Catalytic Pyrolysis Of Biomass Research Articles

Overview of catalytic upgrading of biomass pyrolysis vapors toward the production of fuels and high‐value chemicals

The application of heterogeneous catalysis in biomass pyrolysis is considered as one of the most promising methods to improve bio‐oil quality by minimizing its undesirable properties (high viscosity, corrosivity, instability, etc.) and producing renewable fuels and high‐value chemicals. Catalytic fast pyrolysis (CFP) of biomass refers both to the “in situ” and “ex situ or two‐stage” upgrading. A plethora of catalytic materials have been investigated in the literature for both approaches, including conventional microporous zeolites, ordered mesoporous aluminosilicates, promoted or not with several transition metals, as well as various metal (nano)oxide catalysts with Lewis acidity. Recently, hybrid micro/mesoporous and basic materials have been also suggested exhibiting most promising results due to combined micro/mesoporosity and adequate balance of acid and basic sites. Optimum catalysts are required to retain deoxygenation, enhance yields of aromatics, and other valuable compounds (such as phenolics), while limiting coke formation. Coke formation is one of the reasons of catalyst deactivation; a very challenging issue during biomass CFP, especially using zeolites. The deactivation process is affected by many factors, including the composition of the feedstock (inorganic minerals present in the feedstock may also deposit on the catalyst), reaction conditions, and the nature/properties of the catalysts used in CFP. Precoking on the surface of zeolites or MgO deposition are among the proposed effective ways to suppress coke formation and thus, catalyst deactivation.This article is categorized under: Bioenergy > Science and Materials Energy Research & Innovation > Science and Materials Energy and Transport > Science and Materials

Synthesis and physicochemical characterization of hierarchical ZSM-5: Effect of organosilanes on the catalyst properties and performance in the catalytic fast pyrolysis of biomass

Abstract Two series of ZSM-5 catalysts with hierarchical porosity were hydrothermally synthesized by adding two types of organosilane reagents (OSA) into the medial synthesis system. The effects of the types and addition amounts of OSA on the pore characteristics, crystallinity, morphology and acidity of the ZSM-5 zeolites were studied by XRD, SEM, TEM, N2-adsorption, 27Al MAS NMR and NH3-TPD. Mesopores were generated by introducing appropriate amounts of OSA. In addition, the catalytic performance of the hierarchical ZSM-5s were investigated for the catalytic fast pyrolysis (CFP) of cellulose. The increase in the mesoporosity leads to a reduced amount of coke. However, the highest yield of aromatics was obtained for the mesoporous sample with the greatest microporosity. Thus, the right balance between meso- and microporosity is critical for achieving high aromatic yields. In addition, the distribution of aromatic products is directly related to the microporosity.

Enhancement of aromatics production from catalytic pyrolysis of biomass over HZSM-5 modified by chemical liquid deposition

The catalytic pyrolysis of biomass is a promising technology for producing high-quality fuels and value-added chemicals. However, the development of this technology has been hindered by high coke formation and low target product yield. In this study, chemical liquid deposition (CLD) was adopted to improve the catalytic performance of HZSM-5 in the catalytic pyrolysis of biomass. The changes of the characteristics, including crystallographic structure, porosity and acidity, of the HZSM-5 zeolite after modification were analyzed by XRD, N2 adsorption-desorption, FTIR and NH3-TPD. The results showed that CLD modification reduced the mesopore volume, pore opening size and the number of external acid sites without changing the micropore structure. Py-GC/MS (a pyrolyzer equipped with a gas chromatography-mass spectrometer) and kinetic analysis were used to analyze the catalytic performance of the parent and CLD-modified zeolites. It was found that the production of aromatics increased first and later decreased, reaching optimal levels at a 4% deposition of SiO2, while the selectivity of monoaromatics increased continuously. Additionally, CLD modification raised the energy barriers for the char/coke formation reactions and could inhibit its production. The deposition amount of 4% showed the best char/coke inhibitory effects for catalytic pyrolysis of cellulose, while the char/coke formation decreased continuously with the increase of the deposited amount of SiO2 for catalytic pyrolysis of lignin.

