Research On Catalytic Esterification Deacidification Reaction Based On LDHs

The presence of naphthenic acids in high acid crude oil often causes severe corrosion to refinery equipment and pipeline.Therefore,removing petroleum acids from crude oil is one of the important challenges in refinery.Catalytic esterification is an interesting method to decrease the naphthenic acid concentration of highly acidic petroleum,while improving the activity of catalyst is considered to be a key factor for further application of esterification deacidification method.In previous work,the results demonstrated that layered double hydroxide(LDH)is an effective catalyst for the esterification of ethylene glycol(EG)and naphthenic acid from high acid crude oil.However,there are many problems,for example,the high dosage of EG,the high reaction temperature and the long reaction time.Therefore,the catalytic efficiency should be enhanced further.In this thesis,the interlayer catalytic esterification of ethylene glycol(EG)intercalated layered double hydroxides(LDHs)was established due to the confined space of LDHs,which could improve the reaction efficiency with the increased EG utilization.Firstly,to synthesize EG intercalated LDHs under mild reaction conditions,the prepareation method of EG intercalated LDHs was investigated.Secondly,EG intercalated LDH was used as catalyst for the esterification deacidification of crude oil to prove the promotion of catalytic efficiency.Thirdly,the mechanism and process of interlayer catalytic esterification in model system was investigated by XRD,FT-IR and TG-DSC characterizations of liquid product and LDHs.Fourthly,the kinetics of interlayer catalytic esterification was investigated.Finally,the interlayer space of EG intercalated LDHs could be adjusted.And the relation between the structure of EG intercalated LDHs and the efficiency of interlayer catalytic esterification was obtained.1.EG intercalated LDH was synthesized via ion exchange method under mild conditions by the aid of alkoxides or KOH.Nitrate LDH and EG were used as precursor and solvent,respectively.EG intercalated LDH with high crystallinity and single phase can be synthesized at 80? for 12 h or at 120? for 6 h.Compared to the literature(in liquid EG at 80? for 12 h or in vapor EG for 30 h),the reaction conditions were reduced significantly.The characterization results of XRD,TG-DSC,FT-IR,elemental analysis and 13C MAS NMR were adopted to investigated the effect of synthesis condition on the structure of EG intercalated LDHs and confirm the successful intercalation of EG in LDH.It is found that EG anions with a negative charge may be accommodated in the interlayer in a tilted bilayer arrangement.2.The synthesis time of EG intercalated LDH was shortened further via microwave-assisted ion exchange method.The effects of microwave conditions on the structure of EG intercalated LDH were investigated.It is found EG intercalated LDH with high crystallinity could be prepared under 170 mA at 120? for 10 min.3.EG intercalated LDH was used as catalyst for the esterification between high acid crude oil and EG.The effect of liquid EG dosage,catalyst dosage,reaction temperature and time on the deacidification ratio was investigated.The interlayer catalytic esterification was proved by XRD and FT-IR.4.An interlayer catalytic esterification between EG intercalated NiAl LDH and cyclohexanecarboxylic acid(Cyc)is developed.LDH before and after the interlayer reaction were characterized by XRD,FT-IR and TG-DSC.And the liquid product was analyzed by GC-MS,FT-IR and1H NMR.It is found that Cyc diffused into the interlayer space react with EG anions and 2-hydroxy ethyl cyclohexanecarboxylate is produced.Deacidification ratio and EG conversion of interlayer reaction reach up to 69.80%and 91.09%,respectively,extremely higher than those of the bulk catalytic reaction(2.33%and 7.22%).The confined interlayer enhances the collision probability between EG anions and Cyc.EG anions preintercalated in LDH display increased nucleophilicity and eliminate the diffusion limitation,moreover,the enlarged interlayer space facilitates Cyc diffusing into the interlayer.5.The influences of initial Cyc concentration,EG intercalated LDH quantity and reaction temperature on the interlayer esterification have been discussed.The reaction follows an interlayer reaction-controlled mechanism represented by Kroger and Ziegler kinetic model with the apparent activation energy of 35.02 kJ/mol.The apparent activation energy of the bulk reaction under the similar reaction conditions indicating interlayer reaction could decrease the apparent activation energy.6.The diffierent basal spacings 003 reflection(d003)of EG intercalated LDHs from 7 to 13 A were adjusted by changing synthesis condition including the drying temperature,the basal spacing of precursor and reaction temperature.The d003 12.51,9.56 and 7.82 A of EG intercalated LDHs were applied in the interlayer catalytic esterification.The reaction efficiency of EG intercalated LDH with d003 9.56 A is the highest.EG intercalated LDH with lower d0037.82 A processes the lower reaction efficiency,due to the narrow gallery of LDH blocking the diffusion of Cyc into the interlayer space of LDHs.On the other hand,the reaction efficiency of EG intercalated LDH with larger d003 12.51 A is the lowest,because excessively high liquidity of the interlayer Cyc could weaken the confined effect.Meanwhile,the host-guest interaction characterized by DSC of EG intercalated LDH with d003 9.56 A is the smallest and the interlayer EG removes from LDH sheet easily.This weak interaction could improve the reaction efficiency.