Catalytic pyrolysis of mandarin residue from the mandarin juice processing industry

Recent advances of thermochemical conversion processes for biorefinery

Lignocellulosic biomass is one of the most promising renewable resources and can replace fossil fuels via various biorefinery processes. Through this study, we addressed and analyzed recent advances in the thermochemical conversion of various lignocellulosic biomasses. We summarized the operation conditions and results related to each thermochemical conversion processes such as pyrolysis (torrefaction), hydrothermal treatment, gasification and combustion. This review indicates that using thermochemical conversion processes in biorefineries is techno-economically feasible, easy, and effective compared with biological processes. The challenges experienced in thermochemical conversion processes are also presented in this study for better understanding the future of thermochemical conversion processes for biorefinery. With the aid of artificial intelligence and machine learning, we can reduce time-consumption and experimental work for bio-oil production and syngas production processes.

A critical review on metal-based catalysts used in the pyrolysis of lignocellulosic biomass materials

This review discusses the technical aspects of improving the efficiency of the pyrolysis of lignocellulosic materials to increase the yield of the main products, which are bio-oil, biochar, and syngas. The latest aspects of catalyst development in the biomass pyrolysis process are presented focusing on the various catalyst structures, the physical and chemical performance of the catalysts, and the mode of the catalytic reaction. In bio-oil upgrading, atmospheric catalytic cracking is shown to be more economical than catalytic hydrotreating. Catalysts help in the upgrading process by facilitating several reaction pathways such as polymerization, aromatization, and alkyl condensation. However, the grade of bio-oil must be similar to that of diesel fuel. Hence, the properties of the pyrolysis liquid such as viscosity, kinematic viscosity, density, and boiling point are important and have been highlighted. Switching between types of catalysts has a significant influence on the final product yields and exhibits different levels of durability. Various catalysts have been shown to enhance gas yield at the expense of the yields of bio-oil and biochar that shift the overall purpose of pyrolysis. Therefore, the catalytic activity as a function of temperature, pressure, and catalyst biomass ratio is discussed in detail. These operational parameters are crucial because they determine the overall yield as well as the ratio of the oil, char, and gas products. Although significant progress has been made in catalytic pyrolysis, the economic feasibility of the process and the catalyst cost remain the major obstacles. This review concludes that the catalytic process would be feasible when the fuel selling price is reduced to less than US $ 4 per gallon of gasoline-equivalent, and when the selectivity of catalysts is further enhanced.

Enhancement of the production of bio-aromatics from renewable lignin by combined approach of torrefaction deoxygenation pretreatment and shape selective catalytic fast pyrolysis using metal modified zeolites

In this work, combined approach of torrefaction deoxygenation pretreatment (TDP) and shape selective catalytic fast pyrolysis (SS-CFP) using bifunctional catalyst (metal modified HZSM-5) were employed to improve the yield of bio-BTX derived from the renewable starting material of lignin. Results showed that after TDP, the oxygen element could be removed effectively. The oxygen removal efficiency reached its maximum value of 22.27% at 300 °C, resulting in markedly decrease of unnecessary oxygenates in bio-oil. Compared to parent HZSM-5, all metal modified HZSM-5 (Ga/HZSM-5, Zn/HZSM-5, and Ga-Zn/HZSM-5) promoted the formation of bio-BTX. Zn/HZSM-5 showed the highest selective yield of bio-BTX because of the enhancement deoxygenation reaction of oxygenates and the aromatization reaction of olefins. The combined approach of TDP and SS-CFP remarkably improved the selective yield of bio-BTX, reaching the maximum value of 65.19%, which was much higher than that from single approach of TDP (33.84%) and SS-CFP (47.36%).

Recent advances in zeolite-encapsulated metal catalysts: A suitable catalyst design for catalytic biomass conversion

Metal clusters and nanoparticles, which have been used to tune the acidity of zeolite support, are beneficial for promoting the catalytic performance of various reaction processes, including biomass conversion. However, catalytic instabilities resulting from metal coalescence, sintering and leaching are major problems that need to be resolved. Therefore, metal encapsulation within the zeolite structure has been proposed as a feasible solution for this issue, particularly for biomass conversions that require high temperatures. In this current review, recent developments in metal confinement techniques are described along with experimental examples of biomass upgrading reactions. The present and future perspectives of zeolite-encapsulated metal catalysts in biomass conversions are also given.

