Reprocessing of contaminated oils

A process is disclosed for reprocessing contaminated oils, such as used crankcase oil from automobile engines, by thermal treatment, such as visbreaking, in the presence of other hydrocarbon feedstocks, followed by fractional distillation for the recovery of a gasoline fraction, a carboxylic acid fraction, a gas oil fraction containing chlorinated hydrocarbons and a high boiling bottoms fraction. The gas oil fraction is subjected to catalytic hydrocracking with the simultaneous destruction of chlorinated hydrocarbons. The resulting hydrocracked oils, after separation of hydrogen chloride, are free from chlorine compounds and other contaminants.

The present invention relates to a process for reprocessing of contaminated 
oils by treatment in a cracking step, distillative separation of the 
products and subsequent hydrogenative treatment of distillate fractions. 
BACKGROUND OF THE INVENTION 
During the last decade experts have increasingly attended to reprocessing 
of used oils, which are also known as waste oils, under environmental safe 
conditions, whereby the term "contaminated" or "used" oils is to be 
considered as the more general definition. 
Although a precise definition of the term "waste oil" is not available (see 
for example chapter 1 in K. Muller, "Reprocessing of waste oils", Erich 
Schmidt Verlag, Berlin 1982), the most general meaning embraces used 
lubricants and functional fluids, which cannot be used directly, and which 
are predominantly based on mineral oil, but may also be based on coal tar, 
plants, animals and synthesis. These materials may also be of solid or 
semi-solid consistency at normal temperature. 
Unused lubricants and functional fluids contain numerous additives, like 
for example corrosion inhibitors, oxidation inhibitors, anti-foaming 
additives, detergents, dispersants, metal deactivators, colour 
stabilizers, viscosity index improvers, pour point reducing additives, 
wear control additives, emulsifiers etc. 
By these additives, compounds of oxygen, sulfur, nitrogen, phosphorus, of 
metals like heavy metals, but also of other metals, halogens, silicons, 
numerous synthetic materials, and other compounds are present in 
lubricating oils and functional fluids. 
During usage of fresh oil as lubricants and functional fluids, alterations 
of the additives take place by physical effects, like increased 
temperature and wear, but also by chemical processes, like for example 
oxidation. As a result the products of these transformations and changes 
are also present in used oils, like finely distributed metals, asphalthene 
materials, respectively materials of resin consistency and other secondary 
products formed by chemical changes of the additives. 
Often contaminated oils of completely different origin are jointly 
collected. As a consequence the mixture may contain numerous solvents, 
water and solids. In these mixtures and in waste oils in general, the 
content of chlorinated compounds, in particular of polychlorodiphenyls, 
polychloroterphenyls, polychlorodiphenylmethans and other chlorine 
containing contaminations is of particular importance. 
On account of these chlorocompounds, but also of metals and metal 
compounds, incineration of waste oils is very problematic, since the 
formation of toxic materials like dioxins or polychlorodibenzofurans and 
their emission into the environment cannot be excluded. 
Regarding the very large quantities of waste oils and their importance as a 
raw material, incineration, which is also called energy recycling, i.e. 
recovery of heat energy by incineration, cannot be considered as an 
optimal way of handling, since materials, which are rich in hydrogen and 
which are therefore of great importance as fuels or feed materials for 
olefin plants, are only converted into water, CO.sub.2 and energy. As a 
consequence many processes have been developed for reprocessing of used 
oils into re-usable oils. Reprocessing of used oils is often called 
secondary refining. 
The conventional process is the sulfuric acid process, whereby waste oils 
are treated with 96 weight percent sulfuric acid. In this process 
so-called acid resins are formed and deposited. In a subsequent stage 
neutralization is carried out and the oil treated in this way is finally 
distilled. In general this treatment is repeated. The remaining oils which 
still contain contamination, have a dark colour and bad odour. As a result 
they are difficult to re-use. In addition disposal of the acid resins is 
very prolematic. 
An improvement is considered to be the sulfuric acid/clay-process, whereby 
after treatment of the oil with sulfuric acid it is contacted with clay 
and subsequently distilled under vacuum (R. Meixlsperger in W. Kumpf, K. 
Maas, H. Straub: Garbage and waste disposal, page 395, Nr. 4010). 
extraction precedes the sulfuric acid treatment (R. Dutrian and D. V. 
Quang, Chemical Engineering 79 (1972), page 4). A more modern process 
comprising a refining step with hydrogen is the KTI-process (R. F. 
Westerduin in: Polytechnisch tijdschrift/process-techniek 34 (1979), page 
5). This process is characterized by a first vacuum distillation, followed 
by a distillation under high vacuum. Finally a treatment with hydrogen at 
approximately 50 bars and 300.degree.-350.degree. C. is carried out. 
Obviously, in spite of these processes, an urgent need continues to exist 
for solutions according to which in a technically simple way the large 
quantities of waste oils can be worked up under conditions which take into 
account environmental and economical requirements. 
