催化学报
催化學報
최화학보
CHINESE JOURNAL OF CATALYSIS
2010年
8期
972-978
,共7页
朗格缪尔吸附等温线%Langmuir-Hinshelwood动力学%吸附物种%拟稳态假设%速控步骤%微观动力学
朗格繆爾吸附等溫線%Langmuir-Hinshelwood動力學%吸附物種%擬穩態假設%速控步驟%微觀動力學
랑격무이흡부등온선%Langmuir-Hinshelwood동역학%흡부물충%의은태가설%속공보취%미관동역학
Langmuir adsorption isotherm%Langmuir-Hinshelwood kinetics%adsorbed species%pseudo-steady state hypothesis%rate-determining step%microkinetics
使用Langmuir-Hinshelwood(L-H)动力学的学者大部分未注意到该动力学包含了所有吸附物种采用拟稳态假设的隐含条件,因而他们通常忽视了确认实验条件是否允许采用拟稳态假设.然而,对于大部分气固催化反应,拟稳态假设的成立需基于催化活性位浓度很小的前提.对于催化活性位浓度高的反应体系,其覆盖度较高的吸附物种不满足拟稳态假设.因此,在这种情况下通过实验测定的动力学常数没有物理意义,而仅为该实验条件下的数学回归参数.本文将活性位浓度小于最高反应气浓度的十分之一视为拟稳态假设成立的充分条件,通过估算发现许多催化剂并不满足该条件.
使用Langmuir-Hinshelwood(L-H)動力學的學者大部分未註意到該動力學包含瞭所有吸附物種採用擬穩態假設的隱含條件,因而他們通常忽視瞭確認實驗條件是否允許採用擬穩態假設.然而,對于大部分氣固催化反應,擬穩態假設的成立需基于催化活性位濃度很小的前提.對于催化活性位濃度高的反應體繫,其覆蓋度較高的吸附物種不滿足擬穩態假設.因此,在這種情況下通過實驗測定的動力學常數沒有物理意義,而僅為該實驗條件下的數學迴歸參數.本文將活性位濃度小于最高反應氣濃度的十分之一視為擬穩態假設成立的充分條件,通過估算髮現許多催化劑併不滿足該條件.
사용Langmuir-Hinshelwood(L-H)동역학적학자대부분미주의도해동역학포함료소유흡부물충채용의은태가설적은함조건,인이타문통상홀시료학인실험조건시부윤허채용의은태가설.연이,대우대부분기고최화반응,의은태가설적성립수기우최화활성위농도흔소적전제.대우최화활성위농도고적반응체계,기복개도교고적흡부물충불만족의은태가설.인차,재저충정황하통과실험측정적동역학상수몰유물리의의,이부위해실험조건하적수학회귀삼수.본문장활성위농도소우최고반응기농도적십분지일시위의은태가설성립적충분조건,통과고산발현허다최화제병불만족해조건.
Users of Langmuir-Hinshelwood kinetics often neglect that it invokes the pseudo-steady state hypothesis (PSSH) for all adsorbed species, and they do not check that the PSSH is validly used. However, with solid catalyzed reactions, the validity of the PSSH must often be based on the concentration of active sites being very small. With a high site concentration catalyst, the PSSH would be incorrect for adsorbates with significant coverages, which would make the deduced kinetic parameters lose their physical meaning and be only the parameters of curve fitting. It is estimated that many catalysts do not meet the criterion for their site concentration to be less than one-tenth the highest reactant concentration.
