Propylene production

Refinery Production. Refinery propylene is formed as a by-product of fluid catalytic cracking of gas oils and, to a far lesser extent, of thermal processes, eg, coking. The total amount of propylene produced depends on the mix of these processes and the specific refinery product slate. For example, in the United States, refiners have maximized gasoline production. This results in a higher level of propylene production than in Europe, where proportionally more heating oil is produced. 

Production estimates for propylene can only be approximated. Refinery propylene may be diverted captively to fuel or gasoline uses whenever recovery is uneconomic. Steam-cracker propylene production varies with feedstock and operating conditions. Moreover, because propylene is a by-product, production rates depend on gasoline and ethylene demand. 

Worldwide propylene production and capacity utilization for 1992 are given in Table 6 (74). The world capacity to produce propylene reached 41.5 X 10 t in 1992 the demand for propylene amounted to 32.3 x 10 t. About 80% of propylene produced worldwide was derived from steam crackers the balance came from refinery operations and propylene dehydrogenation. The manufacture of polypropylene, a thermoplastic resin, accounted for about 45% of the total demand. Demand for other uses included manufacture of acrylonitrile (qv), oxochemicals, propylene oxide (qv), cumene (qv), isopropyl alcohol (see Propyl alcohols), and polygas chemicals. Each of these markets accounted for about 5—15% of the propylene demand in 1992 (Table 7). 

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. 

The propylene fractionator operates at a pressure of 1.8 to 2.0 MPa with more than 160 trays required for a high purity propylene product. Often a two-tower design is employed when polymer grade (99.5%+) is required. A pasteurization section may also be used when high purity is required. The bottoms product contains mainly propane that can be recycled to the cracking heaters or used as fuel. Typical tower dimensions and internals for a 450,000 t/yr ethylene plant with naphtha feed are summarized in Table 7. 

Like ethylene, propylene (propene) is a reactive alkene that can be obtained from refinery gas streams, especially those from cracking processes. The main source of propylene, however, is steam cracking of hydrocarbons, where it is coproduced with ethylene. There is no special process for propylene production except the dehydrogenation of propane. 

Optimal flow rates for cracking furnace for different restrictions on ethylene and propylene production... 

Suppose the inequality constraints on ethylene and propylene production were changed to equality constraints (ethylene = 50,000 propylene = 20,000). The optimal solution for these conditions is shown as case 2 in Table E14.1B. This specification forces the use of DNG as well as ethane. 

Chemical food preservation, 12 85-86 Chemical formula, defined, 21 336 Chemical fossils, 18 571 Chemical gas scavengers, 12 77 Chemical gel stabilization, 23 71 Chemical-grade limestone, 15 27 Chemical-grade propylene, product specification for, 20 1111 Chemical hazards, 21 833-846... 

Polymer-grade propylene, product specifications for, 20 1111 Polymer grades, data concerning,... 

Propylene production, 24 259 Propylene urea resins, 2 639 n-Propyl formate, physical properties, 6 292t... 

Ethylene/propylene products reign supreme among the copolymers. They are elastomers. Plastics containing about 20% or more propylene perform like natural rubber and can be cured by peroxide cross-linking. They are faster to chemical and to ageing than other types of natural rubber. 

Chen, J.Q., Bozzano, A., Glover, B., Fuglerud, T., and Kvisle, S. (2005) Recent advancements in ethylene and propylene production using the UOP/ hydro MTO process. Catal. Today, 106, 103-107. 

C Novel FCC Catalysts and Processing Methods for Heavy Oil Conversion and Propylene Production... 

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

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. 

Comparison of Propylene Production of Different Zeolite Combination... 

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. 

The petrochemical plant and refinery integration schemes offer lower cost routes to incremental ethylene/propylene production either via revamp modifications or in grassroots application [5,6],... 

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. 

Fuel uses are a potential application which would require substantial volumes of methanol. As mentioned earlier they are reviewed in the following chapter. A fuel related potential use of methanol is as a replacement for water used to carry coal in pipelines. Methanol is being considered for this use because it would eliminate a demand for water, which is often scarce in areas where coal is mined, and methanol could be burned as a fuel with the coal at its destination. Methanol has also been touted as a good feedstock for gases used in the direct reduction of iron ore. If this use of methanol is realized, it will not be before the mid to late 1980 s. Other potential new uses for methanol include a feedstock for ethylene and propylene production (9) and a feedstock for gasoline production (10). 

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... 

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... 

Fig. 12.8 Relationship of Ethylene/Propylene product ratio over MTO-lOO catalyst with thermodynamic equilibrium...

---