Increasing Propylene Production

CATALYTIC CRACKING PROCESSES AND CATALYSTS FOR INCREASING PROPYLENE PRODUCTION... 

The production of propylene from the oxydehydrogenation of propane is an exothermic process and thermodynamically limited. For this reason, a large number of catal tic systems have been studied for increasing propylene production. The majority of the catalysts investigated in the literature are based on vanadium compounds. They show propylene yield between 5% on vanadium-magnesium-oxide [1] and almost 30% on V-silicalite [2]. 

It has been clearly demonstrated that increasing propylene production, even at the expense of gasoline yield, is a commercial proposition in an integrated refining-petrochemical complex. 

Dehydrogenation of propane (DHP) is becoming an important process for increasing propylene productivity. In this review, the DHP over Pt-based catalysts is surveyed from the kinetic point of view. After a short introduction of propane dehydrogenation process in Section 1, the DFT calculation results of the main and side reactions of the DHP over different Pt crystal planes as well as on Pt-Sn alloys are summarized in Section 2 to provide a fundamental understanding of the reaction mechanism of... 

A typical process scheme for the direct hydration of propylene is shown ia Figure 2. Turnkey plants based on this technology are available (71,81). The principal difference between the direct and iadirect processes is the much higher pressures needed to react propylene direcdy with water. Products and by-products are also similar, and refining systems are essentially the same. Under some conditions, the high pressures of the direct process can increase the production of propylene polymers. 

Significant products from a typical steam cracker are ethylene, propylene, butadiene, and pyrolysis gasoline. Typical wt % yields for butylenes from a steam cracker for different feedstocks are ethane, 0.3 propane, 1.2 50% ethane/50% propane mixture, 0.8 butane, 2.8 hill-range naphtha, 7.3 light gas oil, 4.3. A typical steam cracking plant cracks a mixture of feedstocks that results in butylenes yields of about 1% to 4%. These yields can be increased by almost 50% if cracking severity is lowered to maximize propylene production instead of ethylene. 

Manufacturing (NAICS 326), Rubber Products (NAICS 3262) totals 35.3 billion, of which Tires (NAICS 32621) makes up 15.4 billion, showing the dominance of the automobile tire market in this sector of the chemical industry. The top polymer production summary in Table 1.16 gives a numerical list of important synthetic elastomers. Styrene-butadiene rubber (SBR) dominates the list at 1.93 billion lb for U.S. production. All other synthetic elastomers are much smaller. While elastomers had a slight increase in production from 1980-1990, only 0.5% annually, SBR was down 2.3% per year. From 1990-2000 it was up 1.0% per year. The fastest growing elastomer is ethylene-propylene, up 5.2% annually for 1990-2000. Table 18.1 gives a breakdown in percent production of synthetic elastomers and consumption of natural rubber in the U.S. 

Propylene is a coproduct of steam cracking, the yield of which accounts for nearly half of the ethylene yield. Currently, propylene demand exceeds ethylene demand and steam cracking cannot keep up with the required propylene/ethylene balance. To close the gap, an increase in propylene production from the FCC process is needed. 

With the application of DMMC-1 catalyst, the propylene yield is 17.80 wt%, which is higher by 2.43% as compared with the MMC-2 catalyst. The light ends yield increases by 0.64%, and the coke yield decreases by 0.56 wt%. Furthermore, the olefin content of gasoline decreases by 4.5 v%. Thus the worldwide leading position of DCC in propylene production from catalytic cracking has been advanced further. 

DCC is a novel technology derived from the FCC process for light olefins production, particularly propylene and isobutylene. New generation catalyst DMMC-1 can help to convert heavier feedstocks with increased propylene yield. 

Increasing ethane feedstock, hence less steam cracking propylene production... 

As discussed in Section 12.3, the triolefin process to transform propylene to ethylene and 2-butene developed by Phillips135,136 is not practiced at present because of the increased demand for propylene. The reverse process, that is, cross-metathesis of ethylene and 2-butene, however, can contribute to satisfy the global demand for propylene. Lyondell Petrochemical operates a 136,000-t/y (ton/year) plant for the production of propylene.236 In a joint project by BASF and FINA, Phillips metathesis technology will be used to enhance propylene production.237 A similar project was also announced by DEA.238 In a continuous process jointly developed by IFP and Chines Petroleum Corporation, cross-metathesis of ethylene and 2-butene is carried out in the liquid phase over Re207-on-Al203 catalyst (35°C, 60 bar).239,240... 

Yield Pattern. Table XI presents a feed/product summary for a naphtha based billion lb/yr ethylene plant at various severities of 23, 25, and 27 wt % ethylene (once-through basis). The naphtha feed is the same one as referred to earlier (see Table III). It is immediately apparent that feed requirements are increased at lower severities for a given ethylene production rate. Also, production of olefin by-products increases as severity decreases. Note especially the 36% increase in propylene production as severity is dropped from 27% ethylene to 23% ethylene. Butadiene production goes up somewhat, while butylenes production jumps by over 100% going from 27 to 23% ethylene. 

