Paraffinic lubes

The abbreviation N is for neutral as understood in acid/base terms and is applied to paraffinic lube distillates. Solvent extracted base stocks are sometimes given the prefix SNO (solvent neutral oil) before the SUS viscosity (e.g., SNO-100). Hydrocracked base stocks are usually designated as neutrals (e.g., 40N. 650N, etc.), but the neutral is not really necessary any longer and many base stock manufacturers have dropped it. Naphthenic base stocks may have the prefix N. 

Dewaxing of paraffinic lube stocks is an essential step in the production of lubricants which will remain fluid and permit machinery to operate at winter temperatures. The next two chapters outline the technologies that have been developed for this purpose (except solvent dewaxing, which was discussed in Chapter 6). These processes reflect the historical development of dewaxing chemical knowledge during this century, first using chemical separation processes and more recently, chemical conversion. 

Viscosity index or VI is based on an arbitrary scale that is used to measure the change in viscosity as a function of temperature. The scale was first developed in 1928 and was based on the best and worst known lubes at the time. The best paraffinic lube was assigned a value of VI = 100 and the worst naphthenic was assigned a VI = 0. The quality of Base stock has been improved dramatically since 1928 with the VI of high quality Base stock in the 140+ range. 

Pig. 6. Typical stmctures in lube oil (a) / -paraffin, (b) isoparaffin, (c) cycloparaffin, (d) aromatic hydrocarbon, and (e) mixed aUphatic and aromatic ring... 

Catalysis. As of mid-1995, zeoHte-based catalysts are employed in catalytic cracking, hydrocracking, isomerization of paraffins and substituted aromatics, disproportionation and alkylation of aromatics, dewaxing of distillate fuels and lube basestocks, and in a process for converting methanol to hydrocarbons (54). 

A few companies, eg, Enichem in Italy, Mitsubishi in Japan, and a plant under constmction at Eushun in China, separate the olefins from the paraffins to recover high purity (95—96%) linear internal olefins (LIO) for use in the production of oxo-alcohols and, in one case, in the production of polylinear internal olefins (PIO) for use in synthetic lubricants (syn lubes). In contrast, the UOP Olex process is used for the separation of olefins from paraffins in the Hquid phase over a wide carbon range. 

Liquid propane is a selective hydrocarbon solvent used to separate paraffinic constituents in lube oil base stocks from harmful asphaltic materials. It is also a refrigerant for liquefying natural gas and used for the recovery of condensable hydrocarbons from natural gas. 

On the other hand, liquid propane also has a high affinity for paraffinic hydrocarbons. Propane deasphalting removes asphaltic materials from heavy lube oil base stocks. These materials reduce the viscosity index of lube oils. In this process, liquid propane dissolves mainly paraffinic hydrocarbons and leaves out asphaltic materials. Higher extraction temperatures favor better separation of the asphaltic components. Deasphalted oil is stripped to recover propane, which is recycled. 

Paraffin isomerization of heavy alkane feeds is often used to alter the cloud or pour point of diesel or lube fractions. Catalysts for this reaction are almost always dual-function catalysts of Pt supported on a one-dimensional zeolite. Using a onedimensional zeolite allows control of the isomerized product to contain few branches, usually methyl branches (Table 12.4). 

The use of n-paraffins recovered include octane value enhancement of gasoline, solvents and raw materials for biodegradable detergents, fire retardants, plasticizers, alcohol, fatty acids, synthetic proteins, lube oil additives, and a-olefins. A detailed discussion on n-paraffin separation processes is available (1). 

Because of the high molecular weight materials at the upper end of the boiling range for medium lube oil stocks, the desorption technique of choice should probably employ a displacement chemical with a high heat of adsorption, in order to overcome the high heat of adsorption of the in-paraffins. Ammonia at temperatures near 660 K and near atmospheric pressure appears to have good potential. 

The combination supercritical fluid volatility amplification-molecular sieve process has the potential for producing two valuable products simultaneously from gas oil-lube oil petroleum stocks. In a flow-through molecular sieve bed, the leading adsorption front operates in the lean molecular sieve loading range, providing the conditions needed for the n-paraffin removal needed to produce low pour lube oil, while the trailing adsorption... 

The applications of the ZSM-5 family of zeolites for shape-selective cracking of paraffins in the gasoline (2, 10), distillate (11) and lube oil range (12) have all been reported. In this paper, we have established evidence of the converse reaction, shape-selective polymerization, to produce hydrocarbons in the same product range. 

Figure 5 schematically illustrates the concepts of reactant shape selectivity. Only linear paraffins that are able to diffuse and are adsorbed inside the pores can undergo a chemical transformation, e.g., acid catalyzed cracking. The property is exploited in some chemical processes, such as the dewaxing of lubes and middle distillates, through the selective cracking or isomerization of the linear paraffin fraction. 

Pyrolysis was carried out on a feed composed of a 50/50 mixture by weight of low-density polyethylene (LDPE) and hydrotreated FT wax. Yields are given in Table 13.2, showing a 385°C- - yield of 57.5 wt%. The yield for a broader lube feed, 343°C- -, was 66.0 wt%. While there was considerable 538°C- - in the feed to the pyrolyzer, there was little 538°C- - in the product, which is believed here to be advantageous for low cloud point. Oleflnicity in the pyrolysis overhead was 76 wt% by PONA analysis. The olefinic overhead liquids from the pyrolysis of both FT wax and LDPE/FT wax were analyzed using gas chromatography. This showed the cracked product to be almost entirely 1-normal olefins and normal paraffins. 

Liquid paraffin, Lubri-Tears, Lacri-Lube, Dry eye conditions... 

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