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A series of iron (Fe) modified CuO-ZnO-ZrO2-Al2O3 (CZZA) catalysts, with various Fe loadings, were prepared using a co-precipitation method. A bifunctional catalyst, consisting of Fe-modified CZZA and HZSM-5, was studied for dimethyl ether (DME) synthesis via CO2 hydrogenation. The effects of Fe loading, reaction temperature, reaction pressure, space velocity, and concentrations of precursor for the synthesis of the Fe-modified CZZA catalyst on the catalytic activity of DME synthesis were investigated. Long-term stability tests showed that Fe modification of the CZZA catalyst improved the catalyst stability for DME synthesis via CO2 hydrogenation. The activity loss, in terms of DME yield, was significantly reduced from 4.2% to 1.4% in a 100 h run of reaction, when the Fe loading amount was 0.5 (molar ratio of Fe to Cu). An analysis of hydrogen temperature programmed reduction revealed that the introduction of Fe improved the reducibility of the catalysts, due to assisted adsorption of H2 on iron oxide. The good stability of Fe-modified CZZA catalysts in the DME formation was most likely attributed to oxygen spillover that was introduced by the addition of iron oxide. This could have inhibited the oxidation of the Cu surface and enhanced the thermal stability of copper during long-term reactions.

Direct dimethyl ether (DME) synthesis from CO2 and H2 is considered a promising production route. However, this process is thermodynamically and kinetically restricted by the presence of water as a byproduct. In this study, a water-conduction membrane was incorporated into the direct DME synthesis reactor to generate a dry reaction environment. In the absence of water, the activities of the CO2 hydrogenation catalyst (CZA) and methanol dehydration catalyst (HZSM-5) were boosted 4- and 10-fold, respectively, and single-pass CO2 conversion of up to 73.4%, far beyond equilibrium, and DME yields of up to 54.5% were obtained. Moreover, the good protection of the catalysts against fast deactivation was demonstrated.

Water-selective zeolite membranes The yield of many gas-phase industrial reactions is limited by the formation of water as a by-product. Li et al. harnessed the water-sieving properties of NaA zeolite crystals by forming them into continuous defect-free membranes within tube reactors (see the Perspective by Carreon). These membranes can let water pass but reject gases such as hydrogen, carbon monoxide, and carbon dioxide (CO 2 ). When these membranes were used in CO 2 hydrogenation to form methanol with water as a by-product, substantial increases were observed in both the CO 2 conversion and methanol yield. Science , this issue p. 667 ; see also p. 624

Zirconium (Zr) modified CuO/ZnO/Al2O3 (CZA) catalysts with different aluminum (Al) and Zr contents were synthesized by the co-precipitation method. The synthesized CuO/ZnO/ZrO2/Al2O3 (CZZA) catalysts were comprehensively characterized and studied for methanol synthesis via CO2 hydrogenation. The CZZA catalyst showed the highest methanol yield of 12.4 % at 220 °C and 2.76 MPa with an optimized catalyst composition of Cu/Zn/Zr/Al (atomic ratio) at 4:2:1:0.5. The CZZA catalyst showed better activity than that of the CZA catalyst and a superior stability for methanol synthesis. There was no decrease in the BET surface area and very little coke formation for the spent CZZA catalyst, after 300 h of methanol synthesis. Bifunctional catalysts, composed of CZZA and HZSM-5, were investigated for dimethyl ether (DME) synthesis directly from CO2 hydrogenation, and a maximum DME yield of 18.3 % was obtained at a reaction temperature of 240 °C and a pressure of 2.76 MPa. The stability of the bifunctional CZZA and HZSM-5 catalyst during the DME synthesis also significantly improved, as compared to that of the CZA and HZSM-5. A significant decrease in the BET surface area and an increase in coking on the spent CZZA catalyst were observed after 100 h of DME synthesis, indicating a detrimental effect on CZZA stability when a HZSM-5 catalyst was present. The changes in structural properties (e.g., BET surface area and crystallinity) and coking for HZSM-5 could be responsible for the deactivation of the bifunctional catalyst.

