Catalytic Fast Pyrolysis Of Cellulose Research Articles

Levoglucosenone production by catalytic fast pyrolysis of cellulose mixed with alkali metal-doped Keggin heterpolyacid salt

Levoglucosenone (LGO) has shown a promising potential in the application of the sustainable chemistry. In this work, alkali metal-doped phosphotungstic acids, M2.5H0.5PW12O40 (M = Li, Na, K, Rb and Cs), were synthesized and employed for catalytic fast pyrolysis of cellulose to selectively produce LGO. The results show that levoglucosan, the main precursor of LGO, was produced with a yield of 33.5 wt% by non-catalytic pyrolysis of cellulose, while LGO by catalytic fast pyrolysis of cellulose is mainly regulated by the strong/weak acid sites of the M2.5H0.5PW12O40. Increasing the atomic radius of the alkali metals from Li to Cs doping to phosphotungstic acid led to an increase of LGO yield, attaining to 15.6 wt% at 300 °C over Cs2.5H0.5PW12O40 due to a high strong/weak acid site ratio. In addition, LGO yield was further enhanced to 19.2 wt% over (NH4)2HPO4 modified Cs2.5H0.5PW12O40 as a result of an increase of moderate strong acid sites. This study provides a potential method for LGO production by catalytic pyrolysis of cellulose.

Anchoring Effect of Organosilanes on Hierarchical ZSM-5 Zeolite for Catalytic Fast Pyrolysis of Cellulose to Aromatics.

As an essential chemical feedstock, aromatics can be obtained from biomass by catalytic fast pyrolysis (CFP) technology, in which diffusion limitation is still a problem. In this study, several ZSM-5 zeolites with intercrystal stacking macropores were synthesized by adding organosilanes (OSAs) with different alkyl chain groups. Due to the structure-directing effect of the OSA, the prepared ZSM-5 zeolites possess a larger external surface area and pore volume than Blank-Z5. Moreover, the pore size is related to the extent of anchoring of the OSA and silicon–aluminum species in the zeolite precursor. Pyridine Fourier transform infrared (Py-FTIR) and NH3-temperature-programmed desorption (TPD) analyses show that the obtained ZSM-5 zeolites have a higher Brønsted acidity and total number of acid sites. In addition, excessive addition of OSA is not conducive to the growth of ZSM-5 zeolites. The catalytic performance of the synthesized ZSM-5 zeolites was evaluated by Py-GC/MS. The larger external surface area and pore volume improve the accessibility of the acid sites and thus promote the conversion of biomass into aromatics.

Glucose‐Assisted Synthesis of Hierarchical HZSM‐5 for Catalytic Fast Pyrolysis of Cellulose to Aromatics

AbstractHierarchical ZSM‐5 zeolites have been successfully synthesized via an introduction of pre‐formed ZSM‐5 precursors and glucose‐assisted method. The influence of the amounts of glucose on the zeolite's characteristics of crystallinity, morphology, pore, and acidity of the HZSM‐5 zeolites were studied detailedly. The synthesized material showed a high mesoporous surface area (164.4–182.7 m2/g) and volume (0.14–0.15 m3/g), while the total acidity amount decreased slightly and Brønsted acidity amount increased. Amongst hierarchical ZSM‐5 zeolites samples, the highest aromatic yield of 43.3 % was obtained, more than the yields of the traditional ZSM‐5 (36.3 %). The increase of mesoporousity is the main reason for the increasing of aromatics yield and reducing of the amount of coke.

Insight into the role of varied acid-base sites on fast pyrolysis kinetics and mechanism of cellulose.

In the present research, a series of metal oxides were employed to investigate the role of varied acid-base site on kinetics and mechanism for catalytic fast pyrolysis of cellulose using TG-MS and Py-GC/MS. The results showed that the modulation of acidity-to-basicity value via altering metal oxides constituents significantly affected the transformation pathway for cellulose pyrolysis. Higher acidity-to-basicity ratios accelerated the proceeding of deoxygenation process, wherein 39.4% aromatics and 34.7% aliphatic hydrocarbons were achieved using Al2O3 (acidity-to-basicity value of 1.38) at 750°C with a catalyst/cellulose mass ratio of 15:1. In comparison, lowering acidity-to-basicity ratios mainly facilitated the ketonization and aldol condensation, therefore over 70% ketones was attained in the case of CaO catalysis. The kinetic studies further verified the promotional role of acid-base sites on cellulose pyrolysis with apparent activation energy as low as 33.72kJ/mol, in comparison with that of cellulose pyrolysis without adding catalysts. From another aspect, the composite metal oxides with better porous structures contributed to deoxygenation conversion for the production of aromatics and aliphatic hydrocarbons. Moreover, plausible reaction pathway for cellulose pyrolysis over metal oxides was proposed. This work would provide a good reference for the realization of product regulation from cellulose pyrolysis via adjusting acid-base sites in metal oxides.