First pilot scale study of basic vs acidic catalysts in biomass pyrolysis: Deoxygenation mechanisms and catalyst deactivation

In order for catalytic biomass pyrolysis to be economically sustainable, low cost and highly efficient catalysts are needed. In a previous work, Magnesium oxide (MgO) basic catalysts produced from natural magnesite (MgCO3) were found to be highly efficient alternatives to zeolitic catalysts which apart from their relatively high cost, they are easily deactivated due to biomass alkali deposition. In order to validate these findings in pilot scale, these natural MgO catalysts were investigated in a circulating fluidized bed pilot scale unit and were compared to a commercially available ZSM-5 catalyst. This is to the best of our knowledge the first attempt to evaluate a basic catalyst in biomass fast pyrolysis in a pilot unit employing commercially relevant process technology. The basic sites of the MgO catalysts enhanced ketonization and aldol condensation reactions, as it was verified by 2DGC-TOFMS analyses of the produced bio-oils. Deoxygenation was achieved mainly via formation of CO2, while H2O yield was substantially reduced in comparison to the ZSM-5 catalyst. As a result, bio-oils richer in hydrogen were obtained by the use of MgOs. However, the MgO catalysts led to a significant increase of the catalytically produced coke compared to ZSM-5. The effect of MgO properties, such as surface area and basicity on product yields and bio-oil composition was elaborated. In contrast to the acidic ZSM-5, no alkali metals were found to deposit on MgO, indicating different deactivation mechanisms between acidic and basic catalysts in biomass fast pyrolysis.

Aqueous-Phase Synthesis of Hydrocarbons from Furfural Reactions with Low-Molecular-Weight Biomass Oxygenates

Catalytic pyrolysis of lignocellulosic biomass generates water-soluble low-molecular-weight oxygenates such as acetic acid, acetone, furfural, butanone, guaiacol, phenol, etc. These compounds are usually not suitable for conventional hydrocarbon fuel applications. A new heterogeneous catalyst has been developed that simultaneously catalyzes alkylation, hydrodeoxygenation, and hydrogenation of these small oxygenate molecules in aqueous media to produce C6 to C14 hydrocarbons in a one-pot synthesis. In these syntheses, acetic acid, propionic acid, furfural, butanone, pentanone, heptanone, and 2,6-dimethyl-4-heptanone reacted to produce straight- and branched-chain alkanes. The aldehydes reacted with furan to form straight-chain liquid hydrocarbons, while the ketones reacted with 2-methylfuran to produce branched-chain liquid hydrocarbons. All the reactions occurred in aqueous media at 350 °C. The gaseous products included low-molecular-weight hydrocarbons such as methane, propane, butane, and pentane.

Catalytic fast pyrolysis of biomass over Mg-Al mixed oxides derived from hydrotalcite-like precursors: Influence of Mg/Al ratio

In this work we examine a series of Mg-Al mixed oxides derived from hydrotalcite-like precursors prepared with different Mg/Al ratios i.e. Mg/Al = 2, 3, and 4, as catalysts for the catalytic fast pyrolysis (CFP) of wheat straw. Characterization of the Mg-Al mixed oxides by N2 adsorption, X-ray diffraction and CO2 temperature programmed desorption revealed a decrease in the surface area and a higher number and proportion of basic sites corresponding to an increase in the Mg concentration in the hydrotalcite precursors. The Mg-Al mixed oxides derived from hydrotalcite precursors are active materials for the catalytic fast pyrolysis of biomass. The removal of oxygen during the catalytic fast pyrolysis of biomass over the Mg-Al-mixed oxides depends on their Mg/Al ratio, and an increase in gas production with a strong improvement in the decarboxylation capacity as the Mg concentration in the mixed oxides decreased, was observed. The Al-Mg mixed oxide catalyst with the lowest Al concentration (Mg/Al = 4.0) maintained the deoxygenation and bio-oil energy yield at levels comparable to those achieved over an acidic ZSM-5 zeolite widely used in the CFP of biomass. A moderate increment in ketone formation for the catalyst with Mg/Al = 4.0 suggests that these basic materials promote the aldol condensation and ketonization of pyrolytic compounds by removing the oxygen in the form of H2O and CO2.

