Hydrogen Production Based On HyPr-RING Method—In Situ CO₂ Sorption And CO PROX Cat-alyzed By Co₃O₄

Hydrogen, with a wide variety of sources, well combustion performance, high energy density, clean and various forms of utilization, is a secondary energy for the 21st century. For China’s energy structure, coal has been the foremost source of primary energy consumption, and it is expected to remain in that position over a long period of time. Thus, large-scale production of hydrogen has to rely on coal. However, fossil fuels are finite and leading to the concern of energy security and environmental sustainability. Researchers are currently focused on hydrogen production with high-efficiency low-emissions coal technologies.In situ CO2 capture coal gasification method named HyPr-RING(Hydrogen Production by Reaction Integrated Novel Gasification) is one of the best candidates for hydrogen production by high-efficiency low-emissions coal technologies, but it is then undeveloped. In gasifier, high temperature CO2 adsorbent CaO may not strong enough during cycle. The gas products of gasification always contain little amounts of CO.For the above challenges, the following researches were carried out. Deeply understand the relationship between multicycle stability of high temperature solid CO2 absorbent CaO and its physical property. In order to apply CO2 adsorption enhanced water gas shift to remove CO, it is necessary to improve the adsorption capability of moderate temperature solid CO2 absorbent-LDO. Another method is to use catalyst for CO preferential oxidation, so high quality production of hydrogen can be directly used for fuel cell.The main works and conclusions are as follows:1. Four kinds of pure CaO was prepared under simple calcinations with four calcium precursors. A particle model was proposed to explain the capacity and stability of pure CaO, and the key parameters are CaO particles’ surface area and distance of carbonated CaO particles. Analysis sorption capability under particle model, the initial CO2 uptake capacity depends on CaO particles’ surface area. The CO2 uptake stability is determined by distance of carbonated CaO particles. Based on our model, uniform distributed magnesium oxide (MgO) in CaO can improve the stability. Samples with different ratio of Ca:Mg was achieved by simple ball milling of raw material. For this kind of composite, the stability decrease with increase CaO ratio. The stability of CaO-MgO composite with 1:1 Ca:Mg atom ratio was greatly improved as CaO conversion only had loss of 0.97% after 100 cycles, and its first conversion of CaO was 100%. The stability of composites proved our model.2. Layered double hydroxides (LDH) with sand flower morphology was prepared by co-precipitation method at pH=10 with stirring. Compared with normal LDH, the sand flower LDH prepared with stirring had high surface area and cumulative pore volume. Magnesium-aluminum layered double oxides (Mg-Al-LDO) derived from calcination of LDH at 400℃ can preserve its morphology. The sand flower LDO has better CO2 adsorption performance, proving the advantage of sand flower morphology. The formation process of the sand flower LDH is investigated in details and the morphology evolution mechanism is related to stirring. The sand flower morphology is Simi-stable state, which can only remain stable below 100℃ after hydrothermal treatment and reconstruction.3. Co3O4 nanorods were synthesized with a well-controlled wet chemistry protocol solution. Catalytic performance of PROX on Co3O4 nanorods with different pretreatment were tested by fix bed reactor. The catalytic performance showed that all Co3O4 nanorods was active for CO PROX. Specially, Co3O4 nanorods under 200℃ 5% H2 pretreatment exhibited a conversion of 100% of CO of a mixture consisting of 1% CO,1% O2,70% H2, and 28% He at 110℃, and relative selectivity is 73%. In situ AP-XPS data reveal the reason is the formation of O vacancy during pretreatment. The selectivity of Co3O4 was decreased as reaction temperature increased, but the non-stoichiometric Co3O4 remains its catalytic performance at 130℃ for more than 96 hours, which reveal its super stability. Pt/ Co3O4 with different loading of Pt were prepared with deposition precipitation method. As Pt is quite active for CO oxidation at a temperature higher than 120℃, the conversion and selectivity for CO is increased largely. Compare with Co3O4, the catalytic performance of Pt/ Co3O4 for CO PROX was worse, especially at low temperature.4. Co3O4 under different pretreatment performance different catalytic activity for CO PROX. The detailed evolution of the Co3O4 surface under various pretreatment conditions was investigated in situ by mean of in-house AP-XPS. The formation of oxygen vacancies under certain pretreatment conditions were confirmed by the change of atomic ratio of O/Co, which is very important for catalytic activity. The conclusions are fellows:When pretreatment in UHV, it does not lead to the formation of O vacancies. When pretreated with N2, it creates the O vacancies, and doesn’t result the reduction of Co3O4, which would yield the improvement of catalytic activity of Co3O4. When pretreated with CO+O2 reaction gases, the negative pretreatment effect that obtained with the high CO/O2 ratio was attributed to the saturation of the Co3O4 surface with chemisorbed CO molecules. The active phase is Co3O4 under the reaction conditions.