Preparation of bio-oil derived from catalytic upgrading of biomass vacuum pyrolysis vapor over metal-loaded HZSM-5 zeolites

The Fe-, Co-, Cu-loaded HZSM-5 zeolites were prepared via impregnation method. The upgrading by catalyst on biomass pyrolysis vapors was conducted over modified zeolites to investigate their catalytic upgrading performance and anti-coking performance. The Brønsted acid sites amount on Cu-,Co-loaded HZSM-5 decreased sharply, while that of Lewis both increased. The yield of liquid fraction and refined bio-oil over metal loaded ZSM-5 catalysts decreased, while that of char almost kept constant. The physical property of refined bio-oil was promoted in terms of pH value, dynamic viscosity and higher heating value (HHV). FT-IR analysis revealed that the chemical structure of refined bio-oil obtained over Fe-, Co-, Cu-loaded HZSM-5 zeolites was highly similar. The yield of monocyclic aromatic and aliphatic hydrocarbon over Fe-,Co-loaded HZSM-5 were boosted by around 2.5 times compared with original ZSM-5 zeolites. Data analysis revealed that Cu/HZSM-5 presented the worst deoxygenation ability. The anti-coking capability of Fe/HZSM-5 was obviously better, i.e., the coke content showed an approximate decrease of 38%. Thus, this study provided an efficient Fe/HZSM-5 catalysts for preparation of bio-oil derived from catalytic upgrading of biomass pyrolysis vapor.     

Tungstophosphoric acid incorporated hierarchical HZSM-5 catalysts for direct synthesis of dimethyl ether

HZSM-5 zeolites are active materials in dimethyl ether (DME) production with high surface acidity. In this study, hierarchical HZSM-5 catalysts were synthesized with steam-assisted crystallization (SAC) method and then in order to increase its surface acidity, TPA was loaded into the HZSM-5 catalyst having various mass ratios (5, 10, 25%) by wet impregnation method. Synthesized catalysts were characterized by N₂ physisorption (BET analysis), X-Ray diffraction and pyridine adsorbed diffuse reflectance FTIR spectroscopy techniques. Characterization analysis of tungstophosphoric acid (TPA) impregnated catalysts indicated that hierarchical HZSM-5 possesses mesoporous structures. The average pore size distribution of TPA impregnated HZSM-5 catalysts were between 17 and 20 nm. TPA impregnation promoted Brønsted acid sites of the catalyst, which favors methanol dehydration reaction. Activity tests have been performed at reaction temperatures of 200–300 °C at 50 bar reaction pressure in the presence of admixed catalysts (physically mixed commercial HifuelR-120 and HZSM-5 based catalysts with a weight ratio of 1:1). Results revealed that the increase in the amount of heteropoly acid has enhanced DME selectivity and CO conversion. Maximum DME selectivity of 57% and CO conversion of 46% were achieved in the presence of the 25TPA@HZSM-5 catalyst at the optimum reaction temperature of 275 °C. TGA analysis result of spent catalysts presented the highest amount of coke over HZSM-5. TPA incorporation decreased coke formation due to suppression of the Lewis acid site, which is responsible for the coke formation.     

Slow catalytic pyrolysis of rapeseed cake: Product yield and characterization of the pyrolysis liquid

The performance of three catalysts during slow catalytic pyrolysis of rapeseed cake from 150 to 550 °C over a time period of 20 min followed by an isothermal period of 30 min at 550 °C was investigated. Na₂CO₃ was premixed with the rapeseed cake, while γ-Al₂O₃ and HZSM-5 were tested without direct biomass contact. Catalytic experiments resulted in lower liquid and higher gas yields. The total amount of organic compounds in the pyrolysis liquid was considerably reduced by the use of a catalyst and decreased in the following order: non-catalytic test (34.06 wt%) > Na₂CO₃ (27.10 wt%) > HZSM-5 (26.43 wt%) > γ-Al₂O₃ (21.64 wt%). In contrast, the total amount of water was found to increase for the catalytic experiments, indicating that dehydration reactions became more pronounced in presence of a catalyst. All pyrolysis liquids spontaneously separated into two fractions: an oil fraction and aqueous fraction. Catalysts strongly affected the composition and physical properties of the oil fraction of the pyrolysis liquid, making it promising as renewable fuel or fuel additive. Fatty acids, produced by thermal decomposition of the biomass triglycerides, were converted into compounds of several chemical classes (such as nitriles, aromatics and aliphatic hydrocarbons), depending on the type of catalyst. The oil fraction of the pyrolysis liquid with the highest calorific value (36.8 MJ/kg) was obtained for Na₂CO₃, while the highest degree of deoxygenation (14.0 wt%) was found for HZSM-5. The aqueous fraction of the pyrolysis liquid had opportunities as source of added-value chemicals.     

