Propylene glycol production operation

Propylene glycol production Maximization of economic benefit and minimization of environmental indicator. In addition process robustness measures (deviation ratio) were also considered. Normal boundary intersection method Sustainable process index was used as environmental indicator. Product revenue less capital and operating costs was the economic indicator Kheawhom and Hirao (2002)... 

Two options are being developed at the moment. The first is to produce 1,2-propanediol (propylene glycol) from glycerol. 1,2-Propanediol has a number of industrial uses, including as a less toxic alternative to ethylene glycol in anti-freeze. Conventionally, 1,2-propanediol is made from a petrochemical feedstock, propylene oxide. The new process uses a combination of a copper-chromite catalyst and reactive distillation. The catalyst operates at a lower temperature and pressure than alternative systems 220°C compared to 260°C and 10 bar compared to 150 bar. The process also produces fewer by-products, and should be cheaper than petrochemical routes at current prices for natural glycerol. The first commercial plant is under construction and the process is being actively licensed to other companies. 

We now consider what can happen to a CSTR operating at an upper steady state when an upset occurs in either the ambient temperature, the entering femperature, the flow rate, reactor temperature, or some other variable. To illustrate, let s reconsider the production of propylene glycol in a CSTR. 

Slovakia. The Slovakian petrochemical industry is dominated by Slovnaft, which operates two petrochemical sites. The complex at Bratislava has a naphtha cracker, three LDPE units, two propylene plants, and an aromatics unit. Most of the ethylene produced goes to LDPE and ethylene oxide/ ethylene glycol production. Some ethylene goes to vinyl chloride monomer... 

The stream from the reaction section is first distilled to remove unconverted propylene, whose recycle, added to the make-up, represents the feed of the first epoxidation stage. Excess propane is also removed by distillation (—50 to 60 trays) to prevent its buildup in tfie synthesis loop. The heavy end of the first column is sent to the purification train for products for which the temperatures cannot exceed 100°C to avoid undesirable degradation. On account of the boiling points at standard pressure of the components present, this makes operation under vacuum necessary. Crude propylene oxide is collected at the top of the first distillation column (50 trays), and r-butyl alcohol at the1bottom, with some hydroperoxide, the catalyst, propylene glycol, aldehydes, esters etc. This stream is sent to a r-butyl alcohol separation column (35 to 40 trays), where the alcohol is recovered at the top. 

Which operation do you recommend, constant volume or constant mass Took at the conversion of propylene oxide and production rate of propylene glycol for the two cases. What are you wasting in constant mass... 

According to components bubble point (table 2), the distillation involves the separation of the methanol and the resultant reactants (for the most part water) from the reaction mixture. Propylene glycol and by-products are then recovered from the boiler. The overhead batch distillation column consists of a packed column of 50 cm in length and 10 cm in diameter. A condenser equipped with a complex controlled reflux device completes this process. A heat transfer fluid supply reactor jacket with a temperature varying from 10 to 170°C according to the operating steps. 

In this part of the study, optimisation of the production is carried out according to a global approach. The reaction step and the successive distillation step are considered simultaneously in the evaluation of the optimal operating conditions. In order to compare these results with the classical approach ones an operating time criterion has been chosen. Thus, the optimisation problem lies in the minimisation of the operating time required for the propylene glycol synthesis. According to the previous optimisations, two kinds of production have been studied a production with yield and purity constraints and a production with an additional by-products constraint. In order to compare the different approaches, the same constraints have been adopted. 

Prior to this time, other ventures had already been operating to produce commercial quantities of aliphatic chemicals from petroleum sources. Truly commercial production of ethylene glycol had been achieved by 1925 (10) using natural gas fractions as a starting material, and even earlier (about 1920) there had been the manufacture of isopropyl alcohol from cracking plant propylene (20), which may be termed the pioneer operation on a successful, continuing basis in the sphere of aliphatic synthesis from petroleum. 

---