollow HZSM-5 with mesoporous shell

To solve the issue of narrow micropores in traditional protonic type Zeolite Socony Mobil-5 (HZSM-5) catalysts in the restricting of large-molecular reactants/products diffusion, hollow HZSM-5 with a mesoporous shell was prepared using a hydrothermal method combined with a tetrapropylammonium hydroxide (TPAOH) treatment process. Applying for in-situ catalyst upgrading of bio-oil from rapid pyrolysis of biomass, the obtained most efficient catalyst of Hollow(30)-TP resulted in aromatic hydrocarbon yields in the range of 78.49–78.67% for cellulose and hemicellulose, which is much greater than those using the traditional HZSM-5 (61.06–68.26%). Furthermore, in the case using real biomass (cedar) with an optimal biomass/catalyst weight ratio of 1:2, the aromatic hydrocarbon yield reached up to 80.16%. In addition, this catalyst exhibited excellent reusability and regeneration property due to the increased accessibility to the acid sites in the hollow HZSM-5 for the improving of the reaction rate as well as the reducing of coking.

Effect of potassium on catalytic characteristics of ZSM-5 zeolite in fast pyrolysis of biomass-based furan

The effect of potassium in biomass on the catalytic activity of ZSM-5 zeolite in the fast pyrolysis of biomass was investigated using 2-methylfuran (2-MF) as the typical model compound. The mechanism of action of potassium was explored in detail, along with the physicochemical properties of ZSM-5, including crystallinity, pore structure, and surface acidity. The physicochemical properties of ZSM-5 deteriorated to varying degrees after being tainted with different potassium sources (KOH, K2CO3, KAc, and KCl). Compared with neutral KCl and strong alkali KOH, K2CO3, and KAc, with weaker alkalinity but larger crystal structure, exerted a larger influence on ZSM-5. Changes in ZSM-5 tainted with K2CO3 were the greatest, and crystallinity, surface area, acidity, and the corresponding yields of valuable aromatic hydrocarbons and gas products, all declined significantly, compared with raw ZSM-5. When the amount of K(CO32−) on ZSM-5 was less than 0.5 wt%, only minor (<10 %) changes were observed in crystallinity and surface area, but total acidity decreased by over 30 percent. The conversion of 2-MF was increased using ZSM-5 tainted with less than 0.5 wt% K(CO32-) and less liquid oxygenated compounds and more CO2 were produced. Appropriate total acidity, adjusted by a tiny amount of K2CO3, could promote deoxygenation to CO2. However, the decarbonylation reaction was inhibited, causing a negative effect on monocyclic aromatic hydrocarbons, which was attributed to the large-scale loss of both acidity and physical structure of ZSM-5 caused by more than 1.0 wt% K(CO32-).

Mo-based catalyst for chemical looping deoxygenation of phenolic compounds to aromatic hydrocarbons

A novel MoO3-SiO2 material was prepared by stepwise precipitation and was used as catalyst and oxygen-carrier in the chemical looping deoxygenation of lignin-derived phenolic compounds. In this recycle, hydrocracking reaction of phenolic compounds take place first, obtaining the aromatic hydrocarbons and higher-valence molybdenum oxide. Subsequent, the higher-valence molybdenum oxide was reduced by H2, yielding the lower-valence molybdenum oxide and H2O, thereby completing a redox cycle. High yield of aromatic hydrocarbons (71.5%) was obtained at 340 °C when guaiacol was used as model compound in the chemical looping deoxygenation. Moreover, large proportion of toluene was observed in products because that the strong acidity of the MoO3-SiO2 catalyst promotes the transmethylation. This work provides a new process for production of aromatic hydrocarbon from lignin via phenolic compounds.

Improving hydrocarbons production via catalytic co-pyrolysis of torrefied-biomass with plastics and dual catalytic pyrolysis

