We report the activity and the selectivity of several heterogeneous nickel catalysts for the supercritical water gasification (SCWG) of biomass. The effects of catalyst support on the carbon conversion and hydrogen selectivity were demonstrated using 44 different materials, covering a wide range of chemical and physical properties. At 5% nickel loading, α-Al₂O₃, carbon nanotubes (CNTs), and MgO supports resulted in high carbon conversions, while SiO₂, Y₂O₃, hydrotalcite, yttria-stabilized zirconia (YSZ), and TiO₂ showed modest activities. Utilization of different γ-Al₂O₃ supports resulted in a wide range of catalytic activities from almost inactive to highly active. Other catalyst carriers such as zeolites, molecular sieves, CeO₂, and ZrO₂ had insignificant activity under the conditions tested (i.e., 380 °C, 2 wt% feed). Aside from the catalytic activity, the stable metal oxide supports under the experimental conditions of this work, as identified by XRD, were α-Al₂O₃, boehmite, YSZ, and TiO₂. Given the high hydrogen yield and carbon conversion as well as its superior stability in supercritical water, α-Al₂O₃ was chosen for a more elaborate investigation. It was found that when using the same amount of nickel, the methane yield significantly decreased by increasing the nickel to support ratio whereas the carbon conversion was only slightly affected. At a given nickel to support ratio, a threefold increase in methane yield was observed by increasing the temperature from 350 to 410 °C. The catalyst activation conditions (e.g., calcination and reduction) had a small impact on its catalytic performance. The catalyst activity increased with the addition of alkali promoters (i.e., K, Na, Cs) and decreased with the addition of tin. The highest catalytic activity was obtained with the addition of 0.5% potassium. In summary, nickel loading and alkali promoters improved the hydrogen selectivity and the carbon conversion of the Ni/α-Al₂O₃ catalyst.

Lignin, the second most plentiful biopolymer, is produced on a large scale as the waste of the pulp and paper industries. Conventionally, lignin is incinerated for energy generation, while less than 2% of the produced mass is converted to value-added products. Herein, we employed hydrophilic sulfonated kraft lignin (SKL) to modify the selective layer of thin-film composite (TFC) forward osmosis (FO) membranes. Different concentrations of SKL (1, 3, and 6 wt %) were dispersed in m-phenylenediamine solution prior to the polymerization reaction with trimesoyl chloride-heptane solution. The modified membrane with a maximum amount of SKL (M3) provided 33.5 LMH water flux, a twofold improvement compared to the pristine membrane, when tested in the FO configuration with 2 M NaCl and deionized water as draw and feed solutions, respectively. Moreover, M3 showed a significantly lower flux decline than the unmodified membrane in the fouling experiments against sodium alginate solution as a synthetic wastewater and boiler feed water as an industrial process-affected water of the oil sands industry. The water contact angle decreased from 88.7° for the pristine membrane to 70.6° for M3, indicating the enhanced wettability of the modified membranes by the incorporation of SKL particles. Our work presents a novel application for SKL to be used as a hydrophilic modifier in the synthesis of TFC polyamide membranes with enhanced permeation and antifouling performance.