Experimental Study On The Sorption Enhanced Steam Reforming Of Ethanol With Lithium Orthosilicate Sorbent From Expanded Perlite

Sorption enhanced steam reforming of ethanol for hydrogen production（SE-SRE）has received widespread attention,which has many advantages such as high purity of hydrogen production,controllable greenhouse gas emissions and the use of renewable raw materials.Lithium orthosilicate is a promising sorbent for steam reforming reaction due to its favorable sorption capacity and cyclic stability.However,the high synthesis cost limits the practical application of sorbents.In this work,a new cheap lithium orthosilicate sorbent was prepared and then pelletized via one-step graphite moulding method.Moreover,the experimental conditions and cyclic performance steam reforming of ethanol enhanced by the sorbent pellets were studied.In this work,Li₄Si O₄ sorbent using expanded perlite as raw material was successfully synthesized.The physicochemical properties and CO₂ sorption performance of the prepared sorbents were determined by several analytical methods such as XRF,XRD,FSEM,BET and TGA.It was found from the experimental results that the metal impurities of EP can result in a rough morphology with smaller size particles of the synthesized sorbent,improving the sorption performance of sorbent.Compared with P-Li₄Si O₄,EP-Li₄Si O₄ had a wider operating temperature window.In addition,EP-Li₄Si O₄ possessed a higher sorption capacity in the temperature range of 500-650°C.During cyclic sorption/desorption tests,EP-Li₄Si O₄ also showed good cyclic stability and sorption performance.In the actual reforming system for hydrogen production,the powdered sorbent is easily elutriated out from the reactor,leading to reduce the hydrogen production efficiency and increase the supplementary cost of the sorbent.In this work,Li₄Si O₄ pellets from EP were prepared by one-step graphite moulding method and the sorption performance and mechanical properties were tested.Due to the hydrophobic force and shrinking force during the granulation process,the densification of the microstructure and the reduction of the specific surface area resulted in the deterioration of the CO₂ sorption performance of the pellets.The addition of agar or using organic lithium source can effectively enhance the sorption capacities of pellets due to the improvement of the microscopic pore structure.Moreover,the results from the compression and anti-attrtion tests showed that the pellets had good mechanical properties.In this work,the feasibility of using sorbent pellets in SE-SRE was studied,and the effect of process conditions was also discussed.The cycle tests were also carried out under the selected optimal conditions to test cyclic stability.The results showed that the sorbent pellets can achieve fine sorption enhancement effect in SE-SRE system.The optimal operating conditions obtained through experiments were as follows:the reaction temperature was 525°C,space velocity was 0.9 m L/（h·g）,the molar ratio of water to ethanol was 8:1,and the ratio of sorbent to catalyst was 3:1.In the multi-cycle test,the SE-SRE system showed excellent cyclic performance.