Study On Removal Of Low Content Sulfur In FCC Gasoline By Adsorbent

With the continuous improvement of people’s living standards, the demand forenvironmental quality is becoming higher, the environmental awareness is also growing, andthe production of cleaner fuels to meet environmental requirements is becoming the generaltrend of global refining business development. Coupled with increasing sulfur content ofcrude oil in recent years, the air pollution caused by vehicle exhaust has aroused widespreadconcern around the world, and accompanied by increasingly strict quality guidelines ofgasoline, therefore, the desulfurization of vehicle gasoline fuel has become increasinglyimportant, as well as the production of low-sulfur gasoline and sulfur-free gasoline becomesthe priority of gasoline quality upgrading, it has also become the domestic oil refiningcompanies to produce clean oil facing severe challenges.In China, fluid catalytic cracking gasoline in motor gasoline accounted for more than75%. It is characterized by poor stability, poor quality, and high sulfur content, which can notmeet the new quality standards of gasoline in our country. Currently, in order to solve thequestion of high sulfur content of gasoline, mainly using hydrodesulfurization and adsorptiondesulfurization reduce the sulfur content in gasoline. Among them, the hydrodesulfurization isused widely, very mature in technology and process, and can effectively remove most of themercaptan, thioether and other sulfide in gasoline, but the removal efficiency of thiophenesulfide is bad, and it is difficult to remove completely. Furthermore, in the process of thehydrodesulfurization of removal the sulfide in gasoline while part of the light olefins ingasoline are hydrogenated in a saturated low octane alkane, resulting in a decline in the octanenumber of the gasoline, the rise in the cost of production. The adsorption desulfurizationtechnology has mild operating conditions, low production cost, good desulfurization effect,desulfurization and hydrogenation of olefins process will not cause saturation resultingdecline in gasoline octane and other advantages. Therefore, the world refining companiesincreasingly turned their attention to the development of research on adsorptiondesulfurization technology.This paper studies on the removal of trace sulfur in catalytic cracking gasoline, whichbased on the FCC (Fluid-bed Catalytic Cracking, referred to as FCC) gasolinehydrodesulfurization technology meet the quality requirement of national standard IV, usingadsorbent and a fixed-bed reactor technology. Through this research, we expect to develop aFCC gasoline adsorption desulfurization technology with fixed-bed reactor, and could produce the low sulfur content of FCC gasoline meeting the new gasoline quality requirementof national standard V.This paper studies the different adsorbents, investigates the effects of sorbent preparationmethods, preparation conditions and modification way on the experiment of adsorptiondesulfurization. The results show that the modified Y zeolite adsorption desulfurizationperformance is the best, MCM-41molecular sieve, followed by titanium silicon molecularsieve worst; The sorbent prepared by wet-kneading method has larger specific surface area,pore volume, better desulfurization activity, and smaller loss of octane number afterdesulfurization of FCC gasoline; The optimum composition of the laboratory preparation ofdiatomite sorbents is SiO2/Al2O3mass ratio of1to2, Ni/ZnO mass ratio of0.1to0.16; Theoptimum processing conditions of the sorbent prepared is calcination temperature500℃,calcination time3h; The best sorbent modified way is adopting wet-kneading methodintroduced metallic potassium ions, which KNO3quality content is1.6to3.2percent.This paper studies the physical properties of the modified adsorbent, investigates theadsorbent preparation repeatability and the desulfurization performance of diatomiteadsorbent under the best modified way. The results show that the physical properties of themodified sorbent remain substantially constant; Physical properties and desulfurizationactivity of sorbent prepared repeatedly is consistent basically, with good preparationreproducibility; Under the best modified way, the effect of modified adsorbent desulfurizationincreased significantly, and the loss of octane number, after desulfurization of FCC gasoline,decreased obviously.This paper studies with zeolite adsorbents for the adsorption