Experimental Study On Sorption Enhanced Steam Reforming Of Ethanol Using Lithium Orthosilicate As CO₂ Acceptor

Catalytically reforming for producing hydrogen is the most widely used among the hydrogen production methods.Ethanol is a renewable bio-fuel which can be used for producing hydrogen by reacting with steam.Adding catalyst for speeding up the process and adsorbent for adsorption of CO₂ in the process can improve the reaction rate and hydrogen concentration,the whole process is called sorption-enhanced steam reforming of ethanol?SE-SRE?.The different preparation methods of catalysts,the rice husk lithium silicate?RH-Li₄SiO₄?and different coupling methods of catalyst and adsorbent were studied in this work.The selection of catalyst is crucial in the SE-SRE system.Different catalysts have different selectivity for the side reactions and the preparation methods of catalysts have great influence on the performance of catalysts.In this work,15 wt%Ni/Al₂O₃ was prepared by excess impregnation,co-precipitation and sol-gel.The experiment was carried out by fixed bed reactor.It showed that the performance of 15 wt%Ni/Al₂O₃ prepared by sol-gel is best with higher H₂ selectivity and lower CO,CO₂ and CH₄ selectivity,at the same time,the whole process of producing gas was more stable.The results of BET showed that the catalyst prepared by sol-gel method has the largest specific surface area,larger pore volume and smaller pore size which can load more active components.The results of XRD indicated that more NiO diffraction peaks were found in the catalyst prepared by sol-gel method.The results of H₂-TPR implied that the catalyst prepared by sol-gel method has a higher and wider reduction peak,indicating that it has the best reduction.Based on the thermogravimetric curves of RH-Li₄SiO₄ and P-Li₄SiO₄ and the XRD characterization,It further showed that RH-Li₄SiO₄ had better adsorption properties.Due to the complexity of the SE-SRE,the thermodynamic simulation of steam reforming of ethanol was carried out in this work,It implied that simulation results fit well with the experimental results,meanwhile,it is found that steam has a great influence on the adsorption properties of RH-Li₄SiO₄.In order to explore the influence of steam on adsorption properties of RH-Li₄SiO₄,based on the above simulation results,the changes of adsorption properties of RH-Li₄SiO₄ in the atmosphere of 0%,20%,40%,50%and 60%were studied,at the same time,the isothermal adsorption data of RH-Li₄SiO₄ in these five atmospheres were studied.It indicated that the higher the concentration of steam,the faster the adsorption rate of RH-Li₄SiO₄.When steam concentration changed from 0%to 50%,the adsorption capacity of RH-Li₄SiO₄ increased with the increase of steam concentration,steam concentration was 60%,the adsorption capacity decreased,the steam concentration was 50%,RH-Li₄SiO₄ adsorption capacity is the largest.The effect of steam on the adsorption and desorption temperature of RH-Li₄SiO₄ was not significant.The results of isothermal adsorption properties showed that the addition of steam increased the reaction rate of the chemical reaction stage and the diffusion stage,and the reaction rate increased with the increase of steam concentration.Different coupling modes of adsorbent and catalyst was further studied in this work.The influence of temperature and feed rate on SE-SRE system was also studied in this work.It showed that the temperature has little effect on the whole SE-SRE reaction when in the range of 525?⁵75?,and when the feed rate changed from 0.03 ml/min to 0.01ml/min,the catalyst and adsorbent can achieve better coupling.Studies on different coupling modes of catalyst and adsorbent are shown that the coupling effect was the best when the catalyst and adsorbent was placed at four intervals.When the catalyst reacted with adsorbent once,it had a better coupling effect in the SE-SRE reaction.