Biomass Pyrolysis Volatiles Research Articles

Electrified catalytic steam reforming for renewable syngas production: Experimental demonstration, process development and techno-economic analysis

Biomass is a key renewable feedstock for producing green fuels; however, renewable feedstock presents a high risk for catalyst deactivation and poor stability. In addition, the heat source of industrial reforming processes comes from fuel combustion and most heat is lost in the flue gas. In this study, a Ni/Al2O3/FeCrAl-based monolithic catalyst with a periodic open cellular structure (POCS) was designed and 3D-printed. A reforming process was then conducted by directly heating the catalyst using electricity instead of fuel combustion. This e-reformer technology was demonstrated in continuous catalytic steam reforming of biomass pyrolysis volatiles. A high H2 yield of ≈7.1 wt % of biomass has been obtained at a steam-to-biomass (S/B) ratio of 4.5, reforming temperature of 800 °C and weight hourly space velocity (WHSV) of 310 h−1, resulting in an energy consumption of 8 kWhel kg−1 biomass (66% energy efficiency). The results show a successful demonstration of the electrified technology with improvement potential; in addition, a process was designed and assessed economically for synthetic natural gas (SNG) production of 80 MWHHV, comparing electrification and partial oxidation in different scenarios.

Catalytic conversion of biomass pyrolysis volatiles over composite catalysts of activated carbon and HY zeolite

Bio-oil has complex compositions and high oxygen content, which restricts its high-value utilization. Commercial activated carbon (AC) and HY zeolite were used as composite catalysts to study their effect on pyrolysis volatiles from rice straw and poplar sawdust by changing the mixing modes of two catalysts. The results showed that the loading modes of AC and HY zeolite obviously affected the products distribution and bio-oil components. The lowest yield of bio-oil was obtained when HY zeolite and AC were mechanically mixed at a mass ratio of 1:1 (YACM). But the loading mode of YACM was beneficial to the deoxidation and aromatic hydrocarbon generation. Under the mode of YACM, the aromatics content in rice straw and poplar sawdust bio-oil can be increased from 13.8% and 8.0% without catalyst to 56.4% and 53.1%, respectively. However, the layered loading with upper HY zeolite and lower AC (YTACL) was favorable for formation of phenolic compounds. The selectivity to monocyclic and bicyclic aromatic hydrocarbons followed the order of YTACL > ACTYL > YACM, and YACM > ACTYL > YTACL, respectively. Compared with HY zeolite, AC catalyst possessed smaller pore size and fewer acidity, and the active sites of AC were conducive to rearrangement of furan compounds to generate cyclopentanone, 2-cyclopentenone and methyl-cyclopentenone, and further rearrangement to form phenol. Therefore, the loading mode of YTACL exhibited a promotion effect on the formation of phenol, cresol, toluene, ethylbenzene and p-xylene. The strong acidic sites of HY zeolite were favorable for the aromatization, so the loading mode of ACTYL had good selectivity to the formation of naphthalene, methylnaphthalene, anthracene and pyrene. This work will provide a guide for products regulation from biomass pyrolysis and enrich aromatics and phenols in bio-oil.

Performance evaluation of carbon-negative syngas production via chemical looping reforming of methane from biomass pyrolysis volatiles

To realize the clean and efficient directional conversion of biomass, chemical looping reforming of biomass volatile CH4 based on a decoupling strategy is expected to carry out carbon-negative production of hydrogen-rich syngas. In this paper, a multi-functional oxygen carrier (NiFe2O4@SBA-16) for encapsulating the active metal oxide component NiFe2O4 with a three-dimensional interconnecting pore molecular sieve SBA-16 was designed. The experimental results showed that the modification strategy of composite metal oxide encapsulation improved syngas selectivity and CH4 conversion based on the fixed-bed reactor. 20 %NiFe2O4@SBA-16 showed 22.1 % CH4 conversion and 92.6 % CO selectivity under 750 °C, and it maintained good cycle stability after 15 cycles. The H2/CO ratio was effectively improved by adding part of CO2 into the feed gas, and the CH4 conversion reached over 35 %. This study provides essential data for the clean preparation of hydrogen-rich syngas from biomass and the development and design of multifunctional oxygen carriers.

