Study On High Value Utilization Of Oil Refining Waste Soapstock

Vegetable oil refining waste soapstock has great utilization value due to its high content of fatty acid salts and neutral oils.However,soapstock is still in the current situation of low utilization and conversion into low-value products.It is urgent to adopt green and mild methods to produce value-added products to alleviate environmental pressure and obtain economic benefits.In this context,it is of great significance to transform soapstock into fatty acids which can be used as chemical raw materials and biofuel which can be used for transportation.However,the current technology of converting soapstock into fatty acids has some shortcomings such as low efficiency,high energy consumption and high pollution.The introduction of ultrasonic assisted technology in the reaction process can improve the efficiency and alleviate the pollution.In addition,the bio-oil produced by pyrolysis or catalytic pyrolysis of soapstock contains a large number of components（oxygen-containing compounds and alkenes）that are not conducive to the direct use of fuel,and further high pressure quality improvement treatment will trigger secondary polymerization of products,resulting in the reduction of fuel yield.In view of this,the pyrolysis and vapor-phase hydrogenation of soapstock can produce oxygen-free and alkene-free biofuel under mild conditions by using pyrolysis coupled on-line quality improvement method.Bio-jet fuel is a kind of biofuel composed of multifunctional components in the range of C₈-C₁₆.Its preparation process involves complex isomerization or aromatization reactions,which is easy to reduce the yield of jet fuel.In view of this,the bio-jet fuel with bifunctional components（n-alkanes and aromatics）was prepared by co-pyrolysis of soapstock and polystyrene waste plastic and subsequent vapor-phase hydrotreating process.The main research contents and conclusions are as follows:The effect of reaction conditions on the preparation of fatty acids by pressure hydrolysis of peony seed oil soapstock was investigated by ultrasonic-assisted method,and the content and quality of fatty acids of products were identified.The results indicate that the introduction of ultrasound can accelerate the process of acidification hydrolysis reaction through emulsification and stirring dispersion.With formic acid as the catalyst,under the conditions of reaction temperature 220℃,reaction time 110min,ultrasonic power 1050W,and ultrasonic duration 7s,the highest acid value and yield of the product were 184mg KOH/g and 79.9%,respectively.The order of factors affecting the yield of product from primary to secondary were reaction temperature,ultrasonic duration,ultrasonic power,and reaction time.The fatty acid content in the product reached 97.4%,saponification value reached 190mg KOH/g,iodine value reached 157g I/100g,and unsaponifiable matter content reached 0.54%.The effects of catalyst,pyrolysis temperature,and hydrogenation temperature on n-alkanes were investigated by pyrolysis and subsequent vapor-phase hydrogenation process using peony seed oil soapstock.Experimental results indicated that the primary intermediates（Acids,alcohols,alkene,etc）of pyrolysis were completely deoxygenated and hydrogenated with Ni/Al₂O₃-Si O₂catalyst,and the relative content of C₅-C₁₇ n-alkanes increased from15.8%to 97.3%,compared with that of the non-catalytic.The yield of n-alkanes initially increased and then decreased with increase of pyrolysis temperature,and the highest yield was observed at 550℃.The yield of n-alkanes gradually decreased with increase of hydrogenation temperature,and the highest yield was observed at 300℃.The highest yields of target n-alkanes were generated at a pyrolysis temperature of 550°C and a gaseous hydrogenation temperature of 300°C,with a diesel range hydrocarbon selectivity of 75.9%.The effects of supported Pd-based catalysts on the formation of bio-jet fuel with bifunctional components（aromatics and n-alkanes）were investigated using palm kernel oil（oil components of soapstock）and polystyrene（PS）foam by co-pyrolysis vapor-phase hydrogenation experiment.On this basis,the process conditions were optimized and the application of this process in different plastics and oils was expanded.The results showed that the formation of bio-jet fuel with bifunctional components depended on the acidity of the supported Pd-based catalyst.With Pd/SBA-15 as the catalyst,under the conditions of pyrolysis temperature 480℃,vapor-phase hydrogenation temperature 350℃,and catalyst loading 5mg,the highest yield of bio-jet fuel with double-components was 71.0wt%,which is 14.3 times higher than under non-catalytic conditions.However,hydrocracking/isomerization reactions occurred over Pd/HZSM-5 and Pd/USY catalysts with a higher acid content,producing 35.5wt%and 18.1wt%of jet fuel range hydrocarbons,respectively.In addition,bio-jet fuel with bifunctional components was obtained from different plastics and oils,and the yield was 43-71wt%,indicating that this process has great potential for the conversion of plastics and oils/soapstock into bio-jet fuel with bifunctional components.