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.

Boosting the selectivity of aromatic hydrocarbons via ex-situ catalytic fast pyrolysis of cellulose over Pt–Sn–Ce/γ-Al2O3 catalyst

Pt–Sn–Ce/γ-Al2O3 catalysts were synthesized by the impregnation method and used to produce aromatic hydrocarbons (AHs)-rich bio-oil via catalytic fast pyrolysis of cellulose. The upgraded products were on-line analyzed by pyrolysis-comprehensive two-dimensional gas chromatography/mass spectrometry (Py-GC × GC/MS). It was found that Pt–Sn–Ce/γ-Al2O3 catalysts were effective for improving the relative content of AHs in bio-oil. Especially, Pt–Sn–Ce/γ-Al2O3 contributed the highest AHs content (85.82%), which was 3 times than that of γ-Al2O3, and increased 85.44% compared with non-catalytic. In addition, Pt–Sn–Ce/γ-Al2O3 and Pt–Sn/γ-Al2O3 can generate the highest monocyclic aromatic hydrocarbons (MAHs) with the relative content of 60.24% and 51.92%, respectively. Pt–Sn–Ce/γ-Al2O3 catalyst can be reused five times with stable catalytic activity to produce AHs-rich bio-oil.

Selective preparation of 5-hydroxymethylfurfural by catalytic fast pyrolysis of cellulose over zirconium-tin mixed metal oxides

5-Hydroxymethylfurfural (5-HMF) is a value-added platform chemical, which can be obtained from pyrolysis of biomass materials, whereas related investigation on its selective production via catalytic fast pyrolysis (CFP) process is still insufficient. In this work, a zirconium-tin mixed metal oxide (ZrO2-SnO2) catalyst was developed for the selective production of 5-HMF from the in-situ CFP of cellulose. According to pyrolysis-chromatography/mass spectrometry (Py-GC/MS) tests, the ZrO2-SnO2 catalyst has better performance on the selective preparation of 5-HMF than single nano oxide ZrO2, SnO2, or their physical mixture. 5-HMF was sensitive to the reaction conditions, and its yield and selectivity always exhibited the tide of first increasing followed by decreasing along with the increase of Zr loading and catalyst-to-cellulose (CA-to-CL) ratio. At the optimum conditions with ZrO2-SnO2 of 15 wt% Zr loading (ZrO2-SnO2-15), pyrolysis temperature of 350 °C and CA-to-CL ratio of 2:1, the 5-HMF yield was 6.49 wt%, which was 4 times more than that of the non-catalytic process (1.35 wt%). Correspondingly, the selectivity of 5-HMF was up to 23.50 %. The catalyst characterization combined with the pyrolysis texts of several typical saccharides, including cellobiose, maltose, glucose, and mannose indicated that the ZrO2-SnO2-15 could promote the breakage of glycosidic bonds with the formation of reducing ends and the selective conversion of the reducing end to 5-HMF due to its mild acidity. Overall, the ZrO2-SnO2 is expected a promising catalyst for the CFP of cellulose to prepare 5-HMF.

Catalytic fast pyrolysis of cellulose for selective production of 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one using nickel-tin layered double oxides

As a value-added chiral chemical, 1-hydroxy-3,6-dioxobicyclo[3.2.1]oct-2-one (LAC) can be obtained via cellulose pyrolysis, but its yield is extremely low in the conventional pyrolysis process. Herein, novel nickel-tin layered double oxide (NiSn-LDO) catalysts were developed for the selective production of LAC from the in-situ catalytic fast pyrolysis (CFP) of cellulose. Several layered double oxides (LDOs) were prepared and evaluated via pyrolysis-chromatography/mass spectrometry (Py-GC/MS) tests for the in-situ CFP of cellulose. NiSn-LDO was determined as the most capable catalyst for selective LAC preparation, and further experiments were conducted to confirm the optimal condition to produce LAC over several essential factors of reaction temperature, Ni/Sn molar ratio in the NiSn-LDO catalyst, and catalyst-to-cellulose (CA-to-CL) ratio. The results demonstrated that LAC was sensitive to the reaction conditions, and its yield always exhibited the tide of first increasing followed with decreasing along with the increase of pyrolysis temperature, Ni/Sn molar ratio, and CA-to-CL ratio. The maximal LAC yield reached 9.11 wt% over the pyrolysis temperature of 320 °C using NiSn-LDO with a Ni/Sn molar ratio of 2/1 at the CA-to-CL ratio of 1/1, which was more than 5 times of that from the non-catalytic process (1.72 wt%). In addition, the NiSn-LDOs possessed much better catalytic capability to yield LAC with high selectivity than previously reported catalysts.

