Biobased Aromatic Chemicals by Lignin Depolymerization and Defunctionalization

Nowadays, the production of chemicals is heavily dependent on fossil resources. Alternatives are required for sustainable development, and the use of renewable carbon sources such as biomass is an attractive option. In particular, lignin is interesting for this purpose, as currently, it is mainly used for energy generation and thus highly underutilized. Due to its aromatic structure, lignin can serve as a renewable resource to produce aromatic chemicals, especially phenolics.In this PhD research, experimental studies were performed with the objective to valorize technical lignins to biobased aromatic chemicals with an emphasis on phenolics. Catalytic hydrotreatment played a central role throughout the research. It entails a treatment of the lignins with molecular hydrogen in combinaton with a catalyst at elevated temperatures and pressures. New non-precious metal catalysts (e.g., Ni, MoO3, and Cu catalysts) were developed for the purpose of obtaining high yields of the desired low molecular weight phenolic products, and particularly their long-term stability was evaluated. Besides catalyst development, a pretreatment method combined with hydrotreatment and an integrated approach (pyrolysis + staged condensation + hydrotreatment) were investigated in detail for improved phenolic yields. The research described in this thesis provides new insights and solutions for producing bio-based phenolics from lignin

Selective Demethoxylation of Guaiacols to Phenols using Supported MoO 3 Catalysts

Lignin-derived monomers with methoxy substituents are abundantly present in bioliquids derived from lignocellulosic biomass. Examples are the products obtained from the reductive catalytic fractionation of lignin (RCF) and pyrolysis of lignocellulosic biomass and hydrotreated products thereof. An attractive valorization step for these liquids involves demethoxylation to obtain alkylated phenols through selective catalytic hydrodeoxygenation (HDO). Within the context of sustainable chemistry, there is a strong drive to use cheap, non-precious metal catalysts for this purpose. In this study, the HDO of guaiacol (5 wt% in toluene) was investigated in a continuous fixed-bed reactor at 380 °C, 20 bar over supported MoO3 catalysts. MoO3 (5 %) supported on TiO2 (P25) was shown to give superior performance compared with MoO3 supported on anatase TiO2, Al2O3, SiO2, Nb2O5, CeO2, and ZrO2. Additional studies involving variation of the Mo loading and process conditions were performed, and the highest selectivity to demethoxylated phenolics like phenol and methylated phenols was 82 % at 97 % conversion of guaiacol. Both 4-n-propylguaiacol and a realistic guaiacols-rich feed isolated from a representative pyrolysis oil were also successfully demethoxylated with the 5 % MoO3/TiO2 catalyst

Catalytic Hydrotreatment of Biomass-Derived Fast Pyrolysis Liquids Using Ni and Cu-Based PRICAT Catalysts

Biomass-derived fast pyrolysis liquids (PLs) are not directly applicable as transportation fuels due to their high oxygen content and limited storage stability. Catalytic hydrotreatment is an efficient technology to convert such PLs to finished fuels or intermediates that can be used as a co-feed for existing oil refinery units. In this paper, we report catalyst screening studies for the mild hydrotreatment of PLs using commercially available Ni and Cu-based PRICAT catalysts at rather mild conditions (200 °C, initial 140 bar H2pressure) in a batch setup for 4 h. Among all catalysts, PRICAT NI 62/15 showed the best performance for mild catalytic hydrotreatment in terms of product properties (highest H/C ratio and lowest TG residue). The best catalysts were also tested for deep hydrotreatment at more severe conditions (350 °C, initial 100 bar H2pressure). Here, the PRICAT NI catalysts showed better performance than the benchmark Picula Ni-Mo catalyst when considering oil yield and H/C ratio. Advantageously, the hydrogen consumption during deep hydrotreatment is also reduced, rationalized by a lower methanation activity

Enhanced Catalytic Depolymerization of a Kraft Lignin by a Mechanochemical Approach

Kraft lignin is an abundantly available side product from the pulp and paper industry. It has a complex aromatic structure and has great potential to serve as a feedstock for renewable aromatic chemicals. In this communication, we show that a simple mechanochemical pretreatment (viz., ball milling) of commercial Indulin AT kraft lignin before solvent-free hydrotreatment results in a 15% increase in the recovered oil yield with 15% more alkylphenols and a 33% reduction in solids compared to the unmilled sample. This increase raises the carbon efficiency toward the oil based on elemental composition from 76 to 91%, respectively. This enhanced catalytic performance is attributed to improved heat transfer and allowing for better contact between the kraft lignin particles of reduced size and the catalyst particles, prompting enhanced depolymerization at an earlier stage of the reaction, thereby preventing charring