Upgrading of a wood-derived oil over various catalysts

The upgrading of a bio-oil using a fixed bed micro-reactor operating at 1 atm, 3.6 WHSV and 330–410°C over various catalysts is reported. The catalysts used were HZSM-5, silicalite, H-mordenite, H-Y and silica-alumina. The yield of hydrocarbons as well as the extent of deoxygenation, coke formation and conversion of the non-volatile portion of the bio-oil were used as measures of catalyst performance. The maximum hydrocarbon yield when HZSM-5 was used occurred at 370°C and was 39.3 wt% of the bio-oil. For the other catalysts, the hydrocarbon yields increased with temperature and were up to 22.1 wt% for silicalite; 27.5 wt% for H-mordenite; 21.0 wt% for H-Y; and 26.2 wt% for silica-alumina at 410°C. The hydrocarbon selectivity with HZSM-5 and silicalite catalysts was mostly for gasoline range hydrocarbons (C₆ to C₁₂) and for H-mordenite and H-Y for kerosene range hydrocarbons (C₉ to C₁₅). The hydrocarbon fraction obtained with silica-alumina did not produce any defined distribution. The pore size, catalyst acidity and catalyst shape selectively affected the product distribution. The overall performance followed the order: HZSM-5 > H-mordenite > H/Y > silica-alumina, silicalite.     

Unique structure of fibrous ZSM-5 catalyst expedited prolonged hydrogen atom restoration for selective production of propylene from methanol

A unique mesostructured fibrous silica@ZSM-5 (HSi@ZSM-5) catalyst was synthesized via microemulsion ZSM-5 zeolite seed assisted synthesis method and successfully applied in enhanced propylene formation in methanol to olefin (MTO) process. Characterization of the catalysts were carried out by FESEM, TEM, XRD, TGA, N₂ adsorption-desorption, NH₃ and KBr probed FTIR. Catalytic performance of as-synthesized catalyst was examined using a micro-pulse reactor and compared with the commercial HZSM-5. The reaction mechanism was elucidated by in-situ methanol FTIR spectroscopy. It was found that HSi@ZSM-5 produced higher propylene selectivity (56%) and was stable for long time on stream (80 h), nearly three-fold higher than that of commercial HZSM-5. In addition, HSi@ZSM-5 displayed higher rate of methanol dehydration, surface methoxy species generation and olefin methylation, indicating that alkene catalytic cycle is the dominant reaction mechanism. The higher selectivity towards propylene was correlated to the existence of moderate acidity which impeded the formation of paraffins and polymethylbenzene intermediates. These observations are further supported by KBr probed FTIR findings which revealed negligible paraffinic carbon species on HSi@ZSM-5. Thus, the unique fibrous silica@ZSM-5 retarded coke deposition due to suppression of undesired side reactions thereby signifying intensified propylene formation, which is highly desirable in commercial MTO processes.     

