To overcome mass transfer limitation and adjust zeolite's acidity, the modification of beta zeolite via etching with hydrofluoric acid/ammonium fluoride (HF/NH4F) solution was revealed and the modified beta zeolite was then applied as a support of nickel (Ni) catalysts used for hydroisomerization of palm olein. HF/NH4F solution containing 0.25 M HF concentration was appropriate to enlarge original existing intercrystalline mesopores of beta zeolite (beta-0.25), which resulted to the higher pore volume. The Ni/beta-0.25 catalyst also exhibited the better Ni dispersion and lower acidity. These features suppressed overcracking and provided 43.4 wt% bio-jet fuel yield with 22.1 wt% iso-alkanes fraction when hydroisomerization was operated under 40 bar initial hydrogen (H2) pressure at 340 degrees C for 5 h. At 0.75 M HF concentration, the excessive leaching of aluminum species out of the zeolite framework provided beta-0.75 with very low acidity, which was ineffective to convert molecules of palm olein to bio-jet fuel range. Initial H2 pressure at 40 bar was sufficient to activate the hydroisomerization of palm olein over Ni/beta-0.25 catalyst to produce liquid biofuel containing iso-/n-alkane ratio of 2.61. The liquid biofuel/Jet A-1 blend at 50% (v/v) had freezing point and gross heating value of-58.9 degrees C and 43.7 MJ/kg, respectively.

In this work, to efficiently utilize waste fruit and low-rank coal for the hydrogen (H2)-rich syngas production, steam co-gasification of banana peel (BP) and brown coal (BC) was studied in a fixed-bed reactor. The results showed that the gasification rate of BC was highly enhanced after mixing it with BP and the obvious synergistic effect was observed in all investigated three mixing weight ratios (i.e., 1:1, 1:4, 4:1), resulting in a higher carbon conversion as well as a H2-rich gas production yield for the co-gasification. However, the extent of promotion by synergistic effect was affected by the reaction temperature, mixing ratio, and steam amount. It was found that the high potassium (K) species content in the BP provided the catalytic effect not only on water-gas shift reaction but also on tar reforming/cracking, thereby enhancing the gasification of BC. In addition, it is confirmed that steam should be an important factor to promote the synergistic effect and H2-rich gas production.

Effects of biomass type and zeolite catalyst type on bio-oil upgrading were investigated in this study, in which terrestrial (rice husk and cedar) and marine (eelgrass) biomass and various commercial zeolites with different frameworks including H-USY, H-Mordenite, H-Ferrierite, H-ZSM-5, H-Beta zeolites were used. The catalytic performance of each catalyst was evaluated with a Py/GC-MS instrument. Thereafter, in-situ catalytic upgrading of the bio-oil derived from fast pyrolysis over those zeolite catalysts with high activity and selectivity towards aromatic hydrocarbons were further investigated in a fixed bed reactor. A highest aromatic hydrocarbons yield up to 77.28% in the upgraded bio-oil was achieved when using eelgrass as the biomass feedstock and a H-ZSM-5-40 zeolite as the catalyst. In addition, the spent catalysts after used for several times can be well regenerated only via a simple calcination at 550 degrees C for 2 h in air, which showed similar activity as the fresh one. It is expected that such a zeolite catalyst can be applied for the bio-oil upgrading in an industrial scale.

Fast pyrolysis of biomass is an attractive way to produce bio-oil since it can convert most of biomass components directly into liquid fuel. However, the bio-oils obtained from such a fast pyrolysis process always have highly complex oxygenated compounds with high viscosity, serious corrosivity, and rather instability. Thus, before the raw bio-oils are used as fuel or chemical feedstock, they must be upgraded, especially deoxygenated. Cracking of bio-oils over porous solid catalysts such as zeolite-based catalysts at ambient pressure is considered one of effective ways for the bio-oil upgrading, especially in which hydrogen gas is not necessary. Herein, zeolite-based catalysts (mainly HZSM-5 based catalysts) for the upgrading of pyrolysis bio-oils are critically reviewed. The effects of porous structure, acidity and other parameters including biomass type, biomass/catalyst ratio and operation temperature on cracking activity, selectivity, stability and deactivation are summarized. While, the proposed mechanisms on the bio-oil upgrading over the zeolite-based catalysts and the possibility for the application of the developed catalysts in the industrial process are discussed. Furthermore, the main strategies including metal modification, construction of zeolites with a hierarchical structure and synthesis of special morphologies with hollow structure or core/shell structure and nanosheet structures for the improvement of deoxygenation property performance are introduced. It is expected to provide a guidance for the design and fabricate more excellent zeolite-based catalysts and their application for high-quality bio-oil production from fast biomass pyrolysis.

