Changyan Yang

Catalytic hydroprocessing of microalgae-derived biofuels: a review

The algal biofuel technology has been accelerated greatly during the last decade. Microalgae can be processed into a broad spectrum of biofuel precursors, which mainly include crude algal oil recovered by extraction and bio-crude oils produced from hydrothermal liquefaction and pyrolysis processes. Due to the high protein content in algal species and the limitations of conversion technologies, these biofuel precursors require the further catalytic removal of heteroatoms such as oxygen, nitrogen, and sulfur, being upgraded to biofuels like green diesel and aviation fuel. This article reviews the state-of-the-art in the hydroprocessing of microalgae-based biofuels, as well as the catalyst development and the effect of process parameters on hydrotreated algal fuels. Hydroprocessing of algal fuels is a new and challenging task, and still underdeveloped. For the long term, an ideal catalyst for this process should possess the following characteristics: high activities towards deoxygenation and denitrogenation, strong resistance to poisons, minimized leaching problems and coke formation, and an economically sound preparation process.

Catalytic conversion of microwave-assisted pyrolysis vapors.

Abstract The effect of the following catalysts: MS (Molecular sieve) 4A, Fe2O3/MS 4A, CoO/MS 4A, NiO/MS 4A, MgO/MS 4A, PtO/MS 4A, Al2O3/MS 4A, La2O3/MS 4A, Cl−/MS 3A, SO2− 4/MS 3A, Na2O/MS 3A, CaO/MS 3A, K2O/MS 3A, CoO/ZrO2, NiO/ZrO2, La2O3/ZrO2, NiO/CaO-ZrO2, Cl−/ZrO2, SO2− 4/ZrO2, Na2O/ZrO2, CaO/ZrO2, and MgO/ZrO2, on chemical profile of the products from microwave-assisted pyrolysis of biomass was studied. A microwave oven with a frequency of about 2.4 gigahertz, and a power of about 1–1.3 kilowatt was used to pyrolyze aspen (Populus tremuloides). The steam that evolved was removed from the oven and passed to a catalyst column where the temperature was controlled at about 350–600°C, and the converted vapors were then condensed to bio-oils. The chemical profiles of the bio-oils were determined using gas chromatography-mass spectrometry. Solid acids were proved to be effective catalysts to decompose pyrolysis vapors, while solid alkaline and other catalysts do not seem to affect the composition of the liquid products from microwave-assisted pyrolysis. Increasing the temperature of the catalyst bed and the ratio of catalysts to biomass adversely affected the liquid yield.

The pyrolysis of duckweed over a solid base catalyst: Py-GC/MS and TGA analysis

ABSTRACT The possibility of using the solid base as the pyrolysis catalyst to synthesize chemicals from duckweed (Lemna minor) was explored. Thermogravimetric analyses indicated that the conversion of duckweed in slow pyrolysis was approximately 60 wt%. Direct pyrolysis of duckweed could form various hydrocarbons and precursors for industrious products. When pyrolyzing this species with the solid base catalyst, new chemicals such as 3-methyl-butanal, cyclobutanol, 2-methyl-1H-pyrrole, ethylbenzene, 2-pyrrolidinone, and 4-ethyl-phenol were synthesized. The results indicated that the application of the solid base in pyrolysis mainly enhanced the alkyl substitution reactions and could direct complex pyrolysis reactions to preferred products.

Recent Developments in Commercial Processes for Refining Bio-Feedstocks to Renewable Diesel

The process technologies for conversion of bio-feedstocks such as vegetable oils, animal fats, and algal oil into renewable diesel have been developed and commercialized during the last decade. The global annual production capacity of renewable diesel is approaching to 5.5 million tons per year. The refining process generally includes pretreatment of the renewable feedstock to remove impurities, hydroprocessing and isomerization to produce hydrocarbons, and distillation to produce a fuel suitable for use as diesel or jet fuel. This article reviews recent development in the commercial production of renewable diesel, pretreatment technologies, chemistry of deoxygenation and cracking of triglycerides, the effect of reaction parameters on the relative activities of different reaction pathways, catalyst development, and the technical details of commercial processes for refining bio-feedstocks.

Biomass harvesting and collection

Abstract With the development of bioenergy a substantial increase in biomass demand directly caused challenges to biomass harvesting. This chapter introduces the harvesting system for woody biomass, corn stover, sugarcane, and energy grasses. Woody biomass and roundwood are normally harvested using conventional one-pass or two-stage timber harvesting systems, while small-scale timber harvesting systems are becoming more attractive. As a predominant source of biomass, corn stover is often collected with conventional multipass forage harvest systems. Meanwhile agricultural machinery manufacturers are developing the single-pass combined stream harvesting system, which has been proposed as a viable harvest strategy for corn. For sugarcane harvesting, manual cutting with open-burning is not preferred, while green cane harvesting using whole stalk or chopper harvesters have become more favorable. In addition, harvesting of energy crops such as Giant Miscanthus, switchgrass, reed canary grass, and some other grasses can be done with conventional hay harvesting equipment. From the point of view of machinery, integration often provides more benefits to the cost reduction but fewer impacts on the environment; the application of new technologies in precision agriculture will subsequently improve the efficiency and the economy. Intensive biomass harvesting affects the ecosystem in terms of greenhouse gas emissions, soil quality, hydrology, and biodiversity. Life cycle assessment is an emerging tool to comprehensively analyze environmental impacts of harvesting activities, and its results could provide guidance to policy makers and scientists. Furthermore, biomass harvesting best management practices should be established based on science and then applied widely to reduce harmful effects due to biomass removal. Economically, governments should provide sufficient incentives to ensure growers’ incomes and the development of bioenergy.