Comprehensive research of in situ upgrading of sawdust fast pyrolysis vapors over HZSM-5 catalyst for producing renewable light aromatics

Catalytic fast pyrolysis of sawdust was investigated over HZSM-5 zeolites (SiO₂/Al₂O₃ = 25, 50 and 80) in a drop tube quartz reactor for production of green aromatics and olefins. The effects of temperature, weight hourly space velocity (WHSV), SiO₂/Al₂O₃ ratio and atmosphere on yield and selectivity of aromatics were investigated. The results show that almost all small organic oxygen species in initial volatiles were converted into gaseous hydrocarbons and aromatics after in situ catalysis of HZSM-5. HZSM-5 whose SiO₂/Al₂O₃ is 25 exhibited the best performance with the aromatics yield of 21.8% on carbon basis at 500 °C. However, HZSM-5 can act as cracking and aromatization catalyst, but not as an agent to promote hydrogenation. The ESI-MS revealed the most abundant macromolecular compounds in initial volatiles were O₁O₂₇ species with 0–20 double bond equivalent (DBE) values and 5–40 carbon numbers, while the macromolecules were O₁O₉ species with 2–12 DBE and 10–25 carbon numbers after upgrading. Furthermore, the formation of coke on catalysts was influenced by the properties of HZSM-5 and experimental conditions.     

Production of aromatic compounds from catalytic fast pyrolysis of Jatropha residues using metal/HZSM-5 prepared by ion-exchange and impregnation methods

Metal based-zeolite catalysts were successfully prepared by two different methods including ion-exchange and wet impregnation. HZSM-5 synthesized by hydrothermal method at 160 °C was used as a support for loading metals including Co, Ni, Mo, Ga and Pd. The metal/HZSM-5 had surface area and pore size of 530–677 m²/g and 22.9-26.0 Å. Non- and catalytic fast pyrolysis of Jatropha residues using metal/HZSM-5 were studied using an analytical pyrolysis-GC/MS at 500 °C. Non-catalytic pyrolysis vapors contained primarily high levels acid (50.7%), N-containing compounds (20.3%), other oxygenated compounds including ketones, alcohols, esters, ethers, phenols and sugars (25.0%), while generated small amount of aromatic and aliphatic hydrocarbons of 3.0% and 1.0%. The addition of synthesized metal/HZSM-5 improved the aromatic selectivity up to 91–97% and decreased the undesirable oxygenated (0.6–4.0%) and N-containing compounds (1.8–4.6%). The aromatic selectivity produced by metal-ion exchanged catalysts was slightly higher than that produced by impregnated ones. At high catalyst content (biomass to catalyst ratio of 1:10), Mo/HZSM-5 showed the highest aromatic selectivity of 97% for ion-exchanged catalysts and Ga/HZSM-5 revealed the highest aromatics of 95% for impregnated catalysts. The formation of aromatic compounds could be beneficial to improve calorific values of bio-oils. The presence of metal/HZSM-5 from both preparation methods greatly enhanced MAHs selectivity including benzene, toluene, and xylene (BTX), while substantially reduced unfavorable PAHs such as napthalenes.     

Py-GC/MS技术用于Chaetoceros sp. 硅藻的催化热解研究

采用热裂解−气质联用（Py-GC/MS）技术研究Chaetoceros sp. 硅藻粉末的催化热解特性。以HZSM-5为催化剂,考察了不同Si/Al比的HZSM-5催化剂对硅藻热解产物的影响,并考察了催化剂的使用量、热解升温速率、热解反应时间对产物的影响。结果表明：未加催化剂时,硅藻热解产物以脂肪酸为主,含量为50.05%,苯系物含量仅为0.87%;加入HZSM-5催化剂后,硅藻热解产物中脂肪酸含量减少,芳香类化合物显著增加。热解实验结果发现,Si/Al比为38、硅藻和HZSM-5比例为1∶9、热解速率10 000℃/s、热解时间为10 s时,能得到较理想的热解产品,其中苯系物产率可达57.76%,脂肪酸含量为2.63%。这说明HZSM-5（38）具有较好的脱氧和芳构化功能,有利于硅藻催化热解生成高品质的生物油产品。     

Catalytic upgrading pyrolysis vapors of Jatropha waste using metal promoted ZSM-5 catalysts: An analytical PY-GC/MS

