Producción de propileno mediante craqueo con vaporDurante el proceso de craqueo con vapor de hidrocarburos (ver capítulo del Etileno), elpropileno se separa por destilación de la fracción C3, compuesta por propano, propilenoy otros componentes menores. En la torre C3, el propileno se separa por cabeza de lacolumna, mientras que por fondo se separa una mezcla rica en propano. El tamaño de lacolumna varía según el grado de pureza buscado para el propileno (el grado poliméricorequiere mayor número de platos).Producción de propileno en refineríaEn refinería, el propileno se obtiene principalmente como subproducto del craqueocatalítico en lecho fluido (FCC) de gasóleos. De nuevo, la producción depende deldestino al que se orienta la refinería (por ejemplo, las refinerías de Estados Unidos, másorientadas a maximizar la producción de gasolina, producen más propileno que las deEuropa).Dado que el propileno de refinería va acompañado de mayor proporción de propano (delorden de un 30 %, frente a un 8-10 % en el propileno de craqueo térmico), el gradoobtenido en general es inferior al correspondiente al propileno de craqueo con vapor.Las especificaciones del propileno son: grado refinería (50 – 70 % de pureza), gradoquímico (92 – 94 %), y grado polímero (> 99 %).

Rutas de producción isopropanol

La producción de propanol se realiza por vías de hidratación de propeno; una hidratación indirecta con ácido sulfúrico en fase liquida o por hidratación directa de la cual hay en fase liquida y fase gas

El primer proceso indirecto se usa muy poco al ser contaminante

Hidratación indirecta

Este proceso tiene lugar en fase liquida con diferentes concentraciones de acido sulfúrico y es un proceso de 2 etapas . primero se ponen en contacto el propeno y una solución ocncentrada de acido sulfúrico que forman un semiester de sulfato acido. Luego se diluyen para hidrlizar el ester y formar el alcohol en una solución del 40% de acido sulfúrico. La primer aetapa con acido concentrado traba con acido del 94% a 10-12 bares. También se puede usar un proceso con acido sulfúrico diluido de una sola etapa que trabaja con 70% de acido a 60-65 °C y 25 bares en un reactor mesclado con una flauta de burbujas por donde entra el propeno. Se obtienen selectividades del orden del 90% pero también baja conversión aunque mas alta que la de fase gaseosa

ISOPROPYL ALCOHOL3.1. Indirect HydrationIndirect hydration is based on a two-step reaction of propylene and sulfuric acid. In the first step, mixed sulfateesters, primarily isopropyl hydrogen sulfate, but also diisopropyl sulfate, form. These are then hydrolyzed,forming the alcohol and sulfuric acid.

3.1.1. By-ProductsDiisopropyl ether is the principal by-product formed by reaction of the intermediate sulfate esters with isopropylalcohol.

The principal reactions are reversible and a mixture of products and reactants is found in the crudesulfate. High propylene pressure, high sulfuric acid concentration, and low temperature shift the reactiontoward diisopropyl sulfate. However, the reaction rate slows as products are formed, and practical reactorsoperate by using excess sulfuric acid. As the water content in the sulfuric acid feed is increased, more of thehydrolysis reaction (Step 2) occurs in the main reactor. At water concentrations near 20%, diisopropyl sulfateis not found in the reaction mixture. However, efforts to separate the isopropyl alcohol from the sulfuric acidsuggest that it may be partially present in an ionic form (56, 57).

The principal reactions are reversible and a mixture of products and reactants is found in the crudesulfate. High propylene pressure, high sulfuric acid concentration, and low temperature shift the reactiontoward diisopropyl sulfate. However, the reaction rate slows as products are formed, and practical reactorsoperate by using excess sulfuric acid. As the water content in the sulfuric acid feed is increased, more of thehydrolysis reaction (Step 2) occurs in the main reactor. At water concentrations near 20%, diisopropyl sulfateis not found in the reaction mixture. However, efforts to separate the isopropyl alcohol from the sulfuric acidsuggest that it may be partially present in an ionic form (56, 57).

Other by-products include acetone, carbonaceous material, and polymers of propylene. Minor contaminantsarise from impurities in the feed. Ethylene and butylenes can form traces of ethyl alcohol and 2-butanol.Small amounts of n-propyl alcohol carried through into the refined isopropyl alcohol can originate from cyclopropane[75-19-4] in the propylene feed. Acetone, an oxidation product, also forms from thermal decompositionof the intermediate sulfate esters, eg,(CH3)2 CHOSO3H −h−e→at CH3COCH3 + SO2 + H2O

In addition to generating malodorous sulfur dioxide [7446-09-5], the acetone formed can undergo furthercondensation in the acidic medium to generate mesityl oxide [141-79-7], (CH3)2C CHCOCH3, and higherproducts.High propylene concentrations in the presence of acids can form dimers, trimers, and higher homologues,which can polymerize or hydrate to C6, C9, or higher alcohols, and olefins. These derivatives can emit musty,woody, and camphoraceous odors, and their reaction products with sulfur-containing compounds can give acat-like odor to the product (58). Odor can be improved by employing appropriate reaction conditions and bycontacting isopropyl alcohol with various metals, eg, copper and nickel, or certain partially reduced metaloxides (59, 60).