Optimizing the Aromatic Product Distribution from Catalytic Fast Pyrolysis of Biomass Using Hydrothermally Synthesized Ga-MFI Zeolites

A series of gallium-containing MFI (Ga-MFI) zeolites with varying Ga2O3/Al2O3 ratios were synthesized using hydrothermal synthesis and tested as catalyst in catalytic fast pyrolysis (CFP) of beech wood for aromatic production. The results show that the incorporation of Ga slightly reduced the effective pore size of Ga-MFI zeolites compared to conventional HZSM-5 zeolites. Therefore, the Ga-MFI zeolites increased the aromatic selectivity for smaller aromatics such as benzene, toluene, and p-xylene and decreased the aromatic selectivity for bulkier ones such as m-xylene, o-xylene, and polyaromatics in CFP of beech wood relative to HSZM-5. In particular, the yield and selectivity of p-xylene, the most desired product from CFP of biomass, increased considerably from 1.64 C% and 33.3% for conventional HZSM-5 to 2.98–3.34 C% and 72.1–79.6% for the synthesized Ga-MFI zeolites. These results suggest that slightly reducing the pore size of MFI zeolite by Ga incorporation has a beneficial effect on optimizing the aromatic selectivity toward more valuable monoaromatic products, especially p-xylene, during CFP of biomass.

Characterisation of bio-oil and its sub-fractions from catalytic fast pyrolysis of biomass mixture

The present study aim is to characterise catalytic and non-catalytic biomass pyrolysis liquid products. Turkey is the world's largest hazelnut producer and also ranks fifth in tea production, so a mixture of hazelnut shell, tea bush and hazelnut knot was selected as the biomass sample, and vanadium pentoxide (V₂O₅) was also used as a catalyst. Considering the biomass mixture and catalyst used, this research is unique for the literature. Bio-oils, which are obtained by catalytic and non-catalytic processes and collected in two sub-fractions, were characterised. The sub-fractions of toluene and ethyl acetate, there was a significant increase in calorific values compared with the mixture without catalyst, because of the decrease in the amount of oxygen and increase in the amount of carbon. The increase in this calorific value in the toluene sub-fraction is about 76% higher than the raw material mixture. In the sub-fractions of toluene and ethyl acetate produced by catalytic pyrolysis, an increase in carbon content was observed when compared with non-catalytic products, while the amounts of oxygen decreased. Considering the results, the toluene sub-fraction is generally composed of phenolic structures. Generally, the ethyl acetate sub-fraction comprises the carbonyl group - containing ketone and aldehyde structures as well as aromatic and phenolic compounds. The resulting bio-oil has the potential to be used as a liquid fuel both in terms of calorific values and in terms of the H/C and O/C ratio.

Increased Aromatics Formation by the Use of High-Density Polyethylene on the Catalytic Pyrolysis of Mandarin Peel over HY and HZSM-5

High-density polyethylene (HDPE) was co-fed into the catalytic pyrolysis (CP) of mandarin peel (MP) over different microporous catalysts, HY and HZSM-5, with different pore and acid properties. Although the non-catalytic decomposition temperature of MP was not changed during catalytic thermogravimetric analysis over both catalysts, that of HDPE was reduced from 465 °C to 379 °C over HY and to 393 °C over HZSM-5 because of their catalytic effects. When HDPE was co-pyrolyzed with MP over the catalysts, the catalytic decomposition temperatures of HDPE were increased to 402 °C over HY and 408 °C over HZSM-5. The pyrolyzer-gas chromatography/mass spectrometry results showed that the main pyrolyzates of MP and HDPE, which comprised a large amount of oxygenates and aliphatic hydrocarbons with a wide carbon range, were converted efficiently to aromatics using HY and HZSM-5. Although HY can provide easier diffusion of the reactants to the catalyst pore and a larger amount of acid sites than HZSM-5, the CP of MP, HDPE, and their mixture over HZSM-5 revealed higher efficiency on aromatics formation than those over HY due to the strong acidity and more appropriate shape selectivity of HZSM-5. The production of aromatics from the catalytic co-pyrolysis of MP and HDPE was larger than the theoretical amounts, suggesting the synergistic effect of HDPE co-feeding for the increased formation of aromatics during the CP of MP.