WO2001070393A1

WO2001070393A1 - Desulfurization and novel sorbents for same

Info

Publication number: WO2001070393A1
Application number: PCT/US2001/007300
Authority: WO
Inventors: Gyanesh P. Khare
Original assignee: Phillips Petroleum Company
Priority date: 2000-03-21
Filing date: 2001-03-06
Publication date: 2001-09-27
Also published as: AU2001245496A1

Abstract

Particulate sorbent compositions consisting essentially of zinc ferrite and a binder, wherein the zinc ferrite is of reduced valence, are provided for the desulfurization of a feedstream of cracked-gasoline or diesel fuels in a desulfurization zone by a process which comprises contacting of such feedstreams in a desulfurization zone followed by separation of the resulting low sulfur-containing stream and sulfurized sorbent and thereafter regenerating and activating the separated sorbent by reduction thereof before recycle of same to the desulfurization zone.

Description

DESULFURIZATION AND NOVEL SORBENTS FOR SAME FIELD OF THE INVENTION This invention relates to the removal of sulfur from fluid streams of cracked-gasolines and diesel fuels. In another aspect this invention relates to sorbent compositions suitable for use in the desulfurization of fluid streams of cracked- gasolines and diesel fuel. A further aspect of this invention relates to a process for the production of sulfur sorbents for use in the removal of sulfur bodies from fluid streams of cracked gasolines and diesel fuels.

The phrases "consists essentially of and "consisting essentially of do not exclude the presence of other steps, elements, or materials that are not specifically mentioned in this specification, as long as such steps, elements, or materials, do not affect the basic and novel characteristics of the invention, additionally, they do not exclude impurities normally associated with the elements and materials used.

The above terms and phrases are intended for use in areas outside of U.S. jurisdiction. Within the U.S. jurisdiction the above terms and phrases are to be applied as they construed by U.S. courts and the U.S Patent Office.

BACKGROUND OF THE INVENTION The need for cleaner burning fuels has resulted in a continuing world wide effort to reduce sulfur levels in gasoline and diesel fuels. The reducing of gasoline and diesel sulfur is considered to be a means for improving air quality because of the negative impact the fuel sulfur has on the performance of automotive catalytic converters. The presence of oxides of sulfur in automotive engine exhaust inhibits and may irreversibly poison noble metal catalysts in the converter. Emissions from an inefficient or poisoned converter contain levels of non-combusted, non-methane hydrocarbon and oxides of nitrogen and carbon monoxide. Such emissions are catalyzed by sunlight to form ground level ozone, more commonly referred to as smog.

Most of the sulfur in gasoline comes from the thermally processed gasolines. Thermally processed gasolines such, as for example, thermally cracked gasoline, visbreaker gasoline, coker gasoline and catalytically cracked gasoline

(hereinafter collectively called "cracked-gasoline") contains in part olefins, aromatics, and sulfur-containing compounds.

Since most gasolines, such as for example automobile gasolines, racing gasolines, aviation gasoline and boat gasolines contain a blend of at least in part cracked-gasoline, reduction of sulfur in cracked-gasoline will inherently serve to reduce the sulfur levels in such gasolines.

The public discussion about gasoline sulfur has not centered on whether or not sulfur levels should be reduced. A consensus has emerged that lower sulfur gasoline reduces automotive emissions and improves air quality. Thus the real debate has focused on the required level of reduction, the geographical areas in need of lower sulfur gasoline and the time frame for implementation.

As the concern over the impact of automotive air pollution continues, it is clear that further efforts to reduce the sulfur levels in automotive fuels will be required. While the current gasoline products contain about 330 parts per million

(ppm) sulfur, the U.S. Environmental Protection Agency recently issued regulations requiring the average sulfur content in gasoline to be less than 30 ppm average with an

80 ppm cap. By 2006 the standards will effectively require every blend of gasoline sold in the United States to meet the 30 ppm level. hi view of the ever increasing need to be able to produce a low sulfur content automotive fuel, a variety of processes have been proposed for achieving industry compliance with the Federal mandates.

One such process which has been proposed for the removal of sulfur from gasoline is called hydrodesulfurization. While hydrodesulfurization of gasoline can remove sulfur-containing compounds, it can result in the saturation of most if not all, of the olefins contained in the gasoline. This saturation of olefins greatly affects the octane number (both the research and motor octane number) by lowering it. These olefins are saturated due to, in part, the hydrodesulfurization conditions required to remove thiophenic compounds (such as, for example, thiophene, benzothiophene, alkyl thiophenes, alkylbenzothiphenes and alkyl dibenzothiophenes), which are some of the most difficult sulfur-containing compounds to removed. Additionally, the hydrodesulfurization conditions required to remove thiophenic compounds can also saturate aromatics.

