Catalytic reforming cracking chemistry chemical process. Catalysts include zeolite, aluminum hydrosilicate, bauxite and silicaalumina. Chemistry before describing the reaction chemistry of the catalytic reforming process as used in petroleum refineries, the typical naphthas used as catalytic reforming feedstocks will be discussed. However, safety concerns by many teachers and availability of equipment in some schools mean that this key and interesting experiment is often done as a demonstration. Dehydrogenation, an important component of reforming, is a strongly endothermic reaction, and as such, requires the reactor vessel to be externally heated. Cracking is the process of breaking higher hydrocarbons into lower hydrocarbons. Therefore, an upstream hydrotreater lowers the sulfur content of reformer feeds to cracking larger hydrocarbons to produce smaller alkanes that can be converted into petrol. The blend of sophisticated straight chain, branched, and aromatic hydrocarbons is precise dependent on the temp etc. Cracking, in petroleum refining, the process by which heavy hydrocarbon molecules are broken up into lighter molecules by means of heat and usually pressure. Thus, from the chemistry of the thermal decomposition of pure compounds and assuming little or no interference from other molecular species in the reaction mixture, predictions can be made of the product types that arise from the thermal cracking of various feedstocks. Thermal cracking produces shorter straight chain alkanes from longer straight chains found in gas oils or other crude oil fractions. Methane steam reforming is a chemical process to produce hydrogen and synthesis gas mixture by combination of steam and methane in a reformer at appropriate temperature and pressure in presence of suitable metalbased catalysts 4.
Thermal cracking is the process of breaking down large compounds into small compounds at high temperatures and high pressures. Chemistry of catalytic reforming the important reactions figure 4 which ocelli. Before describing the reaction chemistry of the catalytic reforming process as used in petroleum refineries, the typical naphthas used as catalytic reforming feedstocks will be discussed. In chemistry, it is a process of breaking down large alkane into simpler alkenes and alkanes. Due to the presence of the hydrocarbon atoms present in the fossil fuels, the importance is really beneficial for the people who work in the. Oil, and the gases associated with it, consists of a mixture of hundreds of different hydrocarbons.
Cracking is the name given to breaking up large hydrocarbon molecules into smaller and more useful bits. Doc browns advanced a level organic chemistry revision notes. Catalytic reforming wikimili, the free encyclopedia. Model the industrial process of cracking larger hydrocarbons to produce smaller alkanes that can be converted into petrol. Petroleum cracking, reforming of hydrocarbon chemical pedia. Comparative assessment of catalytic partial oxidation and. Photo courtesy phillips petroleum company catalysts used in catalytic cracking or reforming. Thermal cracking also known as steam cracking, is used for manufacture of ethylene. In chemistry terms, cracking is a process in which complicated organic molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules e. These are treated in several ways including cracking, isomerisation and reforming. In reforming or aromatisation, cyclic and acyclic alkanes containing six to eight carbon atoms are heated at.
As chemistry aqa cracking alkanes teaching resources. As nouns the difference between cracking and reforming is that cracking is chemistry the thermal decomposition of a substance, especially that of crude petroleum in order to produce petrol gasoline while reforming is chemistry a catalytic process, whereby shortchain molecules are combined to make larger ones. This section of revision science covers getting hydrocarbons from oil. The most important product is currently the gasoline fraction c5c12, but its only 19% of the crude oil. Sep 27, 2017 what is the difference between catalytic cracking and catalytic reforming comparison of key differences. Cracking chemistry simple english wikipedia, the free. Chemical processing how oil refining works science. I did take several chemistry classes and had a small lab set up in my bedroom as a child.
Cracking, as the name suggests, is a process in which large hydrocarbon molecules are broken down into smaller and more useful ones, for example. Chemguide is a free resource for chemistry learning at school level for 11 and 12. What is difference between reforming and cracking answers. What is the difference between catalytic cracking and. Many industrial chemical processes are taught as distinct contrasting reactions when in fact the unifying comparisons are greater than the contrasts. Catalytic cracking of a polyolefin mixture over different.
Cracking and reforming effectively increase the gasoline yield from 19% to 47%. Cracking is the process of breaking longer chained alkanes down into smaller alkanes and alkenes, sometimes for polymer manufacture, and sometimes to improve octane number. Cracking is the most important process for the commercial production of gasoline and diesel fuel. First, crack the vapour of liquid paraffin by passing it over a heated catalyst to produce and collect a mixture of gaseous shortchain hydrocarbons. Petrol and other fuels are produced from it using fractional distillation. How fast the cracking process is and how long it takes for the end products to form are very dependent on the temperature and any existing catalysts.
