Producción de anhídrido

Design of Phthalic Anhydride Production Process
Student Contest Problem Competition 2009 - EURECHA
Acácio Mendes, acacio.mendes@ist.utl.pt Ana Rita Seita, anaritaseita@gmail.com Instituto Superior Técnico – Av. Rovisco Pais, 1049-001, Lisboa, Portugal

Abstract
This paper illustrates a way of producing phthalic anhydride (PA) in a continuous plant, with an annual production of 80,000 tonnesof PA (99.8 % wt purity), through the oxidation of o-xylene. Maleic anhydride is also obtained as a by-product of the process with 99.5% wt purity. The process was simulated using the process simulator software ASPEN Plus 2006.5 . A market demand forecast was made, as well as a capital and operating cost estimation. The payback time and profitability were calculated.
®

1. IntroductionPhthalic Anhydride (PA) is an organic product which can be obtained from substances as oxylene or naphthalene, through oxidation in presence of a catalyst, usually a vanadium/titanium oxide. PA is an important chemical intermediate. Its major outlets are phthalate plasticizers, unsaturated polyesters and alkyd resins for surface coatings while its smaller volume applications include polyester polyols,pigments, dyes, sweeteners and flame retardants. The major outlet for phthalic anhydride (PA), accounting for just over half of production, is in the manufacture of phthalate plasticizers, the main product being dioctyl phthalate (DOP) which is used as a plasticizer in polyvinyl chloride (PVC). Hence, the consumption of PA is mainly dependent on the growth of flexible PVC, which is sensitive togeneral economic conditions as it is consumed in the construction and automobile industries.
Others 10% Unsaturated Polyesters 18%

Plasticizers 57%

Alkyd Resins 15%
Figure 1 – Main applications of PA in industry
[1]

.

2. Market Demand Forecast
2.1. PA market
[2]

Global demand for PA was forecasted by consultants to have been around 3,600,000 tonnes/year in 2006 with worldwidegrowth rates expected to be around 3.0-3.5%/year over the next five years. This growth is led by the Asia-Pacific region where demand is forecast to

increase at 4.0-4.5%/year. Demand growth in the US and Western Europe is much lower at 1.01.5%/year. For example, demand in the US is only expected to grow at a relatively modest rate of 1.5%/year to 2009. CMR predicted that PA production would reach458,000 tonnes in 2009, whereas demand in Europe is growing at 2-3%/year, but this is mainly due to the rising consumption in central and east European markets, notably from the construction sector. Demand growth in northwest Europe is to remain low, but stable.

Crude oil

o-xylene

PA

Plasticizers

PVC

Applications

Figure 2 – Major product chain of phthalic anhydride in chemicalindustry.

2.2. Plasticizers

[3]

Plasticizers are organic esters added to polymers to facilitate processing and to increase the flexibility and toughness of the final product by internal modification of the polymer molecule. Flexible polyvinyl chloride (PVC) accounts for 80–90% of world plasticizer consumption. Flexible applications for PVC accounted for 35% of PVC consumption in 2005.From 2002 to 2005, world capacity for plasticizers grew at an average annual rate of 3.8%, a much higher rate than world consumption, which grew at an average annual rate of 2.0% during the same period. The following pie chart shows world consumption of plasticizers and the large percentage of consumption accounted for Other Asia, excluding Japan.

Figure 3 – World consumption of plasticizers in2006.

The United States, Europe and Asia including Japan are the largest markets for plasticizers, accounting for nearly 89% of world demand in 2005. Demand for plasticizers in the United States and Western Europe is expected to grow moderately at an average annual rate of 1.0– 1.5% until 2010. Increasing imports of finished vinyl products, mainly from Asia (primarily China), softening demand...