To solve the issue of narrow micropores in traditional protonic type Zeolite Socony Mobil-5 (HZSM-5) catalysts in the restricting of large-molecular reactants/products diffusion, hollow HZSM-5 with a mesoporous shell was prepared using a hydrothermal method combined with a tetrapropylammonium hydroxide (TPAOH) treatment process. Applying for in-situ catalyst upgrading of bio-oil from rapid pyrolysis of biomass, the obtained most efficient catalyst of Hollow(30)-TP resulted in aromatic hydrocarbon yields in the range of 78.49-78.67% for cellulose and hemicellulose, which is much greater than those using the traditional HZSM-5 (61.06-68.26%). Furthermore, in the case using real biomass (cedar) with an optimal biomass/catalyst weight ratio of 1:2, the aromatic hydrocarbon yield reached up to 80.16%. In addition, this catalyst exhibited excellent reusability and regeneration property due to the increased accessibility to the acid sites in the hollow HZSM-5 for the improving of the reaction rate as well as the reducing of coking.

Co-pyrolysis of two different types of biomass among apple tree branch (ATB), knotweed stem (KWS), seaweed (SW) and rice straw (RSt) was conducted to obtain co-pyrolysis char (co-char), and then the steam gasification of those co-chars was compared with the steam co-gasification of the physically mixed individual biochars to investigate the synergetic effect resulted from alkali and alkali earth metal (AAEM) in each biomass involved. It is found that the silica species in the RSt had negative effect on the activity of co-char due to the formation of alkali silicate compounds. However, combination of RSt with some non-woody biomass such as SW also showed promoting effect. In particular, the gasification of the co-char from the combination of various biomass with low or no silica content showed improved gasification efficiencies due to the synergetic effect AAEM species in the co-char from the different biomass. Therefore, the biomass selection should play a significant role in the co-pyrolysis of different biomass in the two-stage gasification system.

In this study, steam gasification and co-gasification of Japanese cedarwood and its commercial biochar were performed in a lab-scale fixed-bed reactor to investigate the feasibility for producing H2-rich syngas. Ultimate analysis, proximate analysis, Brunauer-Emmett-Teller (BET) surface area analysis, and scanning electron microscopy (SEM) were conducted to understand the changes caused by the carbonization process. The effects of gasification temperature and steam flow rate on gas production yield from the steam gasification of the individual samples were investigated at first, which showed larger gas production yield and less tar yield for the steam gasification of the commercial biochar than that of raw cedarwood, indicating that the commercial biochar obtained from the carbonization process was more beneficial for the gasification. The co-gasification of raw Japanese cedarwood and its commercial biochar with different mixing ratios was conducted at different reaction temperatures. The synergistic effect was obviously observed. Especially, the commercial biochar with the highly porous structure and high content of alkali and alkaline earth metal (AAEM) species might provide the catalytic effect on cracking and reforming of tar derived from the raw cedarwood, resulting in a larger H2 yield. However, the catalytic effect and gasification reactivity of biochar would decrease by increasing the amount of raw-cedarwood in the blends due to the coke deposition on the surface of biochar.

