Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/02—Apparatus characterised by being constructed of material selected for its chemically-resistant properties
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/28—Preparation of carboxylic acid esters by modifying the hydroxylic moiety of the ester, such modification not being an introduction of an ester group
  • C07C67/297—Preparation of carboxylic acid esters by modifying the hydroxylic moiety of the ester, such modification not being an introduction of an ester group by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/02—Apparatus characterised by their chemically-resistant properties
  • B01J2219/025—Apparatus characterised by their chemically-resistant properties characterised by the construction materials of the reactor vessel proper
  • B01J2219/0277—Metal based
  • B01J2219/0286—Steel

Definitions

• Vinyl acetate is a large-scale article of commerce having wide utility in the production of polymeric compounds. While a variety of techniques have been proposed in the prior art for the preparation of this material, one recently proposed method appears of particular commercial interest. This method involves the vapor phase pyrolysis of a feedstock consisting essentially of ethylene glycol diacetate (i.e., 1,2-diacetoxyethane) to produce vinyl acetate and, as a by-product, acetic acid.
• ethylene glycol diacetate i.e., 1,2-diacetoxyethane
• the process of this invention involves what appear to be surface phenomena, it is, of course, clearly unnecessary for the material used in construction of the pyrolysis zone to be entirely made up of stainless steel. It is only necessary for the surfaces in contact with the feedstock and/ or reaction products to be of this material. Thus, any material capable of withstanding the temperatures encountered can be employed in the construction so long as those surfaces in contact with the feedstock and/or reaction products meet the requirements of this invention. Accordingly, clad materials, bimetallic tubes and the like can be employed to inimize materials cost while achieving the advantages provided by this invention. Nor is it necessary for the surface in contact with the reaction mixture within the pyrolysis zone to consist entirely of stainless steel.
• temperatures referred to are bulk temperatures unless otherwise stated.
• the ethylene glycol diacetate feedstock especially when prepared in accordance with the process of the Belgian patent, often can contain, even after purification, some quantity, typically 20% (mole basis) or less of ethylene glycol monoacetate, ethylene glycol, diethylene glycol, and diethylene glycol diacetate and monoacetate, as well as smaller amounts of the formate analogues of the preceding acetates. Smaller amounts, preferably under 20 ppm. but possibily up to 1,000-2,00 ppm. (weight basis), of halogenated impurities such as halohydrin, ethylene dihalide, ethylene haloacetate, diethylene glycol monoholadie and diethylene glycol haloacetate can also be present.
• halogenated impurities such as halohydrin, ethylene dihalide, ethylene haloacetate, diethylene glycol monoholadie and diethylene glycol haloacetate can also be present.
• the pyrolysis would normally be carried out on a partial conversion basis, i.e., ,only from about 5% to about 60% of the ethylene glycol diacetate will be converted per pass through the pyrolysis zone and unconverted material together with by-products unavoidably formed during previous passes of the feedstock through the pyrolysis zone would be recycled.
• a partial conversion basis i.e., ,only from about 5% to about 60% of the ethylene glycol diacetate will be converted per pass through the pyrolysis zone and unconverted material together with by-products unavoidably formed during previous passes of the feedstock through the pyrolysis zone would be recycled.
• Such by products can thereby build up in the feedstock to an appreciable extent and, even though purged in part, can accumulate to a point amounting to as much as 20% (mole basis) of the total feed.
• Such byproducts that can build up in this maner include additional ethylene glycol monoacetate, acetone, acetaldehyde, acetic anhydride, ketene, ethylidene diacetate and high-boiling materials of unknown structural formulae.
• the variety of material in the feedstock to the pyrolysis outlined in the preceding paragraphs together with reaction products and by-products are all permissible components of the reaction mixture.
• the feedstock despite the presence of the other materials therein, is characterized as one consisting essentially of ethylene glycol diacetate since it is this material which undergoes highly selective pyrolysis to vinyl acetate and, except as hereinabove noted, these other materials display no effect on build-up of carbonaceous material and display no adverse effect upon the pyrolysis.
• the mass velocity (computed on the basis of contained ethylene glycol diacetate) within the pyrolysis zone should be in excess of 200 lbs./hr./ft. of pyrolysis zone cross-sectional area.
• the upper limit of mass velocity employable within the pyrolysis zone is not associated with factors directly related to selectivity but rather is associated with economic considerations. These economic considerations normally dictate the use of mass velocities through the pyrolysis zone which are less than about 500,0001bs./hr./ft. of pyrolysis zone cross-sectional area, desirably less than 300,000 lbs./hr./ft. of pyrolysis zone cross-sectional area and preferably less than 200,000 lbs./hr./ft. of pyrolysis zone cross-sectional area.
• pyrolysis temperatures between about 435 C. and about 560 C. and preferably between about 445 C. and about 550 C.
• Residence times within the pyrolysis zone between about 0.10 and about 200 seconds, preferably between about one second and seconds are employed. Residence times within the pyrolysis zone, as used throughout this specification, are determined at the arithmetic average of inlet and outlet pyrolysis zone temperature and pressure and are determined on the basis of feedstock without consideration of increase in the number of moles of gas flowing (and hence in gas velocity) as the feedstock is pyrolyzed.
• 0 is the residence time of the feedstock within the pyrolysis zone in seconds and T represents the arithmetic average of inlet and outlet of pyrolysis zone temperatures expressed in degrees Kelvin and is at least 708 K. but not greater than 833 K.
• A is a number which varies from a minimum of 31.7002 to a maximum of 28.8l75.
• the value of A in the foregoing equation varies from a minimum of 30.980() to a maximum of 29.0945 while 0 is restricted to a value of 60 seconds or less and T is at least 728 K. but not above 823 K.
• the configuration of the pyrolysis zone itself is not of substantial importance to this invention and any convenient type can be employed.
• the pyrolysis zone itself can be in the form of a furnace with the feedstock flowing through the tubes thereof or it can be in the form of a shell-and-tube heat exchanger with the feedstock flowing through either the shell or the tube side thereof.
• the surface in contact with the reaction mixture should be an austenitic stainless steel of the requisite chromium and nickel contents.
• the heating medium employed in the pyrolysis zone is of no significance to this invention nor is the material of construction in contact therewith.
• An ethylene glycol diacetate feedstock is charged as a liquid to an electrically heated one-inch diameter steel tube which acts as a vaporizer.
• a small amount (0.2-2.5 wt. percent) of acetic acid is added to the feedstock in each run.
• this tube is packed with glass beads.
• a process for producing vinyl acetate which comprises subjecting a feedstock consisting essentially of ethylene glycol diacetate to pyrolysis in the vapor phase at 435 C.-560 C. within a pyrolysis zone having surfaces in direct contact with the feedstock and its pyrolysis reaction products consisting essentially of austenitic stainless stesls having a chromium content of at least 8 wt. percent and a nickel content of at least 6 wt. percent.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (8)

Cited By (3)

• 0
  • BE BE792736D patent/BE792736A/xx unknown
• 1971
  • 1971-12-16 US US00208903A patent/US3787485A/en not_active Expired - Lifetime
• 1972
  • 1972-12-01 NL NL7216320.A patent/NL156681B/nl unknown
  • 1972-12-15 FR FR7244677A patent/FR2163648B1/fr not_active Expired
  • 1972-12-15 IT IT7254771A patent/IT974116B/it active
  • 1972-12-15 GB GB5803472A patent/GB1411118A/en not_active Expired
  • 1972-12-15 DE DE2261562A patent/DE2261562C3/de not_active Expired
  • 1972-12-16 JP JP47126681A patent/JPS4867214A/ja active Pending

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