Char-based Fe-Ni-Ca material for capturing AAEM from biomass pyrolysis volatiles and recyclability in catalytic reforming of volatiles

Hydrogen production derived from biomass catalytic pyrolysis has received increasing attention, to solve the excessive consumption of renewable energy. However, considerable amounts of the issues (e.g., slag formation, corrosion, and scaling on the heat exchange surface) related to alkali and alkali earth metals (AAEM) have hindered its application. To address these challenges and improve the yield of H2, char-based Fe-Ni-Ca material is proposed to capture AAEM from biomass pyrolysis volatiles while increasing the H2. Char-based materials exhibit excellent AAEM capture ability, with K, Na, and Mg contents detected in spent materials being 3.4 times, 1.4 times, and 1.5 times higher than those in fresh, respectively. Besides, the spent Fe-Ni-Ca exhibits excellent stability after regeneration, with H2 production comparable to that of fresh material, and CO production exceeding that of fresh Fe-Ni-Ca. It was disclosed that the char support can adsorb AAEM in volatiles, and then chemical reactions will occur between metal elements (Fe, Ni, and Ca) in the material and AAEM in the volatiles, trapping AAEM in the material and catalytic reforming volatiles. This work provides a novel strategy to deal with AAEM in volatiles.

Improving the Quality of Bio-oil Using the Interaction of Plastics and Biomass through Copyrolysis Coupled with Nonthermal Plasma Processing.

Bio-oil produced from the pyrolysis of biomass is chemically complex, viscous, highly acidic, and highly oxygenated. Copyrolysis of biomass and plastics can enhance oil quality by raising the H/C ratio, leading to improved biofuel properties. In this work, copyrolysis of polystyrene and biomass was passed to a second-stage dielectric barrier discharge nonthermal plasma reactor with the aim to further improve the product bio-oil. Pyrolysis of the polystyrene and biomass produces volatiles that pass to the second stage to undergo cracking and autohydrogenation reactions under nonthermal plasma conditions. There was a synergistic interaction between biomass and polystyrene in terms of overall oil and gas yield and composition even in the absence of the nonthermal plasma. However, the introduction of the nonthermal plasma produced a marked increase in monocyclic aromatic hydrocarbons (e.g., ethylbenzene), whereas polycyclic aromatic compounds decreased in concentration. Most notably, the influence of the plasma markedly reduced the quantity of oxygenated compounds in the product oil. It is suggested that the unique reactive environment produced by the plasma involving high-energy electrons, excited radicals, ions, and intermediates increases the interaction of the polystyrene and biomass pyrolysis volatiles. Increasing input plasma power from 50 to 70 W further enhanced the effects of the nonthermal plasma.

Mechanisms of catalytic reforming of biomass pyrolysis volatiles by Ce promoted Fe–Ni/biochar under N2 and steam atmosphere

In this work, the promotion mechanism of Ce as Fe and Ni catalyst promoter for the catalytic reforming of biomass pyrolysis volatiles was investigated. Fe–Ni–Ce/biochar catalysts were prepared and evaluated for their catalytic performance under N2 and steam atmospheres. The yield of Fe–Ni–Ce/biochar catalyzed syngas (H2+CO) increased from 224.36 mL/g to 1299.14 mL/g (800 °C) with the change of N2 to steam atmosphere. The addition of Ce can introduce a large number of oxygen vacancies to the catalyst, and the increase of oxygen vacancies reduces the reaction barrier of the tar, thus promoting the catalytic activity of the catalyst. In the N2 atmosphere, the electron transfer of Ce3+ ⇄ Ce4+ during catalytic process promotes the production of Fe2+ to ensure the catalytic activity of the catalyst. In the steam atmosphere, Ni will activate the active sites in a steam atmosphere in water molecules. The activated active sites increase the catalyst activity by cyclic reaction with the oxygen vacancies introduced by Ce, resulting in a higher catalytic capacity of Fe–Ni/biochar than Fe–Ce/biochar. To provide the theoretical basis for the preparation of efficient catalysts based on Fe and Ni.

Ex-situ catalytic upgrading of biomass pyrolysis volatiles over thermal-decomposition products of spent lithium-ion batteries for bio-oil deoxygenation and hydrogen-rich syngas production

Spent lithium-ion batteries rich in transition metals are highly potential to catalyze the biomass pyrolysis process. This research provided insight into the performance and mechanism of ex-situ catalytic upgrading of biomass pyrolysis volatiles over the thermally pyrolyzed spent Ni–Co–Mn ternary batteries (PyNCM) for the first time. The results showed that the PyNCM exhibited high catalytic activities for the secondary decompositions of pyrolysis volatiles, resulting in 12.6% reduction on bio-oil yield and 57.5% promotion on syngas productivity. The magnetic Ni and Co compounds in PyNCM were primarily responsible for the enhanced volatile deoxygenations, and the maximum H2 yield reached 2.66 mmol g−1 biomass. Two levels of synergistic catalysis were identified: (1) the synergy among the transition metals established multiple active centers to promote the H2 selectivity; (2) the non-magnetic graphite and lithium could probably improve the dispersion and surface oxygen vacancies of nickel and cobalt to further enhance the catalytic activity.

