Catalytic Fast Pyrolysis Research Articles

Enhanced production of hydrocarbons from the catalytic pyrolysis of maize straw over hierarchical ZSM-11 zeolites

The ZSM-11 zeolite has been revealed as an undervalued catalyst for the catalytic fast pyrolysis (CFP) of biomass to produce hydrocarbon-rich bio-oil. However, the importance of hierarchical ZSM-11 in bio-oil production is still unknown. Herein, a series of ZSM-11 with varied morphologies, acidities, and secondary mesopores were synthesized and tested as catalysts in the CFP of maize straw. For the morphology series, ZSM-11 with separate nanorods (Nano-ZSM-11) or aggregated nanosized single-crystal (NS-ZSM-11) performed better in bio-oil production than microsized Micro-ZSM-11. Regarding the NS-ZSM-11 series, optimal acidity facilitated the deoxygenation of biomass vapor, while introduced intracrystal mesopores tended to improve bio-oil yield. NS-ZSM-11(20)-0.3 possessing both adequate acidity and coupling inter/intracrystal mesopores led to a satisfactory bio-oil yield (23.6 wt%) and hydrocarbon selectivity (63.6 area%), which were 1.1 and 1.3 times those for Nano-ZSM-11 (bio-oil yield: 22.0 wt%; hydrocarbon selectivity: 47.8 area%), respectively. NS-ZSM-11(20)-0.3 also showed excellent reusability in regeneration-pyrolysis cycles.

Processing of Leucaena Leucocepphala for renewable energy with catalytic fast pyrolysis

This research aimed processing of Leucaena Leucocepphala in a fluidized-bed reactor with catalysts for renewable energy. The reaction was tested over different type of catalysts such as natural zeolite, kaolin and dolomite. These catalysts were loaded under the heating zone with a supplementary hot filter. The rate of feedstock added in the reactor was 1 kg/h and the pyrolysis temperature was 500 °C. Product yields was calculated after each experiment was completed.The results demonstrated an optimum bio-oil yield of 65.1 wt% after undergoing fast pyrolysis. A reduction in bio-oil yield was observed when natural zeolite, kaolin and dolomite was employed during fast pyrolysis. The minimum bio-oil yield recorded for the dolomite catalyst was 54.5 wt%. On the other hand, kaolin catalyst produces a maximum bio-oil yield of 59.6 wt%. The organic content of bio-oil from kaolin catalyst increased significantly compared with other catalysts. Addition of an ESP condenser, instead of water-cooled condenser resulted in bio-oil with the highest heating value (HHV). Higher heating value of bio-oil derived from natural zeolite catalyst maximized at 35.8 MJ/kg and 37.3 MJ/kg, respectively. The range of hydrocarbon component of bio-oil was C15–C44 for ESP condenser and C12–C35 for water-cooled condenser. The availability of bio-oil was optimized when natural zeolite catalyst added into the process. On the other hand, density and viscosity of bio-oil was increased when dolomite catalyst was used. Additionally, the presence of dolomite catalyst reduced acidic compounds such as 2-Octenoic acid (C8H14O2) and Methyl propiolate (C4H4O2) in the bio-oil. Bio-oil yield was found to be significantly improved by the large pore diameter and small surface area of the catalyst. Among the three catalysts in was observed that kaolin catalyst gave the highest bio-oil yield. Natural zeolite catalyst was found to improved bio-oil product’s thermal quality. However, bio-oil with better viscosity and lower acidity was produced from the dolomite catalyst.

Products distribution during in situ and ex situ catalytic fast pyrolysis of Chinese herb residues.

Catalytic fast pyrolysis (CFP) for biomass treatment is a research hotspot but there is little information about the difference between the in situ and ex situ methods. In present work, the Ni-Fe/CaO-Al2O3 catalysts with different Ni/Fe ratios have been synthesized by coprecipitation method, and the product distribution about the Chinese herb residue (CHR) catalytic fast pyrolysis by in situ and ex situ methods in a quartz tube reactor system has been investigated. The results show that the CFP pyrolysis would upgrade the quality of bio-oil but decrease the yields, no matter in situ or ex situ CFP process. During the in situ CFP process, heteroatoms may be absorbed by the catalyst support and cannot be transferred to the bio-oil, but the results of ex situ CFP are the opposite. In addition, the ex situ CFP reaction significantly increases the content of aromatic hydrocarbons. As to the gas products' distribution, the effect of Fe in catalysts to promote CH4 formation is reflected in in situ CFP process, while the promotion effect of H2 generation for Ni added in catalyst is mainly reflected in ex situ CFP process. However, due to the high reaction temperature (800°C), the adsorption of CO2 by CaO support is not particularly significant. The possible mechanism of CHR in CFP process has also been summarized for understanding the process of in situ and ex situ CFP, and this study may provide a choice or reference for CHR treatment.