In addition to the need for removal of sulfur from cracked-gasolines, there is also presented to the petroleum industry a need to reduce the sulfur content of diesel fuels. In removing sulfur from diesel by hydrodesulfurization, the cetane is improved but there is a large cost in hydrogen consumption. This hydrogen is consumed by both hydrodesulfurization and aromatic hydrogenation reactions.

Thus there is a need for a process wherein desulfurization without hydrogenation of aromatics is achieved so as to provide a more economical process for the treatment of diesel fuels .

As a result of the lack of success in providing successful and economically feasible process for the reduction of sulfur levels in both cracked-gasolines and diesel fuels, it is apparent that there is still needed a better process for the desulfurization of both cracked-gasolines and diesel fuels which has minimal affect of octane while achieving high levels of sulfur removal.

It is desirable to provide a novel sorbent system for the removal of sulfur from fluid streams of cracked-gasolines and diesel fuels.

Again it is to provide a process for the production of novel sorbents which are useful in the desulfurization of such fluid streams. Once again it is desirable to provide a process for the removal of sulfur-containing compounds from cracked-gasolines and diesel fuels which minimize saturation of olefins and aromatics therein.

Yet again it is desirable to provide a desulfurized cracked-gasoline that contains less than about 100 parts per million of sulfur based on the weight of the desulfurized cracked-gasoline and which contains essentially the same amount of olefins and aromatics as were in the cracked-gasoline from which it is made.

Other aspects, objects and the several advantages of this invention will be apparent from the following description of the invention and the appended claims.

SUMMARY OF THE INVENTION The present invention is based upon my discovery that through the utilization of a reduced zinc ferrite sorbent in a sorbent composition consisting essentially of reduced zinc ferrite and a binder there is achieved a novel sorbent composition which permits the ready removal of sulfur from streams of cracked-gasolines or diesel fuels with a minimal effect on the octane rating of the treated stream. Accordingly, in one aspect of the present invention there is provided a novel sorbent suitable for the desulfurization of cracked-gasolines or diesel fuels which consists essentially of a reduced zinc ferrite in association with a binder wherein the zinc ferrite has a reduced valence and wherein the reduced zinc ferrite is present in an amount to permit the removal of sulfur from cracked-gasolines or diesel fuels. In accordance with another aspect of the present invention, there is provided a process for the preparation of a novel sorbent composition which comprises admixing zinc oxide, iron oxide, binder, acid and water so as to form a wet mix, dough, paste or slurry thereof, particulating the wet mix, dough, paste or slurry thereof so as to form a particulate granule, extrudate, tablet, sphere, pellet or microsphere thereof, drying the resulting particulate, calcining the dried particulate under conditions to form zinc ferrite and reducing the resulting calcined zinc ferrite containing product with a suitable reducing agent, such as hydrogen, so as to produce a sorbent composition having a reduced valence zinc ferrite content in an amount which is sufficient to permit the removal with same of sulfur from a cracked-gasoline or diesel fuel stream.

In accordance with a further aspect of the present invention, there is provided a process for the desulfurization of a cracked-gasoline or diesel fuel stream which comprises desulfurizing in a desulfurization zone a cracked-gasoline or diesel fuel with a solid reduced zinc ferrite sorbent, separating the desulfurized cracked-gasoline or diesel fuel from the sulfurized sorbent, regenerating at least a portion of the sulfurized solid zinc ferrite sorbent to produce a regenerated desulfurized zinc ferrite sorbent, activating at least a portion of the regenerated desulfurized sorbent to produce a reduced zinc ferrite sorbent and thereafter, returning at least a portion of the resulting reduced valence zinc ferrite containing sorbent to the desulfurization zone. DETAILED DESCRIPTION OF THE INVENTION The term "gasoline" as employed herein is intended to mean a mixture of hydrocarbons boiling from 37.7°C (about 100 °F) to approximately 204.4°C (400°F) or any fraction thereof. Such hydrocarbons will include, for example, hydrocarbon streams in refineries such as naphtha, straight-run naphtha, coker naphtha, catalytic gasoline, visbreaker naphtha, alkylate, isomerate or reformate.

