Steam reforming of bio-compounds with auto-reduced nickel catalyst

As an extension of chemical looping combustion, chemical looping steam reforming (CLSR) has been developed for H2 production. During CLSR, a steam reforming (SR) process occurs following the reduction of catalysts by the reforming feedstock itself (termed ‘auto-reduction’), as opposed to a separate, dedicated reducing agent like H2. This paper studied SR performances of four common bio-compounds (ethanol, acetone, furfural and glucose) with a nickel catalyst that had undergone auto-reduction. A packed bed reactor was used to carry out the experiment of auto-reduction and subsequent SR. Effects of temperature and steam to carbon ratio (S/C) on carbon conversions of the bio-compounds to gases and yields of gaseous products were investigated. The carbon deposition on spent catalysts was characterized by CHN elemental analysis and SEM-EDX. The SR performance with the auto-reduced catalyst was close to that with H2-reduced catalyst. In general, an increase in temperature or S/C would lead to an increase in H2 yields. The dependence of SR performance on temperature or S/C was specific to the type of bio-compounds. Accordingly, main bottlenecks for SR of each bio-compound were summarized. A large amount of CH4 existed in the reforming product of ethanol. Severe carbon deposition was observed for SR of acetone at temperatures below 650 °C. A high thermal stability of furfural molecules or its derivatives restricted the SR of furfural. For SR of glucose, the main problem was the severe agglomeration of catalyst particles due to glucose coking

Effect of hydrocarbon fractions, N₂ and CO₂ in feed gas on hydrogen production using sorption enhanced steam reforming: Thermodynamic analysis

H₂ yield and purity from sorption enhanced steam reforming (SE-SR) are determined by temperature, S:C ratio in use, and feed gas composition in hydrocarbons, N₂ and CO₂. Gases with high hydrocarbons composition had the highest H₂ yield and purity. The magnitude of sorption enhancement effects compared to conventional steam reforming (C-SR), i.e. increases in H₂ yield and purity, and drop in CH₄ yield were remarkably insensitive to alkane (C1-C3) and CO₂ content (0.1-10 vol%), with only N₂ content (0.4-70 vol%) having a minor effect. Although the presence of inert (N₂) decreases the partial pressure of the reactants which is beneficial in steam reforming, high inert contents increase the energetic cost of operating the reforming plants. The aim of the study is to investigate and demonstrate the effect of actual shale gas composition in the SE-SR process, with varied hydrocarbon fractions, CO₂ and N₂ in the feedstock

Temperature-programmed reduction of nickel steam reforming catalyst with glucose

Temperature-programmed reduction (TPR) of a NiO/α-Al2O3 steam reforming catalyst with glucose under a N2 flow was investigated using TGA-FTIR technique. A series of catalyst samples obtained at different temperatures during the TPR were characterised by XRD, CHN elemental analysis, SEM-EDX and TPO. Results showed that the whole TPR covering from room temperature to 900 °C consisted of two reactive processes. They were glucose pyrolysis producing carbonaceous materials (char), and NiO reduction by the char resulting in CO2 as a main product. When the initial mass ratio of glucose to the catalyst was 1:10, the catalyst could be completely reduced without carbon remaining. Moreover, two mass loss peaks were observed at around 440 °C and 670 °C, respectively, during the reduction. Based on the experiments of char characterisation, H2 TPR and excess glucose TPR, a two-stage reduction mechanism was proposed. The first reduction stage was attributed to a solid reaction between NiO and char. The second stage was assigned to NiO being reduced by the CO produced by char gasification with CO2. Their apparent activation energies were 197 ± 19 kJ/mol and 316 ± 17 kJ/mol, respectively, estimated using the Kissinger method

