• Energy Research

orrefaction is a promising thermal pretreatment process to prepare biomass for use in energy production. Torrefaction of corn stover, switchgrass, and prairie grass at three selected temperatures (250°C, 300°C, or 350°C) for 3 h was carried out using a laboratory-scale batch reactor. Torrefaction of a blend of these three feedstocks at the same conditions was also examined. The effects of temperature and feedstock type on the yields and properties of the products (bio-char, bio-oil, and torrefaction off-gases) were analyzed. The bio-char produced from all of the feedstocks had higher carbon content and higher heating value (HHV) and lower moisture content (MC) when the torrefaction temperature increased. The HHV of bio-chars produced at 350°C were 25.15 MJ kg-1 for corn stover, 27.94 MJ kg-1 for switchgrass, 28.75 MJ kg-1 for prairie grass, and 28.79 MJ kg-1 for the blend. The carbon contents of the bio-chars increased from 42.36% to 60.31% for corn stover, from 43.94% to 70.95% for switchgrass, from 44.27% to 66.28% for prairie grass, and from 43.52% to 64.47% for the blend with torrefaction at 350°C. The results also indicated that the bio-oil and off-gases produced at lower temperatures had low value for further utilization. The MCs of the bio-oils produced in the torrefaction process were very high: 52.41% to 71.75% for corn stover, 58.01% to 74.22% for switchgrass, 65.44% to 75.07% for prairie grass, and 79.70% to 83.33% for the blend. The concentrations of combustible gases (H2 and CO) in the off-gas were less than 12% for all feedstocks. Compared to the individual feedstocks, the blend exhibited a very limited synergistic effect. Blending different biomass species for torrefaction may be an option to produce a uniform feedstock for biofuel production.

Abstract Catalytic cracking of camelina oil over Zn/ZSM-5 catalyst in a fixed-bed tubular reactor was investigated. An optimization study on the catalytic cracking conditions based on nine well-planned orthogonal experiments was carried out. Three main operation conditions including reaction temperature, liquid hourly space velocity and oil extraction press frequency were studied to examine their effects on the yield and quality of hydrocarbon biofuel produced. Characterization of the catalyst, hydrocarbon biofuel and non-condensable gas was conducted. There was no significant difference between the bulk structures of fresh Zn/ZSM-5 and used Zn/ZSM-5. Small ZnO particles dispersed well on the parent ZSM-5. Hydrocarbon biofuel contained 65.18% hydrocarbons and its properties including dynamic viscosity, density and higher heating value were improved after upgrading, compared to camelina oil. It was found that the oil extraction press frequency was the most important factor and liquid hourly space velocity was the least important factor for the hydrocarbon biofuel production. In addition, the optimum conditions for camelina oil upgrading were a combination of reaction temperature of 550 °C, a liquid hourly space velocity of 1.0 h −1 and an oil extraction press frequency of 15 Hz.

To address the issues of greenhouse gas emissions associated with fossil fuels, vegetable oilseeds, especially non-food oilseeds, are used as an alternative fuel resource. Vegetable oil derived from these oilseeds can be upgraded into hydrocarbon biofuel. Catalytic cracking and hydroprocessing are two of the most promising pathways for converting vegetable oil to hydrocarbon biofuel. Heterogeneous catalysts play a critical role in those processes. The present review summarizes current progresses and remaining challenges of vegetable oil upgrading to biofuel. The catalyst properties, applications, deactivation, and regeneration are reviewed. A comparison of catalysts used in vegetable oil and bio-oil upgrading is also carried out. Some suggestions for heterogeneous catalysts applied in vegetable oil upgrading to improve the yield and quality of hydrocarbon biofuel are provided for further research in the future.

Abstract Large amounts of plastics are discarded worldwide each year, leading to a significant mass of waste in landfills and pollution to soil, air, and waterways. Upcycling is an efficient way to transform plastic waste into high-value products and can significantly lessen the environmental impact of plastic production/consumption. In this article, current advances and future directions in plastic waste upcycling technologies are discussed. In particular, this review focuses on the production of high-value materials from plastic waste conversion methods, including pyrolysis, gasification, photoreforming, and mechanical reprocessing. Plastic waste compositions, conversion products, reaction mechanisms, catalyst selection, conversion efficiencies, polymer design, and polymer modification are also explored. The main challenges facing the adoption and scale-up of these technologies are highlighted. Suggestions are given for focusing future research and development to increase the efficiency of upcycling practices.

The massive consumption of fossil fuels and associated environmental issues are leading to an increased interest in alternative resources such as biofuels. The renewable biofuels can be upgraded from bio-oils that are derived from biomass pyrolysis. Catalytic cracking and hydrodeoxygenation (HDO) are two of the most promising bio-oil upgrading processes for biofuel production. Heterogeneous catalysts are essential for upgrading bio-oil into hydrocarbon biofuel. Although advances have been achieved, the deactivation and regeneration of catalysts still remains a challenge. This review focuses on the current progress and challenges of heterogeneous catalyst application, deactivation, and regeneration. The technologies of catalysts deactivation, reduction, and regeneration for improving catalyst activity and stability are discussed. Some suggestions for future research including catalyst mechanism, catalyst development, process integration, and biomass modification for the production of hydrocarbon biofuels are provided.

AbstractA series of Co‐Mo/HZSM‐5 catalysts was prepared using an impregnation method for the thermal conversion of prairie cordgrass (PCG). The catalysts were characterized by BET measurements, XRD, FTIR spectroscopy, and TEM. The Co‐Mo/HZSM‐5 catalysts were tested in the thermal conversion of PCG to produce hydrocarbon biofuel in a two‐stage catalytic pyrolysis system. The products were analyzed and included incondensable gas, bio‐oil, and biochar. Compared to non‐catalytically obtained bio‐oil, the chemical composition, water content, higher heating value, viscosity, and density of the catalytic bio‐oils were improved. The results indicated that 4 %Mo‐2 %Co/HZSM‐5 showed a robust ability in the catalytic cracking of PCG with the highest yield of hydrocarbons at 41.08 %.

Biogas produced in landfills contains large amounts of methane (a potent greenhouse gas) and hence requires collection and treatment according to EPA regulations.

Individually, sunflower oil produced from inedible sunflower seeds with hulls and sunflower meats without hulls were catalytically cracked over the ZSM-5 catalyst in a fixed-bed reactor at three reaction temperatures (450 °C, 500 °C, and 550 °C). Characterizations of hydrocarbon biofuel, distillation residual, and non-condensable gas were carried out. The reaction temperature on the hydrocarbon biofuel yield and quality from sunflower seed oil and sunflower meat oil were discussed and compared. In addition, a preliminary cost analysis of the sunflower seed dehulling was carried out. The results showed that the highest hydrocarbon biofuel yield was obtained from upgrading sunflower meat oil at 500 °C. The highest meat hydrocarbon biofuel yield was 8.5% higher than the highest seed hydrocarbon biofuel yield. The reaction temperature had a significant effect on the distribution of non-condensable gas components. Furthermore, the reaction temperature affected the yield and properties of hydrocarbon biofuel. The unit cost of producing sunflower meat oil was lower than that of producing sunflower seed oil. Comprehensively, sunflower meat could be a more economical feedstock than sunflower seed to produce hydrocarbon biofuel.