New Olefin Production Technologies in SINOPEC

8/11/2019 New Olefin Production Technologies in SINOPEC

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19th World Petroleum Congress, Spain 2008Forum 12: Progress in olefin production

World Petroleum Council

New olefin production technologies in SINOPECSRIPT

Mr Jiawei Teng, SINOPEC, China

Mr Rongwei Wang, SINOPEC, ChinaMr Zaiku Xie, SINOPEC, ChinaMr Yongsheng Gan, SINOPEC, China

AbstractIt is widely recognized that naphtha steam crackers and fluid catalytic cracking (FCC) unitsare the main current sources of ethylene and propylene. On the condition of high crude oilprice, olefin producers are striving to develop new economical routes to produce ethylene andpropylene with low-cost feed stocks.

As is the case today, the new olefin production is projected to come from a number of

sources, which are methanol based, biological materials based or olefinic streams based.

SINOPEC SRIPT has developed a number of new olefin production technologies, thesealternatives can be categorized into the following three groups:
Natural Gas or Methanol to Olefins (MTO and MTP)Biological Ethanol to Olefins (ETO)Olefin Conversion (Olefin Cracking and Metathesis)

Each of these alternatives can be the competitive route to ethylene and propylene in certainsituations. This paper provides an update from SINOPEC SRIPT on the latest development inthese technologies as well as a comparison of these alternatives. SINOPEC has thetechnologies and experience to help you determine which routes to ethylene and propylene fityour opportunities.

9th WPC preprint paper. For delegate use only. Do not circulate.


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INTRODUCTION

Ethylene and propylene are the most important basic organic products. Almost all theethylene is supplied from thermal steam cracking of hydrocarbon feedstocks (primarilynaphtha and ethane). And the supply of propylene is more diversified than that of ethylene, as

shown in Figure 1. The naphtha steam cracking process is the main propylene source withabout 65% share in the primary production. Propylene could also be generated in FCC units,increased production of light olefins directly from the FCC unit has been achieved throughchanges in operations, base faujasite cracking catalyst and additive catalysts, and inhardware design.On the condition of high oil price, what is the best way to produce ethylene and propylene?Olefin manufacturers are seeking cost effective options to increase the ethylene andpropylene production. There are more options available today than ever before for theproduction of olefins, especially for the production of propylene. Each of these routes canoffer competitive economics in certain situations. Most importantly for a particular olefinmanufacturer is to understand how to select the right routes.

NEW OLEF

PRODUCTION TECHNOLOGIES DEVELOPED BY SINOPEC SRIPT

SINOPEC SRIPT has developed a number of new olefin production technologies, thesealternatives can be categorized into the following three groups:Natural Gas or Methanol to Olefins (MTO and MTP)Biological Ethanol to Olefins (ETO)Olefin Conversion (Olefin Catalytic Cracking and Metathesis)There are two types of methanol-to olefins (MTO) processes available. The first is the S-MTO,

which converts methanol to ethylene and propylene at 80% carbon selectivity in a fluidizedbed reactor. The second is a methanol-to-propylene (MTP) process, which producespropylene.

METHANOL TO OLEFINS (MTO)

S-MTO Process (Figure 2) was developed by SINOPEC for selective production of ethyleneand propylene from methanol. The catalyst used in the process is based on asilicoaluminophosphate, SAPO-34, which has very high carbon selectivity to lower olefins. Anindustrial demonstration plant, which scale capacity is 100 tons methanol per day, was builtand stared up in 2007 in China. The experimental results show that S-MTO Process convertsmethanol to ethylene and propylene at above 80% carbon selectivity in a fluid bed reactorwith continuous regeneration. The carbon selectivity approaches 90% if butenes are alsoaccounted for as part of the product. Other co-products include very small amounts of C1-C4paraffins, hydrogen, CO and CO2, as well as ppm levels of heavier oxygenates.