Chemical looping Steam reforming of Acetic Acid in a Packed Bed Reactor

Chemical looping steam reforming of acetic acid (CLSR-HAc) was carried out in a packed bed reactor at 650 °C and 1 atm using two nickel-based catalysts (‘A’ with alumina support and ‘B’ with calcium aluminate support) to study the effect of the temperature of oxidation (TOX) on the efficiency of the process and the materials properties of the catalysts upon cycling. CLSR-HAc could not be sustained with steady outputs with TOX of 600°C for catalyst A, but it was conducted successfully at temperatures up to 800°C, whereas with B it could be operated reaching close to equilibrium conditions over five cycles with TOX of 600°C. CLSR-HAc can run efficiently for further cycles at the right operating conditions (S/C of 3, WHSV of 2.5 hr-1, TOX 800°C, TSR 650°C) even in the presence of the side reactions of acetic acid decomposition and coking. The yield of hydrogen produced had a minimum efficiency of 89% compared to equilibrium values, and the acetic acid conversion was in excess of 95% across 10 chemical looping steam reforming cycles. High purity hydrogen (>90% compared to equilibrium values) was also produced in this study. Chemigrams obtained from TGA-FTIR analysis indicates that two forms of carbon were formed on the catalyst during CLSR-HAc; TEM images and diffraction patterns indicate that poly graphitic carbon and amorphous carbon were formed while SEM images of the oxidised catalyst showed that the carbon was eliminated during the oxidation step of CLSR. A full carbon elemental balance of the process confers that majority of the carbon share (ca 90%) was utilised for efficient steam reforming of acetic acid with ca 10% of the carbon input deposited during the reduction step and subsequently burned during oxidation over the CLSR cycles

Feasibility of hydrogen production from steam reforming of biodiesel (FAME) feedstock on Ni-supported catalysts

The catalytic steam reforming of biodiesel was examined over Ni-alumina and Ni-ceria-zirconia catalysts at atmospheric pressure. Effects of temperatures of biodiesel preheating/ vapourising (190-365 °C) and reforming (600-800 °C), molar steam to carbon ratio (S/C=2-3), , and residence time in the reformer, represented by the weight hourly space velocity ‘WHSV’ of around 3 were examined for 2h. Ni supported on calcium aluminate and on Ceria-zirconia supports achieved steady state hydrogen product stream within 90% of the equilibrium yields, although 4% and 1% of the carbon feed had deposited on the catalysts, respectively, during the combined conditions of start-up and steady state. Addition of dopants to ceria-zirconia supported catalyst decreased the performance of the catalyst. Increase in S/C ratio had the expected positive effects of higher H2 yield and lower carbon deposition

Hydrogen from ethanol reforming with aqueous fraction of pine pyrolysis oil with and without chemical looping

Reforming ethanol (‘EtOH’) into hydrogen rich syngas using the aqueous fraction from pine bio-oil (‘AQ’) as a combined source of steam and supplementary organic feed was tested in packed bed with Ni-catalysts ‘A’ (18 wt%/-Al2O3) and ‘B’ (25 wt%/-Al2O3). The catalysts were initially pre-reduced by H2, but this was followed by a few cycles of chemical looping steam reforming, where the catalysts were in turn oxidised in air and auto-reduced by the EtOH/AQ mixture. At 600 °C, EtOH/AQ reformed similarly to ethanol for molar steam to carbon ratios (S/C) between 2 and 5 on the H2-reduced catalysts. At S/C of 3.3, 90% of the carbon feed converted on catalyst A to CO2 (58%), CO (30%) and CH4 (2.7%), with 17 wt% H2 yield based on dry organic feedstock, equivalent to 78% of the equilibrium value. Catalyst A maintained these outputs for four cycles while B underperformed due to partial reduction