The term "cracked-gasoline" as employed herein is intended to mean hydrocarbons boiling from 37.7°C (about 100°F) to approximately 204.4°C (400°F) or any fraction thereof that are products from either thermal or catalytic processes that crack larger hydrocarbon molecules into smaller molecules. Examples of thermal processes include coking, thermal cracking and visbreaking. Fluid catalytic cracking and heavy oil cracking are examples of catalytic cracking. In some instances the cracked-gasoline may be fractionated and/or hydrotreated prior to desulfurization when used as a feed in the practice of this invention. The term "diesel fuel" as employed herein is intended to mean a fluid composed of a mixture of hydrocarbons boiling from 149°C (about 300°F) to approximately 399°C (750°F) or any fraction thereof. Such hydrocarbon streams include light cycle oil, kerosene, jet fuel, straight-run diesel and hydrotreated diesel. The term "sulfur" as employed herein is intended to mean those organosulfur compounds such as mercaptans or those thiophenic compounds normally present in cracked gasolines which include among others thiophene, benzothiophene, alkyl thiophenes, alkyl benzothiophenes and alkyldibenzothiophenes as well as the heavier molecular weights of same which are normally present in a diesel fuel of the types contemplated for processing in accordance with the present invention. The term "gaseous" as employed herein is intended to mean that state in which the feed cracked-gasoline or diesel fuel is primarily in a vapor phase.

The term "reduced zinc ferrite" as used herein is intended to mean that zinc ferrite compound produced through the calcination of zinc oxide and iron oxide which has been subjected to reduction with an appropriate reducing agent, preferably hydrogen, so that the valence of one or both of the metals of the zinc ferrite compound have been reduced to a state below that at which they normally are present. The present invention is based upon the discovery by applicant that a reduced valence zinc ferrite in a particulate composition consisting essentially of zinc ferrite and a binder results in a sorbent system which permits the removal of thiophenic sulfur compounds from fluid streams of cracked-gasolines or diesel fuels without having a significant adverse affect on the olefm content of such streams, thus avoiding a significant reduction of octane values of the treated stream. Moreover, the use of such novel sorbents results in a significant reduction of the sulfur content of the resulting treated fluid stream. a presently preferred embodiment of this invention, the sorbent composition has a zinc ferrite content in the range of from about 5 to about 90 weight percent.

The zinc oxide used in the preparation of the sorbent composition can either be in the form of zinc oxide, or in the form of one or more zinc compounds that are convertible to zinc oxide under the conditions of preparation described herein. Examples of such zinc compounds include, but are not limited to, zinc sulfide, zinc sulfate, zinc hydroxide, zinc carbonate, zinc acetate and zinc nitrate. Preferably, the zinc oxide is in the form of powdered zinc oxide.

The iron oxide used in the preparation of the sorbent composition can either be in the form of iron oxide, or in the form of one or more iron compounds that are convertible to iron oxide under the conditions of preparation described herein. Examples of such iron compounds include, but are not limited to, iron sulfide, iron sulfate, iron hydroxide, iron carbonate, iron acetate and iron nitrate. Preferably, the iron oxide is in the form of powdered iron oxide.

In addition to the formation of a mixture of zinc oxide and iron oxide, the novel sorbent system of this invention has present a binder which serves to bind the resulting zinc ferrite particles into a cohesive system.

The binder component can be any suitable compound that has cement-like properties, or clay-like properties, which can help to bind the particulate composition together. Suitable examples of such binder components include, but are not limited to alumina, silica, cements such as for example, gypsum plaster, common lime, hydraulic lime, natural cements, Portland cements, and high alumina cements, and clays, such as for example, attapulgite, bentonite, halloysite, hectorite, kaolinite, montmorillonite, pyrophylite, sepiohte, talc and vermiculite. The amount of binder used is in the range of from about 0.1 to about 30 weight percent, based on the total weight of the components. However, an amount in the range of about 1 to about 20 weight percent is preferred.

In a presently preferred embodiment of this invention, the binder employed is alumina or silica or mixtures thereof. Any suitable commercially available alumina or aluminosilicate materials including hydrated alumina, flame hydrolyed alumina, colloidal alumina solution and, generally, those alumina compounds produced by the dehydration of alumina hydrates are useful in preparing the sorbent system of this invention. One particularly preferred alumina is Catapal alumina available from Condea Vista Company, Houston, Texas.

In the formation of the sorbent system, it is also presently preferred that a pore forming material be added to the initial mixture of zinc oxide, iron oxide and binder. Such materials are normally burned off during the calcination of the particulate sorbent system so as to provide porosity to the resulting zinc ferrite system. Examples of such pore forming materials are cellulose, cellulose gel, microcrystalline cellulose, zinc stearate, ammonium carbonate, ammonium nitrate and graphite. In one presently preferred embodiment of the present invention there is utilized Lattice® NT- 100, a microcrystallme cellulose available from FMC Corporation, Philadelphia, PA.