Biofuels from biomass toward a net-zero carbon and sustainable world

Biofuels have attracted increasing attention due to their renewable sources. Two reports, one in <i>Chem Catalysis</i> by Schaidle and one in <i>Metabolic Engineering</i> by Pfleger, demonstrate that biofuels from lignocellulosic biomass can be produced by a multi-scale method for biocrude upgrading in catalytic fast pyrolysis and engineered microbes.

Selective catalytic conversion of Kraft lignin into monoaromatic hydrocarbons over niobium oxide catalysts

Catalytic fast pyrolysis (CFP) of lignin targeting for benzene, toluene and xylenes is attractive considering lignin's chemical structures. Zeolites have been widely used for producing aromatic hydrocarbon via a well-known hydrocarbon pool mechanism from lignocellulose pyrolysis vapors because of their unique shape-selective catalytic abilities, however, the large amount of phenols existing in the product reveals the catalyst's deficiency in direct deoxygenating of phenols. Finding a catalyst with a strong deoxidization ability against various lignin pyrolysis intermediates is necessary. Here, two niobium oxide-based catalysts, niobium oxophosphate (m-NbOP) and niobium oxide (m-NbO) with uniform mesoporous structures (pore sizes of 2-5 nm), large external areas (487 m2·g−1 for m-NbOP and 244 m2·g−1 for m-NbO), and strong acidities (1.25 mmol·g−1for m-NbOP and 0.69 mmol·g−1 for m-NbO) were synthesized and used without need for hydrogen in lignin CFP at 650 °C. Compared to zeolites, both niobium oxide-based catalysts considerably increased aromatic's contents and the selectivity to benzene, toluene, and xylenes but decreased the contents of phenols to some extent, indicating the improved abilities in direct deoxygenation by aromatic CO bond cleavage of lignin. A total carbon yield of benzene, toluene and xylenes of 39.2% was achieved over m-NbOP.

Accelerating catalyst development for biofuel production through multiscale catalytic fast pyrolysis of biomass over Mo2C

Advanced catalytic materials play an enabling role in producing renewable fuels and chemicals from biomass, thereby helping meet the global climate-change goals set forth by the Intergovernmental Panel on Climate Change. Herein, we present a multiscale approach to accelerate the catalyst-process development cycle for catalytic fast pyrolysis (CFP) of biomass over Mo 2 C. Mo 2 C has been shown to possess co-localized acidic and metallic sites and exhibit high activity for deoxygenation of biomass pyrolysis model compounds. However, critical knowledge gaps remain regarding the effectiveness of this catalyst for CFP of whole biomass. We address these knowledge gaps and demonstrate that Mo 2 C is effective at deoxygenating biomass-pyrolysis products in the presence of H 2 but that it undergoes rapid selective and non-selective deactivation. The knowledge gaps addressed from this integrated study, targeting appropriate experiments across scales and feed types, enabled identification of critical modifications for advancing the CFP catalyst-process development cycle. • A multiscale evaluation of Mo 2 C for biomass catalytic fast pyrolysis is performed • Mo 2 C exhibits both selective and non-selective deactivation with whole biomass • Process and catalyst modifications are proposed for reducing deactivation • Model compound studies are essential but insufficient at predicting performance Catalytic fast pyrolysis (CFP) of biomass is an attractive process for producing bio-oils that can be further refined into fuels and chemicals, thus helping to reduce greenhouse-gas emissions. To meet the emissions reduction goals set forth by the Intergovernmental Panel on Climate Change, catalysts and processes for generating renewable products need to be rapidly designed and developed, calling for an accelerated catalyst-process development timeline. However, in the case of CFP, biomass pyrolysis produces a complex stream involving hundreds of molecules with multifunctional groups, steam, and metal impurities, which makes catalyst design challenging. This integrated study on biomass CFP over a promising multifunctional catalyst, Mo 2 C, addresses knowledge gaps critical to accelerating development of this catalyst and process. The intended outcome is to share lessons learned toward accelerating catalyst-process development cycles for systems with similar complex reaction chemistries. Accelerating the catalyst-process development cycle for complex chemistries, especially biomass processing, requires multiscale studies spanning model compound experiments to integrated, bench-scale tests with realistic feedstocks.

