Study On Catalytic Biochemical Coupling Conversion Of Syngas To Ethanol

With the continuous progress of human society and the increasing demand for fossil fuels,the unrestricted use of these non-renewable energy sources will lead to a protracted energy crisis.Moreover,heavy dependence on fossil fuels will produce a large amount of toxic and harmful gas emissions,which will cause serious harm to the human living environment.To this end,our country has put forward a strategic development plan to vigorously develop new energy and renewable energy and optimize the energy structure.Fuel ethanol has always been considered as one of the ideal renewable alternative clean fuels for gasoline,with good antiknock and low pollution,and can be produced from biomass resources or exhaust gas using microbial conversion method at normal temperature and pressure.However,there are problems such as low ethanol yield and poor selectivity in the microbial conversion method.Therefore,the purpose of this study is to combine microorganisms and inorganic catalysts to conduct catalytic and biochemical coupling conversion of syngas,so as to achieve the purpose of efficiently converting syngas to ethanol under normal temperature and pressure.First,the effects of culture temperature,medium p H,reactor headspace pressure,the amount of Ca-pantothenate and Co SO₄×7H₂O in the nutrient substances on ethanol production by the Clostridium ljungdahlii strain were studied.Taking the ethanol production as the starting point for batch experiments,it was determined that the culture temperature was 37°C,the p H of the medium was 4.75,the headspace pressure of the reactor was 1.5bar,and the addition amounts of Ca-pantothenate and Co SO₄×7H₂O were2.5 mg/L and 0.09 g/L,respectively.The final ethanol production reached408.17±11.38 mg/L.Then,20 g/L of Pt/Al₂O₃ and Pt/Fe₂O₃ catalysts were added to the anaerobic fermentation system of Clostridium ljungdahlii strain to construct a synthesis gas catalytic biochemical coupled conversion reaction system.The results showed that the consumption of syngas in the anaerobic fermentation experimental group with the addition of Pt/Al₂O₃ catalyst increased by 26.72%compared with the control group,and the ethanol production reached 613.08±29.65 mg/L,an increase of 59.35%compared with the control group.The coupled system was subsequently subjected to semi-continuous experiments.After the reaction time of 576 hours,the ethanol production of the coupled system reached 2011.10±71.58 mg/L,which was 74.62%higher than that of the control group,the CO consumption was increased by 49.03%,and the ethanol selectivity reached56.54%.Finally,the catalyst of the synthesis gas catalytic biochemical coupling conversion system was characterized,and the reasons for the increase of ethanol production were analyzed from the catalyst level.The morphology of the microbes and the catalyst in the catalytic biochemical coupling system was observed by SEM;the crystal phase composition and morphology of the Pt/Fe₂O₃ and Pt/Al₂O₃ catalysts were analyzed by XRD,H₂-TPR and N₂adsorption-desorption;The Pt/Al₂O₃ was characterized by situ-DRIFTS.Finally,the formation of bicarbonate,formic acid and acetic acid was found on the surface of the catalyst.The analysis proved that the Pt/Al₂O₃ catalyst can strengthen the anaerobic fermentation system of Clostridium ljungdahlii strain from the aspects of enhancing gas-liquid mass transfer and producing intermediate products.Based on this,this project successfully realized the purpose of catalytic biochemical coupled conversion to efficiently convert syngas to ethanol at room temperature and pressure,which can provide new ideas for syngas conversion.