Study on the regeneration characteristics of Fe-Ni-Ca/Al2O3 catalyst in the reforming process of biomass pyrolysis volatiles

The activity and stability of polymetallic catalysts during the regeneration cycle were investigated in a fixed bed reactor on a laboratory scale, and the catalysts were characterized by various characterization methods. The results show that the activity and stability of the recycled catalyst are higher than that of the regenerated catalyst, which is related to the structural changes of the regenerated catalyst by XRD and Raman characterization. The Fe-Ni-Ca/Al2O3 catalyst shows good performance in recycling, which provides a theoretical basis for the application of the catalyst in industry.

Elucidating coke formation and evolution in the catalytic steam reforming of biomass pyrolysis volatiles at different fixed bed locations

Elucidating coke formation and evolution in the catalytic steam reforming of biomass pyrolysis volatiles at different fixed bed locations

Advanced application of a geometry-enhanced 3D-printed catalytic reformer for syngas production

Catalyst research on reforming processes for syngas production has mainly focused on the active metals and support materials, while the effect of the catalyst’s geometry on the reforming reactions has been poorly studied. The application of 3D-printed materials with enhanced geometries has recently started to be studied in heterogeneous catalysis and is of interest to be implemented for reforming biomass and plastic waste to produce H2-rich syngas. In this study, a geometry-enhanced 3D-printed Ni/Al2O3/FeCrAl-based monolithic catalyst with a periodic open cellular structure (POCS) was designed and fabricated. The catalyst was used for batch steam reforming biomass pyrolysis volatiles for syngas production at different parameters (temperature and steam-to-carbon ratio). The results showed complete reforming of pyrolysis volatiles in all experimental cases, a high H2 yield of ≈ 7.6 wt% of biomass was obtained at the optimized steam-to-carbon ratio of 8 and a reforming temperature of 800 °C, which is a higher yield compared to other batch reforming tests reported in the literature. Moreover, CFD simulation results in COMSOL Multiphysics demonstrated that the POCS configuration improves the reforming of pyrolysis volatiles for tar/bio-oil reforming and H2 production thanks to enhanced mass and heat transfer properties compared to the regular monolithic single-channel configuration.

Chemical looping reforming characteristics of methane and toluene from biomass pyrolysis volatiles based on decoupling strategy: Embedding NiFe2O4 in SBA-15 as an oxygen carrier

To realize the directional conversion of biomass to produce hydrogen-rich syngas, biomass gasification with a complex reaction system was decoupled into two sub-processes. NiFe2O4@SBA-15 was prepared by an embedding strategy via the impregnation method to achieve high reactivity during the volatile chemical looping reforming process. The chemical looping reforming of methane and toluene was investigated based on a fixed-bed reactor and on-line mass spectrometry and gas chromatography. It was found that the selectivity and conversion were improved after embedding, and the conversion of toluene reached 97.5 % at 750 °C. The NiFe2O4@SBA-15 maintained good stability after 15 cycles, and the reaction performance had not obviously decreased. Real-time reaction performance showed that the conversion of lattice oxygen could reach 100% above 750 °C. The reaction system belonged to the phase boundary-controlled mechanism based on the conversion of lattice oxygen, and the activation energy was 43.10 kJ·mol−1. In addition, in-situ diffuse reflectance infrared spectroscopy(DRIFTS) study had shown that the dissociation of methane and toluene and the further conversion of formate might be the reaction rate-limiting steps. Although methane and toluene competed in adsorption, the reaction processes were independent.

Insight into the biomass pyrolysis volatiles reaction with an iron-based oxygen carrier in a two-stage fixed-bed reactor

The reaction between biomass pyrolysis volatiles and oxygen carrier (OC) is a non-negligible issue in the chemical looping combustion or chemical looping reforming of pyrolysis gas. This study systematically investigated the reaction characteristic of biomass pyrolysis volatiles with iron-based oxygen carriers, aiming to produce hydrogen by chemical looping reforming of pyrolysis gas. This work also examined the evolution of three-phase product distribution (carbon deposition, tar, and gas), which was generated through the reaction between biomass pyrolysis volatiles and an iron-based oxygen carrier. The results indicate that increasing the amount of oxygen carrier and temperature facilitated the tar conversion into more gas and less deposited carbon. The low valent state of Fe promotes tar cracking, decreasing tar content while increasing carbon deposition. Moreover, an increase in OC usage formed more naphthalene in tar, which gets much more pronounced with the low valent state of iron oxides. The consumption of CO in the biomass volatile matter (VM) reforming reaction is significant, and the carbon in tar is mainly transformed into CO2. The tar conversion with biomass VM produces less carbon deposition and higher gas yield than coal VM due to large amounts of light tar. The concentration of reducing gas is sufficient to reduce Fe2O3 to FeO, which is essential for the chemical looping hydrogen generation.

