Catalytic Pyrolysis Of Biomass Research Articles

ChemInform Abstract: Catalytic Fast Pyrolysis of Lignocellulosic Biomass

AbstractReview: 354 refs.

Decoupling HZSM-5 catalyst activity from deactivation during upgrading of pyrolysis oil vapors.

The independent evaluation of catalyst activity and stability during the catalytic pyrolysis of biomass is challenging because of the nature of the reaction system and rapid catalyst deactivation that force the use of excess catalyst. In this contribution we use a modified pyroprobe system in which pulses of pyrolysis vapors are converted over a series of HZSM-5 catalysts in a separate fixed-bed reactor controlled independently. Both the reactor-bed temperature and the Si/Al ratio of the zeolite are varied to evaluate catalyst activity and deactivation rates independently both on a constant surface area and constant acid site basis. Results show that there is an optimum catalyst-bed temperature for the production of aromatics, above which the production of light gases increases and that of aromatics decrease. Zeolites with lower Si/Al ratios give comparable initial rates for aromatics production, but far more rapid catalyst deactivation rates than those with higher Si/Al ratios.

Production of upgraded bio-oils by biomass catalytic pyrolysis in an auger reactor using low cost materials

Production of upgraded bio-oils by catalytic pyrolysis of wood biomass was studied in an auger reactor using low cost materials as catalysts. These materials included several clay minerals (sepiolite, bentonite and attapulgite) and an industrial waste from alumina production, known as red mud. The influence of temperature (400–500°C) and the effect of catalyst to biomass ratio (3:1–1:6, in weight) were also analysed. A temperature of 450°C and the lowest catalyst proportion (1:6, in weight) were selected as the most appropriate to aim the pyrolysis for bio-oil production. Catalyst to biomass ratio resulted critical since an excess on catalyst addition seemed to reduce liquid production while char yield increased. Under the selected conditions, the catalysts tested improved the characteristics of the obtained bio-oil as fuel (viscosity, acidity, oxygen content and calorific value). For every catalyst, the viscosity of the organic liquid fraction decreased (up to 34% in case of bentonite) while lower heating value increased (up to 20% in red mud tests). Concerning acidity, sepiolite and red mud produced a decrease in the total acid number (around 29% and 23%, respectively). The stability of the organic fraction after aging test (equivalent to long time storage) was also improved by each catalyst.

Catalytic fast pyrolysis of waste pepper stems over HZSM-5

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

Catalytic fast pyrolysis of cellulose and biomass to produce levoglucosenone using magnetic SO42−/TiO2–Fe3O4

Magnetic superacid (SO42−/TiO2–Fe3O4) was prepared for catalytic fast pyrolysis of cellulose and poplar wood to produce levoglucosenone (LGO). Its catalytic activity was evaluated via pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) experiments, and compared with the non-magnetic SO42−/TiO2, phosphoric acid (H3PO4) and sulfur acid (H2SO4) catalysts. Moreover, the LGO yield was quantitatively determined. The results indicated that the magnetic SO42−/TiO2–Fe3O4 was effective to selectively produce LGO from both cellulose and poplar wood. Its catalytic capability was a little better than the non-magnetic SO42−/TiO2 and H3PO4, and much better than the H2SO4. The maximal LGO yields from both cellulose and poplar wood were obtained at 300°C with the feedstock/catalyst ratio of 1/1, reaching as high as 15.43wt% from cellulose and 7.06wt% from poplar wood, respectively.

Catalytic Fast Pyrolysis of Biomass Pretreated by Torrefaction with Varying Severity

Pretreatment of corncobs using torrefaction was performed in a tubular reactor with varying reaction temperature (210, 240, 270, or 300 °C) and residence time (20, 40, or 60 min). The torrefied corncobs were subsequently catalytically fast pyrolyzed over nanosized HZSM-5 in a semibatch pyroprobe reactor. The torrefied corncobs were characterized by elemental analysis, thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (FTIR), and FTIR. The aromatic production was online analyzed by gas chromatography mass spectroscopy. The effect of torrefaction severity on product distribution and aromatic selectivity from catalytic fast pyrolysis of torrefied corncobs was investigated. The experimental results show that torrefaction can serve as an effective thermal pretreatment for improving the selectivity of BTX (benzene, toluene, and xylenes). Light and mild torrefaction (torrefaction at 210 and 240 °C) has little impact on the aromatic yield. However, severe torrefaction (torrefaction at 270 or 300 °C) can lead to the sharp increase of coke yield and reduction of aromatic yield. The results could be explained by the serious cross-linking and charring of corncob under severe torrefaction conditions. The optimal torrefaction condition is 210–240 °C with residence time of 40 min.

