Heterogeneously Catalyzed Hydroprocessing of Organosolv Lignin in Sub- and Supercritical Solvents

A highly effective method for catalytic hydroprocessing of lignin to liquid products has been developed in supercritical ethanol (scEtOH) medium at moderate reaction conditions. The problems associated with the low lignin conversion (<20%) and char formation at higher temperatures in hot compressed water (HCW) were overcome in scEtOH. A significant increase in the calculated “higher heating value” (HHV) of the formed liquid was observed in a reaction using a heterogeneous catalyst compared to a reaction without a catalyst. The liquid product contains mainly substituted phenols, such as guaiacols and syringols, as major components. On the basis of the product distribution, a possible reaction pathway for the formation of the phenolic products is described. A maximum HHV up to 36.2 MJ/kg was calculated for a product obtained over 5% Ru/γ-Al₂O₃ at 300 °C after 20 h of reaction time. Lignin conversion of ca. 98% was observed. The yield for the liquid product reached values up to 92%

Selective Catalytic Reduction of NO_<i>x</i> of Ship Diesel Engine Exhaust Gas with C₃H₆ over Cu/Y Zeolite

Various solid Cu-containing catalysts were prepared. Their performance in the selective catalytic reduction of NO_<i>x</i> using propene as reducing agent from 150 to 450 °C in an O₂-rich model exhaust gas in the presence of water vapor was investigated. This research aimed at the development of a catalytic NO_<i>x</i> to N₂ (DeNO_<i>x</i>) step to be part of a ship diesel exhaust abatement system in combination with other techniques, such as nonthermal plasma. Among the catalysts tested, Cu on zeolite Y with an optimized load of 16 wt % (denoted as 16Cu/Y) displayed excellent DeNO_<i>x</i> activity with highest selectivity toward N₂ at 290 °C. The influence of other variables, such as Cu load, calcination temperature, feed composition, and GHSV on the performance of 16Cu/Y was studied, as well. The highest N₂ yield of 98% was achieved using 2000 ppm of propene in the gas feed. The presence of O₂ proved to be a crucial factor for promoting the selective reduction of NO_<i>x</i> with C₃H₆ over this catalyst. On the other hand, the presence of water in the feed decreased NO_<i>x</i> to N₂ conversion. However, the catalyst showed excellent stability over 120 h, even at high water concentration, and also after repeated heating from ambient temperature to 450 °C, and it was reusable after downtimes without remarkable loss in activity. The nature of the Cu species was studied by XPS, XRD, and TPR experiments

Efficient VO_<i>x</i>/Ce_1–<i>x</i>Ti_<i>x</i>O₂ Catalysts for Low-Temperature NH₃‑SCR: Reaction Mechanism and Active Sites Assessed by in Situ/Operando Spectroscopy

Supported V₂O₅/Ce_1–<i>x</i>Ti_<i>x</i>O₂ (3, 5, and 7 wt % V; <i>x</i> = 0, 0.1, 0.3, 0.5, 1) and bare supports have been tested in the selective catalytic reduction (SCR) of NO by NH₃ at different gas hourly space velocities (GHSVs) and were comprehensively characterized using XRD, pseudo in situ XPS, and UV–vis DRS as well as EPR and DRIFTS in in situ and operando mode. The best V/Ce_1–<i>x</i>Ti_<i>x</i>O₂ (<i>x</i> = 0.3, 0.5) catalysts showed almost 100% NO conversion and N₂ selectivity already at 190 °C with a GHSV value of 70000 h^–1, which belongs to the best performances observed so far in low-temperature NH₃-SCR of NO. The corresponding bare supports still converted around 80% to N₂ under the same conditions. On bare supports, SCR proceeds via a Langmuir–Hinshelwood mechanism comprising the reaction of adsorbed surface nitrates with adsorbed NH₃. On V/Ce_1–<i>x</i>Ti_<i>x</i>O₂, nitrate formation is not possible, and an Eley–Rideal mechanism is working in which gaseous NO reacts with adsorbed NH₃ and NH₄⁺. Lewis and Brønsted acid sites, though adsorption of NH₃, do not scale with the catalytic activity, which is governed rather by the redox ability of the materials. This is boosted in the supports by replacing Ce with the more redox active Ti and in catalysts by tight connection of vanadyl species via O bridges to the support surface forming −Ce–O–V­(O)–O–Ti– units in which the equilibrium valence state of V under reaction conditions is close to +5

Hierarchical ZSM‑5 Materials for an Enhanced Formation of Gasoline-Range Hydrocarbons and Light Olefins in Catalytic Cracking of Triglyceride-Rich Biomass

A hierarchical ZSM-5 material with a high fraction of mesoporosity coupled to well-preserved intrinsic zeolite characteristics has been successfully prepared by postsynthesis modifications involving optimization of base treatment and subsequent strong acid washing of commercial Al-rich ZSM-5 (parent ZSM-5). The resulting hierarchical ZSM-5 material was thoroughly characterized before being tested in the cracking of triglyceride-rich biomass, i.e., model feedstock triolein and real feedstock waste cooking oil under fluid catalytic cracking conditions. The results show that the introduction of intracrystalline mesoporosity enhances the utilization of zeolite acid sites by the enlarged external surface, leading to an increased conversion. At the same time, it partially suppresses the undesired secondary reactions by shortening micropore diffusion path lengths. With such a hierarchical ZSM-5 material, higher selectivities toward the desired products, i.e., gasoline-range hydrocarbons and light olefins, than with commercial ZSM-5 have been achieved