To increase the low yield and selectivity of aromatic hydrocarbons during the biomass pyrolysis process, we torrefied the biomass and then co-pyrolyzing with plastics such as high-density polyethylene (HDPE), polystyrene (PS), ethylene–vinyl acetate (EVA) and polypropylene (PP) and also single and dual catalyst layouts were investigated by Py-GC/MS. The results showed that non-catalytic fast pyrolysis (CFP) of raw bagasse (RBG) generated no aromatics. After torrefaction non-CFP of torrefied bagasse (TBG) generated low aromatic yield. Indicating that torrefaction would enhance the proportion of aromatics during the pyrolysis process. The CFP of TBG 200°C and TBG 240°C over ZSM-5 produced the total aromatic yield of 1.96 and 1.88 times higher, respectively, compared to non-CFP of TBG. Furthermore, the addition of plastic could increase H/Ceff ratio of the mixture, consequently, increase the yield of aromatic compounds. Among the various torrefied-bagasse/plastic mixtures, the CFP of TBG/EVA (7:3 ratio) mixture generated the highest the total aromatic yield of 7.7 times more than the CFP of TBG alone. The dual catalyst layout could enhance the yield of aromatics hydrocarbons. The dual-catalytic co-pyrolysis of TBG 200°C /plastic (1:1) ratio over USY (ultra-stable Y zeolite)/ZSM-5, improved the total aromatics yield by 4.33 times more than the catalytic pyrolysis of TBG 200oC alone over ZSM-5 catalyst. The above results showed that the yield and selectivities of light aromatic hydrocarbons can be improved via catalytic co-pyrolysis and dual catalytic co-pyrolysis of torrefied-biomass with plastics.

Effect of the mixing ratio of methylcyclohexane and n-dodecane on the product composition and coke formation in the catalytic decomposition reaction of blended fuels

Analyzing the products obtained from the catalytic reaction of jet fuels is challenging because the fuels consist of several components. It is crucial to select suitable model compounds as representatives of the fuel to study its catalytic reaction, and methylcyclohexane (MCH) and n-dodecane were selected consequently. Further, the change in the products obtained from the reaction (catalyzed by commercial HZSM-5 in a flow reactor under a supercritical condition (550°C and 5MPa)) was investigated by varying the ratios of MCH and n-dodecane in the blended fuels. Although the fuel conversion and gas yield were proportional to the n-dodecane fraction in the fuel, the yield of aromatic compounds at each time, which was relative to the yield at the initial time, did not indicate any relation with it. The relative yields of the aromatic hydrocarbons obtained from the blended fuel reduced much slower than those obtained from the pure fuels. Particularly, the fuel containing an n-dodecane mass fraction of 0.2 exhibited the lowest reduction rate regarding the relative yields of aromatic hydrocarbons. The change in the relative yields of the products regarding the fuels was not crucial to coke formation.

A novel production of monocyclic aromatic hydrocarbons via one-step catalytic conversion of pine sawdust and waste plastics over Pd/trap-HZSM-5

A novel method is proposed to one-step convert pine sawdust (PW) and high-density polyethylene (HDPE) into monocyclic aromatic hydrocarbons under solvent-free conditions. The aim is to strengthen the collision ability of small molecules and stabilize active oxygenates by using pressurization and hydrogen atmospheres, so as to significantly enhance the thermal interaction between PW and HDPE. A series of Pd/trap-HZSM-5 catalysts were prepared by different methods. Among them, self-reduction Pd/trap-HZSM-5 catalyst with smallest Pd nanoparticle size and highest hydrogen adsorption capabilities combined with hydrogenation ability and moderate acidity bi-functions, so it shows the highest activity. Under the optimal conditions (400℃, 1 MPa H2, Si/Al ratio of 50, catalyst-to-reactant ratio of 0.1, and plastics-to-biomass ratio of 4), both the high selectivity of aromatic hydrocarbons in bio-oil (88.9%) and the high yield of bio-oil (45.5 wt%) are ensured. The calculated total aromatic hydrocarbons yield reached 40.5 wt%, of which only 0.7 wt% were polycyclic aromatic hydrocarbons, and the vast majority were moncyclic aromatic hydrocarbons. The synergistic effect between PW and HDPE relatively increased the yield of aromatic hydrocarbons by 44.5%.

In-situ catalytic upgrading of bio-oil derived from fast pyrolysis of sunflower stalk to aromatic hydrocarbons over bifunctional Cu-loaded HZSM-5

