Catalytic Fast Pyrolysis Process Research Articles

Catalytic pyrolysis of biomass waste using montmorillonite-supported ultrafine iron nanoparticles for enhanced bio-oil yield and quality

The catalytic fast pyrolysis process is a promising method for converting biomass waste into bio-oil, where the catalyst plays a crucial role in determining the yield and quality of the products. In this study, ultrafine iron nanoparticles were incorporated onto a montmorillonite substrate through the pyrolyzing coordinated polymer method to enhance liquid fuel production via catalytic pyrolysis of biomass waste. The catalyst showed a uniform distribution of iron on the montmorillonite surface, indicating that the incorporation was successful. Catalytic pyrolysis led to an increase in liquid yields and a decrease in gas product yields compared to direct pyrolysis. The highest bio-oil yield obtained was 56.9% during the catalytic pyrolysis of corncob, which was found to be particularly well-suited for the production of bio-oil. Furthermore, the proposed reaction pathway was based on identifying the composition of the bio-oil, which was further supported by quantum chemical calculations of chemical bond strength and the likelihood of free radical attacks. These findings demonstrate the potential of using montmorillonite-supported ultrafine iron nanoparticles to enhance bio-oil yield and quality in biomass pyrolysis processes.

Examination of in situ and ex situ catalytic fast pyrolysis and liquid fractionation utilizing a free-fall reactor

This study examines biomass valorization through thermochemical conversion by an integrated catalytic fast pyrolysis process with liquid fractionation using a free-fall reactor, γ-alumina, as a catalyst and methanol for direct quenching. The novelty lies within the process intensification (i.e., a single-step conversion and fractionation pathway) to improve pyrolysis oil yield and quality. In particular, the conversion bioprocess utilizes in situ or ex situ catalytic free-fall fast pyrolysis reactors at 550°C and 10–15 psi to produce pyrolysis oil and char (bio-oil and biochar) from pinewood feedstocks. The results from the gas chromatography–mass spectrometry show that the main volatile fractions of bio-oil compounds are levoglucosan, furfural, hydroxy acetone, methyl acetate, and catechol. The electrospray ionization–mass spectrometry results determine the average molar mass, revealing improved cracking, thermal treatment, and fraction stabilization. The Fourier transform infrared spectroscopy and thermal aging provide insight into the change in functional groups in relation to experimental parameters. The outcomes indicate that γ-alumina successfully decreased acidic compounds and increased esters and phenolic content in the bio-oil. The bio-oil produced from the ex situ catalytic pyrolysis also shows the highest liquid yield (~41%), high phenolic content, and thermally stable properties. The in situ catalytic pyrolysis exhibits lower yields but favors high ketone formation. Fractions condensed in methanol exhibit the highest thermal stability and esterification potential; however, they still possess relatively high amounts of acidic compounds. It is concluded that ex situ catalytic pyrolysis, using γ-alumina catalyst and fractionation with methanol, can improve conversion reactions, particularly bio-oil quality, yield, and thermal stability.

Enhanced production of naphtha-range compounds from arundo donax via catalytic fast pyrolysis using SAPO-11

Arundo donax, acknowledged for its elevated energy content, substantial biomass yield and rapid growth, stands as an alluring candidate for biofuel production. In this investigation, a molecular sieve-based catalyst was utilized to scrutinize the catalytic fast pyrolysis (CFP) of Arundo donax, aiming for the production of naphtha-range compounds. The study also encompassed the evaluation of pyrolysis product yields within a fixed-bed reactor. The systematic exploration included an assessment of the impacts arising from catalyst type, temperature, weight hourly space velocity (WHSV), and N2 flow rate. The results demonstrated that at 500 °C, WHSV of 1 h−1 and N2 flow rate of 300 ml/min, SAPO-11 exhibited a selectivity of 64.55% to naphtha-range compounds and 64.55% to isomerous naphtha-range compounds. This was in stark contrast to the control group, which contained no catalyst (with a selectivity of 41.40% and 3.19%, respectively), SAPO-41 (with a selectivity of 11.02% and 9.55%, respectively) and HZSM-5 (with a selectivity of 59.89% and 53.51%, respectively). Additionally, SAPO-11 yielded the highest bio-oil compared to other catalysts (SAPO-11 of 28.52 wt% > none of 19.48 wt% > HZSM-5 of 18.90 wt% > SAPO-41 of 13.11 wt%). The conclusions drawn from these findings imply that the synthesized SAPO-11 catalyst exhibited superior catalytic activity and isomerization proficiency in contrast to other catalysts (SAPO-41 and HZSM-5). Remarkably, under the specified conditions of SAPO-11 catalyst, temperature = 500 °C, WHSV = 1 h−1 and N2 flow rate = 200 ml/min, the CFP process yielded a remarkable maximum absolute yield of the naphtha-range compound at 25.82 wt%, with an isomerized naphtha-range compound absolute yield of 25.35 wt%.

