CN1299802A - Acetaldehyde diethyl acetal producing process - Google Patents

Abstract

It uses absolute alcohol and acetaldehyde as raw material, uses anhydrous calcium chloride as dewatering agent, uses sulfuric acid as catalyst, uses caustic lime as neutralization dewatering agent and makes the condensation reaction implement under the condition of normal temp., and makes the rectifying process implement under the condition of anhydrous state and faintly alkaline reaction. The rate of said invented production can be up to above 90%, and product content can be up to above 98%, and it has the advantages of low raw material consumption, low production cost, good product quality, and is applicable to production of acetal with various applications.

Description

Acetaldehyde diethyl acetal producing process

The present invention relates to the production technique of acetal, be applicable to the production of the acetal of various uses.

Acetal claims again " acetal acetal " that be called for short " acetal ", structural formula is CH ₃CH (OC ₂H ₅) ₂, colourless transparent liquid, 103 ℃ of boiling points, relative density 0.8254 (20 ℃), specific refractory power 1.3819 (20 ℃), water-soluble, ethanol and ether, stable in alkalescence.Acetal is a kind of novel fragrance of higher gears, also is one of important aroma component of liquor, also is widely used in the synthetic of medicine, dyestuff, plastics and spices simultaneously, and the organic synthesis of protection aldehyde radical.

Before the present invention makes, in the related domestic and international publication, as follows about the more representational document of acetaldehyde diethyl acetal producing process: (Fan Nengting writes (1) " organic synthesis topical reference book ", press of Beijing Institute of Technology, January in 1992 the 1st edition, 741 pages); (2) " meticulous Organic Chemicals and intermediate handbook (Xu Kexun chief editor, Chemical Industry Press, June in 1998 the 1st edition, 1-144 page or leaf); (3) " Fine Organic Chemical product technical manual " first volume (Zhang Sigui chief editor, Science Press, July in 1991 the 1st edition, 3-4 page or leaf); (4) " the synthetic flavor handbook (U.S. " Fenaroli spices handbook third part " synthetic perfume " translation, Jinan City's light industry institute compiling, light industry press, September in 1985 the 1st edition, 206 pages); (5) " practical Minute Organic Synthesis handbook (Duan Hangxin compiles, Chemical Industry Press, January in 2000 the 1st edition, 64 pages).In above document, all introduced the Preparation of acetaldehyde diethyl acetal method, roughly as follows: ethanol and acetaldehyde are in the presence of Calcium Chloride Powder Anhydrous and small amounts of inorganic acid, and controlled temperature is carrying out condensation reaction below 8 ℃, again through the Anhydrous potassium carbonate drying, after rectifying gets the acetal finished product.Above-mentioned preparation method has following weak point: 1. setting-up point must be controlled at below 8 ℃, and promptly condensation course needs refrigeration system, and this will cause the increase of production cost; 2. above-mentioned condensation reaction is reversible reaction, and reaction formula is: ${\mathrm{CH}}_3\mathrm{CHO}+{2C}_2{H}_3\mathrm{OH}\stackrel{H^{+}}{\⇔}{\mathrm{CH}}_3\mathrm{CH}({\mathrm{OC}}_2{H}_5{)}_2++H_{2}O$

Because acetal solubleness in water is very big, as adopt clear water washing or soda lye wash to remove wherein mineral acid, to cause increasing of raw material consumption, again because the Anhydrous potassium carbonate drying effect is poor, and acetal just very easily is hydrolyzed into acetaldehyde and ethanol in a small amount of diluted acid, thereby above-mentioned preparation method's productive rate only is 65～70%, and the content of finished product acetal only is 85～90%.

Look into new center through Jiangsu Province Inst. of Science ﹠ Technology Information and search, do not see report (the novelty assessment report numbering: SCXQ000984) that the pertinent literature identical with the present invention, patent and achievement are arranged to the retrieval of domestic literature with by Internet.

The object of the present invention is to provide a kind of productive rate height, good economy performance, quality product height and the reliable acetaldehyde diethyl acetal producing process of stable operation.

The objective of the invention is to be achieved through the following technical solutions: in the condensation reaction still, add dehydrated alcohol and Calcium Chloride Powder Anhydrous and a small amount of vitriol oil, at the uniform velocity drip acetaldehyde at normal temperature (15～30 ℃) with under stirring, the proportion of raw materials of above-mentioned condensation reaction is a dehydrated alcohol: acetaldehyde: Calcium Chloride Powder Anhydrous=1.8～2.6: 1: 0.18～0.26 (mol ratio); Dropwise the back and continue reaction 1～2 hour, left standstill then 8～10 hours, discard the calcium chloride hydrated crystal, filtrate being treated the rectifying thing; In rectifying still, add and treat the rectifying thing, and add in unslaked lime (CaO) conduct and dewatering agent, the unslaked lime consumption is 3～8% (weight ratios) for the treatment of the rectifying thing, be stirred to treat that the rectifying thing is weakly alkaline (pH7.5～8.0) after, atmospheric distillation operation is carried out in heating, steams earlier＜96 ℃ foreshot (content about 50%, be used for the condensation batching after merging for several times), steam 96～108 ℃ of fractions again and be the acetal finished product, be colourless transparent liquid, content 〉=98%.

