Preparation Of Modified Nano Tin Oxide Catalyst And Its Application In Zinc-nitrobenzene Study On Electrocatalytic Performance Of Primary Battery

Aromatic amines are important organic chemical raw materials and intermediates,and have a wide range of applications in the fields of petrochemicals,organic pigments,medicines,and pesticides.Reduction of aromatic nitro compounds to produce aniline mainly includes chemical and electrochemical methods.Chemical reduction methods usually use active metals（such as iron,zinc,aluminum,etc.）or hydrogen as reducing agent.Raw materials,products and by-products are mixed together in the reaction process,complicated follow-up separation operations are required,and a large amount of three-pollutant pollutants are generated at the same time.The chemical energy during the reaction is also not used.These disadvantages make it difficult to apply to modern industrial production and are in an embarrassing situation that will be eliminated.Electrochemical method has always been considered as a"green chemistry"method.Electrochemical method can not only solve the deficiencies in chemical methods,reduce costs,greatly shorten the process,but also has obvious advantages in the environment and energy.In recent years,it has received close attention from people.Inspired by zinc-air batteries and fuel cells,this paper designs the reaction of reducing nitrobenzene with zinc into a galvanic cell reaction.Zinc powder undergoes an oxidation reaction at the negative electrode to form a zinc salt,and nitrobenzene is reduced at the positive electrode to prepare arylamine.At the same time,a kind of nanocatalyst with high catalytic activity and selectivity and low price was prepared and used in the reaction of zinc-nitrobenzene battery.The main contents and results are as follows:1.A zinc-nitrobenzene galvanic cell reactor was constructed.This article uses a three-chamber two-membrane reactor to electroreduce nitrobenzene.The reactor contains a negative electrode chamber,an intermediate chamber,and a positive electrode chamber.The active material in the negative electrode compartment is zinc powder.During the reaction,the zinc powder is oxidized to form a zinc salt,the intermediate compartment is a hydrochloric acid solution,the intermediate compartment and the cathode compartment are membrane electrodes,and the nitrobenzene in the anode compartment is electroreduced on the membrane electrode to form aromatic amines.Through the relevant thermodynamics calculations,the standard electrode potential of this redox reaction is 1.7 V,indicating that the reaction can proceed spontaneously.2.Preparation of SnO₂ nano-catalyst by hydrothermal preparation of different solvents（ethanol,isopropanol and n-butanol）and preparation of SnO₂ membrane electrode by the preparation process of fuel cell membrane electrode.The morphology of SnO₂ was characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）and transmission electron microscopy（TEM）.At the same time,the electrochemical performance of the catalyst was investigated by cyclic voltammetry and discharge experiments.Quantitative analysis of nitrobenzene reduction products by Gas Chromatography.The results show that SnO₂ prepared from ethanol is a kind of volcanic rock structure formed by massive aggregates,while isopropanol is a solid microsphere with a diameter of 0.5-2μm,and SnO₂-n-butanol is a sparse porous coral structure.Although their morphologies are different,the smallest nanoparticle size that constitutes their topography is about 10nm.Electrochemical tests showed that SnO₂prepared from ethanol had the best catalytic activity for reducing nitrobenzene by zinc,SnO₂-n-butanol had the lowest catalytic activity,and SnO₂ ethanol membrane electrode reduced the maximum discharge power of nitrobenzene primary battery by25.5 mW·cm^-2.3.The effects of the concentration of tin tetrachloride,the ratio of tin tetrachloride and urea,and the hydrothermal reaction temperature and time on the performance of the synthesized catalyst were investigated by orthogonal experiments.Among them,the orthogonal experiment 3 had the best catalytic performance.The maximum power of the battery was 26.2 mW·cm^-2.The results of the orthogonal table show that the most important factor affecting the catalytic performance is the concentration of tin tetrachloride,followed by the molar ratio of SnCl₄·5H₂O to urea,the hydrothermal reaction time and the reaction temperature,and the optimal reaction conditions for the hydrothermal reaction are the concentration of tin tetrachloride is 0.333 mol·L^-1,the ratio of tin tetrachloride and urea is 1:3,the hydrothermal temperature is 160°C,and the hydrothermal time is 7 h.In addition,the effects of catalyst loading,nafion content,hot pressing temperature and pressure on the performance of SnO₂ membrane electrode were also investigated.The results showed that the optimal preparation conditions were:SnO₂ loading 1 mg·cm^-2,Nafion content 40%,hot-pressing temperature 135°C,pressure 12 Mpa,time 120 s.Membrane electrodes prepared under the optimum conditions were found to have a maximum power density of 31.1 mW·cm^-2 in the zinc-nitrobenzene primary battery reaction.4.Prepare the catalyst with Ru metal modified SnO₂.The results showed that Ru/SnO₂ composites tend to form a spherical shape with the increase of Ru incorporation ratio（10%,20%,and 30%）,the spherical shape is formed by the density of nano particles that are about 10 nm in size.No characteristic peak of RuO₂ diffraction was found in the XRD pattern.XPS results showed that Ru replaced the Sn atoms in the tetragonal rutile lattice to form a Ru-Sn-O solid solution.Cyclic voltammetry and discharge performance tests show that the doping of niobium is beneficial to improve the catalytic activity of the catalyst for the electro-reduction of nitrobenzene,and when the doping is 30%,the prepared nanomaterial has the best catalytic performance and the power density is 35.5 mW·cm^-2.5.MWCNTs/SnO₂ nanocomposites were prepared using multiwalled nitrogen-doped carbon nanotubes as carriers,and the effects of the addition ratio of SnO₂ and carbon nanotubes on the structure and properties of the composites were investigated.The TEM results show that when the ratio of SnO₂ to carbon nanotubes is 1:4,SnO₂nanoparticles with a size of about 5 nm are densely packed on the surface of the carbon nanotubes,and the agglomeration phenomenon is serious.When the ratio of SnO₂ to carbon nanotubes is 1:16,the obtained composite material not only ensures the high loading of SnO₂,but also does not cause catalyst agglomeration.Both the CV and the discharge performance test results showed that the performance of the catalytic composite prepared at 1:16 was the best.The maximum power density is 45.1 mW·cm^-2,and the selectivity of aniline is 68.4%,which are greatly improved compared with pure SnO₂ and Ru/SnO₂.