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J.S. Plotkin / Catalysis Today 106 (2005) 10–14 11

Fig. 1. Global propylene demand pattern, 1970–2004.

refinery grade propylene to either chemical grade or polymer

ethylene’s growth rate. For instance, in the U.S., the P/E grade propylene. Fig. 5 shows the breakdown of propylene

demand ratio has increased from 0.43 in 1992 to 0.54 in sources on a regional basis. In all regions, refineries are an

2004. The same phenomenon is seen in West Europe and important source of propylene, but especially so in the U.S.

Asia Pacific, but to an even greater degree. In Asia Pacific, as steam cracking feeds in the U.S. are relatively light and

the P/E demand ratio is a very high 0.77. The Middle East is produce lesser amounts of propylene than those regions

still heavily ethylene-centric due to the availability of very using liquid feedstocks. Fortunately, the large installed FCC

low cost ethane with the P/E ratio staying relatively flat since capacity base in the U.S. allows the propylene supply gap to

1996. be bridged relatively easily. But it should also be noted that

As propylene growth rate continues to outpace ethylene other sources of propylene have also become necessary.

growth rate, this will continue to put stress on traditional These are the so-called ‘‘on purpose propylene’’ technol-

propylene sources, in particular steam crackers. Historically,

propylene has been considered a by-product of ethylene

production. The amount of propylene coming out of a steam

cracker is a function of the cracking feedstock used. For

example, if ethane is the feedstock, only 0.019 t of propylene

are produced for every ton of ethylene made. As feedstocks

get heavier, propylene output increases as shown in Fig. 4.

Thus, the amount of propylene able to be produced in steam

crackers is fixed (with some limited amount of flexibility

based on operating severity and the ability to change feeds

from gas to liquids that some crackers have).

To make-up this shortfall, refineries are able to capture

propylene from fluid catalytic crackers (FCC) and purify Fig. 3. Regional propylene/ethylene demand ratio growth, 1992–2004.

Fig. 2. Regional polypropylene demand. Fig. 4. Ton of propylene per ton of ethylene for various cracker feeds.

12 J.S. Plotkin / Catalysis Today 106 (2005) 10–14

bonds of olefins are broken in the reaction, and different

olefins are formed using parts of the reactants. The species

present, stoichiometry of each species, catalysts emplo-

yed and operating temperature will determine which

reaction predominates, and therefore, which products will

form.

In order to make propylene, this technology combines

ethylene and butylenes from the naphtha crackers C stream.

4

This process also has the option of dimerizing ethylene into

2-butene or using n-butenes from C fractions, followed by

4

Fig. 5. Regional propylene supply sources, 2004. the metathesis reaction between ethylene and 2-butene to

yield propylene.

ogies and include propane dehydrogenation, olefin metath-

esis and other emerging processes.

What does the future look like with regards to propylene

supply? Fig. 6 gives Nexant ChemSystems’ forecast of

incremental ethylene and propylene demand from 2004 to

2012 by region on a relative basis. The incremental P/E

demand ratios are also shown for each region. In the North

American, West European and Asia Pacific regions, the P/E ABB Lummus Global purchased Phillips’ Olefins

demand ratio is expected to continue to increase over the Conversion Technology (OCT, also known as Triolefins)

current high levels. This will put further stress on in 1997. BASF and Fina are operating a plant using this

conventional propylene sources and spur further develop- technology as an addition to their joint venture liquids steam

ment and commercialization plans for propylene-boosting cracker at Port Arthur, TX. With the addition of the OCT, the

technologies for petrochemical plants, refineries and stand- nameplate capacity of the cracker is 1.8 billion pounds

alone units. This paper will focus on those technologies (816,000 metric tons) per year ethylene and 1.95 billion

geared for increasing propylene yields from steam crackers pounds (885,000 metric tons) per year propylene. OCT has

and FCC units. also been implanted at Mitsui Chemicals olefins plant in

Osaka, Japan. Lummus has announced several other OCT

contract awards. Axens is also licensing metathesis

3. On-purpose propylene technologies technology. The IFP-CPC Meta-4 process was jointly

developed by Institut Français du Pétrole (IFP) and Chinese

The impending propylene supply/demand gap has Petroleum Corporation (CPC) of Taiwan. A demonstration

stimulated technology developers to improve or tweak pilot plant using this metathesis technology was operated

conventional technologies to increase the amount of from April 1988 to September 1990.

propylene from them or develop whole new ways to make Lummus has also developed ways olefin metathesis

propylene ‘‘on-purpose’’. technology can be incorporated within an FCC facility to

boost propylene output.

3.1. Olefin metathesis 3.2. C /C olefin interconversion

Olefin metathesis or disproportionation, provides an 4 5

opportunity to achieve olefin interchangeability. The double Propylene via selective C /C cracking technology is

4 5

generating interest due to the possibility/potential of

producing more propylene. Selective C /C cracking

4 5

technology is similar to metathesis in that low value

hydrocarbon streams are converted to higher value olefins.

However, the differences between the technologies are

many. With selective C /C cracking technologies, C

4 5 5

streams can be converted along with the C stream,

4

including isobutene. Normal butenes do not have to be

isomerized. In addition, ethylene is not consumed in the

process; in fact, additional ethylene is produced along with

the main propylene product.

This type of process has been described by several

Fig. 6. Regional P/E ratios of incremental ethylene and propylene demand, companies in recent years. Mobil Technology has developed

2004–2012.


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DESCRIZIONE DISPENSA

Materiale didattico per il corso di Chimica Industriale II del Prof. Pietro Moggi. Trattasi di un articolo di Jeffrey S. Plotkin dal titolo "The changing dynamics of olefin supply/demand", all'interno del quale è analizzata la situazione dell'industria petrolchimica europea in relazione all'esplosione della domanda di propilene rispetto a quella dell'etilene.


DETTAGLI
Corso di laurea: Corso di laurea in chimica industriale e tecnologie del packaging
SSD:
Università: Parma - Unipr
A.A.: 2007-2008

I contenuti di questa pagina costituiscono rielaborazioni personali del Publisher Atreyu di informazioni apprese con la frequenza delle lezioni di Chimica industriale II e studio autonomo di eventuali libri di riferimento in preparazione dell'esame finale o della tesi. Non devono intendersi come materiale ufficiale dell'università Parma - Unipr o del prof Moggi Pietro.

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