Chevrons

The Octane Requirement Increase, ORI, is a phenomenon manifested by the appearance of knocking and is due to the increase in engine octane demand with time. This phenomenon is correlated with the increase of solid deposits in the combustion chamber. Although the causes have not been determined with certainty, some companies have patented additives which modify the deposits. The effect is to limit the increase in octane demand (Bert et al., 1983 Chevron, 1988 Nelson et al., 1989). 

Rieker T P, Clark N A, Smith G S, Parmar D S, Sirota E B and Safinya C R 1987 Chevron local layer structure in surface-stabilized ferroelectric smectic-C cells Phys.Rev.Lett 59 2658-61... 

Another way in which academic chemists keep in touch with industry is through consulting. During the years I consulted at different times for Exxon, Chevron, Cyanamid, ENICHEM (Italy), and Pechiney-Kuhlman (Erance, when a friend, Lucien Sobel, was a research director). I enjoyed these contacts, because they kept me aware of current industrial developments and interests. At the same time, it was also rewarding to be able to suggest to my industrial friends new approaches and directions that on occasion were useful and resulted in practical applications. 

Cherts CHESS Chevrefeuille Chevrel phase Chevron-Gulf process Chevron process... 

Currendy, about 40% of the PX produced woddwide uses crystallization technology. A number of crystallization processes have been commercialized over the years. The more common ones are those developed by Chevron, Kmpp, Amoco, ARCO (LyondeU), and Phillips. Some of the features of these processes are discussed herein. 

Currendy, there are three commercially available PX adsorption processes UOP s Parex, IFP s Eluxyl, and Toray s Aromax (not to be confused with Chevron s Aromax process for reforming naphtha into aromatics). In all of these processes, the feed and desorbent inlets and the product oudet ports are moved around the bed, simulating a moving bed. 

The Aromax process was developed in the early 1970s by Toray Industries, Inc. in Japan (95—98). The adsorption column consists of a horizontal series of independent chambers containing fixed beds of adsorbent. Instead of a rotary valve, a sequence of specially designed on—off valves under computer control is used to move inlet and withdrawal ports around the bed. Adsorption is carried out in the Hquid phase at 140°C, 785—980 kPA, and 5—13 L/h. PX yields per pass is reported to exceed 90% with a typical purity of 99.5%. The first Aromax unit was installed at Toray s Kawasaki plant in March 1973. In 1994, IFP introduced the Eluxyl adsorption process (59,99). The proprietary adsorbent used is designated SPX 3000. Individual on-off valves controlled by a microprocessor are used. Raman spectroscopy to used to measure concentration profiles in the column. A 10,000 t/yr demonstration plant was started and successfully operated at Chevron s Pascagoula plant from 1995—96. IFP has Hcensed two hybrid units. 

Hybrid Crystallization/Adsorption Process. In 1994, IFP and Chevron announced the development of a hybrid process that reportedly combines the best features of adsorption and crystallization (59,99). In this option of the Eluxyl process, the adsorbent bed is used to initially produce PX of 90—95% purity. The PX product from the adsorption section is then further purified in a small single-stage crystallizer and the filtrate is recycled back to the adsorption section. It is reported that ultrahigh (99.9+%) purity PX can be produced easily and economically with this scheme for both retrofits of existing crystallization units as well as grass-roots units. A demonstration plant was built at Chevron s Pascagoula refinery in 1994. 

Amorphous Silica—Alumina Based Processes. Amorphous siHca—alumina catalysts had been used for many years for xylene isomerization. Examples ate the Chevron (130), Mamzen (131), and ICI (132—135). The primary advantage of these processes was their simpHcity. No hydrogen was requited and the only side reaction of significance was disproportionation. However, in the absence of H2, catalyst deactivation via coking... 

The Chevron process was used in two U.S. plants, although it is no longer used. Cycle lengths tanged from 6—30 d, depending on catalyst age and OX content of the feed. Operating conditions were temperature of 370—470°C and space velocity of about 0.5/h. Addition of 5 wt % steam reduced disproportionation losses. 

Chevron Pascagoula, Miss. St. James, La. Chevron Mobil 242 771... 

Bechtel Corporation, Calfomia Euel Methanol Cost Study Chevron Corporation, U.S., Vol. 1 (Executive Summary, Jan. 1989) Vol. 2, (Einal Report, Dec. 1988), San Francisco, Calif., 1988-1989. 

A.luminum Jilkyl Chain Growth. Ethyl, Chevron, and Mitsubishi Chemical manufacture higher, linear alpha olefins from ethylene via chain growth on triethyl aluminum (15). The linear products are then used as oxo feedstock for both plasticizer and detergent range alcohols and because the feedstocks are linear, the linearity of the alcohol product, which has an entirely odd number of carbons, is a function of the oxo process employed. Alcohols are manufactured from this type of olefin by Sterling, Exxon, ICI, BASE, Oxochemie, and Mitsubishi Chemical. 

HF-D Akzo Chevron FMC Houghton Mobil Monsanto Quaker British Petroleum Fina Houghton Mobil Monsanto... 

Technical data, WorldEnerg Outlook, Chevron Corp., Richmond, Calif., Apr. 1990. 

Carbon-Graphite Group Calvert City, Ky. Chevron Cedar Bayou, Tex. calcium carbide 34 acetylenic chemicals... 

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