A review on ex situ catalytic fast pyrolysis of biomass

Catalytic fast pyrolysis (CFP) is deemed as the most promising way to convert biomass to transportation fuels or value added chemicals. Most works in literature so far have focused on the in situ CFP where the catalysts are packed or co-fed with the feedstock in the pyrolysis reactor. However, the ex situ CFP with catalysts separated from the pyrolyzer has attracted more and more attentions due to its unique advantages of individually optimizing the pyrolysis conditions and catalyst performances. This review compares the differences between the in situ and ex situ CFP operation, and summarizes the development and progress of ex situ CFP applications, including the rationale and performances of different catalysts, and the choices of suitable ex situ reactor systems. Due to the complex composition of bio-oil, no single approach was believed to be able to solve the problems completely among all those existing technologies. With the increased understanding of catalyst performances and reaction process, the recent trend toward an integration of biomass or bio-oil fractionation with subsequent thermo/biochemical conversion routes is also discussed.

Hydrogen production via catalytic pyrolysis of biomass in a two-stage fixed bed reactor system

This study introduces an innovative process of generating hydrogen-rich gas from biomass through the catalytic pyrolysis of biomass in a two-stage fixed bed reactor system. Water hyacinth was used as the biomass feedstock. The effects of various factors such as pyrolysis temperature, catalytic bed temperature, residence time, catalyst, and the nickel content of the catalyst on the pyrolysis productivity were investigated and the yields of H2, CO, CH4, and CO2 were obtained. Results showed that the high productivity of hydrogen can be obtained particularly by increasing the catalytic bed temperature, residence time, and catalysts. The favorable reaction conditions are as follows: a first-stage pyrolysis temperature of 650 °C–700 °C, a second-stage catalytic bed temperature of 800 °C, a catalytic pyrolysis reaction time of 17 min, and a nickel content of 9% (wt %).

Catalytic Pyrolysis of Biomass with Fe/La/SBA-15 Catalyst using TGA–FTIR Analysis

Biomass pyrolysis or gasification can convert low-energy density biomass into a high-energy density gaseous fuel. In this paper, pyrolysis of pine sawdust with and without the addition of a catalyst was investigated using a thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TGA-FTIR). The effects of modified SBA-15 catalysts on the formation characteristics of CO, CO2, and CH4 were studied. The two prepared catalysts, La/SBA-15 and Fe/La/SBA-15, retained the hexagonal order of the SBA-15 material and showed high thermal stability in the temperature range of the TGA-FTIR experiments. The results showed that the pyrolysis behavior of biomass is remarkably improved in the presence of La/SBA-15 and Fe/La/SBA-15 catalysts. The modified SBA-15 materials favored thermal cracking of macromolecular substances, resulting in an apparent decrease in the tar and coke fraction, an increase in the yield of light gases, and much higher gas production. Meanwhile, a significant increase in CH4 led to a much higher energy density gaseous product.

High quality bio-oil from catalytic flash pyrolysis of lignocellulosic biomass over alumina-supported sodium carbonate