Effect of H2 as Pyrolytic Agent on the Product Distribution during Catalytic Fast Pyrolysis of Biomass Using Zeolites

Bio-oil generated from catalytic fast pyrolysis or hydrotreating processes represents one of the most promising alternatives to liquid fossil fuels. The use of H2 as carrier gas in the pyrolysis of ...

Restoring ZSM-5 performance for catalytic fast pyrolysis of biomass: Effect of regeneration temperature

Zeolite catalysts used for biomass catalytic fast pyrolysis (CFP) deactivate rapidly, similar to a fluidized catalytic cracking (FCC) catalyst used in refining. To operate effectively when there is rapid deactivation, biomass CFP can take place in a riser FCC-style reactor in which the catalyst has a short contact time (seconds) with reactants before it is regenerated. The regeneration, therefore, has two major needs for effective operation: 1) heat balance, since the heat required for the CFP reactions is brought into the reactor by the hot catalyst and 2) relatively short (minutes) regeneration to restore the catalyst activity to be near its initial state. In order to understand effective conditions to regenerate zeolites used for CFP, a series of experiments were performed to determine the effect of regeneration temperature on the activity of ZSM-5 (SiO2/Al2O3 = 30). After use for pine pyrolysis vapor upgrading, the catalyst was oxidized in 4% O2 at temperatures between 500–700 °C and reevaluated for the upgrading of pine pyrolysis vapors to assess the extent of regeneration. Additional testing was performed using ethylene aromatization as a surrogate reaction to probe regeneration efficiency. Regeneration experiments were performed for either a fixed length of time (20 min) or until there was no further CO2 measured in the effluent gas. Results from the ethylene aromatization reactions were shown to serve as an excellent surrogate for CFP reactivity and indicated that the use of model compound studies can effectively be used to understand reaction and regeneration processes from biomass CFP. Both sets of results indicate that a spent ZSM-5 used for biomass CFP could be fully regenerated at 650°C and 700°C within 20 min, whereas regeneration temperatures of 550 °C and 600 °C required longer regeneration temperatures and in the case of regeneration at 500 °C, there may be coke species that are not removed and the catalyst activity may never be fully restored. Characterization by pyridine diffuse reflectance infrared spectroscopy, thermogravimetric analysis coupled with infrared spectroscopy, and N2 physisorption showed that higher regeneration temperatures are more effective for restoring Brønsted acid sites and catalyst mesoporosity by rapidly removing aromatic coke deposits. Additionally, regeneration at 650 °C and 700 °C led to a slightly higher total porosity as compared to the pristine catalyst, which was attributed to the formation of additional mesoporosity from catalyst steaming.

Role of Biopolymers in the Deactivation of ZSM-5 during Catalytic Fast Pyrolysis of Biomass

Rapid coking and catalyst deactivation are significant problems during catalytic fast pyrolysis of biomass. Cellulose and lignin were found to coke via different mechanisms, resulting in two distinct types of catalyst deactivation. Lignin pyrolysis vapors cause coke formation mainly by external surface coking without limiting access to the active acid sites in the microchannels. Lignin deactivates the surface cracking capability of ZSM-5, resulting in unreacted primary vapors passing through while maintaining aromatization reactions. Cellulose pyrolysis vapors generate coke mainly as an extension of the aromatization reactions on the acid sites, which leads to occlusion of the internal acid sites. This deactivates the upgrading reactions, resulting in decreased aromatics formation, generation of oxygenated intermediates and increased alkylation of 1-ring aromatics and reduced multi-ring aromatics selectivity. The results indicate that the decrease in aromatics formation observed during catalytic pyrolysis...

