HYDROGEN PEROXIDE

1.Introduction

Hydrogen peroxide is primarily used in bleaching textile fibers and wood pulp, various chemical processe and for manufacture of organic peroxides and perforate used in laundry detergens. Other minor uses include military applications, foam rubber, etching in electronic circuit boards, etc.

The chemical formula for hydrogen peroxide is H2O2 or more simply a water molecule H2O combined with an additional oxygen atom. It can be produced in any concentration up to 70%. The product is water-like in appearance.

2. Hydrogenation

In AO process, 2-ethylanthraquinone is hydrogenated in presence of a palladium catalyst and the anthrahydroquinone thus obtained is oxidized by oxygen from air to obtain hydrogen peroxide and 2-ethylanthraquinone. The hydrogen peroxide produced is the extracted with de-ionized water to produced crude hydrogen peroxide of 35%-40% w/w concentration.

2-ethylanthraquinone (2-EAQ) is a solid in the form of flakes. To circulate it through hydrogantion, oxidation and extraction stages a soltion is prepared using two main organic solvents. One is the SC-150, mixture of aromatic hydrocarbons (C9-C12 range) which dissolves the quinones and the other is the sextate, 2-methyl cyclohexyl acetate which dissolves the hydroquinone.

The solution obtained by dissolving 2-EAQ in SC-150 and sextate is called working solution (WSN).

During the cyclic hydrogenation and oxidation a small part of the 2-EAQ undergoes undesirable side reactions. Some products of the side reactions can be converted to quinones which yield hydrogen peroxide and the balance should be removed from the working solution periodically.

For this removal, part if the working solution is continously treated with caustic soda.

The crude peroxide produced is polished and can then either be concentrated and/or purified up to 70% in a distillation unit and/or stored in storage tanks. In the storage tanks, adjustments can be made to meet certain quality requirements, before filling in bulk containers or jerry cans.

3. Working Solution Preparation

The working solution is primarily composed os sextate (2-methylcyclohexylacetate), SC-150 (an aromatic solvent) and 2-ethylanthraquinone-based products. The EAQ is yellow organic solid that is subjected to chemical reactions during the operation. Sexttate is a clear, water-like organic liquid and primarily serves as a solvent for the reduced EAQ (EAQH2).

SC-150 is also a clear, water-like organic liquid. It reduces the density, viscosity and water solubility of the working soluition in addition to its solvent properties. These are desirable properties to facilitate recovery of hydrogen peroxide from the working solution in the extractor.

The working solution is prepared by first pumping SC-150 and sextate from barrels by solvent Drum Pump into the WSN preparation Tank. The mixture of solvents is heated and homogenized by WSN Preparation Tank Agitator before a specified amount of EAQ ia added.

Agitation is continued until all EAQ is dissolved. Then the working solution prepared by this procedure is transferred into the WSN treatment through the fresh WSN filter by the fresh WSN Transfer pump. For the first filling of the plant the fresh working solution can also be transferred into the WSN Storagre Tank.

4. Workintg Solution Preparation cont.

Solvent contaminated water from the solvent Recovery System and the Coalescer is collected in the Aqueous Draining Tank. Solvent overflow from the Crude Scrubbers and solvent from Wash tank Filter are also fed to this tank. The contonouos aqueous overflow from this vessel is drained to the organic Separation Sump.

The aqueous streams entering the Aqueous Draining tank may contain a small amount of solvents wich separate in the tank. The solvents collected form organic phase in the upper part of the vessel. The Organic phase is pumped by the the Aqueous Draining Transfer pump to the WSN preparation Tank. Solvent from the solvent Recovery System is collected in Reovered Solvent Tank. Water contaned in the solvent streams settles at the bottom of the Recovered Solvent Tank and is drained to the Organic Separation Sump from time to time. The solvents from the Recovered Solvent Tank can be transferred to the WSN Preparation Tank. The Recovered Solvent tank, the Filter Wash Tank or the Hydrogen Recycle Compressor by the Recovered Solvent Transfer Pump.

During normal plant operations, the solvents collected in Aqeous Draining tank, Recovered Solvent Tank and fresh Sextate make up can be used for dissolving 2-EAQ.

5. Working Storage

The WSN Storage Tank is teh starting point of the working solution cycle. Working Solution returning from the coalescer and the WSN treatment Return pump flows to this tank. During the first filling of the plant, fresh working solution is also fed to the WSN Storage through the fresh WSN Filter.

The working solution returning from the Coalescer also carrier some water into WSN Storage Tank. The phase water settles out at the bottom of the tank and flows to the Settler. It is drained from this tank from time to time and fed to the Organic Separation Sump.

Working solution above the water phase is drawn from the WSN Storage Tank and pumped by the Hydrogenation Feed Pump through the Oxidizer Economizer. In this heat exchanger the working solution is heated up by cooling down the hydrogenated working solution, thus recovering the heat of reaction produced in the hydrogenation.

A small side of the working solution returning from the oxidizer Economizer is taken from the line upstream the Hydrogenation Feed Heater and fed to working solution treatment in order to remove undesirable by-products.

6. Working Solution Storage cont.

The major part of the working solution flows through the Hydrogenation Feed Heater. This heat exchanger is required to heat up the working solution during start up of the plant. After passing through the Hydrogenation Feed Heater the working solution flows to the hydrogenation.

The degree of conversion of EAQ to EAQH2 in the Hydrogenation is very much depent on the temperature in the Hydrogenation and the quantity of catalyst suspended in the system. Fresh catalyst must be added to the Hydrogenation periodically to sustain the desired rate of reaction. This is done by means of the Catalyst Addition Chamber that is tied into the main working soluiton line leading to the Hydrogenation via bypass valve arrangement. It is therefore possible to divert a part of the working solution flow through this vessel. This working solution the transfers as known amount of catalyst that has been placed in this chamber into Hydrogenation.

7. Working Soluiton Treatment.

During the repeated hydrogenation and oxidation cycles side reactions accur in the working solution which results in formation of inert materials and other undesirable by-products.

Working Solution Treatment cont.

therefore, the overall economics of the process is very much dependent on the conversion of these back into compounds capable of producing hydrogen peroxide through s unit call Working Solution Treatment. Also a small part of the degraded compounds which cannot be reconverted to useful compounds is discarded.

partial removal of the by-products is accomplished by heating up mixture of oxidized and reduced working solution and subjecting this mixture to a treatment with caustic soda. Hydrogenated working solution from safety Filter.......