Low Aromatic Solvents

Low Aromatic Solvents



Low Aromatic Solvents

MGT PetrOil Company as a major producer, supplier and exporter of several petrochemical products in the Middle East, is located in Iran. MGT PetrOil Company is an active company in exporting especially in case of Low Aromatic Solvents.

Iran holds the world's fourth-largest proved crude oil reserves and the world's second-largest natural gas reserves. Iran also ranks among the world's top 10 oil producers and top 5 natural gas producers. The Strait of Hormuz, off the southeastern coast of Iran, is an important route for oil exports from Iran and other Persian Gulf countries. Liquefied natural gas (LNG) volumes also flow through the Strait of Hormuz.

National Petrochemical Company (NPC) was established in 1963 to spearhead the development and policy-making for Iran’s petrochemical industry. Iran’s petrochemical industry is the oldest in the Middle East and in ethylene production it is the second oldest after Turkey. During 1964-1977 Razi, Abadan, Pazargad, Ahwaz carbon black, Kharg, Farabi and Shiraz expansion projects were completed.

 

What is Low Aromatic Solvents?

Petroleum solvents are generally defined and differentiated by certain physical properties and by chemical composition. Among the properties of importance, depending on the intended end-use of the solvent, are boiling range, flash-point, solvent strength (solvency), color, odor, aromatic content and sulfur content. Some of these properties are interrelated; for example, increasing the aromatic content often increases solvency, but also increases odor. ln addition, the same property may be measured in different ways in different industries or in different geographic regions; for example, kauri-butanol value (the amount of petroleum solvent in milliliters required to cause cloudiness in a solution of kauri gum and n-butanol) and aniline point (the minimal temperature for complete mixing of aniline with a petroleum solvent) are both indicators of solvency but kauri-butanol value is more commonly used in Europe and aniline point more commonly in the USA.

It is not surprising, then, that the same names may be used for solvents that are not identical, and that different classification systems or names may be more common in one industry or geographic region than another. 'White spirits', for example, is a common term in Europe but is seldom used in the USA. The vagaries in the names used for petroleum solvents, however, make it important that some physical/chemical properties be included in any discussion of their toxic effects.

 

Low Aromatic Solvents Production

Petroleum Solvents are volatile fractions derived from petroleum and are composed mainly of paraffinic, naphthenic and aromatic hydrocarbons in varying proportions.

Petroleum Solvents are usually clear and water-white, apart from a few exceptions which are yellowish to brown in color, which are generally classified by the temperatures at which they start and finish boiling i.e. by their boiling ranges, and can be divided into three main categories;

 

SPECIAL BOILING POINT SPIRITS (S.B.P.s)

S.B.P.s may be narrow or wide boiling fractions, generally within the range 35°C and 160°C. They are fractionally distilled to specially selected distillation ranges and subsequently refined to enable a suitable grade to be chosen for any particular industrial purpose.

 

WHITE SPIRITS

They are fractions intermediate between motor spirit and kerosene, and boil within the range 140°C ~ 225°C. They are also known as Mineral Spirits, Petroleum Spirits, etc.

 

KEROSENE TYPE SOLVENTS

They have boiling range between 160°C to 300°C and have final boiling points above 220°C.

 

PURE AROMATICS

They are pure hydrocarbon compound and boil off at one temperature. Products like benzene, toluene and xylene fall under the above category.

 

PROCESS FLOW DESCRIPTION

To produce various solvent products in the variance with feedstock, two kinds of processes are involved.

One is distillation process for naphtha A, B, C, with each different boiling points, while the other MEROX sweetening process for HSR (Heavy Straight Run) naphtha.

 

ATMOSPHERIC DISTILLATION PROCESS

The feedstock is processed in two distillation units, where naphtha A is distilled in the one unit at the temperature ranging from 170°C to 180°C, while naphtha B, C heavier than naphtha A at around 350°C max. The simplified process flow diagram for the distillation of naphtha #A is shown in Figure 1.

The distillation process separates the major constituents of the naphtha into overhead, light and heavy and bottom product. Each column contains approx. 30 ~ 35 fractionation bubble cap trays, which is equipped with an overhead reflux system and three side heat exchangers/coolers for each cut stream.

The feed naphtha A is gradually preheated through heat exchangers in each cut stream prior to entering the distillation column. In the meantime, the bottom fraction is further heated in the reboiler, where its temperature is raised to the optimum temperature of the feed tray. The partially vaporized light fraction returns the column, while the heavy fraction flows into the bottom-cut storage tank through heat exchanger and cooler or the other distillation column as feedstock for re-distillation.

At each tray, vapors from below enter perforations under the bubble caps. The latter permit the vapors to bubble through the liquid on the tray, causing some condensation at the temperature of that tray. An over- flow pipe drains the condensed liquid from each tray back to the tray below, where the higher temperature causes re-evaporation. The evaporation and condensation is repeated until the desired degree of product purity is reached. Then side-cut streams from the certain trays are taken off to obtain desired fractions.

The light vapor from the overhead is condensed in an overhead condenser and enters an accumulator where the liquid is accumulated. Reflux pump draws liquid from the bottom of the accumulator and pumps part of the liquid back as a reflux to the distillation column. The balance of the liquid is sent to product storage tanks through the last after-cooler.

As side streams, the light-cut fraction and heavy-cut fraction are drawn from the tray at each part of the column and then flow to product storage tank through heat exchangers and coolers.

Figure 1. Process Flow Diagram (Solvent-Distillation Process)

 

Figure 1. Process Flow Diagram (Solvent-Distillation Process)

 

MEROX SWEETENING PROCESS

Since low molecular weight mercaptans are soluble in caustic soda (NaOH), when treating feedstock such as naphtha, it is feasible to remove these mercaptans by NaOH extraction.

