Review of Denitrogenation of Algae Biocrude Produced by Hydrothermal Liquefaction

Recently, algae biocrude has drawn considerable attention as algae are considered to be one of the major fuel feedstocks of the future. Based on some impressive results achieved under appropriate conditions, the algae hydrothermal liquefaction(HTL) process has proven to be energy efficient. However, the HTL of biocrude is characterized by a high nitrogen content, which prevents its use in the field of transportation due to the associated nitrogen oxide emissions. Despite this toxicity, few research efforts have focused on the denitrogenation of algae biocrude. In this study, we review the effect of different strain-specific operation parameters and process upgrades with respect to the nitrogen content of biocrude. To achieve denitrogenation, chemical engineering may be required, although some improvements in biocrude properties have been achieved in a number of process upgrades. The use of similar successful pathways has the potential to improve the field of HTL biocrude denitrogenation. These methods, including the adsorptive and extractive denitrogenations of fossil fuels and the hydrodenitrogenation of the main nitrogen compounds, are helpful for developing a better understanding of the potential of denitrogenation for algae HTL biocrude. We also recommend the use of some available catalysts and corresponding operation parameters to promote continued research on denitrogenation.

Hydrothermal Liquefaction of Water Hyacinth: Effect of Process Conditions and Magnetite Nanoparticles on Biocrude Yield and Composition

In this work, an efficient way of converting the water hyacinth to biocrude oil using magnetite nanoparticles (MNPs) as potential catalysts was demonstrated for the first time. MNPs were synthesised by co-precipitation and used in the hydrothermal liquefaction (HTL) of water hyacinth at different reaction conditions (temperature, reaction time, MNPs to biomass ratio and biomass to water ratio). The best reaction conditions were as follows: temperature— 320, reaction time—60 minutes, MNPs to biomass ratio – 0.2 g/g and biomass to water ratio – 0.06 g/g. HTL in presence of MNPs gave higher biocrude yields compared to HTL in absence of MNPs. The highest biocrude yield was 58.3 wt% compared to 52.3 wt% in absence of MNPs at similar reaction conditions. The composition of biocrude oil was analysed using GC-MS and elemental analysis. GC-MS results revealed that HTL in presence of MNPs led to an increase in the percentage area corresponding to hydrocarbons and a reduction in the percentage area corresponding to oxygenated compounds, nitrogenated compounds and sulphur compounds. Elemental analysis revealed an increase in the hydrogen and carbon content and a reduction in the nitrogen, oxygen and sulphur content of the biocrude when HTL was done in presence of MNPs compared to HTL in absence of MNPs. The nanoparticles were recovered from the biochar by sonication and magnetic separation and recycled. The recycled MNPs were still efficient as HTL catalysts and were recycled five times. The application of MNPs in the HTL of water hyacinth increases the yield of biocrude oil, improves the quality of biocrude through removal of hetero atoms, oxygen and sulphur compounds and is a potentially economical alternative to the traditional petroleum catalysts since MNPs are cheaper, widely available and can be easily recovered magnetically and recycled. This will potentially lead to an economical, environmentally friendly and sustainable way of producing biofuels from biomass.

Integration of biocrude production from fast pyrolysis of biomass with solar PV for dispatchable electricity production

This article analyses the integration of distributed biocrude production facilities using fast pyrolysis with solar photovoltaic(PV)for dispatchable electricity production.The strong growth of intermittent electricity generation from solar PV and wind is leading to a greater need for energy storage at grid scale and dynamic demand management.Various forms of energy storage,including electrochemical(e.g.batteries),mechanical(e.g.flywheels)and gravitational(e.g.pumped-hydro),are being developed.This work studies the issues of integrating fast pyrolysis of biomass to produce biocrude that can be readily stored in tanks and combusted to produce electricity when required to supplement the electricity generation from a solar PV unit to meet an arbitrary energy demand curve.The use of biomass pyrolysis in this application has a range of benefits,including the flexibility to augment intermittent renewables,the integration of more bioenergy into the electricity sector and the creation of commercial quantities of biocrudes that can be refined into renewable transport fuels such as jet fuel for which few other alternatives exist.Biocrudes,especially partially upgraded,can be stored and used when required in engines and gas turbines,making them a suitable fuel for augmenting the intermittent nature of solar and wind projects.The development of the distributed 100%renewable power stations using a mix of biomass/biocrude and solar PV and/or wind would also increase the certainty of supply,knowledge of quality and price of raw biocrudes that can also be used to supply a centralized biorefinery,thereby substantially reducing the risk of investing in new biorefinery capacity.

High yield bio-oil production by hydrothermal liquefaction of a hydrocarbon-rich microalgae and biocrude upgrading

A green colonial microalgae Botryococcus braunii was hydrothermally processed under subcritical water conditions without the addition of catalysts,obtaining an oil yield as high as 68%.The higher heating value of liquefaction products is close to that of petroleum crude oil.The oil fraction from Botryococcus braunii liquefaction was specified for the first time,and the liquefaction mechanism was proposed.Due to the high lipid content of Botryococcus braunii,the liquefaction product distribution is quite distinct from other microalgae.The produced biocrudes contain
9%oxygen,with oleic acid as the main source.Amides derived from oleic acid and proteins are the major nitrogenates in the biocrudes.The biocrude was processed using catalytic cracking and hydrotreating.Catalytic cracking mostly produces aromatics,while the majority of hydrotreating products are straight and branched hydrocarbons.The oxygen content in the catalytic cracking products was very low.The presence of amides in the hydrotreating feed changes the reaction pathway from hydrodecarboxylation to hydrodeoxygenation as a result of the competitive adsorption of amides on the active sites for hydrodecarboxylation.Both processes show satisfactory denitrogenation performance.Catalytic cracking displays superior ability than hydrotreating with regards to the removal of oxygen.

Nitrogen distribution in the products from the hydrothermal liquefaction of Chlorella sp. and Spirulina sp.

The high contents of nitrogen-containing organic compounds in biocrude obtained from hydrothermal liquefaction of microalgae are one of the most concerned issues on the applications and environment.In the project,Chlorella sp.and Spirulina sp.were selected as raw materials to investigate the influence of different reaction conditions(i.e.,reaction temperature,residence time,solid loading rate)on the distribution of nitrogen in the oil phase and aqueous phase.Three main forms of nitrogen-containing organic compounds including nitrogen-heterocyclic compounds,amide,and amine were detected in biocrudes.The contents of nitrogen-heterocyclic compounds decreased with temperature while amide kept increasing.The effect of residence time on the components of nitrogen-containing organic compounds was similar with that of temperature.However,the influence of solid loading rate was insignificant.Moreover,it was also found that the differences of amino acids in the protein components in the two microalgae might affect the nitrogen distribution in products.For example,nitrogen in basic amino acids of Spirulina sp.preferred to go into the aqueous phase comparing with the nitrogen in neutral amino acids of Chlorella sp.In summary,a brief reaction map was proposed to describe the nitrogen pathway during microalgae hydrothermal liquefaction.