Commercial HZSM-5 zeolite (Si/Al = 24) was modified with Cu species using the wet impregnation method, and applied in the in-situ upgrading of bio-oil from the fast sunflower stalk pyrolysis with a catalyst to biomass ratio of 1:1 at 500 °C. The main objective was to study the Cu doping effect on the HZSM-5 catalytic performance in terms of the selectivity to aromatic hydrocarbons (especially the specific aromatic hydrocarbons including benzene, toluene and xylene) yield. It was found that Cu/HZSM-5 with low Cu loading amounts preserved HZSM-5 crystalline structure as well as its acid sites. The HZSM-5 with 0.5 wt.% Cu loading amount exhibited the best catalytic performance with a high relative amount of aromatic hydrocarbons of 73.2 % and a yield of specific aromatic hydrocarbons as high as 56.5 mg/g-biomass (d.a.f), which were much higher than those based on the parent HZSM-5 (55.0 % and 26.0 mg/g-biomass (d.a.f)). It should be mainly attributed to its suitable acidity and best textural properties for the deoxygenation of the bio-oil thanks to the optimum Cu loading amount. In addition, the 0.5 wt.% Cu loaded HZSM-5 catalyst also showed excellent catalytic reusability and regeneration property, and the spent catalyst was easily recovered by a simple calcination in air for a short time.

Promoted production of hydrocarbons in the catalytic pyrolysis of rape straw over composite HZSM-5@MCM-41 catalysts

In order to promote the production of hydrocarbons in the catalytic pyrolysis of rape straw, a core-shell catalyst fabricated by external recrystallization method was employed. The composite catalyst HZSM-5@MCM-41 was prepared by varying the mass ratio of template and HZSM-5 (THR), and the effect of zeolite acidity and mesoporosity on the production of hydrocarbons was analyzed. A final pyrolysis temperature of 500 °C was suitable to obtain high yield of hydrocarbons over composite catalysts. Compared with ZSM-5 with a favorable pyrolysis temperature of 550 °C, a lower pyrolysis temperature meant a more efficient process, which may be related closely to the good diffusion of large-sized pyrolysis vapors over HZSM-5@MCM-41 catalysts. In addition, the highest yield of monocyclic aromatic hydrocarbons obtained over HZSM-5@MCM-41 with THR of 1 was 11.43 wt.%, which was boosted by 2.5 times compared with HZSM-5. A proper THR was suitable to fabricate a core-shell catalyst with excellent crystallinity, acidity and mesoporosity, and resulting in a high yield of hydrocarbons. Furthermore, the core-shell catalyst presents less formation of graphite-like coke, which indicated the easier removal of coke. Therefore, the composite HZSM-5@MCM-41 catalysts were more appropriate for upgrading of pyrolysis vapors for hydrocarbons.

Catalytic Conversion of a ≥ 200 °C Fraction Separated from Low-Temperature Coal Tar into Light Aromatic Hydrocarbons.

A ≥ 200 °C fraction (CT200F) of low-temperature coal tar was prepared by a rotary film evaporator. The catalytic conversion experiments of CT200F and six model compounds were conducted on the pyrolysis gas chromatography–mass spectrometer. The yields of catalytic conversion products benzene, toluene, xylene, and naphthalene (BTXN) were analyzed by semi-quantitative analysis according to the chromatographic peak areas. Additionally, the possible formation pathways and mechanisms of the target products BTXN generated over different catalysts were investigated. The results show that the yield of aromatic hydrocarbons increases and the yield of acid compounds decreases during CT200F pyrolysis over ZSM-5, HY, USY, and β-zeolite compared with that of its non-catalytic pyrolysis, especially the yields of BTXN obtained over USY and β-zeolite increase by 128 and 108%, respectively. The pore structure of ZSM-5 is suitable to produce BTX, while the suitable acidity and pore structure of USY, HY, and β-zeolite are more beneficial for the selective preparation of naphthalene than that of ZSM-5. The conversion pathways of six model compounds into BTXN over zeolites were obtained, and the following conclusions can be drawn: The dehydroxylation effect of zeolites shows the order of ZSM-5 > HY > USY > β-zeolite. The catalytic effect of zeolites on the cracking and ring opening of PAHs in CT200F shows the order of β-zeolite > USY > HY > ZSM-5. The catalytic effect of catalysts on the cracking and aromatization of aliphatic compounds shows the order of ZSM-5 > β-zeolite > USY > HY. β-zeolite has an outstanding catalytic performance in the conversion of PAHs into naphthalene. ZSM-5 and HY can effectively remove phenolic hydroxyl groups in phenol and naphthol. During the catalytic conversion processes of the coal tar fraction and model compounds, the catalytic effect of the pore constructions of zeolites is more important than their acidities, which determines whether large molecules can enter and whether acid sites in non-micropores can be effectively utilized.

