Alkylation sulfuric acid catalyst

A multitude of 1,4-dicarbonyls (1) undergo the Paal-Knorr reaction with and ranging from H to alkyl, aryl, carbonyl, nitrile, and phosphonate, while R and R vary between H, alkyl, aryl, trialkylsilyl, and O-alkyl. Protic acid catalysts are typically used with sulfuric, hydrochloric, and p-toluenesulfonic acids the most popular. Conversion to the furan takes place either at room temperature or upon heating with reaction times varying from five minutes to 24 hours and yields ranging from 17-100%. 

Figure 4.11. Alkylation unit (sulfuric acid catalyst).

Such reactions can take place predominantly in either the continuous or disperse phase or in both phases or mainly at the interface. Mutual solubilities, distribution coefficients, and the amount of interfadal surface are factors that determine the overall rate of conversion. Stirred tanks with power inputs of 5-10 HP/1000 gal or extraction-type equipment of various kinds are used to enhance mass transfer. Horizontal TFRs usually are impractical unless sufficiently stable emulsions can be formed, but mixing baffles at intervals are helpful if there are strong reasons for using such equipment. Multistage stirred chambers in a single shell are used for example in butene-isobutane alkylation with sulfuric acid catalyst. Other liquid-liquid processes listed in Table 17.1 are numbers 8, 27, 45, 78, and 90. 

In the production of aviation and motor alkylates, both propylene and amylenes are inferior feed stocks when compared with the butylenes. These feeds produce lighter and heavier alkylates, respectively, than the butylenes, both alkylates having a lower octane than the trimethylpentane produced from butylenes. Also, acid consumption when sulfuric acid catalyst is used is two or more times as great with propylene or amylenes than with butylenes. Hydrofluoric acid catalyst, on the other hand, is not consumed at a higher rate on propylene and amylene feeds but does make a higher percentage of tar. 

The newer Alkylation units are designed to produce octane numbers of 98 F-l clear and 111 F-l with 3 cc TEL. This is the case with both hydrofluoric and sulfuric acid catalysts. When operating to make these high octanes, the acid consumptions are down considerably. On these units, acid consumptions have been obtained as low as 0.3 lbs. H2S04 per gallon of alkylate and 0.1 lbs. HF per barrel of alkylate. Also, the production of heavy alkylate is considerably reduced, the Engler end point being as low as 350°F. on the total alkylate produced. 

The sulfuric acid alkylation process for making aviation or motor gasoline from isobutane and olefins from cracked gases requires a relatively high isobutane-to-olefin ratio in the reaction zone to insure high octanes, good yields, and low polymer formation in the acid. The sulfuric acid catalyst can make use not only of the relatively pure external isobutane... 

Because of the relatively high normal butane tolerance in HF units, all of the recycle isobutane can be made from the effluent stream with little rectification. The purity of the recycle under these conditions is 75 to 85 % isobutane. Even though such a relatively impure external isobutane recycle can be used without appreciably lowering the quality of the alkylate, an increase in the internal isobutane-to-olefin ratio does not improve the quality as is the case with sulfuric acid catalyst. When the external isobutane recycle is charged to the first of a series of reaction zones and the olefinic feed is divided between the individual reaction zones, there is no apparent improvement in quality. This indicates that any increase in the isobutane-to-olefin ratio over and above the external ratio which may be... 

Alkylation is usually used to increase performance of a product and involves the conversion of, for example, an amine to its alkylated homologs as in the reaction of aniline with methyl alcohol in the presence of sulfuric acid catalyst ... 

