Nuclear Magnetic Resonance Characterization of Renewable Products from a Two‐Step Ex‐Situ Hydropyrolysis Vapor Upgrading Process

Abstract

A novel two-step ex-situ hydropyrolysis vapor upgrading (HPVU) process can generate tailored oxygenated hydrocarbon products from lignocellulosic biomass by adjusting vapor upgrading temperature. Such products, containing varied oxygen contents (ranging from 2 to 17 wt%), are different from traditional petroleum hydrocarbons and conventional biomassderived pyrolysis oil. Elucidation of the comprehensive structural motif of these unconventional products is critical for development and deployment of the HPVU process. To this end, two-dimensional heteronuclear 1 H-13 C NMR techniques were employed to first provide single-and multiple-bond correlations between protons and carbons characteristic of different organic functional groups. The distribution of carbon functional groups was further determined by quantitative 13 C NMR spectroscopy with full relaxation and well-defined chemical shift regions obtained from diverse NMR methods. Phenols and ketones were identified as the main oxygenate species in these renewable products. At higher vapor upgrading temperatures, a decrease in oxygenate species and an increase in alkylation on aromatic rings were observed. Of particular importance, compared to pyrolysis oil, the amounts of thermally unstable oxygenate species, such as aldehyde, carboxylic acid, and carbohydrate, were found to be minimal, suggesting good thermal stability of these renewable hydrocarbon products.

Transportation fuels from biomass fast pyrolysis, catalytic hydrodeoxygenation, and catalytic fast hydropyrolysis

“…The carbon atom yield for the low oxygen bio-oils was 35 to 44%, which is similar to the results achieved with pressurized catalytic fast hydropyrolysis by Marker et al [363,364] and Dayton et al [357]. In a follow up NMR study of their bio-oils they showed that alkylation and/or transalkylation reactions on aromatic compounds took place in the HDO reactor with increasing significance at higher temperatures (particularly at 425 °C) where the degree of deoxygenation increases [369].…”

“…When using only the fluid bed reactor the oxygen content was 1.8wt%. Interestingly, the downstream fixed bed reactor both increased the carbon yield and decreased the oxygen content, indicating that alkylation reactions with olefins on aromatic compounds occurred over the NiMo/Al2O3 HDO catalyst, as also reported by the group at Philips 66[369].…”

Catalytic hydropyrolysis of biomass using supported CoMo catalysts – Effect of metal loading and support acidity

“…The decrease in the concentration of phenols is not enough to explain the increased concentration of monoaromatics and naphthenes, thus it is very likely that some of the oxygenated aliphatics have participated in alkylation reactions with the aromatics, thus increasing the monoaromatic yield. Similarly Lai et al [51] observed alkylation reactions when upgrading catalytic hydropyrolysis vapors in a fluid bed reactor.…”

New insights into the effect of pressure on catalytic hydropyrolysis of biomass

“…Melligan et al [15] investigated the effect of hydrogen pressure at 600 °C using a Ni/H-ZSM-5 catalyst and found that increasing the hydrogen pressure increased the higher heating value (HHV) of the products, due to an increased degree of deoxygenation. Other groups have investigated hydropyrolysis either using a cyclone reactor or fluid bed reactor followed by a fixed bed catalytic HDO reactor [16][17][18][19].…”