The effects of three different mixing methods of CuO/ZnO/Al2O3 (CZA) and HZSM-5 bifunctional catalyst on the stability for dimethyl ether (DME) synthesis from carbon dioxide (CO2) hydrogenation were investigated. When the bifunctional catalyst was prepared by method A (mixing powder without pelletization), there was no significant change in DME production and catalyst stability when the HZSM-5 loading was varied between 0.1 g and 0.5 g with a fixed CZA loading of 0.5 g,. When the bifunctional catalysts were prepared by method B (pressed into pellets of CZA and pellets of HZSM-5 and then mixed) and method C (mixed CZA and HZSM-5 powders, then pressed into pellets), the mixing methods did not initially impact CO2 conversion and had a minor effect on DME yield. However, long-term tests (100 h) indicated that the mixing method had a significant influence on the catalyst stability. Method B showed the best stability and the extent of catalyst deactivation followed the sequence of method B

The torrefaction bio-oil is composed of a number of chemical compounds with low concentrations, which results in a low efficiency of its application. To improve the concentrations of high-value chemicals such as furfural in the torrefaction bio-oil, four metal chlorides and hydrochloric acid were investigated as catalysts in the torrefaction of Douglas fir by microwave heating. The number of chemical compounds in the attained bio-oil was significantly reduced with introducing MgCl2, FeCl3, and AlCl3 being into the process of torrefaction. The bio-oil obtained with these three catalysts were dominated by furfural with the concentration over 20 mg/g with the torrefaction temperature, time, and catalyst/reactant ratio of 250 °C, 10 min, and 8 wt.%, respectively. The effects of torrefaction conditions on product yield were investigated by selecting MgCl2 as the catalyst, and the results indicated that the yield of torrefied biomass decreased significantly with the increase of reaction temperature, time, and catalyst loading while the yield of bio-oil collected simultaneously was increased. Further analysis for the bio-oil suggested that low temperature, long reaction time, and high catalyst loading favored furfural production. The analysis for non-condensable gas suggested that high reaction temperature and catalyst loading promoted the methane and carbon monoxide production during torrefaction. According to bio-oil and non-condensable gas analysis, a reaction pathway was proposed to explain biomass catalytic torrefaction using MgCl2.

Highly active and selective Cu-ZnO based catalysts with high BET surface areas and Cu surface areas were prepared using the co-precipitation method. The Cu-ZnO based catalysts were systematically characterized and studied for methanol synthesis. Bifunctional catalysts, composed of Cu-ZnO based catalysts and HZSM-5 were studied for one-step dimethyl ether (DME) synthesis via CO2 hydrogenation. The effects of catalyst preparation conditions, reaction temperature, and pressure on methanol and DME synthesis were investigated and the optimum reaction conditions were determined. The optimized catalyst showed a BET surface area of 128 m2/g and a Cu surface area of over 59.3 m2/g, and demonstrated a high catalytic activity for CO2 hydrogenation. A bifunctional catalyst, prepared by a synthesized Cu-ZnO catalyst and HZSM-5, showed a high DME selectivity in one-step CO2 hydrogenation and methanol dehydration. The high activity and selectivity of the catalysts were attributed to the microstructure of the catalysts, which can be greatly affected by the catalyst preparation process. A long-term stability test showed a considerable decrease in activity within the first 20 h; however, the CO2 conversion (21.4%) and DME selectivity (55.5%) were still very high after 100 h.