The extraction reaction is shown by the following equation:

 R-SH + NaOH     ======>     NaS-R + H2O

Extraction equilibrium is favored by lower molecular weight mercaptans and lower temperatures. The rich caustic containing the extracted mercaptans in the form of mercaptides, is regenerated as shown in the equation given below:

4 NaS-R + O2 + H2O     ======>     2 RS-SR + 4 NaOH

MEROX sweetening involves the catalytic oxidation of mercaptans to disulfides in the presence of oxygen and alkalinity. Air provides the oxygen, and caustic provides the alkalinity.

Prior to flowing to the reactor, the feedstock is passed through a caustic pre-wash in order to reduce the naphthenic acid present in the HSR (Heavy Straight Run) naphtha. The Merox unit consists of a fixed-bed reactor followed by a caustic settler. Air, the source of oxygen, is injected into the feedstock upstream of the reactor. The mixture enters the top of the reactor and percolates downward through the catalyst bed.

The operating pressure is chosen to assure that the air required for sweetening is completely dissolved at the operating temperature. The sweetened H.S.R exits the reactor and flows to the reactor caustic settler.

The caustic settler contains a reservoir of caustic for use in keeping Merox catalyst alkaline. The caustic is periodically circulated over the reactor bed, while maintaining operations.

The H.S.R leaving the caustic settler passes through a water wash which removes traces of caustic as well as water soluble surfactants. Solvent product leaving the water wash flows to a sand filter containing a simple bed of coarse sand that is used to remove free water and a portion of the dissolved water from the product.

Figure 2. Process Flow Diagram (Solvent-Merox Process)

 

 

Different Grades of Low Aromatic Solvents

Some common grades of solvents are mentioned in the table 1. Each of them has got different usages in the relevant industry which some of them have been mentioned in the next section.

 

Table 1. Specification of some common Solvents

  TEST ITEMS

  TEST

METHOD

  Extraction Solvent

  Adhesive Solvent

  Rubber Solvent

  Cleaning

  Paint

  Rust Prevent Oil

Specific Gravity, 15°C/4°C

ASTM D 1298

064~0.66

067~0.70

070~0.72

073~0.77

077~0.81

0.80~0.83

Doctor Test

ASTM D 235

Negative

Negative

Negative

Negative

Negative

Negative

Reactive Test

ASTM D 1093

Neutral

Neutral

Neutral

Neutral

Neutral

Neutral

Copper Strip Corrosion 50°C, 3Hr

ASTM D 130

<1

<1

<1

<1

<1

<1

Color, Saybolt

ASTM D 156

30<

30<

30<

30<

27<

(+)0<

Aniline Point, °C

ASTM D 611

58<

58<

44~55

43~53

47~55

65<

Flash Point, TCC, °C

-

Report

Report

Report

Report

Report

90<

Distillation, °C

I.B.P

ASTM D 86

30<

40<

40<

80<

150<

220<

50%

<60

<80

<100

<120

<180

<245

E.P.

<90

<130

<150

<160

<210

<275

 

Low Aromatic Solvents Usages

The present day solvent market is on the order of 20 million metric tonnes (MMT) and worth tens of billions of US dollars annually to the global economy. European solvent production provides about one quarter of the worldwide market, with annual bio-based solvent use in the European Union projected to grow to over one MMT by 2020.  

 

Figure 3. Solvent uses in different industries

 

At present solvent use is dictated by two influencing factors: regulation (compulsory) and organizational preference (not necessarily enforced). Regulations control the use of certain solvents and permissible residues in final products. This is true in the plant extraction industry for foodstuffs, and in the pharmaceutical sector for example. Legislation has begun to rule out certain solvents from use completely because of environmental health and safety concerns. Benzene and carbon tetrachloride are two well-known examples of strongly regulated chemicals that were once popular solvents.  

Solvents already subject to restrictions include benzene in products for public use, cyclohexane in neoprene-based contact adhesives, dichloromethane in paint strippers, the glycols ethers ethylene glycol monomethyl ether and diethylene glycol monobutyl ether (applicable to specific paint products), toluene (not to be used in spray paints).

After regulations have defined the set of solvents that may be used from a legal perspective, individual organizations can establish their own preference for certain solvents based on green chemistry principles.  

 

Table 2. Applications of different grades of Solvents

EXTRACTION

SOLVENT

ADHESIVE

SOLVENT

RUBBER

SOLVENT

CLEANING

SOLVENT

PAINT &

THINNER

PAINT

SOLVENT

Aromatic &

Oil Extraction

Rubber Glue

Tire Industry

Textile Industry

Special Ink

Solvent

Paint Solvent/

Diluent

Fatty Acid

Extraction

Neoprene

Rubber

M/C Cleaning

Dry Cleaning

Aluminum

Rolling Oil

Ink Solvent/

Diluent

Dry Cleaning

Dilution Agent

Oil Diluent

Cold Cream

M/C & Metal

Cleaning

Phenol Resin

Solvent/Diluent

Precision M/C

Cleaning

Precision M/C

Cleaning

-

Dye Diluent

Cutting Oil

Base Material

Dry Cleaning

Solvent

-

Hi-Speed Drying

Paint Diluent

-

Paint Thinner

Asphalt Solvent

Insectside Base

Diluent

-

-

-

Precision M/C

Cleaning

-

M/C & Metal

Cleaning

-

-

-

-

-

Oil & Mineral Oil

Remover

 


Contact Us

Phone:+98 21 88 63 5592
Fax: +98 21 88 63 5568
Email: Info@mgtpetroil.com