UPGRADING OF WHEAT/BARLEY AND MISCANTHUS BIO-OIL OVER A SULPHIDED CATALYST

摘要

In recent years, the production of biofuels from non-food crops wastes and harvesting residues plays an important role in the improvement of the global environment and in the replacement of declining oil reserves~1. Hydrogenation of lignocellulosic bio-oil is attracting much attention as a suitable way to produce petroleum-refinery compatible feedstock. Primarily, hydrogenation of bio-oil is carried out under severe reaction conditions in two-stage fixed-bed reactors, filled with a noble metal catalyst in the first zone and with a sulphided catalyst in the second zone2. This setup allows producing low-oxygen upgraded bio-oil, however, it is economically unviable and operationally complicated. Here, we present the results from 80 h long hydrogenation experiments of miscanthus and wheat/barley straw bio-oils obtained by one-stage condensation (2-5 °C) or fractional condensation (75 °C) ablative fast pyrolysis (AFP). Bio-oils from fractional condensation, in contrast to those from one-stage condensation, were stable and did not separate into an aqueous and organic phase. In that case, operation with these bio-oils was much easier than with bio-oils from one-stage condensation. Upgrading of bio-oils was performed in a one-stage fixed bed reactor filled with a laboratory-made NiMo/Al_2O_3 catalyst under constant reaction conditions (340 °C, 4 MPa and WHSV 1 h~(-1)), which we identified in our previous research as suitable reaction conditions. Hydrogenated products separated spontaneously into an aqueous phase, formed predominantly by water, and an organic phase. In this work, we used various analytical methods for the determination of physicochemical properties (density, viscosity, elemental analysis etc.) and chemical composition (CAN, Carbonyls by Faix, GC-MS for volatile compounds and hydrocarbons) of the organic products. In addition, we used FTIR in combination with the principle component analysis (PCA) to take a snapshot of the catalyst health and product quality. In all hydrogenated products, we have observed a drop in the quality with the increasing time-on-stream, which may be caused by catalyst deactivation and coke formation, as it shown in Figure 2. Nevertheless, the coke formation and reactor clogging, during the hydrogenation of miscanthus bio-oil, was so high that we were forced to stop the experiment after 36 hours. The observed decrease in Micro Conradson Carbon residues and CAN of the products from wheat/barley straw bio-oil indicated a significant improvement of the product stability. The laboratory-made NiMo/Al_2O_3 catalyst was suitable for the upgrading of straw bio-oil, from one-stage and from fractional condensation AFP, and can be further developed for the upgrading for other feedstocks.