From Biomass to Fuel Blendstocks via Catalytic Fast Pyrolysis and Hydrotreating: An Evaluation of Carbon Efficiency and Fuel Properties for Three Pathways.

Biomass was upgraded to fuel blendstocks via catalytic fast pyrolysis (CFP) followed by hydrotreating using three approaches: ex situ CFP with a zeolite catalyst (HZSM-5), ex situ CFP with a hydrodeoxygenation catalyst (Pt/TiO2) and cofed hydrogen, and in situ CFP with a low-cost mixed metal oxide catalyst (red mud). Each approach was evaluated using a common pine feedstock and the same hydrotreating procedure. The oxygen contents in the CFP oils ranged from 17 to 28 wt % on a dry basis, and the carbon efficiencies for the CFP processes were in the range of 28-38%. The residual oxygen was reduced to <1 wt % during hydrotreating, which was operated for 104-140 h for each CFP oil without plugging issues. The hydrotreating carbon efficiencies were 81-93%. The CFP pathway with the hydrodeoxygenation catalyst gave the highest overall carbon efficiency from biomass to fuel blendstocks (34%) but, at the same time, also the highest cumulative hydrogen consumption during CFP and hydrotreating. The zeolite pathway produced the largest fraction boiling in the gasoline range and the highest estimated octane number due to the high aromatic content in that CFP oil. The in situ red mud pathway produced the largest fraction of diesel-range products with the highest derived cetane number. However, advances in the CFP and hydrotreating process are required to improve the fuel blendstock properties for all pathways.

Hollow ZSM-5 encapsulated with single Ga-atoms for the catalytic fast pyrolysis of biomass waste

The development of efficient metal-zeolite bifunctional catalysts for catalytic fast pyrolysis (CFP) of biomass waste is highly desirable for bioenergy and renewable biofuel production. However, conventional metal-loaded zeolites often suffer from metal sintering during pyrolysis and are thus inactivated. In this study, single-site Ga-functionalized hollow ZSM-5 (GaOx@HS-Z5) was synthesized via an impregnation-dissolution-recrystallization strategy without H2 reduction. The Ga atom was coordinated to four oxygen atoms in HS-Z5 frameworks. Benefitting from the highly dispersed single-Ga atoms and hollow zeolite framework, 3GaOx@HS-Z5 performed the best in producing hydrocarbon-rich bio-oil compared to impregnated 3GaOx/HS-Z5 and H2-reduced 3Ga@HS-Z5 in the maize straw CFP. In particular, 3GaOx@HS-Z5 delivered the highest bio-oil yield (23.6 wt%) and hydrocarbon selectivity (49.4 area%). 3GaOx@HS-Z5 also retained its structural integrity and catalytic activity after five pyrolysis-regeneration cycles, demonstrating its advantage in practical biomass CFP. The elimination of H2 reduction during the synthesis of catalyst provides an additional advantage for simplifying the CFP process and reducing operating costs. The retained Ga micro-environment and anti-sintering properties were unique for 3GaOx@HS-Z5, as severe metal sintering occurred during pyrolysis for other metals (e.g., NiOx, ZnOx, FeOx, and CoOx) that encapsulated HS-Z5.

