Hydrogen rich gas production by thermocatalytic decomposition of kenaf biomass

Kenaf (Hibiscus cannabinus L.), a well known energy crop and an annual herbaceous plant grows very fast with low lodging susceptibility was used as representative lignocellulosic biomass in the present work. Thermocatalytic conversions were performed by aqueous phase reforming (APR) of kenaf hydrolysates and direct gasification of solid biomass of kenaf using 5% Pt on activated carbon as catalyst. Hydrolysates used in APR experiments were prepared by solubilization of kenaf biomass in subcritical water under CO₂ gas pressure.     

Carbon nanotubes and hydrogen production from the reforming of toluene

Catalytic steam reforming of liquid hydrocarbons is one of the promising alternatives for hydrogen production. However, coke deposition on the reacted catalyst results in catalyst deactivation and also CO₂ emission during reforming are among the main challenges in the process. In this work, the production of high-value carbon nanotubes (CNTs) during hydrogen production from catalytic reforming of toluene has been investigated. Thus, less carbon emission and higher product values can be expected from the process. A two-stage fixed bed pyrolysis-reforming reactor was used in this work. The results showed that the addition of a Ni–Mg–Al catalyst, with an additional downstream stainless steel mesh, increased hydrogen production from 24.8 to 54.8 (mmol H₂ g⁻¹ toluene), when water (steam) was injected at a rate of 0.01 g min⁻¹. CNTs were also produced in the process in the presence of the Ni–Mg–Al catalyst and with a water injection rate of 0.01 g min⁻¹ had the highest band ratio of G′/G when analyzed by Raman spectrometry, indicating the highest purity of CNTs. In addition, Raman spectra of the generated CNTs showed that the purity of CNTs was reduced with the addition of water for reforming without the Ni–Mg–Al catalyst. The presence of the Ni–Mg–Al catalyst significantly increased the yield of CNTs formed on the surface of the stainless steel mesh and also improved the quality of the CNTs in relation to the distribution of diameters and their length.     

Coal gasification development and commercialization of the texaco coal gasification process

The development of the Texaco coal gasification process utilizing an entrained bed downflow slagging gasifier is discussed. the advantages of the process including its simplicity and lack of formation of environmentally unacceptable and undesirable by-products are emphasized. Treatment of the crude gasification product gas to produce a clean gas for use as fuel or as feed stock for chemical manufacture is also covered. Status of the commercialization of the process is included.     

Thermodynamics research on hydrogen production from biomass and coal co-gasification with catalyst

A model comprises two sub-models, i.e. combustion and gasification models, is developed to simulate a single fluidized bed two-step gasification process and to predict H₂ production under different conditions. The combustion sub-model which consists of volatile precipitation and char combustion sub-models. The combustion sub-model is used to forecast residual char. The gasification sub-model, based on the mass and energy balance, is used to examine thermodynamically the effect on the hydrogen production of calcium oxide as the catalyst. Moreover, the effects of the operational conditions on the hydrogen production such as biomass/coal (mass ratio), temperature, steam/coke, and calcium/coke, are simulated. The results indicate that the addition of calcium oxide at certain conditions can significantly improve hydrogen production and lower the required temperature for gasification. The model predicts that the maximum hydrogen production of 60% can be achieved under the conditions of temperature in the range of 800-850 °C, calcium/coke, steam/coke, and coal/biomass (mass ratio) are 0.5, 1.8, and 1/4, respectively. The model predictions are in good agreement with the experimental data.     

A preliminary study of a novel catalyst Al2O3·Na2O·xH2O/NaOH/Al(OH)3 for production of hydrogen and hydrogen-rich gas by steam gasification from cellulose

The new catalyst, Al₂O₃·Na₂O·xH₂O/NaOH/Al(OH)₃, was made by means of hydrolyzation and hydration of sodium aluminum oxide (Al₂O₃·Na₂O). Hydrogen and hydrogen-rich gas were produced through the reaction of cellulose with the catalyst and steam. In order to avoid production of tar, the gasification temperature is controlled at ≤673 K. The temperature of producing hydrogen is controlled at about 473–623 K. The conversion degree of hydrogen from cellulose at about 473–673 K could come up to 59.63%. The production of hydrogen-rich gas was set at about 673 K. The gasification residue could be used as material for combustion. Al₂O₃·Na₂O could be regenerated from the byproducts Al₂O₃ and Na₂CO₃ produced in the combustion process. The catalyst could be re-prepared from the regenerative Al₂O₃·Na₂O.     

Hydrogen production from molten metal gasification

As fossil fuel reserves are depleted, more innovative technologies are needed to facilitate fuel production, such as molten media gasification. This technique uses a liquid metal bath in a two-stage process: Stage 1) superheated steam is injected into the melt, with metal oxides formed, and H₂ released; Stage 2) carbon is injected, the oxide is reduced, and CO and CO₂ are released. The main study objective was to develop and test the first stage of this process. The results showed that hydrogen production peaked 100 s into the test, and then levelled off, with a maximum output of 13.6% hydrogen. XRD analysis of the metal samples showed that no tin oxides or magnetite were formed during the process, only a form of wustite (FeO). The syngas produced was very clean, and would need little gas cleaning for use as a feedstock in industrial processes or fuel cells.     

Hydrogen generation by hydrolysis of Mg-Mg2Si composite and enhanced kinetics performance from introducing of MgCl2 and Si

This paper reported the performance and mechanism of hydrogen generation via hydrolysis of ball-milled Mg-Mg₂Si composite (5.3 wt % Si-94.7 wt % Mg) in deionized water and in MgCl₂ solution. The results showed that the obtained Mg-Mg₂Si composite presented relatively higher hydrogen generation performance than pure magnesium. Adoption of 0.5 M MgCl₂ solution to replace deionized water sufficiently and vastly enhanced the hydrolysis properties of the Mg-Mg₂Si composite. The composite in 0.5 M MgCl₂ solution generated 445 mL/g hydrogen in 5 min, 688 mL/g hydrogen in 10 min and 889 mL/g hydrogen (conversion rate 99%) in 40 min at 328 K. This remarkable improvement is due to that the addition of Si element in the composite and the introduction of MgCl₂ in solution, as well as the special preparation process of the materials, could decrease the formation of continuous magnesium hydroxide passive layer on the particle surface, directly or indirectly. Moreover, the apparent activation energies for composite hydrolysis in deionized water, in 0.5 and 2.0 M MgCl₂ solution were calculated to be 30.1 ± 0.6, 9.5 ± 0.1 and 3.7 ± 0.2 kJ/mol, respectively. This work demonstrates that the hydrogen generation system based on low-cost and high-performance Mg-Mg₂Si composite is very applicable and promising; and it may open a new avenue for onsite hydrogen supply.