ProcessA typical indirect hydration process is presented in Figure 1. In the process, propylene reacts with sulfuric acid(>60 wt%) in agitated reactors or absorbers at moderate (0.7–2.8 MPa (100–400 psig)) pressure. The isopropylsulfate esters form and are maintained in the liquid state at 20–80◦C. Low propylene concentrations, ie, 50wt %, can be tolerated, but concentrations of 65 wt % or higher are preferred to achieve high alcohol yields.Because the reaction is exothermic, internal cooling coils or external heat exchangers are used to control thetemperature.There are two general operational modes for conducting the reaction. In the two-step strong acid process,

separate reactors are used for the propylene absorption and sulfate ester hydrolysis stages. The reaction occursat high sulfuric acid concentration (>80 wt%), at 1–1.2 MPa (130–160 psig) pressure, and low (eg, 20–30◦C)temperature. The weak acid process is conducted in a single stage at low acid (60–80 wt %) concentration andat higher (2.5 MPa (350 psig)) pressure and (60–65◦C) temperature. Chemical selectivity to isopropyl alcoholand diisopropyl ether are above 98% for each process.The sulfate ester hydrolysate is stripped to give a mixture of isopropyl alcohol, isopropyl ether, and wateroverhead, and dilute sulfuric acid bottoms. The overhead is neutralized using sodium hydroxide and refinedin a two-column distillation system. Diisopropyl ether is taken overhead in the first, ie, ether, column. Thisstream is generally recycled to the reactors to produce additional isopropyl alcohol by the following equilibriumreaction:((CH3)2 CH)2O+H2SO4

−−−→←−−− (CH3)2 CHOSO3H+(CH3)2 CHOHWet isopropyl alcohol (87 wt % and 91 vol %) is taken overhead in the second still. More than 93% of thecharged propylene is converted to isopropyl alcohol in this system. If available, a propylene column mayrecover unreacted feedstock.The bottoms from the stripper (40–60 wt % acid) are sent to an acid reconcentration unit for upgradingto the proper acid strength and recycling to the reactor. Because of the associated high energy requirements,reconcentration of the diluted sulfuric acid is a costly operation. However, a propylene gas stripping process,which utilizes only a small amount of added water for hydrolysis, has been described (63). In this modification,the equilibrium quantity of isopropyl alcohol is stripped so that acid is recycled without reconcentration.Equilibrium is attained rapidly at 50◦C and isopropyl alcohol is removed from the hydrolysis mixture. Similarly,the weak sulfuric acid process minimizes the reconcentration of the acid and its associated corrosion andpollution problems.The 91 vol % alcohol is sold as such or is dehydrated by azeotropic distillation using either diisopropylether or cyclohexane to produce an anhydrous product (see Table 2) (see Distillation, azeotropic and extractive)(64). Wet isopropyl alcohol is fed at about the center of a dehydrating column, and the azeotroping agent is fednear the top. As the ternary azeotrope forms, it is taken overhead, condensed, and the layers are separated.The upper layer, which is mainly azeotroping agent and alcohol, is returned to the top of the column as reflux.Anhydrous isopropyl alcohol is removed from the base of the column. The lower layer is mostly water. It is fed to a stripping column for recovery of isopropyl alcohol and azeotroping agent. A purge may be taken to remove

by-products such as acetone.

Acid corrosion presents a problem in isopropyl alcohol factories. Steel (qv) is a satisfactory material

of construction for tanks, lines, and columns where concentrated (>65 wt%) acid and moderate (<60◦C)

temperatures are employed. For dilute acid and higher temperatures, however, stainless steel, tantalum,

Hastelloy, and the like are required for corrosion resistance and to ensure product purity (65).

The extent of purification depends on the use requirements. Generally, either intense aqueous extractivedistillation, or post-treatment by fixed-bed absorption (qv) using activated carbon, molecular sieves (qv), andcertain metals on carriers, is employed to improve odor and to remove minor impurities. Essence grade isproduced by final distillation in nonferrous, eg, copper, equipment (66).Manufacturing plants in the United States are believed to use solely indirect propylene hydration. SeveralEuropean companies, eg, British Petroleum, Shell, and Deutsche Texaco, also employ this older technology inplants in Europe and Japan (67).

hidratación en fase gas

Proceso sobre acido fosfórico

Usa catalizador acido de H3PO4 fijado sobre oxido de silicio solido o sobre una resina a altas presiones y bajas temperaturas (reacción exotérmica) para favorecer que el equilibrio se desplace hacia la derecha. La hidratación directa transcurre con una selectividad del 97% y una conversión del 6%, por lo que es necesario reciclar el propeno que no ha reaccionado. Es un proceso de una sola etapa y aunque la reacción se favorece con la disminución de la temperatura, elcatalizador no puede enfriarce porque dejaría de ser activo

Hay datos raros de presión ente distintos autores

Como catalizadores se utilizan WO3/SiO2 (requiere P = 250 atm y 270°C) o H3PO4/SiO2 (P = 25 -45 atm y 170-190 °C) (acidos minerales o heteropoliacidos). El isopropanol se purifica por destilación y el agua del azeótropo se elimina por destilación con benceno (Veba en Alemania).

