Research On Preparation Of Tert-Butanol From Isobutylene Hydration By Tower Reactor

The petrochemical industry has developed rapidly in recent years.With the continuous production of hydrocarbon pyrolysis units and fluid catalytic cracking units,C₄ hydrocarbon resources are more abundant.In 2020,due to the compulsory use of ethanol gasoline in China and methyl tert-butyl ether?MTBE?has the potential to cause groundwater pollution and carcinogenicity.Isobutylene as a raw material for the production of MTBE needs to find other ways.As a commonly used fine chemical raw material,tert-butanol can be used to produce internal combustion engine fuel and gasoline additives,etc.And it has a bright industrialization prospect.Commonly used domestic processes of tert-butanol include sulfuric acid hydrosynthesis,cation exchange resin cocurrent hydrosynthesis,tank reaction hydrosynthesis,and catalytic distillation hydrosynthesis.Among them,the catalyst used in the sulfuric acid hydrosynthesis is corrosive and causes serious environmental pollution.Cation exchange resin cocurrent hydrosynthesis,the catalyst loading is complicated,the effective utilization area is small,the cation exchange resin thermal stability is poor,and the conversion rate is low.The tank reaction hydrosynthesis needs to overcome the mass transfer resistance to eliminate the influence of the diffusion factor.Although the cost is low,it is only suitable for small-scale production,and under the high temperature and high pressure reaction conditions,the safety factor is low.This work uses tower reactors to combine counter current with reactive distillation technology—atmospheric pressure continuous reaction distillation.The new process doesn't need to add solvent and tert-butanol in advance under normal pressure,C₄ hydrocarbons can enter directly from the bottom of the tower and contact with the counter-flowing heteropolyacid catalyst aqueous solution in the reaction zone of the tower.The mixture after the hydration reaction leaves the distillation tower as a light component after the distillation section.The equilibrium concentration of the product tert-butanol in the rectification tower is reduced,which promotes the positive progress of the hydration reaction and at the same time improves the product yield.The hydrosynthesis is simple,less investment and it can achieve a high conversion rate with fewer distillation units.In this work,Keggin-type phosphomolybdenum and phosphotungstic acid with good water solubility,moderate price,easy preparation,stable structure,and good repeatability are selected as isobutylene hydration catalysts.After preparation of phosphomolybdenum acid using molybdenum trioxide and phosphoric acid at normal pressure,characterize it and determine the suitable preparation process conditions:molybdenum to phosphorus ratio 12?mol:mol?,reaction time 50 h,water to molybdenum ratio 70?mol:mol?.The experiment uses isobutene in C₄ hydrocarbons and water as raw materials to study the hydration effect of two tower reactor processes,and compares it with a fixed bed reactor?molecular sieve as catalyst?process:?1?The multi-stage countercurrent sieve-tray tower is used for atmospheric gas phase hydration reaction,and the suitable process conditions for isobutylene hydration reaction are determined as follows:reaction temperature 80?,catalyst concentration 16?18%?wt/%?,C₄ hydrocarbon flow 0.4?0.45 L/min,water-to-carbon ratio 5?5.5?molar ratio of water to isobutene in extracted C4 hydrocarbon?,the conversion rate of isobutene is 74.01%,the selectivity of tert-butanol is 100%.?2?The continuous reaction rectification?filler?tower is used for atmospheric gas phase hydration reaction,and the suitable process conditions for isobutylene hydration reaction are determined as follows:reaction temperature 80?85?,reflux ratio R=3,catalyst concentration 18%?wt/%?,C₄ hydrocarbon flow 0.2?0.25 L/min,water-to-carbon ratio 5.5?mol:mol?,the conversion rate of isobutene is 84.15%,the selectivity of tert-butanol is 100%.?3?Atmospheric fixed bed reactor is used to evaluate the catalytic activity of HZSM-5and H?catalysts in the hydration of isobutylene from C4 hydrocarbons.It is confirmed that the catalytic activity of H?catalyst with silicon-to-aluminum ratio of 25 is slightly higher than that of HZSM-5 catalyst with silicon-aluminum ratio of 38.When H?is used as a catalyst,suitable hydration process conditions are:reaction temperature 115?,mass airspeed is 1.0 h^-1,water-to-carbon ratio 4.5?mol:mol?,the conversion rate of isobutene is64.09%,the selectivity of tert-butanol is 100%.