Maximum Hydrogen Evolution Research Articles

Process development of continuous hydrogen production by Enterobacter aerogenes in a packed column reactor

Hydrogen bioproduction from agro-industrial residues by Enterobacter aerogenes in a continuous packed column has been investigated and a complete reactor characterization is presented. Experimental runs carried out at different residence time, liable of interest for industrial application, showed hydrogen yields ranging from 1.36 to 3.02 mmolH2mmol−1glucose or, in other words, from 37.5% to 75% of the theoretical hydrogen yield. A simple kinetic model of cell growth, validated by experimental results and allowing the prediction of biomass concentration profile along the reactor and the optimization of superficial velocity, is suggested. By applying the developed approach to the selected operative conditions, the identification of the optimum superficial velocity v0,opt of about 2.2 cm h−1 corresponding to the maximum hydrogen evolution rate H˙2g,max, was performed.

Studies of post-production ageing effects in atomised aluminium powder

The evolution of hydrogen gas from the reaction between a series of atomised aluminium powder samples and 2.5 M HCl was monitored over time. The pattern of hydrogen evolution in each case was similar in that after an initial period of slow gas production there was a rapid increase followed by slow gas production again. These studies also showed differences in the time taken to reach maximum hydrogen evolution for similarly aged powders. Lower purity aluminium powder (99.7 vs. 99.93%) or samples with a higher proportion of smaller particles reached the maximum rate of hydrogen evolution more quickly. Changes in the time taken to reach maximum gas evolution were also noted for all the powders as they aged; the time to reach a maximum generally increasing with time after atomisation. However, for each powder a short regression occurred between ca. 21 and 35 d. This suggests that changes continue to take place in the surface layer of the aluminium particulates long after atomisation has taken place.

Isolation of a hydrogen-producing bacterium, Clostridium beijerinckii strain AM21B, from termites

Clostridium beijerinckii strain AM21B was isolated from termites. At uncontrolled pH, it produced 108.9 mmol of hydrogen in 24 h from 10 g of glucose at a conversion rate of 105.7 mmol/g dry cells, and it produced 101.6 mmol of hydrogen in 24 h from 10 g of starch at pH 6.0, at a conversion rate of 77.6 mmol/g dry cells at pH 7.0. The hourly maximum hydrogen evolution rates were 22.3 mmol/h from glucose and 18.3 mmol/h from starch at pH 6.5 and 36 °C. Strain AM21B also produced hydrogen from arabinose, cellobiose, fructose, galactose, lactose, sucrose, and xylose at conversion efficiencies ranging from 15.7 to 19.0 mmol/g of substrate for 24 h.Key words: hydrogen production, carbohydrates, bacteria, termites, Clostridium beijerinckii.

Adsorption and Calorimetric Investigations on Carbon Black Surfaces I. Immersional Energetics of Heat Treated Channel and Furnace Blacks

Abstract Adsorption of gases under reversible conditions on carbon blacks can provide important basic information revealing the highly heterogeneous nature of the surface electronic fields and relating to physical interactions between the black and elastomeric molecules. Precise, immersional, calorimetric measurements likewise document the strongly heterogeneous surface energies and provide a powerful technique for measuring both physical and chemisorptive interactions between the surface and organic adsorbates. In the first phase of this study a broad spectrum of channel and reinforcing furnace blacks has been studied by immersional calorimetry to provide a survey of both integral and, to a lesser extent, differential heats of adsorption using methanol, n-decane, benzene, and water as adsorbates. The blacks studied were thermally treated at appropriate temperatures so that a wide span of surface conditions could be investigated, including the entire range of coverage by oxygenated functional groups and the regions of maximum hydrogen evolution and incipient graphitization. With these heat-treated blacks, marked integral immersional heat differences between channel and furnace blacks were observed with some adsorbates but not with others, and these results are discussed in terms of black surface conditions. Subtle differences between furnace blacks revealed by differential immersional heats are also presented.