Study On The Performance Of Vermiculite-based Catalysts For Acrylic Acid Carbonylation To Acrylic Acid

As we all know,acrylic acid(AA)is a very important basic chemical raw material and polymer element.It has been universally used in the synthesis of various other chemical derivatives,including acrylates,polymers,and plastics,etc.According to current reports,the industrialized production of AA in China is mainly through the oxidation of propylene.However,it is worth pondering that,because propylene mainly comes from petroleum resources,this will inevitably increase the consumption of a large amount of petroleum resources.In particular,in recent years,with the continuous depletion of global petroleum resources,the gap between oil supply and demand has become increasingly prominent and the price of crude oil has continued to rise,which has brought uncertainties to the two-step oxidation of petroleum-based propylene to AA.In order to get rid of dependence on petroleum resources propylene and follow the development path of energy self-sufficiency in our country,the reasonable development of propylene raw material substitutes to synthesize AA is the only option.The synthesis of high value-added AA through the acetylation of coal to acetylene is a very important and promising process route.It is based on the reaction of water,CO and acetylene and is ideal for atomic economic reactions.It makes full use of the acetylene and CO products of calcium carbide,and is an ideal substitute for the oxidation of propylene to AA.Based on current research reports,this paper uses nickel oxide as the active metal and treated vermiculite as the carrier.A comprehensive study of supported catalysts was carried out from the comparison of the supports,the different calcination methods and the modification of the supports.The specific reaction properties of vermiculite-based catalysts for acetylene carbonylation to AA were investigated.The main research contents are summarized as follows:(1)This paper first selected NaY molecular sieve,HY molecular sieve,MCM-41molecular sieve,talc(TP)and expanded two-dimensional layered vermiculite(2D-VT)as carriers,and NiO/NaY,NiO/HY,NiO/MCM-41,NiO/TP and NiO/2D-VT catalysts with different supports were obtained after loading nickel oxide with nickel element at 11.4 wt%.After optimization of a series of conditions,NiO/2D-VT catalyst was obtained the best AA yield(83.14%)with tetrahydrofuran(THF)as the solvent,CuBr2 as the co-catalyst,the initial pressure was 3 MPa by reaction at 235°C for 60 min.Through various characterization methods,it was found that the two-dimensional layered structure of vermiculite(VT)itself with a hydroxyl structure provides a loading site for the active metal NiO,which promotes the formation of a hydrogen carboxyl group.In addition,the 2D-VT carrier has good thermal stability,and the NiO/2D-VT catalyst loaded with nickel oxide shows the least negative deposits in the acetylene carbonylation to AA reaction,showing better AA selectivity.In the catalyst cycle test,compared with other catalysts,the activity of NiO/2D-VT catalyst decreases more slowly and the catalytic performance is better.At the same time,we investigated the reasons for the deactivation of the NiO/2D-VT catalyst and found that the loss of nickel oxide supported on the 2D-VT surface was the main reason for the catalyst deactivation.(2)After comparing the above various supported catalysts,we found that although the NiO/2D-VT catalyst is more active,the grain size of nickel oxide supported on the 2D-VT surface is larger after calcination,which may drive us to solve this problem.Therefore,we started from the key point of the problem,using Ni(NO3)2·6H2O/2D-VT as the precursor composite material,and using different calcination methods to obtain different calcined catalysts for acetylene carbonyl reaction to synthesize AA.The catalyst was characterized and evaluated by various methods.We found that microwave(MW)radiation calcination catalyst(MW-NiO/2D-VT)showed better catalytic performance than muffle furnace(MF)calcination catalyst(MF-NiO/2D-VT).This is mainly due to the fast heating speed of microwave radiation and short baking time.The nano-NiO particles formed instantaneously have better dispersibility and uniformity,which is more conducive to the performance of nickel oxide.Under the optimal reaction conditions,the yield of AA reached 86.3%.And during the reaction,compared with the MF-NiO/2D-VT catalyst,the MW-NiO/2D-VT catalyst showed more stability and produced less side deposits.It is more conducive to improving the selectivity of AA.In addition,theoretical calculations show that the MW-NiO/2D-VT catalyst exhibits lower apparent activation energy,which kinetically explains that the MW-NiO/2D-VT catalyst is an excellent catalyst.(3)Although the expanded two-dimensional layered vermiculite has a unique two-dimensional structure,the specific surface area is very low.We know that the specific surface area has a certain effect on the performance of the catalyst.In this work,2D-VT was etched with a mixture of different volumes of nitric acid and hydrochloric acid to obtain2D-VT_x carriers with different pore structures(x represents the volume of the etched mixed acid),These carriers were used to support NiO nanoparticles to prepare different specific surface area catalysts(NiO/2D-VT_x),and used to synthesize AA.Compared with the almost non-porous nano-NiO(NiO/2D-VT4),the prepared NiO/2D-VT56 has some advantages,it shows a considerable specific surface area,rich voids and stronger acidity and ability to adsorb acetylene.The supported NiO nanoparticles show better crystallinity and catalytic ability,and richer hydroxyl groups.They enrich the active sites of the catalyst and promote the formation of hydrogen carboxyl groups,which is more conducive to the expression of catalytic performance.Under the optimal reaction conditions,the yield of AA can reach90.6%,and excellent catalytic performance has been achieved.