Effect of organic loading rate on hydrogen production from sugarcane vinasse in thermophilic acidogenic packed bed reactors

This study evaluated the effect of organic loading rate (OLR) on hydrogen production in up-flow anaerobic packed bed reactors (APBR) continuously fed with sugarcane vinasse. Four thermophilic up-flow APBR were operated in parallel at different ORL. Continuous hydrogen production was detected. The optimum OLR of 84.2 kg-COD m⁻³ d⁻¹ was assessed by polynomial adjustment, which predicted a maximum Volumetric Hydrogen Production (VHP) and hydrogen yield (YH₂)$\left(Y_{{\text{H}}_2}\right)$ of 1117.2 mL-H₂ d⁻¹ L⁻¹_reactor and 2.4 mol-H₂ mol⁻¹_{total carbohydrates}, respectively. The microbial composition was monitored using 16S rRNA gene by Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis and quantification of Fe-hydrogenase gene by real-time PCR which was affected by the OLR. The number of the Fe-hydrogenase genes was proportional to the monitored hydrogen production and yield. Hydrogen-producing strains were isolated, and the 16S rRNA gene sequences were highly homologous to those of Thermoanaerobacterium thermosaccarolyticum. The ability of vinasse as substrate for hydrogen production was confirmed for both strains.     

Catalytic performance of Pt-promoted cobalt-based catalysts for the steam reforming of ethanol

In this study, Pt-promoted Co_x/ZrO₂ catalysts (including 1.5 wt% Pt and Co loading of 0.75, 1.5, 3.0, 6.0, 9.0, 12, 24 and 48 wt%, respectively) were prepared by the incipient wet impregnation method for hydrogen production by steam reforming of ethanol (SRE). Evaluation of catalytic activities and products distribution toward the SRE reaction were carried out in a fixed-bed reactor with 100 mg of catalyst under an H₂O/EtOH molar ratio of 13.0 and gas hourly space velocity (GHSV) of 22,000 h⁻¹. The results revealed that the optimal loading of cobalt could enhance the capacities of catalytic performance and C–C scission, further raised the yield of hydrogen (YH₂)$\left({\text{Y}}_{{\text{H}}_2}\right)$ and lowered the deposited carbon, CH₄ and CO side-products due to the combination effect of cobalt and platinum. The Pt_1.5Co₁₂/ZrO₂ catalyst exhibited superiority in the SRE reaction, where complete conversion of ethanol was achieved at 275 °C. The (YH₂)$\left({\text{Y}}_{{\text{H}}_2}\right)$ approached 4.95, and only minor CO (<2%), CH₄ (<4%), and carbon deposition (<0.5%) were detected at 500 °C. In addition, the ethanol conversion still remained complete, and the selectivity of hydrogen exceeded 70% during a 116 h time-on-stream test under the same condition.     

Ti–Ni alloys as MH electrodes in Ni–MH accumulators

In hydrogen solid–gas reaction at 300 K and 1 bar, the hydrogen content for Ti_3.87Ni_1.73Fe_0.7O_x (0.2≤ × ≤0.8) alloys was in range 1.93–0.05 (Cwt.H,%), and discharge capacity of 360–235 A h/kg was achieved accordingly. The ΔHH₂$\Delta H_{{\text{H}}_2}$ and ΔSH₂$\Delta S_{{\text{H}}_2}$ values of −32.29 kJ mol⁻¹ and −111.04 J mol⁻¹ K⁻¹, respectively, for Ti_3.87Ni_1.73Fe_0.7O_0.5 alloy were obtained using experimental PCT relations, where hysteresis effect was only slightly visible. The half-cell potentials (vs. Hg/HgO) of metal hydride (MH) electrodes based on Ti_3.87Ni_1.73Fe_0.7O_x (0.2≤ ×≤ 0.8) alloys were calculated.