Research On Catalytic Conversion Poly(3-Hydroxybutyrate) Into Liquid Fuel

Poly-3-hydroxybutyrate?PHB?is an energy storage material formed from renewable raw materials in many bacterial species.This paper introduces several catalytic degradation technologies,degradation products distribution and possible degradation mechanism of PHB materials.The degradation technologies mainly include thermal pyrolysis,hydrolysis,alcoholysis and enzymatic hydrolysis.A series of catalysts?multiple solid phosphates,triruthenium dodecacarbonyl and cerium oxide?have been developed on the basis of thermal pyrolysis technology to catalytically prepare the high-grade liquid fuels and propylene by PHB reforming.The optimal process conditions for PHB reforming under different catalyst conditions were studied by controlling the variables.The conversion mechanism of partial PHB reforming processes was revealed and the products were analyzed and compared.The quality of the oil and the recycling of the catalyst were tested and analyzed.The experimental results show that both the aluminum dihydrogen phosphate and cerium oxide catalysts can catalyze the PHB thermal pyrolysis deoxygenation reaction and oligomerization to form liquid hydrocarbon oil(C₆-C₁₈)in a one-pot method.The reaction product is accompanied by a small amount of propylene?C₃H₈?,carbon monoxide?CO?,water?H₂O?and some coke-like solids.The aluminum dihydrogen phosphate catalyzed PHB reforming produced an oil yield of up to 35 wt%,which has similar elemental composition and HHV?up to 42.3 MJ/kg?to commercial gasoline,indicating that the catalyst has good catalytic effect.The chemical structure and carbon number of the main compounds of the oil product were analyzed by gas chromatography-mass spectrometry?GC-MS?,and the composition of the oil product was analyzed.The results showed that the PHB was compared with the traditional biomass fuel derived from plant biomass.The oil has a high content of olefin or aromatic hydrocarbon compounds.This benefits to a large extent from solid phosphate catalysts.The ruthenium oxide catalyst?CeO2?exhibits a more excellent catalytic effect in the one-step catalyzed PHB reforming process.240°C is considered to be the necessary reaction temperature based on DSC analysis.Under relatively mild reaction conditions?240°C?,the formation of solid residues was completely inhibited,while the yields of oil and propylene were 35 wt%and 17 wt%,respectively.The oil contains ketones,esters,hydrocarbons,ethers,alcohols and N-containing compounds.Although the calorific value is lower than that of conventional commercial gasoline,the HHV is about 33.3 MJ/kg.However,due to its good catalytic activity,excellent stability,reusability,environmental friendliness and low cost,especially after mixing with a certain proportion of water,it can completely inhibit the formation of coke during PHB reforming.This can greatly improve atomic utilization and conform to the advanced concept of green chemistry.Interestingly,the triruthenium dodecacarbonyl can catalyze the PHB reforming process in one pot.The yield of propylene product was up to 22.9wt%and the propylene gas selectivity was as high as 46.8%,with a small amount of oil product?9 wt%?.By comparing the catalytic effects of the other two catalysts,it can be found that the triruthenium dodecacarbonyl catalyst can selectively regulate the synthesis of propylene by PHB,and to some extent inhibit the formation of oil products.In other words,the triruthenium-based catalyst is more advantageous for catalyzing the synthesis of propylene products rather than oil products by PHB.Factors affecting the yield of PHB oil and propylene include the type of catalyst,the amount of catalyst used,the time of catalyst catalytic reaction,and the temperature during the reaction.