Regulation of 3β-Hydroxysteroid Dehydrogenase/∆5-∆4 Isomerase: A Review

This review focuses on the expression and regulation of 3β-hydroxysteroi ddehydrogenase/Δ5-Δ4 isomerase (3β-HSD), with emphasis on the porcine version. 3β-HSD is often associated with steroidogenesis, but its function in the metabolism of both steroids and xenobiotics is more obscure. Based on currently available literature covering humans,rodents and pigs, this review provides an overview of the present knowledge concerning the regulatory mechanisms for 3β-HSD at all omic levels. The HSD isoenzymes are essential in steroid hormone metabolism, both in the synthesis and degradation of steroids. They display tissue-specific expression and factors influencing their activity, which therefore indicates their tissue-specific responses. 3β-HSD is involved in the synthesis of a number of natural steroid hormones, including progesterone and testosterone, and the hepatic degradation of the pheromone androstenone. In general, a number of signaling and regulatory pathways have been demonstrated to influence 3β-HSD transcription and activity, e.g., JAK-STAT, LH/hCG, ERα, AR, SF-1 and PPARα. The expression and enzymic activity of 3β-HSD are also influenced by external factors, such as dietary composition. Much of the research conducted on porcine 3β-HSD is motivated by its importance for the occurrence of the boar taint phenomenon that results from high concentrations of steroids such as androstenone. This topic is also examined in this review

National Outbreak of Salmonella Serotype Saintpaul Infections: Importance of Texas Restaurant Investigations in Implicating Jalapeño Peppers

BACKGROUND: In May 2008, PulseNet detected a multistate outbreak of Salmonella enterica serotype Saintpaul infections. Initial investigations identified an epidemiologic association between illness and consumption of raw tomatoes, yet cases continued. In mid-June, we investigated two clusters of outbreak strain infections in Texas among patrons of Restaurant A and two establishments of Restaurant Chain B to determine the outbreak's source. METHODOLOGY/PRINCIPAL FINDINGS: We conducted independent case-control studies of Restaurant A and B patrons. Patients were matched to well controls by meal date. We conducted restaurant environmental investigations and traced the origin of implicated products. Forty-seven case-patients and 40 controls were enrolled in the Restaurant A study. Thirty case-patients and 31 controls were enrolled in the Restaurant Chain B study. In both studies, illness was independently associated with only one menu item, fresh salsa (Restaurant A: matched odds ratio [mOR], 37; 95% confidence interval [CI], 7.2-386; Restaurant B: mOR, 13; 95% CI 1.3-infinity). The only ingredient in common between the two salsas was raw jalapeño peppers. Cultures of jalapeño peppers collected from an importer that supplied Restaurant Chain B and serrano peppers and irrigation water from a Mexican farm that supplied that importer with jalapeño and serrano peppers grew the outbreak strain. CONCLUSIONS/SIGNIFICANCE: Jalapeño peppers, contaminated before arrival at the restaurants and served in uncooked fresh salsas, were the source of these infections. Our investigations, critical in understanding the broader multistate outbreak, exemplify an effective approach to investigating large foodborne outbreaks. Additional measures are needed to reduce produce contamination

Search for top squarks in the four-body decay mode with single lepton final states in proton-proton collisions at s \sqrt{s} = 13 TeV

A search for the pair production of the lightest supersymmetric partner of the top quark, the top squark (t∼1), is presented. The search targets the four-body decay of the t∼1, which is preferred when the mass difference between the top squark and the lightest supersymmetric particle is smaller than the mass of the W boson. This decay mode consists of a bottom quark, two other fermions, and the lightest neutralino (χ∼01), which is assumed to be the lightest supersymmetric particle. The data correspond to an integrated luminosity of 138 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC. Events are selected using the presence of a high-momentum jet, an electron or muon with low transverse momentum, and a significant missing transverse momentum. The signal is selected based on a multivariate approach that is optimized for the difference between m(t∼1) and m(χ∼01). The contribution from leading background processes is estimated from data. No significant excess is observed above the expectation from standard model processes. The results of this search exclude top squarks at 95% confidence level for masses up to 480 and 700 GeV for m(t∼1) − m(χ∼01) = 10 and 80 GeV, respectively