Catalytic reforming is a chemical process used to convert petroleum refinery. The highest activities were obtained over hmcm41, nhzsm5 zeolite, with nanometer crystal size, and hbeta zeolite. The hydrocracking of paraffins into smaller molecules as exemplified by the cracking of normal heptane into isopentane and. Covers thermal and catalytic cracking, ppt file, application questions, answers and an assessed homework activity with mark scheme. Catalytic cracking is when you take a longer organic molecule and break it down into smaller more us. The process forms a higher proportion of branched and cyclic hydrocarbons than thermal cracking see also reforming and.
Isomerisation, reforming and cracking the student room. Chemical processing how oil refining works howstuffworks. But i fail to see how reforming and isomerisation are different, they are both just taking straight chain alkanes, heating them in the presence of a cataylst and product is formed. A microscale experiment, cracking the hydrocarbons in paraffin to form shorter alkanes and alkenes.
Catalytic uses a catalyst to speed up the cracking reaction. Steam hydrocarbon cracking and reforming journal of chemical. Petrol and other fuels are produced from it using fractional distillation and cracking. Cracking is generally employed for the production of good quality gasoline, from heavier fractions of petroleum.
Start studying chapter 5 chemistry homework connect. In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or longchain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon carbon bonds in the precursors. What are the differences between reforming and cracking in. Compared to thermal cracking, catalytic cracking occurs at lower temperatures and pressures, is more selective and flexible, and incorporates a catalyst. Catalytic reforming is a chemical process used to convert petroleum. The process is frequently applied to lowquality gasoline stocks to improve their combustion characteristics. The reforming reactions produce large quantities of hydrogen, and one should remember that the dehydrogenation catalysts used in reforming can also catalyze hydrogenation and hydrocracking of aromatics during catalytic reforming. Catalytic cracking and catalytic reforming are two processes used in the conversion of crude oil into useful products. In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby. Cracking is used to convert long alkanes into shorter, more useful hydrocarbons. It may be performed in three ways, thermal cracking, catalytic cracking and steam cracking. Steam hydrocarbon cracking and reforming journal of. This is all in reference to the petroleum industry.
Thermal reforming alters the properties of lowgrade naphthas by converting. Catalytic cracking is the breakdown of large compounds into small hydrocarbons using an acid catalyst. Catalytic cracking processes have evolved over the years, and are an exemplary display of che. The process of breaking higher hydrocarbons with high boiling points into a variety of lower. We depend largely on crude, the gases associated with it and natural gas mainly methane as the source of liquid fuels petrol, diesel and the feedstock for the chemical industry. Thermal reforming alters the properties of lowgrade.
The rate of cracking and the end products are strongly dependent on the temperature and presence of catalysts. We also look at alkenes and how we test for alkenes using bromine water. Cracking and reforming of petroleum how to increase octane. Cracking of hydrocarbons is illustrated in the below diagram. This type of cracking is referred to as catalytic cracking. Cracking chemistry wikimili, the best wikipedia reader. This doesnt satisfy the demand for gasoline, and therefore two process are employed that increase the yield of gasoline from every barrel of crude oil, cracking and reforming. The general categories of the desired reactions in catalytic reforming are identified in list below, along with the catalysts used in the process. In general, each reforming stage is characterized by one or more reforming reactor vessels, each containing a catalyst and maintained at reforming reaction conditions. Hydrogen production via the catalytic cracking of ethane over nisio2 catalysts. Cracking meaning types of cracking organic chemistry.
Graded with a video link and mark schemes for everything. Reforming is a process of conversion of straight alkanes into ring moleculescycloalkanes and arenes. The first thermal cracking process for breaking up large nonvolatile hydrocarbons into gasoline came into use in 19. All but the hydrocracking reaction releases hydrogen which can be used in the. Oct 24, 2019 the sensitivity of catalytic reforming to contamination by sulfur and nitrogen requires hydrotreating the naphtha before it enters the reformer, adding to the cost and complexity of the process. Cracking hydrocarbons on a microscale resource rsc. Catalytic reforming catalysts catalytic reforming catalysts contain highly dispersed platinum pt, the activity of which is inhibited by sulfur. Cracking hydrocarbons in liquid paraffin with a catalyst.