Figure 1 Propylene Supply in 2005 (Source: CMAI 2006)



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Coke accumulates on the catalyst and must be removed to maintained catalyst activity. Thecatalyst activity is maintained by continuous transfer of coked catalyst from the reactionsection to the regeneration section where the coke is burned with air.Example results of tests performed in the fluid bed reactor with continuous regenerationshowed that variations in propylene-ethylene ratios are possible depending on catalystcomposition and operating conditions. Typically, the ratio of propylene- ethylene can range

from 0.6 to 1.3. When combined with the SINOPEC Olefin Catalytic Cracking process (to bediscussed later) to convert the heavier olefins, the overall yield of ethylene and propyleneincrease to over 85% and propylene- ethylene ratios of more than 1.5 are achievable.

METHANOL TO PROPYLENE (MTP)

Methanol to Propylene (MTP) process was developed for selective production of propylenefrom methanol. The catalyst used in the process is based on a proprietary SINOPEC ZSM-5catalyst, which has very high carbon selectivity to propylene. Typical results show that MTPprocess converts methanol to propylene at 40-50% carbon selectivity in a fixed-bed reactorfor single pass. The carbon selectivity approaches 65-70% if co-product hydrocarbons arerecycled. Other co-products include gasoline and very small amounts of C1-C4paraffins.After a cycle approximately 600-800 hours of operation, the catalyst has to be regenerated byburning coke with a nitrogen/air mixture. Catalyst regeneration is done in-situ. Nitrogen andamount of air are mixed and introduced into the reactor to burn the coke deposits on thecatalyst. The regeneration is carried out at temperatures similar to the reaction itself, hencethe catalyst particles do not experience any temperature stress during the in-situ catalystregeneration procedure.

BIOLOGICAL ETHANOL TO OLEFINS (ETO)

SINOPEC ETO (S-ETO) process (Fig.3) was developed for selective production of ethylenefrom biological ethanol. A number of catalysts are effective in promoting the reaction;activated alumina and silica-alumina, are the most efficient catalysts in the reaction. Theactivated alumina catalyst developed by SRIPT SINOPEC has very high carbon selectivity toethylene. Typical results show that ETO process converts ethanol to ethylene at 97% carbonselectivity in a fixed-bed reactor, and the conversion of ethanol is over 99% for single pass.Other co-products include very small amounts of C4 hydrocarbon, propylene and ethane.Moreover, Coking tendency is suppressed efficiently, so no continuous catalyst regenerationis required, and the catalyst cycle time is over one year.

The dehydration of ethanol to ethylene is a strong endothermic reaction, the temperaturecontrol is important, since low temperature result in the presence of ether in the reactor

Figure 2 SINOPEC S-MTO Process



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product and high temperature produce aldehydes. Temperatures in the range of 340-390 are suitable for the activated alumina catalystCompared with the other olefins production routes, the catalytic dehydration of ethanol toolefins is a simple process, and S-ETO process gives very high carbon selectivity to ethylene,only very small amounts of co-products was produced, so it does not require the sale orutilization of co-products.

OLEFIN CATALYTIC CRACKING (OCC)

SINOPEC SRIPT has developed a process that allows high selective production of propyleneand ethylene by conversion of low value by-product streams containing C4/C5olefins fromcrackers and refineries. Figure 4 depicts the reaction scheme of OCC. Low value olefins fromsteam crackers or and refineries were catalytic cracked into propylene and ethylene on ashape selective ZSM-5 type zeolite catalyst at the temperature of 500-600.

A simplified process flow diagram of OCC unit is shown in Figure 5. The liquid feedstockcontaining olefins is vaporized and further heatedagainst the reactor effluent and in a fired heaterbefore entering the fixed-bed reactor. The effluentfrom the reactor is cooled and compressed to do

further separation. Most of C4fraction is recycled to the OCC reactor to increase the totalpropylene and ethylene yield. Part of the C4fraction is purged to avoid the accumulation ofparaffins in the system. The C5

+fraction is cut to further process as pyrolysis gasoline.