HZSM-5 with high surface area of 625 m²/g was successfully synthesized by hydrothermal method at 160 °C for 72 h. The metal promoted on HZSM-5 catalyst was prepared by liquid ion exchange method. From XRD results, the addition of metals such as Co and Ni did not change the HZSM-5 structure. The metal/HZSM-5 showed lower crystallinity and surface area than the parent HZSM-5 because of the metal dispersion on the HZSM-5 surface. The metal contents of Co/HZSM-5 and Ni/HZSM-5 detected by EDX were less than 1 wt%. Catalytic fast pyrolysis of Jatropha waste using HZSM-5 and metals/HZSM-5 was investigated in terms of biomass to catalyst ratios (1:0, 1:1, 1:5 and 1:10) and types of metals (Co and Ni). From the results, it can be concluded that both biomass to catalyst ratios and the presence of metals had an effect on the increase in aromatic hydrocarbons yields as well as the decrease in the oxygenated and N-containing compounds. Both Co/HZSM-5 and Ni/HZSM-5 promoted the production of aliphatic compounds. Additionally, the PAHs compounds such as napthalenes and indenes, which caused the formation of coke, could be inhibited by metal/HZSM-5, particularly, Ni/HZSM-5. Among catalysts, Ni/HZSM-5 showed the highest hydrocarbon yield of 97.55% with N-containing compounds remained only 1.78%. The formation of hydrocarbon compounds increased the heating values of bio-oils while the elimination of the undesirable oxygenated compounds such as acids and ketones could alleviate problem regarding acidity and instability in bio oils.     

Catalytic copyrolysis of metal impregnated biomass and plastic with Ni-based HZSM-5 catalyst: Synergistic effects,kinetics and product distribution

The present work aims to investigate the thermal behavior, kinetics, thermodynamics, and product distribution during copyrolysis of transition metal salt (Ni, Co, Zn, Cu, and Fe)-added biomass and model compounds with low density polyethylene(LDPE) over a Ni-based HZSM-5 catalyst by TGA and fixed bed reactor. The interactions and reaction mechanisms during copyrolysis were evaluated. The influence of Ni-impregnated biomass (C-M) and Ni-modified HZSM-5 (Ni/HZ) on the formation of pyrolysis bio-oil from biomass and model compounds and its subsequent effect on catalytic pyrolysis vapor upgrading was discussed. The results indicated that the presence of transition metal decreased the thermal degradation temperature and thermodynamics parameters; maximum decomposition rate, and reaction complexity. Ni/HZ catalyst could further decrease the activation energy, accelerate the reaction rate and change reaction process, and the modified samples/LDPE under copyrolysis with HZSM-5 catalyst presented a more significant effect than Ni/HZ catalyst. Subsequently, the Ea of pine, cellulose and lignin changed from 24.11, 18.29, and 28.68 kJ/mol (CP@Ni/HZ) to 56.04, 69.84, and 16.21 kJ/mol (CP-Ni@HZSM-5), respectively. In addition, Ni could inhibit the depolymerization of cellulose and promoted the formation of char, coke, and lignin derived phenolics. And Ni-impregnated biomass reduced the formation of desired aromatic hydrocarbons, but result in increasing of the char and non-condensable gases. But Ni/HZ catalysts promote the conversion of biomass to target products.     

Enhancing the aromatic hydrocarbon yield from the catalytic copyrolysis of xylan and LDPE with a dual-catalytic-stage combined CaO/HZSM-5 catalyst

The high concentration of oxygenated compounds in pyrolytic products prohibits the conversion of hemicellulose to important biofuels and chemicals via fast pyrolysis. Herein CaO and HZSM-5 was developed to convert xylan and LDPE to valuable hydrocarbons by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and elucidate the reaction mechanism were also investigated in detail. The results indicated that xylan/LDPE copyrolysis was more complicated than pyrolysis of the individual components. LDPE hindered the thermal decomposition and aromatic hydrocarbon formation from xylan at temperatures under 350 °C and had a synergistic effect at high temperatures. 50% LDPE was proven to be more beneficial than other percentages for the formation of monocyclic aromatic hydrocarbons. Simultaneously, the addition of CaO/HZSM-5 significantly reduced the reaction Ea and increased the reaction rate. CaO can effectively improve the deoxygenation and aromatization reaction, enhancing the yield and selectivity of aromatics to a certain extent. The maximum yield of hydrocarbons (96.01%), mono-aromatic hydrocarbons (88.53%) and S_BTXE (85.79%) were obtained at a CaO/HZSM-5 ratio of 1:2, a pyrolysis temperature of 450 °C, a catalytic temperature of 550 °C, a catalyst dose of 1:2 and a xylan-to-LDPE ratio of 1:1 via an ex situ process. The system was dominated by toluene, xylene and alkyl benzene. Diels-Alder reactions of furans and hydrocarbon pool mechanism of nonfuranic compounds improved aromatic formation. This study provides a fundamental for recovering energy and chemicals from pyrolysis of hemicellulose.     