Production of bio‐based p‐xylene via catalytic pyrolysis of biomass over metal oxide‐modified HZSM‐5 zeolites

AbstractBACKGROUNDp‐Xylene is an important bulk chemical in the petrochemical industry, and the production of bio‐based p‐xylene is of great significance in both academic and industrial arenas. However, the biggest challenge for the production of p‐xylene from biomass is how to increase the yield and selectivity of p‐xylene.RESULTSThe highest p‐xylene yield of 20.7 C‐mol% with a p‐xylene/xylenes ratio of 91.6% was obtained by the co‐catalytic pyrolysis of sawdust with 50 wt% methanol over the 20%La2O3/HZSM‐5(80) catalyst. Adding a La, Mg, Ce or Zn element into HZSM‐5 promoted the alkylation of benzene and toluene to form xylenes, and the isomerization of m/o‐xylenes to p‐xylene.CONCLUSIONThis work developed a one‐pot process in which lignocellulosic biomass (sawdust) was directionally converted into p‐xylene by coupling the catalytic pyrolysis of biomass into aromatic monomers, the alkylation of light aromatics to xylenes and the isomerization of m/o‐xylenes to p‐xylene over the metal oxide‐modified HZSM‐5 catalysts. The selectivity and yield of p‐xylene strongly depended on the acidity of the catalysts, reaction temperature and methanol additive during the catalytic pyrolysis of sawdust. © 2018 Society of Chemical Industry

Cultivation, characterization, and properties of Chlorella vulgaris microalgae with different lipid contents and effect on fast pyrolysis oil composition.

A systematic study of the effect of nitrogen levels in the cultivation medium of Chlorella vulgaris microalgae grown in photobioreactor (PBR) on biomass productivity, biochemical and elemental composition, fatty acid profile, heating value (HHV), and composition of the algae-derived fast pyrolysis (bio-oil) is presented in this work. A relatively high biomass productivity and cell concentration (1.5g of dry biomass per liter of cultivation medium and 120 × 106 cells/ml, respectively) were achieved after 30h of cultivation under N-rich medium. On the other hand, the highest lipid content (ca. 36wt.% on dry biomass) was obtained under N-depletion cultivation conditions. The medium and low N levels favored also the increased concentration of the saturated and mono-unsaturated C16:0 and C18:1(n-9) fatty acids (FA) in the lipid/oil fraction, thus providing a raw lipid feedstock that can be more efficiently converted to high-quality biodiesel or green diesel (via hydrotreatment). In terms of overall lipid productivity, taking in consideration both the biomass concentration in the medium and the content of lipids on dry biomass, the most effective system was the N-rich one. The thermal (non-catalytic) pyrolysis of Chlorella vulgaris microalgae produced a highly complex bio-oil composition, including fatty acids, phenolics, ethers, ketones, etc., as well as aromatics, alkanes, and nitrogen compounds (pyrroles and amides), originating from the lipid, protein, and carbohydrate fractions of the microalgae. However, the catalytic fast pyrolysis using a highly acidic ZSM-5 zeolite, afforded a bio-oil enriched in mono-aromatics (BTX), reducing at the same time significantly oxygenated compounds such as phenolics, acids, ethers, and ketones. These effects were even more pronounced in the catalytic fast pyrolysis of Chlorella vulgaris residual biomass (after extraction of lipids), thus showing for the first time the potential of transforming this low value by-product towards high added value platform chemicals.

Hydrogen assisted catalytic biomass pyrolysis. Effect of temperature and pressure

Beech wood has been converted into a mixture of oxygen-free naphtha and diesel boiling point range hydrocarbons by using catalytic hydropyrolysis in a fluid bed reactor with a CoMoS/MgAl2O4 catalyst, followed by deep hydrodeoxygenation (HDO) in a fixed bed reactor loaded with a NiMoS/Al2O3 catalyst. The effect of varying the temperature (365–511 °C) and hydrogen pressure (1.6–3.6 MPa) on the product yield and organic composition was studied. The mass balance closed by a mass fraction between 90 and 101% dry ash free basis (daf). The yield of the combined condensed organics and C4+ varied between a mass fraction of 17 and 22% daf, corresponding to an energy recovery of between 40 and 53% in the organic product. The yield of the non-condensable gases varied between a mass fraction of 24 and 32% daf and the char yield varied between 9.6 and 18% daf. The condensed organics contained a mass fraction of 42–75% aromatics, based on GC × GC-FID chromatographic peak area, and the remainder was primarily naphthenes with minor amounts of paraffins. The condensed organics were essentially oxygen free (mass fraction below 0.001%) when both reactors were used. Bypassing the HDO reactor increased the oxygen concentration in the condensed liquid to a mass fraction of 1.8%. The results show that catalytic hydropyrolysis may be a viable way to process solid biomass into liquid and gaseous fuels.

