Lower-boiling products

Low temperature filtration (qv) is a common final refining step to remove paraffin wax in order to lower the pour point of the oil (14). As an alternative to traditional filtration aided by a propane or methyl ethyl ketone solvent, catalytic hydrodewaxing cracks the wax molecules which are then removed as lower boiling products. Finished lubricating oils are then made by blending these refined stocks to the desired viscosity, followed by introducing additives needed to provide the required performance. Table 3 Usts properties of typical commercial petroleum oils. Methods for measuring these properties are available from the ASTM (10). 

Another process for silicon carbide fibers, developed by Verbeek and Winter of Bayer AG [45], also is based on polymeric precursors which contain [SiCH2] units, although linear polysilmethylenes are not involved. The pyrolysis of tetramethylsilane at 700°C, with provision for recycling of unconverted (CHg Si and lower boiling products, gave a polycarbosilane resin, yellow to red-brown in color, which was soluble in aromatic and in chlorinated hydrocarbons. Such resins could be melt-spun but required a cure-step to render them infusible before they were pyrolyzed to ceramic... 

Low-APl fuel oil (heavy industrial fuel oil) is a medium-viscosity product that are highly variable and often blended with lower-boiling products. The blends may be unstable and the oil may separate when spilled onto the ground or onto a waterway. The oil may be buoyant or sink in water,... 

As the need for the lower-boiling products developed, petroleum yielding the desired quantities of the lower-boiling products became less available and refineries had to introduce conversion processes to produce greater quantities... 

Elemental analysis of fuel oil often plays a more major role that it may appear to do in lower-boiling products. Aromaticity (through the atomic hydrogen/carbon ratio), sulfur content, nitrogen content, oxygen content, and metals content are all important features that can influence the use of residual fuel oil. 

Catalytic cracking the conversion of high-boiling feedstocks into lower-boiling products by means of a catalyst that may be used in a fixed or fluid bed. 

The polymerization of ethylene in the presence of aluminum chloride is fundamentally changed by the presence of metallic aluminum (Hall and Nash, 72). The product which was obtained at a reaction temperature of 100-200° under superatmospheric pressure was a mobile fuming liquid which was shown to contain diethyl aluminum chloride, a liquid spontaneously inflammable in air. Less conjunct polymerization occurred, the lower-boiling product consisting of olefins mixed with only minor amount of paraffins. 

The catalyst components are generally dissolved in methyl acetate which acts as both reactant and solvent. Other solvents may be used and in fact, upon several batch recycles where lower boiling products are distilled off, the solvent is an ethylidene diacetate-acetic acid mixture. Any water introduced in the reaction mixture will be consumed via ester and anhydride hydrolysis, therefore anhydrous conditions are warranted. Typical batch reaction examples are presented in Table 1. There is generally sufficient reactivity when carbon monoxide and hydrogen are present at 200-500 psi. Similar results were obtained from the pilot plant using a continuous stirred tank reactor (CSTR). The reaction can also be run continuously over a supported catalyst with a feed of methyl acetate, methyl iodide, CO, and hydrogen. 

The primary objective in the Upgrading process is to convert the heavy oil into a lower boiling product with low sulphur and nitrogen content. Sulphur is a by-product of this process. Figure 3 presents a schematic of Syncrude s Upgrading and will be used to describe the disposition of sulphur and its recovery at various stages in the process. 

The replacement of the nitro group by fluorine in aliphatic compounds appears to be much less well known than in the aromatic series. The possibility of nitro group displacement in aromatic compounds was noted during the study of halide displacement in halo-substituted 2,4-dinitrobenzenes. The appearance of brown fumes and formation of traces of lower boiling products resulted in studying the exchange of the nitro group in 2,3,5,6-tetrachloro-l-nitroben-... 

With shorter periods of standing and lower temperatures, the yield falls off materially. Thus in one experiment in which the mixture was allowed to stand for twenty-four hours at 5-8°, a large proportion of a lower-boiling product (apparently diphenylmethane) was formed, and only 109 g. of crude tri-phenylmethane was obtained. 

Finally, and before a discussion of the various reactor-bed types used in hydrodesulfurization, a note that the once-popular once-through reactors, where the incompletely converted or unconverted fraction of the feedstock is separated from the lower-boiling products are being replaced by recycle reactors. In these reactors, any unconverted feedstock is sent back (recycled) to the reactor for further processing. In such a case, the volume flow of the combined (fresh and unconverted) feedstock is the sum of the inputs of the fresh feedstock and recycled feedstock ... 

The high-boiling distillates, such as the atmospheric and vacuum gas oils, are not usually produced as a refinery product but merely serve as feedstocks to other processes for conversion to lower-boiling materials. For example, gas oils can be desulfurized to remove more than 80% of the sulfur originally in the gas oil with some conversion of the gas oil to lower-boiling materials (Table 6-11). The treated gas oil (which has a reduced carbon residue as well as lower sulfur and nitrogen contents relative to the untreated material) can then be converted to lower-boiling products in, say, a catalytic cracker where an improved catalyst life and volumetric yield may be noted. 

A wide choice of commercial processes is available for the catalytic hydrodesulfurization of heavy oils and residua (Chapter 9). The suitability of any particular process depends not only upon the nature of the feedstock but also on the degree of desulfurization that is required. There is also a dependence on the relative amounts of the lower-boiling products that are to be produced as feedstocks for further refining and generation of liquid fuels. 

Isocracking process a hydrocracking process for conversion of hydrocarbons which operates at relatively low temperatures and pressures in the presence of hydrogen and a catalyst to produce more valuable, lower-boiling products. 

This chapter reports results of applying a catalytic hydrorefining process to four coal liquids solvent-refined coal (SRC) process filter feed, SRC extract product, Synthoil, and H-Coal process hydroclone underflow. The achieved upgrading is evaluated in terms of reduction in benzene and heptane insolubles, reduction in sulfur, nitrogen, and oxygen, an increase in hydrogen content, and a yield of lower boiling products. 

Variations of the above procedures are sometimes employed. /S-Keto esters may be obtained by alcoholysis of the intermediate diacyl esters by sodium methoxide in methanol, as in the preparation of methyl /3-oxocaprylate (88%). The starting /S-keto ester can be converted to the new /S-keto ester in a single step. Thus, in the synthesis of ethyl ben- > zoylacetate (55%)> ethyl acetoacetate and ethyl benzoate are converted directly to this keto ester by distilling the lower-boiling product, ethyl acetate, thereby forcing the reaction to completion. ... 

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