Propylene shortage

Technologies for the reverse process to produce propylene from ethylene and 2-butenes were also developed.138 139 The Arco process139 dimerizes ethylene to 2-butenes, which, in turn, are metathesized with ethylene to yield propylene. The process is not practiced at present, but it is a potential technology in case of a propylene shortage. 

Attention to the propylene shortage had crystallized with the publication of a major study by Stobaugh (56) in 1967, in which he analyzed thoroughly the sources and markets for propylene. He suggested that by 1970 over-all propylene production from both refining and chemical sources would probably not exceed 19 billion lbs, and chemical demand would have increased to 7.5 billion lbs at a value of 2.5 cents/lb. Stobaugh lists both U.S. propylene producers and their plant capacities as well as propylene consumers. 

At present there is no question that the propylene shortage is a reality, and there is need to assess the potential as well as the actual sources of propylene. In this respect, the price that propylene should seek will provide a frame of reference. Consider that the gasoline value of propylene equals approximately 2.8 cents/lb (12.5 cents/gal -s- 4.35 lb/gal) and that propylene recovery costs should not exceed 0.2 cents/lb. The total—3.0 cents/lb—is a break-even area for a refiner. He will be sorely tempted to release propylene above this price and satisfy gasoline commitments by other means. The exact price, of course, will vary for each refinery and will be a function not only of its raw materials vs. sales picture but also of its accounting techniques. The 3.0 cents/lb figure could vary by as much as 0.5 cents/lb, and will depend on surplus of refining capacity (pool octane), isobutane, refining processes in place, etc. 

Acrylonitrile (ACN) is extensively used for the production of acrylic fibers, rubbers, plastics, and adiponitrile. Today, ACN is produced by a process involving the reaction of propylene, aimnonia, and oxygen over complex mixed-metal molybdates. There is currently a great deal of interest in developing catalytic systems for the direct aimnoxidation of propane, due to the abundance and lower cost of propane relative to propylene, the increasing demand for ACN, and the risk of a propylene shortage due to increasing demand from the petrochemical industry. 

During World War II a shortage of natural rubber in the United States prompted an intensive program to produce synthetic rubber. Most synthetic rubbers (called elastomers) are made from petroleum products such as ethylene, propylene, and butadiene. For example, chloroprene molecules polymerize readily to form polychloroprene, commonly known as neoprene, which has properties that are comparable or even superior to those of natural rubber ... 

Propylene demand will grow to the 11-billion lb level by 1973. Propylene from either heavier ethylene feed stocks or European imports will not alleviate the shortage completely. On the other handy it is not expected that price will exceed 3.1 cents/lb. In spite of decreasing propylene availability, refiners will consider release of alkylate stocks at this level. Development of an economic process for direct propylene production is in the future. Dehydrogenation or iodinative partial oxidation processes for propylene from propane are neither commercially proved nor have they been demonstrated to have economic promise. Dehydrogenation in the presence of sulfur may bypass propane dehydrogenation equilibrium limits, and preliminary experimental data are presented. 

There are two main sources of propylene production— refinery and chemical. The former is derived from catalytic cracking and is used mainly for refinery purposes—i.e., polymer gasoline and alkylate. The latter is derived from ethylene plants and is marketed mainly for petrochemical usage. In both cases, the propylene is a by-product and not a directly manufactured product. In 1963 Davis (19) described propylene as the bargain olefin at 2.25 cents/lb and predicted no shortage in sight. He pointed out that 1962 total domestic refinery derived propylene capacity was 17.1 billion lbs annually, and chemically derived propylene was 3.4 billion lbs annually. All of the propylene cannot be recovered economically. Davis estimated that available propylene amounted to 17 billion lbs, of which chemical uses constituted... 

Ockerbloom and Mitchell (II, 43) pointed out that the shortage predicted by 1970 could be aggravated by factors such as growth of propylene chemical demand even beyond forecast levels and by legislation against lead alkyls. 

When one contemplates the shortage of propylene and the availability of propane, it is natural to postulate whether catalytic dehydrogenation of propane rather than pyrolysis of propane would be an inherently economic process. Unwanted side reactions are minimized in catalytic processes, and the reaction ... 

Polydiene rubber is a common low voltage electrical insulation material, used because of its low electrical conductivity and elasticity. But, it can degrade rapidly by peroxidation, even if there are antioxidant stabilisers in the system, which can lead to electrical shortages and fires. Polydiene rubbers are recently being replaced by saturated ethylene-propylene (EP) rubbers or plasticised PVC. 

Coal can liberate the U. S. from the plastics shortage as well as the energy crisis. It is abundant, and we have the technology to convert it to precursors for plastics at costs that are suddenly cheap compared to the price tags on chemicals from Imported petroleum. Ethylene, propylene, benzene, toluene, xylene, phenol and other raw materials for polymers and plastics can become plentiful again but we must speed up R D as well as plant construction. 

Cardiovascular Six patients developing phlebitis and two patients thrombophlebitis after administration of etomidate formulated in propylene glycol, during a period of propofol shortage [22 ]. 

The outlook for further increase of the oxo capacities is bright, although many people foresee a shortage of propylene which is the key product among the starting materials [886-890, 1033, 1038-1040]. In Western Europe the oxo-producers have already become the biggest propylene consumers [890]. 

Physical, chemical and biochemical conversion of plant-based oligo- and polymers into industrial bulk products as well as into specialties is a well established technology, which favourably extends the product spectrum obtained through petrochemical synthesis. Volumewise, less than SO million tons p.a. of chemical intermediates and end-products are derived from renewable plant-based raw materials and constitute less than 15% of about 400 million tons provided by petrochemistry. This imbalance is not so much a result of a relative shortage or lack of availability of renewables compared to petrochemical feedstocks, rather, it reflects the versatility of ethylene, propylene and olefin based chemical synthesis in meeting the product and product range requirements of an industrialized world. 

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