Production of renewable alkyl-phenols from catalytic pyrolysis of Douglas fir sawdust over biomass-derived activated carbons

The catalytic conversion of Douglas fir sawdust into bio-phenols on activated carbons (AC) obtained by chemical activation of corn stover with H3PO4 was investigated. Taguchi experimental design was used to optimize the preparation of AC using microwave assisted pyrolysis. Based on an overall consideration of AC yield, bio-oil yield, and phenols content, the optimized conditions were phosphoric acid to biomass ratio of 0.8, microwave power of 600 W and reaction time of 20 min. The bio-oils were rich in phenolic compounds (up to 90 area %) that mainly comprised phenol, methyl and ethyl phenol. During the catalytic pyrolysis of biomass with AC, phenolic compounds could either be derived from decomposition of lignin, followed by deoxygenation, or derived from furfurals, which were degradation products of carbohydrates. The catalytic activities of ACs were mainly owing to the well-developed porosity and abundant acidic surface functional groups. The porous structures of ACs were characterized by N2 isotherms, showing a strong dependence on the acid impregnation ratio and microwave irradiation power. The presence of acidic phosphoric-containing surface functional groups was confirmed by SEM/EDX, FTIR and NH3-TPD.

Fast pyrolysis of waste pepper stem over waste FCC catalyst

Fast pyrolysis of waste pepper stem was investigated using waste FCC catalyst and HY zeolite with a SiO2/Al2O3 ratio of 5.1. The pyrolysis oil obtained from the pyrolysis at 500 °C was analyzed using GC/MS. Oxygenates were converted, in particular when the catalyst dose was high, to furans and aromatics. The contents of low-molecular-mass phenolics and aromatics increased with increasing quantity of acid sites deployed. On the other hand, the content of high-molecular-mass phenolics was increased by catalysis with the biomass:catalyst ratio of 1:1, whereas it was decreased by catalysis with the biomass:catalyst ratio of 1:10. This was explained by the pathway of lignin-to-aromatics conversion: lignin → high-molecular-mass phenolics → low-molecular-mass phenolics → aromatics. Activated waste FCC catalyst showed a little weaker catalytic activity for the conversion of low-molecular-mass phenolics to aromatics than HY, leading to a higher phenolics content and a lower aromatics content. The results of this study indicate that the catalytic pyrolysis of lignin-rich biomass over waste FCC catalyst can be a promising way of recycling waste FCC catalyst for the production of high-value-added chemicals, such as furans, phenolics and aromatics.

Catalytic upgrading of pyrolysis vapours: Effect of catalyst support and metal type on phenolic content of bio-oil