Separation facilities depend on how the unit is integrated into the processing system.

Cracker C4/C

5

FCC C4/C

5

FCC Gasoline

Ethylene

Propylene

Ethanol WasteWater

WasteAlkaline

HeavyEnds

EthyleneProduct

LightEnds

WaterScrubber

AlkalineWash

EthyleneColumn Stripper

Purge

Reactor

Fired Heater

Olefin feed C4 Recycle

C5+

Depropanizer Debutinizer

Light olefins

Figure 5 Process Flow Diagram of OCC Unit

Figure 3 Biological Ethanol to Olefins Process

Figure 4 Reaction Scheme of OCC



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The OCC (Olefins Catalytic Cracking) process features fixed-bed adiabatic reactors operatingat temperatures 500-600and pressures 0.1-0.2MPa. The main characteristic of OCC is that noinert diluent is added into the system, at the same time, the catalyst can be operated at veryhigh space velocities. Accordingly, the reactor size and operating costs are minimizednotably.The OCC process utilizes a proprietary ZSM-5 zeolite catalyst developed by SRIPT

SINOPEC. In the optimized process conditions, typically 28-30wt% propylene and 8-10wt%ethylene are obtained in pilot plant for per pass. If the produced butylenes are recycled,propylene yield can be increased to 45wt. % and ethylene yield can be increased to 12wt. %.Other co-products include gasoline and very small amounts of C1-C4paraffins.A swing reactor system is used for catalyst regeneration, catalyst regeneration is done in-situ.Nitrogen and small amount of air are mixed and introduced into the reactor to burn the cokedeposits on the catalyst.The catalyst exhibits little sensitivity to common impurities such as diolefins, sulphurcompounds and nitrogen compounds.

OLEFIN METATHESIS TECHNOLOGY (OMT)

The Olefin Metathesis Technology (OMT) from SINOPEC is used to combine n-butenes withethylene to produce polymer-grade propylene. Two chemical reactions take place: propyleneis formed by the metathesis of ethylene and butene-2; and butene-1 is isomerized to butene-2as butene-2 is consumed in the metathesis reaction. OMT greatly enhances an excellent co-product flexibility of cracker. When integrated with a grassroots steam cracker, the ratio ofpropylene to ethylene can increase from the typical 0.5 to greater than 1.0. As propylenedemand continues to grow, the impact of OMT (Figure 6) in existing or grassroots ethyleneand/or refinery applications becomes evident.The catalyst (WO3/SiO2and MgO) promotes the reaction of ethylene and butene-2 to formpropylene, and simultaneously isomerizes butene-1 to butene-2. The per-pass conversion ofbutene is greater than 70%, with overall selectivity to propylene exceeding 95%. The productfrom the metathesis reactor is primarily propylene and unreacted feed, the co-product includevery small amount of C5and C6olefins.A small amount of coke is formed on the catalyst, so the beds are periodically regeneratedusing nitrogen diluted air. Typically, the catalyst cycle time approaches 900 hours.

PurgeReactor

C4 feed C4 Recycle

EthyleneColum

Ethylene Recycle Ethylene

PropyleneColum

Propylene

Purge

Guard Bed

Figure 6 OMT Process Flow Diagram



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COMPARISONS OF NEW OLEFIN PRODUCTION ROUTES

Several factors must be considered when selecting a new olefin production routes. Processeconomics are always an important factor, but on the condition of high oil price, each of theabovementioned alternatives can be the competitive route to ethylene and propylene incertain situations. Most importantly for a particular olefin manufacturer is to understand how to

select the right routes. The key factors to consider include:Feedstock availability and costOlefins yield and co-product distributionApplicationsThe key factors are compared between each of the alternative routes to olefins below.

