Quan Bu

A review of catalytic hydrodeoxygenation of lignin-derived phenols from biomass pyrolysis

Catalytic hydrodeoxygenation (HDO) of lignin-derived phenols which are the lowest reactive chemical compounds in biomass pyrolysis oils has been reviewed. The hydrodeoxygenation (HDO) catalysts have been discussed including traditional HDO catalysts such as CoMo/Al(2)O(3) and NiMo/Al(2)O(3) catalysts and transition metal catalysts (noble metals). The mechanism of HDO of lignin-derived phenols was analyzed on the basis of different model compounds. The kinetics of HDO of different lignin-derived model compounds has been investigated. The diversity of bio-oils leads to the complexities of HDO kinetics. The techno-economic analysis indicates that a series of major technical and economical efforts still have to be investigated in details before scaling up the HDO of lignin-derived phenols in existed refinery infrastructure. Examples of future investigation of HDO include significant challenges of improving catalysts and optimum operation conditions, further understanding of kinetics of complex bio-oils, and the availability of sustainable and cost-effective hydrogen source.

Production of phenols and biofuels by catalytic microwave pyrolysis of lignocellulosic biomass

Catalytic microwave pyrolysis of biomass using activated carbon (AC) was investigated to determine the effects of pyrolytic conditions on the yields of phenol and phenolics. Bio-oils with high concentrations of phenol (38.9%) and phenolics (66.9%) were obtained. These levels were higher than those obtained by pyrolysis without AC addition and were closely related to the decomposition of lignin. A high concentration of esters (42.2% in the upgraded bio-oil) was obtained in the presence of Zn powder as catalyst and formic acid/ethanol as reaction medium. Most of the esters identified by GC-MS were long chain fatty acid esters. The high content of phenols and esters obtained in this study can be used as partial replacement of petroleum fuels after separation of oxygenates or as feedstock for organic syntheses in the chemical industry after purification.

Phenol and phenolics from lignocellulosic biomass by catalytic microwave pyrolysis

Catalytic microwave pyrolysis of biomass using activated carbon was investigated to determine the effects of pyrolytic conditions on the yields of phenol and phenolics. The high concentrations of phenol (38.9%) and phenolics (66.9%) were obtained at the temperature of 589 K, catalyst-to-biomass ratio of 3:1 and retention time of 8 min. The increase of phenol and its derivatives compared to pyrolysis without catalysts has a close relationship with the decomposition of lignin under the performance of activated carbon. The concentration of esters was also increased using activated carbon as a catalyst. The high content of phenols obtained in this study can be used either directly as fuel after upgrading or as feedstock of bio-based phenols for chemical industry.

The effects of torrefaction on compositions of bio-oil and syngas from biomass pyrolysis by microwave heating.

Microwave pyrolysis of torrefied Douglas fir sawdust pellet was investigated to determine the effects of torrefaction on the biofuel production. Compared to the pyrolysis of raw biomass, the increased concentrations of phenols and sugars and reduced concentrations of guaiacols and furans were obtained from pyrolysis of torrefied biomass, indicating that torrefaction as a pretreatment favored the phenols and sugars production. Additionally, about 3.21-7.50 area% hydrocarbons and the reduced concentration of organic acids were obtained from pyrolysis of torrefied biomass. Torrefaction also altered the compositions of syngas by reducing CO2 and increasing H2 and CH4. The syngas was rich in H2, CH4, and CO implying that the syngas quality was significantly improved by torrefaction process.

Bio-based phenols and fuel production from catalytic microwave pyrolysis of lignin by activated carbons

The aim of this study is to explore catalytic microwave pyrolysis of lignin for renewable phenols and fuels using activated carbon (AC) as a catalyst. A central composite experimental design (CCD) was used to optimize the reaction condition. The effects of reaction temperature and weight hourly space velocity (WHSV, h(-1)) on product yields were investigated. GC/MS analysis showed that the main chemical compounds of bio-oils were phenols, guaiacols, hydrocarbons and esters, most of which were ranged from 71% to 87% of the bio-oils depending on different reaction conditions. Bio-oils with high concentrations of phenol (45% in the bio-oil) were obtained. The calorific value analysis revealed that the high heating values (HHV) of the lignin-derived biochars were from 20.4 to 24.5 MJ/kg in comparison with raw lignin (19 MJ/kg). The reaction mechanism of this process was analyzed.