Co-processing catalytic fast pyrolysis oil in an FCC reactor

Studies of co-processing catalytic fast pyrolysis (CFP) oil with vacuum gas oil (VGO) are conducted in a Davison Circulating Riser (DCR). The CFP oil (CFPO) for this study was produced by upgrading fast-pyrolysis vapors from pine in an ex-situ fixed-bed reactor. CFPOs were co-processed at up to a volume fraction of 0.05 with VGO at 521 °C and 257 kPa. The yields of oil, aqueous phase, tail gas, and coke were measured. The amount of coke was determined from the carbon containing components in the regenerator flue gas. A compositional analysis was conducted with gas chromatography and elemental analyzers. The organic liquids were distilled into gasoline, jet-fuel, diesel, and resid fractions. A biocarbon analysis was conducted on the organic phase and its individual boiling-point fractions. The results show a small decrease in liquid yield and a generally increased gas yield when co-processing CFPO with VGO. The experiments showed that 75%–100% of biocarbon is incorporated into liquid fuels relative to fossil carbon, depending on catalyst and CFPO. The measurements indicate that cracked CFPO components are predominantly included in the jet-fuel and diesel fractions. A techno-economic analysis (TEA) estimated the minimum fuel selling price (MSFP) for fuel-range products derived from FCC co-processing of CFPO at 24 to 29 $/GJ ($2.90 to $3.50 per gasoline-gallon equivalent; GGE) at a yield of 4.87–7.14 GJ/t(biomass) or 40–58 GGE/t.

Catalytic fast pyrolysis of steam-exploded biomass for long-chain ethers precursors

A novel valorization pathway for steam-exploded corn stalk conversion to long-chain ethers was proposed in the work. The procedure enabled the transformation of multifunctional components in catalytic fast pyrolysis (CFP) vapors using Fe-Ce mixed oxides into carbonyl compounds (ketones, aldehydes and furans with carbonyl group) suitable for preparing long-chain oxygenated fuels in a fluidized-bed/fixed-bed consolidation reactor. A series of Fe-Ce bimetallic oxides were explored and the results indicated that the catalyst with 0.3 of molar ratio of Fe to Ce (Fe/Ce(0.3)) showed highly active in converting levoglucosan and acetic acid into linear and cyclic ketones. Moreover, the conversion rate of acetic acid and levoglucosan in pyrolytic vapors was close to 100% and 90.07%, respectively. The carbon yield of carbonyl compounds (28.91%) in ex-situ CFP was achieved under optimal conditions. The continuous operation showed that Fe/Ce(0.3) remained highly active and there was little coke and carboxylates on the catalyst surface after 200 min.

Enhancing production of hydrocarbon-rich bio-oil from biomass via catalytic fast pyrolysis coupled with advanced oxidation process pretreatment

This study aims to propose a method for upgrading biomass pyrolysis products based on the combination of sodium persulfate pretreatment and fast catalytic pyrolysis. Combined with the analysis of components and thermogravimetric analysis, the result showed that after pretreatment the biomass structure was gradually depolymerized, the contents of lignin, the reaction of activation energy and the crystallinity of cellulose decreased. Due to the destructive effect of persulfate radicals, in fast pyrolysis, the relative contents of acids and oxygen-containing substances decreased, and the relative content of phenols can significantly increase to 19.20%. The yield of aromatic hydrocarbons and total hydrocarbons had a high value under the catalytic pyrolysis in the best performance which amount of yield reached 28.66% and 33.72%, respectively. Sodium persulfate pretreatment was beneficial in the production of hydrocarbon-rich bio-oils and high-value chemicals since the radicals can effectively depolymerize lignin which promoted the process of pyrolysis.