In the formation of the desired zinc ferrite component of the sorbent system there is generally employed a zinc oxide and iron oxide in an amount such that the ratio of zinc to iron is in the range of about 0.5:2 to about 1.5:2. Presently a ratio of about 1 :2 is preferred.

The binder such as alumina is utilized in amounts such that there is achieved a binding of zinc ferrite in the ultimate sorbent composition. Generally such binders are employed in an amount in the range of about 0.1 to about 30 weight percent based on the total weight of the sorbent composition. The pore forming compounds are generally added to the initial mix of zinc oxide and iron oxide in an amount to achieve a desired porosity in the final calcined sorbent product. Generally an amount in the range of from about 0.1 to about 15 weight percent based on the total weight of the initial mix of zinc oxide, iron oxide and binder employed. hi the manufacture of the sorbent composition, the primary components of zinc oxide, iron oxide and alumina are combined together in appropriate proportions by any suitable manner which provides for the intimate mixing of the components to provide a substantially homogeneous mixture.

Any suitable means for mixing the sorbent components can be used to achieve the desired dispersion of the materials. Such means include, among others, tumblers, stationary shells or troughs, Muller mixers, which are of the batch or continuous type, impact mixers and the like. It is presently preferred to use a Muller mixer in the mixing of the iron oxide, alumina and zinc oxide components.

Once the sorbent components are properly mixed to provide a shapeable mixture, the resulting mixture can be in the form of wet mix, dough, paste or slurry. If the resulting mix is in the form of a wet mix, the wet mix can be densifϊed and thereafter particulated through the granulation of the densifϊed mix following the drying and calcination of same. When the admixture of zinc oxide, iron oxide and alumina results in a form of the mixture which is either in a dough state or paste state, the mix can be shaped to form a particulate granule, extrudate, tablet, sphere, pellet or microsphere. Presently preferred are cylindrical extrudate having from 1/32 inch to VΪ inch diameter and any suitable length. The resulting particulate is then dried and then calcined. When the mix is in the form of a slurry, the particulation of same is achieved by spray drying the slurry to form microspheres thereof having a size of from about 20 to about 500 microns. Such microspheres are then subjected to drying and calcination. Following the drying and calcination of the particulated mixture, there is achieved a zinc ferrite containing particulate.

Following calcination the resulting particulate consisting essentially of zinc ferrite and binder is subjected to reduction with a suitable reducing agent, preferably hydrogen, so as to produe a zinc ferrite composition having a reduced valence content with such reduced zinc, ferrite being present in an amount to permit the removal with same of sulfur from a cracked-gasoline or diesel fuel fluid stream. The solid reduced zinc ferrite sorbent of this invention is a composition that has the ability to react with and/or chemisorb with organo-sulfur compounds, such as thiophenic compounds. It is also preferable that the sorbent removed diolefins and other gum forming compound from the cracked-gasoline. The solid reduced zinc ferrite sorbent of this invention consists essentially of zinc ferrite that is in a reduced valence state and binder. Presently the reduced metal is iron. The amount of reduced zinc ferrite in the solid reduced sorbents of this invention is that amount which will permit the removal of sulfur from a cracked-gasoline or diesel fuel fluid stream. Such amounts are generally in the range of from about 5 to about 90 weight percent of the total weight of the sorbent composition.

The adsorbent composition may contain insignificant amounts of separate solid phases of individual metal oxides of iron and zinc which have not been converted to the desired zinc ferrite form during the preparation of the zinc ferrite through calcination of the iron oxide, zinc oxide mix. Such minor amounts of such metals which have not been chemically combined in the zinc ferrite are not expected to significantly affect the absorption capacity and performance of the sorbent compositions of this invention.

From the above, it can be appreciated that the sorbent compositions which are useful in the desulfurization process of this invention can be prepared by a process which comprises:

(a) admixing zinc oxide, iron oxide and inorganic binder so as to form a mix of same in the form of one of a wet mix, dough, paste or slurry;

(b) particulating the resulting mix to form particulates thereof in the form of one of granules, extrudates, tablets, pellets, spheres or microspheres;

(c) drying the resulting particulate;

(d) calcining the dried particulate;

(e) reducing the calcined zinc ferrite particulate product of (d) with a suitable reducing agent so as to produce a particulate composition having a reduced valence iron content therein and wherein the reduced valence iron content is present in an amount sufficient to permit the removal with same of sulfur from a cracked-gasoline or diesel fuel fluid stream when contacted with the resulting substantially reduced zinc ferrite particulated sorbent.