Fractionation of crude bio-oil into an organic phase and an aqueous phase by simply adding water and research strategies targeted at producing hydrogen, fuels, or other value-added chemicals from the fractions have been proposed. However, the stability of the bio-oil fractions has not been comprehensively investigated. The objective of this study was to comparatively investigate the stability of crude bio-oil and its two fractions by evaluating their physicochemical properties during long-term storage at room temperature and accelerated aging at 40 °C and 60 °C. Comparing with crude bio-oil, the resulted aqueous phase is more stable; for the organic phase, the stability is also improved in terms of the changes in viscosity and average molecular weight, but not in terms of the increasing water content and total acid number. In overview for all the crude bio-oil and its two fractions, the water content, viscosity, total acid number, and average molecular weight increased with the increase of aging time and temperature; except for acetic acid and propionic acid, which slightly increased in content at all aging conditions, all the other 13 measured chemical contents decreased with the increasing aging time and temperature, indicating that the aging process involved all the six chemical groups of anhydrosugars, carboxylic acids, alcohols, furans, ketones, and phenolics, accelerated at higher temperature.

Despite the potential carbon-neutrality of switchgrass bio-oil, its high acidity and diverse chemical composition limit its utilization. The objectives of this research are to investigate pH neutralization of bio-oil by adding various alkali solutions in a batch system and then perform neutralization using process intensification devices, including a static mixer and a centrifugal contactor. The results indicate that sodium hydroxide and potassium hydroxide are more appropriate bases for pH neutralization of bio-oil than calcium hydroxide due to the limited solubility of calcium hydroxide in aqueous bio-oil. Mass and total acid number (TAN) balances were performed for both batch and continuous-flow systems. Upon pH neutralization of bio-oil, the TAN values of the system increased after accounting the addition of alkali solution. A bio-oil heating experiment showed that the heat generated during pH neutralization did not cause a significant increase in the acidity of bio-oil. The formation of phenolic comp...

The chemical complexity of bio-oil aqueous phase limits its efficient utilization. To improve the efficiency of the bio-oil biorefinery, this study focused on the separation of chemical groups from the bio-oil water-extract via sequential organic solvent extractions. Due to their high recoverability and low solubility in water, four solvents (hexane, petroleum ether, chloroform, and ethyl acetate) with different polarities were evaluated, and the optimum process conditions for chemical extraction were determined. Chloroform had high extraction efficiency for furans, phenolics, and ketones. In addition to these classes of chemical, ethyl acetate had a high extraction efficiency for organic acids. The sequential extraction using chloroform followed by ethyl acetate resulted in 62.2 wt.% of original furans, ketones, alcohols, and phenolics being extracted into chloroform, while 62 wt.% acetic acid was extracted into ethyl acetate, leaving behind a high concentration of levoglucosan (∼53.0 wt.%) in the final aqueous phase. Chemicals separated via the sequential extraction could be used as feedstocks in a biorefinery using processes such as catalytic upgrading of furans and phenolics to hydrocarbons, fermentation of levoglucosan to produce alcohols and diols, and hydrogen production from organic acids via microbial electrolysis.

Robust, gas-impeding water-conduction nanochannels that can sieve water from small gas molecules such as hydrogen (H

Producing value-added chemicals from glycerol is imperative for the sustainable future of biodiesel. Despite worldwide efforts, the commercial production of acrylic acid from glycerol faces challenges, both technologically and economically. Based on our new technology using CO2 as a reaction medium in a two-step process to catalytically convert glycerol to acrylic acid, we established computer simulation models to analyze the energy efficiency and estimate production costs at different scenarios. The analysis was conducted in conjunction with published data of a typical, intermediate-sized biodiesel facility, aiming at the feasibility of producing acrylic acid on-site in the context of a circular economy. Variable analysis in response to the market value of glycerol, the source and cost of carbon dioxide recycling, and the changes in process scale and conditions are also presented. Results indicates that a cost-effective supply of CO2 to the acrylic acid plant is key to the further research and development.

Supercritical carbon dioxide (SC‐CO2) has been used for the first time as a reaction medium for the dehydration of glycerol to acrolein catalyzed by a solid acid. Unprecedented catalyst stability over 528 hours of time‐on‐stream was achieved and the rate of coke deposition on the zeolite catalyst was the lowest among extensive previous studies, showing potential for industrial application. Coking pathways in SC‐CO2 were also elucidated for future development. The results have potential implications for other dehydration reactions catalyzed by solid acids.

