Production of aromatics through current-enhanced catalytic conversion of bio-oil tar

Fates of heavy organics of bio-oil in hydrotreatment: The key challenge in the way from biomass to biofuel

Heavy organics in bio-oil generally refer to the sugar oligomers and lignin-derivatives. They are important fractions in bio-oil and their effective conversion in hydrotreatment determines carbon yield from biomass or bio-oil to biofuel. Fates of the heavy organics largely determine intrinsic reaction behaviors of bio-oil during hydrotreatment. The heavy organics in bio-oil have high tendency towards polymerization upon thermal treatment, which is one of the main precursors for coke formation and catalyst deactivation. Furthermore, the heavy organics have some other unique characteristics in hydrotreatment such as the steric hindrance for contacting active sites on surface of catalyst. How to effectively convert the heavy organics has been regarded as the bottle-neck issue in hydrotreatment of bio-oil and the key barrier in the roadmap from biomass to biofuels. Thus, this review particularly focuses on the progress in understanding reaction behaviors of the heavy organics in hydrotreatment of bio-oil, a central challenge to be resolved. The results indicated that coke formation from heavy organics in bio-oil remains main obstacle in hydrotreatment and further fundamental studies are required to develop suitable catalyst and process to stabilize the heavy organics in bio-oil. In particular, the mechanism for coke formation from the heavy species of varied chemical family should be clarified and corresponding measures should be developed to tackle high tendency of coking. Techno-economic feasibility should be considered in the first place in development of catalysts or process for tackling the heavy fractions of bio-oil.

Multivariate Optimization of an SPME Technique for GC-MS Analysis of Urinary BTX

Volatile organic compounds (VOCs), such as benzene, toluene and xylenes (BTX), are recognized as environmental contaminants due to their acute and chronic toxic effects, and toluene is a substance contained in products used in inhalants. In this way, methods able to determine these substances in non-invasive matrices offer great applicability for assessing acute exposure. In this study, a functionalized polymer, chloropropyltrimethoxysilane/polydimethylsiloxane, was evaluated as a potential material to be used in solid-phase microextraction for the quantification of BTX in urine by gas chromatography coupled to mass spectrometry (GC-MS). The method optimization was performed by using fractional factorial planning 2 (4-1) and the Doehlert's experiment. Desorption time and salinity were the most important factors that impact the sensitivity of the method. Spectroscopic and thermogravimetric characterization demonstrated the functionalization of the material and its thermal stability up to 390°C. This allowed it to be used for ~60 analytical cycles without loss of efficiency. The proposed method demonstrated a satisfactory analytical performance to determine the VOCs studied. The protocol agrees with the principles of green analytical chemistry since the procedure reduced the reagents consumed and wastes generated. It represents a promising tool for acute exposure assessment to BTX since urine tests demonstrated its applicability.

Hydrodeoxygenation of Guaiacol over Pd–Co and Pd–Fe Catalysts: Deactivation and Regeneration

In bio-oil upgrading, the activity and stability of the catalyst are of great importance for the catalytic hydrodeoxygenation (HDO) process. The vapor-phase HDO of guaiacol was investigated to clarify the activity, stability, and regeneration ability of Al-MCM-41 supported Pd, Co, and Fe catalysts in a fixed-bed reactor. The HDO experiment was conducted at 400 °C and 1 atm, while the regeneration of the catalyst was performed with an air flow at 500 °C for 240 min. TGA and XPS techniques were applied to study the coke deposit and metal oxide bond energy of the catalysts before and after HDO reaction. The Co and Pd–Co simultaneously catalyzed the CArO–CH3, CAr–OH, and multiple C–C hydrogenolyses, while the Fe and Pd–Fe principally catalyzed the CAr–OCH3 hydrogenolysis. The bimetallic Pd–Co and Pd–Fe showed a higher HDO yield and stability than monometallic Co and Fe, since the coke formation was reduced. The Pd–Fe catalyst presented a higher stability and regeneration ability than the Pd–Co catalyst, with consistent activity during three HDO cycles.

