Chapter 6Hydrogenation and dehydrogenation process
Hydrogenation and dehydrogenation process Chapter 6
6.1IntroductionHydrogenation reaction types(1)Hydrogenation of double bond of unsaturatedalkyne and alkeneC+ H2→
6.1 Introduction 一、Hydrogenation reaction types (1) Hydrogenation of double bond of unsaturated alkyne and alkene
(2)AromatichydrogenationCH11-CH=CH2H24H2-C2H5NixSelectivityhydrogenation3) Hydrogenation of the compound containing oxygenCO + 2H2CH3OH(CH3)2CO +. H2-(CH3)2CHOHRCOOH + 2H2→RCH2OH + H2C
(2) Aromatic hydrogenation (3) Hydrogenation of the compound containing oxygen Selectivity hydrogenation H2 4H2
(4)Hydrogenation of the compound containing nitrogenN2+3H2*2NH3N=C(CH)C=N+4H2--→HN(CH2NH2NH2NO.+ 2H20+ 3H2(5)HydrogenolysisC6HsCH3 +H2+ CH6 + CH4CHsSH + H2 →C2H6 + H2SCsHsN + 5H2 CsH12 + NH
(4) Hydrogenation of the compound containing nitrogen (5) Hydrogenolysis
二、Dehydrogenationreactionltypes(1)Dehydrogenation of alkanes to produce alkenes, dienes andaromaticsn-C4H10+n-C4H8CH2-CH-CH--CH2C12H26 - n -C12H24 + H2n-CH14→CH6 + 4H2(2)Dehydrogenationofalkenestoproducedienesi-CsH10→ CH2-CH--C(CH3)-CH2 + H
二、Dehydrogenation reaction types (1) Dehydrogenation of alkanes to produce alkenes, dienes and aromatics (2) Dehydrogenation of alkenes to produce dienes
(3)DehydrogenationofalkylaromaticstoproducealkenylaromaticsCH5CHs -→ C,HsCHCH2 + H2CHsC6H4CHs-→ CH2---CH---C6H4CH--CH2 + 2H(4)Dehydrogenation of alcohols toproduce aldehydes and ketones→CH3CHO + H2CH3CH2OH-CH3CHOHCH3 →CH3COCH3 + H
(3) Dehydrogenation of alkyl aromatics to produce alkenyl aromatics (4) Dehydrogenation of alcohols to produce aldehydes and ketones
6.2 General rules of hydrogenation,dehydrogenation reactionsGeneralrules of catalytic hydrogenationreactionsl.Thermodynamic analysisTable 6-1Thermal effectvalueof hydrogenation reactionat25℃反AHe/(kI/mol)应式174.3CH4CH2+H2132.7CH4 + H2 -→ CH690.8CO+2H2---→ CH3OH176.9CO+3H2CH4+H2O56.2CHCOCH3+H2→(CH)2CHOH69.1CH3CH2CH2CHO+H2"→CH3(CH2)3OH208.1CgH, + 3H2 CH1242.0CHsCH3+H2-→CH+CH4101.2+CsHeCsHs + H2
6.2 General rules of hydrogenation, dehydrogenation reactions 一、General rules of catalytic hydrogenation reactions 1. Thermodynamic analysis Table 6-1 Thermal effect value of hydrogenation reaction at 25℃
AHo(1)TemperatureInk△H<0, :.T↑, Kp↓.RT2dTDKp is large in a wide temperature range, almost irreversiblereaction.Kp is large at medium temperature, Kpdecreases at hightemperature,thermodynamicsis dominant?Kpislarge at lowtemperature,butKp deceases in theavailable temperature range,thermodynamics unfavorablechemical equilibriumbecomes a keyfactor
（1）Temperature △ H < 0， ∴ T↑ ，K P ↓. ① KP is large in a wide temperature range, almost irreversible reaction. ② KP is large at medium temperature, KP decreases at high temperature, thermodynamics is dominant ③ KP is large at low temperature, but KP deceases in the available temperature range, thermodynamics unfavorable, chemical equilibrium becomes a key factor
(2)Pressure△ n<0,For hydrogenation reaction,:. P↑ , Kp↑, balance yield↑
（2）Pressure For hydrogenation reaction，△ n<0， ∴ P↑ ，Kp↑ ，balance yield↑
(3)hydrogenratioBA+H2HVHH2↑Advantages: conversion (X)increases, andit is favorableto removereactionheatDisadvantages:concentration of product (yp)decreases,and separationdifficult,alargeamountof Hzcyclelargeenergyconsumption
（3）hydrogen ratio A +H2 B H2↑ Advantages: conversion (X) increases, and it is favorable to remove reaction heat Disadvantages: concentration of product (yB) decreases, and separation difficult, a large amount of H2 cycle, large energy consumption