Investigation Of The Synthesis And Performance Of The Kaolin-based Catalyst And Adsorbent For Deep Desulfurization

Environmental issues have become a global focus,and protecting the environment brooks no delay.Among them,serious acid rain and smog problems have become the top priority of governance because they are closely related to human living conditions.The culprit of these problems is mainly sulfur oxides（SOx）contained in motor vehicle exhaust.In order to achieve the long-term goal of a good ecological environment in 2035 and create a sustainable production model,it is urgent and imperative to achieve deep desulfurization of fuel oil.Nowadays,countries in the world have issued strict standards to limit the sulfur content of fuels.The National VI standard that has been fully implemented since July 1,2020 in my country also requires that the sulfur content in fuels is not higher than 10 ppmw.At the same time,a large amount of fuel used in fuel cells needs to be deeply desulfurized to prevent catalyst poisoning,which also promotes the research and development of fuel deep desulfurization.In response to this serious problem,the most commonly used in the industry is still the traditional hydrodesulfurization method,but it has the problem of severe reaction conditions and the inability to efficiently remove thiophene,benzothiophene,and dibenzothiophene.Therefore,oxidative desulfurization and adsorption desulfurization methods with mild reaction conditions and more efficient reactions have gradually attracted attention.In terms of the selection of catalyst support materials,this work focuses on the development of kaolin,a cheap natural clay,and designs and develops oxidative desulfurization catalysts and adsorption desulfurization adsorbent systems suitable for industrial production applications.For the first time in the modification of kaolin,a simple process was used to prepare a catalyst carrier with a mesoporous structure using kaolin as the main raw material,which is expected to be used in petrochemical catalysts.Compared with traditional Al₂O₃ and Ti O₂ carriers,kaolin catalyst carrier materials have significant price advantages and have huge market potential in the future.On this basis,this work is the first to design a vanadium pentoxide/mesoporous kaolin oxidative desulfurization catalyst system,innovatively adopt a one-step hydrothermal synthesis process,greatly simplify the process flow and reduce production costs.At the same time,this work combines transition metal elements,rare earth elements and kaolin 4A molecular sieve to prepare a fuel oil deep desulfurization adsorbent,which significantly increases the added value of kaolin products.The main research work and results of this paper are as follows:1.Using the top-down method to prepare the mesoporous kaolin catalyst carrier.The first step is to pre-treat the kaolin by acidification with hydrochloric acid,and then use cetyltrimethylammonium bromide（CTAB）as a template to synthesize the mesoporous kaolin catalyst carrier in an alkaline hydrothermal environment.The preparation of the catalyst uses one-step water The vanadium pentoxide is supported by thermal method.The research results show that with the increase in the amount of hydrochloric acid,the catalytic performance of the catalyst continues to improve.After comprehensively considering the pollution and post-treatment of the acid waste liquid,we improved the acidification conditions to achieve 15 minutes under the condition of a lower concentration of hydrochloric acid.Within～98.81%of dibenzothiophene（DBT）removal rate.The prepared vanadium pentoxide/mesoporous kaolin catalyst has a large specific surface area and a mesoporous structure.The vanadium pentoxide mainly exists in the form of nanocrystals and is uniformly distributed on the carrier.The catalyst has excellent cycle stability,and the removal rate of 91.38%is still achieved within 60 minutes after five tests.By comparing the XRD spectra before and after the catalyst reaction,the existence of the oxidation product dibenzothiophene sulfone（DBTO₂）is confirmed,and the acid solution can be reused in the synthesis process,which reduces the production cost.2.A bottom-up method was used to prepare Al-MCM41 mesoporous molecular sieve catalyst carrier with kaolin as part of the silicon source and aluminum source,and ethyl orthosilicate（TEOS）as a supplementary silicon source.Sex.The research determined the optimal vanadium loading,and synthesized an excellent oxidation desulfurization catalyst.We confirmed the successful construction of mesoporous molecular sieves and their structural parameters.Both the Al-MCM41 catalyst support and the 10V-Al-MCM41 catalyst have high specific surface area and concentrated mesopore pore size distribution.The study found that part of vanadium will replace silicon into the framework structure during the synthesis process,and there are also vanadium oxide nanocrystals uniformly distributed on the molecular sieve.The microstructure of the catalyst is mainly composed of spherical particles of about 200nm～500nm.TEM results can observe obvious pore structure and orderly arrangement.The catalyst achieves a 97.97%DBT removal rate within 20 minutes.We researched and determined that the optimal reaction conditions for the system were:T=60℃,oil/catalyst=1g/8mg,O/S=4.The cycle performance of the catalyst is stable,and the DBT removal rate of 92.36%can still be achieved within 60 minutes after five tests.3.The 4A molecular sieve synthesized from kaolin is used as the adsorbent carrier,and the copper and cerium bimetallic modification is carried out by ion exchange and impregnation methods.This part of the work systematically studied the effects of single metal modification,bimetal modification,metal loading sequence and loading amount on the adsorption performance of the adsorbent,and determined the best sequence to be copper modification first and then cerium modification.The best-performing adsorbent can achieve a DBT removal rate of 90.43%.Studies have shown that the increase in the specific surface area and pore size of the adsorbent,the increase in the amount of Lewis acid on the surface of the adsorbent,theπ-complexation of copper species and the S-M bonding of cerium species are the main reasons for the excellent adsorption and desulfurization performance.