To efficiently utilize water-soluble compounds in bio-oil and evaluate the potential effects of these compounds on processes such as microbial electrolysis, this study investigated the physicochemical properties of bio-oil and the associated aqueous phase generated from switchgrass using a semi-pilot scale auger pyrolyzer. Combining separation and detection strategies with organic solvent extraction, an array of analytical instruments and methods were used to identify and quantify the chemical constituents. Separation of an aqueous phase from the crude bio-oil was achieved by adding water (water: crude bio-oil at 4:1 in weight), which resulted in a partition of 61 wt.% of the organic compounds into a bio-oil aqueous phase (BOAP). GC/MS analysis for BOAP identified over 40 compounds of which 16 were quantified. Acetic acid, propionic acid, and levoglucosan are the major components in BOAP. In addition, a significant portion of chemicals that have the potential to be upgraded to hydrocarbon fuels was extracted to BOAP (77 wt.% of the alcohols, 61 wt.% of the furans, and 52 wt.% of the phenolic compounds in crude bio-oil). Valorization of the BOAP may require conversion methods capable of accommodating a very broad substrate specificity. A better separation strategy is needed to selectively remove the acidic and polar components from crude bio-oil to improve economic feasibility of biorefinery operations.

Applications of bio-oil are limited by its challenging properties including high moisture content, low pH, high viscosity, high oxygen content, and low heating value. Separation of switchgrass bio-oil components by adding water, organic solvents (hexadecane and octane), and sodium hydroxide may help to overcome these issues. Acetic acid and phenolic compounds were extracted in aqueous and organic phases, respectively. Polar chemicals, such as acetic acid, did not partition in the organic solvent phase. Acetic acid in the aqueous phase after extraction is beneficial for a microbial-electrolysis-cell application to produce hydrogen as an energy source for further hydrodeoxygenation of bio-oil. Organic solvents extracted more chemicals from bio-oil in combined than in sequential extraction; however, organic solvents partitioned into the aqueous phase in combined extraction. When sodium hydroxide was added to adjust the pH of aqueous bio-oil, organic-phase precipitation occurred. As the pH was increased, a bi...

With the aim to directly use the mixture of glycerol and methanol from the biodiesel production for value-added chemical production, catalytic conversion of refined glycerol to lactic acid (LA) and propylene glycol (PG) using mixed solid catalysts of CaO and CuO in methanol medium was first investigated. At the optimum condition, the yields of LA and PG achieved were 46 mol% and 35 mol%, respectively. For recycling the catalysts, a combined process of glycerol conversion to alkyl lactate was further investigated. Using this integrated process, 45 mol% methyl lactate yield and 28 mol% PG yield were achieved in methanol medium, and 45 mol% ethyl lactate and 18 mol% PG yield were achieved in ethanol medium. The test for crude glycerol conversion showed that the impurities had slightly negative effects on glycerol conversion and product yield in methanol medium but no obvious effect in ethanol medium. Similar glycerol conversion and product yield were obtained when the mixture of glycerol, methanol, and CaO from biodiesel production were directly used as starting material. This result suggests that the mixture from biodiesel production can be directly used to produce valued-added chemicals such as methyl lactate and PG.

A new approach to hydrogen production using an integrated pyrolysis–microbial electrolysis process is described. The aqueous stream generated during pyrolysis of switchgrass was used as a substrate for hydrogen production in a microbial electrolysis cell, achieving a maximum hydrogen production rate of 4.3 L H2/L anode-day at a loading of 10 g COD/L-anode-day. Hydrogen yields ranged from 50 ± 3.2% to 76 ± 0.5% while anode Coulombic efficiency ranged from 54 ± 6.5% to 96 ± 0.21%, respectively. Significant conversion of furfural, organic acids and phenolic molecules was observed under both batch and continuous conditions. The electrical and overall energy efficiency ranged from 149–175% and 48–63%, respectively. The results demonstrate the potential of the pyrolysis–microbial electrolysis process as a sustainable and efficient route for production of renewable hydrogen with significant implications for hydrocarbon production from biomass.