Preliminary Study on The Bio-Oil Production from Multi Feed-Stock Biomass Waste via Fast Pyrolysis Process

Biomass is a good resource for renewable energy. Biomass can be converted into bio-fuel (bio-oil) through a catalytic fast pyrolysis process. Previous studies only used single feedstock biomass as raw material for bio-oil production. In this study, bio-oil production is based on a multi-feedstock biomass waste consisting of rice husk, sugar cane bagasse, and palm oil empty fruit bunch. The mixture of biomass waste as a raw material is expected to enhance the yield and quality of the bio-oil produced. This study aimed to investigate the bio-oil products obtained from catalytic pyrolysis of the biomass waste mixture. Mixture Design from Design Expert was used to study the effect of biomass composition on the bio-oil products. Each biomass, i.e., rice husk, sugar cane bagasse, and palm oil empty fruit bunch, was previously chopped and sieved into a uniform 60 mesh. The pyrolysis process was conducted at 500°C with an N2 flow rate of 3 L min-1. The mixture of biomass waste husks contains more phenolic compounds than single-feedstock. The chemical characterization also showed that the multi-feedstock bio-oil compound was dominated by aldehydes, esters, and phenolic compounds.

Improvement of wheat (T. aestivum) straw catalytic fast pyrolysis for valuable chemicals production by coupling pretreatment of acid washing and torrefaction

The present work investigated the coupling pretreatment of acid washing and torrefaction to address secondary cracking of target products and condensation of intermediates and improved bio-oil quality and hydrocarbon selectivity of the catalytic fast pyrolysis (CFP) process. The total hydrocarbon yields in CFP increased from 28.06 wt% to 55.31 wt% by torrefaction and 46.29 wt% by coupling pretreatment. The acid washing resulted in fewer acids and phenols and more sugars in bio-oil by decreasing the AAEMs. The removal rate of the potassium was up to 96.7 %, and other elements were above 83 %. Torrefaction elevated the C/O ratio and the higher calorific value of biomass. It could also decrease the acid content in obtained bio-oil in the CFP process. In addition, the TG/TGA results showed that higher torrefaction temperature decreased the total weight loss of biomass. Meanwhile, the acid washing pretreatment improved the resolution of the two pyrolysis peaks of the DTG curve. These results showed that the AAEMs removal and intermediates inhibition could elevate the selectivity of the valuable chemical. • Acid washing removed 83 wt% of AAEMs to facilitate valuable chemicals conversion; • Torrefaction elevated the C/O ratio and the higher calorific value of wheat straw; • The coupling pretreatment improved bio-oil quality and hydrocarbons selection; • The CFP with pretreated biomass reduced phenols, acids, and ketones production.

Product regulation and catalyst deactivation during ex-situ catalytic fast pyrolysis of biomass over Nickel-Molybdenum bimetallic modified micro-mesoporous zeolites and clays

Ni-Mo bimetallic modified micro-mesoporous zeolite catalysts were prepared and employed in the process of ex-situ catalytic fast pyrolysis (CFP) of poplar to produce liquid fuel. Clay catalysts were incorporated to further improve the products quality. The mass yield of monocyclic aromatic hydrocarbons (MAHs) increased under the catalysis of composite catalysts AZM and NiMo/AZM. HAP&Zeolite dual catalyst system reduced coke yield of NiMo/AZM to 5.01 wt%. Through real-time monitoring of gas products, the catalytic performance of zeolites began to decrease after the ratio of biomass and catalyst was more than 1. A series of characterization results futher demonstrated that AZM and NiMo/AZM possessed more stable catalytic ability and higher catalytic activity during the whole CFP process. N2 adsorption–desorption measurement and Raman characterization illustrated the formation and structure of coke, catalyst deactivation and the protective mechanism of mesopores on micropores.

Model quantification of the effect of coproducts and refinery co-hydrotreating on the economics and greenhouse gas emissions of a conceptual biomass catalytic fast pyrolysis process