Product Distribution of Chemical Product Using Catalytic Depolymerization of Lignin

Lignin depolymerization is a very promising process which can generate value-added products from lignin raw materials. The main objective of lignin depolymerization is to convert the complex molecules of lignin into small molecules. Nevertheless, lignin is natural polymer which the molecules of lignin are extremely complicated due to their natural variability, and it will be a big challenge to depolymerize lignin, particularly high water yield. The various technology and methods are developed to depolymerize lignin into biofuels or bio chemical products including acid/base/metallic catalyzed lignin depolymerization, pyrolysis of lignin, hydroprocessing, and gasification. The distribution and yield of chemical products depend on the reaction operation condition, type of lignin and kind of catalyst. The reactor type, product distributions and specific chemicals (benzene, toluene, xylene, terephthalic acid) production of lignin depolymerization are intensive discussed in this review. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Renewable Aromatics from Tree-Borne Oils over Zeolite Catalysts Promoted by Transition Metals

Despite the ever-growing demand for benzene-toluene-xylene (BTX), the alternative route of production from tree-borne oils is rarely investigated and poorly understood. Here, we have synthesized a Zn-loaded Y-zeolite catalyst for the continuous production of bio-BTX from tree-borne oils (nonedible seed oil), e.g., neem oil. Our approach involves low-temperature selective cracking-dehydrogenation-aromatization of neem oil over metal-supported catalysts to xylene-rich aromatics. The physicochemical properties of the prepared catalyst were characterized using powder XRD, N₂ physisorption, TEM, NH₃-TPD, XPS, Py-FTIR, solid-NMR, and TG analyses. Mesoporous Y-zeolites with a pore diameter of 7.4 Å showed better selectivity toward aromatics and were found to be the most effective catalyst for the aromatization process, especially for BTX. The aromatic yield was found to increase with the addition of Zn, and the highest conversion of 90-94% with an ∼75% BTX yield was achieved with the ZnY catalyst. During aromatization, a sizable number of short alkanes and olefins were also obtained on acidic Y-zeolites. The off-gas composition shows the presence of ∼45% C₂-C₄ olefins with 8.9% H₂. The incorporation of Zn species can promote the dehydrogenation activity, and the subsequent aromatization required a suitable pore network. The optimized ZnY catalyst inspires the formation of toluene and xylenes, inhibiting the formation of benzene and gaseous alkanes.

Combustion performance of biocrude oil from solvolysis liquefaction of Chlorella pyrenoidosa by thermogravimetry-Fourier transform infrared spectroscopy

The kinetic behavior and evolution characteristics of gaseous products during the combustion of biocrude oil from solvolysis liquefaction of Chlorella pyrenoidosa were investigated by thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). The results indicated the biocrude oil obtained from different ethanol/water mixed ratio had obvious difference with each other. The ignition temperature of biocrude oil from ethanol-water co-solvent was lower than that from pure water solvent, which promoted the comprehensive combustion index. Especially, BO40 (biocrude oil obtained from 40% ethanol content) achieved the lowest ignition temperature (163.4°C) and high comprehensive combustion index (1.24×10^-06min^-2°C^-3). CH, CO, CC, CO₂, CO and HCN were the main gaseous products. Compared to other biocrude oil samples, BO40 had high first peak intensity of CH, CO and CC, and low peak intensity of CO, which performed better combustion characteristic.

Selective catalytic conversion of bio-oil over high-silica zeolites

Four high silica zeolites, i.e., HSZ-385, 890, 960, and 990 were utilized for the selective catalytic conversion of bio-oil from Fallopia japonica to certain chemicals in a fixed-bed reactor. The Beta-type HSZ-960 zeolite showed the highest selectivity to hydrocarbons, especially to aromatics as well as PAH compounds with the lowest unwanted chemicals while HSZ-890 showed high selectivity to aromatics. NH3-Temperature Programmed Desorption (TPD) analysis indicated that different amounts of acid sites in different zeolites determined the catalytic activity for the oxygen removal from bio-oil, in which the acid sites at low temperature (LT) region gave more contribution within the utilized temperature region. The reusability test of HSZ-960 showed the stability of hydrocarbons yield at higher temperature due to the significant contribution of coke gasification which assisted further deoxygenation of bio-oil. These results provide a guidance to select suitable zeolite catalysts for the upgrading of bio-oil in a practical process.

Production of aromatic hydrocarbons through catalytic pyrolysis of 5-Hydroxymethylfurfural from biomass

Catalytic pyrolysis of 5-Hydroxymethylfurfural (HMF) was conducted on a fixed bed reactor at atmospheric pressure. HMF could be converted into aromatic hydrocarbons through catalytic pyrolysis. The catalysts and reaction conditions were both critical in maximizing the aromatic hydrocarbons selectivity. Four catalysts, β-zeolite, HZSM-5, Ga/HZSM and In/HZSM were tested in this study. HZSM-5 (Si/Al=50) was found to be the most effective catalyst in both reactivity and selectivity among these catalysts. Under the reaction temperature of 600 °C, the highest carbon yield of 48.99% of aromatic hydrocarbons was achieved from catalytic pyrolysis HMF with HZSM-5 (Si/Al=50) as catalyst. Moreover, the HZSM-5 (Si/Al=50) catalyst was recycled for five times without shown deactivation of the catalyst.