Catalytic hydrogenation of levulinic acid to ɣ-valerolactone: Insights into the influence of feed impurities on catalyst performance in batch and flow

γ-Valerolactone (GVL) is readily obtained by the hydrogenation of levulinic acid (LA) and is considered a sustainable platform chemical for the production of biobased chemicals. Herein, the performance and stability of Ru-based catalysts (1 wt % Ru) supported on TiO 2 (P25) and ZrO 2 (monoclinic) for LA hydrogenation to GVL is investigated in the liquid phase in batch and continuous-flow reactors using water and dioxane as solvents. Particular attention is paid to the influence of possible impurities in the LA feed on catalyst performance for LA hydrogenation. Benchmark continuous-flow experiments at extended times on-stream showed that the deactivation profiles are distinctly different for both solvents. In dioxane, the Ru/ZrO 2 catalyst is clearly more stable than Ru/TiO 2, whereas the latter is slightly more stable in water. Detailed characterization studies on spent catalysts after long run times showed that the deactivation of Ru/TiO 2 is strongly linked to the reduction of a significant amount of Ti 4+ species of the support to Ti 3+ and a decrease in the specific surface area of the support in comparison to the fresh catalyst. Ru/ZrO 2 showed no signs of support reduction and displayed morphological and structural stability; however, some deposition of carbonaceous material is observed. Impurities in the LA feed such as HCOOH, H 2SO 4, furfural (FFR), 5-hydroxymethylfurfural (HMF), humins, and sulfur-containing amino acids impacted the catalyst performance differently. The results reveal a rapid yet reversible loss of activity for both catalysts upon HCOOH addition to LA, attributed to its preferential adsorption on Ru sites and possible CO poisoning. A more gradual drop in activity is found when cofeeding HMF, FFR, and humins for both solvents. The presence of H 2SO 4, cysteine, and methionine all resulted in the irreversible deactivation of the Ru catalysts. The results obtained provide new insights into the (ir)reversible (in)sensitivity of Ru-based hydrogenation catalysts to potential impurities in LA feeds, which is essential knowledge for next-generation catalyst development

Electronic structure and interface energetics of CuBi2O4 photoelectrodes - data

In this study, the electronic structure of CuBi2O4 has been studied by a combination of hard X-ray photoemission, resonant photoemission and X-ray absorption spectroscopies, and compared with density functional theory (DFT) calculations. The photoemission study indicates that there is a strong Bi 6s-O 2p hybrid electronic state at 2.3 eV below the Fermi level, whereas the valence band maximum (VBM) has a predominant Cu 3d – O 2p hybrid character. XAS at the O K-edge supported by DFT calculations provides a good description of the conduction band, indicating that the conduction band minimum (CBM) is composed of unoccupied Cu 3d-O 2p states. The combined experimental and theoretical results suggest that the low charge carrier mobility for CuBi2O4 derives from an intrinsic charge localization at the VBM. Also, the low-energy visible light absorption in CuBi2O4 may result from a direct but forbidden Cu d–d electronic transition, leading to a low absorption coefficient. Additionally, the ionization potential (IP) of CuBi2O4 is higher than that of the related binary oxide CuO or that of NiO, which is commonly used as hole transport/extraction layer in photoelectrodes. This work provides solid electronic basis for topical materials science approaches to increase the charge transport and improve the photoelectrochemical properties of CuBi2O4-based photoelectrodes. Data comprise: Valence band photoemission spectra of CuBi2O4 taken using photon energies near the Cu L3. Cu L3 X-ray absorption spectrum of CuBi2O4 indicating the selected photon energies for the resonant photoemission experiment. Valence band photoemission of CuBi2O4 near the Fermi level showing the spectral intensity difference between on-resonance (at hν = 933.1 eV) and off-resonance (at hν = 929.8 eV) spectra. Experimental VB photoemission spectra of CuBi2O4 measured with 1486 eV (Al Kα1), 4068 eV, and 8133 eV ionizing photon energy. Photoionization cross section dependence on the ionizing photon energy for valence orbitals in CuBi2O4. Calculated VB photoemission spectra of CuBi2O4 at 8133 eV ionizing photon energy. O K-edge XAS of CuBi2O4 along with that of CuO for comparison. Empty PDOS from DFT calculations for CuBi2O4; the O K-edge XAS is included in the same scale for comparison. (C) UV−vis absorption spectrum of CuBi2O4. Measured and calculated electron affinity (CBM) and ionization potential (VBM) of CuBi2O4, CuO, and NiO with respect to the vacuum level. Chopped-light linear sweep voltammetry scans for CuBi2O4 (black) and NiO/CuBi2O4 (red) photoelectrodes. Chopped-light linear sweep voltammetry scans for CuO (black) and NiO/CuO (red) photoelectrodes. PEC measurements were done in 0.2 M K2SO4 + 0.1M phosphate buffer solution (pH 6.8) with 0.3% w/w H2O2

Genome-wide association identifies nine common variants associated with fasting proinsulin levels and provides new insights into the pathophysiology of type 2 diabetes

OBJECTIVE - Proinsulin is a precursor of mature insulin and C-peptide. Higher circulating proinsulin levels are associated with impaired b-cell function, raised glucose levels, insulin resistance, and type 2 diabetes (T2D). Studies of the insulin processing pathway could provide new insights about T2D pathophysiology. RESEARCH DESIGN AND METHODS - We have conducted a meta-analysis of genome-wide association tests of ;2.5 million genotyped or imputed single nucleotide polymorphisms (SNPs) and fasting proinsulin levels in 10,701 nondiabetic adults of European ancestry, with follow-up of 23 loci in up to 16,378 individuals, using additive genetic models adjusted for age, sex, fasting insulin, and study-specific covariates. RESULTS - Nine SNPs at eight loci were associated with proinsulin levels (P < 5 × 10-8). Two loci (LARP6 and SGSM2) have not been previously related to metabolic traits, one (MADD) has been associated with fasting glucose, one (PCSK1) has been implicated in obesity, and four (TCF7L2, SLC30A8, VPS13C/ C2CD4A/B, and ARAP1, formerly CENTD2) increase T2D risk. The proinsulin-raising allele of ARAP1 was associated with a lower fasting glucose (P = 1.7 3 10-4), improved b-cell function (P = 1.1 × 10-5), and lower risk of T2D (odds ratio 0.88; P = 7.8 × 10-6). Notably, PCSK1 encodes the protein prohormone convertase 1/3, the first enzyme in the insulin processing pathway. A genotype score composed of the nine proinsulin-raising alleles was not associated with coronary disease in two large case-control datasets. CONCLUSIONS - We have identified nine genetic variants associated with fasting proinsulin. Our findings illuminate the biology underlying glucose homeostasis and T2D development in humans and argue against a direct role of proinsulin in coronary artery disease pathogenesis