With imported naphtha at, say 1.1 /lb and aromatics at current values, ethylene cost is 1.94 /lb. However, with finished aromatics valued at 5 /gal over the current base values, production cost drops to 1.59 /lb. The breakeven curves for naphtha vs. ethane, propane, and n-butane are given in Figures 8, 9, and 10. These assume premium byproducts, with aromatics valued above current levels, but do not include the effect of increased propylene and butylene valuations that would further accentuate the picture. With 1.1 /lb naphtha and aromatics at 5 /gal above current prices, the breakeven prices for ethane, propane, and n-butane are 0.33, 0.7, and 0.83 /lb, respectively. Such prices are... 

Ethylene production has increased many fold in the last 40 to 50 years. In the United States, from 1960 to 2000, ethylene production increased from about 2.6 to 30 million metric tons/year while propylene production increased from 1.2 to 14 million tons/year. The growth rates on a yearly basis have, of course, depended in this time period on economic conditions in both the United States and worldwide. In 2000, worldwide production of ethylene was about 88 million tons/year the production capacity was 104 million tons/year. In 1960, about 70% of both the ethylene and the propylene produced was in the United States. Relative growth rates in the last few years of both ethylene and propylene production have... 

South Africa. Sasol produces many products from coal-derived syngas, including ethylene, propylene, a-olefins, alcohols, and ketones. They have also increased their production of methanol, synthetic lubricants, detergent alcohols, acrylic acid and acrylates, oxo-alcohols, styrene and polystyrene, propylene oxide, and propylene glycol. 

Production of light olefins (propylene, n-butenes and isobutene) will be one of the main targets of FCC untis in the near future. These olefins can be fed to alkylation and etherification units to produce additional high octane environmentally acceptable gasoline components, or used as petrochemical feedstock. Johnson and Avidan (85) used higher amounts of ZSM-5 (10-20%) to increase the production of light olefins, mainly propylene. 

The ever increasing demand for light olefins (propylene) products The need to reduce the sulfur level of the gasoline produced in the FCC unit The need to reduce the emissions of the FCC unit itself (NOx emitted from the regenerator)... 

Evidence for the equilibration of light olefins within SAPO-34 prior to diffusion out of the crystalline structure has been obtained by comparing the ethylene/propylene ratio in the MTO product with that calculated from thermodynamic equilibrium. Figure 12.7 shows the thermodynamic ratios of the C2-C5 olefins at 0 psig as a function of temperature. The concentration of ethylene increases at higher temperatures. The influence of equilibrium on the ethylene/propylene product ratio obtained with the MTO-100 catalyst over a range... 

Other applications for molecular sieve catalysts for the production of olefins include the use of ZSM-5 additives in FCC units to increase propylene yield and the... 

Economics Capital costs and economics depend on feed composition as well as the desired increase in ethylene and propylene production in the steam cracker. 

In the past few years workers at Sinopec have been prominent in developing FCC operations which target propylene as a major product. The increased propylene yield is a function of catalyst developments and increasing the cracking temperature. This variation is known as Deep Catalytic Cracking (DCC) and there are two main variants. Table 10.3 illustrates typical yields that can be achieved . 

This figure shows that propylene production cost increases rapidly with increasing oil price. This is based on the assumption that propane is priced according to the world parity price for LPG. In some parts of the world, propane comes from large scale gas developments and is not necessary priced on a world parity basis and this offers lower production... 

Dehydrogenation routes to propylene also increase the amount of carbon emissions relative to the production of propylene from naphtha. Increasing propylene output from FCC operations also increases emissions. Although this is the case for a standalone facility, it is not clear if a full cradle-to-grave analysis would ameliorate or exacerbate the emissions relative to naphtha cracking. 

The world propylene production capacity based on the use of catalytic dehydrogenation of propane has increased steadily over the past lOyr and is expected to grow even further under the right economic conditions relative to the availability and pricing of pro-pane. On the other hand, environmental concerns on the use of methyl-/ r/-butyl ether (MTBE), an oxygenated gasoline additive, are expected to adversely impact the future expansion of isobutane dehydrogenation applications. 

Current global production of propylene stands at about 54 million metric tons per year (tpy) and is valued roughly at 17 billion. The bulk of propylene production and consumption is concentrated in North America, Western Europe, and Japan. These areas represent about 68% of world capacity and 70% of demand. Propylene demand is expected to grow fast and to nearly double in the next 10 yr, reaching more than 91 million tons by 2010 at a growth rate of 4.7%/yr.P Because world consumption is forecast to grow faster than production capacity, propylene has been termed as olefin of the future. This increase is driven by the demand for derivatives, especially polypropylene. 

Addifion of Ba(N03)2 to Au/Ti-based catalysts has also been shown to increase propylene conversion, presumably by mitigating any catalyst surface acidify and aiding fhe production of hydroperoxy-like oxidizing agents [71]. The addition of 1 wf.% Ba(N03)2 resulfed in an increase in PO production from 64.9 to 91.6 gpo kg/jj h at 150 °C with only a slight loss in PO selectivity and H2 efficiency. The addifion of 2.4 wt.% Ba(N03)2 to Au/Ti-TUD catalysts did not appear to generate as substantial an increase in activity [57]. 

---