Analysis of hydrogenation products of biocrude obtained from hydrothermally liquefied algal biomass by comprehensive gas chromatography mass spectrometry (GC×GC-MS)

Fuels produced from microalgae are a promising alternative for fuels from fossil resources. Algae biomass may be transformed by hydrothermal liquefaction (HTL) into biocrudes, which need upgrading by hydrotreatment to meet transportation fuel requirements. In this study, analyses of HTL biocrude catalytically hydrogenated in a batch reactor at temperatures between 360 and 400 °C and residence times between 2.5 and 10.2 h are presented. Selected samples were investigated by comprehensive gas chromatography mass spectrometry (GC×GC) using flame ionization (FID) or mass spectrometry (MS). The main components of the samples before and after the hydrogenation are hydrocarbons of different unsaturation including alkanes, alkenes, monocyclic and bicyclic hydrocarbons and monocyclic aromatic hydrocarbons. Also, small amounts of polyaromatic hydrocarbons are formed. The most frequent class of heteroatomic compounds are nitrogen and oxygen containing compounds. Oxygen containing compounds are primarily of phenolic nature, whilst nitrogen containing compounds show aromatic amine (alkylated aniline and isomers) and pyrrolic structures (alkylated indoles and carbazoles and isomers). Upon proceeding hydrogenation, an increasing content of lower molecular weight hydrocarbons is observed. The analyses allow to track the decrease of heteroatomic compounds and reveal the structure of refractory compounds. Ultimately, the results allow to identify optimum parameters for the hydrogenation of HTL biocrudes from algae, which correspond to a maximum yield of hydrocarbons and acceptable levels of heteroatomic compounds

LOHC-bound hydrogen for catalytic NOx reduction from O2-rich exhaust gas

The present study demonstrates a novel method for the NOx reduction by H2 in lean exhaust gases using H2 released from a Liquid Organic Hydrogen Carrier (LOHC). The concept implies the simultaneous H2 production and H2-deNOx reaction, which both take place on the same catalyst. In a first approach, the catalyst was suspended in the LOHC, while the exhaust flowed through the slurry. The experiments performed with a O2-rich model exhaust and perhydro dibenzyltoluene as LOHC as well as Pd/C, Pt/C and Pt/Al2O3 catalysts evidenced the feasibility of this transfer hydrogenation. As a result, the Pd/C catalyst revealed best H2-deNOx performance providing NOx conversions up to ??% and N2 selectivities of ??°C above 200°C. The characterization of the catalysts by temperature-programmed desorption of CO suggested that the superiority of the Pd/C sample is associated with its pronounced number of active Pd sites. Furthermore, the investigations also showed some LOHC degradation releasing CO, CO2 and hydrocarbons. However, additional experiments excluded significant participation of the formed CO in the H2-deNOx reaction at 210°C and above