Influence of Biomass Inorganics on the Functionality of H+ZSM-5 Catalyst during In-Situ Catalytic Fast Pyrolysis

In this study, the contamination of H+ZSM-5 catalyst by calcium, potassium and sodium was investigated by deactivating the catalyst with various concentrations of these inorganics, and the subsequent changes in the properties of the catalyst are reported. Specific surface area analysis of the catalysts revealed a progressive reduction with increasing concentrations of the inorganics, which could be attributed to pore blocking and diffusion resistance. Chemisorption studies (NH3-TPD) showed that the Bronsted acid sites on the catalyst had reacted with potassium and sodium, resulting in a clear loss of active sites, whereas the presence of calcium did not appear to cause extensive chemical deactivation. Pyrolysis experiments revealed the progressive loss in catalytic activity, evident due the shift in selectivity from producing only aromatic hydrocarbons (benzene, toluene, xylene, naphthalenes and others) with the fresh catalyst to oxygenated compounds such as phenols, guaiacols, furans and ketones with increasing contamination by the inorganics. The carbon yield of aromatic hydrocarbons decreased from 22.3% with the fresh catalyst to 1.4% and 2.1% when deactivated by potassium and sodium at 2 wt %, respectively. However, calcium appears to only cause physical deactivation.

Processing of propane-butane fraction on zeolite-containing catalysts

Abstarct. Processing of propane-butane and propane-propylene fractions in light hydrocarbons on the zeolite catalysts modified by zinc, manganese, cobalt, lanthanum was studied. It was shown that the degree of conversion on the Zn-La-Co-ZSM-AI2O3 catalyst increases from 40.2 to 99.0% as the temperature increasesfrom450to600 °C. The maximum yield of aromatic hydrocarbons was 31.4%. As the temperature increases from 450 to 600С, the cracking of hydrocarbons intensifies resulting in the formation of methane and ethane. New generation catalysts based on zeolites have the prospect of being used in technologies for processing various types of hydrocarbon raw materials. The activity of catalysts in the processing of light hydrocarbons depends on the structure and state of the active centers. The physicochemical characteristics of the developed catalysts have been studied. One of the possible ways to control the catalytic properties is to introduce a variable valence catalyst as modifiers into the composition.

Data-driven prediction of biomass pyrolysis pathways toward phenolic and aromatic products

This study clarifies the reaction pathway for biomass pyrolysis to phenolic compounds and aromatic hydrocarbons by analyzing 20 biomass samples using a central composite design and response surface plot. The pyrolysis reaction was performed using two integrated fixed-bed reactors. The product yield was significantly affected by pyrolysis temperature when utilizing the thermal cracking, repolymerization, and Boudouard reaction pathways. The bio-oil used in the study was obtained from the volatile matter fraction, where the fixed carbon content strongly affected biochar yield. Regarding bio-oil composition, both pyrolysis temperature and biomass constituents, including hemicellulose and lignin, significantly affected the yield of phenolics and aromatic hydrocarbons. In addition, biomass pyrolysis reaction pathways toward phenolic compounds and aromatic hydrocarbons were proposed.

Improving the monocyclic aromatic hydrocarbons production from fast pyrolysis of biomass over Fe‐modified ZSM‐5 catalysts

SummaryFe‐modified ZSM‐5 (Fe/ZMS‐5) catalysts were prepared and used during catalytic fast pyrolysis of biomass (CFP) to achieve high yields of monocyclic aromatic hydrocarbons (MAHs) and inhibit the formation of polycyclic aromatic hydrocarbons (PAHs). The catalytic effects on the yield and selectivity of aromatic hydrocarbons (aromatics) under various reaction conditions were evaluated. Under the optimal reaction conditions at 600°C and mass ratio of catalyst to biomass (catalyst/biomass) of 10/1, the 15 wt% Fe/ZMS‐5 catalyst displayed the highest productions of MAHs and PAHs with the values of 212.2 mg and 94.5 mg per gram biomass, corresponding to the MAHs selectivity of 69.2%, which were significantly higher than those obtained over ZSM‐5 alone. The origins of aromatic hydrocarbons were explored by CFP of three typical components of biomass. Combined the characterization and reaction performance of catalysts, the catalytic mechanisms of Fe/ZSM‐5 catalyst for biomass pyrolysis to produce aromatic hydrocarbons were put forward.

