Optical neural network can process information in parallel by using the technology based on free-space and integrated platform. Over the last half century, the development of integrated circuits has ...been limited by Moore's law. We know that neural network is based on the digital computer for successive calculation, most of which cannot be made into real-time processing system. Therefore, it is necessary to develop ONN for real-time processing and device miniaturization. In this paper, we review the progress of optical neural networks. Firstly, based on the principle of artificial neural networks, we elaborate the essence of optical matrix multiplier for linear operation. Then we introduce the optical neural network achieved by free-space optical interconnection and waveguide optical interconnection. Finally we talk about the nonlinearity in optical neural networks. With the gradual maturity of nanotechnology and the rapid advancement of silicon photonic integrated circuits, the progress of integrated photonic neural network has been promoted. Therefore, the construction of optical neural network on the future integrated photonic platform has potential application value.
It is promising to convert waste oil and plastics to renewable fuels and chemicals by microwave catalytic co-pyrolysis, enabling pollution reduction and resource recovery. The purpose of this study ...was to evaluate the effect of catalysts on the product selectivity of microwave-assisted co-pyrolysis of waste cooking oil and low-density polyethylene and optimize the pyrolysis process, including pyrolysis temperature, catalytic temperature, waste cooking oil to low-density polyethylene ratio, and catalyst to feedstocks ratio. The results indicated that catalysts had a great influence on the product distribution, and the yield of BTX (benzene, toluene, and xylenes), which increased in the following order: SAPO-34 < Hβ < HY < HZSM-5. HZSM-5 was more active for the formation of light aromatic hydrocarbons as compared to others, where the concentrations of toluene, benzene and xylenes reached 252.59 mg/mL, 114.7 mg/mL and 132.91 mg/mL, respectively. The optimum pyrolysis temperature, catalytic temperature, waste cooking oil to low-density polyethylene ratio and catalyst to feedstocks ratio could be 550 °C, 450 °C, 1:1 and 1:2, respectively, to maximize the formation of BTX and inhibit the formation of polycyclic aromatic hydrocarbons.
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•Microwave co-pyrolysis of waste cooking oil and LDPE comprehensively investigated.•HZSM-5 was the most effective aromatization catalyst for light aromatics.•This co-pyrolysis increased the content of monocyclic aromatic hydrocarbons.•Benzene, toluene, xylenes, ethylbenzene, and styrene were quantified.
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•Composite catalysts (ZSM-5/MCM-41) were synthesized and its optimum catalytic conditions were studied.•Microwave-assisted catalytic fast co-pyrolysis (co-MACFP) was adopted in this ...experiment.•The synergistic effect of lignin and catalyst promotes the formation of aromatic compounds.
Microwave-assisted catalytic fast co-pyrolysis (MACFP) of lignin and waste oil with SiC as microwave absorbent and hierarchical ZSM-5/MCM-41 as catalyst were implemented in a microwave-induced reactor. ZSM-5/MCM-41 is a kind of composite catalyst with MCM-41 as shell and ZSM as core. The effects of catalyst temperature, the ratio of feedstock-to-catalyst and the ratio of two reactants (lignin and waste oil) on product distribution and yield were studied. The study shows that catalytic co-pyrolysis is a complex reaction process, and many reaction conditions could affect the final reaction results. The optimum reaction conditions are as follows: catalytic temperature 400 °C, the feedstock-to-catalyst ratio of 10:1 and the ratio of lignin to waste oil of 2:1. Under this reaction condition, the conversion of feedstocks reached 76.00%, the proportion of aromatics was 50.31% and the selectivity of monocyclic aromatic hydrocarbons (MAHs) was 42.83%.
To take full advantage of the application of neural networks to optical systems, we design an optical neural network based on the principle of free-space optical convolution. In this article, ...considering the need for a high-power light source to excite the nonlinearity of an optical material, we describe how to reduce the power consumption of the system by quantifying the output of each layer after the softmax operation as an 8-bit value and loading these values into amplitude-only spatial light modulators (SLMs). In addition, we describe how to load the matrix with positive and negative values in the amplitude-only SLM by utilizing Fourier properties of the odd-order square matrix. We apply our six-layer optical network to the classification of Mixed National Institute of Standards and Technology database (MNIST) and Fashion-MNIST and find that the accuracy reaches 92.51% and 80.67%, respectively. Finally, we consider the error analysis, power consumption, and response time of our framework.
In this work,
Camellia oleifera
Abel shell was used as a feedstock to prepare biochar by HNO
3
impregnation and pyrolysis. The biochar was used for the catalytic pyrolysis of waste vegetable oil to ...prepare bio-oil. Experimental results showed that HNO
3
solution treatment had an important effect on the groups and structure of the biochar catalyst. When the solid/liquid ratio of pretreatment was 1:3, the Brunauer–Emmett–Teller specific surface area of the 1:3–600°C biochar is 392.65 m
2
/g, which is approximately 677 times higher than that of untreated biochar. Moreover, the biochar catalyst had a remarkable catalytic performance. The selectivity of the monocyclic aromatic hydrocarbon in the bio-oil was up to 78.82%, and the oxy-compound could be completely removed at the catalytic temperature of 600°C. However, the increase of the catalyst-to-waste vegetable oil ratio and catalytic temperature decreased the bio-oil yield.