With regard to the direct reprocessing of waste oils together with crude 
oil in refineries, it is disclosed in K. Muller, "Reprocessing of waste 
oils", published by Erich Schmidt Verlag, Berlin 1982 on page 101: 
"Considering the original properties, the obvious possibility of adding 
waste oil to crude oil before processing of the latter, in order to 
increase the portion of lubricant oils, can be completely excluded owing 
to the typical contaminations present and the negative consequences caused 
by these contaminations with regard to catalysts and operating conditions 
applied in crude oil processing. For these reasons special secondary 
refining processes for the reprocessing of waste oils into high quality 
base lube oils are mandatory." 
SUMMARY OF THE INVENTION 
In contrast to these prejudices resulting from the state of the art, 
applicant surprisingly has been successful in developing a process, which 
has already been applied in a technical scale in a refinery with very good 
results and which makes it possible to reprocess waste oils resp. used 
oils with excellent results within the scope of a conventional refinery, 
characterized in that a thermal treatment of contaminated oils is carried 
out in a thermal or catalytic cracking stage, that separation of 
fractions, which contain chlorocompounds is carried out by distillation of 
the cracking product and that hydrogenative refining of distillate 
fractions containing chlorocompounds is carried out. 
DETAILED DESCRIPTION OF THE INVENTION 
It is generally known that the conventional methods of processing in 
refineries are distillation, cracking, refining and reforming. Cracking 
processes used are thermal cracking, catalytic cracking and hydrocracking. 
Thermal cracking has the advantage that high boiling and heavily 
contaminated oils can be used as feed material. 
Conventional thermal cracking processes are visbreaking, which is carried 
out at relatively low temperatures of approx. 400.degree.-500.degree. C., 
furthermore normal thermal cracking at approx. 500.degree.-600.degree. C. 
and coking, which is carried out at approx. 500.degree. C. Catalytic 
cracking processes are carried out in general in a fixed-bed, fluid-bed or 
fluidized-bed process. The latter processes can also be applied according 
to the invention. 
By refining of refinery streams hetero atoms, in particular nitrogen and 
sulfur, which are present in crude oil fractions as chemical compounds, 
are removed. 
Although chemical refining processes are available, like the oxidation of 
intensely smelling mercaptans to disulfides with only a weak odour, 
refining by hydrogenation in the presence of a catalyst, which is stable 
with regard to sulfur and which contains metal components mostly 
consisting of combinations of Ni, Co, Mo and W, is the refining process 
predominantly used. By this process the heteroatoms S,N and 0 are 
transformed into H.sub.2 S, NH.sub.3 and H.sub.2 O. Unsaturated compounds 
are converted into saturated hydrocarbons. Hydrogenative refining can be 
applied at very different conditions. Typical conditions are for example 
25-100 bars and 300.degree.-400.degree. C., however also considerably 
higher pressures like for example 300 bars may be applied. 
In conventional refinery operation, bottoms from atmospheric distillation, 
vacuum distillation or mixtures thereof are cracked by thermal cracking. 
The investigations of applicant have led to the result that work-up of 
contaminated oils is not possible, if they are, even in pre-purified 
condition after separation of water and filtration, directly fed into an 
atmospheric or vacuum distillation, because as a result of the low thermal 
stability of waste oils compared to crude oil fractions, coking and 
depositing of various material take place already after a short time of 
operation inside of the distillation columns, to such an extent that the 
columns have to be shut down and to be purified. If however, under 
consideration of other inventive characteristics, the contaminated oils 
are fed at first into a thermal treatment stage, surprisingly a 
troublefree operation is possible, although the total quantity of cracking 
product is fed into the distillation. 
The investigations of applicant have shown that by heating of contaminated 
oils like waste oils, considerable quantities of carboxylic acids, in 
particular of acetic acid are formed besides HCl. 
If for example after a rough separation of water, contaminated oil like 
waste oil is fed without pre-purification into a visbreaker, which is 
operated at standard conditions of approx. 10 bars, a residence time of 20 
minutes and a temperature of up to 450.degree. C., considerable chemical 
transformations take place, which may lead to formation of carboxylic 
acids and separation of HCl. The individual steps of the former 
transformation are not known. 
Although feeding into a visbreaker as a thermal cracking stage is preferred 
according to the invention, other thermal or catalytic cracking processes 
are also within the scope of the present invention, leading to very good 
results, although these processes may be operated at very different 
conditions as known to the artisan. 
From the atmospheric distillation column, which is preceded by the 
visbreaker, carboxylic acids, in particular acetic acid are withdrawn 
overhead or as an upper side-stream, where also HCl is withdrawn. 
It is of advantage according to the invention, to adjust the head 
temperature of the distillation column to above 150.degree. C., preferably 
to above 180.degree. C. in order to avoid corrosion. The temperature can 
be adjusted by controlling the quantity of product withdrawn. 