Feedstock and catalyst impact on bio-oil production and FCC Co-processing to fuels

NREL's thermochemical biomass conversion research is focused on ex-situ upgrading of biomass fast-pyrolysis (FP) vapors as an efficient route to completely biogenic pyrolysis-based fuel precursors, fuels, and value-added chemicals depending on catalyst and process conditions. A near term pathway being developed uses these liquids for co-processing with petroleum feedstocks to assess biogenic carbon incorporation in hydrocarbon fuel feedstocks for potential refinery use. In this work, the impact of feedstock and catalyst on catalytic fast pyrolysis oil (CFPO) composition was determined with the oils then assessed for biogenic fuel production via FCC (fluidized catalytic cracking) co-processing. Biomass vapors were generated via fast pyrolysis with destabilizing vapor components (char, inorganics, tar aerosols) removed by hot gas filtration to produce clean vapors more responsive to catalytic upgrading. A Davison Circulating Riser (DCR), a petroleum industry standard for fluidized catalytic cracking (FCC) catalyst evaluation, was coupled to a custom pyrolyzer system designed to produce consistent-composition pyrolysis vapors as feed to the DCR. Pyrolysis vapors, derived from pure hardwood and softwood, were upgraded using commercially available modified zeolite-based catalysts to produce CFPOs. These upgraded oils were analyzed via 31P and 13C NMR spectroscopy, GCxGC-TOF/MS, carbonyl and ultimate analysis (CHNO), and simulated distillation (SIMDIS) to assess both oil chemistry and distillation behavior as they relate to catalyst and feedstock type for producing fungible hydrocarbon product liquids. These exploratory vapor-phase-upgrading results demonstrated the feasibility of producing refinery-compatible hydrocarbon fuel intermediates entirely from biomass-derived fast-pyrolysis vapors using an industry-accepted DCR system for catalytic upgrading. The FCC co-processing results demonstrated the feasibility of using CFPOs with VGO feeds in FCC refinery operations to produce biogenic carbon containing fuels.

Insight into the synergistic reaction mechanism of biomass pseudo components and low-density polyethylene for the production of light aromatics through co-catalytic fast pyrolysis over hierarchical HZSM-5

Co-feeding of waste plastics during biomass catalytic fast pyrolysis can improve remarkably the yield of aromatic hydrocarbons. In this work, the simulated biomass by using its model components of cellulose, xylan, and lignin at different proportions was Co-CFP with LDPE to investigate the synergistic reaction mechanism between biomass and low-density polyethylene (LDPE) over hierarchical HZSM-5. Results showed that biomass and its model components were oxygen-enriched feedstock, while LDPE was the hydrogen-enriched feedstock with H/Ceff over 2. The synergistic effect between biomass model components and LDPE was ordered as cellulose and LDPE > xylan and LDPE > lignin and LDPE. Because pyrolysis of cellulose produced higher yield of furans than that of xylan and lignin which acted as the key synergistic compounds in Diels-Alder reaction to form light aromatics. The transfer of hydrogen free radical from the LDPE-derived hydrocarbons to the biomass-derived oxygenates promoted the deoxygenation reaction of oxygenates in hierarchical HZSM-5. Diels-Alder reaction between furans and olefins was the key synergistic reaction which highly improved the yield of hydrocarbon aromatics. In general, the difference of the pyrolysis oxygenated intermediate among the biomass pseudo components resulted in different yields of light aromatics, where cellulose presented highest extent of synergistic reaction to LDPE.

In-depth study of synergism between torrefaction and catalyst for balanced production of bio-oil from rice husk pyrolysis based on hydrocarbons production, energy yield and deoxygenation degree