Performance of a novel alumina-supported sodium carbonate catalyst was studied to produce a valuable bio-oil from catalytic flash pyrolysis of lignocellulosic biomass. Post treatment of biomass pyrolysis vapor was investigated in a catalyst fixed bed reactor at the downstream of the pyrolysis reactor. In-situ catalytic upgrading of biomass pyrolysis vapor was conducted in an entrained flow pyrolysis reactor by feeding a premixed feedstock of the catalyst and biomass. Na2CO3/γ-Al2O3 was very effective for de-oxygenation of the pyrolysis liquid and oxygen content of the bio-oil was decreased from 47.5wt.% to 16.4wt.%. An organic rich bio-oil was obtained with 5.8wt.% water content and a higher heating value of 36.1MJ/kg. Carboxylic acids were completely removed and the bio-oil had almost a neutral pH. This bio-oil of high calorific low, low water and oxygen content may be an attractive fuel precursor. In-situ catalytic upgrading of biomass pyrolysis vapor produced a very similar quality bio-oil compared to post treatment of pyrolysis vapors, and shows the possible application of Na2CO3/γ-Al2O3 in a commercial type reactor system such as a fluidized bed reactor.

Selective Production of Phenolic-rich Bio-oil from Catalytic Fast Pyrolysis of Biomass: Comparison of K3PO4, K2HPO4, and KH2PO4

Phenolic-rich bio-oil can be selectively produced from catalytic fast pyrolysis of biomass impregnated with K3PO4, K2HPO4, or KH2PO4. In this study, the catalytic effects of the three catalysts on the pyrolytic product distribution were investigated and compared via analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments. The results indicated that the three catalysts were all able to inhibit the pyrolytic decomposition of holocellulose to form volatile organic products, while promoting the formation of phenolic compounds from lignin. Hence, phenolic-rich bio-oil could be selectively produced. Among the three catalysts, K3PO4 and K2HPO4 possessed similar capability to increase the yield of the phenolics, which was better than KH2PO4. The phenolic contents among the total pyrolytic products steadily increased as the K3PO4 or K2HPO4 dosage increased. The maximal peak area of the phenolics reached as high as 68.8% (at 50 wt.% K3PO4) or 50.6% (at 50 wt.% K2HPO4) of the total peak area. Therefore, based on these results, K3PO4 was the best catalyst for the selective production of phenolic-rich bio-oil.

Study on Pyrolysis of Pine Sawdust with Solid Base and Acid Mixed Catalysts by Thermogravimetry–Fourier Transform Infrared Spectroscopy and Pyrolysis–Gas Chromatography/Mass Spectrometry

Catalytic fast pyrolysis of biomass with microporous ZSM-5 to produce aromatics is a promising technology for biomass use. To improve the aromatic yield, meso- and macroporous [CaO, MgO, and fluidized catalytic cracking (FCC)] catalysts were added in a microporous catalyst (ZSM-5). The added catalysts can crack large-molecule oxygenates from pyrolysis into small-molecule oxygenates, and then these small-molecule oxygenates were converted to aromatics over ZSM-5. The experiments of pine wood catalytic pyrolysis with two mixed catalysts were performed and analyzed using thermogravimetry–Fourier transform infrared spectroscopy (TG–FTIR) and pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). The TG–FTIR results show that CaO and ZSM-5 mixed catalysts produced more aromatic rings and C–H bonds than pure ZSM-5. The Py–GC/MS results show that CaO and MgO mixed with ZSM-5 improved the aromatic yield significantly. The maximum aromatic yield that boosted 30% of that with pure ZSM-5 was obtained with CaO as the additive. It was obtained with a biomass/CaO/ZSM-5 mass ratio of 1:4:4. According to the disposal mode of feedstock and two catalyst studies, the completely separated mode of feedstock, CaO, and ZSM-5 (mode 3) produced the highest yield of indene and its derivatives and other hydrocarbons. This paper provides a simple way to improve the aromatic yield from biomass catalytic pyrolysis.

Aromatic hydrocarbons production from ex situ catalysis of pyrolysis vapor over Zinc modified ZSM-5 in a packed-bed catalysis coupled with microwave pyrolysis reactor