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•White pollution and energy crisis can be alleviated via fuels conversion from plastic wastes.•The application of efficient catalysts enables directional selection of targeted ...products.•The downstream upgrading towards high-value products creates added value to a plastic-to-fuel process.•Techno-economic assessment of catalytic pyrolysis systems for plastic wastes shows attractive industrialization prospects.
With the continuous increase of plastic wastes and the decrease of fossil energy, pyrolysis has emerged as a promising technology for the valorization of plastic wastes to produce fuels and chemicals. Properties of common plastics, mainly polyethylene terephthalate (PET), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS) and their mixtures are discussed with a focus on the pyrolysis mechanism and product distribution. The application of the most common catalysts (microporous/mesoporous zeolites, base catalysts, and clays) shows overwhelming advantages over thermal cracking, and an in-depth understanding of catalysts in several catalytic processes (ex-situ catalysts, tandem catalysts, bi-functional catalysts, multi-modal pore catalysts, and regenerated catalysts) is critical for efficient fuel production. Despite high-quality liquid fuels obtained, further upgrading (filtration, hydrogenation, distillation, liquid–liquid extraction or blending with conventional fuels) is required before their commercial application. Non-condensable gas is another co-product that can be upgraded for heat generation or as the precursor of high-value products (ethylene, propylene, carbon nanotubes (CNTs), etc.). Finally, a more integrated techno-economic assessment process is conducted based on feedstock logistics, utilization of liquid fuels, full use of co-products, capital and operating costs. This review aims to inspire both fundamental and applied research efforts for the production of high-value products from the catalytic pyrolysis of plastic wastes and their full utilization to create the necessary technological and economic push for a circular economy.
Increasing fossil fuel consumption and global warming has been driving the worldwide revolution towards renewable energy. Biomass is abundant and low-cost resource whereas it requires environmentally ...friendly and cost-effective conversion technique. Pyrolysis of biomass into valuable bio-oil has attracted much attention in the past decades due to its feasibility and huge commercial outlook. However, the complex chemical compositions and high water content in bio-oil greatly hinder the large-scale application and commercialization. Therefore, catalytic pyrolysis of biomass for selective production of specific chemicals will stand out as a unique pathway. This review aims to improve the understanding for the process by illustrating the chemistry of non-catalytic and catalytic pyrolysis of biomass at the temperatures ranging from 400 to 650 °C. The focus is to introduce recent progress about producing value-added hydrocarbons, phenols, anhydrosugars, and nitrogen-containing compounds from catalytic pyrolysis of biomass over zeolites, metal oxides, etc. via different reaction pathways including cracking, Diels-Alder/aromatization, ketonization/aldol condensation, and ammoniation. The potential challenges and future directions for this technique are discussed in deep.
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•Properties of lignocellulosic biomass and its pyrolysis chemistry are extensively reviewed.•Catalytic pyrolysis of lignocellulosic biomass for selective production of valuable chemicals is outlined.•Different catalytic reforming pathways are summarized.•Future research directions and technological challenges are proposed.
•Catalytic pyrolysis of waste oil for the hydrocarbon fuels production was reviewed.•Comparison of electric and microwave heating pyrolysis of waste oil was outlined.•Catalysts used in waste oil ...pyrolysis have been extensively introduced.•In-situ catalytic and ex-situ catalytic reactors were introduced and compared.
The deterioration of environment and the depletion of fossil fuels have inspired the exploration for alternative fuels based on renewable raw materials. This review presented the catalytic pyrolysis of waste oil for producing renewable hydrocarbon fuels. After the discussion of various process parameters, including waste oil characteristics, microwave absorbents, co-pyrolysis technology, catalysts, and reactor types, the best conditions for improving the yield and quality of hydrocarbon fuels were obtained. The advantages and limitations of microwave-assisted pyrolysis and conventional electric heating were discussed. Microwave-assisted pyrolysis is a relatively new technology compared with traditional electric heating pyrolysis, which has great development potential. In the future, the catalysts with low pressure drop and coking rate need to be developed and their microwave absorption characteristics in microwave-assisted pyrolysis must be fully investigated. Simultaneously, a continuous microwave-assisted pyrolysis system needs to be constructed to achieve the large-scale production of renewable hydrocarbon fuels from waste oil.
•Microwave-assisted acid pretreatment of alkali lignin process was developed.•Microwave temperature was the most influential factor.•The thermal stability of lignin after pretreatment was ...dramatically improved.•The phenols content significantly increased and methoxyl groups decreased.
This study performed microwave-assisted acid pretreatment on pure lignin. The effects of microwave temperature, microwave time, and hydrochloric acid concentration on characteristics and pyrolysis behavior of lignin were examined. Results of ultimate analysis revealed better properties of all pretreated samples than those of raw lignin. Fourier transform infrared spectroscopy analysis showed breakage of βO4 bond and aliphatic side chain, decrease in OH groups, and formation of CO groups in pretreatment. Microwave temperature exerted more significant influence on lignin structure. Thermal stability of treated lignin was improved and insensitive to short microwave time and acid concentration under mild conditions. Resulting from improved alkyl-phenols and decreased alkoxy-phenols, microwave-assisted acid pretreatment of lignin yielded bio-oil with excellent quality. Total yield of phenols in pyrolysis vapors (200 °C) improved to 14.15%, whereas that of guaiacols decreased to 22.36%. This study shows that microwave-assisted acid pretreatment is a promising technology for lignin conversion.
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