Rapid consumption of petroleum and concerns about carbon emissions have promoted utilization of renewable energy such as biomass. Pyrolysis of biomass is one of effective sustainable routes for ...aromatic hydrocarbons production. However, it has not been applied commercially on a large scale. One of the biggest challenges is inferior characteristics of biomass, including complex crosslinking structure, high content of alkali and alkaline earth metals (AAEMs), and low hydrogen to carbon effective ratio (H/Ceff). Main objective of this review is to investigate main methods that enhance aromatic hydrocarbons production, while screening out option to maximize aromatic hydrocarbons production, taking economic analysis and technical application progress as a reference. Results show that pre enhancement methods including physical, thermal, chemical and biological biomass pretreatments are mainly used to break crosslinking structure and remove AAEMs. The most significantly influential factor limiting biomass conversion is low H/Ceff, and thus in-process enhancement methods including deoxidation via catalysis, and hydrogenation via co-pyrolysis and atmosphere regulation are more effective for improving aromatic hydrocarbons. Industrial problems, existed in co-pyrolysis (great characteristics differences, etc.) and atmosphere regulation (high investment cost, etc.), have not been solved yet. By comparison, development of catalysts is relatively mature, and there are successful commercial cases. Total production cost of catalytic pyrolysis of biomass is only 67% of petroleum refining route, showing best economic potential. Accurate design and construction of catalysts with high activity and long life based on biomass characteristics is the most feasible and promising development direction.
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•Biomass inferior properties affecting aromatics conversion by pyrolysis are given.•Physical, thermal, chemical and biological pretreatment enhancement is introduced.•Deoxidation enhancement via zeolites and modified zeolites catalysis is described.•Hydrogenation enhancement via co-pyrolysis and atmosphere regulation is described.•Optimization of key operational parameters during biomass pyrolysis is summarized.
•A newly developed continuous fast microwave-assisted pyrolysis system was used.•It is the first time to pyrolysis Camellia oleifera shell with microwave.•The effects of temperature and feed rate on ...pyrolysis were studied.
In this study, a continuous fast microwave-assisted pyrolysis system was developed to produce bio-oil, gas, and biochar from rice straw and Camellia oleifera shell. The effects of different pyrolysis temperatures (400 °C, 500 °C, and 600 °C) and feed rates (rice straw: 25, 45, and 66 g/min; C. oleifera shell: 100, 200, and 400 g/min) on bio-oil production were investigated. Experimental results showed that the yields of bio-oil (31.86 wt%) and gas (54.49 wt%) produced by the microwave-assisted pyrolysis of rice straw increased with increasing temperature. By contrast, the yields of bio-oil (27.45 wt%) and biochar (35.47 wt%) produced by the pyrolysis of C. oleifera shell decreased with increasing temperature. The contents of phenols, aldehydes, and alcohols in bio-oil produced from the shell were higher than those in bio-oil derived from rice straw.
With the advent of the era of big data, artificial intelligence has attracted continuous attention from all walks of life, and has been widely used in medical image analysis, molecular and material ...science, language recognition and other fields. As the basis of artificial intelligence, the research results of neural network are remarkable. However, due to the inherent defect that electrical signal is easily interfered and the processing speed is proportional to the energy loss, researchers have turned their attention to light, trying to build neural networks in the field of optics, making full use of the parallel processing ability of light to solve the problems of electronic neural networks. After continuous research and development, optical neural network has become the forefront of the world. Here, we mainly introduce the development of this field, summarize and compare some classical researches and algorithm theories, and look forward to the future of optical neural network.
•Fe modified bio-char catalyst was prepared from low-cost rich husk.•The yields and selectivities of phenol and cresol in bio-oil were significantly increased.•Catalyst deactivation and regenation ...tests were conducted to evaluate the lifetime of the catalyst.
Microwave-assisted catalytic pyrolysis of torrefied corn cob into phenol-rich bio-oil on Fe modified bio-char catalyst was investigated in this study. The well-developed surface pore was confirmed by scanning electronic microscope (SEM) images and nitrogen adsorption/desorption isotherms, indicating that the porous structure of bio-char depended on the Fe modification to a large extent. Temperature-programmed desorption of NH3 (NH3-TPD) analysis showed that the Fe modified bio-char catalyst mainly presented strong acid sites. The use of bio-char catalyst can decrease the bio-oil yield and increase the gas yield but the biochar did not experience any significant change because of the ex-situ catalysis mode. Catalytic pyrolysis of torrefied corn cob using Fe modified bio-char catalyst was able to produce the higher yields and selectivities of phenol and cresol, where the catalytic performance of the bio-char catalyst was superior to commercial activated carbon. In addition, the catalyst deactivation and regenation tests were also conducted to evaluate the service life of the catalyst.
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•The synergism on co-pyrolysis of polyethylene and lignin is promoted by pressure.•Radical mass transfer efficiency is regulated by pressure and raw material ratio.•Pressure helps to ...inhibit coke by promoting radical transfer and water release.•Aromatics with smaller steric hindrance are easier to alkylate and polycondensate.