Ex situ catalytic pyrolysis of biomass through a packed-bed catalysis close coupled with microwave pyrolysis was investigated to convert Douglas fir sawdust pellets to aromatic hydrocarbons by Zn/ZSM-5 catalyst. A comparison test from five different Zn loadings (0, 0.5, 1, 2, 5wt.%) was first conducted, and it was found that the highest amount of aromatic hydrocarbons was produced from 0.5% Zn loaded on ZSM-5. Then a central composite experimental design (CCD) was used to optimize the upgraded bio-oil and syngas yields with 0.5% Zn loaded in ZSM-5. In comparison to the non-catalytic experiment, all the catalysts decreased the bio-oil yield and increased the syngas production. The product yields from Zn/ZSM-5 were sensitive with reaction conditions as the bio-oil yields varied between 22.3% and 44.8% compared with 32.2% and 37.8% over ZSM-5 catalyst, and syngas yields from 33.3% to 55.5% vs. 38.8% to 43.7% on ZSM-5 catalyst. GC/MS analysis showed that aromatic hydrocarbons become the most abundant compounds in the bio-oil. The high amount of aromatic hydrocarbons in the upgraded bio-oils from GC/MS analysis was confirmed by the FTIR analysis. The aromatic hydrocarbon was increased when the packed-bed temperature and inverse weight hourly space velocity (WHSV)−1 were increased. The comparison of coking on ZSM-5 and Zn/ZSM-5 catalysts at different reaction conditions showed that the coking increased with increasing (WHSV)−1 and decreasing packed-bed temperatures. Zn/ZSM-5 had lower coking than ZSM-5 on all the reaction conditions except packed-bed temperature at 269°C and (WHSV)−1 at 0.048.

Catalytic pyrolysis of wood biomass in an auger reactor using calcium-based catalysts.

Wood catalytic pyrolysis using calcium-based materials was studied in an auger reactor at 450°C. Two different catalysts, CaO and CaO·MgO were evaluated and upgraded bio-oils were obtained in both cases. Whilst acidity and oxygen content remarkable decrease, both pH and calorific value increase with respect to the non-catalytic test. Upgrading process was linked to the fact that calcium-based materials could not only fix the CO2-like compounds but also promoted the dehydration reactions. In addition, process simulation demonstrated that the addition of these catalysts, especially CaO, could favour the energetic integration since a lowest circulation of heat carrier between combustor and auger reactor should be needed. An energy self-sustained system was obtained where thermal energy required for biomass drying and for pyrolysis reaction was supplied by non-condensable gas and char combustion, respectively.

Production of Phenolic Compounds from Low Temperature Catalytic Fast Pyrolysis of Biomass with Activated Carbon

Activated carbon (AC) was reported as a promising catalyst to selectively produce phenolic compounds from biomass using the micro-wave assisted catalytic pyrolysis technique. In order to evaluate the catalytic performance of the AC under the traditional fast pyrolysis process, analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) technique was applied for the catalytic fast pyrolysis of biomass mixed with the AC. Polar wood was selected as the feedstock, and experiments were conducted to reveal the AC-catalyzed poplar wood pyrolysis behavior and product distribution. The results indicated that the AC was also effective for the phenolics production in the traditional fast pyrolysis process at 350 °C. It could promote the formation of phenolic compounds, and inhibit most of the other pyrolytic products. The maximal phenolics yield was obtained at the biomass to catalyst ratio of 1:4, with the peak area% over 50%.

Catalytic Co-pyrolysis of Biomass and Different Plastics (Polyethylene, Polypropylene, and Polystyrene) To Improve Hydrocarbon Yield in a Fluidized-Bed Reactor

Biomass catalytic fast pyrolysis can produce aromatics and olefins, which are used as petrochemicals. However, the yields of aromatics and olefins are still very low. In this work, catalytic co-pyrolysis of pine sawdust and plastics (polyethylene, polypropylene, and polystyrene) was conducted in a fluidized-bed reactor to improve the yields of aromatics and olefins. The effects of different temperatures, polyethylene/pine sawdust ratios, different catalysts, and plastics on the product distributions were studied. The results show there are some positive synergistic effects between the two feedstocks. The maximum carbon yield of petrochemicals (71%) was obtained at 600 °C with a spent fluidized catalytic cracking (FCC) catalyst and polyethylene/pine sawdust ratio of 4:1. LOSA-1 presents better catalytic performances than Al2O3 and spent FCC catalysts. The petrochemical carbon yield with LOSA-1 is almost 2 times that without catalyst. Catalytic co-pyrolysis of polystyrene and pine sawdust produced the highest and lowest yields of aromatics (47%) and olefins (11.4%), respectively.