FEEDSTOCKS

In the process of producing light olefins, the most significant component of the costs ofproduction is the cost of raw materials. The ability to effectively utilize a secure source of low-cost feedstock is the most important factor in competitiveness, especially on the condition ofhigh crude oil price. Identifying the feedstocks that are available can greatly help narrow thechoice of the various routes.One of main character of new olefin production technologies in SINOPEC SRIPT is thediversity of raw materials. The feedstock for the abovementioned routes to producing ethyleneand propylene can be categorized into the following three groups:

Coal or natural gas based methanol (MTO, MTP)Biology based ethanol (ETO)C4 olefins from ethylene plant and/or refinery (OCC, OMT)

The proven reserve life time for coal is about 230 years, and the proven natural gas reservesto production ratio, i.e. lifetime is about 100 years for Africa and 260 years for the MiddleEast. Compared with the reserve lifetime of 41years for petroleum, there is no doubt that coaland natural gas will be a key fuel component in the 21

thcentury. In recent years, the Mega-

Methanol process for plants with a production of 5000 tons of methanol per day has madegreat progress, methanol will be available at a constant low price in the foreseeable future. Insome areas of the world have abundant supplies of coal or natural gas but have very limitedlocal demand for its use, in those locations, the local price of coal or natural gas is very low.This offers opportunities to access low-cost coal or natural gas for other applications such asethylene and propylene production via methanol combined with methanol to olefins (MTO,MTP).The feedstocks for ETO derive from local agricultural sources and thus avoid balance ofpayment. Compared with the unrenewable fossil raw material, the feedstocks for biologicalethanol include corn, sugarcane, sugar beet, plant stalk etc. are renewable.The OCC process can operate with different feedstocks, especially those feeds that areavailable from steam crackers and refineries, the favourable feedstocks are as follows:

FCC or Coker C4OlefinsFCC C5OlefinsFCC gasolineSteam cracking C4Olefins (Butadiene extraction or Selective hydrogenation)C4Olefins from MTBE synthesis (FCC or Steam Cracker)The mixture of the above hydrocarbons

In a word, the feedstock of OCC process is very flexible. There are several constrains for thefeedstock of OCC process with respect to purity and composition. Feedstocks containing highor low concentrations of olefins can be processed. Naturally, feedstocks with higher olefinscontent are more favourable. Paraffins, cycloalkanes, cycloalkenes and aromatics maybepresent in the feedstocks, these compounds are considered as non-convertibles. However,

the feedstock should be controlled to less than 1.0wt% of diolefins, these components arecontributed to coke formation.



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recycle to the furnaces to further enhance the light olefin yields, this allows stream cracker toreduce the amount of naphtha feed and maintain the light olefin capacity at the same time.The C5

+gasoline can be further processed as pyrolysis gasoline to increase the production of

BTX.OMTThe Olefin Metathesis Technology (OMT) is a true on-purpose propylene producer and it

offers very high selectivity to propylene, the overall selectivity to propylene exceeds 95%. Theco-products include very small amount of C5 and C6olefins.

APPLICATIONS

The abovementioned routes to light olefins offer a wide variety of opportunities to produceethylene and propylene. Each of these alternatives can be the best route to light olefins incertain situations. Most importantly for a particular olefin manufacturer is to understand how toselect the right routes.MTO/MTPMTO and MTP are driven by the desire to utilize natural gas or coal and the market demandsfor ethylene and propylene. Natural gas or coal prices are generally independent of crude oil

and naphtha market prices, so MTO and MTP provides another means for olefin producers todiversity the cost structure for their feedstocks. MTO and MTP can provide much lower costsof production and higher returns on investment than oil based routes on the condition of highcrude oil price.MTO and MTP process may benefit from economies of integration with mega-methanolproduction processes. First, the amount of methanol required for an MTO or MTP project isconsistent with the methanol production from the latest mega-methanol plant (5000 t/dmethanol or more). Second, the use of crude methanol directly from the methanol convertermay eliminate the need for the usual fractionation requirements for producing chemical gradeor fuel grade methanol. Typical commercial methanol specifications limiting DME co-productproduction may become less of a factor in methanol converter design and operatingconditions, which may lead to further methanol production economies.Perhaps the optimum integration option would be the location of an entire mega-