Ex-situ catalytic co-pyrolysis of plastic and biomass to aromatics has been extensively investigated, simultaneously, aromatization have been reported to be promoted under pressure, but available research did not discuss the combined effect of catalytic co-pyrolysis and pressure on aromatics production. In this work, ex-situ catalytic co-pyrolysis of polyethylene and lignin over HZSM-5 under a series of pressure (0.1–0.8 MPa) in a Py-GC/MS system was investigated. We show that pressurized operation during co-pyrolysis of polyethylene and lignin leads to a large increase in BTEX relative yield while maintaining catalyst stability. A very high BTEX relative yield of 70.94% can be achieved at temperature of 650 °C, pressure of 0.5 MPa, polyethylene to lignin ratio of 1:1, and catalyst to raw material ratio of 4:1. Ratio of two raw materials significantly affects efficiency of hydrogen radicals-mass transfer by regulation of hydrogen radical emission and reception. A peak value of BTEX relative yield of 70.27% was obtained at a polyethylene to lignin ratio of 4:3. Among BTEX, benzene and toluene are more prone to alkylate and polycondensate into highly branched and polycyclic aromatics, due to a lower steric hindrance. Hydrogen radicals-mass transfer has a significant effect on BTEX production, and mass transfer efficiency can be regulated by appropriate pressure and raw materials ratios. Meanwhile, pressurized operation has a dual positive effect on coke inhibition via promoting hydrogen radicals-mass transfer and water release, such that catalyst stability and BTEX production are promoted. This study offers new insight into efficient production of BTEX.
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•Microwave-driven HZSM-5@SiC ceramic foam was prepared and characterized.•The deactivation characteristics of HZSM-5@SiC ceramic foam were studied.•Process of microwave catalytic ...pyrolysis of soapstock for aromatic oil was studied.
In view of the poor selectivity of aromatic hydrocarbons in bio-oil from biomass pyrolysis and the high pressure drop and rapid coking and deactivation of catalyst in industrial scale, a microwave-driven HZSM-5@SiC ceramic foam has been constructed, and applied to the ex-situ catalytic fast pyrolysis of soapstock to improve the content of aromatic hydrocarbons in bio-oil. The effects of different catalysts and heating modes and mass ratios of HZSM-5@SiC ceramic foam to soapstock on the distribution of pyrolysis products have been investigated. In addition, combined with the comparison of microwave and electric heating, the deactivation characteristics of HZSM-5@SiC ceramic foam have been studied. Finally, the process of preparing aromatic oil by microwave-driven catalytic pyrolysis of soapstock was discussed. Experimental results indicate that compared with HZSM-5, HZSM-5@SiC ceramic foam has a higher yield of bio-oil and higher aromatization activity. Under microwave heating, the relative content of aromatic hydrocarbons increases from 25.18% to 100% when the mass ratio of HZSM-5@SiC ceramic foam to soapstock increases from 0:1 to 1:1. Compared with electric heating catalysis, HZSM-5@SiC ceramic foam has the lowest yield of coke under microwave heating. After five consecutive uses, it still maintains more than 90% catalytic activity and has higher stability, which provides a scientific basis for the pilot scale experiments of soapstock catalytic pyrolysis.
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•The addition of MCM-41 was beneficial in prolonging the life of HZSM-5.•The optimal operating conditions were determined.•Co-pyrolysis of soapstock with straw advanced the ...deoxygenation especially phenol.•Co-pyrolysis with a dual-catalyst system is a promising technology.
Microwave-assisted co-pyrolysis of low hydrogen-to-carbon and high hydrogen-to-carbon effective ratio materials with the aid of HZSM-5 and MCM-41 is a promising technique to improve the bio-oil quality. The low content of hydrocarbons and short life cycle of catalyst limit the application of pyrolysis technology in biomass energy conversion. The effects of catalytic temperature, and HZSM-5-to-MCM-41, feedstock-to-catalyst, and straw-to-soapstock ratios on the yield and composition of bio-oil were studied in this work. The quality of bio-oil during biomass pyrolysis can be improved by adjusting the operating conditions. The optimal catalytic temperature, and ratios of HZSM-5-to-MCM-41, feedstock-to-catalyst, and straw-to-soapstock were 400 °C, 1:1, 2:1, and 1:2, respectively. The addition of MCM-41 was beneficial in prolonging the life of HZSM-5 since the macromolecular compounds cracked when MCM-41 was added which restrain the generation of coke. The co-pyrolysis of soapstock with straw advanced the deoxygenation of oxygen-containing compounds especially phenol from straw during pyrolysis.
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•Pyrolysis of waste oil over metal oxides and HZSM-5 co-catalysis was studied.•Six kinds of benzene series, including benzene, toluene, and xylene were quantified.•Alkaline earth ...metal oxides showed a salient deoxygenation for waste oil pyrolysis.•Ex-situ separate catalysis was better for alkaline earth metal oxides.•Benzene series concentration was up to 702.20 mg/ml with CaO and HZSM-5 catalysts.