desulfurization experiment,the raw material is FCC heavy gasoline fractions, which is separated by FCC gasolinedistillation and produced by Lanzhou Petrochemical Company, and it tests in200mLfixed-bed reactor. The results show that the time of adsorption desulfurization reaction isshort, when the zeolite adsorbent removes the sulfur in FCC gasoline, the averagedesulfurization rate is low, and the loss of olefin in FCC gasoline after desulfurization isincreased. Overall, the adsorption desulfurization performance of zeolite adsorbent is poor.This paper studies with diatomite adsorbents prepared by China University of Petroleum(Beijing), the raw material is FCC gasoline, which is prepared by Ningxia PetrochemicalCompany, and it tests in200mL fixed-bed reactor. The results show that the optimumoperating conditions for adsorption desulfurization reaction are adsorption temperature350℃,adsorption pressure2.0MPa, volume ratio of hydrogen to feed oil60, gasoline feedvolumetric space velocity7h-1; Under the optimum operating conditions, using diatomitesorbent, the sulfur content in FCC gasoline can be reduced to lower than10μg/g, the loss of olefin in FCC gasoline after desulfurization is1.10percentage points, and the loss of octanenumber (RON) is only0.5units.This paper studies the long-periodic adsorption desulfurization way to experiment witheight kinds of adsorbents, and examines the impact of the distillation process in combinationwith adsorption desulfurization technology for desulfurization performance of sorbent. Theresults show that, one of the best in the desulfurization sorbent performance tested, theadsorption desulfurization reaction time reach348h, the sulfur capacity achieve13.7percent,and the loss of olefin is5.4percentage point; By using a combination of distillation andadsorption desulfurization process, we can reduce the octane number loss of desulfurizationFCC gasoline, and produce blended gasoline that its sulfur content is less than10μg/g,meeting the gasoline quality requirement of national standard V.This paper studies the regeneration of the adsorbent, and examines the effects of sorbentregeneration process conditions and methods for desulfurization performance of sorbentregeneration. The results show that, compared to the fresh sorbent, the desulfurization activityof sorbent is decreased slightly after the regeneration; The impact is little, which regenerationfrequency for desulfurization activity of the regenerated adsorbent, the desulfurizationcapability of adsorbent remain stable after repeated regeneration, essentially unchanged; Theoptimum operating conditions and methods of sorbent regeneration is that, firstly, at atemperature of400℃, under pure nitrogen atmosphere, heated30min, secondly, switch to theconcentration of0.4φ%O2atmosphere, thermostated3h, then up to450℃, switch to theconcentration of2φ%O2atmosphere, under an atmosphere of constant temperaturethermostated7h, up to510℃, thermostated2h, finally, cooled to500℃, pure air atmosphereand thermostated2h.This paper studies the physicochemical properties of the sorbent regeneration, andcarries on the desulfurization performance of regenerated adsorbent under optimal conditionsfor the regeneration process. The results show that the physical and chemical properties of theregenerated adsorbent are not changed obviously; Under optimum conditions of regeneration,the active component of regenerated sorbent does not be sintered, the adsorbent is regeneratedcompletely, and the performance of regenerated adsorbent is still good. And in the process ofadsorption desulfurization reaction, the regenerated adsorbent removes the sulfide in gasolinestably, and the desulfurization activity has not declined.By adsorption desulfurization experiment, research of this paper achieved the anticipatedtarget, which could remove low content sulfides in FCC gasoline effectively. On the basis ofselective hydrodesulfurization as the main technology, using FCC gasoline as the rawmaterial, the sulfur content in FCC gasoline is in conformity with the quality guidelines ofnational standard IV, and combined fixed-bed reactor with adsorption desulfurization technology, we can make the sulfur content in FCC gasoline be reduced to less than10μg/g,achieve the goal of deep desulfurization, make the loss of octane number in desulfurizationgasoline be much smaller, and produce FCC clean gasoline which could meet the gasolinequality requirements of national standard V.