Pour point reversion

It is recommended that any higher-viscosity product such as residual oil or heavy distillate fuel be evaluated for changes in low-temperature handling properties over time. Testing for reversion in pour point by the Shell Amsterdam Reversion Test or the British Admiralty Pour Point Reversion Test are recommended. Also, viscosity increase versus temperature decrease determinations are recommended for products stored at low temperatures for extended periods of time. 

The pour point and low-temperature viscosity of a residual fuel or heavy fuel oil can be reduced by using a heavy fuel wax crystal modifier. Often, pour point reversion can be prevented by using the correct wax crystal modifier. 

Pour point reversion can occur in oils treated with a pour point improver. Often, pour point reversion can be overcome by increasing the cold flow improver treat rate by about 25% to 50%. 

This procedure can be utilized to determine whether heavy fuel wax crystal modifiers will lose their performance properties after long-term storage at fluctuating temperatures. Daily heating and overnight cooling may interfere with the ability of some wax crystal modifiers to maintain their performance properties in some residual oils and crude oils. This loss of performance is frequently termed pour point reversion. The British Admiralty Pour Point Test can be utilized to help predict these reversion tendencies. 

This problem differs from the problem of pour point increase after shearing and heating. In the case of pour point reversion, an increase in the pour point of a crude oil or heavy fuel oil occurs upon long-term storage. 

Identify whether the oil treated with a wax crystal modifier will revert in pour point by testing utilizing either the British Admiralty Pour Point Reversion Test or the Shell Amsterdam Reversion Test. 

Wang, Sophia L. 1993. (Internal report) VGO pour point reversion. 93/734. Sugar Land, Tex. Nalco/Exxon Energy Chemicals, L.P. 

In order to achieve very low pour points and filtration temperatures in some fuels, high levels of wax crystal modifiers must be used. On occasion, high concentrations of a WCM can cause the pour point or filtration temperature to reverse. This is due to the influence of the high viscosity of these inhibitors at the low test temperatures. 

Compare the pour point obtained with the value determined from a standard ASTM D-97 pour point test. If the pour point temperature obtained is higher than the standard ASTM D-97 value, a reversion in pour point has occurred. 

PROBLEM REVERSION AND ACTUAL INCREASE IN THE POUR POINT OF A CRUDE OIL OR RESIDUAL FUEL OIL... 

Sometimes, reversion tendencies cannot be overcome by the addition of higher treat rates of a wax crystal modifier. Under these circumstances, only dilution by low-viscosity products or the constant addition of heat will keep the oil fluid at temperatures below its base pour point. 

Although poly(n-alkyl acrylates)(PA-esters) with long side-chain have been used early as depressant for pour-point of petrolic oil(1), no studies have been reported on the poly-(vinyl alcohol aliphatic acid esters)(PVA-esters) in this application. We suppose there would exist such possibility as the structures of PA-esters and PVA-esters are very similar to each other except that their forms of ester linking are in reverse order. Therefore it is valuable to investigate the structural features of PA-esters and PVA-esters, and their effects on pour-point depression of oil, not only for scientific interest but also for practical use. 

The column is then pre-equilibrated with the first solvent in the elution series. Enough solvent is put through the column to completely wet the column (e.g., for a 60-mL column, put through approx 75-100 mL). Release the vacuum before the column goes dry and pour off the wash solvent. It is very important that the column not be allowed to go dry at this point. Allowing reverse phase columns to go dry at this point can lead to icing up of the column and extremely slow flow rates. 

It is important to avoid mr bubbles in the lower ends of the tubes. This is done as follows The cathode compartment is turned upside down, and the tubes are inserted. The anode ends of the tubes thus point directly upwards. In the anode end of each tube there should now be placed a drop of the same phorphoric acid solution used in the anode compartment. The cathode compartment and the tubes are now reversed, and the anode ends of the tubes are inserted into the anode compartment. The catholyte should be poured into the upper cathode compartment. It consists of 10 ml ethanolamine in 500 ml 10% sucrose solution. 

Polymer Studies. General Procedure. The desired amount of BPA (generally 45.35g), sodium or potassium hydroxide, phase transfer catalyst (Aliquat 336 or tetrabutylammonium bromide), p - t-butylphenol (0.75% as a chain stopper) and methylene chloride or methylene chloride/chlorobenzene (1/3) were heated at reflux for a period of 5 hr under nitrogen. At this point the reaction mixture was diluted with methylene chloride and filtered through Celite. The mixture was then either a) poured directly into methanol to precipitate the polymer or b) split into two portions one portion was precipitated by methanol, the second was reverse precipitated using methanol/acetone. (see below)... 

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