This study investigated alkyl lactate production from glycerol by tandem processes which included glycerol conversion to calcium lactate using solid catalysts and subsequent transesterification of calcium lactate to alkyl lactate using methanol/ethanol and carbon dioxide. The effect of reaction conditions on alkyl lactate production was systematically investigated. A central composite design (CCD) and response surface methodology were used to design the experiments and evaluate the optimum process conditions. At the optimum conditions, the methyl lactate yield reached 57 mol% with a glycerol conversion of 94 mol% using refined glycerol. A yield of approximately 42 mol% for ethyl lactate was obtained using refined glycerol at the optimum conditions. Similar glycerol conversion and alkyl lactate yields were obtained using crude glycerol, indicating that the impurities in the crude glycerol had no significant effects on alkyl lactate production. The examination of regenerated catalysts that had been reused twice showed no negative effects on glycerol conversion and methyl lactate production. Compared to the traditional lactic acid and alkyl lactate production, this two-step process for alkyl lactate production from glycerol is both economical and environmentally benign since no gypsum was produced and the solid catalysts can be regenerated and reused.

This study investigated a fed-batch process for glycerol conversion to lactic acid with sodium hydroxide (NaOH) as homogeneous catalyst, with the aim to reduce the corrosiveness of catalyst to reactor. At the optimal conditions of the fed-batch process (1.1 M initial glycerol concentration, reaction time of 220 min, reaction temperature of 300 °C, NaOH concentration around 0.2 M), lactic acid yield reached 82 mol%, with 93 mol% of glycerol conversion. A first order kinetic model in the fed-batch conversion of glycerol was developed and validated under different process conditions. The corrosiveness to stainless steel reactor in glycerol conversion in the fed-batch process, measured as Fe3+ at the end of reaction, decreased from 9.5 to 1.5 ppm Fe3+ when compared to a batch process using a homogeneous 1.25 M NaOH as catalyst. Application of the fed-batch reactor in the crude glycerol conversion reached the maximum lactic acid yield of 72.9 mol% with 92.4 mol% glycerol conversion, but high soap content in crude glycerol has negative effects on both lactic acid yield and glycerol conversion.

Ex situ catalytic pyrolysis of biomass through a packed-bed catalysis close coupled with microwave pyrolysis was investigated to convert Douglas fir sawdust pellets to aromatic hydrocarbons by Zn/ZSM-5 catalyst. A comparison test from five different Zn loadings (0, 0.5, 1, 2, 5 wt.%) was first conducted, and it was found that the highest amount of aromatic hydrocarbons was produced from 0.5% Zn loaded on ZSM-5. Then a central composite experimental design (CCD) was used to optimize the upgraded bio-oil and syngas yields with 0.5% Zn loaded in ZSM-5. In comparison to the non-catalytic experiment, all the catalysts decreased the bio-oil yield and increased the syngas production. The product yields from Zn/ZSM-5 were sensitive with reaction conditions as the bio-oil yields varied between 22.3% and 44.8% compared with 32.2% and 37.8% over ZSM-5 catalyst, and syngas yields from 33.3% to 55.5% vs. 38.8% to 43.7% on ZSM-5 catalyst. GC/MS analysis showed that aromatic hydrocarbons become the most abundant compounds in the bio-oil. The high amount of aromatic hydrocarbons in the upgraded bio-oils from GC/MS analysis was confirmed by the FTIR analysis. The aromatic hydrocarbon was increased when the packed-bed temperature and inverse weight hourly space velocity (WHSV)−1 were increased. The comparison of coking on ZSM-5 and Zn/ZSM-5 catalysts at different reaction conditions showed that the coking increased with increasing (WHSV)−1 and decreasing packed-bed temperatures. Zn/ZSM-5 had lower coking than ZSM-5 on all the reaction conditions except packed-bed temperature at 269 °C and (WHSV)−1 at 0.048.