Microwave pyrolysis of distillers dried grain with solubles (DDGS) for biofuel production

Microwave pyrolysis of distillers dried grain with solubles (DDGS) was investigated to determine the effects of pyrolytic conditions on the yields of bio-oil, syngas, and biochar. Pyrolysis process variables included reaction temperature, time, and power input. Microwave pyrolysis of DDGS was analyzed using response surface methodology to find out the effect of process variables on the biofuel (bio-oil and syngas) conversion yield and establish prediction models. Bio-oil recovery was in the range of 26.5-50.3 wt.% of the biomass. Biochar yields were 23.5-62.2% depending on the pyrolysis conditions. The energy content of DDGS bio-oils was 28 MJ/kg obtained at the 650°C and 8 min, which was about 66.7% of the heating value of gasoline. GC/MS analysis indicated that the biooil contained a series of important and useful chemical compounds: aliphatic and aromatic hydrocarbons. At least 13% of DDGS bio-oil was the same hydrocarbon compounds found in regular unleaded gasoline.

Renewable phenols production by catalytic microwave pyrolysis of Douglas fir sawdust pellets with activated carbon catalysts

The effects of different activated carbon (AC) catalysts based on various carbon sources on products yield and chemical compositions of upgraded pyrolysis oils were investigated using microwave pyrolysis of Douglas fir sawdust pellets. Results showed that high amounts of phenols were obtained (74.61% and 74.77% in the upgraded bio-oils by DARCO MRX (wood based) and DARCO 830 (lignite coal based) activated carbons, respectively). The catalysts recycling test of the selected catalysts indicated that the carbon catalysts can be reused for at least 3-4 times and produced high concentrations of phenol and phenolic compounds. The chemical reaction mechanism for phenolics production during microwave pyrolysis of biomass was analyzed.

A review of catalytic microwave pyrolysis of lignocellulosic biomass for value-added fuel and chemicals

Lignocellulosic biomass is an abundant renewable resource and can be efficiently converted into bio-energy by a bio-refinery. From the various techniques available for biomass thermo-chemical conversion; microwave assisted pyrolysis (MAP) seems to be the very promising. The principles of microwave technology were reviewed and the parameters for the efficient production of bio-oil using microwave technology were summarized. Microwave technology by itself cannot efficiently produce high quality bio-oil products, catalysts are used to improve the reaction conditions and selectivity for valued products during MAP. The catalysts used to optimize MAP are revised in the development of this article. The origins for bio-oils that are phenol rich or hydrocarbon rich are reviewed and their experimental results were summarized. The kinetics of MAP is discussed briefly in the development of the article. Future prospects and scientific development of MAP are also considered in the development of this article.

Hydrocarbon and hydrogen-rich syngas production by biomass catalytic pyrolysis and bio-oil upgrading over biochar catalysts

The focus of this study is to investigate the influences of biochar as a catalyst in biomass pyrolysis and bio-oil upgrading. The biochar catalyst enhanced the syngas and improved the bio-oil quality in biomass pyrolysis. The high concentrations of phenols (46 area%) and hydrocarbons (16 area%) were obtained from torrefied biomass catalytic pyrolysis over biochar catalysts. High-quality syngas enriched in H2, CO, and CH4 was observed. The amounts of H2 and CO in syngas were up to 20.43 vol% and 43.03 vol% in raw biomass catalytic pyrolysis, and 27.02 vol% and 38.34 vol% in torrefied biomass catalytic pyrolysis. Thermal gravimetric (TG) analysis showed that the raw and recycled biochar catalysts had good thermal stability. Upgraded bio-oil was dominated by phenols (37.23 area%) and hydrocarbons (42.56 area%) at high biochar catalyst loadings. The biochar catalyst might be used as a cost-competitive catalyst in biomass conversion and bio-oil upgrading.

Thermal behavior and kinetic study for co-pyrolysis of lignocellulosic biomass with polyethylene over cobalt modified ZSM-5 catalyst by thermogravimetric analysis.

The thermal behavior and kinetic study of lignocellulosic biomass (rice straw (RS)) and linear low-density polyethylene (LLDPE) pyrolysis over modified ZSM-5 catalyst were investigated using thermo-gravimetric analysis (TGA). Cellulose and lignin were used as model compounds of biomass in order to investigate the reaction mechanism of lignocellulosic biomass and polyethylene co-pyrolysis. Results showed that RS&LLDPE co-pyrolysis was more complicated than that of the individual components. The activation energy (E) of RS, and RS&LLDPE pyrolysis were 79.61kJ/mol and 59.70kJ/mol respectively, suggesting that there was a positive synergistic interaction between RS and LLDPE. The addition of LLDPE with lignin co-pyrolysis obtained a lower apparent activation energy (33.39kJ/mol) compared to raw lignin pyrolysis (53.10kJ/mol). Results indicated that the Cobalt modified ZSM-5 catalyst was able to improve the reaction rate of RS and LLDPE co-pyrolysis; also the addition of Co/ZSM-5 catalyst resulted in a lower apparent activation energy during cellulose and LLDPE co-pyrolysis.