Previous studies concerning biomass to bio-oil mainly focused on hydrocarbons production, and how to balance the bio-oil production in terms of hydrocarbons production, energy yield and deoxygenation degree is a challenging issue. After the pretreatment of torrefaction, catalytic fast pyrolysis (CFP) was performed at two-zone fixed-bed reactor. The synergism between torrefaction and catalyst during torrefaction-catalytic fast pyrolysis (T-CFP) was investigated for the balanced production of bio-oil from rice husk. Firstly, the results of two catalysts（ZrO2/n-ZSM-5 and ZrO2/n-ZSM-5/attapulgite) indicated that the catalyst with the incorporation of attapulgite (ATP) could realize the balance between the acid and basic sites, which resulted in deeper deoxygenation. Then, the results of torrefaction-catalytic pyrolysis showed that, among three torrefaction temperatures adopted, mild torrefaction (210 °C) had better synergistic effects with both catalysts. Specifically, catalytic pyrolysis of biomass after mild torrefaction over both catalysts realized the enhancement of deoxygenation degree and energy yield. Moreover, with the pretreatment of mild torrefaction, the performance of ZrO2/n-ZSM-5/ATP turned out to be obviously superior to ZrO2/n-ZSM-5 in terms of hydrocarbons production (7.5%＞0.8%) and deoxygenation mode. Therefore, the combination of ZrO2/n-ZSM-5/ATP and mild torrefaction could achieve more balanced production of bio-oil from T-CFP process.

9,10-dihyroanthrancene assisted catalytic pyrolysis of bagasse over N-doped activated carbon to enhance 4-ethyl phenol production

The N-doped activated carbon (NAC) was prepared for bagasse (BAG) pyrolysis with 9,10-dihydroanthracene (DHA) to selectively improve production of individual 4-ethyl phenol (4-EP). Both pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and lab-scale apparatus were employed to conduct catalytic fast pyrolysis (CFP) experiments. The effects of N-doping modification, pyrolysis temperature, DHA/BAG ratio and NAC/BAG ratio on yield and selectivity of 4-EP were comprehensively investigated. Results indicated that the NAC exhibited excellent catalytic abilities in improving 4-EP production. About 3.03 wt % of 4-EP was obtained over NAC in the absence of DHA, whereas the 4-EP yield over activated carbon was only 2.46 wt %, indicating an increment of 23.17 % via N-doping modification. The 4-EP yield reached the maximum of 4.75 wt % with a selectivity of 25.12 % at temperature of 350 °C with a DHA/BAG ratio of 7:20 and NAC/BAG ratio of 3:1, indicating 88.45 % of 4-VP (5.37 wt %) was converted into 4-EP. Result of lab-scale tests showed that 4-EP production attained the highest value (4.02 wt %) with a selectivity of 25.53 % at temperature of 350 °C with DHA/BAG and NAC/BAG ratios of 1:5 and 1.5:1, respectively. Finally, the possible mechanism on 4-EP formation from BAG pyrolysis with co-assist of NAC and DHA was inferred.

Bio-fuel production from catalytic fast pyrolysis of Jatropha wastes using pyroprobe GC/MS and drop tube pyrolyzer

The effects of temperature and catalytic activity on the decomposition of Jatropha waste to bio-oil under rapid pyrolysis were investigated in this study. The pyrolytic conversion of Jatropha wastes was performed at the temperature range of 400–700 °C. The reactions were conducted and compared between two operations, an analytical pyroprobe GC/MS (µg-scale reactor) and a larger scale, drop tube pyrolyzer. Added catalysts were modified metal (Ce, Co, Ni, and Pd) over activated carbon (Ac) support. In non-catalytic trials, Jatropha wastes pyrolyzed at 600 °C yielded vapor products of mainly oxygenated compounds of acid-ester, aldehyde, and ketone. Addition of Ni/Ac and Pd/Ac catalysts resulted in significantly higher aromatic and total hydrocarbon (aliphatic and cyclic) fractions. The findings suggested that these catalysts are suitable for further investigation with a scaled-up fast pyrolysis sequential process, a drop tube reactor, to convert Jatropha waste into bio‐oil as well as various gaseous and solid byproducts depending on the operating conditions. In this case, the maximum liquid products (bio-oil) yield of 40 wt% was obtained at the reaction temperature of 600 °C and particle size of 0.125–0.425 mm with the presence of Ac. Reaction at 600 °C with Pd/Ac catalyst yielded bio-oil with the highest HHV of 29.20 MJ/kg with a pH of 6.78. Analysis of bio-oil by GC/MS revealed the main favorable products as phenols, aromatics, and hydrocarbons which increased almost two folds from base case with Ni/Ac and Pd/Ac addition. Since low oxygenated compounds, high aromatics, and hydrocarbon compounds of bio-oil are desirable, the results indicate that the bio-oil at the optimized condition can be readily applied as biofuel. Moreover, the obtained biochar as a co-product from fast pyrolysis of Jatropha wastes can be used as an alternative solid fuel.