The process to use the novel sorbents to desulfurize cracked-gasoline or diesel fuels to provide a desulfurized cracked-gasoline or diesel fuel comprises: (a) desulfurizing in a desulfurization zone a cracked-gasoline or diesel fuel with a solid reduced zinc ferrite containing sorbent;

(b) separating the desulfurized cracked-gasoline or desulfurized diesel fuel from the resulting sulfurized solid reduced zinc ferrite sorbent;

(c) regenerating at least a portion of the sulfurized solid sorbent to produce a regenerated desulfurized solid sorbent;

(d) reducing at least a portion of the regenerated desulfurized solid sorbent to produce a solid reduced zinc ferrite containing sorbent thereafter and;

(e) returning at least a portion of the regenerated solid reduced zinc ferrite containing sorbent to the desulfurization zone. The desulfurization step (a) of the present invention is carried out under a set of conditions that includes total pressure, temperature, weight hourly space velocity and hydrogen flow. These conditions are such that the solid reduced zinc ferrite containing sorbent can desulfurize the cracked-gasoline or diesel fuel to produce a desulfurized cracked-gasoline or desulfurized diesel fuel and a sulfurized sorbent. In carrying out the desulfurization step of the process of the present invention, it is preferred that the feed cracked-gasoline or diesel fuel be in a vapor phase. However, in the practice of the invention it is not essential, albeit preferred, that the feed be totally in a vapor or gaseous state.

The total pressure can be in the range of about 103 kPa to about 10.33 MPa (about 15 psia to about 1500 psia). However, it is presently preferred that the total pressure be in a range of from about 344 kPa to 3445 kPa (about 50 psia to about 500 psia).

In general, the temperature should be sufficient to keep the cracked-gasoline or diesel fuel essentially in a vapor phase. While such temperatures can be in the range of from about 37.7°C to about 537.7°C (about 100°F to about 1000°F), it is presently preferred that the temperature be in the range of from about about 204.4 °C to about 426.6 °C (400 °F to about 800 °F) when treating as cracked- gasoline and in the range of from about 260 °C to about 482 °C (about 500 °F to about 900 °F) when the feed is a diesel fuel.

Weight hourly space velocity (WHSV) is defined as the pounds of hydrocarbon feed per pound of sorbent in the desulfurization zone per hour, the practice of the present invention, such WHSV should be in the range of from about 0.5 to about 50, preferably about 1 to about 20 hr^"1.

In carrying out the desulfurization step, it is presently preferred that an agent be employed which interferes with any possible chemisorbing or reacting of the olefinic and aromatic compounds in the fluids which are being treated with the solid zinc ferrite sorbent. Such an agent is presently preferred to be hydrogen.

Hydrogen flow in the desulfurization zone is generally such that the mole ratio of hydrogen to hydrocarbon feed is the range of about 0.1 to about 10, and preferably in the range of about 0.2 to about 3.0. The desulfurization zone can be any zone wherein desulfurization of the feed cracked-gasoline or diesel fuel can take place. Examples of suitable zones are fixed bed reactors, moving bed reactors, fluidized bed reactors and transport reactors. Presently, a fluidized bed reactor or a fixed bed reactor is preferred.

If desired, during the desulfurization of the vaporized fluids, diluents such as methane, carbon dioxide, flue gas, and nitrogen can be used. Thus it is not essential to the practice of the process of the present invention that a high purity hydrogen be employed in achieving the desired desulfurization of the cracked-gasoline or diesel fuel.

It is presently preferred when utilizing a fluidized system that a solid sorbent be used that has a particle size in the range of about 20 to about

1000 micrometers. Preferably, such sorbents should have a particle size of from about 40 to about 500 micrometers. When a fixed bed system is employed for the practice of the desulfurization process of this invention, the sorbent should be such as to have a particle size in the range of about 1/32 inch to about V inch diameter. It is further presently preferred to use solid zinc ferrite containing sorbents that have a surface area of from about 1 square meter per gram to about 1000 square meters per gram of solid sorbent.

The separation of the gaseous or vaporized desulfurized fluids and sulfurized sorbent can be accomplished by any means known in the art that can separate a solid from a gas. Examples of such means are cyclonic devices, settling chambers or other impingement devices for separating solids and gases. The desulfurized gaseous cracked-gasoline or desulfurized diesel fuel can then be recovered and preferably liquefied.

The gaseous cracked-gasoline or gaseous diesel fuel is a composition that contains in part, olefins, aromatics and sulfur-containing compounds as well as paraffins and naphthenes.