Distribution and toxicity of polycyclic aromatic hydrocarbons during CaO-assisted hydrothermal carbonization of sewage sludge

Hydrothermal carbonization (HTC) of sewage sludge (SS) with and without calcium oxide (CaO) introduction was conducted at 160–240 °C, and the yield and distribution of polycyclic aromatic hydrocarbons (PAHs) were evaluated for the first time. PAHs (2972.99 μg/kg) and toxic equivalent quantity (TEQ) (373.09 μg/kg) yields in SS decreased by 13.61% and 14.65%, respectively, after treatment at 160 °C and substantially increased as temperatures increased. More PAHs were distributed in the hydrochar than in the aqueous products. Hydrochar yields decreased linearly with temperature, thus increasing PAH concentration in hydrochar; 6221.98 μg/kg of PAHs in hydrocar at 240 °C exceeded agricultural use standard limits. PAH and TEQ yields at 200 °C decreased by 5.55–15.98% and 2.88–3.54%, respectively, when 3–9% CaO was added, which could be ascribed to CaO inhibition in the free radical reaction for PAH generation. Additionally, 6% CaO addition substantially weakened the acceleration effect of high temperatures on PAH formation; the decrease of PAH yield at 240 °C was 22.14%, which is higher than that at other temperatures. Consequently, the PAH concentration in hydrochar declined by 2.33–22.37%. PAH content in hydrochar obtained from CaO-assisted HTC of SS fell within agriculture use standard limit and exhibits potential for use as a soil conditioner. However, condition with a CaO amount of 15% would significantly increase TEQ yields. Considering both PAH and TEQ yields and the ecological risks of PAHs in hydrochar derived from HTC of SS, the appropriate reaction conditions were found to be 200 °C with 3–6% added CaO.

Catalytic co-pyrolysis of polycarbonate and polyethylene/polypropylene mixtures: Promotion of oil deoxygenation and aromatic hydrocarbon formation

The co-pyrolysis of polycarbonate (PC) and polyethylene (PE)/polypropylene (PP) in the presence of HZSM-5 catalyst was studied in a two-stage tube reactor with the objective of promoting simultaneous deoxygenation and aromatic hydrocarbon formation, at atmospheric pressure and without external hydrogen addition. As the blending ratio of PE/PP increased, the yield of oil phase product, coke, and solid decreased, and the yield of gas phase increased significantly. At the blending ratio of 75% PP, the concentration of oxygenates in the oil was reduced to 2.9% and that of aromatic hydrocarbons increased to 97.1%. Increasing the reaction temperature from 500 °C to 700 °C increased the yield of aromatic hydrocarbons further to 98.1%. Catalyst regeneration decreased the acidity of the HZSM-5 catalyst, resulting in a slight decrease in the deoxygenation and aromatization effects. The results showed that PP is an effective hydrogen donor in the catalytic deoxygenation and aromatization process; the hydrogen provided enhanced the adsorption of phenols produced by the pyrolysis of PC on HZSM-5 and their direct deoxygenation to form new aromatic hydrocarbons.

Breaking the lignin conversion bottleneck for multiple products: Co-production of aryl monomers and carbon nanospheres using one-step catalyst-free depolymerization

Lignin is considered as a renewable and sustainable resource for producing value-added aromatic chemicals and functional carbon materials. Herein, we develop a one-step catalyst-free depolymerization strategy to convert lignin into aryl monomers and carbon nanospheres simultaneously. Importantly, microwave-assisted depolymerization (MAD) in conjunction with dichloromethane (CH2Cl2) vapors is developed. The total mass yield of guaiacols reached the highest amount of 225.1 mg/g at 600 °C, and the highest yields of phenols (49.0 mg/g) and aromatic hydrocarbons (155.1 mg/g) were obtained at 700 °C. Hydrogen radicals and hydrogen chloride (HCl) are in-situ formed from CH2Cl2, significantly decreasing the activation barrier and reforming pyrolysis vapors to promote the formation of aryl monomers. Interestingly, uniform carbon nanospheres with an average size of 140 nm were produced as co-products at 700 °C. The microwave “hot-spots”, allied with the continuous surface erosion and the decrease in surface energy of lignin-derived carbon precursors by CH2Cl2 vapor, can be considered the driving force for the ultimate formation of carbon nanospheres. The CH2Cl2/MAD system produces aryl monomers (26.8 wt% yield) and carbon nanospheres (36.6 wt% yield) at 700 °C. We provide a facile, intriguing and scalable approach to convert lignin to valuable aryl monomers and sustainable carbon materials that can be applied in the chemistry, energy and environmental fields.