Compared with prior art, the present invention has low cost, high-quality advantage: condensation course adopts specific proportioning raw materials and drips the mode of acetaldehyde, thereby condensation reaction can be carried out at normal temperatures smoothly, do not need refrigeration system, improve the dehydrating effect and the feed stock conversion of Calcium Chloride Powder Anhydrous simultaneously, and shortened the reaction times; Rectifying adopts in the cheap unslaked lime conduct and dewatering agent, thereby distillation operation is carried out under anhydrous state and weakly alkaline, avoided the reversed reaction under acidic conditions, made the productive rate of ethanol and acetaldehyde all reach more than 90%, the content of finished product acetal reaches more than 98%.

The present invention will be described in more detail by following examples:

Embodiment 1:

The 2000ml four-hole circle flask of band whipping appts, Dropping feeder and thermometer is placed the water-bath device, add 1000g dehydrated alcohol (content 99.2%), 240g Calcium Chloride Powder Anhydrous (content 92.4%) and the 3g vitriol oil, keep 25 ℃ by water-bath device control reacting liquid temperature, at the uniform velocity drip 450g acetaldehyde (content 99.5%), 5.5 hour dropwise, continue to stir 1 hour, left standstill then 8.5 hours, discard moisture calcium chloride crystal, must treat rectifying thing 1248g.To treat that the rectifying thing is added in the 2000ml four-hole circle flask of band rectifier unit, add 40g ordinary student lime earlier, regulate pH to 7.5, carry out the atmospheric distillation operation then, steam earlier＜96 ℃ foreshot 214g (content 50.4%), steam 96～108 ℃ of fraction 928g (content 98.4%) again, be the acetal finished product, productive rate 91.2%.

Embodiment 2:

The 2000ml four-hole circle flask of band whipping appts, Dropping feeder and thermometer is placed the water-bath device, add 1350g foreshot (content 48.5%), 100g dehydrated alcohol (content 99.3%), 150g Calcium Chloride Powder Anhydrous (content 92.4%) and the 3g vitriol oil, keep 27 ℃ by water-bath device control reacting liquid temperature, stirring reaction 4 hours, left standstill then 9 hours, discard moisture calcium chloride crystal, must treat rectifying thing 1316g.To treat that the rectifying thing is added in the 2000ml four-hole circle flask of band rectifier unit, add 40g ordinary student lime earlier, regulate pH to 8.0, carry out the atmospheric distillation operation then, steam earlier＜96 ℃ foreshot 226g (content 51.7%), steam 96～108 ℃ of fraction 994g (content 98.1%) again, be the acetal finished product, productive rate 90.6%.

Embodiment 3:

In 2000 condensation reaction stills of band whipping appts, Dropping feeder, chuck heating-cooling device and thermometer, add 900kg dehydrated alcohol (content 99.2%), 250kg Calcium Chloride Powder Anhydrous (content 91.8%) and the 3kg vitriol oil, by 28 ℃ of chuck heating-cooling device control reacting liquid temperatures, splash into 430kg acetaldehyde (content 99.6%) by 100kg/ hour flow, 4.3 hour dropwise, continue to stir 2 hours, left standstill then 10 hours, discard moisture calcium chloride crystal, must treat rectifying thing 1172kg.To treat that the rectifying thing is added in 20001 rectifying stills of band rectifier unit, add 38kg ordinary student lime earlier, regulate pH to 8.0, carry out the atmospheric distillation operation then, go out earlier＜96 ℃ foreshot 227kg (content 49.6%), steam 96～108 ℃ of fraction 859kg (content 99.3%) again, be the acetal finished product, productive rate 90.8%.

Claims (3)

1. acetaldehyde diethyl acetal producing process, it comprises that with dehydrated alcohol and acetaldehyde be raw material, with the Calcium Chloride Powder Anhydrous is dewatering agent, with sulfuric acid is catalyzer, produce acetal through processes such as batching, condensation and rectifying, it is characterized in that: proportion of raw materials is a dehydrated alcohol: acetaldehyde: Calcium Chloride Powder Anhydrous=1.8～2.6: 1: 0.18～0.26 (mol ratio); Setting-up point is 15～30 ℃; Add in unslaked lime (CaO) conduct in rectifying and dewatering agent, the unslaked lime consumption is 3～8% (weight ratios) for the treatment of the rectifying thing.

2. technology according to claim 1, it is characterized in that acetaldehyde joins in the mode that at the uniform velocity drips carries out condensation reaction in the solution of being made of dehydrated alcohol, Calcium Chloride Powder Anhydrous and sulfuric acid, after reaction finishes, left standstill 8～10 hours, branch goes aqueous calcium chloride crystal, cleaner liquid to be and treats the rectifying thing.

3. technology according to claim 1 is characterized in that earlier unslaked lime being joined before rectifying and treats in the rectifying thing and be stirred to treat that the rectifying thing is weakly alkaline (pH7.5～8.0), heats distillation operation then under anhydrous state and weakly alkaline.