Study On Supported Catalyst For Hydrogen Production From Supercritical Water Catalytic Gasification Of Oily Sludge

Oily sludge is a harmful solid waste composed of oil,wastewater,and solid particles generated during the process of crude oil extraction,storage,and refining.However,it has high water content and is rich in hydrocarbons.The process of hydrogen production from oily sludge using supercritical water gasification technology has the advantages of high hydrogen conversion rate,fast reaction speed,and no pollution products.It is a green,circular,low-carbon,and efficient treatment method,It is also one of the effective ways to alleviate energy and environmental pressure in the future.However,the harsh reaction conditions such as high temperature and pressure required for the supercritical water gasification process will inevitably increase equipment investment and operating costs.In order to reduce reaction energy consumption,improve reaction efficiency,and achieve product orientation selection,adding catalysts to the supercritical water gasification reaction is a common strategy.In response to this phenomenon,this article selected an iron based oxide catalyst FeOOH rich in hydroxyl and ferrite groups,and prepared a supported catalyst by loading it onto a stable carrier to solve its agglomeration phenomenon,reduce reaction activation energy,improve catalytic activity,and reuse rate.Firstly,FeOOH supported catalysts were prepared using Al₂O₃,AC,and Zn O as carriers,and their apparent morphology and loading capacity were characterized by XRD,field emission electron microscopy,and other means;Using hydrogen production rate as the main evaluation indicator,catalysts of different carrier types were optimized based on the distribution of solid and liquid phase products.Secondly,optimized catalysts with different loading amounts were prepared,and the effects of loading amounts and catalyst concentrations on gas-liquid solid three-phase products were analyzed.A reaction kinetics model was established to analyze the effect of catalyst addition on reaction activation energy.The gasification reaction pathway was analyzed from a microscopic perspective,and the mechanism of action of supported catalysts was explained.Finally,the optimal heating rate was optimized through experiments,and the influence of heating rate on the conversion rate and reaction activation energy of oily sludge was studied using the model free kinetics established by the equal conversion rate method.The supercritical water gasification process of oily sludge was explained from an energy perspective.The main conclusions obtained from this study are as follows:1.The addition of carrier and active component FeOOH has a positive catalytic effect on the supercritical water gasification reaction of oily sludge,and its binding effect is stronger than its individual effect.Under the same conditions,the catalytic effect sequence is FeOOH/AC>FeOOH/Al₂O₃>FeOOH/Zn O.2.The activity of the catalyst shows a trend of first increasing and then decreasing with the increase of load and concentration.When the load is 10 wt%and the concentration is 5%,the catalytic effect is the best,and the hydrogen yield increases by 70.78%.3.FeOOH/AC changes the gasification reaction path of oily sludge through adsorption and carrier effects,reduces the activation energy of the reaction,and accelerates the reaction rate,thereby promoting the generation of gas-phase products and the cracking of heavy components.The active Featoms on the surface of FeOOH/AC can strongly bond with water and oily sludge molecules,accelerating the cracking of water and oily sludge.The active Featoms on the surface can promote the breaking of C-C,C-H,and C-O bonds in oily sludge components,and cause the heavy components of crude oil to split into light components.Under the catalysis of FeOOH/AC,the activation energy E is 53.958 k J/mol,and the pre exponential factor A is 6.44977 min^-1;In the non catalyst group,the activation energy is63.031 k J/mol,and the pre exponential factor A is 19.2335 min^-1.4.High heating rate is beneficial for the supercritical water gasification of oily sludge.With the increase of heating rate,HE shows a trend of first increasing and then decreasing,but CE continues to increase.The optimal heating rate obtained through experiments is12K/min.5.The isoconversional method was used to analyze the supercritical water gasification process of oily sludge.It was found that the heating rate was negatively correlated with the conversion rate,and the activation energy of oily sludge was not a constant value.When the conversion rate continued to increase,the activation energy of oily sludge increased first and then decreased.The kinetic parameter error obtained by KAS method was the smallest.The results show that the activation energy value in the initial stage of the reaction is about 64.49k J/mol,which mainly corresponds to the arbitrary fracture reaction of the weak bond in the polymer chain,and the reaction speed is very fast.The activation energy E gradually increases with the reaction.When the conversion rate reaches 0.7,the average value of E at this stage is about 109.54 k J/mol.The reaction is mainly the fracture and depolymerization of the polymer chain itself.When the conversion rate reaches 0.8,the E value decreases rapidly,with an average value of about 87.35 k J/mol,and the reaction is mainly chain termination reaction.