In this work we present model results for a scaled-up conceptual process informed by bench scale biomass catalytic fast pyrolysis (CFP) and hydrotreating experimental data. This process uses a Pt/TiO2 catalyst during CFP, which produces a partially deoxygenated organic biocrude intermediate that is then hydroprocessed to a hydrocarbon fuel blendstock; the catalyst also enables high yields of acetone and methyl-ethyl-ketone (MEK) coproducts. Two options for hydroprocessing were modeled: (A) co-hydrotreating at a petroleum refinery using hydrogen sourced from steam reforming of natural gas and (B) standalone hydrotreating at a biorefinery using hydrogen sourced from CFP off gases. The results revealed that Case A was economically advantageous with a modeled minimum fuel selling price (MFSP) of $2.83/GGE or gallon gasoline equivalent (in 2016 US dollars), while the additional cost of standalone hydrotreating facilities in Case B increased the MFSP to $3.13/GGE. Conversely, greenhouse gas (GHG) emissions were lower for Case B (3.9 g CO2e/MJ) compared to Case A (21.5 g CO2e/MJ) due to the use of biogenic (Case B) and fossil-derived (Case A) hydrogen. In a third option (Case C), the requirements for separation and purification of acetone and MEK were removed from the refinery co-processing scenario (Case A) to evaluate the impacts of this process simplification. Elimination of these coproducts increased the MFSP to $3.21/GGE and GHG emissions to 35 g CO2e/MJ. These comparisons based on our detailed conceptual models provide economic and sustainability guidance regarding processing choices for future biorefineries. While refinery coprocessing using existing equipment and the production of relatively valuable coproducts can benefit the economics, the hydrogen-source and biogenic coproducts can have significant impacts on the sustainability of the process, and feasibility to use CFP off-gases or other renewable sources for hydrogen production can help lower GHG emissions.

Study on the reaction mechanism of nitrogenous compounds in zeolite-catalyzed pyrolysis of blue-green algae

The ex-situ catalytic fast pyrolysis (CFP) of blue-green algae (BGA) and its nitrogenous model compounds over HZSM-5 was conducted in a microfluidized bed reactor (MFBR) combined with a U-shape fixed bed reactor (U-FBR). A single photoionization mass spectrometer (SPI-MS) was used for on-line studying the dynamics of volatiles formation with the biomass-to-catalyst ratio (BCR). In the CFP of BGA, six different groups of products were differentiated by statistical analysis of SPI mass spectra, which were obtained with the cumulative BCRs. The relative concentration of each group has its own evolution with catalyst deactivation, indicating the different formation pathways of six groups. In combination with results from the CFP of six model compounds, the reaction pathways of nitrogenous compounds in the CFP of BGA over HZSM-5 were proposed. The benzyl nitrile could be fully converted to hydrocarbons while this is hard to achieve N-cyclic compounds (particularly the pyridines). Besides, most of nitrogenous compounds could be interconvertible in the CFP process. Transmethylation is the favorite way for catalytic conversion. In addition, the CFP of BGA and its N-cyclic compounds would lead to the fast coking of HZSM-5, especially the hard coke.

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.

Fast pyrolysis of bagasse catalyzed by mixed alkaline-earth metal oxides for the selective production of 4-vinylphenol

4-Vinylphenol (4-VP) is a value-added phenol compound, which can be obtained from the pyrolysis of herbaceous biomass, and its yield can be further improved through the in-situ catalytic fast pyrolysis process. Herein, a barium-magnesium mixed metal oxide (BaMg-MMO) catalyst was developed and employed for the selective production of 4-VP from bagasse fast pyrolysis. The effects of Ba/Mg molar ratio in the BaMg-MMO catalyst, pyrolytic temperature, catalyst-to-bagasse (CA-to-BA) ratio were carefully investigated based on pyrolysis-chromatography/mass spectrometry (Py-GC/MS) tests. The 4-VP yield reached a maximal of 7.3 wt% with the corresponding selectivity of 44.4% at 300 °C under the Ba/Mg molar ratio of 1:1 and the CA-to-BA ratio of 4:1, compared with that of 5.0 wt% in the non-catalytic process. Moreover, a series of lab-scale fast pyrolysis tests of bagasse were carried out in a fixed bed reactor using BaMg-MMO with a Ba/Mg molar ratio of 1:1. The highest 4-VP yield and selectivity were 7.1 wt% and 56.6% at 300 °C with the CA-to-BA ratio of 1:1. The results indicated that BaMg-MMO could provide a promising catalytic performance on the formation of 4-VP during the fast pyrolysis of bagasse.