It is also of advantage to add corrosion inhibitors to the condensation 
system at the head of the column in order to avoid corrosion in this 
system. The gas oil fraction with the usual boiling range of 
170.degree.-360.degree. C., which may however deviate from the range if 
desired, still contains chlorocompounds. 
The bottoms of the atmospheric distillation, submitted to a vacuum 
distillation, furnish a vacuum distillate which also contains 
chlorocompounds. 
The distillate obtained by atmospheric distillation, which is lower boiling 
than gas oil, as well as the bottoms of the vacuum distillation, are free 
however of chlorine containing compounds like polychlorobiphenyls and 
polychloroterphenyls or polychlorodiphenylmethans. 
According to the invention, gas oil and/or vacuum distillate are subjected 
to hydrogenative catalytic refining, whereby active hydrogenation metals 
are used, in particular combinations of Ni, Co, Mo and W, deposited on 
conventional carriers like amorphous or crystalline zeolites, Al.sub.2 
O.sub.3, aluminum silicates or SiO.sub.2 and others. 
Hydrogenative refining can be carried out in a broad pressure range of 
25-300 bars and a temperature of 280.degree.-500.degree. C. A preferred 
range of operation according to the state of the art is 25-100 bars and 
280.degree.-400.degree. C.; particularly preferred is the range of 30-70 
bars and 300.degree.-380.degree. C. 
The products thus obtained are completely free of chlorine and can be 
further processed like conventional refinery streams. 
According to the invention it is preferred to add a base, in particular 
NaOH, to the thermal or optionally to the catalytic cracking stage. It is 
of advantage to add 20-40 mole percent per gramatom of chlorine contained 
in the feed. However the quantity of NaOH can be added in a broad range of 
up to stoichiometric or overstoichiometric quantities. A quality which is 
smaller than 20 mole percent per gramatom of chlorine is less preferable. 
The quantity of contaminated oil like for example waste oil may amount to 
greater than 0 and up to 35 weight percent based on the total feed to the 
thermal treatment (cracking) stage, preferably greater than 0 and up to 20 
weight percent and particulary preferable, to greater than 0 and up to 15 
weight percent. 
If higher quantities than 35 weight percent are added, heavy coke formation 
and foaming may occur. In order to minimize or prevent foaming, an 
anti-foaming additive may be added, whereby additives known to the artisan 
may be used. 
In case that no vacuum distillation is applied, the bottoms of the 
atmospheric distillation may for example be directly fed to a gasification 
reactor, whereby soot formed during gasification essentially adsorbs the 
ash resulting from the contaminated oils.

EXAMPLE 
The invention is explained in more detail with the aid of the example, 
represented in the figure. 
From tank (1) 10 weight percent of a waste oil, consisting of numerous 
components were fed into visbreaker (3) in combination with 90 weight 
percent of a vacuum residue (2) from a vacuum distillation unit of the 
refinery. For the purpose of increasing the residence time, a soaker (4) 
is installed behind (3). The thermal cracking units are to be considered 
as examples. Also catalytic cracking units and other thermal cracking 
units and other thermal cracking units than visbreakers can be used 
according to the invention with very good results. 
The cracking product is fed through (5) into atmospheric distillation (6). 
Through (7) light gasoline is withdrawn and through (10) acetic acid 
respectively acetic acid containing water is withdrawn. Through (8) a 
naphtha fraction is withdrawn and through (9) a gas oil fraction 
containing chlorocompounds. 
The bottoms of (6) are fed to a vacuum distillation (11). Vacuum distillate 
flows through (12) to reactor (13) for hydrogenative refining. Through (9) 
gas oil can also be directly fed to (13). Through (14) hydrogen is added. 
From hydrogenation reactor (13) a hydrocarbon product (15) is obtained, 
which is completely free of chlorine The unit was operated as described, 
for 16 weeks without any problem. 
For comparison waste oil was transferred from (1) through (16) directly to 
(6). After 2 weeks, inside the column heavy coke deposits were found in 
particular in the hot part of the column, as well as deposits resulting 
from amino compounds, to such an extent that the column had to be shut 
down. This result confirms the citation on page 4 from reference: K. 
Muller, "Reprocessing of waste oils", page 101. 
The present invention discloses for the first time a process, which makes 
it possible to work up large quantities of contaminated oils with 
conventional refinery operation without any problems, whereby perfectly 
pure hydrocarbon fractions are obtained, which can be further processed by 
conventional methods. The bottoms of vacuum distillation (11) can be fed 
into a gasification unit like Shell or Texaco gasification (17) or other 
gasification units for example fluidized bed gasifications, or can be 
withdrawn through (18) as heavy heating oil. Bottoms of column (6) may 
also be transferred directly through (19) to (17) or (18). At (20) 
synthesis gas is obtained.