methanol/MTO or MTP/PE or PP production complex in the vicinity of a natural gas or coalproduction location. This may be particularly advantageous for extremely remote locationswhere transportation conditions may limit the desirability of any products other than the solidpolyethylene or polypropylene products.ETOThe Ethanol to Olefin (ETO) is a true on-purpose ethylene alternative which is based on localagricultural sources. As compared with hydrocarbon pyrolysis, it is a simple process, it canutilize a local produced feedstock derived from agricultural sources and thus avoid balance-of-payment problems, it is suitable for small-scale installation, and it does not require the saleor utilization of co-products. ETO is of interest in some locations, where there are abundantagricultural sources and government incentives are provided to reduce dependence onimported hydrocarbons.OCCThe OCC process was developed to utilize low value by-product streams containing olefinsfrom steam crackers and refineries.Steam Cracker IntegrationThere are several possible integration schemes for an OCC unit into a steam cracker. Thesimplest option is that product separation is done completely at the ethylene plant. Theintegration scheme is shown in Figure 8.



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C4stream from butadiene extraction or Selective hydrogenation or MTBE synthesis units arefed into the OCC unit. The effluent from the reaction section is processed by the separation ofthe ethylene plant. To avoid the accumulation of paraffins in the system, part of the C4fractionis purged in the option. This integration maybe the most economic solution for a new-buildingplant, where additional capacity required separating the effluent from OCC unit can be

reserved in the ethylene plant. Therefore, no independent separation system for OCC unit isneeded to build.Another option features integrating OCC unit with its own separation system. Only C3

-or C2

-

fraction is processed by the separation system of ethylene plant. The option is favourable foran existing ethylene plant, where the additional capacity is limited.Refinery IntegrationThe refinery integration scheme is shown in Figure 9. The OCC converts C4fraction orcracking gasoline to desirable light olefins, mostly propylene and ethylene. The volume ofolefins in the gasoline stream is lowered from 45% to 15%, at the same time, the octanenumber is improved at least retained due to a mount of aromatics formed.

Figure 8 Steam Cracker Integration



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OMTOMT is generally economical when propylene is valuedhigher than or equal to ethylene, though approximately 0.33tons of ethylene are consumed per ton of propylene

produced, 0.67 tons of low-valued C4olefins are converted to high-valued propylene per tonof propylene produced. OMT unit can be integrated with a steam cracker or a refinery.OMT combined with a steam cracker can significantly vary the propylene-to-ethylene productration and improve overall plant flexibility and economics. Typical steam crackers with liquidfeedstocks operate with a propylene-to-ethylene ratio range of 0.45-0.65, depending oncracking severity. If butadiene in not required as a product, it can be selectively hydrogenatedto butenes to provide additional butylenes feed for metathesis. The steam cracker/OMTcombination can result in propylene-to-ethylene ratios exceeding 1.0 as determined by thequantity of butylenes available.

FCC unit profitability is significantly enhanced by operating at higher propylene productionrates. A low cost, reliable ethylene recover system is needed, and then ethylene recoverfollowed by butylenes/ethylene metathesis to propylene can improve overall FCC planteconomics.

SUMMARY

On condition of high crude oil price, the new olefin production technologies, which aremethanol based, biological materials based or olefin streams based, offer a wide variety ofopportunities for olefins producer to produce ethylene and propylene. Each of these routescan offer competitive economics in certain situations. Most importantly for a particular olefinmanufacturer is to understand how to select the right routes. SINOPEC has the technologies

and experience to help you determine which routes to ethylene and propylene fit youropportunities.

Figure 9 Refinery Integration

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New Olefin Production Technologies in SINOPEC