In-Gu Lee

Recent advances in the catalytic hydrodeoxygenation of bio-oil

Owing to the increasing interest in alternative energy, there is a focus on bio-oil production from biomass because it is an abundant and renewable energy source. Among the various kinds of biomass conversion technologies, pyrolysis has been investigated widely to produce bio-oil. However, the direct use of bio-oil is difficult because of its poor quality due to the large amounts of oxygen-containing compounds, such as acids, ketones, and esters. Therefore, an additional suitable upgrading process for bio-oil is required. Hydrodeoxygenation (HDO) is considered effective for the deoxygenation of bio-oil. This paper reviews the recent progress in the catalytic HDO of bio-oil. In addition, the effects of the solvent and catalyst applied to the HDO of bio-oil are reviewed intensively together with a discussion of the deactivation behavior of the catalyst during HDO.

Catalytic upgrading of lignin derived bio-oil model compound using mesoporous solid catalysts

The catalytic upgrading of a lignin-derived bio-oil model compound, the hydrodeoxygenation of guaiacol, was performed using mesoporous solid catalysts. Platinum supported on silica and mesoporous silica (SBA-15 and KIT-6) were used as catalysts. The level of platinum incorporation and aluminum grafting did not alter the physical properties of the supports, such as surface area and pore size distribution. On the other hand, these treatments drastically affected the catalytic activities. A catalyst with platinum alone converted guaiacol to oxygenate compounds. In contrast, a series of catalysts with both platinum incorporation and aluminum grafting enhanced hydrodeoxygenation by converting guaiacol into hydrocarbons (cyclohexane and benzene). A comparison of the catalyst supports revealed the ordered mesoporous silica, SBA-15 and KIT-6, with high surface area, to have a higher hydrocarbon yield than conventional silica.

Stabilization of bio-oil over a low cost dolomite catalyst

A low cost alkaline catalyst of dolomite (CaMg(CO3)2) was used to stabilize acacia sawdust bio-oil mixed with methanol. The upgrading efficiency was evaluated in terms of the total acid number (TAN) and viscosity. A change in the dolomite calcination temperature from 700 to 900 °C led to a significant change in the TAN and viscosity of the methanol-added bio-oil. Dolomite activated at higher temperatures had larger amounts of active CaO and MgO species due to the enhanced decarboxylation of calcium and magnesium carbonates. An increase in the dolomite content (1-5 wt%) decreased the TAN value of bio-oil remarkably. A thermal aging test of the methanol-added bio-oil upgraded using dolomite (calcined at 900 °C) at 50 °C for 24 h was carried out by storing the bio-oil at 80 °C for one week. Although the TAN value increased after the aging process, it was still lower than the TAN of raw bio-oil. In addition, increasing the methanol content (10-30 wt%) decreased the TAN and viscosity of the bio-oil significantly.

Catalytic rapid pyrolysis of Quercus variabilis over nanoporous catalysts

Catalytic rapid pyrolysis of Quercus variabilis, a Korean native tree species, was carried out using Py-GC/MS. Mesoporous MFI, which has both nanopores and micropores, and three nanoporous materials, Al-MCM-41, Al-SBA-15, and γ-Al2O3, were used as the catalyst. The acid sites of mesoporous MFI were strong Bronsted acid sites, whereas those of nanoporous materials were mostly weak acid sites. The composition of the product bio-oil varied greatly depending on the acid characteristics of the catalyst used. Phenolics were the most abundant species in the bio-oil, followed by acids and furanics, obtained over Al-MCM-41 or Al-SBA-15 with weak acid sites, whereas aromatics were the most abundant species produced over mesoporous MFI with strong acid sites, followed by phenolics. Aromatics, phenolics, and furanics are all important chemicals contributing to the improvement of bio-oil quality.

In-Situ Upgrading of Organosolv Lignin- and Cellulose-Derived Pyrolyzates Over Ce-MCM-41 Catalyst