Abstract Bio-oil from low-cost and renewable lignocellulosic biomass is a complex mixture of organic compounds and water. It is necessary to selectively control the biomass pyrolysis pathways to obtain specific bio-oils rich in value-added chemicals. Microporous and mesoporous catalysts can be good candidates for the catalytic pyrolysis of biomass leading to the production of valuable components such as aromatic hydrocarbons and phenolics. In this study, in-situ catalytic upgrading of pyrolysis vapours from acid pre-treated walnut shell was carried out in a lab scale fixed bed reactor with microporous nickel or cobalt impregnated Zeolite Socony Mobil–5 and mesoporous aluminum or iron impregnated Santa Barbara Amorf-15 catalysts. The effects of catalyst modification on product yields, bio-oil quality and the variation of the phenolic compounds in pyrolytic-oil were examined using elemental analysis, gas chromatography and mass spectrometry. The major improvement in the bio-oil quality by the catalyst addition was the reduction of the oxygen content of the bio-oil's organic fraction and the increase in valuable chemicals (aromatics and phenolics), while the total liquid yield (bio-oil) decreased. Catalysts also increased the gaseous product yields. In comparison to non-catalytic experiments, all the Proton-exchanged Zeolite Socony Mobil-5 catalysts decreased both the total liquid and the total organic content yield due to the H+-form zeolite catalysing hydrocarbon conversion reactions. Compared to Proton-exchanged Zeolite Socony Mobil-5, the metal impregnated catalysts yielded less water, but favoured the formation of gas products. It was evident that impregnation with metals changed the mechanism of oxygen removal. Cobalt/Proton-exchanged Zeolite Socony Mobil-5 favoured the formation of carbon dioxide over carbon monoxide, while nickel/Proton-exchanged Zeolite Socony Mobil-5 favoured the formation of carbon monoxide over carbon dioxide. When using Proton-exchanged Zeolite Socony Mobil-5 instead of silica sand, the guaicols and syringol that are formed from the thermal decomposition of the lignin fraction in the sulphuric acid treated walnut shell are significantly reduced and are mainly converted to alkylated phenols and aromatic and polyaromatic hydrocarbons. With the impregnation of metals on the Santa Barbara Amorf-15, the selectivity of the Santa Barbara Amorf-15 exhibited a shift from catechol- and pyrogallols-type compounds to alkylated phenols, especially at 10% aluminum, 30% and 50% iron metal loadings. As a result, the bio-oil composition and quality can be improved by utilizing different metals and metal impregnation ratios during catalytic upgrading. According to the preliminary economic analysis, pyrolysis oil production cost predicted from catalytic pyrolysis of walnut shell is higher than catalytic pyrolysis of woody biomass because of lower pyrolysis oil yield of walnut shell.

Catalytic Fast Pyrolysis of Biomass Impregnated with Potassium Phosphate in a Hydrogen Atmosphere for the Production of Phenol and Activated Carbon.

A new technique was proposed to co-produce phenol and activated carbon (AC) from catalytic fast pyrolysis of biomass impregnated with K3PO4 in a hydrogen atmosphere, followed by activation of the pyrolytic solid residues. Lab-scale catalytic fast pyrolysis experiments were performed to quantitatively determine the pyrolytic product distribution, as well as to investigate the effects of several factors on the phenol production, including pyrolysis atmosphere, catalyst type, biomass type, catalytic pyrolysis temperature, and catalyst impregnation content. In addition, the pyrolytic solid residues were activated to prepare ACs with high specific surface areas. The results indicated that phenol could be obtained due to the synergistic effects of K3PO4 and hydrogen atmosphere, with the yield and selectivity reaching 5.3 wt% and 17.8% from catalytic fast pyrolysis of poplar wood with 8 wt% K3PO4 at 550°C in a hydrogen atmosphere. This technique was adaptable to different woody materials for phenol production. Moreover, gas product generated from the pyrolysis process was feasible to be recycled to provide the hydrogen atmosphere, instead of extra hydrogen supply. In addition, the pyrolytic solid residue was suitable for AC preparation, using CO2 activation method, the specific surface area was as high as 1,605 m2/g.

Effect of Li-LSX-zeolite on the in-situ catalytic deoxygenation and denitrogenation of Isochrysis sp. microalgae pyrolysis vapours

In this work, we report for the first time the use of Li-LSX-zeolite as catalyst for the catalytic pyrolysis of biomass (Isochrysis sp. Microalgae). Li-LSX-zeolite showed a good catalytic performance, principally for bio-oil denitrogenation (mainly in form of NH3), and good activity for olefins and aromatics production. At 500 °C, 11.8% aromatics and 23.1% aliphatics were produced. The increase of temperature led to transfer of C to the gas phase, coke formation on the catalyst surface and decrease in N-compounds in the bio-oil. The increase of the catalyst to biomass ratio from 0 to 3:1 resulted in the aromatics being five-fold those non-catalytically obtained and in a higher cracking power that reduced the bio-oil to 23% at expenses of olefins rich gas. However, a linear correlation between coke formation and aromatic yield was observed as the catalyst to microalgae ratio was increased. Therefore, the experimental results indicate that Li-LSX-zeolite could be used as catalyst for in-situ denitrogenation of microalgae bio-oil and for enhancing aliphatics and aromatics formation to be blend in gasoline and diesel and olefins in gas phase.