Commercial HZSM-5 zeolite (Si/Al = 24) was modified with Cu species using the wet impregnation method, and applied in the in-situ upgrading of bio-oil from the fast sunflower stalk pyrolysis with a catalyst to biomass ratio of 1:1 at 500 ?C. The main objective was to study the Cu doping effect on the HZSM-5 catalytic performance in terms of the selectivity to aromatic hydrocarbons (especially the specific aromatic hydrocarbons including benzene, toluene and xylene) yield. It was found that Cu/HZSM-5 with low Cu loading amounts preserved HZSM5 crystalline structure as well as its acid sites. The HZSM-5 with 0.5 wt.% Cu loading amount exhibited the best catalytic performance with a high relative amount of aromatic hydrocarbons of 73.2 % and a yield of specific aromatic hydrocarbons as high as 56.5 mg/g-biomass (d.a.f), which were much higher than those based on the parent HZSM-5 (55.0 % and 26.0 mg/g-biomass (d.a.f)). It should be mainly attributed to its suitable acidity and best textural properties for the deoxygenation of the bio-oil thanks to the optimum Cu loading amount. In addition, the 0.5 wt.% Cu loaded HZSM-5 catalyst also showed excellent catalytic reusability and regeneration property, and the spent catalyst was easily recovered by a simple calcination in air for a short time.

Hierarchical HZSM-5 zeolites were prepared by desilication of commercial HZSM-5 in aqueous NaOH solutions with the assistance of tetrapropylammonium hydroxides (TPAOH), and applied for the catalytic upgrading of bio-oil derived from the fast pyrolysis of sunflower stalk. The hierarchical HZSM-5 by using 0.2 M NaOH with 0.25 M TPAOH for the desilication exhibited the best catalytic performance and the relative total peak area related to the aromatic hydrocarbons reached 65.8% with a yield of the detected aromatic hydrocarbons up to 45.2 mg/g-bio-oil. With the assistance of 0.25 M TPAOH for the desilication, the formation of mesopores became highly controllable, resulting in the increase in the surface area and maintainment of enough acid amounts, however, the coking on the surface of catalyst was not hindered. To solve the coking problem and increase the aromatic hydrocarbons production, the hierarchical HZSM-5 with the best performance was modified by various metals. It is found that 0.25 wt% Cu loaded hierarchical HZSM-5 increased the yield of the detected aromatic hydrocarbons up to 54.5 mg/g-bio-oil with a decrease in the coke formation. (C) 2021 Elsevier Ltd. All rights reserved.

Steam co-gasification of banana peel with other biomass, i.e., Japanese cedar wood, rice husk and their mixture, was carried out for the hydrogen-rich gas production in a fixed-bed reactor. For the co-gasification process, the banana peels were physically mixed with rice husk, Japanese cedarwood and their mixture respectively by different mixing weight ratios. The effects of reaction temperature and the addition amount of banana peel on the gas production yield were investigated by comparing the experimental data with the calculated ones based on the individual biomass gasification at the same condition. It was found that the banana peel with a high content of alkali and alkaline earth metal (AAEM) species exhibited not only high gasification reactivity but also a significant enhancing catalytic effect on the co-gasification process at the low temperature, especially with the biomass containing no silica species. The high content of silica species in the rice husk had a negative effect on the gasification reactivity of banana peel during the co-gasification since it could hinder the release of AAEM from the biomass and/or lead to the possible formation of inactive alkaline silicates. However, the combination of these three samples with the suitable weight ratio could improve the gasification performance at the low temperature due to the synergetic effect provided by high contents of potassium and calcium from banana peel and cedarwood respectively. Moreover, the addition of calcined seashells as the CaO source could further improve the gas production yield, especially the hydrogen gas yield at a relatively low gasification temperature of 750 ℃.

Sustainable carbon acid catalysts exhibited high-performance in the conversion of citronellal to p-menthane-3,8-diol via a carbocation-hydration pathway.

Pyrolysis of lignocellulosic biomass is a promising method to produce bio-oils in high yields. However, the obtained bio-oils via the pyrolysis process always contain large amounts of oxygenated compounds such as phenols, ketones sugars and acids, which could make them unstable, corrosive and have low heating value. Thus, the original bio-oils need to be firstly upgraded before its application as transportation fuel. Herein, upgrading of bio-oils by using several typically highly-active solid catalysts with metal modification are introduced. Especially, the effects of pore size and acidic-basic properties of the solid catalysts on their activity, selectivity, stability and deactivation are critically reviewed. In this chapter, fundamental reaction pathways for the conversion of oxygenated compounds into aromatic hydrocarbons and coke via catalytic pyrolysis are summarized in detail along with an outline of future research needs.