Catalytic fast pyrolysis of cellulose over Ce0.8Zr0.2-xAlxO2 catalysts to produce aromatic hydrocarbons: Analytical Py-GC × GC/MS

Analytical pyrolysis-comprehensive two-dimensional gas chromatography/mass spectrometry (Py-GC × GC/MS) was employed for the on-line analysis of cellulose via catalytic pyrolysis with different catalysts and catalytic temperatures to study the products and aromatic hydrocarbons selectivity. The catalysts were subjected to characterization methods, including XRD, TEM, NH3-TPD, to investigate the effects of the physicochemical properties of the catalyst on the product distribution. Results showed that the Ce0.8Zr0.2-xAlxO2 could significantly promote the formation of aromatic hydrocarbons under 400–550 °C. A lower catalytic temperature (≤350 °C) favored the formation of furan compounds, and a higher catalytic temperature (≥450 °C) supported the formation of aromatic hydrocarbons. The relative peak area of the aromatics prepared by using the Ce0.8Zr0.15Al0.05O2 catalyst was the highest being 85.24% at 550 °C. Moreover, the selectivity of the single-ring aromatics, such as benzene, toluene and xylene, were significantly affected by the presence of the Ce0.8Zr0.2-xAlxO2 catalysts. The higher total acidity of Ce0.8Zr0.15Al0.05O2 favored the formation of benzene and toluene. Additionally, the Ce0.8Zr0.15Al0.05O2 catalyst had a great thermal stability. The catalyst recycling tests showed that the Ce0.8Zr0.15Al0.05O2 catalyst can be reused five times to produce aromatic-rich bio-oil via catalytic fast pyrolysis.

Insight into the formation mechanism of levoglucosenone in phosphoric acid-catalyzed fast pyrolysis of cellulose

Abstract The catalytic fast pyrolysis of cellulose impregnated with phosphoric acid (H3PO4) offers a promising method for the selective production of levoglucosenone (LGO), a valuable anhydrosugar product. However, the fundamental mechanism for selective LGO formation is unclear. Herein, quantum chemistry calculations and catalytic fast pyrolysis experiments were performed to reveal the formation mechanism of LGO in H3PO4-catalyzed cellulose pyrolysis. H3PO4 significantly decreased the energy barriers of the pyrolytic reactions and altered the competitiveness of the LGO formation pathways, promoting LGO formation. Through different pathways in the non-catalytic and H3PO4-catalyzed conditions, LGO is mainly produced from the primary decomposition of glucose units of cellulose and secondary conversion of levoglucosan. The major catalytic formation pathways of LGO comprise similar reactions, with dehydration at the 3-OH + 2-H site as the rate-determining step. Importantly, secondary conversion of 1,4;3,6-dianhydro-α- d -glucopyranose is not feasible for LGO formation, in contrast to previous reports. In addition, a high degree of polymerization is beneficial for the selectivity of LGO formation in the catalytic process, because the glycosidic bond is important for the formation of the bicyclic structure (1,5- and 1,6-acetal rings).

Enhancement of Bio-based para-Xylene Selectivity in Catalytic Fast Pyrolysis of Cellulose Using a Surface-modified Mg/P/HZSM-5 Catalyst

With the growing consumption of oil, the production of p-xylene(PX) from renewable biomass has gained significant attention recently. This work demonstrated that cellulose, a main component in lignocellulosic biomass, was directly converted into PX over the Mg/P surface-modified zeolites. The catalysts modified by the incorporation of P2O5 and MgO into HZSM-5(HZ) promoted the isomerization of m-/o-xylenes to p-xylene. The PX selectivity was greatly enhanced using the modified zeolites due to the deactivation of external surface and the adjustment of pore entrance. In addition, the addition of methanol to cellulose was beneficial to increase the selectivity of xylenes due to the alkylation reactions and the Diels-Alder reactions between cellulose-derived furans and methanol-derived olefins. The highest PX yield of 10.7%(molar fraction) with a high PX selectivity in xylenes(97.1%) was obtained over the 10%Mg/5%P/HZ catalyst. The reaction pathway for the formation of p-xylene was addressed according to the study of the key reactions and the characterization of catalysts.