Two previous studies (Moser et al., 2007, 2006) explored the effects of synthetic compounds with hydrocarbon tail-group structures resembling those of FAME with attached bulky moieties on the CP and PP of SME. These studies examined novel fatty ethers made from the reaction of various alcohols (C2—Cm) with epoxidized alkyl oleates in the presence of sulfuric acid catalyst. Bulky esters (isopropyl and isobutyl) were chosen to further enhance the low temperature fluidity of the synthetic adducts produced. As the chain length of the ether moiety attached to the fatty backbone increased in length, a corresponding improvement in low temperature performance was noticed. Although the materials had improved low temperature properties over that of neat SME, none of the synthesized compounds demonstrated effectiveness in decreasing CP or PP when added to SME. 

This discussion is aimed primarily at alkylation processes, which are characterized by two-phase emulsions. The traditional process includes a hydrocarbon phase in contact with a sulfuric acid catalyst to form the environment for proper alkylation. In the petroleum industry, the desired product is a high octane alka-late, but other alklation processes have other desired products. 

In making all operating and design decisions. It Is Important to keep in mind the definition of the true reaction zone. Fundamentally, this Is the Interfaclal area between the immiscible hydrocarbon and acid catalyst liquid phases in the reactor. Reactants and products flow across this boundary. The olefins In the feed stream react Instantaneously with the sulfuric acid catalyst and combine with the relatively small amount of isobutane present In solution In the acid catalyst to form alkylate. Alkylate passes out through the Interfaclal surface reaction boundary into the hydrocarbon phase while Isobutane passes in to resaturate the catalyst. To suppress undesirable polymerization and other reactions It Is necessary to ... 

Relatively low temperatures are required in alkylation reactors using sulfuric acid catalyst. They are necessary in order to slow down polymerization reactions and reduce the formation of undesirable acid soluble and hydrocarbon soluble by-products. Typically, most commercial units operate with reaction temperatures in the range of 35 F. to 65 F. Design temperatures are usually set at 50 F. For minimum acid make-up the reactor section should be operated as cold as possible. This means operating... 

In the early days, in the late 1930 s and early 1940 s, of the alkylation of isobutane with olefins using a sulfuric acid catalyst, the acid catalyst was low in cost, the production of alkylate was limited, and the discarded or used catalyst could be used in other processes, such as naphtha and lube oil treating... 

Since the hydrocarbons or conjunct polymers in the used sulfuric acid catalyst are unsaturated, attempts have been made to hydrogenate the catalyst in an effort to saturate the polymers, and thus make them insoluble in the acid. Attempts have also been made to conduct the alkylation under hydrogen pressure. 

The acid charge to the absorber is the used sulfuric acid catalyst from the alkylation settler. It usually is of about 90% titratable acidity with about 3-5% water and 3-6% conjunct polymer. The alkylation catalyst is no longer active as an alkylation catalyst when the acidity drops to about 80% due to the pick up of conjunct polymer and alkyl sulfates. However, it is still active for the absorption of propylene until substantially all of the acid is converted to alkyl sulfates. Since the formation of alkyl sulfates from olefins and sulfuric acid are equilibrium reactions, conditions should be used which will shift the equilibrium to the right, or to the dialkyl sulfate, with minimum formation of alkyl acid sulfate. 

Alkylation of isobutaine vdth olefin Is accomplished by the carbonlum Ion mechanism when the sulfuric acid catalyst purity is maintained at a high level — generally above 90-92 tltratable acidity. At lower concentrations olefin polymerization to the dimer is accelerated and alkylation to tri-rnethy1-pentanes retarded. Alkylate product quality is effected. 

Some normal butane is also produced from butylenes but this is estimated at only 4-6%. The higher octane isobutylene alkylate and a claimed yield increase must be contrasted with normal paraffin production from olefins and a higher isobutane requirement. The typical mixed 03 = 704= feed can be made to produce a high octane alkylate with either acid catalyst by the optimization of other variables. The highest alkylate octane numbers reported are produced with sulfuric acid catalyst, alkylating with a typical cat cracker butylene olefin. 

