Sulfuric acid process, production

Product removal during reaction. Separation of the product before completion of the reaction can force a higher conversion, as discussed in Chap. 2. Figure 2.4 showed how this is done in sulfuric acid processes. Sometimes the product (or one of the products) can be removed continuously from the reactor as the reaction progresses, e.g., by allowing it to vaporize from a liquid phase reactor. 

Citric Acid Separation. Citric acid [77-92-9] and other organic acids can be recovered from fermentation broths usiag the UOP Sorbex technology (90—92). The conventional means of recovering citric acid is by a lime and sulfuric acid process ia which the citric acid is first precipitated as a calcium salt and then reacidulated with sulfuric acid. However, this process generates significant by-products and thus can become iaefficient. 

Processes for Triacetate. There are both batch and continuous process for triacetate. Many of the considerations and support faciUties for producing acetate apply to triacetate however, no acetyl hydrolysis is required. In the batch triacetate sulfuric acid process, however, a sulfate hydrolysis step (or desulfonation) is necessary. This is carried out by slow addition of a dilute aqueous acetic acid solution containing sodium or magnesium acetate (44,45) or triethanolamine (46) to neutrali2e the Hberated sulfuric acid. The cellulose triacetate product has a combined acetic acid content of 61.5%. 

Because of restrictions in equipment si2e, magnesium nitrate processes were initially limited to small plants. Improvements in the materials of constmction have led to increased capacities and a lower capital cost. Sulfuric acid processes are usually preferred when reconcentration of the sulfuric acid is not requited, ie, when the dilute sulfuric can be used to make another product. 

The reduction ia tetraethyl lead for gasoline production is expected to iacrease the demand for petroleum alkylate both ia the U.S. and abroad. Alkylate producers have a choice of either a hydrofluoric acid or sulfuric acid process. Both processes are widely used. However, concerns over the safety or potential regulation of hydrofluoric acid seem likely to convince more refiners to use the sulfuric acid process for future alkylate capacity. 

Isopropyl Ether. Isopropyl ether is manufactured by the dehydration of isopropyl alcohol with sulfuric acid. It is obtained in large quantities as a by-product in the manufacture of isopropyl alcohol from propylene by the sulfuric acid process, very similar to the production of ethyl ether from ethylene. Isopropyl ether is of moderate importance as an industrial solvent, since its boiling point Hes between that of ethyl ether and acetone. Isopropyl ether very readily forms hazardous peroxides and hydroperoxides, much more so than other ethers. However, this tendency can be controlled with commercial antioxidant additives. Therefore, it is also being promoted as another possible ether to be used in gasoline (33). 

Nitric acid, or aqua fortis as it was called in medieval times, has been known and used by mankind for centuries. At first, it was produced by heating a mixture of sodium nitrate (Chile saltpeter) and sulfuric acid. The product obtained was sodium hydrogen sulfate, and the nitric acid vapors escaping during this process were condensed ... 

Another improvement (less by-products) has been made over the fuming sulfuric acid process operated commercially for the hydrolysis of 2-perfluoroal-kylethyl iodides. It entails the use of sulfur trioxide in liquid sulfur dioxide [52, 5J (equation 52). 

Mathieson (1) A process for making chlorine dioxide gas by passing sulfur dioxide, diluted with air, into aqueous sodium chlorate and sulfuric acid. The product is absorbed in water. Operated in the United States on a large scale for pulp-bleaching. 

Stratco A process for making a high-octane gasoline component by alkylation of C3 - C5 hydrocarbons with isobutane, catalyzed by sulfuric acid. The product is known as an alkylate. Operated in several oil refineries in the United States. 

This step is essential in the manufacture of detergent active ingredients as it converts the sulfonic acids or sulfuric acid esters (products produced by processes I-M) into neutral surfactants. It is a potential source of some oil and grease, but occasional leaks and spills around the pump and valves are the only expected source of wastewater contamination. A process flow diagram is shown in Figure 14. 

Wet Process Phosphoric Acid. A production process flow diagram is shown in Figure 8. Insoluble phosphate rock is changed to water-soluble phosphoric acid by solubilizing the phosphate rock with an acid, generally sulfuric or nitric. The phosphoric acid produced from the nitric acid process is blended with other ingredients to produce a fertilizer, whereas the phosphoric acid produced from the sulfuric acid process must be concentrated before further use. Minor quantities of fluorine, iron, aluminum, sUica, and uranium are usually the most serious waste effluent problems. 

One liter of water is added to the mixture then the precipitate is separated by suction filtration, pressed on the funnel, and washed with about 500 ml. of water. The product is transferred to a beaker, stirred well with about 500 ml. of cold water, then filtered and washed again on the funnel. This process is again repeated if necessary to remove the odor of acetic acid. After drying to constant weight in a vacuum desiccator over sulfuric acid, the product melts in the range between 55° and 60° (Note 8). The yield is 306-324 g. (85-90%) (Notes 9 and 10). 

Catalytic oxidation of ammonia to nitric oxide is the basis of production of nitric acid. It is also used in other processes, of which may be mentioned hydroxylamine synthesis (Section XIII) and the chamber process for the production of sulfuric acid. The products of the reaction are nitric oxide, water, and nitrogen, so that the reaction can be described by the equation... 

Sulfuric acid (3) has been used in the past as a polymerization catalyst both in the Cold Sulfuric Acid Process and the Hot-Acid Polymerization Process. Its main utility today lies in its use for selectively absorbing isobutylene from mixed butane-butylene streams for use in the production of synthetic rubber. The products are a di-isobutylene polymer and a butane-normal butylene mixture. The di-isobutylene is also used to a small extent by the chemical industry. 

Figure 12. Production cost vs. process efficiency for hybrid sulfuric acid process...

Knoche, K.F. and Funk, J.E., "Entropy Production, Efficiency, and Economics in the Thermochemical Generation of Synthetic Fuels. I. The Hybrid Sulfuric Acid Process, Int. J. Hydrogen Energy 2, No. 4, 377-386 (1977). 

The basic steps in the contact process are (1) production of sulfur dioxide (2) cooling and, for smelters, cleaning of the process gas (3) conversion of the sulfur dioxide to sulfur trioxide (4) cooling of the sulfur trioxide gas and (5) absorption of the sulfur trioxide in sulfuric acid.28 Figure 25.8 is a photograph of a contact process plant. A simplified diagram of a double absorption contact sulfuric acid process is shown in Fig. 25.9. Because sulfur dioxide is produced by several processes, it is convenient to separate the discussion of sulfur dioxide production from its conversion to sulfuric acid. 

Although the majority of early alkylation units used sulfuric acid as a catalyst, there has been a trend over recent years in favor of the hydrofluoric (HF) process. Today, the installed capacity of each process is roughly the same. The HF alkylation process is offered by two licensors, Universal Oil Products and Phillips Petroleum. The reaction is carried out at temperatures between 75 and 115°F, which is considerably higher than the sulfuric acid process. 

---