Effect of low-temperature hydrothermal treatment of HZSM-5 extrudates on the production of deeply-deoxygenated bio-oil via ex-situ catalytic fast pyrolysis of biomass

Catalytic fast pyrolysis (CFP) of biomass has high potential for producing deoxygenated bio-oil in one single process. HZSM-5 is a widely used catalyst for this purpose and various parameters have already been extensively investigated on this catalytic material. Limited studies were performed on the effect of low-temperature hydrothermal treatment of the catalyst with none being applied in ex-situ CFP in a lab-scale pyrolysis unit. The current paper therefore reports the investigation of HZSM-5 characteristics and activities when hydrothermally treated by steam at 550 °C for 5 h. The treatment modified the catalyst in a positive way that can increase 30% of the non-aqueous catalytic bio-oil yield. A maximum organic liquid yield of 11.4 wt% was achieved with 6.7 wt% being heavy fraction and 4.7 wt% being light fraction. These heavy and light bio-oils had very low oxygen contents of 4.3 and 1.6 wt%, respectively. This is equivalent to 93% oxygen removal compared to its corresponding non-catalytic bio-oil. Based on the elemental, FTIR, and GC/MS analyses, the hydrothermal treatment slightly increased the bio-oil oxygen content. Characterization of the catalysts reveal irreversible catalyst deactivation by dealumination. The severity of the deactivation increased continuously with higher amount of biomass being fed to the process. However, the catalyst deoxygenation ability was still acceptable for producing partially-deoxygenated bio-oil even after applying the biomass-to-catalyst ratio of 20.5.

Catalytic pyrolysis of holocellulose followed by integrated aldol condensation and hydrogenation to produce aviation fuel

The carbonyl platform compound from the catalytic pyrolysis of holocellulose was employed for the integrated aldol condensation and hydrogenation to produce hydrocarbons in the range of jet fuel. By the carbonylation of the pyrolysis vapor from holocellulose prepared from rape straw, bagasse and poplar (RS-Holo, BG-Holo and PL-Holo), it was revealed that BG-Holo rich in cellulose as the raw material presented the most production of carbonyl compounds including aldehydes and ketones. The optimal temperature for carbonylation of pyrolysis vapor from holocellulose was determined to be 400 °C, with the maximized carbon yield of carbonyls reaching 46.11%, which was boosted to the summit of 53.59% with more addition of ZrO2 catalyst. The integrated aldol condensation and hydrogenation were carried out using the catalytic pyrolysis bio-oil as the reactant over Ni/Mg-Al-O/AC bifunctional catalyst, with the highest carbon yield of hydrocarbons reaching 78.11%. The production mechanism of the final targeted alkanes was speculated, and it was discovered that ketones and aldehydes with short carbon chains are more prone to secondary condensation than those with long carbon chains, resulting in high-energy–density aviation fuel. Furthermore, the heating value of final oil was calculated based on an empirical formula, which was comparable to that of Jet A, meeting the standard of ASTM7566. The final oil’s distillation range distribution was simulated, and most of it fell in the range of aviation fuel. In this study, catalytic fast pyrolysis of holocellulose followed by integrated aldol condensation and hydrogenation was proved to be a promising way for producing aviation fuel.

Study on the effect of red mud and its component oxides on the composition of bio-oil derived from corn stover catalytic pyrolysis

Red mud (RM) waste rich in metal elements was selected as a cheap catalyst for fast catalytic pyrolysis to obtain high value-added bio-oil. The structural patterns and the main oxide components of the RM were determined. In addition, the catalytic effects and mechanisms of the metal oxide components on the bio-oil composition from corn stover (CS) was elucidated. The results showed the content of ketones, furans and alkylphenol significantly increased, while the content of acids and aldehydes greatly decreased under the catalytic effects of the 800 ℃-calcined RM. Fe2O3 and CaO were the main contributor. CaO promoted the production of ketones, and the catalytic effect of Fe2O3 resulted in a good selectivity for acids and furans. Al2O3, TiO2 and SiO2 inhibited the production of methoxyphenols and promoted the production of acids. Main oxide components promoted the production of alkylphenols. The results provided scientific guidance for producing high value-added bio-oil with cheap RM catalyst.

