Feedstock feed impurities

The catalyst is reported to be a true solid acid without halogen ion addition. In the patent describing the process (239), a Pt/USY zeolite with an alumina binder is employed. It was claimed that the catalyst is rather insensitive to feed impurities and feedstock composition, so that feed pretreatment can be less stringent than in conventional liquid acid-catalyzed processes. The process is operated at temperatures of 323-363 K, so that the cooling requirements are less than those of lower temperature processes. The molar isobutane/alkene feed ratio is kept between 8 and 10. Alkene space velocities are not reported. Akzo claims that the alkylate quality is identical to or higher than that attained with the liquid acid-catalyzed processes. 

Current zeolite catalysts already operate at process temperatures that require minimal external heat addition. Heat integration and heat management will be of increasing concern at the lower benzene to propylene ratios because the cumene synthesis reaction is highly exothermic (AHf= -98 kJ/mole). Recycle, particularly in the alkylation reactor, is likely to become increasingly important as a heat management strategy. The key will be how to limit the build-up of byproducts and feed impurities in these recycle loops, particularly as manufacturers seek cheaper and consequently lower quality feedstocks. As in the case of ethylbenzene, process and catalyst innovations will have to develop concurrently. 

According to the open literature, other solid acid alkylation catalysts are generally susceptible to poisoning/deactivation by water and other common feed impurities (e.g., oxygenates, sulfur compounds, dienes, etc.), thus necessitating (potentially costly) feedstock pretreatment for their removal. In some cases, this requirement is further mandated by the potential corrosion problems associated with the use of halogens in the catalyst system. 

The first step is performed in liquid phase with air as oxidizing agent under pressures of 3.5-5 atm to maintain liquid conditions. With a cobalt naphthenate-catalyst, temperatures in the range of 120-130 C are adequate, whereas without catalyst the temperatures need to reach 145-150 0. An important feature of the process is the relatively low per-pass conversion of about 15 per cent of the cyclohexane charge. Water formed by the oxidation reaction and impurities in the feedstock such as sulfur-containing compounds and other hydrocarbons are removed azeotropically as reaction proceeds. Unless reaction water is removed, the air-oxidation ceases after about 25-30 per cent conversion. Removal of feed impurities and oxidation by-products results in a clean recycle stream. 

The principal consideration of coal beneficiation is to upgrade the quality of coal for direct use in steam and power generation, or for special uses such as chemical feedstock, feed to liquefaction, and gasification. The properties and quantities of impurities in coal are known to be the major factors that place limitations on coal utilization. All coals are not the same (Chapters 1 and 2). Thus, the type of coal beneficiation technology and the extent of beneficiation depend mostly on the type of coal, the means of mining, and the clean coal utilization. 

The carbon monoxide product is removed from the top of the column and warmed against recycled high pressure product. The warm low pressure stream is compressed, and the bulk of it is recycled to the system for process use as a reboder medium and as the reflux to the carbon monoxide column the balance is removed as product. The main impurity in the stream is nitrogen from the feed gas. Carbon monoxide purities of 99.8% are commonly obtained from nitrogen-free feedstocks. 

The hterature consists of patents, books, journals, and trade Hterature. The examples in patents may be especially valuable. The primary Hterature provides much catalyst performance data, but there is a lack of quantitative results characterizing the performance of industrial catalysts under industrially reaHstic conditions. Characterizations of industrial catalysts are often restricted to physical characterizations and perhaps activity measurements with pure component feeds, but it is extremely rare to find data characterizing long-term catalyst performance with impure, multicomponent industrial feedstocks. Catalyst regeneration procedures are scarcely reported. Those who have proprietary technology are normally reluctant to make it known. Readers should be critical in assessing published work that claims a relevance to technology. 

The circulating catalyst in the FCC unit is called equilibrium catalyst, or simply E-cat. Periodically, quantities of equilibrium catalyst are withdrawn and stored in the E-cat hopper for future disposal. A refinery that processes residue feedstocks can use good-quality F-cat from a refinery that processes light sweet feed. Residue feedstocks contain large quantities of impurities, such as metals and requires high rates of fresh catalyst. The use of a good-quality E-cat in conjunction with fresh catalyst can be cost-effective in maintaining low catahst costs. 

Impurities in the crude tBA feed, most notably water, methanol, acetone, and heavies , do not appear to significantly inhibit the dehydration process (eq 1), although the presence of methanol clearly leads to the formation of additional MTBE (either through etherification of the tBA feedstock, or the isobutylene coproduct). 

Often model systems are used in mechanistic studies. Use of a single-component feed rather than a broad boiling range greatly simplifies analysis schemes. However, part-per-million quantities of impurities in real feedstocks can sometimes severely complicate catalyst usage, selectivity, and life. 

As a simulation example we treat the production of biodiesel from rapeseed in a plant capacity of 200 ktonne per year. The feedstock has a high content of oleic acid triglyceride, around 65%, such that the kinetic data from Section 14.6 can be used for sketching the design of the reaction section. For simplification, we consider that the oil was pretreated for removing impurities and gums, as well as FFA by esterification over solid catalyst. The free fatty acids and water content in oil feed should be less than 0.5%w. NaOH and KOH in 0.5 to 1.5% w/w are used as catalysts. 

Salts such as sodium, calcium, and magnesium chloride are generally contained in water suspended in the oil phase of hydrocarbon feedstocks.9 Other impurities are also present in crude oils as mechanical suspensions of silt (dirt), iron oxides, sand, and crystalline salt.14 These contaminants must be removed before processing the crude oil feeds thus, the best method is mixing the crude oil with water and creating an emulsion.12... 

---