Effect of zeolite structure on light aromatics formation during upgrading of cellulose fast pyrolysis vapor

Promising technology for the conversion of cellulose to aromatics by catalytic fast pyrolysis (CFP) was investigated using five zeolite catalysts, i.e., 5A, SAPO-34, HY, BETA and HZSM-5. The relationship between the porosity and acidity of different zeolites with product selectivity was studied. The results showed that both the acidity and pore size of the zeolite significantly affected the production of aromatics and coke, especially the bio-oil composition. The bio-oils obtained over 5A or SAPO-34 (small pore<5.5 nm) have relatively high oxygen content. The BTEXN (benzene, toluene, ethylbenzene, xylenes and naphthalene) carbon yields over weak acidic zeolites of HY and BETA are only 6.5% and 9.0%, respectively. Due to the appropriate pore size distribution and acid position, HZSM-5 gave the highest BTEXN carbon yield of 21.1%. Moreover, the coke deposited on the spent zeolites was analyzed by temperature programmed oxidation. Furthermore, three possible mechanisms that the acid sites catalyze vapor towards non-condensable gases, aromatics and coke were also studied. HZSM-5 achieved satisfactory deoxygenation and aromatic production simultaneously, made it a potential catalyst for producing light aromatics from reforming the biomass pyrolytic vapors.     

Fe/HZSM-5 synergizes with biomass pyrolysis carbon to reform CH4–CO2 to syngas in microwave field

CO₂ reforming of CH₄ to syngas, an important chemical raw material, has received widespread attention. However, the use of noble metal catalysts and high energy consumption limit their application. In this study, microwave-assisted dry reforming over mixtures of Fe/HZSM-5 and biomass pyrolysis carbon (BPC) was studied. Additionally, the influence of different reaction conditions and catalysts on the reforming efficiency was examined. Our results demonstrated that microwave heating improved the dry reforming process while reducing the cost of catalysts used. At a microwave power of 700 W, and the space velocity of 2.4 L/(h?g), CO₂ and CH₄ conversion reached 91.27% and 63.03%, respectively. In addition, Fe/HZSM-5 showed synergistic effects with BPC, and the migration of active metals was responsible for the synergistic effects. The microwave reforming effect was better than that of conventional heating reforming, and the unique effects of microwave fields facilitated the conversion process. This study makes a useful contribution to the improvement of new dry reforming methods.     

Microwave-assisted catalytic pyrolysis of cellulose for phenol-rich bio-oil production

The microwave-assisted catalytic pyrolysis (MACP) of cellulose was carried out using modified HZSM-5 catalysts for bio-oil production. The catalysts of Fe/HZSM-5, Ni/HZSM-5 and Fe–Ni/HZSM-5 were developed and characterized by the X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The bio-oil was characterized by the Fourier transform infrared analyzer (FTIR) and gas chromatography/mass spectrometry (GC/MS). Results showed that Fe/HZSM-5 enhanced the yields of bio-oil by 11.4% and decreased the coke by about 24% compared to HZSM-5 without modification. The saccharides in bio-oil disappeared and were totally converted into phenols and low molecular compounds with the catalysis of Fe–Ni/HZSM-5. Fe–Ni/HZSM-5 showed high selectivity of phenols (20.86%) in the bio-oil. It was a unique finding because usually phenols can only be obtained by the pyrolysis of lignin, not cellulose. The formation of phenols from MACP of cellulose was probably caused by the conversion of furans to aromatics in the pores of HZSM-5, and followed by further conversion of aromatics into phenols on the external surface of HZSM-5.     