Supplemental processes which can be operated in conjunction with alkylation and/or sulfuric acid production can influence the overall economics. Examples are (1) the integration of normal butane-to-isobutane isomerization with alkylation, utilizing common fractionation equipment and (2), utilizing 65% sulfuric acid extraction of isobutylene or isoamylene from olefins fed to alkylation, justified by monetary return on sale of the high purity iso-olefin as a petrochemical feedstock, which reduces quantity of alkylate produced and reduces isobutane required while producing still higher quality alkylate with sulfuric acid catalyst. 

Alkyl esters are formed by addition of the hydrogen halide promoter used with aluminum halide or of hydrogen fluoride or sulfuric acid catalyst to the olefin. Their formation is also inherent in the reaction of the second step of the chain mechanism. If conditions are not favorable for the reaction of these esters with the isoparaffin (by the reaction of step 1 or step 3), the esters are obtained as impurities in the alkylate. In general, they are produced under the same conditions which led to polymerization rather than alkylation. Usually very little ester is presnt in the alkylation product. 

In the formation of ether and water, or of ethylene and water from alcohol and sulfuric acid, or the reverse reactions, sulfuric acid plays the part of the catalyst, and the intermediate addition compound may be represented by alkyl sulfuric acid, RSO4H, or a hydrate of it. 

Yields for several alcohols were determined for the reaction of particle board at 190°C for 40 min reaction time (2% sulfuric acid catalyst). The results for the various alcohols are given in Table II. Methanol and ethanol are essentially equivalent in forming the alkyl levulinate on a weight percent basis. For longer-chain alcohols, the yields drop off substantially with size. In the case of the aminoethanol, methoxyethanol, and hexanol, the solid material is recovered as brown granules and cannot be dried easily. No alkyl levulinate is found in the solvent phase. By comparison with water as the solvent, the charcoal yield was 46 wt% and the levulinic acid was 18% as determined by gas chromatography. 

Acetic anhydride adds to acetaldehyde in the presence of dilute acid to form ethyUdene diacetate [542-10-9], boron fluoride also catalyzes the reaction (78). Ethyfldene diacetate decomposes to the anhydride and aldehyde at temperatures of 220—268°C and initial pressures of 14.6—21.3 kPa (110—160 mm Hg) (79), or upon heating to 150°C in the presence of a zinc chloride catalyst (80). Acetone (qv) [67-64-1] has been prepared in 90% yield by heating an aqueous solution of acetaldehyde to 410°C in the presence of a catalyst (81). Active methylene groups condense acetaldehyde. The reaction of isobutfyene/715-11-7] and aqueous solutions of acetaldehyde in the presence of 1—2% sulfuric acid yields alkyl-y -dioxanes 2,4,4,6-tetramethyl-y -dioxane [5182-37-6] is produced in yields up to 90% (82). 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

The synthesis of 2,4-dihydroxyacetophenone [89-84-9] (21) by acylation reactions of resorcinol has been extensively studied. The reaction is performed using acetic anhydride (104), acetyl chloride (105), or acetic acid (106). The esterification of resorcinol by acetic anhydride followed by the isomerization of the diacetate intermediate has also been described in the presence of zinc chloride (107). Alkylation of resorcinol can be carried out using ethers (108), olefins (109), or alcohols (110). The catalysts which are generally used include sulfuric acid, phosphoric and polyphosphoric acids, acidic resins, or aluminum and iron derivatives. 2-Chlororesorcinol [6201-65-1] (22) is obtained by a sulfonation—chloration—desulfonation technique (111). 1,2,4-Trihydroxybenzene [533-73-3] (23) is obtained by hydroxylation of resorcinol using hydrogen peroxide (112) or peracids (113). 

In the presence of strong acid catalysts such as sulfuric acid, aUphatic (R CHO) aldehydes react with alkyl hydroperoxides, eg, tert-55ky hydroperoxides, to form hydroxyalkyl alkyl peroxides (1), where X = OH R, = hydrogen, alkyl and = tert — alkyl. 

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