Study On Catalyst And Process Enhancement Of Gas-liquid Acetylene Dimerization

Vinyl acetylene?MVA?is a very important chemical intermediate in the production process of chloroprene rubber?CR?.Because of its good chemical and mechanical properties,chloroprene rubber is resistant to acid,alkali,light,ozone,high temperature,etc.It is relatively good and stable under the conditions,so it has a wide and indispensable application value in the construction materials industry,rubber product manufacturing,adhesive manufacturing and other production industries.At present,MVA is mainly produced through acetylene dimerization.This route is more dependent on coal,which corresponds to the energy characteristics of our country.However,the Nieuwland catalyst?NC?used in the acetylene dimerization process has a poor catalytic effect,and has the disadvantages of lower C₂H₂ conversion,more by-products,and relatively short life,which greatly restricts the use of acetylene.Production method of CR monomer production method.The research team reported earlier that nitrogen-containing carboxylic acid modified NC can effectively improve the catalyst efficiency.Based on this,this paper further studied the influence of phosphonic acid-NC and sulfonic acid-NC on acetylene dimerization.At the same time,research on the strengthening of the response process was carried out in order to improve the shortcomings and deficiencies of traditional NC.The specific work is as follows:?1?First,we selected six ligands that are Glyphosine?P₁?,risedronic acid?P₂?,cytidine5'-monophosphate?P₃?,hydroxyphosphono-acetic acid?P₄?,2-phosphonobutane-1,2,4-tricarboxylic acid?P₅?and phenylphosphonic acid?P₆?.The containing phosphonic acid group modified Nieuwland catalysts were applied in acetylene dimerization,and the fundamental reasons for the structure of modified catalysts and the improvement of catalytic activity were investigated by characterization.The Nieuwland catalyst modified by risedronic acid?P₂?achieved relatively high catalytic activity in the acetylene dimerization reaction due to the coordination between the ligand and the catalyst.With an optimized amount of phosphonic acid ligand P₂?5%?,P₂-NC has an acetylene conversion rate of49.2%and an MVA selectivity of 80.3%at acetylene space velocity 105h^-1 and reaction temperature of80°C.The characteristics of NC and P₂-NC are characterized by FT-IR,HR-TEM,TG/DTG,XPS and ICP.The results show that the coordination between Cu and phosphonic acid ligand P₂ enhances the thermal stability of Cu ions.During the reaction,ligand P₂ effectively inhibited the oxidation of the active ingredient Cu⁺.In addition,addition of ligand P₂ also suppresses the loss of Cu ions in the catalyst,which greatly improved the use stability of the catalyst in the reaction process.Therefore,ligand P₂ is an excellent phosphorus-containing modifier for NC,with high catalytic activity and long-term stability.?2?Inspired by research on phosphonic acid modified catalysts,we selected eight ligands that are4-Aminobenzenesulfonic acid?S₁?,2-?bis?2-hydroxyethyl?amino?ethane-1-sulfonic acid?S₂?,2-??1,3-dihydroxy-2-?hydroxymethyl?propan-2-yl?amino?ethane-1-sulfonicacid?S₃?,2,2'-?piperazine-1,4-diyl?bis?ethane-1-sulfonic acid??S₄?,sulfamic acid?S₅?,5-aminonaphthalene-1-sulfonic acid?S₆?,benzenesulfonic acid?S₇?,4-hydrazinylbenzenesulfonic acid?S₈?.These eight sulfonate ligands have similar structures but different functional groups,so that we study the effect of different functional groups on the catalytic activity of the modified catalyst.The experimental results show that hydrazine-4-sulfonic acid?S₈?modified Nieuwland catalyst has the highest catalytic activity,and the catalytic system containing 5%S₈-NC shows excellent catalytic performance and good stability.At 80°C,the yield of MVA was maintained at 42.9%,and the 80 h^-1GHSV?C₂H₂?,which increased by 18.8%compared to the NC.?3?Inspired by our previous research,we used microchannel reactors as process enhancement equipment for acetylene dimerization.Compared with the traditional reactors,the microchannel reactor has excellent heat and mass transfer capabilities for materials,which can greatly reduce the mixing time of materials and achieve efficient heat transfer.We screened the catalytic solution concentration,reaction temperature,and acetylene flow rate,and tested the best sulfonic acid and phosphonic acid ligand-modified catalysts in the previous experiments in a microchannel reactor.In the previously used bubbling bed reactor,the acetylene dimerization reaction has only about 30%conversion and the MVA selectivity is only 70%.In the microchannel reaction,the C₂H₂ conversion was increased to 70%,and the MVA selectivity also exceeded 85%.It can be found that the microchannel reactor has a better strengthening effect on the acetylene dimerization reaction.This is because the microchannel reactor increases the number of gas-liquid contact,and has an excellent mixing effect on materials and efficient heat transfer,which can achieve uniform Mixing materials and promoting the catalytic effect of the catalyst has been improved.It is of great significance in the process enhancement of acetylene dimerization and provides a strong research basis.