Influence of micromixing on parallel reactions - ETH E
Transcription
Influence of micromixing on parallel reactions - ETH E
Diss ETH No. 10257 Influence of micromixing parallel reactions on A dissertation submitted to the SWISS FEDERAL INSTITUTE OF TECHNOLOGY ZURICH for the degree of Doctor of Technical Sciences presented by Louis Alfred De Boni Serge dipl. Chem.-Ing. born May 17, citizen of Bonfol accepted on ETH 1963 (JU) the recommendation of Prof. Dr. J.R. Bourne, examiner Prof. Dr. S. Hartland, co-examiner Zurich 1993 V Abstract When the characteristic time of of the order of same magnitude chemical reaction is much shorter a as that of micromixing, the or transport of fresh reagents to the reaction site controls the conversion rate. In the of case a complex reaction the product The rules of chemical kinetics alone evolution time Baldyga of the and Bourne take of the concentrations developed model), which shows how turbulent flow, distribution are no more building fluid in also be affected. Involved substances. 1989 the E-model ( completely two can able to describe the misclble Engulfment- liquids mix In a laminae in which the chemical reactions place. After having reactions in applied been previous work, reaction schemes. Systems to a system of consecutive, competitive the E-model had to be evaluated for other of parallel, competitive of fast and Instantaneous reactions, A+B A+C reactions, made up studied in this work. are P k2 Q Consider, for example, the system of parallel, competitive reactions, sketched above, where the ratio of the rate constants ki/k2 is about 1010. The reactions containing the A is slowly expected are reagents semi-batch reactor already these and 1/2 Xq, is 10"10, according to the laws of chemical kinetics. actually measured. The E-model could Values of about 30 % k2/ki a added. The portion of A-molecules reacting with C, to be about reproduce carried out in B and C at the same concentrations, into which were experimental depending results and predicts upon the intensity of mixing. values between vi Two different reaction two reactions: of a systems ions and of the alcaline one were tested. The first neutralisation between hydrolysis of one hydroxide methyl is composed and chloroacetate. The second is made up of three reactions: of the same neutralisation and of the alcaline hydrolyses pyruvate. The experiments This was operated into the reactor The were a better ethyl chloroacetate carried out in a of the E-model was were good experimentally, knowledge an before methyl hydroxide was fed acidic solution of esters. compared with the in the sense that the while of the as and baffled stirred tank. in the semi-batch mode. Sodium agreement confirmed needed were already containing predictions results. The of of hydronium a more experimental predicted trends quantitative agreement hydrodynamic parameters turbulent flow, where the reactions took place. of the vii Resume Lorsque plus temps caracteristique d'une le court l'apport ou du de reactifs frais conversion et reactions chimique est beaucoup que celui du melange, reaction grandeur le site de reaction limlte le taux de sur peut modifier la distribution des produits Les lois de la chimiques complexes. parviennent alors plus la ordre de meme concentration a des reproduire de ne dans le seules revolution dans le substances (Engulfment-model) developpe facon dont deux cas cinetique chimique impliquees. Le Baldyga par Bourne et liquides parfaitement misclbles se en temps de modele «E» 1989 decrit la melangent en milieu turbulent, formant des lamelles de fluides dans lesquelles les reactions chimiques Apres ont lieu. avoir ete systeme de confronte applique reactions dans ce avec succes, competitives, consecutives, travail a lors de travaux systeme de un precedents, a un le modele «E» reactions est paralleles, competitives. ki A + B P k2 A+C Considerons, par constantes de vitesses un meme ki/k2 est reacteur semi-continu concentration, et molecules de A reagissant on avec valeur de 10"10 selon la cinetique l'ordre de 30 % ont pu etre egal qui auquel de systeme ci-dessus, competitives, represents dans le exemple, Q - C pour a lequel environ contient ajoute reactions deja le 1010. On laisse reagir les reactifs B et C a la lentement A. La fraction de plutot qu'avec B, Xg, chimique. Cependant, mesurees paralleles, rapport des dans la admet une des valeurs de partie experimentale de ce vlii travail. Le modele «E» est experimentaux predits et 1/2 selon l'intensite de Deux hydronium deuxieme, et quant chloracetate et de deja predictions experimentaux. tendances du milieu une du La Xg methyle trois de pyruvate. Une partie experimentale generates quantitative plus alcaline de l'hydroxide de k2/ki a de sodium hydroxide et la ete meme ethyle de et chicanee agitee travail. On a compose de chloracetate. Le alcaline d' cuve ce se reactions: precedemment, l'hydrolyse mode semi-continu. De contenait resultats ces variant de reactions ont ete testes. L'un comprend lui, a methyle ete utilisee pour la compte de neutralisation entre des ions hydrolyse une de rendre des valeurs de l'agitation. une neutralisation que Les meme systemes differents de de deux reactions: qui en mesure a ajoute travaille au a en reacteur solution acide d'esters. modele «E» concordance ont ete exacte ont est ou comparees ce aux resultats sens que les confirmees, tandis qu'une description requiert des hydrodynamlque ete bonne dans connaissances les reactions se plus approfondies deroulent.