Extract Nitrogen-Containing Compounds in Biocrude Oil Converted from Wet Biowaste via Hydrothermal Liquefaction

Abstract

This study demonstrates that water can serve as a green solvent to achieve denitrogenation of biocrude oil converted from wet biowaste via hydrothermal liquefaction (HTL) under previously determined optimal reaction conditions (300°C with a 1 h reaction time for swine manure and Chlorella; 300°C with a 0.5 h reaction time for Spirulina). It was hypothesized that water could extract relatively polar chemicals, such as some of the nitrogen-containing compounds, from HTL biocrude oil. This hypothesis was examined by different extraction techniques using water as a solvent to HTL biocrude oil converted from swine manure (SM) and low-lipid algae. The water solubilities of biocrude oil and product yields (water extract, biocrude oil, solid residue, and aqueous and gas products) were measured. Compared to that of the biocrude oil without extraction by water, the nitrogen content of biocrude oil converted from SM decreased from 4.32 to 3.23%. Gas chromatography−mass spectrometry (GC−MS) analyses of treated biocrude oil and water extract demonstrated that water can extract nitrogen-containing compounds and separate fatty acid derivatives that were originally in biocrude oil. When an ultrasonically assisted extraction by water was conducted, the nitrogen content in algal biocrude oil decreased from 6.83 to 5.75% with improved carbon and hydrogen content. In addition, GC−MS analyses of treated biocrude oil and water extract suggest that fatty acid derivatives may behave like surfactants and help in emulsifying nitrogen-containing compounds into water.

Anaerobic digestion of wastewater generated from the hydrothermal liquefaction of Spirulina: Toxicity assessment and minimization

“…The instrument variability was within the standard acceptance limit (5%). More details can be found in previous studies [9,10,27].…”

A perspective on hydrothermal processing of sewage sludge

“…HTL biocrude oil converted from high-protein feedstocks typically has a 3-7% nitrogen content, which is inappropriate for fuel application [8]. To date, denitrogenation of HTL biocrude oil has been investigated with hydrotreating [30,31], cracking [31,32], chemical extraction/separation from HTL biocrude oil [33,34], and super-critical fluid treatment [35][36][37]. However, the high nitrogen content of biocrude oil generated by HTL would result in fouling of conventional catalysts (e.g., zeolites) because of the high basicity caused by the nitrogen-heterocyclic compounds [15,34,38].…”

Renewable Diesel Blendstocks and Biopriviliged Chemicals Distilled from Algal Biocrude Oil Converted via Hydrothermal Liquefaction

“…The concentrations of n-heterocyclic compounds and amino acids were much lower in the distillates than in the biocrude oil. N-heterocyclic compounds and amino acids tend to partition into the aqueous phase rather than the oil phase [38]. Majority of the nheterocyclic compounds and amino acids could exist in the aqueous phase distilled at 98-120°C.…”

“…This is probably due to the loss of light amines. For instance, the SP-derived biocrude oil contains propylamine and butylamine that have boiling points below 80°C [38].…”