Journal of Petroleum & Environmental Biotechnology

Isomerization and Effect of Temperature on Alkanes Utilized by Refiners

Fei He^* Department of Petroleum Engineering, Northeast Petroleum University, Heilongjiang, China
^*Correspondence: Fei He, Department of Petroleum Engineering, Northeast Petroleum University, Heilongjiang, China, Email:

Received: 02-May-2022, Manuscript No. JPEB-22-16778; Editor assigned: 06-May-2022, Pre QC No. JPEB-22-16778(PQ); Reviewed: 20-May-2022, QC No. JPEB-22-16778; Revised: 27-May-2022, Manuscript No. JPEB-22-16778(R); Published: 06-Jun-2022, DOI: 10.35248/2157-7463.22.13.464

Description

To make high-octane gasoline components from low-octane light naphtha fractions, modern refiners use the isomerization process. The majority of passenger cars in the world use gasoline as their primary fuel. Benzene, toluene, xylene, methyl benzene, normal and isomers of hexane, heptane, and octane are among the hydrocarbon chemicals found in petrol. The exhaust of a petrol car is considered to be harmful because it often contains unburned gasoline, which is a severe health threat. It becomes particularly hazardous when the exhaust contains benzene, and many nations have banned petrol containing more than 1.0 percent benzene. Because benzene is formed during the naphtha reforming process, the feed must be free of C₆ hydrocarbons, which could be a precursor for benzene production. Because C₆ hydrocarbons (alkane and naphthene) make up a large part of naphtha, removing them will dramatically lower petrol yield. Because the octane number of light alkanes increases with the degree of branching, alkane isomerization plays an important role. For example, n-hexane has a RON of only 31, whereas 2- methylpentane, 3-methylpentane, 2, 2-dimethylbutane, and 2, 3- dimethylbutane have RONs of 74, 76, 94, and 105 respectively. The efficiency of a hydrocarbon as a fuel ingredient improves as its octane number rises. Isomerase has low Sulphur and benzene content, making it an excellent blending component in refinery gasoline pools. The anti-knocking quality of a certain fuel or component is determined by the octane rating of the components used in the creation of various commercial gasoline types. Octane is less essential in the case of butanes because the majority of isobutane is used to make motor fuel alkylates and oxygenates. The highest-octane values are seen in the most heavily branched isomers of C₅ and C₆ alkanes. Antiknock qualities are measured using two empirical octane measurement methods like (ASTM D 2699) and motor (ASTM D 2700). The average of these two figures is frequently used to indicate gasoline components or blends overall engine performance.

Isomerization of n-alkanes in a generalized process

Carbenium ions serve as important intermediates in the isomerization of n-alkanes. Carbenium ions are active not only in skeletal isomerization but also in unwanted side reactions that diminish selectivity for the intended isomers. The alkane isomerization mechanisms of acid and bifunctional catalysts are described for mono functional homogeneous acid catalysts and then for heterogeneous acid catalysts. Acid sites and metallic sites are present in bifunctional heterogeneous catalysts for skeletal isomerization and hydrogenation/dehydrogenation processes, respectively. The isomerization process of these bifunctional acidic catalysts on the acidic sites is similar to that of mono functional acidic catalysts.

Temperature effect on alkane isomerization

Alkane isomerization reactions are mildly exothermic. From a thermodynamic standpoint, low reaction temperatures favor the formation of highly branched isomers. Low temperatures prefer the desired highly branched isomers, while high temperatures are required to activate and convert the unreactive alkanes. The equilibrium of metal site reactions swings towards dehydrogenation as the temperature rises, resulting in coke production and poly-nuclear aromatics. Temperature increases, however, do not influence acid site equilibrium, but rather increase reaction rates. As a result, there must be an optimum temperature for isomer production, which must be determined before the working temperature is set. Unwanted olefins, coke, and poly nuclear aromatics may increase above this temperature. High hydrogen pressure is used to keep dehydrogenation at bay. More hydro-cracking will occur as a result of high temperature and pressure than isomerization. When all other variables are equal, the most active catalyst can produce the highest-octane products. Isomerization progress is frequently driven by the introduction of new, more active or stable catalysts. Isomerization reactions are usually reversible and reach equilibrium with the highest concentration of isomeric products at lower temperatures. As a result, the catalyst plays a crucial role in isomerization. At lower temperatures, the severity of undesired side reactions decreases, whereas higher temperatures enhance unwanted cracking, hydrogenation, and polymerization processes. As a result, isomerizing catalysts must offer the best possible reaction rate at the lowest feasible temperature.