Lignocellulosic biomass, principally consisting of cellulose, hemicellulose and lignin, is a main renewable source for the production of biofuels and valuable chemicals. For instance, the polyaromatic structure of lignin fraction of biomass makes it a high potential feedstock for the production of valuable aromatic chemicals such as phenolic compounds. In this work, selective conversion of the organosolv lignin-derived pyrolyzates to alkylphenols was carried out using Ce-MCM-41 as In-Situ catalyst. Catalytic fast pyrolysis of the organosolv lignin was carried out on a tandem micro-pyrolyzer coupled with gas chromatography and mass spectrometry (GC-MS) detectors. The refined pyrolytic vapor was mainly consisting of phenolics (phenol, alkylphenols, guaiacol and alkylguaiacols), monoaromatic hydrocarbons (benzene, toluene and xylenes), esters (formic acid ethyl ester, acetic acid methyl ester and hexadecanoic acid methyl ester), aldehydes (formaldehyde and methylbenzaldehyde), acids (hydroxyacetic acid and benzoic acids), furans (2-methylfuran and dihydrofuran) and ethanol. Our data showed that the selectivity of products was influenced by pyrolysis temperature (500, 550 and 600 °C). Maximum selectivity of alkylphenols (10.3%) was obtained at 550 °C. Besides In-Situ pyrolysis of organosolve lignin, the In-Situ upgrading of the cellulose-derived pyrolyzates was carried out using Ce-MCM-41 at 550 °C. In-Situ pyrolysis of cellulose using Ce-MCM-41 could obtain high selectivity of aldehydes (11.4%), furans (9.6%) and ketones (3.2%).

In-Situ Catalytic Pyrolysis of Waste Lignin Over Desilicated Beta

Desilicated Beta (DeBeta) was applied as the catalyst to the catalytic pyrolysis of waste lignin for the formation of aromatic hydrocarbon, and its performance was compared with that of the unmodified Beta. Large amounts of oxygen containing pyrolyzates were efficiently converted to stable aromatic hydrocarbons over both Beta and DeBeta catalysts. Compared to Beta, DeBeta exhibited the higher performance for the formation of aromatic hydrocarbons due to the enhanced diffusion efficiency through the mesopore.

Hydrodeoxygenation of Pyrolysis Bio-Oil Over Ni Impregnated Mesoporous Materials

The catalytic hydrodeoxygenation (HDO) of bio-oil over Ni-supported mesoporous materials was performed using a high pressure autoclave reactor. The actual pyrolysis oil of cork oak wood was used as a sample, and Ni/Al-SBA-15 and Ni/Al-MSU-F were used as catalysts. In addition, supercritical ethanol was added as solvent. Both Ni-supported mesoporous catalysts showed efficient HDO reaction ability. A higher heating value and pH of bio-oil were achieved by the HDO reaction over both catalysts and upgraded bio-oil had a lower viscosity. Compared to Ni/Al-MSU-F, Ni/Al- SBA-15 produced more upgraded bio-oil with a lower oxygen content and higher heating value via a catalytic HDO process.

In-Situ Catalytic Pyrolysis of Xylan and Dealkaline Lignin over SAPO-11

Silicoaluminophosphate molecular sieve, SAPO-11, was applied for the first time to the catalytic pyrolysis of xylan and dealkaline lignin. The isothermal fast catalytic pyrolysis of xylan and dealkaline lignin over different amounts of SAPO-11 and their product analysis were performed concurrently using a pyrolyzer GC/MS. Large amounts of oxygenated pyrolyzates produced from the non-catalytic pyrolysis of xylan at 500 °C were converted to furans, light hydrocarbons, and aromatic hydrocarbons using SAPO-11. When the catalyst to sample ratio was increased from 1:1 to 5:1 and 10:1, the selectivity toward aromatic hydrocarbons was increased dramatically. Phenolic compounds, such as guaiacols and vanillin, were the main products of the non-catalytic pyrolysis of dealkaline lignin. These phenolic compounds were upgraded efficiently into aromatics by the catalytic pyrolysis of dealkaline lignin over SAPO-11. By increasing the catalyst to sample ratio from 1:1 to 10:1, much larger amounts of aromatic hydrocarbons were obtained due to the increased catalyst acid sites. A phenolic pool mechanism was suggested as the major reaction pathway for the catalytic pyrolysis of dealkaline lignin over SAPO-11.

Catalytic Conversion of Pinus densiflora Over Mesoporous Catalysts Using Pyrolysis Process.

Catalytic pyrolysis experiments were conducted to investigate the possibility of obtaining valuable chemicals from Pinus densiflora, a native Korean tree species occupying 21.4% of the total area under forests in South Korea. Two representative mesoporous catalysts, Al-MCM-41 and Al-MSU-F, as well as hierarchical mesoporous MFI (Meso-MFI) that has both mesopores and micropores, were used as catalysts. Compared to non-catalytic pyrolysis, catalytic pyrolysis was shown to reduce the fractions of levoglucosan, phenolics, and acids in bio-oil, while increasing the fractions of aromatics, PAHs, and furans. Meso-MFI with strong acid sites showed a high selectivity toward aromatics and PAHs, whereas Al-MCM-41 and Al-MSU-F with weak acid sites exhibited a high selectivity toward furanic compounds. The results of this study indicate that choosing a catalyst with an adequate quantity of acidic sites with the required strength is critical for enhancing the production of desired chemicals from Pinus densiflora.