Enhancement of light aromatics from catalytic fast pyrolysis of cellulose over bifunctional hierarchical HZSM-5 modified by hydrogen fluoride and nickel/hydrogen fluoride

Pore structure and accessible active sites of HZSM-5 (Z5) are the key factors for its catalysis. The bifunctional hierarchical Z5 were prepared with leaching agent HF and loading Ni, and their performance for catalytic fast pyrolysis (CFP) of cellulose was investigated in a drop tube quartz reactor. Z5 modified with 0.5 mol/L HF (0.5F-Z5) showed excellent light aromatics (LAs) yield, which can be attributed to the enhancement in the small mesopores (2–10 nm) and the decrease of Brønsted acid sites during dealumination. Simultaneously, the loading of a 1 wt% Ni produced more LAs than 0.5F-Z5, due to the improvement in deoxidation/hydrogenation reactions. The highest LAs yield (31.3%) was obtained over 1%Ni-0.5 mol/LHF-Z5, which increased by 44.9% compared to the parent Z5. In addition, the reaction routes over different active centers and acid-catalyzed reactions were analyzed, based upon the composition of bio-oils and catalyst characterization.

Enhancing the production of light olefins and aromatics from catalytic fast pyrolysis of cellulose in a dual-catalyst fixed bed reactor

In this study, the effects of a macroporous catalyst (CaO), mesoporous catalyst (MCM-41), and microporous catalysts (ZSM-5 and SAPO-34) on the production of light olefins and aromatics from cellulose catalytic fast pyrolysis were investigated in a dual-catalyst fixed bed reactor. Further the fractional catalytic pyrolysis of MCM-41 or CaO with ZSM-5 or SAPO-34 was explored. The results showed that ZSM-5 was the most efficient catalyst for the formation of light olefins and aromatics followed by MCM-41, CaO and SAPO-34, and no aromatics were found with SAPO-34 only. Moreover, 15% CaO combined 85% ZSM-5 produced the highest yield of light olefins (5.59%) and aromatic (13.42%). The addition of CaO and MCM-41 promoted the selectivity of C2H4 and decreased the production of naphthalene.

Catalytic fast pyrolysis of cellulose to aromatics over hierarchical nanocrystalline ZSM-5 zeolites prepared using sucrose as a template

In this work, hierarchical ZSM-5 zeolites were prepared by a hard template method (pre-crystallization and dry gel) using sucrose to obtain suitable mesopores for the catalytic fast pyrolysis (CFP) of cellulose to produce aromatics. As the sucrose added decrease, the mesopore surface area and mesopore volume of the zeolites decreased while the micropore surface area and micropore volume increased. The mesoporous structure introduced by sucrose promoted the CFP of cellulose to aromatics by increasing the mass transfer of molecules. The highest aromatic yield of 37.0% was obtained over the hierarchical ZSM-5 zeolites prepared by the pre-crystallization method with sucrose*12/SiO2 = 0.15.

Catalytic fast pyrolysis of cellulose for increasing contents of furans and aromatics in biofuel production

The catalytic fast pyrolysis of cellulose, cellobiose and glucose with the zeolite catalyst of NaY was carried out using thermogravimetric analyzer (TG) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results from TG showed that all samples presented significant mass loss at low temperature and exhibited high residual chars with NaY. The activation energies of cellulose, cellobiose and glucose were significantly decreased with NaY. PY-GC/MS showed that saccharides were significantly decreased or even completely eliminated and converted into furans, aromatics, phenols and light oxygenates with NaY. The contents of furans of cellulose, cellobiose and glucose with NaY were increased from 17.48%, 18.79% and 28.77% to 46.71%, 52.11% and 67.81%, respectively. Pyrolysis of cellulose and cellobiose presented high selectivity of BTX (Benzene, Toluene, and Xylene). The furans are mainly formed on the surface of NaY by dehydration, fragmentation/retro-aldol condensation, decarbonylation, or decarboxylation. The pyrolysis intermediates of anhydro-oligosaccharides dominated the formation of aromatics and phenols during the catalytic fast pyrolysis of cellulose in the zeolite catalyst pores at the active sites.

