(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