Catalytic Oligomerization of ethylene over nano-sized HZSM-5

The nano-sized HZSM-5 zeolites with different Si/Al ratios were pretreated, characterized, and tested in ethylene oligomerization performed in a fixed-bed reactor under relatively mild conditions. The effects of catalyst acidity and reaction temperature on the activity, selectivity and stability were investigated, and a possible reaction route of ethylene over acidic sites of nano-sized HZSM-5 catalyst was proposed. In comparison with micro-sized HZSM-5 zeolite, nano-sized HZSM-5 zeolites exhibited higher activity and better resistance to deactivation. Under optimal conditions (T = 275–300 °C, P = 3.0 MPa, WHSV = 1.0 h⁻¹), The average ethylene conversion was 62.5% over the nano-sized HZSM-5 with an Si/Al ratio of 80, while the selectivity to C₄₊ olefins and α-olefins was 64.3% and 13.3%, respectively. Furthermore, the products of ethylene oligomerization were a complex hydrocarbon mixture due to the acid-catalyzed secondary reactions, for which the distribution of even and odd numbered carbon atoms formed a continuous volcanic shape mainly centered on C₆–C₁₀. Furthermore, these tests demonstrate that the activity and selectivity of ethylene oligomerization depend on the operating conditions and the acidity of the catalysts. These results indicate that the Brønsted acid sites may be mainly responsible for secondary reactions and deactivation of the catalyst, whereas the Lewis acid sites may be more advantageous for ethylene oligomerization.     

Hydrodeoxygenation of lignin model compounds to alkanes over Pd–Ni/HZSM-5 catalysts

In this work, a bimetallic catalyst of Pd and Ni supported on HZSM-5 was designed and evaluated in the hydrodeoxygenation of model compounds representing various C–O bonds in lignin. The effects of temperature, holding time, and initial H₂ pressure on the catalytic performance of the Pd–Ni/HZSM-5 catalyst were investigated. The results indicated that the Pd–Ni/HZSM-5 catalyst exhibited superior catalytic activity towards the conversion of the model compounds to alkanes compared to its monometallic counterparts. Direct cleavage of the C–O bond in DPE was achieved under low H₂ pressure, mainly producing benzene and minor amounts of phenol and cyclohexane, while at high H₂ pressure, the reaction pathway was altered towards hydrogenation of the benzene ring, followed by then cleavage of the C–O bond to afford only cyclohexane. Moreover, the Pd–Ni/HZSM-5 catalyst showed high activities when applying other substrates including anisole, veratrole, guaiacol, benzyloxybenzene, phenethyl phenyl ether, and dibenzyl ether.     

One-pot production of γ-valerolactone from furfural using Zr-graphitic carbon nitride/H-β composite

In order to efficiently produce γ-valerolactone (GVL) from furfural, a Zr-graphitic carbon nitride/H-β composite (ZrCN/H-β) had been simply prepared via an impregnation-calcination protocol. The morphology and structure, elemental information, and total acid and base properties of the ZrCN/H-β and related catalysts (H-β, CN/H-β, and Zr/H-β) were determined by SEM, TEM, X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD-NH₃, CO₂) characterizations. The effects of reaction temperature and time, and the furfural dosage on GVL production as well as the recyclability of ZrCN/H-β were investigated. With a catalyst/furfural dosage of 0.1/0.22 g, the ZrCN/H-β produced a remarkable 76.5% of GVL yield at 160 °C in 18 h using isopropanol as the solvent. The results of NH₃, CO₂-TPD experiments indicated that the simultaneous introduction of Zr species and carbon nitride onto H-β formed new types of acid and base, which should be responsible for the high efficient conversion of furfural to GVL. Additionally, the recyclability of ZrCN/H-β was reasonable.     

