Reactor modeling of methanol reforming in supercritical water

A kinetic model for the methanol reforming in supercritical water (SCW) at 600°C and 280 bar was developed. The model is a general two dimensional kinetic model considering diffusion and surface reactions. In this model, major reactions, e.g., steam reforming, water gas shift, methanation, and dry methanation, were considered. The experimental values obtained were in close agreement with the model predictions. The model predicted the experimental gas yields for a range of methanol loadings and at different residence times. It also predicted the equilibrium composition that agreed well with the thermodynamic calculations. This indicates that the reactions included in the model and the parameter estimates are adequate for describing the SCWG of methanol under the conditions explored. The kinetics of methanol reforming in SCW was sensitive to a very limited number of reactions and in the given conditions. Wall and wall diameter had a strong effect on the reactions. This is an abstract of a paper presented at the CHISA 2012 - 20th International Congress of Chemical and Process Engineering and PRES 2012 - 15th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (Prague, Czech Republic 8/25-29/2012)

Supercritical water gasification of organic acids and alcohols: the effect of chain length

We report the influence of the molecular structure on the gasification behaviour for a homologous series of linear chain (C1–C8) carboxylic acids and alcohols in supercritical water (600 °C and 250 bar) at two different concentrations (10 and 20 wt%). The initial concentration of carboxylic acids had a significant influence on the gasification efficiency (GE), whereas no such effect was found for the alcohol series studied. Alcohols were found to be much easier to gasify than the organic acids and the carbon GE trend of alcohols was opposite to that of acids, especially for the short chain compounds. With increasing chain length the GE stabilizes to around 50% at the conditions chosen. From gas and liquid phase product analysis decomposition schemes were proposed for the short chain compounds. A remarkable oscillatory behaviour of the methane and CO2 product yield with increasing chain length of the acids and alcohols was found experimentally. A simple model was derived, based on essentially a β-scission cracking mechanism, which was able to explain the observed product spectrum and the oscillatory behaviour. Additionally, the influence of the number and positioning of OH groups on the gasification behaviour was studie

Hydrogen from ethylene glycol by supercritical water reforming supported noble and base metal catalysts

Catalytic reforming of ethylene glycol (5 and 15 wt%) in supercritical water (450 °C and 250 bar) in the presence of alumina supported mono- and bi-metallic catalysts based on Ir, Pt and Ni was studied. Pt catalyst showed the highest hydrogen yields compared to Ir and Ni. Varying the Pt loading (0.3–1.5 wt%) showed that the intrinsic reforming activities improved with decreasing Pt loadings. However, a lower Pt loading had a large negative effect on the H2 selectivity and catalyst stability. It was found that the presence of Ni in a Pt–Ni bimetallic catalyst improved hydrogen yields by suppressing methane formation. Moreover, the presence of Ni also enhanced catalyst stability. Results reported here were obtained at WHSV of 18 h−1. The Pt–Ni/Al2O3 having a total metal loading of 1.5 wt% (molar ratio Pt:Ni = 1), is identified as a promising catalyst for the reforming of ethylene glycol in supercritical water and may prove suitable for various other SCWG application

Catalyst screening for the hydrothermal gasification of aqueous phase of bio-oil

The catalytic gasification in supercritical water of the water soluble fraction of bio-oil, either obtained directly by phase-separated pyrolysis-oil from ligno-cellulosic biomass or by hydrotreatment of that oil, is reported in this study. Several heterogeneous metal catalysts Pt, Pd, Ru, Rh, and Ni supported on alumina were tested for their gasification efficiency (GE). The GE for the metals is decreasing in the order Ru > Pt > Rh ∼ Pd > Ni. For optimum H2 selectivity the order of the catalysts is Pd > Ru ∼ Rh > Pt > Ni. Pd catalysts with different supports have been screened and no significant changes in the GE were found for the different supports. However, the composition of the product gas differed significantly with the support type. High H2 selectivity was obtained with Al2O3 and Ce–ZrO2 supports. With increasing the organic concentration from 5 to 50 wt% the GE as well as the H2 and CO2 selectivities dropped significantly. High reaction temperatures, long residence time, low feed stock concentrations and high catalyst loadings favored the high carbon to gas conversion. The aqueous wastes streams obtained from the hydrodeoxygenation process for the pyrolysis oil are easier to reform in supercritical in comparison to the feedstocks obtained directly as pyrolysis condenser fraction or as phase-separated aqueous fraction. Complete conversion of the made-up and the fast pyrolysis condenser fraction was obtained at low feed concentrations (5 wt%) using a continuous flow reactor in the presence of Ru/Ce–ZrO2 catalyst. However, the catalyst quickly deactivated with the made-up fraction but the same catalyst retained its stability and activity with the pyrolysis condenser fraction during the 3 h test run. The supercritical water gasification seems therefore a very suitable step for treating the aqueous phase obtained after hydrotreatment of pyrolysis oil in a (biomass) refinery concept

The global burden of adolescent and young adult cancer in 2019: a systematic analysis for the Global Burden of Disease Study 2019

Background In estimating the global burden of cancer, adolescents and young adults with cancer are often overlooked, despite being a distinct subgroup with unique epidemiology, clinical care needs, and societal impact. Comprehensive estimates of the global cancer burden in adolescents and young adults (aged 15–39 years) are lacking. To address this gap, we analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, with a focus on the outcome of disability-adjusted life-years (DALYs), to inform global cancer control measures in adolescents and young adults. Methods Using the GBD 2019 methodology, international mortality data were collected from vital registration systems, verbal autopsies, and population-based cancer registry inputs modelled with mortality-to-incidence ratios (MIRs). Incidence was computed with mortality estimates and corresponding MIRs. Prevalence estimates were calculated using modelled survival and multiplied by disability weights to obtain years lived with disability (YLDs). Years of life lost (YLLs) were calculated as age-specific cancer deaths multiplied by the standard life expectancy at the age of death. The main outcome was DALYs (the sum of YLLs and YLDs). Estimates were presented globally and by Socio-demographic Index (SDI) quintiles (countries ranked and divided into five equal SDI groups), and all estimates were presented with corresponding 95% uncertainty intervals (UIs). For this analysis, we used the age range of 15–39 years to define adolescents and young adults. Findings There were 1·19 million (95% UI 1·11–1·28) incident cancer cases and 396 000 (370 000–425 000) deaths due to cancer among people aged 15–39 years worldwide in 2019. The highest age-standardised incidence rates occurred in high SDI (59·6 [54·5–65·7] per 100 000 person-years) and high-middle SDI countries (53·2 [48·8–57·9] per 100 000 person-years), while the highest age-standardised mortality rates were in low-middle SDI (14·2 [12·9–15·6] per 100 000 person-years) and middle SDI (13·6 [12·6–14·8] per 100 000 person-years) countries. In 2019, adolescent and young adult cancers contributed 23·5 million (21·9–25·2) DALYs to the global burden of disease, of which 2·7% (1·9–3·6) came from YLDs and 97·3% (96·4–98·1) from YLLs. Cancer was the fourth leading cause of death and tenth leading cause of DALYs in adolescents and young adults globally. Interpretation Adolescent and young adult cancers contributed substantially to the overall adolescent and young adult disease burden globally in 2019. These results provide new insights into the distribution and magnitude of the adolescent and young adult cancer burden around the world. With notable differences observed across SDI settings, these estimates can inform global and country-level cancer control efforts