The effect of NaOH treatment of rice husk on its catalytic fast pyrolysis under decomposed methane for the production of aromatics

Here, catalytic fast pyrolysis (CFP) was studied as a method to valorize rice husk (RH). Specifically, the effects of RH pretreatment, i.e., NaOH treatment, on the CFP efficiency and selectivity over a Ga-loaded HZSM-5 (SiO2/Al2O3 ratio = 38) were investigated. In addition to NaOH pretreatment, it was investigated how pyrolysis medium (N2, CH4, or a gas stream evolved from ex-situ CH4 decomposition over a Ni/La2O3/CeO2/Al2O3 catalyst (Ni/La2O3/CeO2 = 2/1/1) at 923 K (d-CH4)) influences the CFP of pretreated RH. The NaOH treatment reduced the content of ash and increased the content of cellulose in the RH sample. Thus, the effect of pyrolysis medium on the CFP of cellulose was studied at first, followed by that on CFP of NaOH-treated RH. With regard to the pyrolysis medium, the yield of aromatic compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) achieved with both cellulose and the NaOH-treated RH enhanced in an order; d-CH4 > CH4 > N2. The removal of ash from RH with the NaOH pretreatment increased the BTEX yield up to 22.3 wt% as ash (mineral impurities) affects pyrolytic behavior of cellulose and lowers accessibility of pyrolytic volatiles to acid sites on zeolite. This study gives helpful information about how different parameters influence the conversion of RH into BTEX via CFP process.

Conversion of Oil Palm Empty Fruit Bunch (EFB) Biomass to Bio-Oil and Jet Bio-Fuel by Catalytic Fast-Pyrolysis Process

Oil palm empty fruit bunch (EFB) biomass is a potential source of renewable energy. Catalytic fast-pyrolysis batch process was initially performed to convert oil palm EFB into bio-oil, followed by its refinement to jet bio-fuel. Crystalline zeolites A and Y; synthesised from rice husk ash (RHA), were applied as heterogeneous catalysts. The catalytic conversion of oil palm EFB to bio-oil was conducted at a temperature range of 320-400°C with zeolite A catalyst loadings of 0.6 - 3.0 wt%. The zeolite catalysts were characterised by XRD, FTIR and FESEM. The bio-oil and jet bio-fuel products were analysed using GC-MS and FTIR. The batch fast-pyrolysis reaction was optimised at 400°C with a catalyst loading of 1.0 wt%, produced 42.7 wt% yields of liquid bio-oil, 35.4 wt% char and 21.9 wt% gaseous products. Analysis by GCMS indicates the compound distribution of the liquid bio-oil are as follows: hydrocarbons (23%), phenols (61%), carboxylic acids (0.7%), ketones (2.7%), FAME (7.7%) and alcohols (0.8%). Further refinement of the liquid bio-oil by catalytic hydrocracking over zeolite Y produced jet bio-fuel, which contains 63% hydrocarbon compounds (C8-C18) and 16% of phenolic compounds.

Bio-BTX production from the shape selective catalytic fast pyrolysis of lignin using different zeolite catalysts: Relevance between the chemical structure and the yield of bio-BTX

As the most abundant aromatic bio-polymer in nature, lignin can be converted into bio-BTX via the shape selective catalytic fast pyrolysis process (SS-CFP). In this work, three types of MWL were isolated from softwood (Chinese fir), hardwood (poplar), and herbaceous biomass (corn stover), namely CF-MML, P-MWL, and CS-MWL. The chemical structural of lignin was analyzed by gel permeation chromatography (GPC), 2D-HSQC-NMR, and 31P NMR. Five types of the parent zeolites (HZSM-5 (25), HZSM-5 (85), Al-MCM-41, HY, and USY) and the Zn modified HZSM-5 (25) with different loading amounts (1% to 4%) were screened. Results showed that CF-MWL had the highest carbon content (59.90%). P-MWL had highest content of β-O-4 linkage (53.90%) and Mw (2778 g/mol). Among the five parent zeolites, HZSM-5 (25) was the most effective catalyst to produce bio-BTX with the highest selective yield of 56.56% at the optimal operation parameters. As a bi-functional catalyst, the incorporation of Zn on zeolite promoted the formation of BTX, where metal promoted the reaction rates of de‑oxygenation reaction and aromatization reaction, while the HZSM-5 remains the ability of shape selectivity. The maximum selective yields of BTX were 65.02% (CF-MWL) > 63.77% (CS-MWL) > 63.41% (P-MWL) when the Zn loading amount was 2%.