Catalytic mechanism of N-containing biochar on volatile-biochar interaction for the same origin pyrolysis

Nitrogen, as a common element, is widely present in biomass. The effects of nitrogenous substances on the same origin pyrolysis of biomass and the consequences of N-containing biochar on the catalytic process of volatiles are important for further analyzing the pyrolysis mechanism of biomass. In this research, N-containing biochar was prepared under different conditions, and the interaction between N-containing biochar and biomass pyrolysis volatiles at 400–700 °C was studied. The results show that N-containing biochar can simultaneously participate in reactions as adsorbents, catalysts, and reactants. Its catalytic effect is obviously different for various N configurations. Pyridinic N and pyrrolic N can promote the cracking of lignin into methoxy phenol compounds and promote the further cracking of 5-hydroxymethylfurfural. Graphitic N and oxidized N can promote the further decomposition of phenol and the conversion of D-xylose into small-molecule ketones. In addition, oxidized N can also inhibit the cracking of lignin to produce guaiacol. In the long-term interaction, the highly active pyridinic N tends to convert to a more stable graphitic N.

Elucidating Coke Formation and Evolution in the Catalytic Steam Reforming of Biomass Pyrolysis Volatiles at Different Fixed Bed Locations

Elucidating Coke Formation and Evolution in the Catalytic Steam Reforming of Biomass Pyrolysis Volatiles at Different Fixed Bed Locations

Direct synthesis of methane-rich gas from reed biomass pyrolysis volatiles over its biochar-supported Ni catalysts

Thermochemical conversion of biomass into methane is a promising way for bioenergy recovery and alleviate natural gas shortage; however, the available technologies are queried by the complex procedures. This paper proposed a new approach for the direct synthesis of methane-rich gases from reed pyrolysis volatile at atmospheric pressure, according to which the reed pyrolysis volatiles are catalyzed over reed biochar-supported Ni catalysts in two stages to be converted. Seawater and freshwater reeds were compared for preparing effective catalysts, and the influences of inorganic salts in reed biomass on the catalytic performance were explored. The reed biochar-supported Ni catalysts were also compared with γ-Al2O3-supported Ni catalyst (Ni/γ-Al2O3) to evaluate their activities. It has been found that freshwater reed biochar-supported Ni catalysts (Ni/FWBs) performed better than seawater reed biochar-supported catalysts (Ni/SWBs) and Ni/γ-Al2O3 owing to their large specific surface areas, uniform Ni particle dispersions, and appropriate Ni/biochar interactions. The Ni/FWB with biochar support produced at 600 °C (Ni/600FWB) was the best, and its corresponded tar-free gas product was characterized by a methane yield of 188.38 L/kg reed after two-stage catalytic conversion. The SWBs with higher alkali metal contents corresponded to larger Ni loading amounts than that of FWBs under the same conditions; however, they suffered from Ni particle aggregation and fusion, which deteriorated their catalytic activities. The findings indicated that the inexpensive Ni/FWBs were effective for the direct synthesis of methane from biomass pyrolysis volatiles, and the approach developed in this study provides an alternative to produce methane from biomass economically.

Synthesis and characterization of different activated biochar catalysts for removal of biomass pyrolysis tar

The use of low-cost and high-efficiency catalysts is a promising approach to remove tar and increase the gas yield in the catalytic reforming of biomass pyrolysis volatiles. In this study, using rice husk biochar (RHC) as a precursor, four typical activated biochar catalysts were prepared using both chemical (H3PO4 and KOH) and physical (CO2 and H2O) activators. The experiments demonstrated that high surface areas were obtained upon activation. The chemical activators introduced inorganic elements in the biochar, while physical activators were beneficial to the formation of high micropore volume. The effects of varying the catalyst type, catalyst to feedstock ratio, and catalytic cracking temperature on the tar decomposition efficiency and gas yield were studied. The results showed that maximum tar decomposition efficiency (91.75%) and gas yield (704.85 mL/g) were achieved using the RHC-KOH catalyst at a catalytic cracking temperature of 800 °C and a catalyst to feedstock ratio of 2:1. The introduction of the catalysts changed the gas composition, and the yield of H2/CO increased significantly. The increase in catalytic cracking temperature promoted the secondary cracking reaction of tar and the biochar self-gasification reaction in addition to facilitating the cyclopolymerization of some tar components.