Catalytic Fast Pyrolysis of Cellulose by Integrating Dispersed Nickel Catalyst with HZSM-5 Zeolite

The effect of integrating dispersed nickel catalyst with HZSM-5 zeolite on upgrading of vapors produced from pyrolysis of lignocellulosic biomass was investigated. The active component nickel nitrate was introduced onto the cellulose substrate by impregnation technique. Based on TGA experimental results, we discovered that nickel nitrate first released crystallization water, and then successively decomposed into nickel oxide which was reduced in-situ to metallic nickel through carbothermal reduction reaction. In-situ generated nickel nanoparticles were found highly dispersed over carbon substrate, which were responsible for catalyzing reforming and cracking of tars. In catalytic fast pyrolysis of cellulose, the addition of nickel nitrate caused more char formation at the expense of the yield of the condensable liquid products. In addition, the selectivity of linear oxygenates was increased whereas the yield of laevoglucose was reduced. Oxygen-containing compounds in pyrolysis vapors were deoxygenated into aromatics using HZSM-5. Moreover, the amount of condensable liquid products was decreased with the addition of HZSM-5.

Controlled synthesis of hierarchical ZSM-5 for catalytic fast pyrolysis of cellulose to aromatics

Zeolite materials play a significant role throughout the oil refining and petrochemical industry.

Catalytic fast pyrolysis of cellulose to produce furan compounds with SAPO type catalysts

Furans, such as furfural (FF) and 5-hydroxymethyl-furfural (HMF), are recognised as target high-value chemicals produced through catalytic fast pyrolysis (CFP) of biomass. In this work, a series of SAPO type catalysts were introduced in the CFP of cellulose to promote the generation of furans. Results indicate that under the catalysis of SAPO type catalysts, the formation of furans is promoted while the content of sugars decreases considerably. AlCu-SAPO-34 and ZrCu-SAPO-18 performed best for furan formation: their furans peak area% was 56.94% and 63.86%, respectively. Furthermore, these two catalysts had more mild acidity (lower density and strength), which favoured the formation of furans. Meanwhile, 500–600°C was selected as the optimum operation temperature when using SAPO catalysts. The formation of furans with SAPO type catalysts may be favoured because the catalyst promotes the direct conversion of oligosaccharides to furans.

Catalytic Fast Pyrolysis of Cellulose and Biomass to Selectively Produce Levoglucosenone Using Activated Carbon Catalyst

Activated carbon (AC) prepared by chemical activation with H3PO4 (named AC-P) was employed for catalytic fast pyrolysis of cellulose and biomass to selectively produce levoglucosenone (LGO). The catalytic pyrolysis behaviors and product distributions were revealed via both analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and lab-scale experiments. Moreover, the performance of AC-P catalyst was compared with previously reported strong acid catalysts and other ACs prepared by different activation methods. In addition, reusability and stability of the AC-P catalyst have been examined via recycling experiments. The results indicated that the AC-P catalyst was effective for selectively preparing LGO from both cellulose and biomass and performed better than other catalysts. Among the three biomass materials (pine wood, poplar wood, and bagasse), pine wood showed the best selectivity for producing LGO. The maximal LGO yields of 18.1 and 9.1 wt % were obtained from cellulose and pine wood, res...

Catalytic fast pyrolysis of cellulose in a microreactor system using hierarchical zsm-5 zeolites treated with various alkalis

Hierarchical ZSM-5 catalysts were prepared by desilication using NaOH, Na2CO3 and TPAOH with different concentrations under the same treatment conditions. Their structures and acidities were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption and desorption (N2-BET) and ammonia temperature-programmed desorption (NH3-TPD). The catalytic fast pyrolysis (CFP) of cellulose to produce aromatics over the hierarchical ZSM-5 catalysts prepared using different alkali treatments was investigated. The alkali treatment by Na2CO3 (0.4∼0.8M) was much milder than treatment by NaOH, which allowed the desilication process to be highly controllable, resulting in an increase of both the amount and strength of the strong acid sites, and the formation of hierarchical structures combining micro- and mesoporosity. The organic hydroxide TPAOH did not change the pore structure of ZSM-5, but it greatly increased the relative crystallinity. The CFP of cellulose with HZSM-5 produced 35.5% liquid aromatic hydrocarbons and 32.7% coke. The yield of aromatics increased after Na2CO3 treatment but decreased after NaOH treatment. In addition, the yield of coke showed the opposite trend. The highest aromatic yield (38.2%) and lowest coke yield were obtained in the CFP of cellulose with the desilicated zeolite treated with 0.6M Na2CO3. The increased acidity in hierarchical ZSM-5 treated with Na2CO3 increased the selectivity of highly valuable aromatics, such as benzene, toluene, and xylene, and decreased the selectivity of large aromatics. TPAOH-treated HZSM-5 showed a slightly increased yield of aromatics due to the repair effect of TPAOH, but this treatment did not form a mesoporous structure.