A review on the role of hierarchical zeolites in the production of transportation fuels through catalytic fast pyrolysis of biomass

Design of highly active catalysts plays a critical role in catalytic fast pyrolysis (CFP) of lignocellulosic biomass. Advanced catalysts can improve the deoxygenation rate of pyrolysis vapors and boost the production of fuel precursors. Zeolites are suitable frameworks for catalyzing pyrolysis vapors into species of transportation fuel value. However, their nano-sized structure limits the diffusion of reactants into pores and over active sites. Consequently, the aggregation of large molecules outside micropores leads to a massive coke formation, blocking pore channels, and thus, preventing the accessibility to acid sites. This could cause quick deactivation and instability of the catalyst, necessitating frequent catalyst regeneration and replenishment. Hierarchical micro/mesopore-structured zeolites are promising candidates to cope with the mentioned challenges. In addition to their adjusted pore structure and increased accessibility of acid sites, the formation of mesoporosity in zeolites provides an adequate room for the deposition of additional active phases such as metal nanoparticles, further boosting the catalytic activity. Different strategies used for preparing hierarchical zeolites can tremendously alter their attributes, and consequently affect product selectivity during CFP of biomass. Focusing on the precursors of transportation fuels (i.e., aromatic hydrocarbons and olefins), the present paper critically reviews the impacts of methods used for synthesizing hierarchical zeolite, on CFP of bio-based feedstocks. Moreover, the role of metal addition to hierarchical zeolites in biomass catalytic pyrolysis is also discussed briefly. Among the different synthesis techniques, desilication treatment using alkaline solutions is the most promising owing to its simplicity, high productivity, and scalability. In terms of product selectivity, the addition of Ga species to hierarchical zeolites can increase aromatic hydrocarbons while Ce incorporation can increase the yield of valuable oxygenates such as furan. Despite the advantages of mono-metallic hierarchical zeolites in producing cherished chemicals, future studies should scrutinize the influence of bi-metallic hierarchical zeolites in bio-based CFP processes.

Comparative study on pyrolysis of bamboo in microwave pyrolysis-reforming reaction by binary compound impregnation and chemical liquid deposition modified HZSM-5

The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis (CFP) process. To reduce the coke formation, binary compound impregnation (BCI) and chemical liquid deposition (CLD) were used to modify HZSM-5 catalysts. At the same time, the self-designed microwave reactor separated the pyrolysis of bamboo and catalytic upgrading of primary vapor, which made the catalytic effect more thorough. Experimental results indicated that CLD used TiO2 deposition to cover external acid sites, while BCI by phosphorus-nickel could cover and partly destroy superficial acid sites through two different ways. Within the scope of the loaded amount studied, the yield of aromatic hydrocarbons in the oil phase increased at first and then decreased, while the coke formation reduced continuously. BTX (benzene, toluene and xylene), the most valuable product in bio-oil, drastically increased by 39.1% and 22.6% respectively over the CLD and BCI modified catalysts. Considering the catalytic performance as well as cost, CLD over HZSM-5 has more advantages in the CFP process to upgrade bio-oil.

Conversion of Loblolly pine biomass residues to bio-oil in a two-step process: Fast pyrolysis in the presence of zeolite and catalytic hydrogenation

In the present study, Loblolly pine biomass residue was converted to bio-oil in a two-step process, consisting of 1) fast pyrolysis in the presence of zeolite ZSM-5 as a catalyst to produce pyrolysis oil, 2) hydrogenation of pyrolysis oil using formic acid as the hydrogen source in presence of Ru/activated carbon catalyst. Pyrolysis oils were analyzed by 13C, 31P and HSQC-NMR and the results revealed that the zeolite-induced catalytic fast pyrolysis process led to effective demethoxylation, producing more catechol and p-hydroxy-phenyl hydroxyl groups in the bio-oils, resulting in a decrease in the methoxyl group content by about 85 % and rich aromatic structures in the pyrolysis oils. The properties of pyrolysis oil with and without zeolite were in the bio-oil range. Hydrogenated pyrolysis oil showed that 79 % of the aromatic protons are eliminated and 87 % of protons are aliphatic in nature, with no oxygen attached to the α-carbon.