Coking behavior and syngas composition of the char supported Fe catalyst of biomass pyrolysis volatiles reforming

The biomass for flammable gas production and its carbon deposition behaviour has been studied in a lab-scale fixed bed reactor, comprising pyrolysis and subsequent volatiles reforming produced in situ reaction. The distribution of pyrolysis products varies greatly with the addition of WS@5 Fe catalyst. During catalyst cycle process, both the char and heavy oil yield decreases significantly from 27.34% and 6.73% to 20.41% and 4.12%, respectively. This work also focuses on the carbon deposition of the WS@5 Fe catalyst used in the second step. The amount of coke on quartz tube wall (coke 1) decrease with increasing the temperature, and the surface carbon of the catalyst (coke 2) is found. Deactivated catalyst samples are recovered. The results present that the deactivation is attributed to the wrapping and covering of Fe by coke. There are reactions such as the coke deposition, the coke consumption, and the gasification reaction of char.

CeO2 and La2O3 Promoters in the Steam Reforming of Polyolefinic Waste Plastic Pyrolysis Volatiles on Ni-Based Catalysts

Based on the promising results of La2O3- and CeO2-promoted Ni/Al2O3 catalysts in the reforming of biomass pyrolysis volatiles, the performance of these catalysts and the non-promoted one was evalua...

The deterioration of bio-oil and catalyst during the catalytic upgrading of biomass pyrolysis volatiles

ABSTRACT The tin (Sn)-modified HZSM-5 was employed to upgrade biomass pyrolysis volatiles to prepare bio-oil, and the deterioration of bio-oil and catalyst was focused. A new parameter indicating the physicochemical properties was defined as the comprehensive fuel-grade index (CFI). The catalyst initially demonstrated the better performance to transform oxygen-containing organics to hydrocarbons; consequently, the bio-oil had a higher CFI value. The fresh catalyst produced 33.43% of bio-oil with the higher hydrocarbon content of 41.60%, and the proportions of monocyclic aromatic hydrocarbons (MAHs) and light aliphatic hydrocarbons (LAHs) reached 74.59% and 20.02%, respectively. However, with the extension of catalyst using-time, the obvious decrease of hydrocarbons caused the significant decrease of CFI. Furthermore, the cracking and reforming diffusion performance supported by the acid and textural properties of the catalyst deteriorated severely, which contributed to the proportion increase of polycyclic aromatic hydrocarbons (PAHs). The decrease of the acid and textural properties were attributed to the coke generated and deposited into the pores and on the surface of the catalyst. The deposited cokes could be divided into two types including semihydrogenated coke and carbonaceous coke, and the former was the main one. The carbonaceous coke was formed in the initial stage of catalytic reaction, gradually inducing more precursors to cover active sites and block pores, and then generated more semihydrogenated coke, eventually causing the catalyst performance deterioration. This study provided an insight for improving sustainability in terms of understanding process deterioration.

Assessment of product yields and catalyst deactivation in fixed and fluidized bed reactors in the steam reforming of biomass pyrolysis volatiles

The performance of fixed and fluidized bed reactors in the steam reforming of biomass fast pyrolysis volatiles was compared, with especial attention paying to the differences observed in catalysts deactivation. The experiments were carried out in continuous regime in a bench scale unit provided with a conical spouted bed for the pyrolysis step. They were carried out on a Ni-Ca/Al2O3 commercial catalyst and under optimum conditions determined in previous studies, i.e., pyrolysis temperature 500 °C, reforming temperature 600 °C and a steam/biomass ratio of 4. Moreover, the influence of space time was analysed in both reforming reactors. The fixed bed reactor showed higher initial conversion and H2 yield, as it allowed attaining a H2 yield higher than 90 % with a space time of 10 gcat min gvolatiles−1. However, a space time of 15 gcat min gvolatiles−1 was required in the fluidized bed to obtain a similar H2 yield. Moreover, the fixed bed also led to lower catalyst deactivation. Catalyst deactivation was mainly related to coke deposition, and higher coke contents were observed in the catalysts used in the fluidized bed reactor (1.2 mgcoke gcat−1 gbiomass−1) than those in the fixed bed one (0.6 mgcoke gcat−1 gbiomass−1). Therefore, the differences in the performance of the two reactors were analysed and their practical interest was discussed.