The reaction is generally carried out by passing steam and propylene in a molar ratio of 0.5～2.0:

Moreover, the disadvantages inherant to supported mineral acid catalysts are decrease in hydration activity and the incidence of corrosion13) on the metal surfaces in contact with the product owing to migration and depletion of the acid.

Sean determinado otros tipos de proceso en la región supercrítica lo que mejora la velocidad de reacción

El mecanismo transcurre con formación de un carbocatión previa adición del protón al

doble enlace.  La hidratación de alquenos es Markovnikov, es decir, el protón se

adiciona al carbono menos sustituido del alqueno (carbono con más hidrógenos); esto

se da a causa de que este es el lugar mas estable para la existencia de una especie

intermedia

 

Etapa 1. Ataque del alqueno al protón (adición electrófila)

 

Etapa 2. Ataque nucleófilo del agua al carbocatión formado

 

 

Etapa 3. Desprotonación del alcohol.  El agua actúa como base.

 

Hidratación en fase líquida.consiste en la introducción de agua líquida y propeno gas en un reactor que contiene una resina de intercambio iónico de tipo sulfonico . Se opera a ( 130-160 (C y80- 100 atm 1800 psig. Se consiguen conversiones del 75% y una selectividad en torno al 94%. Los restos que no han sido reaccionados también se pueden llevar a una planta de produccion por via de acido ya que pueden contener gran cantidad de inertes. Se introduce una relación alta de agua respecto a la de propeno para evitar la oligomerizacion del propanol. La solución final contiene de 12 a 15 % de ipropanol y los demás subproductos son 2 a 4% de diisopropileter y algunos alcoholes poliméricos, algo de acetona y n propílico

Isopropyl alcohol selectivity is ca 96% for thegas-phase process. Owing to equilibrium limitations in the gas phase at high temperature and low pressure,a low propylene conversion (5–6%) results and thus a large amount of unreacted propylene is recycled. Bothprocesses involve high plant costs owing to high pressure requirements, gas recycles, and the requirement forhigh purity propylene (ca 99 wt %).

Deutsche Texaco developed a trickle-bed process to avoid the disadvantages of the gas-phase process. Inthe trickle-bed process, a mixture of liquid water and propylene gas in a molar ratio of 12 to 15:1 is introducedat the top of a fixed-bed reactor and allowed to trickle down over a sulfonic acid ion-exchange resin. Reactionbetween the liquid and gas phases takes place at 130–160◦C and 8–10 MPa (80–100 atm), forming aqueousisopropyl alcohol. Propylene conversions per pass are greater than 75%, and isopropyl alcohol selectivity is93%. Only 92 wt % propylene purity is needed for this process. Approximately 5% diisopropyl ether and somealcohols of the higher oligomers form as by-products. The life of the cation-exchange resin is at least eightmonths.

se usa un reactor tipo pfr o de slurry dependiendode las necesidades de produccionen el proceso en donde la resina esta en forma de granulos quese hinchan con el agua y la idea es que exista un gran mesclado liquido gas

solia hacerse con agua liquida y propeno a altas presiones propylene and liquid water at a mole ratio of water to propylene between 10 and 15 over the catalyst bed at a temperature from 230 to 270℃ and a pressure from 200 to 300atm. For the hydration in the presence of liquid water, tungsten oxide is widely used as an effective component of catalyst14).

La vida de la resina es de 8 meses aproximadamente porque sufre desulfonacion con el contacto entre agua y el grupo sulfonilo y se requeriría que

También se han venido usandoformas de catalizado de wolframio diluido que permite una conversión del 60-70% con una selectividad de isopropanol hasta del 99%

Luego de desorver y separar las sustancias de bajo punto de ebullición se destila el agua delsistema hasta producir un azeotropo y luego con benceno se genera el isopropanol anhidro

Referencias

http://www.eii.uva.es/organica/qoi/tema-06.php

Química orgánica industrial wesnteingnet https://hidratacionparalaproducciondeisopropanol.wordpress.com/

Vistos

http://profesionseg.blogspot.com/2007/06/usos-de-los-alcoholes-n-propanol.html

http://www.sigmaaldrich.com/chemistry/solvents/products.html?TablePage=17292086

http://www.shell.com/global/products-services/solutions-for-businesses/chemicals/products/solvents/chemical-solvents/alcohols.html

odor threeshold

Isopropyl alcohol 7.8400 490.0000 Pleasant 490.00