Activity of calcined scallop shell (CSS) for the catalytic pyrolysis of wasted fishing net (WFN) to the epsilon-caprolactam monomer was investigated in a micro-furnace type temperature programmable pyrolyzer combined with a gas chromatography/mass spectrometry (Py-GC/MS) analysis system. Evolved gas analysis (EGA/MS) indicates that the peak temperature for the decomposition of WFN in the absence of catalysts was around 420 - 480 degrees C whereas the temperature decreased down to 380 - 420 degrees C in the presence of CSS or commercial CaO catalysts. The yield of epsilon-caprolactam reached 66 wt.% in a catalytic depolymerization condition at 410 degrees C for 2 min with a 1:5 WFN/CSS weight ratio by using the Py-GC/MS system. Based on these experimental results, CSS should be an alternative catalyst for the recovery of the epsilon-caprolactam monomer from the WFN.

In the future, hydrogen will be an important energy carrier and industrial raw material. Catalytic steam reforming of bio-oils is a promising and economically viable technology for hydrogen production. However, during the reforming process, the catalysts are rapidly deactivated due to coke formation and sintering. Thus, maintaining the activity and stability of catalysts is the key issue in this process. Optimized operation conditions could extend the catalyst lifetime by affecting the coke morphology or promoting coke gasification. This article summarizes the recent developments in the field of catalytic steam reforming of bio-oils, focusing on the operation conditions, the properties of the catalysts, and the effects of the catalyst supports. The expected insights into the catalytic steam reforming of bio-oils will provide further guidance for hydrogen production from bio-oils.

In this study, steam gasifications of a kind of marine biomass, i.e., Zostera marina (eelgrass), and the biochars derived from pyrolysis of it were carried out for the biohydrogen production in a fixed-bed reactor. The effects of reaction temperature and water injection rate on the hydrogen production were investigated. In order to understand the effect of sea salts attached on the surface of eelgrass for the hydrogen production, the eelgrass washed by water (washed-eelgrass) was also used as the feedstock. It was observed that hydrogen productions from the gasification of washed-eelgrass as well as its biochar were higher than those of raw eelgrass and its biochar, indicating that the impurities of raw eelgrass had a negative effect on the hydrogen production. The biochar derived from the pyrolysis of washed eelgrass at 550 °C had the largest amount of hydrogen yield at the gasification temperature of 850 °C with a water injection rate of 0.15 g/min. It was found that both the hydrogen production and reaction rates were enhanced by mixing washed-eelgrass biochar obtained at 350 °C with the calcined seashells at a weight ratio of 1 to 2, especially at the gasification temperature of 650 °C. Meanwhile, in the presence of the calcined seashell, CO2 content decreased sharply whereas the hydrogen yield had no obvious increase.

Catalytic upgrading of bio-oils derived from fast pyrolysis of sunflower stalk, cedar, knotweed and apple tree stem over H-ZSM-5, H-beta and H-USY zeolites with high alumina content was investigated at a reaction temperature of 500 degrees C. All catalysts showed high catalytic activity and selectivity towards aromatic hydrocarbons in the conversions of oxygenated compounds in the bio-oils, and 56.2-100% of aromatic hydrocarbons were found in the upgraded bio-oils which can be detected by GC/MS. Naphthalene was favored to be produced by using H-ZSM-5 while more monocyclic aromatic hydrocarbons such as p-xylene, toluene and alkylbenzene were generated by using H-beta as well as H-USY. Furthermore, all catalysts maintained high activity and selectivity with the maximum aromatic hydrocarbons amount of 70% in the upgraded bio-oils detected in the third cycle. In addition, the spent catalysts were easily regenerated by simple calcination at 650 degrees C for 30 min, and the regenerated catalysts showed almost the same activity as the fresh ones. It is expected that these high alumina zeolites can be widely used in practical bio-oil upgrading processes. (C) 2018 Elsevier Ltd. All rights reserved.