Study Of Catalytic Pyrolysis Of Cholrella With Activated Alumina

Chlorella samples were used in this paper. Chlorella posses several attractivecharacteristics: low costs associated with the harvesting and transportation; it can beeasily chemically treated; algae can be grown under conditions which are unsuitablefor conventional crop production. Chlorella has great potential in the resourcesdevelopment.In this paper, the pyrolysis characteristics of chlorella were studied by using thethermogravimetric analysis method, and the experimental results obtained at differentheating rates (10,20,30℃/min) were analyzed. The analyses of TG/DTG curvesshowed that pyrolysis behavior of chlorella could be divided into four obvious reactionstages. Chlorella pyrolysis temperature was lower than that of terrestrial biomass suchas wood. The characteristic parameters of pyrolysis at different heating rates werecompared, and the releasing index of pyrolysis was calculated as well, showing that thehigher the heating rate, the quicker the pyrolysis reaction. The p yrolysis reactionkinetic was investigated by Coats-Redfern method, indicating that the mechanismfunctions of chlorella was second-order reaction model at a given temperature range.The corresponding activation energy E and frequency factor A and imitative straightline equation were obtained by the best mechanism function.In this paper, pyrolysis experiments of chlorella were conducted in a fixed bedreactor. Composition, acidity distribution, specific surface area and pore size ofactivated alumina were characterized by XRD, NH3-TPD and BET method. And thecatalytic performances could be evaluated by both yields of products and the heatingvalues of liquid products and bio-oils. By contrast with the results of products fromnon-catalytic pyrolysis and catalytic pyrolysis with activated alumina, the results wereshowed that activated alumina has a higher activity. Under the catalytic pyrolysis, liquid maximum yields is51.58%, the bio-oil calorific value raised36.09MJ kg-1. Themost probable mechanism of catalytic pyrolysis with activated alumina is structurechange of Al2O3during the reaction. L acids can change into B acids when the H2Ojoined the reaction. This change can provided active centers for pyrolysis.Orthogonal experiment was designed in the catalytic pyrolysis of chlorella. Thebest experimental conditions: the temperature is600℃, the heating rate is5℃/min, thecarrier flow is75ml/min. The regeneration times of activated alumina were tested. By theanalysis of XRD, the phase of Al2O3changed from cubic to monoclinic.In this paper, M/γ-Al2O3(M:Mo, Ni, Co) catalysts were synthesized by theimpregnation method. These catalysts were used for the catalytic pyrolysis of chlorella.The results showed that Mo/γ-Al2O3catalyst had the best activity. The best content ofMo was12%. By contrast with products from catalytic pyrolysis with activatedalumina, the results were not good. The catalyst was characterized by SEM-EDS,XRD and BET method. The results showed that the content of Mo was too low, hightemperature caused the agglomeration and sintering of fine particles, Mo had reactedwith γ-Al2O3.