The amount of olefins in gaseous cracked-gasoline is generally in the range of from about 10 to 35 weight percent based on the weight of the gaseous cracked-gasoline. For diesel fuel there is essentially no olefin content.

The amount of aromatics in gaseous cracked-gasoline is generally in the range of about 20 to about 40 weight percent based on the weight of the gaseous cracked gasoline. The amount of aromatics in gaseous diesel fuel is generally in the range of about 10 to about 90 weight percent.

The amount of sulfur in cracked-gasolines or diesel fuels can range from about 100 parts per million sulfur by weight of the gaseous cracked-gasoline to about 10,000 parts per million sulfur by weight of the gaseous cracked-gasoline and from about 100 parts per million to about 50,000 parts per million for diesel fuel prior to the treatment of such fluids with the sorbent system of the present invention.

The amount of sulfur in cracked-gasolines or in diesel fuels following treatment of same in accordance with the desulfurization process of this invention is less than 100 parts per million.

In carrying out the process of this invention, if desired, a stripper unit can be inserted before the regenerator for regeneration of the sulfurized sorbent which will serve to remove a portion, preferably all, of any hydrocarbons from the sulfurized sorbent or before the hydrogen reduction zone so as to remove oxygen and sulfur dioxide from the system prior to introduction of the regenerated sorbent into the sorbent activation zone. The stripping comprises a set of conditions that includes total pressure, temperature and stripping agent partial pressure.

Preferably the total pressure in a stripper, when employed, is in a range of from about 172 kPa to about 3445 kPa (about 25 psia to about 500 psia).

The temperature for such strippers can be in the range of from about 37.7°C to about 538°C (about 100°F to about 1000°F).

The stripping agent is a composition that helps to remove hydrocarbons from the sulfurized solid sorbent. Presently, the preferred stripping agent is nitrogen.

The sorbent regeneration zone employs a set of conditions such that at least a portion of the sulfurized sorbent is desulfurized. The total pressure in the regeneration zone is generally in the range of from about 68.9 kPa to about 10.33 MPa (about 10 to about 1500 psia). Presently preferred is a total pressure in the range of from about 172 kPa to about 3445 kPa (about 25 psia to about 500 psia).

The sulfur removing agent partial pressure is generally in the range of from about 1 percent to about 100 percent of the total pressure.

The sulfur removing agent is a composition that helps to generate gaseous sulfur oxygen-containing compounds such a sulfur dioxide, as well as to burn off any remaining hydrocarbon deposits that might be present. Currently, oxygen-containing gases such as air are the preferred sulfur removing agent. The temperature in the regeneration zone is generally from about

37.7°C to about 825 °C (about 100°F to about 1500°F) with a temperature in the range of about 427°C to about 649°C (about 800°F to about 1200°F) being presently preferred.

The regeneration zone can be any vessel wherein the desulfurizing or regeneration of the sulfurized sorbent can take place.

The desulfurized sorbent is then reduced in an activation zone with a reducing agent so that at least a portion of the zinc ferrite content of the sorbent composition is reduced to produce a solid reduced zinc ferrite sorbent having an amount of reduced metal therein to permit the removal of sulfur components from a stream of cracked-gasoline or diesel fuel.

In general, when practicing the process of this invention, the reduction of the desulfurized sorbent is carried out at a temperature in the range of about 37.7°C to about 815 °C (about 100°F to about 1500°F) and a pressure in the range of about 103 kPa to about 10.33 MPa (about 15 to 1500 psia). Such reduction is carried out for a time sufficient to achieve the desired level of iron reduction in the sorbent system. Such reduction can generally be achieved in a period of from about 0.01 to about 20 hours.

Following the activation of the regenerated particulate sorbent, at least a portion of the resulting activated (reduced) sorbent can be returned to the desulfurization unit. When carrying out the process of the present invention in a fixed bed system, the steps of desulfurization, regeneration, stripping, and activation are accomplished in a single zone or vessel.

The desulfurized cracked-gasoline resulting from the practice of the present invention can be used in the formulation of gasoline blends to provide gasoline products suitable for commercial consumption.

The desulfurized diesel fuels resulting from the practice of the present invention can likewise be used for commercial consumption where a low sulfur-containing fuel is desired.

EXAMPLES The following examples are intended to be illustrative of the present invention and to teach one of ordinary skill in the art to make and use the invention. These examples are not intended to limit the invention in any way.

