Study On The Production Of Hydrogen By Catalytic Steam Reforming Of Waste Cooking Oil

Hydrogen is a sustainable energy source with high efficiency and low pollution and plays a significant role in energy utilization.However,conventional chemical hydrogen production methods mainly rely on nonrenewable fossil fuels,which consume large amounts of energy and have low economic value.Therefore,using renewable energy to produce hydrogen is a hot research topic at home and abroad.The advantages of steam reforming are that the cost of hydrogen production is low,the generated gas has a higher calorific value,it is safer,and it is easier to control.Hydrogen production from waste cooking oil(WCO)can solve environmental pollution while turning waste into treasure.Therefore,hydrogen production from WCO can be carried out through steam reforming.In this paper,using WCO as raw material,a theoretical simulation study on steam reforming of WCO to produce hydrogen was conducted using ASPEN PLUS software,providing a theoretical basis for the experiment.On this basis,the hydrogen production experiments were carried out by steam catalytic reforming.The effects of reaction temperature(600-800 ℃),steam to carbon molar ratio(S/C=0.64-10.95),H-ZSM-5,n Ni/ZSM-5(n=5,10,and 15 wt%),and the addition of promoter(La)on the experimentally generated hydrogen yield and catalyst carbon deposition were studied.The primary studies are as follows:(1)Simulation experiments were conducted on WCO steam reforming using ASPEN PLUS software to simulate the effects of temperature(T=300-1400℃),pressure(P=0-5 MPa),and steam to carbon molar ratio(S/C=0.64-10.95)on the volume fractions of products(H2,CH4 CO,and CO2).The simulation results showed that the higher the pressure,the lower the volume fraction of H2.The high temperature was favorable for the preparation of hydrogen.The reaction reached equilibrium after 700℃.With the increase of S/C,the volume fraction of H2 and CO2 increased,while the volume fraction of CH4 and CO decreased.(2)Thermogravimetric(TG)analysis of WCO and the mixture of WCO and H-ZSM-5 uniformly mixed in a 1:1 ratio was carried out in the N2 atmosphere to study the relationship between temperature and mass in the WCO.The functional groups of WCO were analyzed by Fourier transform infrared spectroscopy(FT-IR).GC/MS and PY-GC/MS analysis methods were used to study the possible compounds in the pyrolysis products of WCO.And the changes in the volume fractions of various gases and carbon deposition under the experimental conditions of T=600-800℃,S/C=0.64-10.95,and the presence or absence of H-ZSM-5 were studied by steam reforming methods.The results of TG showed that the pyrolysis of WCO had two weight loss ranges,corresponding to the decomposition of fatty acids and the complete combustion of carbon in the sample.After in addition of H-ZSM-5,the two weight loss ranges of WCO became one,which indicated that the addition of the catalyst could accelerate the decomposition of fatty acids and carbon combustion in WCO.FT-IR results indicated that the infrared results of the WCO used were similar to those of the WCO in related studies.The results of GC/MS and PY-GC/MS indicated that WCO was mainly composed of long-chain carboxylic acids,esters,and a small number of aldehydes.When T≥ 650℃ the WCO was cracked entirely.At high temperatures,the ester group of WCO breaks to form alcohols and carboxylic acids,where alcohols are dehydrated to form olefins.The experimental results of steam reforming of WCO showed that the volume fraction of H2 increased with the temperature increase and tended to flatten out after 700℃.As the S/C increased,the volume fractions of H2 and CO2 were increased,while the volume fractions of CH4 and CO were decreased.After in addition of H-ZSM-5 in the experiment,the volume fraction of hydrogen generated in the experiment was higher than without adding H-ZSM-5.The volume fraction of hydrogen increased from 41.20%to 51.74%at P=0.1 MPa,T=700 ℃,S/C=5.25,and space-time(τ)=0.56 gcatalysth(gWCO)-1.(3)Ni/ZSM-5(n=5,10,and 15 wt%)and 6 wt%La-10 wt%Ni/ZSM-5 catalysts were prepared by H-ZSM-5 as a carrier used impregnation method.The catalysts were characterized before and after use by ICP-OES,NH3-TPD,O2-TPO,FT-IR,XRD,and SEM.And the WCO catalytic steam reforming experiments were conducted in a fixed bed reactor to investigate the effects of Ni loading and La addition on the volume fraction of hydrogen and carbon deposition produced in the experiment.The characterization results indicated that the actual load values of all modified catalysts were close to the theoretical values.The introduction of La can affect the type of surface acid and the number of surface acid sites of a 10 wt%Ni/ZSM-5 catalyst.The 6 wt%La-10 wt%Ni/ZSM-5 catalyst used has strong coking resistance and catalytic activity.H-ZSM-5 has high stability and can maintain its crystal structure unchanged after loading metal and calcination.The experimental results of WCO catalytic steam reforming showed that used n Ni/ZSM-5(n=5,10,and 15 wt%)catalysts for catalytic steam reforming of WCO,the effect of 10 wt%Ni/ZSM-5 catalyst was better under the condition at P=0.1 MPa,T=700℃,S/C=5.25,and space-time(τ)=0.56 gCatalysth(gWCO)-1.Under this condition,the volume fraction of hydrogen was 64.43%,and the carbon deposition was 7.8%.Under the same experimental conditions,using 6 wt%La-10 wt%Ni/ZSM-5 catalyst,the volume fraction of hydrogen generated in the experiment increased to 74.58%,and the carbon deposition decreased to 0.38%.