The integrated process of torrefaction and pyrolysis of corn stover were investigated in this study. The effects of torrefaction conditions on both torrefaction and pyrolysis products were determined. The heating values of torrefied biomass were similar to those of coals and increased comparing to raw biomass. The torrefaction oils contained high value chemicals such as furans and phenolics. The torrefaction process caused a decrease in the pyrolytic oil yields but the total bio-oil yield from torrefaction and pyrolysis were similar to those from raw biomass pyrolysis. The pyrolytic oil from torrefied biomass contained more hydrocarbons and phenols and less organic acids than raw biomass pyrolysis, which indicates that the quality of pyrolytic oil was improved with torrefaction as a thermal pretreatment. The optimum torrefaction condition for both high yield and quality of pyrolytic oil was determined at the reaction temperature around 275 °C and torrefaction time of 30 min. This study implied that torrefaction as a pretreatment can be combined with the pyrolysis for high quality biofuel production.

In the valorization of glycerol as byproduct of biodiesel production, although recent progress in glycerol conversion to lactic acid using homogeneous chemocatalysis showed promising high yield, the used high alkalinity entails high corrosiveness to reactors and problematic downstream separations. In this study, five solid base catalysts were screened for converting glycerol to lactic acid with the aim to ease corrosiveness, focusing on inexpensive CaO as a promising solid base. Process conditions were systematically investigated for optimization. The highest yield of lactic acid achieved was 40.8 mol% with a glycerol conversion of 97.8 mol% at the optimum conditions using refined glycerol. Similar conversion rate and lactic acid yield were also obtained in the conversion of crude glycerol using CaO if the water content in crude glycerol is lower than 10%. CaO exhibited lower activation energy in converting glycerol to lactic acid compared to homogeneous NaOH catalyst. Corrosiveness to reactor using CaO was proven much lower than that using homogeneous NaOH catalyst. CaO as catalyst for both biodiesel production and subsequent crude glycerol conversion to lactic acid was investigated, revealing its potential industrial applications for the production of both biodiesel and lactic acid.

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.

The thermal decomposition behaviour and kinetics of Douglas fir sawdust torrefaction and torrefied sawdust pyrolysis were investigated using a thermogravimetric analyser (TGA). The mass loss of samples in torrefaction was highly related to the torrefaction temperature. The two-step reaction model fitted well for Douglas fir sawdust torrefaction. The activation energies of the first and second reaction stages were 112 kJ mol−1 and 150 kJ mol−1, respectively. Torrefied biomass exhibited different thermo decomposition behaviours compared to untreated biomass. The start point of torrefied biomass decomposition was shifted and the degree of shift increased with the severity of torrefaction. The final biochar yield of torrefied biomass was also increased with the increase of torrefaction temperature. Derivative thermogravimetric (DTG) curves showed that the shoulder of hemicelluloses decomposition in torrefied biomass pyrolysis was eliminated. The decomposition rate of torrefied biomass has a decreasing trend due to the mass depletion in torrefaction. A first-order one-step global model with the average activation energies in the range of 195–204 kJ mol−1 can describe the raw and torrefied biomass pyrolysis. The kinetic analysis also showed that the torrefied biomass pyrolysis from high torrefaction temperature might be multiple-step reactions.