Catalytic Fast Pyrolysis of Biomass over Microporous and Hierarchical Zeolites: Characterization of Heavy Products

The conversion of lignocellulosic biomass by catalytic fast pyrolysis (CFP) is a promising route to producing green aromatics and sustainable biofuels. The zeolite catalysts present a strong ability to produce light aromatics but also heavy products. In this work, these heavy products are monitored by a well-established petroleomic approach. The selectivity toward the heavy bio-oil components of both a common HZSM-5 zeolite and a hierarchical zeolite was investigated. Part of the molecular species from lignin derivatives is still present in the upgraded bio-oils. Deoxygenation and aromatization are the main modifications of the heavy compounds caused by zeolites, especially for the sugar derivatives. These effects are stronger for the hierarchical zeolite for which numerous heavy hydrocarbons (not oxygenated) are generated due to enhanced mass transfers within the crystallites. Moreover, this catalyst demonstrates a better stability upon an increase in the biomass-to-catalyst ratio.

Catalytic fast pyrolysis of rice straw to aromatic compounds over hierarchical HZSM-5 produced by alkali treatment and metal-modification

The synthesis of highly selective catalysts for the catalytic fast pyrolysis (CFP) of biomass into valuable aromatics remains a challenge. This report describes the synthesis of hierarchical ZSM-5 catalysts by the NaOH desilication of conventional HZSM-5 for the CFP of rice straw to aromatics in a Tandem μ-reactor system coupled directly to a GC/MS equipped with FID and TCD. Catalysts were treated with a mild HCl wash and metal loading to increase the catalytic activity and reduce the deactivation. The effects of acidity, mesoporosity and incorporation of metals on the production of aromatics were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption and desorption (N2-BET) and temperature-programmed desorption of NH3 (NH3-TPD). The highest total acidity, especially the strong acidity, of the hierarchical ZSM-5 treated by 0.2 and 0.4 NaOH followed by HCl washing (AHZ-0.2 and AHZ-0.4) gave the highest yields of aromatics. Suitable mesopores introduced by alkali treatment enhanced mass transfer of reactants, increasing the yield of aromatics. Finally, the loading of a suitable amount of Ni and Cu produced more aromatics than standard HZSM-5 due to the improved decarboxylation/decarbonylation reactions leading to higher yields of olefins.

Catalytic pyrolysis of larch sawdust for phenol-rich bio-oil using different catalysts

Abstract Different kinds of catalysts have a great influence on the characteristics and products of the biomass catalytic pyrolysis. Catalysts of Cu/C, Pd/C, Pd Ag and H-Zeolites socony mobil #5 (HZSM-5) were selected and characterized by the X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM). Decomposition behaviors of the larch catalytic pyrolysis were studied by the thermogravimetric analyzer (TG). The total carboxylic acids (TCAs) and total phenolic compounds (TPCs) in bio-oil were determined using the non-aqueous potentiometric titration method. The chemical distribution of bio-oil was investigated by the gas chromatography/mass spectrometry (GC/MS). Results showed that the temperature of the maximum weight loss rate of larch was decreased by adding these four catalysts. The carbon residue rate was increased by using HZSM-5. The content of GC-detected phenols increased from 25.28% to 35.11% (area) by adding Pd/C. However, TCAs in bio-oil were decreased sharply with Pd Ag and Pd/C. HZSM-5 promoted the formation of phenols and enhanced TPCs in bio-oils (26.56 wt%), which increased by approximately 35% compared to that from the non-catalytic pyrolysis process. This phenol-rich bio-oil can be used to replace the traditional phenol for the manufacturing of high-value biomaterials.