Microwave-assisted pyrolysis of waste cooking oil is an environmentally friendly and economical method for obtaining benzene, toluene, ethylbenzene, and xylene (BTEX) which are important industrial chemicals. This study provides new routes to produce of BTEX and the utilization of waste cooking oil. The effect of catalytic temperatures (350 °C, 400 °C, 450 °C, 500 °C, and 550 °C), types of metal oxide (CoO, NiO, ZrO2, SrO, CeO2, and CaO), catalytic modes (ex-situ mixed catalysis, ex-situ separate catalysis, and in-situ separate catalysis), and ratio of HZSM-5 to metal oxide (HZSM-5 only, 4:1, 2:1, 1:1, 1:2, and CaO only) were studied. Results showed high catalytic temperature promoted the formation of monocyclic aromatic hydrocarbons at the cost of a decrease in bio-oil yield. But the concentration of BTEXS (benzene, toluene, ethylbenzene, xylene, and styrene) only increased from 256.58 mg/ml to 259.55 mg/ml with a temperature increase from 500 °C to 550 °C. Alkaline earth metal oxides (CaO, SrO) showed a significant deoxygenation capability during co-catalysis with HZSM-5. However, when CaO was applied under ex-situ mixed catalysis, the concentration of polycyclic aromatic hydrocarbons was up to 35.47%, which was much higher than 9.18% under HZSM-5 only. Also, the concentration of BTEXS decreased from 256.58 mg/ml (HZSM-5 only) to 167.54 mg/ml (HZSM-5 mixed with CaO). Further investigation of catalytic mode showed that ex-situ separate catalysis was more suitable for co-catalysis of alkaline earth metal oxides and HZSM-5. The concentration of BTEXS were both significantly higher than that of HZSM-5 only, which increased by 121.81 mg/ml for CaO and 108.52 mg/ml for SrO under ex-situ separate catalysis. Further study showed that the highest concentration of BTEXS was 702.20 mg/ml obtained when the ratio of HZSM-5 to CaO was 2:1. It was almost 2.8 times higher than HZSM-5 alone and 42.2 times higher than non-catalytic results.
Pyrolysis of nitrogen-containing biomass holds tremendous potential for producing varieties of high value-added products, alleviating energy depletion. Based on the research status about ...nitrogen-containing biomass pyrolysis, the effect of biomass feedstock composition on pyrolysis products is first introduced from the aspects of elemental analysis, proximate analysis, and biochemical composition. The properties of biomass with high and low nitrogen used in pyrolysis are briefly summarized. Then, with the pyrolysis of nitrogen-containing biomass as the core, biofuel characteristics, nitrogen migration during pyrolysis, the application prospects, unique advantages of nitrogen-doped carbon materials for catalysis, adsorption and energy storage are introduced, as well as their feasibility in producing nitrogen-containing chemicals (acetonitrile and nitrogen heterocyclic) are reviewed. The future outlook for the application of the pyrolysis of nitrogen-containing biomass, specifically, how to realize the denitrification and upgrading of bio-oil, performance improvement of nitrogen-doped carbon materials, as well as separation and purification of nitrogen-containing chemicals, are addressed.
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•The research status of biomass pyrolysis containing nitrogen is reviewed.•Transformation of N is associated with the formation of N containing components.•Solid products have obvious advantages in catalysis, adsorption and energy storage.•Acetonitrile and N-heterocyclic chemicals can be prepared from nitrogenous biomass.
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•Downdraft reactor was applied in microwave-assisted pyrolysis.•The optimal catalytic parameters and feed rate were determined.•HZSM-5 performed well after five replications under ...optimal conditions.•Applications of microwave-absorbent and downdraft reactor improved bio-oil quality.
Microwave-assisted pyrolysis of biomass with HZSM-5 coupled with SiC as microwave-absorbent in a downdraft reactor is a promising method for obtaining hydrocarbon-rich bio-oil. The hydrocarbon content limits the economic and commercial viability of the bio-oil produced by pyrolysis. In this study, the effects of catalytic temperature, feedstock-to-catalyst ratio, and WHSV on the yield and composition of bio-oil are studied. In addition, this study compared the influence of downdraft reaction and updraft reaction on the yield and composition of bio-oil. Furthermore, the stability of the catalyst is studied. Catalytic temperature and feedstock-to-catalyst ratio played pivotal roles in the yield and composition of bio-oil. WHSV has minimal influence on the bio-oil yield and composition within the scope of our research. Furthermore, the optimal catalytic temperature, feedstock-to-catalyst ratio and WHSV were 400 °C, 2:1, and 72 h−1, respectively. The results illustrated that the downdraft coupled with the microwave-absorbent was conducive to the formation of aromatic hydrocarbons. The HZSM-5 performed well in five replicate experimental cycles under optimal conditions in terms of bio-oil yield and aromatic hydrocarbon yield.
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