Microwave assisted catalytic pyrolysis was investigated to convert Douglas fir pellets to bio-oils by a ZSM-5 zeolite catalyst. A central composite experimental design (CCD) was used to optimize the catalytic pyrolysis process. The effects of reaction time, temperature and catalyst to biomass ratio on the bio-oil, syngas, and biochar yields were determined. GC/MS analysis results showed that the bio-oil contained a series of important and useful chemical compounds. Phenols, guaiacols, and aromatic hydrocarbons were the most abundant compounds which were about 50–82% in bio-oil depending on the pyrolysis conditions. Comparison between the bio-oils from microwave pyrolysis with and without catalyst showed that the catalyst increased the content of aromatic hydrocarbons and phenols. A reaction pathway was proposed for microwave assisted catalyst pyrolysis of Douglas fir pellets.

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.

Microwave torrefaction of Douglas fir pellets was investigated and the effects of process conditions on the yields of products were determined. The reaction temperature and time significantly influenced the yields of torrefied biomass, bio-oil, and noncondensable gases. Three linear models were developed to predict the product yield, as a function of reaction temperature and time. Gas chromatography/mass spectroscopy (GC/MS) analysis for bio-oils showed that the bio-oils were mainly composed of furans, phenolics, sugars, ketones/aldehydes, and organic acids. The amounts of each compound varied with the reaction conditions. Over the reaction temperature of 275 °C, noncondensable gases were mainly composed of CO2 and CO and its yields and compositions were significantly influenced by the temperature. Higher heating values (HHVs) of torrefied biomass were 20.90–25.07 MJ/kg, which is an ∼6%–31% increase, compared to the HHV of raw biomass. The energy yields of torrefied biomass, 67.03%–90.06%, implied that mo...

Microwave pyrolysis of Douglas fir sawdust pellet was investigated to determine the effects of reaction temperature and time on the yields of bio-oil, syngas, and charcoal using a central composite design (CCD) and response surface analysis. The research results indicated that thermo-chemical conversion reactions can take place rapidly in large-sized biomass pellet by using microwave pyrolysis. The yields of bio-oil and syngas were increased with the reaction temperature and time. The highest yield of bio-oils was 57.8% (dry biomass basis) obtained at 471 °C and 15 min. GC/MS analysis indicated that the bio-oils were mainly composed of phenols, guaiacols, furans, ketones/aldehydes, and organic acids. The yield of specific chemicals such as furans and phenolic compounds were highly related to the reaction temperature. The syngas contained high value chemicals, such as carbon monoxide, methane, and short chain hydrocarbons. A third-order reaction mechanism fits well the microwave pyrolysis of Douglas fir pellet with activation energy of 33.5 kJ/mol and a frequency factor of 3.03 s−1.

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.

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.

This study investigated microwave pyrolysis of corn stover with particle sizes from 0.5 to 4 mm and determined the effects of reaction temperature and time of pyrolytic conditions on the yields of bio-oil, syngas, and biochar. Mineral and GC/MS analysis were used to study the pyrolysis of corn stover. A prediction model was satisfactorily developed to describe the biofuel conversion yield as a function of reaction temperature and time. Corn stover with different particle sizes was found to be similarly pyrolyzed by microwave heating. The research results indicate that thermochemical conversion reactions can take place rapidly in large-sized corn stover by using microwave pyrolysis. Mineral analysis indicates that most minerals stayed with the biochar. GC/MS analysis indicates that the bio-oil contained a series of important and useful chemical compounds: phenols, aliphatic hydrocarbons, aromatic hydrocarbons, and furan derivatives. These chemical compounds evolved were related to the pyrolysis conditions.

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 CO 2 and increasing H 2 and CH 4 . The syngas was rich in H 2 , CH 4 , and CO implying that the syngas quality was significantly improved by torrefaction process.

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. The bio-oils with high concentrations of phenol (38.9%) and phenols (including phenol and alkyl substituted phenol) (66.9%) were obtained. The increase of phenols and decrease of guaiacols compared to pyrolysis without AC addition had a close relationship with the decomposition of lignin under the performance of activated carbon. The high content of phenol and phenolics obtained in this study can be used either as partial substituent of transportation fuel after hydroprocessing or as feedstock for organic synthesis and chemical industry after purification.