EXAMPLE I A solid zinc ferrite sorbent was produced by dry mixing 70 grams of zinc oxide, 142.5 grams of iron oxide (Bayferrox 130M Pigment, Miles Inc.,

Pittsburgh, PA), 37.5 grams of inorganic binder (Catapal D-hydrated alumina) and 10 grams of crystalline microcellulose porosity agent (Lattice®NT 100). Following mixing of the dry powders for 10 minutes a solution consisting of 6.25 grams acetic acid in 100 grams of distilled water were added to the mixture. Following mixing in a Sigma mixer, the resulting paste was then extruded by means of a Bonnot extruder employing 1/8 inch diameter copper die. The resulting extrudates were dried at 95 °C in an oven for about 3 hours and then calcined at a temperature of 815 °C for a period of 1 hour. The porosity agent was completely oxidized to gaseous products (CO₂, H₂O) during the calcining step.

EXAMPLE π

The particulate solid zinc ferrite sorbent as prepared in Example I was tested for its desulfurization ability as follows.

A 1-inch quartz reactor tube was loaded with 10 grams of the sorbent ground to -12 to 20 mesh of Example I. This solid zinc ferrite sorbent was placed in the middle of the reactor and subjected to reduction with hydrogen flowing at a rate of 300 cc/min with a bed temperature of 685 °F for a period of 2 hours.

Following reduction of the sorbent, cracked-gasoline having about 345 parts per million sulfur by weight sulfur-containing compounds based on the total weight of the gaseous cracked-gasoline, and having about 95 weight percent thiophenic compounds based on the weight of sulfur containing compounds in the gaseous cracked-gasoline was pumped upwardly through the reactor. The rate of flow of cracked-gasoline was 13.4 ml/hr. A flow of 300 cc/min of hydrogen was maintained during the treatment of the cracked gasoline with reduced zinc ferrite sorbent.

This produced sulfurized sorbent and desulfurized gaseous cracked-gasoline. A series of samples were collected at one hour intervals for a 5 hour period and subjected to analysis for sulfur content. The following results were obtained.

The above data indicates that a significant reduction in sulfur content is achieved when utilizing the reduced zinc ferrite sorbent system. EXAMPLE IU

Recycle of the sorbent system of Example II was carried out by first regenerating the spent sorbent for 2.5 hrs with a stream of a mixture of air and nitrogen containing four volume percent oxygen (flow rate: 300 cc/min) and a bed temperature of 896 °F. On termination of air to the reactor, the sorbent was purged with nitrogen and then hydrogen was introduced at a flow rate of 300 cc/min for a period of one hour at abed temperature of 700 °F.

Following reduction of the sorbent, cracked-gasoline was introduced into the reactor at a flow rate of 13.4 ml/hr with a hydrogen flow of 300 cc/min.

A series of samples were obtained at one hour intervals over a 4 hour period and analyzed for sulfur content.

The following results were obtained.

The above data demonstrate that the zinc ferrite sorbents of this invention are regenerable and are still effective in removing sulfur from cracked-gasoline even after regeneration.

The specific examples herein disclosed are to be considered as being primarily illustrative. Various changes beyond those described will no doubt occur to those skilled in the art; and such changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

Claims

C L A I M S

1. A sorbent composition suitable for removal of sulfur from cracked gasolines and diesel fuels which consists essentially of:

(a) zinc ferrite; and (b) a binder wherein said zinc ferrite is present in a substantially reduced valence state and in an amount which effects the removal of sulfur from a stream of cracked-gasoline or diesel fuel when contacted with same under desulfurization conditions.

2. A sorbent composition in accordance with claim 1 , wherein said zinc ferrite is present in an amount in the range of about 5 to about 90 weight percent.

3. A sorbent composition in accordance with claim 1, wherein said sorbent composition is a particulate in the form of one of granule, extrudate, tablet, sphere, pellet or microsphere.

4. A sorbent composition in accordance with claim 1 , wherein said binder is selected from the group consisting of alumina, silica, cements, high alumina cements, and clays.

5. A sorbent composition in accordance with claim 1, wherein said binder is selected from the group consisting of alumina and silica.

6. A sorbent composition in accordance with claim 1 , wherein said binder is present in an amount in the range of about 0.1 to about 30 weight percent and said zinc ferrite is present in an amount in the range of from about 5 to about 90 weight percent, based upon the total weight of the sorbent composition.

7. A sorbent composition in accordance with claim 1, wherein said binder is alumina.

8. A process of the production of a sorbent composition suitable for the removal of sulfur from a cracked-gasoline or diesel fuel stream which comprises:

(a) admixing zinc oxide, iron oxide and an inorganic binder so as to form a mix thereof;

(b) particulating the resulting mix so as to form particles thereof; (c) drying the particulate of step (b);

(d) calcining the dried particulate of step (c); and (e) reducing the resulting calcined particulate of step (d) with a suitable reducing agent under suitable conditions to produce a particulate sorbent composition having a reduced zinc ferrite content such that the reduced zinc ferrite will affect the removal of sulfur from a stream of cracked-gasoline or diesel fuel when contacted with same under desulfurization conditions.