Experimental studies on a combined pyrolysis/staged condensation/hydrotreatment approach to obtain biofuels and biobased chemicals

Fast pyrolysis is an efficient technology to convert lignocellulosic biomass to a liquid product. However, the high contents of oxygenated compounds and water hinder the direct utilization of pyrolysis oils. Here, we report an upgrading concept to obtain liquid products with improved product properties and enriched in valuable low molecular weight chemicals and particularly alkylphenols. It entails two steps, viz. i) pyrolysis with in-situ staged condensation at multiple kg scale followed by ii) a catalytic hydrotreatment of selected fractions using a Ru/C catalyst. Of all pyrolysis oil fractions after staged condensation, the product collected in a condenser equipped with an electrostatic precipitator (ESP) at 120 °C was identified as the most attractive for hydrotreatment when considering product yields and composition. The best hydrotreatment results (Ru/C, 350 °C, 100 bar H2, 4 h) were achieved using beechwood and walnut shells as feedstock, resulting in a high oil yield (about 64 wt% based on pyrolysis oil fraction intake) with a higher heating value of about 37 MJ/kg and enriched in alkylphenols (about 16 wt%). Overall, it was shown that the type of biomass (beech sawdust, walnut granulates, and pine/spruce sawdust) has a limited impact on liquid and alkylphenols yields which implies feedstock flexibility of this integrated concept

The ratio of CRP to prealbumin levels predict mortality in patients with hospital-acquired acute kidney injury

<p>Abstract</p> <p>Background</p> <p>Animal and human studies suggest that inflammation and malnutrition are common in acute kidney injury (AKI) patients. However, only a few studies reported CRP, a marker of inflammation, albumin, prealbumin and cholesterol, markers of nutritional status were associated with the prognosis of AKI patients. No study examined whether the combination of inflammatory and nutritional markers could predict the mortality of AKI patients.</p> <p>Methods</p> <p>155 patients with hospital-acquired AKI were recruited to this prospective cohort study according to RIFLE (Risk, Injury, Failure, Lost or End Stage Kidney) criteria. C-reactive protein (CRP), and the nutritional markers (albumin, prealbumin and cholesterol) measured at nephrology consultation were analyzed in relation to all cause mortality of these patients. In addition, CRP and prealbumin were also measured in healthy controls (n = 45), maintenance hemodialysis (n = 70) and peritoneal dialysis patients (n = 50) and then compared with AKI patients.</p> <p>Results</p> <p>Compared with healthy controls and end-stage renal disease patients on maintenance hemodialysis or peritoneal dialysis, patients with AKI had significantly higher levels of CRP/prealbumin (<it>p </it>< 0.001). Higher level of serum CRP and lower levels of albumin, prealbumin and cholesterol were found to be significant in the patients with AKI who died within 28 days than those who survived >28 days. Similarly, the combined factors including the ratio of CRP to albumin (CRP/albumin), CRP/prealbumin and CRP/cholesterol were also significantly higher in the former group (<it>p </it>< 0.001 for all). Multivariate analysis (Cox regression) revealed that CRP/prealbumin was independently associated with mortality after adjustment for age, gender, sepsis and sequential organ failure assessment (SOFA, <it>p </it>= 0.027) while the others (CRP, albumin, prealbumin, cholesterol, CRP/albumin and CRP/cholesterol) became non-significantly associated. The hazard ratio was 1.00 (reference), 1.85, 2.25 and 3.89 for CRP/prealbumin increasing according to quartiles (<it>p </it>= 0.01 for the trend).</p> <p>Conclusions</p> <p>Inflammation and malnutrition were common in patients with AKI. Higher level of the ratio of CRP to prealbumin was associated with mortality of AKI patients independent of the severity of illness and it may be a valuable addition to SOFA score to independent of the severity of illness and it may be a valuable addition to SOFA score to predict the prognosis of AKI patients.</p

Pt/CeO2 as Catalyst for Non-Oxidative Coupling of Methane:Oxidative Regeneration

Direct non-oxidative coupling is a promising route for methane upgrading, yet its commercialization is hindered by the lack of efficient catalysts. Pt/CeO2 catalysts with isolated Pt species have attracted increasing interest in recent years. Herein, we studied the catalytic role and evolution of isolated Pt centers on CeO2 prepared by flame spray pyrolysis under the harsh reaction conditions of non-oxidative methane coupling. During the reaction at 800 °C, the isolated Pt sites sinter leading to a loss of the ethylene and ethane yield. The agglomerated Pt can be redispersed by using an in situ regeneration strategy in oxygen. We found that isolated Pt centers are only able to activate methane at the initial reaction stage, and the CePt5 alloy acts as the active phase in the prolonged reaction