Effect of alkali-treated HZSM-5 zeolite on the production of aromatic hydrocarbons from microwave assisted catalytic fast pyrolysis (MACFP) of rice husk

We performed microwave-assisted catalytic fast pyrolysis (MACFP) of rice husk (RH) over an alkali-treated HZSM-5 zeolite, for production of hydrocarbons. The treatment consisted in the modification of the HZSM-5 by the organic base tetrapropylammonium hydroxide (TPAOH) solution at several concentrations. We characterized the resulting catalysts by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption, and temperature-programmed sorption of ammonia (NH3-TPD). The results suggest that the TPAOH treatment generated mesoporous structures in the HZSM-5, while preserving its microporous structure and crystallinity. We obtained the highest yield (45.9%) of hydrocarbons from MACFP of rice husk (RH) at 550 °C. As the TPAOH concentration increases, the relative content of BTEX hydrocarbons (benzene, toluene, ethylbenzene, and xylene) reaches a maximum value of 22.9% at 2.0 mol/L. A comparison of results obtained over the organic base TPAOH (HZSM-5 modified by 2.0 mol/L TPAOH solution) with those obtained over an inorganic base (HZSM-5 modified by 2.0 mol/L NaOH solution) shows a 4.3% increase in the relative content of monocyclic aromatic hydrocarbons for the TPAOH. In addition, the TPAOH-treated catalyst shows excellent selectivity of BTEX (58.5%), which is higher than the selectivity obtained with the parent HZSM-5 (51.2%) and NaOH-treated HZSM-5 (53.9%). The TPAOH-modified HZSM-5 catalyst effectively reduced coke formation by 4.6% compared to MACFP over the parent HZSM-5, most likely because TPAOH decreases the concentration of strong acidic sites on the outer surface of the catalyst, creating a mesoporous structure while retaining the weak acidic sites on the HZSM-5 inner surface. The new catalyst generated in this work contains a moderate amount of mesopores structures, which allows for effective upgrading of pyrolysis vapors while simultaneously reducing coke formation, thereby addressing a significant problem in the development of the catalytic fast pyrolysis process.

The role of catalyst acidity and shape selectivity on products from the catalytic fast pyrolysis of beech wood

The catalytic fast pyrolysis (CFP) of biomass represents an efficient integrated process to produce deoxygenated stable liquid fuels and valuable chemical products from lignocellulosic biomass. The zeolite ZSM-5 is a widely studied catalyst for the CFP process. However, its microporous structure may limit the diffusion of high molecular weight pyrolysis intermediates to its active sites. Mesoporous aluminosilicates such as Al-SBA-15 are promising materials with larger pore sizes that can overcome these diffusional limitations. Previous comparisons between mesoporous aluminosilicates and ZSM-5 for the CFP process have neglected the disproportionately high acidity of ZSM-5. In this study, an Al-SBA-15 catalyst has been synthesised with high acidity, comparable to that of a ZSM-5 catalyst with a Si:Al ratio of 15:1. The synthesised Al-SBA-15 catalyst was characterised by N2 physisorption, XRD and propylamine-TPD, and was compared to a ZSM-5 catalyst and a typical industrial equilibrium fluid catalytic cracking catalyst (e-FCC). All three catalysts were used at three different catalyst to biomass (C/B) ratios, to investigate the effect of varying concentrations of acid sites on the product distribution from the catalytic fast pyrolysis of beech wood. Interestingly, despite their dissimilar structural architectures, all three solid acid catalysts displayed similar reaction pathways towards the cracking of high molecular weight products such as levoglucosan and formation of intermediates including phenolics and furans. However, the selectivity towards the final catalytic products was dictated mainly by the structure of the catalysts. Despite their very similar surface area and acidity, the ZSM-5 exhibited high selectivity for the formation of desirable aromatic hydrocarbon products due to its shape-selective micropore structure, while Al-SBA-15 instead shifted the selectivity towards the formation of undesirable coke. The results highlighted the importance of catalyst shape-selectivity in the catalytic fast pyrolysis of biomass for the conversion of pyrolysis vapours into desirable products and the suppression of undesirable solid byproduct formation.