Microwave torrefaction of corn stover with particle size of 4 mm was investigated and the effects of reaction temperature and time on the yields of volatile, bio-oil and torrefied biomass were determined. The response surface analysis of the central composite design (CCD) showed that the yields of volatile, bio-oil and torrefied biomass were significantly affected by the reaction temperature and time. Three linear models were developed to predict the yields of conversion products as a function of temperature and time. A first order reaction kinetics was also developed to model the corn stover torrefaction. Ph values of torrefaction bio-oils ranged from 2.3 to 2.76 which were similar to those of bio-oils from biomass pyrolysis. GC/MS analysis for torrefaction bio-oils showed that the organic acid was about 2.16% to 12.00%. The torrefaction bio-oils also contain valuable chemical compounds such as phenols, furan derivatives and aliphatic hydrocarbons determined by a GC/MS. There are no aromatic compounds and polycyclic aromatic hydrocarbons (PAHs) detected in the torrefaction bio-oils. The torrefaction biogas was mainly consisted of ch4, c2h6, c3h8, which was about 56 wt% of the total bio-gas. The biogas can be used for chemical synthesis or electricity generation. The heating values of torrefied biomass were from 18.64–22.22 MJ/kg depending on the process conditions. The heating values of torrefied biomass were significantly greater than those of raw biomass and similar to those of coals. The energy yields of torrefied biomass from 87.03–97.87% implied that most energy was retained in the torrefied biomass. Economic analysis indicated that the biomass microwave torrefaction plant located in a farm is profitable.

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.

Microwave torrefaction of corn stover with particle size of 4 mm was investigated and the effects of reaction temperature and time on the yields of volatile, bio-oil and torrefied biomass were determined. The response surface analysis of the central composite design (CCD) showed that the yields of volatile, bio-oil and torrefied biomass were significantly affected by the reaction temperature and time. Three linear models were developed to predict the yields of conversion products as a function of temperature and time. A first order reaction kinetics was also developed to model the corn stover torrefaction. GC/MS analysis for torrefaction bio-oils showed that the organic acid was about 2.16% to 12.00%. The torrefaction bio-oils also contain valuable chemical compounds such as ketones/aldehydes, furan derivatives and aliphatic hydrocarbons determined by a GC/MS. There are no aromatic compounds and polycyclic aromatic hydrocarbons (PAHs) detected in the torrefaction bio-oils. The torrefaction biogas was mainly consisted of CH4, C2H6, C3H8, which was about 56 wt% of the total biogas. The biogas can be used for chemical synthesis or electricity generation. The heating values of torrefied biomass were from 18.64-22.22 MJ/Kg depending on the process conditions. The heating values of torrefied biomass were significantly greater than those of raw biomass and similar to those of coals. The energy yields of torrefied biomass from 87.03- 97.87% implied that most energy was retained in the torrefied biomass.

Microwave pyrolysis of Douglas fir sawdust pellet was investigated to determine the effects of reaction temperature and time on the yields of bio-oil, biogas, and biochar using a central composition design (CCD) and response surface analysis. The research results indicated that thermochemical conversion reactions can take place rapidly in large-sized biomass pellet by using microwave pyrolysis. The yields of bio-oil and biogas were increased with the reaction temperature and time. The highest yield of bio-oil was 53.9% (wet biomass basis) obtained at 470.7°C and 15min. GC/MS analysis indicated that the bio-oils were mainly composed of phenols, guaiacols, furans, ketones/aldehydes, and organic acids. The phenols and guaiacols accounted for the largest amount of chemicals in the bio-oil, which represented 59.7–78.6% under different conditions. The biogases contained high value chemicals, such as carbon monoxide, methane, and short chain hydrocarbons. A third-order reaction mechanism fits well the microwave pyrolysis of Douglas fir pellet with activation energy of 33.5 kJ/mol and a frequency factor of 3.03 s–1.