9. A process in accordance with claim 8, wherein there is additionally present in the mix (a) a pore forming agent.

10. A process in accordance with claim 8, wherein said mix is in the form of one of a wet mix, dough, paste or slurry.

11. A process in accordance with claim 8, wherein said particles are in the form of one of granules, extrudates, tablets, spheres, pellets or microspheres.

12. A process in accordance with claim 8, wherein said zinc oxide is present in an amount in the range of from about 2 to about 70 weight percent and said iron oxide is present in an amount in the range of from about 3 to about 70 weight percent.

13. A process in accordance with claim 8, wherein said particulate is dried at a temperature in the range of from about 37.7°C to about 260°C (about 100°F to about 500 °F).

14. A process in accordance with claim 8, wherein said dried particulate is calcined at a temperature in the range of from about 315.5 ° C to about 1093 ° C (about

600 °F to about 2000 °F.

15. A process in accordance with claim 8, wherein said calcined particulate is reduced in a reducing zone with a reducing agent under suitable conditions to effect a reduction of the valence of the resulting zinc ferrite therein so as to provide an amount of reduced valence zinc ferrite such that the resulting sorbent composition will effect the removal of sulfur from a cracked-gasoline or diesel fuel when treated with same under desulfurization conditions.

16. A process in accordance with claim 15, wherein said reduced valence zinc ferrite is present in an amount in the range of from about 5 to about 90, based on the total weight of the sorbent composition.

17. A process in accordance with claim 8, wherein the reduction of zinc ferrite is carried out at a temperature in the range of from about 37.7 °C to about 815°C (about 100°F to about 1500°F) and at a pressure in the range of about 103.3 kPa to about 10.33 MPa (about 15 to about 1500 psia) for a time sufficient to permit the formation of the desired reduced valence zinc ferrite.

18. The sorbent product of the process of claim 8.

19. A process for the removal of sulfur from a stream of a cracked-gasoline or a diesel fuel which comprises:

(a) contacting said stream with a sorbent composition consisting essentially of zinc ferrite and an inorganic binder, wherein said zinc ferrite is present in a reduced valence state and in an amount which will effect the removal of sulfur from said stream in a desulfurization zone under conditions such that there is formed a desulfurized fluid stream of cracked-gasoline or diesel fuel and a sulfurized sorbent;

(b) separating the resulting desulfurized fluid stream from said sulfurized sorbent; (c) regenerating at least a portion of the separated sulfurized sorbent in a regeneration zone so as to remove at least a portion of the sulfur absorbed thereon;

(d) reducing the resulting desulfurized sorbent in an activation zone so as to provide a reduced zinc ferrite content therein which will affect the removal of sulfur from a stream of a cracked-gasoline or diesel fuel when contacted with same; and thereafter

(e) returning at least a portion of the resulting desulfurized, reduced sorbent to said desulfurization zone.

20. A process in accordance with claim 19, wherein said desulfurization is carried out at a temperature in the range of from 37.7 °C to about 537.7 °C (about 100°F to about 1000°F) and a pressure in the range of from about 103.35 kPa to about 10.33 MPa (about 15 to about 1500 psia) for a time sufficient to affect the removal of sulfur from said stream.

21. A process in accordance with claim 19, wherein said regeneration is carried out at a temperature in the range of 37.7°C to about 815.5°C (about 100°F to about 1500°F) and a pressure in the range of about 68.9 kPa to about 10.33 MPa (about 10 to about 1500 psia) for a time sufficient to effect the removal of at least a portion of sulfur from the sulfurized sorbent.

22. A process in accordance with claim 21, wherein there is employed an oxygen containing gas as a regeneration agent in said regeneration zone.

23. A process in accordance with claim 22, wherein said oxygen containing gas is air.

24. A process in accordance with claim 19, wherein said regenerated sorbent is subject to reduction with hydrogen in a hydrogenation zone which is maintained at a temperature in the range of 37.7°C to about 815.5°C (about 100°F to about 1500°F) and at a pressure in the range of about 103.3 kPa to about 10.33 MPa (about 15 to about 1500 psia) and for a period of time sufficient to affect the reduction of the valence of the zinc ferrite content of said sorbent.

25. The cracked-gasoline product of the process of claim 19.

26. The diesel fuel product of the process of claim 19 .