Enhancement of BTX production via catalytic fast pyrolysis of almond shell, olive pomace with polyvinyl chloride mixtures

This work addresses enhanced benzene, toluene and xylene (BTX) production by catalytic fast co-pyrolysis from agroindustrial biomass blended with PVC and the use of prepared NaZSM-5 and HZSM-5. Results from catalytic fast pyrolysis of biomass indicates that oxygen-containing compounds decreased whereas aromatics increased. The catalytic effect of mineral content altered the co-pyrolysis intermediates by increasing the formation of mono-aromatics while reducing poly-aromatic hydrocarbons. Furthermore, the addition of PVC strongly influenced thermal decomposition of agricultural waste biomass, where BTX yields were enhanced up to 26.6% and 25.1% for 1:2 OP/PVC-HZ and 1:2 AS/PVC-HZ, respectively. Yields of toluene and xylene peaked at 19% and 10.5% hydrocarbon yields with 1:2 OP/PVC-HZ blend. Additionally, from the pyrolytic gas, CH4 yields increased while the CO2 yield fell due to oxygen removal by decarboxylation. These findings could provide a great insight into the olive pomace and almond shell valorization through an inexpensive and straightforward easy process.

Pretreatment of HZSM-5 with organic alkali and cobalt: Application in catalytic pyrolysis of lignin to produce monocyclic aromatic hydrocarbons

In this work, we adopted organic alkali and cobalt pretreated HZSM-5 zeolites as catalysts for monocyclic aromatic hydrocarbons production via catalytic fast pyrolysis of lignin in a two-stage fixed bed reactor. For the treatment, four kinds of organic hydroxides (tetraalkylammonium hydroxides, denoted as TMAOH, TEAOH, TPAOH, and TBAOH) were chosen as the desilication agent, and cetyltrimethylammonium bromide (CTAB) was introduced as assistant to control the pretreating process. In addition, cobalt modification was further conducted over the optimized alkali-treated sample for acidity adjustment. The treated zeolites were systematically characterized by XRD, SEM, NH3-TPD, and N2-adsorption/desorption techniques. The characterization results were analyzed together with the catalytic testing data to reveal the structure-function relationship of the catalysts in catalytic pyrolysis of lignin. As it turned out, the HZSM-5 zeolite pretreated by 0.5 mol/L of TPAOH in the presence of CTAB exhibits a coordinated micropore/mesopore proportion, proper average mesopore size, and a successful preservation of acidic properties. The addition of CTAB in the alkali treatment process was not only beneficial to preventing the over-treatment of HZSM-5, but could also regulate the mesoporous structure of zeolite. Eventually, the highest production of monocyclic aromatic hydrocarbons (31.8%, relative content) was achieved by the TPAOH pretreated HZSM-5 (2C-0.5TPHZ) at 500 °C, far exceeding that of the parent HZSM-5 (17.3%, relative content). Further modification of the 2C-0.5TPHZ sample with 1 wt% of cobalt could enhance the acidity of the alkali-treated zeolite, leading to a further improvement of the monocyclic aromatic hydrocarbons production to 38.3%. The reusability of the pretreated sample was further evaluated by cyclic reaction for 5 times, which demonstrated its reactivity stability for monocyclic aromatic hydrocarbons production.

Influence of the porosity and acidic properties of aluminosilicate catalysts on coke formation during the catalytic pyrolysis of lignin

Five aluminosilicate catalysts with different textural and acidic properties are used to study the influence of their acidic and porous properties on the coke formation during the fast catalytic pyrolysis of lignin. The competition between coke formation and target product (hydrocarbons) formation in regard to different pore sizes and Si/Al ratios is classified via performing X-Ray Diffraction (XRD), nitrogen adsorption-desorption, pyrolysis–gas chromatography–mass spectrometry (Py-GCMS), kinetic calculations, and thermogravimetric (TG)/temperature programmed oxidation (TPO) measurements. The results indicated that a pore size consistent with the critical diameters of the pyrolysis products of lignin is a prerequisite for a catalyst to reach a high selectivity for the desired products with less coke formation. A relatively large pore size can cause severe coke formation; however, large pores are favorable for increasing the reaction rate by increasing the diffusion efficiency. A catalyst with sufficient acidity is also essential for high selectivity towards target products.