Effect of zeolite to binder ratio on product yields and composition during catalytic steam pyrolysis of biomass over transition metal modified HZSM5

Catalytic pyrolysis of biomass over metal modified zeolites (multifunctional catalysts) is a very promising route for production of hydrocarbons and less oxygenated liquid feedstock suitable for fuels and/or chemicals. In this work the effect of zeolite to binder ratio (Z/B) of a metal modified HZSM5, on products yields and composition during steam pyrolysis of biomass has been investigated. Increased zeolite content resulted in lower liquid yield and increased coke formation; however, more deoxygenated liquids obtained at higher zeolite loadings. Char yield is not significantly affected by the zeolite content. Declining catalytic activity is observed at longer time on stream because of coke deposition. While acidic function of the catalyst deoxygenates carboxylic acids and carbonyls, metal functions seem to selectively convert phenols and methoxy phenols. Competitive steam adsorption on the acid sites of the zeolite seems to lower the conversion to aromatics. The high availability of acid sites, at higher zeolite loading, increases aromatics concentration exponentially. Increased yields of hydrogenated products have been obtained indicating that the Ni–V/HZSM5 catalyst exhibits some hydrogenation activity.

Catalytic fast pyrolysis of lignocellulosic biomass in a process development unit with continual catalyst addition and removal

Catalytic fast pyrolysis (CFP) of wood was studied using a spray-dried ZSM-5 catalyst in a process development unit (PDU) consisting of a bubbling fluidized bed reactor with on-stream particle input and output. The PDU was capable of maintaining constant product yield of aromatics over an extended reaction period (6h) with continuous catalyst addition and removal. The yields and selectivity for aromatics and olefins were dependent on temperature, biomass weight hourly space velocity (WHSV), catalyst to biomass ratio, fluidization gas velocity, and catalyst bed weight. The overall aromatic yield increased up to 15.5 carbon% with decreasing gas velocities due to the increased vapor residence time and the improved mass transfer from smaller bubble sizes. A simulated recycle stream of CFP product gases consisting of CO, CO2 and olefins was used to test the viability of subsequent olefin aromatization in the presence of CO and CO2. Olefins were converted into additional aromatics while CO and CO2 remained inert during CFP. The spray-dried ZSM-5 catalyst was stable in a series of 30 reaction/regeneration cycles.

Hydrocarbon and hydrogen-rich syngas production by biomass catalytic pyrolysis and bio-oil upgrading over biochar catalysts

A renewable biochar catalyst was developed with high porosity, high surface area, high minerals and surface functional groups. It enhanced hydrogen (27.02 vol% in syngas) and hydrocarbons (42.56 area% in upgraded bio-oil) production in biomass catalytic pyrolysis and bio-oil upgrading. The biochar catalysts had good thermal stability and durability with less coking according to the thermal gravimetric (TG) analysis.

Catalytic Pyrolysis of Microcrystalline Cellulose with Five Molecular Sieve Based Catalysts in Py-GC-MS

Catalytic pyrolysis of biomass has the potential to produce bio-oil , which is rich in aromatic hydrocarbons and can be used as transportation fuel. In this paper, microcrystalline cellulose were pyrolysis with HZSM-5(Si/Al=25), HZSM-5(Si/Al=50), HZSM-5(Si/Al=100), HY, Hβin a CDS5200 pyroprobe at temperature ranging from 450-650̊C. GC-MS is used to analyze the liquid product in the catalytic pyrolysis. Except the catalysts and pyrolysis temperature, this work also evaluated the influences of heating rate, catalyst-to-biomass ratios on the production yield of aromatic hydrocarbons and product distribution. HZSM-5(Si/Al=50) has the highest yield among the five catalysts. Catalytic pyrolysis at 500̊C、20K/ms heating rate and 5:1catalyst to biomass ratio is most suitable to produce aromatic hydrocarbons. Benzene, toluene, xylene and naphthalene are the main aromatic hydrocarbon products in catalytic pyrolysis of microcrystalline cellulose.