Optimizing Ni–Ce/HZSM-5 catalysts for ex-situ conversion of pine wood pyrolytic vapours into light aromatics and phenolic compounds

The main objective of the present work is to investigate the influence of nickel to cerium ratio on hydrogen exchanged Zeolite Socony Mobil-5 (HZSM-5) towards the catalytic upgrading of pine derived oxygenated pyrolysis vapours into aromatic hydrocarbon and phenol in pyrolysis oil via ex-situ fixed bed reactor. The presence of CeO₂ could change electron density of Ni, promote the reduction of Ni species, accelerate the transfer of carbon species, and suppress the production of carbon deposits (17.53%–25.11%) compared with the parent HZSM-5 catalyst (28.95%); it also improved the hydrodeoxygenation ability of all xNiyCe/HZSM-5(nickel and cerium bimetal modified HZSM-5) catalysts, resulting increases in noncondensable gas content (from 31.46% to 52.99%–65.53%). Ni to Ce ratio of 1:1 and 1:2 produced highest aromatic hydrocarbon (32.14%) and phenols (55.51%) relative peak areas. The acid center of HZSM-5 and the metal acid center of the Ni:Ce = 1:1 catalyst obviously fine-tuned the formation of coke; and promoted hydrocarbon production. Moreover, high Ni content promoted alkylation of benzene at C6–C9 and increased C10⁺ PAHs relative peak area; high Ce content promoted the formation of olefin and Increasing the cleavage of C–O bonds and promoted hydrogenation or dehydrogenation, reduced polycyclic aromatic hydrocarbons and coke yield, and increased phenols and alkylphenols selectivity.     

Catalytic fast pyrolysis of waste pepper stems over HZSM-5

Catalytic fast pyrolysis over HZSM-5 of red pepper stems, a representative agricultural residue material in the southern area of South Korea, was carried out. The SiO₂/Al₂O₃ ratio of the catalyst were 23 and 280. Pyrolysis-gas chromatography/mass spectrometry was used to pyrolyze the pepper stem samples at 550 °C and directly analyze the product distribution. The main product species of the non-catalytic pyrolysis of pepper stems were phenolics, followed by oxygenates and acids. The production of aliphatic and aromatic hydrocarbons was marginal. On the contrary, catalytic pyrolysis over HZSM-5 reduced the fractions of phenolics and acids significantly, while considerably increasing the fractions of aliphatic and aromatic hydrocarbons. The catalytic activity of the HZSM-5 with a SiO₂/Al₂O₃ ratio of 23 was much higher, owing to its much larger amount of strong Brønsted acid sites, than the one with a SiO₂/Al₂O₃ ratio of 280. Conversion of carbohydrate via furans to aromatics over strong acid sites was observed, which was in good agreement with previous studies. This study suggests that the catalytic pyrolysis of lignin-rich biomass over acidic zeolite catalysts can be a promising method to produce valuable chemicals such as aromatic compounds.     

Fast and catalytic pyrolysis of xylan: Effects of temperature and M/HZSM-5 (M= Fe,Zn) catalysts on pyrolytic products

Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to achieve fast pyrolysis of xylan and on-line analysis of pyrolysis vapors. Tests were conducted to investigate the effects of temperature on pyrolytic products, and to reveal the effect of HZSM-5 and M/HZSM-5 (M= Fe, Zn) zeolites on pyrolysis vapors. The results showed that the total yield of pyrolytic products first increased and then decreased with the increase of temperature from 350°C to 900°C. The pyrolytic products were complex, and the most abundant products included hydroxyacetaldehyde, acetic acid, 1-hydroxy-2-propanone, 1-hydroxy-2-butanone and furfural. Catalytic cracking of pyrolysis vapors with HZSM-5 and M/HZSM-5 (M= Fe, Zn) catalysts significantly altered the product distribution. Oxygen-containing compounds were reduced considerably, and meanwhile, a lot of hydrocarbons, mainly toluene and xylenes, were formed. M/HZSM-5 catalysts were more effective than HZSM-5 in reducing the oxygen-containing compounds, and therefore, they helped to produce higher contents of hydrocarbons than HZSM-5.