In petroleum refining, this process is used in the production of petrol, diesel, and gasoline. Catalyst, catalytic cracking, catalytic reforming, fluid catalytic cracking, hydrocracking, isoparaffins, naphtha, octane number, paraffin, reformate products. Catalytic reforming an overview sciencedirect topics. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Cracking, in petroleum refining, the process by which heavy hydrocarbon molecules are broken up into lighter molecules by means of heat and usually pressure and sometimes catalysts. Cracking and reforming of petroleum how to increase. The process of breaking higher hydrocarbons with high boiling points into a variety of lower hydrocarbons that are more volatile low boiling, is called cracking or pyrolysis. Catalytic cracking is the breakdown of large hydrocarbon compounds into small hydrocarbon molecules with the use of moderate temperatures and pressures in the presence of catalysts. Main difference catalytic cracking vs catalytic reforming. Catalytic reforming and isomerization the demand of todays automobiles for highoctane gasolines has stimulated the use of catalytic reforming in catalytic reforming, the change in the boiling point of the stock passed through the unit is relatively small as the hydrocarbon molecular structures are rearranged to form higheroctane aromatics with only a minor amount of cracking. Difference between catalytic cracking and catalytic reforming. Cracking and related refinery processes the essential chemical.
Difference between thermal cracking and catalytic cracking. Crude oil cracking reforming and isomerisation youtube. A petroleum refinery includes many unit operations and unit processes. Nov 14, 2017 in this video, we look at how cracking is used to convert longchain hydrocarbons into shorterchain hydrocarbons.
First i will state that i am not a professional chemist. Difference between thermal cracking and catalytic cracking definition. This is achieved by using high pressures and temperatures without a catalyst, or lower temperatures and pressures in the presence of a catalyst. The refining of crude oil requires separation, distillation, reforming, cracking and related processes to resolve the mixture of components into products.
This lecture explains about cracking of petroleum and its types such as thermal, catalytic and steam cracking and then it discusses about reforming and how can we increase octane number in. Year 12 lesson graded outstanding to teach cracking. Cracking and alkenes crude oil, hydrocarbons and alkanes. Because of the free radical chemistry, thermal cracking of gas oil would produce gasoline with relatively low octane numbers, as will be discussed later in this section. A multistage reforming process comprises the passage of a refinery stream through at least two reforming stages in series 24. Cracking cracking is the breaking down of an unsaturated hydrocarbon into smaller hydrocarbons. Many industrial chemical processes are taught as distinct contrasting reactions when in fact the unifying comparisons are greater than the. Reforming, in chemistry, processing technique by which the molecular structure of a hydrocarbon is rearranged to alter its properties.
Reforming involves the conversion of open chain hydrocarbons and cycloalkanes in the presence of a catalyst to aromatic hydrocarbons. We examine steam hydrocarbon reforming and steam hydrocarbon cracking as an example of two processes that operate under different chemical reactivity regimes. One family of hydrocarbons produced from crude oil is called the alkanes. Aqa alevel chemistry fractional distillation and cracking duration. Crude oil cracking reforming and isomerisation machemguy. Reforming takes straight chain hydrocarbons in the c 6 to c 8 range from the gasoline or naphtha fractions and rearranges them into compounds containing benzene rings. Typical naphtha feedstocks a petroleum refinery includes many unit processes and unit operations. Cracking the hydrocarbons in paraffin to form shorter alkanes and alkenes can be done as a class practical. The high surface area and large pores present in hmcm41 are responsible for the high.
This lecture explains about cracking of petroleum and its types such as thermal, catalytic and steam cracking and then it discusses about reforming and how c. Considering that the main purpose of the process is to increase the octane number of heavy naphtha, conversion of naphthenes to aromatics and isomerization of. Free radicals reactive species with unpaired electrons, but no electronic charge are the active species that govern thermal cracking reactions. Hydrocracking reaction an overview sciencedirect topics. The major unification process is called catalytic reforming and uses a catalyst platinum, platinumrhenium mix to combine low weight naphtha into aromatics, which are used in making chemicals and in blending gasoline. Hydrogen is produced as a byproduct of the reactions. In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or longchain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carboncarbon bonds in the precursors. In context chemistry langen terms the difference between cracking and reforming is that cracking is chemistry the thermal decomposition of a substance, especially that of crude petroleum in order to produce petrol gasoline while reforming is chemistry a catalytic process, whereby shortchain molecules are combined to make larger ones.
Methane steam reforming an overview sciencedirect topics. Reforming definition, the process of cracking lowoctane petroleum fractions in order to increase the octane number. We dont have to tell you how tough sat chemistry isor how helpful a stellar exam score can be for your chances of getting into your topchoice college. Reforming definition of reforming by the free dictionary. The cracking products, such as ethene, propene, buta1,3diene and c 4 alkenes, are used to make many important chemicals.
436 1344 822 493 1526 984 616 1289 1520 1327 805 1311 1267 405 685 1463 976 145 205 1465 729 486 1140 776 1441 1184 345 699 1266 136 858 1437 1111 100 418 1425 919 695 1068 1364